P-methyl benzyl chloride production process and production system thereof

Abstract

The invention discloses a p-methyl benzyl chloride production process and a production system thereof, p-xylene side chains and chlorine are subjected to a gas phase substitution reaction under micro negative pressure and visible light catalysis to generate crude methyl benzyl chloride and hydrogen chloride, and 99.0% methyl benzyl chloride, a small amount of benzyl dichloride and 31% hydrochloric acid are respectively generated through rectification and absorption; the device consists of four working sections of chlorination, rectification, hydrochloric acid absorption and distillation. According to the method, the defects in the prior art are overcome, on one hand, chlorine is introduced, and an aromatic ring chlorination reaction is carried out under visible light catalysis; on one hand, a supported catalyst filler is arranged at the bottom of a chlorination tower, and a zeolite molecular sieve modified by long-chain alkylsilane and supported by metal salt is used as a catalyst to catalyze chloromethylation reaction, on the other hand, the hydrophobicity of the modified catalyst is obviously enhanced, and meanwhile, the density of acidic sites is not reduced; the contact opportunity of the catalyst and a reaction substrate is greatly increased, and the catalytic efficiency of the catalyst is improved.

Description

Technical Field

[0001] The invention relates to the technical field of chemical industry, and in particular to a production process of p-methylbenzyl chloride and a production system thereof. Background Art

[0002] 4-Methyl benzyl chloride, as a fine chemical product, has a wide range of applications in organic synthesis, medicine, pesticides, etc. The research and development of its synthesis process is of great significance to meet market demand, improve product quality and reduce production costs.

[0003] The synthesis of p-methylbenzyl chloride mainly uses p-xylene as raw material. p-xylene is an easily available chemical raw material with a wide range of sources and a relatively stable price. During the synthesis process, p-xylene undergoes a substitution reaction with chlorine under light and heating conditions to generate p-methylbenzyl chloride.

[0004] The reaction mechanism mainly involves free radical substitution reaction. Under light conditions, chlorine molecules absorb light energy and decompose into chlorine radicals (Cl·). These chlorine radicals attack hydrogen atoms in p-xylene molecules to generate methylphenyl radicals (C6H4CH3·). Subsequently, the methylphenyl radicals combine with chlorine radicals to generate p-methylbenzyl chloride.

[0005] With the continuous development of the chemical industry, the demand for methylbenzyl chloride is increasing. It has broad application prospects in organic synthesis, medicine, pesticides and other fields, and has great market potential. However, the current synthesis process of methylbenzyl chloride still faces some challenges:

[0006] Raw material cost: The price fluctuation of paraxylene as raw material may have an impact on production cost. Therefore, it is of great significance to find more economical and environmentally friendly raw material alternatives.

[0007] Environmental pollution: Wastewater, waste gas and other pollutants generated during the synthesis process may have adverse effects on the environment. Therefore, it is crucial to strengthen the research and development and application of environmental protection measures and energy-saving and emission reduction technologies.

[0008] Product quality: As the market's requirements for product quality continue to increase, the requirements for the purity, stability and other indicators of methylbenzyl chloride are becoming more and more stringent. Therefore, it is necessary to continuously improve and optimize the synthesis process to improve product quality and competitiveness.

[0009] As an important fine chemical product, p-methylbenzyl chloride has broad application prospects in organic synthesis, medicine, pesticides and other fields. Through the research and optimization of its synthesis process, the synthesis efficiency and product quality can be improved, the production cost can be reduced, and the market demand can be met. Summary of the invention

[0010] In order to solve the problems mentioned in the above background technology, the present invention provides a production process and a production system of p-methylbenzyl chloride, wherein the p-xylene side chain undergoes a gas phase substitution reaction with chlorine under a slight negative pressure and visible light catalysis to generate crude methylbenzyl chloride and hydrogen chloride, which are then distilled and absorbed to generate 99.0% methylbenzyl chloride, a small amount of dibenzyl chloride and 31% hydrochloric acid respectively; the device consists of four sections: chlorination, distillation, hydrochloric acid absorption and distillation.

[0011] Reaction principle:

[0012]

[0013] The reaction is exothermic.

