JP4965928B2 - Carbon dioxide separator and method - Google Patents

Description

The present invention dioxide to retrieve the raw material gas contains at least carbon dioxide and water vapor to a predetermined main component gas is supplied to the raw material side of the CO ₂ -facilitated transport membrane, the carbon dioxide that has passed through the CO ₂ -facilitated transport membrane from the permeate side More particularly, the present invention relates to a carbon dioxide separation apparatus and method for separating carbon dioxide contained in a reformed gas for a fuel cell containing hydrogen as a main component at a high selection ratio with respect to hydrogen.

  In the reforming system for the hydrogen station currently under development, the hydrocarbon is reformed to hydrogen and carbon monoxide (CO) by steam reforming, and further, the carbon monoxide is reacted with steam using a CO shift reaction. Produces hydrogen.

However, these techniques has been developed as a large-scale hydrogen production processes for chemical plants, Nissan number 100,000 m ³ or more ones are usually large, yet installed in the factory, high-continuous Driving is assumed. On the other hand, in the hydrogen station that produces hydrogen on-site from natural gas and oil as an important infrastructure that will support the future hydrogen energy society and supplies hydrogen to fuel cell vehicles, etc., the scale, installation environment, and operation of hydrogen production The pattern is greatly different from the conventional large-scale hydrogen plant, and many problems resulting from it remain.

  As a performance problem, in the case of a hydrogen station, it is necessary to respond to frequent start / stop and load changes in response to hydrogen demand (specifically, the number of fuel cell vehicles to be supplied with hydrogen, etc.). In particular, the CO transformer having the largest size and the largest heat capacity among reforming systems needs to be improved in terms of start-up time and load response.

  In addition, even for DSS (daily start / stop) operation in home systems, which is essential for promoting the reforming of fuel cell reforming systems, the CO transformer is also used in reforming systems in terms of start-up time and load responsiveness. Many problems remain, and in particular, downsizing and lowering the temperature of the CO transformer are the biggest problems.

  In addition, the steam reforming method has a large gap with respect to the target in terms of size and start-up time for automotive applications, and the on-board reforming in the automotive industry is rather more efficient than steam reforming, which is highly efficient. There is a tendency to aim at practical use with a partial oxidation method with excellent temperature reactivity. However, in the partial oxidation method, although the reformer can be expected to be greatly reduced in size, since it is accompanied by a CO converter, downsizing of the CO converter is a major issue for practical use. Thus, it can be said that downsizing of the CO converter is a common problem not only for the hydrogen station but also for the fuel cell reforming system including for automobiles.

  Also, from the viewpoint of efficiency, when steam reforming is performed, a decrease in S / C (molar ratio of steam to carbon (raw hydrocarbon)) is desirable in terms of thermal efficiency, but due to restrictions on the chemical equilibrium of the CO shift reaction. Highly efficient low S / C conditions were not employed.

  As a cost issue, PSA (Pressure Swing Adsorption) accounts for the largest percentage of the total cost of the hydrogen station, so there is a reforming method that increases the hydrogen concentration that directly leads to cost reduction. It was desired. The reformer outlet gas composition contains about 10% carbon monoxide and carbon dioxide in addition to hydrogen. In the CO converter, carbon monoxide decreases, but carbon dioxide increases. In steam reforming + CO conversion), about 20% of carbon dioxide and less than 1% of carbon monoxide remain together with about 1% of methane, and a large and high-cost PSA system is installed for purification. I had to do it.

  In conventional CO converters, a large amount of CO conversion catalyst is required as a cause of hindering miniaturization and shortening of the start-up time due to restrictions on the chemical equilibrium of the CO conversion reaction shown in the following (Chemical Formula 1). Can be mentioned. As an example, a reforming system for a 50 kW PAFC (phosphoric acid fuel cell) requires 20 L of reforming catalyst, whereas a CO conversion catalyst requires 77 L, which is about four times as much as the catalyst. This is a major factor that hinders downsizing the CO transformer and shortening the startup time.

(Chemical formula 1)
CO + H ₂ O → H ₂ + CO ₂

Therefore, the CO converter is provided with a CO ₂ facilitated transport membrane that selectively allows carbon dioxide to permeate, and the right-side carbon dioxide generated by the CO conversion reaction of (Chemical Formula 1) is efficiently removed outside the CO converter. As a result, the chemical equilibrium can be shifted to the hydrogen production side (right side), and a high conversion rate can be obtained at the same reaction temperature. As a result, carbon monoxide and carbon dioxide can be removed beyond the limit due to equilibrium constraints. It becomes possible. 18 and 19 schematically show this state. FIGS. 19A and 19B show changes in the concentrations of carbon monoxide and carbon dioxide with respect to the catalyst layer length of the CO converter with and without the CO ₂ facilitated transport membrane, respectively. ing.

The CO converter (CO ₂ permeable membrane reactor) equipped with the above CO ₂ facilitated transport membrane makes it possible to remove carbon monoxide and carbon dioxide beyond the limits due to equilibrium constraints. The PSA load and S / C can be reduced, and the cost and efficiency of the entire hydrogen station can be reduced. Further, by providing the CO ₂ facilitated transport film, the CO conversion reaction can be speeded up (higher SV), so that the reforming system can be downsized and the startup time can be shortened.

As a prior example of such a CO ₂ permeable membrane reactor, there is one disclosed in the following Patent Document 1 (or Patent Document 2 having the same contents by the same inventor).

The reforming systems proposed in Patent Documents 1 and 2 are directed to purifying reformed gas and water gas shift reaction generated when reforming a fuel such as hydrocarbon or methanol into hydrogen for a fuel cell vehicle on the vehicle. The present invention provides a CO ₂ facilitated transport membrane process useful for (CO shift reaction), and representative four types of processes are shown in FIGS. When hydrocarbons (including methane) are used as raw materials, carbon monoxide is selectively removed using a membrane reactor equipped with a CO ₂ facilitated transport membrane in the water gas shifter to increase the carbon monoxide reaction rate. While reducing the carbon oxide concentration, the purity of the produced hydrogen is improved. In addition, carbon monoxide and carbon dioxide remaining in the generated hydrogen are reacted with hydrogen by a methanator and converted to methane to reduce the concentration, thereby preventing a decrease in efficiency due to poisoning of the fuel cell.

In Patent Documents 1 and 2, a hydrophilic polymer film such as PVA (polyvinyl alcohol) mainly containing a halogenated quaternary ammonium salt ((R) ₄ N ⁺ X ⁻ ) as a carbon dioxide carrier is used as the CO ₂ facilitated transport film. in use. In Example 6 of Patent Documents 1 and 2, a PVA membrane having a film thickness of 49 μm and 50 wt% containing 50 wt% of tetramethylammonium fluoride salt as a carbon dioxide carrier and porous PTFE (tetrafluoride tetrafluoride) supporting the PVA membrane. A method for producing a CO ₂ facilitated transport film formed of a composite film made of an ethylene polymer) film is disclosed. In Example 7, a mixed gas (25% CO ₂ , 75% H ₂ ) is mixed with a total pressure of 3 atm. The membrane performance of the CO ₂ facilitated transport membrane when treated at 23 ° C. is disclosed. As the membrane performance, CO ₂ permeance R _CO2 is 7.2 GPU (= 2.4 × 10 ⁻⁶ mol / (m ² · s · kPa)), and CO ₂ / H ₂ selectivity is 19, which will be described later. Thus, it cannot be said that the performance is sufficient for application to the CO ₂ facilitated transport membrane of the CO ₂ permeable membrane reactor.

Special table 2001-511430 gazette US Pat. No. 6,579,331

Since the CO ₂ facilitated transport membrane selectively separates carbon dioxide as a basic function, development for the purpose of absorbing or removing carbon dioxide causing global warming has also been performed. However, when considering application to a CO ₂ permeable membrane reactor, the CO ₂ facilitated transport membrane is required to have a certain performance or more with respect to the operating temperature, CO ₂ permeance, CO ₂ / H ₂ selectivity, etc. . In other words, since the performance of the CO shift catalyst for use in the CO shift reaction tends to decrease with temperature, the use temperature is considered to be at least 100 ° C. CO ₂ permeance (one of the performance indicators of carbon dioxide permeability) shifts the chemical equilibrium of the CO shift reaction to the hydrogen production side (right side) and limits the carbon monoxide concentration and carbon dioxide concentration due to equilibrium constraints. Over a certain level, for example, about 0.1% or less, and in order to speed up the CO shift reaction (high SV), for example, 2 × 10 ⁻⁵ mol / (m ² · s · kPa) = 60 GPU or more) is considered necessary. Furthermore, when the hydrogen produced by the CO shift reaction is discarded outside together with carbon dioxide through the CO ₂ facilitated transport membrane, a process of separating and recovering hydrogen from the waste gas is required. Since hydrogen is naturally smaller in molecular size than carbon dioxide, a membrane that can permeate carbon dioxide can also permeate hydrogen, but only carbon dioxide is selectively passed from the membrane supply side to the permeate side by the carbon dioxide carrier in the membrane. It is considered that a facilitated transport membrane that can be transported toward the surface is required, and the CO ₂ / H ₂ selectivity in that case is required to be about 90 to 100 or more.

By the way, the CO ₂ facilitated transport membrane needs moisture to sufficiently exhibit the facilitated transport function (membrane function) of carbon dioxide. More specifically, the reaction of carbon dioxide (CO ₂ ) and primary amine (RNH ₂ ) in the membrane usually repeats the reaction shown in the following reaction formula (Chemical Formula 2), and as a whole (Chemical Formula 3) ) Shows the chemical reaction shown in the general reaction formula. From this, it can be seen that as the moisture in the membrane increases, the chemical equilibrium shifts to the product side (right side) and the permeation of carbon dioxide is promoted.

(Chemical formula 2)
CO ₂ + 2RNH ₂ → RNHCOO ⁻ + RNH ₃ ⁺
RNHCOO ⁻ + H ₂ O → RNH ₂ + HCO ₃ ⁻
(Chemical formula 3)
CO ₂ + 2RNH ₂ + H ₂ O → HCO ₃ ⁻ + RNH ₃ ⁺

  However, when the operating temperature is higher than 100 ° C., the moisture in the membrane evaporates, and the membrane function, that is, the facilitated transport function of carbon dioxide is lowered. Such a decrease in membrane function has become a common sense of conventional facilitated transport membranes. On the other hand, the higher the temperature, the higher the rate of the chemical reaction, so the inventors of the present application can fully demonstrate the membrane function by ensuring the amount of water in the membrane by increasing the partial pressure of water vapor in the gas phase under pressure. Confirmed that it will be.

