A method for regenerating a palladium catalyst for hydrogen peroxide

Abstract

The present invention discloses a regeneration method for a palladium catalyst for hydrogen peroxide, belonging to the technical field of catalyst regeneration. The regeneration method includes: classification, ball milling, primary mixing, hydrothermal synthesis, forming, primary treatment, secondary treatment, and secondary mixing; in the classification, the palladium catalyst particles to be regenerated are classified according to particle size. The palladium catalyst particles to be regenerated with a particle size greater than or equal to 2 mm are used as intact palladium catalyst particles, and the palladium catalyst particles to be regenerated with a particle size less than 2 mm are used as crushed palladium catalyst particles; after regeneration by the regeneration method of the present invention, the service life of the palladium catalyst particles is long, and it can solve the problems of crushing and desorption of palladium catalyst particles in the fluidized bed method catalyzed by palladium catalyst. After regeneration, palladium catalyst particles with uniform particle size are obtained, and there is no need to dissolve the palladium catalyst.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst regeneration, and particularly relates to a method for regenerating a palladium catalyst for hydrogen peroxide. Background Art

[0002] Hydrogen peroxide, also known as aqueous hydrogen peroxide solution, is a colorless transparent liquid with a slight pungent odor. It is mainly used as a strong oxidizing agent and disinfectant and is widely used in fields such as sterilization and disinfection, sewage treatment, dyeing and weaving, and bleaching. The commonly used mass concentration of hydrogen peroxide is 3 - 30%. The higher the mass concentration of hydrogen peroxide, the stronger the oxidizing property.

[0003] The production methods of hydrogen peroxide include the anthraquinone method, the electrolytic ammonium persulfate method, the isopropanol oxidation method, the oxygen cathode electrolytic reduction method, and the direct synthesis method of hydrogen and oxygen. Among them, the most commonly used production method is the anthraquinone method. Utilizing the property that quinone substances can be re - converted back to quinone substances through oxidation after being hydrogenated and reduced, the anthraquinone method is to dissolve alkyl anthraquinone in an organic solvent to obtain an alkyl anthraquinone solution, and then under the action of a hydrogenation catalyst, hydrogenate and reduce the alkyl anthraquinone in the alkyl anthraquinone solution to obtain the corresponding alkyl hydroanthraquinone, and then oxidize it to generate hydrogen peroxide. At the same time, the alkyl hydroanthraquinone is converted back to alkyl anthraquinone, and then pure water is used to extract the generated hydrogen peroxide to obtain hydrogen peroxide, and the alkyl anthraquinone solution is treated and recycled.

[0004] According to different reaction devices and catalysts, the anthraquinone method is mainly divided into the suspension kettle method catalyzed by a nickel catalyst, the fixed - bed method catalyzed by a palladium catalyst, and the fluidized - bed method catalyzed by a palladium catalyst. Compared with the suspension kettle method catalyzed by a nickel catalyst, the fixed - bed method catalyzed by a palladium catalyst and the fluidized - bed method catalyzed by a palladium catalyst have the advantages of less catalyst consumption, high catalyst activity, and easy catalyst regeneration. Therefore, the currently commonly used production methods of hydrogen peroxide are the fixed - bed method catalyzed by a palladium catalyst and the fluidized - bed method catalyzed by a palladium catalyst.

[0005] Different from the fixed-bed process catalyzed by palladium catalyst, in the fluidized-bed process catalyzed by palladium catalyst, during hydrogenation reduction, the palladium catalyst particles, as the dispersed phase of the alkyl hydrogen anthraquinone solution, are always in a suspended motion state with the flow of the alkyl hydrogen anthraquinone. The active sites on the surface of the palladium catalyst particles can adsorb hydrogen and activate hydrogen into atomic state. At the same time, the palladium catalyst particles can also adsorb alkyl anthraquinone through the active sites on the surface. Then, the active sites on the surface of the palladium catalyst particles can promote the reaction between hydrogen atoms and alkyl anthraquinone to obtain the corresponding alkyl hydrogen anthraquinone. The alkyl hydrogen anthraquinone undergoes desorption and detaches from the active sites on the surface of the palladium catalyst particles. The active sites on the surface of the palladium catalyst particles then re-adsorb hydrogen and alkyl anthraquinone and continue to promote the reaction between hydrogen and the remaining alkyl anthraquinone. The fluidized-bed process catalyzed by palladium catalyst is more conducive to the replenishment of the palladium catalyst and can also achieve fully acidic reaction conditions, avoiding the explosion risk caused by the alternation of acidic and alkaline production conditions in some fixed-bed processes catalyzed by palladium catalyst, which may lead to the accidental entry of hydrogen peroxide into the alkaline environment and violent decomposition reactions. However, the fluidized-bed process catalyzed by palladium catalyst will accelerate the fragmentation of the palladium catalyst particles. To prevent the loss of the palladium catalyst with the alkyl hydrogen anthraquinone solution, the alkyl hydrogen anthraquinone solution is filtered in the fluidized-bed process catalyzed by palladium catalyst, and the filter residue obtained by filtration is regenerated and then used continuously.

[0006] In the fluidized-bed process catalyzed by palladium catalyst, there is also a problem of palladium catalyst deactivation. The palladium catalyst in the commonly used palladium catalyst particles is mainly a supported palladium catalyst with porous alumina as the carrier. When preparing the palladium catalyst particles, first, the palladium precursor is mixed with the porous alumina carrier with a high specific surface area. The palladium precursor is evenly adsorbed on the surface of the porous alumina carrier with a high specific surface area. Then, the palladium precursor supported on the surface of the porous alumina carrier is converted into palladium black to obtain the supported palladium catalyst. During long-term use, macromolecular by-products will block the pores of the porous alumina carrier in the palladium catalyst particles and also cover the surface of the palladium catalyst, resulting in the deactivation of the palladium catalyst. For the deactivation of the palladium catalyst, the most commonly used regeneration method is to remove the macromolecular by-products through high-temperature water washing or saturated steam treatment.

