Photocatalysis tower type continuous preparation process of 1, 3-bromochloropropane

Abstract

The invention discloses a photocatalytic tower type continuous preparation process of 1, 3-bromochloropropane, and belongs to the technical field of unsaturated halogenated hydrocarbons, the process comprises the following steps: preparation of a thermocoagulation phase transfer agent, preparation of a premix, photocatalytic reaction and post-treatment; the photocatalytic reaction method comprises the following steps: by taking a glass plate type tower as a reactor, maintaining the temperature of a reaction system to be stable through a water bath jacket, turning on an ultraviolet lamp, spraying a premix from the top of the tower to enable the height of a solution in the reaction tower to reach the position of an overflow port, then reversely flowing hydrogen bromide from the bottom of the tower, refluxing 1 / 2-2 / 3 of a crude product mixed solution produced after the reaction to a mixing kettle, and carrying out heat preservation for 2-3 hours; cooling the residual mixed solution, filtering through an ultrafiltration membrane to recover the thermocoagulation type phase transfer agent, and refluxing the recovered thermocoagulation type phase transfer agent to the mixing kettle to obtain a residual product, namely a 1, 3-bromochloropropane crude product. According to the invention, efficient, environment-friendly and continuous production of 1, 3-bromochloropropane is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of unsaturated halogenated hydrocarbons, and particularly relates to a photocatalytic tower continuous preparation process of 1,3-bromochloropropane. Background Art

[0002] 1,3-Bromochloropropane is an important organic synthesis intermediate and is widely used in the fields of medicine, pesticides, spices and fine chemical preparation. In current industrial production, the free radical addition reaction is mainly carried out between allyl chloride and hydrogen bromide gas under the initiation of a solid catalyst benzoyl peroxide.

[0003] However, the traditional batch production process has significant defects: (1) Batch production requires frequent adjustment of temperature, pressure and feeding. The auxiliary operation time accounts for a relatively large proportion in a single production cycle, resulting in low production efficiency; (2) The mass transfer and heat transfer efficiency of the batch reaction is low, resulting in a reaction time as long as 8-10 hours. And the solid catalyst benzoyl peroxide needs to be continuously added. Impurities such as benzoic acid generated by its decomposition will adsorb on the reactor wall, affecting subsequent reactions and increasing the purification difficulty; (3) The wastewater containing benzoate generated during the use of benzoyl peroxide increases the wastewater treatment cost, and the catalyst residue needs to be removed by multiple steps of washing, resulting in a reduction in raw material utilization rate. Replacing the solid catalyst benzoyl peroxide with ultraviolet photocatalysis can solve problems such as easy introduction of impurities and wastewater treatment. However, photocatalysis also faces problems such as long photocatalytic reaction time, extremely short half-life of bromine radicals formed by photocatalytic hydrogen bromide gas, easy inactivation, low reaction efficiency, and large consumption of hydrogen bromide gas.

[0004] Therefore, developing an efficient, environmentally friendly and continuous production process has become the key to solving the bottleneck of the existing technology. Summary of the Invention

[0005] In view of the deficiencies of the existing technology, the present invention provides a photocatalytic tower continuous preparation process of 1,3-bromochloropropane, which obtains a product with high purity, more sufficient reaction, improves the yield of 1,3-bromochloropropane, reduces the consumption of hydrogen bromide gas, does not use organic solvents during the catalytic reaction process, is more environmentally friendly and has high economic efficiency.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A photocatalytic tower continuous preparation process of 1,3-bromochloropropane, comprising the following steps: preparing a thermally induced coagulation type phase transfer agent, preparing a premix, photocatalytic reaction, and post-treatment.

[0007] The method for preparing the thermally induced aggregation type phase transfer agent is as follows: Add dimethyloctadecylamine and brominated polyethyleneglycol methyl ether into absolute ethanol, reflux at 80 - 85 °C for 18 - 24 hours. After the reflux ends, distill off the solvent under reduced pressure. Wash the residue with ether 3 - 4 times and dry it under vacuum to obtain the intermediate. Dissolve the intermediate in acetonitrile, dropwise add methyl iodide at 0 - 5 °C, react at room temperature for 10 - 12 hours, add sodium dicyandiamide, continue stirring for 5 - 6 hours, then add dichloromethane and water. After shaking, separate the aqueous phase to remove water-soluble impurities. Dry the organic phase with anhydrous sodium sulfate and filter. Concentrate the filtrate under reduced pressure at 35 - 40 °C. Recrystallize the concentrated product with acetone to obtain the thermally induced aggregation type phase transfer agent; The molecular weight of the brominated polyethyleneglycol methyl ether is 350 - 450; The mass ratio of dimethyloctadecylamine, brominated polyethyleneglycol methyl ether and absolute ethanol is 300:350 - 450:600 - 800; The mass ratio of the intermediate, acetonitrile, methyl iodide, sodium dicyandiamide, dichloromethane and water is 300:400 - 500:80 - 85:50 - 55:150 - 200:200 - 300; The pressure for the reduced pressure concentration is 40 - 60 mbar; The mass ratio of the concentrated product and acetone is 100:200 - 300; Dynamic light scattering detection of the thermally induced aggregation type phase transfer agent shows that when the temperature drops from 35 °C to 20 °C, the particle size increases from <10 nm to >500 nm, and the Zeta potential > +30 mV, which is beneficial to solid-liquid separation. The thermally induced aggregation type phase transfer agent dissolves in the form of monomers at temperatures above 30 °C and forms micron-sized micelle aggregates at low temperatures below 25 °C, and can be recovered by filtration.

