JP3447494B2 - Method for producing dimethyl ether - Google Patents

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 As a technique for directly producing dimethyl ether (DME) from a synthesis gas containing carbon monoxide and hydrogen as main raw materials, a technique in which a raw material gas is passed through a fixed bed catalyst layer and reacted is disclosed ( For example, Japanese Patent Laid-Open No. 2-280
No. 836, Japanese Patent Laid-Open No. 3-8446). Further, a technique of synthesizing dimethyl ether in a high yield by allowing a raw material gas to pass through a slurry reactor in which catalyst fine particles are suspended in a high boiling point medium oil to react with each other is also disclosed (for example, Japanese Patent Laid-Open Publication No. Hei 10 (1999) -242242). 3-52835 and Japanese Patent Publication No. 7-577
39, US Department of Energy report: DOE / PC /
90018-T7).

In the above-mentioned method for directly synthesizing dimethyl ether from carbon monoxide and hydrogen, hydrogen is generated from carbon monoxide represented by the following formulas (1), (2) and (3). Methanol synthesis, dimethyl ether synthesis produced by dehydration reaction from the synthesized methanol, and water produced as a byproduct of the dimethyl ether synthesis reacts with carbon monoxide to produce hydrogen 3
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, as shown by the reaction formula of the following formula (4), hydrogen and carbon monoxide are converted into dimethyl ether. Equivalent to carbon dioxide will be produced.

3CO + 3H ₂ → CH ₃ OCH ₃ + CO ₂ ---------- (4) However, the reactions of the above formulas (1) to (3) are equilibrium reactions controlled by temperature and pressure. Therefore, in the actual synthetic 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% conversion of the raw material hydrogen and carbon monoxide as represented by the formula (4) does not occur, and the gas flowing out from the reactor contains DME and carbon dioxide, which are reaction products, as well as It includes unreacted hydrogen and carbon monoxide. Therefore, normally, the unreacted hydrogen and carbon monoxide are not discarded, but after being separated from the product, they are recycled to the reactor and effectively used as a part of the raw material gas. The gas flowing out from the reactor further contains reaction intermediates such as methanol and water. However, conventionally, carbon dioxide as a reaction product has been discarded after being separated from DME. When carbon dioxide is discarded, it is environmentally unfavorable such as global warming, and carbon resources in raw materials are discarded without being used.

FIG. 2 shows the DOE / PC / 90008-T7.
2 shows a flow diagram of an example of a conventional DME manufacturing process disclosed in. This apparatus comprises 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, and a makeup gas line 1 for supplying new raw material gas and a recycle gas line 7a for circulating and supplying unreacted CO and H ₂ are circulated to the raw material gas line 2. Are connected. Make-up gas 1 'is mainly of CO gas and H ₂ gas. From the top of the reactor R, the reaction gas line 3 for discharging the reaction product 3 ′ is connected to the inlet of the methanol / water separator S1, and the methanol of the methanol / water separator S1 and the methanol at the outlet of the water 4 ′ are methanol. A water line 4 and a reaction gas line 5 at the outlet of the reaction product 5 '. The other end of the reaction gas line 5 is connected to the inlet of the unreacted gas separator S2, and the other end of the recycled gas line 7a is connected to the outlet of the recycled gas 7'of the unreacted gas separator S2. A purge line 10 for extracting a part of the recycled gas 7'is connected from the connection between the recycled gas lines 7 and 7a. The DME and CO ₂ 6 'outlet of the unreacted gas separator S2, DME · C O ₂ line 6 is connected, DME ·
The other end of the CO ₂ line 6 is connected to the CO ₂ separator S3,
Then, the CO ₂ 8 'exit of CO ₂ separator S3 CO ₂
Line 8 and DME line 9 at exit DME 9 '
Are connected respectively. In the CO ₂ separator S3, CO ₂ is separated from DME, and CO ₂ is discarded.

As described above, in the conventional DME manufacturing technology (hereinafter referred to as the prior art), the methanol / water separator S1 first separates methanol and water 4'from the reaction product 3 ', and then the unreacted gas. Unreacted C in separator S2
The O and H ₂ separates the recycle gas 7 'mainly, by recycling it to the reactor R thereby improving the material utilization efficiency.