When the CO ₂ facilitated transport membrane is used in combination with the CO shift reaction, the CO shift reaction is an exothermic reaction, so the lower the temperature, the more the chemical equilibrium shifts to the product side (right side), but the catalytic activity decreases. In addition, since the volume of the catalytic reactor is increased, it is considered that the temperature range of about 140 to 200 ° C. is appropriate. Furthermore, although CO ₂ permeation rate according to the operating under pressure reaction rate and CO ₂ facilitated transport membrane is possible to reduce the size of the increases and device, as the pressure from the pressure-resistant apparatus, and safety and about 150~800kPa desirable Conceivable. On the other hand, the amount of water in the CO ₂ facilitated transport membrane depends on the operating temperature and the partial pressure of water vapor in the gas phase, and therefore, if the operating temperature and pressure are set independently, sufficient water in the membrane can be secured. In addition, there is a possibility that sufficient membrane performance (CO ₂ permeance, CO ₂ / H ₂ selectivity) according to individual use conditions cannot be obtained. Therefore, an index indicating an appropriate relationship between the use temperature and pressure corresponding to each use situation is required.

The present invention has been made in view of the above problems, its object is used sufficient film performance can exert a CO ₂ -facilitated transport membrane at elevated temperature and pressure conditions above 100 ° C. Carbon dioxide It is to provide a separation apparatus and method.

In order to achieve the above object, a carbon dioxide separator according to the present invention provides a raw material gas containing at least carbon dioxide and water vapor in a predetermined main component gas at a supply temperature of 100 ° C. or more on the raw material side surface of the CO ₂ facilitated transport membrane. A carbon dioxide separator for supplying and removing carbon dioxide permeated through the CO ₂ facilitated transport membrane from a permeation side surface, wherein the CO ₂ facilitated transport membrane is added to the polyvinyl alcohol-polyacrylic acid copolymer gel membrane; A CO ₂ facilitated transport film formed by adding 3-diaminopropionic acid, the total pressure of the source gas supplied to the CO ₂ facilitated transport film, the partial pressure of water vapor in the source gas as the supply temperature The water vapor saturation specified by the ratio divided by the saturated water vapor pressure determined in the above is the pressure at which the water vapor saturation is the lower limit saturation set within the range of 0.3 to 0.6, and the water vapor saturation is The first, comprising a pressure adjusting means for adjusting the pressure below the pressure which becomes.

Furthermore, in the carbon dioxide separator according to the present invention, in addition to the first feature, the CO ₂ facilitated transport membrane is obtained by adding 2,3-diaminopropionic acid to a polyvinyl alcohol-polyacrylic acid copolymer gel membrane. A second feature is that the gel layer is supported on a hydrophilic porous film.

  Furthermore, in addition to the second feature, the carbon dioxide separator according to the present invention has a third feature that the gel layer supported on the hydrophilic porous membrane is covered and supported by a hydrophobic porous membrane. Features.

  Furthermore, in the carbon dioxide separator according to the present invention, in addition to the second or third feature, the gel layer comprises an aqueous solution containing a polyvinyl alcohol-polyacrylic acid copolymer and 2,3-diaminopropionic acid. A fourth feature is that the cast solution is produced by gelling after casting into the hydrophilic porous membrane.

  Furthermore, the carbon dioxide separator according to the present invention includes 2,3-diaminopropionic acid in addition to any one of the first to third features described above, in the polyvinyl alcohol-polyacrylic acid copolymer gel membrane. In addition, as an additive for promoting carbon dioxide permeability, ionic fluid (also called ionic liquid), glycerin, polyglycerin, polyethylene glycol, polypropylene glycol, polyethylene oxide, polyethyleneimine, polyallylamine, poly The fifth feature is that it contains a chemical substance selected from acrylic acid.

  Furthermore, in the carbon dioxide separator according to the present invention, in addition to the fifth feature, the gel layer promotes the carbon dioxide permeability with polyvinyl alcohol-polyacrylic acid copolymer, 2,3-diaminopropionic acid and the carbon dioxide. A sixth feature is that a cast solution made of an aqueous solution containing an additive for forming is cast into a hydrophilic porous membrane and then gelled.

  Furthermore, in the carbon dioxide separator according to the present invention, in addition to the fifth or sixth feature, the ionic fluid is a chemical substance selected from a compound comprising a combination of the following cation and anion, and the cation Is substituted with an imidazolium having the following substituents at the 1,3-positions and having an alkyl group, hydroxyalkyl group, ether group, allyl group, aminoalkyl group as a substituent group, or a quaternary ammonium cation. It has an alkyl group, a hydroxyalkyl group, an ether group, an allyl group, an aminoalkyl group as a group, and the anion is chloride ion, bromide ion, boron tetrafluoride ion, nitrate ion, bis (trifluoromethanesulfonyl). Imido ion, hexafluorophosphate ion, or trifluoromethanesulfonic acid ion A fifth feature that it is down.

In addition, the carbon dioxide separation method according to the present invention for achieving the above-described object provides a raw material gas containing at least carbon dioxide and water vapor in a predetermined main component gas to the raw material side surface of the CO ₂ facilitated transport membrane, A carbon dioxide separation method for removing carbon dioxide permeated through a CO ₂ facilitated transport membrane from a permeation side surface, wherein the CO ₂ facilitated transport membrane is formed on a polyvinyl alcohol-polyacrylic acid copolymer gel membrane with 2,3-diaminopropionic acid. CO ₂ facilitated transport film formed by adding the raw material gas to the supply temperature of 100 ° C. or higher, and the water vapor partial pressure in the raw material gas is divided by the saturated water vapor pressure determined by the supply temperature. At a total pressure below the pressure at which the water vapor saturation is 1 above the pressure at which the water vapor saturation specified by the ratio is not less than the lower limit saturation set in the range of 0.3 to 0.6. And supplying the raw material side of the serial CO ₂ -facilitated transport membrane.

According to the carbon dioxide separator having the first feature described above, the CO ₂ facilitated transport membrane is formed of 2,3-diaminopropionic acid (DAPA) in a polyvinyl alcohol-polyacrylic acid (PVA / PAA) copolymer gel membrane. Carbon dioxide which captures and transports carbon dioxide from the high concentration side interface (raw material side surface) to the low concentration side interface (permeation side surface) of the PVA / PAA gel layer in which the DAPA is a permeable substance. It functions as a carrier, and even at a high temperature of 100 ° C. or higher where the amount of water in the CO ₂ facilitated transport membrane decreases, the water vapor saturation is set within a range of 0.3 to 0.6, Since the proper pressurization state (increase in water vapor partial pressure) according to the supply temperature of the raw material gas is obtained at a pressure higher than or equal to the pressure, and a sufficient amount of water can be secured in the film, the film performance is determined by the lower limit saturation. CO ₂ permeance, CO ₂ selectivity) can be achieved regardless of the supply temperature of the raw material gas. The basis for this will be described below.

The factor governing the amount of water in the CO ₂ facilitated transport membrane that affects the membrane function is the water vapor pressure, but it should be considered that it is not the water vapor pressure but the water vapor saturation for the following reason. The water vapor saturation is usually also referred to as relative humidity or relative humidity, and is defined by (water vapor partial pressure Pw) / (saturated water vapor pressure Ps at that temperature) and corresponds to the activity of water vapor. Even if the partial pressure of water vapor in the gas phase (raw material gas) is constant, the saturated vapor pressure increases as the temperature increases, so the amount of water in the gel film decreases. However, if the water vapor saturation (Pw / Ps) is constant, it is considered that the amount of water in the gel film is determined regardless of the temperature. This is supported by the following experimental example.

FIG. 6 shows a raw material gas containing nitrogen as a main component gas (water vapor molar fraction is 63.5%) using a CO ₂ facilitated transport membrane having a composition ratio (% by weight) of DAPA in the gel layer of 50%. ) With respect to CO ₂ permeance and nitrogen selectivity (CO ₂ / N ₂ ) under three temperature conditions of 125 ° C., 140 ° C., and 160 ° C., the total pressure of the raw material gas is within a pressure range of 150 kPa to 600 kPa. changing a graph showing the result of measurement, the vertical axis is respectively CO ₂ permeance and to nitrogen selectivity (CO 2 / _{N 2),} the horizontal axis is the total pressure of the material gas (kPa). Since the measurement method and measurement conditions will be described in detail in an embodiment of the present invention described later, the detailed description thereof is omitted here. The relationship between the gas phase total pressure and the water vapor saturation is shown in FIG. 7, where temperature is a parameter. Since the molar fraction of water vapor in the raw material gas is 63.5%, the water vapor saturation becomes 1 when 63.5% of the total pressure is equal to the saturated water vapor pressure. From FIG. 7, for example, the total pressure when the water vapor saturation is 0.4 is 146 kPa, 228 kPa, and 390 kPa at temperatures of 125 ° C., 140 ° C., and 160 ° C., respectively. It is recognized that the CO ₂ permeance at each temperature in FIG. 6 tends to saturate almost at the peak even when the water vapor saturation is increased to a pressure equal to or higher than 0.4. Further, when the horizontal axis of the graph of FIG. 6 is converted into the water vapor saturation (Pw / Ps) using the relationship of FIG. 7 and rewritten, the graph shown in FIG. 9 is obtained. From FIG. 9, the CO ₂ permeance at each temperature of 125 ° C., 140 ° C., and 160 ° C. tends to reach a peak at approximately the same water vapor saturation and is saturated. In this case, the partial pressure of water vapor in the gas phase increases and the pressure required to secure the amount of water in the film can be estimated.

Furthermore, from FIG. 6 and FIG. 9, for example, when the lower limit saturation is about 0.3, the source gas containing nitrogen as the main component gas is about 90 to 100 or more regardless of the supply temperature of the source gas. A nitrogen selectivity (CO ₂ / N ₂ ) and a CO ₂ permeance of about 2 × 10 ⁻⁵ mol / (m ² · s · kPa) (= 60 GPU) or more can be achieved.

Further, FIG. 5 shows a raw material gas having a main component gas of hydrogen (a water vapor molar fraction of 63.3%) using a CO ₂ facilitated transport film in which the composition ratio (% by weight) of DAPA in the gel layer is 20%. 5%), CO ₂ permeance and hydrogen selectivity (CO ₂ / H ₂ ) under three temperature conditions of 125 ° C., 140 ° C. and 160 ° C., and the total pressure of the raw material gas is from 150 kPa to 600 kPa. In the graph showing the results of measurement with varying ranges, the vertical axis represents CO ₂ permeance and hydrogen selectivity (CO ₂ / H ₂ ), and the horizontal axis represents the total pressure (kPa) of the raw material gas. Since the measurement method and measurement conditions will be described in detail in an embodiment of the present invention described later, the detailed description thereof is omitted here. FIG. 8 is a diagram in which the horizontal axis of the graph of FIG. 5 is converted to water vapor saturation (Pw / Ps) using the relationship of FIG. Compared with 9), there is a discrepancy between the measured value of 140 ° C. and the other measured values of 125 ° C. and 160 ° C., but the measured value of CO ₂ permeance at each temperature crosses the total pressure of the raw material gas. Compared to the case of the axis, each measured value approaches, so by using the water vapor saturation as an index, the water vapor partial pressure in the gas phase increases at each temperature, and the amount of water in the film is secured. It is possible to estimate the pressure required for the operation.

