A supported noble metal catalyst and its preparation method and application

Abstract

The present invention relates to the field of catalyst technology, discloses a supported noble metal catalyst and its preparation method and application, the catalyst includes a first carrier and a coating loaded on the first carrier, the raw material composition for preparing the coating includes a second carrier, an active component precursor, an auxiliary agent precursor, a binder and a dispersant; the first carrier is cordierite, mullite or cordierite-mullite; the second carrier is titanium dioxide and / or aluminum oxide; the active component precursor is selected from at least one of a platinum precursor, a palladium precursor and a rhodium precursor; the auxiliary agent precursor is a combination of a cerium precursor, a zirconium precursor and a neodymium precursor; the binder is a mixture of an organic binder, an inorganic binder and a coupling agent. The supported noble metal catalyst has low production cost, high catalytic activity, strong anti-poisoning ability and long service life, can be used for the removal of volatile organic compounds, and is particularly suitable for the removal of flue gases such as ethylene and propane with large air volume and low concentration of organic small molecule hydrocarbons.

Description

Technical Field

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

[0002] With the rapid development of industrialization, emissions of volatile organic compounds (VOCs) have continued to increase, causing serious impacts on the environment and human health. In recent years, national and local governments have introduced a series of policies and measures to promote the control of VOC emissions. The coal chemical industry is a major emitter of VOCs, releasing large amounts of hydrocarbons such as ethylene, propane, and propylene into the atmosphere annually. Due to the low VOC content in coal chemical exhaust and the high safety requirements of plant sites, catalytic degradation is an important technical means of controlling VOC emissions, and VOC oxidation catalysts are key to this technology. Currently, commercial catalysts used for VOC removal are primarily Pt-based catalysts, which have the advantage of high low-temperature activity. However, due to the stable molecular structures of short-chain alkane and olefin VOCs, existing catalysts are less than ideal for removing these VOCs. Therefore, there is an urgent need to develop precious metal catalytic oxidation catalysts with excellent catalytic activity for short-chain hydrocarbons. Summary of the Invention

[0003] The purpose of the present invention is to overcome the problem that the catalysts in the prior art are not effective enough in removing short-chain hydrocarbons in VOCs, and to provide a supported noble metal catalyst and its preparation method and application.

[0004] To achieve the above object, the present invention provides a supported precious metal catalyst, comprising a first carrier and a coating supported on the first carrier, wherein a raw material composition for preparing the coating comprises a second carrier, an active component precursor, an auxiliary agent precursor, a binder, and a dispersant;

[0005] The first carrier is selected from any one of cordierite, mullite and cordierite-mullite;

[0006] The second carrier is titanium dioxide and / or aluminum oxide;

[0007] The active component precursor is selected from at least one of a platinum precursor, a palladium precursor and a rhodium precursor;

[0008] The auxiliary agent precursor is a combination of a cerium precursor, a zirconium precursor and a neodymium precursor;

[0009] The binder is a mixture of an organic binder, an inorganic binder and a coupling agent.

[0010] Preferably, the platinum precursor is platinum tetrachloride and / or chloroplatinic acid;

[0011] Preferably, the palladium precursor is palladium chloride and / or palladium nitrate;

[0012] Preferably, the rhodium precursor is rhodium trichloride and / or rhodium chloride.

[0013] Preferably, the cerium precursor is selected from at least one of cerium nitrate, cerium sulfate and cerium chloride;

[0014] Preferably, the zirconium precursor is selected from at least one of zirconium oxychloride, zirconium sulfate and zirconium nitrate;

[0015] Preferably, the neodymium precursor is selected from at least one of neodymium nitrate, neodymium oxalate and neodymium sulfate.

[0016] Preferably, the inorganic binder is selected from at least one of silica-alumina sol, aluminum sol, silica sol and phosphate-alumina sol;

[0017] Preferably, the organic binder is hydroxypropyl methylcellulose and / or polyethylene fiber;

[0018] Preferably, the coupling agent is a silane coupling agent and / or a titanate coupling agent;

[0019] Preferably, the dispersant is selected from at least one of sodium tripolyphosphate, sodium hexametaphosphate, sodium stearate and sodium citrate.

[0020] Preferably, the content of the active component is 100-300 mg / kg based on the total weight of the supported noble metal catalyst.

[0021] Preferably, in the supported noble metal catalyst, the weight ratio of the active component to cerium, zirconium and neodymium is 1:50-80:50-80:5-20.

[0022] A second aspect of the present invention provides a method for preparing a supported noble metal catalyst, the method comprising the following steps:

[0023] (1) mixing an active component precursor solution and an auxiliary agent precursor solution to obtain a mixed solution, impregnating a second carrier in the mixed solution, and then drying and calcining to obtain a noble metal powder catalyst;

[0024] (2) mixing a binder, a dispersant, water and a precious metal powder catalyst, and grinding the mixture with a sand mill to obtain a coating slurry;

[0025] (3) coating the coating slurry on the pretreated first carrier, and then drying and calcining to obtain a supported noble metal catalyst;

[0026] The first carrier is selected from any one of cordierite, mullite and cordierite-mullite;

[0027] The second carrier is titanium dioxide and / or aluminum oxide;

[0028] The active component precursor is selected from at least one of a platinum precursor, a palladium precursor and a rhodium precursor;

[0029] The auxiliary agent precursor is a combination of a cerium precursor, a zirconium precursor and a neodymium precursor;

[0030] The binder is a mixture of an organic binder, an inorganic binder and a coupling agent.

[0031] Preferably, in step (1), based on the total weight of the precious metal powder catalyst, the mass fraction of the active component is 0.05-0.5%, and the mass fraction of the auxiliary agent is 2-40%;

[0032] Preferably, in step (2), the weight ratio of the noble metal powder catalyst, binder, dispersant and water is 10:2~38:0.005~8:10~150.

