JPH10182534A - Production of dimethyl ether - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing dimethyl ether using CO and H2 as the main feedstocks, designed to quickly and easily adjust the H2 /CO molar concentration ratio for the recycled gas consisting mainly of both unreacted CO and H2 to a specified value. SOLUTION: First, steam 14' is brought into contact with a recycled gas 7b' to adjust the H2 /CO molar concentration ratio for the recycled gas to a specified value by shift reaction. The resultant recycled gas 11' is then mixed with a makeup gas 1' so as to adjust the H2 /CO molar concentration ratio for the gas 2' after mixed to a value close to 1. Thus, the H2 /CO molar concentration ratio for the gas for synthesizing dimethyl ether can be controlled independently of fluctuations in the extent of advancement of dimethyl ether synthetic reaction and the like, thus enabling stable operation of the stock feed system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing dimethyl ether using carbon monoxide and hydrogen as main raw materials.

[0002]

2. Description of the Related Art Heretofore, as a commercial production method of dimethyl ether, a method has been employed in which methanol is used as a raw material and one molecule of water is dehydrated from two molecules thereof. On the other hand, recently, a technique for synthesizing dimethyl ether directly from carbon monoxide and hydrogen is being developed. As a method for directly synthesizing dimethyl ether from carbon monoxide and hydrogen as described above, a method in which a raw material gas is passed through a fixed bed catalyst layer to cause a reaction (see, for example,
No. 280,836) and a method of passing a raw material gas through a slurry reactor in which catalyst fine particles are suspended in a medium oil having a high boiling point (for example, Japanese Patent Publication No. 5-810069). .

[0003] In the above-mentioned method for directly synthesizing dimethyl ether from carbon monoxide and hydrogen, the dimethyl ether is formed from hydrogen and carbon monoxide represented by the following formulas (1), (2) and (3). Methanol synthesis, dimethyl ether synthesis generated by a dehydration reaction from the synthesized methanol, and water produced as a byproduct of the dimethyl ether synthesis and carbon monoxide react to generate hydrogen.
Kinds of reactions proceed simultaneously.

CO + 2H ₂ → CH ₃ OH ---------- (1) 2CH ₃ OH → CH ₃ OCH ₃ + H ₂ O ---------- (2) H ₂ O + CO → H ₂ + CO ₂ ---------- (3) When the formulas (1) to (3) are summarized, dimethyl ether (hereinafter referred to as DME) represented by the following formula (4) and carbon dioxide: Will be produced in equivalent amounts from the raw material hydrogen and carbon monoxide.

3CO + 3H ₂ → CH ₃ OCH ₃ + CO ₂ (4) However, the reactions of the above formulas (1) to (3) are equilibrium reactions governed by temperature and pressure. Therefore, in the actual synthesis process, the above three reactions do not proceed 100%. Therefore, the reaction of the formula (4), which is a summary of the above three reactions, does not proceed 100%. Therefore, 100% of the raw material hydrogen and carbon monoxide as represented by the formula (4) are not converted, and the gas at the outlet of the reactor always contains unreacted hydrogen and carbon monoxide. Therefore, normally, the unreacted hydrogen and carbon monoxide are not discarded, but are separated from other products and then recycled to the reactor to be used as a part of the raw material gas, and are effectively used.

As described above, as a method for directly synthesizing DME by recycling unreacted hydrogen and carbon monoxide to a reactor, for example, DOE / PC / 90018-T7 is described in the following production process (hereinafter referred to as “prior art”). Technology 1 ”).

FIG. 3 shows a flow diagram of a conventional DME manufacturing process described in a report from the US Department of Energy: DOE / PC / 90018-T7. This production apparatus includes a reactor R, a methanol / water separator S1, an unreacted gas separator S2, and a CO ₂ separator S3.
A raw material gas line 2 is connected to the bottom of the reactor R. The raw material gas line 2 has a makeup gas line 1 for supplying a new raw material gas and a recycled gas line 7a for circulating and supplying unreacted CO and H _2. Is connected. From the top of the reactor R, a reaction gas line 3 for discharging the reaction product 3 'is connected to the inlet of the methanol / water separator S1, and the methanol / water 4' outlet of the methanol / water separator S1 has methanol. A water line 4 and a reaction gas line 5 at the outlet of the reaction product 5 ';
The other end of the reactive gas line 5 is connected to the inlet of the unreacted gas separator S2, and the other end of the recycle gas line 7a is connected to the outlet of the recycled gas 7 'of the unreacted gas separator S2. This recycled gas line 7 and 7a
Is connected to a purge line 10 for extracting a part of the recycle gas 7 'from the connection portion. The DME · CO ₂ 6 'outlet of the unreacted gas separator S2, DME · CO line 6 is connected, the other end of DME · CO ₂ line 6 is CO
₂ separator S3, and a CO ₂ line 8 at the CO ₂ 8 ′ outlet of the CO ₂ separator S3, and DME
DME lines 9 are connected to the 9 'outlets, respectively.

