JP2017148754A - Hydrogen gas separation material, its manufacturing method, manufacturing method of hydrogen-containing gas using hydrogen gas separation material and membrane reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separation material which efficiently separates useful hydrogen-containing gas from exhaust gas of blast furnace gas or the like.SOLUTION: A hydrogen gas separation material 10 includes: a porous substrate 11 composed of a porous supporter 11a and an intermediate layer 11b supported by the porous supporter 11a; and a silica membrane 12 supported by the porous substrate 11. Therein, hydrogen permeability of the silica membrane 12 is 1.0×10mol/msPa or more and the selectivity (H/N) of hydrogen for nitrogen is 45 or more. In a steam resistance test in which a sample gas containing steam of 5 vol% or more is used and it is set that temperature of the silica membrane is 300°C, pressure of the supply side is 300 kPa and pressure of the permeation side is 100 kPa, deterioration of the hydrogen permeability after 48 h is 33% or less, permeability of hydrogen is 0.7×10mol/msPa or more and the selectivity (H/N) of hydrogen gas for nitrogen gas is 0.45 or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hydrogen gas separator, a method for producing the same, and use of the hydrogen gas separator.

In the process of reducing iron ore in the blast furnace and producing pig iron, a large amount of Blast Furnace Gas (BFG) is discharged. BFG _{typically, H 2: 4vol%, N} 2: 52vol%, CO: 22vol%, CO 2: having the composition of 22 vol%, contains only a small hydrogen, contains a large amount of nitrogen . Therefore, it is difficult to effectively use BFG, and it is usually discarded or used for combustion.

  On the other hand, as a method for separating a gas containing a high concentration of hydrogen from a gas containing a low concentration of hydrogen, a method using an amorphous silica film having excellent hydrogen selective permeability is known. Although it is desired to use BFG effectively by using such a silica membrane, when the silica membrane is applied to hydrogen generation and concentration by water gas shift of BFG, the low water vapor resistance of the silica membrane becomes a problem. .

  Among silica films, a silica film using tetramethoxysilane (TMOS) or hexamethyldisiloxane (HMDSO) as a silica source has a relatively high water vapor resistance.

  Regarding a silica film having water vapor resistance, Patent Document 1 proposes that a silica film is formed on a porous substrate and then reacted with oxygen to stabilize the silica film.

  Patent Document 2 proposes supplying the raw material gas of the silica film to the substrate while pressurizing in order to suppress the defects of the silica film. As the source gas, a gas obtained by vaporizing an organic silicon compound by bubbling nitrogen or the like into a liquid organic silicon compound is used.

  In Patent Document 3, in order to stabilize the quality of the silica film, a silica film is formed by a first vapor deposition step in which a silicon compound is vapor-deposited on a substrate and a second step in which another silicon compound is further vapor-deposited thereafter. Propose to do.

  However, the conventional silica membrane with water vapor resistance has low hydrogen permeability, and it has been difficult to apply it to practical hydrogen purification and concentration treatment.

JP 2009-202096 A JP 2007-216106 A JP 2008-246299 A

  As a method of separating gas containing high-concentration hydrogen from exhaust gas such as BFG, hydrogen concentration is increased by modifying BFG by water gas shift reaction, and then nitrogen and carbon dioxide are separated by PSA (Pressure Swing Adsorption) method. Is also possible. However, although the PSA method is suitable for producing high-value-added high-purity gas on a small or medium scale, it is too expensive to produce a low-cost gas containing a relatively large amount of impurities other than hydrogen. It is.

  The inexpensive gas is, for example, a gas containing hydrogen at a concentration of 50 vol% or more and 90 vol% or less (hereinafter referred to as intermediate purity hydrogen gas), and has industrially sufficient utility value. For example, the reducing gas used when reducing iron ore in a blast furnace does not need to be high-purity hydrogen gas, and intermediate-purity hydrogen gas can be used.

  As for the silica membranes proposed in Patent Documents 1 to 3, it is possible to produce hydrogen gas with high hydrogen selectivity and high purity. However, since hydrogen permeability is low, a hydrogen-containing gas is industrially used. Not suitable for manufacturing. In particular, it is very difficult to produce intermediate purity hydrogen gas from BFG discharged in large quantities from a blast furnace.

One aspect of the present invention includes a porous substrate and a silica film supported by the porous substrate, and the hydrogen permeability at 300 ° C. of the silica film is 1.0 × 10 ^−6. The present invention relates to a hydrogen gas separation material having mol / m ² · s · Pa or more and hydrogen gas selectivity to nitrogen gas (H ₂ / N ₂ ) of 45 or more.

  The hydrogen gas separation material has high water vapor resistance. Therefore, in a water vapor resistance test in which a sample gas containing 5 vol% or more of water vapor is used, the temperature of the silica membrane is set to 300 ° C., the supply side pressure is set to 300 kPa, and the permeation side pressure is set to 100 kPa, The decrease rate of the hydrogen permeability after time can be suppressed to 33% or less, for example.

Another aspect of the present invention is a method for producing the hydrogen gas separation material, wherein a silica source, which is a raw material for the silica membrane, is added at 1 mol / m in a first space communicating with pores of the porous base material. ^{The present} invention relates to a method for producing a hydrogen gas separation material, which includes a step of supplying the silica source at a concentration of ³ or less and heating the silica source to form the silica membrane.

  Still another aspect of the present invention includes (i) a step of reacting a raw material gas containing carbon monoxide with water vapor to obtain a modified gas, and (ii) using the hydrogen gas separation material, from the modified gas. And a step of separating the hydrogen-containing gas with an increased hydrogen concentration.