[0033] Preferably, in step (1), the drying conditions include: a temperature of 90-120°C and a time of 2-4 hours;

[0034] In step (1), the calcination conditions include: a temperature of 500-700°C and a time of 4-7 h;

[0035] In step (3), the drying conditions include: a temperature of 90-120°C and a drying time of 1-2 h;

[0036] In step (3), the calcination conditions include: a temperature of 500-800°C and a time of 4-7 h.

[0037] Preferably, the preparation process of the pretreated first carrier comprises: washing the first carrier with water and acid, and then drying it.

[0038] Preferably, the water absorption rate of the pretreated first carrier is 20-50%, and the specific surface area is 10-30 m 2 / g.

[0039] The third aspect of the present invention further provides use of the above-mentioned supported noble metal catalyst or the supported catalyst prepared by the above-mentioned method in the catalytic oxidation of volatile organic compounds.

[0040] In the present invention, by designing the auxiliary agent precursor, the surface oxygen vacancy formation of the oxide auxiliary agent on the obtained supported precious metal catalyst is increased, the surface active sites are increased and dispersed, thereby improving the redox performance and anti-toxicity of the supported precious metal catalyst, while effectively reducing the cost of the supported precious metal catalyst; by using a compounded binder, the adhesion of the active components, auxiliary agents, etc. in the coating to the first carrier is improved, the coating loading is increased while maintaining a low shedding rate, thereby increasing the service life of the supported precious metal catalyst. Therefore, the supported precious metal catalyst of the present invention has low production cost, high catalytic activity, strong anti-poisoning ability, high mechanical strength, and long service life, and can be used for the removal of volatile organic compounds, and is particularly suitable for the removal of flue gases such as ethylene and propane with large air volume and low concentration of organic small molecule hydrocarbons. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 1 is a graph showing the catalytic activity test results of the supported noble metal catalysts prepared in Examples 1-4 of the present invention. DETAILED DESCRIPTION

[0042] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0043] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0044] The present invention provides a supported noble metal catalyst, which includes a first carrier and a coating supported on the first carrier, wherein a raw material composition for preparing the coating includes a second carrier, an active component precursor, an auxiliary agent precursor, a binder, and a dispersant;

[0045] The first carrier is selected from any one of cordierite, mullite and cordierite-mullite;

[0046] The second carrier is titanium dioxide and / or aluminum oxide;

[0047] The active component precursor is selected from at least one of a platinum precursor, a palladium precursor and a rhodium precursor;

[0048] The auxiliary agent precursor is a combination of a cerium precursor, a zirconium precursor and a neodymium precursor.

[0049] The supported catalyst provided by the present invention comprises an active component comprising at least one of platinum, palladium, and rhodium, and a promoter comprising a cerium-zirconium-neodymium composite oxide. By selecting these active components and promoters, the resulting supported precious metal catalyst is capable of catalytically oxidizing volatile organic compounds and is particularly useful for the catalytic combustion treatment of ethylene waste gas.

[0050] The present invention does not impose any particular limitation on the specific selection of the platinum precursor for providing platinum, and it can be a platinum precursor commonly used in the art. In a specific embodiment, the platinum precursor is platinum tetrachloride and / or chloroplatinic acid.

[0051] In a preferred embodiment, the second carrier is anatase titanium dioxide and / or γ-alumina. By selecting the above raw materials, the second carrier has good thermal stability and a high specific surface area.

[0052] Further preferably, the second support is anatase titanium dioxide and γ-alumina. By compounding the two, the overall performance of the prepared supported precious metal catalyst is improved. More preferably, when the second support is a mixture of anatase titanium dioxide and γ-alumina, the weight ratio of anatase titanium dioxide to γ-alumina is 1:0.5 to 4, specifically, for example, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, or 1:4.

[0053] The present invention does not limit the specific selection of the palladium precursor, and it can be a palladium precursor commonly used in the art. In a specific embodiment, the palladium precursor is palladium chloride and / or palladium nitrate.

[0054] The present invention is not limited to the specific selection of the rhodium precursor, and it can be a rhodium precursor commonly used in the art. In a specific embodiment, the rhodium precursor is rhodium trichloride and / or rhodium chloride.

[0055] Taking into account the comprehensive effect of catalytic ethylene oxidation and production costs, in a preferred embodiment, the active component precursor is a platinum precursor. By using platinum as the active component of the catalyst, the catalyst has a good catalytic effect on ethylene and the amount of platinum used is low.

[0056] In a specific embodiment, the cerium precursor is selected from at least one of cerium nitrate, cerium sulfate and cerium chloride.

[0057] In a specific embodiment, the zirconium precursor is selected from at least one of zirconium oxychloride, zirconium sulfate and zirconium nitrate.

[0058] In a specific embodiment, the neodymium precursor is selected from at least one of neodymium nitrate, neodymium oxalate and neodymium sulfate.

[0059] In the present invention, the binder is a mixture of an organic binder, an inorganic binder and a coupling agent. By using the compounded binder, the adhesion between the components in the coating and the first carrier is improved, the shedding rate is reduced and the mechanical strength of the catalyst is greatly improved, thereby extending the service life of the catalyst.

[0060] In a preferred embodiment, the inorganic binder is selected from at least one of silica-alumina sol, alumina sol, silica sol and phosphoalumina sol, more preferably a mixture of alumina sol and silica sol.

[0061] In a preferred embodiment, the organic binder is hydroxypropyl methylcellulose and / or polyethylene fiber, more preferably a mixture of hydroxypropyl methylcellulose and polyethylene fiber.

