Method for treating waste gas generated in synthesis of ethyl chloroformate

Abstract

The invention discloses an ethyl chloroformate synthesis waste gas treatment method, and belongs to the technical field of ethyl chloroformate synthesis waste gas treatment.The ethyl chloroformate synthesis waste gas treatment method comprises the following steps that S1, waste gas is guided into 2-3 condensers connected in series, and the waste gas is condensed, liquefied, separated and recycled; s2, introducing the uncondensed waste gas into an adsorption tower for adsorption treatment; s3, the waste gas subjected to adsorption treatment enters a catalytic hydrolysis tower to be subjected to catalytic oxidation treatment; s4, finally, the waste gas enters an alkali liquor destroying tower to be treated before being emptied, and the standard waste gas can be discharged at high altitude. According to the ethyl chloroformate synthesis waste gas treatment method, a condensation liquefaction method, an adsorption method, a catalytic oxidation method and alkali liquor treatment are combined and cooperate with one another, recycling of ethyl chloroformate synthesis waste gas can be improved, and the waste gas purification effect can also be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of waste gas treatment from ethyl chloroformate synthesis, and particularly relates to a waste gas treatment method from ethyl chloroformate synthesis. Background Art

[0002] The molecular formula of ethyl chloroformate is C3H5ClO2, and the molecular weight is 108.53. It is a colorless transparent liquid with a pungent odor. Ethyl chloroformate is mainly used in the production of chemical products such as medicines and herbicides, such as cefazolin, tetrachlorazole acetic acid, nicosulfuron, etc. In addition, it is also used as a solvent and amino protective agent. The industrial synthesis method of ethyl chloroformate is to react ethanol and phosgene to produce waste gas during the production process. The waste gas of ethyl chloroformate mainly contains phosgene, hydrogen chloride, nitrogen, and a small amount of ethanol, carbon monoxide, etc. Phosgene (COCl2), also known as carbonyl chloride or chloroformyl chloride, is a colorless gas at room temperature, easy to liquefy, with a strong pungent odor and suffocation, non-flammable, soluble in water, and easily soluble in organic solvents such as benzene, toluene, xylene, chloroform, and carbon tetrachloride. Phosgene is a highly toxic substance. Acute poisoning can easily cause pulmonary edema, pneumonia, chest tightness, chest pain, and difficulty breathing. Since phosgene is highly toxic and easily volatile and diffuses, it will cause serious air pollution and affect human health. Hydrogen chloride gas has a very strong irritating effect on the respiratory mucosa and eyes. If it is directly discharged into the atmosphere, it will seriously pollute the environment and endanger human health, and at the same time cause great waste. Existing treatment technologies are generally difficult to remove completely, and the waste gas is corrosive, which will not only damage equipment but also pollute the environment, waste resources, reduce work results, and increase production costs.

[0003] Based on this, we proposed a waste gas treatment method for the production of methyl thiophanate, hoping to solve the shortcomings of the existing technology. Summary of the invention

[0004] The purpose of the invention is to provide a method for treating waste gas from ethyl chloroformate synthesis in view of the existing problems.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for treating waste gas from the synthesis of ethyl chloroformate comprises the following steps:

[0007] S1. Introduce the waste gas into 2-3 condensers connected in series to condense, liquefy, separate and recycle the waste gas;

[0008] S2, passing the uncondensed waste gas into an adsorption tower for adsorption treatment;

[0009] S3, the waste gas after adsorption treatment enters the catalytic hydrolysis tower for catalytic oxidation treatment;

[0010] S4. Finally, the waste gas enters the alkali liquid destruction tower to be treated before being discharged. After reaching the standards, the waste gas can be discharged into the air.

[0011] Further preferably, the adsorption treatment in step S2 adopts solid adsorption, and the adsorbent used is a sepiolite / diatomaceous earth composite adsorbent.

[0012] Further preferably, the preparation of the sepiolite / diatomite composite adsorbent comprises the following steps:

[0013] (1) adding sepiolite to the treating agent, stirring at 200-300 rpm and 80-86° C. for 2-3 hours, filtering, drying to constant weight, placing in a muffle furnace, roasting at 400-500° C. for 4-8 minutes, placing in a grinder, grinding at 2000-3000 rpm for 10-20 minutes to obtain modified sepiolite;

[0014] (2) placing the diatomaceous earth in a muffle furnace, calcining at 500-600° C. for 3-4 hours, cooling to room temperature, immersing in a 3 mol / L hydrochloric acid solution, stirring at 500-600 W microwave conditions for 8-12 minutes, filtering, drying, and grinding in a grinder at 2000-3000 rpm for 16-20 minutes to obtain modified diatomaceous earth;

[0015] (3) Sodium alginate and polyvinyl alcohol are added to distilled water in a mass ratio of 1:3-4, and stirred in a water bath at 80-90° C. until completely dissolved to obtain a mixed solution;

[0016] (4) The modified sepiolite and modified diatomite are ground and mixed in a mass ratio of 1:2-3, and then ultrasonically dispersed in deionized water to obtain a uniformly dispersed aqueous suspension. The aqueous suspension is uniformly added to the mixed solution, and after stirring and mixing, the mixed solution is added dropwise to a 2% calcium chloride saturated boric acid solution using a rubber-tipped dropper to obtain a hydrogel ball and solidify it for 12 hours. Finally, the hydrogel ball is rinsed with distilled water for 3-5 times and placed in a vacuum drying oven, and dried at 40-50°C to constant weight to obtain a sepiolite / diatomite composite adsorbent.

[0017] Further preferably, the components and corresponding weight percentages in the treatment agent described in step (1) are: 4-6% nitric acid, 2-3% sulfuric acid, 3-6% hexadecyltrimethylammonium bromide, and the balance is deionized water.

[0018] Further preferably, the weight volume ratio of sodium alginate to distilled water in step (3) is 1 g:20-26 mL.

[0019] Further preferably, during the grinding and mixing in step (4), the grinding speed is controlled to be 1000-2000 rpm, and the grinding time is 14-20 min.

[0020] Further preferably, the preparation of the catalyst used in the catalytic oxidation treatment in step S3 comprises the following steps:

[0021] 1) Ultrasonic dispersion of silicon carbide powder in deionized water, adding 0.07-0.09% tartaric acid by mass of silicon carbide powder after uniform dispersion, stirring at 200-300 rpm for 2-3 hours, placing in a cryogenic mill, cryogenically grinding at -100--80°C for 20-30 minutes, and then placing in a vacuum drying oven, drying at 10-20°C to constant weight to obtain modified silicon carbide;

[0022] 2) La(NO3)3·6H2O, Zn(NO3)2·6H2O and anhydrous citric acid are added to deionized water in sequence and stirred to mix well. The total molar amount of cations is 0.02-0.03 mol, and the molar ratio of La to Zn is 40-60:1. After complete dissolution, modified silicon carbide and additives are added, the temperature is raised to 70-80°C, and stirred until a gel is formed. The gel is dried in a drying oven at 100°C to become a fluffy solid, then placed in a muffle furnace, calcined at 700-800°C for 4-5h, and then placed in a bead mill for grinding.