[0008]

In the above-mentioned prior art, since the unreacted CO and H ₂ are separated from the reaction gas and recycled to the reactor, the CO in the raw material gas is reduced.
It also helps to improve the conversion rate of H ₂ and H ₂ . However, the CO ₂ separated from the DME is discarded. When CO ₂ is released to the atmosphere in this way, it is not desirable for the environment such as the global warming phenomenon as described above, and the carbon resource in the raw material is discarded without being used, which is desirable for resource conservation. Absent.

On the other hand, it should be noted that H₂And CO
When directly synthesizing DME from the stoichiometric reaction formula
Is 3CO + 3H as shown in the equation (4).₂→ C
H ₃OCH₃(DME) + CO₂Is. Therefore, efficiency
In order to carry out this synthetic reaction,
Source gas H supplied₂And the molar ratio of CO is 1:
The closer it is to 1, the better. Therefore, H of the source gas₂When
The precondition is that the molar ratio with CO should be close to 1: 1.
And then the above CO₂Must stop the disposal of
Yes.

Therefore, an object of the present invention is to stop the disposal of carbon dioxide generated as a reaction product and to remove this CO ₂ when producing dimethyl ether directly by using carbon monoxide and hydrogen as main raw materials. An object of the present invention is to provide a method for effectively using dimethyl ether.

[0011]

The present inventor has earnestly studied to develop a method for producing dimethyl ether from the above viewpoint.

In order to solve the above problems, the present inventor
First, the following measures were taken. First, as mentioned in FIG.
Recycled gas containing unreacted gases CO and H ₂ 7
a'is used as a part of a raw material gas for DME synthesis, and secondly, C which is a main component of makeup gas.
That is, a saturated hydrocarbon gas such as natural gas is used as a raw material for producing O and H ₂ .

The reason for the first reason is to effectively use the raw material gas resource. The reason for the second reason will be explained. When reforming hydrocarbon gas to generate H ₂ and CO, saturated hydrocarbon gas can be reformed into H ₂ and CO most efficiently by using saturated hydrocarbon gas. Therefore, we decided to use saturated hydrocarbon gas. Next, the reforming of the saturated hydrocarbon gas is performed by, for example, steam, C
O _2, oxygen (air), or carried out in combination thereof, the chemical reaction formula (5) below, (6) and (7)
This is illustrated by the formula.

CH ₄ + H ₂ O → 3H ₂ + CO ---------------- (5) CH ₄ + CO ₂ → 2H ₂ + 2CO ----------- ----- (6) 2CH ₄ + O ₂ → 2CO + 4H ₂ ---------------- (7) From formulas (5), (6) and (7), steam, It can be seen that the H ₂ / CO molar concentration ratio produced is usually 1 or more by reforming using either CO ₂ or oxygen (air). Therefore, H of makeup gas
_In order to bring the molar concentration ratio of ₂ and CO close to 1: 1,
It is advantageous to reform the saturated hydrocarbon gas according to the formula (6) as much as possible. Therefore, when CO ₂ is recycled to be used for producing makeup gas, it is found that it is suitable to use saturated hydrocarbon gas as the main raw material of makeup gas.

As described above, the molar concentration ratio of H ₂ and CO in the reform make-up gas is increased to 1: 1.
The reason for choosing to approach is as follows. As mentioned above, when DME is directly synthesized from CO and H ₂ ,
In the actual synthetic process, the reactions represented by the formulas (1), (2) and (3) occur, and none of them proceed 100%. Therefore, the reactor R (Fig. 2
In the reaction product 3'flowing out from the reference product), reaction products DME and CO ₂ , unreacted gases H ₂ and C are contained.
O, and reaction intermediates CH ₃ OH and H ₂ O are included. Of these, the reaction intermediate CH ₃ OH
And between H ₂ O items H atoms contained both in the total gas of /
A value of 2 is greater than the number of carbon atoms. This is 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 inlet / outlet mass balance for the reactor R that the CO molar concentration flowing out of the reactor R as unreacted gas is always higher than the H ₂ molar concentration and is excessive. Therefore, of course, the recycled gas 7 after purging
CO in the unreacted gas in a'is always in reaction equivalent excess with respect to H ₂ in the unreacted gas. Recycle gas 7 with an excessive CO molar concentration
If a'is continuously supplied to the raw material gas line 2, the raw material gas 2 '
Since the H ₂ / CO molar concentration ratio of is decreased, the production efficiency of DME is significantly impaired.

