Production process and production system of m-methylbenzyl chloride

Abstract

The invention relates to the technical field of preparation of organic intermediates, in particular to a production process and a production system of m-methylbenzyl chloride, and the production process comprises the following steps: conveying m-xylene to an m-xylene metering tank, standing, pumping into an evaporation kettle, heating until m-xylene is vaporized, introducing into a chlorination tower filled with a composite photocatalyst, introducing liquid chlorine into the chlorination tower after liquid chlorine is vaporized, the method comprises the following steps: in a micro-negative pressure environment, carrying out chlorination reaction with m-xylene gas under the catalysis of visible light to obtain a crude benzyl feed liquid containing m-methylbenzyl chloride and a byproduct m-dichlorobenzyl and tail gas, enabling the crude benzyl feed liquid to flow into a rectifying kettle and enter a rectifying section to be rectified to obtain a finished product m-methylbenzyl chloride, and enabling the tail gas to enter a hydrogen chloride absorption section to be treated. The product prepared by the production process disclosed by the invention has higher purity and weight yield, and meanwhile, the cost of raw materials is lower, so that the method is suitable for industrial production and has more economic benefits.

Description

Technical Field

[0001] The invention relates to the technical field of organic intermediate preparation, and in particular to a m-methylbenzyl chloride production process and a production system thereof. Background Art

[0002] 3-Methylbenzyl chloride (CAS No. 620-19-9), chemical formula is C 8 H 9 Cl, which contains a chlorine atom in its molecular structure, is directly connected to the benzyl group and is an important organic halogenated hydrocarbon. Meta-methylbenzyl chloride has high chemical activity and is often used in strong tear gas agents. It is used in the pharmaceutical industry to synthesize Mincozolin, etc. Meta-methylbenzyl chloride has a boiling point of 195-196°C, a relative density of 1.064, and a refractive index of 1.5327. It is almost insoluble in water, but can be mixed with pure ethanol and ether. The common preparation methods of meta-methylbenzyl chloride include: meta-xylene undergoes a substitution reaction with thionyl chloride under the action of a catalyst to generate meta-methylbenzyl chloride and sulfur dioxide; meta-methylbenzoic acid undergoes a chlorination reaction under the action of a chlorinating agent (such as phosphorus oxychloride, phosphorus trichloride, etc.) to generate meta-methylbenzyl chloride and the corresponding acyl chloride or anhydride; meta-hydroxybenzaldehyde is converted into meta-hydroxybenzyl alcohol through a reduction reaction, and then reacts with a chlorinating agent (such as hydrochloric acid, hydrogen chloride, etc.) to generate meta-methylbenzyl chloride.

[0003] In the prior art, m-toluic acid or m-hydroxybenzaldehyde is used as raw material, and the raw material itself is relatively high, which increases the cost of industrial production and is difficult to mass-produce. In addition, in the traditional preparation method, there are many by-products, which reduces the purity of the product, increases the difficulty of subsequent separation and purification, and further reduces the production efficiency. Summary of the invention

[0004] In order to solve the problems mentioned in the above background technology, the present invention provides a m-methylbenzyl chloride production process and a production system thereof.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A process for producing m-methylbenzyl chloride comprises the following steps:

[0007] The meta-xylene is pumped to the meta-xylene metering tank through a closed pipeline pump, and after standing for 24 hours to remove iron ions, it is pumped into an evaporator, and a heat transfer oil jacket is introduced to raise the temperature of the evaporator to 140-180°C. After the meta-xylene is vaporized, it is introduced into a chlorination tower equipped with a composite photocatalyst. After the liquid chlorine is vaporized (the chlorine pressure is stabilized at 0.035MPa), it is introduced into the chlorination tower. The entire system is a micro-negative pressure environment of (-101.3)-0kPa, and a chlorination reaction occurs with the meta-xylene gas under visible light catalysis. A ceramic ring filler is provided at the bottom of the chlorination tower to increase the contact area of ​​the reaction. After the reaction for 32-36 hours, a crude benzyl liquid and tail gas containing meta-methylbenzyl chloride and a by-product of meta-dichlorobenzyl chloride are obtained. The crude benzyl liquid flows into a distillation kettle, and after naturally cooling to 80-85°C, it enters the distillation section for distillation to obtain the finished meta-methylbenzyl chloride, and the tail gas enters the hydrogen chloride absorption section for treatment.

