Preparation method of methyl m-cyanomethyl benzoate

Abstract

The invention relates to the technical field of compound preparation, in particular to a preparation method of methyl m-cyanomethyl benzoate, which comprises the following steps: acylation: reacting m-toluic acid with thionyl chloride to synthesize m-methylbenzoyl chloride; chlorination: carrying out substitution reaction on m-methyl benzoyl chloride and chlorine under the action of a catalytic group to synthesize m-chloromethyl benzoyl chloride; esterification: carrying out esterification reaction on m-chloromethyl benzoyl chloride and methanol to obtain methyl m-chloromethyl benzoate; cyaniding: carrying out reaction on methyl m-chloromethyl benzoate and sodium cyanide to synthesize methyl m-cyanomethyl benzoate; the method is ingenious in design and novel in route; used raw materials are low in price and easy to obtain, and the process is simple and feasible; the yield is high, and the obtained final product is high in purity and good in quality; a dangerous process is avoided, and a highly toxic substance cyanide and an expensive cyaniding reagent used in traditional synthesis are avoided; the requirement on equipment is simple, and the production difficulty and the production cost investment are reduced; industrial production is facilitated, and the economic benefit is good.

Description

Technical Field

[0001] The invention relates to the technical field of compound preparation, and in particular to a method for preparing methyl m-cyanomethylbenzoate. Background Art

[0002] Methyl m-cyanomethylbenzoate is a key intermediate for the synthesis of ketoprofen. In the prior art, the synthesis of methyl m-cyanomethylbenzoate has the following schemes: Scheme 1, as disclosed in patent No. US20140275003, is prepared by coupling reaction of methyl m-bromobenzoate and 4-isoxazole boronic acid as raw materials, and the yield of this route reaches 69%, but the 4-isoxazole boronic acid and the catalyst triphenylphosphine palladium chloride used are relatively expensive; Scheme 2, as disclosed in Bioorganic & Medicinal Chemistry, 2013, 21, 2056-2067, WO 2012173784, is prepared by using methyl m-bromomethylbenzoate as raw material and NaCN or potassium cyanide as raw material, and the route is simple and has a high yield, but the route uses highly toxic substances such as sodium cyanide and potassium cyanide; Scheme 3: as disclosed in WO 2012006475 discloses a method for preparing methyl m-bromomethylbenzoate and trimethylsilicononitrile as raw materials, and the yield of this method reaches 65%, but the cyanation reagent used in this route is relatively expensive, which limits its use; Scheme 4, as disclosed in WO 2000039125, uses methyl m-bromomethylbenzoate and 2-methyl-2-hydroxypropionitrile as raw materials for preparation, and the reagents used in this method are relatively expensive; the solutions of the prior art either have a low yield or a high production cost, or have highly toxic reagents, and cannot be used for large-scale production. Therefore, it is urgent to develop a new preparation method for methyl m-cyanomethylbenzoate to meet production needs. Summary of the invention

[0003] Based on the above purpose, the present invention provides a method for preparing methyl m-cyanomethyl benzoate.

[0004] A method for preparing methyl m-cyanomethyl benzoate, characterized in that it comprises the following steps:

[0005] Step 1: Acylation: m-toluic acid and thionyl chloride are reacted to obtain m-toluoyl chloride:

[0006]

[0007] Step 2, chlorination: m-methylbenzoyl chloride and chlorine are subjected to substitution reaction under the action of a catalyst to synthesize m-chloromethylbenzoyl chloride:

[0008]

[0009] Step 3, esterification: esterification reaction of m-chloromethylbenzoyl chloride and methanol to obtain methyl m-chloromethylbenzoate:

[0010]

[0011] Step 4: Cyanidation: Methyl m-chloromethylbenzoate is reacted with sodium cyanide to obtain methyl m-cyanomethylbenzoate:

[0012]

[0013] In step 1, the acylation comprises the following specific steps:

[0014] Step (1), feeding: adding methyl benzoic acid into a reaction kettle, closing the solid feed port of the reaction kettle; pumping methyl benzoyl chloride into the reaction kettle;

[0015] Step (2), heating: turning on the jacket steam, heating the material in the reactor to 40-60°C, stirring and dissolving;

