Propane dehydrogenation catalyst for producing propylene and preparation method thereof

Abstract

A propane dehydrogenation catalyst for preparing propylene comprises an alumina carrier and active components whose contents are as follows, calculated on the basis of the carrier: 0.1-1.5% by mass of group VIII metal, 0.1-1.5% by mass of group IVA metal, 0.5-3.0% by mass of group IA metal, 0.1-0.4% by mass of lanthanum and / or samarium, and 0.3-3.0% by mass of halogen. The catalyst is used for preparing propylene by dehydrogenation of propane, has high activity and selectivity, and has low carbon deposition rate.

Description

Technical Field

[0001] The present invention relates to a catalyst for producing olefins by dehydrogenating alkanes and a preparation method thereof, in particular to a catalyst for producing propylene by dehydrogenating propane and a preparation method thereof. Background Art

[0002] As my country's crude oil processing volume increases, the catalytic cracking and other processes in refineries will produce a large amount of low-carbon alkanes such as ethane, propane, and isobutane. How to effectively utilize these resources and convert them into high-value-added low-carbon olefins is of great significance to improving the economic benefits of refineries.

[0003] Propylene is an important basic organic chemical raw material, widely used in the production of polypropylene, acetone, acrylonitrile, propylene oxide, acrylic acid and other chemical products. The supply of propylene mainly comes from the by-products of naphtha cracking to produce ethylene and petroleum catalytic cracking. Since 2014, the gap between the market demand for propylene and the traditional propylene production capacity has become increasingly larger and continues to expand. With the continuous increase in the demand for propylene, the traditional propylene production process can no longer meet the demand for propylene in the chemical industry, and it is necessary to accelerate the development of other alternative process technologies, among which the propane dehydrogenation process to produce propylene has attracted the most attention. In recent years, the propane catalytic dehydrogenation process has developed rapidly and has become an important source of propylene. At present, in the main domestic propylene production routes, the proportion of propylene produced by propane dehydrogenation has increased to 17%.

[0004] Since propane dehydrogenation reaction is limited by thermodynamic equilibrium, the reaction must be carried out under harsh conditions of high temperature and low pressure. Too high reaction temperature will intensify the cracking reaction and deep dehydrogenation, accelerate the carbon deposition rate of the catalyst, and deactivate the catalyst. Therefore, the development of a dehydrogenation catalyst with high activity, high stability and low carbon deposition rate has become the key to this technology.

[0005] Supported platinum-based catalysts are an important type of propane dehydrogenation catalysts. Alumina is usually used as a carrier and modified by adding VIA group metals, alkali metals, etc. to improve the activity and selectivity of the catalyst. In addition, rare earth metals have shown good performance in promoting catalysis and have attracted people's attention. CN101138734B adds an inorganic oxide binder, an extrusion aid and an acidic peptizing agent to a heat-resistant oxide, rolls a ball or extrudes a strip to obtain a catalyst carrier, and then impregnates a rare earth metal, H2PtCl6 and SnCl4 aqueous solution to obtain a catalyst. The heat-resistant oxide is one or more of A-type molecular sieve, X-type molecular sieve, Y-type molecular sieve or ZSM-5 type molecular sieve, and the rare earth metal is La or Ce.

[0006] CN101884922B adds Sn to alumina or silica sol to obtain a carrier, and then introduces platinum and a metal selected from M by impregnation, wherein M is selected from at least one rare earth element selected from La, Ce, Pr, Pm, Sm, Eu, Gd, Tb, Tm or Y and / or at least one transition metal selected from Fe, Ni or Ag. The impregnated solid is dried and calcined, dechlorinated with water vapor, and then reduced with hydrogen to obtain a catalyst.

[0007] CN103420769B discloses a method for preparing propylene by dehydrogenating propane, wherein the dehydrogenation catalyst used contains an active component selected from Pt group metals, IIB group elements, rare earth metals and IIA group metals and a carrier, and the carrier is selected from at least one of α-A12O3, γ-A12O3, δ-A12O3, θ-A12O3 or spinel.

[0008] CN104755167B discloses an alkane dehydrogenation catalyst composition, which supports a Group IIIA metal, a Group VIII noble metal, at least one dopant and an optional metal promoter on a carrier, wherein the dopant is selected from iron, chromium, vanadium and a combination thereof, and the carrier may be silica, alumina, a silica-alumina composite material, or rare earth-modified alumina.

