Preparation method of supported bimetallic catalyst and its application in treatment of TDI wastewater

Abstract

The present invention provides a preparation method of a supported bimetallic catalyst and its application in the treatment of TDI wastewater. The catalyst is a palladium and molybdenum supported catalyst. The catalyst of the present invention has excellent catalytic activity and can efficiently catalyze the diazotization and coupling reactions of organic substances in wastewater; the epoxy acrylate resin can improve the adhesion of the metal active components on the carrier, and at the same time can adsorb organic substances, accelerating the cross-linking of azo compounds and other organic substances to form organic precipitates; compared with other methods in the industry, the TDI wastewater treatment method of the present invention has the advantages of high treatment efficiency, mild conditions, low cost and simple process.

Description

Technical Field

[0001] The present invention belongs to the technical field of TDI wastewater treatment, and particularly relates to a preparation method of a supported bimetallic catalyst and its application in TDI wastewater treatment. Background Art

[0002] In the production process of toluene diisocyanate (TDI), two alkaline wastewaters, namely nitrification wastewater and hydrogenation wastewater, are mainly generated. Toluene is nitrified to obtain crude dinitrotoluene, and the crude dinitrotoluene is washed with acid, alkali, and neutral water to obtain dinitrotoluene products and generate nitrification wastewater. While toluenediamine is produced by hydrogenating the dinitrotoluene product, hydrogenation wastewater is generated at the same time. The nitrification wastewater and hydrogenation wastewater are collectively referred to as TDI wastewater. Among them, the nitrification wastewater contains a large amount of nitrobenzene and phenol substances and a small amount of nitrite, and the hydrogenation wastewater contains a large amount of aniline substances. These two wastewaters are characterized by poor biodegradability, difficult degradation, and high biological toxicity, and cannot be degraded by simple biochemical treatment techniques. Therefore, it is necessary to pretreat the TDI wastewater to reduce the biological toxicity and improve the biodegradability.

[0003] Patent CN 210974232U uses microelectrolysis + Fenton oxidation + neutralization flocculation precipitation technology to pretreat TDI wastewater. Although the biodegradability of the wastewater is improved, due to the relatively high cost of Fenton reagent, the cost of treating high-concentration organic wastewater is relatively high. In addition, advanced oxidation methods such as supercritical oxidation, photochemical oxidation, and electrocatalytic oxidation also have problems such as high treatment cost, difficult operation, and difficulty in industrialization. When using activated carbon adsorption to treat TDI wastewater, due to the high content of organic matter in the wastewater, the amount of activated carbon used is huge, the number of regenerations in industrial applications is small, the treatment cost of a large amount of waste activated carbon is high, and the waste activated carbon belongs to hazardous waste. Patent CN 103288283A uses macroporous styrene-based adsorption resin to adsorb DNT and uses organic solvents to desorb and regenerate the resin to recover DNT, but the resin used has the disadvantages of poor selectivity, low adsorption capacity, and high energy consumption for desorbent regeneration.

[0004] Based on this, the treatment methods of TDI wastewater in the prior art still have great limitations, with high treatment cost and poor effect. How to create a TDI wastewater treatment method with simple treatment method, high recovery rate, and good treatment effect has become an urgent problem to be solved in the industry. Summary of the Invention

[0005] In view of the above problems, the purpose of the present invention is to provide a preparation method of a supported bimetallic catalyst and its application in TDI wastewater treatment. The supported catalyst of the present invention can efficiently catalyze the diazotization and coupling reactions of organic substances in TDI wastewater, and at the same time promote the formation of organic substance precipitation, reduce the content of organic substances in TDI wastewater, and improve the recovery rate.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A preparation method of a supported bimetallic catalyst, comprising the following steps:

[0008] Step 1: Mix a silicon source and an optional titanium source with an alkali solution, wash with deionized water until neutral, dry, and calcine at a high temperature under an inert gas atmosphere to prepare a catalyst support.

[0009] Step 2: Mix the catalyst support prepared in Step 1 with a palladium salt solution, a molybdate solution, and a pore-forming agent in a certain proportion, adjust the pH to 7-10, react in a high-pressure hydrothermal autoclave, and separate the solid and liquid.

[0010] Step 3: Calcinate the solid obtained in Step 2 at a high temperature under an inert gas atmosphere, wash with deionized water until neutral, and dry.

[0011] Step 4: Mix and impregnate the product obtained in Step 3 with epoxy acrylate resin and oscillate for a certain time, then dry to obtain a supported catalyst.