[0062] In a preferred embodiment, the coupling agent is a silane coupling agent and / or a titanate coupling agent. The silane coupling agent may be silane coupling agent KH-560 and / or silane coupling agent KH-792. More preferably, the coupling agent is a mixture of silane coupling agent KH-560, silane coupling agent KH-792, and titanate coupling agent.

[0063] In a preferred embodiment, in the binder, the weight ratio of the inorganic binder, the organic binder, and the coupling agent is 8:0.1-4:0.1-2.

[0064] In a preferred embodiment, the binder comprises a mixture of aluminum sol, silica sol, hydroxypropyl methylcellulose, polyethylene fiber, and a coupling agent. Further preferably, in this embodiment, the weight ratio of the aluminum sol, silica sol, hydroxypropyl methylcellulose, polyethylene fiber, and coupling agent is 4:1-6:0.1-1:0.2-0.8:0.1-1. Further preferably, in this embodiment, the coupling agent is a mixture of silane coupling agent KH-560, silane coupling agent KH-792, and titanate coupling agent, and the weight ratio of silane coupling agent KH-560, silane coupling agent KH-792, and titanate coupling agent is 5:2-6:0.5-2.

[0065] In the present invention, the raw material composition for preparing the coating contains a dispersant. The addition of the dispersant uniformly disperses the components in the coating slurry, thereby achieving high dispersion of the active components and additives in the resulting catalyst, thereby improving the catalytic activity of the catalyst. In a preferred embodiment, the dispersant is selected from at least one of sodium tripolyphosphate, sodium hexametaphosphate, sodium stearate, and sodium citrate.

[0066] In the present invention, the active component content is 100-300 mg / kg, based on the total weight of the supported precious metal catalyst. By designing various raw material components (e.g., active component, additive, etc.), the present invention enables the production of a catalyst with excellent catalytic activity even with an extremely low precious metal content.

[0067] Preferably, in the supported noble metal catalyst, the weight ratio of the active component to cerium, zirconium and neodymium is 1:50-80:50-80:5-20. Under the above dosage relationship, the catalytic performance of the supported noble metal catalyst is better.

[0068] The present invention also provides a method for preparing a supported noble metal catalyst, which comprises the following steps:

[0069] (1) mixing an active component precursor, an auxiliary agent precursor and an acid solution to obtain a mixed solution, impregnating a second carrier in the mixed solution, and then drying and calcining to obtain a noble metal powder catalyst;

[0070] (2) mixing a binder, a dispersant, water, and a precious metal powder catalyst to obtain a coating slurry;

[0071] (3) coating the coating slurry on the pretreated first carrier, and then drying and calcining to obtain a supported noble metal catalyst;

[0072] The first carrier is selected from any one of cordierite, mullite and cordierite-mullite;

[0073] The second carrier is titanium dioxide and / or aluminum oxide;

[0074] The active component precursor is selected from at least one of a platinum precursor, a palladium precursor and a rhodium precursor;

[0075] The auxiliary agent precursor is a combination of a cerium precursor, a neodymium precursor and a zirconium precursor;

[0076] The binder is a mixture of an organic binder, an inorganic binder and a coupling agent.

[0077] In the present invention, the average particle size of the precious metal powder catalyst prepared in step (1) is 0.2-1.0 μm, and the specific surface area is 60-150 m 2 / g.

[0078] In a specific embodiment, in step (1), the drying conditions include: a temperature of 90-120° C. and a drying time of 2-4 hours.

[0079] In a specific embodiment, in step (1), the calcination conditions include: a temperature of 500-700° C. and a time of 4-7 hours.

[0080] In a specific embodiment, step (1) includes:

[0081] A1. Mixing an active component precursor with concentrated hydrochloric acid and water to obtain an active component precursor solution;

[0082] A2, mixing the additive precursor with the mixed acid solution to obtain an additive precursor solution;

[0083] A3, mixing the active component precursor solution and the auxiliary agent precursor solution to obtain a mixed solution;

[0084] A4. Immersing the second support in the mixed solution, then thermally concentrating it, removing it, and then drying and calcining it to obtain a precious metal powder catalyst;

[0085] The mixed acid solution is obtained by mixing concentrated hydrochloric acid, nitric acid and water.

[0086] In a preferred embodiment, the present invention does not limit the specific amounts of the active component precursor, the auxiliary agent precursor, and the second carrier in step (1), and can be designed according to the specific selection of the active component precursor and the auxiliary agent precursor, as long as the mass fraction of the active component in the obtained precious metal powder catalyst is 0.05-0.5% and the mass fraction of the auxiliary agent is 2-40%.

[0087] Furthermore, in the noble metal powder catalyst, the mass fraction of the second carrier is 60% to 97%.

[0088] In a preferred embodiment, in step (2), the weight ratio of the precious metal powder catalyst, binder, dispersant and water is 10:2~38:0.005~8:10~150, more preferably 10:5~15:0.005~1:50~100. Within the above dosage range, the production cost of the catalyst is low and the overall performance is better.

[0089] In the present invention, the first carrier is pretreated to increase the specific surface area of ​​the first carrier. In a preferred embodiment, the preparation process of the pretreated first carrier includes: washing the first carrier with water and acid, and then drying.

[0090] More preferably, the acid used in the pickling is oxalic acid and / or nitric acid.

[0091] In a specific implementation, the preparation process of the pretreated first carrier includes: placing the first carrier in deionized water for ultrasonic washing for 0.5 to 2 hours, drying it in an oven at 100 to 120°C for 2 to 4 hours, taking it out, and cooling it to room temperature in a dryer; treating the cooled first carrier with a nitric acid or oxalic acid solution with a mass fraction of 10% to 30% in a water bath at 60 to 90°C for 1 to 3 hours, then washing it with deionized water until it is neutral, and drying it in an oven at 100 to 120°C for 2 to 4 hours.

