Process for treating waste gas generated in production of phenylenediamine

Abstract

The invention relates to the technical field of industrial waste gas treatment, and discloses a phenylenediamine production waste gas treatment process. According to the process, an ozone coupling alkaline washing pretreatment and multi-stage adsorption-catalytic combustion synergistic technology is adopted, waste gas pollutants are deeply degraded through an ozone oxidation and alkaline absorption synergistic system, and efficient enrichment of the pollutants is achieved through a composite adsorbent. The composite adsorbent is prepared by compounding a mesoporous carbon-based composite material and dual-modified mesoporous alumina, and the adsorption performance on benzene series and nitrogen-containing pollutants is remarkably improved through a synergistic effect. After adsorption saturation, high-temperature combustion tail gas countercurrent desorption is adopted, desorbed gas is treated through a double-section type catalytic combustion system, and deep mineralization of organic matter is achieved through concerted catalysis of metal oxide and a carrier. According to the process, complex pollutants in waste gas can be efficiently removed, secondary pollution is reduced, the treatment efficiency is remarkably improved, the purification effect is excellent, and good industrial application value is achieved.

Description

Technical Field

[0001] The present invention relates to the field of industrial waste gas treatment, and more specifically, to a process for treating waste gas produced in the production of phenylenediamine. Background Art

[0002] In the field of fine chemical production, phenylenediamine is an important intermediate. The waste gas discharged during its production contains benzene organic compounds, nitrogen-containing volatile pollutants (such as aniline and nitrobenzene compounds), and a small amount of acidic gas, which has the characteristics of complex composition, high toxicity, and difficult treatment. If such waste gas is directly discharged without effective treatment, it will not only pollute the atmospheric environment but also may endanger human health and ecological safety. Therefore, developing an efficient, stable, and adaptable process for treating waste gas produced in the production of phenylenediamine has become a research focus in the field of industrial waste gas treatment.

[0003] At present, industrial waste gas treatment technologies mainly include adsorption method, absorption method, catalytic combustion method, biological method, etc. The adsorption method uses adsorbents to adsorb and separate pollutants in the waste gas. Common adsorbents include activated carbon, zeolite, etc. It has the advantages of simple operation and low investment cost, but its treatment effect on high-concentration waste gas is limited, and the adsorbent needs to be replaced or regenerated regularly, resulting in relatively high long-term operating costs. The absorption method transfers pollutants to the absorbent through physical or chemical reactions between the liquid absorbent and pollutants in the waste gas, which is suitable for treating high-concentration waste gas, but there are problems such as difficulty in recovering the absorbent after treatment and high energy consumption. The catalytic combustion method oxidizes and decomposes combustible pollutants in the waste gas into harmless substances at a lower temperature under the action of a catalyst. Although it can achieve the oxidation and decomposition of pollutants, its treatment effect highly depends on the performance of the catalyst. The catalytic activities of traditional single catalysts for pollutants with different functional groups vary greatly, and phenomena such as catalyst sintering and loss of active components are likely to occur under high-temperature conditions, resulting in insufficient system operation stability. The biological method degrades pollutants in the waste gas through the metabolic action of microorganisms, with simple equipment, low operating costs, and no secondary pollution, but its treatment efficiency for complex pollutants is relatively low, and it has relatively strict requirements for environmental conditions. In practical applications, a single waste gas treatment technology often fails to meet the requirements for efficiently treating complex pollutants in waste gas produced in the production of phenylenediamine. For example, only using the adsorption method is difficult to deeply mineralize organic substances and is prone to secondary pollution; while the single catalytic combustion method has poor treatment effect on low-concentration waste gas and high energy consumption. Therefore, the present invention provides a process for treating waste gas produced in the production of phenylenediamine to solve the above-mentioned technical problems. Summary of the Invention

[0004] To solve the above problems, the present invention provides a process for treating waste gas produced in the production of phenylenediamine. This process can efficiently remove complex pollutants in the waste gas, reduce secondary pollution, significantly improve the treatment efficiency, have excellent purification effects, and possess good industrial application value.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A process for treating waste gas from the production of phenylenediamine comprises the following steps:

[0007] S1. Using ozone-coupled alkaline solution washing process, the production waste gas is treated with NaOH solution with a pH value of 10-11 and 30-50ppm ozone to obtain pre-treated waste gas;

[0008] S2, passing the pretreated waste gas into an adsorption tower, and performing adsorption treatment by a composite adsorbent in the adsorption tower;

[0009] S3, using 275-285℃ combustion tail gas to carry out countercurrent desorption of the composite adsorbent, and the desorbed gas is sequentially passed through the dual catalyst sections for catalytic combustion treatment.

[0010] Preferably, in step S1, the liquid-gas ratio is controlled at 0.8-1.2 L / m³, the ORP value of the system is adjusted to 600-800 mV, and the reaction temperature is maintained at 70-90°C.

