JP2007055973A - Methanol-producing device and methanol-producing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a methanol-producing device which is used for producing methanol from a gas containing carbon dioxide and hydrogen as a raw material gas, can sufficiently enhance a methanol conversion rate over an equilibrium conversion rate at the prescribed temperature and pressure, does not need a methanol distillation process for the separation of the methanol and the water which are reaction products, and can lower production cost. <P>SOLUTION: This methanol-producing device for reacting a raw material gas containing hydrogen and carbon dioxide in a reactor 1 in the presence of a catalyst and an organic solvent to produce the methanol is characterized in that the reactor 1 is formed to react the raw material gas in such reaction conditions that the methanol as one of the reaction products becomes a gas and by-produced water as the other becomes a liquid, and has a membrane separator 11 for extracting a part of the liquid phase containing the by-produced water from the reactor to selectively separate off the water from the liquid phase, so that a phase rich in the organic solvent is returned and circulated to the reactor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a methanol production apparatus and a methanol production method for producing methanol by reacting a raw material gas containing hydrogen and carbon dioxide in the presence of a catalyst.

As a method for synthesizing methanol, a catalytic hydrogenation method is generally known in which a raw material gas composed of hydrogen and carbon monoxide and / or carbon dioxide is subjected to a catalytic reaction under predetermined reaction conditions. These synthesis methods include a gas phase synthesis method and a liquid phase synthesis method. These reaction formulas are as follows.

CO + 2H ₂ = CH ₃ OH (1)
CO ₂ + 3H ₂ = CH ₃ OH
+ H ₂ O (2)

When a raw material gas containing hydrogen and carbon dioxide is used, methanol and equimolar water are produced as shown in the above equation (2). This water has a problem of deteriorating the catalyst.

  Further, the above formula (2) is an exothermic reaction and is an equilibrium reaction with a reduced number of moles. Therefore, in terms of chemical equilibrium, the reaction is more advantageous for methanol synthesis at lower temperature and higher pressure conditions.

  The equilibrium conversion rate of methanol is determined by the thermodynamic equilibrium constant of the above equation (2), and is as low as 21% under the condition of 250 ° C. and 5 MPa, for example. Increasing the reaction pressure to 15 MPa, for example, improves the equilibrium conversion rate to 40%, but increases the compression power of the raw material gas. Therefore, in a methanol synthesis reaction using a raw material gas containing hydrogen and carbon dioxide, a high one-pass conversion rate cannot be obtained unless it is freed from restrictions on chemical equilibrium. In order to release from the constraint of chemical equilibrium, it is necessary to shift the chemical equilibrium to the production side, and the following methods have been studied so far.

(A) A liquid phase synthesis method in which dodecane or the like that hardly dissolves an aqueous methanol solution is used as a reaction solvent, and the reaction solvent and the aqueous methanol solution are continuously discharged out of the reaction vessel from the reaction vessel is disclosed in Japanese Patent Publication No. 7-47554 (Patent Document 1). ) Or JP-A-9-227423 (Patent Document 2).
In the former publication, when methanol is produced from a raw material gas, the reaction is carried out under a high enough pressure so that at least a part of methanol and water in the reactor exist as a liquid, and methanol as a reaction product and It is described that water is separated and removed as an aqueous methanol solution and discharged out of the reactor.

(B) A method for producing methanol in which a raw material gas and a reaction product (methanol and water) are separated while being synthesized with a polymer membrane is described in JP-A-9-511509 (Patent Document 3).
Here, it is described that the polymer membrane separates methanol and / or water as reaction products. However, the specifically disclosed polymer membrane is only a membrane made of a perfluorinated ionomer such as a perfluorinated cation exchange membrane, which separates methanol and water together from unreacted gas. is there. The specification of this publication does not specifically describe a polymer membrane that separates and removes only water.
Furthermore, before conducting the synthesis reaction, the lithium chloride solution is brought into contact with the polymer membrane to dope lithium ions into the membrane so that one side is stable against chemicals and the other side is about It is described as having good temperature stability up to 250 ° C. That is, the polymer film disclosed here requires a pretreatment of doping lithium ions before being used for the synthesis reaction.

Japanese Patent Publication No. 7-47554 JP-A-9-227423 JP 9-511509 A

  In the methanol synthesis method described in the above Japanese Patent Publication No. 7-47554 of (A), the temperature is lowered in order to separate the liquid phase taken out from the reactor into an organic solvent and an aqueous alcohol solution. The recycled organic solvent must be reheated to the reaction temperature before being recycled and returned to the reactor. Furthermore, since the reaction product is separated as an aqueous methanol solution, a methanol distillation step is further required to separate methanol and water. For this reason, the energy for the said reheating and distillation was added and became the hindrance of the cost reduction.

