阅读说明：本技术 一种具有梯度结构的催化剂氧化铝载体材料及其制备方法 (Catalyst alumina carrier material with gradient structure and preparation method thereof ) 是由 南洋 霍存宝 刘俊涛 全民强 杨红强 刘肖飞 李燕 景志刚 常晓昕 谢元 马好文 于 2019-11-22 设计创作，主要内容包括：本发明涉及一种具有梯度结构的催化剂氧化铝载体材料及其制备方法。该载体材料在孔径20～2000nm,比表面积1～140m～2/g,孔容0.1～1.2ml/g,压碎强度10～200N/cm范围内连续变化。主要是以氢氧化铝粉末为原料,通过粉末床熔融3D打印技术制备。根据梯度功能要求将氧化铝多孔材料的三维模型分为不同区域,不同区域采用不同激光能量密度对原料粉末进行加工,通过对激光能量密度的改变获得内部空间具有梯度结构的氧化铝载体材料。本发明解决了以氧化铝为原料,经不同激光能量密度照射后材料结构改变范围有限的问题。(The invention relates to a catalyst alumina carrier material with a gradient structure and a preparation method thereof. The carrier material has a pore diameter of 20-2000 nm and a specific surface area of 1-140 m 2 The pore volume is 0.1-1.2 ml/g, and the crushing strength is continuously changed within the range of 10-200N/cm. The aluminum hydroxide powder is mainly used as a raw material and is prepared by a powder bed melting 3D printing technology. Dividing a three-dimensional model of the alumina porous material into different areas according to the gradient function requirement, processing the raw material powder in the different areas by adopting different laser energy densities, and obtaining the inner part by changing the laser energy densitiesAn alumina carrier material with a gradient structure in the part space. The invention solves the problem that the change range of the material structure is limited after the aluminum oxide is used as the raw material and is irradiated by different laser energy densities.)

1. A catalyst alumina carrier material with a gradient structure is characterized in that the aperture of the carrier material is 20-2000 nm, and the specific surface area is 1-140 m²The pore volume is 0.1 to 1.2ml/g, and the crushing strength is continuously changed within the range of 10 to 200N/cm.

2. A method for preparing the catalyst alumina carrier material with the gradient structure in claim 1, which is characterized by mainly comprising the following steps:

(1) preparing raw material powder: the raw material powder is prepared by uniformly mixing aluminum hydroxide powder and inorganic additive powder, wherein the aluminum hydroxide powder accounts for 65-98 wt% of the total mass of the raw material powder;

(2) modeling: establishing a three-dimensional model of the alumina porous material in modeling software, dividing the model into different areas according to the gradient function requirement, slicing the model by adopting slicing software, and introducing a slice file into powder bed fusion 3D printing equipment for processing;

(3)3D printing: processing the raw material powder by adopting different laser energy densities for different partitions in the step (2), and obtaining an alumina carrier material with a gradient structure in an internal space by changing the laser energy densities in the printing process;

(4) and (3) post-treatment: and (4) carrying out post-treatment sintering process on the alumina gradient functional porous material formed in the step (3), wherein the treatment temperature is 400-900 ℃.

3. The method for preparing a catalyst alumina support material having a gradient structure according to claim 2, wherein the aluminum hydroxide in the step (1) is an aluminum hydroxide having a chemical formula which can be written AlOOH and an aluminum hydroxide having a chemical formula which can be written Al (OH)₃And (3) one or more of aluminum hydroxide.

4. A method of preparing a catalyst alumina support material with a gradient structure as claimed in claim 3, characterised in that the aluminium hydroxide of formula AlOOH, preferably pseudoboehmite, of formula al (oh)₃The aluminum hydroxide of (a) is preferably alpha-alumina trihydrate.

5. The method for preparing a catalyst alumina support material with a gradient structure as claimed in claim 2, wherein the D50 particle size of the aluminum hydroxide powder of step (1) is 20 μm to 60 μm.

6. The method for preparing the catalyst alumina carrier material with the gradient structure according to claim 2, wherein the inorganic additive powder in the step (1) is composed of boron carbide and one or more of silicon powder, silicon oxide and magnesium oxide, wherein the boron carbide accounts for 3 wt% to 100 wt% of the total mass of the inorganic additive powder.