5 and 8, when the lower limit saturation is about 0.5, the source gas containing hydrogen as the main component gas is less than about 90 to 100 regardless of the supply temperature of the source gas. It becomes possible to achieve a hydrogen selectivity (CO ₂ / H ₂ ) and a CO ₂ permeance of about 2 × 10 ⁻⁵ mol / (m ² · s · kPa) (= 60 GPU) or more.

As described above, according to the carbon dioxide separator having the first feature, the total pressure is adjusted within the range of the lower limit pressure at which the water vapor saturation becomes the predetermined lower limit saturation and the upper limit pressure at which the water vapor saturation becomes 1. Thus, depending on the supply temperature of the raw material gas, a high CO ₂ permeance in the saturation region or in the vicinity thereof can be obtained, and if the raw material gas supply temperature and the water vapor mole fraction are known, an appropriate total pressure is obtained. Water vapor saturation is given as an index.

In addition, according to the carbon dioxide separation device of the second feature, since the porous membrane supporting the PVA / PAA gel layer is hydrophilic, a gel layer with few defects can be stably produced, and high CO ₂ selectivity (when the main component of the source gas is hydrogen) can be maintained. In general, when the porous membrane is hydrophobic, it is possible to prevent moisture in the PVA / PAA gel membrane from entering the pores in the porous membrane at 100 ° C. or lower and lowering the membrane performance. Since it is considered that the same effect can be expected even in a situation where the water content in the PVA / PAA gel membrane decreases, the use of a hydrophobic porous membrane is recommended, and the CO ₂ used in the carbon dioxide separator of the present invention is recommended. In the facilitated transport membrane, by using a hydrophilic porous membrane for the following reasons, it has become possible to stably produce a CO ₂ facilitated transport membrane with few defects and capable of maintaining a high hydrogen selectivity.

When a cast solution made of an aqueous solution of PVA / PAA copolymer and DAPA is cast on a hydrophilic porous membrane, the pores of the porous membrane are filled with the liquid, and the cast solution is applied to the surface of the porous membrane. . When the cast solution is gelled, not only the surface of the porous membrane but also the pores are filled with the gel layer, so that defects are less likely to occur, and the success rate of forming the gel layer is increased. Considering the ratio of the pores (porosity) and the fact that the pores are not perpendicular to the membrane surface but bends (flexibility), the gel layer in the pores has a large resistance to gas permeation. As compared with the gel layer on the surface of the porous membrane, the permeability is lowered and the gas permeance is lowered. On the other hand, when the cast solution is cast on the hydrophobic porous membrane, the inside of the pores of the porous membrane is not filled with liquid, but the cast solution is applied only to the surface of the porous membrane and the pores are filled with gas. The gas permeance in the upper gel layer is higher in both hydrogen and carbon dioxide compared to the hydrophilic porous membrane. However, the gel layer on the membrane surface is more likely to have defects than the gel layer in the pores, and the success rate of film formation of the gel layer is reduced. Hydrogen has a smaller molecular size than carbon dioxide, so hydrogen may have higher gas permeance than carbon dioxide at small defects or where the gas permeance is locally high. Since the permeation rate of carbon dioxide is much larger than the hydrogen permeance that permeates through the physical dissolution and diffusion mechanism, the carbon dioxide permeance is hardly affected by local defects in the membrane, whereas the hydrogen permeance is Significant increase due to defects. As a result, the selectivity for hydrogen (CO ₂ / H ₂ ) when using a hydrophobic porous membrane will be lower than when using a hydrophilic porous membrane. Therefore, from the viewpoint of practical use, the stability and durability of the CO ₂ facilitated transport membrane are very important, and it is advantageous to use a hydrophilic porous membrane having a high selectivity to hydrogen (CO ₂ / H ₂ ). Become. The use of the hydrophilic porous membrane can be realized on the assumption that high CO ₂ permeance can be achieved by adding DAPA as a carbon dioxide carrier to the PVA / PAA gel layer. Note that the difference in gas permeance due to the difference between the hydrophobic porous membrane and the hydrophilic porous membrane is the same as the gel in the pores even if the cast solution is impregnated after gelation without adding the carbon dioxide carrier DAPA in advance. The point that the layer has a large resistance to gas permeation is the same, and it is presumed that the layer develops similarly.

From the above, according to the carbon dioxide separation device of the second feature, the operating temperature of 100 ° C. or higher, 2 × 10 ⁻⁵ mol / (m ² · s · CO ₂ permeance of about kPa) (= 60 GPU) or more and CO ₂ / H ₂ selectivity of about 90 to 100 or more can be realized, and a CO ₂ facilitated transport membrane applicable to a CO ₂ permeable membrane reactor can be provided. Thus, the CO transformer can be downsized, the startup time can be shortened, and the speed can be increased (higher SV).

Furthermore, according to the carbon dioxide separator having the third feature, the hydrophilic porous membrane carrying the gel layer is protected by the hydrophobic porous membrane, and the strength of the CO ₂ facilitated transport membrane during use is increased. As a result, when the carbon dioxide separator is applied to a CO ₂ permeable membrane reactor, it is sufficient even if the pressure difference on both sides (inside and outside the reactor) of the CO ₂ facilitated transport membrane is large (for example, 2 atmospheres or more). Film strength can be secured. Furthermore, since the gel layer is covered with a hydrophobic porous membrane, even if water vapor is condensed on the membrane surface of the hydrophobic porous membrane, the porous membrane is hydrophobic and water is repelled and penetrates into the gel layer. Is preventing. Therefore, the hydrophobic porous membrane can dilute the carbon dioxide carrier in the gel layer with water, and can prevent the thinned carbon dioxide carrier from flowing out of the gel layer.

Furthermore, according to the carbon dioxide separator having the fourth feature, a cast solution in which the distribution of carbon dioxide carriers to the membrane material (PVA / PAA) is appropriately adjusted is prepared in advance when the CO ₂ facilitated transport membrane is produced. Therefore, optimization of the mixing ratio of carbon dioxide carrier in the final PVA / PAA gel membrane can be easily realized, and high performance of the membrane performance of the CO ₂ facilitated transport membrane can be realized.

Furthermore, according to the carbon dioxide separators of the fifth to seventh characteristics, the gel layer of the CO ₂ facilitated transport membrane has ions having both hydrophilicity, compatibility with the carbon dioxide carrier, and affinity for carbon dioxide. Since carbon dioxide permeation is promoted and water in the PVA / PAA gel membrane at 100 ° C. or higher is reduced, high CO ₂ permeance can be realized. When the CO ₂ facilitated transport membrane is used in a high temperature environment of 100 ° C. or higher, the cross-linking of the PVA / PAA gel membrane further proceeds, and the facilitated transport of carbon dioxide by the carbon dioxide carrier may be inhibited, resulting in a decrease in carbon dioxide permeability. However, it is considered as a reason for the high CO ₂ permeance that the addition of the additive suppresses the progress of the crosslinking, thereby suppressing the decrease in carbon dioxide permeability due to use at high temperatures. The effect of the additive depends on the temperature, but at a specific temperature, the pressure difference between both sides of the CO ₂ facilitated transport membrane (inside and outside the reactor) appears remarkably at 3 atm or less, and at 2 atm or less. It is recognized from the experimental results that it appears more prominently.

  By the way, although carbon dioxide is facilitated and transported even when there is no moisture in the membrane, its permeation rate is generally very small, so that moisture in the membrane is indispensable for obtaining a high permeation rate. Therefore, by using a hydrophilic additive, moisture can be retained in the membrane as much as possible, and carbon dioxide permeability is promoted. In addition, by using an additive having compatibility with carbon dioxide carrier and affinity for carbon dioxide, the additive is DAPA without inhibiting the facilitated transport of carbon dioxide of DAPA as a carbon dioxide carrier. At the same time, it can be uniformly distributed in the membrane, and carbon dioxide permeability is promoted.

In particular, according to the carbon dioxide separator having the sixth feature, a cast solution in which the distribution of carbon dioxide carriers and additives to the membrane material (PVA / PAA) of the CO ₂ facilitated transport membrane is appropriately adjusted is prepared in advance. Therefore, optimization of the mixing ratio of the carbon dioxide carrier and the additive in the final PVA / PAA gel membrane can be easily realized, and high performance of the membrane performance can be realized.

According to the carbon dioxide separation method having the above characteristics, the CO ₂ facilitated transport membrane contains 2,3-diaminopropionic acid (DAPA) in the polyvinyl alcohol-polyacrylic acid (PVA / PAA) copolymer gel membrane. , Which functions as a carbon dioxide carrier that captures and transports carbon dioxide from the high concentration side interface (raw material side surface) to the low concentration side interface (permeation side surface) of the PVA / PAA gel layer where the DAPA is a permeating substance In addition, even at a high temperature of 100 ° C. or higher where the amount of water in the CO ₂ facilitated transport membrane decreases, the water vapor saturation is not less than the pressure at which the lower limit saturation is set within the range of 0.3 to 0.6. proper pressure state corresponding to the supply temperature of the raw material gas (increased water vapor partial pressure) is obtained at, since it is possible to ensure a sufficient amount of water in the membrane, membrane performance (CO determined by the lower limit saturation Permeance, CO ₂ selectivity) can be achieved regardless of the supply temperature of the raw material gas.

Further, similarly to the explanation for the carbon dioxide separator according to the first feature, the lower limit pressure at which the water vapor saturation is set within the range of 0.3 to 0.6 and the upper limit pressure at which the lower limit pressure is 1. By adjusting the total pressure within the range, it is possible to obtain a high CO ₂ permeance in the saturation region or its vicinity depending on the supply temperature of the raw material gas, and the supply temperature of the raw material gas and the water vapor mole fraction are known. If present, the proper total pressure is given as an index of water vapor saturation.

  Embodiments of a carbon dioxide separation apparatus and method according to the present invention (hereinafter referred to as “the present invention apparatus” and “the present invention method” as appropriate) will be described with reference to the drawings.

