JP7797193B2 - Reactor and liquid fuel synthesis method - Google Patents

Description

The present invention relates to a reactor and a method for synthesizing liquid fuel.

In recent years, reactors have been developed that can improve the efficiency of the conversion reaction from feed gases containing hydrogen and carbon dioxide to liquid fuels such as methanol and ethanol (specifically, fuels that are liquid at room temperature and pressure) by separating the by-product water vapor.

For example, Patent Document 1 discloses a reactor comprising a water vapor separation membrane, a first flow path provided on the non-permeation side of the water vapor separation membrane and in which a catalyst is disposed, and a second flow path provided on the permeation side of the water vapor separation membrane. A raw material gas is supplied to the first flow path. A sweep gas is supplied to the second flow path for sweeping up the water vapor that has permeated the water vapor separation membrane. The sweep gas flowing through the second flow path absorbs reaction heat while taking in water vapor, thereby improving conversion efficiency through an equilibrium shift effect.

Japanese Patent Application Laid-Open No. 2018-8940

In the reactor described in Patent Document 1, the direction of the sweep gas flowing through the second flow path is the same as the direction of the raw material gas flowing through the first flow path, so the catalyst located in the upstream region of the first flow path can be cooled by the sweep gas. This makes it possible to prevent thermal degradation of the catalyst in the upstream region of the first flow path.

On the other hand, while the amount of water vapor contained in the sweep gas increases in the downstream region of the second flow path, the direction of the sweep gas flowing through the second flow path is the same as the direction of the raw material gas flowing through the first flow path, so the water vapor cannot be smoothly transferred from the downstream region of the first flow path to the downstream region of the second flow path. As a result, the conversion efficiency is low in the downstream region of the first flow path.

The present invention was made in consideration of the above-mentioned circumstances, and aims to provide a reactor and liquid fuel synthesis method that can simultaneously suppress thermal degradation of the catalyst and improve conversion efficiency.

The reactor according to the present invention comprises a water vapor separation membrane, a first flow path, a second flow path, and a catalyst. The water vapor separation membrane allows water vapor, a by-product of the conversion reaction from a feed gas containing at least hydrogen and carbon dioxide to liquid fuel, to pass through. The first flow path is provided on the non-permeation side of the water vapor separation membrane. The feed gas flows through the first flow path. The second flow path is provided on the permeation side of the water vapor separation membrane. A sweep gas flows through the second flow path to sweep up the water vapor that has permeated the water vapor separation membrane. The catalyst is disposed in the first flow path and drives the conversion reaction from the feed gas to liquid fuel. The second flow path has a first inlet at one end of the second flow path, a second inlet at the other end of the second flow path, and an outlet between the first inlet and the second inlet.

The present invention provides a reactor and a liquid fuel synthesis method that can simultaneously suppress thermal degradation of the catalyst and improve conversion efficiency.

Schematic diagram showing the configuration of a reactor according to an embodiment. AA cross-sectional view of FIG. BB cross section of FIG. 1C-C cross section 2. D-D cross-sectional view of FIG. Schematic diagram showing the configuration of a reactor according to Modification 1. Schematic diagram showing the configuration of a reactor according to Modification 1.

Next, an embodiment of the present invention will be described with reference to the drawings. However, the drawings are schematic and the ratios of dimensions may differ from those of the actual product.

(Reactor 1)
Fig. 1 is a perspective view of the reactor 1. Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1. Fig. 3 is a cross-sectional view taken along line B-B in Fig. 1. Fig. 4 is a cross-sectional view taken along line C-C in Fig. 1. Fig. 5 is a cross-sectional view taken along line D-D in Fig. 2.

The reactor 1 is a so-called membrane reactor for converting a raw material gas into a liquid fuel. The raw material gas contains at least hydrogen and carbon dioxide. The raw material gas may contain carbon monoxide. The raw material gas may be so-called synthesis gas (Syngas). The liquid fuel is a fuel that is in a liquid state at room temperature and pressure. Examples of the liquid fuel include methanol, ethanol, liquid fuels represented by C _n H _2(m-2n) (m is an integer less than 90, and n is an integer less than 30), and mixtures thereof.