[0092] In a preferred embodiment, the water absorption rate of the first carrier after pretreatment is 20-50%, and the specific surface area is 10-30 m 2 / g.

[0093] In a preferred embodiment, the inorganic binder is selected from at least one of silica-alumina sol, alumina sol, silica sol and phosphoalumina sol, more preferably a mixture of alumina sol and silica sol.

[0094] In a preferred embodiment, the organic binder is hydroxypropyl methylcellulose and / or polyethylene fiber, more preferably a mixture of hydroxypropyl methylcellulose and polyethylene fiber.

[0095] In a preferred embodiment, the coupling agent is a silane coupling agent and / or a titanate coupling agent. The silane coupling agent may be silane coupling agent KH-560 and / or silane coupling agent KH-792. More preferably, the coupling agent is a mixture of silane coupling agent KH-560, silane coupling agent KH-792, and titanate coupling agent.

[0096] In a preferred embodiment, in the binder, the weight ratio of the inorganic binder, the organic binder, and the coupling agent is 8:0.1-4:0.1-2.

[0097] In the method of the present invention, in a preferred embodiment, the binder comprises a mixture of aluminum sol, silica sol, hydroxypropyl methylcellulose, polyethylene fiber, and a coupling agent. Further preferably, the weight ratio of the aluminum sol, silica sol, hydroxypropyl methylcellulose, polyethylene fiber, and coupling agent is 4:1-6:0.1-1:0.2-0.8:0.1-1. Further preferably, the coupling agent is a mixture of silane coupling agent KH-560, silane coupling agent KH-792, and titanate coupling agent, with the weight ratio of silane coupling agent KH-560, silane coupling agent KH-792, and titanate coupling agent being 5:2-6:0.5-2.

[0098] In a specific embodiment, step (2) comprises: mixing the binder and the dispersant with water, ultrasonically stirring at 23-27° C. for 1-2 h, then adding the precious metal powder catalyst, continuing ultrasonic stirring for 1-2 h, and grinding using a horizontal sand mill for 30-60 min to obtain a coating slurry.

[0099] In a preferred embodiment, step (3) specifically includes: immersing the pretreated first carrier in the coating slurry, applying the coating slurry to the carrier by vacuum coating, blowing off excess slurry and then drying, repeating the vacuum coating multiple times (2 to 10 times), and then calcining to obtain a monolithic supported precious metal catalyst.

[0100] In a preferred embodiment, in step (3), the drying conditions include: a temperature of 90-120° C. and a drying time of 1-2 h.

[0101] In a preferred embodiment, in step (3), the calcination conditions include: a temperature of 500-800° C. and a time of 4-7 hours.

[0102] The present invention also proposes the use of the above-mentioned supported noble metal catalyst or the supported noble metal catalyst prepared by the above-mentioned method in catalytic oxidation of volatile organic compounds.

[0103] Preferably, the volatile organic compound is ethylene.

[0104] The present invention will be described in detail below through examples, but the protection scope of the present invention is not limited thereto.

[0105] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all commercially available.

[0106] In the following examples and comparative examples, the test methods involved are as follows:

[0107] Test of coating mass as a percentage of the first carrier mass: The calculation formula for coating mass percentage is (M1

[0108] -M0) / M0×100%, wherein the mass of the finally prepared supported noble metal catalyst is recorded as M1; the mass of the first carrier is recorded as M0.

[0109] Platinum loading test: The platinum content in the catalyst samples was analyzed using an inductively coupled plasma optical emission spectrometer. The samples were digested using a digestion instrument before analysis.

[0110] Neodymium loading test: The neodymium content in the catalyst samples was analyzed using an inductively coupled plasma optical emission spectrometer. The samples were digested using a digestion instrument before analysis.

[0111] Example 1

[0112] (1) Pretreatment of the first carrier: The cordierite carrier (specifications: 150 mm * 150 mm * 150 mm) was ultrasonically cleaned in deionized water for 1 h, dried in an oven at 110 °C for 4 h, and then taken out and cooled to room temperature in a desiccator; the cordierite carrier cooled to room temperature was treated with a 20% nitric acid solution in an 80 °C water bath for 2 h, then washed with deionized water until neutral, and dried in an oven at 110 °C for 4 h.

[0113] (2) Preparation of precious metal powder catalyst: 0.084 g of chloroplatinic acid was dissolved in a solution of 25 ml of concentrated hydrochloric acid and 25 ml of deionized water under heating conditions at 60 °C in a water bath to obtain an active component precursor solution; 6.055 g of cerium nitrate hexahydrate, 5.847 g of zirconium oxychloride octahydrate, and 1.042 g of neodymium nitrate hexahydrate were dissolved in 50 ml of a mixed acid solution under heating conditions at 60 °C in a water bath to obtain an auxiliary agent precursor solution, wherein the mixed acid solution was obtained by mixing nitric acid, concentrated hydrochloric acid, and deionized water in a volume ratio of 1:1:1; the active component precursor solution and the auxiliary agent precursor solution were mixed and ultrasonically stirred at 25 °C for 1 h to obtain a mixed solution;

[0114] 7.38 g of titanium dioxide (anatase type) and 7.38 g of γ-alumina were added to the mixed solution and ultrasonically stirred until uniform. The mixture was concentrated by a rotary evaporator and then taken out. The mixture was dried in an oven at 110 °C for 4 h and calcined in a muffle furnace at 600 °C for 6 h to prepare a precious metal powder catalyst.

