A dehydrogenation catalyst and its preparation method and application

Abstract

The present invention relates to the field of catalysts, and in particular to a dehydrogenation catalyst, a preparation method thereof and an application thereof. The dehydrogenation catalyst comprises a carrier, a noble metal active component and an auxiliary agent; the carrier is an α-Al2O3 ball, the active component is one or two of the noble metals Pd and Pt, and the auxiliary agent is a metal auxiliary agent and a rare earth element auxiliary agent; the metal auxiliary agent is Cu or Mo, and the rare earth element auxiliary agent is at least one of Y, Gd or Dy; wherein, based on the weight of the carrier, the active component content is 0.08-0.13wt%. The catalyst of the present invention reduces the content of the noble metal by selecting a suitable auxiliary agent while ensuring the dehydrogenation accuracy and stability, thereby reducing the production cost of the dehydrogenation agent.

Description

Technical Field

[0001] The present invention relates to the field of catalysts, and in particular to a dehydrogenation catalyst and a preparation method and application thereof. Background Art

[0002] In recent years, with the continuous emergence of global climate issues, countries have paid more attention to carbon emissions. my country has promised that by 2030, carbon dioxide emissions will no longer increase, and will gradually decrease after reaching the peak. The key to controlling carbon emissions is to control carbon dioxide emissions. In industrial production, carbon dioxide, as a by-product, is purified and reused, such as producing urea and food-grade carbon dioxide, which not only reduces emissions but also brings benefits to enterprises. In this process, dehydrogenation catalysts are key technologies. For example, urea is obtained by reacting ammonia and carbon dioxide under high pressure in industry. Carbon dioxide, as one of the reactants, contains about 1% hydrogen in its atmosphere, which may cause explosions and other dangerous accidents during the reaction. To ensure production safety, hydrogen in the carbon dioxide raw gas can be removed by catalytic combustion before the reaction. Therefore, while meeting production needs, reducing production costs is the development trend of high-concentration carbon dioxide dehydrogenation catalysts.

[0003] CN1035256A discloses a catalyst for removing hydrogen from high-concentration carbon dioxide raw gas, which is characterized by using Al2O3 balls as carriers, palladium and platinum as active components, and at least one element of Na, K, Mg, Ca, Ba, Fe, Co, Ni, Cu, Cr, and V as an auxiliary agent. The active components and the auxiliary agents are prepared by an impregnation method in a certain proportion.

[0004] CN1069426A discloses a dehydrogenation catalyst with high sulfur resistance, which is suitable for dehydrogenation of high-concentration carbon dioxide raw gas. Its characteristics are that palladium and iron are used as active components, alkali metal elements are used as auxiliary agents, and they are carried on a γ-Al2O3 carrier. The active components and auxiliary agents are prepared by impregnation method in a certain proportion.

[0005] CN1125638A discloses a method for catalytically removing hydrogen from high-concentration carbon dioxide raw gas. The catalyst used in the invention uses gold as the active component and iron oxide or composite oxide MFe (M is a Group IIA or Group VIII metal) as the carrier, and the catalyst is prepared by coprecipitation.

[0006] CN1249964A discloses a catalyst for removing hydrogen from high-concentration carbon dioxide raw gas and its preparation. The invention is characterized in that the Pt content in the catalyst is higher than that of Pd, rare earth metal elements are added, and a composite oxide Al or Al-ZrO carrier is used. The catalyst is prepared by an impregnation method and a hydrated hydrazine wet method is reduced at room temperature without high-temperature calcination reduction.

[0007] CN1334140A discloses a catalyst for removing hydrogen from high-concentration carbon dioxide raw gas containing multiple rare earth elements. The invention is composed of Pt and Pd active components, at least one element auxiliary agent among rare earth metals La, Ce, Pr, Sm and at least one element auxiliary agent among Nd, Eu, Er, Yb, Lu, and an Al or Al-ZrO composite carrier. The active components and auxiliary agents are prepared by impregnation method according to a certain proportion.