[0023] Further preferably, the molar ratio of the anhydrous citric acid to the cation in step 2) is 3-4:1.

[0024] Further preferably, the amount of modified silicon carbide added in step 2) is 1-2 times that of La(NO3)3·6H2O;

[0025] The amount of additive added is 0.9-1.5 times that of La(NO3)3·6H2O;

[0026] The auxiliary agent is one of microcrystalline cellulose and carboxymethyl cellulose.

[0027] Further preferably, the alkali solution in step S4 is a mixture of a 5% sodium carbonate solution and a 2% sodium bicarbonate solution, and the volume ratio of the sodium carbonate solution to the sodium bicarbonate solution is 1:0.3-0.5.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] The invention provides a method for treating waste gas from ethyl chloroformate synthesis, which combines a condensation liquefaction method, an adsorption method, a catalytic oxidation method and an alkali solution treatment, and cooperates with each other to not only improve the recycling of waste gas from ethyl chloroformate synthesis, but also improve the effect of waste gas purification.

[0030] First, the waste gas is introduced into the condenser for condensation and liquefaction to recover part of the phosgene, and then enters the adsorption tower for adsorption treatment using a special sepiolite / diatomite composite adsorbent. In the preparation of the sepiolite / diatomite composite adsorbent, the sepiolite is treated with a treatment agent, and the impurities on its surface will be removed, and the surface becomes rougher and the number of pores increases. The sepiolite is then calcined, and the adsorbed water, crystal water and structural water in the sepiolite are removed. At the same time, the silanol on the surface of the sepiolite is converted into a silicon-oxygen tetrahedral structure, which expands its channel size, increases the specific surface area and adsorption performance. At the same time, the diatomite is modified to obtain modified diatomite. The modified diatomite has a larger specific surface area, and the amorphous SiO2 in the diatomite is more converted to crystalline SiO2, the impurities attached to its surface are reduced, the specific surface area and pore volume are increased, and the adsorption performance is enhanced. Mechanical grinding is then used to improve the dispersibility of the powder and the contact frequency between particles. At the same time, during the grinding process, large particles are continuously ground into small particles, the contact area is greatly increased, and the dispersibility is improved. Using polyvinyl alcohol and sodium alginate as the matrix, the modified sepiolite and diatomaceous earth are more evenly dispersed in it through cross-linking, so that it has a rich pore structure and greatly increases the specific surface area. And after the preparation of the composite adsorbent material, the modified sepiolite and diatomaceous earth still maintain the high selective adsorption performance of waste gas. This composite adsorbent not only has good acid and alkali resistance, stable structure, long service life, reduces the production cost to a certain extent, but also has a significant adsorption and purification effect on waste gas.

[0031] Secondly, the ultrafine SiC powder after silicon carbide is crushed has an irregular particle shape, and due to its small particle size and high surface energy, the powder particles are easily agglomerated, resulting in poor powder dispersibility. Therefore, it is necessary to modify the powder to improve its dispersibility and stability. Therefore, the present invention uses tartaric acid to modify it, and then adds it to a deionized water system of La(NO3)3·6H2O, Zn(NO3)2·6H2O, and anhydrous citric acid in combination with an auxiliary agent to form a gel, and then dries and roasts it to finally prepare a highly active and highly stable catalyst. It is used in the treatment of waste gas from the synthesis of ethyl chloroformate. It can not only catalyze the decomposition of waste gas, but also can be repeatedly recycled and has a long service life, thereby further reducing production costs. DETAILED DESCRIPTION

[0032] In order to further explain the present invention, it is described below in conjunction with the following specific embodiments.

[0033] Example 1

[0034] A method for treating waste gas from the synthesis of ethyl chloroformate comprises the following steps:

[0035] S1. Introduce the waste gas into two condensers connected in series to condense, liquefy, separate and recover the waste gas;

[0036] S2, passing the uncondensed waste gas into an adsorption tower for adsorption treatment;

[0037] The adsorption treatment adopts solid adsorption, and the adsorbent used is a sepiolite / diatomite composite adsorbent.

[0038] The preparation of the sepiolite / diatomite composite adsorbent comprises the following steps:

[0039] (1) Adding sepiolite to the treating agent, stirring at 200 rpm and 80° C. for 2 h, filtering, drying to constant weight, placing in a muffle furnace, roasting at 400° C. for 4 min, placing in a grinder, grinding at 2000 rpm for 10 min to obtain modified sepiolite; the components and their corresponding weight percentages in the treating agent are: 4% nitric acid, 2% sulfuric acid, 3% hexadecyltrimethylammonium bromide, and the balance is deionized water;

[0040] (2) placing the diatomaceous earth in a muffle furnace, calcining at 500° C. for 3 h, cooling to room temperature, and then immersing in a 3 mol / L hydrochloric acid solution, stirring for 8 min under a 500 W microwave condition, and then filtering, drying, and grinding in a grinder at 2000 rpm for 16 min to obtain modified diatomaceous earth;

[0041] (3) sodium alginate and polyvinyl alcohol were added into distilled water in a mass ratio of 1:3, and stirred in a water bath at 80° C. until they were completely dissolved to obtain a mixed solution;

[0042] The weight volume ratio of sodium alginate to distilled water is 1 g:20 mL;

[0043] (4) The modified sepiolite and modified diatomaceous earth were ground at a mass ratio of 1:2 at 1000 rpm for 14 min, and then ultrasonically dispersed in deionized water to obtain a uniformly dispersed aqueous suspension. The aqueous suspension was uniformly added to the mixed solution, and after stirring, the mixed solution was added dropwise to a 2% calcium chloride saturated boric acid solution using a rubber-tipped dropper to obtain hydrogel balls, which were cured for 12 h. Finally, the balls were rinsed with distilled water three times, placed in a vacuum drying oven, and dried at 40° C. to constant weight to obtain a sepiolite / diatomaceous earth composite adsorbent.

[0044] S3, the waste gas after adsorption treatment enters the catalytic hydrolysis tower for catalytic oxidation treatment;

[0045] The preparation of the catalyst used in the catalytic oxidation treatment comprises the following steps:

[0046] 1) Ultrasonic dispersion of silicon carbide powder in deionized water, adding 0.07% tartaric acid by mass of silicon carbide powder after uniform dispersion, stirring at 200 rpm for 2 h, placing in a cryogenic mill, cryogenically grinding at -100°C for 20 min, and then placing in a vacuum drying oven, drying at 10°C to constant weight to obtain modified silicon carbide;

[0047] 2) La(NO3)3·6H2O, Zn(NO3)2·6H2O and anhydrous citric acid are added to deionized water in sequence and stirred to mix. The total molar amount of cations is 0.02 mol, the molar ratio of La to Zn is 40:1, and the molar ratio of anhydrous citric acid to cations is 3:1. After complete dissolution, modified silicon carbide with a mass of 1 times that of La(NO3)3·6H2O and microcrystalline cellulose with a mass of 0.9 times that of La(NO3)3·6H2O are added. The temperature is raised to 70°C and stirred until a gel is formed. The gel is dried in a drying oven at 100°C to become a fluffy solid, then placed in a muffle furnace, calcined at 700°C for 4 hours, and then ground in a bead mill.