[0016] Step (3), adding thionyl chloride dropwise; adding thionyl chloride dropwise from the dropping tank to the reactor, with the dropping speed being such as to ensure that the gas overflows smoothly and safely;

[0017] Step (4), mid-control: when 1800 kg of thionyl chloride is added, stop adding, stir for 30 min, take samples for analysis, and calculate the amount of thionyl chloride to be added according to 1.05 equivalents based on the methyl benzoic acid content;

[0018] Step (5), heat preservation; after adding thionyl chloride, stirring for 60 minutes; sampling and analysis, the reaction end point is when the methyl benzoic acid content is less than 0.5%;

[0019] Step (6), cooling; open the jacket cooling water, reduce the temperature of the material in the kettle to below 35°C, release 1000kg from the bottom valve into a ton barrel as the next batch of solvent, and transfer the rest to the chlorination reaction kettle, about 2270kg;

[0020] In step 2, the chlorination comprises the following specific steps:

[0021] Step (1), adding the acyl chloride and azobisisobutyronitrile into a synthesis reaction kettle and stirring;

[0022] Step (2), heating: turning on the jacket steam to raise the material temperature to 60-80°C;

[0023] Step (3), passing chlorine: maintaining the temperature in the reactor at 60-80°C, passing chlorine gas into the reactor;

[0024] Step (4), central control: after 624 kg of chlorine gas is introduced, sampling is performed for central control, the purity of chloromethylbenzoyl chloride is 30%, and the purity of dichloro is less than 1%, and the chlorine is stopped;

[0025] Step (5), transferring the reaction materials to a distillation kettle;

[0026] Step (6), distillation: starting the vacuum pump, heating the thermal oil, and fractionating the unreacted methyl benzoyl chloride;

[0027] Step (7), central control; when the material in the receiving tank reaches about 3.8 tons, there are 1.5-1.6 tons of material in the kettle, sampling is taken from the kettle, and the purity of methyl benzoyl chloride is less than 2%, and the distillation is stopped;

[0028] Step (8), material transfer: transfer the material in the kettle, about 1550 kg, to the esterification reactor, and transfer the material in the receiving tank to the chlorination reactor;

[0029] Preferably, when the chlorine depth is about 30%, the dichloride is generally about 0.7-1.0%. After fractionation, the purity of chloromethylbenzoyl chloride increases to 3-4%, which may cause the impurity content in methyl cyanomethylbenzoate to exceed the standard.

[0030] Preferably, the chlorination depth is increased to 50%, the dichloro content is 3-5%, and after the unreacted methyl benzoyl chloride is diverted, the dichloro content is increased to 6-8%, and chloromethyl benzoyl chloride is continuously distilled. Although the yield decreases by about 3%, the production efficiency is increased by 1 times, and the comprehensive economic benefits should be more reasonable.

[0031] Therefore, it can be considered to transfer methyl benzoyl chloride from the receiving tank to the chlorination reactor after the distillation is completed, and the receiving tank is used to receive chloromethyl benzoyl chloride for further distillation, so as to ensure that its dichloride content is low enough to ensure the quality of the final product.

[0032] In step 3, the esterification comprises the following specific steps:

[0033] Step (1), feeding; turning on the jacket steam, heating the reactor to 100-120°C, turning off the steam, transferring chloromethylbenzoyl chloride from the distillation reactor; pumping methanol into the methanol dropping tank;

[0034] Step (2), cooling: After the material is transferred, the jacket is opened with cooling water, and the material temperature is lowered to 50° C. under stirring;

[0035] Step (3), adding methanol; maintaining 45-50° C., adding methanol dropwise into the synthesis reactor, the dropping speed being based on the stable overflow of gas;

[0036] Step (4), reflux: After the methanol is added dropwise, heat and reflux for 60 minutes;

[0037] Step (5), mid-control: sampling and analysis, the raw material disappears;

[0038] Step (6), distilling off the methanol; changing the reflux to distillation, and starting the vacuum pump to distill off the excess methanol, and continue to evacuate until the pH of the material is 5-6;

[0039] Step (7), material transfer: transfer the material to the cyanidation reactor, about 2300 kg;

[0040] In step 4, the cyanidation comprises the following specific steps:

[0041] Step (1), adding materials: In a 6300L reactor, add 1500kg of methyl chloromethylbenzoate (8.15kmol), 2000kg of methanol, and sodium cyanide (500kg, 10.2kmol);

