JP7398427B2 - Membrane reactor, membrane reactor system and method for producing methanol - Google Patents

Description

The present invention relates to a membrane reactor for continuously synthesizing methanol and water from carbon dioxide and hydrogen, a membrane reactor system, and a method for producing methanol.

In order to reduce the negative impact on the global environment, there is a need to reduce carbon dioxide, and methanol synthesis technology using carbon dioxide is attracting attention.
Currently, the technologies for which plants have been constructed and mass-produced include a process in which carbon dioxide and hydrogen are reacted using a catalyst under high temperature and pressure, a process in which methanol and water are separated by cooling the reaction product, and a process in which methanol and water are separated by cooling the reaction product. The process consists of a step of dehydrating the methanol and water mixture using a distillation method.

However, the above technology requires a huge amount of energy, especially in the reaction process using a catalyst under high temperature and high pressure, resulting in the generation of a large amount of carbon dioxide during the production of the input electrical energy, and the overall process is Carbon dioxide emissions have not been reduced.

Therefore, we focused on a production technology using a membrane reactor as a methanol production technology that can reduce the energy input when reacting carbon dioxide and hydrogen using a catalyst.

Some prior art techniques have already been disclosed as techniques for producing methanol using a membrane reactor. Patent Document 1 discloses a reactor for methanol production using a water selectively permeable membrane body that selectively separates and removes water produced by the reaction out of the reaction system. Further, Patent Document 2 discloses a methanol production method including a step of flowing a sweep gas to cause water vapor that has passed through a water vapor separation membrane to flow out. Nitrogen or air is used as the sweep gas. In either technique, the reaction can proceed by removing water vapor from the reaction product using a separation membrane, and the energy required for the reaction can be reduced.

Japanese Patent Application Publication No. 2007-55970 Unexamined Japanese Patent Publication No. 2018-8940

However, the technique disclosed in Patent Document 1 uses a vacuum pump to suck water that has passed through a water selectively permeable membrane, and requires energy to operate the vacuum pump. Furthermore, the technique disclosed in Patent Document 2 requires energy to operate a sweep gas supply device in order to circulate the sweep gas.

The present invention has been made in view of the above circumstances. The present invention provides a membrane reactor, a membrane reactor system, and a method for producing methanol that can reduce the energy required for producing methanol and simplify the equipment for supplying sweep gas. The purpose is to

The present inventor studied a sweep gas used to discharge methanol and water produced by the reaction of carbon dioxide and hydrogen out of the system in a methanol production method using a membrane reactor. As a result, they discovered that by using a mixed gas that did not pass through the gas separation membrane in the catalyst support section, a sweep gas supply device was no longer required and the energy required for methanol production could be reduced. , we have completed the present invention.

(1) The membrane reactor of the present invention is a membrane reactor that continuously synthesizes methanol and water from carbon dioxide and hydrogen, and has a structure in which a catalyst support part and a gas separation membrane are stacked, A supply means for supplying carbon dioxide and hydrogen to the upstream side of the supporting section, the catalyst supporting section supporting a catalyst for synthesizing methanol and water from carbon dioxide and hydrogen, and a mixed gas of carbon dioxide, hydrogen, methanol and water. the gas separation membrane that selectively permeates methanol and water ; means for discharging the methanol and water that have permeated through the gas separation membrane together with the sweep gas ; The present invention is characterized in that it includes a bypass passage that flows from the supporting part to the downstream side of the gas separation membrane, and the mixed gas that has not passed through the gas separation membrane is used as the sweep gas.

(2) The membrane reactor of the present invention is the membrane reactor according to (1) above, wherein the membrane reactor has a cylindrical structure in which the catalyst supporting part and the gas separation membrane are stacked. , the catalyst support portion constitutes an outer layer of the cylindrical structure, the gas separation membrane constitutes an inner layer of the cylindrical structure, carbon dioxide and hydrogen are supplied from outside the outer layer of the cylindrical structure, and the gas Methanol and water that have passed through the separation membrane flow through a space inside the inner layer of the cylindrical structure and are discharged together with the sweep gas, and the bypass passage communicates with the upstream side of the flow of the sweep gas in the space. It is preferable.