[0008] The method for preparing the premix is as follows: Add the thermally induced aggregation type phase transfer agent and 1,3-bromochloropropane into a mixing kettle and mix them. Stir at 40 - 45 °C until completely dissolved, then add allyl chloride and mix evenly at 30 - 35 °C to obtain the premix; The mass ratio of allyl chloride, 1,3-bromochloropropane and the thermally induced aggregation type phase transfer agent is 100:350 - 400:10 - 12.

[0009] The method of the photocatalytic reaction is as follows: using a glass plate column as the reactor, maintaining the temperature of the reaction system stable through a water bath jacket, setting the circulating water bath at 34 - 36 °C, turning on the ultraviolet lamp, spraying the premixed material from the top of the tower to make the solution height in the reaction tower reach the overflow port position, then introducing hydrogen bromide countercurrently from the bottom of the tower to start the reaction. Observe the weight of the lye for tail gas absorption, and keep the lye without obvious weight gain. After the reaction, 1 / 2 - 2 / 3 of the produced crude product mixture is refluxed to the mixing kettle, and then the remaining mixture is cooled to 19 - 21 °C, and the thermally induced coagulation type phase transfer agent is recovered by ultrafiltration membrane filtration. The recovered thermally induced coagulation type phase transfer agent is also refluxed to the mixing kettle, and the remaining product is the crude product of 1,3 - bromochloropropane; The feeding rate of the premixed material is 19 - 21 mL / min; The feeding rate of hydrogen bromide is 900 - 1100 mL / min; The wavelength of the ultraviolet lamp is 395 nm, and the power is 50 - 60 W; The recovered thermally induced coagulation type phase transfer agent is purified once every 3 - 4 cycles; The purification method is as follows: washing the recovered product with ether 3 - 4 times to remove fat - soluble impurities, and after drying, recrystallizing with acetone for further purification.

[0010] The post - treatment method is as follows: adding a sodium carbonate solution to the crude product of 1,3 - bromochloropropane, stirring at 20 - 25 °C for 3 - 5 min for neutralization. After neutralization is completed, let it stand for stratification for 25 - 30 min, collect the organic phase, then wash the organic phase with deionized water 2 - 3 times, let it stand for stratification for 10 - 20 min, collect the washed organic phase, and then add anhydrous sodium sulfate to dry it for 20 - 30 min, and filter to obtain 1,3 - bromochloropropane; The concentration of the sodium carbonate solution is 5 - 8 wt%; The mass ratio of the crude product of 1,3 - bromochloropropane to the sodium carbonate solution is 100:10 - 15; The mass ratio of the organic phase to the deionized water used for each washing is 100:10 - 15; The mass ratio of the washed organic phase to anhydrous sodium sulfate is 100:6 - 8.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In the preparation method of the thermally induced coagulation type phase transfer agent of the present invention, dimethyloctadecylamine and brominated poly(ethylene glycol) methyl ether are refluxed in ethanol, and an intermediate (alkylamine - PEG conjugate structure) is formed through a nucleophilic substitution reaction. The intermediate is quaternized with methyl iodide to form a positively charged quaternary ammonium salt, which contains a long - chain alkyl group, a PEG chain, and an iodide ion pair; then it reacts with sodium dicyandiamide to introduce a strong electron - withdrawing group of dicyandiamide anion to form an ion - pair structure.

[0012] During the photocatalytic reaction process, the thermally aggregating phase transfer agent forms an ion pair with HBr, promoting the transfer of HBr from the gas phase to the organic phase. Through polarization, the H-Br bond is weakened, accelerating the generation of free radicals. At the same time, due to the large steric hindrance effect of the long-chain alkane of the thermally aggregating phase transfer agent, the addition of bromine radicals from the proximal end of the double bond is hindered, guiding them to attack from the distal end, thereby improving the selectivity of 1,3-bromochloropropane products, promoting the directional generation of 1,3-bromochloropropane rather than 1,2-bromochloropropane, and improving the purity and yield of 1,3-bromochloropropane finished products.