[0042] Step (2), heating; stirring and reflux, 63°C, reaction for 4h;

[0043] Step (3), distillation; recover methanol, reduce the material temperature to 80°C, and continue to reflux for 2h;

[0044] Step (4), sampling control; the raw material is less than 1%; if it is unqualified, continue the reflux reaction;

[0045] Step (5): After the product is qualified, methanol is recovered under reduced pressure, combined and weighed, and used for the next batch of reaction;

[0046] Step (6), add 3000L of toluene, below 30°C, and add 1500L of water;

[0047] Step (7), stirring for 1 hour, standing for 1 hour, the water layer enters the cyanide treatment tank, the emulsified layer is filtered, and the filtrate enters the suction filtration tank;

[0048] Step (8), add 1500 L of water to the organic phase, raise the temperature to 40-45° C., stir for 30 min, let stand for 1 h, separate the phases, and the aqueous layer enters the cyanide treatment tank;

[0049] Step (9), add 1500 L of water to the organic phase and separate the phases according to the above method;

[0050] Step (10), distilling the organic phase under reduced pressure to recover toluene;

[0051] Step (11), the two batches of residues are combined and fed into a 3000L distillation kettle, and about 1800-2000kg of product is intercepted, with a purity greater than 95%.

[0052] The beneficial effects of the present invention are as follows: the present invention has an ingenious design and a novel route; the raw materials used are cheap and easily available, and the process is simple and easy to operate; the yield is high, and the final product obtained has high purity and good quality; there is no dangerous process, and the highly toxic substance cyanide and expensive cyaniding reagent used in traditional synthesis are avoided; the equipment requirements are simple, and the production difficulty and production cost investment are reduced; it is conducive to realizing industrial production and has good economic benefits. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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.

[0054] Example 1 Acylation

[0055] 1. Feeding amount

[0056] Material Name Molecular weight Feeding amount (kg) Mole (kmol) Remark Methylbenzoic acid 136 2000 14.7 Thionyl chloride 119 2000 16.8 Overdose 14% Methylbenzoyl chloride 154.5 1000 As solvent

[0057] 2. Main equipment

[0058] Device Name Specification use Remark Enamel reactor 5000L Synthesis reaction With reflux condenser and connected to chilled brine Enamel storage tank 2000L Thionyl chloride dropping tank Measuring scale required Diaphragm pumps Feed Water circulation pump Vacuum distillation Use when thionyl chloride is excessive

[0059] 3. Operation process

[0060] 3.1. Check the equipment

[0061] 3.2, feeding: add methyl benzoic acid into the reactor, close the solid feeding port of the reactor; pump methyl benzoyl chloride into the reactor;

[0062] 3.3, pump thionyl chloride into the dropping tank;

[0063] 3.4, Heating: Turn on the jacket steam, heat the materials in the reactor to 40-60℃, and stir to dissolve;

[0064] 3.5, Add thionyl chloride dropwise: Add thionyl chloride dropwise from the dropping tank to the reactor, and the dropping speed should be set to ensure that the gas overflows smoothly and safely;

[0065] 3.6, Central control: When 1800 kg of thionyl chloride is added, stop adding, stir for 30 minutes, take samples for analysis, and calculate the amount of thionyl chloride to be added based on 1.05 equivalents according to the methyl benzoic acid content;

[0066] 3.7, heat preservation: after adding thionyl chloride, stir for 60 minutes; take samples for analysis, and the reaction end point is when the methyl benzoic acid content is less than 0.5%;

[0067] 3.8, Cooling: Turn on the jacket cooling water to reduce the temperature of the material in the kettle to below 35°C, release 1000kg from the bottom valve into the ton barrel (as the solvent for the next batch), and transfer the rest into the chlorination reactor, about 2270kg.

