NO20130812L - Oil for synthesis with slurry bed and process for the preparation of dimethyl ether and a mixture of dimethyl ether and methanol - Google Patents

Abstract

A medium oil used for synthesis reaction in a slurry-bed reaction procedure comprises, as a major component, a branched, saturated aliphatic hydrocarbon having 16 to 50 carbon atoms, 1 to 7 tertiary carbon atoms, 0 quaternary carbon atoms, and 1 to 16 carbon atoms in the branched chain. bonded to the tertiary carbon atoms; and at least one of the tertiary carbon atoms is bonded to hydrocarbon chains having a chain length having 4 or more carbon atoms in three directions. Also disclosed is a process for preparing dimethyl ether or a mixture of dimethyl ether and methanol comprising passing a crude gas containing carbon monoxide and hydrogen through a catalyst slurry containing a mixture comprising (1) the medium oil (2) a methanol synthesis catalyst and (3) a methanol dehydration catalyst and a methanol catalyst catalyst or a methanol dehydration / shift catalyst.

Description

Technical area

The present invention relates to a medium oil which is used for synthesis reaction with a slurry-bed reaction procedure as a medium, and a method for the production of dimethyl ether, and for the production of a mixture of dimethyl ether and methanol.

Background technology

A synthesis gas containing hydrogen and carbon monoxide is used as a raw material for the synthesis of F-T, methanol, ammonia or the like.

The synthesis gas is produced from various organic compounds. It is known that a method for producing synthesis gas is a reaction of the organic compound with steam and/or carbon dioxide, a partial oxidation of the organic compound with oxygen and/or air, etc.

Specifically, with respect to a gaseous organic compound, the following methods are used: (1) a method of reacting an organic compound with steam and/or carbon dioxide at high temperatures in the presence of a catalyst, (2) a method comprising a partial oxidation of an organic compound with oxygen and/or air to generate the heat, where the steam and/or carbon dioxide are mixed and reacted in a catalytic bed, and (3) a combination of (1) and (2).

However, the above methods have disadvantages as follows.

In method (1), as carbon is produced on a catalyst by decomposing an organic compound at high temperatures, an upper limit to the temperature arises. In method (2), an organic compound is rapidly decomposed by means of oxygen, but the organic compound as a heat source is preferably consumed as little as possible. Therefore, the method preferably requires a low temperature. Furthermore, since the methods in (1) to (3), a reaction that produces carbon on a catalyst from a produced carbon monoxide can also occur, a lower limit is given for the temperature.

To solve these problems, subsequent methods are described.

As a method for producing a synthesis gas, the use of a catalyst, for example, patent document 1 describes a method where a catalyst that has suppressed carbon deposition activity is used for the reaction of the unedited carbon-containing organic compound in a high-temperature mixed gas with carbon dioxide and/ or steam. Patent document 2 describes a method in which, for the purpose of providing a catalyst for the production of a synthesis gas with a methane conversion reaction, a high activity catalyst for methane conversion can be obtained by modifying the catalyst by supporting it to a support or by mixing into the catalyst a specific amount of at least one metal compound selected from platinum group metal elements.

On the other hand, for a process for a synthesis gas without a catalyst, patent document 3 describes that the formation temperature is set to approximately 1000 to 1900 °C.

Patent document 1

PCT Japanese Translation Patent Republication Number W098/46525

Patent document 2

Japanese Unexamined Patent Application Publication Number 9-131533.

Patent document 3

Japanese Examined Patent Application, Publication Number 52-46192.

Description of the invention

Problems to be solved by the invention

However, in a process using a catalyst, in the case where H 2 /CO in a synthesis gas is reduced to 2 or less, the increase in carbon dioxide concentration in the produced synthesis gas is not negligible. For example, in a process to synthesize dimethyl ether using the following reaction formula (1), a synthesis gas having a ratio of 1:1 of hydrogen to carbon monoxide is required, but in a process using a catalyst, carbon dioxide reaches the concentration in the produced synthesis gas 20 to 40% on a dry matter basis.

Carbon dioxide present in a raw gas inhibits the reaction, thus adversely affecting the manufacturing process. Furthermore, circulation of a large amount of carbon dioxide in a reaction system is not desirable, due to the fact that it increases apparatus costs and operating costs.

To prevent these disadvantages, one can consider a process to remove CO2 from the raw gas, but this will result in an increase in equipment costs and operating costs.

Furthermore, it is known that in a catalytic bed, carbon is produced with the following reaction, where a pressure drop in the catalyst bed increases, and also the activity of the catalyst is reduced due to coverage of the surface of the catalyst, which prevents operation of the apparatus.

When producing a synthesis gas where H2/CO is as low as 1, the concentration of CO in the gas is increased, so that carbon is particularly easily produced.

On the other hand, in a process that does not use a catalyst, in order not to retain a hydrocarbon which is an intermediate, or an unreacted organic compound, the reaction temperature tends to be high. The high temperature can be achieved by burning the fuel, but the ratio between raw materials to be converted into H2 and CO in relation to what is to be changed into heat increases, so that the energy efficiency is reduced. In order to increase energy efficiency, it is also considered that the reaction temperature is reduced. However, if the reaction temperature is reduced, a hydrocarbon including metal or acetylene is formed in the produced gas. The resulting methane lowers the reactivity of the downstream process using the synthesis gas, and the remaining acetylene makes it difficult to compress the synthesis gas, and there is also a risk of producing an explosive acetylide in the factory system.

The present invention has been developed in light of these conditions. Thus, an object of the present invention is to provide a medium oil which is used for synthesis reaction with a slurry-bed reaction procedure as a medium, and a method for the production of dimethyl ether, and for the production of a mixture of dimethyl ether and methanol.

Means to solve the problems

In order to solve the above-mentioned problems, the inventors of the present invention have studied the equilibrium temperature. As a result, the inventors have achieved the following.

If the temperature to reach an equilibrium state (the starting temperature of the catalyst bed) is set to 1100 to 1300 °C, even if the ratio of hydrogen to carbon monoxide is reduced, soot is not produced, and the amount of carbon dioxide as an auxiliary raw material can also be reduced. As a result, when using an LNG fuel, it is possible to reduce the carbon dioxide concentration in the produced gas to 10 vol% or less. When using an LPG fuel, it is possible to produce a carbon dioxide concentration in the produced gas of 5 vol%. Also, since a catalyst operates efficiently at high temperatures, a high-cost catalyst containing noble metals is not necessary, and the amount of catalyst can be reduced.

In addition, the catalyst bed inlet temperature is reduced by setting the gas retention time upstream of the catalyst bed to 2 seconds or more.

The present invention is based on the knowledge stated above, and is the application from which the present application is divided from stated "as the fifth invention", and is discussed later in this document. In order to have a full understanding of the technology, the other solutions are also described, indicated as "aspects", but these are not part of the present invention which is defined in the accompanying patent claims.

The aspect described in aspect 1 is a method for producing a synthesis gas combustion chamber having hydrogen and carbon monoxide as main components, which is produced by converting a gas with a catalyst, where the gas is produced by a partial combustion of hydrocarbons using a synthesis gas producing combustion chamber where a catalyst bed is formed inside thereof, characterized in that the carbon dioxide concentration in the produced synthesis gas is 10% or less by setting the outlet temperature in the catalyst bed to 1100 to 1300

°C.

The aspect described in aspect 2 is characterized by the gas retention time upstream of the catalyst bed being 2 seconds or more.

The aspect described in aspect 3 is characterized by the fact that, after termination of the catalytic reaction, the synthesis gas is cooled rapidly to 600 °C or less.

The aspect described in aspect 4 is a method for producing dimethyl ether from a synthesis gas containing carbon monoxide and hydrogen, characterized by using the synthesis gas produced by the method in accordance with one of aspects 1-3.

The aspect described in aspect 5 is a method for producing dimethyl ether from a synthesis gas containing carbon monoxide and hydrogen with a ratio of 1:0.8 to 1.2, characterized by using the synthesis gas produced by the method in accordance with one of aspects 1-3.

The aspect described in aspect 6 is a production combustor for producing a synthesis gas comprising effusion of feedstock containing at least one hydrocarbon and an oxidizing agent from a burner mounted at the top of the combustor; partial combustion of the hydrocarbon in a space above the catalyst bed formed inside the combustion chamber; and producing a synthesis gas containing hydrogen and carbon monoxide in the catalyst layer, characterized in that it has a space that meets the conditions given in equations (1) and (2), above the catalyst layer:

1) L> D/2xcotan 01(and

2) The gas retention time in the room is 2 seconds or more,

where L is a height of the space above the catalyst bed, D is an inside diameter of the combustion chamber, & i is 1/2 angle of an apex angle in the vertical cross-section of a conical width of an effusion stream seeping into the inside of the combustion chamber from the burner, which is in the range of 6.5 ° £ 9i £ 9°.

The aspect described in aspect 7 is the combustion chamber for producing a synthesis gas described in aspect 6, characterized in that it further satisfies condition in (3): (3) 92^ 25°, where 92 is a 1/2 angle of the apex angle in the vertical cross-sections section of the conically shaped top part of the combustion chamber.

The aspect described in aspect 8 is a combustion chamber for producing a synthesis gas containing hydrogen and carbon monoxide in a catalyst bed by effusion of a raw material containing at least a hydrocarbon and an oxidizing agent from a burner mounted on the top part of the combustion chamber, and partially burning the hydrocarbon in a space above the catalyst layer formed on the inside of the combustion chamber, characterized in that it has a space that fulfills the conditions in the following (1), (2) and (4) on the catalyst layer:

(1) L> D/2xcotan 01(

(2) The gas retention time in the room is 2 seconds or more, and

(4) L< 10d,

where L is a height of the space above the catalyst bed, D is an inside diameter of the combustion chamber, 01 is 1/2 angle of an apex angle in the vertical cross-section of a conical width of an effusion stream discharging into the inside of the combustion chamber from the burner, which is in the area of 6.5° < 0!<<>9°, and d is a minimum diameter of a circle capable of covering all the gas discharge holes in the burner.

The aspect described in aspect 9 is a combustion chamber for producing a synthesis gas containing hydrogen and carbon monoxide in a catalyst bed by discharging a raw material containing at least one hydrocarbon and an oxidizing agent from a burner mounted at the top of the combustion chamber, and partially burning hydrocarbons in a space above the catalyst bed formed on the inside of the combustion chamber, characterized by having a space that meets the conditions in the following (1), (2), (3) and (5), above the catalyst bed.

(1) L> D/2xcotan 01(

(2) A gas retention time in the room is 2 seconds or more,

(3) 0225°, and

(5) D 3d,

where L is a height in the space above the catalyst bed, D is an inside diameter of the combustion chamber, 01 is 1/2 angle of an apex angle in the vertical cross-section of a conical width of an effusion stream discharging into the inside of the combustion chamber from the burner, which is in the area of 6.5 ° < 0! < 9°,

02 is a 14 angle of the apex angle in the vertical cross-section of the upper conical part of the combustion chamber, and d is a minimum diameter of a circle capable of covering all the gas discharge holes in the burner.

The aspect described in aspect 10 is the combustion chamber for producing a synthesis gas described in aspect 9, characterized in that it further satisfies the conditions in (4). (4) L< 10d.

The aspect described in aspect 11 is the combustion chamber for producing a synthesis gas in accordance with one of aspects 6-10, characterized in that the carbon dioxide concentration in the synthesis gas produced is 10 vol% or less by setting the outlet temperature in the catalyst bed to 1100 to 1300°C.

The aspect described in aspect 12 is the combustion chamber for the production of a synthesis gas described in aspect 11, characterized in that, after termination of the catalytic reaction, the synthesis gas is rapidly cooled to 600 °C or less.

The aspect described in aspect 13 is the combustion chamber for producing a synthesis gas described in one of aspects 6-12, characterized in that dimethyl ether is produced from the synthesis gas containing carbon monoxide and hydrogen, which is produced by the combustion chamber for producing the synthesis gas.

The aspect described in aspect 14 is the combustion chamber for producing a synthesis gas described in one of aspects 6-12, characterized in that dimethyl ether is produced from the synthesis gas containing carbon monoxide and hydrogen having a ratio of 1:0.8 to 1.2, which is produced by the combustion chamber for the production of the synthesis gas.

Brief description of the figures

Fig. 1 is a construction diagram showing a combustion chamber for the production of a synthesis gas. Fig. 2 is a vertical cross-sectional view of a combustion chamber for the production of a synthesis gas. Fig. 3 is a vertical cross-sectional view of a combustion chamber for the production of a synthesis gas (showing the definition of Øi). Fig. 4 is a vertical cross-sectional view of a combustion chamber for producing a synthesis gas. Fig. 5 is a vertical cross-sectional view of a combustion chamber for producing a synthesis gas. Fig. 6 is a vertical cross-sectional view of a combustion chamber for producing a synthesis gas. Fig. 7 is a vertical cross-sectional view of a conventional combustion chamber for producing a synthesis gas. Fig. 8 is a schematic diagram showing a combustion chamber for the production of a synthesis gas. Fig. 9 is a schematic diagram showing a combustion chamber for the production of a synthesis gas. Fig. 10 is a flow diagram of an embodiment of an apparatus for producing DME.

Fig. 11 is a detailed view showing a gas-liquid separator.

Fig. 12 is an experimental apparatus for determining the composition of a product as MeOH is returned to a reactor. Fig. 13 is a graph showing a temporal variation in CO conversion as the purity of MeOH changes. Fig. 14 is a construction diagram for explaining the synthesis apparatus for the synthesis of dimethyl ether.

Best way to perform the aspect

As for a first aspect

Hereafter, the present aspect will be described in detail.

In a conventional process for the production of a synthesis gas, the remaining of an excess of carbon dioxide will inhibit the reaction, thus adversely affecting a production process. First, the results of the investigation of this drawback will be described.

For example, in a process for synthesizing dimethyl ether from a raw gas containing carbon monoxide and hydrogen, as represented in formula (1) below, a synthesis gas having a 1:1 ratio of hydrogen to carbon monoxide is needed.

However, in the case of producing a synthesis gas (a mixed gas having mainly (containing) hydrogen and carbon monoxide) from a natural gas or a propane gas as a raw material, in general, the molar ratio of hydrogen/carbon monoxide is 2 or more, and therefore it must molar ratios of hydrogen/carbon monoxide in the synthesis gas are reduced in the case of using the synthesis gas in the process for synthesizing dimethyl ether. To reduce the proportion of hydrogen in the synthesis gas, for example, it is effective to increase the carbon monoxide by introducing carbon dioxide to the reaction system of the synthesis gas and reacting with hydrogen, in accordance with formula (2).

However, since the above-mentioned reaction (2) is an equilibrium reaction, not all of the carbon dioxide introduced will react, and the unreacted, namely excess carbon dioxide, remains in a produced synthesis gas. Also, in practice, in order to maintain the 1:1 ratio of hydrogen to carbon monoxide, carbon dioxide is generally added more than the flow rate of a raw gas, such as natural gas, etc., whereby the concentration of carbon dioxide contained in the produced synthesis gas reaches 20 to 40% based on dry substance.

Therefore, the inventors have further investigated to solve the problem of reducing the carbon dioxide concentration. As a result, they have achieved the following.

A produced synthesis gas contains carbon monoxide, carbon dioxide, hydrogen and water (steam), which maintains an equilibrium by a shift reaction represented by the following reaction formula (3)

In order to increase carbon monoxide (CO) and decrease hydrogen (hb), it is preferred that the reaction goes towards the left side of the formula by adding carbon dioxide (CO2) to the reaction system. However, the carbon dioxide concentration in a synthesis gas is increased as described above. On the other hand, since the reaction goes to the left at higher temperature and to the right at lower temperature, to increase H2, that is, to increase CO, the reaction can be carried out at high temperature. The low ratio of H2/CO can be realized by raising the temperature, thereby inhibiting CO2 added to the system and reducing the concentration of CO2 contained in the produced gas. However, since a catalyst generally has a limiting heat resistance temperature, the temperature must not exceed this temperature. There is a Ni catalyst that is generally used, but the melting point of Ni is 1455°C, and therefore the maximum temperature for using a catalyst of finely divided Ni particles supported on a support is 1455°C or less.

A synthesis gas is produced herein by using a combustion chamber to produce a synthesis gas where a catalyst layer is provided therein. That is, the combustion chamber for producing a synthesis gas is an autothermal converter (hereinafter referred to as ATR) where a gas produced by a partial combustion of hydrocarbons is converted with a catalyst, whereby a synthesis gas containing hydrogen and carbon monoxide as main components is produced. Furthermore, although the temperature of the synthesis gas obtained is approximately 1000°C since the inlet temperature of the catalyst bed in the ATR is generally approximately 1400°C, the ATR is generally operated at 1400°C or less.

The inventors have controlled the temperature difference between an inlet and an outlet of a catalyst layer on the inside of an ATR. As a result, they found that a gas introduced into the catalyst bed containing methane flowed out of a partial combustion region, which is the main reason for the temperature difference between the inlet and outlet of the catalyst bed. That is, methane reacted with ambient CO2 or H2, and is converted to CO + H2, which is an endothermic reaction. In the case where a gas contains 10% of methane at a temperature of 1400 °C at the entrance to the catalyst bed, all decompose in the catalyst bed, and the exit temperature of the catalyst bed is approximately 1000 °C as it is calculated from an endothermic amount.

Reaction equilibrium exists at the output of a catalyst bed that has a sufficient capacity to be able to consume methane, and therefore the CO2 concentration of a produced synthesis gas will be determined by this temperature.