[0013] (2)The polyethylene glycol segment in the thermally aggregating phase transfer agent unfolds at high temperature, and the thermally aggregating phase transfer agent dissolves in the organic phase in the form of monomers. When the temperature drops, the polyethylene glycol segment contracts, and the catalyst aggregates into micron-sized micelles (particle size > 500 nm, Zeta potential > +30 mV) through hydrophobic interactions, which is easy to achieve solid-liquid separation without introducing new impurities into the product, realizing the recycling of "high-temperature reaction and low-temperature recovery".

[0014] (3)The use of a glass plate tower in the present invention can make the gas-liquid mixing more uniform, the reaction more complete, and reduce the gas loss; the tower continuous process adopts a strong circulation system, and the mass transfer and heat transfer are more efficient than the batch process, which can improve the reaction efficiency and reduce the reaction time; the present invention uses ultraviolet lamp catalysis instead of catalysts such as peroxides, thereby reducing the environmental pollution caused by the catalyst.

[0015] (4)In the 1,3-bromochloropropane finished product prepared by the present invention, the content of 1,3-bromochloropropane is 97.18 - 97.54%, and the content of allyl chloride is 0.10 - 0.16%; after normal operation and recycling for 24 h, the yield of 1,3-bromochloropropane is 96.6 - 98.3%; the amount of hydrogen bromide gas used is 1.04 - 1.05 times the theoretical value. Detailed implementation manners

[0016] In order to have a clearer understanding of the technical features, objectives, and effects of the present invention, the specific implementation manners of the present invention are now described.

[0017] Example 1 A photocatalytic tower continuous preparation process for 1,3-bromochloropropane includes the following steps: (1)Prepare a thermally aggregating phase transfer agent Add dimethyloctadecylamine and brominated polyethylene glycol methyl ether to anhydrous ethanol, reflux at 80 °C for 24 hours. After the reflux is completed, remove the solvent under reduced pressure. Wash the residue with ether 3 times and dry it under vacuum to obtain the intermediate. Dissolve the intermediate in acetonitrile, add methyl iodide dropwise at 0 °C, react at room temperature for 12 hours, add sodium dicyandiamide, continue stirring for 6 hours, then add dichloromethane and water. After shaking, separate the aqueous phase to remove water-soluble impurities. Dry the organic phase with anhydrous sodium sulfate and filter. Concentrate the filtrate under reduced pressure at 35 °C. Recrystallize the concentrated product with acetone to obtain the thermally induced coagulation type phase transfer agent; The molecular weight of the brominated polyethylene glycol methyl ether is 350; The mass ratio of dimethyloctadecylamine, brominated polyethylene glycol methyl ether and anhydrous ethanol is 300:350:600; The mass ratio of the intermediate, acetonitrile, methyl iodide, sodium dicyandiamide, dichloromethane and water is 300:400:80:50:150:200; The pressure of the reduced pressure concentration is 40 mbar; The mass ratio of the concentrated product and acetone is 100:200; Dynamic light scattering detection of the thermally induced coagulation type phase transfer agent shows that when the temperature drops from 35 °C to 20 °C, the particle size increases from 6 nm to 650 nm, and the Zeta potential is +33 mV, which is conducive to solid-liquid separation.

[0018] (2) Preparation of the premix Add the thermally induced coagulation type phase transfer agent and 1,3-bromochloropropane to the mixing kettle and mix them. Stir at 40 °C until completely dissolved, then add allyl chloride and mix evenly at 30 °C to obtain the premix; The mass ratio of allyl chloride, 1,3-bromochloropropane and the thermally induced coagulation type phase transfer agent is 100:350:10.

[0019] (3) Photocatalytic reaction Use a glass plate tower as the reactor, maintain the temperature of the reaction system stable through a water bath jacket. Set the circulating water bath at 34 °C, turn on the ultraviolet lamp, spray the premix from the top of the tower to make the solution height in the reaction tower reach the overflow port position, then introduce hydrogen bromide countercurrently from the bottom of the tower to start the reaction. Observe the weight of the alkali solution for tail gas absorption and keep the alkali solution without obvious weight gain. After the reaction, reflux 1 / 2 of the produced crude product mixture back to the mixing kettle, then cool the remaining mixture to 19 °C, filter through an ultrafiltration membrane to recover the thermally induced coagulation type phase transfer agent, and also reflux the recovered thermally induced coagulation type phase transfer agent back to the mixing kettle. The remaining product is the crude product of 1,3-bromochloropropane; The reaction tower is 1200 mm high, 33 mm in inner diameter, and has a liquid holdup of 600 mL; The feeding rate of the premix is 19 mL / min; The feeding rate of hydrogen bromide is 900 mL / min; The wavelength of the ultraviolet lamp is 395 nm and the power is 50 W; The recycled thermally aggregating phase transfer agent is purified once every 3 cycles; The purification method is to wash the recovered product with ether 3 times to remove fat-soluble impurities, and after drying, recrystallize with acetone for further purification.

