KR100285908B1 - Method for producing palladium-impregnated alumina-silica composite membrane through multi-step pore structure improvement - Google Patents

Abstract

The present invention is to reduce the pore size of the α-alumina support by using in-situ silica sol-gel method and immersion coating method respectively using two kinds of silica sol having different sizes, and then improved soaking and vapor deposition method (enhanced soaking and vapor deposition method) : Palladium-impregnated alumina-silica composite membrane having excellent hydrogen separation and permeability even at high pressure difference and high temperature above atmospheric pressure by forming ESFD) continuously between outer and inner layers of alumina-silica composite membrane Provide a method. Since the palladium-impregnated alumina-silica composite membrane prepared by the method of the present invention exhibits practically high hydrogen pressure separation characteristics at a high pressure difference of higher than normal pressure and a high temperature of 600K or higher, the pretreatment step for producing high purity hydrogen in a high temperature and high pressure chemical process, etc. It can be used to show high hydrogen separation efficiency and can be used for various purposes such as mixing with pressure swing adsorption (PSA) process and application to membrane reactor in hydrogenation reaction.

Description

Method for manufacturing palladium-impregnated alumina-silica composite membrane by improving multi-stage pore structure

The present invention relates to a method for producing a palladium-impregnated alumina-silica composite membrane through multi-step pore structure improvement. More specifically, the present invention reduces the pore size of the α-alumina support by using In-situ silica sol-gel method and immersion coating method, respectively, using two kinds of silica sol having different sizes, and then improved permeation deposition. Successive soaking and vapor deposition method (ESVD) forms an intermediate layer of palladium between the outer and inner layers of the alumina-silica composite membrane, providing excellent hydrogen separation (selectivity) and permeability even at high pressure differentials above atmospheric pressure and at elevated temperatures It relates to a method for producing a palladium-impregnated alumina-silica composite membrane having a.

The research on gas separation membranes has been rapidly developed since the mid-1980s, and the manufacturing method and method characteristics thereof have been studied considerably. Recently, the research has been conducted to increase the separation efficiency by using the physical and chemical properties of the separation targets. In order to impregnate the pores of the inorganic material membrane with the catalyst material, and the research to obtain the molecular sieve effect by distributing the pore size small and evenly as small as the molecular size of the gas to be separated. This attempt has been initiated as a way to overcome the disadvantage that the separation mechanism has low selectivity as Knudsen diffusion in case of gas separation using a conventional inorganic material film, the following contents have been reported.

Lin et al. Prepared a porous membrane in the form of an oxide by chemically depositing an organometallic mixture on the surface of the porous support (see US Pat. No. 5,415,891), and Anderson et al. Reaction was performed to prepare a membrane on the surface of the support (US Pat. No. 5,342,431).

Trocha et al. Densified an inorganic material film having a large pore size of about 2000 mm 3 to about 100 to 200 mm by a diffusion-controlled method using water-soluble colloidal silica (see M. Trocha and WJ Koros). , J. Membr. Sci., 87: 281 (1994). The pore structure improvement method is a method that can be mainly applied to the regeneration process of the water treatment membrane because the size of the colloidal silica that can be used is limited.

In addition, Yan et al. Prepared an inorganic film free of pores by forming a palladium layer using metal-organic chemical vapor deposition (MOCVD) on the outer surface of the alumina support (see S. Yan et. al., Ind. Eng. Chem. Res., 33: 616 (1994)), the electric MOCVD method shows a relatively simple and high hydrogen separation, but is only suitable for the production of inorganic membranes with somewhat poor permeability and small size. That is, since the size (φ 2.6 mm × L 10 mm) of the alumina film used as the support was so small that the palladium acetate could be uniformly coated, alumina having fine pores could be uniformly coated by the MOCVD method.

Thus, in order to use the asymmetric alumina membrane of the size actually used for ultrafiltration as a support for the separation of hydrogen gas, the upper edge is about 30 times larger than the alumina membrane used by Yan et al. Using an α-alumina membrane having a thick, sparse and dense asymmetrical structure as a support, an inorganic material membrane for hydrogen separation with improved separation and permeability to hydrogen was prepared (Korean Patent No. 158431). According to this method, palladium acetate is dissolved in acetone in a saturated state and deposited on an asymmetrical alumina film to allow palladium to enter the inside of the alumina film by capillary force, thereby making most of the palladium (II) in the outer coarse thick layer. The acetate precursor was stored and vacuum was applied while raising the temperature to evaporate the palladium (II) acetate precursor to form a palladium interlayer between the outer and inner layers of the alumina film.