As shown above, by lowering the concentration of methane in the inlet of a catalyst bed, the temperature difference between the inlet and outlet of the catalyst bed in an ATR is eliminated, and it is possible to lower the concentration of CO2 in a synthesis gas by raising the outlet temperature in the catalyst bed while maintaining the inlet temperature in the catalyst bed below the limiting heat-resistant temperature of the catalyst.

It has further been found that even if the amount of oxygen used for a partial combustion of a hydrocarbon is increased to raise the outlet temperature of the catalyst bed, the increase in the inlet temperature of the catalyst bed is less than that of the outlet temperature thereof. This is caused by the decrease in the amount of methane flowing out by accelerating the partial combustion reaction due to an increase in the temperature in the region where the partial combustion takes place.

As shown above, in order to reduce the concentration of CO2 achieved in a produced gas, the outlet temperature of a catalyst bed is preferably high. However, since it is possible to reduce the concentration of CO2 in the catalyst bed by increasing the outlet temperature of the catalyst bed, the energy efficiency is reduced. Thus, in order to be able to get the concentration of CO2 to be 10% or less, the outlet temperature of the catalyst bed is set at 1100 to 1300 °C.

Furthermore, in a catalyst layer, it is known that carbon is produced by the following reaction, where the pressure drop of the catalyst layer is increased. It is also known that the surface of the catalyst is covered, whereby the activity of the catalyst is lowered, which prevents operation of the apparatus.

2C0 -► C + C02

Since this reaction is an exothermic reaction, carbon will be more easily produced at a lower temperature. As for this point (inhibition of carbon formation), it is beneficial to increase the temperature of the catalyst bed. In practice, by increasing the outlet temperature of the catalyst bed to 1100 °C or more, formation of carbon on the surface of the catalyst was prevented even in the case of producing a synthesis gas having an H2/CO ratio of 1, under the reaction conditions of about 30 atm .

On the other hand, even in the case of supplying a raw gas to set the outlet temperature of the catalyst bed to 1300°C, a hydrocarbon gas such as methane and acetylene remained in a gas introduced into the catalyst bed. As described above, the residual methane lowers the reactivity of the downstream process using the synthesis gas, and the residual acetylene makes it difficult to compress the synthesis gas, and there is also a risk of producing exclusive acetylide in a factory system. That is, a catalyst indispensable in this process, whereby it is possible to have a low concentration of CO2 with high heat efficiency.

As described above, the production of a synthesis gas is carried out by setting the temperature it reaches to an equilibrium, that is, the temperature of the catalyst bed (output) to 1100 to 1300 °C, where even in the case of lowering the ratio of oxygen to fuel, then soot formation is prevented because it is not in the area of soot production. In addition, the shift reaction can be regulated with temperature, and to reduce hydrogen (H2), it is not required to add a conventional amount of carbon dioxide (CO2) to a reaction system, and the amount of an auxiliary raw material: carbon dioxide can be reduced to achieve a required amount of H2/CO (for example the ratio is 1 in the synthesis gas with DME). As a result, the carbon dioxide concentration in the produced gas in an LNG fuel can be 10 vol% or less. In an LPG fuel, since the ratio between carbon/hydrogen in a molecule is high, it is easy to increase the concentration of CO, and the carbon dioxide concentration can be 5 vol%. In addition, since a catalyst operates efficiently at high temperatures, a smaller amount of catalyst is required.

As described above, in a process for producing a synthesis gas having hydrogen and carbon monoxide as main components by converting a gas produced by a partial combustion of a hydrocarbon with a catalyst, the temperature in the catalyst bed is 1100 to 1300 °C, and the carbon dioxide concentration in the synthesis gas is 10% or less.

Furthermore, a space is provided upstream of the catalyst bed. That is, by producing a sufficient gas retention time, where the decomposition reaction of methane is accelerated, we have shown that the inlet temperature of a catalyst bed is further reduced. Upstream of the catalyst bed, the gas retention time is 2 seconds or more, preferably 3 seconds or more. With the safe way of designing a room where the gas retention time upstream of the catalyst bed is 2 seconds or more, in the case of supplying a raw gas, where the outlet temperature of the catalyst bed is 1300 °C, then the inlet temperature of the catalyst bed is regulated to approximately 1400 °C. Furthermore, in a high temperature Ni catalyst, some sintering occurred, where the initial activity thereof was reduced. However, since it is used at a high reactive high temperature, it has been shown that a necessary activity is sufficiently maintained for a long duration.

Furthermore, it is preferred that a synthesis gas obtained by the reaction stated above is rapidly cooled to 600°C or less immediately after termination of the catalytic reaction, whereby a gas having the same mixture at the outlet of the catalyst bed passes into a downstream synthesis reaction. Since the reaction rate is reduced at 600 °C or less, whereby the change of the gas mixture in the following reaction is approximately negligible, the ratio of H2/CO can be maintained at a predetermined value, and there is no increase in methane or CO2 to inhibit the downstream synthesis reaction.

Furthermore, by passing the obtained synthesis gas rapidly through a temperature region where changes in the gas composition are not negligible, the rapid cooling is carried out more preferably within 0.1 seconds after termination of the reaction.

A method for rapidly cooling a synthesis gas is not particularly limited. For example, there is a method for direct cooling with spray water for a gas coming out of a catalyst bed and a method for indirect cooling using a heat exchanger.

Fig. 1 shows an embodiment of a combustion chamber for the production of a synthesis gas.

In this embodiment, an inlet 2 for a raw gas is provided at the upper end of a combustion chamber 1 to produce a synthesis gas, and an outlet 3 of the synthesis gas is formed at the lower end thereof, and a catalyst layer 4 is also provided inside the the combustion chamber 1 for producing the synthesis gas.

In the above construction, in the bottom part of the catalyst bed 4, an adiabatic bed 5 is provided to hold the catalyst bed 4 and a water-cooling metal pipe 6 is provided in this order. In addition, in this manufacturing combustion chamber, a cooling means 7 is provided for cooling the produced synthesis gas by performing such cooling as water spray, etc., directly under the water cooling metal pipe 6. With the above concentration, the inside of the manufacturing combustion chamber is in a compact structure, and the catalyst bed 4 is also easily held by the adiabatic layer 5 and the water cooling metal tube 6.

In accordance with the combustion chamber for producing the synthesis gas, the raw gas is introduced to the inside of the combustion chamber 1 for producing the synthesis gas through the raw gas inlet 2, which provides contact with the catalyst bed 4 in the process of flowing the lower part of the combustion chamber 1, and the desired synthesis gas is obtained. Then, the synthesis gas contacts the adiabatic bed 5, which then contacts the water cooling metal tubes 6 and refrigerants 7, and the synthesis gas is rapidly cooled to 600°C or less. Further, the synthesis gas having C02 concentration of 10% or less is discharged from the combustion chamber from outlet 3 of the synthesis gas.

The type of catalyst used is not particularly limited if a heat resistance is satisfied at a reaction temperature of 1100 to 1300 °C. Examples of catalysts include a metal such as titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, potassium, yttrium, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, gold, cadmium, indium, tin, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, silver, mercury, tellurium, lead, bismuth, thallium, uranium, lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, boron, aluminium, scandium, thorium, lead and lanthanoid, and oxides thereof, and the like.

The catalyst may be supported on a support. The carrier can be used alone or in combination with two or more selected from the group consisting of silica, aluminium, titanium, zirconium, magnesium, zeolite, etc.

The particle size of the catalyst is not particularly limited.

The hydrocarbon in a raw gas can be methane, a hydrocarbon having approximately 2 to 5 carbon atoms and a mixture thereof, a natural gas, methane produced from coal or other materials, LPG, etc., and a suitable mixture thereof can be used.

Oxygen can be pure oxygen, air, etc.

The reactor is not particularly limited. The gas used in the reaction can be a hydrocarbon, oxygen, carbon dioxide gas and steam, where nitrogen can be included.

As a reaction condition except for the temperature of the catalyst bed, the pressure may be in the range of atmospheric pressure to 50 atm, but this is not particularly limited.

As described above, the aspect can produce a synthesis gas which does not contain hydrocarbon in the produced synthesis gas and which has a low carbon dioxide concentration. Furthermore, due to a low carbon dioxide in the synthesis gas in the case of using synthesis gas as a raw material in other processes (for example, a process synthesis of dimethyl ether), the process to remove carbon dioxide is not necessary, and the raw material can be directly supplied to the process as it is. As a result, for example, dimethyl ether can be produced from the synthesis gas with higher efficiency.

As for another aspect

Technical area

This aspect relates to a combustion chamber for the production of a synthesis gas where a hydrocarbon is converted into a synthesis gas containing carbon monoxide and hydrogen.

Background technology

In general, a combustion chamber for producing a synthesis gas, which is referred to as an autothermal converter (hereinafter referred to as ATR) is known. In the ATR, the temperature is increased by a partial combustion of a hydrocarbon on the inside of the combustion chamber, whereby the conversion is carried out with heat.

Fig. 7 shows a cross-sectional view of a conventional ATR. It is considered that in the conventional ATR, a flame is formed for partial oxidation of the hydrocarbon over a catalyst bed, and a produced gas with partial oxidation is introduced to the catalyst bed, and then the reaction of the produced gas is carried out until it reaches an equilibrium in the catalyst bed. It is considered that a space above the catalyst layer is sufficient if there is a height at which the flame does not come into contact with the catalyst layer.

Description of the invention

Problems solved by the invention

A raw material radiating from a burner to a combustion chamber forms a flame in the burner, which then diffuses with a conical shape. An angular width (spreading angle) changes depending on the shape of the burner, but is approximately 13 to 18 °. A gas radiating from a burner ordinarily exists in a region of turbulence, but the spreading angle of this turbulent effusion flow does not change approximately even as the pressure of the gas flow changes.

In a conventional ATR, since the effusion flow collides with the catalyst bed before diffusing to the inner wall of the combustion chamber, a large circulation flow is generated, where a gas flowing in the lateral direction rises up the inner wall of the combustion chamber, and thus joins the effusion flow from the burner, and then descends downwards again. That is, in a space above the catalyst layer in a conventional ATR, a gas that is sprayed to the catalyst layer flows beyond the catalyst layer, and a circulating flow, which is returned to the upper part by colliding with the combustion chamber wall is formed.

If the circulation flow is generated, since the gas that diffused from the burner sinks downwards with the large circulation flow, then the gas sprayed from the burner will have a very short time to be in contact with the catalyst bed by passing only part of the space above the catalyst bed, as it does not ensure that sufficient volume initially. Since the produced gas, which is not in a prominent form in the reaction, flows into the catalyst layer, the temperature of the upper part of the catalyst layer will be high.

Furthermore, since the gas velocity passing through the center of the catalyst bed becomes high in the catalyst bed, it is also possible to carry out an efficient reaction using uniformly the entire area of the catalyst bed.

The inventors have found that a space above the catalyst bed greatly contributes to the reaction, and optimization of the space has been considered as an important means of solving the above-mentioned problems.

Means to solve the problems

In order to solve the above problems, the inventors have provided the catalyst bed by downstream location of the point at which the effused flow from the burner reaches the inner wall of the combustion chamber, and the flow with the combustion chamber cross-section is completely directed downwards.

That is, the invention described in aspect 6 is for the production of a combustion chamber for the production of a synthesis gas comprising the effusion of a raw material, containing at least one hydrocarbon and an oxidizing agent, from a burner mounted at the top of the combustion chamber; partial combustion of the hydrocarbon in a space above a catalyst bed formed inside the combustion chamber; and production of the synthesis gas containing hydrogen and carbon monoxide in the catalytic layer, and the combustion chamber is characterized by having a space that meets the conditions in equations (1) and (2), above the catalyst layer:

(1) L> D/2xcotan 01( and

(2) A gas retention in the room is 2 seconds or more,

where L is a height of a space above the catalyst bed, D is an inside diameter of the combustion chamber, 9i is 1/2 angle of an apex angle in the vertical cross-section of a conical width of an effusion stream effused on the inside of the combustion chamber from the burner, which is in the area of 6.5 ° < 0! < 9°.

The aspect described in aspect 7 is the combustion chamber for the production of synthesis gas as described in aspect 6, where the combustion chamber is characterized by the fact that it further fulfills condition in (3): (3) 02* 25°,

where 02 is a 1/2 angle of the apex angle in the vertical cross sections of the conically shaped top part of the combustion chamber.

The aspect in aspect 8, is in a combustor for producing a synthesis gas containing hydrogen and carbon monoxide in a catalyst bed by effusion of a raw material containing at least one hydrocarbon and an oxidizing agent from a burner mounted on the top part of the combustor, and partially combusting the hydrocarbon in a space above the catalyst layer formed on the inside of the combustion chamber, where the combustion chamber is characterized by having a space that meets the conditions in equations (1), (2) and (4), above the catalyst layer.

(1) L> D/2xcotan 01(

(2) The gas retention time in the space is 2 seconds or more, and (4) L< 10d,

where L is a height in the space above the catalyst bed, D is an inside diameter of the combustion chamber, 01 is 1/2 angle of an apex angle in the vertical cross-section of a conical width of an effusion stream effused on the inside of the combustion chamber from a burner, which is in the region of 6.5° £ 01£ 9°, and d is a minimum diameter of a circle capable of covering all the gas effusion openings in the burner.

The aspect described in aspect 9 is a combustor for producing a synthesis gas containing hydrogen and carbon monoxide in a catalyst bed by discharging a raw material containing at least one hydrocarbon and an oxidizing agent from a burner mounted on the top of the combustor, and partially combusting the hydrocarbons in a space above a catalyst layer formed on the inside of the combustion chamber, the combustion chamber being characterized in that it has a space that meets the conditions in subsequent (1), (2), (3) and (5), above the catalyst layer.

(1) L> D/2xcotan 01(

(2) A gas retention time in the range is 2 seconds or more, (3) 02^25°, and

(5) D > 3d,

where L is a height of a space above the catalyst bed, D is an inside diameter of the combustion chamber, 01 is 1/2 angle of an apex angle in the vertical cross-section of a conical width of an effusion flow radiated on the inside of the combustion chamber from the burner, which is in the region of 6.5 ° < 0!<<>9°, 02 is a 14 angle of an apex angle in the vertical cross-section of the conically shaped top part of the combustion chamber, and d is a minimum diameter of a circle capable of covering all the gas diffusion openings in the burner .

The aspect described in aspect 10 relates to a combustion chamber for the production of a synthesis gas described in aspect 9, where the combustion chamber is characterized by the fact that it further fulfills the condition in (4). (4) L< 10d.

The aspect described in aspect 11 relates to the combustion chamber for producing a synthesis gas in accordance with any of aspects 6-10, characterized in that the carbon dioxide concentration in the synthesis gas produced by setting the outlet temperature of the catalyst bed 1100 to 1300 °C is 10 vol% or less.

The aspect described in aspect 12 relates to the combustion chamber for the production of a synthesis gas described in aspect 6, characterized in that, after termination of the catalytic reaction, the synthesis gas is rapidly cooled to 600 °C or less.

The aspect described in aspect 13 relates to the combustion chamber for producing a synthesis gas described in any of aspects 6-12, characterized in that dimethyl ether is produced from the synthesis gas containing carbon monoxide and hydrogen, which is produced with the combustion chamber for producing the synthesis gas.

The aspect described in aspect 14 relates to the combustion chamber for producing a synthesis gas described in any of aspects 6-12, characterized in that dimethyl ether is produced from the synthesis gas containing carbon monoxide and hydrogen having a ratio of 1:0.8 to 1.2, which is produced with the combustion chamber for the production of the synthesis gas.

Effects of the aspect

In accordance with this aspect, it is possible to carry out a reaction in the absence of a catalyst efficiently in a space above a catalyst bed, which is provided downstream of the location where a radiated flow from a burner reaches the inner wall of a combustion chamber, and where the flow at the cross section of the combustion chamber is completely directed downwards. For this reason, after sufficiently carrying out a reaction in the absence of the catalyst in the space above the catalyst bed, it is possible to further continue the reaction in the catalyst bed. Furthermore, a uniform downward flow can be introduced into the catalyst bed, and thus it is possible to carry out an efficient reaction using uniformly the entire area of the catalyst bed.

Best Mode for Carrying Out the Invention

Hereafter, an implementation of the aspect will be described in detail.

Fig. 2 shows an ATR as a combustion chamber for the production of a synthesis gas. In the ATR, a natural gas or a propane gas is provided as a fuel; oxygen or air as an oxidizing agent; a vapor as an auxiliary raw material; and carbon dioxide, if necessary, is emitted from the burner 1 provided at the top of the combustion chamber, to the inside of the combustion chamber. The natural gas is partially combusted in a space above the catalyst layer 2, and a gas produced by the partial combustion is reacted in the catalyst layer provided on the inside of the combustion chamber up to equilibrium, whereby the natural gas is converted into a synthesis gas which has hydrogen and carbon monoxide as main components.

The combustion chamber for producing the synthesis gas shown in fig. 2 is characterized in that its entire shape is thin and long, compared to a conventional flat combustion chamber for the production of synthesis gas shown in fig. 7. This is to carry out efficient reaction in the absence of catalyst in the space above the catalyst bed 2.

A radiated flow from the burner 1 when the inner wall of the combustion chamber and the catalyst bed is provided downstream of the location where the flow at the cross section of the combustion chamber is completely directed downwards, whereby it is possible for the effusion flow to carry out the reaction by effectively using the volume on the inside of the combustion chamber. That is, as shown in fig. 3, if a height L of the space above the catalyst bed, which is given in the following formula, is ensured with respect to an inside diameter D of the combustion chamber, a good flow in the combustion chamber can be formed even where the pressure or the gas flow rate is changed.

