JP2000103757A - Production of dimethyl ether from lower hydrocarbon gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for profitably producing dimethyl ether, capable of preventing carbon deposition and capable of producing the dimethyl ether at a high carbon utilization ratio. SOLUTION: This method for producing dimethyl ether comprises (i) adding water or steam to lower hydrocarbons containing 30-70 mol% of carbon dioxide (CO2) as raw materials to prepare a mixed gas satisfying the following inequality: 0.5 <=([CO2]+[H2O]/[C] <=2.5 ([CO2] and [H2O] are the moles of CO2 and H2O, respectively; [C] is the moles of C in the lower hydrocarbons), (ii) subjecting the lower hydrocarbons contained in the mixed gas to a catalytic reaction, which is carried out at 10-75 atm and at 600-1,000 deg.C in the presence of a catalyst comprising Rh and/or Ru metal supported on an MgO2 carrier in an amount of 0.10-5,000 ppm based on the weight of the carrier metal oxide and having a specific surface area of <=5 m2/g, to form a synthesis gas having a molar ratio of H2/CO in a range of 0.5-1.5, (ii) subjecting the produced synthesis gas to a reaction in the presence of one or several catalyst having catalytic activities for methanol synthesis, dehydration and CO equilibrium-shifting to form the dimethyl ether, and (iv) separating the dimetyl ether from the formed reaction mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing dimethyl ether from a lower hydrocarbon gas containing carbon dioxide gas.

[0002]

2. Description of the Related Art Low-grade hydrocarbon gas is produced in the presence of carbon dioxide gas.
It is known that a reforming reaction (synthesis gas generation reaction) is performed with a limited amount of steam to convert the gas into a synthesis gas composed of hydrogen and carbon monoxide, and dimethyl ether is produced from the synthesis gas. In such a method, a problem of catalyst poisoning due to carbon deposition occurs in the reforming step. The prior art related to such a method is as follows. JP-A-60-235889, U.S. Pat. No. 4,640,766 In these documents, a Ni-containing catalyst is used in the reforming step, and there is no disclosure of a technique capable of solving the problem of carbon deposition on the catalyst. US Pat. No. 5,621,155 and US Pat. No. 5,620,670 These methods aim at converting carbon dioxide into hydrocarbons. However, in order to increase the production efficiency of syngas, carbon deposition is also encountered in the reforming step. Will be. However, these methods also use a conventional Ni-containing catalyst, and there is no technical disclosure about carbon deposition prevention.

As described above, a method is known in which a lower hydrocarbon gas containing carbon dioxide gas is subjected to a reforming reaction to produce a synthesis gas, which is then subjected to a dimethyl ether synthesis reaction to produce dimethyl ether. The problem of this method is to increase production efficiency in a synthesis gas production process requiring high energy consumption and equipment cost. Increasing the production efficiency in the synthesis gas production process is nothing less than increasing the amount of synthesis gas produced relative to the total amount of lower hydrocarbon gas, carbon dioxide gas and steam to be treated. For this purpose, a synthesis gas suitable for dimethyl ether synthesis is directly produced at a carbon dioxide gas concentration that maximizes the efficiency of conversion of carbon dioxide to carbon monoxide (carbon conversion efficiency) in the reforming reaction step of lower hydrocarbon gas. It is necessary to carry out the reforming reaction with the minimum amount of steam addition necessary for the reaction. However, in the case of such a method, when the amounts of carbon dioxide gas and steam mixed into the lower hydrocarbon gas as a raw material gas are adjusted to a low concentration range, a significant amount of the lower hydrocarbon gas is formed on the catalyst in the reforming step. , And the catalyst is deactivated in a short time.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a method for producing dimethyl ether from lower hydrocarbons, which comprises a synthesis gas production step and a dimethyl ether synthesis reaction step. It is an object of the present invention to provide a method for industrially producing dimethyl ether by preventing dimethyl ether.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. That is, according to the present invention, in a method for converting a lower hydrocarbon gas containing carbon dioxide into dimethyl ether, (i) adding water and / or steam to a raw material lower hydrocarbon gas containing 30 to 70 mol% of carbon dioxide; Preparing a mixed gas in which each component satisfies the following formula: 0.5 ≦ ([CO ₂ ] + [H ₂ O] / [C] ≦ 2.5 (where [CO ₂ ] is CO ₂ [H ₂ O] is H ₂ O
And [C] represent the number of moles of carbon contained in the lower hydrocarbon gas.) (Ii) The lower hydrocarbon gas contained in the mixed gas is converted into rhodium and / or Or a catalyst carrying a ruthenium catalyst metal, wherein the specific surface area of the catalyst is 5 m ² / g or less, and the amount of the catalyst metal supported is 0.10 to 0.10 relative to the carrier metal oxide on a metal atom basis.
Contacting the catalyst at 5000 ppm by weight at a pressure of 10 to 75 atm and a temperature of 600 to 1000 ° C. to produce a synthesis gas having a hydrogen / carbon monoxide molar ratio of 0.5 to 1.5; (Iii) reacting the synthesis gas in the presence of one or more catalysts having methanol synthesis activity, dehydration reactivity and CO shift reaction activity to produce a reaction product containing dimethyl ether; (iv) Separating dimethyl ether from the reaction product.

[0006]

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a reforming reaction for converting a raw material hydrocarbon gas containing carbon dioxide gas into hydrogen and carbon monoxide so as to be promoted with improved carbon conversion efficiency. In the reforming reaction step, a synthesis gas having a hydrogen / carbon monoxide ratio required for dimethyl ether synthesis is produced while sufficiently utilizing carbon dioxide gas. In dimethyl ether synthesis, the composition of the synthesis gas is H ₂
/ CO ratio = 1 is ideal, and in practice, 0.5-1.
It is necessary to adjust around 5. As a technique to convert light hydrocarbon to synthesis gas composition required for dimethyl ether synthesis, a method of light hydrocarbons to CO ₂ reforming represented by the following formula (1) is suitable. CH ₄ + CO ₂ = 2H ₂ + 2CO (1) In this reaction, a gas having a stoichiometry of H ₂ /CO=1.0 is produced, but under actual reforming reaction conditions, the following formula (2) The reverse shift reaction shown in ()) occurs. H ₂ + CO ₂ = H ₂ O + CO (2) As a result, the generated H ₂ reacts with the unreacted CO ₂ to generate CO and H ₂ O, so that the synthesis gas composition is H ₂ / CO
An excess gas of CO is generated than = 1.0. Therefore,
In order to arbitrarily control the H ₂ / CO ratio in the range of 0.5 to 1.5, H ₂ O is added to the raw material and the following formula (3)
It is necessary to combine the steam reforming reactions shown in FIG. CH ₄ + H ₂ 0 = 3H ₂ + CO (3) Accordingly, both the reforming of the carbon dioxide gas of the above formula (1) and the reaction of the steam reforming of the above formula (3) proceed simultaneously, and the molar ratio of hydrogen / carbon monoxide is reduced. Generating 0.5 to 1.5 synthesis gas is the basic reaction principle of the present invention. The problem to be solved here is to increase the production efficiency in the synthesis gas production process requiring high energy consumption and equipment cost. In this case, increasing the production efficiency in the synthesis gas generation step involves increasing the ratio of the amount of the synthesis gas to the total amount of the lower hydrocarbon gas, carbon dioxide gas, and steam to be treated (synthesis gas production efficiency), which is represented by the following equation. That is.