[0009] CN105251486B discloses a method for preparing a supported platinum catalyst for dehydrogenating propane to propylene, wherein the catalyst component is PtSnN2 / N1-Al2O3, wherein Pt is an active component, Sn is a main auxiliary component, Nl and N2 are secondary auxiliary components, N1 is selected from one of the rare earth metals La and Ce, and N2 is selected from one of the alkali metals Cs, K, and Na. In the catalyst, the content by mass percentage is: Pt is 0.1% to 0.5%, Sn is 0.2% to 1.0%, Nl is 0.5% to 6%, N2 is 0.5% to 5%, and the balance is Al2O3.

[0010] CN109701588A discloses a dehydrogenation catalyst, comprising (a) 0.1 to 5 parts of at least one metal selected from the Group VIII elements of the periodic table or its alloy; (b) 0.1 to 3 parts of at least one element selected from the rare earth elements or its oxide; (c) 75 to 99 parts of a carrier. The Group VIII element is preferably platinum, (b) is one or at least one selected from La, Ce, Yb, and Ac, and (c) is one or at least one selected from alumina, silicon oxide, and molecular sieves. The carrier needs to be treated with a nitride to obtain a nitrogen-modified carrier. Summary of the invention

[0011] The purpose of the present invention is to provide a propane dehydrogenation catalyst for preparing propylene and a preparation method thereof. The catalyst is used for the propane dehydrogenation catalyst for preparing propylene, has high activity and selectivity, and has a low carbon deposition rate.

[0012] The catalyst for producing propylene by dehydrogenating propane provided by the present invention comprises an alumina carrier and an active component having the following contents calculated based on the carrier:

[0013]

[0014] The present invention adds an appropriate amount of lanthanum and / or samarium to a catalyst containing Group VIII metals, Group IVA metals and Group IA metals, thereby improving the dehydrogenation activity and selectivity of the catalyst, reducing carbon deposition and extending the service life of the catalyst. DETAILED DESCRIPTION

[0015] The present invention uses an alumina carrier containing a Group IVA metal and lanthanum and / or samarium, introduces a Group VIII metal and a halogen by an impregnation method, and then loads a Group IA metal, and obtains a catalyst by calcination and reduction. The lanthanum and / or samarium introduced into the catalyst can interact with the Group VIII metal in the catalyst, improve the stability of the catalyst, reduce the carbon deposition of the catalyst, and thus improve the activity and stability of the catalyst.

[0016] Preferably, the catalyst has the following active component content:

[0017]

[0018]

[0019] In the catalyst of the present invention, the molar ratio of the Group VIII metal to lanthanum and / or samarium is 0.3 to 3.0. The Group VIII metal is preferably platinum, the Group IVA metal is preferably tin, the Group IA metal is preferably potassium, and the halogen is preferably chlorine. The alumina carrier is preferably θ-alumina. The alumina carrier is preferably spherical, and the average diameter of the carrier spheres is preferably 1.5 to 2.0 mm.

[0020] In the θ-alumina carrier, the pore volume of pores with a diameter of 2 to 10 nanometers accounts for 4 to 15% of the total pore volume, the pore volume of pores with a diameter of 10 to 50 nanometers accounts for 66 to 80% of the total pore volume, and the pore volume of macropores with a diameter greater than 50 nanometers but not greater than 10 microns accounts for 10 to 19% of the total pore volume.

[0021] Preferably, in the θ-alumina carrier, the pore volume of pores with a diameter of 2 to 10 nanometers accounts for 8 to 15% of the total pore volume, the pore volume of pores with a diameter of 10 to 50 nanometers accounts for 70 to 80% of the total pore volume, and the pore volume of macropores with a diameter greater than 50 nanometers but not greater than 10 microns accounts for 12 to 19% of the total pore volume.

[0022] The specific surface area of ​​the alumina carrier of the present invention is preferably 50 to 130 m 2 / g, and the pore volume is preferably 0.6 to 0.8 ml / g.

[0023] The preparation method of the catalyst of the present invention comprises impregnating an alumina carrier containing a Group IVA metal and lanthanum and / or samarium with a solution containing a Group VIII metal compound and a halogen, drying, roasting, and then impregnating with a solution of a water-soluble compound containing a Group IA metal, drying, roasting, and reducing.