The palladium-impregnated inorganic material film produced by successive soaking and vapor deposition methods (SVD) in the palladium-impregnated alumina film produced by the sol-gel method slightly improved the hydrogen selectivity, but was slightly improved between the inner and outer layers. When the pressure difference is higher than the normal pressure and the temperature is higher than 600K, hydrogen selectivity is still low and there are various problems in practical use. This is because the length of the alumina tube used as the support is 500 mm long so that it is difficult to effectively maintain the high temperature deposition temperature over the entire support. In practice, operation with a low pressure difference between the outer and inner sides of the membrane results in diffusion in the opposite direction and less throughput, so that a membrane with high hydrogen selectivity at a higher pressure difference that would suppress diffusion in the opposite direction Development was essential to the actual process.

Therefore, the present inventors have diligently studied to solve the above problems, and as a result, by using two kinds of silica brushes having different sizes, the pore size of the α-alumina support is reduced by the In-situ silica sol-gel method and the deposition coating method, respectively. The continuous penetration deposition process was then performed to form a palladium intermediate layer between the outer and inner layers of the alumina-silica composite membrane, thereby achieving ideal Knudsen diffusion even at high pressure differences above atmospheric pressure and at temperatures above 600K. It was confirmed that the alumina-silica composite membrane of palladium-impregnated having a hydrogen separation degree exceeding the separation degree (3.74) and having a higher permeability than the conventional polymer membrane was completed, and completed the present invention.

After all, it is an object of the present invention to provide a method for producing a palladium-impregnated alumina-silica composite membrane in which the pore structure of the asymmetric tubular alumina support used in the actual water treatment process for ultrafiltration is improved in multiple stages.

1 is a schematic view of an apparatus for forming a silica sol inside the pores of an alumina support.

1 is a schematic diagram showing the process of improving the pore structure by the In-situ silica sol-gel method.

FIG. 2 is a scanning electron micrograph showing a cross section and Si distribution of an alumina-silica composite film prepared by In-situ silica sol-gel method.

3 is a scanning electron micrograph of the cross-section and the surface of the alumina-silica composite film subjected to the silica sol forming process by the In-situ silica sol-gel method and the deposition coating process using the silica sol.

Figure 4 shows the cross-section of the palladium-impregnated alumina-silica composite film and the distribution of palladium metal through the silica sol formation process by In-situ silica sol-gel method, the deposition coating process by silica sol and the palladium deposition process by improved permeation deposition method. Scanning electron micrograph.

5 is a view schematically showing a gas permeation apparatus.

Figure 6 is a graph showing the gas permeability change of the palladium-impregnated alumina-silica composite membrane of the present invention prepared through the multi-stage pore structure improvement.

7 is a graph showing changes in hydrogen selectivity and permeation coefficient according to the pore structure improvement step.

Explanation of symbols on the main parts of the drawings

1: acidic water-ethanol mixture 2: alumina support

3: TEOS (tetraethylorthosilicate) 4: support rubber stopper

5: thermostat 6: silica sol particles

7: nitrogen gas 8: hydrogen gas

9: 3-way valve 10: flow regulator

11: pressure gauge 12: membrane separation module

13: Furnace 14: Flow meter

15: Needle Valve

Hereinafter, a method of manufacturing the palladium-impregnated alumina-silica composite membrane for hydrogen separation according to the present invention will be described in more detail.

Process 1: Silica Sol Forming Process by In-situ Silica Sol Gel Method

In-situ silica sol-gel method is used as the first pore structure improvement process of alumina support. In other words, the mixture of acidic distilled water-ethyl alcohol and silicate precursors are diffused by capillary force on the inside and outside of the porous alumina support to induce gelation to generate silica sol inside the pores. Subsequently, heat treatment produces an alumina-silica composite membrane having reduced pore size of the support.

In the above, porous supports having various shapes and sizes may be used as the alumina support, but it is preferable to use a tubular support, and more preferably, to maintain a dense internal and mechanical strength with fine pores. An asymmetric tubular alumina support composed of a thick outer layer with pores is used.