[0012] Preferably, the silicon source in Step 1 is one or more of kaolin, bentonite, solid silica gel, and white carbon black.

[0013] Preferably, the titanium source is one or more of titanium dioxide, titanium sulfate, titanium oxysulfate, and titanium tetrachloride, and the addition amount of titanium element in the titanium source is 1-10% of the mass of the silicon source.

[0014] Preferably, the silicon source and the titanium source can be ground to 100 mesh to 300 mesh first and then added to the alkali solution.

[0015] Preferably, the calcination temperature in Step 1 is 300°C to 1200°C, the calcination time is 0.5 h to 10 h, the drying temperature is 90°C to 110°C, and the drying time is 5 h - 24 h.

[0016] Preferably, the alkali in Step 1 is one or more of sodium hydroxide and potassium hydroxide.

[0017] Preferably, the inert gas is a noble gas or nitrogen.

[0018] Preferably, the palladium salt described in step 2 is one or more of palladium chloride, palladium acetate, and bis(triphenylphosphine)palladium dichloride, and the palladium metal loading is 0.1% - 5% of the mass of the silicon source; the molybdate is one or more of sodium molybdate, potassium molybdate, and ammonium molybdate, and the molybdenum metal loading is 0.1% - 6% of the mass of the silicon source; the pore-forming agent is one or more of polyquaternium-10, N,N-dimethyl-N-octyl-1-decylammonium chloride, octadecyl diethanolamine, and polyvinyl alcohol, and the addition amount of the pore-forming agent is 1% - 20% of the mass of the silicon source; the reaction temperature of the hydrothermal reaction is 110°C - 230°C, and the hydrothermal reaction time is 5h - 20h; in step 2, the pH value can be adjusted with an alkali solution, such as potassium hydroxide or sodium hydroxide solution.

[0019] Preferably, the calcination temperature in step 3 is 300°C - 1200°C, the calcination time is 0.5h - 10h, the drying temperature is 90 - 110°C, and the drying time is 5h - 24h.

[0020] Preferably, the epoxy acrylate resin described in step 4 is one or more of bisphenol A epoxy acrylate resin, phenolic epoxy acrylate resin, and epoxidized soybean oil acrylate resin, and the addition amount of the epoxy acrylate resin is 100% - 500% of the mass of the silicon source; the impregnation temperature is 30°C - 80°C, and the impregnation time is 3h - 5h.

[0021] Preferably, in step 4, the drying temperature is 90°C - 110°C, and the drying time is 5h - 24h.

[0022] The present invention also provides the application of the supported bimetallic catalyst prepared by the preparation method in the treatment of TDI wastewater.

[0023] A method for treating TDI wastewater includes the following steps:

[0024] a) Acid adjustment: Mix nitrification wastewater and hydrogenation wastewater in a mass ratio of 10:1 - 1:10, and adjust the pH value of the mixed wastewater to 2 - 7 with an acid.

[0025] b) Reaction: Add a catalyst and sodium nitrite, and stir at 10°C - 90°C for 2min - 60min.

[0026] c) Precipitation: Adjust the pH value of the wastewater after the reaction to 8 - 11, add a flocculant, stir, and let it stand for stratification. The upper layer is the wastewater, and the lower layer is the organic matter precipitate and the catalyst.

[0027] d) Filtration: Filter the upper layer of wastewater. The filtrate is the treated wastewater, and the filter residue is the organic matter precipitate and the catalyst; further screen and separate the organic matter precipitate and the catalyst. The coarse particles are the organic matter precipitate, and the fine particles are the catalyst. The treated wastewater and the organic matter precipitate are respectively subjected to subsequent treatment.

[0028] Preferably, in step a), the nitrification wastewater is the wastewater generated from the pickling and alkali washing after the crude dinitrotoluene prepared by toluene nitrification, and the hydrogenation wastewater is the wastewater generated from the hydrogenation of dinitrotoluene to prepare toluenediamine.

[0029] Preferably, in step b), the addition amount of the catalyst is 0.5% - 30% of the total mass of the nitrification wastewater and the hydrogenation wastewater.

[0030] Preferably, in step b), sodium nitrite can be optionally added, and the mass ratio of the addition amount of sodium nitrite to the total mass of the nitrification wastewater and the hydrogenation wastewater is 1:500 - 1:5000.

