Preparation method of catalyst for catalytic decomposition of chlorobenzene and method for catalytic decomposition of chlorobenzene

Abstract

The present invention discloses a preparation method of a catalyst for catalytically decomposing chlorobenzene and a method for catalytically decomposing chlorobenzene. The present invention uses cobalt as an active component and cerium-zirconium as a dual auxiliary agent, and strengthens the mixed cobalt-cerium-zirconium ternary component by a special chelating agent, which not only improves the dispersion of Co in the catalyst, but also increases the specific surface area of ​​the catalyst, which is beneficial to improving the reaction activity of the catalyst and ensuring that the catalyst has better stability in a hydrogen chloride atmosphere. The catalyst decomposition is carried out in a fixed bed device. The quality of the dry hydrogen chloride product delivered from the isocyanate device is improved, the chlorobenzene content in the dry hydrogen chloride is reduced, and the operational stability of the downstream fixed bed catalytic oxidation device is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of chlorine circulation, and in particular to a method for preparing a catalyst for catalytically decomposing trace chlorobenzene in hydrogen chloride and a method for removing the trace chlorobenzene by catalytic decomposition. Background Art

[0002] The utilization rate of chlorine resources in the isocyanate production process is very low. Chloride mainly exists in the form of reaction intermediates and does not enter the final target product. Taking the phosgene method for producing isocyanates as an example, after carbonyl substitution, most of the chlorine atoms are discharged in the form of hydrogen chloride. Currently, the most effective way to treat the by-product hydrogen chloride in industry is to directly convert it into chlorine gas for recycling. Among them, the catalytic oxidation method is currently widely used in the industrial field and has many advantages such as simple operation, low energy consumption, no other side reactions, and high efficiency. However, in the actual operation process, the operating load and operating conditions of the isocyanate production unit fluctuate, which will affect the content of chlorobenzene delivered to the outside, thereby causing the downstream fixed-bed catalytic oxidation unit to run high, and a large amount of carcinogens such as polychlorinated benzenes are generated in the by-product hydrochloric acid. In order to ensure the quality of the dry hydrogen chloride product delivered by isocyanate, the chlorobenzene content in the dry hydrogen chloride is reduced to further improve the operating stability of the downstream fixed-bed catalytic oxidation unit.

[0003] Chinese patent CN109225226B discloses a method for preparing nanosilica particles by hydrolyzing tetraethyl orthosilicate (TEOS). The particles are then loaded with an oxidizing metal oxide catalyst using an impregnation-calcination process. This catalyst, under visible light catalysis, effectively decomposes soluble chlorobenzene in commercial resveratrol, rendering it edible. The patent focuses on the removal of chlorobenzene dissolved in liquid phases.

[0004] Chinese patent CN113368848A discloses a catalyst prepared from coal-based solid wastes (coal gangue, coal-based bentonite, and kaolin) rich in alumina, along with manganese and cerium active components. The catalyst is separated and enriched with alumina, and then combined with carbon nanotubes to form a composite support to produce a manganese-cerium oxide catalyst. The catalyst's operating temperature is primarily around 350°C, which is too high for a fixed-bed catalytic oxidation process, increasing energy consumption. Furthermore, this operating condition does not consider the hydrogen chloride system, making it impossible to verify its durability. Developing a low-temperature, efficient, and stable catalyst for the catalytic decomposition of chlorobenzene in hydrogen chloride is a key issue that urgently needs to be addressed. Summary of the Invention

[0005] To address the shortcomings of the prior art, the present invention provides a method for preparing a catalyst for the catalytic decomposition of chlorobenzene and a method for the catalytic decomposition of chlorobenzene. The catalyst of the present invention is a cobalt-cerium-titanium composite catalyst that can decompose trace amounts of chlorobenzene in dry hydrogen chloride at low temperatures to produce HCl, CO₂, and H₂O, thereby reducing the chlorobenzene content. The catalyst also exhibits high operational stability, high chlorobenzene decomposition activity, and high chlorobenzene conversion.

[0006] A catalyst Co for catalytic decomposition of chlorobenzene x Ce y O Z / The preparation method of TiO2 comprises the following steps:

[0007] (1) preparing a solution A by mixing polyvinyl pyrrolidone ((C6H9NO)n), anhydrous ethanol, and tetrabutyl titanate; and preparing a mixed solution B of anhydrous ethanol, deionized water, and hydrochloric acid with a pH value of 2 to 4;

[0008] (2) adding solution B dropwise into solution A; drying, calcining, cooling, and crushing to obtain porous TiO2 powder; (3) preparing a water mixture containing a cobalt precursor, a cerium precursor, porous TiO2, and an organic acid, adding the water mixture to ammonia water, stirring until it reaches a gel state, aging, and calcining.