R (CO + H ₂ ) = {([CO] + [H ₂ ] / ([C] + [CO ₂ ] + [H ₂ O])} × 100 (4) R (CO + H ₂ ): synthesis gas Production efficiency (mol%) [CO]: number of moles of CO [H ₂ ]: number of moles of H ₂ [C]: number of moles of carbon contained in lower hydrocarbon gas [CO ₂ ]: number of moles of CO ₂ [H ₂ O]: mole number of steam

In order to improve the synthesis gas production efficiency R (CO + H ₂ ), carbon monoxide produced from carbon dioxide and methane by the reforming reaction of the above reaction formula (1) represented by the following formula (5) It is necessary to carry out the reforming reaction at a carbon dioxide gas concentration that maximizes the ratio (carbon conversion efficiency) and with the minimum amount of steam added to produce a synthesis gas having a composition suitable for the synthesis of dimethyl ether. is there. In short, the efficiency of the reforming reaction is maximized by reducing the supply of carbon dioxide, water vapor, and water to the lower hydrocarbon gas in the feed to the reformer as close as possible to the reaction stoichiometry. . However, both the reactions of the formulas (1) and (3) are reversible reactions with large endotherms, and the degree of progress of the reaction greatly depends on the reaction conditions (temperature and pressure). It will be convenient.

R (CO) = {([CO] / ([C] + [CO ₂ ])} × 100 (5) R (CO): carbon conversion efficiency (mol%) [CO]: number of moles of CO [C]: mole number of carbon contained in lower hydrocarbon gas [CO ₂ ]: mole number of CO ₂

[0010] The actual reformer currently employed industrially is operated in a temperature range of 600 to 1000 ° C with a large excess of steam (2 to 5 times the molar amount of the raw hydrocarbon). A low [H ₂ O] / [C] ratio allows for less steam in the process system and gives better thermoeconomics,
When the [H ₂ O] / [C] ratio is reduced, carbon deposition on the catalyst layer is severe, and there is a danger of stopping the operation due to an increase in the differential pressure, and the limit [H ₂ O] /
The [C] ratio is said to be about 1.5. Further, in order to avoid operation in the limit region of carbon deposition, it is necessary to increase the [H ₂ O] / [C] ratio as the concentration of carbon dioxide in the raw material increases (“Studies in Surfac”).
e Science and Catalysis 8
1, Natural Gas Conversion
II ", ed. By HE Curry-Hyde,
R. F. Howe, p. 25 (1994), ELSEV
IER).

[0011] Water and / or steam are added to a limited concentration region of carbon dioxide and steam applied in the present invention, ie, a lower hydrocarbon gas containing 30 to 70 mol% of carbon dioxide, and ([CO ₂ ] + [H ₂ O]) / [C] is 0.5 to
When the raw material gas adjusted to the range of 2.5 is treated with an existing Ni-based reforming catalyst, a large amount of carbon is deposited on the catalyst layer and operation becomes impossible in a relatively short time. This serious problem can be solved by using a specific catalyst according to the present invention.

The catalyst used in the present invention is a catalyst in which a catalyst metal of rhodium and / or ruthenium is supported on a carrier mainly composed of magnesium oxide, and the specific surface area of the catalyst is 5 m ² / g or less, and The supported amount of metal is 0.10 to 5000 weight p with respect to the carrier metal oxide based on metal atoms.
pm.

In the present invention, the concentration of carbon dioxide in the raw material lower hydrocarbon gas is 30 to 70 mol%, preferably 4 to 70 mol%.
It is defined as 0 to 60 mol%. If the carbon dioxide gas in the lower hydrocarbon gas is outside the above range, the carbon utilization rate of the above formula (5) cannot be increased to 50% or more on a molar basis.

It is preferable that the amount of water and / or steam added is as small as possible because the energy efficiency can be increased, but the molar ratio of hydrogen / carbon monoxide in the synthesis gas is 0.5 to 1.5.
When the lower hydrocarbon gas is CH ₄ , it is necessary to add a molar ratio of 0.4 to 2.0 with respect to carbon atoms when the lower hydrocarbon gas is CH ₄ . Also,
The composition of the raw material of the synthesis gas is calculated as ([CO ₂ ] + [H ₂ O])
By adjusting the / [C] ratio to be in the range of 0.5 to 2.5, preferably 1 to 2, the synthesis gas production efficiency of the synthesis gas generation step can be maintained at a high level of 80% or more. . Further, ([CO ₂ ] + [H ₂ O]) / [C]
Efficiency is further improved by using a mixed gas having a ratio of 1 to 2.

The starting material in the present invention contains a lower hydrocarbon gas or carbon dioxide gas in addition to the lower hydrocarbon gas. Lower hydrocarbon gases include methane, ethane,
A lower hydrocarbon having 1 to 4 carbon atoms such as propane, butane, and isobutane is used. In particular, those containing methane as a main component and other lower hydrocarbons such as ethane, propane, butane, and isobutane are used. In the present invention, the raw material gas is preferably a natural gas, particularly a natural gas containing carbon dioxide gas. When an excessive amount of carbon dioxide gas is contained in the feed gas, a method for adjusting the concentration thereof may be an operating pressure of 10 to 80 atm, more preferably an operating pressure of 20 to 50 atm.
It is effective to use a pressure distillation column having a pressure of atmospheric pressure, mainly separate carbon dioxide from the bottom of the column, and obtain a raw material gas having a predetermined carbon dioxide concentration from the top of the column. If the operating pressure is lower than the above range, a portion below the freezing point of carbon dioxide gas is generated in the distillation column, and solid carbon dioxide gas precipitates and distillation becomes impossible. When the operation temperature is -60 ° C. or higher, pressure distillation can be performed without depositing carbon dioxide gas as a solid. On the other hand, if the pressure exceeds the above range, the cost of equipment and the like will increase, and it will be uneconomical. When high-pressure natural gas containing a large amount of carbon dioxide is used as the raw material of the present invention, the excess natural gas recovered by this pressure distillation is maintained at a high pressure, and is returned to the well. It is also possible.