<First Embodiment>
The present invention apparatus, as shown in FIG. 1, for example, CO ₂ -facilitated transport membrane 10 CO transformer equipped with the (CO ₂ permeable membrane reactor) 20, the carbon dioxide is selectively by CO ₂ -facilitated transport membrane 10 And a back pressure regulator (corresponding to pressure regulating means) 15 provided in the exhaust path of the treated gas FG ′ after separation.

The CO ₂ permeable membrane reactor 20 is configured to convert, for example, carbon monoxide contained in the raw material gas FG other than hydrogen in a steam reformer (not shown) into CO conversion reaction shown in the above (Chemical Formula 1). The carbon dioxide generated by the CO shift reaction is selectively removed to the outside of the CO shift converter by the CO ₂ facilitated transport membrane 10 to shift the chemical equilibrium of the CO shift reaction to the hydrogen generation side. It is possible to remove carbon monoxide and carbon dioxide beyond the limits due to equilibrium constraints with high conversion at the same reaction temperature.

In the apparatus of the present invention, the performance of the CO shift catalyst for the CO shift reaction tends to decrease with temperature. Therefore, the operating temperature is considered to be at least 100 ° C., and is supplied to the raw material side of the CO ₂ facilitated transport membrane 10. The supply temperature of the raw material gas FG is 100 ° C. or higher. Thus, the feed gas FG is the upstream side of the CO ₂ -facilitated transport membrane 10, after being adjusted to a temperature suitable for catalytic activity in CO conversion catalyst, the CO ₂ -facilitated transport membrane 10 through the CO shift reaction (exothermic reaction) Supplied. Note that the raw material gas may be supplied to the CO ₂ facilitated transport film 10 after performing a process for lowering the raw material gas temperature after the CO shift reaction.

The partial pressure of the permeated gas containing carbon dioxide that has passed through the CO ₂ -facilitated transport membrane 10 by lowering, in order to maintain the transmission driving force of CO ₂ facilitated transport membrane 10, for discharging the permeate gas PG to the outside, CO ₂ A sweep gas SG passage 21 is provided along the outer side surface (permeation side surface) of the facilitated transport film 10, and a sweep gas SG such as air is fed from one side of the passage and permeated with the sweep gas SG from the other side. The gas PG is discharged. Specifically, for example, the CO ₂ permeable membrane reactor 20 is configured as a double tube structure, the inner tube is configured as a CO transformer, and the space between the inner tube and the outer tube is configured as a sweep gas passage 21.

The source gas FG is sent from the upstream steam reformer to the CO ₂ permeable membrane reactor 20 at a predetermined pressure. The total pressure of the source gas FG applied to the CO ₂ facilitated transport membrane 10 is Depending on the temperature of the raw material gas supplied to the CO ₂ facilitated transport membrane 10 by the back pressure regulator 15 provided on the downstream side, the water vapor saturation is a predetermined value (0.3 or more and 0.6 or less) in the manner described later. Is adjusted to a pressure equal to or lower than the lower limit saturation). The water vapor saturation is given as a ratio (Pw / Ps) obtained by dividing the water vapor partial pressure Pw in the raw material gas by the saturated water vapor pressure Ps determined by the supply temperature. The upper limit of the total pressure of the raw material gas is limited by the pressure resistance and safety of the CO ₂ facilitated transport membrane 10 and the CO ₂ permeable membrane reactor 20, but is set to a pressure at which the water vapor saturation is 1 or more. However, since the water in the film is in a saturated state, it is desirable to adjust the water vapor saturation to a pressure equal to or lower than 1. The back pressure regulator 15 is configured by a pressure regulating valve or the like.

The lower limit saturation functions as an index for determining the membrane performance of the CO ₂ facilitated transport membrane 10, and is determined in accordance with the specifications of a device (such as a CO ₂ permeable membrane reactor) to which the present invention is applied. Further, the membrane performance of the CO ₂ facilitated transport membrane 10 is, as will be apparent from the description of the examples described later, the membrane composition of the CO ₂ facilitated transport membrane 10 (the blending ratio of carbon dioxide carrier shown below) and the composition of the source gas. Therefore, the lower limit saturation is also determined according to the film composition of the CO ₂ facilitated transport film 10, the composition of the raw material gas, and the target film performance, and is 0.3 or more and 0 as described in Examples below. .6 or less is set.

Next, a CO ₂ facilitated transport membrane (hereinafter referred to as “the membrane of the present invention” as appropriate in the description of the first embodiment) 10 used in the apparatus of the present invention will be described.

  The membrane of the present invention uses a polyvinyl alcohol-polyacrylic acid (PVA / PAA) copolymer as a membrane material and 2,3-diaminopropionic acid (DAPA) as a carbon dioxide carrier. Moreover, in this embodiment, as shown schematically in FIG. 2, the membrane of the present invention comprises two hydrophilic porous membranes 2 each carrying a PVA / PAA gel membrane 1 containing a carbon dioxide carrier. It has a three-layer structure sandwiched between the films 3 and 4. Hereinafter, in order to distinguish a PVA / PAA gel membrane containing a carbon dioxide carrier from a PVA / PAA gel membrane not containing a carbon dioxide carrier, and a membrane of the present invention having a structure comprising two hydrophobic porous membranes, It is abbreviated as “containing gel film” as appropriate. Further, based on the total weight of PVA / PAA and DAPA in the contained gel film, in the contained gel film, PVA / PAA is present in a range of about 20 to 80% by weight, and DAPA is about 20 to 80% by weight. It exists in the range.

DAPA, which is a carbon dioxide carrier, must be neutralized with an alkali such as cesium hydroxide (CsOH) to convert NH ₃ ⁺ dissolved and dissociated in a cast solution described later to NH ₂ . This is because NH ₃ ⁺ does not react with carbon dioxide. Here, even if cesium hydroxide (CsOH) is used as an alkali or cesium carbonate (Cs ₂ CO ₃ ) is used, it is equivalent if the final pH value is the same. However, when cesium carbonate (Cs ₂ CO ₃ ) is used, carbonate ions and hydrogen carbonate ions are present in the contained gel film, but the contribution of the ions to the facilitated transport of carbon dioxide is small. it is conceivable that.

  The hydrophilic porous membrane preferably has, in addition to hydrophilicity, heat resistance of 100 ° C. or higher, mechanical strength, and adhesion with the contained gel membrane, and further has a porosity (porosity) of 55% or more, The pore diameter is preferably in the range of 0.1 to 1 μm. In the present embodiment, a hydrophilic tetrafluoroethylene polymer (PTFE) porous membrane is used as the hydrophilic porous membrane having these conditions.

  In addition to hydrophobicity, the hydrophobic porous membrane preferably has heat resistance of 100 ° C. or higher, mechanical strength, and adhesiveness with the contained gel membrane, and further has a porosity (porosity) of 55% or more, The pore diameter is preferably in the range of 0.1 to 1 μm. In the present embodiment, a non-hydrophilic tetrafluoroethylene polymer (PTFE) porous membrane is used as the hydrophobic porous membrane having these conditions.

  Next, an embodiment of a method for producing a film of the present invention will be described with reference to FIG.

  First, a cast solution composed of an aqueous solution containing a PVA / PAA copolymer and DAPA is prepared (step 1). More specifically, 1 g of a PVA / PAA copolymer (for example, a temporary name SS gel manufactured by Sumitomo Seika), 0.25 g of DAPA monohydrochloride, 0.54 g of cesium hydroxide (CsOH) (DAPA monohydrochloride) 2 equivalents), weighed in a sample bottle, added 20 g of water, and stirred and dissolved at room temperature overnight to obtain a cast solution.

Here, DAPA (NH ₂ —CH ₂ —CH (NH ₂ ) —COOH) is commercially available as its monohydrochloride, and when dissolved in water, [NH ₃ ⁺ —CH ₂ —CH (NH ₃ ⁺ Cl ^-) -COO ^-] dissociates as. Carbon dioxide does not react with protonated NH ₃ ⁺ but reacts with free NH ₂ . Therefore, in order to use DAPA as a carbon dioxide carrier, it is necessary to add 2 equivalents of cesium hydroxide to commercially available DAPA monohydrochloride to convert the amino group into a free amino group that is not protonated.

  Next, in order to remove bubbles in the cast solution obtained in Step 1, centrifugation (rotation speed: 5000 rpm for 30 minutes) is performed (Step 2).

  Next, the cast solution obtained in step 2 is mixed with a hydrophilic PTFE porous membrane (for example, manufactured by Advantech, H010A142C, film thickness 35 μm, pore diameter 0.1 μm, porosity 70%) and hydrophobic PTFE porous membrane (for example, Sumitomo Cast with an applicator on the surface of the porous PTFE porous membrane side of a layered porous membrane in which two sheets made by Denko, Fluoropore FP010, film thickness 60 μm, pore diameter 0.1 μm, porosity 55%) are laminated (Step 3) ). In addition, the cast thickness in the sample of the Example mentioned later is 500 micrometers. Here, the cast solution penetrates into the pores in the hydrophilic PTFE porous membrane, but the penetration stops at the boundary surface of the hydrophobic PTFE porous membrane, and the cast solution does not penetrate to the opposite surface of the layered porous membrane, There is no casting solution on the side surface of the porous porous membrane of the layered porous membrane, and the handling becomes easy.

  Next, the hydrophilic PTFE porous membrane after casting is naturally dried at room temperature for about half a day, and the cast solution is gelled to form a gel layer (step 4). In the method of the present invention, in Step 3, the cast solution is cast on the surface of the layered porous membrane on the hydrophilic PTFE porous membrane side, so in Step 4, the gel layer is formed on the surface (cast surface) of the hydrophilic PTFE porous membrane. In addition to being formed, the pores are filled and formed, so that defects (micro-defects such as pinholes) are less likely to occur, and the success rate of gel layer deposition is increased. In step 4, it is desirable that the naturally dried PTFE porous membrane is further thermally crosslinked at a temperature of about 120 ° C. for about 2 hours. In the samples of Examples and Comparative Examples described later, thermal crosslinking is performed.

  Next, on the gel layer side of the hydrophilic PTFE porous membrane surface obtained in step 4, the same hydrophobic PTFE porous membrane as that of the layered porous membrane used in step 3 is overlaid and schematically shown in FIG. As shown, a membrane of the present invention having a three-layer structure comprising a hydrophobic PTFE porous membrane / gel layer (containing gel membrane supported on a hydrophilic PTFE porous membrane) / hydrophobic PTFE porous membrane is obtained (step 5). In addition, in FIG. 2, a mode that the containing gel film | membrane 1 is filling in the pore of the hydrophilic PTFE porous film 2 is displayed typically linearly.