[0048] S4, finally enters the alkali liquid destruction tower to treat the waste gas before emptying, and the waste gas that meets the standards can be discharged into the air;

[0049] The alkali solution is a mixture of a sodium carbonate solution with a concentration of 5% and a sodium bicarbonate solution with a concentration of 2%, and the volume ratio of the sodium carbonate solution to the sodium bicarbonate solution is 1:0.3.

[0050] Example 2

[0051] A method for treating waste gas from the synthesis of ethyl chloroformate comprises the following steps:

[0052] S1. Introduce the waste gas into two condensers connected in series to condense, liquefy, separate and recover the waste gas;

[0053] S2, passing the uncondensed waste gas into an adsorption tower for adsorption treatment;

[0054] The adsorption treatment adopts solid adsorption, and the adsorbent used is a sepiolite / diatomite composite adsorbent.

[0055] The preparation of the sepiolite / diatomite composite adsorbent comprises the following steps:

[0056] (1) Adding sepiolite to the treating agent, stirring at 250 rpm and 83° C. for 2.5 h, filtering, drying to constant weight, placing in a muffle furnace, roasting at 450° C. for 6 min, placing in a grinder, grinding at 2500 rpm for 15 min to obtain modified sepiolite; the components and their corresponding weight percentages in the treating agent are: 5% nitric acid, 2.5% sulfuric acid, 4.5% hexadecyltrimethylammonium bromide, and the balance is deionized water;

[0057] (2) placing the diatomaceous earth in a muffle furnace, calcining at 550° C. for 3.5 h, cooling to room temperature, immersing in a 3 mol / L hydrochloric acid solution, stirring at 550 W microwave conditions for 10 min, filtering, drying, and grinding in a grinder at 2500 rpm for 18 min to obtain modified diatomaceous earth;

[0058] (3) Sodium alginate and polyvinyl alcohol were added into distilled water in a mass ratio of 1:3.5, and stirred in a water bath at 85° C. until they were completely dissolved to obtain a mixed solution;

[0059] The weight volume ratio of sodium alginate to distilled water is 1 g:23 mL;

[0060] (4) The modified sepiolite and modified diatomaceous earth were ground at a mass ratio of 1:2.5 at 1500 rpm for 17 min, and then ultrasonically dispersed in deionized water to obtain a uniformly dispersed aqueous suspension. The aqueous suspension was uniformly added to the mixed solution, and after stirring and mixing, the mixed solution was added dropwise to a 2% calcium chloride saturated boric acid solution using a rubber-tipped dropper to obtain hydrogel balls, which were cured for 12 h. Finally, the balls were rinsed with distilled water for 4 times, placed in a vacuum drying oven, and dried at 45° C. to constant weight to obtain a sepiolite / diatomaceous earth composite adsorbent.

[0061] S3, the waste gas after adsorption treatment enters the catalytic hydrolysis tower for catalytic oxidation treatment;

[0062] The preparation of the catalyst used in the catalytic oxidation treatment comprises the following steps:

[0063] 1) Ultrasonic dispersion of silicon carbide powder in deionized water, adding 0.08% tartaric acid by mass of silicon carbide powder after uniform dispersion, stirring at 250 rpm for 2.5 h, placing in a cryogenic mill, cryogenically grinding at -90°C for 25 min, placing in a vacuum drying oven, and drying at 15°C to constant weight to obtain modified silicon carbide;

[0064] 2) La(NO3)3·6H2O, Zn(NO3)2·6H2O and anhydrous citric acid are added to deionized water in sequence and stirred to mix. The total molar amount of cations is 0.025 mol, the molar ratio of La to Zn is 50:1, and the molar ratio of anhydrous citric acid to cations is 3.5:1. After complete dissolution, modified silicon carbide with a mass of 1.5 times that of La(NO3)3·6H2O and microcrystalline cellulose with a mass of 1.2 times that of La(NO3)3·6H2O are added. The temperature is raised to 75°C and stirred until a gel is formed. The gel is dried in a drying oven at 100°C to become a fluffy solid, then placed in a muffle furnace, calcined at 750°C for 4.5 hours, and then ground in a bead mill.

[0065] S4, finally enters the alkali liquid destruction tower to treat the waste gas before emptying, and the waste gas that meets the standards can be discharged into the air;

[0066] The alkali solution is a mixture of a sodium carbonate solution with a concentration of 5% and a sodium bicarbonate solution with a concentration of 2%, and the volume ratio of the sodium carbonate solution to the sodium bicarbonate solution is 1:0.4.

[0067] Example 3

[0068] A method for treating waste gas from the synthesis of ethyl chloroformate comprises the following steps:

[0069] S1. Introduce the waste gas into three condensers connected in series to condense, liquefy, separate and recycle the waste gas;

[0070] S2, passing the uncondensed waste gas into an adsorption tower for adsorption treatment;

[0071] The adsorption treatment adopts solid adsorption, and the adsorbent used is a sepiolite / diatomite composite adsorbent.

[0072] The preparation of the sepiolite / diatomite composite adsorbent comprises the following steps:

[0073] (1) Adding sepiolite to the treating agent, stirring at 300 rpm and 86° C. for 3 h, filtering, drying to constant weight, placing in a muffle furnace, roasting at 500° C. for 8 min, placing in a grinder, grinding at 3000 rpm for 20 min to obtain modified sepiolite; the components and their corresponding weight percentages in the treating agent are: 6% nitric acid, 3% sulfuric acid, 6% hexadecyltrimethylammonium bromide, and the balance is deionized water;

[0074] (2) placing the diatomaceous earth in a muffle furnace, calcining at 600° C. for 4 h, cooling to room temperature, immersing in a 3 mol / L hydrochloric acid solution, stirring for 12 min under a 600 W microwave condition, filtering, drying, and grinding in a grinder at 3000 rpm for 20 min to obtain modified diatomaceous earth;

[0075] (3) sodium alginate and polyvinyl alcohol were added into distilled water in a mass ratio of 1:4, and stirred in a 90° C. water bath until completely dissolved to obtain a mixed solution;

[0076] The weight volume ratio of sodium alginate to distilled water is 1 g:26 mL;

[0077] (4) The modified sepiolite and modified diatomaceous earth were ground at a mass ratio of 1:3 at 2000 rpm for 20 min, and then ultrasonically dispersed in deionized water to obtain a uniformly dispersed aqueous suspension. The aqueous suspension was uniformly added to the mixed solution, and after stirring, the mixed solution was added dropwise to a 2% calcium chloride saturated boric acid solution using a rubber-tipped dropper to obtain a hydrogel ball and cured for 12 h. Finally, the ball was rinsed with distilled water for 5 times, placed in a vacuum drying oven, and dried at 50° C. to a constant weight to obtain a sepiolite / diatomaceous earth composite adsorbent.