[0014] In order to achieve the above object, the present invention adopts the following technical solutions:

[0015] (1) Chlorination Section

[0016] S1-1 Heating and vaporizing: p-xylene is pumped to a p-xylene intermediate tank through a closed pipeline, left to stand for 24 hours to remove iron ions, and then pumped into an evaporator (1). After the feeding is completed, a heat transfer oil jacket is introduced to heat the evaporator, and the temperature in the evaporator rises to 135-145° C. The p-xylene in the evaporator is vaporized and rises along the chlorination tower;

[0017] S1-2 Chlorination reaction: After vaporization and metering (chlorine pressure is stabilized at 0.035MPa), chlorine is introduced into the chlorination tower (2), and chlorination reaction occurs with the rising p-xylene gas under visible light catalysis. The entire system is a slightly negative pressure environment (2mm mercury column observed at the gas outlet), and a loaded catalyst filler is provided at the bottom of the chlorination tower; the reaction generates p-methylbenzyl chloride, hydrogen chloride and a small amount of p-dichlorobenzyl chloride. The generated p-methylbenzyl chloride and p-dichlorobenzyl chloride are in liquid state and flow back into the evaporation kettle. The reaction ends after 30-35 hours. Stop passing chlorine and heat transfer oil, and naturally cool to 80°C. The crude benzyl in the kettle is transferred to the distillation kettle (3) of the distillation section through vacuum; the hydrogen chloride gas generated by the reaction enters the hydrogen chloride absorption section;

[0018] The method for preparing the supported catalyst filler comprises the following steps:

[0019] S101, adding a metal salt solution to a zeolite molecular sieve for adsorption, wherein the mass ratio of the metal salt to the zeolite molecular sieve is 0.1-0.5:1.3, so that the metal ions are loaded on the zeolite molecular sieve, and the adsorption temperature is controlled at 65-85° C. for 2-3 hours;

[0020] S102, calcining the zeolite molecular sieve adsorbed with metal ions in an inert atmosphere to remove excess organic matter and moisture, and at the same time to form a stable chemical bond between the metal ions and the zeolite molecular sieve, the calcination temperature is controlled at 550-650° C., and the calcination time is 2-4 hours;

[0021] S103, mixing the calcined zeolite molecular sieve with long-chain alkyl silane, nano silicon oxide and organic solvent for modification treatment, so that the long-chain alkyl silane is loaded on the zeolite molecular sieve, the modification treatment temperature is 80-100° C., and the time is 1-3 hours.

[0022] Preferably, the mass ratio of the calcined zeolite molecular sieve, long-chain alkyl silane and nano-silicon oxide is 1.5:13-17:0.5-1.

[0023] Preferably, the long-chain alkylsilane is tridecafluorooctyltrimethoxysilane or tridecafluorooctyltriethoxysilane;

[0024] Preferably, the metal salt solution is one or more of Ni, Cu, W, Zr or Mo salt solutions;

[0025] Preferably, the organic solvent is one or more of methanol, ethanol and tert-butanol;

[0026] Preferably, the zeolite molecular sieve is ZSM-5 molecular sieve, and its shape and structure are selected from ceramic ring fillers, which include triple Y rings, Raschig rings, cross partition rings, Pall rings, rectangular saddle rings, iso-saddle rings, conjugated rings, flat rings, etc., which can increase the contact area between vapor and liquid and the catalyst and improve the catalytic efficiency.

[0027] (2) Distillation Section

[0028] S2-1 Vacuum distillation: After the crude benzyl is transferred to the distillation kettle, the jet vacuum pump is started to put the distillation system under negative pressure, and heat transfer oil is introduced into the jacket of the distillation kettle to raise the temperature to 140°C. A small amount of unreacted p-xylene in the crude benzyl chloride begins to vaporize and is temporarily stored in the distillation intermediate tank after two-stage water cooling, and then transferred to the evaporator through a closed pipe as the raw material for the next batch; when the temperature rises to 150°C, the valve is switched, and a small amount of product mixed with p-xylene begins to vaporize, and is temporarily stored in the distillation intermediate tank after two-stage water cooling, and then refluxed into the distillation tower through a closed pipe; when the temperature rises to 170°C, the valve is switched, and samples are taken through the sampling port and detected by gas chromatography. When the main component in the distillate is the main product p-methylbenzyl chloride, the valve is switched, and the condensate (product p-methylbenzyl chloride) is collected in the distillation intermediate tank, and then transferred to the p-methylbenzyl chloride finished product tank through a closed pipe for temporary storage. When the temperature in the distillation kettle rises to 190℃, the distillation of the product p-methylbenzyl chloride is basically completed, and p-dichlorobenzyl and some high-boiling-point polymer impurities remain in the distillation kettle, which are transferred to the dichlorobenzyl distillation kettle or the residue collection tank for dichlorobenzyl refining. The entire distillation process is completed in 20-22 hours, and the distillation waste gas (exhaust gas discharged by the vacuum pump) is discharged through the exhaust pipe after a first-stage spray washing + two-stage activated carbon absorption treatment.

