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CN-121988263-A - Method for preparing benzyl chloride by toluene selective chlorination

CN121988263ACN 121988263 ACN121988263 ACN 121988263ACN-121988263-A

Abstract

The invention discloses a method for preparing benzyl chloride by toluene selective chlorination. Toluene in the reaction kettle enters a mixer to be mixed with sulfuryl chloride to obtain sulfuryl chloride-toluene mixed solution, benzoyl peroxide filler is filled in an initiator filler interlayer, the mixer continuously conveys the sulfuryl chloride-toluene mixed solution into a fixed bed filler tower through a first liquid distributor, the sulfuryl chloride-toluene mixed solution is discharged from a liquid outlet hole of a radial liquid distributor and is pre-initiated with the benzoyl peroxide filler in the initiator filler interlayer, and the obtained dispersion liquid enters a heat exchanger from a second liquid distributor and finally enters the reaction kettle to be subjected to chlorination reaction with toluene in the reaction kettle to obtain benzyl chloride. The instant concentration of sulfuryl chloride and free radical initiator in the system is maintained in a low and stable range through the pre-initiation and internal circulation, so that the side chain is efficiently chlorinated under the condition of controllable temperature, the yield and selectivity of the target product are obviously improved, and the exothermic characteristic and industrial amplification adaptability of the process are improved.

Inventors

  • YUE TAO
  • Qi Peicheng
  • FU YONGFENG
  • GAO WEIDAN
  • Gao Xiuzheng
  • XIA XUEQIANG

Assignees

  • 青岛科技大学

Dates

Publication Date
20260508
Application Date
20260108

Claims (10)

  1. 1. The device for producing benzyl chloride is characterized by comprising a reaction kettle, wherein the reaction kettle is sequentially connected with a mixer, a fixed bed packing tower and a heat exchanger to form a closed loop; The inside of the fixed bed filler tower is provided with an initiator filler interlayer, benzoyl peroxide filler is filled in the initiator filler interlayer, a cylindrical radial liquid distributor with one end closed is arranged in the initiator filler interlayer, the other end of the radial liquid distributor is communicated with a first liquid distributor, liquid outlet holes are distributed on the radial liquid distributor, the first liquid distributor is in a conical shape with the upper part being large and the lower part being small, the conical bottom is communicated with a mixer, the top of the initiator filler interlayer is communicated with a second liquid distributor, the top of the second liquid distributor is communicated with a heat exchanger, the second liquid distributor is in a conical shape with the upper part being small and the lower part being large, and screens are arranged on the first liquid distributor and the second liquid distributor.
  2. 2. The device of claim 1, wherein the benzoyl peroxide filler has a particle size of 1 to 2mm.
  3. 3. The device according to claim 1, wherein the equivalent open area of the outlet opening increases gradually from bottom to top in the axial direction.
  4. 4. The device according to claim 3, wherein the equivalent opening area A (z) =0.5 (z/H) n mm 2 of a single liquid outlet hole of the radial liquid distributor at the height z, z is the axial height from the bottom of the radial liquid distributor 6, z is an integer, H is the effective height, 1≤n≤3, and when A (z) is≤0.0314mm 2 , the liquid outlet hole diameter is fixed to be 0.2mm.
  5. 5. Use of the device according to any one of claims 1 to 4 for increasing benzyl chloride selectivity.
  6. 6. A method for preparing benzyl chloride with high selectivity by using the device according to any one of claims 1 to 4, which is characterized in that the method comprises the following steps: toluene in the reaction kettle enters a mixer to be mixed with sulfuryl chloride to obtain sulfuryl chloride-toluene mixed solution, benzoyl peroxide filler is filled in an initiator filler interlayer of a fixed bed filler tower, the mixer continuously conveys the sulfuryl chloride-toluene mixed solution into the fixed bed filler tower through a first liquid distributor, the sulfuryl chloride-toluene mixed solution is discharged from a liquid outlet hole of a radial liquid distributor and is pre-initiated with the benzoyl peroxide filler in the initiator filler interlayer, and the obtained dispersion liquid enters a heat exchanger from a second liquid distributor and finally enters the reaction kettle to be subjected to chlorination reaction with toluene in the reaction kettle to obtain benzyl chloride.
  7. 7. The method according to claim 6, wherein the benzoyl peroxide is contained in an amount of 0.5 to 2% by mole of toluene in the benzoyl peroxide filler.
  8. 8. The method according to claim 6, wherein the addition amount of the sulfuryl chloride is 1 to 1.1 times the molar amount of toluene.
  9. 9. The method according to claim 6, wherein the flow rate of the sulfuryl chloride fed into the fixed bed packed tower is 1.0-1.5 g/min.
  10. 10. The method of claim 6, wherein the chlorination reaction is carried out at a temperature of 60-100 ℃ for a time of 2-6 hours.