7. The method for preparing a catalyst alumina carrier material with a gradient structure as claimed in claim 2, wherein the mold in step (2) is divided into different regions, which are mainly divided according to the functional requirements of the gradient, and the structural properties of the material between the different regions can be continuously or discontinuously.

8. The method for preparing a catalyst alumina carrier material with a gradient structure as claimed in claim 2, wherein the powder bed melt-forming process parameters in the step (3) are as follows: the diameter of a light spot is 0.2-0.3 mm, the thickness of the layer is 0.1-0.2 mm, and the preheating temperature is 150-180 ℃; different laser energy densities are obtained by adjusting the laser power, the scanning speed and the scanning interval, the laser power is 10-60W, the scanning speed is 20-2000 mm/s, the scanning interval is 0.05-0.13 mm, and 38-200J/cm can be obtained²Continuously varying laser energy.

9. The method for preparing the catalyst alumina carrier material with the gradient structure according to claim 2, wherein the step (4) is carried out by heating to 400-900 ℃ at a heating rate of 6-10 ℃/min, keeping the temperature for 2-3 hours, and cooling to room temperature along with a furnace.

Technical Field

The invention relates to a catalyst alumina carrier material and a preparation method thereof.

Background

Supported catalysts are used in a wide variety of petrochemical processes, one of which is a very widely used type of supported catalyst on alumina materials, e.g., pyrolysis gasoline hydrogenation catalyst, C₂Hydrogenation catalysts, catalysts for ethylene epoxidation to ethylene oxide, and the like. The preparation process of the supported catalyst includes soaking the catalyst carrier material in the metal ion containing active componentThen the soaked carrier material is subjected to heat treatment, so that the active component metal is immobilized on the outer surface of the carrier and the inner surface of the microscopic hole, and the catalyst with corresponding catalytic reaction capability is obtained. The catalyst carrier material not only provides an immobilized platform for active components, but also provides a transmission pore channel for the internal diffusion process of components and products in catalytic reaction. Therefore, for the supported catalyst using alumina material as the carrier, the structure and channel properties of the alumina carrier material often greatly affect the result of the catalytic reaction.

Many catalytic reactions whose product is not the final step to which the reaction is to be carried out, for example, the hydrogenation of vinyl acetylene, do not wish to obtain butane from complete hydrogenation, but rather butadiene from an intermediate step of the hydrogenation; as another example, in the epoxidation of ethylene, it is desirable to obtain ethylene oxide from partial oxidation, rather than to allow the ethylene oxide to continue to be deeply oxidized to economically worthless CO₂And water.

In addition to optimizing the ratio of the active components and the auxiliary components of the catalyst, it is more important to optimize the transfer effect during the catalytic reaction process in order to achieve the selective reaction products of the supported catalyst using the alumina material as the carrier. For this reason, many methods have been tried by researchers, for example, by controlling the impregnation conditions and adjusting the loading depth of the active component on the carrier to control the reaction time during the diffusion process inside the carrier, so that the reaction process stays as far as possible in the selective product formation stage without further proceeding into the reaction. For example, people can change the pore size distribution of the alumina carrier to optimize the diffusion effect in the carrier, so that the reaction can be effectively carried out, and meanwhile, the selective product can be timely separated from the inside of the catalyst, the situation that the product is adsorbed again by an active center and reacts deeply in the process of diffusing from the inside of the catalyst to the outside is reduced, and the yield of the target product is improved. The above schemes are technically optimized in the transfer space inside the catalyst, and although a certain effect is achieved, the alumina carrier of the catalyst is made of the same material from outside to inside, the crystal structure and the pore structure are uniform, the change of technical conditions can change the carrier material as a whole, and the structural adjustment and optimization from the outside to the inside of the carrier cannot be achieved, so the improvement on the reaction performance of the catalyst is still limited.

The gradient functional material is a novel composite material which is formed by compounding two or more materials and has continuously gradient change in components and structure. The design requirement of the composite material is that the function and the performance of the composite material are changed along with the change of the internal position of the material, and the composite material is satisfied by optimizing the overall performance of the component.