[0029] S2-2 Filling: Fill the p-methylbenzyl chloride in the p-methylbenzyl chloride finished product can into the packaging barrel through the automatic filling machine.

[0030] (3) Hydrochloric acid absorption section

[0031] S3-1 Water absorption: The tail gas (hydrogen chloride and excess p-xylene) at the top of the chlorination tower in the chlorination section is condensed by a two-stage condenser (4) (one-stage water cooling + one-stage brine cooling), and the p-xylene is refluxed to the chlorination tower for chlorination reaction. The hydrogen chloride tail gas enters the chlorination tail gas condenser under a slightly negative pressure, and is further cooled by brine to separate the very small amount of residual p-xylene, etc., and then enters the three-stage falling film absorber (5). After being absorbed by pure water, a 31% hydrochloric acid by-product is obtained. When the circulating acid concentration is detected to meet the standard, it is pumped into the hydrochloric acid finished product tank (6) for storage. The tail gas is then treated by a first-stage spray washing + two-stage activated carbon absorption and then discharged through an exhaust pipe.

[0032] (4) Refining Section

[0033] S4-1 Vacuum distillation: The residue (benzyl chloride and high-boiling polymer) remaining in the distillation kettle after the distillation process is transferred to the distillation kettle (7) through a closed pipeline. A heat transfer oil jacket is introduced into the distillation kettle to raise the temperature to 200°C. The vacuum pump is started to maintain a slight negative pressure. 40% of the benzyl chloride evaporates and enters the receiving tank (8) after cooling. The receiving tank is equipped with a hot water jacket to keep it warm at 70-80°C in liquid form. The remaining 60% of the residue is treated as hazardous waste and is regularly outsourced for disposal. The distillation process operation time is 45-50 hours.

[0034] S4-2 Recrystallization and centrifugation: After the distillation is completed, the p-dichlorobenzyl in the receiving tank is transferred to a recrystallization kettle (9). The agitator is turned on and ethanol is added to the recrystallization kettle. The mixture is stirred for cooling and crystallization. The recrystallization is completed after 7-9 hours. The material in the recrystallization kettle is filtered through a centrifuge (10) to obtain a byproduct p-dichlorobenzyl wet material. The ethanol liquid obtained by filtration and centrifugation is sent to an ethanol distillation kettle for ethanol refining and recovery.

[0035] S4-3 Ethanol recovery: After the ethanol liquid obtained by filtration and centrifugation is pumped into the ethanol distillation kettle, steam is introduced into the jacket to raise the temperature to 80°C for atmospheric distillation. The evaporated ethanol is cooled by one level of water + one level of frozen brine and then collected in the ethanol receiving tank. The non-condensable gas is discharged through the exhaust pipe after spray washing + two-stage activated carbon treatment.

[0036] S4-4 Drying and packaging: Dry the benzyl dichloride wet material to obtain by-product benzyl dichloride crystals.

[0037] A production system of p-methylbenzyl chloride comprises an evaporating kettle (1) and a chlorination tower (2), wherein the chlorination tower (2) is located above the evaporating kettle (1) and is in communication with the evaporating kettle (1), wherein the top of the chlorination tower (2) is connected to a two-stage condenser (4) via a pipeline, and the two-stage condenser (4) is sequentially connected to a three-stage falling film absorber (5) and a hydrochloric acid finished product tank (6);