  Further, by forming a three-layer structure in which the gel layer is sandwiched between the hydrophobic PTFE porous membranes, one of the hydrophobic PTFE porous membranes is used in Step 3 and Step 4, and is a hydrophilic PTFE porous membrane supporting the contained gel membrane. The other hydrophobic PTFE porous membrane is used to protect the contained gel membrane from the other surface side.

  Furthermore, even if water vapor is condensed on the surface of the hydrophobic PTFE porous membrane, the PTFE porous membrane is hydrophobic and prevents water from being repelled and penetrating into the contained gel membrane. Therefore, it is possible to prevent the carbon dioxide carrier in the contained gel film from being diluted with water by the other PTFE porous membrane, and to prevent the diluted carbon dioxide carrier from flowing out of the containing gel film.

  As mentioned above, as for this invention film produced through the process 1-the process 5, the compounding ratio of (PVA / PAA: DAPA) is (80 weight%: 20 weight%) in order of description. In the example samples for evaluating the relationship between the water vapor saturation and the membrane performance below, the DAPA blending ratio is 35 wt%, in addition to the DAPA blending ratio 20 wt% produced by the above production method, Samples of 50 wt%, 65 wt%, and 80 wt% were also prepared. In this case, the amounts of the PVA / PAA copolymer, DAPA monohydrochloride, and cesium hydroxide in step 1 may be changed according to the blending ratio of DAPA. Each sample used was a four-layer structure in which the above three-layer structure was further reinforced with a polypropylene porous film coated with silicon.

  Next, the configuration of the experimental apparatus and the experimental method for evaluating the film performance of each sample will be described with reference to FIG.

As shown in FIG. 4, each sample 10 has two fluororubber gaskets between the raw material side chamber 12 and the permeation side chamber 13 of a stainless steel flow type gas permeation cell 11 (membrane area: 2.88 cm ² ). It is fixed by using it as a sealing material. Source gas (source gas 1: mixed gas composed of CO ₂ , H ₂ , H ₂ O, or source gas 2: mixed gas composed of CO ₂ , N ₂ , H ₂ O) FG, 2.24 × 10 ^{− The} raw material side chamber 12 is supplied at a flow rate of ² mol / min, and a sweep gas (Ar gas or He gas) SG is supplied to the permeation side chamber 13 at a flow rate of 8.18 × 10 ⁻⁴ mol / min. The pressure in the raw material side chamber 12 is a back pressure adjuster 15 provided on the downstream side of the cooling trap 14 in the exhaust gas discharge path (a back pressure adjuster 15 corresponding to the pressure adjusting means of the apparatus of the present invention shown in FIG. 1). With the same function). The pressure in the transmission side chamber 13 is atmospheric pressure. The gas composition after the water vapor in the sweep gas SG ′ discharged from the permeation side chamber 13 is removed by the cooling trap 16 is quantified by the gas chromatograph 17 and the permeance of CO ₂ and H ₂ from this and the flow rate of Ar in the sweep gas SG. [Mol / (m ² · s · kPa)] is calculated, and the CO ₂ / H ₂ selectivity is calculated from the ratio.

The raw material gas 1 is a mixed gas containing carbon dioxide and water vapor containing hydrogen as main components for simulating the raw material gas in the CO converter, CO ₂ : 3.65%, H ₂ : 32.85%, H ₂ O: Adjusted to a mixing ratio (mol%) of 63.5%. Specifically, water is quantified in a mixed gas flow (flow rate at 25 ° C .: 200 cm ³ / min, 8.18 × 10 ⁻³ mol / min) composed of 10% CO ₂ and 90% H ₂ (mol%). It was fed by the liquid feed pump 18 (flow rate: 0.256 cm ³ / min, 1.42 × 10 ⁻² mol / min), heated to 100 ° C. or more to evaporate the water, and the mixed gas having the above mixing ratio was This was prepared and supplied to the raw material side chamber 12.

The raw material gas 2 is a mixed gas containing carbon dioxide and water vapor whose main components are nitrogen, and a mixing ratio (moles) of CO ₂ : 3.65%, N ₂ : 32.85%, H ₂ O: 63.5%. %). Specifically, water is quantified in a mixed gas flow (flow rate at 25 ° C .: 200 cm ³ / min, 8.18 × 10 ⁻³ mol / min) composed of 10% CO ₂ and 90% N ₂ (mol%). It was fed by the liquid feed pump 18 (flow rate: 0.256 cm ³ / min, 1.42 × 10 ⁻² mol / min), heated to 100 ° C. or more to evaporate the water, and the mixed gas having the above mixing ratio was This was prepared and supplied to the raw material side chamber 12. The source gas 2 is different from the source gas mainly containing hydrogen supplied to the CO ₂ permeable membrane reactor 20 to which the apparatus of the present invention assumed in the present embodiment is applied. It is used for evaluation.

The sweep gas SG is supplied in order to reduce the partial pressure on the permeate side chamber side of the gas to be measured (CO ₂ , H ₂ ) that permeates the sample membrane and maintain the permeation driving force, and is a gas type different from the gas to be measured. (Ar gas for the source gas 1 and He gas for the source gas 2) are used. Specifically, Ar gas or He gas (flow rate at 25 ° C .: 20 cm ³ / min, 8.13 × 10 ⁻⁴ mol / min) was supplied to the permeation side chamber 13.

  Although not shown, in order to maintain the use temperature of the sample film and the temperatures of the source gas FG and the sweep gas SG at a constant temperature, the flow type gas permeable cell 11 with the sample film fixed and the gas are heated. The preheating coil is immersed in an oil thermostat set at a predetermined temperature.

Next, FIG. 5 shows the CO ₂ permeance R _CO2 and CO ₂ / H ₂ selectivity of a sample having a DAPA blending ratio of 20% by weight when the raw material gas 1 containing hydrogen as a main component is used. The result of having measured the pressure of the raw material gas FG in the raw material side chamber 12 in the pressurization state of the range of 150 kPa-600 kPa is shown. FIG. 6 shows the CO ₂ permeance R _CO2 and CO ₂ / N ₂ selectivity of the sample having a DAPA blending ratio of 50 wt% when the raw material gas 2 containing nitrogen as a main component is used. The result of having measured the pressure of raw material gas FG in the pressurization state of the range of 150 kPa-600 kPa is shown. There are three measurement temperatures: 125 ° C., 140 ° C., and 160 ° C.

As shown in FIGS. 5 and 6, at a constant source gas pressure, as the source gas temperature (the use temperature of the sample membrane) increases, the amount of water in the membrane decreases and the membrane performance deteriorates. I understand. Therefore, in order to realize a certain membrane performance (for example, CO ₂ permeance of about 2 × 10 ⁻⁵ mol / (m ² · s · kPa) (= 60 GPU)), the higher the temperature of the raw material gas, It is necessary to adjust the pressure higher. Further, it is recognized that the CO ₂ permeance tends to reach a peak and saturate at each temperature regardless of the composition of the source gas, even if the source gas is pressurized to a certain pressure or higher. Since the pressure at which the CO ₂ permeance is substantially constant increases as the temperature of the raw material gas increases, it is necessary to adjust the pressure higher as the temperature of the raw material gas increases in order to maximize the CO ₂ permeance. is there.

  The gist of the apparatus and the method of the present invention is that the moisture in the film is sufficient to exhibit a predetermined film performance by bringing the pressure of the source gas to a pressurized state in a high temperature state where the temperature of the source gas is 100 ° C. In addition, the back pressure regulator 15 sets an appropriate pressure corresponding to the temperature of the raw material gas using the water vapor saturation (Pw / Ps) as an index.

  FIG. 7 shows the pressure (total pressure) and the water vapor saturation (Pw) of the raw material gas (water vapor mole fraction is 63.5%) with the temperature of the raw material gas (water vapor mole fraction is 63.5%) as parameters. / Ps). Since the molar fraction of water vapor in the source gas is 63.5%, the water vapor saturation becomes 1 if 63.5% of the total pressure (water vapor partial pressure Pw) is equal to the saturated water vapor pressure Ps. As shown in FIG. 7, in order to maintain the water vapor saturation (Pw / Ps) at a constant value, the saturated water vapor pressure Ps increases as the temperature of the raw material gas increases. Therefore, it is necessary to increase the pressure (total pressure) of the raw material gas. I understand. If the pressure of the raw material gas is adjusted so that the water vapor saturation (Pw / Ps) is constant, the temperature of the raw material gas increases and the amount of water in the gel film decreases, but is proportional to the increase of the saturated water vapor pressure Ps. Since the water vapor partial pressure Pw also rises, the water content in the gel film is considered to be determined regardless of the temperature, and the film performance determined by the water vapor saturation (Pw / Ps) is obtained.

FIG. 8 shows the relationship between CO ₂ permeance R _CO2 and water vapor saturation (Pw / Ps) of a sample having a DAPA blending ratio of 20% by weight when raw material gas 1 is used. FIG. 9 shows the relationship between CO ₂ permeance R _CO2 and water vapor saturation (Pw / Ps) of a sample having a DAPA blending ratio of 50% by weight when raw material gas 2 is used. There are three measurement temperatures: 125 ° C., 140 ° C., and 160 ° C. FIG. 8 is a graph rewritten by converting the raw material gas pressure on the horizontal axis of FIG. 5 into water vapor saturation (Pw / Ps) using the relationship of FIG. 7, and FIG. 9 is a graph of the horizontal axis of FIG. It is the graph which converted and rewritten the raw material gas pressure into water vapor saturation (Pw / Ps) using the relationship of FIG.

From FIG. 8, if the water vapor saturation is about 0.5 or more, 2 × 10 ⁻⁵ mol / (m ² · s · kPa) (= 60 GPU) at each temperature, that is, regardless of the supply temperature of the raw material gas 1. It can be seen that a CO ₂ permeance of about or higher can be achieved. Thereby, the water vapor saturation (about 0.5) is set as the lower limit saturation, and the raw material gas pressure is determined based on FIG. 7 with respect to the supply temperature of the raw material gas 1 (125 ° C., 140 ° C., 160 ° C., etc.) If the pressure of the raw material gas is adjusted by a back pressure regulator with the raw material gas pressure as the lower limit, the membrane of the present invention with a DAPA blending ratio of 20 wt% is used to make the raw material gas 1 mainly composed of hydrogen. The CO ₂ permeance can be achieved. Specifically, the raw material gas pressures at the water vapor saturation of about 0.5 at the raw material gas supply temperatures of 125 ° C., 140 ° C., and 160 ° C. are 183 kPa, 285 kPa, and 487 kPa, respectively. When these raw material gas pressures are applied to FIG. 5 as lower limit pressures, it is understood that the CO ₂ permeance can be achieved at each temperature.

