KR100812959B1 - Preparation method of silica-zirconia hydrogen permselective membrane - Google Patents

Abstract

A preparation method of a silica-zirconia(SiO2-ZrO2) based hydrogen separation membrane by chemical vapor deposition is provided such that the silica-zirconia(SiO2-ZrO2) based hydrogen separation membrane is applicable to high temperature and high corrosive environments in a process of producing hydrogen by thermochemical decomposition of water. In a method for preparing a membrane that can be used for separating hydrogen at a high temperature condition by evaporating or thermally decomposing a silica-providing material on a ceramic support(alpha- or gamma-Al2O3) having a pore diameter of not greater than 100 nm and a porosity of not more than 40% as a starting material under the vacuum condition by chemical vapor deposition, thereby bonding the silica-providing material to a surface and pores of a membrane through a chemical reaction such that inner parts of the pores are changed also while the surface is covered with a silica-based ceramic, a preparation method of a silica-zirconia hydrogen separation membrane comprises mixing 30 to 90 wt.% of tetraethoxysilane as the silica-providing material with 10 to 70 wt.% of zirconia butoxide as a zirconia-providing material, supplying the mixture into a reactor using a carrier gas, and adjusting linear speed of the carrier gas to a range of 0.06 to 0.11 m/s to prepare the membrane while controlling performance of a gas separation membrane.

Description

Preparation method of silica-zirconia hydrogen permselective Membrane

1 is a graph showing the gas permeation coefficient of the silica-zirconia gas separation membrane developed in the present invention,

Figure 2 is a cross-sectional photograph of the silica-zirconia gas separation membrane developed in the present invention,

3 is a surface photograph of the silica-zirconia gas separation membrane developed in the present invention.

The present invention relates to a method for producing a silica-zirconia gas separation membrane by CVD for hydrogen separation that can be applied to a high temperature, highly corrosive environment in a hydrogen production process by thermochemical decomposition of water.

As the industry is advanced, the use of fossil fuels such as petroleum, coal, and natural gas is increasing significantly. Such fossil fuels pollute the earth's environment by emitting air pollutants such as NOx, SOx, and CO ₂ after use. In addition, in recent years, the increasing concentration of carbon dioxide emitted by fossil fuel combustion increases the concern of global warming.

In order to solve such a problem, considerable attention has been paid to the process of using a separator as a process for separating carbon dioxide gas from the combustion gas under development as a global warming measure. In this process, the membrane needs the ability to be used at high temperatures.

In addition, the development of high-efficiency, eco-friendly clean energy technology is actively progressing for the preservation of the environment of the earth and the efficient use of energy sources. It is widely used as raw material and process gas of chemical plant, and hydrogen as energy source does not generate global environmental pollutants when used as fuel, and it is easy to use as fuel by direct combustion or as fuel cell. . In addition, hydrogen can be easily transported as a gas or a liquid, and is easily stored in various forms such as high pressure gas, liquid hydrogen, and metal hydride. Hydrogen can be produced using indefinite water as a raw material, and recycled back to water after use.

Hydrogen can be used in almost all fields used in current energy systems such as general fuels, hydrogen vehicles, hydrogen airplanes, fuel cells, etc. from industrial base materials, and is considered to be the most suitable for future energy systems.

In this hydrogen production process, there is hydrogen production by thermochemical decomposition of water. This method includes a method of using high temperature heat of solar heat and a method of producing hydrogen using high temperature heat of nuclear power (hot gas furnace). In particular, one of the processes for producing hydrogen using the high temperature heat of nuclear power is the IS (iodine-sulfur, iodine-sulfur) process.

The IS process consists of three reaction processes: the Bunsen reaction process, the HI decomposition reaction, and the sulfuric acid decomposition reaction represented by the following equation, and water, which is a raw material, is continuously supplied and decomposed to produce hydrogen and oxygen. The material has a cycle-cycle characteristic of circulating inside the process [Ref. 1].

2H ₂ O + I ₂ + SO ₂ = 2HI + H ₂ SO ₄ (bunsen reaction process)

2HI = H ₂ + I ₂ (HI decomposition reaction process)

H ₂ SO ₄ = H ₂ O + SO ₂ + 1 / 2O ₂ (sulfuric acid decomposition reaction process)

In particular, in the HI decomposition reaction, HI is separated from a HIx (HI, I ₂ , H ₂ O mixed solution) solution, and the separated HI is decomposed to produce hydrogen. Currently, catalysts are the most used to decompose HI to produce hydrogen [Ref. 3.2], but the use of a membrane reactor is considered to improve the equilibrium decomposition rate of HI by catalysts as low as 20%. [Ref. 4].