  Still another aspect of the present invention relates to a membrane reactor including the hydrogen gas separator and a catalyst, and further using the membrane reactor to react a raw material gas containing carbon monoxide with water vapor. The present invention relates to a method for producing a hydrogen-containing gas, which obtains a modified gas and separates a hydrogen-containing gas with an increased hydrogen concentration from the modified gas.

  According to the hydrogen gas separator according to the present invention, it is possible to efficiently separate a useful hydrogen-containing gas (especially intermediate purity hydrogen gas) from a raw material gas such as BFG at low cost. Moreover, according to the method for producing a hydrogen gas separator according to the present invention, the silica membrane can have both high hydrogen permeability and water vapor resistance. Therefore, by using the hydrogen gas separating material, it is possible to construct equipment having both high hydrogen permeability and water vapor resistance. Furthermore, a hydrogen-containing gas with an increased hydrogen concentration can be efficiently produced using a water gas shift reaction requiring such equipment.

It is a conceptual diagram which shows the structure of an example of a hydrogen gas separation material. It is a figure which shows the external appearance of an example of a cylindrical hydrogen gas separation material. It is a conceptual diagram for demonstrating the principle of counter diffusion CVD. It is a block diagram which shows an example of the manufacturing apparatus of a hydrogen gas separation material. It is a block diagram of an example of the apparatus for enforcing the manufacturing method of hydrogen containing gas. It is a block diagram of another example of the apparatus for enforcing the manufacturing method of hydrogen containing gas. It is a conceptual diagram which shows the structure of an example of a membrane reactor. It is a figure which shows the dependence with respect to the temperature of the hydrogen permeability of the hydrogen gas separation material which concerns on Example 1, and nitrogen permeability. It is a figure which shows the result of the water vapor resistance test of the hydrogen gas separation material which concerns on Example 1. FIG. It is a figure which shows the result of the water vapor resistance test of the hydrogen gas separation material which concerns on Example 2. FIG. It is a figure which shows the dependence with respect to the temperature of the hydrogen permeability of the hydrogen gas separation material which concerns on the comparative example 1, and nitrogen permeability.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the following embodiments do not limit the present invention.

(Hydrogen gas separator)
FIG. 1 shows an exemplary structure of a hydrogen gas separator according to an embodiment of the present invention.
The hydrogen gas separation material 10 includes a porous substrate 11 and a silica membrane 12 supported by the porous substrate 11. Typically, the porous substrate 11 includes a porous support 11a and an intermediate layer 11b supported by the porous support 11a. The intermediate layer 11b has smaller pores than the porous support 11a. The silica film 12 is supported on the porous support 11a via the intermediate layer 11b. The porous substrate 11 has, for example, a first surface and a second surface, and pores that allow the first surface and the second surface to communicate with each other. In the illustrated example, the intermediate layer 11b is formed on the first surface side of the porous support 11a, and the silica film 12 is supported mainly in the pores of the intermediate layer 11b.

  The porous base material 11 determines the shape of the hydrogen gas separation material 10 and reinforces the strength of the silica membrane 12 and also diffuses the gas supplied to the hydrogen gas separation material 10 into the silica membrane 12 as uniformly as possible. Have The shape of the porous substrate 11 is arbitrarily selected according to the shape of the hydrogen gas separation material 10, and is, for example, a sheet shape, a honeycomb shape, a cylindrical shape, a bellows shape, or the like.

  The material of the porous support 11a is not particularly limited, and α-alumina, γ-alumina, silica, zirconia, silicon nitride, silicon carbide, titania, zeolite, and the like can be used. Among these, it is preferable to use cheap and thermally stable α-alumina.

  The pore size of the porous support 11a is relatively large, and the average pore diameter of the porous support 11a is preferably 700 nm or less, and more preferably 20 nm to 200 nm. In addition, when the porous support 11a is an asymmetric substrate having a multilayer structure of two or more layers, the outer pore diameter is preferably within the above range. Thereby, it becomes easy to form a silica film having an appropriate thickness. If the pores of the porous support 11a are too small, it becomes difficult to form a sufficiently thick silica film.

  The average pore diameter is a median diameter in a volume-based pore diameter distribution measured by a bubble point test method based on JIS K3832, a mercury intrusion method based on JIS R1655, a gas adsorption method based on JIS Z8830, and the like. is there. The pore size distribution of the porous support 11a is desirably measured by a bubble point test method or a mercury intrusion method.

  The intermediate layer 11b has a smaller pore size than the porous support 11a and is an underlayer suitable for forming the silica film 12 that selectively allows hydrogen to permeate. The intermediate layer 11b has a mesoporous structure, for example. The average pore diameter of the intermediate layer 11b is preferably 10 nm or less, and more preferably 4 nm to 8 nm, for example. By supporting the silica film 12 on the porous support 11a via the intermediate layer 11b, the formation of the silica film 12 is facilitated, and the separation and deterioration of the silica film 12 are suppressed.

  The intermediate layer 11b can be formed on the surface of the porous support 11a using a sol-gel method. For example, boehmite sol using aluminum alkoxide as a raw material is dip-coated on the porous support 11a, dried, and then fired at 400 ° C to 900 ° C to obtain the intermediate layer 11b formed of γ-alumina. it can.