[0016] Therefore, in the (4) in order to ideally perform DME synthesis reaction formula, proper molar concentration of H ₂ to CO of 'make-up gas 1 which constitutes the main body of' the source gas 2 excess It is desirable that the H ₂ : CO molar concentration of the raw material gas 2 ′ be as close as possible to 1: 1. The above is the reason for the second measure.

As a method of implementing the above two measures and solving the above problems, CO ₂ which has been conventionally separated after being separated by the separator S3 and discarded is reacted with a saturated hydrocarbon gas to form a part of the makeup gas. I focused on using it. That is, originally, when CO and H ₂ are produced by reforming a hydrocarbon gas such as methane, a reformer is newly provided to the reformer, and when a coal gasification gas or the like is used, a CO is previously discarded. ₂ may be recycled to this reformer, and the saturated hydrocarbon gas may be reformed with CO ₂ by the reaction of the above formula (6).

The present invention was made based on the above findings, and the method for producing dimethyl ether of the present invention uses a mixed gas containing at least carbon monoxide and hydrogen as a main raw material, and the main raw material is subjected to a catalytic reaction. By producing dimethyl ether, by circulating a gas containing carbon monoxide and hydrogen, which remains in the product produced in the synthesis reaction of this dimethyl ether, the dimethyl ether is reused as a part of the main raw material to produce dimethyl ether. The manufacturing method is characterized in that the following steps (a) and (b) are further added. In the above, the steps (a) and (b) are: (a) a step of preparing a mixed gas as a main raw material by a reformer using a saturated hydrocarbon gas as a raw material, and (b) a dimethyl ether Carbon dioxide coexisting in the product produced in the synthesis reaction is separated, and this separated carbon dioxide is circulated to the reformer in the step (a) to be used as a part of the main raw material for dimethyl ether synthesis. It is a process. Advance reaction product DME · C
By cooling with O ₂ separator, after separation into a gas comprising (1) condensed dimethyl ether and the carbon dioxide dissolved in it (2) and the carbon monoxide circulation the hydrogen, the (b) It is desirable to perform the process.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 shows a flow sheet of an example of a dimethyl ether production apparatus for carrying out the method of the present invention.
In FIG. 1, R1 is a reactor for DME synthesis, and R2 is
Is a reformer of saturated hydrocarbon gas. The reformer R2 for saturated hydrocarbon gas is the reactor R1 for DME synthesis.
Is connected via the raw material gas line 2 and other lines. Hereinafter, this apparatus will be described along the flow from the reformer R2 make-up gas line (11, 14 and 15) to the reformer R2 and the reactor R1 to recover the purified and separated DME 9 ′. The saturated hydrogen gas 11 'is CO in the reformer R2.
₂ 14 'and / or water 15' to produce a reforming reaction product 16 ', and the reforming reaction product 16' is dehydrated in the water separator S4 to separate the separated water 1
7'is a dehydration line 17 and a makeup water line 1
It is recycled to 5. Reform reaction product 1 flowing out from the water separator S4
8'is decarbonated by the CO ₂ separator S5 and the CO ₂ separator S5
The CO ₂ 19 ′ separated in 5 flows into the CO ₂ recycle line 8 through the decarbonation line 19. The CO ₂ recycle line 8 is a line in which CO _2, which is one of the reaction products produced by the DME synthesis reaction, is separated from DME and recycled. CO ₂ CO ₂ 19 that has flowed into the recycle line 8 'merges makeup CO ₂ line 14.