[0068] Example 2 Chlorination

[0069] 1. Feeding amount

[0070]

[0071] 2. Main equipment

[0072] Device Name Specification quantity use Remark Enamel reactor 5000L 2 sets Synthesis reaction With reflux condenser Enamel distillation kettle 6300L 2 sets Fractionation feedstocks and products With 8m distillation tower, oil heating Enamel reactor 5000L 2 sets Accept raw materials Preferably with measuring scale Roots water circulation pump 3 sets Distillation vacuum Prepare 1 for 2

[0073] 3. Operation process

[0074] 3.1. Check the equipment

[0075] 3.2, feeding: add acyl chloride and azobisisobutyronitrile into the synthesis reaction kettle and stir;

[0076] 3.3, Heating: Turn on the jacket steam to raise the material temperature to 60-80℃;

[0077] 3.4, Chlorine: Maintain the temperature in the reactor at 60-80°C and introduce chlorine gas into the reactor;

[0078] 3.5, Central control: After 624 kg of chlorine is introduced, sampling is performed for central control. The purity of chloromethylbenzoyl chloride is 30%, and dichloro is less than 1%. Stop the chlorine introduction;

[0079] 3.6, material transfer: transfer the reaction materials to the distillation kettle;

[0080] 3.7, distillation: start the vacuum pump, heat the thermal oil, and fractionate the unreacted methyl benzoyl chloride;

[0081] 3.8, Central control: When the material in the receiving tank reaches about 3.8 tons, there are 1.5-1.6 tons of material in the kettle. Samples are taken from the kettle. The purity of methyl benzoyl chloride is less than 2%, and the distillation is stopped;

[0082] 3.9, Material transfer: transfer the material in the kettle, about 1550 kg, to the esterification reactor, and transfer the material in the receiving tank to the chlorination reactor.

[0083] 4. Notes

[0084] 4.1, when the chlorine depth is about 30%, the dichloro is generally around 0.7-1.0%. After fractionation, the purity of chloromethylbenzoyl chloride increases to 3-4%, which may cause the impurity content in methyl cyanomethylbenzoate to exceed the standard.

[0085] 4.2, increase the chlorination depth to 50%, dichloro at 3-5%, after the unreacted methyl benzoyl chloride is diverted, increase the dichloro to 6-8%, and continue to distill chloromethyl benzoyl chloride. Although the yield drops by about 3%, the production efficiency is increased by 1 times, and the comprehensive economic benefits should be more reasonable.

[0086] Therefore, it can be considered to transfer methyl benzoyl chloride from the receiving tank to the chlorination reactor after the distillation is completed, and the receiving tank is used to receive chloromethyl benzoyl chloride for further distillation, so as to ensure that its dichloride content is low enough to ensure the quality of the final product.

[0087] Example 3 Esterification

[0088] 1. Feeding amount

[0089] Material Name Molecular weight Feeding amount (kg) Mole (kmol) Remark Chloromethylbenzoyl chloride 189 3100 16.4 2 kettles of chlorinated products merged Methanol 32 790 24.6 50% overdose

[0090] 2. Main equipment

[0091] Device Name Specification use Remark Enamel reactor 5000L Synthesis reaction With reflux condenser and connected to chilled brine Storage tank 1000L Methanol dropping tank Measuring scale required Diaphragm pumps Feed Water circulation pump Vacuum distillation Use when thionyl chloride is excessive

[0092] 3. Operation process

[0093] 3.1. Check the equipment

[0094] 3.2, Feeding: Turn on the jacket steam, heat the reactor to 100-120°C, turn off the steam, transfer chloromethylbenzoyl chloride from the distillation kettle; pump methanol into the methanol dropping tank;

[0095] 3.3, Cooling: After the material transfer is completed, the jacket is opened with cooling water, and the material temperature is lowered to 50°C under stirring;

[0096] 3.4, Add methanol: Maintain 45-50℃, add methanol dropwise into the synthesis reactor, the dropping speed shall be subject to the stable overflow of gas;

[0097] 3.5, reflux: After the methanol is added dropwise, heat and reflux for 60 min;

[0098] 3.6, Central Control: Sampling and analysis, raw materials disappear;

[0099] 3.7, Distill out methanol: Change reflux to distillation, and start the vacuum pump to distill out excess methanol, and continue to vacuum until the pH of the material reaches 5-6.

[0100] 3.8, Material transfer: Transfer the material to the cyanide reactor, about 2300 kg.