[0020] (4) Post-treatment Add a sodium carbonate solution to the crude 1,3-bromochloropropane, stir at 20 °C for 5 min for neutralization. After neutralization is completed, let it stand for 25 min to separate layers, collect the organic phase, then wash the organic phase with deionized water 2 times, let it stand for 10 min to separate layers, collect the washed organic phase, then add anhydrous sodium sulfate to it for drying for 20 min, and filter to obtain the finished product of 1,3-bromochloropropane; The concentration of the sodium carbonate solution is 5 wt%; The mass ratio of the crude 1,3-bromochloropropane to the sodium carbonate solution is 100:10; The mass ratio of the organic phase to the deionized water used for each washing is 100:10; The mass ratio of the washed organic phase to anhydrous sodium sulfate is 100:6.

[0021] In the finished product of 1,3-bromochloropropane prepared in this example, the content of 1,3-bromochloropropane is 97.26%, the content of allyl chloride is 0.16%, and the thermally aggregating phase transfer agent is not detected; after normal operation, a total of 7633.5 g of allyl chloride is consumed in 24 h of cycling, and 15173.2 g of 1,3-bromochloropropane is obtained by splitting, with a yield of 96.6%; the amount of hydrogen bromide gas used is 8190.2 g, which is 1.05 times the theoretical value.

[0022] Example 2 A photocatalytic tower continuous preparation process of 1,3-bromochloropropane, comprising the following steps: (1) Preparation of thermally aggregating phase transfer agent Add dimethyloctadecylamine and brominated polyethylene glycol methyl ether to anhydrous ethanol, reflux at 82 °C for 20 hours. After the reflux is completed, distill off the solvent under reduced pressure. The residue is washed with ether 3 times and dried in vacuo to obtain an intermediate. Dissolve the intermediate in acetonitrile, dropwise add methyl iodide at 2 °C, react at room temperature for 11 hours, add sodium dicyandiamide, continue stirring for 5.5 hours, then add dichloromethane and water, shake and separate the aqueous phase to remove water-soluble impurities. The organic phase is dried with anhydrous sodium sulfate and filtered. The filtrate is concentrated under reduced pressure at 38 °C, and the concentrated product is recrystallized with acetone to obtain the thermally aggregating phase transfer agent; The molecular weight of the brominated polyethylene glycol methyl ether is 400; The mass ratio of the dimethyloctadecylamine, brominated polyethylene glycol methyl ether, and absolute ethanol is 300:400:700; The mass ratio of the intermediate, acetonitrile, iodomethane, sodium dicyanamide, dichloromethane, and water is 300:450:82:52:180:250; The pressure for reduced-pressure concentration is 50 mbar; The mass ratio of the concentrated product and acetone is 100:250; Dynamic light scattering detection of the thermally induced aggregation type phase transfer agent shows that when the temperature drops from 35 °C to 20 °C, the particle size increases from 5 nm to 665 nm, and the Zeta potential is +35 mV, which is beneficial for solid-liquid separation.

[0023] (2) Preparation of the premix Add the thermally induced aggregation type phase transfer agent and 1,3-bromochloropropane to a mixing kettle for mixing, stir at 42 °C until completely dissolved, then add allyl chloride, and mix evenly at 32 °C to obtain the premix; The mass ratio of the allyl chloride, 1,3-bromochloropropane, and thermally induced aggregation type phase transfer agent is 100:380:11.