[0038] The bottom of the evaporator (1) is connected to a distillation kettle (3) via a pipeline, the top of the distillation kettle (3) is connected to a distillation kettle (7), the top of the distillation kettle (7) is sequentially connected to a receiving tank (8), a recrystallization kettle (9), and a filtering centrifuge (10), the material in the recrystallization kettle (9) is filtered and centrifuged by the filtering centrifuge (10) to obtain a p-dichlorobenzyl wet material, and then the p-dichlorobenzyl wet material is dried.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1. Among the present invention, on the one hand, chlorine is fed, and aromatic ring chlorination reaction takes place under visible light catalysis; On the one hand, a supported catalyst filler is provided at the bottom of the chlorination tower, and a zeolite molecular sieve modified with long-chain alkylsilane and metal salt is used as a catalyst for catalytic chloromethylation reaction; On the one hand, the hydrophobicity of the modified catalyst is obviously enhanced, and the density of the acidic site can not be reduced simultaneously, thus greatly increasing the contact opportunity of the catalyst and the reaction substrate, and improving the catalytic efficiency of the catalyst; On the other hand, the catalyst has a strong acid position and a micropore volume, thus not only providing a large amount of active sites for the reaction, but also reducing the generation of side reactions; Meanwhile, the catalyst has a stronger mass transfer capacity, and the reaction substrate is easier to desorb from the catalyst surface, thus eliminating or weakening the generation of side reactions such as alkylation, and thus making the main reaction obtain higher reaction selectivity and yield.

[0041] 2. In the catalyst of the present invention, the metal ions in the zeolite molecular sieve and the metal ions in the metal salt can be combined with the long-chain alkylsilane through MO-Si (M is a metal ion) bonding, which can not only enhance the activity of the catalyst, but also reduce the loss rate during use, thereby increasing the service life of the catalyst. Therefore, the catalyst of the present invention is used to catalyze the chloromethylation reaction, and the catalyst can be stably applied, and cooperates with chlorine to produce an aromatic ring chlorination reaction under visible light catalysis, which can greatly improve the production efficiency and is conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] 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.

[0043] Figure 1 It is a schematic diagram of the process flow of the present invention;

[0044] Figure 2 It is a schematic diagram of the system structure of the present invention;

[0045] In the figure: evaporator 1, chlorination tower 2, distillation kettle 3, two-stage condenser 4, three-stage falling film absorber 5, hydrochloric acid finished product tank 6, distillation kettle 7, receiving tank 8, recrystallization kettle 9, filtering centrifuge 10. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in 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.

[0047] Preparation Example 1

[0048] The preparation method of the supported catalyst filler comprises the following steps:

[0049] S101, adding a metal Cu salt solution to a ZSM-5 molecular sieve for adsorption, so that the metal Cu ions are loaded on the zeolite molecular sieve; the shape and structure of the ZSM-5 molecular sieve is a cross-spacer ring, wherein the cross-spacer ring forming process is a prior art and will not be described in detail in this application;

[0050] The adsorption temperature was controlled at 65 °C and the time was 3 h;

[0051] S102, calcining the zeolite molecular sieve adsorbed with metal Cu ions in a nitrogen atmosphere to remove excess organic matter and moisture, and at the same time to form a stable chemical bond between the metal ions and the zeolite molecular sieve; the calcination temperature is controlled at 550° C. and the time is 4 hours;

[0052] S103, mixing the calcined zeolite molecular sieve with tridecafluorooctyltrimethoxysilane, nano silicon oxide and methanol for modification treatment, so that tridecafluorooctyltrimethoxysilane is loaded on the zeolite molecular sieve; the modification treatment temperature is 80° C. and the time is 3 hours.

[0053] The mass ratio of the metal Cu salt to the zeolite molecular sieve is 0.1:1.3.

[0054] The mass ratio of the calcined zeolite molecular sieve, long-chain alkyl silane and nano silicon oxide is 1.5:13:0.5.