[0008] Furthermore, the distillation section is specifically as follows:

[0009] After the crude benzyl liquid is transferred to the distillation kettle, the jet vacuum pump is started to put the distillation system at a negative pressure of (-101.3)-0kPa, and the heat transfer oil is introduced into the jacket of the distillation kettle to raise the temperature to 140-150℃ and keep it warm for 4-5h. A small amount of unreacted m-xylene in the crude benzyl liquid begins to vaporize and is recovered to the distillation intermediate tank 1 for reuse after the first two-stage water cooling. The temperature is continued to rise to 150-170℃ and kept warm for 5-7h. The valve is switched and the temperature is recovered to the distillation intermediate tank 2 after the second two-stage water cooling. Then it flows back into the distillation tower through a closed pipeline and continues to rise to 170-190℃ and kept warm for 9-10h. After the third two-stage water cooling, the condensate and the kettle residue 1 are obtained. The condensate is collected in the m-methylbenzyl chloride finished product tank, and the kettle residue 1 is transferred to the residue refining section for treatment. The distillation waste gas is discharged through the exhaust pipe after the first-stage spray washing and two-stage activated carbon absorption treatment.

[0010] Further, the hydrogen chloride absorption section:

[0011] The tail gas enters the tail gas condenser, and after being condensed by the first-stage water cooling and the first-stage brine cooling in sequence, meta-xylene and hydrogen chloride are obtained. The meta-xylene is refluxed to the chlorination tower, cooled by saturated sodium chloride brine, and the residual meta-xylene is separated. Then it enters the three-stage falling film absorber, and is absorbed by pure water to obtain 31% hydrochloric acid by-product and treated tail gas. The hydrochloric acid is pumped into the hydrochloric acid finished product tank for storage. The treated tail gas is then subjected to the first-stage spray washing and two-stage activated carbon absorption treatment before being discharged through the exhaust pipe.

[0012] Furthermore, the residue refining section is specifically as follows:

[0013] The residue from the kettle is transferred to the distillation kettle through a sealed pipeline. After every 10 batches of residues are collected, distillation is performed once. A heat transfer oil jacket is introduced into the distillation kettle to raise the temperature to 200-210°C and maintain a slight negative pressure of (-101.3)-0kPa. After distillation for 48-50 hours, meta-dibenzyl chloride and the treated residue are obtained. The meta-dibenzyl chloride is introduced into a cooling kettle and cooled to 70-80°C before entering a receiving tank. The receiving tank is provided with a hot water jacket for heat preservation and stored in a liquid state at 70-80°C. The treated residue is stored in barrels temporarily. The meta-dibenzyl chloride in the receiving tank is transferred to a recrystallization kettle, and the agitator is turned on. Add ethanol into the recrystallization kettle, stir and cool and crystallize, recrystallize for 8-10 hours, filter and centrifuge to obtain m-dichlorobenzyl wet material and ethanol waste liquid, dry the m-dichlorobenzyl wet material at 80-90°C to obtain m-dichlorobenzyl crystals, and the ethanol waste liquid enters the ethanol distillation kettle for ethanol refining and recovery, introduce steam into the jacket of the ethanol distillation kettle to raise the temperature to 80-90°C, perform atmospheric distillation, and evaporate the ethanol, cool it with water at one level and with frozen brine at one level to obtain ethanol and kettle residue II, collect the ethanol in the ethanol receiving tank, and barrel the kettle residue II for temporary storage.