In this process, the reaction product 3 '
From First, with methanol-water separator S1 'to separate, then recycle gas 7 to the unreacted CO and H ₂ as main components unreacted gas separator S2' of methanol and water 54 is separated and the reactor this Recycling to improve the efficiency of raw material utilization.

On the other hand, for example, British Patent Publication GB2253
623A, as a raw material gas for synthesis of DME, a raw material gas having a molar concentration of hydrogen higher than the molar concentration of carbon monoxide, that is,
In the case of a DME synthesis process using a raw material gas in which hydrogen is excessive with respect to carbon monoxide, not only unreacted hydrogen and carbon monoxide but also the reaction product carbon dioxide is recycled to the synthesis gas generation system. A technique for reacting with the above-mentioned excess hydrogen to re-produce carbon monoxide has been disclosed (hereinafter referred to as "prior art 2").

[0010]

SUMMARY OF THE INVENTION The prior art 1 described above
Unreacted CO and H from the reaction gas_TwoTo separate
Is recycled to the reactor, so the C
O and H_TwoIs helping to increase the conversion rate. In addition,
In technology 2, unreacted CO and H _TwoOnly
But the reaction product CO_TwoAs a synthesis gas generation system
Because of recycling, the conversion rate of CO in the raw material gas
It can be further improved.

On the other hand, when DME is directly synthesized from H ₂ and CO, the stoichiometric reaction formula is 3CO + 3H ₂ → CH ₃ OCH ₃ (D
ME) + CO ₂ . Therefore, in order to carry out this synthesis reaction efficiently, it is desirable that the molar ratio of H ₂ and CO of the raw material gas supplied to the synthesis reactor be closer to 1: 1. However, as described above, the above (1) to
The three reactions of the formula (3) do not proceed 100% in the actual synthesis process.

That is, in the actual DME synthesis process, the reaction products 3 'of the reaction gas line 3 flowing out of the reactor R contain DME and CO _{2 as} reaction products and H ₂ and CO as unreacted gases. And the reaction intermediate C
H ₃ OH and H ₂ O are included.

Of these, the reaction intermediate CH ₃ OH
Number of H atoms contained in gas obtained by summing both H ₂ O and H ₂ O ×
The value of 2 is greater than the number of carbon atoms. This means that CH ₃ O
To count the H and H ₂ atoms each molecular formula of H and C O, the reaction product 3 'CH ₃ OH and between H ₂ O production ratio to be seen always true that independent of contained in. Therefore, it is clear from the input / output mass balance of the reactor R that the molar concentration of CO flowing out of the reactor R as an unreacted gas is always higher than the molar concentration of H ₂ and is excessive. Therefore, it is natural that the purged recycled gas 7
CO in the unreacted gas in a 'is adapted to always overreact those quantitatively against H ₂ in the unreacted gas. Such a recycled gas 7 having an excessively high CO molar concentration.
'Continuing to supply the raw material gas line 2, a raw material gas 2' a H ₂ / CO molar ratio of decreases monotonically, since H ₂ / CO molar ratio of the raw material gas 2 'continues to decrease, DM
E production efficiency will be significantly impaired.

Therefore, in order to ideally perform the DME synthesis reaction of the formula (4), the molar concentration of H ₂ with respect to CO of the makeup gas 1 ′ constituting the main component of the raw material gas 2 ′ is appropriately increased, and A method of adjusting the molar concentration of H ₂ : CO of the gas 2 ′ to 1: 1 is conceivable.