  In the methanol synthesis method described in JP-A-9-511509 of (B) above, the reaction product is separated and removed from the reaction system by the polymer membrane while synthesizing methanol from the raw material gas. Shifting to the methanol production side can increase the methanol conversion rate. However, according to the specific disclosure, the reaction product methanol and water are separated from unreacted gas together. Therefore, a methanol distillation step is further required to separate methanol and water, and there is a problem that energy is required for distillation and hinders cost reduction.

  In addition, since the polymer film described here requires a pretreatment to be doped with lithium ions before being used in the synthesis reaction as described above, such a pretreatment process is accompanied by an increase in costs associated with the pretreatment process. Even when the treatment was performed, the heat resistance and durability of the polymer film itself were insufficient.

  An object of the present invention is methanol synthesis using a gas containing carbon dioxide and hydrogen as a raw material gas, which can sufficiently increase the methanol conversion rate exceeding the equilibrium conversion rate under a certain temperature and pressure, It is an object of the present invention to provide a methanol production apparatus and a methanol production method that do not require a methanol distillation step for separating methanol and water, and that can reduce costs.

To achieve the above object, the methanol production apparatus according to the first aspect of the present invention produces methanol by reacting a raw material gas containing hydrogen and carbon dioxide in the reactor in the presence of a catalyst and an organic solvent. In the methanol production apparatus, the reactor is configured to react under a reaction condition in which one methanol of the reaction product becomes a gas and the other water produced as a by-product becomes a liquid. A part of the liquid phase containing raw water is extracted, and a separator for separating the liquid phase into water and a phase rich in an organic solvent is provided, and the phase rich in the organic solvent is returned to the reactor and circulated. It is comprised by these.
Here, the phase rich in organic solvent means that the water / organic solvent mixed liquid phase in which water produced as a by-product in the methanol synthesis reaction is mixed is subjected to a separation process by a separator, and the water phase is higher than that before the separation process. The liquid phase in a state where the proportion of the organic solvent is decreased and the proportion of the organic solvent is increased. That is, it means a liquid phase that is separated by a separator in a state in which the proportion of the organic solvent is larger than that of the liquid phase in the reactor and the proportion of water is small.

  According to the present invention, methanol, which is a reaction product, becomes a gas at the same time as generation and is separated from the reaction liquid phase, and by-product water becomes liquid and remains in the reaction liquid phase. Then, since the organic solvent-rich phase separated from water by the separator is continuously returned to the reactor, the equilibrium reaction is shifted to the methanol production side, and the methanol conversion can be increased.

  In addition, methanol and water can be separated simultaneously with the synthesis reaction, eliminating the need for a methanol distillation step. In addition to greatly reducing the energy required for the distillation, the third component required for azeotropic distillation is also unnecessary. Therefore, a significant cost reduction can be achieved.

  The methanol production apparatus according to the second aspect of the present invention is the methanol production apparatus according to the first aspect, wherein the separator performs separation under substantially the same conditions of at least one of a reaction temperature and a reaction pressure set in the reactor. It is comprised so that it may carry out.

  According to the present invention, in the separator, since the separation is performed at the same temperature and pressure as the reaction temperature and reaction pressure set in the reactor, the phase rich in organic solvent after separation is returned to the reactor. When recirculating, there is no need to reheat and it can be returned almost as it is. Therefore, auxiliary heating means for solvent recirculation and the like are not necessary, and the cost of the entire apparatus can be reduced.

  The methanol production method according to the third aspect of the present invention is a method for producing methanol by reacting a raw material gas containing hydrogen and carbon dioxide in a reactor in the presence of a catalyst and an organic solvent, the reactor comprising the reactor In the reaction product, one methanol of the reaction product becomes gas and the other by-product water reacts under the reaction condition of liquid, and a part of the liquid phase containing the by-produced water is extracted from the reactor and separated. The liquid phase is separated into water and a phase rich in an organic solvent by a vessel, and the phase rich in the organic solvent is returned to the reactor and circulated. According to the present invention, the same effect as the first aspect can be obtained.

  According to the present invention, methanol synthesis using a gas containing carbon dioxide and hydrogen as a raw material gas, the methanol conversion rate can be sufficiently increased beyond the equilibrium conversion rate under a certain temperature and pressure, and the reaction product This eliminates the need for a methanol distillation step for separating methanol and water, thereby reducing the cost.