(1)L>D/2xcotan„i

where L is a height in the space above the catalyst bed, D is an inside diameter of the combustion chamber, „i is 1/2 angle of an apex angle in the vertical cross-section of a conical width of the effusion flow radiated into the inside of the combustion chamber from the burner, which is in the area 6.5 ° £ 9i £ 9°.

Since 0! is further precisely described, as shown in fig. 3, since a streamline is curved outward near the inner wall of the combustion chamber, „i is a 1/2 angle of an apex angle of a conical shape formed with the apex part of the effusion flow flowing into the inside of the combustion chamber and the position of the inner wall of the combustion chamber at which the effused flow when, taking the vertical cross-section of the combustion chamber in defining the conical width, which is in the range 6.5 °<<>01 < 9°.

In the case where the diameter of the burner relative to the inside diameter D of the combustion chamber is sufficiently small, as shown in fig. 4, the burner is considered as a point, and the raw material is diffused into a conical shape having a "i angle from an introduction point of the top part of the combustion chamber. In this case, the height L of the space above the catalyst bed is the distance from the apex 3 of the top part of the combustion chamber to the upper end of the catalyst bed 2.

On the other hand, in the case where the burner diameter is so large that it is compared to the inside diameter of the combustion chamber D, then the minimum diameter of the circle that can cover all the gas effusion openings in the burner is d as shown in fig. 5, it is considered that the raw material is diffused with a conical shape that has ,,1 angle from the outside of the circle that has diameter d.

In this case, the height L of the space above the catalyst bed is the distance from the apex 5 of a triangle of an apex angle (200, which passes through the outside of a circle having the diameter d, to an upper end of the catalyst bed 2 in the vertical cross-section of the top part of the combustion chamber.

A circulating stream 6 in the outside of the effusion stream shown in fig. 2 is necessary for protection of the combustion chamber wall. Since the temperature of a flame formed in the burner is extremely high, in case of direct spraying of the flame to the combustion chamber wall, the combustion chamber may melt. In order to separate the flame from the refractory material of the top part of the combustion chamber, it is necessary to circulate a gas, whose temperature has been lowered after termination of the reaction, to the outside of the effusion stream. For the circulation flow formed around the top part of the combustion chamber, if the apex angle at the top part of the combustion chamber having a conical shape is 50° or more, preferably 60° or more, then the circulation flow has a sufficient strength, and it is possible that the temperature of the inner wall of the combustion chamber at the top part of which can be set with the temperature below an ordinary heat-resistant temperature. In this case, as the circulation flow does not reach the catalytic layer. For this reason, as shown in fig. 4 and fig. 5, ,,2, which is a 1/2 angle of an apex angle in the vertical cross-section of the top part of the combustion chamber, which has a conical shape, is set to ,,2^ 25 °.

In the case where the flow from the burner is assumed to be effused from a large, single hole, then a potential core exists in the center of the effusion flow. The potential core is a region that maintains a uniform gas effusion rate and does not mix with the surrounding flow. In order for the potential core to disappear and for the effusion flow to mix uniformly, it is necessary to ensure an effusion distance of 10 times or more with respect to the diameter of the individual hole. In practice, there are many cases of effusion out of a plurality of openings from the burner, but if the height of a space above the catalyst layer has the following height when using d is ensured, then the potential core will disappear in any burner, and it is possible to introduce a uniformly mixed gas to the catalyst bed.

(4) L<>>10d

Also, if a minimum diameter of a circle is d, which can cover all the gas effusion openings in the burner, in the case where d is large compared to the inside diameter D of the combustion chamber, then one cannot ensure a space d capable of forming a sufficient circulation flow. The condition to form sufficient circulation current is as follows:

(5) D<>>3d

From the above description, a shape of the combustion chamber can be obtained, but a method for defining the size thereof is described as follows.

As for an ATR operating under different conditions, a gas is analyzed at different heights in the space above the catalyst bed, cooled rapidly and collected, and analyzed. The inventors have found that a necessary retention time for near completion of the reaction in the absence of a catalyst is 2 seconds or more, preferably 3 seconds or more. Based on this, (2) the retention time of a gas in the room is set to 2 seconds or more. The term "retention time" indicates a passage time for a produced gas through the volume of the space of the catalyst bed, calculated by converting the temperature and pressure of the gas to those of the space.

By ensuring the retention time, the concentration of a hydrocarbon obtained in the gas, which reaches the catalyst bed, can be lowered. Since the decomposition of a hydrocarbon is a strongly endothermic reaction, reducing the concentration of the hydrocarbon will effectively lower the temperature of the gas flowing into the catalyst bed, thereby extending the lifetime of the catalyst. In a conventional ATR, since the concentration of the hydrocarbon is not lowered sufficiently, as to 900 to 1050 °C of the outlet temperature of the catalyst, the inlet temperature of the catalyst is increased up to about 1400 °C, which is a limiting heat-resistant temperature for an ordinary Ni-based catalyst. For this reason, as a heat shield, a catalyst having a high heat resistance is provided at the top of the catalytic layer. That is, a large reduction of the temperature takes place on the inside of the catalyst layer. In contrast, by reducing the concentration of the hydrocarbon in the inlet of the catalyst bed to half or less, it is possible to reduce the increase in temperature inside the catalyst bed to one half or less of that applicable to the case above. Furthermore, in the case where the temperature of the inlet of the catalyst bed is set at 1350 °C, it is possible that the outlet temperature of the catalyst bed is 1100 to 1300 °C, as described below.

Furthermore, by lowering the concentration of hydrocarbon contained in the gas reaching the catalyst, the required amount of catalyst can be reduced.

The above description relates to a method for optimizing the space above the catalyst layer. Furthermore, in order to solve the above-mentioned problems, the inventors have investigated this in the light of an equilibrium temperature. As a result, the following knowledge has been obtained.

The concentration of a hydrocarbon contained in a gas that causes the catalyst bed to be lowered to protect the catalyst, and the outlet temperature of the catalyst bed reaches an equilibrium at 1100 to 1300°C, where soot does not form even if the ratio of hydrogen to carbon monoxide is lowered, and also the amount of carbon dioxide as an auxiliary raw material can be reduced. As a result, it is possible that the carbon dioxide concentration in a produced gas is 10 vol% or less when using natural gas fuel, and the carbon dioxide concentration in the produced gas is 5 vol% or less when using propane gas fuel. Furthermore, since the catalyst is operated efficiently at high temperatures, a catalyst containing a noble metal is not required, and also the amount of catalyst can be reduced.

After termination of the catalytic reaction, it is preferred that the synthesis gas is rapidly cooled to 600°C or less. In this way, then, the gas composition does not need to be changed, and a gas having the gas composition at the outlet of the catalyst bed can be discharged to the downstream synthetic reaction.

The converted synthesis gas is used as a raw material for the synthesis of dimentyl ether (DME), F-T, methanol, ammonia, and so on. Hereafter, a method for the synthesis of diethyl ether (DME) will be described schematically, where the synthesis gas which has carbon monoxide and hydrogen as main components is passed and reacts through a slurry reactor where a catalyst in finely divided particles is suspended in a medium oil with a high boiling point.

A method for the synthesis of dimethyl ether from carbon monoxide and hydrogen is carried out, simultaneously by carrying out the three reactions for the synthesis of

methanol produced from hydrogen and carbon monoxide, synthesis of dimethyl ether produced by a dehydration reaction of the above synthesized methanol, and production of hydrogen by the reaction of carbon monoxide and water bi-produced accompanied by an above synthesis of dimethyl ether, which is represented by the following formulas (A) , (B) and (C).

Summation of (A) to (C) is shown as formula (D) below. Dimethyl ether and carbon dioxide are produced in equal amounts from hydrogen and carbon monoxide.

To be used as a raw material in this reaction, in the case of lowering the ratio of hydrogen to carbon monoxide in a synthesis gas to 2 or less, increase of carbon dioxide concentration in a produced synthesis gas and occurrence of soot is not negligible. In the synthesis process of dimethyl ether using formula (D), a synthesis gas that is 1:1 between the ratio of hydrogen to carbon monoxide is necessary, but in an ordinary ATR, the concentration of carbon dioxide in the synthesis gas produced reaches 20 to 40% by volume based on dry matter basis.

Carbon dioxide contained in a raw gas inhibits the reaction, thus damaging the manufacturing process. Furthermore, the circulation of a large amount of carbon dioxide in the reaction system is not desirable with regard to apparatus costs and operating costs.

To prevent these disadvantages, a process for removing CO2 from a raw gas is being considered, but this will result in an increase in equipment costs and operating costs.

As described above, the temperature which is now an equilibrium is set at 1100 to 1300°C, and the ratio of hydrogen to carbon monoxide (molar ratio) is lowered to close to 1, and also the carbon dioxide concentration is lowered, thus becoming effective in the dimethyl ether synthesis represented by the overall reaction formula ( D).

In addition, the type of catalyst used in this embodiment is not particularly limited if a heat resistance satisfied at the reaction temperature of 1100 to 1300°C. Examples of the catalyst include a metal such as titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, potassium, yttrium, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, gold, potassium, indium, tin, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, silver, mercury, tellurium, lead, bismuth, thallium, uranium, lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium. Barium, boron, aluminium, scandium, thorium, lead and lanthanoid, an oxide thereof, and the like.

The catalyst may be supported on a support. The carrier can be used individually or in combination with two or more selected from the group consisting of aluminium, silica, titanium, zirconium, magnesium, zeolite, etc.

Particle size and shape of the catalyst are not particularly limited, but a large surface area and a sound pressure drop are preferred.

Furthermore, as a fuel introduced to an ATR, a natural gas including a large amount of N2 and CO2, a "coal-bed methane", an associated gas, an organic fermentation of methane, a gas for the production of iron, etc., in addition to a natural gas and an LPG gas are used. As an oxidizing agent, pure O2, air and an O2-enriched air are introduced into the ATR.

The pressure is in the range of atmospheric pressure to 50 atm, but is not particularly limited.

EXAMPLES.

A hydrogen gas was converted into carbon monoxide gas and hydrogen gas using a combustion chamber to produce a synthesis gas as shown in fig. 6. In an upper part and lower part of a catalyst bed, aluminum balls were placed as an adiabatic bed. The catalytic layer was supported by a catalyst carrier. Downstream of the catalyst layer, cooling agents were provided for cooling the synthesis gas by spray water. The internal pressure of the combustion chamber was set to 0.6 MPa. The retention time of a freeboard section was calculated for the volume of the freeboard section, flow rate of a produced gas (wet flow rate), and the temperature and pressure in the freeboard section.

In Examples 1 to 3, the outlet temperature of the catalyst bed was set at 1100 to 1300°C, and the retention time in the freeboard portion, which was a space above the catalyst bed, was set to 2 seconds or more. Furthermore, the ratio of hydrogen to carbon monoxide in the synthesis gas obtained by rapidly cooling the synthesis gas to 600°C or less in the lower part of the catalyst bed was set at 0.8 to 1.2.

In comparative example 1, this was carried out under conditions where the outlet temperature T2 of the catalyst bed was lowered to 960°C.

In comparative example 2 where the aluminum ball layer under the catalyst layer was made thick, and the freeboard part was made small. As for the inlet temperature T1 of the catalytic bed, the temperature immediately above the top of the packed bed, which was increased in height, was measured.

A mixture of the raw gas, the volume of the freeboard part, retention time in the freeboard part, inlet temperature of the catalyst bed, concentration of ChUi the inlet of the catalytic bed, the outlet temperature of the catalytic bed, the temperature after rapid cooling, the mixture of the produced gas, concentration of soot with respect to Examples 1 to 3 and Comparative Examples 1 and 2, are indicated in Table 1 below.

As confirmed in Examples 1 to 3, the concentration of ChUi at the inlet of the catalyst bed was lowered to less than 3.5 vol%, whereby the difference

between the inlet temperature in the catalyst and the outlet temperature thereof became small. Furthermore, the carbon dioxide concentration in the synthesis gas was 10 vol% or less in the case of introducing natural gas as a fuel, and was lowered to 5 vol% in the case where propane gas was introduced. In Example 2, the temperature after the rapid cooling was changed to 595 to 350°C, but the change of the produced gas composition (dry composition) did not occur.

In Comparative Example 1, due to residual ChU, the inlet temperature T1 in the catalyst bed was not lowered as much as the outlet temperature, and furthermore, the carbon dioxide concentration in the synthesis gas was in excess of 20 vol%.

In Comparative Example 2, the concentration of methane in the inlet of a catalyst bed was increased compared to Example 2. Furthermore, the outlet temperature of the catalyst bed in all Comparative Examples 2 and Example 2 was 1200°C\ while the inlet temperature of the catalyst bed in Comparative Example 2 was increased by about . 100°C compared to example 2.

As for a third aspect.

Aspect 1

A method for producing a synthesis gas containing carbon monoxide and hydrogen in the presence of a catalyst using a fuel gas and an oxidizing agent as raw materials, where a proportion of the produced synthesis gas is fed as a proportion of raw materials when the synthesis gas is produced.

Aspect 2

A process for producing a synthesis gas containing carbon monoxide and hydrogen in the presence of a catalyst using a fuel gas and an oxidizing agent as raw materials, wherein a portion of the gas of the following (a) and/or (b): is fed as a portion of raw materials when the synthesis gas is produced. (a) an output gas containing carbon monoxide and hydrogen is discharged from a reaction system in a process using the produced synthesis gas as a raw material; (b) a gas containing carbon monoxide and hydrogen separated from a product in a post process, accompanied by a product obtained in a process using the produced synthesis gas as a raw material.

Aspect 3

Method for producing a synthesis gas in accordance with aspect 1, where a proportion of the produced synthesis gas is mixed with a fuel gas, which is then led to a proportion of raw materials as the synthesis gas is produced.

Aspect 4

Method for producing a synthesis gas in accordance with aspect 2, where a proportion of a gas of (a) or/and (b) is mixed with the fuel gas, which is then fed as a portion of raw materials as the synthesis gas is produced.

Aspect 5

A combustion chamber for producing a synthesis gas containing carbon monoxide and hydrogen in the presence of a catalyst using a fuel gas and an oxidizing agent as raw materials, which is provided with a synthesis gas feed line that feeds a portion of the produced synthesis gas as a portion of raw materials while the synthesis gas is produced.

Technical area.

This aspect relates to a method for producing a synthesis gas from a gas containing a hydrocarbon, carbon dioxide, oxygen, etc. Furthermore, the synthesis gas is suitable as a synthesis gas having the ratio of H2/CO = 0.8 to 1.2 (molar ratio) , which is necessary for a synthesis of dimethyl ether

(DME).

Background technology.

A synthesis gas containing hydrogen and carbon monoxide is used as raw materials for the synthesis of F-T, methanol, ammonia, DME, etc. The synthesis gas is produced from various organic compounds. As a method for producing the synthesis gas, methods such as a reaction of steam and/or carbon dioxide, a partial oxidation with oxygen and/or air, etc., are known.

In particular, for a gaseous organic compound, the following methods may be used: (1) a method of reacting steam and/or carbon dioxide to an organic compound in the presence of a catalyst at high temperatures; (2) a process comprising a partial oxidation of an organic compound using oxygen and/or air to generate heat, whereby steam and/or carbon dioxide are mixed, which are then reacted in a catalytic bed; or (3) a combination of (1) and (2).

Description of the invention.

Problems to be solved by the aspect.

However, in the method of producing a synthesis gas accompanied with a partial oxidation, the temperature in the top part of a furnace rises as the synthesis gas is produced. For this reason, there are problems for factory facilities, such as melting of refractory materials in the combustion chamber, etc.

Therefore, under the conditions stated above, the aspect aims to provide a method for the production of a synthesis gas, which lowers the temperature in the top part of the combustion chamber used for the production of synthesis gas.

The inventors have conducted considerable research to solve the above stated problems. As a result, it has been found that the temperature in the top part of a combustion chamber used in the production of a synthesis gas is lowered by feeding a portion of the synthesis gas containing carbon monoxide and hydrogen, which is produced by a process for the production of the synthesis gas; a portion of an output gas containing carbon monoxide and hydrogen is led out from a reaction system in a process where a produced synthesis gas is used as a raw material; or part of a gas containing carbon monoxide and hydrogen separated from a product in the post process, accompanying with an obtained product in a process where the produced synthesis gas is used as a raw material, preferably where the above fed gas is mixed with a fuel gas.

This aspect has emerged on the basis of the findings described above. This aspect is characterized by: The aspect described in aspect 1 is a method for producing a synthesis gas containing carbon monoxide and hydrogen in the presence of a catalyst using a fuel gas and an oxidizing agent as raw materials, where a proportion of the produced synthesis gas is fed as a share of raw materials when the synthesis gas is produced.

The aspect described in aspect 2 is a method for producing a synthesis gas containing carbon monoxide and hydrogen in the presence of a catalyst using a fuel gas and an oxidizing agent as raw materials, wherein a proportion of the gas of the following (a) and/or (b) : fed as a portion of raw materials as the synthesis gas is accelerated,

(a) an exit gas containing carbon monoxide and hydrogen

is discharged from a reaction system in a process using the produced synthesis gas as a raw material; (b) a gas containing carbon monoxide and hydrogen separated from a product in a post process, accompanied by a product obtained in a process using the produced synthesis gas as a raw material.

The aspect described in aspect 3 is the method for producing a synthesis gas in accordance with aspect, where part of the produced synthesis gas is mixed with a fuel gas, which is then fed as a portion of raw materials in the production of the synthesis gas.