However, it is extremely difficult to always adjust the composition of makeup gas 1 'in accordance with the above-mentioned composition fluctuation of recycle gas 7a'. The reason is, H ₂ / CO molar ratio of recycle gas 7 'or 7a' is dependent on factors such as variations in the progress (depending on the reaction temperature and reaction pressure, etc.) and recycled gas 7a 'of DME synthesis reaction Is done. Therefore, extremely high-level process control is required to control the above factors, and the development of a separate control technique is required. In addition, the H ₂ / CO molar concentration ratio of the recycle gas 7 ′ or 7 a ′ frequently fluctuates due to the above factors. Therefore, it is extremely difficult to frequently adjust the H ₂ / CO molar concentration ratio of the makeup gas 1 ′ according to the composition fluctuation of the recycled gas 7a ′. This is because the make-up gas 1 'is usually generated by coal gasification or natural gas reforming, so that the lot size of the DME synthesis gas is extremely large as compared with the flow size of the recycled gas 7a'.

Accordingly, an object of the present invention is to set the H ₂ / CO molar concentration ratio of the recycle gas 7a ′ to a predetermined value.
A method for quick and easy adjustment is devised, and this method is applied to the adjustment of the H ₂ / CO molar concentration ratio of the recycle gas 7a ′. Thus, the above-described problem is solved, and the raw material gas 2 ′
By constantly adjusting the H ₂ / CO molar concentration ratio to 1: 1 and, as a result, improving the conversion of CO and H ₂ of the feed gas 2 ′,
An object of the present invention is to provide a method for efficiently manufacturing DME.

[0017]

SUMMARY OF THE INVENTION From the above-mentioned viewpoints, the present inventors have conducted intensive studies in order to develop a method for producing dimethyl ether which can effectively utilize a synthesis raw material gas and has high productivity. As a result, the following findings were obtained.

As a measure for solving the above-mentioned problems, the present inventor first maintains the DME production process as technically as possible as possible, and for that purpose, adjusts the composition of the makeup gas. In particular, the present invention has devised a method that can easily adjust the H ₂ / CO molar concentration ratio of the recycle gas to a predetermined value without any problem even when the adjustment is performed exceptionally. Second, in order to use makeup gas resources as efficiently as possible, the purge amount of the recycle gas should be as small as possible, and the H ₂ / CO molar concentration ratio of the recycle gas should not be changed.
We have devised a method that can adjust the molar ratio quickly, accurately and technically stably.

As a method for satisfying the above two conditions, the present inventor newly inserts and installs a shift reaction step represented by the following equation (3) in the middle of the above-mentioned recycle gas line 7a, The surplus CO in the recycle gas 7a 'described above is supplied as a CO source. Thus, the CO concentration of the recycled gas is reduced, and the H ₂ concentration is increased.

H ₂ O + CO → H ₂ + CO ₂ (3) Then, by adjusting the shift reaction conditions, the H ₂ / CO molar concentration ratio of the recycle gas is set to a predetermined constant value. Can be easily adjusted. H ₂ O in shift reaction
What is necessary is just to supply steam.

The present invention has been made on the basis of the above-mentioned findings, and the method for producing dimethyl ether according to the present invention uses a mixed gas containing at least carbon monoxide and hydrogen as a main raw material, and performs a catalytic reaction on the main raw material. To form dimethyl ether. In a method for producing dimethyl ether by circulating a recycle gas containing carbon monoxide and hydrogen remaining in the obtained reaction product and reusing it as part of the main raw material, contacting steam with the recycle gas The ratio between the molar concentration of hydrogen and the molar concentration of carbon monoxide in the recycled gas is adjusted to a predetermined value by a so-called shift reaction of reacting carbon monoxide in the recycled gas with the steam. The method is characterized in that the recycled gas adjusted to a value is reused as a part of the main raw material.

[0022]

Next, the present invention will be described with reference to the drawings. FIG. 1 shows a flow sheet of an example of an apparatus for producing dimethyl ether for carrying out the method of the present invention.
This production apparatus includes a reactor R1 for DME synthesis and a shift reactor R2 for adjusting the components of the recycle gas 7b ', a methanol / water separator S1, and an unreacted gas separator S.
2 and a CO ₂ separator S3. This manufacturing apparatus is different from the conventional manufacturing apparatus shown in FIG.
2 is further added.

A raw material gas 2 'is supplied from the bottom of the reactor R1. Raw material gas 2 ', make-up gas 1 consisting of H ₂ and CO having a predetermined H ₂ / CO molar ratio' and, in the shift reactor R2, is renovated into a predetermined H ₂ / CO molar ratio Recycling It is a mixed gas with the gas 11 '.

