A porous silicon nitride supported pd-m catalyst, its preparation and use in the selective hydrogenation of acetylene

Abstract

The application discloses a porous silicon nitride supported Pd-M catalyst and a preparation method and application thereof in selective hydrogenation of acetylene. The preparation method of the porous silicon nitride supported Pd-M catalyst comprises the following steps: 1) obtaining porous silicon nitride; 2) mixing M-containing precursors, palladium chloride, the porous silicon nitride and a solvent A, stirring uniformly to obtain a mixture 1; 3) placing the mixture 1, waiting until the solution is clear and transparent, and filtering to obtain a mixture 2; 4) performing microwave heating and drying treatment on the mixture 2 to obtain a dried product; 5) performing high-temperature treatment on the dried product by using a joule heating instrument, cooling to room temperature, washing with a solvent B and obtaining a high-temperature treated product; and 6) performing microwave heating and drying on the high-temperature treated product, and grinding to obtain the porous silicon nitride supported Pd-M catalyst. The application also provides application of the porous silicon nitride supported Pd-M catalyst in synthesis of ethylene from selective hydrogenation of acetylene, and the catalyst has good reaction activity and stability.

Description

TECHNICAL FIELD

[0001] The present application relates to a porous silicon nitride supported Pd-M catalyst, its preparation and application in selective hydrogenation of acetylene. BACKGROUND

[0002] Selective hydrogenation of acetylene is an important process for removing acetylene impurities in industrial ethylene production. Even a small amount of acetylene can cause the polymerization catalyst to be deactivated. Therefore, the acetylene content must be reduced to below 5 ppm, while converting as much as possible to ethylene. Currently, Pd-based catalysts are the most commonly used catalysts in industrial acetylene hydrogenation, with high acetylene conversion rate, moderate reaction temperature, etc. Since Pd has good activity and stability for hydrogen, and good affinity for carbon-carbon triple bonds, it exhibits good low-temperature catalytic activity in acetylene semi-hydrogenation reaction. However, the active component Pd of Pd-based catalysts is prone to aggregation, and the adsorption of C2H2 on the bridging Pd site is stronger than the π-type adsorption on the isolated Pd atom, which causes excessive hydrogenation of C2H2 to C2H6, thereby causing low selectivity and carbon deposition problems, making it difficult to maintain high ethylene selectivity, and the catalyst life is also short. Modifying the geometric or electronic structure of the palladium-based catalyst, and using the interaction between palladium nanoparticles and the promoter and carrier to control the size, morphology and distribution of palladium nanoparticles, is the key to improving the activity, selectivity and durability of palladium catalytic hydrogenation. Although using traditional metal oxides (such as Al2O3) as a carrier can improve the dispersion of Pd nanoparticles, there are still challenges in synthesizing high-dispersion nanoparticles with uniform size and the same coordination structure by traditional methods.

[0003] Silicon nitride (Si3N4) belongs to the hexagonal system and can be divided into two crystal types: α-Si3N4 and β-Si3N4. Si3N4 has good mechanical strength, thermal conductivity, chemical stability, low thermal expansion coefficient, high hardness, and relative inertness. It is increasingly valued for its superior performance in high-temperature materials, such as oxidation resistance, corrosion resistance, and thermal shock resistance. Its cost is relatively low, has high separation efficiency (especially for particles in the range of 0.1 to 100 μm), and is biocompatible. Si3N4 is widely used in the ceramic field to manufacture high-performance ceramic products; in the electronics industry, it can be used as a heat dissipation material and an insulating component; in the mechanical manufacturing field, it is often used for wear-resistant parts; and in the metallurgical industry, it can also be used as a refractory material. In addition, these excellent properties of Si3N4 make it have high application value in the fields of national defense, semiconductor heat-conducting substrates, biomedical, and new technologies. Currently, silicon nitride is generally used as a catalyst carrier in the field of catalysis.

[0004] Commercial silicon nitride is usually composed of low-temperature (1200℃) α-Si3N4 or high-temperature (1500℃) β-Si3N4, produced by milling bulk ceramics, resulting in a powder with a low specific surface area (usually less than 10 m 2 CN 116273136 A discloses a Cu / silicon nitride catalyst, its preparation method and application in CO catalytic oxidation. CN 114433246 A discloses a silicon nitride carrier with high specific surface area and its preparation method, which is used to prepare a transition metal catalyst anchored on silicon nitride with high dispersion, and the catalyst is used in CO hydrogenation to alcohol reaction. However, there is no report on the application of silicon nitride in selective hydrogenation of acetylene.

[0005] Therefore, it is necessary to develop a preparation method for introducing a second component of a promoter metal M into a Pd-based catalyst, adjusting the geometric and electronic structure of Pd nanoparticles and producing a synergistic effect, and improving the catalytic performance of the catalyst. SUMMARY

[0006] The present application aims to provide a porous silicon nitride supported Pd-M catalyst and its preparation and application in selective hydrogenation of acetylene, which overcomes the problems of short service life, poor stability and high cost of use of the existing Pd-based catalysts applied in selective hydrogenation of acetylene. The porous silicon nitride supported Pd-M catalyst applied in selective hydrogenation of acetylene shows excellent catalytic performance and stability.

[0007] The technical solutions adopted by the present application are described below.

[0008] In a first aspect, the present application provides a preparation method of a porous silicon nitride supported Pd-M catalyst, wherein M is selected from at least one of Cu, Zn, Ag, Ni, Cr, Ru, and the preparation method comprises the following steps:

[0009] 1) Obtain porous silicon nitride: mix silicon nitride powder with a binder, a promoter and a solvent, knead, then extrude, air dry and cut into strips, dry and calcine to obtain porous silicon nitride; the binder is selected from one or more of polyvinyl alcohol, polyethylene glycol, carboxymethyl cellulose and methyl cellulose; the promoter is selected from one or more of glycerol, starch, urea, wet metatitanic acid (metatitanic acid containing hydrated molecules), ammonium carbonate, citric acid and nitric acid; the solvent is deionized water; the mass ratio of the Si3N4 powder, the binder, the promoter and the solvent is 40-60: 1-10: 1-10: 30-55;

[0010] 2)mixing the M-containing precursor with palladium chloride, the porous silicon nitride prepared in step 1), and solvent A to obtain mixture 1;

[0011] 3) allowing the mixture 1 obtained in step 2) to stand until the solution is clear, and filtering to obtain mixture 2;

[0012] 4) microwave drying the mixture 2 obtained in step 3);

[0013] 5) high-temperature treatment of the dried product obtained in step 4) using a joule heating instrument, cooling to room temperature, and washing with solvent B to obtain a high-temperature treated product;

[0014] 6) microwave drying of the high-temperature treated product obtained in step 5) and grinding to obtain the porous silicon nitride supported Pd-M catalyst.