[0055] Preparation Example 2

[0056] The preparation method of the supported catalyst filler comprises the following steps:

[0057] S101, adding a metal Zr salt solution to a ZSM-5 molecular sieve for adsorption, so that the metal Zr ions are loaded on the zeolite molecular sieve; the shape and structure of the ZSM-5 molecular sieve are three Y rings, wherein the three Y ring forming process is a prior art, and this application will not repeat it;

[0058] The adsorption temperature was controlled at 75 °C and the time was 3 h;

[0059] S102, calcining the zeolite molecular sieve adsorbed with metal Zr ions in a nitrogen atmosphere to remove excess organic matter and moisture, and at the same time to form a stable chemical bond between the metal ions and the zeolite molecular sieve; the calcination temperature is controlled at 600° C. and the calcination time is 3 hours;

[0060] S103, mixing the calcined zeolite molecular sieve with tridecafluorooctyltrimethoxysilane, nano silicon oxide and methanol for modification treatment, so that tridecafluorooctyltrimethoxysilane is loaded on the zeolite molecular sieve; the modification treatment temperature is 90° C. and the time is 2 hours.

[0061] The mass ratio of the metal Zr salt to the zeolite molecular sieve is 0.3:1.3.

[0062] The mass ratio of the calcined zeolite molecular sieve, long-chain alkyl silane and nano silicon oxide is 1.5:15:0.8.

[0063] Preparation Example 3

[0064] The preparation method of the supported catalyst filler comprises the following steps:

[0065] S101, adding a metal Mo salt solution to a ZSM-5 molecular sieve for adsorption, so that the metal Mo ions are loaded on the zeolite molecular sieve; the shape and structure of the ZSM-5 molecular sieve is a ball ring, wherein the ball ring forming process is a prior art, and this application will not be repeated;

[0066] The adsorption temperature was controlled at 85 °C and the time was 2 h;

[0067] S102, calcining the zeolite molecular sieve adsorbed with metal Mo ions in a nitrogen atmosphere to remove excess organic matter and moisture, and at the same time to form a stable chemical bond between the metal ions and the zeolite molecular sieve; the calcination temperature is controlled at 650° C. and the calcination time is 2 hours;

[0068] S103, mixing the calcined zeolite molecular sieve with tridecafluorooctyltrimethoxysilane, nano-silicon oxide and methanol for modification treatment, so that tridecafluorooctyltrimethoxysilane is loaded on the zeolite molecular sieve; the modification treatment temperature is 100° C. and the time is 1 hour.

[0069] The mass ratio of the metal Mo salt to the zeolite molecular sieve is 0.5:1.3.

[0070] The mass ratio of the calcined zeolite molecular sieve, long-chain alkyl silane and nano silicon oxide is 1.5:17:1.

[0071] Example 1

[0072] Reference Figure 1-2 , a process for producing p-methylbenzyl chloride, comprising the following steps:

[0073] (1) Chlorination Section

[0074] S1-1 Heating and vaporizing: Paraxylene is pumped to the paraxylene intermediate tank through a closed pipeline pump, and then pumped into the evaporator 1 after standing for 24 hours to remove iron ions. After the feeding is completed, a heat transfer oil jacket is introduced to heat the evaporator, and the temperature in the evaporator rises to 135°C. The paraxylene in the evaporator is vaporized and rises along the chlorination tower;

[0075] S1-2 Chlorination reaction: After vaporization and metering (chlorine pressure is stabilized at 0.035MPa), chlorine is introduced into chlorination tower 2, and chlorination reaction occurs with rising p-xylene gas under visible light catalysis. The whole system is a slightly negative pressure environment (2mm mercury column observed at the gas outlet), and the bottom of the chlorination tower is provided with a supported catalyst filler prepared in Preparation Example 1; the reaction generates p-methylbenzyl chloride, hydrogen chloride and a small amount of p-dichlorobenzyl chloride. The generated p-methylbenzyl chloride and p-dichlorobenzyl chloride are in liquid state and flow back into the evaporation kettle. The reaction ends after 30 hours. Stop passing chlorine and heat transfer oil, and naturally cool to 80°C. The crude benzyl in the kettle is transferred to the distillation kettle 3 of the distillation section by vacuum; the hydrogen chloride gas generated by the reaction enters the hydrogen chloride absorption section;