[0115] (3) Preparation of coating slurry: 40 ml of aluminum sol with a solid content of 20%, 40 ml of silica sol with a solid content of 20%, 1.0 g of hydroxypropyl methylcellulose, 1.0 g of polyethylene fiber, 1.4 g of coupling agent (silane coupling agent KH-560: silane coupling agent KH-792: titanate coupling agent = 5:4:1), and 0.6 g of sodium hexametaphosphate were added to 120 ml of water and dissolved. The mixture was ultrasonically stirred at 25 °C for 1 h, 20 g of precious metal powder catalyst was added, and ultrasonic stirring was continued for 1 h. The mixture was then ground using a horizontal sand mill at 50 Hz for 90 min to prepare a coating slurry with a solid content of 20%.

[0116] (4) Preparation of integral supported precious metal catalyst: The coating slurry was coated on the pretreated cordierite carrier using a vacuum coating machine for 10 min. After blowing away the excess slurry, the catalyst was dried at 110 °C for 3 h. The coating was repeated three times and the catalyst was calcined at 600 °C for 6 h to obtain the integral supported precious metal catalyst 1#.

[0117] According to the test, in the monolithic supported precious metal catalyst 1#, the coating mass is 8.0%±0.2% of the mass of the first support, the platinum loading is 150 mg / kg, and the neodymium loading is 0.15%.

[0118] Example 2

[0119] The method described in Example 1 was used for implementation, except that step (2) was as follows: preparation of precious metal powder catalyst: 0.042 g of chloroplatinic acid was dissolved in a solution of 25 ml of concentrated hydrochloric acid and 25 ml of deionized water under heating conditions at 60 °C in a water bath to obtain an active component precursor solution; 6.055 g of cerium nitrate hexahydrate, 5.847 g of zirconium oxychloride octahydrate, and 1.042 g of neodymium nitrate hexahydrate were dissolved in 50 ml of a mixed acid solution under heating conditions at 60 °C in a water bath to obtain an auxiliary agent precursor solution, wherein the mixed acid solution was obtained by mixing nitric acid, concentrated hydrochloric acid, and deionized water in a volume ratio of 1:1:1; the active component precursor solution and the auxiliary agent precursor solution were mixed, and ultrasonically stirred at 25 °C for 1 h to obtain a mixed solution; 7.39 g of titanium dioxide (anatase type) and 7.39 g of γ-alumina were added to the mixed solution, and ultrasonically stirred to obtain a uniform mixture. The mixture was concentrated by rotary evaporation and then taken out. The catalyst was dried in an oven at ℃ for 3 h and calcined in a muffle furnace at 600℃ for 6 h to obtain a noble metal powder catalyst.

[0120] In this example, a monolithic supported noble metal catalyst 2# was finally prepared.

[0121] After testing, in the integral supported precious metal catalyst 2#, the coating mass was 8.0%±0.2% of the mass of the first carrier, the platinum loading was 75 mg / kg, and the neodymium loading was 0.15%.

[0122] Example 3

[0123] The method described in Example 1 was carried out, except that step (2) was as follows: preparation of precious metal powder catalyst: 0.084 g of chloroplatinic acid was dissolved in a solution of 25 ml of concentrated hydrochloric acid and 25 ml of deionized water under heating conditions at 60°C in a water bath to obtain an active component precursor solution; 6.055 g of cerium nitrate hexahydrate, 5.847 g of zirconium oxychloride octahydrate, and 0.521 g of neodymium nitrate hexahydrate were dissolved in 50 ml of a mixed acid solution under heating conditions at 60°C in a water bath to obtain an auxiliary agent precursor solution, wherein the mixed acid solution was obtained by mixing nitric acid, concentrated hydrochloric acid, and deionized water in a volume ratio of 1:1:1; the active component precursor solution and the auxiliary agent precursor solution were mixed, and ultrasonically stirred at 25°C for 1 h to obtain a mixed solution; 7.48 g of titanium dioxide (anatase type) and 7.48 g of titanium dioxide (anatase type) were added to the mixed solution. The γ-alumina was ultrasonically stirred and uniformly concentrated, and then taken out after being heat concentrated by a rotary evaporator. It was dried in an oven at 110° C. for 3 h, and calcined in a muffle furnace at 600° C. for 6 h to prepare a noble metal powder catalyst.

[0124] In this embodiment, a monolithic supported noble metal catalyst 3# was finally prepared.

[0125] After testing, in the integral supported precious metal catalyst 3#, the coating mass was 8.0%±0.2% of the mass of the first carrier, the platinum loading was 150 mg / kg, and the neodymium loading was 0.075%.

[0126] Example 4

[0127] The method described in Example 1 is carried out, except that step (2) is as follows: Preparation of precious metal powder catalyst: 0.126 g of chloroplatinic acid is dissolved in a solution of 25 ml of concentrated hydrochloric acid and 25 ml of deionized water under heating conditions at 60°C in a water bath to obtain an active component precursor solution; 6.055 g of cerium nitrate hexahydrate, 5.847 g of zirconium oxychloride octahydrate, and 1.042 g of neodymium nitrate hexahydrate are dissolved in 50 ml of a mixed acid solution under heating conditions at 60°C in a water bath to obtain an auxiliary agent precursor solution, wherein the mixed acid solution is obtained by mixing nitric acid, concentrated hydrochloric acid, and deionized water in a volume ratio of 1:1:1; the active component precursor solution and the auxiliary agent precursor solution are mixed, and ultrasonically stirred at 25°C for 1 h to obtain a mixed solution; 7.37 g of titanium dioxide (anatase type) and 7.37 g of γ-alumina are added to the mixed solution, ultrasonically stirred, and then concentrated by rotary evaporator and taken out, and dried in an oven at 110°C for 3 hours. h, and calcined at 600 °C in a muffle furnace for 6 h to prepare a noble metal powder catalyst.

[0128] In this embodiment, a monolithic supported noble metal catalyst 4# was finally prepared.