[0007] However, when regenerating palladium catalyst particles in a fluidized bed process catalyzed by a palladium catalyst using high-temperature water washing or saturated steam treatment, the following problems exist: First, the cleaning ability of high-temperature water washing or saturated steam treatment is limited, and it is difficult to deeply remove macromolecular by-products inside the pores of the porous support, resulting in a reduction in the active sites of the palladium catalyst particles after regeneration and a decrease in activity, specifically manifested as a shortened service life of the palladium catalyst particles after regeneration; Second, the fluidized bed process catalyzed by a palladium catalyst not only accelerates the fragmentation of palladium catalyst particles but also causes the desorption of the palladium catalyst on the surface of the palladium catalyst particles. As a result, the filter residue obtained after filtering the alkyl hydrogen anthraquinone solution is palladium catalyst particles with inconsistent particle sizes and desorbed palladium black. Using high-temperature water washing or saturated steam treatment will cause the loss of desorbed palladium black, and after regeneration, the palladium catalyst particles with inconsistent particle sizes have a problem of uneven distribution in the fluidized bed. The small-sized palladium catalyst particles will aggregate at positions farther from the air outlet, and the large-sized palladium catalyst particles will aggregate near the air outlet. The uneven distribution of palladium catalyst particles will cause the shift of the reaction area, further affecting the reaction rate of hydrogenation and reduction.

[0008] To address the above problems, the commonly used methods at present are as follows: First, soak with organic solvents and alkaline solutions to remove macromolecular by-products inside the pores of the porous alumina support. However, during the soaking process, further loss of desorbed palladium black will occur, and the service life of the palladium catalyst particles after regeneration will be further shortened; Second, for the fragmented palladium catalyst particles, they need to be thoroughly pulverized, and after dissolving the palladium catalyst with inorganic acids and oxidants, they are re-loaded, transformed, and formed. However, in this method, the loss of palladium catalyst will occur during the dissolution process and the re-loading process. Summary of the Invention

[0009] Aiming at the deficiencies of the existing technology, the present invention provides a regeneration method for a palladium catalyst for hydrogen peroxide. After regeneration, the service life of the palladium catalyst particles is long. It can address the problems of fragmentation and desorption of palladium catalyst particles in the fluidized bed process catalyzed by a palladium catalyst. After regeneration, palladium catalyst particles with uniform particle sizes are obtained, and there is no need to dissolve the palladium catalyst.

[0010] To solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0011] A regeneration method for a palladium catalyst for hydrogen peroxide, comprising: classification, ball milling, primary mixing, hydrothermal synthesis, forming, primary treatment, secondary treatment, and secondary mixing;

[0012] In the classification, the palladium catalyst particles to be regenerated are classified according to particle size. The palladium catalyst particles to be regenerated with a particle size greater than or equal to 2 mm are used as intact palladium catalyst particles, and the palladium catalyst particles to be regenerated with a particle size less than 2 mm are used as fragmented palladium catalyst particles;

[0013] In the classification, the carrier of the palladium catalyst particles to be regenerated is porous alumina, the original palladium content is 0.307 wt%, the original particle size is 2 mm, the original specific surface area is 120 m 2 / g, the original bulk density is 0.65 g / mL, and the original pore volume is 0.60 mL / g;

[0014] In the ball milling, the crushed palladium catalyst particles are put into a planetary ball mill and ball milled at room temperature. After the ball milling is completed, the materials in the planetary ball mill are collected. After separating the alumina grinding balls from the materials, the remaining materials are classified by particle size. The materials with a particle size less than 100 μm are used as small particle size materials, and the materials with a particle size greater than or equal to 100 μm are used as large particle size materials;

[0015] In the ball milling, the grinding balls in the planetary ball mill are alumina grinding balls, the particle size of the alumina grinding balls is 6 mm, the ball-to-material ratio is 5 - 6:1, the ball milling speed is 130 - 150 rpm, and the ball milling time is 9 - 10 min;

[0016] In the first mixing, deionized water and aluminum chloride are added to the small particle size materials, and they are stirred at a stirring speed of 50 - 100 rpm at 70 - 80 °C for 20 - 30 min. Then, triblock copolymer P123 is added and stirring continues for 20 - 30 min to obtain a first mixed solution;

[0017] In the first mixing, the dosage ratio of the small particle size materials, deionized water, aluminum chloride, and triblock copolymer P123 is 102 - 105 g:1.7 - 1.8 L:10 - 11 g:9 - 10 g;

[0018] In the hydrothermal synthesis, the first mixed solution, urea, and polystyrene microspheres are mixed and stirred at a stirring speed of 50 - 100 rpm at room temperature for 20 - 30 min, and then hydrothermally reacted at 150 - 160 °C for 9 - 10 h. After centrifugation, the precipitate is taken, and the precipitate is washed with water and dried to obtain composite microspheres;

[0019] In the hydrothermal synthesis, the particle size of the polystyrene microspheres is 500 nm;

[0020] The dosage ratio of the first mixed solution, urea, and polystyrene microspheres is 1.7 - 1.8 L:20 - 25 g:0.5 - 0.52 g;

[0021] In the forming, the large particle size materials, composite microspheres, gum arabic, and deionized water are added to a mixer and mixed evenly, and then pressed into spheres with a particle size of 2 mm, and then calcined in a nitrogen atmosphere at 400 - 450 °C for 2 - 2.5 h to obtain spherical catalysts;

[0022] During the shaping, the mass ratio of the total mass of the large-particle-size materials and the composite microspheres to the mass of gum arabic and deionized water is 1000:20 - 23:1100 - 1200;