[0014] Furthermore, the composite photocatalyst comprises the following steps to prepare:

[0015] S1. Add ethanol, water and 25% ammonia water into a reaction kettle, slowly add tetraethyl orthosilicate while stirring at a speed of 200-300 rpm, and continue to stir and react at a speed of 100-200 rpm for 24-30 hours after the addition is completed to obtain a suspension of silica microspheres;

[0016] S2. Under nitrogen protection, polyethyleneimine is added to N,N-dimethylformamide, transferred to a reaction kettle, 1-pyrenecarboxylic acid is slowly added, and after stirring evenly, N,N'-dicyclohexylcarboximide and 4-dimethylaminopyridine are added, reacted at room temperature for 24-30 hours, filtered and centrifuged to obtain modified polyethyleneimine;

[0017] S3. Adjust the pH value of the silica microsphere suspension to 6-7, add modified polyethyleneimine into water to obtain a cationic polymer solution, add the silica microsphere suspension dropwise into the cationic polymer solution under stirring at 200-300 rpm, stir for 4-8 hours, filter, centrifuge, wash and dry to obtain a composite photocatalyst.

[0018] Furthermore, in step S1, the mass ratio of ethanol, water, aqueous ammonia and tetraethyl orthosilicate is (10-12): (2-3): (0.5-0.8): (1-2).

[0019] Furthermore, in step S2, the mass ratio of polyethyleneimine, N,N-dimethylformamide, 1-pyrenecarboxylic acid, N,N'-dicyclohexylcarboximide and 4-dimethylaminopyridine is (5-7): (10-15): (2.5-3): (0.4-0.8): (0.01-0.04).

[0020] Furthermore, in step S3, the mass ratio of the silica microsphere suspension to the cationic polymer solution is (1-1.5):1.

[0021] Furthermore, the feed mass ratio of m-xylene, liquid chlorine and composite photocatalyst is (10-12):(6-7):(0.5-0.8).

[0022] According to another aspect of the present invention, there is provided a production system for producing m-methylbenzyl chloride, comprising:

[0023] The meta-xylene supply system includes a meta-xylene metering tank and an evaporator, which are used for conveying, metering, standing and vaporizing the meta-xylene;

[0024] A chlorination reaction system, including a chlorination tower, for chlorination reaction of meta-xylene with liquid chlorine;

[0025] A distillation system, including a distillation kettle, a first distillation intermediate tank, a second distillation intermediate tank and a meta-methylbenzyl chloride finished product tank, is used to distill the crude benzyl liquid after the chlorination reaction to separate and obtain the finished meta-methylbenzyl chloride;

[0026] The hydrogen chloride absorption system includes an exhaust condenser, a falling film absorber and a hydrochloric acid product tank, which is used to treat the exhaust gas generated by the chlorination reaction, recover meta-xylene and absorb hydrogen chloride to generate hydrochloric acid;

[0027] The residue treatment system includes a distillation kettle, a receiving tank, a recrystallization kettle, a drying device, an ethanol distillation kettle and an ethanol receiving tank, which are used to treat the residue in the distillation process and recover and purify benzyl dichloride and ethanol.

[0028] Beneficial effects of the present invention:

[0029] 1. In the technical solution of the present invention, silicon dioxide (SiO 2 ) microspheres are formed by hydrolysis and condensation reaction as inorganic substrates. They have smooth surfaces and are rich in hydroxyl (-OH) functional groups, providing abundant binding sites. Modified polyethyleneimine (PEI-Py) is used as an organic shell. The photosensitive group pyrene is covalently linked to the polyethyleneimine (PEI) molecular chain through an amidation reaction to form a polymer with cationic properties. During the preparation process, PEI-Py is loaded on SiO2 through electrostatic attraction and hydrogen bonding. 2The surface of the microspheres forms a uniform shell structure. This loading method not only ensures the uniform distribution of the photosensitive group pyrene in the composite photocatalyst, but also significantly enhances the overall stability of the catalyst. The composite photocatalyst can efficiently absorb light energy under light conditions and convert it into chemical energy, and then transition to an excited state. The excited pyrene molecules in the composite photocatalyst have high energy and reactivity, and can interact with the surrounding molecules through electron transfer or energy transfer to generate catalytically active species, which can initiate or accelerate the chlorination reaction between m-xylene and liquid chlorine to generate the target products m-methylbenzyl chloride and m-dichlorobenzyl chloride. At the same time, SiO 2 As an inorganic substrate, the microspheres not only provide a stable supporting structure, but also affect the photochemical properties of the photosensitive groups through the interaction with PEI-Py. 2 The hydroxyl groups on the surface of the microspheres form hydrogen bonds with the catalytic active species, changing their activity and selectivity, thereby improving the purity of the product. 2 The high specific surface area of ​​the microspheres also provides more contact opportunities for the reactants, significantly improving the efficiency of the catalytic reaction and further increasing production efficiency.