[0009] In step (1) of the present invention, in the solution A, the mass ratio of polyvinyl pyrrolidone ((C6H9NO)n), anhydrous ethanol and tetrabutyl titanate is 0.1-1:10-30:5-10.

[0010] In step (1) of the present invention, the mass ratio of anhydrous ethanol to deionized water in the solution B is 0.5-1:1-2.

[0011] In step (1) of the present invention, the pH value of solution B is adjusted to 2-4 with hydrochloric acid to obtain solution B.

[0012] In step (2) of the present invention, the mass ratio of solution B to solution A is 1-2:6-12.

[0013] In step (2) of the present invention, the temperature of solution A is 20-60°C during the dropwise addition.

[0014] In step (2) of the present invention, the drying temperature is 50-100°C.

[0015] In step (2) of the present invention, the calcination temperature is 400-800° C., and the calcination time is 2-6 hours.

[0016] In step (2) of the present invention, the specific surface area of ​​the porous TiO2 is 200 to 600 m 2 / g.

[0017] In step (3) of the present invention, the cobalt precursor comprises one or more of cobalt chloride, cobalt nitrate and cobalt sulfate.

[0018] In step (3) of the present invention, the cerium precursor comprises one or more of cerium chloride, cerium nitrate and cerium sulfate.

[0019] In step (3) of the present invention, the organic acid comprises one or more of citric acid, malic acid and glycolic acid.

[0020] As a preferred embodiment, in step (3) of the present invention, the molar ratio of the cobalt precursor, the cerium precursor, the porous TiO2 and the organic acid is 0.01-0.1: 0.01-0.1: 0.005-0.015: 0.012-0.12. Preferably, deionized water is added at a molar ratio of 1-2: 5-10 of the sum of the molar amounts of the cobalt precursor, the cerium precursor, the porous TiO2 and the organic acid to water.

[0021] In step (3) of the present invention, the concentration of the ammonia solution is 15 to 30 wt%.

[0022] As a preferred solution, in step (3) of the present invention, the mass ratio of the ammonia solution to the water mixture is 4-8:1-2.

[0023] In step (3) of the present invention, the stirring temperature is 50-100°C.

[0024] In step (3) of the present invention, the aging temperature is 100-150° C., and the aging time is 10-20 hours.

[0025] In step (3) of the present invention, the calcination temperature is 500-800° C. and the calcination time is 4-8 hours.

[0026] A method for catalytically decomposing chlorobenzene comprises the following steps: in the presence of the catalyst of the present invention, HCl gas containing a trace amount of chlorobenzene reacts with oxygen.

[0027] In the method for catalytically decomposing chlorobenzene of the present invention, the composition of the HCl gas containing trace amounts of chlorobenzene is 98.8-99.2 vol% HCl, 0.78-1.19 vol% N2, and 0.01-0.02 vol% chlorobenzene.

[0028] In the method for catalytically decomposing chlorobenzene of the present invention, the volume ratio of the HCl gas containing trace amounts of chlorobenzene to oxygen is 4-6:1-2.

[0029] In the method for catalytic decomposition of chlorobenzene of the present invention, the catalyst loading amount is based on the feed amount of HCl gas containing trace chlorobenzene, and the mass space velocity is 0.5 to 1.2 h -1.

[0030] In the method for catalytically decomposing chlorobenzene of the present invention, the reaction temperature is 320-360°C.

[0031] The catalyst of the present invention uses Co and Ce as active components and porous TiO2 as a carrier, wherein porous TiO2 is prepared by modifying TiO2. During the deposition process of the active component metal Co / Ce, a Schottky barrier is formed with TiO2 to improve the oxygen vacancies of the active component, thereby improving the catalytic efficiency and activity of the catalyst. By a deposition method, the mixed effect between the Co-Ce / Ti ternary metal is strengthened, not only the dispersity of Co in the catalyst is improved, but also the catalyst specific surface area is improved, which is conducive to improving the reaction activity of the catalyst. Simultaneously, after part of cerium in the CeO2 lattice is replaced by Ti during the preparation process, the CeO2 lattice is deformed and has surface defects due to the difference in the cationic surface, so that the effect between Co and Ce is tight, further improving the catalyst main active site Co under a hydrogen chloride atmosphere (HCl concentration>97%). Under preferred conditions, the chlorobenzene catalytic decomposition activity can reach 98%, and after 96 hours of continuous operation, the chlorobenzene conversion rate does not decline. DETAILED DESCRIPTION

[0032] The present invention will be further described below through specific examples. The examples of the present invention are only for illustration of the present invention and do not limit the scope of the present invention.