[0023] For the primary treatment, load the spherical catalyst into the constant-temperature section of the fixed bed, fill the upper and lower parts with quartz sand, then soak it with toluene. After the soaking is completed, drain the toluene, conduct a primary purge with nitrogen. After the primary purge is completed, conduct a primary cleaning with steam. After the primary cleaning is completed, conduct a secondary cleaning with hot water. After the secondary cleaning is completed, conduct a secondary purge with a mixed gas of nitrogen and hydrogen. After the secondary purge is completed, take out the catalyst and dry it to obtain the first portion of palladium catalyst;

[0024] In the primary treatment, the volume ratio of the toluene used in the soaking to the spherical catalyst is 6 - 7:1, the soaking temperature is 50 - 60 °C, and the soaking time is 30 - 33 h;

[0025] In the primary purge, the flow rate of nitrogen is 480 - 520 mL / min, the primary purge temperature is 50 - 60 °C, and the time is 6 - 7 h;

[0026] In the primary cleaning, the flow rate of steam is 180 - 200 mL / h, the temperature is 100 - 110 °C, and the time is 19 - 20 h;

[0027] In the secondary cleaning, the flow rate of hot water is 120 - 130 mL / h, the temperature is 100 °C, and the time is 8 - 9 h;

[0028] In the secondary purge, the flow rate of the mixed gas of nitrogen and hydrogen is 480 - 520 mL / min, the secondary purge temperature is 70 - 80 °C, and the time is 1.5 - 2 h;

[0029] In the mixed gas of nitrogen and hydrogen, the volume ratio of nitrogen to hydrogen is 4 - 5:1;

[0030] For the secondary treatment, load the complete palladium catalyst particles into the constant-temperature section of the fixed bed, fill the upper and lower parts with quartz sand, then soak them with the mixed solution. While soaking, conduct a primary purge with nitrogen into the mixed solution in the fixed bed, starting from the bottom of the fixed bed. When the soaking is completed, end the primary purge. Then conduct a primary cleaning with steam. After the primary cleaning is completed, conduct a secondary cleaning with hot water. After the secondary cleaning is completed, conduct a secondary purge with nitrogen. After the secondary purge is completed, take out the catalyst and dry it to obtain the second portion of palladium catalyst;

[0031] In the secondary treatment, the volume ratio of the mixed solution used in the soaking to the complete palladium catalyst particles is 3.8 - 4:1, the soaking temperature is 50 - 60 °C, and the soaking time is 30 - 33 h;

[0032] The flow rate of nitrogen in the first purge is 700 - 750 mL / min;

[0033] The flow rate of water vapor in the first cleaning is 180 - 200 mL / h, the temperature is 100 - 110 °C, and the time is 12 - 13 h;

[0034] The flow rate of hot water in the second cleaning is 120 - 130 mL / h, the temperature is 100 °C, and the time is 5 - 6 h;

[0035] The flow rate of nitrogen in the second purge is 480 - 520 mL / min, the temperature of the second purge is 50 - 60 °C, and the time is 1.5 - 2 h.

[0036] The mixed solution is a mixture of toluene and the triblock copolymer polycaprolactone - polyethylene glycol - polycaprolactone. Among them, the volume ratio of toluene to the triblock copolymer polycaprolactone - polyethylene glycol - polycaprolactone is 100:0.9 - 1, and the molecular weight ratio of polycaprolactone to polyethylene glycol in the triblock copolymer polycaprolactone - polyethylene glycol - polycaprolactone is 0.85:1;

[0037] In the second mixing, the first portion of palladium catalyst and the second portion of palladium catalyst are mixed evenly to obtain the regenerated palladium catalyst.

[0038] Compared with the prior art, the beneficial effects of the present invention are:

[0039] (1)The regeneration method of the palladium catalyst for hydrogen peroxide of the present invention is designed specifically for the problem that palladium catalyst particles are prone to breakage in the fluidized bed method catalyzed by the palladium catalyst. Since the palladium catalyst on the surface will desorb after breakage, for the broken palladium catalyst particles, first perform ball milling to mill the surface alumina into powder, and generate heat through ball milling to promote the binding force between palladium and the carrier in the broken palladium catalyst particles, and also promote the decomposition of macromolecular by-products in the broken palladium catalyst particles, which is convenient for subsequent removal. Then, treat the powder after ball milling. Since the powder after ball milling mainly contains palladium catalyst and alumina powder, during the treatment, first mix it with water and aluminum chloride, and then add triblock copolymer P123 after mixing. Triblock copolymer P123 and aluminum chloride are adsorbed on the palladium catalyst and alumina powder to promote the dispersion of the palladium catalyst and alumina powder. Then, perform hydrothermal synthesis. Using polystyrene microspheres as a template, the palladium catalyst and alumina powder adsorbed with triblock copolymer P123 and aluminum chloride are both combined with polystyrene microspheres. After hydrothermal synthesis, aluminum chloride is converted into nano-scale alumina, thus obtaining a combination of nano-scale alumina, palladium catalyst, alumina powder, triblock copolymer P123, and polystyrene microspheres. Through hydrothermal synthesis, on the one hand, it can promote the dispersion of the palladium catalyst and alumina powder, and on the other hand, it can re-bind the detached palladium catalyst to the alumina powder. Then, mix this mixture with the large-particle-size material after ball milling, use gum arabic as a binder to make a slurry, and then form the slurry and calcine it in a nitrogen atmosphere. During calcination, polystyrene microspheres and gum arabic decompose, and finally a porous spherical catalyst is obtained. Then, perform a primary treatment on the porous spherical catalyst to remove impurities and obtain the first portion of palladium catalyst; then, through a secondary treatment, clean the intact palladium catalyst particles that have not broken. During the secondary treatment, soaking and primary purging are combined. In the soaking process, a mixture of toluene and triblock copolymer polycaprolactone-polyethylene glycol-polycaprolactone is used as the mixed liquid. In the primary purging process, nitrogen is directly introduced into the mixed liquid. Triblock copolymer polycaprolactone-polyethylene glycol-polycaprolactone self-assembles into vesicles in toluene. The vesicles can penetrate into the interior of the intact palladium catalyst particles that have not broken under the purging action of nitrogen for purging, and can also combine with macromolecular by-products to promote the dissolution of macromolecular by-products. After the secondary treatment is completed, the second portion of palladium catalyst is obtained. Mix the first portion of palladium catalyst and the second portion of palladium catalyst evenly to obtain palladium catalyst particles with uniform particle size;