The catalyst used in the synthesis gas generation step of the present invention (hereinafter also referred to as the catalyst of the present invention) is a carrier metal oxide having a specific property and at least one selected from rhodium (Rh) and ruthenium (Ru). It is a catalyst that supports a certain kind of catalytic metal. In this case, the catalyst metal may be supported in a metal state, or may be supported in a state of a metal compound such as an oxide. The catalyst of the present invention is characterized in that it retains the activity necessary for the reforming reaction of lower hydrocarbon gas containing carbon dioxide gas and has an effect of remarkably suppressing the carbon deposition reaction which is a side reaction. The catalyst used in the present invention for remarkably suppressing the carbon deposition reaction is (i) a carrier mainly composed of magnesium oxide, (ii) the specific surface area of the catalyst is 5 m ² / g or less, (iii) The supported amount of the metal catalyst is 0.1 to 5000 ppm by weight based on the supported metal oxide. Such a catalyst in which the carbon deposition activity is significantly suppressed has been found for the first time by the present inventors. As a carrier,
In addition to single metal oxide of magnesium oxide (MgO), M
gO / CaO, MgO / BaO, MgO / ZnO, Mg
Composite metal oxides and mixtures such as O / Al ₂ O ₃ , MgO / ZrO ₂ and MgO / La ₂ O ₃ are mentioned. The catalyst having a specific surface area of 5 m ² / g or less used in the present invention can be obtained by calcining the support metal oxide at 300 to 1300 ° C., preferably 650 to 1200 ° C. before supporting the catalyst metal. The upper limit of the firing temperature is not particularly limited, but is usually 1500 ° C or lower, preferably 1300 ° C or lower. In this case, the specific surface area of the resulting catalyst or carrier metal oxide can be controlled by the firing temperature and the firing time. The preferred specific surface area of the catalyst of the present invention or the carrier used in the present invention is 5 m ² / g or less. The lower limit of the specific surface area is about 0.1 m ² / g. The amount of the catalyst metal supported on the carrier metal oxide is 0.1 ppm by weight or more, and the upper limit thereof is about 5000 ppm by weight based on the metal oxide.

In the catalyst of the present invention, the specific surface area of the catalyst and the specific surface area of the carrier metal oxide are substantially the same, and in this specification, the specific surface area of the catalyst and the specific surface area of the carrier metal oxide are used. The term "specific surface area" was used synonymously. In the present specification, the specific surface area of the catalyst or the support metal oxide is a value measured at a temperature of 15 ° C. by a “BET” method. As the measuring device, "SA- made by Shibata Chemical Co., Ltd."
100 "was used.

Such a catalyst used in the present invention has a high specific crystallinity and a small specific surface area of the catalyst, and a very small amount of the catalyst metal carried thereon, so that the carbon deposition activity is significantly suppressed. It has sufficient reforming activity with carbon dioxide gas and steam for the raw material lower hydrocarbon gas. The catalyst used in the present invention can be prepared according to a conventional method. One preferred method of preparing the catalyst of the present invention is an impregnation method. To prepare the catalyst of the present invention by this impregnation method, after adding and mixing a catalyst metal salt or an aqueous solution thereof to a carrier metal oxide dispersed in water, the carrier metal oxide is separated from the aqueous solution, and then dried. And firing. In addition, a method in which a metal salt solution corresponding to the pore volume is added little by little after exhausting the carrier metal oxide to make the surface of the carrier uniformly wet, and then dried and fired (incipient-wetness method) is also effective. . In these methods, a water-soluble salt is used as the catalyst metal salt. Such water-soluble salts include inorganic acid salts such as nitrates and chlorides, and organic acid salts such as acetates and oxalates. Alternatively, a metal acetylacetonate salt or the like may be dissolved in an organic solvent such as acetone and impregnated into the carrier metal oxide. The drying temperature of the metal metal oxide impregnated with the catalyst metal salt as an aqueous solution is from room temperature to 200 ° C, preferably from room temperature to 150 ° C. In the case of preparing the catalyst of the present invention, the metal oxide serving as the carrier can be a commercially available metal oxide or a metal oxide obtained by calcining a commercially available metal hydroxide. The purity of the metal oxide is 97% by weight or more, and preferably 98% by weight or more. However, a component that enhances the activity of carbon separation or a component that decomposes at high temperatures and in a reducing gas atmosphere, such as metals such as iron and nickel, and dioxides Silicon (S
iO ₂ ) and the like are not preferable, and their impurities are
1% by weight or less, preferably 0.1% by weight in metal oxide
It is better to:

A preferred method for preparing the catalyst of the present invention is as follows.
It is as follows. First, in the first step, a support MgO having a specific surface area of 5 m ² / g or less is obtained. In an industrial catalyst, a support formed into a shape such as a pellet or a ring is preferably used.When an MgO shaped body having such a shape is used, the specific surface area of the MgO becomes larger than the above range, and the crystallinity becomes higher. When the MgO compact is immersed in an aqueous solution when the catalyst metal is supported, the M
There is a problem that cracks occur in the gO molded body. In the case of an industrial catalyst, it is usually necessary to have a compressive strength in the radial direction of 30 to 40 kg / piece. However, such a strength is required for an MgO molded body having a specific surface area larger than the above range and a low crystallinity. Will be difficult to obtain. Further, the carrier M
When the crystallinity of gO decreases, the amount of the supported catalyst metal increases, and the acid strength of the catalyst becomes too strong, resulting in unsatisfactory acid properties of the catalyst surface. On the other hand, if the crystallinity of the support MgO is too large, the amount of the supported catalyst metal is too small, and a catalyst having sufficient activity cannot be obtained. From this point, the specific surface area of the support MgO is 0.01 m
^It is preferably at least ² / g.

One method of obtaining a carrier MgO having a specific surface area in the above range is as follows.
0 to 1500 ° C., preferably 1100 to 1300 ° C., and magnesium carbonate or basic magnesium carbonate of 1000 to 150 ° C.
It can be manufactured by baking at 0 ° C, preferably 1100 to 1300 ° C. Also, even when firing at a low temperature of 1000 ° C. or less, the partial pressure of water produced as a by-product during firing is increased to promote crystallization of MgO and to control the specific surface area of MgO to 5 m ² / g or less. Desired carrier M
gO can be obtained. Further, for those having a specific surface area smaller than the above range, such as commercially available MgO, the MgO is heated to 1000 to 1500 ° C., preferably 1100 to 1300 ° C.
The desired carrier MgO can be obtained by calcining at ° C. Further, when obtaining a carrier MgO having a low specific surface area, the crystallization of the MgO can be promoted by forming a high partial pressure of water in the calcination system at a temperature of 1000 ° C. or less. CO ₂ instead of partial pressure
By forming a high partial pressure of a gas (gas) as described above, crystallization of MgO can be promoted. As the atmosphere for the firing, an air atmosphere is usually used, but another gas, for example, an inert gas such as a nitrogen gas may be used. The firing time is 1 hour or more, preferably 3 hours or more, and the upper limit is not particularly limited,
Usually, it is about 72 hours. In addition, not only firing,
If MgO having such a low specific surface area can be obtained,
Any method may be adopted.