[0129] After testing, in the integral supported precious metal catalyst 4#, the coating mass was 8.0%±0.2% of the mass of the first carrier, the platinum loading was 225 mg / kg, and the neodymium loading was 0.15%.

[0130] Example 5

[0131] The method described in Example 1 was followed, except that step (2) was as follows: Preparation of precious metal powder catalyst: (1) 0.084 g of chloroplatinic acid was dissolved in a solution of 25 ml of concentrated hydrochloric acid and 25 ml of deionized water under heating conditions at 60°C in a water bath to obtain an active component precursor solution; 6.055 g of cerium nitrate hexahydrate, 5.847 g of zirconium oxychloride octahydrate, and 1.042 g of neodymium nitrate hexahydrate were dissolved in 50 ml of a mixed acid solution under heating conditions at 60°C in a water bath, wherein the mixed acid solution was obtained by mixing nitric acid, concentrated hydrochloric acid, and deionized water in a volume ratio of 1:1:1; the active component precursor solution and the auxiliary agent precursor solution were mixed, and ultrasonically stirred at 25°C for 1 h to obtain a mixed solution; 7.38 g of titanium dioxide (anatase type) and 7.38 g of γ-alumina were added to the mixed solution, and ultrasonically stirred to obtain a uniform mixture. The mixture was concentrated by rotary evaporation and then taken out and dried in an oven at 110°C for 3 h. h, and calcined at 800 °C in a muffle furnace for 6 h to prepare a noble metal powder catalyst.

[0132] In this embodiment, a monolithic supported noble metal catalyst 5# was finally prepared.

[0133] According to the test, in the monolithic supported precious metal catalyst 5#, the coating mass is 8.0%±0.2% of the mass of the first support, the platinum loading is 150 mg / kg, and the neodymium loading is 0.15%.

[0134] Example 6

[0135] The method described in Example 1 was followed, except that the coupling agent in step (3) was composed of silane coupling agent KH-792: titanate coupling agent = 9:1.

[0136] Example 7

[0137] The method described in Example 1 was followed, except that in step (3), the polyethylene fiber was replaced by an equal amount of hydroxypropyl methylcellulose.

[0138] Example 8

[0139] The method described in Example 1 was followed, except that step (3) was as follows: 72 ml of silica sol with a solid content of 20%, 0.9 g of hydroxypropyl methylcellulose, 0.9 g of polyethylene fiber, 1.26 g of silane coupling agent KH-560, and 0.54 g of sodium hexametaphosphate were added to 128 ml of water for dissolution, and ultrasonic stirring was performed at 25 °C for 1 h. 22 g of precious metal powder catalyst was added, and ultrasonic stirring was continued for 1 h. The mixture was then ground using a horizontal sand mill at a speed of 50 Hz for 90 min to prepare a coating slurry with a solid content of 20%.

[0140] Comparative Example 1

[0141] The method described in Example 1 was followed, except that step (2) was as follows: Preparation of precious metal powder catalyst: 0.084 g of chloroplatinic acid was dissolved in a solution of 25 ml of concentrated hydrochloric acid and 25 ml of deionized water under heating at 60°C in a water bath, and ultrasonically stirred at 25°C for 1 h to obtain an active component precursor solution;

[0142] 9.98 g of titanium dioxide (anatase type) and 9.98 g of γ-alumina were added to the active component precursor solution and ultrasonically stirred uniformly. The solution was thermally concentrated using a rotary evaporator and then taken out. The solution was dried in an oven at 110°C for 3 h and calcined in a muffle furnace at 800°C for 6 h to prepare a precious metal powder catalyst.

[0143] In this example, a monolithic supported noble metal catalyst D1 was prepared.

[0144] According to the test, in the monolithic supported precious metal catalyst D1, the coating mass was 8.0%±0.2% of the mass of the first support, and the platinum loading was 150 mg / kg.

[0145] Comparative Example 2

[0146] The method described in Example 1 was followed, except that step (2) was as follows: preparation of a noble metal powder catalyst: 0.084 g of chloroplatinic acid was dissolved in a solution of 25 ml of concentrated hydrochloric acid and 25 ml of deionized water under heating conditions at 60°C in a water bath, and ultrasonically stirred at 25°C for 1 h to obtain an active component precursor solution; 1.024 g of neodymium nitrate hexahydrate was dissolved in 25 ml of nitric acid and 25 ml of deionized water under heating conditions at 60°C in a water bath to obtain an auxiliary agent precursor solution; the active component precursor solution and the auxiliary agent precursor solution were mixed, and ultrasonically stirred at 25°C for 1 h to obtain a mixed solution; 9.78 g of titanium dioxide (anatase type) and 9.78 g of γ-alumina were added to the mixed solution, and ultrasonically stirred to obtain a uniform mixture. The mixture was concentrated by a rotary evaporator, taken out, dried in an oven at 110°C for 3 h, and calcined in a muffle furnace at 800°C for 6 h to obtain a noble metal powder catalyst.

[0147] In this embodiment, a monolithic supported noble metal catalyst D2 was prepared.

[0148] According to the test, in the monolithic supported precious metal catalyst D2, the coating mass is 8.0%±0.2% of the mass of the first support, the platinum loading is 150 mg / kg, and the neodymium loading is 0.15%.