[0078] S3, the waste gas after adsorption treatment enters the catalytic hydrolysis tower for catalytic oxidation treatment;

[0079] The preparation of the catalyst used in the catalytic oxidation treatment comprises the following steps:

[0080] 1) Ultrasonic dispersion of silicon carbide powder in deionized water, adding 0.09% tartaric acid by mass of silicon carbide powder after uniform dispersion, stirring at 300 rpm for 3 hours, placing in a cryogenic mill, cryogenically grinding at -80°C for 30 minutes, and then placing in a vacuum drying oven, drying at 20°C to constant weight to obtain modified silicon carbide;

[0081] 2) La(NO3)3·6H2O, Zn(NO3)2·6H2O and anhydrous citric acid are added to deionized water in sequence and stirred to mix. The total molar amount of cations is 0.03 mol, the molar ratio of La to Zn is 60:1, and the molar ratio of anhydrous citric acid to cations is 4:1. After complete dissolution, modified silicon carbide twice the mass of La(NO3)3·6H2O and microcrystalline cellulose 1.5 times the mass of La(NO3)3·6H2O are added, the temperature is raised to 80°C, and stirred until a gel is formed. The gel is dried in a drying oven at 100°C to become a fluffy solid, then placed in a muffle furnace, calcined at 800°C for 5h, and then placed in a bead mill for grinding.

[0082] S4, finally enters the alkali liquid destruction tower to treat the waste gas before emptying, and the waste gas that meets the standards can be discharged into the air;

[0083] The alkali solution is a mixture of a sodium carbonate solution with a concentration of 5% and a sodium bicarbonate solution with a concentration of 2%, and the volume ratio of the sodium carbonate solution to the sodium bicarbonate solution is 1:0.5.

[0084] Comparative Example 1

[0085] A method for treating waste gas from the synthesis of ethyl chloroformate comprises the following steps:

[0086] S1. Introduce the waste gas into two condensers connected in series to condense, liquefy, separate and recover the waste gas;

[0087] S2, passing the uncondensed waste gas into an adsorption tower for adsorption treatment;

[0088] The adsorption treatment adopts solid adsorption, and the adsorbent used is a sepiolite / diatomite composite adsorbent.

[0089] The preparation of the sepiolite / diatomite composite adsorbent comprises the following steps:

[0090] (1) placing diatomaceous earth in a muffle furnace, calcining at 550° C. for 3.5 h, cooling to room temperature, immersing in a 3 mol / L hydrochloric acid solution, stirring at 550 W microwave conditions for 10 min, filtering, drying, and grinding in a grinder at 2500 rpm for 18 min to obtain modified diatomaceous earth;

[0091] (2) sodium alginate and polyvinyl alcohol were added into distilled water in a mass ratio of 1:3.5, and stirred in a water bath at 85° C. until they were completely dissolved to obtain a mixed solution;

[0092] The weight volume ratio of sodium alginate to distilled water is 1 g:23 mL;

[0093] (3) Sepiolite and modified diatomaceous earth were ground at a mass ratio of 1:2.5 at 1500 rpm for 17 min, and then ultrasonically dispersed in deionized water to obtain a uniformly dispersed aqueous suspension. The aqueous suspension was uniformly added to the mixed solution, and after stirring and mixing, the mixed solution was added dropwise to a 2% calcium chloride saturated boric acid solution using a rubber-tipped dropper to obtain hydrogel balls, which were cured for 12 h. Finally, the balls were rinsed with distilled water four times, placed in a vacuum drying oven, and dried at 45° C. to constant weight to obtain a sepiolite / diatomaceous earth composite adsorbent.

[0094] S3, the waste gas after adsorption treatment enters the catalytic hydrolysis tower for catalytic oxidation treatment;

[0095] The preparation of the catalyst used in the catalytic oxidation treatment comprises the following steps:

[0096] 1) Ultrasonic dispersion of silicon carbide powder in deionized water, adding 0.08% tartaric acid by mass of silicon carbide powder after uniform dispersion, stirring at 250 rpm for 2.5 h, placing in a cryogenic mill, cryogenically grinding at -90°C for 25 min, placing in a vacuum drying oven, and drying at 15°C to constant weight to obtain modified silicon carbide;

[0097] 2) La(NO3)3·6H2O, Zn(NO3)2·6H2O and anhydrous citric acid are added to deionized water in sequence and stirred to mix. The total molar amount of cations is 0.025 mol, the molar ratio of La to Zn is 50:1, and the molar ratio of anhydrous citric acid to cations is 3.5:1. After complete dissolution, modified silicon carbide with a mass of 1.5 times that of La(NO3)3·6H2O and microcrystalline cellulose with a mass of 1.2 times that of La(NO3)3·6H2O are added. The temperature is raised to 75°C and stirred until a gel is formed. The gel is dried in a drying oven at 100°C to become a fluffy solid, then placed in a muffle furnace, calcined at 750°C for 4.5 hours, and then ground in a bead mill.

[0098] S4, finally enters the alkali liquid destruction tower to treat the waste gas before emptying, and the waste gas that meets the standards can be discharged into the air;

[0099] The alkali solution is a mixture of a sodium carbonate solution with a concentration of 5% and a sodium bicarbonate solution with a concentration of 2%, and the volume ratio of the sodium carbonate solution to the sodium bicarbonate solution is 1:0.4.

[0100] Comparative Example 2

[0101] A method for treating waste gas from the synthesis of ethyl chloroformate comprises the following steps:

[0102] S1. Introduce the waste gas into two condensers connected in series to condense, liquefy, separate and recover the waste gas;

[0103] S2, passing the uncondensed waste gas into an adsorption tower for adsorption treatment;

[0104] The adsorption treatment adopts solid adsorption, and the adsorbent used is a sepiolite / diatomite composite adsorbent.