The carrier MgO according to the present invention has a high degree of crystallinity, the surface of the MgO is stabilized, and the MgO has a strong acid point suppressed as much as possible. And, with such stabilized MgO, MgO having only an acid point having an acid strength (Ho) of 2 or more and an amount of less than 0.03 mmol / g can be obtained. Therefore, by using MgO having a high degree of crystallinity, which has been calcined at a high temperature of 1000 ° C. or more, as a carrier for supporting a catalytic metal, the expression of strong acid sites is suppressed as much as possible, and a catalyst having a stable activity in which a carbon deposition reaction is suppressed is obtained. It becomes possible. The specific surface area of MgO used in the present invention is 0.01-5.
m ² / g, preferably 0.05 to ³ m ² / g. When the specific surface area of the support MgO is higher than the above range, the amount of the supported catalyst metal increases, and the acid strength of the catalyst becomes too strong, so that the acid properties of the catalyst surface become unsatisfactory. On the other hand, when the specific surface area of the support MgO is smaller than the above range, the amount of the supported catalyst metal is too small, and a catalyst having sufficient activity cannot be obtained.

In general, it is well known that the surface area of a metal oxide and its crystallite size are substantially inversely proportional. Therefore, the specific surface area of MgO specified in the present invention can be specified by its particle size.
For example, the crystallite size of MgO having a specific surface area of 5 m ² / g or less can be calculated from the density and specific surface area of MgO by assuming that the particles are spherical or cubic uniform particles. This method is described in the document "Catalyst Course 3 (Characterization of Solid Catalysts)" (published in 1985, Kodansha Scientific, edited by the Catalysis Society of Japan, p. 203). For example, a specific surface area of 5 m ² fired at 1010 ° C.
/ G of MgO has a crystallite size of 3500 °. Further, the crystallite size of MgO can be measured by using an X-ray diffraction method. Specific surface area in this specification is 5 m ² / g
When the following crystallite size of MgO was measured by the “line broadening” method using the X-ray diffraction method, the value was 900 ° or more. As a measuring device, an X-ray diffractometer “XRD-6000” manufactured by Shimadzu Corporation was used. When measurement is performed using metal Si as a standard substance,
The crystallite size of MgO was calculated from the half width of the diffraction peak of MgO 2θ = 42.7 ° and the diffraction peak of Si MgO 2θ = 28.4 °. The measurement conditions in the X-ray diffraction measurement are shown below. X-ray tube: Cu (λ = 1.5406 °) Tube voltage: 40.0 kV, tube current: 30.0 mA Measurement range: 40.0 to 80.0 ° Step width: 0.02 ° Counting time: 0.6 Second slit: DS (divergence slit) = 0.5 °, SS (anti-scattering) = 0.5 °, RS (light reception) = 0.15 mm Reference material: metal Si For details of this line broadening method, see the literature "Experiment Chemistry Course 4 (Solid State Physical Chemistry) "(published in 1956, Maruzen, edited by The Chemical Society of Japan, pp. 238-250).

In the second step (catalyst metal supporting step), the carrier magnesium oxide obtained as described above is subjected to an equilibrium adsorption method using an aqueous solution containing a catalytic metal.
The catalyst aqueous solution is supported in eight or more alkali regions.
In the present invention, rhodium and / or ruthenium are used as the catalyst metal. In the supporting step, the catalytic metal is supported on the carrier magnesium oxide in the form of an aqueous solution. In this case, the catalytic metal is used in the form of a water-soluble compound. Examples of such compounds include halides, nitrates, sulfates, organic acid salts (such as acetates), and complex salts (chelates). An equilibrium adsorption method is employed for supporting the catalyst metal aqueous solution on the carrier MgO. In this method, a carrier is immersed in a catalyst aqueous solution, and the catalyst metal in the aqueous solution is adsorbed and supported on the carrier under equilibrium conditions. In this case, the time for supporting the catalyst metal on the carrier (immersion time) is 1 hour or more, preferably 3 hours or more, and the upper limit is not particularly limited, but is usually about 48 hours. The details of this equilibrium adsorption method are described in the document "Catalyst Preparation Chemistry" (published in 1980, Kodansha Scientific, P49).

When the catalyst metal is carried on the carrier MgO as described above, the pH of the catalyst aqueous solution is set to an alkaline region of 8 or more, preferably 8.5 or more. The upper limit is not particularly limited, but is usually about pH 13.
To adjust the pH of the aqueous solution, an alkaline substance such as sodium hydroxide, potassium hydroxide, calcium hydroxide, or magnesium hydroxide is used. In the present invention, the supported amount of the catalyst metal on the carrier MgO is defined as a ratio of 10 to 5,000 wtppm, preferably 100 to 2,000 wtppm, based on the catalyst metal in terms of the catalyst metal. When the amount of the supported catalyst metal is larger than the above range, the cost of the catalyst is increased, and the carbon deposition activity of the catalyst is increased, and the amount of deposited carbon is increased when the catalyst is used. on the other hand,
If it is less than the above range, sufficient catalytic activity cannot be obtained. The adjustment of the amount of the supported catalyst metal can be performed by adjusting the conditions for supporting the aqueous solution of the catalyst metal on the carrier MgO, for example, the concentration of the catalyst metal in the aqueous solution, the surface area of the carrier MgO, and the like.

In the third step (drying step), the catalyst metal-supported MgO obtained by supporting the catalyst metal in the form of an aqueous solution on the carrier MgO as described above is subjected to 35 ° C.
Hold at the following temperature for 6 hours or more and dry. The preferred drying temperature is from 10 to 25C. The drying time may be at least 6 hours, preferably at least 12 hours, and the upper limit is not particularly limited, but is usually about 72 hours. By such a drying treatment, rapid evaporation of water from MgO is avoided, and as a result, the catalyst metal is supported on the carrier MgO in a highly dispersed state without agglomeration. If the drying temperature and the drying time deviate from the above ranges, a catalyst containing a highly dispersible catalytic metal cannot be obtained.

The dried product obtained as described above is fired at a high temperature of 200 ° C. or more (secondary firing) in the fourth step. In this case, air is usually used as the firing atmosphere, but another gas (such as an inert gas) may be used. The firing temperature is 200 ° C. or higher, preferably 5 ° C.
It is at least 00 ° C., and the upper limit is not particularly limited, but is usually about 1100 ° C. Preferred firing time is 2 hours or more, more preferably 3 hours or more,
The upper limit is not particularly limited, but is usually about 24 hours. By this secondary calcination, the thermal stability of the catalyst metal is enhanced, and a catalyst with good thermal stability can be obtained.