[0031] Preferably, the mass ratio of the addition amount of the flocculant to the total mass of the nitrification wastewater and the hydrogenation wastewater is 1:2000 - 1:200000.

[0032] Preferably, the flocculant in step c) is one or more of polyacrylamide, acrylic acid - acrylamide copolymer, polyaluminum chloride, polyferric sulfate, polyferric chloride, and polyaluminum sulfate. The flocculant can be configured into a 0.1wt% - 30wt% solution and then added to the TDI wastewater.

[0033] Preferably, after adding the flocculant in step c), it is stirred at 10°C - 40°C for 2min - 60min, and after standing for 10min - 240min, it is layered. Preferably, in step c), a 5 - 50wt% sodium hydroxide solution can be used to adjust the pH value.

[0034] Preferably, in step d), a filter with 200 - 500 meshes can be used to filter and separate the filtrate and the filter residue; a sieve with 80 - 100 meshes can be used to screen and separate the organic matter precipitate and the catalyst.

[0035] The TDI wastewater mainly contains nitrobenzene - like, phenol - like, and aniline - like substances. The nitrite in the TDI nitrification wastewater is converted into nitrous acid after acid adjustment, which can react with aniline - like substances to form diazonium salts, but this reaction proceeds very slowly and cannot meet the needs of industrial wastewater treatment. Under the catalysis of the catalyst of the present invention, aniline - like substances in the TDI wastewater can react with nitrous acid and sulfuric acid to efficiently form diazonium sulfate salts. Since diazonium sulfate salts are less stable, they will further react with aniline - like substances or phenol - like substances to form azo compounds. In the presence of the catalyst of the present invention, azo compounds will cross - link with other organic substances in the wastewater to form macromolecular organic matter precipitates, which can effectively reduce the COD content in the wastewater.

[0036] Epoxy acrylate resin contains various polar groups such as epoxy groups and has excellent adhesion, corrosion resistance and stability. The catalyst impregnated epoxy resin of the present invention helps to improve the adhesion of palladium-molybdenum metal active components on the carrier, reduce the loss rate of precious metals and improve the catalyst life; on the other hand, it is found that due to its polar groups, it can adsorb azo compounds and other organic substances, accelerate the cross-linking of the two on the catalyst, and promote the formation of macromolecular organic precipitates.

[0037] The significant advantages of the present invention are as follows:

[0038] 1) The catalyst of the present invention is loaded with palladium-molybdenum bimetals and has good catalytic activity, and can efficiently catalyze the diazotization and coupling reactions of organic substances in wastewater. 2) Epoxy acrylate resin can improve the adhesion of metal active components on the catalyst carrier, and at the same time can adsorb organic substances, accelerate the cross-linking of azo compounds and other organic substances to form organic precipitates. 3) Compared with other methods, the TDI wastewater treatment method first proposed in the present invention has the advantages of high treatment efficiency, mild conditions, low cost and simple process. Specific embodiments

[0039] To further disclose rather than limit the present invention, the following examples are used to further illustrate the present invention in detail.

[0040] Kaolin was purchased from Shanghai Yuanye Bio-Technology Co., Ltd., CAS No. 1332-58-7, product number S30588. Bentonite was purchased from Shanghai Yuanye Bio-Technology Co., Ltd., CAS No. 1302-78-9, product number S30525

[0041] Polyquaternium-10 was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with CAS No. 81859-24-7 and product number P341830. Octadecyldiethanolamine was purchased from Shanghai Yuanye Bio-Technology Co., Ltd., with CAS No. 10213-78-2 and product number S90343. Polyvinyl alcohol was purchased from Shanghai Yuanye Bio-Technology Co., Ltd., with CAS No. 9002-89-5 and product number S3016. It was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with CAS No. 81859-24-7 and product number P341830. Polyacrylamide was purchased from Shanghai Yuanye Bio-Technology Co., Ltd., with CAS No. 9003-05-8 and product number S31321. Polyaluminum ferric sulfate was purchased from Henan Fangyuan Environmental Protection Materials Co., Ltd., with CAS No. 35139-28-7. Polyaluminum chloride was purchased from Hubei Chengfeng Chemical Co., Ltd., with CAS No. 1327-41-9 and product number 002. Bisphenol A epoxy acrylate resin was purchased from Dow Chemical Company, USA, with grade DER331. Phenolic epoxy acrylate resin was purchased from Huainan Cody Chemical Technology Co., Ltd., with CAS No. 71281-65-7. Epoxidized soybean oil acrylate resin was purchased from Wuhan Karnos Biotechnology Co., Ltd., with CAS No. 9172-14-4.