[0008] The dehydrogenation catalyst involved in the above disclosed patents has a precious metal content of 0.3-1.5%. Based on the average palladium price of 550 yuan / gram, the cost of one ton of dehydrogenation agent exceeds one million yuan. Therefore, it is necessary to reduce the content of precious metals in the catalyst while ensuring the performance and stability of the dehydrogenation catalyst. At the same time, the performance of the catalyst at low temperatures is improved to reduce the energy consumption of the dehydrogenation device. Summary of the invention

[0009] The purpose of the present invention is to reduce the content of precious metals, lower the production cost of catalysts, and provide a catalyst for catalytic combustion dehydrogenation of high-concentration carbon dioxide feed gas and its preparation.

[0010] To achieve the above object, the technical solution adopted by the present invention is:

[0011] A dehydrogenation catalyst comprises a carrier, a noble metal active component and an auxiliary agent; the carrier is α-Al2O3 ball, the active component is one or two of the noble metals Pd or Pt, and the auxiliary agent is a metal auxiliary agent and a rare earth element auxiliary agent; the metal auxiliary agent is Cu or Mo, and the rare earth element auxiliary agent is one or more of Y, Gd or Dy; wherein the active component content is 0.08-0.13wt% based on the weight of the carrier.

[0012] The molar ratio of the active component to the auxiliary agent is 1:4; wherein the molar ratio of the metal auxiliary agent to the rare earth element auxiliary agent is 2:2.

[0013] A method for preparing the dehydrogenation catalyst comprises the following steps:

[0014] 1) Pre-saturating the carrier with oxygen-containing organic matter;

[0015] 2) dissolving the noble metal precursor compound with HCl, and mixing it with the metal auxiliary agent precursor compound and the rare earth element auxiliary agent precursor compound to prepare an impregnation solution, and impregnating the support obtained in step 1);

[0016] 3) treating the impregnated support in step 2) at high temperature and calcining at 450-700° C. for 4-8 hours;

[0017] 4) The support obtained in step 3) is subjected to reduction treatment using a hydrazine hydrate solution, and then washed and dried to obtain a dehydrogenation catalyst.

[0018] The Pd precursor compound is PdCl2, the Pt precursor compound is H2PtCl6.6H2O, the Cu precursor compound is Cu(NO3)2, the Mo precursor compound is (NH4)2MoO4, the Y precursor compound is Y(NO3)3, the Gd precursor compound is Gd(NO3)3·6H2O, and the Dy precursor compound is Dy(NO3)3.

[0019] The oxygen-containing organic matter in step 1) is 95% ethanol;

[0020] The immersion time in step 2) is 1-5 hours;

[0021] The step 3) high temperature treatment temperature is 500-800° C. and the time is 2-10 minutes;

[0022] In step 4), the concentration of hydrazine hydrate is 0.1%-10%, and the reduction time is 6-8 hours. Preferably, the concentration of hydrazine hydrate is 0.1%-5%.

[0023] The catalyst is used for removing hydrogen from a carbon dioxide gas source.

[0024] The reaction temperature is 95-100℃, the pressure is from normal pressure to 2Mpa, and the space velocity of carbon dioxide raw gas is 5000-30000h -1 .

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] The catalyst of the present invention reduces the content of precious metals while ensuring the dehydrogenation accuracy and stability by selecting suitable additives, thereby reducing the production cost of the dehydrogenator. At the same time, the present invention adopts a non-uniform preparation method, and the prepared catalyst has an eggshell structure. The concentration of the active component has different optimal distribution functions along the radial distribution of the catalyst particles, thereby improving the utilization rate of the unit active component, so that the catalyst has the characteristics of high activity, high stability and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a cross-sectional view of the dehydrogenation catalyst prepared in Example 1. DETAILED DESCRIPTION

[0028] Example 1

[0029] 1) 100 g of α-Al2O3 balls with a diameter of 3-4 mm were pre-saturated with 200 ml of 95% ethanol for 1 hour for use.

[0030] 2) Dissolve 0.15g PdCl2 in 5ml hydrochloric acid, 2.75g Cu(NO3)2 in deionized water, and 7.74g Y(NO3)3 in deionized water. Mix the three salt solutions, add deionized water to 50ml to make an immersion solution, and immerse the reserved α-Al2O3 ball in this solution for 2 hours.

[0031] 3) The impregnated support in step 2) is subjected to high temperature treatment at 750° C. for 5 minutes and then calcined at 500° C. for 6 hours.

[0032] 4) The carrier obtained in step 3) was cooled to room temperature, treated with 0.9% hydrazine hydrate for 7 hours, washed thoroughly and dried at 120° C. for 4 hours to obtain a dehydrogenation catalyst.