For example, the reaction equation (1) for synthesizing methanol by catalytic hydrogenation of a raw material gas containing carbon dioxide and hydrogen in the presence of a catalyst is as follows:

CO ₂ +3H ₂ ⇔ CH ₃ OH + H ₂ O (1)
The above reaction is an equilibrium reaction, and is preferably carried out under high temperature and pressure (e.g., 180°C or higher, 2 MPa or higher) to increase both the conversion efficiency and the reaction rate. The liquid fuel is in a gaseous state when synthesized, and remains in this state at least until it flows out of the reactor 1. The reactor 1 preferably has heat resistance and pressure resistance suitable for the synthesis conditions of the desired liquid fuel.

As shown in FIG. 1, the reactor 1 is formed in a monolithic shape. The term "monolith" refers to a shape with multiple holes penetrating in the longitudinal direction, and is a concept that includes honeycomb. The reactor 1 has a first end face S1, a second end face S2, and a side face S3. The first end face S1 is located on the opposite side of the second end face S2. The side face S3 is continuous with the outer edges of the first end face S1 and the second end face S2. In this embodiment, the reactor 1 is formed in a cylindrical shape, but the outer shape of the reactor 1 is not particularly limited.

As shown in Figures 1 to 5, the reactor 1 includes a porous support 10, a catalyst 20, a water vapor separation membrane 30, a first seal section 40, and a second seal section 50.

The porous support 10 is a columnar body extending in the longitudinal direction of the reactor 1. The porous support 10 is made of a porous material.

Examples of porous materials that can be used include ceramic materials, metal materials, and resin materials, with ceramic materials being particularly suitable. Examples of aggregates for ceramic materials include at least one of alumina (Al ₂ O ₃ ), titania (TiO ₂ ), mullite (Al ₂ O ₃ SiO ₂ ), ceramide, and cordierite (Mg ₂ Al ₄ Si ₅ O ₁₈ ). Examples of inorganic binders for ceramic materials include at least one of titania, mullite, sinterable alumina, silica, glass frit, clay minerals, and sinterable cordierite. However, the ceramic material does not necessarily need to contain an inorganic binder.

As shown in Figures 2 to 4, the porous support 10 has a large number of first flow paths 11 and a plurality of second flow paths 12.

As shown in FIG. 5, each first flow path 11 is formed along the longitudinal direction of the reactor 1. Each first flow path 11 is a through-hole. Each first flow path 11 opens to the first end face S1 and the second end face S2 of the reactor 1. Each first flow path 11 has an inlet e1 formed in the first end face S1 and an outlet e2 formed in the second end face S2. Each first flow path 11 is provided on the non-permeation side of the water vapor separation membrane 30. A raw material gas flows through each first flow path 11. A catalyst 20 is disposed within each first flow path 11. The number, position, and shape of the first flow paths 11 can be changed as appropriate.

Each second flow path 12 is provided on the permeation side of the water vapor separation membrane 30. A sweep gas flows through each second flow path 12 to sweep away water vapor that has permeated the water vapor separation membrane 30. The sweep gas can be an inert gas (e.g., nitrogen) or air. The number, position, and shape of the second flow paths 12 can be changed as appropriate.

Here, as shown in Figures 2 to 4, each second flow path 12 is composed of multiple cells 13, a first inlet slit 14, a second inlet slit 15, and an outlet slit 16.

The multiple cells 13 are aligned in a row along the short side of the reactor 1 (the direction perpendicular to the longitudinal direction). As shown in Figure 5, each cell 13 is formed along the longitudinal direction of the reactor 1. Both ends of each cell 13 are sealed by first and second sealing portions 17, 18. The first and second sealing portions 17, 18 can be made of the porous material described above.

As shown in FIG. 1, the first inlet slit 14 is formed at one end of the reactor 1 in the longitudinal direction. This end of the reactor 1 refers to the portion extending from one end of the raw material gas inlet side to 2/5 of the total length when the reactor 1 is divided into five equal parts longitudinally. The first inlet slit 14 is formed along the shorter side of the reactor 1. As shown in FIG. 2, the first inlet slit 14 penetrates multiple cells 13. Both ends of the first inlet slit 14 open to the side surface S3. The first inlet slit 14 has a pair of first inlets d1 formed on the side surface S3. The pair of first inlets d1 is one end of the second flow path 12 in the longitudinal direction.

As shown in FIG. 1, the second inlet slit 15 is formed at the other end of the reactor 1 in the longitudinal direction. The other end of the porous support 10 is the portion extending from the other end of the liquid fuel outlet side to 2/5 of the way, when the reactor 1 is divided into 5 equal parts in the longitudinal direction. The second inlet slit 15 is formed along the shorter side of the reactor 1. As shown in FIG. 3, the second inlet slit 15 penetrates multiple cells 13. Both ends of the second inlet slit 15 open to the side surface S3. The second inlet slit 15 has a pair of second inlets d2 formed in the side surface S3. The pair of second inlets d2 are the other ends of the second flow paths 12 in the longitudinal direction.