[0042] The nitrification wastewater and hydrogenation wastewater come from Wanhua Chemical Group Co., Ltd. Toluene and nitric acid react under the condition of 45 °C and are catalyzed by 74% sulfuric acid to generate mononitrotoluene. Mononitrotoluene and nitric acid react under the condition of 65 °C and are catalyzed by 78% sulfuric acid to generate crude dinitrotoluene. The crude dinitrotoluene is washed successively with 2% nitric acid solution and 5% sodium hydroxide solution. After the alkali solution washing, the nitrification wastewater is taken out from the upper layer after separation by a static separator, and the organic matter taken out from the lower layer is washed with deionized water to obtain the dinitrotoluene product; the dinitrotoluene product is hydrogenated at 0.9 MPaa and 110 °C to generate a mixture of toluenediamine and hydrogenation wastewater. The mixture is separated by a distillation column, controlling the top pressure at 22 kPaa and the bottom temperature at 75 °C. The dehydrated crude toluenediamine is taken out from the bottom of the column, and the hydrogenation wastewater is taken out from the top of the column.

[0043] Determination of COD (Chemical Oxygen Demand): The COD value was determined by the dichromate method (National Standard HJ 828-2017 "Determination of Chemical Oxygen Demand in Water - Dichromate Method").

[0044] Example 1:

[0045] Mix 100 g of kaolin with 15 g of titanium tetrachloride, grind the mixed particles to 200 mesh, mix the ground particles with 500 g of 32% sodium hydroxide solution, wash with deionized water until neutral, dry at 110 °C for 10 h, and calcine the mixture in a nitrogen atmosphere at 600 °C for 3 h to obtain a catalyst support. Mix the catalyst support with 80 g of 5% palladium chloride solution, 85 g of 5% sodium molybdate solution and 10 g of polyquaternium-10, adjust the pH to 8 with 32% sodium hydroxide solution, react in a 160 °C high-pressure hydrothermal reactor for 10 h, and separate the solid and liquid. Calcinate the separated solid in a nitrogen atmosphere at 600 °C for 3 h, wash with deionized water until neutral, and dry at 110 °C for 10 h. Impregnate the dried product with 200 g of bisphenol A epoxy acrylate resin and shake for 4 h, then dry at 110 °C for 10 h to obtain catalyst A.

[0046] Mix 1000 g of nitrification wastewater and 1000 g of hydrogenation wastewater, and adjust the pH of the mixed wastewater to 5 with 78% sulfuric acid solution. Add 300 g of catalyst A and 1 g of sodium nitrite to the acid-adjusted wastewater, and stir at a reaction temperature of 20 °C for 5 min. Adjust the pH of the reacted wastewater to 8 with 32% sodium hydroxide solution, add 50 g of 0.2% polyacrylamide solution, stir at 20 °C for 5 min, let it stand for 40 min and then layer. The upper layer is wastewater, and the lower layer is organic matter precipitate and catalyst. Filter the upper layer of wastewater through a 400-mesh filter. The filtrate is the treated wastewater, and the filter residue is a mixture of organic matter precipitate and catalyst. Further screen and separate the organic matter precipitate and catalyst with a 90-mesh sieve. The coarse particles are organic matter precipitate, and the fine particles are catalyst. Carry out subsequent treatment on the treated wastewater and organic matter precipitate respectively. The COD contents of the TDI wastewater before and after treatment are shown in Table 1.

[0047] Example 2:

[0048] Mix 100 g of kaolin with 5 g of titanium tetrachloride, grind the mixed particles to 200 mesh, mix the ground particles with 500 g of 32% sodium hydroxide solution, wash with deionized water until neutral, dry at 110 °C for 10 h, and calcine the mixture in a nitrogen atmosphere at 600 °C for 3 h to obtain a catalyst support. Mix the catalyst support with 5 g of 5% palladium chloride solution, 6 g of 5% sodium molybdate solution and 2 g of octadecyl diethanolamine, adjust the pH to 8 with 32% sodium hydroxide solution, react in a 160 °C high-pressure hydrothermal reactor for 10 h, and separate the solid and liquid. Calcinate the separated solid in a nitrogen atmosphere at 600 °C for 3 h, wash with deionized water until neutral, and dry at 110 °C for 10 h. Impregnate the dried product with 150 g of epoxidized soybean oil acrylate resin and shake for 4 h, then dry at 110 °C for 10 h to obtain catalyst B.