[0015] The porous silicon nitride powder obtained in step 1) has a certain geometric shape, a certain mechanical strength, and a pore structure. In the present application, the silicon nitride powder is kneaded using a binder, so that the silicon nitride powder is bonded into a certain shape, thereby achieving the purpose of enhancing the mechanical strength, so that the silicon nitride formed product after the silicon nitride powder is formed has a certain geometric shape. In the present application, the silicon nitride powder is bonded into a certain shape using an auxiliary agent, and at the same time, the silicon nitride material has a good pore structure, which ensures that the silicon nitride material has a high specific surface area and good pore connectivity.

[0016] As a preferred embodiment, the method for preparing the porous silicon nitride comprises the following steps:

[0017] Step a: weighing a certain amount of commercial silicon nitride powder and a binder, mixing them uniformly, and adding an auxiliary agent and a solvent to knead them;

[0018] Step b: extruding the kneaded product obtained in step a) into a long strip shape using an extrusion molding machine;

[0019] Step c: after the strip-shaped product obtained in step b) is preliminarily dried at room temperature, cutting it into a strip-shaped product of a certain length;

[0020] Step d: drying the strip-shaped product obtained in step c);

[0021] Step e: placing the dried sample obtained in step d) in a joule heating instrument, and baking at a temperature of 350-1000°C for 1-10h to obtain the porous silicon nitride.

[0022] As a further preferred embodiment, step b) is to extrude a cylindrical long strip-shaped product with a diameter of 1.5-3mm; and step c) is to cut the strip-shaped product into a length of 3-4mm.

[0023] As a further preference, the drying process of step d) is performed in a microwave oven, the drying temperature is 80-120°C; the drying time is 10-24h.

[0024] As a further preference, the N:Si molar ratio of the commercial silicon nitride is 4:3.

[0025] As a preference, in step 2), the copper-containing precursor is selected from one or more of copper acetate, copper chloride, copper nitrate and copper sulfate; the zinc-containing precursor is selected from one or more of zinc oxide, zinc chloride, zinc acetate, zinc carbonate, zinc nitrate and zinc sulfate; the silver-containing precursor is selected from one or more of silver nitrate, silver oxide, silver sulfate, silver chloride, silver ammine solution and silver acetylacetonate; the nickel-containing precursor is selected from one or more of nickel chloride, nickel nitrate, nickel carbonate, nickel hydroxide, nickel oxalate and nickel sulfate; the chromium-containing precursor is selected from one or more of sodium chromate, potassium chromate, chromium chloride and chromium sulfate; the rhodium-containing precursor is selected from one or more of rhodium chloride, rhodium nitrate and rhodium acetylacetonate.

[0026] As a preference, in step 2), the M-containing precursor, palladium chloride and the porous silicon nitride are added according to the elemental molar ratio M:Pd:N = 1:1:0.5-5.

[0027] As a preference, in step 2), the solvent A is selected from water, methanol, ethanol, acetone, aqueous sucrose solution, aqueous starch solution.

[0028] As a preference, in step 3), the standing temperature of the mixture is room temperature-90°C, and the standing time is 0.5-3h.

[0029] As a preference, in step 4), the microwave heating drying frequency is 2.45GHz, the processing temperature is 60-150°C, the vacuum degree is 100-100000Pa, and the time is 2-20h.

[0030] As a preference, in step 5), the high-temperature processing temperature is 300-1800°C, the high-temperature processing time is 1-30h, and the high-temperature processing atmosphere is an inert atmosphere, specifically helium, argon or nitrogen.

[0031] As a preference, in step 5), the solvent B is selected from at least one of deionized water, hydrogen peroxide, methanol, ethanol, propanol, cyclohexanol, butanol, acetone, liquid ammonia and aqueous ammonia.

[0032] As a preference, in step 6), the microwave heating drying frequency is 2.45GHz, the processing temperature is 60-150°C, the vacuum degree is 100-100000Pa, and the time is 2-20h.

[0033] Further, the grinding in step 6) is grinding into a powder of 10-200 mesh, which can be pressed into different particle sizes according to requirements.

[0034] In a second aspect, the present application provides a porous silicon nitride supported Pd-M catalyst prepared by the preparation method of the first aspect.

[0035] In a third aspect, the present application provides an application of the porous silicon nitride supported Pd-M catalyst of the second aspect in the synthesis of ethylene by selective hydrogenation of acetylene.

[0036] The synthesis of ethylene by selective hydrogenation of acetylene is specifically implemented as follows: the porous silicon nitride supported Pd-M catalyst is loaded into a fixed bed reactor, a raw gas containing hydrogen and acetylene is introduced, the reaction temperature is set to 150-300 ℃, the reaction pressure is set to 0.1-0.5 MPa, and acetylene and hydrogen are allowed to react to generate ethylene.

[0037] Further, in the raw gas, n(H2) / n(C2H2) = 0.8-1.2 / 1. Still further, the raw gas further contains a carrier gas and C2H4, and the carrier gas is nitrogen.

[0038] Further, during the reaction, the acetylene gas space velocity is controlled to be 30-370 h-1. -1 .

[0039] The acetylene hydrogenation catalyst provided by the present application has the following beneficial effects compared with existing catalysts:

[0040] (1) The preparation method of the catalyst of the present application is in-situ synthesis of a porous silicon nitride supported Pd-M catalyst, and the catalyst itself has relatively high activity. The porous Si3N4 prepared by the present application has good mechanical strength and good pore structure, so that the Si3N4 material has a relatively high specific surface area, good pore connectivity and high structural stability.