The aspect described in aspect 4 is the method for producing a synthesis gas in accordance with aspect 2, wherein part of a gas of (a) and/or (b) is mixed with the fuel gas, which is then fed as a portion of raw materials in the production of the synthesis gas .

The aspect described in aspect 5 is a combustion chamber for producing a synthesis gas containing carbon monoxide and hydrogen in the presence of a catalyst using a fuel gas and an oxidizing agent as raw materials, which is provided with a synthesis gas feed line feeding a portion of the produced synthesis gas which a portion of raw materials when the synthesis gas is produced.

Effects of the aspect.

With the present aspect, it is possible to lower the temperature in the top part of a combustion chamber used in the production of synthesis gas. And since the temperature is the top part of the combustion chamber can be lowered, it is not necessary to provide heat resistant to the top part of the manufacturing combustion chamber; the frequency of repair of refractory materials is reduced; or similar, and thus time and costs for maintenance of the factory will not be necessary. Therefore, the aspect is economic. Furthermore, the amount of carbon dioxide in the produced synthesis gas can be effectively reduced without increasing the outlet temperature of a catalyst bed in the combustion chamber by returning synthesis gas containing carbon monoxide and hydrogen as raw material.

Best mode of carrying out the invention.

Hereafter, the aspect will be described in detail.

Fig. 8 is a schematic diagram showing an embodiment of a combustion chamber for the production of a synthesis gas (autothermal converter (ATR)). In the production of synthesis gas (5) containing carbon monoxide and hydrogen, gas is classified as a raw material as fuel gas (1), an oxidizing agent (4) and auxiliary raw materials (2) and (3). The fuel gas (1) is a hydrocarbon comprising a natural gas, an LPG, hydrocarbons (HC) or the like. The oxidizing agent (4) includes oxygen, air or the like. Further, auxiliary raw materials include steam (water) (2), carbon dioxide (3) or the like.

A catalytic layer is provided inside a combustion chamber for the production of the synthesis gas (hereinafter referred to as a production combustion chamber) (6). The synthesis gas containing carbon monoxide and hydrogen, for example, the gas produced by partial oxidation using a diffusion mixture type burner, is prepared from the above-described raw gas in the presence of a catalyst. That is, by means of the combustion chamber for the production of synthesis gas, where the synthesis gas which has hydrogen and carbon monoxide as main components is produced by catalytic conversion of the gas generated with the partial combustion of hydrocarbons.

In fig. 8 is (1) fuel gas, (4) is oxidizing agent, (5) is synthesis gas, and (6) is manufacturing combustion chamber. A feed line for feeding auxiliary raw materials of steam (2) and carbon dioxide (3) is connected to the fuel gas feed line (7) for feeding the fuel gas (1) to the manufacturing combustion chamber (6). Furthermore, before these are introduced into the production combustion chamber (6), steam (2) and carbon dioxide are premixed with the fuel gas (1).

A feed line (8) for feeding oxidizing agent (4) to the production combustion chamber (6) is not connected to the fuel gas feed line (7), but is connected directly to the production combustion chamber (6). The reason for this is that if the oxidizing agent (4) is premixed with fuel gas, then the fuel gas (1) will be burned. It is effective to inhibit soot production or partial increase of the internal temperature of the combustion chamber by preliminarily introducing the raw materials other than the oxidizing agent, namely, steam (2) and carbon dioxide (3) into the manufacturing combustion chamber (6), which are then mixed with the oxidizing agent agent (4) in the manufacturing combustion chamber (6).

A synthesis gas feed line (9) for circulating the manufactured synthesis gas (5) in the manufacturing combustion chamber (6) is branched from a synthesis gas drainage line (10) and is connected to a fuel gas feed line (7). Thus, a portion of the produced synthesis gas (5) is fed to the production combustion chamber (6) which is a portion of the raw gas at the same time as the synthesis gas is produced. Furthermore, it is also preferred that after premixing the circulated synthesis gas with fuel gas (1), carbon dioxide (3) and steam (2), the mixture is fed to the production combustion chamber, and the synthesis gas circulated in the combustion chamber is reacted with oxygen. But the feeding method is not limited to this.

In a conventional combustion chamber for the production of synthesis gas, the temperature of the top part of the combustion chamber increases, so that refractory materials in the combustion chamber melt. Therefore, this problem is in the factory. First, this will be described as follows.

As described above, when producing synthesis gas containing carbon monoxide and hydrogen, a raw gas is classified as a fuel gas and an oxidizing agent, or further an auxiliary raw material. The synthesis gas contains carbon monoxide and hydrogen, for example, the gas produced by partial oxidation using a diffusion mixture type burner, is prepared from the above-described raw gas in the presence of a catalyst. At this time, if a high concentration of oxygen is combined with a high concentration of fuel gas in the reactor, more heat is generated, whereby the top part of the combustion chamber is heated so that its temperature increases.

It was found that it is possible to lower the flame temperature by returning and feeding a proportion of the synthesis gas containing carbon monoxide and hydrogen, as part of the raw materials, obtained by simultaneous production of the synthesis gas, and thus lower the highest temperature of the top part of the combustion combustion chamber. The oxidizing agent is reacted with circulating hydrogen (hb) and carbon monoxide (CO), in addition to the fuel gas. Since the heat generated by the oxidation of hbog CO is small compared to that of fuel gas, the temperature of the region with a high concentration of oxidizing agent will be effectively reduced. hbO and CO2 produced by the oxidation of hb and CO are oxidizing agents in the unreacted fuel gas in the following region, and they are reduced to hb and CO. That is, hbog Co is a medium for oxygen exchange, and since not all of the hbog CO is reacted, the gas volume will increase and the highest temperature in the top part of the combustion chamber will be lowered. Here, the peak temperature of the flame is lowered by reducing the concentration of fuel gas, and at the same time, it is possible to lower the temperature of all the regions of the combustion chamber by adding the unreacted gas, which is ultimately not related to the combustion (ie, the synthesis gas containing carbon monoxide and hydrogen). The added H2 and CO act as an inert gas in the combustion chamber. Furthermore, in contrast to the case of adding inert gas such as ISb etc, the added H2 and CO will not increase the impurities in the produced gas, and the concentration of H2 and CO, which are the useful components in the produced gas, is not reduced, but is increased.

The synthesis gas produced contains carbon monoxide, carbon dioxide, hydrogen and water (steam), which maintains an equilibrium by shift reaction as shown in the following reaction formula (1).

The amounts of introduced hydrocarbon, oxygen, carbon dioxide and steam are maintained, and if hydrogen and carbon monoxide have the same ratio as hydrogen/carbon monoxide as the produced gas is introduced into the manufacturing combustion chamber, which will the inside temperature of the combustion chamber (from the top of the combustion chamber to the exit of the catalyst bed) could be lowered while approximately simultaneously maintaining the composition of the produced gas. This is because the introduced hydrogen and carbon monoxide do not change, and have an effect in diluting the gas in the combustion chamber. Furthermore, since the denominator and the nominator of the equilibrium equation shown as ([CO] x [H2O])/ ([CO2MH2]) of the produced gas increase by the same ratio, then at equilibrium approximately no change is made. This is an effective means of protecting the refractory materials in the combustion chamber due to the fact that the same gas composition can be achieved at lower temperatures.

Furthermore, if the inside temperature of the manufacturing combustion chamber rises, then the amount of carbon dioxide in the manufactured synthesis gas can be reduced. But the amount of carbon dioxide in the produced synthesis gas can be effectively lowered without raising the temperature in the combustion chamber by returning synthesis gas containing carbon monoxide and hydrogen as raw gas. This effect will be described in detail below.

For example, in a method for synthesizing dimethyl ether from a synthesis gas containing carbon monoxide and hydrogen as shown in the following formula (2), there is a need for a synthesis gas having a ratio of hydrogen to carbon monoxide of 1:1.

However, in the case of producing synthesis gas (a mixed gas having hydrogen and monoxide as main components) using a natural gas or a propane gas as a raw material, where the molar ratio of hydrogen/carbon monoxide is generally 2 or more. Therefore, in the case of using the synthesis gas in the process of synthesizing dimethyl ether, the molar ratio of hydrogen/carbon monoxide in the synthesis gas should be reduced. To reduce the ratio of hydrogen in the synthesis gas, for example, carbon dioxide is introduced into the process for producing the synthesis gas, and this is then reacted with hydrogen as shown in the following formula (3), thus effectively increasing carbon monoxide.

However, since formula (3) is an equilibrium reaction, not all of the introduced carbon dioxide will react, so that unreacted carbon dioxide, i.e. excess carbon dioxide, remains in the produced synthesis gas. In practice, in order to achieve a 1:1 ratio between hydrogen and carbon monoxide, carbon dioxide is generally added at more than the flow rate of the raw gas, such as a natural gas, etc., and thus the concentration of carbon dioxide contained in the produced synthesis gas will reach up to 20 to 40 % on a dry matter basis.

The synthesis gas produced comprises carbon monoxide, carbon dioxide, hydrogen and water (steam), which maintains equilibrium by shift reaction as shown in the following reaction formula (1), as described above.

To increase carbon monoxide (CO) and decrease hydrogen (hh), it is possible to shift the reaction to the left side of the equilibrium by adding carbon dioxide (CO2) to the system. However, this increases the carbon dioxide concentration in the synthesis gas, as described above. On the other hand, at higher temperatures, the reaction shifts more to the left side of the equation, while at lower temperatures, the reaction shifts more to the right side of the equation. Thus, to reduce the hydrogen, namely, to increase the carbon monoxide, the reaction should be carried out at higher temperatures. By increasing the temperature, carbon dioxide added to the system will be reduced. It is possible to reduce a low ratio of H2/CO by maintaining the concentration of CO2 contained in the synthesis gas at a low level. That is, as the outlet temperature of the catalyst bed rises, the CO2 concentration of the synthesis gas can be lowered.

As described above, in order to reduce the concentration of CO2 contained in the produced gas, it is preferred that the outlet temperature of the catalytic layers is high. However, on the other hand, although it is possible to reduce the CO 2 concentration by increasing the outlet temperature of the catalytic bed, the energy efficiency is lowered. Furthermore, since the heat loaded into the combustion chamber body increases, cost-controlled material is required, or the lifetime of the combustion chamber body is reduced. Thus, in the present embodiment, to reduce the CO 2 concentration to 10% or less, the outlet temperature of the catalyst bed is set at 1100 to 1300°C.

The inventors have studied a method to further reduce the concentration of CO2 contained in the synthesis gas. As a result, the following has been found.

Carbon dioxide and steam as auxiliary raw materials can lower the temperature of the produced gas, and they are also introduced to regulate the composition of the produced gas. As described above, if hydrogen and carbon monoxide in the produced synthesis gas are introduced into the production combustion chamber, the outlet temperature of the catalyst layer in the production combustion chamber will be lowered. If carbon dioxide and steam, which are the raw gas, are reduced so that they maintain the outlet temperature in the catalytic layer, the CO2 and hh concentrations in the produced gas can be reduced. Although carbon dioxide and steam in the raw gas are involved in the reaction, most of these will exist in the produced gas. Therefore, the CO2 and H2O concentrations in the produced gas can be lowered in proportion to the reduced amount of carbon dioxide and steam present in the raw gas. The procedure for reducing carbon dioxide and steam in the raw gas is regulated by calculating equilibrium, whereby a predetermined ratio of H2/CO can be maintained. That is, as described above, it is possible to further reduce the CO2 concentration in the produced gas which has already been lowered by increasing the outlet temperature of the catalytic layer.

In the case of introducing hydrogen and carbon monoxide for the purpose of lowering the CO 2 concentration, the synthesis gas containing CO 2 and H 2 O, each of the amounts of CO 2 and H 2 O should be reduced from the amounts of CO 2 and steam individually introduced as the auxiliary raw materials. This means that, after the amounts of CO2 and H2O corresponding to the amounts for maintaining the outlet temperature of the catalyst bed are reduced with respect to the introduced hydrogen and carbon monoxide, each of the amounts of CO2 and H2O contained in the synthesis gas is further reduced.

As described above, the aspect is characterized in that, in order to lower the temperature of the top part of the combustion chamber and further reduce the amount of CO2 contained in the synthesis gas, a part of the synthesis gas containing carbon monoxide and hydrogen, which is obtained as the produced gas while preparing the synthesis gas, is returned and fed as part of the raw material at the time of production of the synthesis gas.

As a method of introducing hydrogen and carbon monoxide, a

method for circulating a part of the produced synthesis gas in the synthesis gas production combustion chamber and a method for feeding an output gas containing carbon monoxide and hydrogen that escapes from the reaction system in the process by using produced synthesis gas as raw material are used appropriately.

The same effect as for the above-mentioned method was achieved in the case where we used a portion of a gas containing carbon monoxide and hydrogen, which was separated from the product in a post process, accompanied by the product obtained in a process using the produced synthesis gas as a raw material.

In the conditions for producing the synthesis gas which has a H2O/CO ratio of 1; the amount of steam introduced is low. Therefore, there is a limitation in reducing the amount. In most cases where an output gas containing carbon monoxide and hydrogen is used, which is discharged from the reactor system in the process using the synthesis gas as raw material, H2O is not contained, and therefore it is not necessary to reduce the amount of steam corresponding to the amount of H2O. However, in the case of circulating synthesis gas at temperatures higher than the water-steam condensation temperature, there is a problem. In such cases, it is preferred to reduce the temperature of the synthesis gas to the steam condensation temperature or lower to remove the water vapor, and then introduce the synthesis gas to the manufacturing combustion chamber.

As described above, the production of the synthesis gas is accompanied by the use of a fuel gas, an oxidizing agent or a further auxiliary raw material as raw materials in the presence of catalyst. The type of catalyst is not particularly limited, if a heat resistance is satisfied at the reaction temperature (for example, 1100 to 1300 °C). Examples of the catalyst include a metal such as titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, potassium, yttrium, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, gold, cadmium, indium, tin, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platium, silver, mercury, tellurium, lead, bismuth, thallium, uranium, lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, boron, aluminum, scandium, thorium, lead, lanthanoid, etc; and an oxide thereof, and the like.

The catalyst may be supported on a carrier. The carrier can be used individually or in combination of two or more selected from the group comprising aluminium, silica, titanium, zirconium, magnesium, zeolite, etc.

The particle size of the catalyst size is not particularly limited.

Also, as a fuel gas, methane and a hydrocarbon having about 2 to 5 carbon atoms, a mixture thereof, a natural gas, a methane produced from coal and other substances, an LPG, etc., and a suitable mixture thereof can be used. As an oxidizing agent, the oxygen can be pure oxygen, air, etc. As an auxiliary raw material, steam, water, carbon dioxide, etc. can be used. Furthermore, nitrogen gas can also be used.

The reaction conditions for the production of synthesis gas are such that the reaction is preferably carried out at a pressure of atmospheric pressure to 50 atm. Furthermore, the manufacturing combustion chamber (reactor) used for manufacturing the synthesis gas is not particularly limited.

Fig. 9 is a schematic diagram showing another embodiment of the manufacturing combustion chamber.

In fig. 9, the synthesis gas produced with the production combustion chamber (6) is used as a raw gas in a plant (11) using the synthesis gas. In the process in the plant (11) where the synthesis gas is used, an output gas containing carbon monoxide and hydrogen that emits from the reaction system is fed into the manufacturing combustion chamber (6) as a portion of raw material in the manufacturing combustion chamber (6).

In the manufacturing combustion chamber (6) according to fig. 9, a fuel gas (1) and an oxidizing agent (4) are fed as raw materials into the combustion chamber (6) through a fuel gas feed line (7) and an oxidizing agent feed line (8), and a synthesis gas containing carbon monoxide and hydrogen is produced in the presence of a catalyst. The synthesis gas emits from a synthesis gas drainage line (15) and is fed into the plant (11) which uses synthesis gas. In the process in the plant (11) that uses the synthesis gas, an output gas containing carbon monoxide and hydrogen is emitted from the reaction system through an emission line (12). A part of the output gas emits from the discharge line to the outside of the system, and the remaining part of it is fed into the manufacturing combustion chamber (6) through an output gas feed line (14), which is connected to the fuel gas feed line (7).

Further, herein, the process using synthesis gas as raw material is a manufacturing process using a mixed gas containing hydrogen and carbon monoxide as raw materials. For example, the process can be the synthesis of DME, methanol, F-T, etc.

Furthermore, as described above, the output gas containing carbon monoxide and hydrogen, which is discharged from the reaction system in the method using synthesis gas as raw material, is an unreacted gas which is not used in reaction; an unreacted gas withdrawn to control the pressure in the reaction system; or an unreacted gas which is withdrawn so as not to increase the concentration of the gas inert to the reaction with circulation in the reaction system.

Example

A produced synthesis gas, or a purge gas of a DME synthesis reaction system mixed with a feedstock and introduced. The conditions for this design were such that a synthesis gas could be produced which has a hb/CO ratio of 0.8 to 1.2. Under such conditions, since the amount of steam introduced was small, gas excluding the condensed water was introduced. The outlet temperature of a catalyst bed was set to 1100 to 1300°C, and the synthesis gas was rapidly cooled to 600°C or less in the lower part of the catalytic bed.

In Table 2, comparative examples 1 and 2 show examples of no circulation of synthesis gas, and examples 1 and 2 show examples of circulation of the synthesis gas.

It was found that examples 1 and 2, the amount of introduced CO2 in the raw gas could be lowered, and furthermore the amount of CO2 in the produced gas was also reduced to 8 dry vol%. Since it is not easy to reduce the amount of CO2 in a produced gas with only a dry vol%, the importance of is very large.