[0049] Mix 100 g of nitrification wastewater and 1000 g of hydrogenation wastewater, and adjust the pH value of the mixed wastewater to 2 with 78% sulfuric acid solution. Add 10 g of catalyst B and 0.3 g of sodium nitrite to the acid-adjusted wastewater, and stir for 5 min at a reaction temperature of 20°C. Adjust the pH value of the reacted wastewater to 8 with 32% sodium hydroxide solution, and add 0.1 g of 10% polyferric chloride solution. Stir for 5 min at a temperature of 20°C, let it stand for 40 min and then separate into layers. The upper layer is wastewater, and the lower layer is organic matter precipitate and catalyst. Filter the upper-layer wastewater through a 400-mesh filter. The filtrate is the treated wastewater, and the filter residue is a mixture of organic matter precipitate and catalyst. Further screen and separate the organic matter precipitate and catalyst with a 90-mesh sieve. The coarse particles are organic matter precipitate, and the fine particles are catalyst. Conduct subsequent treatments on the treated wastewater and organic matter precipitate respectively. The COD contents of the TDI wastewater before and after treatment are shown in Table 1.

[0050] Example 3:

[0051] Mix 100 g of bentonite and 36 g of titanium tetrachloride, grind the mixed particles to 200 mesh, mix the ground particles with 500 g of 32% sodium hydroxide solution, wash with deionized water until neutral, and dry at 110°C for 10 h. Calcinate the mixture in a nitrogen atmosphere at 600°C for 3 h to obtain a catalyst support. Mix the catalyst support with 160 g of 5% palladium chloride solution, 250 g of 5% sodium molybdate solution and 18 g of polyvinyl alcohol, adjust the pH to 8 with 32% sodium hydroxide solution, and react in a high-pressure hydrothermal autoclave at 160°C for 10 h to separate the solid and liquid. Calcinate the separated solid in a nitrogen atmosphere at 600°C for 3 h, wash with deionized water until neutral, and dry at 110°C for 10 h. Impregnate the dried product with 450 g of phenolic epoxy acrylate resin and oscillate for 4 h, and dry at 110°C for 10 h to obtain catalyst C.

[0052] Mix 1000 g of nitrification wastewater and 100 g of hydrogenation wastewater, and adjust the pH value of the mixed wastewater to 7 with 78% sulfuric acid solution. Add 320 g of catalyst C and 2 g of sodium nitrite to the acid-adjusted wastewater, and stir for 5 min at a reaction temperature of 20°C. Adjust the pH value of the reacted wastewater to 9 with 32% sodium hydroxide solution, and add 5 g of 10% polyferric sulfate solution. Stir for 5 min at a temperature of 20°C, let it stand for 40 min and then separate into layers. The upper layer is wastewater, and the lower layer is organic matter precipitate and catalyst. Filter the upper-layer wastewater through a 400-mesh filter. The filtrate is the treated wastewater, and the filter residue is a mixture of organic matter precipitate and catalyst. Further screen and separate the organic matter precipitate and catalyst with a 90-mesh sieve. The coarse particles are organic matter precipitate, and the fine particles are catalyst. Conduct subsequent treatments on the treated wastewater and organic matter precipitate respectively. The COD contents of the TDI wastewater before and after treatment are shown in Table 1.

[0053] Example 4:

[0054] Mix 100 g of kaolin with 36 g of titanium tetrachloride, grind the mixed particles to 200 mesh, mix the ground particles with 500 g of 32% sodium hydroxide solution, wash with deionized water until neutral, dry at 110 °C for 10 h, and calcine the mixture in a nitrogen atmosphere at 600 °C for 3 h to obtain a catalyst support. Mix the catalyst support with 110 g of 5% palladium chloride solution, 100 g of 5% sodium molybdate solution and 18 g of polyquaternium-10, adjust the pH to 8 with 32% sodium hydroxide solution, react in a high-pressure hydrothermal autoclave at 160 °C for 10 h, and separate the solid and liquid. Calcinate the separated solid in a nitrogen atmosphere at 600 °C for 3 h, wash with deionized water until neutral, and dry at 110 °C for 10 h. Impregnate the dried product with 300 g of bisphenol A type epoxy acrylate resin and oscillate for 4 h, and dry at 110 °C for 10 h to obtain catalyst D.