[0033] The Pd content of the dehydrogenation catalyst is 0.09%, the Cu content is 0.93%, and the Y content is 2.5%. The active components on the catalyst surface form an eggshell structure. Figure 1 .

[0034] Application Example 1

[0035] The dehydrogenation catalyst synthesized in Example 1 was loaded into a fixed bed reactor, and a high concentration of carbon dioxide was used as the base gas, and 1% hydrogen, 0.99% oxygen, and 0.2% carbon monoxide were used as the raw gas to carry out the dehydrogenation reaction. The reaction conditions were: temperature 100°C, pressure 0.5 MPa, volume space velocity 5000 h -1 , the outlet gas was analyzed by online gas chromatography. Under the reaction conditions, the outlet hydrogen content was 1.6ppm, which met the standard of less than 10ppm. After the catalyst was operated for 500h, the outlet hydrogen content was 5.8ppm, still less than 10ppm. After unloading, the specific surface area, average pore size and total pore volume of the catalyst did not change significantly compared with the fresh catalyst, indicating that the catalyst has a long service life and is fully suitable for high-concentration carbon dioxide dehydrogenation process.

[0036] Example 2

[0037] 1) 100 g of α-Al2O3 balls with a diameter of 3-4 mm were pre-saturated with 200 ml of 95% ethanol for 1 hour for use.

[0038] 2) Dissolve 0.32g H2PtCl6.6H2O in 5ml hydrochloric acid, 2.66g (NH4)2MoO4 in deionized water, 4.33g Y(NO3)3 in deionized water, and 3.74g Gd(NO3)3·6H2O in deionized water. Mix the four salt solutions, add deionized water to 50ml to make an immersion solution, and immerse the reserved α-Al2O3 ball in this solution for 2 hours.

[0039] 3) The impregnated support in step 2) is subjected to high temperature treatment at 750° C. for 5 minutes and then calcined at 500° C. for 6 hours.

[0040] 4) The carrier obtained in step 3) was cooled to room temperature, treated with 2% hydrazine hydrate for 7 hours, washed thoroughly and dried at 120° C. for 4 hours to obtain a dehydrogenation catalyst.

[0041] The Pt content of the dehydrogenation catalyst is 0.12%, the Mo content is 1.3%, the Y content is 1.4%, and the Gd content is 1.3%. The active components on the catalyst surface form an eggshell-type structure.

[0042] Application Example 2

[0043] The dehydrogenation catalyst synthesized in Example 2 was loaded into a fixed bed reactor, and a high concentration of carbon dioxide was used as the base gas, and 1% hydrogen, 0.99% oxygen, and 0.2% carbon monoxide were used as the raw gas to carry out the dehydrogenation reaction. The reaction conditions were: temperature 100°C, pressure 1MPa, volume space velocity 5000h -1 The outlet gas was analyzed by online gas chromatography. Under the reaction conditions, the outlet hydrogen content was 1.8 ppm, which met the standard of less than 10 ppm.

[0044] Example 3

[0045] 1) 100 g of α-Al2O3 balls with a diameter of 3-4 mm were pre-saturated with 200 ml of 95% ethanol for 1 hour for use.

[0046] 2) Dissolve 0.13g PdCl2 in 5ml hydrochloric acid, dissolve 1.84g (NH4)2MoO4 in deionized water, and dissolve 8.36g Y(NO3)3 in deionized water. Mix the three salt solutions, add deionized water to adjust to 50ml to make an immersion solution, and immerse the reserved α-Al2O3 ball in this solution for 2 hours.

[0047] 3) The impregnated support in step 2) is subjected to high temperature treatment at 750° C. for 5 minutes and then calcined at 500° C. for 6 hours.

[0048] 4) The carrier obtained in step 3) was cooled to room temperature, treated with 1.5% hydrazine hydrate for 6 hours, washed thoroughly and dried at 120° C. for 4 hours to obtain a dehydrogenation catalyst.

[0049] The Pd content of the dehydrogenation catalyst is 0.08%, the Mo content is 0.9%, the Y content is 2.7%, and the active components on the catalyst surface form an eggshell structure.