3D printing is a rapidly developing technology in recent years that enables precise fabrication of 3D devices with desired structures, with great potential for application in the fabrication of gradient functional materials. The powder bed melting is a rapid forming method widely applied to the 3D printing technology, mainly takes polymer, ceramic and metal powder as raw materials, and enables the raw materials to be sintered layer by layer under the radiation heating of laser, so that the rapid manufacturing of a complex structure can be realized, the whole manufacturing process does not need the assistance of other machining of a die, the product development period is greatly shortened, and the integration of free design to manufacturing is favorably realized. The 3D printing of the alumina material is carried out by adopting a powder bed melting process, pores are formed inside a manufactured part through the interaction between laser and powder in the manufacturing process, and the pores formed by the process provide a new idea for the preparation of the porous material.

If the alumina carrier material of the catalyst with the gradient functional structure can be manufactured by adopting a powder bed fusion 3D printing process, the structure from the outside to the inside of the carrier is adjusted and optimized, so that the reaction performance of the catalyst is improved.

Through the search of the prior documents and patents, the inventor finds that the research of the catalyst alumina carrier material with a gradient functional structure is not reported in the field of manufacturing the alumina porous material by the powder bed melting process. In a patent "a method for preparing porous ceramics with complex structure based on selective laser sintering" (patent No. CN201610687672.3), although the patent can use ceramic materials such as alumina or cordierite to directly perform 3D printing, the scheme is only to prepare a macroscopically complex outline structure, the material properties are still uniform, and no gradient functional structure on the material properties is formed. In "preparation of a laser sintering 3D printing rapid prototyping alumina powder" (patent No. CN201510284342.5), focus was primarily on the preparation of alumina powder; in the patent "laser sintering and 3DP combined 3D printing processing system and printing method" (patent number: CN 105397088A), the introduction of the equipment is mainly focused, and the two patents do not describe how to prepare the gradient functional material. In addition, the technical schemes take alumina as a raw material to perform powder laser sintering and melting, and the alumina has a relatively stable structure, so that the range of changing the crystal and pore structure after laser energy irradiation is limited, and the alumina carrier material with a large gradient structure range is difficult to directly prepare.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a catalyst alumina carrier material with a gradient structure and a preparation method thereof.

The invention relates to a preparation method of a catalyst alumina carrier material with a gradient structure, which mainly comprises the following steps:

1) preparing raw material powder: the raw material powder is prepared by uniformly mixing aluminum hydroxide powder and inorganic additive powder, wherein the aluminum hydroxide powder accounts for 65-98 wt% of the total mass of the raw material powder, the inorganic additive powder accounts for 2-35 wt% of the total mass of the raw material powder, the inorganic additive powder consists of boron carbide and one or more of silicon powder, silicon oxide and magnesium oxide, and the boron carbide accounts for 3-100 wt% of the total mass of the inorganic additive powder;

2) establishing a three-dimensional model of the alumina porous material in modeling software, dividing the model into different areas according to the gradient function requirement, slicing the model by adopting slicing software, and introducing a slice file into powder bed fusion 3D printing equipment for processing;

3) and (3) processing the raw material powder by adopting different laser energy densities for different subareas in the step (2) according to different functional requirements. The laser energy density and the structural properties of the alumina material have the following rules: the higher the laser energy density used for printing irradiation is, the larger the microscopic pore diameter, the lower the specific surface area and the larger the pore volume of the alumina material formed in the irradiated area are; the lower the energy density of the laser used for printing irradiation, the smaller the microscopic pore diameter, the higher the specific surface area and the smaller the pore volume of the alumina material formed in the irradiated area; the alumina carrier material with a gradient structure in the inner space can be obtained by changing the laser energy density in the printing process;

4) and (3) post-treatment sintering process: and (3) in order to stabilize the material performance, carrying out post-treatment sintering process on the alumina gradient functional porous material formed in the step (3), wherein the treatment temperature range is 400-900 ℃.

The aluminum hydroxide material in the step (1) is aluminum hydroxide with a chemical formula which can be written as AlOOH and aluminum hydroxide with a chemical formula which can be written as Al (OH)₃And (3) one or more of aluminum hydroxide.

The aluminum hydroxide with the chemical formula writable as AlOOH in the step (1) is preferably pseudo-boehmite, and the chemical formula writable as Al (OH)₃The aluminum hydroxide of (a) is preferably alpha-alumina trihydrate.