(3) The membrane reactor system of the present invention includes the membrane reactor described in (1) or (2) above, and a mixed gas of carbon dioxide, hydrogen, methanol, and water downstream of the membrane reactor. A cooling means for separating carbon dioxide and hydrogen as gases and methanol and water as liquids, and a reflux means for refluxing the carbon dioxide and hydrogen separated by the cooling means to the upstream side of the membrane reactor. This is a membrane reactor system that continuously synthesizes methanol and water from carbon dioxide and hydrogen.

(4) The membrane reactor system of the present invention preferably includes a separation means for separating methanol and water by distillation downstream of the cooling means of the membrane reactor system described in (3) above.

(5) The methanol production method of the present invention is a methanol production method that continuously synthesizes methanol and water from carbon dioxide and hydrogen, and includes a membrane having a structure in which a catalyst support part and a gas separation membrane are laminated. A reactor is used to supply carbon dioxide and hydrogen to the upstream side of the catalyst support section, and in the catalyst support section, methanol and water are synthesized from carbon dioxide and hydrogen using the supported catalyst, and the gas A production method in which methanol and water are separated and permeated from a mixed gas of carbon dioxide, hydrogen, methanol, and water using a separation membrane , and the methanol and water that have permeated through the gas separation membrane are discharged together with a sweep gas, The present invention is characterized in that a mixed gas that has not passed through the gas separation membrane in the catalyst supporting portion is used as the sweep gas.

The membrane reactor, membrane reactor system, and methanol production method of the present invention can reduce the energy required for methanol production, and can simplify the equipment for supplying the sweep gas.

FIG. 1 is a schematic cross-sectional view showing the configuration of a membrane reactor according to the present embodiment. FIG. 2 is an enlarged schematic cross-sectional view of a portion II of the schematic cross-sectional view of the membrane reactor in FIG. 1; FIG. 1 is a schematic diagram showing the configuration of a membrane reactor system of this embodiment. FIG. 2 is a schematic diagram showing the configuration of a method for discharging generated methanol and water from a membrane reactor to the outside. (a) is a schematic diagram of the configuration of a manufacturing method using a pressure reducing machine. (b) is a schematic diagram of the configuration of a manufacturing method using an inert gas. (c) is a schematic diagram of the configuration of a manufacturing method using a blower.

Embodiments of the present invention will be described in detail below.

As an environmental measure, various attempts have been made to convert carbon dioxide recovered from exhaust gas and the atmosphere into other useful compounds for effective use.
The method of synthesizing methanol and water from carbon dioxide and hydrogen is already widely known. The reaction formula is the following formula (1). Furthermore, as a reaction via carbon monoxide, methanol may be synthesized via the following equations (2) and (3).
_CO2 + _3H2 → _CH3OH + _H2O ...(1)
CO ₂ + H ₂ → CO + H ₂ O...(2)
CO+ _2H2 → _CH3OH ...(3)

Since the above reaction proceeds at high temperatures, the raw materials carbon dioxide and hydrogen as well as the products methanol and water exist as gases in the reaction system.

The above reaction proceeds in the presence of a catalyst, but since it is an equilibrium reaction, it is effective to discharge the product methanol or water out of the reaction system in order to increase the methanol yield. be. A typical method for discharging methanol or water out of the reaction system is a method using a membrane reactor having a gas separation membrane.

The methanol production method of the present embodiment, which continuously synthesizes methanol and water from carbon dioxide and hydrogen, uses a membrane reactor having a structure in which a catalyst support part and a gas separation membrane are stacked.
The method for producing methanol according to the present embodiment is carried out using a membrane reactor through the following steps.
(a) Carbon dioxide and hydrogen, which are raw material gases, are supplied to the upstream side of the catalyst supporting section.
(b) In the catalyst supporting section, methanol and water are generated from carbon dioxide and hydrogen using the supported catalyst.
(c) A gas separation membrane separates methanol and water from a mixed gas of carbon dioxide, hydrogen, methanol, and water and allows them to permeate.
(d) A sweep gas is caused to flow downstream of the gas separation membrane, and the methanol and water that have passed through the gas separation membrane are discharged to the outside of the reaction system together with the sweep gas.