[0055] Mix 1000 g of nitrification wastewater and 1000 g of hydrogenation wastewater, and adjust the pH of the mixed wastewater to 6 with 78% sulfuric acid solution. Add 300 g of catalyst D and 2 g of sodium nitrite to the acid-adjusted wastewater, and stir at a reaction temperature of 20 °C for 5 min. Adjust the pH of the reacted wastewater to 8 with 32% sodium hydroxide solution, add 80 g of 0.2% polyacrylamide solution, stir at 20 °C for 5 min, let stand for 40 min and then layer. The upper layer is wastewater, and the lower layer is organic matter precipitate and catalyst. Filter the upper layer of wastewater through a 400-mesh filter. The filtrate is the treated wastewater, and the filter residue is a mixture of organic matter precipitate and catalyst. Further screen and separate the organic matter precipitate and catalyst with a 90-mesh sieve. The coarse particles are organic matter precipitate, and the fine particles are catalyst. Carry out subsequent treatment on the treated wastewater and organic matter precipitate respectively. The COD content of the TDI wastewater before and after treatment is shown in Table 1.

[0056] Example 5:

[0057] Mix 100 g of bentonite with 36 g of titanium tetrachloride, grind the mixed particles to 200 mesh, mix the ground particles with 500 g of 32% sodium hydroxide solution, wash with deionized water until neutral, dry at 110 °C for 10 h, and calcine the mixture in a nitrogen atmosphere at 600 °C for 3 h to obtain a catalyst support. Mix the catalyst support with 110 g of 5% palladium chloride solution, 100 g of 5% sodium molybdate solution and 18 g of polyvinyl alcohol, adjust the pH to 8 with 32% sodium hydroxide solution, react in a high-pressure hydrothermal autoclave at 160 °C for 10 h, and separate the solid and liquid. Calcinate the separated solid in a nitrogen atmosphere at 600 °C for 3 h, wash with deionized water until neutral, and dry at 110 °C for 10 h. Impregnate the dried product with 300 g of phenolic epoxy acrylate resin and oscillate for 4 h, and dry at 110 °C for 10 h to obtain catalyst E.

[0058] Mix 1000 g of nitrified wastewater and 1000 g of hydrogenated wastewater, and adjust the pH value of the mixed wastewater to 6 with 78% sulfuric acid solution. Add 300 g of catalyst E and 2 g of sodium nitrite to the acid-adjusted wastewater, and stir for 5 min at a reaction temperature of 20 °C. Adjust the pH value of the reacted wastewater to 8 with 32% sodium hydroxide solution, and add 1.6 g of 10% polyferric sulfate solution. Stir for 5 min at a temperature of 20 °C, let it stand for 40 min and then separate the layers. The upper layer is wastewater, and the lower layer is organic matter precipitate and catalyst. Filter the upper layer of wastewater through a 400-mesh filter. The filtrate is the treated wastewater, and the filter residue is a mixture of organic matter precipitate and catalyst. Further screen and separate the organic matter precipitate and catalyst with a 90-mesh sieve. The coarse particles are organic matter precipitate, and the fine particles are catalyst. Carry out subsequent treatment on the treated wastewater and organic matter precipitate respectively. The COD contents of the TDI wastewater before and after treatment are shown in Table 1.

[0059] Comparative Example 1:

[0060] Mix 100 g of kaolin with 36 g of titanium tetrachloride, grind the mixed particles to 200 mesh, mix the ground particles with 500 g of 32% sodium hydroxide solution, wash with deionized water until neutral, and dry at 110 °C for 10 h. Calcinate the mixture in a nitrogen atmosphere at 600 °C for 3 h to obtain a catalyst support. Mix the catalyst support with 100 g of 5% sodium molybdate solution and 18 g of polyquaternium-10, adjust the pH to 8 with 32% sodium hydroxide solution, and react in a high-pressure hydrothermal autoclave at 160 °C for 10 h to separate the solid and liquid. Calcinate the separated solid in a nitrogen atmosphere at 600 °C for 3 h, wash with deionized water until neutral, and dry at 110 °C for 10 h. Mix and impregnate the dried product with 300 g of bisphenol A type epoxy acrylate resin and oscillate for 4 h, and dry at 110 °C for 10 h to obtain catalyst F.

[0061] Treat the mixed wastewater of 1000 g of nitrified wastewater and 1000 g of hydrogenated wastewater by the same method as in Example 4, the difference is that the catalyst added is catalyst F. The COD contents of the TDI wastewater before and after treatment are shown in Table 1.