The aluminum hydroxide powder of step (1) preferably has a D50 particle size of 20 to 60 μm. In the powder bed melting process, the particle size of the powder is between 20 and 100 mu m, if the particle size is too small, agglomeration can occur, if the particle size is too large, the surface quality of a molded part can be reduced, and the D50 particle size of the tested aluminum hydroxide powder is preferably between 20 and 60 mu m, and the molding quality is the best.

The inorganic additive powder in the step (1) is composed of boron carbide and one or more of carbon powder, silicon oxide and magnesium oxide, and the energy density required by sintering powder can be reduced by adding the boron carbide.

The D50 particle size of the inorganic additive powder in the step (1) is 5-20 μm, theoretically, the smaller the D50 particle size of the inorganic additive powder is, the better the particle size is, which is beneficial to improving the sintering efficiency, but tests show that the agglomeration phenomenon can occur when the particle size of the inorganic additive powder is less than 5 μm, so the D50 particle size of the inorganic additive powder is 5-20 μm.

The method for uniformly mixing the powder in the step (1) is any method capable of uniformly mixing the powder, such as a mechanical mixing method, a wet ball milling method or a solution precipitation method.

The preferred uniform mixing method is a wet ball milling method: under the condition that the volume ratio of raw material powder to a dispersing agent to a grinding medium is 0.5-1: 1: 1-2, pouring aluminum hydroxide powder with a corresponding mass as a raw material into a ball mill, then adding inorganic additive powder with a corresponding mass as a raw material into the ball mill, pouring ethanol as a dispersing agent into the ball mill, adding alumina or zirconia ceramic balls (the diameter is 3-10 mm) as a grinding medium into the ball mill, and carrying out ball milling in the ball mill for 3-24 hours; filtering the obtained slurry by using a screen with more than 100 meshes; drying the slurry at 50 ℃ for more than 24 hours; crushing the dried powder, sieving with a sieve of more than 100 meshes to obtain the mixed powder for preparing the alumina porous material.

The different areas divided by the model in the step (2) are mainly divided according to the gradient function requirement, and the material structure performance between the different areas can be in continuous transition or discontinuous.

The powder bed melting and forming process parameters in the step (3) are as follows: the diameter of the light spot is 0.2-0.3 mm, the thickness of the layer is 0.1-0.2 mm, and the preheating temperature is 150-180 ℃. The different laser energy densities are mainly the adjustment of laser power, scanning speed and scanning interval. The laser power is 10-60W, the scanning speed is 20-2000 mm/s, and the scanning distance is 0.05-0.13 mm, so that 38-200J/cm can be obtained²Continuously varying laser energy. By using the continuously-changed laser energy, the aperture is 20-2000 nm, and the specific surface area is 1-140 m²An alumina carrier material having a pore volume of 0.1 to 1.2ml/g and a crush strength of 10 to 200N/cm which continuously varies. The characterization data of pore diameter, specific surface area and pore volume in the above description are obtained by BET method, and the crushing strength is obtained byMethod in standard HG/T2782-2011.

In order to further stabilize the material performance in the step (4), the alumina gradient functional porous material formed in the step (3) is heated to 400-900 ℃ at a heating rate of 6-10 ℃/min, is kept for 2-3 hours, and is cooled to room temperature along with a furnace.

Compared with the prior art, the invention has the following advantages and beneficial effects:

1. the invention innovatively provides a method for scanning different areas of the same part by utilizing the change of laser irradiation energy density of a powder melting process to realize the conversion from aluminum hydroxide to alumina with different structural characteristics so as to prepare and obtain a catalyst alumina carrier material with a gradient functional structure;

2. the raw material formula of the invention can use aluminum hydroxide powder as a base material for the powder fusion sintering 3D printing process, overcomes the problem of limited material structure change range after irradiation with different laser energy densities by using aluminum oxide as a raw material, and makes the preparation of the aluminum oxide carrier material with a gradient structure possible.

Drawings

Fig. 1 is a schematic diagram and a model of the embodiment of the present invention.

FIG. 2 is a graph showing the variation of parameters used in example 1.

FIG. 3 is a graph showing the variation of parameters used in the area A in example 5.

FIG. 4 is a graph showing the variation of parameters used in the region B in example 5.