In addition, the silicate precursor is tetramethylorthosilicate (TMOS), tetraethylorthosilicate (TEOS), tetra-n-propoxysilane, tetra-n-butoxysilane, tetrakis (2- Most preferably, TEOS can be used, such as tetrakis (2-methoxyethoxy) silane, and the mixture (acid) of distilled water-ethyl alcohol is distilled water: ethyl alcohol = 1-2: 10, 1-2, Most preferably, the mixture is mixed in a molar ratio of 4: 1 and an acid is added so that the pH is 2.5 to 1.7, most preferably pH 2.0. In addition, the heat treatment is performed under a nitrogen atmosphere for 120 minutes to 170 minutes at 450 ℃ to 550 ℃.

This process can form silica sol of various sizes by varying the composition ratio of each component constituting the mixture of distilled water-ethyl alcohol, there is an advantage that can effectively reduce the size of the alumina pores, the inner side than the original support As the pore size becomes smaller, it can be effectively used for various pore structure improvement methods to be implemented subsequently.

Process 2: deposition process of silica

Dip coating of the silica sol is performed to sufficiently reduce the pore size at both ends of the membrane where the chemical vapor deposition of palladium, which will be described later, due to the nonuniformity of the temperature distribution throughout the membrane, is sufficiently performed. That is, both ends of the alumina-silica composite membrane prepared in the above-mentioned step 1 are immersed in a silica sol for immersion coating under vacuum and immersed in silica.

In immersion coating, the pore size was reduced by using a smaller size silica sol than in step 1. The silica sol for immersion coating used a silicate precursor in a molar ratio of 1 to 2, most preferably 1, and distilled water. Ethyl alcohol = 2-5: 3-5, most preferably a mixture of distilled water-ethyl alcohol (acidic acid) mixed in a molar ratio of 4.7: 3.8 and added with an acid so that the pH is 2.8-1.9, most preferably pH 2.3. By using).

The coating apparatus was manufactured to vertically immerse and remove the alumina-silica composite membrane prepared in step 1 in a container containing silica sol, and the deposition time can be varied depending on the coating thickness, but preferably prepared in the above composition. The coated silica sol was applied 6 to 10 times by 1 minute dip coating.

Process 3: penetration deposition process of palladium

The infiltration mixture of the palladium precursor was uniformly flown to the outside of the alumina-silica composite membrane obtained from the above process, the inside of the alumina support was kept in a vacuum to infiltrate the palladium precursor into the pores of the alumina membrane and dried, and then the palladium precursor was The temperature is gradually raised to 170 ° C to 190 ° C while applying a vacuum to the inside of the film to sublimate, thereby depositing palladium on the pore surface of the alumina-silica composite membrane. As a result, an intermediate layer of palladium is formed between the outer and inner layers of the alumina-silica composite film. Then, the inside of the composite film is gradually heated while maintaining the vacuum, and heat-treated at a temperature of 290 ° C. to 310 ° C., thereby producing the palladium-impregnated alumina. Prepare a silica composite membrane.

In the above, the infiltration mixture of the palladium precursor is preferably used a mixture of palladium (II) acetate dissolved in acetone and a small amount of hydrochloric acid.

When the permeate mixture is flowed into the composite membrane according to the present process, the mixed liquid penetrates into the membrane by the capillary force of the micropores. At this time, the inside of the alumina support is kept in a vacuum to infiltrate and store the palladium precursor into the mixed membrane. Is improved. Next, in order to promote deposition of palladium in the pores of the composite film during the deposition of palladium, it is preferable to increase the temperature while flowing nitrogen from the outside to the inside of the film at a predetermined time interval.

The palladium-impregnated alumina-silica composite membrane prepared through the improvement of multi-stage pore structure as described above shows high pressure difference (pressure difference between inner and outer layers) above atmospheric pressure and high hydrogen permeability even at high temperature above 600K, (Knudsen limit, hydrogen separation degree 3.74) or more, hydrogen separation degree is shown.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are only for illustrating the present invention, and it will be apparent to those skilled in the art that the scope of the present invention is not limited to these examples according to the gist of the present invention.

Example 1 Formation of Silica Sol by In-situ Silica Sol Gel Method

In-situ silica sol-gel method was used as the first pore structure improvement process of the alumina support. That is, asymmetric tubular α-alumina support (Noridake Co., Japan; average pore size of 80 nm, outer diameter of 10 mm, inner diameter of 7 mm and length of 500 mm) was put in the apparatus as shown in the upper drawing of FIG. 1 and the temperature was maintained at 80 ° C. The ethanol-water mixture (pH 2.0) added with TEOS on the outside and a small amount of hydrochloric acid on the inside was added to diffuse into the pores of the support to form a silica sol inside the pores. After reacting for one hour, the mixture was dried at room temperature for 20 hours, and then heated at a rate of 0.7 ° C./min at a rate of 0.7 ° C./min in order to prevent cracking during heat treatment, and then treated at 500 ° C. for 150 minutes under nitrogen atmosphere. This process was repeated eight times. The reactants used in the preparation of the silica sol and their compositions are shown in Table 1 below.