The recycle gas 7 is supplied to the shift reactor R2.
b 'and steam 14'. Chemical reaction formula (3)
Based on the formula: H ₂ O + CO → H ₂ + CO ₂ , CO in the recycle gas is oxidized with H ₂ O to generate H ₂ and CO. It is particularly important in this invention to adjust the generated H ₂ / CO molar ratio to a predetermined constant value. That is, the H ₂ / CO molar concentration ratio of the reformed recycle gas 11 ′ is such that the H ₂ / CO molar concentration ratio of the mixed gas mixed with the makeup gas 1 ′, that is, the H ₂ / CO molar concentration ratio of the raw material gas 2 ′ is 1
Adjust so that Thus, the recycle gas 11 'H ₂ / CO molar ratio of the make-up gas 1' H ₂ of
/ CO molar concentration ratio and flow rate, and recycled gas 7
It is easily calculated from the flow rate of b '. Therefore, by determining an appropriate shift reactor and reaction conditions, the H ₂ / CO molar concentration ratio of the recycle gas 11 ′ can be adjusted to a target value.

On the other hand, the reaction formula (3): H ₂ O + CO → H ₂
The so-called shift reaction represented by + CO ₂ is an industrially established technique. Therefore, the target value H ₂ / C
Obtaining a recycle gas 11 'having an O molar concentration ratio can be easily performed by conventional techniques. That is, for example, using a Cr—Fe-based catalyst, the reaction temperature: 330 to 50
A condition of 0 ° C. or a condition of a low-temperature shift reaction (about 200 to 300 ° C.) using a Cu—Zn—Al-based catalyst may be employed.

In the shift reaction which is carried out industrially,
Depending on the required hydrogen purity, a one-stage or two-stage process is applied. In the one-step method, when a Cr—Fe catalyst is used, the reaction can be performed up to a residual CO concentration of about 2 to 3%. When a Cu—Zn-based catalyst is used, the residual CO concentration is 0.1 to 0%. It is possible to carry out gas up to about 0.5%. When high-purity hydrogen is required, the shift reaction is often performed in two stages. In this case, a high-temperature catalyst is generally used in the first stage, and a low-temperature catalyst is generally used in the second stage.

In the shift reaction applied to the present invention, a high reaction conversion rate is not required, and hydrogen gas may be produced by reacting about several to ten and several percent of CO gas in the recycle gas with steam.

The raw material gas 2 'whose H ₂ / CO molar concentration ratio has been adjusted to 1 by the above-described method is supplied to the reactor R1. The type of the reactor R1 may be any of a fixed bed type, a fluidized bed type and a slurry bed type. In particular, the slurry bed type is desirable because the temperature in the reactor is uniform and the amount of by-products is small.

As for the catalyst, a methanol synthesis catalyst and a methanol dehydration catalyst are used, and an aqueous shift reaction catalyst is added as appropriate in order to proceed with each of the above reactions (1) to (3) to synthesize DME. These catalysts are mixed and used.

As the methanol synthesis catalyst, copper oxide-zinc oxide, zinc oxide-chromium oxide, copper oxide-zinc oxide / chromium oxide, copper oxide-zinc oxide / alumina, etc., which are usually used industrially, are used. As a methanol dehydration catalyst, acid-base catalysts such as γ-alumina, silica, silica
Alumina, zeolite, or the like is used. Here, as the metal oxide component of the zeolite, an oxide of an alkali metal such as sodium and potassium, and an oxide of an alkaline earth metal such as potassium and magnesium are used. Since the methanol synthesis catalyst has shift catalytic activity, it can also serve as a water gas shift catalyst. As described above, an alumina-supported copper oxide catalyst can be used as both a methanol dehydration catalyst and a water gas shift catalyst.

The mixing ratio of the above three catalysts does not need to be particularly limited, and may be appropriately selected according to the type of each component or reaction conditions. However, the methanol dehydration catalyst is usually about 0.1 to 5 and preferably about 0.2 to 2 with respect to the methanol synthesis catalyst 1 in terms of weight ratio, and the water gas catalyst is 0.1 to 0.2.
About 2 to 5, preferably about 0.5 to 3 are mixed.
When the methanol synthesis catalyst and the water gas shift catalyst are made of the same substance, and the methanol synthesis catalyst also serves as the water gas shift catalyst, the total amount of both catalysts is used.