As described above, the reformed gas produced by the reformer R2 is dehydrated and decarbonated and purified,
DME synthesis gas (makeup gas for DME synthesis) 1 '
become. Next, make-up gas 1'for DME synthesis
Is the recycled gas line 7a of the DME synthesis line DL
Of the unreacted gas (CO and H ₂ ), which is a main component, is mixed with the recycled gas 7 a ′ and becomes a raw material gas 2 ′ of DME. The raw material gas 2'is supplied from the bottom of the reactor R1.
After the reaction of synthesizing DME in the reactor R1, the reaction gas line 3 for discharging the reaction product 3 ′ is connected to the inlet of the methanol / water separator S1 from the top of the reactor R1. The methanol / water 4 ′ outlet of the water separator S1 is connected to the methanol / water line 4, and the reaction product 5 ′ outlet is connected to the reaction gas line 5.
The reaction gas line 5 is connected to the inlet of the unreacted gas separator S2, and the gas containing the unreacted gas and a small amount of impurity gas separated by the unreacted gas separator S2 becomes a recycled gas 7 '. A part of the recycled gas 7'is withdrawn (purged) in the middle for adjusting the system internal pressure, and is flown into a purge line 10 branched from the recycling line. The recycle line 7 becomes a recycle line 7a after being separated from the purge line 10, and most of the recycle gas 7 ′ 7a ′ passes through the recycle line 7a,
Mix with make-up gas 1'of DME synthesis. The raw material gas 2 ′ thus mixed is supplied from the bottom of the reactor R1. On the other hand, the DME and CO ₂ 6'purified by the unreacted gas separator S2 pass through the DME / CO line 6 to produce CO ₂
Enter the separator S3. The DME 9 purified by separating CO ₂ 8 ′ by the CO ₂ separator S3 is recovered as a product through the DME line. When a very small amount of methanol and water are mixed, they can be separated by a method such as distillation, if necessary. CO ₂ 8 separated by the CO ₂ separator S3 'is recycled without disposal. CO ₂ recycled is CO
₂ Through the recycle line 8, the reformer R2 is mixed with the CO ₂ gas 14 'supplied as makeup gas. The CO ₂ gas 14 'thus mixed is used to reform the saturated hydrocarbon gas 11'.

In the embodiment described above, the reformer R2
The makeup gas supplied to the
11 'and CO₂14 'and / or water 15',
There are three cases in all. That is, Case 1: Saturated carbonization
Hydrogen gas and CO₂Case 2: Case 2: Saturated hydrocarbon gas
In case of gas and water, Case 3: Saturated hydrocarbon gas, CO ₂
And water. DM for which case
Production efficiency of E synthesis, H of recycled gas 7a '₂/ CO
Molar concentration ratio concentration and flow rate, and saturated hydrocarbon gas
From the species composition ratio, etc.,₂: C
It is suitable to make the molar concentration ratio of O as close to 1: 1 as possible.
Then, you can decide the case to be judged.

Next, the operating conditions of the reformer R2 and the reactor R1 will be described. [Operating Conditions of Reformer R2 of Makeup Gas 1 ′] The reformer R2 may be either an internal heat type or an external heat type. In particular, the internal heat type does not require a burner or a steam generator, which is desirable from the viewpoint of saving construction costs. On the other hand, the external heat type can downsize the reactor (tube).

Regarding the catalyst, a known supported Ni catalyst can be used in order to promote the respective reactions (5) and (6) to improve the conversion rate of the saturated hydrocarbon gas. An oxide such as Al ₂ O ₃ or SiO ₂ can be used. Furthermore, by modifying the above catalyst with a noble metal such as Rh, Pd, Ru, Pt, etc., a high effect is exhibited in improving the catalytic activity and suppressing carbon deposition.

The particle size and morphology of the catalyst can be arbitrarily selected as long as the pressure loss is small and the contact with gas and the heat transfer property are kept good. For example, a columnar shape, a cylindrical shape, or a spherical shape can be used.

The reforming temperature is preferably in the range of 400 to 1100 ° C. If the temperature is lower than 400 ° C, the reaction does not proceed sufficiently, while if it is higher than 1100 ° C, the reactor (tube)
Is required to have a high degree of heat resistance, and a large amount of heat must be applied, which is not desirable.