In order to reduce the catalyst cost, the amount of the catalyst metal supported on the carrier is reduced as much as possible, and at the same time, the catalyst metal particles supported on the carrier are aggregated so as to exhibit a sufficient reaction activity. It is necessary to reduce the particle size as much as possible and to make the particles fine. According to the study of the present inventors, the crystallization of the carrier MgO was enhanced to increase its specific surface area to 5 m ^2.
/ G or less, the supported amount of the catalyst metal on the carrier MgO is kept to a very small amount of 10 to 5000 wtppm, and when the catalyst metal is supported on the carrier MgO, the catalyst metal is equilibrated by the equilibrium adsorption method. Under a long period of time, the catalyst metal is supported slowly in an aqueous solution state, and after the support, when slowly dried at a temperature of 35 ° C. or less, the catalyst metal is uniformly supported and sufficient as a catalyst for hydrocarbon reforming. It has been found that an inexpensive catalyst having activity can be obtained.

Various changes can be made in the above-described method for preparing the catalyst. For example, the method for supporting the catalyst metal on the carrier magnesium oxide is not limited to the equilibrium adsorption method, and other methods such as a conventional impregnation method, an immersion method, and an ion exchange method can be used. In addition, in the case of drying after supporting the aqueous solution containing the catalyst metal on the carrier magnesium oxide, a heating condition of about 35 to 200 ° C. may be employed in some cases. Depending on the case, it may be performed at a temperature of about 200 to 800 ° C.

When a catalyst is prepared according to the present invention, the magnesium oxide for forming a catalyst carrier is preferably used as a magnesium oxide molded article formed by mixing a molding aid with magnesium oxide. By using this molding aid, the workability during molding is improved and the strength of the obtained molded body is improved. As a molding aid in this case,
(I) carbon (carbon), (ii) a fatty acid having 12 to 22 carbon atoms or a magnesium salt thereof, (iii) carboxymethyl cellulose (CMC) or a magnesium salt thereof, and (iv) at least one kind selected from polyvinyl alcohol. Preferably, a compound is used. These molding aids are usually used in powder form. As the carbon, carbon black, graphite, activated carbon and the like are used. Examples of the fatty acid include lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid and the like.

In order to manufacture the magnesium oxide compact for a catalyst carrier, a molding aid is added to powdered magnesium oxide, and the mixture is uniformly mixed, and then the mixture is formed into a required shape. The average particle size of the powdered magnesium oxide is 1 to 10
It is 00 μm, preferably 10 to 100 μm. on the other hand,
The molding aid has an average particle size of 1 to 1000 μm, preferably 1 to 1000 μm.
0 to 100 μm. The amount of the molding aid added to the magnesium oxide is 0.1 to 5% by weight, preferably 0.5 to 3.0% by weight, based on the total amount of the magnesium oxide and the molding aid. When forming a mixture of the magnesium oxide and the molding aid, the molding conditions are usually 3000 to 100 kg / cm ² G at room temperature, preferably 200 to 200 kg / cm ² G.
A pressure of 0-200 kg / cm ² is employed. As a molding method, a press molding method is adopted, but a tableting method or the like can also be adopted. The shape of the molded body is not particularly limited, and may be any shape as long as it is used for a normal catalyst. Such shapes include tablets, cylinders,
A ring shape, a hollow cylindrical shape and the like are included. The size of the formed body is usually 3 to 30 mm, preferably 5 to 25 mm in terms of its major axis, but an appropriate size may be adopted according to the catalyst bed.

The magnesium oxide molded article according to the present invention has excellent mechanical strength after firing, and is usually 30 to 70 k.
g / piece radial compressive strength. Therefore, such a molded body has good handleability and is not easily broken during firing. In addition, when the crystallinity of MgO is low, the magnesium oxide compact is usually first fired at a high temperature of 1000 ° C. or higher to obtain a desired carrier magnesium oxide.
By this primary firing, the molding aid in the molded body is oxidized and removed. The magnesium oxide thus obtained is suitable as a carrier magnesium oxide used for preparing the catalyst of the present invention.

In the catalyst of the present invention obtained as described above, the amount of the supported catalyst metal is 1 to the support MgO.
0 to 5000 wtppm, preferably 100 to 2000
wt ppm, and its specific surface area is 0.01 to ⁵ m ² /
g, preferably 0.05 to ³ m ² / g.

The catalyst of the present invention obtained as described above has preferable acidic properties as a catalyst for hydrocarbon reforming. When a large number of strong acid sites are present on the catalyst surface, a carbon deposition reaction, which is a side reaction, is promoted on the acid sites, carbon is deposited, and the deposited carbon causes catalyst poisoning.

The catalyst of the present invention generally has only an acid strength (Ho) of more than 2, preferably at least 3.3 or more, and has a content of less than 0.03 mmol / g, preferably less than 0.03 mmol / g. Is 0.02 mmol / g or less. The adjustment of the acid strength (Ho) can be performed by adjusting the temperature and the time when the support MgO is subjected to the first firing. In the catalyst of the present invention, the expression of strong acid sites is suppressed, and the carbon deposition activity is greatly suppressed.

The acid strength (Ho) referred to in this specification is:
It is expressed as the ability of the catalyst to give a proton to the basic indicator (B ⁻ ) and is expressed by the following formula. ^{_{Ho = pKa (= pK B -}} H +) + log [B] / [B - H +] (1) In the formula, K _B ^- _H ⁺ is a basic indicator B ^- the reaction of the acid point H ⁺ B Thus, the dissociation constant of the acidic form B ^- H ⁺ in the reaction for producing the acidic form (B ^- H ⁺ ) of the basic indicator is shown. ^{[B] / [B - H} +] is, B ^- and B ^- shows the H ⁺ concentration ratio of. As strong acid sites, pK _B ^- the Ho value because more protonate a small indicator _H ⁺ decreases.

The acid strength in the present specification is measured as follows. (Method of Measuring Acid Strength) The acid strength Ho (Hammett index) function in this specification is an acid strength function, which is described in “Catalyst Experiment Handbook” edited by the Catalysis Society of Japan (published in 1986, Kodansha Scientific), p. 172 “Benesi method”
Is measured by Addition of an indicator whose pKa is known to the catalyst and discoloration indicate that Ho has an acid point less than its pKa. When a predetermined amount of butylamine, which is a basic molecule, is adsorbed to acid sites and titrated with an indicator having a different pKa, the number of acid sites is determined from the amount of butylamine as p
The acid strength can be measured from the value of Ka. The measurement temperature is room temperature.

The catalyst of the present invention may be in the form of powder, granule, sphere,
It is used in various shapes such as a columnar shape and a cylindrical shape, and the shape is appropriately selected according to the type of the catalyst bed used.

In order to produce a synthesis gas according to the present invention, a reforming reaction between a lower hydrocarbon gas, a carbon dioxide gas, and steam may be performed in the presence of the catalyst. The reaction temperature is 600-1000 ° C, preferably 650-9.
50 ° C. The reaction pressure is pressurized,
Atmospheric pressure, preferably 15 to 40 atm. When this reaction is carried out in a fixed bed system, the gas space velocity (GHS
V) is 1,000~10,000hr ^-1, preferably 2,000~8,000hr ^-1. The synthesis gas generation step of the present invention includes a fixed bed system, a fluidized bed system, a suspension bed system,
Although it is carried out by various catalyst systems such as a moving bed system, it is preferably carried out by a fixed bed system. Further, the reaction is not limited to one stage, but can be performed in a plurality of stages.