As a fourth aspect

Aspect 1

A process for producing dimethyl ether, which comprises introducing a raw gas containing carbon monoxide and hydrogen into a reactor, and subjecting the raw gas to a catalytic reaction to produce dimethyl ether while simultaneously producing at least methanol as a by-product, wherein the purity of the produced methanol is increased to at least 95% based on the mass, and where the methanol with the increased purity is returned to the reactor.

Aspect 2

A process for producing dimethyl ether, which comprises introducing a raw gas containing carbon monoxide and hydrogen into a reactor, and subjecting the raw gas to a catalytic reaction to produce dimethyl ether while simultaneously producing at least methanol and water as by-products, wherein the methanol is separated from a liquid containing the methanol and water obtained by cooling the produced gas from the reactor, and the separated methanol is returned to the reactor.

Aspect 3

A process for producing dimethyl ether, comprising introducing a raw gas containing carbon monoxide and hydrogen into a reactor, and subjecting the raw gas to a catalytic reaction to produce dimethyl ether while producing at least carbon dioxide, methanol and water as by-products, where it produced gas from the reactor is cooled to separate a liquid (1) containing dimethyl ether, carbon dioxide, methanol and water and a gas containing the unreacted gas component, where carbon dioxide is separated from the obtained liquid (1), dimethyl ether is separated from a liquid (2) from which carbon dioxide is separated, methanol is separated from a liquid (3) from which carbon dioxide and dimethyl ether are separated, and the separated methanol is returned to the reactor.

Aspect 4

Methods for producing dimethyl ether in accordance with aspect 3, wherein the produced gas is brought into contact with the liquid (2) from which carbon dioxide has been separated, and with the liquid (3) from which carbon dioxide and dimethyl ether have been separated.

Aspect 5

An apparatus for the production of dimethyl ether, which is provided with a reactor in which a raw gas containing carbon monoxide and hydrogen is subjected to a catalytic reaction to produce dimethyl ether and at the same time produce at least methanol as a by-product; a methanol purification apparatus where the purity of the produced methanol is increased to at least 95% based on mass; and recycling line where the purified methanol is returned to the reactor.

Aspect 6

An apparatus for the production of dimethyl ether, which is provided with a reactor in which a raw gas containing carbon monoxide and hydrogen is subjected to a catalytic reaction to produce dimethyl ether and at the same time produce at least carbon dioxide, methanol and water as by-products; a methanol purifier for separating methanol from the liquid containing methanol and water obtained by cooling the produced gas from the reactor; and a recycling line where the separated methanol is returned to the reactor.

Aspect 7

Apparatus for the production of dimethyl ether, which is provided with a reactor in which a raw gas containing carbon monoxide and hydrogen is subjected to a catalytic reaction to produce dimethyl ether and at the same time produce at least carbon dioxide, methanol and water as by-products; a gas-liquid apparatus where the produced gas from the reactor is cooled to separate a liquid (1) containing carbon dioxide, dimethyl ether, methanol and water, and a gas containing the unreacted gas component; a CO2 purifier where carbon dioxide is separated from the liquid obtained (1); a DME purifier where dimethyl ether is separated from a liquid (2) from which carbon dioxide is separated; a methanol purification apparatus where methanol is separated from a liquid (3) from which carbon dioxide and dimethyl ether are separated; and a recycling line where the separated methanol is returned to the reactor.

Aspect 8

Apparatus for the production of dimethyl ether in accordance with aspect 7, wherein, in the gas-liquid separation apparatus, the produced gas is brought into contact with the liquid (2) from which carbon dioxide is separated by means of the CO2 purification apparatus, and the liquid (3) from which dimethyl ether is separated by of the DME purifier.

Technical area

The aspect relates to a method and an apparatus for the production of dimethyl ether, using carbon monoxide and hydrogen as the main raw materials.

Background technology

As a technique for the direct production of dimethyl ether (DME) from a synthesis gas which has carbon monoxide and hydrogen as main raw materials, a technique is described in which a raw gas is reacted by passing it through a slurry reactor where a catalyst with finely divided particles is suspended in a high-boiling medium oil , to synthesize dimethyl ether with a high yield (see, for example, patent document 1).

In the method of direct synthesis of dimethyl ether from carbon monoxide and hydrogen, three types of reactions are represented by each of the following formulas (1), (2) and (3), that is, synthesis of methanol produced from hydrogen and carbon monoxide, synthesis of dimethyl ether produced by the dehydration reaction from the synthesized methanol, and the production of hydrogen from the reaction of water with carbon monoxide produced through the synthesis of dimethyl ether occurring simultaneously, where each of the following formulas is satisfied: In summation of the formulas (1) to (3), dimethyl ether and carbon dioxide are produced in equal amounts from hydrogen and carbon monoxide, as represented by the following reaction formula (4)

The reactions in the formulas (1) to (3) are equilibrium reactions, but in many cases, the introduced raw gas does not have sufficient time to reach an equilibrium state in the reactor, and in a practical synthesis process the three reactions described above have not gone to a 100 % completion. Thus, the reaction of the total formula (4) summed from the three reactions as described above does not go to 100% completion. Therefore, there is no case where hydrogen and carbon monoxide as the raw materials are not 100% converted according to formula (4), and for the output gas from the reactor, methanol and water are produced which are the intermediate reaction products as by-products, and likewise DME and carbon dioxide as reaction products. Furthermore, the exit gas from the reactor comprises unreacted hydrogen and carbon monoxide.

Conventionally, after the produced methanol is separated from dimethyl ether, the methanol is further purified as a product, or incinerated for disposal.

However, it was difficult to use the methanol produced in a small amount commercially as products for dimethyl ether production facilities constructed at a natural gas or coal production site, and there has been a need for an increased yield of dimethyl ether.

For this reason, the applicant proposed a method for using the produced methanol effectively, where the liquid containing, as main components, methanol and water obtained by cooling the output gas from the reactor, is returned to the reactor, and thus the yield of dimethyl ether will increase, see patent document 2.

Patent document 1: Japanese unexamined patent application with publication number No. 10-182528

Patent document 2: Japanese unexamined patent application with publication number No. 10-182529.

Description of the invention

Problems to be solved by the invention

However, since it is difficult to separate a liquid containing methanol as a main component by regulating the cooling temperature, a liquid obtained by cooling will inevitably include dimethyl ether, water and carbon dioxide in addition to methanol. Table 3 represents the proportion of each of the components, methanol (MeOH), dimethyl ether (DME), water (H2O) and carbon dioxide (CO2) (relative to the entire amount of gas before cooling) carried to the recovery solution at 5 MPaG and 30 °C.

For dimethyl ether, 20 to 30% of the produced quantity will liquefy at 30 °C. dimethyl ether, carbon dioxide and water as reaction products inhibit the reaction if they are returned to the reactor as they are. In the case where the components other than methanol are separated and discarded, dimethyl ether and carbon dioxide are lost (water may be released from the system).

Furthermore, if water contained in the liquid is returned to the reactor, this will inhibit the reaction, and the catalyst for dimethyl ether synthesis will be damaged. The aspect is aimed at solving the problems described above, and the purpose of the aspect is thus to provide a method for producing dimethyl ether, so that it becomes possible to effectively use methanol as a by-product and to increase the yield of dimethyl ether.

Means to solve the problems

In order to solve these problems, the invention is provided in aspect 1 a method for producing dimethyl ether, which comprises introducing a raw gas containing carbon monoxide and hydrogen into a reactor, and subjecting the raw gas to a catalytic reaction to produce dimethyl ether and simultaneously producing in it least methanol as a by-product, where the purity of the produced methanol is increased to at least 95% based on mass, and where the methanol as increased purity is returned to the reactor.

The aspect of aspect 2 is a method for producing dimethyl ether, which comprises introducing a raw gas containing carbon monoxide and hydrogen into a reactor, and subjecting the raw gas to a catalytic reaction to produce dimethyl ether while simultaneously producing at least methanol and water as by-products, wherein the methanol is separated from a liquid containing methanol and water obtained by cooling the produced gas from the reactor, and where the separated methanol is returned to the reactor.

The aspect of aspect 3 is a method of producing dimethyl ether, comprising introducing a raw gas containing carbon monoxide and hydrogen into a reactor and subjecting the raw gas to a catalytic reaction to produce dimethyl ether while producing at least carbon dioxide, methanol and water as by-products, where the produced gas from the reactor is cooled to separate a liquid (1) containing dimethyl ether, carbon dioxide, methanol and water and a gas containing the unreacted gas component, where carbon dioxide is separated from the obtained liquid (1) dimethyl ether is separated from a liquid (2 ) from which carbon dioxide is separated, methanol is separated from a liquid (3) from which carbon dioxide and dimethyl ether are separated, and the separated methanol is returned to the reactor.

The aspect according to aspect 4, is a method for producing dimethyl ether in accordance with aspect 3, where the produced gas is put in connection with the liquid (2) from which carbon dioxide is separated, and with the liquid (3) from which carbon dioxide and dimethyl ether are separated.

The aspect in aspect 5 is an apparatus for the production of dimethyl ether, which is provided with a reactor in which a raw gas containing carbon monoxide and hydrogen is subjected to a catalytic reaction to produce dimethyl ether and at the same time produce at least methanol as a by-product; a methanol purification apparatus where the purity of the produced methanol is increased to at least 95% based on mass; and a recycling line where the purified methanol is returned to the reactor.

The aspect in aspect 6 is an apparatus for the production of dimethyl ether, which is provided with a reactor in which a raw gas containing carbon monoxide and hydrogen is subjected to a catalytic reaction to produce dimethyl ether and at the same time to produce at least carbon dioxide, methanol and water as by-products; a methanol purifier for separating methanol from the liquid containing methanol and water obtained by cooling the produced gas from the reactor; and a recycling line where the separated methanol is returned to the reactor.

The aspect in aspect 7 is an apparatus for producing dimethyl ether, which is provided with a reactor in which a raw gas containing carbon monoxide and hydrogen is subjected to a catalytic reaction to produce dimethyl ether and at the same time to produce at least carbon dioxide, methanol and water as by-products; a gas-liquid separation apparatus where the produced gas from the reactor is cooled to separate a liquid (1) containing carbon dioxide, dimethyl ether, methanol and water, and a gas containing the unreacted gas component; a CO2 purification device where carbon dioxide is separated from the obtained liquid (1); a DME purifier where dimethyl ether is separated from a liquid (2) from which carbon dioxide is separated; a methanol purification apparatus where the methanol is separated from a liquid (3) from which carbon dioxide and dimethyl ether are separated; and a recycling line where the separated methanol is returned to the reactor.

The aspect in aspect 8 is the apparatus for the production of dimethyl ether in accordance with aspect 7, in which the produced gas in the gas-liquid separation apparatus is brought into contact with the liquid (2) from which carbon dioxide is separated by means of the CO2 purification apparatus, and the liquid (3) from which dimethyl ether is separated using the DME cleaning device.

Effects of the aspect

In accordance with the aspect, it is possible to use methanol as a by-product efficiently and to increase the yield of dimethyl ether. In addition, dimethyl ether, carbon dioxide and water as reaction products do not inhibit the reaction because their tendency to return to the reactor decreases.

Furthermore, according to the invention in aspect 4 or 8, it is possible to increase the yield of dimethyl ether and carbon dioxide.

Best mode for performing the aspect

The aspect will now be described with reference to the figures. Fig. 10 shows an embodiment (a flow diagram) of an apparatus for the production of dimethyl ether (hereinafter referred to as DME) according to the invention. In fig. 10 is (1) a converter for forming a carbon monoxide gas (hereinafter referred to as CO) and a hydrogen gas (hereinafter referred to as hb) from a natural gas, and (2) is a DME synthesis reactor for producing dimethyl ether from a raw gas containing CO and hb . From a liquid obtained by cooling the output reaction gas from the reactor (2), carbon dioxide (hereinafter referred to as CO2), DME and methanol (hereinafter referred to as MeOH) are sequentially separated and purified in the three separation columns [(3), (4) and (5)], separated and purified. The purified MeOH is returned to the reactor (2) through the recycling line (6).

The apparatus will now be explained together with a flow leading to the recovery of the purified and separated DME, which is passed from the converter (1) through the reactor (2).

A natural gas reacts with CO2, O2 and steam in the converter (1) to produce a converted reaction product. The converted reaction product is cooled and dehydrated upstream of a synthesis gas compressor (7) (not shown in the figure), and the conversion product flowing out of the synthesis gas compressor (7) is decarbonated in the CO2 recovery column (8).

The synthesis gas produced in the converter (1) is dehydrated and decarbonised to give a raw gas for DME synthesis (a supplementary gas for DME synthesis). Then, the feed gas for DME synthesis is mixed with a recycle gas consisting mainly of the non-reacted gas (CO and H2) flowing through the recycle gas line (10), and MeOH flowing through the recycle gas line (6), to become a raw gas for DME.

The raw gas is fed from the bottom of the reactor (2). In the reactor (2), the raw materials are subjected to a catalytic reaction so that the DME synthesis reaction runs. Medium oil that flows out of the reactor is recovered and returned to the reactor (2) with the pump (11).

Hereafter, the reactor (2) will be described in detail. The type of reactor (2) can be any type of fixed bed reactor, fluidized bed reactor and slurry bed reactor. In particular, slurry bed reactors are preferred for the reason that the temperature inside the reactor is homogeneous and the amount of by-products is low.

As a catalyst, a catalyst is used for methanol synthesis and methanol dehydration for DME synthesis by carrying out each of the reactions (1) to (3), and appropriately an aqueous shift reaction catalyst is added. Catalysts which have such functions are used in suitable combinations thereof as appropriate.

As a methanol synthesis catalyst, copper oxide-zinc oxide, zinc oxide-chromium oxide, copper oxide-zinc oxide/chromium oxide, copper oxide-zinc oxide/aluminium, etc., which are generally used in industry, can be used. As a methanol dehydration catalyst, aluminum, silica, silica aluminum, zeolite, etc., which is an acid-base catalyst, can be used. As a metal oxide component of zeolite, oxides of alkali metals such as sodium and potassium, oxides of alkaline earth metals such as calcium and magnesium can be used here. Furthermore, since the methanol synthesis catalyst has strong shift catalytic activity, the catalyst can also function as a water gas shift catalyst. Since such catalysts have a combination of methanol synthesis catalyst and water gas shift catalyst, an aluminium-supported copper oxide catalyst can be used. The mixing ratio of the three types of catalyst as described above is not particularly limited, but it can be appropriately selected depending on the type of each component or the reaction conditions. However, in terms of proportions based on weight, generally about 0.1 to 5, preferably about 0.2 to 2 of the methanol dehydration catalyst, and about 0.2 to 5, preferably about 0.5 to 3 of the water gas shift catalyst, are mixed relative to the methanol synthesis catalyst. If the methanol synthesis catalyst and the water gas shift catalyst are identical materials and the methanol synthesis catalyst also functions as a water gas shift catalyst, then the amount of methanol synthesis catalyst that can be used is the sum of both catalysts.

As catalyst form in the case of using a slurry bed reactor, a catalyst that has been pulverized to an average particle size of 300 µm or less, preferably 1 to 200 µm, more preferably 10 to 150 µm, is used. In order to use the catalyst more effectively, a catalyst is used which has particle sizes as described above, which are obtained by compacting, shaping and then repulverizing the mixed powder product.

A medium oil in the slurry bed reactor should be one that maintains a stable liquid state under the reaction conditions. For example, aliphatic, aromatic and alicyclic hydrocarbons, alcohols, ethers, esters, ketones, halides or a mixture thereof can be used. Although the amount of the catalyst in a solvent is appropriately selected depending on the type of solvent and the reaction conditions, but it is generally preferred that the amount is approximately 1 to 50% by weight, relative to the solvent.

As a reaction condition in the slurry bed reactor, the reaction temperature is preferably in the range 150 to 400 °C, particularly preferred in the range 250 to 250 °C. If the reaction temperature is below 150 °C or above 400 °C, the CO conversion in the raw gas is low. The reaction pressure is preferably in the range 10 to 300 kg/cm<2>G, particularly preferred in the range 20 to 70 kg/cm<2>G. If the reaction pressure is below 10 kg/ cm<2>G, the CO conversion is low, and if the reaction pressure is above 300 kg/ cm<2>G, a specific reactor is needed, and likewise a large amount of energy is needed to increase the pressure, and this is uneconomical. The room rate (feed rate of the raw gas under standard conditions, per kg of catalyst) is preferably 100 to 50,000 N1/ kg h, particularly preferably 500 to 7,500 N1/ kg h. If the room rate is above 50,000 N1/ kg h, the CO conversion is low, and if the space velocity is below 100 N1/kg t, an extremely large reactor volume is required, and this is uneconomical.

The reaction gas obtained in reactor 2 includes DME and CO2 as reaction products, CH3OH and H2O as reaction intermediates, the unreacted H2 and CO, the impurities contained in the raw gas, and the like. The composition of the components of the raw gas is as follows: generally, DME: 3 to 25%, CO2: 3 to 25%, CO: 20 to 50%, H2: 20 to 50%, CH3OH: 0.5 to 3%, H20: 0.1 to 0.5%, and others: about 5% or less.

The gas produced from reactor 2 is then cooled using a heat exchanger 12, and separated into liquid (1) containing DME, CO2, MeOH and H2O and gas containing the unreacted gas components using a gas-liquid separator 13. The heat exchanger 12 and the gas-liquid separator 13 form a gas-liquid separation apparatus. With such cooling, the liquid (1) containing DME, MeOH and H2O is condensed, and CO2 is dissolved in the condensed DME. Appropriately, the cooling temperature is approximately -10 °C to -60 °C, preferably approximately -40 °C to -50 °C, and at the same time the pressure is approximately 1 to 30 MPa, preferably approximately 1.5 to 15 MPa.