  Hereinafter, an embodiment of a methanol production apparatus according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a methanol production apparatus according to the present embodiment.

As shown in FIG. 1, the reactor 1 of the methanol production apparatus according to the present embodiment uses a raw material gas 15 containing hydrogen and carbon dioxide in a reaction liquid phase 2 containing a catalyst and an organic solvent in the reactor 1. It is made to react in to produce methanol. The reactor 1 is configured to react under reaction conditions in which one methanol of the reaction product becomes a gas and the other by-product water becomes a liquid.
This reaction condition is realized by setting the reaction temperature to 100 ° C. to 220 ° C. and the reaction pressure to 2 MPa to 7 MPa, and is maintained by temperature adjusting means and pressure variable means (not shown). Desirable reaction conditions are a reaction temperature of 150 ° C. to 170 ° C. and a reaction pressure of 3 MPa to 5 MPa.

  Then, a part of the liquid phase 2 containing the by-produced water is extracted from the reactor 1 by the separator 11, and the liquid phase 2 is separated into water and a phase rich in an organic solvent. The rich phase is continuously returned to the reactor 1 through the circulation line 13.

  For the liquid phase 2 in the reactor 1, a known compound containing Cu / ZnO is used as a catalyst, and the size and shape thereof are appropriately set depending on the configuration and method of the reactor 1. The organic solvent can be selected from those which exhibit a liquid phase under the reaction conditions and can be separated from water at the same temperature as the reaction temperature, saturated hydrocarbons such as decane and dodecane, 1-heptanol, 1-octanol and the like. Alcohols and the like. A plurality of types of organic solvents can also be used in combination.

  A more specific structure, operating principle, and operation of the apparatus according to the present embodiment having such a configuration will be described below. The raw material gas 15 is supplied from below the reactor 1 through the compressor 3 and the preheater 4. The raw material gas 15 comes into contact with the catalyst in the reaction liquid phase 2 and reacts while passing through to generate methanol and water. Here, methanol is produced in a gaseous state, while water is by-produced in a liquid state. Here, water is used in the meaning including water vapor. In addition, you may stir the reaction liquid phase 2 with a stirrer which is not illustrated.

  The generated methanol and unreacted gas are discharged from the gas phase discharge line 5 provided at the top position of the reactor 1. The gas phase discharge line 5 is provided with a cooler 6 so that the organic solvent and water are not discharged together with methanol and unreacted gas, and the organic solvent and water condensed by cooling with the cooler 6 are reacted with the reactor 1. Returned through the return line 16. Thereafter, the methanol and unreacted gas are sent to the gas-liquid separator 8 via the condenser 7 and separated into methanol and unreacted gas. A part of the unreacted gas is removed as a purge gas if necessary, and is returned to the supply flow path of the raw material gas 15 via the compressor 9.

  On the other hand, a part of the reaction liquid phase 2 containing by-produced water is continuously extracted from the reactor 1 through the liquid phase extraction line 10. The liquid phase 2 taken out from the reactor 1 is supplied to the liquid-liquid separator 11 at the same temperature and pressure as the reaction temperature of the reactor 1, where it is separated into water and a phase rich in organic solvent, The solvent phase that is discharged from the system 12 and rich in organic solvent is recirculated from the circulation line 13 into the reactor 1 via the circulation pump 14. In addition, by removing a part of the reaction liquid phase 2 from the reactor 1 in this way, a part of the reaction heat absorbed by the reaction liquid phase 2 is also extracted outside, and the reaction heat is reduced from the reaction system. Has the same effect.

  The reactor 1 is provided with a cooling chamber 17 surrounding the periphery thereof, and the cooling chamber 17 has a cooling heat medium supply port 18 and a cooling heat medium discharge port 19. Since the present invention is a liquid phase reaction, the reaction heat in the methanol synthesis reaction can be efficiently removed in the reaction liquid phase 2. This reaction heat can be removed from the reaction liquid phase 2 by providing the cooling chamber 17. The heat recovered in the cooling chamber 17 can be used, for example, in a heat exchanger.

  As described above, methanol as a reaction product is generated as a gas and removed from the system as it is, while water produced as a by-product remains in the reaction liquid phase as a liquid, and a part of it is taken out to a separator in the subsequent stage. Separation into a phase rich in water and an organic solvent, and the phase rich in the organic solvent is returned to the reactor again, so that the methanol synthesis reaction can be continued while shifting the chemical equilibrium to the production side. As a result, the methanol synthesis reaction is promoted, and a high reaction conversion rate that is not restricted by chemical equilibrium can be obtained. And since the one-pass conversion rate exceeding an equilibrium conversion rate can be obtained, the amount of unreacted gas can be reduced and the gas circulation power can be reduced.