Further, as shown in FIG. 8, when the water vapor saturation is about 0.6 or more, the CO ₂ permeance is close to saturation (at the start of saturation tendency) at each temperature, that is, regardless of the supply temperature of the raw material gas 1. Can be achieved. Thereby, the water vapor saturation (about 0.6) is set as the lower limit saturation, and the raw material gas pressure is determined based on FIG. 7 with respect to the supply temperature of the raw material gas 1 (125 ° C., 140 ° C., 160 ° C., etc.) If the pressure of the raw material gas is adjusted by a back pressure regulator with the raw material gas pressure as the lower limit, the membrane of the present invention with a DAPA blending ratio of 20 wt% is used to make the raw material gas 1 mainly composed of hydrogen. A CO ₂ permeance close to the saturation state can be achieved. Specifically, the raw material gas pressures at the water vapor saturation of about 0.6 at the raw material gas supply temperatures of 125 ° C., 140 ° C., and 160 ° C. are 219 kPa, 342 kPa, and 585 kPa, respectively. When these raw material gas pressures are applied to FIG. 5 as lower limit pressures, it can be seen that the CO ₂ permeance almost reaches saturation at each temperature.

Further, FIG. 9 shows that when the water vapor saturation is about 0.4 or more, CO ₂ permeance close to saturation can be achieved at each temperature, that is, regardless of the supply temperature of the raw material gas 2. Accordingly, the water vapor saturation (about 0.4) is set as the lower limit saturation, and the raw material gas pressure is obtained based on FIG. 7 with respect to the supply temperature of the raw material gas 2 (125 ° C., 140 ° C., 160 ° C., etc.) If the pressure of the raw material gas is adjusted by the back pressure regulator with the raw material gas pressure as the lower limit, the membrane of the present invention with a DAPA blending ratio of 50% by weight is used for the raw material gas 2 mainly composed of nitrogen. A CO ₂ permeance close to the saturation state can be achieved. Specifically, the raw material gas pressures at the water vapor saturation of about 0.4 at the raw material gas supply temperatures of 125 ° C., 140 ° C., and 160 ° C. are 146 kPa, 228 kPa, and 390 kPa, respectively. When these raw material gas pressures are applied to FIG. 6 as lower limit pressures, it can be seen that the CO ₂ permeance almost reaches saturation at each temperature.

Furthermore, as shown in FIG. 9, when the water vapor saturation is about 0.3 or more, it is 2 × 10 ⁻⁵ mol / (m ² · s · kPa) (at any temperature, that is, regardless of the supply temperature of the raw material gas 2). It can be seen that CO ₂ permeance of about 60 GPU or more can be achieved. Accordingly, the water vapor saturation (about 0.3) is set as the lower limit saturation, and the raw material gas pressure is obtained based on FIG. 7 with respect to the supply temperature of the raw material gas 2 (125 ° C., 140 ° C., 160 ° C., etc.) If the pressure of the raw material gas is adjusted by the back pressure regulator with the raw material gas pressure as the lower limit, the membrane of the present invention with a DAPA blending ratio of 50% by weight is used for the raw material gas 2 mainly composed of nitrogen. The CO ₂ permeance can be achieved. Specifically, the raw material gas pressures at the water vapor saturation of about 0.3 at the raw material gas supply temperatures of 125 ° C., 140 ° C., and 160 ° C. are 110 kPa, 171 kPa, and 292 kPa, respectively. When these raw material gas pressures are applied to FIG. 6 as lower limit pressures, it can be seen that the CO ₂ permeance almost reaches saturation at each temperature. However, for 125 ° C., since there is no data on the low pressure side from 150 kPa, the estimation is based on data of 150 kPa or more.

Next, in FIG. 10, the raw material gas 1 containing hydrogen as a main component was used as a raw material gas for each sample in which the blending ratio of DAPA was different from 20% by weight, 35% by weight, 50% by weight, and 65% by weight. for membrane performance showing the results of measurement of the (CO ₂ permeance _{R CO2,} CO ₂ / _H 2 selectivity). Further, in FIG. 11, when the raw material gas 2 containing nitrogen as a main component is used as the raw material gas for each sample having a DAPA blending ratio different from 0%, 20%, 50%, and 80% by weight. The results of measuring the membrane performance (CO ₂ permeance R _CO2 , CO ₂ / N ₂ selectivity) are shown. In addition, all the measurement temperatures are 140 degreeC. As shown in FIGS. 10 and 11, it can be seen that an increase in the blending ratio of DAPA and pressurization of the raw material gas are effective for improving the film performance regardless of the type of the raw material gas.

  Next, in the membrane of the present invention, a hydrophilic PTFE porous membrane is used as the porous membrane supporting the contained gel membrane, and the effect thereof will be described. First, the film composition of each sample of an example using a hydrophilic PTFE porous film and a comparative example using a hydrophobic PTFE porous film as a porous film carrying the gel gel will be described. The sample of the example was manufactured by the above-described manufacturing method. The blending ratio of (PVA / PAA: DAPA) is (80% by weight: 20% by weight) in the order of description. The sample of the comparative example was prepared by using one layer of a hydrophobic PTFE porous membrane in place of the layered porous membrane of the hydrophilic PTFE porous membrane and the hydrophobic PTFE porous membrane in the above-described production method. Therefore, in the sample of the comparative example, as schematically shown in FIG. 12, the PVA / PAA gel film 1 containing carbon dioxide carrier is sandwiched between two hydrophobic porous films 3 and 4. Composed of structure. The blending ratio of (PVA / PAA: DAPA) is the same as in the examples. Each sample used was a four-layer structure in which the above three-layer structure was further reinforced with a polypropylene porous film coated with silicon.

Next, FIG. 13 shows the CO ₂ permeance R _CO2 and CO ₂ / H ₂ selectivity of each sample of the example and the comparative example, and the pressure of the raw material gas FG in the raw material side chamber 12 is in the range of 150 kPa to 350 kPa. The result measured in the state is shown. The measurement temperature is 125 ° C.

From FIG. 13, the CO ₂ permeance is slightly higher in the entire pressure range in the comparative sample using the hydrophobic PTFE porous membrane than in the example using the hydrophilic PTFE porous membrane. In the CO ₂ / H ₂ selectivity, it can be seen that the sample of the example is significantly improved over the sample of the comparative example. This is because when a hydrophilic PTFE porous membrane is used, the gel layer is filled not only on the surface of the PTFE porous membrane but also in the pores, so that defects (minute defects such as pinholes) are less likely to occur. It is considered that gas permeance, particularly hydrogen permeance, is prevented from rising through the defect.

In addition, in the CO ₂ facilitated transport membrane disclosed in Patent Documents 1 and 2, a use temperature of 100 ° C. or more, a CO ₂ permeance of about 2 × 10 ⁻⁵ mol / (m ² · s · kPa), and While none of the CO ₂ / H ₂ selectivity of about 90 to 100 or more is satisfied, each sample of the example and comparative example shown in FIG. 13 generally satisfies all the requirements. It can be seen that good results are obtained in the samples of the examples. In the sample of the comparative example, the CO ₂ / H ₂ selectivity falls below 100 at 300 kPa or more, and the CO ₂ / H ₂ selectivity decreases more significantly when the temperature is further increased.

Next, FIG. 14 shows the CO ₂ permeance R _CO2 and CO ₂ / H ₂ selectivity of each sample of the example and the comparative example, and the pressure of the raw material gas FG in the raw material side chamber 12 is in the range of 150 kPa to 550 kPa. The result measured in the state is shown. The measurement temperature is 140 ° C.

From FIG. 14, both the CO ₂ permeance R _CO2 and the CO ₂ / H ₂ selectivity are decreased by increasing the temperature from 125 ° C. to 140 ° C., but the increase in temperature causes an increase in the PVA / PAA gel membrane. This is due to a decrease in moisture that contributes to facilitated transport of carbon dioxide. However, in the sample of the example, even when the temperature rises to 140 ° C., a higher CO ₂ / H ₂ selectivity than that of the sample of the comparative example can be obtained. Therefore, when the pressure of the source gas FG is 350 kPa or more, 2 × 10 ^{− Both} the CO ₂ permeance of about ⁵ mol / (m ² · s · kPa) and the CO ₂ / H ₂ selectivity of about 90 to 100 or more are generally satisfactory, whereas the sample of the comparative example has CO 2 It has resulted in significantly less than the expected value at _{2 /} H ₂ selectivity.

Second Embodiment
A second embodiment of the device of the present invention will be described. In the apparatus of the present invention of the second embodiment, the CO ₂ facilitated transport membrane 10 to be used has a composition different from that of the CO ₂ facilitated transport membrane used in the first embodiment, and the other configuration and the method for adjusting the raw material gas pressure Is the same as in the first embodiment. Hereinafter, the CO ₂ facilitated transport membrane used in the second embodiment (hereinafter referred to as “the present invention membrane” as appropriate in the description of the second embodiment) will be described.

The membrane of the present invention is a CO ₂ facilitated transport membrane containing a carbon dioxide carrier in a gel membrane containing water, and in order to realize high carbon dioxide permeability, in addition to the carbon dioxide carrier, the carbon dioxide permeability is increased. An additive for promoting is contained in the gel film. Therefore, it is different from the CO ₂ facilitated transport membrane used in the first embodiment in that an additive is added in the gel membrane.

  Specifically, the membrane of the present invention uses a polyvinyl alcohol-polyacrylic acid (PVA / PAA) copolymer as a membrane material, and uses 2,3-diaminopropionic acid (DAPA) as a carbon dioxide carrier. , Glycerin or ionic fluid is used as an additive. The membrane of the present invention has a three-layer structure in which a hydrophilic porous membrane 2 carrying a PVA / PAA gel membrane containing a carbon dioxide carrier and an additive is sandwiched between two hydrophilic porous membranes 3 and 4 (see FIG. 2 is the same as the three-layer structure of the first embodiment shown in FIG. Hereinafter, a PVA / PAA gel film containing a carbon dioxide carrier and an additive, a PVA / PAA gel film containing no carbon dioxide carrier and an additive, and a membrane of the present invention having a structure comprising two hydrophobic porous films In order to distinguish them from each other, they are appropriately abbreviated as “containing gel film”. Further, based on the total weight of PVA / PAA, DAPA and additives in the containing gel film, PVA / PAA is present in the range of about 20 to 80% by weight in the containing gel film, and DAPA is about 20 to It is present in the range of 80% by weight, and the additive is present in the range of about 0-30% by weight.