The reforming pressure can be arbitrarily selected depending on the type of reaction, but considering the heat resistance and pressure resistance of the reactor (tube), it is preferably within the range of 0 to 50 kg / cm ² G. The superficial velocity is preferably 50,000 to 500,000 h ⁻¹ . When greater than 500,000 ^-1, the conversion is lowered, while when less than 50,000 h ^-1, a large reactor is required.

Thus, in the reforming reaction product 16 'obtained by the reformer R2, in addition to H ₂ and CO,
It contains unreacted saturated hydrocarbon gas, as well as CO ₂ , H ₂ O and impurities. The component composition of the reforming gas is usually CO: 20 to 50%, H ₂ : 20 to 50% and the H ₂ / CO molar concentration ratio is 1 to 3, and other components are the same as those of the reformer make-up gas. Change depending.

Water in the reforming reaction product 16 'is separated by cooling the reaction gas, and CO _{2 is} separated by a method such as amine absorption and cooling. If the unreacted saturated hydrocarbon gas is supplied to the reactor R1 while remaining in the make-up gas 1'of DME synthesis as long as it is in a small amount as described above, it does not affect the DME synthesis reaction and the purge gas 10 There is no particular problem because the accumulation in the system can be prevented by adjusting the amount of '. Purge gas 10 'is reformer R
It can be returned to 2 and used again as a reaction raw material.

[Operating Conditions of DME Synthesis Reactor]: The reactor R1 may be of a fixed bed type, a fluidized bed type, or a slurry bed type. In particular, the slurry bed type is desirable because the temperature inside the reactor is uniform and the amount of by-products is small.

Regarding the catalyst, a methanol synthesis catalyst and a methanol dehydration catalyst are used for advancing the respective reactions (1) to (3) to synthesize DME, and an aqueous shift reaction catalyst is appropriately added.

As the methanol synthesis catalyst, usually used are copper oxide-zinc oxide, zinc oxide-chromium oxide, copper oxide-zinc oxide / chromium oxide, copper oxide-zinc oxide / alumina and the like. As the methanol dehydration catalyst, γ-alumina, silica, silica
Alumina and zeolite are used. Here, as the metal oxide component of zeolite, oxides of alkali metals such as sodium and potassium, and oxides of alkaline earth such as potassium and magnesium are used. In addition,
Since the methanol synthesis catalyst has a strong 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.

[0032]

Regarding the form of the catalyst, when a slurry bed type reactor is used, the average particle diameter is 300 μm or less, preferably 1 to 200 μm, more preferably 10 to 150 μm.
Good what was ground to a degree. In order to use it more effectively, the mixed powder is appropriately compacted, molded, and pulverized again,
The one prepared to the above particle size is used.

When using a slurry bed reactor, the medium oil must be one that maintains 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 catalyst to be present in the solvent can be appropriately determined depending on the type of solvent and reaction conditions, etc.
About 1 to 50% by weight is desirable with respect to the solvent.

The reaction temperature in the slurry bed reactor is preferably in the range of 150 to 400 ° C.,
In particular, the temperature is preferably within the range of 250 to 350 ° C. Whether the reaction temperature is lower than 150 ° C or higher than 400 ° C,
The conversion rate of CO in the raw material gas becomes low. Reaction pressure is 1
Within the range of 0 to 300 kg / cm ² G, particularly preferably 2
It is preferably in the range of 0 to 70 Kg / cm ² G. Reaction pressure is 1
0 kg / cm ² less and CO conversion rate of lower than G, whereas if greater than 300 Kg / cm ² G, except that the reactor becomes a special, not economical since it takes a great deal of energy for boosting . The space velocity (feed rate of the raw material gas in the standard state per 1 kg of catalyst) is 100 to 500.
00Nl / kg · h is desirable, especially 500 to 3000
Nl / kg · h is desirable. Space velocity is 50000Nl
If it is larger than / kg · h, the conversion rate of CO will be low,
On the other hand, if it is less than 100 Nl / kg · h, the reactor becomes extremely large, which is not economical.