[0033] The main sources of raw materials are shown in Table 1:

[0034] Table 1 Main sources of raw materials

[0035]

[0036] Unless otherwise specified, other raw materials and reagents were purchased through common commercial channels.

[0037] The present invention adopts a fixed bed reactor with an inner diameter of 30 mm and a length of 50 cm.

[0038] In the present invention, the chlorobenzene composition in the gas before and after entering and leaving the fixed bed reactor is tracked by an ethanol absorption method.

[0039] Example 1

[0040] Solution A was prepared by combining polyvinylpyrrolidone ((C6H9NO)n), anhydrous ethanol, and tetrabutyl titanate in a mass ratio of 0.5:15:7.5. Solution B was prepared by combining anhydrous ethanol and deionized water in a mass ratio of 0.6:1.5, and adjusting the pH to 3 with hydrochloric acid. Solution B was then added dropwise to Solution A at a mass ratio of 1.5:9. The addition rate was 3 drops / s, and the temperature of Solution A was 40°C. The product was then dried at 75°C, calcined at 600°C for 4 hours, cooled, and pulverized to obtain TiO2 powder.

[0041] Cobalt chloride, cerium chloride, porous TiO2 and citric acid are placed in a beaker at a molar ratio of 0.05:0.05:0.01:0.0066, and then deionized water is added at a molar ratio of the total molar amount of the above mixture to deionized water of 1.5:7.5 to obtain a suspension; the suspension is added to the ammonia water at a mass ratio of the suspension to ammonia water of 1.5:6, stirred at 75°C to a gel state, aged at 125°C for 15 hours, and then calcined at 650°C for 6 hours to obtain a catalyst.

[0042] The catalytic decomposition of chlorobenzene was carried out in a fixed-bed reactor. HCl gas containing 98.8 vol% HCl, 1.19 vol% N2, and 0.01 vol% chlorobenzene and high-purity oxygen were introduced at a volume ratio of 5:1.5. The reaction mass space velocity was 0.85 h -1 When reacting at 340℃, the catalytic decomposition activity of chlorobenzene reached 98%, and the chlorobenzene conversion rate did not decrease after 96 hours of continuous operation.

[0043] Example 2

[0044] Solution A was prepared by combining polyvinylpyrrolidone ((C6H9NO)n), anhydrous ethanol, and tetrabutyl titanate in a mass ratio of 0.1:10:5. Solution B was prepared by combining anhydrous ethanol and deionized water in a mass ratio of 1:1 and adjusting the pH to 2 with hydrochloric acid. Solution B was then added dropwise to Solution A at a mass ratio of 2:6. The addition rate of Solution B was 1 drop / s, and the temperature of Solution A was 20°C during the addition. The product was then dried at 50°C, calcined at 400°C for 2 hours, cooled, and pulverized to obtain TiO2 powder.

[0045] Cobalt chloride, cerium chloride, porous TiO2 and citric acid are placed in a beaker at a molar ratio of 0.01:0.01:0.015:0.012, and then deionized water is added at a molar ratio of the total molar amount of the above mixture to deionized water of 2:5 to obtain a suspension; the suspension is added to the ammonia water at a mass ratio of the suspension to ammonia water of 2:4, stirred at 50°C to a gel state, aged at 100°C for 10 hours, and then calcined at 500°C for 4 hours to obtain a catalyst.

[0046] The catalytic decomposition of chlorobenzene was carried out in a fixed-bed reactor. HCl gas containing 98.8 vol% HCl, 1.19 vol% N2, and 0.01 vol% chlorobenzene and high-purity oxygen were introduced at a volume ratio of 5:1.5. The reaction mass space velocity was 0.85 h -1 , reacting at 340 ° C, the catalytic decomposition activity of chlorobenzene reached 85%. After 96 hours of continuous operation, the chlorobenzene conversion rate dropped to 76%.

[0047] Example 3

[0048] Solution A was prepared by combining polyvinylpyrrolidone ((C6H9NO)n), anhydrous ethanol, and tetrabutyl titanate in a mass ratio of 1:30:10. Solution B was prepared by combining anhydrous ethanol and deionized water in a mass ratio of 0.5:2, and adjusting the pH to 4 with hydrochloric acid. Solution B was then added dropwise to Solution A at a mass ratio of 1:12. The addition rate was 4 drops / s, and the temperature of Solution A was 60°C during the addition. The product was then dried at 100°C, calcined at 800°C for 8 hours, cooled, and pulverized to obtain TiO2 powder.