Fig. 11 represents a detailed map of the gas-liquid separator 13. The gas-liquid separator 13 is connected to the output side of heat exchanger 12 which is a condenser. Two layers comprise the packing materials 14, 14 such as the Rasking ring is placed on the inside of the gas-liquid separator 13, and a solution reservoir is placed in the lower part. Nozzles are placed in the upper space of each layer of packing materials 14, 14 to spray approximately uniformly on the top surface of the packing material layers. An input of the produced gas that is cooled in the heat exchanger is established in the space between the solution reservoir in the gas-liquid separator 13 and the lower part of the packing material layer 14; and a liquid phase outlet containing DME, CO2 and MeOH, and a gas phase outlet containing the unreacted gas are provided at the lower part and the upper part respectively. A methanol feeder pipeline is connected to the nozzles in the space above the upper part of the packing material layer 14, and a DME feed pipeline is connected to the nozzles in the space above the lower part of the packing material layer 14.

From the nozzles in the gas-liquid separator 13, a bottom liquid of the CO2 separation column 3 is sprayed as described later (a liquid 2, i.e. raw form of DME, from which CO2 is separated by means of the CO2 separation column), and a bottom liquid of the DME separation column 4 as described later (a liquid 3, which is the raw form MeOH, from DME is separated using the DME separation columns), and the absorbed liquids are combined with the produced gas. Raw DME and raw MeOH can be fed at any time after or before the condensation of the DME in the produced gas, but it is more efficient for these to be supplied so that they are brought into contact with the produced gas after the condensation, i.e. the gas phase containing it unreacted gas. Both DME and MeOH can be fed before and after, or they can be fed simultaneously. Furthermore, they can be preliminarily mixed and then fed. However, in the case where the produced gas after the condensation of DME is treated using the absorption column as shown in fig. 11, it is preferred to combine this with DME, and then MeOH in order to reduce the DME concentration in the discharge gas.

The bottom liquid (untreated DME) in the CO2 separation column and the bottom liquid (untreated MeOH) in the DME separation column are combined with the gas in the gas-liquid separator 13, thus increasing the recovery rate of CO2 and DME. To reduce the DME concentration in the gas that is recycled into reactor 2, MeOH is needed which does not contain CO2 and DME. Since the presence of the DME separation columns 4 enables the feeding of MeOH absorption liquid and the feeding of MeOH that does not contain CO2 and DME into the reactor, which leads to an increase in the amount of recovered and produced DME.

The gas, which comprises an unreacted gas containing the separated CO and H2 as main components and a gas containing trace amounts of impure gas, is recycled as gas. Most of the gas passes through a recycle gas line 10 and is mixed with make-up gas for DME synthesis. Thus, the mixed raw gas is fed from the bottom of reactor 2.

The liquid (1) containing MeOH, H2O, CO2 and DME as main components is introduced into the CO2 separation column 3 (CO2 purifier), to, first, separate the CO2. In the CO2 separation column 3, CO2 is separated and purified, for example by distillation.

In the CO2 separation column 3, the liquid (2) from which CO2 is separated is separated and introduced to the DME separation column 4 (DME purifier) to separate DME. In the DME separation column 4, the DME is separated and purified, for example by distillation. High purity DME after purification passes through the DME line and is recovered as product.

The liquid (3) from which CO2 and DME are separated comprises MeOH and H2O as main components. This liquid is introduced into the methanol separation column 5 (the methanol purifier) to separate MeOH. In the methanol separation column 5, MeOH which has a high purity of 96% based on mass, or more, is separated and purified, for example by distillation. The separated high purity MeOH passes through the recirculation line 6, and is introduced to the make-up gas for DME synthesis and evaporated. Thus, the raw gas with which the MeOH is mixed is fed from the lower part of the reactor 2.

In accordance with the present embodiments, since the MeOH is purified and H 2 O is not introduced into the reactor 2, the catalyst is not damaged. Furthermore, since H2O, CO2 and DME are not introduced into the reactor, there is an advantage that the DME production reaction is not inhibited. In addition, an efficient process is achieved where untreated MeOH (3) is recycled into the gas-liquid separator 13, high purity MeOH is introduced into the reactor, and MeOH is not discharged from the system.

Examples.

Fig. 12 represents an experimental apparatus for determining the combustion of the product as MeOH is returned to the reactor. The experimental apparatus is on a smaller scale than the practical apparatus for producing DME.

CO and H2 are fed into the reactor as a raw gas. The slurry inside the reactor consists of 388 g of catalyst and 1552 g of a medium oil as shown in the following Table 4.

The reaction conditions in reactor 2 are such that the temperature is 260°C and the pressure is 5 MpaG, as shown in subsequent table 5.

The produced gas from the reactor is cooled at 30°C in the heat exchanger, and separated into liquid containing MeOH and H2O as main components, and gas containing the unreacted gas components, CO2 and DME in the gas-liquid separator. The liquid recovered in the gas-liquid separator was discharged through a reduction valve, and volatilized CO2 and DME under normal pressure to obtain MeOH and H2 as liquid. For gas that was produced under reduced pressure, the flow rate was measured by means of a gas meter and then the composition is analyzed using a gas chromatograph. For the liquid obtained, the weight is measured, and then the composition was analyzed using a gas chromatograph. For the gas separated in the gas-liquid separator, the flow rate was measured using a gas meter, and then the composition was analyzed using a gas chromatograph. In this experiment, the amount corresponding to the total amount of MeOH contained in the gas and liquid obtained from the gas-liquid separator is returned into the reactor. Here the raw gas was preheated to 110°C, and the MeOH was preheated at 120°C.

In this experimental setup, the MeOH sprayed into the raw gas was completely evaporated.

Furthermore, the flow rates of CO and H2 fed into the reactor as raw gas are approx. 18 NL/min. each. Thus, since the amount of product is not sufficient for stable operation in the distillation column, no distillation column is provided.

Table 6 compares the composition of the products obtained in the case where MeOH is not introduced into the reactor (comparative examples) and in the case where MeOH is introduced to the reactor (examples). The flow rates of H2 and CO as raw materials were measured with mass flow meters. MeOH was converted to gas flow rate from weight rate of MeOH injected with a micropump. The product was obtained from the results of the gas flow rate and the gas chromatography analyses, and the results of the recovered liquid weight measurements and analysis of the gas chromatogram. A "MeOH concentration in the recovered liquid subwater cooling" is the MeOH concentration obtained by cooling the produced gas to 30°C to recover the liquid, volatilizing DME and CO2 from the recovered liquid under normal pressure, and then analyzing the remaining H 2 O and MeOH by gas chromatograph. 20 to 25% of produced DME also dissolve in the recovered liquid.

Flow rates of CO and H2 as raw material in both examples and comparative examples are set to be identical. In the examples, since the loading of the catalyst increases in relation to the amount of MeOH introduced, it was considered to attempt a reduction of the flow rates of CO and H2 as raw material. However, herein, the same flow rates as for the comparative examples were maintained. In the examples, increased flow rates of the CO and H2i products will indicate that there is some feedstock that has not been converted to DME. However, the flow rates of the CO and H2i products did not change. In the case where MeOH is introduced, the sum of the flow rate for CO plus the H2i product was found to be reduced. However, the amount of DME among the products was increased as the amount of introduced MeOH was increased, but the amount of MeOH in the products was not increased. In this experiment, all of the methanol introduced into the reactor was converted inside the reactor. From this experiment it was confirmed that since the flow rates of CO and H2 as the introduced raw materials were not reduced and the flow rates of CO and H2 in the products were approximately not increased, it was not necessary to increase the purge gas to be discharged.

That is, according to the experiment, even if the entire amount of MeOH flowing out of reactor 2 was introduced, the conversions of CO and H 2 did not change nearly, and the amount of DME corresponding to introduced MeOH was increased. The amount of MeOH flowing out of reactor 2 remains approximately unchanged. In addition, even if the amount of MeOH equal to or more than the amount discharged was introduced, the amount of DME increased corresponding to the introduced amount of MeOH. Thus, since excess MeOH can be treated in the reactor, it is possible to treat MeOH introduced from outside the system.

It was also considered that since MeOH is an intermediate product of the DME synthesis reaction, the introduction of MeOH would inhibit the reaction and thus not increase the yield of DME. In other words, it was considered that there is a limitation in relation to the amount of DME produced in the reactor, and that when MeOH is introduced, CO and H2 will not react and remain as an unreacted gas. However, it has been shown that as MeOH is introduced from the inlet of the reactor, the amount of DME produced increases, even when using the same amount of catalyst.

It is believed that this is due to the methanol dehydration catalyst at the bottom of reactor 2 having an excess of catalytic capacity, which is effectively used. The slurry-bed reactor 2 is vertically long in structure, and has sections which carry out the reactions represented by the formulas (1) to (3) on the upper side and the lower portions. At the lower portion of reactor 2, H2 and CO are reacted to produce MeOH in accordance with the reaction formula (1), however, it is possible that the dehydration catalyst that performs the reaction in formula (2) and the shift catalyst that performs the reaction in formula (3) are not enabled.

It is considered that, if MeOH is introduced into the lower part of reactor 2, the reactions in formulas (2) and (3) continue with the dehydration catalyst and the shift catalyst, and thus the amount of produced DME is increased.

Fig. 13 is a graph showing the change in CO conversion over time in cases where the purity of the MeOH introduced into the reactor 2 is changed. MeOH of a predetermined purity was prepared by adding distilled water (H2O) to MeOH. The amounts of the introduced raw material are the same as the examples. However, the amount of MeOH was set as the amount of MeOH in H2O. The amount of raw material introduced is the same as in the examples. If the purity of MeOH is reduced, the flow rates of H2, CO and MeOH do not change, but the amount of H2 is increased. The value of CO conversion indicates how much CO is thread material that is converted into the product. It was confirmed that if the MeOH purity is 95% based on mass, then the CO conversion was not reduced approximately at all, but if the MeOH purity is 80% based on mass, then the CO conversion was somewhat reduced. That is, with 95% based on mass purity of MeOH, the change over time is negligible, while with 80% MeOH purity based on water, the destruction over time is not negligible.

Furthermore, various modifications can be made with the aspect without limiting the embodiment set forth above. For example, the aspect is not limited to the method where equal amounts of DME and CO2 are produced, using the overall formula (4), but covers the general methods where MeOH is produced as a by-product during the synthesis of DME.

Furthermore, in the embodiments described above, the liquid containing DME, CO2, MeOH and H2, and the gas containing unreacted gas components are separated using a single-stage gas-liquid separation device, but they are also separated using a two-stage gas-liquid separation device. In this case, the produced gas is first cooled to approx. 30°C in the first stage of the gas-liquid separation device to obtain a liquid containing MeOH and H2 as main components. The produced gas is then cooled to approx. -30 to -50°C in the second stage of the gas-liquid separation device to obtain a DME liquid having CO2 dissolved therein. Furthermore, MeOH is purified from the liquid containing MeOH and H2O as main components, which is separated in the first step in a gas-liquid separation device, and then MeOH can be returned to the reactor.

The invention according to this divisional patent application relates to what is stated in the original application as "a fifth invention".

Crawl

A medium oil used for synthesis reaction with a slurry-bed reaction procedure as a medium comprises as a main component a branched, saturated aliphatic hydrocarbon having 16 to 50 carbon atoms, 1 to 7 tertiary carbon atoms, 0 quaternary carbon atoms, and 1 to 16 carbon atoms in the branched chain attached to the tertiary carbon atoms; and at least one of the tertiary carbon atoms is attached to hydrocarbon chains with a chain length having 4 or more carbon atoms in three directions.

Requirement 2

Medium oil used for the slurry-bed reaction procedure according to claim 1, wherein the branched, saturated aliphatic hydrocarbon has 20 to 40 carbon atoms and 1 to 4 tertiary carbon atoms.

Requirement 3

Medium oil used for slurry-bed reaction procedure in accordance with claims 1 and 2 where the branched, saturated aliphatic hydrocarbon is represented by formula (I):

where R<1>, R2 and R4 are independently n- or iso-alkyl group having 4 to 16

carbon atoms, R3 is n- or iso-alkyl group having 1 to 3 carbon atoms, m is an integer in the range 1 to 7, n is an integer in the range 0 to 37, and p is an integer in the range 0 to 12, given that -(CR<2>H)-, - (CH2) - and (CH<3>H)- in [ ] are bonded in any order and that the total number of each unit is m, n and p, respectively.

Requirement 4

Medium oil used for the slurry-bed reaction procedure according to any one of claims 1-3, wherein the branched, saturated aliphatic hydrocarbon is any of dimers to octamers of "-olefins" having 6 to 18 carbon atoms.

Requirement 5

Medium oil used for slurry-bed reaction procedure in accordance with one of claims 1 -4, which has a pour point of -10°C or lower.

Requirement 6

Medium oil used for slurry-bed reaction procedure in accordance with one of claims 1-5, where the synthesis reaction with the slurry-bed reaction procedure comprises the production of an oxygen-containing organic compound from a raw gas containing carbon monoxide and hydrogen.

Claim 7

Medium oil used for the slurry-bed reaction procedure in accordance with claim 6, wherein the oxygen-containing organic compound is usually dimethyl ether.

Claim 8

Process for the production of dimentyl ether, comprising passing a raw gas containing carbon monoxide and hydrogen through a catalyst slurry containing a mixture comprising (1) medium oil described in any of claims 1 to 7, (2) a methanol synthesis catalyst and (3) a methanol hydrogenation catalyst and a methanol shift catalyst , or a methanol dehydration/shift catalyst.

Claim 9

Process for preparing a mixture of dimethyl ether and methanol comprising passing a raw gas containing carbon monoxide and hydrogen through a catalyst slurry containing a mixture comprising (1) medium oil described in one of claims 1 to 7, (2) a methanol synthesis catalyst and (3) a methanol dehydration catalyst and a methanol shift catalyst or a methanol dehydration shift catalyst.

Field of the invention.

The present invention relates to a medium oil used for a slurry-bed reaction and a method for producing dimethyl ether.

As used herein, the term "medium oil" is, for example, a liquid used as a medium in a slurry-bed reactor (sometimes so-called a suspension bubble column reactor or gas-liquid-solid-mixed-flow reactor) which means that the liquid (at least includes a material in liquid form under a reaction condition that is desired) capable of forming a catalytic slurry as a mixture of the solid catalyst introduced into the reactor and the liquid described above.

Background technology.

Conventionally, dimethyl ether has been prepared by methanol dehydration, generally using methanol as a raw material, but recently a process has been developed for the direct synthesis of dimethyl ether from a raw gas containing carbon monoxide and hydrogen.

In such a process, synthesis of dimethyl ether is carried out with a reaction represented by the following reaction purposes (1) and (2) in the presence of a methanol dehydration catalyst (i.e. a methanol conversion catalyst), such as alumina, etc. First, methanol is produced from carbon monoxide and hydrogen with a methanol synthesis catalyst, followed by dehydration and condensation of the produced methanol with a methanol dehydration catalyst to produce dimethyl ether and water. The produced water further reacts with carbon monoxide in accordance with reaction formula (3) and gives carbon dioxide and hydrogen.

Reaction formula 2

The above synthesis is a strongly exothermic reaction, and has as a problem that the catalyst used can be deactivated due to high temperatures.

For this reason, the synthesis of dimethyl ether has been studied using a slurry-bed reaction procedure that can effectively remove reaction heat in large quantities and easily regulate the temperature.

In such a slurry-bed reaction procedure, a catalyst slurry prepared by suspending a catalyst in a suitable medium oil is used. The medium oil used in the above procedure must satisfy some performance criteria, for example such as (1) that it has high stability, i.e. it is inactive for reaction, and does not change over time, and gives neither thermally polymerized nor thermally decomposed, or reductively decomposed ; (2) that it has a high solubility of a raw gas such as CO, 2Hz (3) that it has a high boiling point; and (4) that it has a low freezing point.

The process for producing dimethyl ether using a slurry-bed reactor is described, for example, in patent document 1 of Air Products and Chemicals, Inc. In this process, medium oil is used to form the catalyzed slurry in the reactor, and the oil includes, for example, paraffin-based hydrocarbons or mixtures thereof, and in the examples in the document, a medium oil purified from a natural mineral oil designated as "Witco 70". Air Products and Chemical, Inc. also reports the synthesis of dimethyl ether using the slurry-bed procedure where a purified natural mineral oil, designated as Drakeol 10 is used as a medium oil in non-patent document 1.

In addition, Patent Document 2 by Sunggyu Lee et al. describes the synthesis of gasoline components such as a light oil to dimethyl ether from hydrogen and carbon monoxide as raw materials using a slurry-bed reactor. In this case, medium oil derived from natural mineral oils such as Witco 40, Witco 70 or Freezene 100, etc. is used. Similarly, synthesis of dimethyl ether using the slurry-bed procedure where Witco 40 or Witco 70 is used as a medium oil is also described in documents other than non-patent documents 2.

For the above medium oils, mentioned as Witch 40, Witch 70, Freezene 100 and Drakeol 10, the inventors have performed a ring analysis using the n-d-M method (ASTM D 3238) and as a result it was found that %CP (percent of the number of paraffinic carbon atoms in relation to the total number of carbon atoms) is below 70. Furthermore, the results of the analysis for molecular structures from Wich 40, Witco 70, Freezene 100 and Drakeol 10 by means of NMR, etc. indicated that the fraction of carbon atoms having branches, namely the number of carbon atoms having not less than 3 carbon-carbon bonds is not less than 20% of the total number of carbon atoms.