Description

Method for preparing benzyl chloride by toluene selective chlorination Technical Field The invention relates to the technical field of organic synthesis, in particular to a method for preparing benzyl chloride by toluene selective chlorination. Background Benzyl chloride (chemical formula: C 6H5CH2 Cl) is an important organic synthesis intermediate and fine chemical raw material, and is widely applied to the fields of medicines (such as penicillin and barbiturates), pesticides (such as pyrethroid), dyes, fragrances (such as Benzyl alcohol and benzaldehyde), surfactants, synthetic resins and the like. Currently, the dominant method for industrial mass production of benzyl chloride is toluene side-chain chlorine chlorination. The process is typically carried out by passing chlorine (Cl 2) into liquid toluene (C 6H5CH3) in the presence of light (usually ultraviolet light) or an initiator (e.g., peroxide) to effect free radical substitution. The basic reaction formula is as follows: C6H5CH3 + Cl2 →C6H5CH2Cl+HCl。 In the prior art, toluene is used as a raw material, and chlorine is introduced to directly perform chlorination reaction in the presence of Lewis acid catalysts such as FeCl 3、AlCl3 and the like. The patent CN95106153.4 discloses a production method of benzyl chloride with high conversion rate, toluene is used as raw material, chlorine is used as chlorinating agent, transparent cylindrical chlorination reactor is set in the reaction kettle under illumination condition, the reaction kettle is mainly used as evaporation kettle, the reaction kettle is heated, the liquid in the reaction kettle and the chlorination reactor are continuously evaporated and condensed, then the liquid is refluxed into the chlorination reactor to participate in reaction, when the reaction reaches the optimal end point (the content of benzyl chloride is 70% -75%), continuous chlorination method can be adopted, namely, raw material toluene and chlorine are continuously and uniformly added into the chlorination reactor, correspondingly, the chlorinated solution is continuously and uniformly discharged from the kettle bottom, and then the finished product is obtained through fractional distillation. Patent CN201710818278.3 proposes a method for producing benzyl chloride by using illumination catalysis and chlorine to chloro toluene, which comprises the following steps of firstly adding toluene into a chlorination reactor, then carrying out continuous free radical substitution reaction through chlorine at the speed of 100-400 Nm < 3 >/h, and carrying out illumination catalysis through a light source, wherein the yield of benzyl dichloride is less than 4%. However, in the method, the chlorine needs special storage and transportation equipment, the leakage risk is high, partial excessive chlorine diffusion in the reaction can cause excessive chlorination of partial products (byproducts such as dichlorobenzyl are generated), and the selectivity of target products is often lower than 85%. the byproduct HCl needs additional treatment, the traditional catalyst is difficult to recycle, environmental pollution .Chlorinations with Sulfuryl Chloride, The Peroxide-Catalyzed Chlorination of Hydrocarbons (DOI：10.1021/ja01877a048) is easy to cause, toluene, sulfuryl chloride and benzoyl peroxide are taken as raw materials, side chain chlorination is carried out by heating and refluxing in a dark place, toluene, sulfuryl chloride and benzoyl peroxide are all added into a reactor at one time, and the reaction is finished after gas (SO 2 and HCl) basically stops escaping under the condition of normal pressure refluxing. Although the process can realize the rapid chlorination of toluene in a short time, the process still has the defects of concentrated heat release, difficult accurate temperature control caused by one-time feeding, higher concentration of sulfuryl chloride and benzoyl peroxide in the initial stage of reaction, rapid start of free radical chlorination chain reaction, high heat release rate and easy rapid local temperature rise in the aspects of industrial amplification and fine control. The process is generally controlled in a rough way only by reflux condensation and manual temperature monitoring, local overheating and even boiling and flushing are easy to occur during amplification, and the thermal safety margin is smaller, so that the continuous stable operation on an amplification scale is not facilitated. In the one-pot method one-time feeding mode, the instantaneous concentration of the sulfuryl chloride is high, the chlorination degree and the selectivity are difficult to finely control, the concentration of the sulfuryl chloride at the initial stage of the reaction is high, the sulfuryl chloride cannot be regulated according to the real-time reaction progress, and toluene is easy to be continuously overchlorinated into benzylidene dichloride after benzyl chloride is generated. In summary, the prior art still has the bot