[0049] Cobalt chloride, cerium chloride, porous TiO2 and citric acid are placed in a beaker at a molar ratio of 0.1:0.1:0.005:0.015, and then deionized water is added at a molar ratio of the total molar amount of the above mixture to deionized water of 1:10 to obtain a suspension; the suspension is added to the ammonia water at a mass ratio of the suspension to ammonia water of 1:8, stirred at 100°C to a gel state, aged at 150°C for 20 hours, and then calcined at 800°C for 8 hours to obtain a catalyst.

[0050] The catalytic decomposition of chlorobenzene was carried out in a fixed-bed reactor. HCl gas containing 98.8 vol% HCl, 1.19 vol% N2, and 0.01 vol% chlorobenzene and high-purity oxygen were introduced at a volume ratio of 5:1.5. The reaction mass space velocity was 0.85 h -1 , reacting at 340 ° C, the catalytic decomposition activity of chlorobenzene reached 76%. After 96 hours of continuous operation, the chlorobenzene conversion rate dropped to 62%.

[0051] Example 4

[0052] Solution A was prepared by combining polyvinylpyrrolidone ((C6H9NO)n), anhydrous ethanol, and tetrabutyl titanate in a mass ratio of 0.5:15:7.5. Solution B was prepared by combining anhydrous ethanol and deionized water in a mass ratio of 0.6:1.5, and adjusting the pH to 3 with hydrochloric acid. Solution B was then added dropwise to Solution A at a mass ratio of 1.5:9. The addition rate was 3 drops / s, and the temperature of Solution A was 40°C. The product was then dried at 75°C, calcined at 600°C for 4 hours, cooled, and pulverized to obtain TiO2 powder.

[0053] Cobalt chloride, cerium chloride, porous TiO2 and citric acid are placed in a beaker at a molar ratio of 0.05:0.05:0.01:0.0066, and then deionized water is added at a molar ratio of the total molar amount of the above mixture to deionized water of 1.5:7.5 to obtain a suspension; the suspension is added to the ammonia water at a mass ratio of the suspension to ammonia water of 1.5:6, stirred at 75°C to a gel state, aged at 125°C for 15 hours, and then calcined at 650°C for 6 hours to obtain a catalyst.

[0054] The catalytic decomposition of chlorobenzene was carried out in a fixed-bed reactor. HCl gas containing 98.8 vol.% HCl, 1.19 vol.% N2, and 0.01 vol.% chlorobenzene and high-purity oxygen were introduced at a volume ratio of 5:1.5 and a mass space velocity of 0.85 h-1. -1 When reacting at 340℃, the catalytic decomposition activity of chlorobenzene reached 80%. After 96h of continuous operation, the chlorobenzene conversion rate dropped to 72%.

[0055] Example 5

[0056] Solution A was prepared by combining polyvinylpyrrolidone ((C6H9NO)n), anhydrous ethanol, and tetrabutyl titanate in a mass ratio of 0.5:15:7.5. Solution B was prepared by combining anhydrous ethanol and deionized water in a mass ratio of 0.6:1.5, and adjusting the pH to 3 with hydrochloric acid. Solution B was then added dropwise to Solution A in a mass ratio of 1.5:9. The addition rate was 3 drops / s, and the temperature of Solution A was 40°C during the addition. The product was then dried at 75°C, calcined at 600°C for 4 hours, cooled, and pulverized to obtain TiO2 powder.

[0057] Cobalt chloride, cerium chloride, porous TiO2 and citric acid are placed in a beaker at a molar ratio of 0.05:0.05:0.01:0.0066, and then deionized water is added at a molar ratio of the total molar amount of the above mixture to deionized water of 1.5:7.5 to obtain a suspension; the suspension is added to the ammonia water at a mass ratio of the suspension to ammonia water of 1.5:6, stirred at 75°C to a gel state, aged at 125°C for 15 hours, and then calcined at 650°C for 6 hours to obtain a catalyst.

[0058] The catalytic decomposition of chlorobenzene was carried out in a fixed-bed reactor. HCl gas containing 98.8 vol.% HCl, 1.19 vol.% N2, and 0.01 vol.% chlorobenzene and high-purity oxygen were introduced at a volume ratio of 5:1.5 and a mass space velocity of 0.85 h-1. -1 , reacting at 340 ° C, the catalytic decomposition activity of chlorobenzene reached 76%. After 96 hours of continuous operation, the chlorobenzene conversion rate dropped to 52%.