The additive is a low vapor pressure liquid such as an ionic fluid or an oligomer, and requires hydrophilicity, thermal stability, affinity for carbon dioxide, and compatibility with DAPA which is a carbon dioxide carrier. As an ionic fluid having such conditions, a chemical substance selected from a compound comprising a combination of the following cation and anion can be used.
Cation: Imidazolium having the following substituents at positions 1 and 3, substituted with an alkyl group, hydroxyalkyl group, ether group, allyl group, aminoalkyl group as a substituent group, or substituted with a quaternary ammonium cation A group having an alkyl group, a hydroxyalkyl group, an ether group, an allyl group or an aminoalkyl group as a group.
Anion: Chloride ion, bromide ion, boron tetrafluoride ion, nitrate ion, bis (trifluoromethanesulfonyl) imide ion, hexafluorophosphate ion, or trifluoromethanesulfonate ion.

  Specific examples of the ionic fluid include 1-allyl-3-ethylimidazolium bromide, 1-ethyl-3-methylimidazolium bromide, 1- (2-hydroxyethyl) -3-methylimidazolium bromide, 1 -(2-methoxyethyl) -3-methylimidazolium bromide, 1-octyl-3-methylimidazolium chloride, N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium tetrafluoroborate, Ethylmethylimidazolium bis (trifluoromethanesulfonyl) imide, ethylmethylimidazolium bistrifluoromethanesulfonic acid, ethylmethylimidazolium dicyanamide, trihexyl tetradecylphosphonium chloride, and the like can be used. In addition to the ionic fluid, a chemical substance selected from glycerin, polyglycerin, polyethylene glycol, polypropylene glycol, polyethylene oxide, polyethyleneimine, polyallylamine, and polyacrylic acid can be used as an additive.

Since DAPA, which is a carbon dioxide carrier, a hydrophilic porous membrane, and a hydrophobic porous membrane are the same as those used in the CO ₂ facilitated transport membrane of the first embodiment, overlapping description is omitted.

  Next, an embodiment of a method for producing a film of the present invention will be described with reference to FIG.

  First, a cast solution composed of an aqueous solution containing a PVA / PAA copolymer, DAPA and an additive is prepared (step 1). More specifically, 1 g of a PVA / PAA copolymer (for example, a temporary name SS gel manufactured by Sumitomo Seika), 0.25 g of DAPA monohydrochloride, 0.54 g of cesium hydroxide (CsOH) (DAPA monohydrochloride) 2 g), 0.2 g of additive (ionic fluid AEB, etc.), weighed in a sample bottle, added with 20 g of water, and stirred at room temperature for 24 hours to dissolve to obtain a cast solution. Except for the point that an additive is added to the cast solution, it is the same as the manufacturing method of the first embodiment, and the description of the DAPA processing method is omitted.

  Next, in order to remove bubbles in the cast solution obtained in Step 1, centrifugation (rotation speed: 5000 rpm for 30 minutes) is performed (Step 2).

  Next, the cast solution obtained in step 2 is mixed with a hydrophilic PTFE porous membrane (for example, manufactured by Advantech, H010A142C, film thickness 35 μm, pore diameter 0.1 μm, porosity 70%) and hydrophobic PTFE porous membrane (for example, Sumitomo Cast with an applicator on the surface of the porous PTFE porous membrane side of a layered porous membrane in which two sheets made by Denko, Fluoropore FP010, film thickness 60 μm, pore diameter 0.1 μm, porosity 55%) are laminated (Step 3) ). In addition, the cast thickness in the sample of the Example and comparative example which are mentioned later is 254 micrometers.

  Next, the hydrophilic PTFE porous membrane after casting is naturally dried at room temperature for about half a day, and the cast solution is gelled to form a gel layer (step 4). In the method of the present invention, in Step 3, the cast solution is cast on the surface of the layered porous membrane on the hydrophilic PTFE porous membrane side, so in Step 4, the gel layer is formed on the surface (cast surface) of the hydrophilic PTFE porous membrane. In addition to being formed, the pores are filled and formed, so that defects (micro-defects such as pinholes) are less likely to occur, and the success rate of gel layer deposition is increased. In step 4, it is desirable that the naturally dried PTFE porous membrane is further thermally crosslinked at a temperature of about 120 ° C. for about 2 hours. In the samples of Examples and Comparative Examples described later, thermal crosslinking is performed.

  Next, the same hydrophobic PTFE porous membrane as that of the layered porous membrane used in Step 3 is stacked on the gel layer side of the hydrophilic PTFE porous membrane surface obtained in Step 4, and the hydrophobic PTFE porous membrane / A membrane of the present invention comprising a gel layer (containing gel membrane supported on a hydrophilic PTFE porous membrane) / hydrophobic PTFE porous membrane is obtained (step 5). Each process of step 2 to step 5 is exactly the same as the manufacturing method of the first embodiment.

As described above, the membrane of the present invention produced through the steps 1 to 5 has a membrane performance applicable to a CO ₂ permeable membrane reactor, that is, at a use temperature of 100 ° C. or more with respect to a source gas mainly containing hydrogen, A CO ₂ permeance of about 2 × 10 ⁻⁵ mol / (m ² · s · kPa) (= 60 GPU) or more and a CO ₂ / H ₂ selectivity of about 100 or more can be realized.

  Further, by forming a three-layer structure in which the gel layer is sandwiched between the hydrophobic PTFE porous membranes, one of the hydrophobic PTFE porous membranes is used in Step 3 and Step 4, and is a hydrophilic PTFE porous membrane supporting the contained gel membrane. The other hydrophobic PTFE porous membrane is used to protect the contained gel membrane from the other surface side.

  Hereinafter, each membrane performance is demonstrated with reference to each sample of four Examples 1-4 which used the following four types of ionic fluid as an additive individually. The four ionic fluids are: Example 1: 1-allyl-3-ethylimidazolium bromide, Example 2: 1- (2-hydroxyethyl) -3-methylimidazolium bromide, Example 3: 1-octyl -3-Methylimidazolium chloride, Example 4: N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium tetrafluoroborate.

  First, the film composition of each sample of Examples 1 to 4 will be described. The sample of Example 1 was prepared by the above-described preparation method using 1-allyl-3-ethylimidazolium bromide as an additive. The blending ratio of (PVA / PAA: DAPA: additive) is (66.3 wt%: 20 wt%: 13.7 wt%) in the order of description. The sample of Example 2 was made by the above-described preparation method using 1- (2-hydroxyethyl) -3-methylimidazolium bromide as an additive. The blending ratio of (PVA / PAA: DAPA: additive) is (66.3 wt%: 20 wt%: 13.7 wt%) in the order of description. The sample of Example 3 was prepared by the above-described preparation method using 1-octyl-3-methylimidazolium chloride as an additive. The blending ratio of (PVA / PAA: DAPA: additive) is (66.3 wt%: 20 wt%: 13.7 wt%) in the order of description. The sample of Example 4 was prepared by the above-described preparation method using N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium tetrafluoroborate as an additive. The blending ratio of (PVA / PAA: DAPA: additive) is (66.3 wt%: 20 wt%: 13.7 wt%) in the order of description.

  Next, a comparative sample in which no additive is added to the PVA / PAA gel membrane prepared in order to evaluate the effect of the additive used in each sample of Examples 1 to 4, that is, the carbon dioxide permeability promoting effect. Are manufactured under the same conditions as the sample of the example of the first embodiment (however, the cast thickness is different from that of the sample of the first embodiment). Since the configurations of the experimental apparatus and the experimental method for evaluating the film performance of Examples 1 to 4 and each sample for comparison are the same as those in the first embodiment, redundant description is omitted.

Next, in FIG. 16, CO ₂ permeances R _CO2 and CO ₂ / N of Examples 1 to 4 and each sample for comparison when the source gas 2 containing nitrogen as a main component is used as the source gas FG. ₂ shows the result of measuring the pressure of the raw material gas FG in the raw material side chamber 12 in a pressurized state in the range of 150 kPa to 450 kPa. The measurement temperature is 140 ° C.

From FIG. 16, the membrane of the present invention uses CO ₂ at a high temperature condition of 140 ° C., so that even when the pressure of the raw material gas FG is 350 kPa or less, it is less CO ₂ than the comparative sample using no additive. It can be seen that the permeance is improved. It can also be seen that the CO ₂ / N ₂ selectivity is improved in comparison with the comparative samples in some Examples 1, 2, and 4 in the pressure range of 300 kPa or less.

Next, FIG. 17 shows a measurement result of confirming the CO ₂ permeance improvement by the use of additives in the feed gas of _CO 2 / _{H 2} system. FIG. 17 shows an implementation in which 1-allyl-3-ethylimidazolium bromide of the same ionic fluid as that of Example 1 was added as an additive when the source gas 1 containing hydrogen as a main component was used as the source gas FG. Example 5 and the results of measuring the CO ₂ permeance R _CO2 and CO ₂ / H ₂ selectivity of each sample for comparison and the pressure of the raw material gas FG in the raw material side chamber 12 in a pressurized state ranging from 150 kPa to 450 kPa. Show. The measurement temperature is 140 ° C.

  The sample of Example 5 was prepared by the above-described preparation method using 1-allyl-3-ethylimidazolium bromide as an additive. The blending ratio of (PVA / PAA: DAPA: additive) is (66.3 wt%: 20 wt%: 13.7 wt%) in the order of description. The sample for comparison in which no additive is added in the PVA / PAA gel film was prepared under the same conditions as the sample of the example of the first embodiment (however, the cast thickness is different from the sample of the first embodiment). Is used.

Since the configuration of the experimental apparatus for evaluating the film performance of Example 5 and each sample for comparison is the same as that of the first embodiment, a duplicate description is omitted. However, the film area of Example 5 and each sample for comparison is 3.65 cm ² unlike the samples of the first embodiment and Examples 1-4. The experimental method is the same as that of the first embodiment except for the composition and flow rate of the source gas. A raw material gas 3 (mixed gas composed of CO ₂ , H ₂ , H ₂ O) is used as the raw material gas FG, and supplied to the raw material side chamber 12 at a flow rate of 1.64 × 10 ⁻² mol / min, and a sweep gas (Ar Gas) SG is supplied to the permeation side chamber 13 at a flow rate of 8.18 × 10 ⁻⁴ mol / min.

As the raw material gas 3, a mixed gas composed of CO ₂ , H ₂ and H ₂ O was adjusted to a mixing ratio (mol%) of CO ₂ : 5%, H ₂ : 45%, H ₂ O: 50%. Specifically, water is quantified in a mixed gas flow (flow rate at 25 ° C .: 200 cm ³ / min, 8.13 × 10 ⁻³ mol / min) composed of 10% CO ₂ and 90% H ₂ (mol%). was fed at a liquid feed pump 18 (flow ^{rate: 0.147cm 3 /min,8.06×10 -3 mol / min} ), the water is evaporated by heating to above 100 ° C., a mixed gas of the mixed ratio This was prepared and supplied to the raw material side chamber 12.