[0062] Comparative Example 2:

[0063] Mix 100 g of bentonite with 36 g of titanium tetrachloride, grind the mixed particles to 200 mesh, mix the ground particles with 500 g of 32% sodium hydroxide solution, wash with deionized water until neutral, dry at 110 °C for 10 h, and calcine the mixture in a nitrogen atmosphere at 600 °C for 3 h to obtain a catalyst support. Mix the catalyst support with 110 g of 5% palladium chloride solution and 18 g of polyvinyl alcohol, adjust the pH to 8 with 32% sodium hydroxide solution, react in a high-pressure hydrothermal autoclave at 160 °C for 10 h, and separate the solid and liquid. Calcinate the separated solid in a nitrogen atmosphere at 600 °C for 3 h, wash with deionized water until neutral, and dry at 110 °C for 10 h. Impregnate the dried product with 300 g of phenolic epoxy acrylate resin and oscillate for 4 h, and dry at 110 °C for 10 h to obtain catalyst G.

[0064] Treat the mixed wastewater of 1000 g of nitrification wastewater and 1000 g of hydrogenation wastewater using the same method as in Example 5, with the difference that the catalyst added is catalyst G. The COD content of the TDI wastewater before and after treatment is shown in Table 1.

[0065] Comparative Example 3:

[0066] No catalyst was used for the treatment of TDI wastewater.

[0067] Mix 1000 g of nitrification wastewater and 1000 g of hydrogenation wastewater, and adjust the pH of the mixed wastewater to 6 with 78% sulfuric acid solution. Add 2 g of sodium nitrite to the acid-adjusted wastewater, and stir at a reaction temperature of 20 °C for 5 min. Adjust the pH of the reacted wastewater to 8 with 32% sodium hydroxide solution, and add 1.6 g of 10% polyferric sulfate solution, stir at 20 °C for 5 min, let it stand for 40 min and then layer. The upper layer is wastewater, and the lower layer is organic matter precipitate and catalyst. Filter the upper layer of wastewater through a 400-mesh filter. The filtrate is the treated wastewater, and the filter residue is the organic matter precipitate. The treated wastewater and the organic matter precipitate are respectively subjected to subsequent treatment. The COD content of the TDI wastewater before and after treatment is shown in Table 1.

[0068] Table 1 Ability to treat TDI wastewater under different conditions

[0069]

[0070] The above are only the preferred embodiments of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope covered by the present invention.

Claims

1. A preparation method of a supported bimetallic catalyst, characterized in that, It includes the following steps: Step 1: Mix a silicon source and an optional titanium source with an alkali solution, wash with deionized water until neutral, dry, and calcine at a high temperature under an inert gas atmosphere to prepare a catalyst support; Step 2: Mix the catalyst support prepared in Step 1 with a palladium salt solution, a molybdate solution, and a pore-forming agent in a certain proportion, adjust the pH to 7-10, react in a high-pressure hydrothermal autoclave, and separate the solid and liquid; Step 3: Calcine the solid obtained in Step 2 at a high temperature under an inert gas atmosphere, wash with deionized water until neutral, and dry; Step 4: Mix and impregnate the product obtained in Step 3 with an epoxy acrylate resin and oscillate for a certain time, then dry to obtain a supported catalyst.

2. The preparation method according to claim 1, characterized in that, The silicon source described in Step 1 is one or more of kaolin, bentonite, solid silica gel, and white carbon black.

3. The preparation method according to claim 2, wherein The titanium source is one or more of titanium dioxide, titanium sulfate, titanium oxysulfate, and titanium tetrachloride.

4. The preparation method according to claim 1, characterized in that, The addition amount of titanium element in the titanium source is 1-10% of the mass of the silicon source.

5. The preparation method according to claim 1, wherein The calcination temperature in Step 1 is 300°C-1200°C, the calcination time is 0.5h-10h, the drying temperature is 90°C-110°C, and the drying time is 5h-24h.

6. The preparation method according to claim 1, wherein The alkali in Step 1 is one or more of sodium hydroxide and potassium hydroxide.

7. The preparation method according to claim 1, characterized in that The inert gas is a noble gas or nitrogen.

8. The preparation method according to claim 1, characterized in that, The palladium salt described in Step 2 is one or more of palladium chloride, palladium acetate, and bis(triphenylphosphine)palladium dichloride, and the palladium metal loading is 0.1%-5% of the mass of the silicon source.