[0041] (2) In the preparation process of the porous silicon nitride supported Pd-M catalyst, the precursor, Si3N4 and the solvent are adjusted to controllably adjust the physicochemical properties of the catalyst.

[0042] (3) In the preparation process of the porous silicon nitride supported Pd-M catalyst of the present application, a microwave oven is used for heating, which is energy-saving and efficient, has uniform heating, is easy to operate, has controllable conditions, and is helpful to obtain high-purity products and expand the application range.

[0043] (4) In the preparation process of the porous silicon nitride supported Pd-M catalyst of the present application, a joule heating instrument is used for high-temperature treatment of the material, which has the advantages of fast response, high repeatability, precise control, cleanliness, high energy utilization rate and good stability.

[0044] (4) The Pd-M / Si3N4 material of the present application has many advantages, and the dispersion of the catalyst is obviously improved. The introduction of the auxiliary agent M promotes the dispersion of the metal Pd, and inhibits the agglomeration of the Pd species in the reaction process, and has high research value.

[0045] (5) The Pd-M / Si3N4 catalyst described in the present application has good reactivity in the above-mentioned acetylene hydrogenation reaction. After 100 hours of reaction, the acetylene conversion rate can be up to 92.5% or more, and the ethylene selectivity can be up to 99% or more. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 The adsorption-desorption curve and pore size distribution diagram of the porous silicon nitride prepared in Example 1. DETAILED DESCRIPTION

[0047] The present application will be described below with specific examples. It is necessary to point out that the examples are only used to further illustrate the present application, but cannot be understood as limiting the protection scope of the present application, and the present application is not limited in any way. Those skilled in the art can make some non-essential improvements and adjustments according to the content of the above-mentioned application.

[0048] The polymer used in the example of the present application is polyvinyl alcohol CAS: 9002-89-5; the molecular weight of the starch is 342;

[0049] The Si3N4 powder used in the example of the present application is commercially purchased, and the properties are: powder, specific surface area 49m 2 / g, off-white, average particle size 1 μm, crystal form β phase.

[0050] In the example of the present application, the specific conditions not specified are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used without specifying the manufacturer are conventional products that can be obtained by conventional technical means or obtained by commercial purchase.

[0051] Example 1

[0052] (1) The commercial Si3N4 powder, polyvinyl alcohol, glycerol and deionized water are mixed and kneaded according to a certain mass fraction ratio of Si3N4 powder: polyvinyl alcohol: glycerol: deionized water = 50:5:5:50; the obtained kneaded product is extruded into a cylindrical strip with a particle size of 2mm by an extrusion molding machine; the obtained cylindrical strip is preliminarily dried at room temperature, and then cut into long particles with a length of 3mm; the obtained long particles are dried in a microwave oven at a vacuum degree of 1000Pa at 80℃ for 10h; the dried sample is calcined at 350℃ for 2 hours by a joule heating instrument, and porous silicon nitride is obtained; the compressive strength of the porous silicon nitride is 35N / cm, and the specific surface area is 175m 2 / g, the most probable pore size is 100 nm, the pore volume is 0.35 mL / g, and the crystal structure is anatase;

[0053] (2) 9.13 g of copper acetate, 8.865 g of palladium chloride, and 7 g of porous silicon nitride were weighed out, 10 mL of deionized water was added, and stirring was performed for 2 h to allow them to be mixed thoroughly;

[0054] (3) The mixture was left to stand at 60°C for 1 h, and after the solution became clear and transparent, the mixture was filtered to obtain a mixture;

[0055] (4) The mixture was subjected to microwave heating and drying treatment at 110°C and 10,000 Pa for 2 h;

[0056] (5) The mixture after drying was subjected to high-temperature treatment at 1100°C at a heating rate of 10°C / min using a Joule heating instrument under a nitrogen atmosphere for 2 h; -1

[0057] (6) The treated catalyst was cooled to room temperature and washed with deionized water three times;

[0058] (7) The catalyst after washing was subjected to microwave heating and drying treatment at 110°C and 10,000 Pa for 2 h, and the particle size was ground to 20 mesh;

[0059] (8) Acetylene hydrogenation reaction evaluation was performed on a fixed bed reactor device: the acetylene hydrogenation reaction was performed at 220°C, an acetylene space velocity of 120 h -1 -1, and a hydrogen:acetylene volume ratio of 1:1.2, and the raw material gas also contained a carrier gas and C2H4, and the carrier gas was nitrogen (a hydrogen:acetylene:nitrogen:ethylene volume ratio of 1:1.2:200:100); after the reaction was completed, the catalyst performance was an acetylene initial conversion rate of 70%, an ethylene selectivity of 99%, and after 100 h, the acetylene initial conversion rate decreased to 63%, and the ethylene selectivity was maintained at 99%.

[0060] Example 2

[0061] (1) Commercial Si3N4 powder, polyvinyl alcohol, glycerol, and deionized water were mixed and kneaded in a mass ratio of Si3N4 powder:polyvinyl alcohol:glycerol:deionized water = 40:1:1:30; the obtained kneaded product was extruded into a cylindrical strip with a particle size of 1.5 mm by an extrusion molding machine; the obtained cylindrical strip was preliminarily dried at room temperature, and then cut into long particles with a length of 3 mm; the obtained long particles were dried in a microwave oven at a vacuum degree of 1000 Pa at 90°C for 12 h; the dried sample was calcined at 400°C for 1 hour using a Joule heating instrument to obtain porous silicon nitride; the compressive strength of the porous silicon nitride was 32 N / cm, the specific surface area was 165 m 2 ​ / g, with a most probable pore size of 95nm, a pore volume of 0.38mL / g, and an anatase crystal structure.

[0062] (2) Weigh 5.378g of copper chloride, 7.0928g of palladium chloride, and 4.2g of porous silicon nitride, add 12ml of deionized water, and stir for 1.5h to make them fully mixed;

[0063] (3) Place the above mixture at 90°C and let it stand for 0.5 h until the solution is clear and transparent, then filter to obtain the mixture;

[0064] (4) The above mixture was microwave-dried at 80°C and 1000Pa for 12 hours.