The cross section of the alumina-silica composite membrane thus prepared and the distribution of silicon elements were observed through a scanning electron microscope. In FIG. 2, white lines represent Si.

The alumina-silica composite membrane prepared above exhibited high permeability (see FIGS. 6 and 7), but the hydrogen selectivity was 3 to 4, which showed a degree of separation (SF = 3.74) by ideal nucenus diffusion. Bar additional pore structure improvement methods were required as in the following examples.

Composition of reactants for the production of silica sol (molar ratio) Reactant Type TEOS Ethyl alcohol Distilled water Reaction catalyst In-situ silica sol gel method ND ^* One 4 Hydrochloric acid Dipping Coating Method of Silica Sol One 3.8 4.7 nitric acid

*: N.D. = not determined

Example 2: Dipping Coating of Silica

For gas separation through effective surface diffusion, a chemical vapor deposition method of impregnating palladium into membrane pores was required for further pore structure improvement, as in Example 3 described later. However, it was very difficult to deposit palladium on the pore surface of the alumina-silica composite membrane layer by maintaining a uniform temperature throughout the film through this chemical vapor deposition method.

Thus, deposition coating of silica sol was performed to sufficiently reduce the pore size at both ends of the membrane where the chemical vapor deposition could not occur sufficiently due to the temperature distribution. Deposition coating of silica sol was performed on the entire 500 mm portion of the alumina-silica composite membrane and on the 150 mm portion at both ends. In the deposition coating of silica sol, a smaller sized silica sol was used to reduce the pore size. The reactants and their composition used in the preparation of the silica sol for deposition coating are shown in Table 1 below. The pH of the water mixture was 2.3. The coating apparatus was manufactured to vertically immerse and remove the alumina-silica composite membrane prepared in Example 1 in a container containing silica sol, and an air compressor and an air cylinder were used to minimize vibration during the operation. In addition, a vacuum pump was connected so that the silica sol was sufficiently sucked into the support during coating, and a vacuum was applied to the inside of the support during deposition and drying. Deposition time is a factor that has a large influence on the coating thickness, in this Example was coated 8 times by 1 minute using a silica sol prepared in the composition shown in Table 1.

As described above, the cross-section and the surface of the alumina-silica composite membrane having improved pore structure through two steps are shown in FIG. 3.

The permeability of the composite membrane prepared in this example was decreased in the case of both hydrogen and nitrogen, the hydrogen selectivity increased as a whole, in particular, the hydrogen selectivity at low pressure was significantly increased as 5-7.

Example 3 Infiltration of Palladium

As a final pore structure improvement step of the alumina-silica composite membrane in which the pore structure was improved in two steps using a silica sol, the permeation deposition method used by Sang Sang Lee et al. (See Republic of Korea Patent No. 158431) was used.

In order to impregnate the palladium metal in the pores of the alumina-silica composite membrane, first, 5 g of palladium (II) acetate was dissolved in 200 mL of acetone, and 5 mL of hydrochloric acid was added thereto, followed by vigorous stirring to prepare an infiltration mixture of the palladium precursor.

In Example 2, one part of the alumina-silica composite membrane having improved pore structure was blocked, placed in a glass tube having a diameter of 15 mm and a length of 52 cm, and then the permeation mixture solution of the palladium precursor prepared before was poured into the outside of the composite membrane. Then, the penetrating mixture of the palladium precursor penetrates into the inner layer of the alumina membrane by capillary force, and stores palladium (II) acetate uniformly throughout the membrane. Thus, the penetration mixture of the palladium precursor was uniformly supplied for 1 hour to obtain a uniform inorganic membrane. After 1 hour, the infiltration mixture of the palladium precursor gathered inward through the alumina membrane and the infiltration mixture of the outward palladium precursor were recovered.