[0105] The preparation of the sepiolite / diatomite composite adsorbent comprises the following steps:

[0106] (1) Adding sepiolite to the treating agent, stirring at 250 rpm and 83° C. for 2.5 h, filtering, drying to constant weight, placing in a muffle furnace, roasting at 450° C. for 6 min, placing in a grinder, grinding at 2500 rpm for 15 min to obtain modified sepiolite; the components and their corresponding weight percentages in the treating agent are: 5% nitric acid, 2.5% sulfuric acid, 4.5% hexadecyltrimethylammonium bromide, and the balance is deionized water;

[0107] (2) sodium alginate and polyvinyl alcohol were added into distilled water in a mass ratio of 1:3.5, and stirred in a water bath at 85° C. until they were completely dissolved to obtain a mixed solution;

[0108] The weight volume ratio of sodium alginate to distilled water is 1 g:23 mL;

[0109] (3) The modified sepiolite and diatomaceous earth were ground at a mass ratio of 1:2.5 at 1500 rpm for 17 min, and then ultrasonically dispersed in deionized water to obtain a uniformly dispersed aqueous suspension. The aqueous suspension was uniformly added to the mixed solution, and after stirring and mixing, the mixed solution was added dropwise to a 2% calcium chloride saturated boric acid solution using a rubber-tipped dropper to obtain hydrogel balls, which were cured for 12 h. Finally, the balls were rinsed with distilled water 4 times, placed in a vacuum drying oven, and dried at 45° C. to constant weight to obtain a sepiolite / diatomaceous earth composite adsorbent.

[0110] S3, the waste gas after adsorption treatment enters the catalytic hydrolysis tower for catalytic oxidation treatment;

[0111] The preparation of the catalyst used in the catalytic oxidation treatment comprises the following steps:

[0112] 1) Ultrasonic dispersion of silicon carbide powder in deionized water, adding 0.08% tartaric acid by mass of silicon carbide powder after uniform dispersion, stirring at 250 rpm for 2.5 h, placing in a cryogenic mill, cryogenically grinding at -90°C for 25 min, placing in a vacuum drying oven, and drying at 15°C to constant weight to obtain modified silicon carbide;

[0113] 2) La(NO3)3·6H2O, Zn(NO3)2·6H2O and anhydrous citric acid are added to deionized water in sequence and stirred to mix. The total molar amount of cations is 0.025 mol, the molar ratio of La to Zn is 50:1, and the molar ratio of anhydrous citric acid to cations is 3.5:1. After complete dissolution, modified silicon carbide with a mass of 1.5 times that of La(NO3)3·6H2O and microcrystalline cellulose with a mass of 1.2 times that of La(NO3)3·6H2O are added. The temperature is raised to 75°C and stirred until a gel is formed. The gel is dried in a drying oven at 100°C to become a fluffy solid, then placed in a muffle furnace, calcined at 750°C for 4.5 hours, and then ground in a bead mill.

[0114] S4, finally enters the alkali liquid destruction tower to treat the waste gas before emptying, and the waste gas that meets the standards can be discharged into the air;

[0115] The alkali solution is a mixture of a sodium carbonate solution with a concentration of 5% and a sodium bicarbonate solution with a concentration of 2%, and the volume ratio of the sodium carbonate solution to the sodium bicarbonate solution is 1:0.4.

[0116] Comparative Example 3

[0117] A method for treating waste gas from the synthesis of ethyl chloroformate comprises the following steps:

[0118] S1. Introduce the waste gas into two condensers connected in series to condense, liquefy, separate and recover the waste gas;

[0119] S2, passing the uncondensed waste gas into an adsorption tower for adsorption treatment;

[0120] The adsorption treatment adopts solid adsorption, and the adsorbent used is sepiolite adsorbent.

[0121] The preparation of the sepiolite adsorbent comprises the following steps:

[0122] (1) Adding sepiolite to the treating agent, stirring at 250 rpm and 83° C. for 2.5 h, filtering, drying to constant weight, placing in a muffle furnace, roasting at 450° C. for 6 min, placing in a grinder, grinding at 2500 rpm for 15 min to obtain modified sepiolite; the components and their corresponding weight percentages in the treating agent are: 5% nitric acid, 2.5% sulfuric acid, 4.5% hexadecyltrimethylammonium bromide, and the balance is deionized water;

[0123] (2) sodium alginate and polyvinyl alcohol were added into distilled water in a mass ratio of 1:3.5, and stirred in a water bath at 85° C. until they were completely dissolved to obtain a mixed solution;

[0124] The weight volume ratio of sodium alginate to distilled water is 1 g:23 mL;

[0125] (3) Ultrasonic dispersion of the modified sepiolite in deionized water to obtain a uniform aqueous suspension, uniformly adding the aqueous suspension to the mixed solution, stirring and mixing, and then adding the mixed solution to a 2% calcium chloride saturated boric acid solution using a rubber dropper to obtain hydrogel spheres, which were cured for 12 h. Finally, the spheres were rinsed with distilled water for 4 times and placed in a vacuum drying oven, and dried at 45° C. to constant weight to obtain a sepiolite / diatomaceous earth composite adsorbent.

[0126] S3, the waste gas after adsorption treatment enters the catalytic hydrolysis tower for catalytic oxidation treatment;

[0127] The preparation of the catalyst used in the catalytic oxidation treatment comprises the following steps:

[0128] 1) Ultrasonic dispersion of silicon carbide powder in deionized water, adding 0.08% tartaric acid by mass of silicon carbide powder after uniform dispersion, stirring at 250 rpm for 2.5 h, placing in a cryogenic mill, cryogenically grinding at -90°C for 25 min, placing in a vacuum drying oven, and drying at 15°C to constant weight to obtain modified silicon carbide;

[0129] 2) La(NO3)3·6H2O, Zn(NO3)2·6H2O and anhydrous citric acid are added to deionized water in sequence and stirred to mix. The total molar amount of cations is 0.025 mol, the molar ratio of La to Zn is 50:1, and the molar ratio of anhydrous citric acid to cations is 3.5:1. After complete dissolution, modified silicon carbide with a mass of 1.5 times that of La(NO3)3·6H2O and microcrystalline cellulose with a mass of 1.2 times that of La(NO3)3·6H2O are added. The temperature is raised to 75°C and stirred until a gel is formed. The gel is dried in a drying oven at 100°C to become a fluffy solid, then placed in a muffle furnace, calcined at 750°C for 4.5 hours, and then ground in a bead mill.

[0130] S4, finally enters the alkali liquid destruction tower to treat the waste gas before emptying, and the waste gas that meets the standards can be discharged into the air;

[0131] The alkali solution is a mixture of a sodium carbonate solution with a concentration of 5% and a sodium bicarbonate solution with a concentration of 2%, and the volume ratio of the sodium carbonate solution to the sodium bicarbonate solution is 1:0.4.

[0132] Comparative Example 4

[0133] A method for treating waste gas from the synthesis of ethyl chloroformate comprises the following steps:

[0134] S1. Introduce the waste gas into two condensers connected in series to condense, liquefy, separate and recover the waste gas;

[0135] S2, passing the uncondensed waste gas into an adsorption tower for adsorption treatment;

[0136] The adsorption treatment adopts solid adsorption, and the adsorbent used is diatomaceous earth composite adsorbent.