[0011] Preferably, the preparation steps of the composite adsorbent in step S2 are:

[0012] A1. The mesoporous carbon was immersed in a methanol solution containing 0.5-0.8 mol / L 2-methylimidazole, and polystyrene microspheres and Pluronic F127 were added. After ultrasonic treatment for 30-35 min, 0.2-0.5 mol / L cobalt nitrate methanol solution was added and stirred at 60-80 ° C for 6-8 h;

[0013] A2. The product obtained in step A1 was mixed with thiourea in a mass ratio of 1:0.1-0.3, and calcined in an inert gas at a gradient temperature, calcined at 300-320°C for 2-3h in the first stage, and calcined at 800-900°C for 3-4h in the second stage. After cooling, it was acid-washed with 0.1-0.3mol / LHCl to obtain a mesoporous carbon composite material;

[0014] A3. The mesoporous alumina and 3-mercaptopropyltrimethoxysilane were uniformly dispersed in toluene, refluxed at 80-85°C for 5-7h, oxidized with hydrogen peroxide to obtain sulfonated mesoporous alumina, and then dispersed with trimethyl phosphate in toluene, refluxed at 90-100°C for 5-8h, washed and dried to obtain modified mesoporous alumina;

[0015] A4. The mesoporous carbon composite material and the modified mesoporous alumina are uniformly mixed in a mass ratio of 1-3:1, an appropriate amount of deionized water is added, stirred evenly, and dried at 80-90° C. to obtain a composite adsorbent.

[0016] Preferably, in step A1, by weight: 50 - 55 parts of mesoporous carbon, 90 - 100 parts of 2 - methylimidazole methanol solution, 10 - 15 parts of polystyrene microspheres, 5 - 10 parts of Pluronic F127, and 30 - 40 parts of cobalt nitrate methanol solution.

[0017] Preferably, in step A3, by weight: in the sulfonation stage, 25 - 30 parts of mesoporous alumina, 5 - 10 parts of 3 - mercaptopropyltrimethoxysilane, 100 - 120 parts of toluene, and 12 - 16 parts of hydrogen peroxide; in the phosphorylation stage, 35 - 40 parts of sulfonated mesoporous alumina, 10 - 15 parts of trimethyl phosphate, and 100 - 120 parts.

[0018] Preferably, in step S3, the flow rate of the counter - current desorption is 0.5 - 1.5 m³ / h, and the filling amount of the catalyst in the double - catalyst section is 10 - 20% of the adsorption tower volume.

[0019] Preferably, in step S3, the first - stage catalyst in the double - catalyst section is prepared as follows: Dissolve 30 - 35 parts of copper nitrate, 8 - 12 parts of bismuth nitrate, and 15 - 20 parts of cerium nitrate in 130 - 140 parts of deionized water, add 0.3 - 0.7 parts of polystyrene microspheres, stir and react at 65 - 70 °C for 2 - 4 h, then add 28 - 32 parts of γ - Al2O3 and ultrasonically treat for 20 - 30 min, dry and calcine in an inert gas at 500 - 600 °C for 3 - 5 h.

[0020] Preferably, the second - stage catalyst in the double - catalyst section is prepared as follows:

[0021] (1) Dissolve 20 - 25 parts of strontium nitrate and 30 - 35 parts of tetrabutyl titanate in 100 - 110 parts of a mixed solvent, add 16 - 24 parts of PEG - PLA, 1 - 2 parts of oxalic acid, and 2 - 3 parts of triethoxysilane, dropwise add 10 - 15 parts of ammonium dihydrogen phosphate aqueous solution in an ice - water bath at 0 - 5 °C, then stand and age at 20 - 30 °C for 20 - 28 h, vacuum - dry, and calcine in an inert gas at 600 - 700 °C for 4 - 6 h to obtain the carrier;

[0022] (2) Immerse the carrier in 120 - 130 parts of a mixed solvent containing 10 - 15 parts of CoSO4 and 20 - 25 parts of MnCl2, add 1 - 2 parts of azobenzene - 4,4'-dicarboxylic acid and 0.5 - 1 part of o - phenanthroline, stir and react for 0.5 - 1 h under light - shielding conditions at 20 - 30 °C, then irradiate and treat successively with ultraviolet light of 365 nm and 254 nm at 20 - 30 °C, with a total light - irradiation reaction time of 2 - 4 h, and finally heat up to 400 - 500 °C in an air atmosphere and calcine for 3 - 5 h.

[0023] Preferably, in the step (1), the mixed solvent consists of ethyl acetate and ethanol with a mass ratio of 2 - 4:1; in the step (2), the mixed solvent consists of acetonitrile and water with a mass ratio of 1 - 3:1.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] The present invention adopts a coupling system of ozone oxidation and alkaline absorption, strengthens the free radical chain reaction under specific reaction conditions, significantly improves the oxidation degradation efficiency of benzene series compounds and nitrogen-containing pollutants, effectively neutralizes acidic gas components at the same time, and reduces the load of subsequent treatment units. Through the synergistic compounding of mesoporous carbon-based composites and double-modified mesoporous alumina, combined with the dual-functional sites of sulfonic acid groups and phosphoric acid groups and the hierarchical pore structure, the efficient selective adsorption of different polar pollutants is realized, and the problem of decreased adsorption capacity caused by competitive adsorption is avoided. By using the high-temperature combustion tail gas countercurrent desorption process and combining the multi-stage oxidation characteristics of the two-stage catalytic combustion system, the deep mineralization of the desorbed gas is realized at low temperature, the energy consumption is significantly reduced, and the generation of secondary pollutants is avoided. Through the carrier mesoporous structure design and the directional loading technology of active components, the anti-sintering performance and anti-poisoning ability of the catalyst are improved, ensuring that it maintains high catalytic activity in a complex reaction environment for a long time and reducing the process operation cost.