Such conventional medium oils derived from natural mineral oils by purification have a problem in that the synthesis efficiency of dimethyl ether becomes lower with time. More specifically, as described in non-patent document 1, the slurry-bed synthesis of dimethyl ether using Drakeol 10 causes a significant decrease in the amount of dimethyl ether produced over time, thus resulting in a decrease in the amount of dimethyl ether produced by approximately half during approx. . 500 hours. In addition to Drakeol 10, in the case of slurry-bed synthesis of dimethyl ether using generally known medium oils such as Witco 70 or Freezene 100, etc, it was found that the amount of dimethyl ether produced was significantly reduced over time. Furthermore, as the natural mineral oil thermally decomposes at high temperatures, the generation of carbon units cannot be avoided. That is to say, if such natural mineral oils are used as medium oil, the catalyst may be deactivated due to the coking process of the medium oil. Furthermore, in general, a suitable level of fluidity in the medium oil at a desired temperature is required to be able to handle the medium oil.

In view of this, the inventors have intensively studied to solve the problems and proposed a medium oil used in the production of an oxygen-containing organic compound of which dimethyl ether is representative, which comprises a hydrocarbon as a main component and has 70% or more paraffinic carbon atoms, in relation to total number of carbon atoms in patent document 3. Representative example of above-mentioned medium oil includes polybutene obtained by copolymerization of isobutene and n-butene as main components.

Patent document Japanese examined patent application with publication number no. 07-057739.

Patent Document 2 US Patent No. 5,459,166

Patent document 3 Japanese unexamined patent application with publication number No. 2000-109437.

Non-Patent Document 1 USA DOE report, DOE/PC/89865-T6 (September, 1992)

Non-Patent Document 2 Sunggyu Lee, et al. "A Single-Stage, Liquid-Phase Dimethyl Ether Synthesis Process from Syngas I. Dual Catalytic Activity and Process Feasibility", Fuel Science and Technology lnt'1, 9(6), 653-679 (1991).

Description of the invention

Problems solved by the invention

A medium oil such as the polybutene described in patent document 3 has high thermal stability and a low freezing point, and ensures high reactivity for the synthesis of, for example, dimethyl ether as a medium oil, compared to conventional medium oils derived from natural mineral oils.

However, it was found that the medium oil described in the above-mentioned document was decomposed, volatilized, and thus the amount increased slowly over time.

Thus, the present invention aims to provide a medium oil which has high reactivity for the synthesis of, for example, dimethyl ether etc., as a medium oil which has a high boiling point, a low freezing point and excellent stability.

Means to solve the problems

In order to solve the above-mentioned problems, the present invention aims to provide a medium oil used as a medium for synthesis with a slurry-bed reaction procedure, which comprises, as a main component, a branched saturated aliphatic hydrocarbon having 16 to 50 carbon atoms, 1 to 7 tertiary carbon atoms, 0 quaternary carbon atoms, and 1 to 16 branched chain carbon atoms attached to the tertiary carbon atoms; and at least one of the tertiary carbon atoms is attached to hydrocarbon chains with a chain length having 4 or more carbon atoms in three directions.

The medium oil for the slurry-bed reaction procedure of the present invention preferably comprises a branched, saturated aliphatic hydrocarbon having 20 to 40 carbon atoms and 1 to 4 tertiary carbon atoms. The branched saturated aliphatic hydrocarbon according to the present invention is represented by formula (I):

where R<1>, R2 and R4 are independently n- or isoalkyl groups having 4 to 16 carbon atoms, R<3> is an n- or isoalkyl group having 1 to 3 carbon atoms, m is an integer in the range 1 to 7, n is an integer in the range 0 to 37, and p is an integer in the range 0 to 12, given that -(CR<2>H)-, -(CH2)- and -(CR<3>H)- in [ ] are bound in any order and that the total number of each unit is m, n and p, respectively. The branched saturated aliphatic hydrocarbon in the medium oil is any one of dimers to octamers of "-olefins" having 6 to 18 carbon atoms.

The medium oil for the slurry-bed reaction procedure according to the present invention preferably has a pour point of -10°C or lower.

Furthermore, the present invention relates to an oxygen-containing organic compound from a raw gas containing carbon monoxide and hydrogen, more specifically dimethyl ether is produced through the synthesis reaction with the slurry-bed reaction procedure.

An object of the present invention is to solve the problems stated above, and is a method for producing dimethyl ether, which comprises passing a raw gas containing carbon monoxide and hydrogen through a catalyst slurry containing a mixture comprising (1) a medium oil for the slurry-bed reaction procedure which described above, as a medium oil, (2) a methanol synthesis catalyst and (3) a methanol dehydration catalyst and shift catalyst, or a methanol dehydration/shift catalyst.

Another object of the present invention is to solve the above-mentioned problems, and is a method for producing a mixture of dimethyl ether and methanol, which comprises passing a raw gas containing carbon monoxide and hydrogen through a catalyst slurry containing a mixture comprising (1) a medium oil for the slurry-bed reaction procedure as described above, as a medium oil, (2) a methanol synthesis catalyst and (3) a methanol dehydration catalyst and shift catalyst or a methanol-

Effects of the invention

With the medium oil in accordance with the present invention, it is possible to improve the synthesis efficiency of an oxygen-containing organic compound such as dimethyl ether and to maintain the synthesis efficiency for a long time, and at the same time stably use the medium oil for a long time without decomposition, volatilization or the like over time. Therefore, the present invention has a significant advantage in the production of oxygen-containing organic compounds such as dimethyl ether which require a high production efficiency.

Best mode of carrying out invention

The present invention will be described in detail with reference to the following examples.

The medium oil for the synthesis reaction with the slurry-bed reaction procedure i

according to the present invention comprises, as a main component, a branched saturated aliphatic saturated hydrocarbon having 16 to 50 carbon atoms, 1 to 7 tertiary carbon atoms, 0 quaternary carbon atoms and 1 to 16 carbon atoms in branched chains attached to the tertiary carbon atoms; and at least one of the tertiary carbon atoms is attached to hydrocarbon chains with a chain length having 4 or more carbon atoms.

As used herein, the term "a major component" denotes a component containing not less than 70% by weight, preferably not less than 90% by weight, of the medium oil.

In the medium oil according to the present invention, the branched saturated aliphatic hydrocarbon has as main component 16 to 50 carbon atoms. If the number of carbon atoms is less than 16, the boiling point of the hydrocarbon is reduced and this causes, for example, that the hydrocarbon with the desired properties is not obtained. If the number of carbon atoms rises above 50, the solubility of the raw gas will not be sufficient. The branched saturated aliphatic hydrocarbon has more preferably 20 to 40, and most preferably 30 to 40 carbon atoms, although this depends on the molecular structure of the hydrocarbon.

The number of tertiary carbon atoms is in the range of 1 to 7. Since the number of tertiary carbon atoms is 0, with the hydrocarbon having a total number of carbon atoms in the range of 16 to 50, the freezing point will increase and this will cause the hydrocarbon

solidifies at ambient temperature, and this results in difficulties in treating the medium oil. If the number of tertiary carbon atoms exceeds 7, molecular stability will gradually decrease and cause easy decomposition or polymerization thereof, and if the number of branched chains increases, the liquid viscosity will increase. As the liquid viscosity is increased, not only will the resistance of the liquid to its flow increase, but also the diameter of bubbles dispersed in the slurry-bed reactor will increase and cause a reduction in gas and a reduction in reactivity, which is undesirable. The number of tertiary carbon atoms in the range preferably from 1 to 4, more preferably from 1 to 3.

The medium oil according to the present invention has no quaternary carbon atoms. If the quaternary carbon atom is present in the medium oil, as in the polybutene medium oil described in patent document 3, then it will cause thermal decomposition overtime, and thus result in a problem in terms of stability. Since the quaternary carbon induces easy dissociation of intramolecular bonds compared to the tertiary carbon, it is preferred to construct the desired branched chains with the tertiary carbon.

In the medium oil according to the present invention, the number of carbon atoms in the branched chains that bind to the tertiary carbon atom is generally in the range from 1 to 16. If the number of carbon atoms exceeds 16, the total number of carbon atoms will exceed 50. Here, the main chain is the longest carbon chain in one molecule while the branched chain is the carbon chain branched from the main chain.

Furthermore, in the medium oil according to the present invention, at least one tertiary carbon is bound to a hydrocarbon chain having 4 or more carbon atoms in three directions. With such a molecular structure, it is possible to stretch the temperature range in which a liquid state exists between the pour point and the boiling point with the least branched chains. Since the dissociation of the intramolecular bonds is easily induced at the branching part, it is preferred to make the branching as small as possible. The tertiary carbon is preferably attached to the hydrocarbon chain which has 8 or more of the carbon atoms in three directions.

Such branched saturated aliphatic hydrocarbons in medium oil in accordance with the present invention include, but are not limited to, the compound represented by the following formula (I):

where R<1>, R2 and R<4> are independently n- or isoallyl groups having 4 to 16 carbon atoms, R<3> is an n- or isoalkyl group having 1 to 3 carbon atoms, m is an integer in the range 1 to 7, n is an integer in the range 0 to 37, and p is an integer in the range 0 to 12, given that -(CR<2>H)-, -(CH2)- and -(CR<3>H)- in [ ] is bound in any order and that the total number of each unit is m, n and p, respectively.

In formula (I) above, R<1>, R2 and R<3> preferably include, but are not limited to, n-hexyl, n-pentyl, ethylhexyl, n-octyl, n-nonyl and n-decyl groups.

Furthermore, in the above formula (I), R<4> preferably includes, for example, methyl, ethyl, n-propyl and isopropyl groups, but is not limited to these.

The medium oil according to the present invention can further include conventionally known medium oils as a main component (for example the medium oil described in the above section (background of related technology)), in addition to branched, saturated aliphatic hydrocarbon as a main component. Furthermore, the medium oil according to the present invention may comprise a hydrocarbon containing impurities such as oxygen, nitrogen, silicone and halogen, and the like, in addition to the above-mentioned main component and minor components. Furthermore, as the main component, the branched saturated aliphatic hydrocarbon can be used in a combination of 2 or more different types of hydrocarbons.

The medium oil according to the present invention can be derived from synthetic oil or natural oil in raw materials, but is preferably from synthetic materials.

In order to produce the medium oil according to the present invention which has the above-mentioned characteristics, a method is proposed for separating paraffin from a natural oil using adsorption on a molecular sieve; a separation process using distillation or a combination of distillation and oLfctrahorinn\/oH ot ImcorniHHol- an h\/Hrnnanarinncmatnrlo frir nati irnliorv an synthesis process using a process with product selectivity (ie selectivity for paraffin) such as Fischer-Tropsch synthesis, etc; or a process for polymerization and/or copolymerization of an -olefin.

The polymerization or copolymerization process of the --olefin includes, but is not limited to, a process for obtaining dimers to octamers of the -olefin having 6 to 18 carbon atoms, more preferably dimers to pentamers of the --olefin having 8 to 12 carbon atoms so such as 1-octene, 1-decene, 1-dodecene, etc. One of the most preferred examples can be, for example, poly-1-decene (a trimer).

The polymerization or copolymerization of the - -olefin can be carried out in the presence of a polymerization catalyst such as a Friedel-Crafts catalyst including, for example, complexes comprising aluminum trichloride, boron trifluoride or boron trifluoride and water, alcohols such as ethanol, propanol or butanol, or esters such as ethyl acetate or ethyl propionate .

Furthermore, the Fischer-Tropsch synthesis is a method for synthesizing a liquid hydrocarbon with the reaction of carbon monoxide and hydrogen in the presence of a catalyst (for example an iron, cobalt or nickel-based catalyst or a ruthenium catalyst).

The branched, saturated aliphatic hydrocarbon according to the present invention satisfies the reaction conditions described above and does not release hydrogen, decompose or polymerize even at temperatures as high as 300°C. Thus, in contrast to conventionally known natural mineral oils used as medium oils, the medium oil according to the present invention does not produce carbon residues as a result of thermal decomposition at high temperatures. Furthermore, the catalyst used according to the present invention car could be carefully deactivated by the cooking process.

In the medium oil according to the present invention, the percentage of saturated aliphatic hydrocarbon in the medium oil (%CP) with respect to the total number of carbon atoms in the medium oil (namely the sum of the number of carbon atoms in the main component hydrocarbons plus the number of carbon atoms in the minor components) is 70% or more, preferably 80% or more. Since the %CP of the medium oil is less than 70%, it is sometimes possible to maintain the synthesis efficiency of the oxygen-containing organic compound for a long time. The content of the saturated aliphatic hydrocarbon in the medium oil, in relation to the total number of carbon atoms in the medium oil, can be determined by the following analytical procedure, without limitation thereto, including, for example, a ring analysis using the n-d-M method (ASTM D 3238). The content of the saturated aliphatic hydrocarbon in the present description is a value determined by the n-d-M method. The term "ring analysis" denotes a method of analyzing the arrangement of carbon atoms (such as %Ca, %Cn, %Cr, %CP) in all the compounds that make up an oil (ie an oil composition and/or an oil mixture from a calculation formula predetermined based on physical and chemical properties of the oil, where %Ca is a percentage of aromatic carbon atoms contained in the oil being analyzed, based on the total carbon atoms in the above oil, i.e. the number of carbon atoms that make up the aromatic ring, %C is the percentage of naphthenic carbon atoms contained in the oil being analyzed, based on the total number of carbon atoms in the above oil (ie the number of carbon atoms making up the alicyclic ring), %Cr is a percentage of aromatic carbon atoms and naphthenic carbon atoms contained in the oil being analyzed, based on total carbon atoms in the oil above, and %CP is a percentage of paraffinic carbon atoms contained in the oil as analyzed, based on the total carbon atoms in the oil above (ie, the number of carb onatoms that make up the saturated aliphatic hydrocarbon chain). In the medium oil according to the present invention, most aliphatic hydrocarbons are paraffin-based hydrocarbons and unsaturated aliphatic hydrocarbons are almost not present, so that %Ca + %Cn+ %CP = 100 or %CP = 100.

The medium oil according to the present invention has an average molecular weight in the range from 200 to 800, without limitation thereto, with preferably from 280 to 600 and most preferably from 400 to 600. If the weight average molecular weight is less than 170, the amount of medium oil which is evaporated is too large, and thus the capacity of a trap for the evaporated medium oil is provided downstream of the reactor or the capacity of an oil recirculation pump is increased. For this reason, factory costs will increase. Furthermore, it is sometimes difficult to regulate the amount of oil in the reactor, and subsequently to regulate the temperature. On the other hand, as the weight average molecular weight in the medium oil exceeds 800, the viscosity of the oil will increase while the solubility of CO and H2 is reduced, and this may cause a reduction in the reaction efficiency of the synthesis process. The average molecular weight of the medium oil according to the present invention can be determined, for example, by means of mass spectroscopy or gel permeation chromatography.

The pour point of the medium oil according to the present invention is not particularly limited, but is preferably -10°C or less, more preferably -20°C or less, and most preferably -30°C or less. If the pour point is higher than -10°C, the medium oil may be frozen at ambient temperature or at general temperatures in winter. For this reason, factory costs will increase because additional treatments such as keeping the pipelines warm are necessary, or it is difficult to perform work such as oil handling. Furthermore, in the case of dissolved CO 2 as a by-product of DME generated by DEM synthesis reaction, it is effective to cool the generated gas in a cooler to -20°C or lower. However, since there is a risk that the cooler may be closed as the vaporized medium oil is transferred to the cooler, the pour point is preferably -20°C or lower, and more preferably -30°C or lower. The pour point can be determined for example using JIS K 2269. The pour point as described according to the present specification is a value determined by JIS K 2269.

The viscosity of the medium oil according to the present invention is not particularly limited, but preferably 0.05 to 10 cP at the reaction temperature. If the viscosity is much above 10 cP, the movement speed (i.e. the flow rate) of the raw gas and the product dissolved in the liquid phase in the slurry-bed reaction layer will be reduced, and furthermore, gas retention and the total surface area in the bubbles will be reduced due to an increase in bubble diameter, and this will result in a reduction of the reaction efficiency. Furthermore, in the case of an exothermic reaction such as DEM synthesis, a heat exchanger will be installed in the reactor to remove heat from the reactor. In this case, the heat transfer coefficient will be reduced as the viscosity of the medium oil is increased, which requires an increase in the heat transfer surface. Since the viscosity of the medium oil according to the present invention is far below 0.05 cP, the catalyst is easily precipitated and is slightly dispersed. Thus, the degree of contact between the catalyst and the raw gas becomes poor and the reaction efficiency may be lowered. Such viscosity can be determined, for example, by calculating the kinematic viscosity and the specific gravity of the medium oil after measuring the kinematic viscosity and specific gravity. In the present description, the viscosity was determined using methods as described above.

The content of sulfur in the medium oil is preferably several ppm or less, and more preferably 1 ppm or less. If the content of sulfur exceeds the range indicated above, the catalyst can be poisoned by sulfur and can be deactivated.

The 50% distillation point (namely the temperature at which 50% of the oil evaporates under normal pressure) of the medium oil in accordance with the present invention is preferably 230°C or higher. If the 50% distillation point or lower than the temperature above, and if the amount of evaporated oil is greater under a condition of reaction temperature and pressure, it is sometimes necessary to increase the capacity of the trap for the evaporated medium oil supplied downstream from the reactor, and thus will factory costs increase.