[0024] In the above method, there are two methods for preparing the alumina carrier containing Group IVA metals and lanthanum and / or samarium. The first method is to introduce Group IVA metals and lanthanum and / or samarium by co-precipitation during the carrier molding process; the second method is to impregnate the alumina containing Group IVA metals with a solution of a compound containing lanthanum and / or samarium.

[0025] The first method for preparing a carrier containing a Group IVA metal and lanthanum and / or samarium comprises:

[0026] (1) Acid peptization is added to aluminum hydroxide to obtain an alumina sol, a pore-enlarging agent and a compound containing a Group IVA metal, a compound containing lanthanum and / or samarium are added to the alumina sol, and drop-shaped balls are formed.

[0027] (2) After the wet balls formed in step (1) are dried, they are calcined at 580-680°C for a first stage, and then the temperature is raised to 900-1100°C for a second stage of calcination to obtain a θ-alumina carrier containing Group IVA metals and lanthanum and / or samarium.

[0028] The second method for preparing a carrier containing a Group IVA metal and lanthanum and / or samarium comprises:

[0029] (1) Acid colloid is added to aluminum hydroxide to obtain aluminum oxide sol, a pore-enlarging agent and a compound containing Group IVA metal are added to the aluminum oxide sol, and drop-shaped balls are formed.

[0030] (2) drying the wet balls formed by the drop ball forming in step (1), performing a first-stage calcination at 580-680° C., and then raising the temperature to 900-1100° C. for a second-stage calcination to obtain a θ-alumina carrier containing a Group IVA metal,

[0031] (3) A θ-alumina carrier containing a Group IVA metal is impregnated with a solution of a compound containing lanthanum and / or samarium. The solid obtained after impregnation is dried and calcined to obtain a θ-alumina carrier containing a Group IVA metal and lanthanum and / or samarium.

[0032] In the above method, step (1) is to form a ball by dropping alumina sol, and the pore-enlarging agent added to the alumina sol is preferably C 10 ~C 16 The C 10 ~C 16 The hydrocarbon is preferably kerosene.

[0033] The mass ratio of the added pore-enlarging agent to the alumina contained in the alumina sol is preferably 0.1 to 0.3. The acid added to prepare the alumina sol is preferably nitric acid or hydrochloric acid, and an organic acid such as acetic acid or citric acid may also be added.

[0034] When the pore-enlarging agent used is C 10 ~C 16 When the aluminum sol contains hydrocarbon, it is preferred to add a surfactant as a demulsifier to the aluminum sol. The surfactant can be fatty alcohol polyoxyethylene ether or nonylphenol polyoxyethylene ether.

[0035] The method for forming the alumina sol into drop balls in step (1) can be hot oil column forming or oil-ammonia column forming.

[0036] Step (2) is to calcine the formed wet ball to prepare a spherical carrier. The calcination is divided into two stages, the first stage to form γ-alumina, and the second stage to form θ-alumina. The calcination time of the two stages is preferably 1 to 20 hours.

[0037] In the above method, the compound containing the Group VIII metal is preferably chloroplatinic acid or ammonium chloroplatinate, the halogen contained in the impregnation solution for introducing the Group VIII metal in the preparation of the catalyst is preferably chlorine, and the compound for introducing chlorine in the impregnation solution is preferably hydrochloric acid. The Group IVA metal is preferably tin, and the water-soluble compound of the Group IA metal is preferably potassium hydroxide, potassium nitrate or potassium chloride.

[0038] When preparing the θ-alumina carrier containing Group IVA metals and lanthanum and / or samarium, the first method is adopted, and the compound containing lanthanum and / or samarium is preferably introduced into the aluminum sol by coprecipitation in step (1) and is preferably a nitrate or chloride thereof. Preferably, a hydrochloric acid solution containing the Group IVA metal compound and a solution containing the compound containing lanthanum and / or samarium are added to the aluminum oxide sol. The second method is adopted, and the compound containing lanthanum and / or samarium used in the solution containing the compound containing lanthanum and / or samarium prepared in step (3) is preferably a nitrate or chloride thereof. Preferably, the solution containing the compound containing lanthanum and / or samarium used for impregnation contains hydrochloric acid.

[0039] The Group IVA metal in the alumina carrier is introduced during carrier molding, that is, a Group IVA metal compound is introduced into the alumina sol. The Group IVA metal compound is preferably tin chloride or organic compound, such as stannous bromide, stannous chloride, tin tetrachloride, tin tetrachloride pentahydrate or tetrabutyltin.