[0026] In summary, through the optimized design of each link of this process, the operation process is simplified, the risk of secondary pollution is reduced, the resource utilization rate is improved, and the energy consumption and process cost are reduced. In addition, the high stability of the composite catalyst in an alkaline environment, the low dissolution rate of active components, and the characteristics of being recyclable multiple times further improve the economy and reliability of the process, providing an efficient, environmentally friendly and industrially applicable solution for the treatment of waste gas from phenylenediamine production. Specific embodiments

[0027] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0028] The experimental methods in the following embodiments are all conventional methods unless otherwise specified, and the test materials used are all purchased from conventional biochemical reagent stores unless otherwise specified. In the following embodiments, all quantitative tests are set with three repeated experiments, and the data are the average or average ± standard deviation of the three repeated experiments.

[0029] Mesoporous carbon, purchased from Yumu (Ningbo) New Materials Co., Ltd., CAS No. 1333 - 86 - 4;

[0030] Polystyrene microspheres, purchased from Shanghai Lingjun Biotechnology Co., Ltd., CAS No. 9003-53-6;

[0031] Pluronic F127, purchased from Nanjing Xingye Biotechnology Co., Ltd., CAS No. 9003-11-6;

[0032] γ-Al2O3, purchased from Zhejiang Zhitaina Micro-New Materials Co., Ltd., CAS No. 1344-28-1;

[0033] PEG-PLA, purchased from Chongqing Yusai Medical Technology Co., Ltd., product number: YS-PLAP2101.

[0034] Example 1

[0035] A process for treating waste gas from phenylenediamine production, comprising the following steps:

[0036] S1. Pass the waste gas from phenylenediamine production into a scrubbing tower at a flow rate of 100 m³ / h, and perform synergistic treatment with a NaOH solution having a pH value of 10 and a liquid-gas ratio of 0.8 L / m³ and 30 ppm of ozone, adjust the ORP value of the system to 600 mV, and maintain the reaction temperature at 70 °C to obtain pretreated waste gas;

[0037] S2. Pass the pretreated waste gas into an adsorption tower, and the adsorption tower is filled with a composite adsorbent; the preparation steps of the composite adsorbent are as follows: A1. Weigh 50 parts of mesoporous carbon, immerse it in 90 parts of methanol solution containing 0.5 mol / L 2-methylimidazole, then add 10 parts of polystyrene microspheres and 5 parts of Pluronic F127, and perform ultrasonic treatment for 30 min (ultrasonic power 100 W, frequency 35 kHz); then add 30 parts of cobalt nitrate methanol solution with a concentration of 0.2 mol / L, and react at 60 °C and a stirring speed of 200 r / min for 6 h to obtain product A1; A2. Mix product A1 with thiourea in a mass ratio of 1:0.1, and perform gradient temperature calcination in an inert gas. The first stage is calcined at 300 °C for 2 h, and the second stage is calcined at 800 °C for 3 h. After cooling, wash with 0.1 mol / L HCl to obtain a mesoporous carbon composite material; A3. Uniformly disperse 25 parts of mesoporous alumina and 5 parts of 3-mercaptopropyltrimethoxysilane in 100 parts of toluene, reflux at 80 °C and a stirring speed of 250 r / min for 5 h, and then oxidize with 12 parts of hydrogen peroxide to obtain sulfonated mesoporous alumina; then disperse it and 10 parts of trimethyl phosphate in 100 parts of toluene, reflux at 90 °C and a stirring speed of 300 r / min for 5 h, and obtain modified mesoporous alumina after washing and drying; A4. Uniformly mix the mesoporous carbon composite material and the modified mesoporous alumina in a mass ratio of 1:1, add an appropriate amount of deionized water and stir evenly, and dry at 80 °C to obtain a composite adsorbent;

[0038] S3. The composite adsorbent is desorbed by countercurrent with the combustion exhaust gas at 275 °C at a flow rate of 0.5 m³ / h. The desorbed gas is catalytically combusted through the dual-catalyst section in sequence. The filling amount of the catalyst in the dual-catalyst section is 10% of the volume of the adsorption tower;

[0039] The first-stage catalyst in the dual-catalyst section is prepared as follows: Dissolve 30 parts of copper nitrate, 8 parts of bismuth nitrate and 15 parts of cerium nitrate in 130 parts of deionized water, add 0.3 part of polystyrene microspheres, react at 65 °C with a stirring speed of 300 r / min for 2 h, then add 28 parts of γ-Al2O3 and perform ultrasonic treatment for 20 min, and calcine in an inert gas at 500 °C for 3 h after drying;