Detailed Description

The following examples illustrate the invention in detail: the present example is carried out on the premise of the technical scheme of the present invention, and detailed embodiments and processes are given, but the scope of the present invention is not limited to the following examples, and the experimental methods without specific conditions noted in the following examples are generally performed according to conventional conditions.

Example 1

1) Mixing the raw material powders using a wet ball milling method: under the condition that the volume ratio of the raw material powder to the dispersing agent to the grinding medium is 1:1:1, taking 900g of aluminum hydroxide powder (D50 with the grain diameter of 25 microns), 50g of boron carbide powder (D50 with the grain diameter of 5 microns) and 50g of silicon powder (D50 with the grain diameter of 5 microns) as the raw material powder, sequentially adding the raw material powder into a ball mill, adding ethanol as the dispersing agent into the ball mill, adding zirconia ceramic balls (the diameter of 3-10 mm) as the grinding medium into the ball mill, and carrying out ball milling in the ball mill for 3 hours; drying the slurry at 50 ℃ for 24 hours; crushing the dried powder, and sieving by using a 100-mesh sieve to obtain mixed powder for preparing the alumina porous material;

2) a three-dimensional model of the alumina support material is established in modeling software. The carrier material is hollow cylindrical, the length of the cylinder is 7mm, and the outer diameter is D₁7mm, middle hole external diameter d₁2mm, according to the gradient function requirement, the model is divided into a region with continuous gradient change of material property from the outer ring to the inner ring of the middle hole, and the outermost layer (namely the distance D from the central axis of the cylinder)₁Position/2) the material performance index is designed as follows:

average pore diameter is 1500nm, specific surface area is 1.5m²The pore volume is 0.9ml/g, and the strength is 160N/cm.

The innermost layer (i.e. d from the cylinder central axis)₁Position/2) the material performance index is designed as follows:

average pore diameter of 30nm and specific surface area of 120m²The pore volume is 0.2ml/g, and the strength is 50N/cm.

3) Placing the powder obtained in the step 1) in a powder fusion bed 3D printer, setting printing initial parameters to be 0.2mm in spot diameter, 0.1mm in layer thickness and 150 ℃ in preheating temperature according to the material gradient performance setting in the step 2, and setting the parameters from the outermost layer (namely, the distance from the center axis D of the cylinder)₁At/2) to the innermost layer (i.e. d from the central axis of the cylinder)₁And/2) processing the raw material powder by using continuously different laser energy densities. For convenience of description, the parameters are continuously changed as shown in FIG. 2;

4) and (4) heating the alumina porous material formed in the step (3) to 900 ℃ at the heating rate of 6 ℃/min, preserving the heat at the temperature for 3 hours, and cooling to room temperature along with the furnace. The catalyst carrier 1 was obtained.

Comparative example 1

Comparative example 1 is different from example 1 in that the mold was not provided with a region where the material property was continuously graded in step 2), the printing laser energy density was not changed in step 3), the parameters were set to 52W for the laser power, 400mm/s for the scanning speed, and 0.13mm for the scanning pitch. The catalyst carrier 2 is prepared.

Comparative example 2

The difference from example 1 is that in step 1) the aluminum hydroxide was entirely replaced by α -alumina powder having a D50 particle size of 30 μm, and a catalyst carrier 3 was prepared.

Comparative example 3

Weighing 12.0 g of pseudoboehmite in a beaker, adding 50ml of deionized water, and uniformly dispersing the pseudoboehmite by magnetic stirring; dropwise adding a nitric acid solution into the solution to adjust the pH of the solution to be about 2, and continuously stirring until the solution is gradually dissolved to form a semitransparent sol system; then 0.722 g of tetraethyl orthosilicate is added into the sol system drop by drop, stirred for 1h at room temperature and heated to 60 ℃ and kept at the constant temperature for 2 h; the sol was transferred to a crucible and placed in an oven to be dried at 80 ℃ for 8 hours. The solid obtained after drying is heated from room temperature to 550 ℃ by a temperature-raising rate of 15 ℃/min, and is roasted for 2 hours at 550 ℃ to obtain the alpha-Al which is uniformly mixed₂O₃And SiO₂The nanoparticles of (1). Heating the mixed nano particles to 1200 ℃ by a program of 15 ℃/min, and keeping the temperature at 1200 ℃ for roasting for 6 hours to form alpha-Al₂O₃And mullite. alpha-Al is added₂O₃Adding the composite oxide mixed with mullite into 50ml of 20 percent hydrofluoric acid water solution, heating and soaking for 6h at 60 ℃ to realize the reaction of alpha-Al₂O₃Chemical etching to dope alpha-Al₂O₃And removing the mullite. And washing the etched solid by deionized water until the pH value is 7, then transferring the solid powder into an oven to dry for 6 hours at 80 ℃, and roasting the dried sample for 4 hours at 700 ℃ in an air atmosphere to obtain the carrier 4.