[0040] (2)In the regeneration method of the palladium catalyst for hydrogen peroxide of the present invention, the service life of the regenerated palladium catalyst particles is long. The palladium content of the regenerated palladium catalyst for hydrogen peroxide is 0.301 - 0.302 wt%, the hydrogen efficiency is 7.12 - 7.31 g (H 2 O 2 ) / L, and the specific surface area is 130 - 137 m2 / g;

[0041] (3)The regeneration method of the palladium catalyst for hydrogen peroxide of the present invention can address the problems of fragmentation and desorption of palladium catalyst particles in the fluidized bed process catalyzed by the palladium catalyst, and after regeneration, palladium catalyst particles with uniform particle size can be obtained;

[0042] (4)The regeneration method of the palladium catalyst for hydrogen peroxide of the present invention can address the problems of fragmentation and desorption of palladium catalyst particles in the fluidized bed process catalyzed by the palladium catalyst, and there is no need to dissolve the palladium catalyst. Detailed Embodiments

[0043] In order to have a clearer understanding of the technical features, objectives, and effects of the present invention, the specific embodiments of the present invention will now be described.

[0044] Example 1

[0045] A regeneration method of a palladium catalyst for hydrogen peroxide is specifically as follows:

[0046] 1. Classification: Classify the palladium catalyst particles to be regenerated according to particle size. The palladium catalyst particles to be regenerated with a particle size greater than or equal to 2 mm are used as intact palladium catalyst particles, and the palladium catalyst particles to be regenerated with a particle size less than 2 mm are used as fragmented palladium catalyst particles;

[0047] The carrier of the palladium catalyst particles to be regenerated is porous alumina, the original palladium content is 0.307 wt%, the original particle size is 2 mm, the original specific surface area is 120 m 2 / g, the original bulk density is 0.65 g / mL, and the original pore volume is 0.60 mL / g;

[0048] 2. Ball milling: Put the fragmented palladium catalyst particles into a planetary ball mill and conduct ball milling at room temperature. The grinding balls in the planetary ball mill are alumina grinding balls with a particle size of 6 mm, the ball-to-material ratio is 5:1, the ball milling speed is 130 rpm, and the ball milling time is 9 min. After the ball milling is completed, collect the materials in the planetary ball mill. After separating the alumina grinding balls from the materials, classify the remaining materials according to particle size. The materials with a particle size less than 100 μm are used as small particle size materials, and the materials with a particle size greater than or equal to 100 μm are used as large particle size materials;

[0049] 3. Primary mixing: Add deionized water and aluminum chloride to the small particle size materials, stir at a stirring speed of 50 rpm at 70 °C for 20 min, add the triblock copolymer P123, and continue stirring for 20 min to obtain a primary mixed solution;

[0050] The dosage ratio of the small particle size materials, deionized water, aluminum chloride, and triblock copolymer P123 is 102 g: 1.7 L: 10 g: 9 g;

[0051] 4. Hydrothermal synthesis: After mixing the primary mixed solution, urea, and polystyrene microspheres, stir at a stirring speed of 50 rpm for 20 min at room temperature, conduct hydrothermal reaction at 150 °C for 9 h, take the precipitate after centrifugation, wash the precipitate with water and dry it to obtain composite microspheres;

[0052] The particle size of the polystyrene microspheres is 500 nm;

[0053] The dosage ratio of the primary mixed solution, urea, and polystyrene microspheres is 1.7 L: 20 g: 0.5 g;

[0054] 5. Shaping: Add all the large-particle-size materials obtained in the ball milling step in step 2, all the composite microspheres obtained in the hydrothermal synthesis step in step 4, arabic gum, and deionized water into a mixer and mix evenly, then press them into spheres with a particle size of 2 mm, and then calcine them at 400 °C for 2 h in a nitrogen atmosphere to obtain spherical catalysts;

[0055] The mass ratio of the total mass of the large-particle-size materials and the composite microspheres to arabic gum and deionized water is 1000: 20: 1100;

[0056] 6. Primary treatment: Load all the spherical catalysts obtained in the shaping step in step 5 into the constant temperature section of a fixed bed, fill the upper and lower parts with quartz sand, then soak them with toluene, control the volume ratio of toluene to spherical catalysts used in the soaking to be 6: 1, the soaking temperature to be 50 °C, and the soaking time to be 30 h. After the soaking is completed, release the toluene, conduct a primary purge with nitrogen, control the nitrogen flow rate in the primary purge to be 480 mL / min, the primary purge temperature to be 50 °C, and the time to be 6 h. After the primary purge is completed, conduct a primary cleaning with steam, control the steam flow rate in the primary cleaning to be 180 mL / h, the temperature to be 100 °C, and the time to be 19 h. After the primary cleaning is completed, conduct a secondary cleaning with hot water, control the hot water flow rate in the secondary cleaning to be 120 mL / h, the temperature to be 100 °C, and the time to be 8 h. After the secondary cleaning is completed, conduct a secondary purge with a mixed gas of nitrogen and hydrogen, control the flow rate of the mixed gas of nitrogen and hydrogen in the secondary purge to be 480 mL / min, the secondary purge temperature to be 70 °C, and the time to be 1.5 h. After the secondary purge is completed, take out the catalyst and dry it to obtain the first portion of palladium catalyst;