[0076] (2) Distillation Section

[0077] S2-1 Vacuum distillation: After the crude benzyl is transferred to the distillation kettle, the jet vacuum pump is started to put the distillation system under negative pressure, and heat transfer oil is introduced into the jacket of the distillation kettle to raise the temperature to 140°C. A small amount of unreacted p-xylene in the crude benzyl chloride begins to vaporize and is temporarily stored in the distillation intermediate tank after two-stage water cooling, and then transferred to the evaporator through a closed pipe as the raw material for the next batch; when the temperature rises to 150°C, the valve is switched, and a small amount of product mixed with p-xylene begins to vaporize, and is temporarily stored in the distillation intermediate tank after two-stage water cooling, and then refluxed into the distillation tower through a closed pipe; when the temperature rises to 170°C, the valve is switched, and samples are taken through the sampling port and detected by gas chromatography. When the main component in the distillate is the main product p-methylbenzyl chloride, the valve is switched, and the condensate (product p-methylbenzyl chloride) is collected in the distillation intermediate tank, and then transferred to the p-methylbenzyl chloride finished product tank through a closed pipe for temporary storage. When the temperature in the distillation kettle rises to 190℃, the distillation of the product p-methylbenzyl chloride is basically completed, and the remaining p-dichlorobenzyl and some high-boiling polymer impurities in the distillation kettle are mainly transferred to the dichlorobenzyl distillation kettle or the residue collection tank for dichlorobenzyl refining. The entire distillation process is completed in 20 hours, and the distillation waste gas (exhaust gas discharged by the vacuum pump) is discharged through the exhaust pipe after a first-stage spray washing + two-stage activated carbon absorption treatment.

[0078] S2-2 Filling: Fill the p-methylbenzyl chloride in the p-methylbenzyl chloride finished product can into the packaging barrel through the automatic filling machine.

[0079] (3) Hydrochloric acid absorption section

[0080] S3-1 Water absorption: The tail gas (hydrogen chloride and excess p-xylene) at the top of the chlorination tower in the chlorination section is condensed by a two-stage condenser 4 (one-stage water cooling + one-stage brine cooling), and p-xylene is refluxed to the chlorination tower for chlorination reaction. The hydrogen chloride tail gas enters the chlorination tail gas condenser under a slightly negative pressure, and is further cooled by brine to separate the very small amount of residual p-xylene, etc., and then enters the three-stage falling film absorber 5. After being absorbed by pure water, 31% hydrochloric acid by-product is obtained. When the circulating acid concentration is detected to be up to standard, it is pumped into the hydrochloric acid finished product tank 6 for storage. The tail gas is then treated by a first-stage spray washing + two-stage activated carbon absorption and then discharged through the exhaust pipe.

[0081] (4) Refining Section

[0082] S4-1 Vacuum distillation: The residue (benzyl dichloride and high-boiling polymer) remaining in the distillation kettle after the distillation process is transferred to the distillation kettle 7 through a closed pipeline. A heat transfer oil jacket is introduced into the distillation kettle to raise the temperature to 200°C. The vacuum pump is started to maintain a slight negative pressure. 40% of the benzyl dichloride evaporates and enters the receiving tank 8 after cooling. The receiving tank is equipped with a hot water jacket to keep it warm at 70-80°C for liquid storage. The remaining 60% of the residue is treated as hazardous waste and is regularly outsourced for disposal. The distillation process operation time is 45h.

[0083] S4-2 Recrystallization and centrifugation: After the distillation is completed, the benzyl dichloride in the receiving tank is transferred to the recrystallization kettle 9, the agitator is turned on, ethanol is added to the recrystallization kettle, and the mixture is stirred for cooling and crystallization. The recrystallization is completed after 7 hours. The material in the recrystallization kettle is filtered through a centrifuge 10 to obtain a by-product benzyl dichloride wet material. The ethanol liquid obtained by filtration and centrifugation is sent to the ethanol distillation kettle for refining and recovery of ethanol.

[0084] S4-3 Ethanol recovery: After the ethanol liquid obtained by filtration and centrifugation is pumped into the ethanol distillation kettle, steam is introduced into the jacket to raise the temperature to 80°C for atmospheric distillation. The evaporated ethanol is cooled by one level of water + one level of frozen brine and then collected in the ethanol receiving tank. The non-condensable gas is discharged through the exhaust pipe after spray washing + two-stage activated carbon treatment.

[0085] S4-4 Drying and packaging: Dry the benzyl dichloride wet material to obtain by-product benzyl dichloride crystals.

[0086] Example 2

[0087] Reference Figure 1-2 The difference between this embodiment and embodiment 1 is that the supported catalyst filler prepared in preparation example 2 is provided at the bottom of the chlorination tower.