[0149] Comparative Example 3

[0150] The method described in Example 1 was used for implementation, except that step (2) was as follows: preparation of precious metal powder catalyst: dissolving 0.084 g of chloroplatinic acid in a solution of 25 ml of concentrated hydrochloric acid and 25 ml of deionized water under heating conditions at 60°C in a water bath to obtain an active component precursor solution; dissolving 6.055 g of cerium nitrate hexahydrate and 1.042 g of neodymium nitrate hexahydrate in a solution of 25 ml of nitric acid and 25 ml of deionized water under heating conditions at 60°C in a water bath to obtain an auxiliary agent precursor solution; mixing the active component precursor solution and the auxiliary agent precursor solution, and stirring ultrasonically at 25°C for 1 h to obtain a mixed solution;

[0151] 8.61 g of titanium dioxide (anatase type) and 8.61 g of γ-alumina were added to the mixed solution and ultrasonically stirred until uniform. The mixture was concentrated by a rotary evaporator and then taken out. The mixture was dried in an oven at 110 °C for 4 h and calcined in a muffle furnace at 600 °C for 6 h to prepare a precious metal powder catalyst.

[0152] In this example, a monolithic supported noble metal catalyst D3 was prepared.

[0153] According to the test, in the monolithic supported precious metal catalyst D3, the coating mass is 8.0%±0.2% of the mass of the first support, the platinum loading is 150 mg / kg, and the neodymium loading is 0.15%.

[0154] Comparative Example 4

[0155] The method described in Example 1 was followed, except that step (2) was as follows: Preparation of precious metal powder catalyst: 0.084 g of chloroplatinic acid was dissolved in a solution of 25 ml of concentrated hydrochloric acid and 25 ml of deionized water under heating conditions at 60°C in a water bath to obtain an active component precursor solution; 5.847 g of zirconium oxychloride octahydrate and 1.042 g of neodymium nitrate hexahydrate were dissolved in 50 ml of a mixed acid solution under heating conditions at 60°C in a water bath to obtain an additive precursor solution, wherein the mixed acid solution was obtained by mixing nitric acid, concentrated hydrochloric acid and deionized water in a volume ratio of 1:1:1; the active component precursor solution and the additive precursor solution were mixed, and ultrasonically stirred at 25°C for 1 h to obtain a mixed solution; 8.61 g of titanium dioxide (anatase type) and 8.61 g of γ-alumina were added to the mixed solution, and ultrasonically stirred to obtain a uniform mixture. The mixture was concentrated by a rotary evaporator and then taken out and dried in an oven at 110°C for 4 h. h, and calcined at 600 °C in a muffle furnace for 6 h to prepare a noble metal powder catalyst.

[0156] In this example, a monolithic supported noble metal catalyst D4 was prepared.

[0157] According to the test, in the monolithic supported precious metal catalyst D4, the coating mass is 8.0%±0.2% of the mass of the first support, the platinum loading is 150 mg / kg, and the neodymium loading is 0.15%.

[0158] Comparative Example 5

[0159] The method described in Example 1 was followed, except that no coupling agent was added. In step (3), the coating slurry was prepared by adding 43.5 ml of aluminum sol with a solid content of 20%, 43.5 ml of silica sol with a solid content of 20%, 1.0 g of hydroxypropyl methylcellulose, 1.0 g of polyethylene fiber, and 0.6 g of sodium hexametaphosphate to 120 ml of water for dissolution, stirring the mixture ultrasonically at 25 °C for 1 h, adding 20 g of a precious metal powder catalyst, continuing ultrasonic stirring for 1 h, and grinding the mixture at 50 Hz for 90 min using a horizontal sand mill to prepare a coating slurry with a solid content of 20%.

[0160] In this example, a monolithic supported noble metal catalyst D5 was prepared.

[0161] Comparative Example 6

[0162] The method described in Example 1 was followed, except that no organic binder (hydroxypropyl methylcellulose and polyethylene fiber) was added, wherein step (3) was as follows: preparation of coating slurry: 45 ml of aluminum sol with a solid content of 20%, 45 ml of silica sol with a solid content of 20%, 1.4 g of coupling agent (silane coupling agent KH-560: silane coupling agent KH-792: titanate coupling agent = 5:4:1), and 0.6 g of sodium hexametaphosphate were added to 120 ml of water, and ultrasonically stirred at 25 °C for 1 h, 20 g of precious metal powder catalyst was added, ultrasonically stirred for 1 h, and then ground using a horizontal sand mill at 50 Hz for 90 min to prepare a coating slurry with a solid content of 20%.

[0163] In this example, a monolithic supported noble metal catalyst D6 was prepared.

[0164] Test Case

[0165] 1. Catalytic activity test

[0166] The supported noble metal catalysts prepared in the examples and comparative examples were subjected to ethylene catalytic oxidation tests. The experimental conditions were as follows: the catalytic reactor used a quartz tube with a diameter of 50 mm and a length of 500 mm, and the catalyst filling volume was 25 mm*25 mm*50 mm; the reaction gas conditions were 1000 ppm C2H4, 20% O2, and N2 balance gas, the total gas flow rate was about 1 L / min, and the catalytic combustion space velocity was 20000 h -1 The temperature was raised by an electric heating tube furnace, and the reaction temperature was measured by a K-type thermocouple. The C2H4 before and after treatment was quantitatively analyzed by a Fourier transform infrared spectrometer. The catalytic activity evaluation results of Examples 1-8 and Comparative Examples 1-6 are shown in Table 1 and Figure 1 As shown, Figure 1 In the figure, T90 represents the temperature at which the ethylene conversion rate reaches 90%.

[0167] 2. Shedding rate test

[0168] The supported precious metal catalyst samples prepared in the examples and comparative examples were cut into pieces of 25 mm * 25 mm * 50 mm in size, placed in an oven at 110 ° C. and dried for 30 min. They were taken out of the oven and naturally cooled to room temperature in a desiccator and then weighed M1. At a distance of 1.5 cm from the end face of the catalyst sample, the end face of the catalyst was evenly and slowly purged with 0.55 MPa oil-free compressed air until no obvious dust fell off. The mass of the sample after purging was tested, M2, where the shedding rate was equal to the ratio of the coating loss to the coating mass of the catalyst. The shedding rate was calculated as follows: μ = (M1-M2) / M3 × 100%, where μ is the shedding rate, M1 is the mass of the catalyst sample before the test; M2 is the mass of the catalyst sample after the test; and M3 is the coating mass in the catalyst. The test results are shown in Table 1.