[0065] (5) The dried mixture was heated in a helium atmosphere using a Joule heater at 10°C / min. -1 The heating rate was increased to 1300℃ for high-temperature treatment for 2.5 hours;

[0066] (6) Cool the catalyst after the above high-temperature treatment to room temperature and wash it three times with ethanol;

[0067] (7) The catalyst after the above washing treatment was microwave heated and dried at 80°C and 1000Pa for 12 hours, and its particle size was ground to 30 mesh.

[0068] (8) Evaluation of acetylene hydrogenation reaction in a fixed-bed reactor: The acetylene hydrogenation reaction was carried out at 200℃ and an acetylene space velocity of 100 h⁻¹. -1 The reaction was carried out under conditions where the volume ratio of hydrogen to acetylene was 1:1. The feed gas also contained a carrier gas and C2H4, and the carrier gas was nitrogen (the volume ratio of hydrogen:acetylene:nitrogen:ethylene was 1:1:202:100). After the reaction, the catalyst performance was as follows: the initial conversion rate of acetylene was 95%, the selectivity of ethylene was 99%, and after 100 h, the initial conversion rate of acetylene decreased to 92%, while the selectivity of ethylene remained at 99%.

[0069] Example 3

[0070] (1) Commercial Si3N4 powder, carboxymethyl cellulose, starch, and deionized water were mixed and kneaded in a certain mass ratio of Si3N4 powder: carboxymethyl cellulose: starch: deionized water = 60:10:10:55. The resulting mixture was extruded into cylindrical strips with a particle size of 2.5 mm using an extruder. After the cylindrical strips were pre-dried at room temperature, they were cut into long particles of 3.5 mm. The long particles were dried in a microwave oven at 100°C for 14 h under a vacuum of 1000 Pa. The dried sample was calcined at 500°C for 3 h using a Joule heating instrument to obtain porous silicon nitride. The porous silicon nitride had a compressive strength of 34 N / cm and a specific surface area of ​​177 m². 2 / g, the most probable pore size is 103 nm, the pore volume is 0.41 mL / g, and the crystal structure is anatase.

[0071] (2) 5.63 g of copper nitrate, 5.32 g of palladium chloride, and 5.6 g of porous silicon nitride are weighed out, 8 ml of methanol is added, and stirring is performed for 1.5 h to allow them to be mixed thoroughly;

[0072] (3) The mixture is left to stand at room temperature for 3 h, and when the solution is clear and transparent, filtration is performed to obtain a mixture;

[0073] (4) The mixture is subjected to microwave heating and drying treatment at 60°C and 5000 Pa for 10 h;

[0074] (5) The mixture after drying is subjected to high-temperature treatment at 300°C for 4 h at a heating rate of 10°C / min using a Joule heating apparatus under an argon atmosphere; -1

[0075] (6) The catalyst after high-temperature treatment is cooled to room temperature, and washed with methanol three times;

[0076] (7) The catalyst after washing treatment is subjected to microwave heating and drying treatment at 60°C and 5000 Pa for 10 h, and the particle size is ground to 50 mesh;

[0077] (8) Acetylene hydrogenation reaction evaluation is performed on a fixed bed reactor device: acetylene hydrogenation reaction is performed at 180°C, acetylene space velocity is 30 h -1 -1, the volume ratio of hydrogen to acetylene is 0.8:1, and the raw gas further contains a carrier gas and C2H4, and the carrier gas is nitrogen (the volume ratio of hydrogen to acetylene to nitrogen to ethylene is 0.8:1:202:100); after the reaction is completed, the catalyst performance is that the initial acetylene conversion rate is 99%, the ethylene selectivity is 99%, and after 100 h, the initial acetylene conversion rate decreases to 90% and the ethylene selectivity decreases to 97%.

[0078] Example 4

[0079] (1) Commercial Si3N4 powder, carboxymethyl cellulose, starch, and deionized water are mixed and kneaded in a mass ratio of Si3N4 powder: carboxymethyl cellulose: starch: deionized water = 50:5:5:50; the obtained kneaded product is extruded into a cylindrical strip with a particle size of 2 mm by an extrusion molding machine; the obtained cylindrical strip is preliminarily dried at room temperature, and then cut into long particles with a length of 3 mm; the obtained long particles are dried at 100°C for 16 h in a microwave oven with a vacuum degree of 1000 Pa; the dried sample is calcined at 600°C for 4 hours using a Joule heating apparatus, and porous silicon nitride is obtained; the compressive strength of the porous silicon nitride is 36 N / cm, the specific surface area is 170 m 2 ​ / g, with a most probable pore size of 104nm, a pore volume of 0.40mL / g, and an anatase crystal structure.

[0080] (2) Weigh 4.0g of copper sulfate, 4.43g of palladium chloride, and 3.5g of porous silicon nitride, add 15ml of acetone, and stir for 1.5h to mix them thoroughly.

[0081] (3) Place the above mixture at 70°C and let it stand for 2 hours until the solution is clear and transparent. Then filter to obtain the mixture.

[0082] (4) The above mixture was microwave-dried at 120°C and 2000Pa for 15 hours.

[0083] (5) The dried mixture was heated in a nitrogen atmosphere using a Joule heater at 10°C / min. -1 The heating rate was increased to 800℃ for high-temperature treatment for 14 hours;

[0084] (6) Cool the catalyst after the above high-temperature treatment to room temperature and wash it three times with hydrogen peroxide;

[0085] (7) The catalyst after the above washing treatment was microwave heated and dried at 120°C and 2000Pa for 15 hours, and its particle size was ground to 10 mesh.

[0086] (8) Evaluation of acetylene hydrogenation reaction in a fixed-bed reactor: The acetylene hydrogenation reaction was carried out at 200℃ and an acetylene space velocity of 150 h⁻¹. -1 The reaction was carried out under conditions where the volume ratio of hydrogen to acetylene was 1:1, and the feed gas also contained a carrier gas and C2H4, wherein the carrier gas was nitrogen; (the volume ratio of hydrogen:acetylene:nitrogen:ethylene was 1:1:202:100). After the reaction, the catalyst performance was as follows: the initial conversion rate of acetylene was 80%, the selectivity of ethylene was 99%, and after 100 h, the initial conversion rate of acetylene remained at 80%, while the selectivity of ethylene decreased to 98%.