[0101] Example 4 Cyanidation

[0102] 1. Feeding amount

[0103] Material Name Molecular weight Feeding amount (kg) Mole (kmol) Remark Methyl chloromethylbenzoate 184.5 1500 8.1 Each kettle of esterification product is divided into two kettles of cyanidation Sodium Cyanide 49 500 10.2 25% overdose Methanol 2000 Toluene 3000L Triethylamine 20

[0104] 2. Main equipment

[0105] Device Name Specification use Remark Enamel reactor 6300L Synthesis reaction With reflux condenser Methanol storage tank 3000L Measuring scale required Toluene storage tank 3000L distillation kettle 3000L Distillation products Product storage tank 3000L Receiving Products Roots water circulation pump Vacuum distillation It is best to have 2 units, 1 for backup Filter tank

[0106] 3. Operation process

[0107] 3.1. Check the equipment

[0108] 3.2, Add materials: In a 6300L reactor, add 1500kg of methyl chloromethylbenzoate (8.15kmol), 2000kg of methanol, and sodium cyanide (500kg, 10.2kmol);

[0109] 3.3, Heating: Stir and reflux, 63°C, reaction for 4h;

[0110] 3.4, distill and recover methanol until the material temperature reaches 80°C, and continue to reflux for 2h;

[0111] 3.5, sampling control, raw materials less than 1%; unqualified to continue reflux reaction;

[0112] 3.6, after passing the test, recover the methanol under reduced pressure, weigh them together and use them for the next batch of reactions;

[0113] 3.7, add 3000L of toluene, below 30℃, add 1500L of water;

[0114] 3.8, stir for 1 hour, let stand for 1 hour, the water layer enters the cyanide treatment tank, the emulsion layer is filtered, and the filtrate enters the suction filtration tank;

[0115] 3.9, add 1500L of water to the organic phase, heat to 40-45℃, stir for 30min, let stand for 1h, separate the phases, and the water layer enters the cyanide treatment tank;

[0116] 3.10, add 1500L of water to the organic phase and separate the phases according to the above method;

[0117] 3.11, distill the organic phase under reduced pressure to recover toluene;

[0118] 3.12, the two batches of residues are combined and fed into a 3000L distillation kettle, and about 1800-2000kg of product is intercepted, with a purity greater than 95%.

[0119] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

Claims

1. A method for preparing methyl m-cyanomethyl benzoate, characterized in that: The steps include: Step 1: Acylation: m-toluic acid and thionyl chloride are reacted to obtain m-toluoyl chloride: Step 2, chlorination: m-methylbenzoyl chloride and chlorine are subjected to substitution reaction under the action of a catalyst to synthesize m-chloromethylbenzoyl chloride: Step 3, esterification: esterification reaction of m-chloromethylbenzoyl chloride and methanol to obtain methyl m-chloromethylbenzoate: Step 4: Cyanidation: Methyl m-chloromethylbenzoate is reacted with sodium cyanide to obtain methyl m-cyanomethylbenzoate:

2. A method for preparing methyl m-cyanomethylbenzoate according to claim 1, characterized in that: In step 1, the acylation comprises the following specific steps: Step (1), feeding: adding methyl benzoic acid into a reaction kettle, closing the solid feed port of the reaction kettle; pumping methyl benzoyl chloride into the reaction kettle; Step (2), heating: turning on the jacket steam, heating the material in the reactor to 40-60°C, stirring and dissolving; Step (3), adding thionyl chloride dropwise; adding thionyl chloride dropwise from the dropping tank to the reactor, with the dropping speed being such as to ensure that the gas overflows smoothly and safely; Step (4), mid-control: when 1800 kg of thionyl chloride is added, stop adding, stir for 30 min, take samples for analysis, and calculate the amount of thionyl chloride to be added according to 1.05 equivalents based on the methyl benzoic acid content; Step (5), heat preservation; after adding thionyl chloride, stirring for 60 minutes; sampling and analysis, the reaction end point is when the methyl benzoic acid content is less than 0.5%; Step (6), cooling; open the jacket cooling water to reduce the temperature of the material in the kettle to below 35°C, release 1000kg from the bottom valve into a ton barrel as the next batch of solvent, and transfer the rest to the chlorination reactor, about 2270kg.