[0088] For other structures not described, refer to Example 1.

[0089] Example 3

[0090] Reference Figure 1-2 The difference between this embodiment and embodiment 1 is that the supported catalyst filler prepared in preparation example 3 is provided at the bottom of the chlorination tower.

[0091] For other structures not described, refer to Example 1.

[0092] 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 p-methylbenzyl chloride, characterized in that: The following steps are involved: (1) Chlorination Section S1-1 Heating and vaporizing: After removing the iron ions from paraxylene, pump it into the evaporator (1). After the feeding is completed, a heat transfer oil jacket is introduced to heat the evaporator. The temperature in the evaporator rises to 135-145°C. The paraxylene in the evaporator vaporizes and rises along the chlorination tower. S1-2 Chlorination reaction: Chlorine gas is vaporized and metered and then introduced into a chlorination tower (2) to react with the rising p-xylene gas under the catalysis of visible light. A supported catalyst filler is provided at the bottom of the chlorination tower; The reaction generates p-methylbenzyl chloride, hydrogen chloride and p-dibenzyl chloride. The generated p-methylbenzyl chloride and p-dibenzyl chloride are in liquid form and flow back into the evaporator. The reaction is completed after 30-35 hours. The chlorine gas and heat transfer oil are stopped and the temperature is naturally lowered to 80° C. The crude benzyl in the reactor is transferred to the distillation reactor (3) of the distillation section by vacuum. (2) Distillation Section S2-1 Vacuum distillation: After the crude benzyl is transferred to the distillation kettle, the jet vacuum pump is started to put the distillation system under negative pressure, and heat transfer oil is introduced into the jacket of the distillation kettle to raise the temperature to 140°C. A small amount of unreacted p-xylene in the crude benzyl chloride begins to vaporize, and is temporarily stored in the distillation intermediate tank after two-stage water cooling, and then transferred to the evaporator through a closed pipeline as the raw material for the next batch; when the temperature rises to 150°C, the valve is switched, and a small amount of product mixed with p-xylene begins to vaporize, and is temporarily stored in the distillation intermediate tank after two-stage water cooling, and then refluxed into the distillation tower through a closed pipeline; when the temperature rises to 170°C, the valve is switched, and samples are taken through the sampling port, and detected by gas chromatography. When the main component in the distillate is the main product of p-methylbenzyl chloride, the valve is switched, and the condensate is collected in the distillation intermediate tank, and then transferred to the p-methylbenzyl chloride finished product tank through a closed pipeline for temporary storage; when the temperature in the distillation kettle rises to 190°C, the distillation of the product p-methylbenzyl chloride is basically completed; S2-2 Filling: Fill the p-methylbenzyl chloride in the p-methylbenzyl chloride finished product can into the packaging barrel through the automatic filling machine; (3) Hydrochloric acid absorption section S3-1 Water absorption: After the tail gas from the top of the chlorination tower in the chlorination section is condensed by a two-stage condenser (4), p-xylene is refluxed to the chlorination tower for chlorination reaction. The hydrogen chloride tail gas enters the chlorination tail gas condenser under a slightly negative pressure, is further cooled by brine, and the very small amount of residual p-xylene is separated. Then, it enters the three-stage falling film absorber (5), and is absorbed by pure water to obtain a 31% hydrochloric acid by-product. When the circulating acid concentration is detected to meet the standard, it is pumped into the hydrochloric acid finished product tank (6) for storage. The tail gas is then treated by a first-stage spray washing + a two-stage activated carbon absorption and then discharged through an exhaust pipe; (4) Refining Section S4-1 Vacuum distillation: The residue remaining in the distillation kettle in the distillation process is transferred to the distillation kettle (7) through a closed pipeline. A heat transfer oil jacket is introduced into the distillation kettle to raise the temperature to 200°C. The vacuum pump is started to maintain a slight negative pressure. 40% of the p-dibenzyl chloride evaporates and enters the receiving tank (8) after cooling. The receiving tank is equipped with a hot water jacket to keep the temperature at 70-80°C in liquid state. The distillation process operation time is 45-50 hours; S4-2 Recrystallization and centrifugation: After the distillation is completed, the p-dichlorobenzyl in the receiving tank is transferred to a recrystallization kettle (9), the stirrer is turned on, ethanol is added to the recrystallization kettle, and the mixture is stirred to cool and crystallize. The recrystallization is completed after 7-9 hours. The material in the recrystallization kettle is filtered and centrifuged (10) to obtain a byproduct p-dichlorobenzyl wet material. The ethanol liquid obtained by suction filtration and centrifugation is sent to an ethanol rectification kettle for ethanol refining and recovery; S4-3 Ethanol recovery: After the ethanol liquid obtained by filtration and centrifugation is pumped into the ethanol distillation kettle, steam is introduced into the jacket to raise the temperature to 80°C for atmospheric distillation. The distilled ethanol is cooled by one level of water and one level of frozen brine and then collected in the ethanol receiving tank. The non-condensable gas is discharged through the exhaust pipe after spray washing and two-stage activated carbon treatment; S4-4 Drying and packaging: Dry the benzyl dichloride wet material to obtain by-product benzyl dichloride crystals.