In the present invention, the synthesis gas obtained in the above synthesis gas generation step is used as a raw material gas for dimethyl ether synthesis having a composition in which the molar ratio of hydrogen / carbon monoxide is 0.5 to 1.5. In the present invention, this synthesis gas can be directly introduced into the dimethyl ether synthesis reaction step without going through the step of separating the hydrogen and / or carbon dioxide gas to adjust the composition of the synthesis gas. Is an advantage. In the present invention, the synthesis gas is reacted in the presence of a catalyst to generate a reaction product containing dimethyl ether. The reaction in this case occurs by a combination of (a) a methanol synthesis reaction, (b) a methanol dehydration reaction, and (c) a CO shift reaction, as shown by the following reaction formula. _{2H 2 + CO = CH 3 OH} (a) 2CH 3 OH = CH 3 OCH 3 (b) CO + H 2 O = CO 2 + H 2 O (c) wherein the reaction (a), (b) and (c) Is as follows. _{3CO + 3H 2 = CH 3 OCH} 3 + CO 2 (d) Reaction Scheme (a), as can be seen from (b) and (c), as the catalyst for dimethyl ether synthesis, the reaction (a), (b) Any substance having an activity of promoting (c) and (c) may be used, and various conventionally known substances may be used.
In this case, the dimethyl ether synthesis reaction catalyst can be composed of a single kind of catalyst, or can be composed of a combination of two or more kinds of plural kinds of catalysts. When a catalyst obtained by combining two or more kinds of catalysts is shown, for example, a first catalyst which promotes the reaction (a), a reaction (b) and a reaction (b)
A combination of a first catalyst that promotes the reactions (a) and (b) with a second catalyst that promotes the reaction (c); and a combination of the first catalyst that promotes the reaction (c), and the reactions (a) and (c) A combination of a first catalyst for promoting the reaction (b) and a second catalyst for promoting the reaction (b), the first catalyst for promoting the reaction (a), the second catalyst for promoting the reaction (b), and the reaction (c) Can be shown. When such a combination of a plurality of catalysts is used, those catalysts can be used as a mixed catalyst bed obtained by mixing them,
Each catalyst can be used as a multilayer catalyst bed or a multi-stage catalyst bed. Specific examples of the catalyst used in the dimethyl ether synthesis reaction include, for example, catalysts having a methanol synthesis reaction activity include copper oxide-zinc oxide /
There are chromium oxide, copper oxide-zinc oxide / alumina and the like. Since a methanol synthesis catalyst usually has a catalytic activity for promoting a CO shift reaction, it can also serve as a CO shift catalyst. Al ₂ O ₃ , S
TiO ₂ · Al ₂ O ₃ , solid phosphoric acid, ThO ₂ , TiO ₂ , Z
Examples thereof include metal oxide catalysts such as rO ₃ , zeolites, layered silicates, and ion exchange resins. Typical examples of the CO shift catalyst include iron / chromium catalysts, copper / zinc catalysts, and copper / chromium / zinc catalysts. The reaction conditions for synthesizing dimethyl ether are a temperature of 150 to 400 ° C., a pressure of 20 to 70 Kg / cm ² G, and a reactor of various types such as a fixed bed system, a fluidized bed system, a suspension bed system, and a moving bed system. In the form of As can be seen from the above reaction formula (d), the synthesis gas composition for synthesizing dimethyl ether is ideally H ₂ / CO = 1, and in the present invention, the synthesis gas generation conditions are controlled to 0.5%. Adjust to around 1.5.

[0040]

Next, the present invention will be described in more detail with reference to examples.

Catalyst Preparation Example 1 Commercially available magnesium oxide (Mg) having a purity of 98.1 wt%
O) powder was mixed with 3.0 wt% of carbon as a molding aid, and tablet-formed 1/8 inch pellets were fired in air at 1100 ° C. for 3 h and then impregnated with 0.075 wt% Rh. And in the air, 9
By baking at 00 ° C., a Rh-supported MgO catalyst was obtained. This impregnated body is obtained by converting the baked MgO pellets to rhodium (II
I) Immersion in an aqueous solution of acetate salt for about 12 hours, followed by filtration, drying in air at room temperature for 24 hours,
It was calcined at 00 ° C. for 3 hours to obtain a Rh-supported MgO catalyst (specific surface area: 0.6 m ² / g).

Catalyst Preparation Example 2 A commercially available magnesium oxide having a purity of 98.1% by weight (Mg)
O) powder was mixed with 2.0% by weight of magnesium stearate as a molding aid, and tablet-formed 1/8 inch pellets were fired in air at 1050 ° C. for 3 hours and then impregnated with 0.1% by weight. % Ru, and calcining in air at 800 ° C.
An O catalyst was obtained. This impregnated body is obtained by immersing the calcined MgO pellets in a methanol solution of ruthenium (III) acetonate for about 12 hours, filtering, and then immersing in air at room temperature for 24 hours.
After drying for 3 h at 800 ° C. for 3 h in the same atmosphere, a Ru-supported MgO catalyst (surface area: 1.1 m ² / g) was obtained.

Catalyst Preparation Example 3 A commercially available magnesium oxide having a purity of 98.7 wt% or more (M
gO) powder was mixed with 3.0% by weight of carbon as a molding aid, and 1/8 inch pellets formed as tablets were fired in air at 1060 ° C. for 3 hours (hours), and this was used as a catalyst carrier MgO (A). Using. Next, the rhodium (III) acetate aqueous solution containing 3.9 wt% Rh was added for 26 hours.
(Time) Dipped. The pH of the aqueous solution was adjusted to 9.7 using an aqueous solution of magnesium hydroxide. Thus, after Rh is equilibrium-adsorbed on the catalyst support MgO (A),
Filtration, catalyst support MgO adsorbing Rh in aqueous solution
(A) was obtained. The amount of Rh supported in this case is 3750 wtppm relative to the carrier MgO (A) in terms of Rh metal.
It is. Next, the MgO (A) carrier on which Ru was adsorbed was dried in air at a temperature of 35 ° C. for 52 hours, and then calcined in air at 850 ° C. for 3 hours to obtain a catalyst (A) of the present invention. This catalyst (A) uses Rh as Rh metal and supports MgO
And the surface area was 1.2 m ² / g. The acid sites consisted only of acid sites having an acid strength (Ho) of 3.3 or more, and the content was 0.01 mmol / g.