[0024] (3) Photocatalytic reaction Using a glass plate column as the reactor, maintain the temperature of the reaction system stable through a water bath jacket, set the circulating water bath at 35 °C, turn on the ultraviolet lamp, spray the premix from the top of the tower to make the solution height in the reaction tower reach the overflow port position, then introduce hydrogen bromide countercurrently from the bottom of the tower to start the reaction, observe the weight of the alkali solution for tail gas absorption, keep the alkali solution without obvious weight gain, after the reaction, reflux 1 / 2 of the produced crude product mixture to the mixing kettle, then cool the remaining mixture to 20 °C, filter through an ultrafiltration membrane to recover the thermally induced aggregation type phase transfer agent, and also reflux the recovered thermally induced aggregation type phase transfer agent to the mixing kettle. The remaining product is the crude product of 1,3-bromochloropropane; The reaction tower is 1200 mm high, 33 mm in inner diameter, and has a liquid holdup of 600 mL; The feeding rate of the premix is 20 mL / min; The feeding rate of the hydrogen bromide is 1000 mL / min; The wavelength of the ultraviolet lamp is 395 nm and the power is 55 W; The recovered thermally induced aggregation type phase transfer agent is purified once every 3 cycles; The purification method is to wash the recovered product 3 times with ether to remove fat-soluble impurities, and then recrystallize with acetone after drying for further purification.

[0025] (4) Post-treatment Add sodium carbonate solution to the crude 1,3-bromochloropropane, stir for 4 min at 22 °C for neutralization. After the neutralization is completed, let it stand for 28 min to separate layers, collect the organic phase, then wash the organic phase with deionized water twice, let it stand for 15 min to separate layers, collect the washed organic phase, then add anhydrous sodium sulfate to it for drying for 25 min, and filter to obtain the finished product of 1,3-bromochloropropane; The concentration of the sodium carbonate solution is 6 wt%; The mass ratio of the crude 1,3-bromochloropropane to the sodium carbonate solution is 100:12; The mass ratio of the organic phase to the deionized water used for each washing is 100:12; The mass ratio of the washed organic phase to anhydrous sodium sulfate is 100:7.

[0026] In the finished product of 1,3-bromochloropropane prepared in this example, the content of 1,3-bromochloropropane is 97.54%, the content of allyl chloride is 0.11%, and the thermally induced aggregation phase transfer agent is not detected; after normal operation, a total of 8319.2 g of allyl chloride is consumed in 24 h of circulation, and 16826.8 g of 1,3-bromochloropropane is obtained by splitting, with a yield of 98.3%; the amount of hydrogen bromide gas used is 9027.9 g, which is 1.04 times the theoretical value.

[0027] Example 3 A photocatalytic tower continuous preparation process of 1,3-bromochloropropane, comprising the following steps: (1) Prepare a thermally induced aggregation phase transfer agent Add dimethyloctadecylamine and brominated polyethylene glycol methyl ether to anhydrous ethanol, reflux at 85 °C for 18 hours. After the reflux is completed, distill off the solvent under reduced pressure. Wash the residue with ether 4 times and dry it under vacuum to obtain an intermediate. Dissolve the intermediate in acetonitrile, dropwise add methyl iodide at 5 °C, react at room temperature for 12 hours, add sodium dicyandiamide, continue stirring for 5 hours, then add dichloromethane and water, shake and separate the aqueous phase to remove water-soluble impurities. Dry the organic phase with anhydrous sodium sulfate and filter. Concentrate the filtrate under reduced pressure at 40 °C. Recrystallize the concentrated product with acetone to obtain a thermally induced aggregation phase transfer agent; The molecular weight of the brominated polyethylene glycol methyl ether is 450; The mass ratio of dimethyloctadecylamine, brominated polyethylene glycol methyl ether and anhydrous ethanol is 300:450:800; The mass ratio of the intermediate, acetonitrile, methyl iodide, sodium dicyandiamide, dichloromethane and water is 300:500:85:55:200:300; The pressure of the reduced pressure concentration is 60 mbar; The mass ratio of the concentrated product and acetone is 100:300; The dynamic light scattering detection of the thermally induced condensation type phase transfer agent shows that when the temperature drops from 35 °C to 20 °C, the particle size increases from 6 nm to 655 nm, and the Zeta potential is +35 mV, which is beneficial to solid-liquid separation.

[0028] (2)Preparation of premix Add the thermally induced condensation type phase transfer agent and 1,3-bromochloropropane into a mixing kettle and mix them. Stir at 45 °C until completely dissolved, then add allyl chloride and mix evenly at 35 °C to obtain the premix; The mass ratio of the allyl chloride, 1,3-bromochloropropane and the thermally induced condensation type phase transfer agent is 100:400:12.