As a gas separation membrane used in a membrane reactor that decomposes HI and produces hydrogen, a ceramic series is considered to be more promising than a polymer series, and a study on manufacturing such a gas separation membrane has been published in the paper [Refs. 4, 5, 6] ].

However, in order to decompose HI to produce hydrogen, it is required to develop a hydrogen separation membrane that can be applied to a high temperature and high corrosive environment.

An object of the present invention for solving the above problems is silica-zirconia (SiO ₂ -ZrO ₂ ) by CVD for hydrogen separation that can be applied to high temperature, high corrosive environment in the hydrogen production process by thermochemical decomposition of water. The present invention provides a method for manufacturing a system separator.

The present invention, which achieves the object as described above and performs the task for eliminating the conventional defects, is to separate the mixture in the gas state, and a method of manufacturing a ceramic-based gas separation membrane that can be used in a high temperature or high corrosion conditions The present invention relates to tetraethoxysilane (TEOS) and zirconia by vacuum evaporation (CVD) in pores of alumina (α- or γ-Al ₂ O ₃ , pore diameter <100 nm, porosity <40%) serving as a support. By evaporating or pyrolyzing butoxide (Zr-butoxide), silica and zirconia are bonded to the surface and pores constituting the membrane by a chemical reaction with each other, and the surface is coated with a silica-zirconia (SiO ₂ -ZrO ₂ ) ceramic. In addition, the present invention provides a method of manufacturing a separator that can be used for gas separation under high temperature conditions by changing to silica-zirconia.

In detail, the surface of the ceramic (α- or γ-Al ₂ O ₃ , pore diameter <100 nm, porosity <40%) is coated with a silica-zirconia (SiO ₂ -ZrO ₂ ) -based ceramic, The inside also changes to silica-zirconia, which can be used for gas separation under high temperature conditions. In addition, tetraethoxysilane (TEOS) and zirconia butoxide (Zr-butoxide), which are silica-zirconia-providing materials, are used as carrier gas ( He, Ar, N ₂ ), wherein the performance of the gas separation membrane depends on the linear velocity of the gas supplied into the reactor and the ratio of silica-zirconia.

The mixing ratio of tetraethoxysilane (TEOS) and zirconia butoxide (Zr-butoxide) is composed of 30wt% ~ 90wt% tetraethoxysilane (TEOS) and 10wt% ~ 70wt% zirconia butoxide (Zr-butoxide) .

That is, it is possible to manufacture by changing the zirconia butoxide (Zr-butoxide) in the total mixture consisting of two materials to 10wt% ~ 70wt%.

The reason for this limitation is that if the mixing ratio of zirconia butoxide is greater than 70wt%, the Zr precursor becomes viscous with time and the efficiency of the film formation decreases, and it is difficult to introduce Zr precursor into the reaction tube. It becomes a state.

In addition, when the mixing ratio of zirconia butoxide (Zr-butoxide) is less than 10wt%, the Zr precursor is decomposed and difficult to be coated on the separator, and most of the silica occupies only silica.

The preferred mixing ratio of tetraethoxysilane (TEOS) and zirconia butoxide (Zr-butoxide) is 1: 1 when mixed with 50 wt% tetraethoxysilane (TEOS) and 50 wt% zirconia butoxide (Zr-butoxide). At the time of mixing, the best membrane manufacturing result was obtained.

As described above, the mixing ratio of tetraethoxysilane (TEOS) and zirconia butoxide (Zr-butoxide) is 30wt% to 90wt% tetraethoxysilane (TEOS) and 10wt% to 70wt% zirconia butoxide (Zr-butoxide). The method to be achieved is a method in which a solution containing a mixture of tetraethoxysilane (TEOS) and zirconia butoxide (Zr-butoxide) in advance in a container and supplied by a carrier gas, and tetraethoxysilane (TEOS) and Zirconia butoxide (Zr-butoxide) is put in a different container, and then controlled by the ratio of the carrier gas flow rate to supply any of the methods.

In the reaction, when the linear velocity of the carrier gas of the present invention is 0.06-0.11 m / s, the performance of the gas separation membrane was the best. If the linear velocity of gas is less than 0.06, the coating time of silica-zirconia is small, and the processing time is long. If the gas is higher than 0.11, the carrier flow velocity in the reaction tube is fast, so that the precursors of tetraethoxysilane (TEOS) and zirconia butoxide (Zr-butoxide) ) Is discharged out of the reactor before decomposing, showing the best results in the numerical range.