Thus, in the reaction gas 3'obtained in the reactor R1, in addition to DME, CO ₂ , CO, H ₂ , H ₂ O
And CH ₃ OH, as well as 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 to 25%, CO: 20 to 50%, H ₂ : 20 to
_{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 the separator S1 to obtain C
Separate H ₃ OH and H ₂ O. This separation means utilizes, for example, the difference in condensation temperature. 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
_In the gas phase separated from ₂ , the unreacted gases H ₂ and C
O remains. The gas phase flow, that is, the main components of the recycled gas 7'are H ₂ and CO. Then, the H ₂ / CO molar concentration ratio of this recycled gas 7'is 2 '
Is always smaller than the H ₂ / CO molar concentration ratio of. The reason is, as described above, DM in the reactor R1.
The reaction intermediates of E synthesis, H ₂ is relative to CO, it is always contained in excess. Therefore, the source gas H ₂
/ CO molar ratio as was 1, H ₂ / CO molar ratio of recycle gas 7a 'is smaller than always 1. In this way, the H ₂ / CO molar concentration ratio of the recycled gas 7 ′ flowing out from the reactor R1 always tries to proceed in the direction in which CO is concentrated. Therefore, reformer R2
Makeup gas 1'H of DME synthesis supplied from H
_{As for the 2} / CO molar concentration ratio, it is desirable that the H ₂ / CO molar concentration ratio of the recycled gas 7 ′ be suppressed to be excessive CO by adjusting H ₂ to an appropriate excessive tendency.

[0039]

Next, the method of the present invention will be described in detail with reference to Examples. (Example) The method of the present invention was carried out using the apparatus for producing dimethyl ether shown in FIG.

A methane reformer was used as the saturated hydrocarbon gas reformer R2, and a bubble column reactor was used as the reactor R1 for the DME synthesis. The methane reformer R2, as the saturated hydrocarbon gas 11 'is a make-up gas, and supplying the 9.6Nl / min the 15.0Nl / min and CO ₂ and CH _4. The methane reformer R2 was operated at a temperature of 850 ° C. and a pressure of 1 Kg / cm ² G.

On the other hand, the bubble column reactor R1 for DME synthesis is
Reaction temperature: 280 ° C., pressure: 50 Kg / cm² Driving with G
did. In the bubble column reactor R1, n-he as medium oil is
Xadecane: Copper oxide-zinc oxide / aluminum to 7600 g
Powder consisting of a mixture of copper and copper oxide / alumina (2: 1)
Powdered catalyst: 1140 g was added to make a suspension. Bubble tower
Methanol in the reaction product 3'flowing out of the reactor R1
And water 4'are separated by a methanol / water separator S1,
The reaction product flowing out from the methanol / water separator S1
DME and CO in object 5 '₂6'to DME / CO₂Minute
Separation by separator S2 (condensing operation temperature: -40 ° C), unreacted
Purifies gas and recycles as recycled gas 7 '
It flowed to the gas line 7. Then, purge the specified amount.
Recycling gas 7a 'after recycling
Mixed with DME synthetic makeup gas 1'for use
A raw material gas 2'was prepared. On the other hand, the above DME / C
O ₂DME and CO separated by the separator S2₂Mixture with
From 6 ', CO₂CO in the separator S3₂8 separated, DM
E9 'was purified and recovered. On the other hand, the CO₂Separator S3
CO separated by₂8 was previously discarded, but this
In the invention of₂By line 8, the methane reformer
Armor R2 recycled to make-up CO₂
It was made to flow into the line 14. Thus, DME synthesis line
CO separated by DL₂Riff without discarding the 8 '
Effectively used as part of the makeup gas of Homer R2
I used it.

The amount of DME produced in this case is 16.8 mo.
It was 1 / h. And the DME carbon yield in this case is
51.0 based on methane reformer make-up gas
%Met. The DME carbon yield is defined by the following formula (8).