[0087] Example 5

[0088] (1) Commercial Si3N4 powder, methylcellulose, urea, and deionized water were mixed and kneaded in a certain mass ratio of Si3N4 powder: methylcellulose: urea: deionized water = 50: 5: 5: 50. The resulting mixture was extruded into cylindrical strips with a particle size of 3 mm using an extruder. After the cylindrical strips were preliminarily dried at room temperature, they were cut into long particles with a diameter of 4 mm. The long particles were dried in a microwave oven with a vacuum degree of 1000 Pa at 120°C for 18 h. The dried sample was calcined at 600°C for 4 h using a Joule heating instrument to obtain porous silicon nitride. The compressive strength of the porous silicon nitride was 39 N / cm, and the specific surface area was 165 m². 2 / g, the most probable pore size is 105 nm, the pore volume is 0.43 mL / g, and the crystal structure is anatase.

[0089] (2) 4.08 g of zinc chloride, 5.5 g of palladium chloride, and 4.6 g of porous silicon nitride were weighed out, 15 mL of deionized water was added, and stirring was performed for 1.5 h to allow for thorough mixing;

[0090] (3) The mixture was left to stand at 90°C for 1 h, and after the solution became clear and transparent, the mixture was filtered;

[0091] (4) The gel-like substance was subjected to microwave heating and drying treatment at 150°C and 10,000 Pa for 11 h;

[0092] (5) The dried mixture was subjected to high-temperature treatment at 300°C for 18 h using a Joule heating apparatus at a heating rate of 10°C / min under an argon atmosphere; -1

[0093] (6) The high-temperature treated catalyst was cooled to room temperature and washed with cyclohexanol three times;

[0094] (7) The washed catalyst was subjected to microwave heating and drying treatment at 150°C and 10,000 Pa for 11 h, and the particle size was ground to 80 mesh;

[0095] (8) Acetylene hydrogenation reaction evaluation was performed on a fixed bed reactor device: the acetylene hydrogenation reaction was performed at 170°C, an acetylene space velocity of 200 h -1 -1, and a hydrogen:acetylene volume ratio of 1.2:1, and the raw material gas also contained a carrier gas and C2H4, and the carrier gas was nitrogen (a hydrogen:acetylene:nitrogen:ethylene volume ratio of 1.2:1:202:100); after the reaction was completed, the catalyst performance was an acetylene initial conversion rate of 80%, an ethylene selectivity of 99%, and the acetylene initial conversion rate was maintained at 80% and the ethylene selectivity was maintained at 99% after 100 h.

[0096] Example 6

[0097] (1) Commercial Si3N4 powder, polyvinyl alcohol, wet metatitanic acid, and deionized water were mixed and kneaded in a mass ratio of Si3N4 powder:polyvinyl alcohol:wet metatitanic acid:deionized water = 40:1:1:30; the obtained kneaded product was extruded into a cylindrical strip with a particle size of 2.5 mm using an extrusion molding machine; the obtained cylindrical strip was preliminarily dried at room temperature, and then cut into long particles with a length of 3 mm; the obtained long particles were dried at 110°C for 18 h in a microwave oven with a vacuum degree of 1,000 Pa; the dried sample was calcined at 800°C for 6 hours using a Joule heating apparatus, and porous silicon nitride was obtained; the compressive strength of the porous silicon nitride was 33 N / cm, the specific surface area was 178 m 2 ​ / g, the most probable pore size is 106 nm, the pore volume is 0.41 mL / g, and the crystal structure is anatase.

[0098] (2) 14.61 g of nickel nitrate, 8.866 g of palladium chloride, and 4 g of porous silicon nitride are weighed out, 15 ml of a 20% sucrose solution (water as solvent) is added, and stirring is performed for 1.5 h to allow them to be mixed thoroughly;

[0099] (3) The mixture is left to stand at 50°C for 2.5 h, and after the solution becomes clear and transparent, the mixture is filtered;

[0100] (4) The mixture is subjected to microwave heating and drying treatment at 140°C and 8000 Pa for 20 h;

[0101] (5) The dried mixture is subjected to high-temperature treatment at 1600°C for 6 h at a heating rate of 10°C / min using a Joule heating instrument under an argon atmosphere; -1

[0102] (6) The high-temperature treated catalyst is cooled to room temperature and washed with liquid ammonia three times;

[0103] (7) The washed catalyst is subjected to microwave heating and drying treatment at 140°C and 8000 Pa for 20 h, and the particle size is ground to 20 mesh;

[0104] (8) The acetylene hydrogenation reaction is evaluated on a fixed bed reactor device: the acetylene hydrogenation reaction is performed at 300°C, an acetylene space velocity of 300 h -1 -1, and a hydrogen:acetylene volume ratio of 1:1, and the raw material gas also contains a carrier gas and C2H4, and the carrier gas is nitrogen (hydrogen:acetylene:nitrogen:ethylene volume ratio of 1:1:202:100); after the reaction is completed, the catalyst performance is that the initial acetylene conversion rate is 95%, the ethylene selectivity is 99%, and after 100 h, the initial acetylene conversion rate is maintained at 95% and the ethylene selectivity is reduced to 99%.

[0105] Example 7

[0106] (1) Commercial Si3N4 powder, polyethylene glycol, ammonium carbonate, and deionized water are mixed and kneaded in a mass ratio of Si3N4 powder:polyethylene glycol:ammonium carbonate:deionized water = 50:5:5:50; the obtained kneaded product is extruded into a cylindrical strip with a particle size of 2.5 mm by an extrusion molding machine; the obtained cylindrical strip is preliminarily dried at room temperature, and then cut into long particles with a length of 3.5 mm; the obtained long particles are dried in a microwave oven at a vacuum degree of 1000 Pa at 120°C for 20 h; the dried sample is calcined at 800°C for 6 hours using a Joule heating instrument, and porous silicon nitride is obtained; the compressive strength of the porous silicon nitride is 38 N / cm, and the specific surface area is 171 m​2 / g, with a most probable pore size of 108nm, a pore volume of 0.39mL / g, and an anatase crystal structure.