Carrier gases include He, Ar, and N ₂ , which are inert gases. Use any one selected from.

The temperature of the tetraethoxysilane (TEOS) and zirconia butoxide (Zr-butoxide) is maintained at 20 ~ 40 ℃. The reason for maintaining the temperature in this way is to control the amount transferred with the carrier gas.

That is, TEOS and Zr-butoxide have different amounts of evaporation depending on the temperature. When the temperature is the most preferable temperature of 30 ℃, a certain amount of mixed gas of TEOS and Zr-butoxide is evaporated, and when this is transported to the carrier gas, the evaporated mixed gas is transferred by the flow rate of the carrier gas. If the temperature is raised further, the evaporation of TEOS and Zr-butoxide increases, and the decrease of the temperature decreases. Therefore, when the amount of evaporation is large, the flow rate of the carrier gas is reduced, and when the amount of evaporation is small, the flow rate of the carrier gas is increased. However, when the temperature is less than 20 ° C or greater than 40 ° C the evaporation amount of the present invention is too small or too large to control the flow rate is limited to such a numerical range.

The reactor temperature of the present invention is Maintain at 600 ° C to 750 ° C. The reason for this limitation is that the amount of Zr-Si to be coated is less when the temperature is less than 600 ° C, which requires a very long time. This is because the weakened coating is peeled off.

Hereinafter, the configuration and the operation of the embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 1 is a graph showing the gas permeability coefficient of the silica-zirconia gas separation membrane developed in the present invention, measuring the permeation rate according to the gas permeation coefficient (N ₂ , H ₂ ) of the silica-zirconia membrane produced as shown It was. The permeation rate of hydrogen was higher than 10 ⁻⁷ (mol / Pa · m ² · s), and the selectivity of hydrogen to nitrogen was also higher than 10. Therefore, the prepared silica-zirconia membrane is considered to be very useful for separating hydrogen gas.

Figure 2 is a cross-sectional picture of the silica-zirconia gas separation membrane developed in the present invention, as shown in the lower part of the Figure 2 (1.10μm or less indicated portion) is the ceramic substrate used in this experiment, 1.10μm indicated portion is coated Si -Zr. In addition, it can be seen that Zr-Si is also coated on the ceramic substrate by vacuum suction used in this experiment.

Figure 3 shows a surface photograph of the silica-zirconia gas separation membrane developed in the present invention, it shows that these countless spherical Si-Zr is bonded as the coating Si-Zr as shown.

Hereinafter is a preferred embodiment of the present invention.

Example 1

Tetraethoxysilane (TEOS) and zirconia butoxide (ceramic) were used in ceramics (α- or γ-Al ₂ O ₃ , pore diameter <100 nm, porosity <40%) as starting materials by chemical vapor deposition (CVD) in vacuum. By thermal decomposition of Zr-butoxide, silica-zirconia is bonded to the surface and pores that make up the film by chemical reaction.Since the surface is coated with silica-zirconia (SiO ₂ -ZrO ₂ ) ceramic, Silica-zirconia-based hydrogen separation membrane was prepared that can be used for hydrogen separation under high temperature conditions.

Specifically, tetraethoxysilane (hereinafter referred to as 'TEOS') is used as a precursor of silica (SiO ₂ ), and zirconia butoxide (hereinafter referred to as 'Zr-butoxide') is used as a precursor of zirconia. It was.

TEOS and Zr-butoxide were maintained at 30 ° C.

In addition, TEOS and Zr-butoxide were mixed in a 1: 1 ratio while using nitrogen as a carrier gas, and introduced into the reactor, and silicon was formed on the surface and pores constituting the film by pyrolysis of TEOS and Zr-butoxide at a reactor temperature of 700 ° C. By chemically bonding to each other, the surface is coated with silica-zirconia (SiO ₂ -ZrO ₂ ) -based ceramics, and the inside of the pore is also changed to silica-zirconia to form a silica-zirconia-based hydrogen separation membrane which can be used for hydrogen separation at high temperature conditions. Produced.

An important factor here is the linear velocity of the carrier gas in the reactor, which is 0.11 m / s here.

The temperature dependence of the gas permeability coefficients (N ₂ , H ₂ ) of the prepared silica-zirconia membrane was examined. The temperature dependence of the gas permeation coefficient of the produced membrane showed almost the same tendency, and the selectivity of hydrogen to nitrogen at each measurement temperature had almost the same value (see FIG. 1).

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by any person having ordinary skill in the art without departing from the gist of the present invention claimed in the claims. Of course, such changes will fall within the scope of the claims.