[0030] 2. In the technical solution of the present invention, m-xylene and hydrogen chloride are used as raw materials to produce m-methylbenzyl chloride. Compared with the method of using m-toluic acid, m-hydroxybenzaldehyde, etc., the cost of raw materials is lower, which is suitable for industrial production and more economical. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 It is a process flow chart of the present invention;

[0033] Figure 2 It is a block diagram of the device connection of the present invention;

[0034] In the figure, 1, m-xylene metering tank; 2, evaporator; 3, chlorination tower; 4, chlorination tower; 5, distillation kettle; 6, distillation intermediate tank 1; 7, distillation intermediate tank 2; 8, m-methylbenzyl chloride finished product tank; 9, tail gas condenser; 10, falling film absorber; 11, hydrochloric acid finished product tank; 12, distillation kettle; 13, receiving tank; 14, recrystallization kettle; 15, drying device; 16, ethanol distillation kettle; 17, ethanol receiving tank. DETAILED DESCRIPTION

[0035] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Unless otherwise specified, the raw materials used in the present invention are all conventional products purchased from the market.

[0037] Preparation Example 1

[0038] The composite photocatalyst comprises the following steps to prepare:

[0039] S1. Add 10 kg of ethanol, 2 kg of water and 0.5 kg of 25% ammonia water into a reaction kettle, add 1-2 kg of ethyl orthosilicate dropwise while stirring at 200 rpm, and stir at 100 rpm for 24-30 hours to obtain a suspension of silica microspheres;

[0040] S2. Under nitrogen protection, 5 kg of polyethyleneimine was added to 10 kg of N, N-dimethylformamide, transferred to a reactor, 2.5 kg of 1-pyrenecarboxylic acid was added, and after stirring evenly, 0.4 kg of N, N'-dicyclohexylcarboximide and 0.01 kg of 4-dimethylaminopyridine were added, and the mixture was reacted at room temperature for 24 hours, filtered and centrifuged to obtain modified polyethyleneimine;

[0041] S3. Adjust the pH value of the silica microsphere suspension to 6, add 4 kg of modified polyethyleneimine into 20 kg of water to obtain a cationic polymer solution, and add 10 kg of the silica microsphere suspension dropwise into 10 kg of the cationic polymer solution under stirring at 200 rpm, stir for 4 hours, filter, centrifuge, wash, and dry to obtain a composite photocatalyst.

[0042] Preparation Example 2

[0043] The composite photocatalyst comprises the following steps to prepare:

[0044] S1. Add 11 kg of ethanol, 2.5 kg of water and 0.7 kg of 25% ammonia water into a reaction kettle, add 1.5 kg of ethyl orthosilicate dropwise while stirring at 250 rpm, and stir at 150 rpm for 28 hours to obtain a suspension of silica microspheres;

[0045] S2. Under nitrogen protection, 6 kg of polyethyleneimine was added to 12.5 kg of N, N-dimethylformamide, transferred to a reactor, 2.8 kg of 1-pyrenecarboxylic acid was added, and after stirring evenly, 0.65 kg of N, N'-dicyclohexylcarboximide and 0.02 kg of 4-dimethylaminopyridine were added, and the mixture was reacted at room temperature for 27 hours, filtered and centrifuged to obtain modified polyethyleneimine;

[0046] S3. Adjust the pH value of the silica microsphere suspension to 6, add 4 kg of modified polyethyleneimine to 20 kg of water to obtain a cationic polymer solution, and add 12.5 kg of the silica microsphere suspension dropwise to 10 kg of the cationic polymer solution under stirring at 250 rpm, stir for 6 hours, filter, centrifuge, wash, and dry to obtain a composite photocatalyst.