Catalyst Preparation Example 4 A commercially available magnesium oxide having a purity of 99.9 wt% or more (M
A 1/8 inch pellet of MgO formed using gO) was fired in air at 1000 ° C. for 2 hours (hour), and this was used as a catalyst support MgO (B). Next, 0.1wt
% Ruthenium (III) chloride aqueous solution for 19 h (hour). The pH of the aqueous solution was adjusted to 9.7 using an aqueous solution of magnesium hydroxide. After Ru is equilibrium-adsorbed on the catalyst carrier MgO (B) in this way, the catalyst carrier Mg on which Ru is adsorbed in the form of an aqueous solution is filtered.
O (B) was obtained. In this case, the amount of supported Ru is 125 wtppm in terms of the amount of Ru metal with respect to the carrier MgO (B). Next, the MgO (B) carrier on which Ru was adsorbed was dried in air at a temperature of 30 ° C. for 72 hours, and then calcined in air at 860 ° C. for 2.5 hours to obtain a catalyst (B) of the present invention. This catalyst (B) uses Ru as Ru metal and supports MgO
It was contained at a rate of 125 wtppm with respect to (B), and its surface area was 4.8 m ² / g. The acid sites consisted only of acid sites having an acid strength (Ho) of 3.3 or more, and the content was 0.03 mmol / g.

Catalyst Preparation Example 5 A commercially available magnesium oxide (Mg) having a purity of 98.0 wt%
A 1 / 8-inch pellet of MgO formed using O) was fired in air at 1200 ° C. for 2.5 hours (hour), and this was used as a catalyst support MgO (C). Next, 2.6w
It was immersed in a rhodium (III) acetate aqueous solution containing t% Rh for 26 h (hour). The pH of the aqueous solution was adjusted to 9.7 using an aqueous solution of magnesium hydroxide. In this manner, the Rh is equilibrium-adsorbed on the catalyst support MgO (C), and then filtered, and the Rh is adsorbed in the form of an aqueous solution.
O (C) was obtained. The amount of Rh supported in this case is 1750 wtpp with respect to the support MgO (C) in terms of Rh metal.
m. Next, the MgO (C) carrier on which Rh was adsorbed was dried in air at a temperature of 20 ° C. for 34 hours, and then calcined in air at 950 ° C. for 3.5 hours to obtain the catalyst (C) of the present invention.
I got This catalyst (C) uses Rh as Rh metal and the carrier M
It contained 1750 wtppm based on gO and had a surface area of 0.2 m ² / g. The acid sites consisted only of acid sites having an acid strength (Ho) of 3.3 or more, and the content was 0.002 mmol / g.

Comparative Catalyst Preparation Example 1 Magnesium oxide calcined at 370 ° C. for 3 hours in the air was sized to 0.27 to 0.75 mm, and Rh was impregnated.
And further calcined in air at 370 ° C. to obtain a Rh-supported MgO catalyst (Rh is supported at 2.6 × 10 ⁻³ g per 1 g of Mg, and the supported amount in terms of mol is 0.1 mol / g). 10 mol%). This impregnated body is calcined MgO
An aqueous solution of rhodium (III) acetate is dropped by a very small amount, and the mixture is shaken for each drop. The Rh concentration in the aqueous rhodium (III) acetate solution dropped was 1.
7 wt%. This impregnated body is in air at 120 ° C.
For 2.5 h, and calcined at 370 ° C. for 3 h in the same atmosphere to obtain a Rh-supported MgO catalyst (surface area 98 m ² / g).

Carbon Dioxide Distillation Example 1 As raw materials, 72.5 mol% of carbon dioxide, methane
3 mol%, ethane 2.9 mol%, propane 0.3 m
Carbon dioxide gas was separated from natural gas containing ol% by distillation. The theoretical stage of the distillation column is 7 stages, and the pressure is 40 kg / c.
Distillation was carried out under the conditions of m ² G, tower temperature of 23.4 ° C., tower temperature of 5.0 ° C., and reflux ratio = 1.5.
0.0 mol%, methane 45.6 mol%, ethane 4.
A gas having a composition of 3 mol% and 0.1 mol% of propane was obtained.

Example 1 (1) Synthesis Gas Generation Step Carbon dioxide gas 50.0 obtained from the above carbon dioxide distillation example 1
Catalyst preparation example 1 using a top gas containing mol% as a raw material
A synthesis gas production test was carried out using the catalyst shown in (1). After reducing the catalyst by about 1.5 HR at 900 ° C. in advance, the molar ratio of water to the total number of lower hydrocarbons in the raw material gas is 1: 0.
H ₂ O was added so as to be 36 (CO ₂ + H ₂ O / carbon atom of lower hydrocarbon = 1.28), and the catalyst layer outlet temperature was set to 90.
The temperature was 0 ° C., the pressure was 20 kg / cm ² G, and the GHSV based on the total amount of the inlet gas was 4500 HR ⁻¹ . The conversion of CH _{4 in} the reaction was 67%, and the composition of the resulting synthesis gas was H
_{2 = 38.5mol%, CO = 38.5mol} % (H 2 /
CO = 1.0), CH ₄ = 7.7 mol%, CO ₂ = 6.
5 mol% and H ₂ O = 8.8 mol%.

(2) Dimethyl ether synthesis step The synthesis gas obtained in the synthesis gas generation step is cooled,
After removing ₂ O, a dimethyl ether synthesis test was performed as a raw material gas for dimethyl ether synthesis. As the catalyst, a Cu—Zn—Al-based (CuO: 42 wt%, Zn
(O: 47 wt%, Al ₂ O ₃ : 11 wt%) A methanol synthesis catalyst and a methanol dehydration catalyst in which CuO is supported on γ-Al ₂ O ₃ by 15 cc were physically mixed. The raw syngas is reacted at a reaction temperature of 250 in the presence of the catalyst.
° C, pressure 50kg / cm ² G, GHSV = 4000HR
As a result of reacting under the reaction condition of ^-1 , the CO conversion was 84.7.
%, And the yield of dimethyl ether from the synthesis gas was 42.9%.

Synthesis Gas Production Reaction Example 1 A reactor was charged with 30 cc of the catalyst prepared in Catalyst Preparation Example 1, and a synthesis gas production test from methane was performed. The catalyst was previously subjected to a reduction treatment in an H ₂ stream at 900 ° C. for 1 h, and then the CH ₄ : CO ₂ : H ₂ O molar ratio = 1: 1.22: 0.
6 (raw material (CO ₂ + H ₂ O) / CH ₄ = 1.82) at a pressure of 20 kg / cm ² G and a catalyst layer outlet temperature of 850.
The treatment was performed under the conditions of C ° C. and GHSV = 5000 hr ^{−1 based on} the raw material gas. The generated gas H ₂ / CO molar ratio was 1.0, and the synthesis gas production efficiency after 98 hours from the start of the reaction was 98.
%, The carbon conversion efficiency was 62%, the synthesis gas production efficiency after 2000 hours from the start of the reaction was 98%, and the carbon conversion efficiency was 62%.

Synthesis gas production reaction example 2 A synthesis gas production test was carried out under exactly the same conditions as in the synthesis gas production reaction example 1 except that 30 cc of the catalyst prepared in catalyst preparation example 2 was charged into the reactor. Carried out. The generated gas H ₂ / CO molar ratio was 2.0, the synthesis gas production efficiency after 5 hours from the start of the reaction was 97%, the carbon conversion efficiency was 61%, and the synthesis after 1500 hours from the start of the reaction. Gas production efficiency is 96%, carbon conversion efficiency is 60%
Met.