Then, in the presence of the infiltration mixture of the palladium precursor on the alumina support, a vacuum was applied at 100 Torr to 300 Torr for 15 minutes from the inside to allow the infiltration mixture of the palladium precursor to enter the inside of the membrane. Vacuum in this case helps capillary forces to improve the storage of precursor solution. Subsequently, the mixture was dried at room temperature for 3 hours and dried in an oven at 100 ° C. for 3 hours to evaporate the acetone solvent in the pores. In this way, a palladium (II) acetate precursor is produced in the pores, vacuum is applied inside the membrane containing the palladium (II) acetate precursor, and the temperature is raised to 180 ° C. at a rate of 6.2 ° C./min. It is easily deposited inside the pores of the alumina-silica composite membrane. For smooth deposition of the palladium metal, nitrogen was flowed 1 minute every 10 minutes through a flow controller (UFC-1500A, UNIT instruments, Inc., USA) at 40-60 mL / min (STP). Further, the entire reactor was maintained at 1 Torr or less while being sucked at 10 ⁻³ Torr from the inside of the inorganic membrane with a vacuum pump.

After the deposition at 180 ° C. for 1 hour as described above, the temperature was heated to 300 ° C. at a rate of 6.0 ° C./min so that the deposited palladium particles completely adhered to the pore walls. The palladium deposition process and the heat treatment process are repeated 5 to 6 times, and as the process is repeated, the storage amount of the palladium (II) acetate precursor solution by capillary force decreases.

A cross-sectional view of the palladium-impregnated alumina-silica composite film and the distribution of palladium metal prepared by the improved penetration deposition method is shown in FIG. 4. In FIG. 4, the white line represents Pd.

Evaluation of Hydrogen Separation and Permeability of Inorganic Material Membranes

In order to examine the gas permeability of the palladium-impregnated alumina-silica composite membrane of the present invention, a permeation experiment of pure gas (N ₂ , H ₂ ) was performed using the gas permeation apparatus as shown in FIG. 5. That is, the amount of gas supplied using the flow regulator was kept constant, and at this time, the inner pressure of the membrane was maintained at atmospheric pressure, and the permeability was measured while changing the outer pressure with the needle valve.

Membrane separation (selectivity) was defined as the ratio of the permeability of each gas permeated, and the permeability of the gas was defined as follows:

Where

Q _i is the volumetric flow rate of gas in the STP;

P is the pressure difference across the membrane; And,

2r and L represent the diameter of the membrane pores and the length of the membrane, respectively.

The hydrogen and nitrogen gas permeability of the palladium-impregnated alumina-silica composite membrane of the present invention are shown in FIG. 6, wherein nitrogen gas was used as the comparator gas. In Figure 6, (○) represents the nitrogen gas permeability of the alumina-silica composite membrane prepared in Example 1, (●) represents the hydrogen gas permeability of the alumina-silica composite membrane prepared in Example 1, (□) The nitrogen gas permeability of the palladium-impregnated alumina-silica composite membrane of the present invention is shown, and (■) represents the hydrogen gas permeability of the palladium-impregnated alumina-silica composite membrane of the present invention, respectively.

As shown in FIG. 6, the palladium-impregnated alumina-silica composite membrane of the present invention exhibits a high pressure difference above atmospheric pressure and high hydrogen permeability even at a high temperature of 600K or higher, and has a hydrogen separation degree above the Knudsen limit (hydrogen separation degree 3.74). Could know.

In addition, in order to compare with the hydrogen separation performance of the conventional polymer membrane, the change in hydrogen permeability coefficient and selectivity according to the pore structure improvement step of the inorganic material membrane of the present invention is shown in FIG. 7 together with the separation limit of the conventional polymer membrane for hydrogen separation. . FIG. 7 is a graph plotting hydrogen gas permeability again at a temperature of 673 K and a pressure of 150 kPa disclosed in FIG. 6. In Figure 7, the solid line represents the hydrogen separation performance limit of the conventional polymer membrane, (●) represents the hydrogen permeation coefficient and selectivity of the alumina-silica composite membrane prepared in Example 1, (■) is the palladium impregnated alumina of the present invention The hydrogen permeability coefficient and selectivity of the silica composite membrane are shown, respectively. In addition, the film thickness in FIG. 7 was estimated from the scanning electron micrograph shown in FIGS.

As shown in FIG. 7, the palladium-impregnated alumina-silica composite membrane prepared by the multi-step process of the present invention exhibits an excellent slope (an inclination of q and n) greater than the solid line representing the hydrogen separation performance limit of the conventional polymer membrane. It can be seen that it has a degree, and also showed a higher transmittance than the conventional polymer membrane.