The silica membrane 12 preferably has an average pore diameter of 0.4 nm or less, more preferably 0.3 nm to 0.35 nm, because it is necessary to selectively permeate hydrogen. However, from the viewpoint of efficiently separating a hydrogen-containing gas (especially intermediate purity hydrogen gas) with an increased hydrogen concentration from a source gas such as BFG produced in a large amount in a blast furnace, the hydrogen permeability of the silica membrane 12 is It is necessary to design it considerably high, and it is desirable to increase the pore diameter as much as possible and to reduce the film thickness. As a result, specifically, the hydrogen permeability of the silica film 12 needs to be 1.0 × 10 ⁻⁶ mol / m ² · s · Pa or more, and is 1.5 × 10 ⁻⁶ mol / m. ² · s · Pa or more is preferable. On the other hand, the selectivity (H ₂ / N ₂ ) of the hydrogen gas with respect to the nitrogen gas is sufficient if it is 45 or more, and if it is 100 or more, the hydrogen gas can be more efficiently separated.

  Here, the hydrogen permeability is a numerical value at an assumed use temperature of the hydrogen gas separator, and for example, the hydrogen permeability at 200 ° C. to 400 ° C. may be within the above range. It is desirable that the hydrogen permeability at 300 ° C. be within the above range. In addition, the hydrogen permeability of the hydrogen gas separator is reduced to a certain extent at the initial stage after the start of use, compared to the initial value before actually being used as the hydrogen gas separator. Here, the initial value of the hydrogen permeability may be within the above range.

Similarly, hydrogen gas selectivity (H ₂ / N ₂ ) (hereinafter referred to as hydrogen selectivity) with respect to nitrogen gas is a numerical value at an assumed use temperature of the hydrogen gas separator, for example, 200 ° C. to 400 ° C. As long as the hydrogen selectivity at is within the above range, it is desirable that the hydrogen selectivity at 300 ° C. be within the above range. Note that the hydrogen selectivity of the hydrogen gas separator does not change significantly before and after the hydrogen gas separator is actually used. Here, the initial value of hydrogen selectivity should just be in the said range.

  When the raw material gas contains carbon monoxide like BFG, it is desirable to modify the carbon monoxide by reacting with water vapor before concentrating the hydrogen gas using the hydrogen gas separator 10. As a result, a modified gas containing hydrogen gas at a higher concentration than the raw material gas can be obtained. When the intermediate purity hydrogen gas is separated from the modified BFG gas, for example, a hydrogen-containing gas containing 70 vol% or more of hydrogen can be separated if the selectivity is 45 or more.

  The reaction of reacting carbon monoxide with water vapor is called a water gas shift reaction. The modified gas produced through the water gas shift reaction contains a large amount of water vapor. Therefore, when the intermediate purity hydrogen gas is separated from the denatured gas using the hydrogen gas separator 10, it is desirable that the silica membrane 12 has excellent water vapor resistance.

  The water vapor resistance of the silica membrane 12 can be evaluated from the decrease in hydrogen permeability when the hydrogen gas separator 10 is exposed to water vapor. The hydrogen permeability of the silica film 12 decreases for about 48 hours after the exposure to water vapor, but thereafter the decrease in hydrogen permeability is saturated. If the hydrogen permeability after 48 hours is sufficient in a predetermined water vapor resistance test, it is considered that the hydrogen permeability hardly decreases thereafter. Based on experience, if a decrease in hydrogen permeability after 48 hours is 33% or less in a predetermined water vapor resistance test, the water vapor resistance is sufficiently practical. However, the higher the steam resistance, the more desirable, and the performance of the hydrogen gas separating material 10 can be further enhanced by further suppressing the decrease in the hydrogen permeability after 48 hours.

In the water vapor resistance test, the hydrogen permeability at 300 ° C. after 48 hours is preferably 0.7 × 10 ⁻⁶ mol / m ² · s · Pa or more, and 1.0 × 10 ⁻⁶ mol / m. More preferably, it is ² · s · Pa or more. Even when the hydrogen permeability decreases in the initial stage after the start of use, the hydrogen permeability at 300 ° C. after that is 0.7 × 10 ⁻⁶ mol / m ² · s · Pa or more, and further 1.0 × 10 If it can maintain ^-6 mol / m ² · s · Pa or more, it can be a target for practical use. At this time, the selectivity (H ₂ / N ₂ ) of the hydrogen gas with respect to the nitrogen gas may be lower than the initial value, but it is desirable to maintain 45 or more.

In the water vapor resistance test, the hydrogen permeability at 300 ° C. after 96 hours is 0.6 × 10 ⁻⁶ mol / m ² · s · Pa or more, and further 0.8 × 10 ⁻⁶ mol / m ² · s. -It is desirable to maintain Pa or higher. After 48 hours, the hydrogen permeability hardly decreases, but the hydrogen permeability at 300 ° C. after 96 hours from the start of the water vapor resistance test is further reduced by about 10% after 48 hours. Is considered acceptable. However, also at this time, it is desirable that the selectivity (H ₂ / N ₂ ) of the hydrogen gas with respect to the nitrogen gas is maintained at 45 or more.

FIG. 2 shows the appearance of an example of the cylindrical hydrogen gas separator 10.
The porous base material 11 is a cylindrical body, has an outer peripheral surface and an inner peripheral surface, and has pores that allow the outer peripheral surface and the inner peripheral surface to communicate with each other. When the silica film 12 is supported on the outer peripheral side of the cylindrical body, the outer peripheral surface is the first surface 21 and the inner peripheral surface is the second surface 22. In this case, the raw material gas or the modified gas is supplied to the hollow of the cylindrical body, and the intermediate concentration hydrogen gas that has passed through the silica film 12 is released from the outer peripheral surface of the cylindrical body. On the other hand, when the silica film 12 is supported on the inner peripheral side of the cylindrical body, the inner peripheral surface is the first surface 21 and the outer peripheral surface is the second surface 22. In this case, the source gas or the modified gas is supplied from the outer peripheral surface of the cylindrical body, and the intermediate purity hydrogen gas that has passed through the silica film 12 is released from the inner peripheral surface of the cylindrical body.