[0057] The volume ratio of nitrogen to hydrogen in the mixed gas of nitrogen and hydrogen is 4: 1;

[0058] 7. Secondary treatment: Load all the intact palladium catalyst particles obtained in the classification step of Step 1 into the constant temperature section of a fixed bed, fill the upper and lower parts with quartz sand, then soak them with a mixed solution. Control the volume ratio of the mixed solution used in the soaking to the intact palladium catalyst particles to be 3.8:1, the soaking temperature to be 50 °C, and the soaking time to be 30 h. While soaking, purge with nitrogen into the mixed solution in the fixed bed once, starting from the bottom of the fixed bed. Control the nitrogen flow rate in the first purge to be 700 mL / min, and end the first purge simultaneously when the soaking ends. Then, conduct a primary cleaning with steam. Control the steam flow rate in the primary cleaning to be 180 mL / h, the temperature to be 100 °C, and the time to be 12 h. After the primary cleaning, conduct a secondary cleaning with hot water. Control the hot water flow rate in the secondary cleaning to be 120 mL / h, the temperature to be 100 °C, and the time to be 5 h. After the secondary cleaning, conduct a secondary purge with nitrogen. Control the nitrogen flow rate in the secondary purge to be 480 mL / min, the temperature of the secondary purge to be 50 °C, and the time to be 1.5 h. After the secondary purge, take out the catalyst and dry it to obtain the second portion of palladium catalyst;

[0059] The mixed solution is a mixture of toluene and the triblock copolymer polycaprolactone - polyethylene glycol - polycaprolactone. Among them, the volume ratio of toluene to the triblock copolymer polycaprolactone - polyethylene glycol - polycaprolactone is 100:0.9, and the molecular weight ratio of polycaprolactone to polyethylene glycol in the triblock copolymer polycaprolactone - polyethylene glycol - polycaprolactone is 0.85:1;

[0060] 8. Secondary mixing: Mix all the first portion of palladium catalyst obtained in the primary treatment step of Step 6 and all the second portion of palladium catalyst obtained in the secondary treatment step of Step 7 evenly to obtain the regenerated palladium catalyst.

[0061] Example 2

[0062] A method for regenerating a palladium catalyst for hydrogen peroxide, specifically:

[0063] 1. Classification: Classify the palladium catalyst particles to be regenerated according to particle size. Use the palladium catalyst particles to be regenerated with a particle size greater than or equal to 2 mm as intact palladium catalyst particles, and use the palladium catalyst particles to be regenerated with a particle size less than 2 mm as crushed palladium catalyst particles;

[0064] The carrier of the palladium catalyst particles to be regenerated is porous alumina, the original palladium content is 0.307 wt%, the original particle size is 2 mm, the original specific surface area is 120 m 2 / g, the original bulk density is 0.65 g / mL, and the original pore volume is 0.60 mL / g;

[0065] 2. Ball milling: Put the crushed palladium catalyst particles into a planetary ball mill and perform ball milling at room temperature. The grinding balls in the planetary ball mill are alumina grinding balls with a particle size of 6 mm. The ball-to-material ratio is 5:1, the ball milling speed is 140 rpm, and the ball milling time is 10 min. After the ball milling is completed, collect the materials in the planetary ball mill. After separating the alumina grinding balls from the materials, classify the remaining materials by particle size. The materials with a particle size less than 100 μm are used as small particle size materials, and the materials with a particle size greater than or equal to 100 μm are used as large particle size materials;

[0066] 3. Primary mixing: Add deionized water and aluminum chloride to the small particle size materials, stir at a stirring speed of 80 rpm at 75 °C for 25 min, add the triblock copolymer P123, and continue stirring for 25 min to obtain a primary mixed solution;

[0067] The dosage ratio of the small particle size materials, deionized water, aluminum chloride, and triblock copolymer P123 is 104 g: 1.8 L: 10.5 g: 9.5 g;

[0068] 4. Hydrothermal synthesis: Mix the primary mixed solution, urea, and polystyrene microspheres, stir at a stirring speed of 80 rpm at room temperature for 25 min, perform hydrothermal reaction at 155 °C for 9.5 h, take the precipitate after centrifugation, wash the precipitate with water and dry it to obtain composite microspheres;

[0069] The particle size of the polystyrene microspheres is 500 nm;

[0070] The dosage ratio of the primary mixed solution, urea, and polystyrene microspheres is 1.8 L: 22 g: 0.51 g;

[0071] 5. Shaping: Add all the large particle size materials obtained in the ball milling step in step 2, all the composite microspheres obtained in the hydrothermal synthesis step in step 4, gum arabic, and deionized water into a mixer and mix evenly, then press them into spheres with a particle size of 2 mm, and then calcine them at 420 °C for 2.5 h in a nitrogen atmosphere to obtain spherical catalysts;

[0072] The mass ratio of the total mass of the large particle size materials and the composite microspheres to the mass of gum arabic and deionized water is 1000: 21: 1150;

[0073] 6. Primary treatment: Load all the spherical catalysts obtained in the forming step of Step 5 into the constant-temperature section of a fixed bed, fill it with quartz sand above and below, then soak it with toluene. Control the volume ratio of toluene to spherical catalysts used in the soaking to be 6:1, the soaking temperature to be 55 °C, and the soaking time to be 32 h. After the soaking, drain the toluene, conduct a primary purge with nitrogen, control the nitrogen flow rate in the primary purge to be 500 mL / min, the primary purge temperature to be 55 °C, and the time to be 6.5 h. After the primary purge, conduct a primary cleaning with steam, control the steam flow rate in the primary cleaning to be 190 mL / h, the temperature to be 105 °C, and the time to be 19.5 h. After the primary cleaning, conduct a secondary cleaning with hot water, control the hot water flow rate in the secondary cleaning to be 125 mL / h, the temperature to be 100 °C, and the time to be 8.5 h. After the secondary cleaning, conduct a secondary purge with a mixed gas of nitrogen and hydrogen, control the flow rate of the mixed gas of nitrogen and hydrogen in the secondary purge to be 500 mL / min, the secondary purge temperature to be 75 °C, and the time to be 2 h. After the secondary purge, take out the catalyst and dry it to obtain the first portion of palladium catalyst;