[0040] In the above method, the temperature for impregnating the active component is preferably 20-70°C, the time is preferably 2-6 hours, the liquid / solid ratio of the impregnation is preferably 1.3-3.0 mL / g, the drying temperature of the solid obtained after impregnation is preferably 100-300°C, the drying time is preferably 2-20 hours, the calcination temperature is preferably 450-630°C, and the calcination time is preferably 2-6 hours.

[0041] In the above catalyst preparation method, the carrier after impregnation with the IA group metal needs to be reduced after drying and calcination to reduce the VIII group metal to the corresponding metallic state. The gas used for reduction is hydrogen or a mixture of hydrogen and an inert gas, wherein the inert gas is a gas that does not react with the active components of the catalyst, preferably nitrogen. The reduction temperature is preferably 450 to 700°C, more preferably 500 to 650°C, and the reduction time is preferably 0.5 to 20 hours, more preferably 2 to 10 hours. The reduction can be carried out before the catalyst is loaded into the reactor, or after the catalyst is loaded into the reactor and before the dehydrogenation reaction.

[0042] The catalyst provided by the present invention is suitable for the reaction of dehydrogenating propane to propylene. Propane is reacted with the catalyst of the present invention in the presence of a diluent at 400-800°C, preferably 550-650°C, and a pressure of 0.1-1.0 MPa, preferably 0.1-0.5 MPa.

[0043] During the reaction, the appropriate mass space velocity of propane contacting the catalyst is 0.1 to 20 h -1 , more preferably 0.5 to 10 hours -1 The diluent material in the above dehydrogenation reaction can be hydrogen, water vapor, argon, methane, ethane or nitrogen. When hydrogen is selected as the diluent material, the molar ratio of hydrogen to propane is preferably 0.1 to 10:1, more preferably 0.3 to 3:1.

[0044] The present invention is further described in detail below by examples, but the present invention is not limited thereto.

[0045] The specific surface area, pore volume and pore distribution of the carriers in the examples and comparative examples were measured by mercury intrusion porosimetry.

[0046] Example 1

[0047] (1) Prepare the alumina carrier described in the present invention.

[0048] 100 g of aluminum hydroxide powder (produced by Sasol, Germany, brand SB, containing 72.5% by mass of aluminum oxide) and an appropriate amount of deionized water were stirred and slurried, with a liquid / solid mass ratio of 2.0. 7.5 ml of dilute nitric acid with a volume ratio of 1:1, 30 g of urea, a predetermined amount of SnCl4 hydrochloric acid solution, and a predetermined amount of lanthanum nitrate solution were added to prepare a sol, so that the Sn content in the solution was 0.30% by mass and the La content was 0.32% by mass (both relative to dry aluminum oxide, the same below), stirred for 1 hour, 10 g of kerosene and 1 g of fatty alcohol polyoxyethylene ether were added and stirred for 1 hour, the mass ratio of the added kerosene to dry aluminum oxide was 0.13, and the sol was dropped into an oil-ammonia column to form a ball. The wet ball was solidified in ammonia water for 1 hour and then filtered. The obtained ball was rinsed with deionized water 2 to 3 times, dried at 60°C for 6 hours, dried at 120°C for 10 hours, and calcined at 600°C for 4 hours to obtain γ-Al2O3 ball containing Sn and La. The temperature was then raised to 1000°C for a second calcination for 4 hours to obtain θ-Al2O3 ball carrier a containing tin and lanthanum. The average diameter of the alumina ball was 1.6 mm. The physical properties are shown in Table 1.

[0049] (2) Preparation of Catalyst

[0050] Take the above-mentioned θ-Al2O3 small ball carrier a containing tin and lanthanum, and impregnate it with a solution containing chloroplatinic acid and hydrochloric acid as an impregnation liquid at 25°C for 4 hours, the impregnation liquid contains 0.30 mass% of platinum and 1.0 mass% of HCl (both relative to the mass of dry alumina), and the liquid / solid ratio is 1.8mL / g. The impregnated solid is dried at 120°C for 12 hours and calcined at 500°C for 4 hours.

[0051] The calcined solid was impregnated with potassium nitrate solution at 25°C for 4 hours, the impregnation solution contained 1.0 mass% potassium (relative to the mass of dry alumina), and the liquid / solid ratio was 2.0 mL / g. The impregnated solid was dried at 120°C for 12 hours, calcined at 600°C for 4 hours, and then reduced with hydrogen at 550°C for 4 hours to obtain catalyst A.