[0137] The preparation of the diatomite composite adsorbent comprises the following steps:

[0138] (1) placing diatomaceous earth in a muffle furnace, calcining at 550° C. for 3.5 h, cooling to room temperature, immersing in a 3 mol / L hydrochloric acid solution, stirring at 550 W microwave conditions for 10 min, filtering, drying, and grinding in a grinder at 2500 rpm for 18 min to obtain modified diatomaceous earth;

[0139] (2) sodium alginate and polyvinyl alcohol were added into distilled water in a mass ratio of 1:3.5, and stirred in a water bath at 85° C. until they were completely dissolved to obtain a mixed solution;

[0140] The weight volume ratio of sodium alginate to distilled water is 1 g:23 mL;

[0141] (3) Ultrasonic dispersion of the modified diatomite in deionized water to obtain a water suspension, uniformly adding the water suspension to the mixed solution, stirring and mixing, and then adding the mixed solution to a 2% calcium chloride saturated boric acid solution with a rubber dropper to obtain hydrogel balls and solidify for 12 hours. Finally, the balls were rinsed with distilled water for 4 times and placed in a vacuum drying oven, and dried at 45°C to constant weight to obtain a sepiolite / diatomite composite adsorbent.

[0142] S3, the waste gas after adsorption treatment enters the catalytic hydrolysis tower for catalytic oxidation treatment;

[0143] The preparation of the catalyst used in the catalytic oxidation treatment comprises the following steps:

[0144] 1) Ultrasonic dispersion of silicon carbide powder in deionized water, adding 0.08% tartaric acid by mass of silicon carbide powder after uniform dispersion, stirring at 250 rpm for 2.5 h, placing in a cryogenic mill, cryogenically grinding at -90°C for 25 min, placing in a vacuum drying oven, and drying at 15°C to constant weight to obtain modified silicon carbide;

[0145] 2) La(NO3)3·6H2O, Zn(NO3)2·6H2O and anhydrous citric acid are added to deionized water in sequence and stirred to mix. The total molar amount of cations is 0.025 mol, the molar ratio of La to Zn is 50:1, and the molar ratio of anhydrous citric acid to cations is 3.5:1. After complete dissolution, modified silicon carbide with a mass of 1.5 times that of La(NO3)3·6H2O and microcrystalline cellulose with a mass of 1.2 times that of La(NO3)3·6H2O are added. The temperature is raised to 75°C and stirred until a gel is formed. The gel is dried in a drying oven at 100°C to become a fluffy solid, then placed in a muffle furnace, calcined at 750°C for 4.5 hours, and then ground in a bead mill.

[0146] S4, finally enters the alkali liquid destruction tower to treat the waste gas before emptying, and the waste gas that meets the standards can be discharged into the air;

[0147] The alkali solution is a mixture of a sodium carbonate solution with a concentration of 5% and a sodium bicarbonate solution with a concentration of 2%, and the volume ratio of the sodium carbonate solution to the sodium bicarbonate solution is 1:0.4.

[0148] Comparative Example 5

[0149] A method for treating waste gas from the synthesis of ethyl chloroformate comprises the following steps:

[0150] S1. Introduce the waste gas into two condensers connected in series to condense, liquefy, separate and recover the waste gas;

[0151] S2, passing the uncondensed waste gas into an adsorption tower for adsorption treatment;

[0152] The adsorption treatment adopts solid adsorption, and the adsorbent used is a sepiolite / diatomite composite adsorbent.

[0153] The preparation of the sepiolite / diatomite composite adsorbent comprises the following steps:

[0154] (1) Adding sepiolite to the treating agent, stirring at 250 rpm and 83° C. for 2.5 h, filtering, drying to constant weight, placing in a muffle furnace, roasting at 450° C. for 6 min, placing in a grinder, grinding at 2500 rpm for 15 min to obtain modified sepiolite; the components and their corresponding weight percentages in the treating agent are: 5% nitric acid, 2.5% sulfuric acid, 4.5% hexadecyltrimethylammonium bromide, and the balance is deionized water;

[0155] (2) placing the diatomaceous earth in a muffle furnace, calcining at 550° C. for 3.5 h, cooling to room temperature, immersing in a 3 mol / L hydrochloric acid solution, stirring at 550 W microwave conditions for 10 min, filtering, drying, and grinding in a grinder at 2500 rpm for 18 min to obtain modified diatomaceous earth;

[0156] (3) Sodium alginate and polyvinyl alcohol were added into distilled water in a mass ratio of 1:3.5, and stirred in a water bath at 85° C. until they were completely dissolved to obtain a mixed solution;

[0157] The weight volume ratio of sodium alginate to distilled water is 1 g:23 mL;

[0158] (4) The modified sepiolite and modified diatomaceous earth were ground at a mass ratio of 1:2.5 at 1500 rpm for 17 min, and then ultrasonically dispersed in deionized water to obtain a uniformly dispersed aqueous suspension. The aqueous suspension was uniformly added to the mixed solution, and after stirring and mixing, the mixed solution was added dropwise to a 2% calcium chloride saturated boric acid solution using a rubber-tipped dropper to obtain hydrogel balls, which were cured for 12 h. Finally, the balls were rinsed with distilled water for 4 times, placed in a vacuum drying oven, and dried at 45° C. to constant weight to obtain a sepiolite / diatomaceous earth composite adsorbent.

[0159] S3, the waste gas after adsorption treatment enters the catalytic hydrolysis tower for catalytic oxidation treatment;

[0160] The preparation of the catalyst used in the catalytic oxidation treatment comprises the following steps:

[0161] La(NO3)3·6H2O, Zn(NO3)2·6H2O and anhydrous citric acid are added to deionized water in turn and stirred to mix. The total molar amount of cations is 0.025 mol, the molar ratio of La to Zn is 50:1, and the molar ratio of anhydrous citric acid to cations is 3.5:1. After complete dissolution, add silicon carbide 1.5 times the mass of La(NO3)3·6H2O and microcrystalline cellulose 1.2 times the mass of La(NO3)3·6H2O. The temperature is raised to 75°C and stirred until a gel is formed. The gel is dried in a 100°C drying oven to become a fluffy solid, then placed in a muffle furnace, calcined at 750°C for 4.5 hours, and then ground in a bead mill.

[0162] S4, finally enters the alkali liquid destruction tower to treat the waste gas before emptying, and the waste gas that meets the standards can be discharged into the air;

[0163] The alkali solution is a mixture of a sodium carbonate solution with a concentration of 5% and a sodium bicarbonate solution with a concentration of 2%, and the volume ratio of the sodium carbonate solution to the sodium bicarbonate solution is 1:0.4.

[0164] Comparative Example 6

[0165] A method for treating waste gas from the synthesis of ethyl chloroformate comprises the following steps:

[0166] S1. Introduce the waste gas into two condensers connected in series to condense, liquefy, separate and recover the waste gas;

[0167] S2, passing the uncondensed waste gas into an adsorption tower for adsorption treatment;

[0168] The adsorption treatment adopts solid adsorption, and the adsorbent used is a sepiolite / diatomite composite adsorbent.