[0029] (3)Photocatalytic reaction Use a glass plate tower as the reactor, maintain the temperature of the reaction system stable through a water bath jacket, set the circulating water bath at 36 °C, turn on the ultraviolet lamp, spray the premix from the top of the tower to make the solution height in the reaction tower reach the overflow port position, then introduce hydrogen bromide countercurrently from the bottom of the tower to start the reaction. Observe the weight of the lye for tail gas absorption, keep the lye without obvious weight gain. After the reaction, 2 / 3 of the produced crude product mixture is refluxed to the mixing kettle, and then the remaining mixture is cooled to 21 °C. The thermally induced condensation type phase transfer agent is recovered by ultrafiltration membrane filtration, and the recovered thermally induced condensation type phase transfer agent is also refluxed to the mixing kettle. The remaining product is the crude product of 1,3-bromochloropropane; The reaction tower is 1200 mm high, with an inner diameter of 33 mm and a liquid holdup of 600 mL; The feeding rate of the premix is 21 mL / min; The feeding rate of the hydrogen bromide is 1100 mL / min; The wavelength of the ultraviolet lamp is 395 nm and the power is 60 W; The recovered thermally induced condensation type phase transfer agent is purified once every 4 cycles; The purification method is to wash the recovered product 4 times with ether to remove fat-soluble impurities, and then recrystallize with acetone after drying for further purification.

[0030] (4)Post-treatment Add sodium carbonate solution to the crude product of 1,3-bromochloropropane, stir at 25 °C for 3 min for neutralization. After neutralization, let it stand for 30 min to separate layers, collect the organic phase, then wash the organic phase 3 times with deionized water, let it stand for 20 min to separate layers, collect the washed organic phase, and then add anhydrous sodium sulfate to dry it for 30 min, and filter to obtain the finished product of 1,3-bromochloropropane; The concentration of the sodium carbonate solution is 8 wt%; The mass ratio of the crude product of 1,3-bromochloropropane to the sodium carbonate solution is 100:15; The mass ratio of the organic phase to the deionized water used for each washing is 100:15; The mass ratio of the washed organic phase to anhydrous sodium sulfate is 100:8.

[0031] In the 1,3-bromochloropropane finished product prepared in this example, the content of 1,3-bromochloropropane is 97.18%, the content of allyl chloride is 0.10%, and the thermally induced coagulation type phase transfer agent is not detected; after normal operation, a total of 8564.7 g of allyl chloride is consumed in 24 h of circulation, 17151.4 g of 1,3-bromochloropropane is obtained, and the yield is 97.3%; the amount of hydrogen bromide gas used is 9281.6 g, which is 1.05 times the theoretical value.

[0032] Example 4 A photocatalytic tower continuous preparation process of 1,3-bromochloropropane includes the following steps: (1) Preparation of premix Add 1,3-bromochloropropane and allyl chloride to a mixing kettle and mix evenly at 32 °C to obtain a premix; The mass ratio of the allyl chloride to 1,3-bromochloropropane is 100:380.

[0033] (2) Photocatalytic reaction Using a glass plate tower as the reactor, maintaining the temperature of the reaction system stable through a water bath jacket, setting the circulating water bath at 35 °C, turning on the ultraviolet lamp, spraying the premix from the top of the tower to make the solution height in the reaction tower reach the overflow port position, then introducing hydrogen bromide countercurrently from the bottom of the tower to start the reaction, observing the weight of the alkali solution for tail gas absorption, keeping the alkali solution without obvious weight gain, and after the reaction, returning 1 / 2 of the 1,3-bromochloropropane crude product flowing out to the mixing kettle, and collecting the remaining product, that is, the 1,3-bromochloropropane crude product; The reaction tower is 1200 mm high, 33 mm in inner diameter, and has a liquid holdup of 600 mL; The feeding rate of the premix is 20 mL / min; The feeding rate of the hydrogen bromide is 1000 mL / min; The wavelength of the ultraviolet lamp is 395 nm and the power is 55 W.

[0034] (3) Post-treatment Add a sodium carbonate solution to the 1,3-bromochloropropane crude product, stir for 4 min at 22 °C for neutralization, after the neutralization is completed, let it stand for 28 min for stratification, collect the organic phase, then wash the organic phase with deionized water 2 times, let it stand for 15 min for stratification, collect the washed organic phase, and then add anhydrous sodium sulfate to dry it for 25 min, and filter to obtain the 1,3-bromochloropropane finished product; The concentration of the sodium carbonate solution is 6 wt%; The mass ratio of the crude 1,3-bromochloropropane to the sodium carbonate solution is 100:12.

[0035] The mass ratio of the organic phase to the deionized water used for each washing is 100:12; The mass ratio of the washed organic phase to the anhydrous sodium sulfate is 100:7.

[0036] In the 1,3-bromochloropropane finished product prepared in this example, the content of 1,3-bromochloropropane is 95.24%, and the content of allyl chloride is 1.23%; after normal operation, a total of 8204.9 g of allyl chloride is consumed in 24 h of circulation, 15273.0 g of 1,3-bromochloropropane is obtained, and the yield is 90.5%; the amount of hydrogen bromide gas used is 8876.5 g, which is 1.13 times the theoretical value.