[0040] The second-stage catalyst is prepared by the following method: (1) Dissolve 20 parts of strontium nitrate and 30 parts of tetrabutyl titanate in 100 parts of a mixed solvent composed of ethyl acetate and ethanol with a mass ratio of 2:1, add 16 parts of PEG-PLA, 1 part of oxalic acid and 2 parts of triethoxysilane, dropwise add 10 parts of ammonium dihydrogen phosphate aqueous solution in an ice-water bath at 0-5 °C, then stand and age at 20-30 °C for 20 h, and after vacuum drying, calcine in an inert gas at 600 °C for 4 h to obtain the carrier;

[0041] (2) Immerse the carrier in 120 parts of a mixed solvent composed of acetonitrile and water with a mass ratio of 1:1 containing 10 parts of CoSO4 and 20 parts of MnCl2, add 1 part of azobenzene-4,4'-dicarboxylic acid and 0.5 part of o-phenanthroline, stir and react for 0.5 h under light-shielded conditions at 20-30 °C, then irradiate and treat with ultraviolet light at 365 nm and 254 nm in sequence at 20-30 °C, with a total light reaction time of 2 h, and finally heat up to 400 °C in an air atmosphere and calcine for 3 h.

[0042] Example 2

[0043] A process for treating waste gas from phenylenediamine production, comprising the following steps:

[0044] S1. The waste gas from phenylenediamine production is introduced into a washing tower at a flow rate of 200 m³ / h, and is co-treated with a NaOH solution with a pH value of 10.5 and a liquid-gas ratio of 1.0 L / m³ and 40 ppm of ozone, and the ORP value of the system is adjusted to 700 mV, and the reaction temperature is maintained at 80 °C to obtain the pretreated waste gas;

[0045] S2. Feed the pretreated waste gas into the adsorption tower which is filled with a composite adsorbent. The preparation steps of the composite adsorbent are as follows: A1. Weigh 52 parts of mesoporous carbon, immerse it in 95 parts of methanol solution containing 0.6 mol / L 2-methylimidazole, then add 12 parts of polystyrene microspheres and 7 parts of Pluronic F127, and perform ultrasonic treatment for 32 min (ultrasonic power 120 W, frequency 35 kHz); subsequently, add 35 parts of cobalt nitrate methanol solution with a concentration of 0.3 mol / L, and react at 70 °C with a stirring speed of 250 r / min for 5.5 h to obtain product A1; A2. Mix product A1 with thiourea in a mass ratio of 1:0.2, and perform gradient temperature calcination in an inert gas. Calcinate at 310 °C for 2.5 h in the first stage and at 850 °C for 3.5 h in the second stage. After cooling, wash with 0.2 mol / L HCl to obtain a mesoporous carbon composite material; A3. Uniformly disperse 28 parts of mesoporous alumina and 8 parts of 3-mercaptopropyltrimethoxysilane in 110 parts of toluene, reflux at 82 °C with a stirring speed of 280 r / min for 6 h, and then oxidize with 14 parts of hydrogen peroxide to obtain sulfonated mesoporous alumina; then disperse it and 12 parts of trimethyl phosphate in 110 parts of toluene, reflux at 95 °C with a stirring speed of 320 r / min for 6 h, and obtain the modified mesoporous alumina after washing and drying; A4. Uniformly mix the mesoporous carbon composite material and the modified mesoporous alumina in a mass ratio of 2:1, add an appropriate amount of deionized water and stir evenly, and dry at 85 °C to obtain the composite adsorbent;

[0046] S3. Use the combustion exhaust gas at 280 °C to perform countercurrent desorption on the composite adsorbent at a flow rate of 1.0 m³ / h. The desorbed gas is successively subjected to catalytic combustion treatment through a double catalyst section. The filling amount of the catalyst in the double catalyst section is 15% of the volume of the adsorption tower;

[0047] The first-stage catalyst in the double catalyst section is prepared as follows: Dissolve 32 parts of copper nitrate, 10 parts of bismuth nitrate and 18 parts of cerium nitrate in 135 parts of deionized water, add 0.5 part of polystyrene microspheres, react at 68 °C with a stirring speed of 350 r / min for 3 h, then add 30 parts of γ-Al2O3 and perform ultrasonic treatment for 25 min, and calcinate in an inert gas at 550 °C for 4 h after drying;

[0048] The preparation steps of the second-stage catalyst are as follows: (1) Dissolve 22 parts of strontium nitrate and 32 parts of tetrabutyl titanate in 105 parts of a mixed solvent composed of ethyl acetate and ethanol with a mass ratio of 2.5:1, add 18 parts of PEG-PLA, 1.2 parts of oxalic acid and 2.2 parts of triethoxysilane, dropwise add 12 parts of ammonium dihydrogen phosphate aqueous solution in an ice-water bath at 0 - 5 °C, then let it stand and age at 20 - 30 °C for 24 h, vacuum dry, and calcinate in an inert gas at 650 °C for 5 h to obtain the carrier;

[0049] (2) Immerse the carrier in 125 parts of a mixed solvent composed of acetonitrile and water with a mass ratio of 1.5:1 containing 12 parts of CoSO4 and 22 parts of MnCl2. Add 1.2 parts of azobenzene-4,4'-dicarboxylic acid and 0.6 parts of o-phenanthroline, and stir and react for 0.8 h under light-shielded conditions at 20 - 30 °C. Then, irradiate and treat with ultraviolet light of 365 nm and 254 nm at 20 - 30 °C in sequence, with a total light irradiation reaction time of 3 h. Finally, heat up to 450 °C in an air atmosphere and calcine for 4 h.