[0074] The volume ratio of nitrogen to hydrogen in the mixed gas of nitrogen and hydrogen is 4.5:1;

[0075] 7. Secondary treatment: Load all the complete palladium catalyst particles obtained in the classification step of Step 1 into the constant-temperature section of a fixed bed, fill it with quartz sand above and below, then soak it with a mixed solution. Control the volume ratio of the mixed solution to complete palladium catalyst particles used in the soaking to be 3.9:1, the soaking temperature to be 55 °C, and the soaking time to be 32 h. While soaking, introduce nitrogen into the mixed solution in the fixed bed for a primary purge, start introducing from the bottom of the fixed bed, control the nitrogen flow rate in the primary purge to be 720 mL / min, and end the primary purge at the same time as the soaking ends. Then conduct a primary cleaning with steam, control the steam flow rate in the primary cleaning to be 190 mL / h, the temperature to be 105 °C, and the time to be 12.5 h. After the primary cleaning, conduct a secondary cleaning with hot water, control the hot water flow rate in the secondary cleaning to be 125 mL / h, the temperature to be 100 °C, and the time to be 5.5 h. After the secondary cleaning, conduct a secondary purge with nitrogen, control the nitrogen flow rate in the secondary purge to be 500 mL / min, the secondary purge temperature to be 55 °C, and the time to be 2 h. After the secondary purge, take out the catalyst and dry it to obtain the second portion of palladium catalyst;

[0076] The mixed solution is a mixture of toluene and the triblock copolymer polycaprolactone - polyethylene glycol - polycaprolactone. Among them, the volume ratio of toluene to the triblock copolymer polycaprolactone - polyethylene glycol - polycaprolactone is 100:0.9, and the molecular weight ratio of polycaprolactone to polyethylene glycol in the triblock copolymer polycaprolactone - polyethylene glycol - polycaprolactone is 0.85:1;

[0077] 8. Secondary mixing: Mix all the first portion of palladium catalyst obtained in the first treatment step of Step 6 and all the second portion of palladium catalyst obtained in the second treatment step of Step 7 evenly to obtain the regenerated palladium catalyst.

[0078] Example 3

[0079] A method for regenerating a palladium catalyst for hydrogen peroxide, specifically:

[0080] 1. Classification: Classify the palladium catalyst particles to be regenerated according to particle size. The palladium catalyst particles to be regenerated with a particle size greater than or equal to 2 mm are used as intact palladium catalyst particles, and the palladium catalyst particles to be regenerated with a particle size less than 2 mm are used as crushed palladium catalyst particles;

[0081] The carrier of the palladium catalyst particles to be regenerated is porous alumina, the original palladium content is 0.307 wt%, the original particle size is 2 mm, the original specific surface area is 120 m 2 / g, the original bulk density is 0.65 g / mL, and the original pore volume is 0.60 mL / g;

[0082] 2. Ball milling: Put the crushed palladium catalyst particles into a planetary ball mill and carry out ball milling at room temperature. The grinding balls in the planetary ball mill are alumina grinding balls with a particle size of 6 mm, the ball-to-material ratio is 6:1, the ball milling speed is 150 rpm, and the ball milling time is 10 min. After the ball milling is completed, collect the materials in the planetary ball mill. After separating the alumina grinding balls from the materials, classify the remaining materials according to particle size. The materials with a particle size less than 100 μm are used as small particle size materials, and the materials with a particle size greater than or equal to 100 μm are used as large particle size materials;

[0083] 3. Primary mixing: Add deionized water and aluminum chloride to the small particle size materials, stir at a stirring speed of 100 rpm at 80 °C for 30 min, add triblock copolymer P123, and continue stirring for 30 min to obtain a primary mixed solution;

[0084] The dosage ratio of the small particle size materials, deionized water, aluminum chloride, and triblock copolymer P123 is 105 g: 1.8 L: 11 g: 10 g;

[0085] 4. Hydrothermal synthesis: Mix the primary mixed solution, urea, and polystyrene microspheres, stir at a stirring speed of 100 rpm at room temperature for 30 min, carry out hydrothermal reaction at 160 °C for 10 h, take the precipitate after centrifugation, wash and dry the precipitate with water to obtain composite microspheres;

[0086] The particle size of the polystyrene microspheres is 500 nm;

[0087] The dosage ratio of the primary mixture, urea, and polystyrene microspheres is 1.8 L: 25 g: 0.52 g;

[0088] 5. Shaping: Add all the large-particle-size materials obtained in the ball-milling step in Step 2, all the composite microspheres obtained in the hydrothermal synthesis step in Step 4, arabic gum, and deionized water into a mixer and mix evenly. Then, press them into spheres with a diameter of 2 mm. Then, calcine them in a nitrogen atmosphere at 450 °C for 2.5 h to obtain spherical catalysts;

[0089] The mass ratio of the total mass of the large-particle-size materials and the composite microspheres to arabic gum and deionized water is 1000: 23: 1200;