As shown in FIG. 1, the outlet slit 16 is formed in the middle of the reactor 1 in the longitudinal direction. The middle of the porous support 10 is the portion between the first inlet slit 14 and the second inlet slit 15 in a side view of the reactor 1. The outlet slit 16 is formed along the short direction of the reactor 1. As shown in FIG. 4, the outlet slit 16 penetrates multiple cells a1. Both ends of the outlet slit 16 open to the side surface S3. The outlet slit 16 has a pair of outlets d3 formed in the side surface S3. The pair of outlets d3 are located between the pair of first inlets d1 and the pair of second inlets d2 in the longitudinal direction.

The catalyst 20 is disposed within each first flow path 11. The catalyst 20 is preferably packed into each first flow path 11, but may also be disposed in the form of a layer on the surface of the water vapor separation membrane 30. The catalyst 20 promotes the conversion reaction from the feed gas to liquid fuel, as shown in formula (1) above.

The catalyst 20 can be any known catalyst suitable for the desired conversion reaction to liquid fuel. Examples of catalysts 20 include metal catalysts (copper, palladium, etc.), oxide catalysts (zinc oxide, zirconia, gallium oxide, etc.), and composite catalysts of these (copper-zinc oxide, copper-zinc oxide-alumina, copper-zinc oxide-chromium oxide-alumina, copper-cobalt-titania, and catalysts modified with palladium, etc.).

The water vapor separation membrane 30 is supported by the porous support 10. The water vapor separation membrane 30 surrounds the first flow path 11. The water vapor separation membrane 30 is disposed between the first flow path 11 and the second flow path 12.

The water vapor separation membrane 30 allows water vapor, a by-product of the conversion reaction from feed gas to liquid fuel, to pass through. This allows the equilibrium shift effect to be utilized to shift the reaction equilibrium of the above formula (1) toward the product side.

The water vapor separation membrane 30 preferably has a water vapor permeability coefficient of 100 nmol/(s·Pa·m ² ) or more. The water vapor permeability coefficient can be determined by a known method (see Ind. Eng. Chem. Res., 40, 163-175 (2001)).

The water vapor separation membrane 30 preferably has a separation factor of 100 or greater. The larger the separation factor, the easier it is for water vapor to permeate and the less permeable it is for components other than water vapor (such as hydrogen, carbon dioxide, and liquid fuel). The separation factor can be determined using known methods (see Fig. 1 in "Separation and Purification Technology 239 (2020) 116533").

An inorganic membrane can be used as the water vapor separation membrane 30. Inorganic membranes are preferred because they are heat-resistant, pressure-resistant, and water vapor-resistant. Examples of inorganic membranes include zeolite membranes, silica membranes, alumina membranes, and composite membranes of these. In particular, LTA-type zeolite membranes, which have a molar ratio (Si/Al) of silicon (Si) to aluminum (Al) of 1.0 or more and 3.0 or less, are preferred because of their excellent water vapor permeability.

As shown in FIG. 1, the first sealing portion 40 covers one end surface of the porous support body 10. The first sealing portion 40 prevents the source gas from entering the porous support body 10. As shown in FIG. 5, the first sealing portion 40 is formed so as not to block the inlet e1 of the first flow path 11. The first sealing portion 40 covers the first plugging portion 17. The first sealing portion 40 can be made of glass, metal, rubber, resin, etc.

As shown in FIG. 1, the second seal portion 50 covers the other end surface of the porous support body 10. The second seal portion 50 prevents liquid fuel from entering the porous support body 10. As shown in FIG. 5, the second seal portion 50 is formed so as not to block the outlet e2 of the first flow path 11. The second seal portion 50 covers the second plugging portion 18. The second seal portion 50 can be made of glass, metal, rubber, resin, etc.

(Liquid fuel synthesis method)
A liquid fuel synthesis method using the reactor 1 will be described with reference to FIG.

The liquid fuel synthesis method according to this embodiment includes a step of flowing a feed gas through a first flow path 11 provided on the non-permeation side of the water vapor separation membrane 30, while flowing a sweep gas through a second flow path 12 provided on the permeation side of the water vapor separation membrane 30.