Example 2

Step 1) mixing raw material powder by using a wet ball milling method: according to the volume ratio of the raw material powder to the dispersing agent to the grinding medium of 1:1:1, taking 800g of aluminum hydroxide powder (D50 with the grain diameter of 25 microns), 100g of boron carbide (D50 with the grain diameter of 5 microns) and 100g of silicon dioxide (D50 with the grain diameter of 20 microns) as raw material powder, sequentially adding ethanol as a dispersing agent into a ball mill, adding zirconium oxide ceramic balls (the diameter of 3-10 mm) as a grinding medium into the ball mill, and carrying out ball milling in the ball mill for 3 hours; drying the obtained slurry at 50 ℃ for 24 hours; crushing the dried powder, and sieving by using a 100-mesh sieve to obtain mixed powder for preparing the alumina porous material; step 2), 3) same as example 1;

and 4) in the step 4), the alumina porous material formed in the step 3 is burnt to 700 ℃ at the heating rate of 6 ℃/min, the temperature is kept for 3 hours at the temperature, and the alumina porous material is cooled to the room temperature along with the furnace to obtain the carrier 5.

Example 3

Step 1) mixing raw material powder by using a wet ball milling method: according to the volume ratio of the raw material powder to the dispersing agent to the grinding medium of 1:1:1, 980g of aluminum hydroxide powder (D50 with the grain diameter of 25 microns), 20g of boron carbide (D50 with the grain diameter of 5 microns) and 5g of silicon dioxide are taken as raw material powder and sequentially added into a ball mill, ethanol is taken as a dispersing agent and added into the ball mill, zirconia ceramic balls (the diameter of 3-10 mm) are taken as a grinding medium and added into the ball mill, and the ball milling time in the ball mill is 3 hours; drying the obtained slurry at 50 ℃ for 24 hours; crushing the dried powder, and sieving by using a 100-mesh sieve to obtain mixed powder for preparing the alumina porous material; step 2), 3) same as example 1; and 4) in the step 4), the alumina porous material formed in the step 3 is burnt to 700 ℃ at the heating rate of 6 ℃/min, the temperature is kept for 3 hours at the temperature, and the alumina porous material is cooled to the room temperature along with the furnace to obtain the carrier 6.

Example 4

Step 1) mixing raw material powder by using a wet ball milling method: according to the volume ratio of the raw material powder to the dispersing agent to the grinding medium of 1:1:1, taking 650g of aluminum hydroxide powder (D50 with the grain diameter of 25 microns), 10.5g of boron carbide (D50 with the grain diameter of 5 microns), 139.5g of silicon powder (D50 with the grain diameter of 5 microns) and 200g of silicon dioxide (D50 with the grain diameter of 20 microns) as raw material powder, sequentially adding ethanol as the dispersing agent into a ball mill, adding zirconium oxide ceramic balls (the diameter of 3-10 mm) as the grinding medium into the ball mill, and carrying out ball milling in the ball mill for 3 hours; drying the obtained slurry at 50 ℃ for 24 hours; crushing the dried powder, and sieving by using a 100-mesh sieve to obtain mixed powder for preparing the alumina porous material; step 2), 3) same as example 1; and 4) in the step 4), the alumina porous material formed in the step 3 is burnt to 700 ℃ at the heating rate of 10 ℃/min, the temperature is kept for 3 hours at the temperature, and the alumina porous material is cooled to the room temperature along with the furnace to obtain the carrier 7.