Synthesis Gas Production Reaction Example 3 30 cc of the catalyst prepared in Catalyst Preparation Example 1 was charged into a reactor, and various mixing ratios of H ₂ O and CO ₂ were added to methane to conduct a synthesis gas production test. The catalyst is about 2.0H at 900 ° C in advance.
R reduction treatment, the catalyst layer outlet temperature is 850 ° C., pressure 2
The raw material CH ₄ , CO ₂ , and H ₂ O ratios were set so that the H ₂ / CO ratio in the product was approximately 1.0, with 0 kg / cm ² G and GHSV of 4000 HR ^{−1 based on the} total amount of the inlet gas composition. Adjustments and reaction tests were performed. The test results are shown in the table below.

[0053]

[Table 1]

Comparative Reaction Example 1 An experiment was conducted in the same manner as in Example 1 except that the catalyst obtained in Comparative Catalyst Preparation Example 1 was used in the synthesis gas generation step (1). In this case, the conversion rate of CH ₄ after 5 hours from the start of the reaction was 65%. In addition, 2
After a lapse of 00 h, the conversion of CH ₄ was 37%.

[0055]

According to the present invention, dimethyl ether can be produced stably and economically with a high yield over a long period of time by using a lower hydrocarbon gas such as methane or natural gas as a starting material.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C07B 61/00 300 C07B 61/00 300 (72) Inventor Masato Tauchi Tsurumi Chuo, Tsurumi-ku, Yokohama-shi, Kanagawa 2-12-1 Chiyoda Chemical Construction Co., Ltd. (72) Inventor Mitsunori Shimura 2--12-1, Tsurumi Chuo, Tsurumi-ku, Yokohama-shi, Kanagawa F-term in Chiyoda Chemical Construction Co., Ltd. 4H006 AA02 AC43 BA05 BA07 BA08 BA09 BA10 BA14 BA19 BA30 BA33 BA35 BA66 BA71 BA72 BE20 BE40 GN05 GP01 GP30 4H039 CA61 CG10

Claims (11)

[Claims] 1. A method for converting a raw material lower hydrocarbon gas containing carbon dioxide into dimethyl ether, comprising: (i) adding water and / or steam to a lower hydrocarbon gas containing 30 to 70 mol% of carbon dioxide; Step of preparing a mixed gas in which each component satisfies the following formula: 0.5 ≦ ([CO ₂ ] + [H ₂ O]) / [C] ≦ 2.5 (where [CO ₂ ] is the CO ₂ Mole number, [H ₂ O] is H ₂ O
And [C] represent the number of moles of carbon contained in the lower hydrocarbon gas.) (Ii) The lower hydrocarbon gas contained in the mixed gas is supplied to a carrier mainly composed of magnesium oxide by adding rhodium and And / or a catalyst carrying a ruthenium catalyst metal, wherein the specific surface area of the catalyst is 5 m ² / g or less, and the amount of the catalyst metal supported is 0.10 relative to the carrier metal oxide based on metal atoms.
Contact with a catalyst at １０〜5000 ppm by weight at a pressure of 10-75 atm at a temperature of 600-1000 ° C.
Generating a synthesis gas having a carbon monoxide molar ratio of 0.5 to 1.5, and (iii) converting the synthesis gas into one or more of methanol synthesis activity, dehydration reaction activity, and CO shift reaction activity. A method for producing a reaction product containing dimethyl ether by reacting in the presence of a catalyst; and (iv) a step of separating dimethyl ether from the reaction product. 2. In the mixed gas preparation step, water and / or water is added to a lower hydrocarbon gas containing 40 to 60 mol% of carbon dioxide gas.
2. The method according to claim 1, wherein steam is added to prepare a mixed gas in which each component satisfies the following formula. 1 ≦ ([CO ₂ ] + [H ₂ O]) / [C] ≦ 2 (where [CO ₂ ] is the number of moles of CO ₂ and [H ₂ O] is H ₂ O
And [C] indicate the number of moles of carbon contained in the lower hydrocarbon gas.) 3. The method according to claim 1, wherein in the syngas generation step, the synthesis gas production efficiency represented by the following formula is 80% or more on a molar basis. {([CO] + [H ₂ ]) / ([C] + [CO ₂ ] + [H
_{2 O])} × 100%} ( wherein, [CO] is the number of moles of CO, [H _2] is the number of moles of H _2, [C] is the number of moles of carbon contained in the lower hydrocarbon gas, [ [CO ₂ ] indicates the number of moles of CO ₂ and [H ₂ O] indicates the number of moles of H ₂ O.) 4. The method according to claim 1, wherein in the synthesis gas producing step, the carbon conversion efficiency represented by the following formula is 50% or more on a molar basis. {[CO] / ([C] + [CO ₂ ])} × 100% (where [CO] is the number of moles of CO, [C] is the number of moles of carbon contained in the lower hydrocarbon gas and [ CO ₂ ] is CO ₂
Shows the number of moles) 5. The method according to claim 1, wherein the lower hydrocarbon gas is natural gas. 6. In order to adjust the concentration of excess carbon dioxide in the lower hydrocarbon gas, the lower hydrocarbon is subjected to an operating pressure of 1%.
The method according to any one of claims 1 to 5, wherein the distillation is performed using a low-temperature pressure distillation column having a pressure of 0 to 80 atm, carbon dioxide is separated from the bottom of the column, and a lower hydrocarbon gas having a predetermined carbon dioxide concentration is obtained from the top of the column. Method. 7. The operating pressure of the low-temperature pressure distillation column is 20 to 5
7. The method of claim 6, wherein the pressure is zero atmosphere. 8. A low-temperature pressure distillation column having an overhead temperature of -60 ° C.
The method according to claim 6, wherein the temperature is the above temperature. 9. The synthesis gas from the synthesis gas generation step,
The method according to any one of claims 1 to 8, wherein the method is directly introduced into a dimethyl ether synthesis reaction step without passing through a step of separating hydrogen and / or carbon dioxide gas. 10. The method according to claim 10, wherein the synthesis gas is a methanol synthesis catalyst,
10. The reaction product according to claim 1, wherein the reaction is carried out in one or more stages in the presence of a catalyst obtained by combining at least two kinds of catalysts selected from a dehydration catalyst and a CO gas shift catalyst to produce a reaction product containing dimethyl ether. the method of. 11. A method for adjusting a carbon dioxide gas concentration in a raw material lower hydrocarbon gas by adjusting a part or all of a gaseous product containing methane, hydrogen and carbon dioxide gas after separating dimethyl ether from the dimethyl ether synthesis reaction product. 6. The process according to claim 5, wherein the circulation is carried out to a low-temperature pressure distillation column.