The raw material gas flows into the first flow path 11 through the inlet e1 of the first flow path 11. Within the first flow path 11, liquid fuel is synthesized according to the above formula (1), and water vapor, a by-product, is generated. The synthesized liquid fuel flows out through the outlet e2 of the first flow path 11. The by-product water vapor sequentially permeates the water vapor separation membrane 30 and the porous support 10, and moves to the second flow path 12.

The sweep gas flows into both ends of the second flow path 12 and then flows out from the middle of the second flow path 12. Specifically, the sweep gas flows into the cell 13 through the first inlet d1 of the first inlet slit 14 and the second inlet d2 of the second inlet slit 15. The sweep gas then flows into the cell 13 through the first inlet slit 14 and the second inlet slit 15. The sweep gas then flows into the cell 13 through the first inlet slit 14, absorbing the by-product water vapor and the heat of reaction generated by the conversion reaction. The sweep gas then flows into the cell 13 through the second inlet slit 15, absorbing the by-product water vapor and the heat of reaction generated by the conversion reaction. The sweep gas then reaches the outlet slit 16 through the first inlet slit 14 and the second inlet slit 15 and is discharged from the outlet d3 of the outlet slit 16.

In this way, by positioning the outlet d3 between the first inlet d1 and the second inlet d2 of the second flow path 12, the sweep gas flowing in from both ends of the second flow path 12 can be discharged from the middle of the second flow path 12. As a result, as shown in FIG. 5, the raw material gas and the sweep gas can flow in parallel directions (i.e., in the same direction) between the first inlet d1 and the outlet d3, and the raw material gas and the sweep gas can flow in opposing directions (i.e., opposite directions) between the second inlet d2 and the outlet d3.

As a result, a relatively low-temperature sweep gas flows between the first inlet d1 and the outlet d3 of the second flow path 12, allowing the catalyst located in the upstream region of the first flow path 11 to be cooled by the sweep gas. This prevents thermal degradation of the catalyst in the upstream region of the first flow path 11. Furthermore, water vapor can be efficiently removed between the second inlet d2 and the outlet d3 of the second flow path 12, allowing water vapor to move smoothly from the liquid fuel outlet region of the first flow path 11 to the second flow path 12, improving conversion efficiency. Therefore, the reactor 1 according to this embodiment can simultaneously prevent thermal degradation of the catalyst and improve conversion efficiency.

The flow direction of the raw material gas in the first flow path 11 refers to the direction from upstream to downstream, where the side of the first flow path 11 closer to the raw material gas source is defined as the upstream side and the side farther from the raw material gas source is defined as the downstream side. The flow direction of the sweep gas in the second flow path 12 refers to the direction from upstream to downstream, where the side of the second flow path 12 closer to the sweep gas source is defined as the upstream side and the side farther from the sweep gas source is defined as the downstream side.

(Modification of the embodiment)
Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the gist of the invention.

(Variation 1)
In the above embodiment, the monolithic reactor 1 has been described as an example of the reactor according to the present invention, but the reactor configuration is not limited to this. The reactor according to the present invention may be, for example, a cylindrical reactor.

Figure 6 is a longitudinal cross-sectional view of a cylindrical reactor 100. The reactor 100 comprises a cylindrical water vapor separation membrane 101, a first flow path 102 provided on the inside (non-permeation side) of the water vapor separation membrane 101 and through which a raw material gas flows, a second flow path 103 provided on the outside (permeation side) of the water vapor separation membrane 101 and through which a sweep gas flows, and a catalyst 102a disposed in the first flow path 102. The second flow path 103 has a first inlet 104 at one end, a second inlet 105 at the other end, and an outlet 106 between them. Even with this cylindrical reactor 100, the sweep gas flowing in from both ends of the second flow path 103 can be discharged from the middle of the second flow path 103.

As shown in Figure 6, the tubular water vapor separation membrane 101 is supported by a tubular porous support 107. The water vapor separation membrane 101 may be disposed on either the inner or outer circumferential surface of the porous support 107. However, when there is a difference between the total pressure of the feed gas and the total pressure of the sweep gas, it is preferable to dispose the membrane on the inner circumferential surface of the porous support 107, as shown in Figure 6. This can prevent cracks from occurring in the water vapor separation membrane 101.