[0107] (2) Weigh 4.63g of nickel carbonate, 6.916g of palladium chloride, and 5g of porous silicon nitride, add 15ml of methanol solution, and stir for 1.5h to mix them thoroughly.

[0108] (3) Place the above mixture at 90°C and let it stand for 0.5 h until the solution is clear and transparent, then filter to obtain the mixture;

[0109] (4) The above mixture was microwave-dried at 140°C and 9000Pa for 17 hours.

[0110] (5) The dried mixture was heated in a helium atmosphere using a Joule heater at 20°C / min. -1 The heating rate was increased to 1800℃ for high-temperature treatment for 2 hours;

[0111] (6) Cool the catalyst after the above high-temperature treatment to room temperature and wash it three times with butanol;

[0112] (7) The catalyst after the above washing treatment was microwave-dried at 140°C and 9000Pa for 17h, and its particle size was ground to 20 mesh.

[0113] (8) Evaluation of acetylene hydrogenation reaction in a fixed-bed reactor: The acetylene hydrogenation reaction was carried out at 200℃ and an acetylene space velocity of 500 h⁻¹. -1 The reaction was carried out under conditions where the hydrogen:acetylene volume ratio was 1:1, and the feed gas also contained a carrier gas and C2H4. The carrier gas was nitrogen (hydrogen:acetylene:nitrogen:ethylene volume ratio was 1:1:202:100). After the reaction, the catalyst performance was as follows: the initial acetylene conversion rate was 91%, the ethylene selectivity was 98%, and after 100 h, the initial acetylene conversion rate decreased to 80%, while the ethylene selectivity remained at 98%.

[0114] Example 8

[0115] (1) Commercial Si3N4 powder, carboxymethyl cellulose, citric acid, and deionized water were mixed and kneaded in a certain mass fraction ratio of Si3N4 powder: carboxymethyl cellulose: citric acid: deionized water = 60:10:10:55. The resulting mixture was extruded into cylindrical strips with a particle size of 1.5 mm using an extruder. After the cylindrical strips were preliminarily dried at room temperature, they were cut into long particles of 3 mm. The long particles were dried in a microwave oven at 120°C for 20 h under a vacuum of 1000 Pa. The dried sample was calcined at 900°C for 8 h using a Joule heating instrument to obtain porous silicon nitride. The compressive strength of the porous silicon nitride was 33 N / cm, and the specific surface area was 178 m².2 / g, the most probable pore size is 99 nm, the pore volume is 0.37 mL / g, and the crystal structure is anatase.

[0116] (2) 6.48 g of sodium chromate, 7.09 g of palladium chloride, and 2.8 g of porous silicon nitride were weighed out, added to 15 ml of an ethanol solution, and stirred for 1.5 h to allow them to be mixed thoroughly;

[0117] (3) The mixture was left to stand at 35°C for 3 h, and after the solution became clear and transparent, the mixture was filtered to obtain a mixture;

[0118] (4) The mixture was subjected to microwave heating and drying treatment at 140°C and 6000 Pa for 18 h;

[0119] (5) The mixture after drying was subjected to high-temperature treatment at 800°C at a heating rate of 10°C / min using a Joule heating instrument under a helium atmosphere for 10 h; -1

[0120] (6) The catalyst after high-temperature treatment was cooled to room temperature and washed with propanol three times;

[0121] (7) The catalyst after washing was subjected to microwave heating and drying treatment at 140°C and 6000 Pa for 18 h, and the particle size was ground to 20 mesh;

[0122] (8) The acetylene hydrogenation reaction was evaluated on a fixed bed reactor device: the acetylene hydrogenation reaction was performed at 160°C, an acetylene space velocity of 600 h -1 -1, and a hydrogen:acetylene volume ratio of 0.8:1, and the raw material gas also contained a carrier gas and C2H4, and the carrier gas was nitrogen (a hydrogen:acetylene:nitrogen:ethylene volume ratio of 0.8:1:202:100); after the reaction ended, the catalyst performance was an acetylene initial conversion rate of 88%, an ethylene selectivity of 99%, and after 100 h, the acetylene initial conversion rate decreased to 86% and the ethylene selectivity was maintained at 99%.

[0123] Example 9

[0124] (1) Commercial Si3N4 powder, polyethylene glycol, nitric acid, and deionized water were mixed and kneaded in a mass fraction ratio of Si3N4 powder:polyethylene glycol:nitric acid:deionized water = 40:1:1:30; the obtained kneaded product was extruded into a cylindrical strip with a particle size of 3 mm by an extrusion molding machine; the obtained cylindrical strip was preliminarily dried at room temperature, and then cut into long particles with a length of 4 mm; the obtained long particles were dried in a microwave oven at a vacuum degree of 1000 Pa at 110°C for 10 h; the dried sample was calcined at 120°C for 24 hours using a Joule heating instrument, to obtain porous silicon nitride; the compressive strength of the porous silicon nitride was 30 N / cm, and the specific surface area was 168 m 2 ​ / g, the most probable pore diameter is 97 nm, the pore volume is 0.33 mL / g, and the crystal structure is anatase.

[0125] (2) 8.36 g of rhodium chloride, 7.09 g of palladium chloride, and 1.40 g of porous silicon nitride were weighed out, 15 mL of deionized water was added, and stirring was performed for 1.5 h to allow for thorough mixing;

[0126] (3) The mixture was left to stand at 50°C for 2.5 h to allow it to become a gel-like substance;

[0127] (4) The mixture was subjected to microwave heating and drying treatment at 140°C and 8000 Pa for 20 h;

[0128] (5) The mixture after drying was subjected to high-temperature treatment at 1600°C at a heating rate of 10°C / min using a Joule heating apparatus under a nitrogen atmosphere for 6 h; -1

[0129] (6) The catalyst after high-temperature treatment was cooled to room temperature and washed with acetone three times;

[0130] (7) The catalyst after washing was subjected to microwave heating and drying treatment at 140°C and 8000 Pa for 20 h, and the particle size was ground to 20 mesh;

[0131] (8) Acetylene hydrogenation reaction evaluation was performed on a fixed bed reactor device: acetylene hydrogenation reaction was performed at 170°C, acetylene space velocity 2000 h -1 , hydrogen: acetylene volume ratio 0.8:1, under conditions in which the raw material gas also contained a carrier gas and C2H4, the carrier gas being nitrogen (hydrogen: acetylene: nitrogen: ethylene volume ratio 0.8:1:202:100); after the reaction was completed, the catalyst performance was acetylene initial conversion 88%, ethylene selectivity 99%, and after 100 h, the acetylene initial conversion decreased to 79% and the ethylene selectivity was maintained at 99%.