Regarding the form of the catalyst, when a slurry bed type reactor is used, the average particle size is 300 μm or less, preferably 1 to 200 μm, more preferably 10 to 150 μm.
What is crushed to the extent is good. In order to use it more effectively, the above-mentioned mixed powder is appropriately compacted and molded, and pulverized again,
Use the one prepared to the above particle size.

When using a slurry bed type reactor, the medium oil must maintain a stable liquid state under the reaction conditions. For example, aliphatic, aromatic and alicyclic hydrocarbons, alcohols, ethers, esters, ketones and halides, and mixtures of these compounds are used. The amount of the catalyst to be present in the solvent can be appropriately determined depending on the type of the solvent, the reaction conditions, and the like.
About 1 to 50% by weight based on the solvent is desirable.

As the reaction conditions in the slurry bed type reactor, the reaction temperature is preferably in the range of 150 to 400 ° C.,
In particular, the temperature is preferably in the range of 250 to 350 ° C. Even if the reaction temperature is lower than 150 ° C or higher than 400 ° C,
The conversion rate of CO in the raw material gas decreases. The reaction pressure is 1
Within the range of 0 to 300 Kg / cm ² G, particularly preferably 2
The range is preferably from 0 to 70 Kg / cm ² G. Reaction pressure is 1
0 kg / cm ² less the conversion of CO is less than G, whereas if greater than 300 Kg / cm ² G, except that the reactor becomes a special, since it takes a great deal of energy for Noborinetsu economic Not. The space velocity (the supply rate of the raw material gas in a standard state per kg of the catalyst) is 100 to 500.
00Nl / kg · h is desirable, especially 500-3000
0 Nl / kg · h is desirable. Space velocity 50,000N
If it is greater than 1 / kg · h, the conversion of CO is low, while if it is less than 100 Nl / kg · h, the reactor becomes extremely large and is not economical.

Thus, the reaction gas 3 'obtained in the reactor R1 contains not only DME but also CO ₂ , CO, H ₂ , H ₂ O
And CH ₃ OH, as well as other reaction by-products such as CH ₄ and impurities contained in the raw material gas.
The component composition of the reaction gas is usually DME: 3 to 25%, C
_{O 2: 3~25%, CO:} 20~50%, H 2: 20~
_{50%, CH 3 OH: 0.5~3} %, H 2 O: 0.1~
0.5% and others: about 5% or less.

The above reaction gas 3 'is passed through a separator S1 and C
Separating the H ₃ OH and H ₂ O. This separation means uses, for example, a condensation temperature difference. When the reaction gas 5 ′ from which CH ₃ OH and H ₂ O have been separated is further cooled, DME is condensed, and the fluid 6 ′ in which CO ₂ is dissolved is passed through the separator S3. In the separator S3, for example, CO ₂ is separated by a distillation method to obtain DME.

On the other hand, in the separator S2, DME and CO
_TwoIs separated into the unreacted gas H_TwoAnd C
O remains. This gas phase flow, ie, the recycled gas
The main component of 7 'is H_TwoAnd CO. And this resai
H of Kurgas 7 '_Two/ CO molar concentration ratio is as follows:
H_Two/ CO molar concentration ratio is always smaller
You. As described above, the reason is as follows.
The reaction intermediate of the E synthesis includes H to CO_TwoBut always
This is because it is included in the surplus. Therefore, the H of the source gas _Two/
Even if the CO molar concentration ratio is 1, recycled gas
H of 7b '_Two/ CO molar concentration ratio is always less than 1.
Become. In this way, always try to move in the direction of CO concentration
H of the recycle gas 7 'flowing out of the reacting reactor R1
_Two/ CO molar concentration ratio in reactor R2 steam reforming
And H_TwoAdjust the / CO molarity ratio.

After purging a part of the recycle gas 7 ', the recycle gas 7b' is supplied to the reactor R2. The reactor R2, 'supplies the recycle gas 7b' steam 14 H ₂ / CO molar ratio of, is adjusted to less than a predetermined target value. In reactor R2, as described above, by controlling the shift reaction conditions, H ₂ / CO molar ratio of the gas after mixing 'the make-up gas 1' recycle gas 11 is always 1 Adjust as follows.