[0047] Preparation Example 3

[0048] The composite photocatalyst comprises the following steps to prepare:

[0049] S1. Add 12 kg of ethanol, 3 kg of water and 0.8 kg of 25% ammonia water into a reaction kettle, add 2 kg of ethyl orthosilicate dropwise while stirring at 300 rpm, and stir at 200 rpm for 30 hours to obtain a suspension of silica microspheres;

[0050] S2. Under nitrogen protection, add 7 kg polyethyleneimine to 15 kg N, N-dimethylformamide, transfer to a reactor, add 3 kg 1-pyrenecarboxylic acid, stir evenly, add 0.8 kg N, N'-dicyclohexylcarboximide and 0.04 kg 4-dimethylaminopyridine, react at room temperature for 30 hours, filter and centrifuge to obtain modified polyethyleneimine;

[0051] S3. Adjust the pH value of the silica microsphere suspension to 7, add 4 kg of modified polyethyleneimine into 20 kg of water to obtain a cationic polymer solution, and add 15 kg of the silica microsphere suspension dropwise into 10 kg of the cationic polymer solution under stirring at 300 rpm, stir for 8 hours, filter, centrifuge, wash, and dry to obtain a composite photocatalyst.

[0052] Example 1

[0053] A process for producing m-methylbenzyl chloride comprises the following steps:

[0054] 10 kg of meta-xylene was transported to a meta-xylene metering tank, allowed to stand for 24 hours, and then pumped into an evaporator, heated to 140° C., and then vaporized into a chlorination tower containing 0.5 kg of the composite photocatalyst prepared in Example 1. 6 kg of liquid chlorine was vaporized and then passed into a chlorination tower, and chlorinated with meta-xylene gas under visible light catalysis under a slightly negative pressure environment of (-101.3) kPa. After the reaction lasted for 32 hours, a crude benzyl liquid and tail gas containing meta-methylbenzyl chloride and by-product meta-dichlorobenzyl chloride were obtained. The crude benzyl liquid flowed into a distillation kettle, naturally cooled to 80° C., and then entered the distillation section for distillation to obtain the finished product meta-methylbenzyl chloride. The tail gas entered the hydrogen chloride absorption section for treatment.

[0055] The distillation section is specifically as follows:

[0056] After the crude benzyl liquid is transferred to the distillation kettle, the temperature is raised to 140°C and kept warm for 4 hours. A small amount of unreacted m-xylene in the crude benzyl liquid begins to vaporize and is recovered to the distillation intermediate tank 1 for reuse after the first two-stage water cooling. The temperature is continued to be raised to 150°C and kept warm for 5 hours. The valve is switched and the liquid is recovered to the distillation intermediate tank 2 after the second two-stage water cooling. The liquid is then refluxed into the distillation tower through a closed pipeline and the temperature is continued to be raised to 170°C and kept warm for 9 hours. After the third two-stage water cooling, a condensate and a kettle residue 1 are obtained. The condensate is collected in the m-methylbenzyl chloride finished product tank, and the kettle residue 1 is transferred to the residue refining section for treatment.

[0057] The specific hydrogen chloride absorption section is as follows:

[0058] The tail gas enters the tail gas condenser, and after being condensed by the first-level water cooling and the first-level brine cooling, meta-xylene and hydrogen chloride are obtained. The meta-xylene is refluxed to the chlorination tower, cooled by brine to separate the residual meta-xylene, and then enters the third-level falling film absorber, and is absorbed by pure water to obtain 31% hydrochloric acid by-product and treated tail gas. The hydrochloric acid is pumped into the hydrochloric acid finished product tank for storage.