  Further, the separation by the latter liquid-liquid separator is carried out at the same temperature and pressure as the reaction conditions of the reactor, so that an effect of reducing the auxiliary heat amount for recirculation of the separated organic solvent-rich phase can be obtained. Furthermore, since the conventional complicated separation and distillation steps related to methanol, organic solvent, and water can be omitted, the required energy can be greatly reduced. Furthermore, the reaction heat of methanol synthesis can be efficiently removed out of the reaction system (outside the reactor) by the separation process in which a part of the reaction liquid phase is taken out.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, the technical scope of this invention is not limited by the following Example. The following examples show results using the bench test class experimental apparatus of the methanol production apparatus shown in FIG.

A raw material gas 15 (composition CO ₂ : 25% by volume, H ₂ : 75% by volume) was supplied to the compressor 3 at a flow rate of 168 NL / h. This raw material gas is combined with unreacted gas (flow rate: 89.2 NL / h) sent from the compressor 9 and supplied to the reactor 1. Reactor 1 was charged with 1.6 L of 1-octanol as an organic solvent and 320 g of catalyst Cu / ZnO / Al ₂ O ₃ and reacted under reaction conditions of a temperature of 170 ° C. and a pressure of 3 MPa.

  A 1-octanol solution containing 9.3% by weight of water is supplied from the liquid phase take-out line 10 to the liquid-liquid separator 11 at 1.6 L / h. Under this condition, 46.1 g / h of water was recovered from the water line 12.

  Methanol etc. evaporate from the reactor 1 to the gas phase side. The gas is partially condensed by the cooler 6 and the condenser 7 and returned to the reactor 1 through the line 16. By maintaining the temperature of the cooler 6 at 110 ° C., a liquid of 86.0 wt% methanol and 14.0 wt% water was recovered from the gas-liquid separator 8 at 132 g / h. The unreacted gas separated by the gas-liquid separator 8 merges with the raw material gas 15 through the compressor 9. At this time, the one-pass methanol conversion was 61.9%. In the conventional reactor for gas phase reaction, the equilibrium reaction rate of methanol under the reaction conditions of 170 ° C. and 3 MPa does not exceed 33.1%, but the equilibrium conversion rate is exceeded by the device of the configuration of FIG. % Methanol conversion could be achieved.

  INDUSTRIAL APPLICABILITY The present invention is applicable to a methanol production apparatus and a methanol production method for producing methanol by reacting a raw material gas containing hydrogen and carbon dioxide in the presence of a catalyst.

It is a schematic block diagram which shows the methanol manufacturing apparatus which concerns on embodiment.

Explanation of symbols

1: Reactor 2: Reaction liquid phase 3: Compressor 4: Preheater 5: Gas phase discharge line 6: Cooler 7: Condenser 8: Gas-liquid separator 9: Compressor 10: Liquid phase take-out line 11: Liquid-liquid separation 12: Water line 13: Circulation line 14: Circulation pump 15: Raw material gas 16: Return line 17: Cooling chamber

Claims (3)

A methanol production apparatus for producing methanol by reacting a raw material gas containing hydrogen and carbon dioxide in a reactor in the presence of a catalyst and an organic solvent,
The reactor is configured to react under reaction conditions in which one methanol of the reaction product becomes a gas and the other by-product water becomes a liquid,
A separator for separating a part of the liquid phase containing the by-produced water from the reactor and separating the liquid phase into water and a phase rich in an organic solvent;
An apparatus for producing methanol, wherein the phase rich in organic solvent is circulated back to the reactor.   2. The methanol production apparatus according to claim 1, wherein the separator is configured to perform separation under substantially the same conditions of at least one of a reaction temperature and a reaction pressure set in the reactor. A method for producing methanol by reacting a raw material gas containing hydrogen and carbon dioxide in a reactor in the presence of a catalyst and an organic solvent,
In the reactor, one methanol of the reaction product becomes a gas, and the other by-product water reacts under reaction conditions that become a liquid,
A part of the liquid phase containing the by-produced water is extracted from the reactor, and the separator separates the liquid phase into water and a phase rich in an organic solvent, and the phase rich in the organic solvent is reacted in the reaction. A method for producing methanol, which is returned to the vessel and circulated.

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