(DME carbon yield) = {(carbon number in produced DME) / (carbon number in make-up methane and make-up carbon dioxide at reformer inlet)} × 100 (%) ------- ----------------- (8) (Comparative Example) While it is within the scope of the present invention (Example), it is outside the scope of the present invention (Comparative Example) ) Was performed as follows. In the dimethyl ether production apparatus shown in FIG. 1, the CO ₂ 8 ′ separated by the CO ₂ separator S3 is not recycled to the methanol reformer R2, and all other operating conditions in the reform line RL and the DME synthesis line DL are implemented. A reaction experiment was conducted according to the example.

As a result, the DME equivalent to that in the embodiment is obtained.
The amount of CO ₂ in the make-up gas of the methane reformer required to obtain the produced amount was 15.0 Nl / min. The DME carbon yield in this case was 41.8% based on the makeup gas of the methane reformer.

As described above, according to the embodiment, it is not necessary to discard the CO ₂ generated in the DME synthesis line, and this CO ₂ is effectively used as a part of the makeup gas of the saturated hydrocarbon gas reformer. You can see that you can.

[0046]

As described above, according to the present invention, the CO ₂ generated in the DME synthesis line can be recycled to the saturated hydrocarbon gas reformer for effective use without being discarded. Therefore, environmental destruction such as global warming can be avoided. Further, since it can be used as a carbon source for DME synthesis, it also improves the carbon yield. INDUSTRIAL APPLICABILITY The present invention can provide a method for producing dimethyl ether having the above effects, and brings industrially useful effects.

[Brief description of 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 is a flow sheet showing an example of a dimethyl ether production apparatus for carrying out a conventional dimethyl ether production method.

[Explanation of symbols]

1 Makeup Gas Line 1'Makeup Gas 2 Source Gas Line 2'Source Gas 3 Reaction Gas Line 3'Reaction Product 4 Methanol / Water Line 4'Methanol and Water 5 Reaction Gas (Including DME, CO ₂ ) Line 5 ' Reaction product (including DME, CO ₂ ) 6 DME / CO ₂ line 6 ′ DME and CO ₂ 7, 7a Recycle gas line 7 ′, 7a ′ Recycle gas 8 CO ₂ recycle line 8 ′ Recycle CO ₂ 9 DME line 9 ′ DME 10 Purge line 10 'Purge gas 11 Saturated hydrocarbon gas line 11' Saturated hydrocarbon gas 14 Makeup CO ₂ line 14 'Makeup CO ₂ gas 15 Makeup water line 15' Makeup water 16 Reaction product line 16 'Reform Reaction product 17 Dehydration line 17 'Water 18 Reform reaction product line 18' Reform reaction product Product 19 Decarbonation line 19'CO ₂ R Reactor (bubble column reactor) R1 Reactor (bubble column reactor) R2 Reformer (CH ₄ reformer) S1 Methanol / water separator S2 DME / CO ₂ separator S3 CO ₂ separator S4 water separator S5 CO ₂ separator DL DME synthesis line RL remodeling line

─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Keiji Tomura 1-2 1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (56) References US Department of Energy Report DOE / PC / 90018-T7 (1993) ) (58) Fields surveyed (Int.Cl. ⁷ , DB name) C07C 41/01, 41/09 C07C 43/04

Claims (2)

(57) [Claims] 1. A mixed gas containing at least carbon monoxide and hydrogen is used as a main raw material, the main raw material is catalytically reacted to produce dimethyl ether, which remains in a product produced in the synthesis reaction of the dimethyl ether. In the method for producing the dimethyl ether by recycling a part of the main raw material by circulating a gas containing carbon monoxide and hydrogen, the following steps (a) and (b) are further added: A method for producing dimethyl ether, comprising: (A) A step of preparing the mixed gas as the main raw material by generating a saturated hydrocarbon gas as a raw material by a reformer. (B) Separation of carbon dioxide coexisting in the reaction product generated in the synthesis reaction of the dimethyl ether, and the separated carbon dioxide is circulated to the reformer of the step (a) to synthesize the dimethyl ether. Utilizing as a part of the main raw material for production. 2. A method in advance reaction product was cooled in DME · CO ₂ separator, (1) condensed dimethyl ether and carbon dioxide dissolved in it (2) the carbon monoxide in the previous circulation
The method for producing dimethyl ether according to claim 1, wherein the step (b) is performed after separating the gas containing hydrogen.