As described above, the DME synthesis reactor R
The H ₂ / CO molar concentration ratio of the source gas 2 ′ supplied to 1 can always be adjusted to 1.

[0040]

Next, the method of the present invention will be described in detail with reference to examples. The method of the present invention was carried out using the apparatus for producing dimethyl ether of the flow sheet shown in FIG. The reactor R1 is a suspended slurry bed type reactor having an inner diameter of 90 mm and a height of 2000 mm. In a reactor R1, 7600 g of a solvent: n- hexadecane, a powdery catalyst (a copper-zinc-aluminum-based catalyst having an average particle size of about 50 microns and a copper-aluminum-based catalyst in a weight ratio of 2:
1100 g) was added to form a suspended slurry. From the bottom of the reactor R1, a raw material gas 2 ′ obtained by mixing a make-up gas 1 ′ composed of H ₂ and CO and a recycled gas 7c ′ was supplied to the slurry reaction bed.

[DME synthesis conditions] Make-up gas 1 '
Is a constant value of H ₂ / CO molar concentration ratio of 1: 1 and 53Nl
/ A constant flow rate of min, 'is reacted with steam in the shift reactor R2, and the resulting preform gas 11' recycle gas 7b the H ₂ / CO molar ratio of 1: adjusted to a constant value of 1, a constant flow rate : 106 Nl / min. Makeup gas 1 'and reform gas 11'
Were mixed to prepare a raw material gas 2 ′. In this way, the H ₂ / CO molar concentration ratio of the raw material gas was adjusted to 1. From the above conditions, the supply rate (space velocity) of the raw material gas 2 ′ into the reactor R1 is 8673 Nl / kg catalyst · h. Then, the reaction temperature: 260 ° C., the reaction pressure: 50 Kg / cm ²
G performed DME synthesis.

The reaction conditions of the reform gas 11 'in the shift reactor R2 are as follows. A Cu-Zn catalyst was used as the shift reaction catalyst. The type of the shift reactor is a fixed bed type. This catalyst is 150-300 ° C
In order to show the shift reaction activity, the reaction was controlled so that the shift reaction did not proceed excessively by controlling the temperature of the shift reactor, and the target shift reaction rate was controlled.

That is, for example, the CO concentration per unit volume in the recycled gas is 50 mol, and the H ₂ concentration is 40 mo.
l, half of the concentration difference, in this case 5 mol of CO reacts with 5 mol of steam by the shift reaction to produce CO ₂ and H _2, and if CO ₂ and H ₂ are produced, the unit volume in the recycle gas exiting the shift reactor CO concentration per unit is 45
mol and H ₂ concentration are also 45 mol, and the H ₂ / CO ₂ concentration ratio is 1: 1. Therefore, in this case, if 5 mol of steam per unit volume in the recycle gas is supplied to the shift reactor, the target shift reaction can be controlled.

[Raw material gas (H_Two+ CO) Theoretical conversion rate
Calculation result] Regarding the DME synthesis reaction (reaction formula (4)),
Of raw material gas supplied to the reactor _Two/ CO molar concentration ratio changes
Of raw material gas (H_Two+ CO) equilibrium reaction conversion
The theoretical calculation result of the ratio is shown in FIG. Calculation is at 280 ° C
The force was performed under the conditions of 30 and 50 atm, respectively.
But in any case H_Two/ CO molar concentration ratio is 1:
When the reaction conversion rate is 1, the reaction conversion rate becomes maximum and H_Two/ CO molar concentration
When the degree ratio deviates from 1: 1, the reaction conversion rate decreases sharply.
You can see that In actual DME synthesis reaction, reaction conversion
Since the rate does not reach this theoretical value, the decrease in the actual conversion rate
It will be remarkable.

As a comparative example with respect to the method (embodiment) of the present invention, a DME based on the flow sheet of the conventional dimethyl ether production apparatus shown in FIG. 3, that is, the case where the shift reactor R2 is removed from the flow sheet of FIG. Was manufactured. Table 1 shows the DME synthesis conditions in the comparative example.