[0050] Example 3

[0051] A process for treating waste gas from phenylenediamine production, comprising the following steps:

[0052] S1. Introduce the waste gas from phenylenediamine production into a scrubbing tower at a flow rate of 300 m³ / h, and perform synergistic treatment with a NaOH solution having a pH value of 11, a liquid-gas ratio of 1.2 L / m³, and 50 ppm of ozone. Adjust the ORP value of the system to 800 mV, and maintain the reaction temperature at 90 °C to obtain pretreated waste gas;

[0053] S2. Introduce the pretreated waste gas into an adsorption tower, and the adsorption tower is filled with a composite adsorbent; the preparation steps of the composite adsorbent are as follows: A1. Weigh 55 parts of mesoporous carbon, immerse it in 100 parts of a methanol solution containing 0.8 mol / L of 2-methylimidazole, then add 15 parts of polystyrene microspheres and 10 parts of Pluronic F127, and perform ultrasonic treatment for 35 min (ultrasonic power 150 W, frequency 35 kHz); subsequently, add 40 parts of a cobalt nitrate methanol solution with a concentration of 0.5 mol / L, and react at 80 °C with a stirring speed of 300 r / min for 5 h to obtain product A1; A2. Mix product A1 and thiourea in a mass ratio of 1:0.3, and perform gradient heating and calcination in an inert gas. Calcinate at 320 °C for 3 h in the first stage and at 900 °C for 4 h in the second stage. After cooling, wash with 0.3 mol / L HCl to obtain a mesoporous carbon composite material; A3. Uniformly disperse 30 parts of mesoporous alumina and 10 parts of 3-mercaptopropyltrimethoxysilane in 120 parts of toluene, reflux at 85 °C with a stirring speed of 300 r / min for 7 h, and then oxidize with 16 parts of hydrogen peroxide to obtain sulfonated mesoporous alumina; then disperse it and 15 parts of trimethyl phosphate in 120 parts of toluene, reflux at 100 °C with a stirring speed of 350 r / min for 8 h, and obtain modified mesoporous alumina after washing and drying; A4. Uniformly mix the mesoporous carbon composite material and the modified mesoporous alumina in a mass ratio of 3:1, add an appropriate amount of deionized water and stir evenly, and dry at 90 °C to obtain a composite adsorbent;

[0054] S3. Use the combustion exhaust gas at 285 °C to carry out countercurrent desorption on the composite adsorbent at a flow rate of 1.5 m³ / h. The desorbed gas is successively subjected to catalytic combustion treatment through a dual-catalyst section, and the filling amount of the catalyst in the dual-catalyst section is 20% of the volume of the adsorption tower;

[0055] The first-stage catalyst in the dual-catalyst section is prepared as follows: Dissolve 35 parts of copper nitrate, 12 parts of bismuth nitrate, and 20 parts of cerium nitrate in 140 parts of deionized water, add 0.7 part of polystyrene microspheres, react at 70 °C with a stirring speed of 400 r / min for 3 h, then add 32 parts of γ-Al2O3 and ultrasonically treat for 25 min, and calcine in an inert gas at 600 °C for 4 h after drying;

[0056] The preparation steps of the second-stage catalyst are as follows: (1) Dissolve 25 parts of strontium nitrate and 35 parts of tetrabutyl titanate in 110 parts of a mixed solvent composed of ethyl acetate and ethanol with a mass ratio of 3:1, add 24 parts of PEG-PLA, 2 parts of oxalic acid, and 3 parts of triethoxysilane, dropwise add 15 parts of ammonium dihydrogen phosphate aqueous solution in an ice-water bath at 0-5 °C, then stand and age at 20-30 °C for 28 h, vacuum dry, and calcine at 700 °C in an inert gas for 6 h to obtain a carrier;

[0057] (2) Immerse the carrier in 130 parts of a mixed solvent composed of acetonitrile and water with a mass ratio of 2:1 containing 15 parts of CoSO4 and 25 parts of MnCl2, add 2 parts of azobenzene-4,4'-dicarboxylic acid and 1 part of o-phenanthroline, stir and react under light avoidance at 20-30 °C for 1 h, then irradiate and treat successively with ultraviolet light of 365 nm and 254 nm at 20-30 °C, with a total light reaction time of 4 h, and finally heat up to 500 °C in an air atmosphere and calcine for 5 h.

