SK53793A3 - Method of continual production of 2-mercaptobenzothiazole - Google Patents

Abstract

2-mercaptobenzothiazole prepared from aniline, carbon disulphide and sulphur in the molar ratio of from 1 : 0,9 to 1,5 : 0,85 to 1,2, with side convertibile components which accompany the synthesis with or without recycle, under pressures of from 8 to 15 MPa and at a temperature of from 130 to 200 degrees of Celsius behind a preheating zone and 130 to 300 degrees of Celsius in a reaction zone. Active components react in three to ten, advantageously in four subsequent stages, which are mutually differentiated by the temperature on the heat carrier side, whereby the temperature on the heat carrier side in the single stages has, with an increasing stage number, a decreasing tendency. The reaction is carrying out in a cascade of independently heated tubular bodies.

Description

Technical field

The invention relates to a process for continuous production

2-mercaptobenzothiazole from aniline, carbon disulphide and sulfur.

BACKGROUND OF THE INVENTION

2-mercaptobenzothiazole is commonly produced by the high pressure reaction of aniline with carbon disulfide and sulfur in discontinuous stirred and continuous tubular reactors. According to DE 2 121 patents

394 and US 3-1105 aniline, carbon disulphide and sulfur react in a system consisting of two reactors in which the temperature is maintained at 250-300 ° C resp. 200-240 ° C and a pressure of up to 150 at., Yielding 2-mercaptobenzothiazole 85-89th theory. CS A0 197 513 provides a process for the continuous preparation of 2-mercaptobenzothiazole from aniline, carbon disulphide and sulfur, wherein liquid sulfur is metered separately into an aniline and carbon disulphide mixture preheated to 130 to 280 C, preferably 150 to 190 C, wherein the sulfur reaction with preheated aniline and The carbon disulfide is carried out at 280 to 290 ° C and a corresponding pressure of 9.5 to 10.5 MPa. The apparatus for carrying out the method comprises a tubular preheating zone connected to the tubular reaction zone such that an outlet from the liquid sulfur dispenser is located between the exit of the preheating zone and the inlet to the reaction zone.

In practice, in the continuous production of 2-mercaptobenzothiazole, the reaction zone is one or two heated tubular reactors, which are characterized by very limited temperature profile controllability, local overheating of the reaction mixture, and large thermal inertia at larger tube volumes. Under these conditions, the reaction of aniline, carbon disulphide and sulfur to form 2-mercaptobenzothiazole in the optimum temperature regime cannot be led, resulting in a lower yield of 2-mercaptobenzothiazole and an increased proportion of by-products such as benzothiazole, methylbenzothiazole, thiocarbanside, 2-phenyl- aminobenzothiazole and more complex polycondensation products of the starting reactants. At the same time, the process of shutting down the tubular reactor after interruption of aniline, carbon disulfide and sulfur dosing is considerably complicated, as the throughput of the tube bed may be impaired due to local overheating of the reaction mixture and increased formation of polycondensation products, reducing process efficiency.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION A process for the continuous production of 2-mercaptobenzothiazole from aniline, carbon disulphide and sulfur in a molar ratio of i: 0.9 to 1.5: 0.85 to 1.2 with or without recycle synthesis of accompanying convertible by-products at 8 to 15 MPa; According to the invention, the active ingredients react in three to ten, preferably four, successive stages distinguished from each other by the temperature on the heat carrier side.

It is preferred that the temperature on the heat carrier side in each step have a decreasing tendency with increasing degree number and the reaction is performed in a cascade of self-heated tubular bodies.

An advantage of the process for the continuous production of 2-mercaptobenzothiazole according to the invention is to obtain an increased content of 2-mercaptobenzothiazole in the raw state and also to obtain its increased yields.

Further, the advantage of the solution will be emphasized in the total recycling of the substances accompanying the synthesis of 2-mercaptobenzothiazole, in which benzothiazole, 2-phenylaminobenzothiazole and thiocarbanilide are decisive.

DETAILED DESCRIPTION OF THE INVENTION

The following examples illustrate but do not limit the invention.