[0059] The specific residue refining section is as follows:

[0060] The first pot residue is transferred to the distillation kettle through a closed pipeline, heated to 200°C, and maintained at a slight negative pressure of (-101.3) kPa. After distillation for 48 hours, meta-dibenzyl chloride and treated residue are obtained. The meta-dibenzyl chloride is passed into the cooling kettle and cooled to 70°C and enters the receiving tank. The receiving tank is provided with a hot water jacket for insulation and stored in liquid form at 70°C. The treated residue is barreled for temporary storage. The meta-dibenzyl chloride in the receiving tank is transferred to the recrystallization kettle, the agitator is turned on, and ethanol is added to the recrystallization kettle. The mixture is stirred for cooling and crystallization. After recrystallization for 8 hours, suction filtration and centrifugation, meta-dibenzyl chloride wet material and ethanol waste liquid are obtained. The meta-dibenzyl chloride wet material is dried at 80°C to obtain meta-dibenzyl chloride crystals. The ethanol waste liquid enters the ethanol distillation kettle for ethanol refining and recovery. Steam is passed into the jacket of the ethanol distillation kettle to raise the temperature to 80°C for atmospheric distillation. After the ethanol is distilled out and cooled by a first-level water cooling and a first-level refrigerated brine cooling, ethanol and pot residue 2 are obtained. The ethanol is collected in the ethanol receiving tank, and the pot residue 2 is barreled for temporary storage.

[0061] Example 2

[0062] The difference between this embodiment and embodiment 1 is that the feed masses of m-xylene, composite photocatalyst and liquid chlorine are 11 kg, 0.65 kg and 6.5 kg respectively, and the composite photocatalyst prepared in preparation example 2 is used, and the remaining steps are the same as those in embodiment 1.

[0063] Example 3

[0064] The difference between this embodiment and embodiment 1 is that the feed masses of m-xylene, composite photocatalyst and liquid chlorine are 12 kg, 0.8 kg and 7 kg respectively, and the composite photocatalyst prepared in preparation example 3 is used, and the remaining steps are the same as those in embodiment 1.

[0065] Comparative Example 1

[0066] The difference between this comparative example and Example 1 is that polyethyleneimine is used instead of the composite photocatalyst, and the remaining steps are the same as those in Example 1.

[0067] Comparative Example 2

[0068] The difference between this comparative example and Example 2 is that 1-pyrenecarboxylic acid is used instead of the composite photocatalyst, and the remaining steps are the same as those in Example 2.

[0069] Comparative Example 3

[0070] The difference between this comparative example and Example 3 is that a silica microsphere suspension is used instead of the composite photocatalyst, and the remaining steps are the same as those in Example 3.

[0071] The purity and weight yield of Examples 1-3 and Comparative Examples 1-3 were determined by HPLC. The results are shown in Table 1:

[0072] Table 1. Purity and weight yield results of Examples 1-3 and Comparative Examples 1-3

[0073] serial number purity(%) Weight yield (%) Example 1 99.5 111.6 Example 2 99.6 118.1 Example 3 99.6 116.9 Comparative Example 1 96.3 108.2 Comparative Example 2 94.7 109.3 Comparative Example 3 94.0 104.5

[0074] As can be seen from Table 1, the purity of Examples 1-3 is higher than 99.5%, indicating that the composite photocatalyst has high selectivity and catalytic efficiency in the chlorination reaction and can reduce the generation of by-products. The weight yield of Example 2 is the highest (118.1%), followed by Example 3 (116.9%) and Example 1 (111.6%). The purity of Comparative Examples 1-3 is lower than that of Examples 1-3, and the weight yield of Comparative Examples 1-3 is also lower than that of Examples 1-3. It may be due to the low catalytic efficiency of the catalyst that the reaction is incomplete, resulting in a reduced yield.