(Method for producing hydrogen gas separator)
This will be described with reference to FIG. FIG. 3 is a conceptual diagram for explaining the principle of the counter diffusion CVD method.
Hydrogen gas separator member 10, the first space 31 communicating with pores porous substrate 11 having, a silica source 32 which is a raw material of the silica film 1 mol / m ³ or less, preferably 0.85 mol / m ³ or less And the silica source 32 can be heated at a high temperature (preferably 200 ° C. to 700 ° C.) to form the silica film 12 by a manufacturing method.

The silica source 32 may be supplied to the first space as a mixed gas containing the vaporized or atomized silica source 32. The mixed gas includes, for example, a silica source 32 and an inert gas. As the inert gas, a rare gas such as argon or helium, nitrogen, or the like can be used. At this time, the concentration of the silica source 32 supplied to the first space, 1 mol / m ³ or less, more preferably controlled to be less than 0.85 mol / m ^3. Thereby, while the silica film 12 grows reliably and generation | occurrence | production of the defect of the silica film 12 is suppressed, a film thickness becomes thin and it becomes possible to improve a hydrogen permeability. Therefore, it is easy to form a silica film 12 that is dense, excellent in water vapor resistance, and has a high hydrogen permeability.

  When the porous substrate 11 has the first surface 21 and the second surface 22 and the first surface 21 and the second surface 22 communicate with each other through pores, the first space 31 is defined as the first surface 21. The silica film 12 can be formed in the pores of the intermediate layer 11b on the first surface 21 side by communicating with the pores. At this time, although not shown, the silica film 12 may be formed to be laminated not only on the inner wall of the pore of the intermediate layer 11b but also on the outermost surface on the first surface 21 side.

  On the other hand, it is desirable to supply an oxidant 34 such as oxygen or ozone into the second space 33 communicating with the pores on the second surface 22. For example, ozone or pure gas containing 100% oxygen may be used as the oxidant 34, or a mixed gas containing oxygen and / or ozone may be used. The concentration of oxygen and / or ozone in the mixed gas may be, for example, 20 vol% to 60 vol%. As the gas other than oxygen and ozone contained in the mixed gas, an inert gas is preferable. Dry air may be used as the mixed gas.

  At a high temperature, preferably 200 ° C. to 700 ° C., more preferably 400 ° C. to 700 ° C., the silica source 32 introduced into the pores from the first surface 21 side and the pores introduced from the second surface 22 side into the pores. By contacting the oxidant 34, the thermal decomposition or oxidation reaction of the silica source 32 proceeds, and the silica film 12 is formed. Such a chemical vapor deposition method (CVD method) is referred to as a counter diffusion CVD method.

In the counter diffusion CVD method, the thickness of the silica film 12 is considered to depend on the concentration of the silica source. When the concentration of the silica source 32 supplied to the first space 31 is controlled to a low concentration of 1 mol / m ³ or less, the thickness of the silica film is reduced and a high hydrogen permeability is obtained. However, when a silica source having a high vapor pressure is used, it is difficult to control the supply amount of the silica source, and it is difficult to form a homogeneous silica film. For precise supply amount control, it is desirable to apply a pump or the like instead of the usual bubbling method.

The silica source may be any silicon compound that reacts with oxygen to produce silica, but it is desirable to use a silicon compound that can be easily vaporized or atomized. Specifically, as a silicon compound, tetraalkoxysilane (tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), etc.), trialkoxysilane (methyltrimethoxysilane, n-octyltriethoxysilane, n-decyltrimethoxy) Silane, etc.), dialkoxysilane (diphenyldiethoxysilane, etc.), monoalkoxysilane, silicon tetrachloride, silane (SiH ₄ ), disiloxane (hexamethyldisiloxane (HMDSO), etc.). Among these, it is desirable to use TMOS and hexamethyldisiloxane (HMDSO) in that a silica film having excellent water vapor resistance can be obtained. In particular, HMDSO can easily make a silica film thin and can easily obtain a high hydrogen permeability. Is preferable.

In FIG. 4, the block diagram of an example of the manufacturing apparatus used when manufacturing the hydrogen gas separation material 10 is shown.
Here, the case where the silica film 12 is formed on the outer peripheral surface side of the porous substrate 11 that is a cylindrical body by the counter diffusion CVD method will be described.

  The manufacturing apparatus 40 supplies an oxidant (oxygen, ozone, air, etc.) to the second space 33 surrounded by the inner peripheral surface (second surface 22) of the porous substrate 11 that is a cylindrical body, and the outer peripheral surface. The silica source can be supplied to the first space 31 communicating with the pores of the porous substrate 11 on the (first surface 21). As shown in FIG. 4, the porous base material 11 is accommodated in a cylindrical chamber 41 containing the first space 31 so as to form a part of the oxidant flow path (second space 33). Yes. An oxidant is introduced into the oxidant flow path, and a silica source is introduced into the first space 31.