[0058] Example 4

[0059] A process for treating waste gas from phenylenediamine production, comprising the following steps:

[0060] S1. Introduce the waste gas from phenylenediamine production into a scrubbing tower at a flow rate of 250 m³ / h, and carry out synergistic treatment using a NaOH solution with a pH value of 10.8, a liquid-gas ratio of 1.1 L / m³, and 45 ppm of ozone, adjust the ORP value of the system to 750 mV, and maintain the reaction temperature at 85 °C to obtain pretreated waste gas;

[0061] S2. Feed the pretreated waste gas into the adsorption tower which is filled with a composite adsorbent. The preparation steps of the composite adsorbent are as follows: A1. Weigh 53 parts of mesoporous carbon, immerse it in 98 parts of methanol solution containing 0.7 mol / L 2-methylimidazole, then add 13 parts of polystyrene microspheres and 8 parts of Pluronic F127, and perform ultrasonic treatment for 33 min (ultrasonic power 130 W, frequency 35 kHz); subsequently, add 37 parts of cobalt nitrate methanol solution with a concentration of 0.4 mol / L, and react at 75 °C with a stirring speed of 280 r / min for 6 h to obtain product A1; A2. Mix product A1 with thiourea in a mass ratio of 1:0.25, and perform gradient temperature calcination in an inert gas. The first stage is calcined at 315 °C for 2.8 h, and the second stage is calcined at 880 °C for 3.8 h. After cooling, perform pickling with 0.25 mol / L HCl to obtain a mesoporous carbon composite material; A3. Uniformly disperse 29 parts of mesoporous alumina and 9 parts of 3-mercaptopropyltrimethoxysilane in 115 parts of toluene, reflux at 83 °C with a stirring speed of 290 r / min for 6.5 h, and then oxidize with 15 parts of hydrogen peroxide to obtain sulfonated mesoporous alumina; then disperse it and 13 parts of trimethyl phosphate in 115 parts of toluene, reflux at 97 °C with a stirring speed of 330 r / min for 7 h, and obtain the modified mesoporous alumina after washing and drying; A4. Uniformly mix the mesoporous carbon composite material and the modified mesoporous alumina in a mass ratio of 2.5:1, add an appropriate amount of deionized water and stir evenly, and dry at 88 °C to obtain the composite adsorbent;

[0062] S3. Use the combustion exhaust gas at 282 °C to perform countercurrent desorption on the composite adsorbent at a flow rate of 1.2 m³ / h. The desorbed gas is successively subjected to catalytic combustion treatment through a double catalyst section. The filling amount of the catalyst in the double catalyst section is 18% of the volume of the adsorption tower;

[0063] The first-stage catalyst in the double catalyst section is prepared as follows: Dissolve 33 parts of copper nitrate, 10 parts of bismuth nitrate, and 17 parts of cerium nitrate in 137 parts of deionized water, add 0.5 parts of polystyrene microspheres, react at 67 °C with a stirring speed of 360 r / min for 3 h, then add 30 parts of γ-Al2O3 and perform ultrasonic treatment for 25 min, and calcine in an inert gas at 580 °C for 4 h after drying;

[0064] The preparation steps of the second-stage catalyst are as follows: (1) Dissolve 23 parts of strontium nitrate and 33 parts of tetrabutyl titanate in 108 parts of a mixed solvent composed of ethyl acetate and ethanol with a mass ratio of 2.2:1, add 20 parts of PEG-PLA, 1.5 parts of oxalic acid, and 2.5 parts of triethoxysilane, dropwise add 13 parts of ammonium dihydrogen phosphate aqueous solution in an ice-water bath at 0 - 5 °C, then stand and age at 20 - 30 °C for 25 h, perform vacuum drying, and calcine in an inert gas at 680 °C for 5 h to obtain the carrier;

[0065] (2) Immerse the carrier in 125 parts of a mixed solvent composed of acetonitrile and water with a mass ratio of 1.2:1 containing 13 parts of CoSO4 and 23 parts of MnCl2. Add 1.5 parts of azobenzene-4,4'-dicarboxylic acid and 0.8 part of o-phenanthroline, and stir and react for 0.7 h under dark conditions at 20-30 °C. Then, irradiate and treat with ultraviolet light of 365 nm and 254 nm at 20-30 °C in sequence, with a total light reaction time of 3.5 h. Finally, heat up to 480 °C in an air atmosphere and calcine for 4.5 h.

[0066] Comparative Example 1

[0067] A process for treating waste gas from phenylenediamine production, which is different from Example 4 in that only NaOH solution washing (pH = 10.8, liquid-gas ratio 1.1 L / m³) is used in the pretreatment stage, ozone is not added, and other conditions are the same as those in Example 4.

[0068] Comparative Example 2

[0069] A process for treating waste gas from phenylenediamine production, which is different from Example 4 in that the composite adsorbent is not calcined and modified with thiourea. That is, in step A2, the product A1 is directly cooled and pickled with 0.25 mol / L HCl, and the gradient temperature calcination step with thiourea is omitted. The remaining steps for preparing the composite adsorbent and the waste gas treatment process are the same as those in Example 4.