The membrane reactor having a structure in which a catalyst support part and a gas separation membrane are stacked is not particularly limited in its form, and may have a flat shape, a curved shape, a cylindrical shape, etc. A typical form of a membrane reactor is a membrane reactor having a cylindrical structure in which a catalyst support part and a gas separation membrane are stacked as inner and outer layers. It is preferable that the catalyst support portion constitutes the outer layer of the cylindrical structure, and the gas separation membrane constitutes the inner layer of the cylindrical structure.

FIG. 1 is a schematic cross-sectional view showing the configuration of a membrane reactor 20 of this embodiment.
The membrane reactor 20 has a cylindrical structure. The outermost layer of the cylindrical structure is the casing 1 for protecting the inside. There is a catalyst support part 2 immediately inside thereof, a gas separation membrane 3 is located inside the catalyst support part 2, and a cavity part 4 is located inside the gas separation membrane 3.

A raw material gas 9 consisting of carbon dioxide and hydrogen is supplied from the raw material gas inlet 5 of the membrane reactor 20 to the outside of the catalyst supporting section 2 in the membrane reactor 20 . Within the catalyst supporting portion 2, a reaction proceeds to generate methanol and water from the raw material gas 9. As a result, carbon dioxide, hydrogen, methanol, and water exist in a mixed state as a gas in the catalyst support portion 2 . Of the mixed gas, methanol and water selectively pass through the gas separation membrane 3. Methanol and water pass through the gas separation membrane 3 and flow into the cavity 4 inside the gas separation membrane 3. That is, the cavity 4 is a space located downstream of the gas separation membrane 3 and inside the inner layer of the membrane reactor 20 having a cylindrical structure.

Sweep gases 11 and 12 flow into the cavity 4 inside the inner layer of the membrane reactor 20 from an inlet 7 on the left side (upstream side) in the figure, and an outlet 8 on the right side (downstream side) in the figure. flowing towards. The methanol and water that have entered the cavity 4 flow through the space together with the sweep gas 11, are discharged from the outlet 8, and exit the reaction system.

Of the mixed gas consisting of carbon dioxide, hydrogen, methanol, and water that was present in the catalyst support section 2, the mixed gas 10 that did not pass through the gas separation membrane is subjected to a membrane reaction from the gas outlet 6 of the membrane reactor 20. It is discharged to the outside of the container 20.

In this embodiment, the catalyst support section 2 is filled with a catalyst supported on a carrier. The catalyst is preferably a metal catalyst containing a transition metal, and the transition metal is preferably Cu, Zn, or the like. Further, as the carrier, a carrier made of a metal oxide such as alumina (Al ₂ O ₃ ) or silica (SiO ₂ ) is preferable.

In the method of synthesizing methanol and water from carbon dioxide and hydrogen using a membrane reactor, there are several methods for using the above-mentioned sweep gas as a means to discharge the generated methanol and water from the membrane reactor to the outside. exists.

FIG. 4 is a schematic diagram showing the configuration of a method for discharging generated methanol and water from a membrane reactor to the outside.
FIG. 4(a) is a schematic diagram of a method for sucking gas existing in a cavity using a pressure reducing machine 61 and discharging it to the outside. In this method, it is necessary to install the pressure reducer 61, and energy is required to operate the pressure reducer 61, which increases the amount of energy used.

FIG. 4(b) is a schematic diagram of a method using an inert gas as the sweep gas. Helium, argon, etc. are used as the inert gas. This method requires the installation of an inert gas cylinder 62, which increases manufacturing costs.

FIG. 4(c) is a schematic diagram of a method using air as the sweep gas and a blower. It is necessary to install a blower 64, and the efficiency of dehydration from the reaction system decreases due to the influence of moisture in the air. Furthermore, the reaction efficiency may vary due to the influence of the outside air condition.