[0052] The catalyst A contained 0.30 mass% of platinum, 0.30 mass% of tin, 0.32 mass% of lanthanum, 1.0 mass% of potassium, and 1.14 mass% of chlorine based on alumina, and the Pt / La molar ratio was 0.67:1.

[0053] Example 2

[0054] The catalyst was prepared according to the method of Example 1, except that in step (1), after adding dilute nitric acid to the aluminum hydroxide slurry, 30 g of urea and a predetermined amount of SnCl4 hydrochloric acid solution and a predetermined amount of samarium chloride solution were added to make the Sn content in the solution 0.30% by mass and the Sm content 0.15% by mass. After drop ball molding and two-stage calcination, a θ-Al2O3 small ball carrier b containing tin and samarium was obtained. Its physical properties are shown in Table 1.

[0055] The above-mentioned θ-Al2O3 pellet carrier b containing tin and samarium was used to prepare a catalyst according to step (2) to obtain catalyst B. The content of platinum in catalyst B, based on alumina, was 0.30 mass%, the content of tin was 0.30 mass%, the content of samarium was 0.15 mass%, the content of potassium was 1.0 mass%, and the content of chlorine was 1.16 mass%. The molar ratio of Pt / Sm was 1.54:1.

[0056] Example 3

[0057] The catalyst was prepared according to the method of Example 1, except that in step (1), after adding dilute nitric acid to the aluminum hydroxide slurry, 30 g of urea and a predetermined amount of SnCl4 hydrochloric acid solution, as well as predetermined amounts of lanthanum chloride and samarium chloride solutions were added to make the Sn content in the solution 0.30 mass %, the La content 0.28 mass %, and the Sm content 0.12 mass %. After drop ball molding and two-stage calcination, a θ-Al2O3 small ball carrier c containing tin, lanthanum and samarium was obtained. Its physical properties are shown in Table 1.

[0058] The above-mentioned θ-Al2O3 pellet carrier C containing tin, lanthanum and samarium was used to prepare a catalyst according to step (2) to obtain catalyst C. The content of platinum in catalyst C, based on alumina, was 0.30 mass%, the content of tin was 0.30 mass%, the content of lanthanum was 0.28 mass%, the content of samarium was 0.12 mass%, the content of potassium was 1.0 mass%, and the content of chlorine was 1.15 mass%. The molar ratio of Pt / (La+Sm) was 0.55:1.

[0059] Example 4

[0060] The carrier was prepared according to the method of step (1) of Example 1, except that in step (1), after adding dilute nitric acid to the aluminum hydroxide slurry, 30 grams of urea and a predetermined amount of SnCl4 hydrochloric acid solution were added to make the Sn content in the solution 0.30% by mass. After drop ball molding and two-stage calcination, a tin-containing θ-Al2O3 small ball carrier d was obtained. Its physical properties are shown in Table 1.

[0061] Take the above-mentioned tin-containing θ-Al2O3 small ball carrier d, and use a solution containing lanthanum chloride, samarium chloride and hydrochloric acid as an impregnation liquid at 25°C for 4 hours. The La content in the impregnation liquid is 0.28% by mass, the Sm content is 0.12% by mass, the HCl content is 1.5% by mass, and the liquid / solid ratio is 1.8mL / g. The impregnated solid is dried at 120°C for 12 hours and calcined at 600°C for 4 hours to obtain a θ-Al2O3 small ball carrier d-1 containing tin, lanthanum and samarium. Its physical properties are shown in Table 1.

[0062] A catalyst was prepared from a θ-Al2O3 pellet carrier d-1 containing tin, lanthanum and samarium according to the method of step (2) of Example 1 to obtain a catalyst D. The content of platinum in the catalyst D was 0.30 mass%, the content of tin was 0.30 mass%, the content of lanthanum was 0.28 mass%, the content of samarium was 0.12 mass%, the content of potassium was 1.0 mass%, and the content of chlorine was 1.15 mass%, based on alumina. The molar ratio of Pt / (La+Sm) was 0.55:1.