[0037] Example 5 A photocatalytic tower continuous preparation process of 1,3-bromochloropropane includes the following steps: (1) Prepare the premix Add tetrahexylammonium bromide and 1,3-bromochloropropane to the mixing kettle and mix them. Stir at 42 °C until completely dissolved, then add allyl chloride and mix evenly at 32 °C to obtain the premix; The mass ratio of the allyl chloride, 1,3-bromochloropropane and tetrahexylammonium bromide is 100:380:11.

[0038] (2) Photocatalytic reaction Use a glass plate tower as the reactor, maintain the temperature of the reaction system stable through a water bath jacket, set the circulating water bath at 35 °C, turn on the ultraviolet lamp, spray the premix from the top of the tower to make the solution height in the reaction tower reach the overflow port position, then introduce hydrogen bromide countercurrently from the bottom of the tower to start the reaction. Observe the weight of the alkali solution for tail gas absorption and keep the alkali solution without obvious weight gain. After the reaction, 1 / 2 of the produced crude product mixture is refluxed to the mixing kettle, and then the remaining mixture is added with deionized water and allowed to stand for 20 - 30 min to separate layers, and the organic phase is collected, that is, the crude 1,3-bromochloropropane; The reaction tower is 1200 mm high, 33 mm in inner diameter, and has a liquid holdup of 600 mL; The feeding rate of the premix is 20 mL / min; The feeding rate of the hydrogen bromide is 1000 mL / min; The wavelength of the ultraviolet lamp is 395 nm and the power is 55 W.

[0039] (3) Post-treatment Add a sodium carbonate solution to the crude 1,3-bromochloropropane, stir for 4 min at 22 °C for neutralization. After the neutralization is completed, let it stand for 28 min to separate the layers, collect the organic phase, then wash the organic phase with deionized water twice, let it stand for 15 min to separate the layers, collect the washed organic phase, then add anhydrous sodium sulfate thereto for drying for 25 min, and filter to obtain the finished product of 1,3-bromochloropropane; The concentration of the sodium carbonate solution is 6 wt%; The mass ratio of the crude 1,3-bromochloropropane to the sodium carbonate solution is 100:12; The mass ratio of the organic phase to the deionized water used for each washing is 100:12; The mass ratio of the washed organic phase to the anhydrous sodium sulfate is 100:7.

[0040] In the finished product of 1,3-bromochloropropane prepared in this example, the content of 1,3-bromochloropropane is 96.72%, the content of allyl chloride is 0.21%, and 0.35% of tetrahexylammonium bromide is also detected; after normal operation, a total of 8153.6 g of allyl chloride is consumed in 24 h of circulation, 15734.4 g of 1,3-bromochloropropane is obtained, and the yield is 93.8%; the amount of hydrogen bromide gas used is 8742.9 g, which is 1.08 times the theoretical value.

[0041] Example 4 omitted the preparation of the thermally aggregating phase transfer agent, and also omitted the addition of the thermally aggregating phase transfer agent in the step of preparing the premix. The purity and yield of 1,3-bromochloropropane in the obtained finished product both decreased significantly, and the amount of hydrogen bromide gas used increased.

[0042] Example 5 omitted the preparation of the thermally aggregating phase transfer agent, and used tetrahexylammonium bromide instead of the thermally aggregating phase transfer agent in the step of preparing the premix. The obtained finished product contains tetrahexylammonium bromide, introducing new impurities into the 1,3-bromochloropropane product and being difficult to remove. The purity and yield of 1,3-bromochloropropane in the finished product both decreased slightly, and the amount of hydrogen bromide gas used increased.

[0043] Unless otherwise specified, the percentages described in this application are all mass percentages.

[0044] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A photocatalytic tower continuous preparation process of 1,3-bromochloropropane, characterized in that, The preparation process includes the following steps: preparing a thermally induced coagulation type phase transfer agent, preparing a premix, photocatalytic reaction, and post-treatment; The method for preparing the thermally induced coagulation type phase transfer agent is as follows: Add dimethyloctadecylamine and brominated polyethylene glycol methyl ether into absolute ethanol, reflux at 80 - 85 °C for 18 - 24 hours. After the reflux ends, remove the solvent under reduced pressure. Wash the residue with ether 3 - 4 times, and dry it under vacuum to obtain an intermediate. Dissolve the intermediate in acetonitrile, dropwise add methyl iodide at 0 - 5 °C, react at room temperature for 10 - 12 hours, add sodium dicyandiamide, continue stirring for 5 - 6 hours, then add dichloromethane and water, shake and separate the aqueous phase. Dry the organic phase with anhydrous sodium sulfate and filter. Concentrate the filtrate under reduced pressure at 35 - 40 °C. Recrystallize the concentrated product with acetone to obtain the thermally induced coagulation type phase transfer agent.