[0090] 6. Primary treatment: Load all the spherical catalysts obtained in the shaping step in Step 5 into the constant-temperature section of a fixed bed, fill the upper and lower parts with quartz sand, and then soak them with toluene. Control the volume ratio of toluene to spherical catalysts used in the soaking to be 7: 1, the soaking temperature to be 60 °C, and the soaking time to be 33 h. After the soaking is completed, drain the toluene, and conduct a primary purge with nitrogen. Control the nitrogen flow rate in the primary purge to be 520 mL / min, the primary purge temperature to be 60 °C, and the time to be 7 h. After the primary purge is completed, conduct a primary cleaning with steam. Control the steam flow rate in the primary cleaning to be 200 mL / h, the temperature to be 110 °C, and the time to be 20 h. After the primary cleaning is completed, conduct a secondary cleaning with hot water. Control the hot water flow rate in the secondary cleaning to be 130 mL / h, the temperature to be 100 °C, and the time to be 9 h. After the secondary cleaning is completed, conduct a secondary purge with a mixed gas of nitrogen and hydrogen. Control the flow rate of the mixed gas of nitrogen and hydrogen in the secondary purge to be 520 mL / min, the secondary purge temperature to be 80 °C, and the time to be 2 h. After the secondary purge is completed, take out the catalyst and dry it to obtain the first portion of palladium catalyst;

[0091] The volume ratio of nitrogen to hydrogen in the mixed gas of nitrogen and hydrogen is 5: 1;

[0092] 7. Secondary treatment: Load all the complete palladium catalyst particles obtained in the classification step of Step 1 into the constant temperature section of the fixed bed, fill it with quartz sand up and down, then soak it with the mixed solution. Control the volume ratio of the mixed solution used in the soaking to the complete palladium catalyst particles to be 4:1, the soaking temperature to be 60 °C, and the soaking time to be 33 h. While soaking, introduce nitrogen into the mixed solution in the fixed bed for a primary purge. Start introducing from the bottom of the fixed bed, and control the nitrogen flow rate in the primary purge to be 750 mL / min. End the primary purge simultaneously when the soaking ends. Then conduct a primary cleaning with steam. Control the steam flow rate in the primary cleaning to be 200 mL / h, the temperature to be 110 °C, and the time to be 13 h. After the primary cleaning, conduct a secondary cleaning with hot water. Control the hot water flow rate in the secondary cleaning to be 130 mL / h, the temperature to be 100 °C, and the time to be 6 h. After the secondary cleaning, conduct a secondary purge with nitrogen. Control the nitrogen flow rate in the secondary purge to be 520 mL / min, the temperature of the secondary purge to be 60 °C, and the time to be 2 h. After the secondary purge, take out the catalyst and dry it to obtain the second portion of palladium catalyst;

[0093] The mixed solution is a mixture of toluene and the triblock copolymer polycaprolactone - polyethylene glycol - polycaprolactone. Among them, the volume ratio of toluene to the triblock copolymer polycaprolactone - polyethylene glycol - polycaprolactone is 100:1, and the molecular weight ratio of polycaprolactone to polyethylene glycol in the triblock copolymer polycaprolactone - polyethylene glycol - polycaprolactone is 0.85:1;

[0094] 8. Secondary mixing: Mix all the first portion of palladium catalyst obtained in the primary treatment step of Step 6 and all the second portion of palladium catalyst obtained in the secondary treatment step of Step 7 evenly to obtain the regenerated palladium catalyst.

[0095] Comparative Example 1

[0096] This comparative example is a comparison for the regeneration method of Example 2. Specifically, on the basis of the regeneration method of Example 2, the mixed solution in the secondary treatment step of Step 7 is omitted, and it is changed to soak with deionized water and then conduct a nitrogen purge. Specifically, change the secondary treatment step of Step 7 to:

[0097] Load all the complete palladium catalyst particles obtained in the first-step classification step into the constant-temperature section of the fixed bed, fill it with quartz sand up and down, and then soak it with deionized water. Control the volume ratio of the deionized water used in the soaking to the spherical catalyst to be 3.9:1, the soaking temperature to be 55 °C, and the soaking time to be 32 h. After the soaking is completed, conduct a primary purge with nitrogen, control the nitrogen flow rate in the primary purge to be 720 mL / min. After the primary purge is completed, conduct a primary cleaning with steam, control the steam flow rate in the primary cleaning to be 190 mL / h, the temperature to be 105 °C, and the time to be 12.5 h. After the primary cleaning is completed, conduct a secondary cleaning with hot water, control the hot water flow rate in the secondary cleaning to be 125 mL / h, the temperature to be 100 °C, and the time to be 5.5 h. After the secondary cleaning is completed, conduct a secondary purge with nitrogen, control the nitrogen flow rate in the secondary purge to be 500 mL / min, the temperature of the secondary purge to be 55 °C, and the time to be 2 h. After the secondary purge is completed, take out the catalyst and dry it to obtain the second portion of palladium catalyst.

[0098] Performance test

[0099] Test the palladium content, hydrogen efficiency, and specific surface area of the regenerated palladium catalysts in Examples 1-3 and Comparative Example 1. The test results are as follows:

[0100]

[0101] It can be seen from the results of the performance test that the hydrogen efficiency and specific surface area of the regenerated palladium catalyst in Comparative Example 1 are lower than those of the regenerated palladium catalyst in Example 2.

[0102] Unless otherwise specified, the percentages used in the present invention are all mass percentages.