9. The preparation method according to claim 1, characterized in that, The molybdate is one or more of sodium molybdate, potassium molybdate, and ammonium molybdate, and the molybdenum metal loading is 0.1%-6% of the mass of the silicon source.

10. The preparation method according to claim 1, characterized in that, The pore-forming agent is one or more of polyquaternium-10, N,N-dimethyl-N-octyl-1-decanaminium chloride, octadecyl diethanolamine, and polyvinyl alcohol, and the addition amount of the pore-forming agent is 1-20% of the mass of the silicon source.

11. The preparation method according to claim 1, characterized in that, The reaction temperature of the hydrothermal reaction is 110°C-230°C, the hydrothermal reaction time is 5h-20h; in Step 2, the pH value is adjusted with an alkali solution.

12. The preparation method according to claim 1, characterized in that, The calcination temperature in Step 3 is 300°C-1200°C, the calcination time is 0.5h-10h, the drying temperature is 90-110°C, and the drying time is 5h-24h.

13. The preparation method according to claim 1, characterized in that, The epoxy acrylate resin described in Step 4 is one or more of bisphenol A type epoxy acrylate resin, phenolic epoxy acrylate resin, and epoxidized oil acrylated soybean oil resin.

14. The preparation method according to claim 1, wherein The addition amount of the epoxy acrylate resin is 100%-500% of the mass of the silicon source.

15. The preparation method according to claim 1, characterized in that, The impregnation temperature in Step 4 is 30°C-80°C, and the impregnation time is 3h-5h.

16. The preparation method according to claim 1, wherein, In Step 4, the drying temperature is 90°C-110°C, and the drying time is 5h-24h.

17. Application of the supported bimetallic catalyst prepared by the preparation method according to any one of claims 1-16 in the treatment of TDI wastewater, wherein the TDI wastewater is nitrification wastewater and hydrogenation wastewater.

18. A method for treating TDI wastewater, including the following steps: a) Acid adjustment: Mix nitrification wastewater and hydrogenation wastewater in a mass ratio of 10:1-1:10, and adjust the pH value of the mixed wastewater to 2-7 with an acid; b) Reaction: Add a catalyst and sodium nitrite, and stir for 2 min to 60 min at 10°C to 90°C; c) Precipitation: Adjust the pH value of the wastewater after the reaction to 8 - 11, add a flocculant, stir, and let it stand for stratification. The upper layer is the wastewater, and the lower layer is the organic matter precipitate and the catalyst; d) Filtration and separation; The catalyst in step b) is a supported bimetallic catalyst prepared by the preparation method described in any one of claims 1 - 16.

19. According to the treatment method described in claim 18, in step a), the nitrification wastewater is the wastewater generated after pickling and alkali washing of the crude dinitrotoluene prepared by toluene nitrification, and the hydrogenation wastewater is the wastewater generated by hydrogenating dinitrotoluene to prepare toluenediamine.

20. According to the treatment method described in claim 18, in step b), the addition amount of the catalyst is 0.5% - 30% of the total mass of the nitrification wastewater and the hydrogenation wastewater.

21. According to the treatment method described in claim 18, the mass ratio of the addition amount of sodium nitrite to the total mass of the nitrification wastewater and the hydrogenation wastewater is 1:500 - 1:5000.

22. According to the treatment method described in claim 18, the mass ratio of the addition amount of the flocculant to the total mass of the nitrification wastewater and the hydrogenation wastewater is 1:2000 - 1:200000.

23. According to the treatment method described in claim 18, the flocculant in step c) is one or more of polyacrylamide, acrylic acid - acrylamide copolymer, polyaluminum chloride, polyferric sulfate, polyferric chloride, and polyaluminum sulfate.

24. According to the treatment method described in claim 18, after adding the flocculant in step c), stir for 2 min to 60 min at 10°C to 40°C, and let it stand for 10 min to 240 min before stratification.

25. According to the treatment method described in claim 18, in step d), filter the upper - layer wastewater. The filtrate is the treated wastewater, and the filter residue is the organic matter precipitate and the catalyst; further screen - separate the organic matter precipitate and the catalyst. The coarse particles are the organic matter precipitate, and the fine particles are the catalyst. Carry out subsequent treatment on the treated wastewater and the organic matter precipitate respectively.

26. According to the treatment method described in claim 18, in step d), a 200 - 500 - mesh filter is used to filter and separate the filtrate and the filter residue; an 80 - 100 - mesh screen is used to screen - separate the organic matter precipitate and the catalyst.

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