[0050] Application Example 3

[0051] The dehydrogenation catalyst synthesized in Example 3 was loaded into a fixed bed reactor, and a high concentration of carbon dioxide was used as the base gas, and 1% hydrogen, 0.99% oxygen, and 0.2% carbon monoxide were used as the raw gas to carry out the dehydrogenation reaction. The reaction conditions were: temperature 100°C, pressure normal pressure, volume space velocity 10000h -1 The outlet gas was analyzed by online gas chromatography. Under the reaction conditions, the outlet hydrogen content was 1.9 ppm, which met the standard of less than 10 ppm.

[0052] Example 4

[0053] 1) 100 g of α-Al2O3 balls with a diameter of 3-4 mm were pre-saturated with 200 ml of 95% ethanol for 1 hour for use.

[0054] 2) Dissolve 0.30g H2PtCl6 in 5ml hydrochloric acid, 2.37g Cu(NO3)2 in deionized water, 4.31g Gd(NO3)3·6H2O in deionized water, and 2.36g Dy(NO3)3 in deionized water. Mix the four salt solutions, add deionized water to 50ml to make an impregnation solution, and immerse the reserved α-Al2O3 ball in this solution for 2 hours.

[0055] 3) The impregnated support in step 2) is subjected to high temperature treatment at 750° C. for 5 minutes and then calcined at 500° C. for 5 hours.

[0056] 4) The carrier obtained in step 3) was cooled to room temperature, treated with 1.7% hydrazine hydrate for 6 hours, washed thoroughly and dried at 120° C. for 4 hours to obtain a dehydrogenation catalyst.

[0057] The Pt content in the dehydrogenation catalyst is 0.11%, the Cu content is 0.8%, the Gd content is 1.5%, and the Dy content is 1.1%. The active components on the catalyst surface form an eggshell-type structure.

[0058] Application Example 4

[0059] The dehydrogenation catalyst synthesized in Example 4 was loaded into a fixed bed reactor, and a high concentration of carbon dioxide was used as the base gas, and 1% hydrogen, 0.99% oxygen, and 0.2% carbon monoxide were used as the raw gas to carry out the dehydrogenation reaction. The reaction conditions were: temperature 100°C, pressure 0.5 MPa, volume space velocity 15000 h -1 The outlet gas was analyzed by online gas chromatography. Under the reaction conditions, the outlet hydrogen content was 3.1 ppm, which met the standard of less than 10 ppm.

[0060] Example 5

[0061] 1) 100 g of α-Al2O3 balls with a diameter of 3-4 mm were pre-saturated with 100 ml of 95% ethanol for 1 hour for use.

[0062] 2) Dissolve 0.15g PdCl2 in 5ml hydrochloric acid, dissolve 0.08g H2PtCl6 in 5ml hydrochloric acid, dissolve 2.96g Cu(NO3)2 in deionized water, and dissolve 7.43g Y(NO3)3 in deionized water. Mix the four salt solutions, add deionized water to 50ml to make an impregnation solution, and immerse the reserved α-Al2O3 ball in this solution for 2 hours.

[0063] 3) The impregnated support in step 2) is subjected to high temperature treatment at 750° C. for 5 minutes and then calcined at 500° C. for 6 hours.

[0064] 4) The carrier obtained in step 3) was cooled to room temperature, treated with 2.0% hydrazine hydrate for 8 hours, washed thoroughly and dried at 120° C. for 4 hours to obtain a dehydrogenation catalyst.

[0065] The Pd content of the dehydrogenation catalyst is 0.09%, the Pt content is 0.03%, the Cu content is 1%, the Y content is 2.4%, and the active components on the catalyst surface form an eggshell-type structure.

[0066] Application Example 5

[0067] The dehydrogenation catalyst synthesized in Example 5 was loaded into a fixed bed reactor, and a high concentration of carbon dioxide was used as the base gas, and 1% hydrogen, 0.99% oxygen, and 0.2% carbon monoxide were used as the raw gas to carry out the dehydrogenation reaction. The reaction conditions were: temperature 100°C, pressure 2MPa, volume space velocity 20000h -1 The outlet gas was analyzed by online gas chromatography. Under the reaction conditions, the outlet hydrogen content was 2.2 ppm, which met the standard of less than 10 ppm.

[0068] Example 6

[0069] 1) 100 g of α-Al2O3 balls with a diameter of 3-4 mm were pre-saturated with 100 ml of 95% ethanol for 1 hour for use.