Figure 7 is a longitudinal cross-sectional view of a cylindrical reactor 200. The reactor 200 comprises a cylindrical water vapor separation membrane 201, a first flow path 202 provided on the outside (non-permeation side) of the water vapor separation membrane 201 and through which a raw material gas flows, a second flow path 203 provided on the inside (permeation side) of the water vapor separation membrane 201 and through which a sweep gas flows, and a catalyst 202a disposed in the first flow path 202. The second flow path 203 has a first inlet 204 at one end, a second inlet 205 at the other end, and an outlet 206 between them. Even with this cylindrical reactor 200, the sweep gas flowing in from both ends of the second flow path 203 can be discharged from the middle of the second flow path 203.

As shown in Figure 7, the tubular water vapor separation membrane 201 is supported by a tubular porous support 207. The water vapor separation membrane 201 may be disposed on either the inner or outer peripheral surface of the porous support 207; however, when there is a difference between the total pressure of the feed gas and the total pressure of the sweep gas, it is preferable to dispose the membrane on the outer peripheral surface of the porous support 207, as shown in Figure 7. This can prevent cracks from occurring in the water vapor separation membrane 201.

(Variation 2)
In the above embodiment, the monolithic reactor 1 has been described as an example of the reactor according to the present invention, but it is possible to appropriately change the configuration of the reactor 1. For example, the second flow path 12 has a pair of first inlets d1, a pair of second inlets d2, and a pair of outlets d3, but the number and positions of these can be appropriately changed.

(Variation 3)
In the above embodiment, the first inlet slit 14 is formed at one end of the reactor 1 (a portion extending from one end to two-fifths of the way up the reactor 1 from the inlet side of the raw material gas), but it is sufficient that at least a portion of the first inlet slit 14 is formed at one end of the reactor 1. Similarly, the second inlet slit 15 is formed at the other end of the reactor 1 (a portion extending from the other end to two-fifths of the way up the reactor 1 from the outlet side of the liquid fuel), but it is sufficient that at least a portion of the second inlet slit 15 is formed at the other end of the reactor 1. However, it is preferable that at least a portion of one or both of the first inlet slit 14 and the second inlet slit 15 is formed at one-fifth of the way up the reactor 1 from the end. This widens the flow range of the sweep gas, thereby suppressing thermal degradation of the catalyst and improving conversion efficiency over a wider range.

DESCRIPTION OF SYMBOLS 1 Reactor 10 Porous support 11 First flow path e1 Inlet e2 Outlet 12 Second flow path 13 Cell 14 First inlet slit d1 First inlet 15 Second inlet slit d2 Second inlet 16 Outlet slit d3 Outlet 17 First plugging portion 18 Second plugging portion 20 Catalyst 30 Water vapor separation membrane 40 First seal portion 50 Second seal portion

Claims (2)

a water vapor separation membrane that allows permeation of water vapor, which is a by-product of a conversion reaction from a feed gas containing at least hydrogen and carbon dioxide to a liquid fuel;
a first flow path provided on the non-permeation side of the water vapor separation membrane and through which the raw material gas flows;
a second flow path provided on the permeation side of the water vapor separation membrane, through which a sweep gas flows for sweeping the water vapor that has permeated the water vapor separation membrane;
a catalyst disposed in the first flow path to promote the conversion reaction;
Equipped with
The second flow path is
a first inlet at one end of the second flow path;
a second inlet at the other end of the second flow path;
an outlet between the first inlet and the second inlet;
and
the source gas and the sweep gas flow in the same direction between the first inlet and the outlet;
the source gas and the sweep gas flow in opposite directions between the second inlet and the outlet;
Monolithic reactor. A method for synthesizing a liquid fuel using a monolith reactor equipped with a water vapor separation membrane that allows permeation of water vapor, which is a by-product of a conversion reaction from a feed gas containing at least hydrogen and carbon dioxide to a liquid fuel, comprising:
a catalyst for promoting the conversion reaction is disposed in a first flow path provided on the non-permeation side of the water vapor separation membrane;
a second flow path provided on the permeation side of the water vapor separation membrane includes a first inlet at one end of the second flow path, a second inlet at the other end of the second flow path, and an outlet between the first inlet and the second inlet,
a step of flowing a sweep gas through the second flow path while flowing the source gas through the first flow path,
the sweep gas flows into both ends of the second flow passage and then flows out from the middle of the second flow passage;
the source gas and the sweep gas flow in the same direction between the first inlet and the outlet;
the source gas and the sweep gas flow in opposite directions between the second inlet and the outlet;
Liquid fuel synthesis method.