  The oxidant flow path includes the porous base material 11, a pipe-shaped first conduit 43 a connected to one end of the porous base material 11 via the first connecting member 42 a, and the other end of the porous base material 11. And a pipe-like second conduit 43b connected to each other via a second connecting member 42b. The first pipe line 43 a is located on the upstream side of the oxidant flow path, and communicates with the oxidant supply unit 45 via the mass flow controller 44 provided outside the cylindrical chamber 41. The second pipe line 43b is located on the downstream side of the oxidant flow path and communicates with the first outlet 46 that discharges the first exhaust gas to the outside. The first exhaust gas includes by-products generated by the reaction of the silica source, in addition to the oxidizing agent that has not been consumed in the reaction with the silica source. The first exhaust gas is, for example, released to the outside air after removing by-products through the first trap 47.

  The first space 31 in the cylindrical chamber 41 (that is, the periphery of the oxidant flow path containing the second space 33) is a flow path for the silica source. Therefore, the cylindrical chamber 41 includes a silica source introduction port 48 on the upstream side of the flow path of the silica source, and includes a second outlet 49 that discharges the second exhaust gas to the outside on the downstream side. The second exhaust gas contains a silica source that was not used to form the silica film. Unused silica source is collected by the second trap 50 communicating with the second outlet 49.

  The silica source introduction port 48 preferably includes a carburetor 51. By using the carburetor 51, for example, an inert gas can be injected or sprayed into the first space 31 from the silica source inlet 48 together with a liquid silica source. Instead of the carburetor, a heater for heating can also be installed and used. Thereby, a silica source is vaporized or atomized and the mixed gas of an inert gas and a silica source produces | generates. In the illustrated example, the carburetor 51 communicates with an inert gas supply unit 53 via a mass flow controller 52 and also communicates with a silica source supply unit 55 via a liquid feed micropump 54.

The liquid-feeding micropump 54 can be transferred to the carburetor 51 while sufficiently and precisely controlling the supply amount of the silica source. Liquid feeding micro pump 54, the concentration of the silica source to be supplied to the first space 31, 1 mol / m ³ or less, preferably in controlling so below 0.85 mol / m ^3, an important role Fulfill. The type of the liquid-feeding micropump 54 is not particularly limited. For example, a volume transfer type is preferable. Specifically, a rotary pump such as a diaphragm type or plunger type reciprocating pump, a gear pump, a screw pump, a syringe pump, or the like can be used. In particular, when a syringe pump is used, the pulsation is small even at a low flow rate, and the supply amount can be controlled more precisely.

  A heater 56 is installed around the cylindrical chamber 41. The heater 56 can control the temperature in the first space 31 to a desired temperature via the cylindrical chamber 41. The silica source is introduced into the first space 31 within an arbitrary temperature range in which the temperature of the porous substrate 11 is selected from a desired temperature, preferably 200 ° C. to 700 ° C., more preferably 400 ° C. to 700 ° C. It is desirable to be performed under stabilized conditions. It is desirable to introduce the silica source into the first space 31 after the temperature of the porous substrate 11 is stabilized within the above temperature range in a state where an oxidizing agent (for example, air) is circulated through the second space 33. .

  The time from when the silica source is introduced into the first space 31 under the flow of the oxidizing agent to the second space 33 until the introduction of the silica source is stopped is the time for forming the silica film. The film formation time may be set as appropriate so that a desired hydrogen permeability is achieved, and is not particularly limited. The film formation time may be about 3 minutes to 60 minutes, for example. In general, the longer the film formation time, the thicker the silica film and the lower the hydrogen permeability.

  In addition to the example of FIG. 4, the oxidizing agent may be circulated in the first space of the cylindrical chamber, and the silica source may be circulated in the second space that is the hollow portion of the porous substrate.

<Measurement method of hydrogen permeability>
Next, a method for measuring the hydrogen permeability will be described.
The hydrogen gas permeability can be calculated from the following formula: QH ₂ = A / {(P1-P2) · S · t}. Here, QH ₂ is the hydrogen gas permeability (mol / m ² · s · Pa), A is the hydrogen permeability (mol), P 1 is the pressure on the gas supply side (Pa), and P 2 is the pressure on the gas permeation side (Pa ), S represents the apparent area (m ² ) of the silica film, and t represents the measurement time (seconds) when the permeation amount is A, respectively.

In the measurement of hydrogen gas permeability, the hydrogen gas separator has a first surface and a second surface, and has pores that allow the first surface and the second surface to communicate, and a silica film on the first surface side. Use a sample in which is supported. The sample is placed in the measurement device so that a first space communicating with the pores on the first surface and a second space communicating with the pores on the second surface are formed. At this time, the first space and the second space are apparently separated by the hydrogen gas separator. In this state, hydrogen and single gas are supplied to the second space. At this time, the differential pressure between the first space and the second space may be controlled to 300 kPa. Then, after stabilizing the hydrogen gas separator at a predetermined temperature (for example, 300 ° C. to 600 ° C.), the hydrogen permeation amount (mol) permeating the hydrogen gas separator (silica membrane) per unit time (1 second) is set. taking measurement. By dividing this permeation amount by the apparent area of the silica membrane and the differential pressure between the first space and the second space, the hydrogen permeability QH ₂ (mol / m ² · s · Pa) can be obtained. When the hydrogen gas separation material is a cylindrical body and a silica film is formed on the outer peripheral surface thereof, the apparent area of the silica film can be regarded as the area of the outer peripheral surface.

<Method for measuring hydrogen selectivity>
Next, the hydrogen-selective alpha, in the same manner as in hydrogen permeability QH _2, the nitrogen permeability QN ₂ calculated, as a ratio of hydrogen permeability QH ₂ to nitrogen permeability _{QN 2 (α = QH 2 /} QN 2) Can be calculated.