The present inventor devised the idea of using a mixed gas that did not pass through the gas separation membrane in the catalyst supporting part as the sweep gas.
Therefore, a bypass passage was installed to allow the mixed gas that did not pass through the gas separation membrane to flow from the catalyst supporting part to the downstream side of the gas separation membrane. We considered supplying the mixed gas that did not pass through the gas separation membrane to the downstream side of the gas separation membrane via the bypass passage and using it as a sweep gas.

FIG. 3 is a schematic diagram showing the configuration of the membrane reactor system of this embodiment.
In FIG. 3, a bypass passage 35 is installed which communicates from the gas outlet of the membrane reactor 31 to the upstream side of the flow of the sweep gas in the space inside the inner layer of the membrane reactor 31. The mixed gas that has not passed through the gas separation membrane is passed through the bypass passage 35 to the upstream side of the flow of the sweep gas in the space inside the inner layer of the membrane reactor 31 . As a result, it became possible to use the mixed gas that did not pass through the gas separation membrane as a sweep gas.

By using the mixed gas that did not pass through the gas separation membrane as the sweep gas, there was no need to use any particular energy to flow the sweep gas. Additionally, it is no longer necessary to install new equipment to flow the sweep gas. That is, the problems that occurred in FIGS. 4(a), (b), and (c) could be solved.

The membrane reactor system of this embodiment shown in FIG. 3 includes a cooling trap 32 as a cooling means downstream of the membrane reactor 31. The cooling trap 32 cools the mixed gas of carbon dioxide, hydrogen, methanol, and water, thereby separating methanol and water as a liquid, and separating carbon dioxide and hydrogen as a gas. Further, the membrane reactor system of this embodiment includes a reflux means 39 that refluxes carbon dioxide and hydrogen separated as gases in the cooling trap 32 to the upstream side of the membrane reactor 31.

The mixed gas that has not passed through the gas separation membrane flows as a sweep gas in the space inside the inner layer of the membrane reactor 31, and at the same time, it is mixed with methanol and water that have passed through the gas separation membrane and exits the reaction system. be discharged. Of the discharged mixed gas 37, methanol and water produced as a result of the reaction are separated as a liquid by the cooling trap 32, and carbon dioxide and hydrogen are separated as a gas. There is no problem because the separated carbon dioxide and hydrogen are refluxed to the upstream side of the membrane reactor by the reflux means 39 and used again as raw material gas for methanol production.

FIG. 2 is an enlarged schematic cross-sectional view of a portion II of the schematic cross-sectional view of the membrane reactor 20 in FIG. Carbon dioxide, hydrogen, methanol, and water exist in a mixed state in the catalyst support portion 2 . On the other hand, in the cavity 4, since the mixed gas that has not passed through the gas separation membrane is used as the sweep gas, a gas mainly consisting of carbon dioxide and hydrogen exists in a mixed state.
Then, the partial pressures of methanol and water are high in the catalyst support portion 2, and the partial pressures of methanol and water are low in the cavity 4. Therefore, methanol and water try to move from the catalyst support part 2, which has a high partial pressure, through the gas separation membrane 3, into the cavity part 4, which has a low partial pressure (see the broken line arrow in FIG. 2). As a result, in the equilibrium reaction of methanol synthesis within the catalyst supporting section 2, the methanol yield is increased.
Carbon dioxide and hydrogen are the main components both in the catalyst support part 2 and in the cavity part 4, and because the partial pressure is high, it is difficult for a partial pressure difference to occur, and carbon dioxide and hydrogen permeate through the gas separation membrane 3. There's not much to do.

The membrane reactor system of this embodiment in FIG. 3 includes a distillation column 33 downstream of the cooling trap 32. The distillation column 33 can separate methanol and water from the mixture of methanol and water separated as a liquid by the cooling trap 32 by distillation. The distillation column 33 is a typical separation means for separating methanol and water by distillation.

In this way, the membrane reactor system of the present embodiment is capable of continuously synthesizing methanol and water using carbon dioxide and hydrogen as raw material gases to obtain methanol.