[0169] The preparation of the sepiolite / diatomite composite adsorbent comprises the following steps:

[0170] (1) Adding sepiolite to the treating agent, stirring at 250 rpm and 83° C. for 2.5 h, filtering, drying to constant weight, placing in a muffle furnace, roasting at 450° C. for 6 min, placing in a grinder, grinding at 2500 rpm for 15 min to obtain modified sepiolite; the components and their corresponding weight percentages in the treating agent are: 5% nitric acid, 2.5% sulfuric acid, 4.5% hexadecyltrimethylammonium bromide, and the balance is deionized water;

[0171] (2) placing the diatomaceous earth in a muffle furnace, calcining at 550° C. for 3.5 h, cooling to room temperature, immersing in a 3 mol / L hydrochloric acid solution, stirring at 550 W microwave conditions for 10 min, filtering, drying, and grinding in a grinder at 2500 rpm for 18 min to obtain modified diatomaceous earth;

[0172] (3) Sodium alginate and polyvinyl alcohol were added into distilled water in a mass ratio of 1:3.5, and stirred in a water bath at 85° C. until they were completely dissolved to obtain a mixed solution;

[0173] The weight volume ratio of sodium alginate to distilled water is 1 g:23 mL;

[0174] (4) The modified sepiolite and modified diatomaceous earth were ground at a mass ratio of 1:2.5 at 1500 rpm for 17 min, and then ultrasonically dispersed in deionized water to obtain a uniformly dispersed aqueous suspension. The aqueous suspension was uniformly added to the mixed solution, and after stirring and mixing, the mixed solution was added dropwise to a 2% calcium chloride saturated boric acid solution using a rubber-tipped dropper to obtain hydrogel balls, which were cured for 12 h. Finally, the balls were rinsed with distilled water for 4 times, placed in a vacuum drying oven, and dried at 45° C. to constant weight to obtain a sepiolite / diatomaceous earth composite adsorbent.

[0175] S3, the waste gas after adsorption treatment enters the catalytic hydrolysis tower for catalytic oxidation treatment;

[0176] The preparation of the catalyst used in the catalytic oxidation treatment comprises the following steps:

[0177] 1) Ultrasonic dispersion of silicon carbide powder in deionized water, adding 0.08% tartaric acid by mass of silicon carbide powder after uniform dispersion, stirring at 250 rpm for 2.5 h, placing in a cryogenic mill, cryogenically grinding at -90°C for 25 min, placing in a vacuum drying oven, and drying at 15°C to constant weight to obtain modified silicon carbide;

[0178] 2) La(NO3)3·6H2O, Zn(NO3)2·6H2O and anhydrous citric acid are added to deionized water in sequence and stirred to mix. The total molar amount of cations is 0.025 mol, the molar ratio of La to Zn is 50:1, and the molar ratio of anhydrous citric acid to cations is 3.5:1. After complete dissolution, modified silicon carbide with a mass of 1.5 times that of La(NO3)3·6H2O is added, the temperature is raised to 75°C, and stirred until a gel is formed. The gel is dried in a drying oven at 100°C to become a fluffy solid, then placed in a muffle furnace, calcined at 750°C for 4.5 hours, and then placed in a bead mill for grinding.

[0179] S4, finally enters the alkali liquid destruction tower to treat the waste gas before emptying, and the waste gas that meets the standards can be discharged into the air;

[0180] The alkali solution is a mixture of a sodium carbonate solution with a concentration of 5% and a sodium bicarbonate solution with a concentration of 2%, and the volume ratio of the sodium carbonate solution to the sodium bicarbonate solution is 1:0.4.

[0181] The methods of Examples 1 to 3 and Comparative Examples 1 to 6 were used to prepare and test sepiolite / diatomite composite adsorbents and catalysts, and used them in the treatment of waste gas from the synthesis of ethyl chloroformate, and then the performance was tested. Specifically:

[0182] 1. Acid and alkali resistance test

[0183] 1.1 Acid resistance test

[0184] The diatomite / diatomite composite adsorbent and catalyst prepared by the methods of Examples 1 to 3 and Comparative Examples 1 to 6 were introduced into a carbon dioxide saturated gas at normal pressure for 7 days, and then the changes of each group of test samples were observed. The test results are shown in Table 1 below.

[0185] 1.2 Alkali resistance test

[0186] The diatomite / diatomite composite adsorbent and catalyst prepared by the methods of Examples 1 to 3 and Comparative Examples 1 to 6 were introduced into a saturated ammonia gas at normal pressure for 7 days, and then the changes of each group of test samples were observed. The test results are shown in Table 1 below.

[0187] Table 1

[0188] Surface state of diatomite / diatomite composite adsorbent Catalyst surface state Example 1 No dust No dust Example 2 No dust No dust Example 3 No dust No dust Comparative Example 1 Slightly dusty No dust Comparative Example 2 Slightly dusty No dust Comparative Example 3 Dust No dust Comparative Example 4 Slightly dusty No dust Comparative Example 5 No dust Slightly dusty Comparative Example 6 No dust Slightly dusty

[0189] Note: No dusting means that the structure of the bubble stone / diatomaceous earth composite adsorbent and catalyst has not changed significantly. Slight dusting means that powdery substances begin to float on the surface of the bubble stone / diatomaceous earth composite adsorbent and catalyst, and a small amount of them has fallen to the outside. Dusting means that a certain amount of powder has appeared on the outside of the bubble stone / diatomaceous earth composite adsorbent and catalyst, and its structure has become loose.

[0190] 2. Waste gas treatment effect test

[0191] The waste gas from the synthesis of ethyl chloroformate was purified by the methods in Examples 1 to 3 and Comparative Examples 1 to 6, the contents of phosgene, hydrogen chloride, nitrogen, etc. in the raw gas and the purified gas were measured, and the waste gas treatment capacity per unit mass of the sepiolite / diatomaceous earth composite adsorbent (catalyst) was calculated by the following formula.

[0192] The exhaust gas treatment capacity per unit mass of adsorbent is calculated using formula (1):

[0193]

[0194] The exhaust gas treatment capacity per unit mass of adsorbent is calculated using formula (2):

[0195]

[0196] The test results are shown in Table 2 below:

[0197] Table 2

[0198]

[0199] From the above performance test results, it can be seen that the adsorption catalytic purification effect of the waste gas synthesized by ethyl chloroformate in Examples 1 to 3 is very good, especially the comprehensive performance of Example 2 is the most outstanding, which is mainly due to the use of sepiolite / diatomaceous earth composite adsorbent and catalyst.