<Water vapor resistance test>
Next, details of the water vapor resistance test will be described.
For example, the water vapor resistance test can be performed using a predetermined sample gas, setting the temperature of the silica film 12 to 300 ° C., the supply side pressure to 300 kPa, and the permeation side pressure to 100 kPa. 99 vol% or more of the sample gas is occupied by nitrogen, argon and water vapor, and contains 5 vol% or more of water vapor. As an example, a gas containing 54:25:50 by volume ratio of nitrogen, argon, and water vapor may be used. Here, the supply side pressure is the pressure of the sample gas supplied to the hydrogen gas separation material, and the temperature of the sample gas is controlled to 300 ° C. in the vicinity of the silica membrane. On the other hand, the permeate side pressure is the pressure of the permeate gas that has passed through the hydrogen gas separation material 10.

  In the water vapor resistance test, the hydrogen gas separation material has a first surface and a second surface, and has pores that allow the first surface and the second surface to communicate, and a silica membrane is supported on the first surface side. Use the sample. The sample is a measurement device similar to that used for measuring the hydrogen permeability so that a first space communicating with the pores on the first surface and a second space communicating with the pores on the second surface are formed. Installed. In this state, sample gas is supplied to the second space. On the other hand, argon is circulated in the first space. At this time, the differential pressure between the first space and the second space may be controlled to 200 kPa. Then, after a predetermined time has elapsed, the hydrogen permeability of the hydrogen gas separation material is measured, and the reduction rate relative to the initial value is calculated.

(Method for producing hydrogen-containing gas)
Next, a method for producing a hydrogen-containing gas using the hydrogen gas separator will be described. Here, a case where intermediate purity hydrogen gas is produced using BFG as a raw material will be mainly described, but the raw material gas is not limited to BFG. The hydrogen concentration in the hydrogen-containing gas that is the product is not particularly limited. The method for producing a hydrogen-containing gas according to the present invention includes all methods capable of increasing the hydrogen concentration in the raw material gas to, for example, 50 vol% to 99 vol%.

(I) Production of modified gas FIG. 5 is a configuration diagram of an example of an apparatus for carrying out a method for producing a hydrogen-containing gas. First, at least a part of carbon monoxide is converted into hydrogen and carbon dioxide by reacting a raw material gas containing carbon monoxide such as BFG with water vapor. Such a reaction
Equation _{(1): CO + H 2} O → H 2 + CO 2
And is referred to as a water gas shift reaction. The product gas in which the carbon monoxide concentration is reduced and the hydrogen concentration is increased by the water gas shift reaction is referred to as a modified gas. The water gas shift reaction can be carried out using a reaction column 57 that can be controlled at a high temperature and high pressure inside.

  The modified gas produced by the water gas shift reaction preferably contains, for example, 3 vol% or more of hydrogen, and more preferably contains 10 vol% or more of hydrogen. An intermediate purity hydrogen gas can be efficiently produced from a modified gas having a hydrogen concentration in this range. On the other hand, from the viewpoint of producing the modified gas having the above hydrogen concentration, the raw material gas preferably contains 3 vol% or more of carbon monoxide, for example, and more preferably contains 10 vol% of carbon monoxide.

  In the water gas shift reaction, the raw material gas is mixed with water vapor, and the obtained mixed gas is introduced into a reaction tower including a catalyst containing a component that promotes the reaction of the formula (1), for example, 150 ° C. to 500 ° C., preferably Proceeds by heating to a temperature of 200 ° C to 400 ° C.

  The catalyst is not particularly limited, but a material in which a metal species is supported on a carrier such as α-alumina or γ-alumina is preferably used. As the metal species, rhodium (Rh), copper (Cu), zinc (Zn), or the like, which has a large effect of promoting the reaction of the formula (1), is used alone or in combination.

(Ii) Separation of hydrogen-containing gas The modified gas produced in the reaction tower is cooled in the cooling tower 58 to remove excess water vapor. Thereafter, the denatured gas from which moisture has been removed is introduced into the hydrogen gas separation tower 59. The hydrogen gas separation tower 59 is filled with the hydrogen gas separation material 10. The denatured gas from which moisture has been removed is introduced into the second space 33 that communicates with the second surface of the hydrogen gas separator 10, and diffuses from the second surface into the pores of the porous substrate. Thereafter, a part of the modified gas permeates the silica film that selectively permeates hydrogen and is released from the first surface to the first space 31. On the other hand, the remaining portion of the modified gas that has not been released from the first surface is recovered from the second space 33.

(Iii) Membrane reactor An apparatus including a reaction separation column 60 having two functions of a reaction column 57 for performing a water gas shift reaction and a hydrogen gas separation column 59 may be used. The reaction separation column 60 includes a membrane reactor 61 using a hydrogen gas separation material as a material. FIG. 6 is a configuration diagram of an example of the reaction separation column 60 including the membrane reactor 61.

  FIG. 7 is a conceptual diagram showing the structure of an example of the membrane reactor 61. The membrane reactor 61 includes the hydrogen gas separation material 10 and a catalyst 71 supported on the second surface 22 (that is, the surface of the porous substrate 11 on the side not including the silica film 12). The catalyst 71 may include a component that promotes the reaction of the formula (1) (that is, the reaction between carbon monoxide and water vapor). Therefore, rhodium (Rh), copper (Cu), zinc (Zn), or the like is used alone or in combination. Here, as the carrier for supporting the catalyst 71, the second surface 22 side of the porous substrate 11 constituting the hydrogen gas separation material 10 can be used.