2. The photocatalytic tower continuous preparation process of 1,3-bromochloropropane according to claim 1, characterized in that, In the step of preparing the thermally induced coagulation type phase transfer agent, The molecular weight of the brominated polyethylene glycol methyl ether is 350 - 450; The mass ratio of dimethyloctadecylamine, brominated polyethylene glycol methyl ether and absolute ethanol is 300:350 - 450:600 - 800; The mass ratio of the intermediate, acetonitrile, methyl iodide, sodium dicyandiamide, dichloromethane and water is 300:400 - 500:80 - 85:50 - 55:150 - 200:200 - 300; The pressure for the reduced pressure concentration is 40 - 60 mbar; The mass ratio of the concentrated product and acetone is 100:200 - 300.

3. The photocatalytic tower continuous preparation process of 1,3-bromochloropropane according to claim 1, characterized in that, The method for preparing the premix is as follows: Add the thermally induced coagulation type phase transfer agent and 1,3 - bromochloropropane into a mixing kettle and mix. Stir at 40 - 45 °C until completely dissolved, then add allyl chloride and mix evenly at 30 - 35 °C to obtain the premix.

4. The photocatalytic tower continuous preparation process of 1,3-bromochloropropane according to claim 3, characterized in that, In the step of preparing the premix, The mass ratio of allyl chloride, 1,3 - bromochloropropane and the thermally induced coagulation type phase transfer agent is 100:350 - 400:10 - 12.

5. The photocatalytic tower continuous preparation process of 1,3-bromochloropropane according to claim 1, characterized in that, The method for the photocatalytic reaction is as follows: Use a glass plate column as the reactor, maintain the temperature of the reaction system stable through a water bath jacket, set the circulating water bath at 34 - 36 °C, turn on the ultraviolet lamp, spray the premix from the top of the tower to make the solution height in the reaction tower reach the overflow port position, then introduce hydrogen bromide countercurrently from the bottom of the tower to start the reaction. Observe the weight of the alkali solution for tail gas absorption, and keep the alkali solution without obvious weight gain. After the reaction, reflux 1 / 2 - 2 / 3 of the produced crude product mixture back to the mixing kettle, then cool the remaining mixture to 19 - 21 °C, filter through an ultrafiltration membrane to recover the thermally induced coagulation type phase transfer agent, and also reflux the recovered thermally induced coagulation type phase transfer agent back to the mixing kettle. The remaining product is the crude product of 1,3 - bromochloropropane.

6. The photocatalytic tower continuous preparation process of 1,3-bromochloropropane according to claim 5, characterized in that, In the step of the photocatalytic reaction, The feeding rate of the premix is 19 - 21 mL / min; The feeding rate of hydrogen bromide is 900 - 1100 mL / min; The wavelength of the ultraviolet lamp is 395 nm and the power is 50 - 60 W.

7. The photocatalytic tower continuous preparation process of 1,3-bromochloropropane according to claim 5, characterized in that, In the step of the photocatalytic reaction, The recovered thermally induced coagulation type phase transfer agent is purified once every 3 - 4 cycles; The purification method is as follows: Wash the recovered product with ether 3 - 4 times to remove fat-soluble impurities, dry it and then recrystallize with acetone for further purification.

8. The photocatalytic tower continuous preparation process of 1,3-bromochloropropane according to claim 1, characterized in that, The post-treatment method is as follows: add a sodium carbonate solution to the crude 1,3-bromochloropropane, stir for 3 - 5 min at a temperature of 20 - 25 °C for neutralization. After the neutralization is completed, let it stand for liquid separation for 25 - 30 min, collect the organic phase, then wash the organic phase with deionized water 2 - 3 times, let it stand for liquid separation for 10 - 20 min, collect the washed organic phase, then add anhydrous sodium sulfate to dry it for 20 - 30 min, and filter to obtain 1,3-bromochloropropane.

9. The photocatalytic tower continuous preparation process of 1,3-bromochloropropane according to claim 8, characterized in that, In the steps of the post-treatment, the concentration of the sodium carbonate solution is 5 - 8 wt%; the mass ratio of the crude 1,3-bromochloropropane to the sodium carbonate solution is 100:10 - 15; the mass ratio of the organic phase to the deionized water used for each washing is 100:10 - 15; the mass ratio of the washed organic phase to anhydrous sodium sulfate is 100:6 - 8.