[0070] 2) Dissolve 0.08g PdCl2 in 5ml hydrochloric acid, dissolve 0.19g H2PtCl6 in 5ml hydrochloric acid, dissolve 2.51g Cu(NO3)2 in deionized water, and dissolve 7.18g Gd(NO3)3·6H2O in deionized water. Mix the four salt solutions, add deionized water to 50ml to make an impregnation solution, and immerse the reserved α-Al2O3 ball in this solution for 2 hours.

[0071] 3) The impregnated support in step 2) is subjected to high temperature treatment at 750° C. for 5 minutes and then calcined at 500° C. for 8 hours.

[0072] 4) The carrier obtained in step 3) was cooled to room temperature, treated with 3.5% hydrazine hydrate for 8 hours, washed thoroughly and dried at 120° C. for 4 hours to obtain a dehydrogenation catalyst.

[0073] The Pd content of the dehydrogenation catalyst is 0.05%, the Pt content is 0.07%, the Cu content is 0.85%, the Gd content is 2.5%, and the active components on the catalyst surface form an eggshell structure.

[0074] Application Example 6

[0075] The dehydrogenation catalyst synthesized in Example 6 was loaded into a fixed bed reactor, and a high concentration of carbon dioxide was used as the base gas, and 1% hydrogen, 0.99% oxygen, and 0.2% carbon monoxide were used as the raw gas to carry out the dehydrogenation reaction. The reaction conditions were: temperature 95°C, pressure 1.5MPa, volume space velocity 30000h -1 The outlet gas was analyzed by online gas chromatography. Under the reaction conditions, the outlet hydrogen content was 4.6 ppm, which met the standard of less than 10 ppm.

[0076] Example 7

[0077] 1) 100 g of α-Al2O3 balls with a diameter of 3-4 mm were pre-saturated with 100 ml of 95% ethanol for 1 hour for use.

[0078] 2) Dissolve 0.10g PdCl2 in 5ml hydrochloric acid, dissolve 0.19g H2PtCl6 in 5ml hydrochloric acid, dissolve 2.45g (NH4) 2MoO4 in deionized water, dissolve 2.48g Y(NO3) 3 in deionized water, dissolve 2.87g Gd(NO3) 3·6H2O in deionized water, and dissolve 1.29g Dy(NO3) 3 in deionized water. Mix the five salt solutions, add deionized water to 50ml to make an impregnation solution, and immerse the reserved α-Al2O3 ball in this solution for 2 hours.

[0079] 3) The impregnated support in step 2) is subjected to high temperature treatment at 750° C. for 5 minutes and then calcined at 500° C. for 5 hours.

[0080] 4) The carrier obtained in step 3) was cooled to room temperature, treated with 4% hydrazine hydrate for 6 hours, washed thoroughly and dried at 120° C. for 4 hours to obtain a dehydrogenation catalyst.

[0081] The dehydrogenation catalyst has a Pd content of 0.06%, a Pt content of 0.07%, a Mo content of 1.2%, a Y content of 0.8%, a Gd content of 1%, a Dy content of 0.6%, and an active component on the catalyst surface forms an eggshell-type structure.

[0082] Application Example 7

[0083] The dehydrogenation catalyst synthesized in Example 7 was loaded into a fixed bed reactor, and a high concentration of carbon dioxide was used as the base gas, and 1% hydrogen, 0.99% oxygen, and 0.2% carbon monoxide were used as the raw gas to carry out the dehydrogenation reaction. The reaction conditions were: temperature 95°C, pressure from normal pressure to 2MPa, volume space velocity 30000h -1 The outlet gas was analyzed by online gas chromatography. Under the reaction conditions, the outlet hydrogen content was 3.9 ppm, which met the standard of less than 10 ppm.

[0084] Comparative Example 1

[0085] 0.32 g of Fe2(SO4)3 was taken to replace PdCl2 in Example 1, dissolved in deionized water, and other conditions were the same as in Example 1 to obtain a dehydrogenation catalyst. The Fe content of the dehydrogenation catalyst was 0.09%, the Cu content was 0.93%, and the Y content was 2.5%.

[0086] The performance of the catalyst was tested according to the reaction conditions of Application Example 1. The results showed that the outlet hydrogen content was 0.98% under the experimental conditions, and the catalyst had almost no activity.