  In the second space 33 communicating with the second surface 22 of the hydrogen gas separation material 10 forming the membrane reactor 61, a mixed gas of raw material gas and water vapor is directly introduced instead of the modified gas. A part of carbon monoxide and water vapor contained in the mixed gas is converted into hydrogen and carbon dioxide by the action of the catalyst 71 supported on the second surface 22 side of the porous substrate 11, and the remainder of the raw material gas and water vapor At the same time, it diffuses in the pores of the porous substrate 11. Therefore, the silica film 12 is directly exposed to water vapor. Thereafter, a part of the modified gas generated inside the membrane reactor 61 passes through the silica membrane 12 that selectively permeates hydrogen and is released from the first surface 21 to the first space 31. On the other hand, the remainder of the modified gas and the water vapor that have not been released from the first surface 21 are recovered from the second space 33.

In the membrane reactor 61 in which the silica film 12 is directly exposed to water vapor, it is important to improve the water vapor resistance of the silica film 12. In this respect, in order to achieve a high hydrogen permeability using a silica source that is superior in terms of water vapor resistance while the hydrogen permeability of the silica membrane tends to be low, the silica source is used in an amount of 1 mol / m ³ or less, preferably 0. It is necessary to manufacture by supplying to the first space at a concentration of .85 mol / m ³ or less. Since such a silica membrane is dense and has few defects, it is excellent in water vapor resistance and has a high hydrogen permeability, and thus is suitable for application to the membrane reactor 61.

  The hydrogen-containing gas that is the target product separated from the denatured gas is sufficiently industrially useful if it contains 50 vol% or more of hydrogen, but according to the above method, for example, hydrogen containing 70 vol% or more of hydrogen. It is possible to stably supply the contained gas.

EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, a following example does not limit this invention.
Example 1
(I) Production of Hydrogen Gas Separation Material An α-alumina cylindrical body having an inner diameter of 4 mm, an outer diameter of 6 mm, and a length of 70 mm was prepared as a porous support. The porous support had a two-layer structure having a pore diameter of 150 nm and 700 nm and an outer peripheral surface of 150 nm. An intermediate layer made of γ-alumina was formed on the outer peripheral surface of the porous support by counter diffusion CVD. The average pore diameter of the intermediate layer was 4 nm, and the thickness of the intermediate layer was 2.5 μm.

(Ii) Production of Silica Film Using an apparatus as shown in FIG. 4, an amorphous silica film was formed on the outer peripheral surface side (intermediate layer side) of the porous substrate by counter diffusion CVD. First, a mixed gas of nitrogen and oxygen (nitrogen flow rate 200 mL / min, oxygen flow rate 20 mL / min) was introduced into the hollow portion (second space) of the porous substrate. On the other hand, after stabilizing the temperature in the cylindrical chamber (that is, the temperature of the porous substrate) at 600 ° C., a mixed gas of HMDSO vapor and nitrogen, which is a silica source, is introduced into the first space of the cylindrical chamber. Introduced. The concentration of HMDSO in the first space was controlled to be 0.72 mol / m ³ . This control was performed by a W plunger type liquid feeding micropump. The film forming time was 5 minutes.

[Evaluation]
(I) Measurement of gas permeability and hydrogen selectivity The hydrogen permeability and nitrogen permeability at 300 ° C. to 600 ° C. of the produced silica membrane were measured, respectively, and the ratio of hydrogen permeability to nitrogen permeability (H ₂ / N ₂ ) Was calculated as hydrogen selectivity. The hydrogen permeability and the nitrogen permeability were measured using a silica membrane production apparatus shown in FIG. That is, while controlling the temperature in the cylindrical chamber to a predetermined temperature, hydrogen gas or nitrogen gas at a predetermined flow rate was supplied from the gas supply source to the second space, which is a hollow portion of the hydrogen gas separator, through the MFC. At this time, the differential pressure between the outer peripheral side (first space) and the inner peripheral side (second space) of the hydrogen gas separation material was controlled to 300 kPa. The apparent area of the silica film can be regarded as the area of the outer peripheral surface of the porous base material that is a cylindrical body, and was 13.2 cm ² .
The results of hydrogen permeability QH ₂ , nitrogen permeability QN ₂ , and hydrogen selectivity α are shown in Table 1 and FIG.

(Ii) Water vapor resistance test The temperature of the hydrogen gas separator was maintained at 300 ° C, and a mixed gas of 30 vol% water vapor and 70 vol% nitrogen was supplied to the second space at a pressure of 300 kPa. On the other hand, the pressure of the first space (gas permeation side) was maintained at 100 kPa by sweeping argon gas into the first space. The hydrogen permeability of the hydrogen gas permeable material was measured every time a predetermined time passed until 48 hours passed after starting the supply of the mixed gas (starting the test). The results are shown in FIG. From FIG. 9, it can be understood that within 48 hours after the start of the test, the hydrogen permeability decreases to a certain degree, but the decrease rate is saturated at about 33%.

Example 2
A hydrogen gas separator having a silica membrane was prepared in the same manner as in Example 1 except that the concentration of HMDSO in the first space was controlled to be 0.62 mol / m ³ and the film formation time was 3 minutes. , Evaluated in the same way.

The results of hydrogen permeability QH ₂ , nitrogen permeability QN ₂ , and hydrogen selectivity α are shown in Table 2 and FIG. From this result, it can be seen that high hydrogen permeability and sufficient hydrogen selectivity were obtained. In addition, when the water vapor resistance test was conducted, the hydrogen permeability after 48 hours decreased from the initial value to the same extent as in Example 1.

<< Comparative Example 1 >>
A hydrogen gas separator having a silica membrane was prepared in the same manner as in Example 1 except that the concentration of HMDSO in the first space was controlled to be 1.81 mol / m ³ and the film formation time was 120 minutes. , Evaluated in the same way.