[0169] Table 1

[0170]

[0171] The results in Table 1 show that the monolithic supported precious metal catalysts prepared in Examples 1-8 of the present invention can achieve an ethylene conversion rate of 90% below 210° C., while having a shedding rate of less than 3.2%, indicating good overall performance. This indicates that the monolithic supported precious metal catalysts obtained in the present invention have high catalytic activity for ethylene, a low shedding rate, and good overall performance due to the design of the auxiliary agent and the binder.

[0172] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A supported noble metal catalyst, characterized in that The catalyst comprises a first carrier and a coating layer supported on the first carrier, and a raw material composition for preparing the coating layer comprises a second carrier, an active component precursor, an auxiliary agent precursor, a binder and a dispersant; The first carrier is selected from any one of cordierite, mullite and cordierite-mullite; The second carrier is titanium dioxide and / or aluminum oxide; The active component precursor is selected from at least one of a platinum precursor, a palladium precursor and a rhodium precursor; The auxiliary agent precursor is a combination of a cerium precursor, a zirconium precursor and a neodymium precursor; The binder is a mixture of an organic binder, an inorganic binder and a coupling agent, wherein the organic binder is a mixture of hydroxypropyl methylcellulose and polyethylene fiber, the inorganic binder is selected from at least one of silica-alumina sol, aluminum sol, silica sol and phosphate-alumina sol, and the coupling agent is a silane coupling agent and / or a titanate coupling agent.

2. The supported noble metal catalyst according to claim 1, characterized in that The platinum precursor is platinum tetrachloride and / or chloroplatinic acid.

3. The supported noble metal catalyst according to claim 1 or 2, characterized in that The palladium precursor is palladium chloride and / or palladium nitrate.

4. The supported noble metal catalyst according to claim 1 or 2, characterized in that The rhodium precursor is rhodium trichloride and / or rhodium chloride.

5. The supported noble metal catalyst according to claim 1, characterized in that The cerium precursor is selected from at least one of cerium nitrate, cerium sulfate and cerium chloride.

6. The supported noble metal catalyst according to claim 1 or 5, characterized in that The zirconium precursor is selected from at least one of zirconium oxychloride, zirconium sulfate and zirconium nitrate.

7. The supported noble metal catalyst according to claim 1 or 5, characterized in that The neodymium precursor is selected from at least one of neodymium nitrate, neodymium oxalate and neodymium sulfate.

8. The supported noble metal catalyst according to claim 1, characterized in that The dispersant is selected from at least one of sodium tripolyphosphate, sodium hexametaphosphate, sodium stearate and sodium citrate.

9. The supported noble metal catalyst according to claim 1, characterized in that Based on the total weight of the supported noble metal catalyst, the content of the active component is 100-300 mg / kg.

10. The supported noble metal catalyst according to claim 1 or 9, characterized in that In the supported noble metal catalyst, the weight ratio of the active component to cerium, zirconium and neodymium is 1:50-80:50-80:5-20.

11. A method for preparing a supported noble metal catalyst, characterized in that: The method comprises the following steps: (1) mixing an active component precursor solution and an auxiliary agent precursor solution to obtain a mixed solution, impregnating a second support in the mixed solution, and then drying and calcining to obtain a noble metal powder catalyst; (2) mixing a binder, a dispersant, water, and a precious metal powder catalyst to obtain a coating slurry; (3) coating the coating slurry on the pretreated first carrier, and then drying and calcining to obtain a supported noble metal catalyst; The first carrier is selected from any one of cordierite, mullite, and cordierite-mullite; The second carrier is titanium dioxide and / or aluminum oxide; The active component precursor is selected from at least one of a platinum precursor, a palladium precursor and a rhodium precursor; The auxiliary agent precursor is a combination of a cerium precursor, a zirconium precursor and a neodymium precursor; The binder is a mixture of an organic binder, an inorganic binder and a coupling agent, wherein the organic binder is a mixture of hydroxypropyl methylcellulose and polyethylene fiber, the inorganic binder is selected from at least one of silica-alumina sol, aluminum sol, silica sol and phosphate-alumina sol, and the coupling agent is a silane coupling agent and / or a titanate coupling agent.

12. The method according to claim 11, characterized in that In step (1), based on the total weight of the noble metal powder catalyst, the mass fraction of the active component is 0.05-0.5%, and the mass fraction of the auxiliary agent is 2-40%.

13. The method according to claim 11 or 12, characterized in that In step (2), the weight ratio of the noble metal powder catalyst, binder, dispersant and water is 10:2-38:0.005-8:10-150.

14. The method according to claim 11, characterized in that In step (1), the drying conditions include: a temperature of 90 to 120° C. and a drying time of 2 to 4 hours; In step (1), the calcination conditions include: a temperature of 500 to 700° C. and a time of 4 to 7 hours; In step (3), the drying conditions include: a temperature of 90 to 120° C. and a drying time of 1 to 2 hours; In step (3), the calcination conditions include: a temperature of 500 to 800° C. and a calcination time of 4 to 7 hours.

15. The method according to claim 11, characterized in that The preparation process of the pretreated first carrier includes: washing the first carrier with water and acid, and then drying it.

16. The method according to claim 11 or 15, characterized in that The water absorption rate of the first carrier after pretreatment is 20-50%, and the specific surface area is 10-30m 2 / g.

17. Use of the supported noble metal catalyst according to any one of claims 1 to 10 or the supported catalyst prepared by the method according to any one of claims 11 to 16 in the catalytic oxidation of volatile organic compounds.

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