[0200] However, the comparative examples are significantly inferior to the embodiments in the corresponding performance tests because they do not adopt the necessary technical solutions. In comparative example 1, unmodified sepiolite is directly used, and in comparative example 2, unmodified diatomite is directly used. It can be seen from the results that the acid and alkali resistance of the adsorbent is reduced, which also affects the effect of waste gas treatment, indicating that the modification treatment can not only improve the dispersibility and structural properties of sepiolite and diatomite, but also affect the effect of waste gas treatment. In the preparation of the composite adsorbent of comparative example 3, the modified diatomite is omitted, and in the preparation of the composite adsorbent of comparative example 4, the modified sepiolite is omitted. The acid and alkali resistance and waste gas treatment capacity of the adsorbent are significantly reduced, indicating that the modified sepiolite and modified diatomite in the sepiolite / diatomite composite adsorbent of the present invention have a technical effect of mutual synergistic enhancement, which also proves the necessity of modifying sepiolite and modified diatomite to improve the performance of the adsorbent at the same time. In the preparation of the catalyst of Comparative Example 5, silicon carbide without modification is directly used. From the results, the acid and alkali resistance of the catalyst is weakened, and the catalytic oxidation effect of it for exhaust gas is poor, indicating that the modification of silicon carbide in the present invention is very necessary, which can not only improve the dispersibility of silicon carbide and improve the performance stability of the final finished catalyst, but also improve the effect of catalytic oxidation, which is conducive to the efficient purification of exhaust gas. In the preparation of the catalyst of Comparative Example 6, the use of auxiliary agents is omitted, and the acid and alkali resistance of the catalyst and the waste gas treatment amount are reduced, indicating that in the preparation of the catalyst of the present invention, the addition of an appropriate amount of auxiliary agent is very necessary, which can further optimize the catalytic effect of the catalyst, thereby improving the purification effect of the entire exhaust gas treatment system.

[0201] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for treating waste gas from the synthesis of ethyl chloroformate, characterized in that: The steps include: S1. Introduce the waste gas into 2-3 condensers connected in series to condense, liquefy, separate and recycle the waste gas; S2, passing the uncondensed waste gas into an adsorption tower for adsorption treatment; S3, the waste gas after adsorption treatment enters the catalytic hydrolysis tower for catalytic oxidation treatment; S4. Finally, the waste gas enters the alkali liquid destruction tower to be treated before being discharged. After reaching the standards, the waste gas can be discharged into the air.

2. A method for treating waste gas from ethyl chloroformate synthesis according to claim 1, characterized in that: The adsorption treatment described in step S2 adopts solid adsorption, and the adsorbent used is a sepiolite / diatomaceous earth composite adsorbent.

3. A method for treating waste gas from ethyl chloroformate synthesis according to claim 2, characterized in that: The preparation of the sepiolite / diatomite composite adsorbent comprises the following steps: (1) adding sepiolite to the treating agent, stirring at 200-300 rpm and 80-86° C. for 2-3 hours, filtering, drying to constant weight, placing in a muffle furnace, roasting at 400-500° C. for 4-8 minutes, placing in a grinder, grinding at 2000-3000 rpm for 10-20 minutes to obtain modified sepiolite; (2) placing the diatomaceous earth in a muffle furnace, calcining at 500-600° C. for 3-4 hours, cooling to room temperature, immersing in a 3 mol / L hydrochloric acid solution, stirring at 500-600 W microwave conditions for 8-12 minutes, filtering, drying, and grinding in a grinder at 2000-3000 rpm for 16-20 minutes to obtain modified diatomaceous earth; (3) adding sodium alginate and polyvinyl alcohol in a mass ratio of 1:3-4 into distilled water, stirring in a water bath at 80-90° C. until completely dissolved to obtain a mixed solution; (4) The modified sepiolite and modified diatomite are ground and mixed in a mass ratio of 1:2-3, and then ultrasonically dispersed in deionized water to obtain a uniformly dispersed aqueous suspension. The aqueous suspension is uniformly added to the mixed solution, and after stirring and mixing, the mixed solution is added dropwise to a 2% calcium chloride saturated boric acid solution using a rubber-tipped dropper to obtain a hydrogel ball and solidify it for 12 hours. Finally, the hydrogel ball is rinsed with distilled water for 3-5 times and placed in a vacuum drying oven, and dried at 40-50° C. to constant weight to obtain a sepiolite / diatomite composite adsorbent.

4. A method for treating waste gas from ethyl chloroformate synthesis according to claim 3, characterized in that: The components and corresponding weight percentages of the treatment agent described in step (1) are: 4-6% nitric acid, 2-3% sulfuric acid, 3-6% hexadecyltrimethylammonium bromide, and the balance is deionized water.

5. A method for treating waste gas from ethyl chloroformate synthesis according to claim 3, characterized in that: The weight volume ratio of sodium alginate to distilled water in step (3) is 1 g:20-26 mL.

6. A method for treating waste gas from ethyl chloroformate synthesis according to claim 3, characterized in that: During the grinding and mixing in step (4), the grinding speed is controlled to be 1000-2000 rpm and the grinding time is 14-20 min.

7. The method for treating waste gas from ethyl chloroformate synthesis according to claim 1, characterized in that: The preparation of the catalyst used in the catalytic oxidation treatment described in step S3 comprises the following steps: 1) Ultrasonic dispersion of silicon carbide powder in deionized water, adding 0.07-0.09% tartaric acid by mass of silicon carbide powder after uniform dispersion, stirring at 200-300 rpm for 2-3 hours, placing in a cryogenic mill, cryogenically grinding at -100--80°C for 20-30 minutes, and then placing in a vacuum drying oven, drying at 10-20°C to constant weight to obtain modified silicon carbide; 2) La(NO3)3·6H2O, Zn(NO3)2·6H2O and anhydrous citric acid are added to deionized water in sequence and stirred to mix well. The total molar amount of cations is 0.02-0.03 mol, and the molar ratio of La to Zn is 40-60:

1. After complete dissolution, modified silicon carbide and additives are added, the temperature is raised to 70-80°C, and stirred until a gel is formed. The gel is dried in a drying oven at 100°C to become a fluffy solid, then placed in a muffle furnace, calcined at 700-800°C for 4-5h, and then placed in a bead mill for grinding.

8. A method for treating waste gas from ethyl chloroformate synthesis according to claim 7, characterized in that: The molar ratio of the anhydrous citric acid to the cation in step 2) is 3-4:

1.

9. A method for treating waste gas from ethyl chloroformate synthesis according to claim 7, characterized in that: The amount of modified silicon carbide added in step 2) is 1-2 times that of La(NO3)3·6H2O; The amount of additive added is 0.9-1.5 times that of La(NO3)3·6H2O; The auxiliary agent is one of microcrystalline cellulose and carboxymethyl cellulose.

10. The method for treating waste gas from ethyl chloroformate synthesis according to claim 1, characterized in that: The alkali solution described in step S4 is a mixture of a sodium carbonate solution with a concentration of 5% and a sodium bicarbonate solution with a concentration of 2%, and the volume ratio of the sodium carbonate solution to the sodium bicarbonate solution is 1:0.3-0.5.

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