2. A process for producing p-methylbenzyl chloride according to claim 1, characterized in that: The preparation method of the supported catalyst filler comprises the following steps: S101, adding a metal salt solution to a zeolite molecular sieve for adsorption, so that the metal ions are loaded on the zeolite molecular sieve; S102, calcining the zeolite molecular sieve adsorbed with metal ions in an inert atmosphere to remove excess organic matter and moisture, and at the same time to form a stable chemical bond between the metal ions and the zeolite molecular sieve; S103, mixing the calcined zeolite molecular sieve with long-chain alkyl silane, nano silicon oxide and an organic solvent for modification treatment, so that the long-chain alkyl silane is loaded on the zeolite molecular sieve.

3. A process for producing p-methylbenzyl chloride according to claim 2, characterized in that: The mass ratio of the metal salt to the zeolite molecular sieve is 0.1-0.5:1.

3.

4. A process for producing p-methylbenzyl chloride according to claim 2, characterized in that: In the S101, the adsorption temperature is controlled at 65-85°C for 2-3 hours; In S102, the calcination temperature is controlled at 550-650° C. and the calcination time is 2-4 hours; The modification treatment temperature in S103 is 80-100° C. and the time is 1-3 hours.

5. A process for producing p-methylbenzyl chloride according to claim 2, characterized in that: The mass ratio of the calcined zeolite molecular sieve, long-chain alkyl silane and nano silicon oxide is 1.5:13-17:0.5-1.

6. A process for producing p-methylbenzyl chloride according to claim 2, characterized in that: The long-chain alkylsilane is tridecafluorooctyltrimethoxysilane or tridecafluorooctyltriethoxysilane.

7. A process for producing p-methylbenzyl chloride according to claim 2, characterized in that: The metal salt solution is one or more of Ni, Cu, W, Zr or Mo salt solutions; The organic solvent is one or more of methanol, ethanol and tert-butanol.

8. A process for producing p-methylbenzyl chloride according to claim 1, characterized in that: The zeolite molecular sieve is a ZSM-5 molecular sieve, and its shape and structure are selected from ceramic ring fillers, which include triple Y rings, Raschig rings, cross partition rings, Pall rings, rectangular saddle rings, iso-saddle rings, conjugated rings and flat rings.

9. A production system for a process for producing p-methylbenzyl chloride according to any one of claims 1 to 8, characterized in that: The invention comprises an evaporating kettle (1) and a chlorination tower (2), wherein the chlorination tower (2) is located above the evaporating kettle (1) and is in communication with the chlorination tower (2), wherein the top of the chlorination tower (2) is connected to a two-stage condenser (4) via a pipeline, and the two-stage condenser (4) is sequentially connected to a three-stage falling film absorber (5) and a hydrochloric acid finished product tank (6); The bottom of the evaporation kettle (1) is connected to a distillation kettle (3) through a pipeline, the top of the distillation kettle (3) is connected to a distillation kettle (7), the top of the distillation kettle (7) is sequentially connected to a receiving tank (8), a recrystallization kettle (9), and a filtering centrifuge (10), the material in the recrystallization kettle (9) is filtered and centrifuged by the filtering centrifuge (10) to obtain a p-dichlorobenzyl wet material, and then the p-dichlorobenzyl wet material is dried.

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