  However, HMDSO was not supplied to the first space using a liquid-feeding micropump and a carburetor, but HMDSO was volatilized and supplied by bubbling nitrogen into liquid 27 ° C. HMDSO. The concentration control of HMDSO was performed by controlling the flow rate of nitrogen introduced into liquid HMDSO with a mass flow controller.

The results of hydrogen permeability QH ₂ , nitrogen permeability QN ₂ , and hydrogen selectivity α are shown in Table 3 and FIG. From this result, it can be seen that the hydrogen permeability is low and it is difficult to put it to practical use. In addition, when the water vapor resistance test was conducted, the hydrogen permeability after 48 hours decreased from the initial value to the same extent as in Example 1.

  According to the hydrogen gas separator according to the present invention, it is possible to efficiently separate a useful hydrogen-containing gas (especially intermediate purity hydrogen gas) from a source gas such as BFG. The hydrogen gas separation material according to the present invention is industrially useful as a hydrogen gas supply facility that is installed in a plant such as an ironworks.

  10: Hydrogen gas separator, 11: Porous substrate, 11a: Porous support, 11b: Intermediate layer, 12: Silica membrane, 21: First surface, 22: Second surface, 31: First space, 32 : Silica source, 33: second space, 34: oxidant, 41: cylindrical chamber, 42a: first connecting member, 42b: second connecting member, 43a: first conduit, 43b: second conduit, 44 , 52: Mass flow controller, 45: Oxidant supply unit, 46: First outlet, 47: First trap, 48: Silica source inlet, 49: Second outlet, 50: Second trap, 51: Carburetor, 53: Inert gas supply unit, 54: micropump for liquid feeding, 55: silica source supply unit, 56: heater, 57: reaction tower, 58: cooling tower, 59: hydrogen gas separation tower, 60: reaction separation tower, 61: Membrane reactor, 71: catalyst

Claims (17)

A porous substrate, and a silica film supported by the porous substrate,
The hydrogen permeability at 300 ° C. of the silica membrane is 1.0 × 10 ⁻⁶ mol / m ² · s · Pa or more, and the selectivity (H ₂ / N ₂ ) of hydrogen gas to nitrogen gas is 45 or more. A hydrogen gas separator.   In a water vapor resistance test using a sample gas containing water vapor of 5 vol% or more, the temperature of the silica membrane set to 300 ° C., the supply side pressure set to 300 kPa, and the permeation side pressure set to 100 kPa, the hydrogen permeability after 48 hours The hydrogen gas separation material according to claim 1, wherein the rate of decrease is 33% or less. In the water vapor resistance test, the hydrogen permeability at 300 ° C. after 48 hours is 0.7 × 10 ⁻⁶ mol / m ² · s · Pa or more, and the selectivity of hydrogen gas to nitrogen gas (H ₂ / The hydrogen gas separation material according to claim 2, wherein N ₂ ) is 45 or more. In the water vapor resistance test, the hydrogen permeability at 300 ° C. after 96 hours is 0.6 × 10 ⁻⁶ mol / m ² · s · Pa or more, and the selectivity of hydrogen gas to nitrogen gas (H ₂ / The hydrogen gas separator according to claim 3, wherein N ₂ ) is 45 or more. The porous substrate has a first surface and a second surface, and has pores for communicating the first surface with the second surface;
The hydrogen gas separator according to any one of claims 1 to 4, wherein the silica membrane is supported on the first surface side. It is a manufacturing method of the hydrogen gas separation material according to claim 1,
A silica source, which is a raw material for the silica film, is supplied to the first space communicating with the pores of the porous substrate at a concentration of 1 mol / m ³ or less, and the silica source is heated to form the silica film. A method for producing a hydrogen gas separation material, comprising the step of forming. The porous substrate has a first surface and a second surface, and the first surface and the second surface communicate with each other through the pores,
The method for producing a hydrogen gas separation material according to claim 6, wherein the first space communicates with the pores on the first surface.   The method for producing a hydrogen gas separator according to claim 7, wherein an oxidizing agent is supplied to the second space communicating with the pores on the second surface.   The method for producing a hydrogen gas separator according to any one of claims 6 to 8, wherein the silica source is a siloxane compound having no alkoxy group.   The method for producing a hydrogen gas separator according to claim 9, wherein the siloxane compound includes hexamethyldisiloxane. The method for producing a hydrogen gas separation material according to claim 6, wherein the silica source is supplied to the first space at a concentration of 0.85 mol / m ³ or less.   A membrane reactor comprising the hydrogen gas separator according to claim 1 and a catalyst.   The membrane reactor according to claim 12, wherein the catalyst includes a component that promotes a reaction between carbon monoxide and water vapor. (I) reacting a raw material gas containing carbon monoxide with water vapor to obtain a modified gas;
(Ii) using the hydrogen gas separating material according to claim 1, separating the hydrogen-containing gas having an increased hydrogen concentration from the modified gas.   The method for producing a hydrogen-containing gas according to claim 14, wherein the source gas containing carbon monoxide is a blast furnace gas.   The method for producing a hydrogen-containing gas according to claim 14 or 15, wherein the hydrogen-containing gas contains 50 vol% or more of hydrogen.   Using the membrane reactor according to claim 12, a raw material gas containing carbon monoxide is reacted with water vapor to obtain a modified gas, and a hydrogen-containing gas with an increased hydrogen concentration is separated from the modified gas. A method for producing a hydrogen-containing gas.

Images