[0103] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for regenerating a palladium catalyst for hydrogen peroxide, characterized in that: include: Classification, ball milling, primary mixing, hydrothermal synthesis, molding, primary treatment, secondary treatment, secondary mixing; The classification includes classifying the palladium catalyst particles to be regenerated according to their particle size, classifying the palladium catalyst particles to be regenerated with a particle size greater than or equal to 2 mm as complete palladium catalyst particles, and classifying the palladium catalyst particles to be regenerated with a particle size less than 2 mm as broken palladium catalyst particles; The ball milling comprises placing the crushed palladium catalyst particles into a planetary ball mill and performing ball milling at room temperature, collecting the material in the planetary ball mill after the ball milling is completed, separating the alumina grinding balls from the material, and classifying the remaining material according to the particle size, wherein the material with a particle size less than 100 μm is regarded as a small particle size material, and the material with a particle size greater than or equal to 100 μm is regarded as a large particle size material; In the primary mixing, deionized water and aluminum chloride are added to the small particle size material, stirred once, and the triblock copolymer P123 is added, stirred twice to obtain a primary mixed solution; In the primary mixing, the usage ratio of the small particle size material, deionized water, aluminum chloride, and triblock copolymer P123 is 102-105 g: 1.7-1.8 L: 10-11 g: 9-10 g; The hydrothermal synthesis comprises mixing the primary mixed solution, urea and polystyrene microspheres, stirring, hydrothermal reaction and post-treatment to obtain composite microspheres; In the hydrothermal synthesis, the dosage ratio of the primary mixed solution, urea, and polystyrene microspheres is 1.7-1.8 L: 20-25 g: 0.5-0.52 g; The molding comprises mixing the large-particle material, the composite microspheres, gum arabic and deionized water, pressing them into a spherical body, and calcining them to obtain a spherical catalyst; In the molding, the mass ratio of the total mass of the large-particle material and the composite microspheres to the mass ratio of gum arabic and deionized water is 1000:20-23:1100-1200; The first treatment comprises soaking the spherical catalyst with toluene, then purging it with nitrogen, washing it with water vapor, washing it twice with hot water, purging it twice with a mixed gas of nitrogen and hydrogen, and drying it to obtain a first portion of palladium catalyst; The secondary treatment comprises soaking the complete palladium catalyst particles with the mixed solution, introducing nitrogen into the mixed solution in the fixed bed for a purge while soaking, introducing the nitrogen into the mixed solution from the bottom of the fixed bed, and ending the purge at the same time as the soaking, and then washing with water vapor, washing twice with hot water, and purge twice with nitrogen, and drying to obtain a second portion of palladium catalyst; The mixed liquid is a mixture of toluene and triblock copolymer polycaprolactone-polyethylene glycol-polycaprolactone, wherein the volume ratio of toluene to the triblock copolymer polycaprolactone-polyethylene glycol-polycaprolactone is 100:0.9-1, and the molecular weight ratio of polycaprolactone to polyethylene glycol in the triblock copolymer polycaprolactone-polyethylene glycol-polycaprolactone is 0.85:1; The secondary mixing is to mix the first portion of the palladium catalyst and the second portion of the palladium catalyst evenly to obtain a regenerated palladium catalyst.

2. The regeneration method of palladium catalyst for hydrogen peroxide according to claim 1, wherein In the classification, the carrier of the palladium catalyst particles to be regenerated is porous alumina, the original palladium content is 0.307wt%, the original particle size is 2mm, and the original specific surface area is 120m 2 / g, the original bulk density is 0.65g / mL, and the original pore volume is 0.60mL / g.

3. The regeneration method of palladium catalyst for hydrogen peroxide according to claim 1, wherein In the ball milling, the grinding balls in the planetary ball mill are alumina grinding balls, the particle size of the alumina grinding balls is 6 mm, the ball-to-material ratio is 5-6:1, the ball milling speed is 130-150 rpm, and the ball milling time is 9-10 min.

4. The regeneration method of palladium catalyst for hydrogen peroxide according to claim 1, wherein In the mixing, the stirring temperature is 70-80°C and the stirring time is 20-30min; The temperature of the secondary stirring is 70-80°C and the time is 20-30 minutes.

5. The regeneration method of palladium catalyst for hydrogen peroxide according to claim 1, wherein In the hydrothermal synthesis, the particle size of the polystyrene microspheres is 500 nm; The stirring temperature is room temperature and the time is 20-30min; The temperature of the hydrothermal reaction is 150-160°C and the time is 9-10h; The post-treatment comprises taking a precipitate after centrifugation, washing the precipitate with water and drying the precipitate.

6. The regeneration method of palladium catalyst for hydrogen peroxide according to claim 1, wherein During the forming process, the particle size of the spherical blank is 2 mm; The calcination is carried out in a nitrogen atmosphere, the calcination temperature is 400-450° C., and the calcination time is 2-2.5 hours.

7. The regeneration method of palladium catalyst for hydrogen peroxide according to claim 1, wherein In the primary treatment, the spherical catalyst is loaded into the constant temperature section of the fixed bed and filled with quartz sand above and below; The volume ratio of toluene to the spherical catalyst used in the soaking is 6-7:1, the soaking temperature is 50-60° C., and the soaking time is 30-33 hours; The flow rate of nitrogen in the primary purge is 480-520 mL / min, the temperature of the primary purge is 50-60° C., and the time is 6-7 h; The flow rate of water vapor in the first cleaning is 180-200 mL / h, the temperature is 100-110° C., and the time is 19-20 h; The flow rate of hot water in the secondary cleaning is 120-130 mL / h, the temperature is 100° C., and the time is 8-9 h; The flow rate of the mixed gas of nitrogen and hydrogen in the secondary purge is 480-520 mL / min, the temperature of the secondary purge is 70-80° C., and the time is 1.5-2 h; The volume ratio of nitrogen to hydrogen in the mixed gas of nitrogen and hydrogen is 4-5:

1.

8. The regeneration method of palladium catalyst for hydrogen peroxide according to claim 1, wherein In the secondary treatment, the complete palladium catalyst particles are loaded into the constant temperature section of the fixed bed and filled with quartz sand above and below; The volume ratio of the mixed solution used in the soaking to the complete palladium catalyst particles is 3.8-4:1, the soaking temperature is 50-60° C., and the soaking time is 30-33 hours; The flow rate of nitrogen in the primary purge is 700-750 mL / min; The flow rate of water vapor in the first cleaning is 180-200 mL / h, the temperature is 100-110° C., and the time is 12-13 h; The flow rate of hot water in the secondary cleaning is 120-130 mL / h, the temperature is 100° C., and the time is 5-6 h; The flow rate of nitrogen in the secondary purge is 480-520 mL / min, the temperature of the secondary purge is 50-60° C., and the time is 1.5-2 h.

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