3. A method for preparing methyl m-cyanomethylbenzoate according to claim 1, characterized in that: In step 2, the chlorination comprises the following specific steps: Step (1), adding the acyl chloride and azobisisobutyronitrile into a synthesis reaction kettle and stirring; Step (2), heating: turning on the jacket steam to raise the material temperature to 60-80°C; Step (3), passing chlorine: maintaining the temperature in the reactor at 60-80°C, passing chlorine gas into the reactor; Step (4), central control: after 624 kg of chlorine gas is introduced, sampling is performed for central control, the purity of chloromethylbenzoyl chloride is 30%, and the purity of dichloro is less than 1%, and the chlorine is stopped; Step (5), transferring the reaction materials to a distillation kettle; Step (6), distillation: starting the vacuum pump, heating the thermal oil, and fractionating the unreacted methyl benzoyl chloride; Step (7), central control; when the material in the receiving tank reaches about 3.8 tons, there are 1.5-1.6 tons of material in the kettle, sampling is taken from the kettle, and the purity of methyl benzoyl chloride is less than 2%, and the distillation is stopped; Step (8), material transfer: transfer the material in the kettle, about 1550 kg, to the esterification reactor, and transfer the material in the receiving tank to the chlorination reactor.

4. A method for preparing methyl m-cyanomethylbenzoate according to claim 3, characterized in that: When the chlorine depth is about 30%, the dichloride content is generally around 0.7-1.0%. After fractionation, the purity of chloromethylbenzoyl chloride increases to 3-4%, which may cause the impurity content in methyl cyanomethylbenzoate to exceed the standard.

5. A method for preparing methyl m-cyanomethylbenzoate according to claim 3, characterized in that: Increase the chlorination depth to 50%, dichloro at 3-5%, and after the unreacted methyl benzoyl chloride is diverted, increase the dichloro to 6-8%, and continue to distill chloromethyl benzoyl chloride. Although the yield drops by about 3%, the production efficiency is increased by 1 times, and the comprehensive economic benefits should be more reasonable.

6. A method for preparing methyl m-cyanomethylbenzoate according to claim 1, characterized in that: In step 3, the esterification comprises the following specific steps: Step (1), feeding; turning on the jacket steam, heating the reactor to 100-120°C, turning off the steam, transferring chloromethylbenzoyl chloride from the distillation reactor; pumping methanol into the methanol dropping tank; Step (2), cooling: After the material is transferred, the jacket is opened with cooling water, and the material temperature is lowered to 50° C. under stirring; Step (3), adding methanol; maintaining 45-50° C., adding methanol dropwise into the synthesis reaction vessel, the dropping speed being based on the stable overflow of gas; Step (4), reflux: After the methanol is added dropwise, heat and reflux for 60 minutes; Step (5), mid-control: sampling and analysis, the raw material disappears; Step (6), distilling off the methanol; changing the reflux to distillation, and starting the vacuum pump to distill off the excess methanol, and continue to evacuate until the pH of the material is 5-6; Step (7), material transfer: transfer the material to the cyanidation reactor, about 2300 kg.

7. A method for preparing methyl m-cyanomethylbenzoate according to claim 1, characterized in that: In step 4, the cyanidation comprises the following specific steps: Step (1), adding materials: In a 6300L reactor, add 1500kg of methyl chloromethylbenzoate (8.15kmol), 2000kg of methanol, and sodium cyanide (500kg, 10.2kmol); Step (2), heating; stirring and reflux, 63°C, reaction for 4h; Step (3), distillation; recover methanol, reduce the material temperature to 80°C, and continue to reflux for 2h; Step (4), sampling control; the raw material is less than 1%; if it is unqualified, continue the reflux reaction; Step (5): After the product is qualified, methanol is recovered under reduced pressure, combined and weighed, and used for the next batch of reaction; Step (6), add 3000L of toluene, below 30°C, and add 1500L of water; Step (7), stirring for 1 hour, standing for 1 hour, the water layer enters the cyanide treatment tank, the emulsified layer is filtered, and the filtrate enters the suction filtration tank; Step (8), add 1500 L of water to the organic phase, raise the temperature to 40-45° C., stir for 30 min, let stand for 1 h, separate the phases, and the aqueous layer enters the cyanide treatment tank; Step (9), add 1500 L of water to the organic phase and separate the phases according to the above method; Step (10), distilling the organic phase under reduced pressure to recover toluene; Step (11), the two batches of residues are combined and fed into a 3000L distillation kettle, and about 1800-2000kg of product is intercepted, with a purity greater than 95%.

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