[0070] Comparative Example 3

[0071] A process for treating waste gas from phenylenediamine production, which is different from Example 4 in that the composite adsorbent in step S2 is replaced with a mixture of ordinary activated carbon and unmodified γ-Al2O3 with a mass ratio of 2.5:1, and other conditions are the same as those in Example 4.

[0072] Comparative Example 4

[0073] A process for treating waste gas from phenylenediamine production, which is different from Example 4 in that the modified mesoporous alumina is not sulfonated. That is, in step A3, the steps of 3-mercaptopropyltrimethoxysilane and hydrogen peroxide oxidation are omitted, and the mesoporous alumina is directly refluxed with trimethyl phosphate. The remaining steps for preparing the composite adsorbent and the waste gas treatment process are the same as those in Example 4.

[0074] Comparative Example 5

[0075] A process for treating waste gas from phenylenediamine production, which is different from Example 4 in that only the first-stage catalyst is used in the catalytic combustion stage, that is, the second-stage catalyst is not filled, and other conditions are the same as those in Example 4.

[0076] Comparative Example 6

[0077] A process for treating waste gas from phenylenediamine production, which is different from Example 4 in that CoSO4 and MnCl2 in the second-stage catalyst are replaced with equimolar amounts of Fe(NO3)3 and NiCl2, and azobenzene-4,4'-dicarboxylic acid and o-phenanthroline are not added, and other conditions are the same as those in Example 4.

[0078] Performance Test

[0079] Performance tests were carried out on the waste gas treatment processes for phenylenediamine production in Examples 1-4 and Comparative Examples 1-6, and the test results are shown in Table 1 below.

[0080] Table 1

[0081] Test Items Waste Gas Treatment Efficiency % Removal Rate of Benzene Series Compounds % Removal Rate of Nitrogen-Containing Pollutants % Removal Rate of Acid Gases % Example 1 92.3 90.8 88.1 95.5 Example 2 95.1 94.6 92.2 96.3 Example 3 96.5 95.1 93.2 97.1 Example 4 98.2 97.7 96.9 99.5 Comparative Example 1 82.8 78.3 75.7 85.3 Comparative Example 2 80.2 75.5 72.0 82.3 Comparative Example 3 75.1 70.7 68.5 78.4 Comparative Example 4 78.6 72.4 70.1 80.8 Comparative Example 5 85.4 80.1 78.3 88.2 Comparative Example 6 83.7 77.2 74.6 85.9

[0082] It can be seen from Table 1 that the waste gas treatment processes for phenylenediamine production in Examples 1-4 are superior to Comparative Examples 1-6 in terms of various performance indicators. Among them, Example 4 has the best performance, with the waste gas treatment efficiency reaching 98%, and the removal rates of benzene series compounds, nitrogen-containing pollutants, and acidic gases being as high as 97%, 96%, and 99% respectively.

[0083] In contrast, the performance of Comparative Examples 1-6 has decreased significantly. In Comparative Example 1, ozone-assisted treatment was not used, resulting in a significant decrease in waste gas treatment efficiency and pollutant removal rate; in Comparative Example 2, the thiourea calcination modification step was omitted, deteriorating the performance of the adsorbent; in Comparative Example 3, a mixture of ordinary activated carbon and unmodified alumina was used to replace the composite adsorbent, resulting in a significant reduction in adsorption and removal effects; in Comparative Example 4, the modified mesoporous alumina was not sulfonated, affecting its adsorption performance for pollutants; in Comparative Example 5, only the first-stage catalyst was used, and the catalytic combustion effect was incomplete; in Comparative Example 6, the catalyst components were replaced and the additives were omitted, resulting in a significant reduction in catalytic activity.

[0084] In summary, the waste gas treatment process for phenylenediamine production of the present invention realizes the efficient removal of complex pollutants in waste gas through the optimization combination of ozone-coupled alkali washing pretreatment, multi-stage adsorption-catalytic combustion synergistic technology, and high-performance composite adsorbent and dual-stage catalyst, providing an effective solution for the treatment of waste gas from phenylenediamine production and having broad industrial application prospects.

[0085] The above content is only an example and illustration of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar methods to replace them. As long as they do not deviate from the invention or exceed the scope defined by the claims of the present invention, they should fall within the protection scope of the present invention.

Claims

1. A process for treating waste gas from the production of phenylenediamine, characterized in that: The following steps are involved: S1. Using ozone-coupled alkaline solution washing process, the production waste gas is treated with NaOH solution with a pH value of 10-11 and 30-50ppm ozone to obtain pre-treated waste gas; S2, passing the pretreated waste gas into an adsorption tower, and performing adsorption treatment by a composite adsorbent in the adsorption tower; S3, using 275-285℃ combustion tail gas to carry out countercurrent desorption of the composite adsorbent, and the desorbed gas is sequentially passed through the dual catalyst sections for catalytic combustion treatment.