[0063] Comparative Example 1

[0064] The tin-containing θ-Al2O3 pellet carrier d prepared in Example 4 was used to prepare a catalyst according to the method of step (2) of Example 1 to obtain Catalyst E. The platinum content of Catalyst E, based on alumina, was 0.30 mass%, the tin content was 0.30 mass%, the potassium content was 1.0 mass%, and the chlorine content was 1.14 mass%.

[0065] Examples 5-9

[0066] In the microreactor, 1.5 g of catalyst was loaded, and a mixture of hydrogen and propane was used as the raw material. The reaction temperature was 620 ° C, 0.21 MPa, and the propane feed mass space velocity was 7.7 h -1 , the reaction was carried out for 30 hours at a molar ratio of hydrogen to propane of 0.5:1, sampling was performed every hour for chromatographic analysis, and the propane conversion rate and propylene selectivity were calculated. The catalysts used in each example and the reaction results are shown in Table 2.

[0067] As can be seen from Table 2, the catalyst of the present invention has higher propane conversion rate and propylene selectivity than the comparative catalyst E, and the catalyst has better performance stability. After 30 hours of reaction, the amount of carbon deposit on the catalyst is low, indicating that the catalyst of the present invention has excellent reaction performance.

[0068] Table 1

[0069]

[0070] Table 2

[0071]

Claims

1. A propane dehydrogenation catalyst for producing propylene, comprising a θ-alumina carrier and an active component having the following contents calculated based on the carrier: Group VIII metals 0.1~1.5% by mass IVA group metal 0.1~1.5% by mass IA group metal 0.5~3.0 mass% Lanthanum and / or samarium 0.1~0.4 mass%, Halogen 0.3~3.0% by mass The Group VIII metal is platinum, the Group IVA metal is tin, and in the θ-alumina carrier, the pore volume of pores with a diameter of 2 to 10 nanometers accounts for 4 to 15% of the total pore volume, the pore volume of pores with a diameter of 10 to 50 nanometers accounts for 66 to 80% of the total pore volume, and the pore volume of macropores with a diameter greater than 50 nanometers but not greater than 10 microns accounts for 10 to 19% of the total pore volume. The specific surface area of ​​the θ-alumina carrier is 50 to 130 m 2 / g, pore volume is 0.6~0.8 ml / g.

2. The catalyst according to claim 1, characterized in that The catalyst has the following active component content: Group VIII metals 0.1~1.0 mass% IVA group metal 0.1~1.0 mass% IA group metal 0.5~2.0 mass% Lanthanum and / or samarium 0.1~0.4 mass%, Halogen 0.5~2.0 mass %.

3. The catalyst according to claim 1 or 2, characterized in that The Group IA metal is potassium and the halogen is chlorine.

4. A method for preparing the catalyst according to claim 1, comprising impregnating an alumina carrier containing a Group IVA metal and lanthanum and / or samarium with a solution containing a Group VIII metal compound and a halogen, drying, calcining, and then impregnating with a solution containing a water-soluble compound of a Group IA metal, drying, calcining, and reducing.

5. The method according to claim 4, characterized in that The alumina carrier containing Group IVA metals and lanthanum and / or samarium is prepared by introducing Group IVA metals and lanthanum and / or samarium through a coprecipitation method during the carrier forming process.

6. The method according to claim 4, characterized in that The alumina carrier containing Group IVA metal and lanthanum and / or samarium is prepared by impregnating alumina containing Group IVA metal with a solution containing lanthanum and / or samarium compounds.

7. The method according to claim 4, characterized in that The compound containing Group VIII metal is chloroplatinic acid or ammonium chloroplatinate, the halogen is chlorine, the Group IVA metal is tin, and the water-soluble compound of Group IA metal is potassium hydroxide, potassium nitrate or potassium chloride.

8. The method according to claim 5, characterized in that The compound used to introduce lanthanum and / or samarium by coprecipitation is its nitrate or chloride.

9. The method according to claim 6, characterized in that The lanthanum and / or samarium compound is its nitrate or chloride.

10. The method according to claim 4, characterized in that The Group IVA metal in the alumina carrier is introduced during the carrier molding. The compound for introducing the Group IVA metal into the alumina carrier is stannous bromide, stannous chloride, stannous chloride, stannous chloride pentahydrate or tetrabutyltin.

11. The method according to claim 4, characterized in that The gas used for reduction is hydrogen or a mixture of hydrogen and inert gas, the reduction temperature is 450~700℃, and the reduction time is 0.5~20 hours.

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