[0132] Example 10

[0133] (1) Commercial Si3N4 powder, polyvinyl alcohol, glycerol, and deionized water were mixed and kneaded in a mass ratio of Si3N4 powder: polyvinyl alcohol: glycerol: deionized water = 50:5:5:50; the resulting kneaded product was extruded into a cylindrical strip having a particle size of 2 mm using an extrusion molding machine; the resulting cylindrical strip was preliminarily air-dried at room temperature and then cut into long particles having a length of 3.5 mm; the resulting long particles were dried in a microwave oven at 110°C for 16 h under a vacuum of 1000 Pa; the dried sample was calcined at 700°C for 8 hours using a Joule heating apparatus to obtain porous silicon nitride; the compressive strength of the porous silicon nitride was 36 N / cm, the specific surface area was 172 m 2 ​ / g, the most probable pore size is 103 nm, the pore volume is 0.35 mL / g, and the crystal structure is anatase.

[0134] (2) 11.56 g of rhodium nitrate, 7.09 g of palladium chloride, and 3.0 g of porous silicon nitride were weighed out, 15 mL of the starch solution was added, and stirring was performed for 1.5 h to allow for thorough mixing;

[0135] (3) The mixture was left to stand at 30°C for 2.5 h, and after the solution became clear and transparent, the mixture was filtered;

[0136] (4) The mixture was subjected to microwave heating and drying treatment at 140°C and 10,000 Pa for 10 h;

[0137] (5) The mixture after drying was subjected to high-temperature treatment at 1600°C at a heating rate of 20°C / min using a joule heating instrument under a helium atmosphere for 6 h; -1

[0138] (6) The catalyst after high-temperature treatment was cooled to room temperature and washed with ammonia water three times;

[0139] (7) The catalyst after washing was subjected to microwave heating and drying treatment at 140°C and 10,000 Pa for 10 h, and the particle size was ground to 20 mesh;

[0140] (8) Acetylene hydrogenation reaction evaluation was performed on a fixed bed reactor device: the acetylene hydrogenation reaction was performed at 300°C, an acetylene space velocity of 800 h -1 -1, and a hydrogen:acetylene volume ratio of 1.2:1, and the raw material gas also contained a carrier gas and C2H4, and the carrier gas was nitrogen (a hydrogen:acetylene:nitrogen:ethylene volume ratio of 1.2:1:200:100); after the reaction ended, the catalyst performance was an acetylene initial conversion rate of 88%, an ethylene selectivity of 99%, and after 100 h, the acetylene initial conversion rate decreased to 80% and the ethylene selectivity was maintained at 99%.

[0141] Comparative Example 1

[0142] (1) Commercial Si3N4 powder, polyvinyl alcohol, glycerol, and deionized water were mixed and kneaded in a mass fraction ratio of Si3N4 powder:polyvinyl alcohol:glycerol:deionized water = 50:5:5:50; the obtained kneaded product was extruded into a cylindrical strip with a particle size of 2 mm using an extrusion molding machine; the obtained cylindrical strip was preliminarily dried at room temperature, and then cut into long particles with a length of 3 mm; the obtained long particles were dried in a microwave oven at a vacuum degree of 1000 Pa at 80°C for 10 h; the dried sample was calcined at 350°C for 2 hours using a joule heating instrument, and porous silicon nitride was obtained; the compressive strength of the porous silicon nitride was 35 N / cm, and the specific surface area was 175 m 2 ​ / g, the most probable pore size is 100 nm, the pore volume is 0.35 mL / g, and the crystal structure is anatase type;

[0143] (2) 8.865 g of palladium chloride and 7 g of porous silicon nitride were weighed out, 10 mL of deionized water was added, and stirring was performed for 2 h to allow them to be mixed thoroughly;

[0144] (3) The mixture was left to stand at 60°C for 1 h, and after the solution became clear and transparent, the mixture was filtered to obtain a mixture;

[0145] (4) The mixture was subjected to microwave heating and drying treatment at 110°C and 10,000 Pa for 2 h;

[0146] (5) The mixture after drying was subjected to high-temperature treatment at 1100°C at a heating rate of 10°C / min using a Joule heating instrument under a nitrogen atmosphere for 2 h; -1

[0147] (6) The treated catalyst was cooled to room temperature and washed with deionized water three times;

[0148] (7) The catalyst after washing was subjected to microwave heating and drying treatment at 110°C and 10,000 Pa for 2 h, and the particle size was ground to 20 mesh;

[0149] (8) The acetylene hydrogenation reaction was evaluated on a fixed bed reactor device: the acetylene hydrogenation reaction was performed at 220°C, an acetylene space velocity of 120 h -1 -1, and a hydrogen:acetylene volume ratio of 1:1.2, and the raw material gas also contained a carrier gas and C2H4, and the carrier gas was nitrogen (a hydrogen:acetylene:nitrogen:ethylene volume ratio of 1:1.2:200:100); after the reaction was completed, the catalyst performance was an acetylene initial conversion rate of 55% and an ethylene selectivity of 60%, and after 100 h, the acetylene initial conversion rate decreased to 30% and the ethylene selectivity decreased to 45%.