Variations on the membrane reactor system embodiment of FIG. 3 include the following (not shown):
A part of the mixed gas that has not passed through the gas separation membrane of the membrane reactor 31 is passed through the bypass passage 35 to the upstream side of the flow of the sweep gas in the space inside the inner layer of the membrane reactor 31. . Then, the other part of the mixed gas that has not passed through the gas separation membrane of the membrane reactor 31 is made to join the flow path 34 of the raw material gas of the membrane reactor 31. By providing a plurality of such mixed gas flow paths, it becomes possible to freely set the flow rate of the sweep gas in the space inside the inner layer of the membrane reactor 31.

As described above, the membrane reactor, membrane reactor system, and methanol production method of this embodiment use the mixed gas that has not passed through the gas separation membrane as the sweep gas, thereby achieving the required amount for methanol production. Energy can be reduced, equipment for supplying sweep gas can be simplified, and methanol yield can be increased.

1 Housing 2 Catalyst supporting part 3 Gas separation membrane 4 Cavity part 5 Raw material gas inlet 6 Gas discharge port 7 Inlet 8 Outlet 9 Raw material gas 10 Mixed gas 11 Sweep gas 12 Sweep gas 20 Membrane reactor 31 Membrane reactor 32 Cooling trap 33 Distillation column 34 Source gas flow path 35 Bypass passage 37 Mixed gas 39 Reflux means

Claims (5)

A membrane reactor that continuously synthesizes methanol and water from carbon dioxide and hydrogen,
It has a structure in which a catalyst support part and a gas separation membrane are laminated,
Supply means for supplying carbon dioxide and hydrogen to the upstream side of the catalyst supporting part;
the catalyst supporting part supporting a catalyst for synthesizing methanol and water from carbon dioxide and hydrogen;
the gas separation membrane that selectively permeates methanol and water from a mixed gas of carbon dioxide, hydrogen, methanol, and water;
means for discharging methanol and water that have passed through the gas separation membrane together with the sweep gas ;
a bypass passage that allows the mixed gas that has not passed through the gas separation membrane to flow from the catalyst supporting part to the downstream side of the gas separation membrane;
A membrane reactor characterized in that a mixed gas that has not passed through the gas separation membrane is used as the sweep gas. The membrane reactor has a cylindrical structure in which the catalyst supporting part and the gas separation membrane are stacked,
The catalyst supporting portion constitutes an outer layer of the cylindrical structure, and the gas separation membrane constitutes an inner layer of the cylindrical structure,
carbon dioxide and hydrogen are supplied from outside the outer layer of the cylindrical structure,
The methanol and water that have passed through the gas separation membrane flow through the space inside the inner layer of the cylindrical structure and are discharged together with the sweep gas,
The membrane reactor according to claim 1, wherein the bypass passage communicates with an upstream side of the flow of sweep gas within the space. The membrane reactor according to claim 1 or 2,
A cooling means for separating carbon dioxide and hydrogen as gases and methanol and water as liquids from a mixed gas of carbon dioxide, hydrogen, methanol and water, downstream of the membrane reactor;
A membrane reactor system for continuously synthesizing methanol and water from carbon dioxide and hydrogen, comprising a reflux means for refluxing carbon dioxide and hydrogen separated by the cooling means to the upstream side of the membrane reactor. . 4. The membrane reactor system according to claim 3, further comprising separation means for separating methanol and water by distillation downstream of said cooling means. A method for producing methanol that continuously synthesizes methanol and water from carbon dioxide and hydrogen,
Using a membrane reactor with a structure in which a catalyst support part and a gas separation membrane are stacked,
Supplying carbon dioxide and hydrogen to the upstream side of the catalyst supporting part,
In the catalyst supporting section, methanol and water are synthesized from carbon dioxide and hydrogen using the supported catalyst,
Separating and permeating methanol and water from a mixed gas of carbon dioxide, hydrogen, methanol and water by the gas separation membrane,
A manufacturing method in which methanol and water that have passed through the gas separation membrane are discharged together with a sweep gas,
A method for producing methanol, characterized in that a mixed gas that has not passed through the gas separation membrane in the catalyst supporting portion is used as the sweep gas.

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