The silica-zirconia membrane prepared as described above can be a gas separation membrane having excellent heat resistance, corrosion resistance, and oxidation resistance even in harsh environmental conditions with high temperature and corrosion resistance, compared to general polymer membranes, and pore size control is possible according to the CVD treatment method. In addition, silica and zirconia are mutually complementary to increase heat resistance, corrosion resistance, and oxidation resistance, and are useful inventions that can obtain the effect of improving the separation permeation performance of the membrane.

[references]

1) Kap-Jin Hwang, Ho-Sang Choi, An-Soo Kang, Jong-Won Kim, Ko-Sung Kim, "Thermochemical Hydrogen Production IS (Iodine-Sulphur) Process," Journal of the Korean Institute of Industrial Chemists, 13 (6), p.600 (2002).

2) N. Ito, Y. Hindu, T. Hakuta, H. Yoshitome, "Enhanced catalytic decomposition of HI by using a microporous membrane", Int. J. Hydrogen Energy, 9 (10), p.825 (1984).

3) Y.Oosawa, T.Kumagai, S.Mizuta, W.Kondo, Y.Takemori, K.Fujii, "Kinetics of the catalytic decomposition of hydrogen iodide in the Mg-I thermochemical cycle", Bull. Chem. Soc. Jpn., 54, p. 742 (1981).

4) Gab-Jin Hwang, K. Onuki, S. Shimizu, "Separation of hydrogen from a H ₂ -H ₂ O-HI gaseous mixture using a silica membrane", AIChE J. 46, p.92 (2000).

5) Gab-Jin Hwang, K. Onuki, "Simulation study on the catalytic decomposition of hydrogen iodide in a membrane reactor with a silica membrane for the thermochemical water-splitting IS process", J. Membrane Sci., 194, p.207 (2001).

6) Gab-Jin Hwang, Jon-Won Kim, Ho-Sang Choi, K. Onuki, "Stability of a silica membrane prepared by CVD using γ- and α-alumina tube as the support tube in the H ₂ O-HI gaseous mixture ", J. Membrane Sci., 215, p. 293 (2003).

Claims (7)

The surface of the film formed by evaporating or pyrolysing a silica donor on a ceramic (α- or γ-Al ₂ O ₃ , pore diameter <100 nm, porosity <40%), which is a starting material, by chemical vapor deposition (CVD) under vacuum. In the method for producing a separator that can be used for hydrogen separation under high temperature conditions by coating the surface of the silica-based ceramic with a silica-based material by bonding the silica-providing material to the pores, As a silica donor, tetraethoxysilane (TEOS) and zirconia donor zirconia butoxide (Zr-butoxide) are mixed and supplied into the reactor using a carrier gas, but the supplied tetraethoxysilane (TEOS) and zirconia butoxide are supplied. The mixing rate of (Zr-butoxide) is 30wt% to 90wt% tetraethoxysilane (TEOS) and 10wt% to 70wt% zirconia butoxide (Zr-butoxide), and the linear velocity of the carrier gas is 0.06-0.11 m. A method for producing a silica-zirconia hydrogen separation membrane, characterized in that to prepare a separator while controlling the performance of the gas separation membrane by adjusting to / s. delete The method of claim 1, The method of producing a silica-zirconia hydrogen separation membrane, characterized in that the temperature of the tetraethoxysilane (TEOS) and zirconia butoxide (Zr-butoxide) is 20 ~ 40 ℃. The method of claim 1, Temperature of the reactor is a method of producing a silica-zirconia hydrogen separation membrane, characterized in that 600 ℃ ~ 750 ℃. The method of claim 1, The method for supplying a silica-providing material mixed with the 30wt% to 90wt% tetraethoxysilane (TEOS) and the 10wt% to 70wt% zirconia butoxide (Zr-butoxide) to the reactor is previously described with tetraethoxysilane (TEOS) and zirconia. A method for producing a silica-zirconia hydrogen separation membrane, characterized in that the mixed solution of butoxide (Zr-butoxide) in accordance with the above ratio in a container and supplied by a carrier gas. The method of claim 1, The method of supplying a silica-providing material mixed with the 30wt% to 90wt% tetraethoxysilane (TEOS) and the 10wt% to 70wt% zirconia butoxide (Zr-butoxide) to the reactor is tetraethoxysilane (TEOS) and zirconia butok A method for producing a silica-zirconia hydrogen separation membrane, characterized in that the side (Zr-butoxide) is put in different containers, and then the ratio is controlled by the flow rate of the carrier gas. delete

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