[0046]

[Table 1]

That is, under the conditions shown in Table 1, only the shift reaction was removed from the flow sheet of FIG. 1, but the adjustment of the H ₂ / CO molar concentration ratio in the recycle gas was not performed. H ₂ / CO molar concentration ratio of 1: 1
Is maintained at a constant value of H ₂ / H ₂ in the recycle gas as the reaction proceeds in the unreacted gas recycle state.
The CO molar concentration ratio becomes a value smaller than 1 and (H ₂ + C
O) The reaction conversion rate also decreases.

Table 2 shows a comparison of the composition of the recycled gas with and without the shift reactor.

[0049]

[Table 2]

[0050] When there is a shift reactor, H ₂ / CO molar ratio of the raw material gas 2 'entering the reaction, the make-up gas, the recycle gas co H ₂ / CO molar ratio of 1.0. On the other hand, when there is no shift reactor, the H ₂ / CO molar concentration ratio in the recycle gas is 40.1 / 5
5.9 = 0.72, therefore, H ₂ / CO molar ratio of H ₂ / CO molar ratio of the raw material gas 2 after having been mixed with the make-up gas is 1.0 'includes a make-up gas Since the flow ratio with the recycle gas is 1: 2, the result is about 0.8.

Table 3 shows the reaction results of the experiments with and without the above-mentioned shift reactor (Example) and without (Comparative Example).

[0052]

[Table 3]

It can be seen that the conversion rate of the CO reaction and the conversion rate of the H ₂ reaction are better in the example than in the comparative example.

[0054]

As described above, according to the present invention, a shift reaction step is newly provided in the middle of the recycle gas line, and the H ₂ / CO _{2 of the} recycle gas line is provided.
The molarity ratio could be adjusted to any given value. Accordingly, the molar concentration of H ₂ : CO of the raw material gas for DME synthesis prepared by mixing the makeup gas and the above-mentioned recycled gas is influenced by the progress of the DME synthesis reaction, the amount of the recycled gas and the like. It is possible to stably and easily control 1: 1. As a result, it is possible to provide a method for producing dimethyl ether capable of stably controlling the operation of not only the DME synthesis reactor but also the raw material gas supply system, resulting in an industrially useful effect.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing an example of a dimethyl ether production apparatus for carrying out the dimethyl ether production method of the present invention.

FIG. 2 DME synthesis reaction: 3CO + 3H ₂ → CH ₃ OC
4 is a graph showing the theoretical calculation results of the equilibrium reaction conversion rate of the raw material gas (H ₂ + CO) when the H ₂ / CO molar concentration ratio of the raw material gas changes with respect to H ₃ + CO ₂ .

FIG. 3 is a flow sheet showing an example of a dimethyl ether production apparatus for implementing a conventional dimethyl ether production method.

[Explanation of symbols]

Reference Signs List 1 makeup gas line 1 'makeup gas 2 raw gas line 2' raw gas 3 reaction gas line 3 'reaction product 4 methanol / water line 4' methanol / water 5 reaction gas (including DME, CO ₂ ) line 5 ' Reaction product (including DME, CO ₂ ) 6 DME, CO ₂ line 6 ′ DME · CO ₂ 7, 7a, 7b Recycle gas line 7 ′, 7a ′, 7b ′ Recycle gas 8 CO ₂ line 8 ′ CO ₂ 9 DME line 9'DME 10 purge line 10 'purge 11 recycle gas line 11' recycle gas (H ₂ / CO molar ratio adjusted) 12 CO line 12'CO 13 H ₂ line 13'H ₂ 14 steam line 14 'steam R Reactor (DME synthesis) R1 Reactor (DME synthesis) R2 Reactor (shift reaction) S1 Methanol / water separator S2 Not yet Response gas separator S3 CO ₂ separator

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Keiji Tomura 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd.

Claims (1)

[Claims] 1. A mixed gas containing at least carbon monoxide and hydrogen is used as a main raw material, and the main raw material is subjected to a catalytic reaction to produce dimethyl ether, which contains carbon monoxide and hydrogen remaining in the reaction product. In the method for producing the dimethyl ether by recycling a part of the main raw material by circulating a recycled gas, in the method, steam is brought into contact with the recycled gas to react carbon monoxide in the recycled gas with the steam. The shift reaction adjusts the ratio between the molar concentration of hydrogen and the molar concentration of carbon monoxide in the recycled gas to a predetermined value, and then recycles the recycled gas adjusted to the predetermined value to a part of the main raw material. A method for producing dimethyl ether, characterized in that it is utilized.