2. A process for treating waste gas from the production of phenylenediamine according to claim 1, characterized in that: In step S1, the liquid-gas ratio is controlled at 0.8-1.2 L / m³, the system ORP value is adjusted to 600-800 mV, and the reaction temperature is maintained at 70-90°C.

3. A process for treating waste gas from the production of phenylenediamine according to claim 1, characterized in that: The preparation steps of the composite adsorbent in step S2 are: A1. The mesoporous carbon was impregnated with a methanol solution containing 0.5-0.8 mol / L 2-methylimidazole, and polystyrene microspheres and Pluronic F127 were added. After ultrasonic treatment for 30-35 min, 0.2-0.5 mol / L cobalt nitrate methanol solution was added and stirred at 60-80 ° C for 6-8 h; A2. The product obtained in step A1 was mixed with thiourea in a mass ratio of 1:0.1-0.3, and calcined in an inert gas at a gradient temperature, calcined at 300-320 ° C for 2-3h in the first stage, calcined at 800-900 ° C for 3-4h in the second stage, and washed with 0.1-0.3 mol / L HCl after cooling to obtain a mesoporous carbon composite material; A3. The mesoporous alumina and 3-mercaptopropyltrimethoxysilane were uniformly dispersed in toluene, refluxed at 80-85°C for 5-7h, oxidized with hydrogen peroxide to obtain sulfonated mesoporous alumina, and then dispersed with trimethyl phosphate in toluene, refluxed at 90-100°C for 5-8h, washed and dried to obtain modified mesoporous alumina; A4. The mesoporous carbon composite material and the modified mesoporous alumina are uniformly mixed in a mass ratio of 1-3:1, an appropriate amount of deionized water is added, stirred evenly, and dried at 80-90° C. to obtain a composite adsorbent.

4. A process for treating waste gas from the production of phenylenediamine according to claim 3, characterized in that: The components in step A1 are as follows, by weight: 50-55 parts of mesoporous carbon, 90-100 parts of 2-methylimidazole methanol solution, 10-15 parts of polystyrene microspheres, 5-10 parts of Pluronic F127 and 30-40 parts of cobalt nitrate methanol solution.

5. A process for treating waste gas from the production of phenylenediamine according to claim 3, characterized in that: In the step A3, the weight parts are as follows: in the sulfonation stage, 25-30 parts of mesoporous alumina, 5-10 parts of 3-mercaptopropyltrimethoxysilane, 100-120 parts of toluene and 12-16 parts of hydrogen peroxide; in the phosphorylation stage, 35-40 parts of sulfonated mesoporous alumina, 10-15 parts of trimethyl phosphate and 100-120 parts.

6. A process for treating waste gas from the production of phenylenediamine according to claim 1, characterized in that: In step S3, the flow rate of the countercurrent desorption is 0.5-1.5 m³ / h, and the filling amount of the catalyst in the dual catalyst section is 10-20% of the volume of the adsorption tower.

7. A process for treating waste gas from the production of phenylenediamine according to claim 1, characterized in that: In step S3, the first stage catalyst in the dual catalyst stage is prepared by the following method: 30-35 parts of copper nitrate, 8-12 parts of bismuth nitrate and 15-20 parts of cerium nitrate are dissolved in 130-140 parts of deionized water, 0.3-0.7 parts of polystyrene microspheres are added, and after stirring and reacting at 65-70° C. for 2-4 hours, 28-32 parts of γ-Al2O3 are added and ultrasonically treated for 20-30 minutes, and after drying, the mixture is calcined in an inert gas at 500-600° C. for 3-5 hours.

8. A process for treating waste gas from the production of phenylenediamine according to claim 1, characterized in that: In step S3, the second stage catalyst in the dual catalyst stage is prepared by the following method: (1) Dissolve 20-25 parts of strontium nitrate and 30-35 parts of tetrabutyl titanate in 100-110 parts of a mixed solvent, add 16-24 parts of PEG-PLA, 1-2 parts of oxalic acid and 2-3 parts of triethoxysilane, add 10-15 parts of an aqueous solution of ammonium dihydrogen phosphate dropwise in an ice water bath at 0-5°C, then age at 20-30°C for 20-28h, vacuum dry, and calcine in an inert gas at 600-700°C for 4-6h to obtain a carrier; (2) The carrier is immersed in 120-130 parts of a mixed solvent containing 10-15 parts of CoSO4 and 20-25 parts of MnCl2, and 1-2 parts of azobenzene-4,4'-dicarboxylic acid and 0.5-1 part of o-phenanthroline are added. The mixture is stirred and reacted for 0.5-1h at 20-30°C in a dark environment. The mixture is then irradiated with 365nm and 254nm ultraviolet light at 20-30°C in turn. The total illumination reaction time is 2-4h. The mixture is finally heated to 400-500°C in an air atmosphere and calcined for 3-5h.

9. A process for treating waste gas from the production of phenylenediamine according to claim 8, characterized in that: In the step (1), the mixed solvent consists of ethyl acetate and ethanol in a mass ratio of 2-4:1; and in the step (2), the mixed solvent consists of acetonitrile and water in a mass ratio of 1-3:1.