Among other physical properties of the medium oil that affect the reaction are solubility or rate of dissolution of the raw material, product and reaction intermediate in the reaction. For example, for the synthesis of dimethyl ether, the solubility and dissolution rate of the raw material such as carbon monoxide or hydrogen, the reaction intermediate such as methanol or water and the product such as dimethyl ether or carbon dioxide will belong to the physical properties of the medium oil that affect the reaction. If the solubility or dissolution rate of the raw material in medium oil is low, the efficiency of raw materials that reach the catalyst and are then converted will be reduced. And, if the solubility of the product such as dimethyl ether or carbon dioxide is high, the reaction on the catalyst to produce dimethyl ether or carbon dioxide will be difficult to develop. In addition, it is desirable that water or methanol as a reaction intermediate compound reaches an activity site in the vicinity of the catalyst site immediately after generation thereof, and that it is converted. The medium oil according to the present invention can satisfy the above-mentioned requirements with respect to solubility and dissolution rate.

The medium oil according to the present invention is a medium oil used in the slurry-bed reaction procedure. Such slurry-bed reaction procedure is not

particularly limited, as long as it performs reaction in the catalyst slurry as a mixture of a solid condenser and a medium and includes, for example, the slurry-bed reaction procedure to synthesize an alternative organic compound (ie, a hydrocarbon) and/or an oxygen-containing organic compound

etc. from the raw gas material comprising the organic compound (i.e. hydrocarbon and/or carbon monoxide and hydrogen.

Medium oil according to the present invention is preferably applied to the slurry-bed reaction procedure to synthesize the oxygen-containing compound from the raw material containing carbon monoxide and hydrogen. Examples of such oxygen-containing organic compounds include, but are not limited to, ethers such as dimethyl ether, methyl tert (tertiary)-butyl ether, ethyl tert-butyl ether or tert-amyl methyl ether; alcohols such as methanol or ethanol; dimethyl carbonate, acetaldehyde, carboxylic acid such as acetic acid; or dimethoxymethane or dimethoxyethane. The medium oil according to the present invention can further be used in the synthesis of olefins such as propylene or ethylene, or hydrocarbons such as petrol components. Similar syntheses include the synthesis of a hydrocarbon or oxygen-containing organic compound as a reaction intermediate other than hydrocarbons or the oxygen-containing organic compound as a final product.

As a process for the production of dimethyl ether according to the invention, any process for the production of dimethyl ether which is conventionally known can be used, with the exception that the medium oil according to the present invention is used. In other words, by passing the raw gas containing carbon monoxide and hydrogen through the catalyst slurry comprising a mixture of the medium oil according to the invention, a catalyst for the synthesis of methanol, a methanol dehydration catalyst or a methanol shift and dehydration catalyst, dimethyl ether is obtained. Furthermore, the method according to the invention is clearly applied to a method using a catalyst which has three functions, such as methanol synthesis, dehydration and shifting. The raw gas material can be supplied by gasification of coal or conversion of methane. The reaction temperature is preferably in the range from 150°C to 400°C, and more preferably from 250°C to 300°C. Furthermore, the reaction pressure is preferably in the range of 1 to 15 MPa and more preferably from 3 to 7 MPa. Furthermore, the amount of catalyst in medium oil is preferably in the range from 1 to 5% by weight, and more preferably from 10 to 30% by weight.

In the process for producing dimethyl ether in accordance with the present invention, the methanol synthesis catalyst includes known methanol catalysts, for example a catalyst represented by the compositional formula: Cu-Zn-M-0 (where M represents an arbitrary metallic atom selected from the group consisting of aluminum, silicon , titanium, zirconium, chromium, cerium and gallium).

In the process for producing dimethyl ether in accordance with the present invention, examples of the methanol dehydration catalyst include a known methanol dehydration catalyst, a known methanol dehydration catalyst comprising alumina as the main component or a dehydration catalyst comprising silica, silica.alumines or zeolite as the main component.

In the process for producing dimethyl ether in accordance with the present invention, an example of shift catalyst includes copper, zinc, iron or chromium.

In the process for producing dimethyl ether in accordance with the present invention, methanol dehydration/shift catalyst can be used instead of a combination of such methanol dehydration catalyst and shift catalyst. Methanol dehydration/shift catalyst is a catalyst with both a methanol dehydration function and a methanol shift function and, for example, a catalyst comprising a methanol dehydration catalyst with an additional copper shift function, i.e. a methanol dehydration/shift catalyst comprising copper oxides, alumina as the main component (form of composition!: Cu-AI-O); methanol dehydration/shift catalyst comprising copper oxides and silicon oxides (form of composition!: Cu-Si-O); or methanol dehydration/shift catalyst comprising copper oxides, silica and alumina (form of composition!: Cu-Si-Al-O). The product produced by the method according to the present invention can be separated and purified by a conventional method.

As a process for producing a mixture comprising dimethyl ether and methanol in accordance with the present invention, any conventional known process for producing the mixture comprising dimethyl ether and methanol can be used, with the exception that the medium oil according to the present invention is used. In other words, by passing the raw gas containing carbon monoxide and hydrogen through the catalyst slurry comprising a mixture of the medium oil according to the present invention, a catalyst for the synthesis of methanol, a methanol dehydration catalyst or a methanol shift and dehydration catalyst, the mixture comprising dimethyl ether and methanol is obtained. In addition, the process according to the present invention is clearly applied to a method using a catalyst that has three functions such as methanol synthesis, dehydration and shift. The raw gas material, methanol synthesis catalyst, methanol dehydration catalyst and methanol shift and dehydration catalyst used in the process for producing the mixture described above may be the same as those used in the process for producing dimethyl ether described above. However, in the case of the process for preparing the mixture comprising dimethyl ether and methanol, it is preferred to use silica or silica and alumina based methanol dehydration catalyst and shift catalyst with the same base; or methanol dehydration/shift catalyst comprising silica as the main component; or methanol dehydration/shift catalyst comprising silica and alumina as the main component.

The following experimental examples are for illustrative purposes of the invention, without limitation.

Example 1.

Purification of medium oil according to the present invention.

By carrying out polymerization of 1 -decene as a raw material in the presence of an aluminum chloride catalyst and water as a promoter at -20 to 30°C, and saturation with the addition of hydrogen, then purification, a product was obtained which was the medium oil. Physical properties thereof were adjusted depending on the composition of the raw material, polymerization temperature and/or conditions of purification (ie distillation). The obtained medium oil was subjected to the determination of chemical properties by the following means.

The weight average molecular weight of medium oil was measured using mass spectroscopy and gel permeation chromatography. The water vapor pressure was determined using a boiling point procedure using an ebulliometer. %CP as a percentage of paraffinic carbon atoms relative to total carbon atoms was determined by the n-d-M method (ASTM D 3238). The viscosity at 260°C was measured using kinematic viscosity and specific gravity. Finally, the pour point was determined by JIS K 2269. As a result, it was identified that the produced ,,-olefin oligomers have a structure represented by formula (I), weight average molecular weight of 427, vapor pressure of 1.2 kPa at 260°C and the pour point at -70°C, in addition to %CP, viscosity, pour point and other physical properties within the desired ranges described above. Furthermore, the content of sulfur in the obtained medium oil was equal to or less than 1 ppm.

The medium oil indicated above as medium oil in example 1.

Comparative examples 1 and 2.

Purification of the medium oil as comparative examples.

By carrying out polymerization of a mixture of n-butene and isobutene (containing a trace amount of butane, etc.) as a raw material in the presence of an aluminum chloride catalyst and water as a promoter at -20 to 30°C and saturation with the addition of hydrogen, and then purification, a product was obtained. Physical properties thereof were adjusted depending on the composition of the raw material, the polymerization temperature and/or the conditions of the purification (ie, distillation). The product was subjected to separation of both aliquots comprising a medium oil having a weight average molecular weight of 300 and other medium oils having a weight average molecular weight of 470. Chemical properties of these medical oils were determined using the same procedures as illustrated in Example 1. It was found that medium the oil that has a weight average molecular weight of 300 has a water vapor pressure of 27 kPa at 260°C and a pour point of -40°C, while the medium oil that has a weight average molecular weight of 470 showed a water vapor pressure of 2.0 kPa at 260°C and a pour point of -20° C.

Hereafter, the medium oil with the weight average molecular weight of 300 will be referred to as medium oil in comparative example 1, and the medium oil with the weight average molecular weight of 470 will be referred to as the medium oil in comparative example...

Example 2.

Synthesis of dimethyl ether/methanol and evaluation of synthesis efficiency.

Fig. 14 shows a construction diagram for a synthesis apparatus illustrating the synthesis of dimethyl ether.

In a reactor synthesizer, 1552 g of medium oil in example 1 were added, then 259 g of a methanol synthesis catalyst based on copper-zinc-alumina (CuO/ZnO/AI203 : 31/16/53) and 129 g of an alumina-based methanol dehydration/shift catalyst ( CuO/SiO2'Al2O3) to form a slurry bed (weight ratio of methanol synthesis catalyst and methanol dehydration/shift catalyst (methanol synthesis catalyst:methanol dehydration/shift catalyst = 2:1, and the total weight of methanol synthesis catalyst and methanol dehydration/shift catalyst is 388 g), a slurry was prepared by mixing the above and then the reactor was closed By passing the raw gas material (carbon monoxide: 18.11 NL/min., hydrogen gas: 18.11 NL/min., the amount passed was determined using mass flowmeter) through the slurry while stirring the slurry in the reactor, and synthesis of dimethyl ether was carried out. The reaction temperature was 260°C, and the reaction pressure was 5 MPa. Furthermore, to bring the catalyst to a suitable reduction state before carrying out the synthesis, a preliminary reduction operation was carried out by passing a 1:1 mixed gas of H2/CO at approx. 220°C for 12 hours under a pressure of 0.5 MPa through the slurry.

In the dimethyl ether synthesis process described above, the gas that passed through was

through the reactor (the produced gas) cooled to approx. 30°C in the heat exchanger, then separated into a liquid phase containing methanol and water and a vapor phase containing unreacted gas components, carbon dioxide and dimethyl ether in the vapor-liquid separator. The liquid recovered from the vapor-liquid separator was discharged from the vapor-liquid separator through a vacuum valve, brought to normal pressure to vaporize CO 2 and DME, and MeOH and H 2 O were obtained as a liquid. The gas generated during depressurization (not shown in Fig. 14) was measured for flow rate with a gas meter and then subjected to analysis for determination of composition by gas chromatograph. For the liquid obtained, after determining the weight of the liquid by sampling a fixed period of recovery time, the composition was analyzed by means of a gas chromatograph. The gas separated from the vapor-liquid separator was measured for flow rate with a gas meter and then subjected to analysis for composition by gas chromatograph. For each of the gases separated from the vapor-liquid separator, the gas generated during the pressure reduction of the liquid and the residual liquid after the pressure reduction, the flow rate of each component was calculated and then summed together, from which the composition of the generated gas was determined. From the above results, carbon monoxide conversion (unit = %) and the yield of dimethyl ether (unit = mol/g of catalyst and time (t)) were calculated with the following equation:

Conversion of carbon monoxide = 100 x (Vjnn- Vut)/Win

where Vinn represents the flow rate of carbon monoxide in the raw gas material while Vuter represents the flow rate of carbon monoxide in the produced gas. The yield of dimethyl ether = VoME/Wcat

where Wdrepresents the amount of dimethyl ether per hour while Wcater the weight of the catalyst.

Furthermore, (1) conversion of carbon monoxide (CO) 100 hours after the reaction was started (unit = %); (2) conversion of carbon monoxide (CO) 300 hours after the reaction was started (unit = %); (3) yield reduction of dimethyl ether (DME)

(unit = %); and (4) amount of medium oil volatilized 300 hours after the reaction was started (unit = g) was investigated. Furthermore, yield reduction of dimethyl ether of above (3) means a reduction ratio of (yield of dimethyl ether 300 hours after the reaction was started (B) in relation to (yield of dimethyl ether 100 hours after the reaction was started (A) represented by (A-B) /A).

Comparative examples 3 and 4.

The procedure illustrated in example 2 was repeated with the exception of using medium oil in comparative examples 1 and 2 instead of medium oil from example 1.

Results from example 2 and comparative examples 3 and 4). The results of above (1) to (4) obtained from Example 2 and Comparative Examples 3 and 4 are listed in Table 7.

As shown in Table 7, it was found that when the medium oil of the present invention obtained from Example 1 was used, it was not only possible to maintain a high rate of synthesis of dimethyl ether for a long time, but also, compared to the medium oil obtained from Comparative Example 1, there was essentially no reduction in the amount of medium oil over a long period of time and a stable synthesis over a long period was ensured.

Specifically, in the case of Comparative Examples 3 (using medium oil from Comparative Example 1), the CO conversion and yield reduction of DME, i.e., deterioration related to time, was substantially similar to that of medium oil in Example 1. However, the amount of medium oil volatilized was 20 times or more than that of the medium oil of Example 1. Molecular weight distribution of the medium oil volatilized in Comparative Example 3 drew close to the molecular weight distribution of a fraction separated by distillation, and, from the results of the GC-MS analysis for the above volatilized medium oil, it was suggested that thermal decomposition occurs in the quaternary carbon unit.

In comparative example 4 (using medium oil from comparative example 2), the volatilized amount of the medium oil was substantially similar to the medium oil in example 1, while the CO conversion at an initial period and after stabilization was lowered and DME- the dividend reduction was increased. It was suggested that this is due to a high viscosity of the medium oil in comparative example 2 and low solubility of the raw gas material. The molecular weight distribution and the medium oil volatilized in Comparative Example 2 also range close to the molecular weight distribution of the fraction separated by distillation, and, from the results of the GC-MS analysis for the above volatilized medium oil, it was suggested that thermal decomposition occurs in the quaternary carbon unit.

As a result of mass spectroscopic analysis, it was found that the medium oil obtained from Example 1 comprised trimer and tetramer as main components and trace amount of dimer, pentamer and hexamer. For the volatilized medium oil, trimer was the main component and minor components were trace amounts of dimer and tetramer, while no thermal decomposition products were included therein.

In addition, all of the medium oils in Example 2 and Comparative Examples 3 and 4 had a reduced amount of volatilized medium oil compared to the volatilized amount calculated from the vapor pressure at 260°C. This is because the temperature that the top part of the reactor is kept at approx. 110°C, and only medium oil flows out in a gas or mist state that has passed through the top of the reactor.

From the medium oil volatilized out of the reactor, a fraction of pure medium oil is typically separated and this is then returned into the reactor by means of a high-pressure pump to maintain a constant concentration of the catalyst. However, the above-mentioned recovery operation was not performed in Example 2 and Comparative Example 4 since the volatilized amounts of the medium oils were low. In comparative examples 3, it was expected that the volatilized amounts were increased by circulation of the medium oil which has a low boiling fraction, and this was thus compensated with fresh medium oil of the same composition by supplying the corresponding weight.

Claims (9)

1. A medium oil used for synthesis reaction with a slurry-bed reaction procedure as a medium comprises as a main component a branched, saturated aliphatic hydrocarbon having 16 to 50 carbon atoms, 1 to 7 tertiary carbon atoms, 0 quaternary carbon atoms, and 1 to 16 carbon atoms in the branched chain bonded to the tertiary carbon atoms; and at least one of the tertiary carbon atoms is attached to hydrocarbon chains with a chain length having 4 or more carbon atoms in three directions. 2. Medium oil used for slurry-bed reaction procedure according to claim 1, wherein the branched, saturated aliphatic hydrocarbon has 20 to 40 carbon atoms and 1 to 4 tertiary carbon atoms. 3. Medium oil used for slurry-bed reaction procedure in accordance with claims 1 and 2 where the branched, saturated aliphatic hydrocarbon is represented by formula (I): where R<1> , R2 and R4 are independently n- or iso-alkyl group having 4 to 16 carbon atoms, R3 is n- or iso-alkyl group having 1 to 3 carbon atoms, m is an integer in the range 1 to 7, n is an integer in the range 0 to 37, and p is an integer in the range 0 to 12, given that -(CR <2> H)-, - (CH2 ) - and (CH <3> H)- in [ ] are bound in any order and that the total number of each unit is m, n and p, respectively. 4. Medium oil used for the slurry-bed reaction procedure according to any one of claims 1-3, wherein the branched, saturated aliphatic hydrocarbon is any of dimers to octamers of "-olefins" having 6 to 18 carbon atoms. 5. Medium oil used for slurry-bed reaction procedure in accordance with one of claims 1-4, which has a pour point of -10°C or lower. 6. Medium oil used for the slurry-bed reaction procedure in accordance with one of claims 1-5, where the synthesis reaction with the slurry-bed reaction procedure comprises the production of an oxygen-containing organic compound from a raw gas containing carbon monoxide and hydrogen. 7. Medium oil used for slurry-bed reaction procedure in accordance with claim 6, where the oxygen-containing organic compound is usually dimethyl ether. 8. Process for the production of dimentyl ether, comprising passing a raw gas containing carbon monoxide and hydrogen through a catalyst slurry containing a mixture comprising (1) medium oil described in one of claims 1 to 7, (2) a methanol synthesis catalyst and (3) a methanol hydrogenation catalyst and a methanol shift catalyst, or a methanol dehydration/shift catalyst. 9. Process for producing a mixture of dimethyl ether and methanol comprising passing a raw gas containing carbon monoxide and hydrogen through a catalyst slurry containing a mixture comprising (1) medium oil described in one of claims 1 to 7, (2) a methanol synthesis catalyst and (3) ) a methanol dehydration catalyst and a methanol shift catalyst or a methanol dehydration shift catalyst.