[0075] The composite photocatalyst is composed of silica microspheres and modified polyethyleneimine, and there may be a certain synergistic effect, in which the silica microspheres are used as carriers and the modified polyethyleneimine is used as an active ingredient. Under visible light irradiation, the modified polyethyleneimine can absorb light energy and excite electrons, thereby promoting the chlorination reaction of meta-xylene with chlorine. Although polyethyleneimine (Comparative Example 1) has a certain alkalinity, its catalytic efficiency and selectivity are low without modification. 1-Pyrenecarboxylic acid (Comparative Example 2) contains a photosensitive group, but it may not be able to effectively catalyze the chlorination reaction when used alone. The silica microsphere suspension (Comparative Example 3) is only used as a carrier and does not have catalytic activity, so it cannot promote the chlorination reaction.

[0076] In summary, the composite photocatalyst exhibited high catalytic activity and selectivity in the production process of m-methylbenzyl chloride, and significantly improved the purity and weight yield of the products obtained in Examples 1-3.

[0077] In the description of the specification, the description with reference to the terms "preparation example", "embodiment", "various embodiments" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or preparation example are included in at least one embodiment or preparation example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or preparation example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or preparation examples in a suitable manner.

[0078] 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 process for producing m-methylbenzyl chloride, characterized in that: The following steps are involved: The meta-xylene is transported to the meta-xylene metering tank, and after standing for 24 hours, it is pumped into the evaporator and heated to 140-180°C. After the meta-xylene is vaporized, it is passed into the chlorination tower equipped with a composite photocatalyst. After the liquid chlorine is vaporized, it is passed into the chlorination tower. Under the micro-negative pressure environment of (-101.3)-0kPa, a chlorination reaction occurs with the meta-xylene gas under the catalysis of visible light. After the reaction for 32-36 hours, a crude benzyl liquid and tail gas containing meta-methylbenzyl chloride and by-product meta-dichlorobenzyl chloride are obtained. The crude benzyl liquid flows into the distillation kettle, and after naturally cooling to 80-85°C, it enters the distillation section for distillation to obtain the finished product meta-methylbenzyl chloride. The tail gas enters the hydrogen chloride absorption section for treatment.

2. A process for producing m-methylbenzyl chloride according to claim 1, characterized in that: The distillation section is specifically as follows: After the crude benzyl liquid is transferred to the distillation kettle, the temperature is raised to 140-150°C and kept warm for 4-5 hours. A small amount of unreacted m-xylene in the crude benzyl liquid begins to vaporize and is recovered to the distillation intermediate tank 1 for reuse after the first two-stage water cooling. The temperature is continued to be raised to 150-170°C and kept warm for 5-7 hours. The valve is switched and the liquid is recovered to the distillation intermediate tank 2 after the second two-stage water cooling. The liquid is then refluxed into the distillation tower through a closed pipeline and the temperature is continued to be raised to 170-190°C and kept warm for 9-10 hours. After the third two-stage water cooling, a condensate and a kettle residue 1 are obtained. The condensate is collected in the m-methylbenzyl chloride finished product tank, and the kettle residue 1 is transferred to the residue refining section for treatment.

3. A process for producing m-methylbenzyl chloride according to claim 1, characterized in that: The specific hydrogen chloride absorption section is as follows: The tail gas enters the tail gas condenser, and after being condensed by the first-level water cooling and the first-level brine cooling, meta-xylene and hydrogen chloride are obtained. The meta-xylene is refluxed to the chlorination tower, cooled by brine to separate the residual meta-xylene, and then enters the third-level falling film absorber, and is absorbed by pure water to obtain 31% hydrochloric acid by-product and treated tail gas. The hydrochloric acid is pumped into the hydrochloric acid finished product tank for storage.