[0059] Comparative Example 1

[0060] Cobalt chloride, cerium chloride, commercial X-TiO2 (BA01-01) and citric acid were placed in a beaker at a molar ratio of 0.05:0.05:0.01:0.0066, and then deionized water was added at a molar ratio of the total molar amount of the above mixture to deionized water of 1.5:7.5 to obtain a suspension; the suspension was added to the ammonia water at a mass ratio of the suspension to ammonia water of 1.5:6, stirred at 75°C to a gel state, aged at 125°C for 15 hours, and then calcined at 650°C for 6 hours to obtain a catalyst.

[0061] The catalytic decomposition of chlorobenzene was carried out in a fixed-bed reactor. HCl gas containing 98.8 vol.% HCl, 1.19 vol.% N2, and 0.01 vol.% chlorobenzene and high-purity oxygen were introduced at a ratio of 5:1.5. The reaction mass space velocity was 0.85 h -1 , reacting at 330 ° C, the catalytic decomposition activity of chlorobenzene reached 70%. After 96 hours of continuous operation, the chlorobenzene conversion rate dropped to 45%.

[0062] Comparative Example 2

[0063] Referring to patent CN113368838B, the material prepared in Example 3 uses manganese and cerium as active components and coal-based solid waste rich in alumina, such as coal gangue, as the carrier raw material.

[0064] The catalytic decomposition of chlorobenzene was carried out in a fixed-bed reactor. HCl gas containing 98.8 vol% HCl, 1.19 vol% N2, and 0.01 vol% chlorobenzene and high-purity oxygen were introduced at a ratio of 6:1. The reaction mass space velocity was 0.5 h -1 , reacting at 320℃, the catalytic decomposition activity of chlorobenzene reached 66%. After 96h of continuous operation, the chlorobenzene conversion rate dropped to 40%.

[0065] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a catalyst for catalytically decomposing chlorobenzene, comprising the following steps: (1) preparing a solution A by mixing polyvinyl pyrrolidone ((C6H9NO)n), anhydrous ethanol, and tetrabutyl titanate; and preparing a mixed solution B of anhydrous ethanol, deionized water, and hydrochloric acid with a pH value of 2 to 4; (2) adding solution B dropwise into solution A; drying, calcining, cooling, and crushing to obtain porous TiO2 powder; (3) preparing a water mixture containing a cobalt precursor, a cerium precursor, porous TiO2 and an organic acid, adding the water mixture into ammonia water, stirring until a gel state, aging, and calcining to obtain Co x Ce y O Z / TiO2.

2. The method according to claim 1, characterized in that In the step (1), in the solution A, the mass ratio of polyvinyl pyrrolidone ((C6H9NO)n), anhydrous ethanol and tetrabutyl titanate is 0.1-1:10-30:5-10.

3. The method according to claim 1, characterized in that In the step (1), the mass ratio of anhydrous ethanol to deionized water in the solution B is 0.5-1:1-2; and the pH value of the solution B is adjusted to 2-4 with hydrochloric acid to obtain solution B.

4. The method according to claim 1, wherein In the step (2), the mass ratio of solution B to solution A is 1-2:6-12; when adding dropwise, the temperature of solution A is 20-60°C.

5. The method according to claim 1, wherein In the step (2), the drying temperature is 50-100° C.; the roasting temperature is 400-800° C., and the roasting time is 2-6 hours.

6. The method according to claim 1, characterized in that In the step (2), the specific surface area of ​​the porous TiO2 is 200 to 600 m 2 / g.

7. The method according to claim 1, characterized in that In the step (3), the mass ratio of the ammonia water to the water mixture is 4-8:1-2; the stirring temperature is 50-100°C; the aging temperature is 100-150°C, and the aging time is 10-20 hours; the roasting temperature is 500-800°C, and the roasting time is 4-8 hours.

8. A method for catalytically decomposing chlorobenzene, comprising the following steps: In the presence of the catalyst prepared by the method according to any one of claims 1 to 7, HCl gas containing a trace amount of chlorobenzene reacts with oxygen.

9. The method according to claim 8, characterized in that In the method for catalytically decomposing chlorobenzene, the composition of the HCl gas containing trace amounts of chlorobenzene is 98.8-99.2 vol% HCl, 0.78-1.19 vol% N2, and 0.01-0.02 vol% chlorobenzene.

10. The method according to claim 8, characterized in that The volume ratio of the HCl gas containing trace chlorobenzene to oxygen is 4-6:1-2; the catalyst loading amount is based on the feed amount of the HCl gas containing trace chlorobenzene, and the mass space velocity is 0.5-1.2h -1 ; The reaction temperature is 320-360°C.

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