From FIG. 17, the membrane of the present invention can be used as a comparative sample that does not use an additive in the entire pressure range of 150 to 450 kPa of the pressure of the raw material gas FG by using an additive even under a high temperature condition of 140 ° C. In comparison, it can be seen that the CO ₂ permeance and the CO ₂ / H ₂ selectivity are improved.

The reason why the CO ₂ permeance improvement effect due to the use of the additive appears on the low pressure side is that the water vapor partial pressure is low and the water content in the PVA / PAA gel membrane is reduced at low pressure, so the additive is a kind of plasticization. This is thought to be due to the role of the agent.

  Hereinafter, another embodiment of the carbon dioxide separator according to the present invention will be described.

<1> In the above embodiment, the pressure adjusting means for adjusting the raw material gas pressure of the apparatus of the present invention is provided in the exhaust path of the raw material gas after the carbon dioxide is selectively separated by the CO ₂ facilitated transport membrane 10. Although the back pressure adjuster is used, the pressure adjusting means is not limited to the back pressure adjuster, and may be adjusted on the upstream side where the source gas is supplied.

<2> In the above embodiment, the CO ₂ facilitated transport membrane used in the apparatus of the present invention is a gel solution prepared from an aqueous solution containing a PVA / PAA copolymer and a carbon dioxide carrier DAPA (or DAPA and an additive). Although it was produced by casting into a hydrophilic PTFE porous membrane for supporting a membrane and then gelled, it may be produced by a production method other than the production method. For example, the PVA / PAA copolymer gel film may be produced by impregnating at least one of DAPA and an additive later.

<3> In the above embodiment, the CO ₂ facilitated transport membrane used in the apparatus of the present invention is hydrophobic PTFE porous membrane / gel layer (containing gel membrane supported on the hydrophilic PTFE porous membrane) / hydrophobic PTFE porous membrane. However, the support structure of the membrane of the present invention is not necessarily limited to the three-layer structure. For example, a two-layer structure composed of a hydrophobic PTFE porous film / gel layer (containing gel film supported on a hydrophilic PTFE porous film) may be used.

<4> In the above embodiment, it is assumed that the device of the present invention is applied to a CO ₂ permeable membrane reactor, but the device of the present invention selectively separates carbon dioxide in addition to the CO ₂ permeable membrane reactor. Can be used for the purpose. Therefore, the raw material gas supplied to the apparatus of the present invention is not limited to the mixed gas exemplified in the above embodiment.

<5> exemplified in the above embodiment, the mixing ratio of each component in the composition of CO ₂ facilitated transport membrane used in the present invention apparatus, dimensions of each part of the film is an illustration for easier understanding of the present invention The present invention is not limited to the case of using those numerical values of the CO ₂ facilitated transport membrane.

The carbon dioxide separation apparatus and method according to the present invention can be used for separation of carbon dioxide, and in particular, carbon dioxide contained in reformed gas for fuel cells and the like mainly composed of hydrogen with a high selectivity to hydrogen. This is useful for a CO ₂ permeable membrane reactor equipped with a separable CO ₂ facilitated transport membrane.

The block diagram which shows typically the schematic structure in one Embodiment of the carbon dioxide separator which concerns on this invention Sectional view schematically showing the structure of an embodiment of a CO ₂ -facilitated transport membrane according to the present invention Process diagram showing a first embodiment of a method for manufacturing a CO ₂ facilitated transport membrane according to the present invention Configuration diagram of an experimental apparatus for evaluating the membrane performance of the CO ₂ facilitated transport membrane according to the present invention It shows the dependence on temperature and pressure of the source gas CO ₂ permeance _{R CO2} and _CO 2 / _{H 2} selectivity of CO ₂ facilitated transport membrane according to the present invention It shows the dependence on temperature and pressure of the source gas CO ₂ permeance _{R CO2} and _CO 2 / _{N 2} selectivity of CO ₂ facilitated transport membrane according to the present invention The figure which shows the relationship between the raw material gas pressure (total pressure) which uses the temperature of raw material gas as a parameter, and water vapor saturation (Pw / Ps) Diagram showing the relationship between CO ₂ permeance _{R CO2} and water vapor saturation of the CO ₂ -facilitated transport membrane according to the present invention corresponding to FIG. 5 (Pw / Ps) Diagram showing the relationship between CO ₂ permeance _{R CO2} and water vapor saturation of the CO ₂ -facilitated transport membrane according to the present invention corresponding to FIG. 6 (Pw / Ps) Shows the dependence on CO ₂ permeance _{R CO2} and _CO 2 / _{H 2} blending ratio of the raw material gas pressure and DAPA selectivity of CO ₂ facilitated transport membrane according to the present invention Shows the dependence on CO ₂ permeance _{R CO2} and _CO 2 / _{H 2} blending ratio of the raw material gas pressure and DAPA selectivity of CO ₂ facilitated transport membrane according to the present invention Sectional view schematically showing the structure of a comparative sample of a CO ₂ -facilitated transport membrane Shows the improvement CO 2 _/ H ₂ selectivity rate by use of a hydrophilic porous membrane of the CO ₂ -facilitated transport membrane according to the present invention Shows the improvement CO 2 _/ H ₂ selectivity rate by use of a hydrophilic porous membrane of the CO ₂ -facilitated transport membrane according to the present invention Process diagram showing a second embodiment of a method for manufacturing a CO ₂ facilitated transport membrane according to the present invention Shows the promoting effect of CO ₂ permeance by additives used for CO ₂ facilitated transport membrane according to the present invention Shows the promoting effect of CO ₂ permeance by additives used for CO ₂ facilitated transport membrane according to the present invention The figure which shows the flow of various gases in the CO transformer equipped with the CO ₂ facilitated transport film Comparison chart of changes in carbon monoxide and carbon dioxide concentrations versus the catalyst layer length of the CO converter with and without a CO ₂ facilitated transport membrane

Explanation of symbols

1: PVA / PAA gel film (gel layer) containing carbon dioxide carrier
2: Hydrophilic porous membrane 3, 4: Hydrophobic porous membrane 10: CO ₂ facilitated transport membrane (sample)
11: Flow type gas permeation cell 12: Raw material side chamber 13: Permeation side chamber 14, 16: Cooling trap 15: Back pressure regulator (pressure regulating means)
17: Gas chromatograph 18: Fixed liquid feed pump 20: CO converter (CO ₂ permeable membrane reactor)
21: Sweep gas passage FG: Raw material gas FG ': Processed gas SG, SG': Sweep gas PG: Permeated gas

Claims (7)

A raw material gas containing at least carbon dioxide and water vapor in a predetermined main component gas is supplied to the raw material side surface of the CO ₂ facilitated transport membrane at a supply temperature of 100 ° C. or more, and the carbon dioxide permeated through the CO ₂ facilitated transport membrane is permeated. A carbon dioxide separator to be taken out from the side,
The CO ₂ facilitated transport membrane is a CO ₂ facilitated transport membrane formed by adding 2,3-diaminopropionic acid to a polyvinyl alcohol-polyacrylic acid copolymer gel membrane,
The water vapor saturation defined by the ratio of the total pressure of the raw material gas supplied to the CO ₂ facilitated transport membrane divided by the water vapor partial pressure in the raw material gas by the saturated water vapor pressure determined by the supply temperature is 0 . Carbon dioxide separation characterized by comprising pressure adjusting means for adjusting the pressure to a lower limit saturation set within a range of 3 to 0.6 and higher than the pressure at which the water vapor saturation is 1 apparatus. The CO ₂ facilitated transport membrane is characterized in that a gel layer obtained by adding 2,3-diaminopropionic acid to a polyvinyl alcohol-polyacrylic acid copolymer gel membrane is supported on a hydrophilic porous membrane. Item 2. The carbon dioxide separator according to Item 1.   3. The carbon dioxide separator according to claim 2, wherein the gel layer supported on the hydrophilic porous membrane is covered and supported by a hydrophobic porous membrane.   The gel layer is produced by casting a cast solution composed of an aqueous solution containing a polyvinyl alcohol-polyacrylic acid copolymer and 2,3-diaminopropionic acid to the hydrophilic porous membrane and then gelling. The carbon dioxide separator according to claim 2 or 3. In the polyvinyl alcohol-polyacrylic acid copolymer gel film, in addition to 2,3-diaminopropionic acid, as an additive for promoting carbon dioxide permeability, an ionic fluid, or glycerin, polyglycerin, Contains a chemical selected from polyethylene glycol, polypropylene glycol, polyethylene oxide, polyethyleneimine, polyallylamine, polyacrylic acid ,
The ionic fluid is a chemical substance selected from a compound consisting of a combination of the following cation and anion,
The cation is an imidazolium having the following substituents at the 1,3-positions, having an alkyl group, a hydroxyalkyl group, an ether group, an allyl group, an aminoalkyl group as a substituent, or a quaternary ammonium cation. , Having an alkyl group, a hydroxyalkyl group, an ether group, an allyl group, an aminoalkyl group as a substituent,
Wherein the anion is chloride, bromide, tetrafluoroborate ions, which nitrate ions, bis (trifluoromethanesulfonyl) imide ion, hexafluorophosphate ion, or wherein the ion der Rukoto trifluoromethanesulfonic acid Item 4. The carbon dioxide separator according to any one of Items 1 to 3.   The gel layer is formed from a cast solution composed of an aqueous solution containing a polyvinyl alcohol-polyacrylic acid copolymer, 2,3-diaminopropionic acid, and the additive for promoting carbon dioxide permeability. 6. The carbon dioxide separator according to claim 5, wherein the carbon dioxide separator is produced by gelling after casting. A raw material gas at least includes carbon dioxide and water vapor is supplied to the raw material side of the CO ₂ facilitated transport membrane to a predetermined main component gas, the carbon dioxide separation method for extracting carbon dioxide that has passed through the CO ₂ -facilitated transport membrane from the permeate side Because
The CO ₂ facilitated transport membrane is a CO ₂ facilitated transport membrane formed by adding 2,3-diaminopropionic acid to a polyvinyl alcohol-polyacrylic acid copolymer gel membrane,
The water vapor saturation defined by the ratio of the source gas to a supply temperature of 100 ° C. or higher and the water vapor partial pressure in the source gas divided by the saturated water vapor pressure determined by the supply temperature is 0.3 to 0 And supplying to the raw material side surface of the CO ₂ facilitated transport membrane at a total pressure not lower than a pressure at which the lower limit saturation is set within a range of 6 or less and not higher than a pressure at which the water vapor saturation is 1. To separate carbon dioxide.