As described and demonstrated in detail above, the present invention forms a silica sol in the pores of the fine porous alumina support by the in-situ silica sol-gel method, and reduces the pore size of the support by depositing a smaller sized silica sol under vacuum. Then, an improved permeation deposition method (ESVD) was carried out continuously to adsorb palladium metal into the pores of the alumina-silica composite membrane, thereby preparing an alumina-silica composite membrane of palladium impregnation. The multi-stage porous hydrogen separation membrane exhibits high hydrogen selectivity and permeability due to surface diffusion due to reduced pore size and selective hydrogen adsorption characteristics of palladium, in addition to nusen diffusion.

As described above, the palladium-impregnated alumina-silica composite membrane prepared by the method of the present invention exhibits practical hydrogen separation characteristics at a high pressure difference of higher than normal pressure and a high temperature of 600K or higher, and thus to produce high purity hydrogen in high temperature and high pressure chemical processes. It can be used for a pretreatment step and the like to show high efficiency, and can also be used for various purposes such as mixing with a pressure swing adsorption (PSA) process and application to a membrane reactor in a hydrogenation reaction.

Claims (10)

(Iii) A silicate precursor and an acidic distilled water-ethyl alcohol mixture are diffused inside and outside the porous alumina support, respectively, to form a silica sol inside the pores, and then gelled and heat treated to reduce the pore size of the support. Manufacturing a membrane; (Ii) immersing both ends of the alumina-silica composite membrane prepared in the above-mentioned process in a immersion coating silica sol under vacuum to immersion coating with silica; And, (Iii) The infiltration mixture of the palladium precursor is evenly flown to the outside of the alumina-silica composite membrane deposited by the above-mentioned process, and the inside of the electrical composite membrane is kept in vacuum to infiltrate the pores of the membrane and dry it. And heating the film to 170 ° C. to 190 ° C. while applying a vacuum to the inside of the membrane to deposit palladium on the pore surface of the alumina-silica composite membrane. doing Method for producing alumina-silica composite membrane impregnated with palladium. The method of claim 1, The alumina support is characterized by the use of an asymmetric tubular alumina support. Method for producing alumina-silica composite membrane impregnated with palladium. The method of claim 1, The silicate precursors are tetramethylorthosilicate (TMOS), tetraethylorthosilicate (TEOS), tetra-n-propoxysilane, tetra-n-butoxysilane and tetrakis (2-methoxy Ethoxy) silane (tetrakis (2-methoxyethoxy) silane) is characterized in that it is selected from the group consisting of Method for producing alumina-silica composite membrane impregnated with palladium. The method of claim 1, The acidic distilled water-ethyl alcohol mixture is a mixture of distilled water: ethyl alcohol = 2 to 10: 1 to 2 molar ratio, and an acid added so as to have a pH of 2.5 to 1.7. Method for producing alumina-silica composite membrane impregnated with palladium. The method of claim 4, wherein The acidic distilled water-ethyl alcohol mixture is a mixture of distilled water: ethyl alcohol = 4: 1 molar ratio and an acid added to a pH of 2.0. Method for producing alumina-silica composite membrane impregnated with palladium. The method of claim 1, Heat treatment is carried out at 450 ℃ to 550 ℃ under a nitrogen atmosphere for 120 to 170 minutes Method for producing alumina-silica composite membrane impregnated with palladium. The method of claim 1, The silica sol for immersion coating uses a silicate precursor in a molar ratio of 1 to 2, distilled water: ethyl alcohol = 2 to 5: 3 to 5 in a molar ratio, and distilled water-ethyl added with an acid so as to have a pH of 2.8 to 1.9. Characterized in that it is prepared using a mixture of alcohols Method for producing alumina-silica composite membrane impregnated with palladium. The method of claim 7, wherein Silica sol for immersion coating is prepared by using a silicate precursor in a molar ratio of 1, mixing in a molar ratio of distilled water: ethyl alcohol = 4.7: 3.8 and adding distilled water-ethyl alcohol to pH 2.3. Characterized by Method for producing alumina-silica composite membrane impregnated with palladium. The method of claim 1, The infiltration mixture of the palladium precursor is characterized by using a mixture solution of palladium (II) acetate dissolved in acetone and hydrochloric acid. Method for producing alumina-silica composite membrane impregnated with palladium. The method of claim 1, Infiltrating the palladium precursor to increase the temperature while flowing nitrogen from the outside of the composite film to the inside during the temperature increase for palladium deposition Method for producing alumina-silica composite membrane impregnated with palladium.