[0150] Comparative Example 2

[0151] (1) Commercial Si3N4 powder, polyvinyl alcohol, glycerol, and deionized water were mixed and kneaded in a mass ratio of Si3N4 powder:polyvinyl alcohol:glycerol:deionized water = 40:1:1:30; the obtained kneaded product was extruded into a cylindrical strip with a particle size of 1.5 mm using an extrusion molding machine; the obtained cylindrical strip was preliminarily dried at room temperature, and then cut into long particles with a length of 3 mm; the obtained long particles were dried in a microwave oven at a vacuum degree of 1000 Pa at 90°C for 12 h; the dried sample was calcined at 400°C for 1 hour using a Joule heating instrument to obtain porous silicon nitride; the compressive strength of the porous silicon nitride was 32 N / cm, the specific surface area was 165 m 2 ​ / g, with a most probable pore size of 95nm, a pore volume of 0.38mL / g, and an anatase crystal structure.

[0152] (2) Weigh 7.0928g of palladium chloride and 4.2g of porous silicon nitride, add 12ml of deionized water, and stir for 1.5h to make them fully mixed;

[0153] (3) Place the above mixture at 90°C and let it stand for 0.5 h until the solution is clear and transparent, then filter to obtain the mixture;

[0154] (4) The above mixture was microwave-dried at 80°C and 1000Pa for 12 hours.

[0155] (5) The dried mixture was heated in a helium atmosphere using a Joule heater at 10°C / min. -1 The heating rate was increased to 1300℃ for high-temperature treatment for 2.5 hours;

[0156] (6) Cool the catalyst after the above high-temperature treatment to room temperature and wash it three times with ethanol;

[0157] (7) The catalyst after the above washing treatment was microwave heated and dried at 80°C and 1000Pa for 12 hours, and its particle size was ground to 30 mesh.

[0158] (8) Evaluation of acetylene hydrogenation reaction in a fixed-bed reactor: The acetylene hydrogenation reaction was carried out at 200℃ and an acetylene space velocity of 100 h⁻¹. -1 The reaction was carried out under conditions where the hydrogen:acetylene volume ratio was 1:1, and the feed gas also contained a carrier gas and C2H4. The carrier gas was nitrogen (hydrogen:acetylene:nitrogen:ethylene volume ratio was 1:1:202:100). After the reaction, the catalyst performance was as follows: the initial acetylene conversion rate was 55%, and the ethylene selectivity was 68%. After 100 hours, the initial acetylene conversion rate decreased to 50%, and the ethylene selectivity decreased to 67%.

Claims

1. The application of a porous silicon nitride-supported Pd-M catalyst in the selective hydrogenation of acetylene to ethylene, characterized in that: The M is selected from at least one of Cu, Zn, Ag, Ni, Cr, and Rh, and the preparation method of the porous silicon nitride supported Pd-M catalyst includes the following steps: 1) Obtaining porous silicon nitride: Silicon nitride powder is mixed with binder, additives and solvent, kneaded, then extruded, dried and cut into strips, dried and calcined to obtain porous silicon nitride; the binder is selected from one or more of polyvinyl alcohol, polyethylene glycol, carboxymethyl cellulose and methyl cellulose; the additives are selected from one or more of glycerol, starch, urea, wet metatitanic acid, ammonium carbonate, citric acid and nitric acid; the solvent is deionized water; the mass ratio of silicon nitride powder, binder, additives and solvent is 40-60:1-10:1-10:30-55; 2) The precursor containing M, palladium chloride, porous silicon nitride obtained in step 1), and solvent A are thoroughly mixed and stirred until homogeneous to obtain mixture 1; the precursor containing M, palladium chloride, and porous silicon nitride are added in an elemental molar ratio of M:Pd:N = 1:1:0.5-5; the solvent A is selected from water, methanol, ethanol, acetone, sucrose aqueous solution, and starch aqueous solution; 3) Let the mixture 1 obtained in step 2) stand until the solution is clear and transparent, then filter to obtain mixture 2; 4) The mixture 2 obtained in step 3) is subjected to microwave heating and drying to obtain the dried product; 5) The dried product obtained in step 4) is subjected to high-temperature treatment using a Joule heater, cooled to room temperature, and thoroughly washed with solvent B to obtain the high-temperature treated product; the high-temperature treatment temperature is 300-1800℃, the high-temperature treatment time is 1-30h, and the high-temperature treatment atmosphere is an inert atmosphere; the solvent B is selected from at least one of deionized water, hydrogen peroxide, methanol, ethanol, propanol, cyclohexanol, butanol, acetone, liquid ammonia, and ammonia water; 6) The high-temperature treated product obtained in step 5) is dried by microwave heating and then ground to obtain a porous silicon nitride supported Pd-M catalyst.

2. The application as described in claim 1, characterized in that: The method for preparing the porous silicon nitride includes the following steps: Step a: Weigh a certain amount of commercial silicon nitride powder and binder, mix them evenly, add additives and solvents, and knead them together; Step b: Extrude the kneaded compound obtained in step a into a long strip using an extrusion molding machine; Step c: After the strips obtained in step b are initially dried at room temperature, cut them into strips of a certain length; Step d: Dry the strips obtained in step c; Step e: Place the dried sample from step d into a Joule heater and calcine it at a temperature of 350–1000℃ for 1–10 hours to obtain porous silicon nitride.

3. The application as described in claim 2, characterized in that: The N:Si molar ratio in the commercial silicon nitride is 4:

3.

4. The application as described in claim 1, characterized in that: In step 2), the copper-containing precursor is selected from one or more of copper acetate, copper chloride, copper nitrate, and copper sulfate; the zinc-containing precursor is selected from one or more of zinc oxide, zinc chloride, zinc acetate, zinc carbonate, zinc nitrate, and zinc sulfate; the silver-containing precursor is selected from one or more of silver nitrate, silver oxide, silver sulfate, silver chloride, silver ammonia solution, and silver acetylacetonate; the nickel-containing precursor is selected from one or more of nickel chloride, nickel nitrate, nickel carbonate, nickel hydroxide, nickel oxalate, and nickel sulfate; the chromium-containing precursor is selected from one or more of sodium chromate, potassium chromate, chromium chloride, and chromium sulfate; and the rhodium-containing precursor is selected from one or more of rhodium chloride, rhodium nitrate, and rhodium acetylacetonate.

5. The application as described in claim 1, characterized in that: Step 3) The mixture is allowed to stand at a temperature of room temperature to 90°C for 0.5 to 3 hours.

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