Example 1 (comparative)

3.6 kmo1 / h of aniline and 3.96 kmol / h of carbon disulphide are added to the preheating zone. The resulting mixture heated to 135 ° C was mixed with 3.6 kmol / h of liquid sulfur and passed into a reaction zone consisting of a single heated tubular body in which an average temperature of 315 ° C was maintained on the heat carrier side. The reaction mixture leaving the 300 ^and C reactor contained 91.5.7 of 2-mercaptobenzothiazole, with the yield of pure component

91.3

Example 2

3.6 kmol / h of aniline, 3.96 kmol / h of carbon disulphide are fed into the preheating zone. The resulting mixture heated to 135 ° C is mixed with 3.6 kmol / h of liquid sulfur and passed into a reaction zone consisting of three individually heated tubular bodies in which average temperatures are maintained on the heat carrier side:

1st stage - 340 ° C, 2nd stage - 310 ° C, 3rd stage - 300 ° C. The reaction mixture exiting from step 3 at 296 ° C contains 92.0.7 of 2-mercaptobenzothiazole, with the yield of pure component 91.9%.

Example 3

3.6 kmol / h of aniline and 3.96 kmol / h of carbon disulphide are added to the preheating zone. The resulting mixture heated to 135 ° C is mixed with 3.6 kmol / h of liquid sulfur and passed into a reaction zone consisting of four individually heated tubular bodies in which the average temperatures are maintained on the heat carrier side: 1st stage - 330 ° C, 2nd stage - 320 ° C, 3rd degree - 310 ° C, 4th degree - 300 ° C. The reaction mixture leaving step 4 at a temperature of 299 ° C contains 93.1.7 of 2-mercaptobenzothiazole, with a yield of pure component 93.5.7.

Example 4 (comparative)

3.6 kmol / h of aniline, 3.96 kmol / h of carbon disulphide and a liquid mixture of substances accompanying the synthesis of 2-mercaptobenzothiazole in the amount of 0.002 kmol / h of thiocarbaniidide, 0.001 kmol / h of 2-phenylamino-benzothiazole, 0.35 kmol / h of benzothiazole are added to the preheating zone. kmol / h of 2-mercaptobenzothiazole. The resulting mixture heated to 135 ° C was mixed with 3.6 kmol / h of liquid sulfur and passed into a reaction zone consisting of a single heated tubular body in which an average temperature of 315 ° C was maintained on the heat carrier side. The reaction mixture exiting the 300 ° C reactor contained 89.5.7 of 2-mercaptobenzothiazole, with the yield of pure component 89.2.7.

Example 5

3.6 kmo1 / h of aniline, 3.96 kmol / h of carbon disulphide and a liquid mixture of substances accompanying the synthesis of 2-mercaptobenzothiazole in the amount of 0.002 kmol / h of thiocarbaniidide, 0.001 kmol / h of 2-phenylaminobenzothiazole, 0.35 kmol / h of benzene are added to the preheating zone. / h of 2-mercaptobenzothiazole. The resulting mixture heated to 135 ° C is mixed with 3.6 kmol / h of liquid sulfur and passed to a reaction zone consisting of four individually heated tubular bodies in which average temperatures are maintained on the heat carrier side: .1. degree - 340 ° C, 2nd degree - 320 ° C, 3rd degree - 310 ° C, 4th degree - 300 ° C. The reaction mixture leaving step 4 at 298 ° C contained 92.8.7 of 2-mercaptobenzothiazole, with a yield of pure component 93.0.7.

Industrial usability

The 2-mercaptobenzothiazole prepared by the process of the present invention is useful in the chemical industry as a rubber vulcanization accelerator or a rubber vulcanizer. a semi-product for the preparation of rubber vulcanization accelerators.

Claims (3)

PATENT CLAIMS A process for the continuous production of 2-mercaptobenzothiazole from aniline, carbon disulphide and sulfur in a polar ratio of 1: 0.9 to 1.5: 0.85 to 2: 1,2 with or without recycle the synthesis of accompanying secondary convertible components at a pressure of 8 to 15 MPa and a temperature of 130 to 200 ° C after the preheating zone and 130 to 300 ° C in the reaction zone, characterized in that the active ingredients react in three up to ten, preferably four, successive stages distinguished from each other by the temperature on the heat carrier side. 2. Method according to claim 1, characterized in that the temperature on the heat carrier side in the individual stages has a decreasing tendency with increasing degree number. 3. The method according to claim 1, characterized in that it is carried out in a cascade of individually heated tubular bodies.