4. A process for producing m-methylbenzyl chloride according to claim 2, characterized in that, The specific residue refining section is as follows: The residue is transferred to the distillation kettle through a sealed pipeline, heated to 200-210°C, maintained at a slight negative pressure of (-101.3)-0kPa, and distilled for 48-50 hours to obtain benzyl chloride and treated residue. The benzyl chloride is passed into a cooling kettle and cooled to 70-80°C before entering a receiving tank. The receiving tank is provided with a hot water jacket for heat preservation and stored in a liquid state at 70-80°C. The treated residue is temporarily stored in barrels. The benzyl chloride in the receiving tank is transferred to a recrystallization kettle, the stirrer is turned on, ethanol is added to the recrystallization kettle, and the mixture is stirred for cooling. The product is crystallized and recrystallized for 8-10 hours. After suction filtration and centrifugation, benzyl dichloride wet material and ethanol waste liquid are obtained. The benzyl dichloride wet material is dried at 80-90°C to obtain benzyl dichloride crystals. The ethanol waste liquid enters the ethanol distillation kettle for ethanol refining and recovery. Steam is introduced into the jacket of the ethanol distillation kettle to raise the temperature to 80-90°C for atmospheric distillation. After the ethanol is evaporated and cooled by water and then by frozen brine, ethanol and kettle residue II are obtained. The ethanol is collected in an ethanol receiving tank and the kettle residue II is barreled for temporary storage.

5. A process for producing m-methylbenzyl chloride according to claim 1, characterized in that: The composite photocatalyst comprises the following steps to prepare: S1. Add ethanol, water and 25% ammonia water into a reaction kettle, add ethyl orthosilicate dropwise while stirring at 200-300 rpm, and stir at 100-200 rpm for 24-30 hours to obtain a suspension of silica microspheres; S2. Under nitrogen protection, polyethyleneimine is added to N,N-dimethylformamide, transferred to a reaction kettle, 1-pyrenecarboxylic acid is added, stirred evenly, N,N'-dicyclohexylcarboximide and 4-dimethylaminopyridine are added, reacted at room temperature for 24-30 hours, filtered and centrifuged to obtain modified polyethyleneimine; S3. Adjust the pH value of the silica microsphere suspension to 6-7, add modified polyethyleneimine into water to obtain a cationic polymer solution, add the silica microsphere suspension dropwise into the cationic polymer solution under stirring at 200-300 rpm, stir for 4-8 hours, filter, centrifuge, wash and dry to obtain a composite photocatalyst.

6. A process for producing m-methylbenzyl chloride according to claim 5, characterized in that: In step S1, the mass ratio of ethanol, water, ammonia water and tetraethyl orthosilicate is (10-12): (2-3): (0.5-0.8): (1-2).

7. A process for producing m-methylbenzyl chloride according to claim 5, characterized in that: In step S2, the mass ratio of polyethyleneimine, N,N-dimethylformamide, 1-pyrenecarboxylic acid, N,N'-dicyclohexylcarboximide and 4-dimethylaminopyridine is (5-7): (10-15): (2.5-3): (0.4-0.8): (0.01-0.04).

8. A process for producing m-methylbenzyl chloride according to claim 5, characterized in that: The mass ratio of the silica microsphere suspension to the cationic polymer solution in step S3 is (1-1.5):

1.

9. A process for producing m-methylbenzyl chloride according to claim 1, characterized in that: The feed mass ratio of m-xylene, liquid chlorine and composite photocatalyst is (10-12):(6-7):(0.5-0.8).

10. A production system for the production process of producing m-methylbenzyl chloride according to any one of claims 1 to 9, characterized in that: include: The meta-xylene supply system includes a meta-xylene metering tank and an evaporator, which are used for conveying, metering, standing and vaporizing the meta-xylene; A chlorination reaction system, including a chlorination tower, for chlorination reaction of meta-xylene with liquid chlorine; A distillation system, including a distillation kettle, a first distillation intermediate tank, a second distillation intermediate tank and a meta-methylbenzyl chloride finished product tank, is used to distill the crude benzyl liquid after the chlorination reaction to separate and obtain the finished meta-methylbenzyl chloride; The hydrogen chloride absorption system includes an exhaust condenser, a falling film absorber and a hydrochloric acid product tank, which is used to treat the exhaust gas generated by the chlorination reaction, recover meta-xylene and absorb hydrogen chloride to generate hydrochloric acid; The residue treatment system includes a distillation kettle, a receiving tank, a recrystallization kettle, a drying device, an ethanol distillation kettle and an ethanol receiving tank, which are used to treat the residue in the distillation process and recover and purify benzyl dichloride and ethanol.

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