Example 5

The difference from the embodiment 1 is that in the step 2), the model is divided into the outermost layer (namely, the distance D from the central axis of the cylinder to the middle hole inner ring) from the outer ring to the middle hole inner ring₁Position/2) to the cylinder central axis D₂At/2 (D)₂4mm) and D from the central axis of the cylinder₂At position/2 to the innermost layer (i.e. d from the central axis of the cylinder)₁Area B of/2), area A processes the raw material powder by adopting continuously different laser energy densities, and the continuous change of the parameters is shown in figure 3; the catalyst support 8 is also prepared in zone B by using successively different laser energy densities, the parameters of which are continuously varied as shown in fig. 4.

20 samples were randomly taken from each of the carriers 1 to 8, 10 of which were cut out with a small blade according to the regions A, B and C indicated in FIG. 1, wherein the region A was a ring-shaped portion from the outermost side of the carrier to a distance of 2.5mm from the axis of the carrier, the region B was a ring-shaped portion from a distance of 2.5mm to a distance of 1.5mm from the axis of the carrier, and the region C was a ring-shaped portion from a distance of 1.5mm to a distance of 1mm from the axis of the carrier, and 10 cut out samples of the carrier materials were collected together and sent as a carrier sample, and the average pore diameter, specific surface area and pore volume were measured by the BET method. The remaining 10 samples of each carrier were measured for lateral pressure using a particle lateral pressure intensity meter and averaged. The test characterization results are shown in table 1:

TABLE 1

Examples 9 to 13:

108 g of silver nitrate are dissolved in 250 ml of water, and 50g of ammonium oxalate are dissolved in 680 ml of water. And carrying out precipitation reaction on the two solutions at room temperature, washing the obtained silver oxalate precipitate with distilled water until no nitrate ions exist, filtering, dropwise adding 50% (V/V) ethylenediamine aqueous solution until the solution is completely dissolved, and adding 0.012 g of cesium nitrate to prepare the silver oxalate-ethylenediamine mixed impregnation solution A. Mixing 10% of the impregnation liquid A with the carriers 1,5,6,7 and 8, drying, treating in 150 ℃ air flow for 30 minutes and 500 ℃ water vapor-air flow with 10% of water content for 30 minutes, and cooling to room temperature under air flow. And (3) fully mixing the rest 90% of impregnation liquid A and the silver-loaded alpha-Al 2O3, carrying out secondary impregnation, drying, and carrying out thermal decomposition treatment for 30 minutes at 150 ℃ in an air atmosphere to obtain the supported silver catalyst 1,5,6,7,8 with the silver grain size of 100-200 nm. These catalysts were tested for initial ethylene conversion and selectivity using a laboratory microreaction evaluation unit. The reactor is a stainless steel reaction tube with the inner diameter of 10mm, and the reaction tube is arranged in a heating electric furnace sleeve. The catalyst loading volume was 4ml and the relevant reaction conditions were as follows:

the molar composition of raw material gas is as follows:

C₂H₄:30％；O₂:8％；CO₂3 percent of; inhibitor (B): trace; n is a radical of₂: the rest(s)

Pressure (gauge pressure): 1.6MPa

Space velocity: 2500h^-1

Catalysts 1,5,6,7,8 were obtained and reaction data were obtained.

Comparative examples 4 to 6:

catalysts 2,3 and 4 were prepared by the methods of examples 9 to 13 from the supports 2,3 and 4, respectively, and performance evaluation was performed on the catalysts by the methods of examples 9 to 13 to obtain reaction data.

The data for the evaluated reactions for catalysts 1-8 are summarized in Table 2:

table 2 catalyst evaluation reaction data

The invention utilizes the change of laser irradiation energy density of the powder melting process to scan different areas of the same part, realizes the conversion from aluminum hydroxide to alumina with different structural characteristics, and obtains the method of the catalyst alumina carrier material with the gradient functional structure. According to the test and characterization results, the carrier material has the pore diameter of 24.52-1999.91 nm and the specific surface area of 1-142.36 m²The pore volume is continuously changed within the range of 0.1-1.15 ml/g, which proves that the alumina carrier material with a larger gradient structure range is prepared by the method. Therefore, the raw material formula of the invention can use aluminum hydroxide powder as a base material for the powder fusion sintering 3D printing process, overcomes the problem of limited material structure change range after the aluminum oxide is used as the raw material and is irradiated by different laser energy densities, and prepares the alumina carrier material with the gradient structure.

The present invention is capable of other embodiments, and various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.