[0087] Comparative Example 2

[0088] 0.185 g of AuCl3 was taken to replace H2PtCl6.6H2O in Example 2, dissolved in ethanol, and other conditions were the same as in Example 2 to obtain a dehydrogenation catalyst. The dehydrogenation catalyst contained 0.12% Au, 1.3% Mo, 1.4% Y, and 1.3% Gd.

[0089] The performance of the catalyst was tested according to the reaction conditions of Application Example 2. The results showed that the hydrogen content at the outlet was 0.85% under the experimental conditions, which did not meet the standard of less than 10 ppm.

[0090] Comparative Example 3

[0091] The performance test of the sample of Example 3 of CN1334140A was carried out according to the reaction conditions of Application Example 6. The results showed that the outlet hydrogen of the CN1334140A sample was 21.3 ppm at 95°C, which did not meet the standard of less than 10 ppm.

[0092] Comparative Example 4

[0093] The performance test of the sample of Example 4 of CN1334140A was carried out according to the reaction conditions of Application Example 7. The results showed that when the pressure was increased from 1.5MPa to 2MPa, the outlet hydrogen of the CN1334140A sample was 13.6ppm, which still did not meet the standard of less than 10ppm.

[0094] It can be seen from the above embodiments and application examples that the catalyst of the present invention reduces the content of precious metals palladium and platinum, saves the cost of catalyst preparation, has a long service life in the dehydrogenation reaction, and the dehydrogenation effect meets the standards, and is suitable for the catalytic combustion dehydrogenation process of high-concentration carbon dioxide feed gas.

Claims

1. An application of a dehydrogenation catalyst, characterized in that: The dehydrogenation catalyst is used for removing hydrogen from a carbon dioxide gas source; the dehydrogenation catalyst comprises a carrier, a noble metal active component and an additive; the carrier is an α-Al2O3 ball, the active component is one or two of the noble metals Pd and Pt, and the additive is a metal additive and a rare earth element additive; the metal additive is Cu or Mo, and the rare earth element additive is one or more of Y, Gd, and Dy; wherein, based on the weight of the carrier, the content of the active component is 0.08-0.13wt%; the dehydrogenation catalyst is an eggshell-type structure.

2. The use of the dehydrogenation catalyst according to claim 1, wherein the reaction temperature is 95-100°C, the pressure is from normal pressure to 2 MPa, and the space velocity of the carbon dioxide feed gas is 5000-30000 h -1 .

3. The use of the dehydrogenation catalyst according to claim 1, characterized in that: The molar ratio of the active component to the auxiliary agent is 1:4; wherein the molar ratio of the metal auxiliary agent to the rare earth element auxiliary agent is 1:

8.

4. The use of the dehydrogenation catalyst according to claim 1, characterized in that: The preparation method of the dehydrogenation catalyst comprises the following steps: 1) Pre-saturating the carrier with oxygen-containing organic matter; 2) dissolving the noble metal precursor compound with HCl, and mixing it with the metal auxiliary agent precursor compound and the rare earth element auxiliary agent precursor compound to prepare an impregnation solution, and impregnating the support obtained in step 1); 3) treating the impregnated support in step 2) at high temperature and calcining at 450-700° C. for 4-8 hours; 4) The support obtained in step 3) is subjected to reduction treatment using a hydrazine hydrate solution, and then washed and dried to obtain a dehydrogenation catalyst.

5. Use of the dehydrogenation catalyst according to claim 4, characterized in that: The Pd precursor compound is PdCl2, the Pt precursor compound is H2PtCl6·6H2O, the Cu precursor compound is Cu(NO3)2, the Mo precursor compound is (NH4)2MoO4, the Y precursor compound is Y(NO3)3, the Gd precursor compound is Gd(NO3)3·6H2O, and the Dy precursor compound is Dy(NO3)3.

6. Use of the dehydrogenation catalyst according to claim 4, characterized in that: The oxygen-containing organic matter in step 1) is 95% ethanol; The immersion time in step 2) is 1-5 hours; The step 3) high temperature treatment temperature is 500-800°C and the time is 2-10 minutes; In step 4), the concentration of hydrazine hydrate is 0.1%-10%, and the reduction time is 6-8 hours.

7. Use of the dehydrogenation catalyst according to claim 6, characterized in that: The concentration of hydrazine hydrate is 0.1%-5%.

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