CS248391B1 - Method of mother liquors treatment from o-toluene sulphonamide production - Google Patents

Abstract

The purpose of the solution was to streamline production o-toluenesulfonamide. This goal will be achieved by providing the mother liquors after crystallization collects and undergoes new crystallization at temperature drop from about 35 ° C to 18 ° C and 22 ° C bhhea 8 to 25 hours. Excluded o-toluenesulfonamide separates and returns to the main production stream.

Description

The invention relates to a process for the treatment of mother liquors from the production of o-toluenesulfonamide.

O-toluenesulfonamide is an intermediate in the production of saccharin by the Pahlberg method. It is produced from technical o-toluenesulfochloride by reaction with dilute ammonia and subsequent washing of the reaction mixture with water. The crude amide thus prepared contains 70 to 75% o-toluenesulfonamide. From the crude amide, pure, i.e. 99.5% o-toluenesulfonamide, is obtained by crystallization from an ethanol-water mixed solvent. The mother liquors at 35 ° C are discarded by recovering the ethanol-water solvent mixture by distilling off the ethyl alcohol, which is used to prepare a new solvent, while draining the distillation residue.

The process of treating the mother liquors from the production of o-toluenesulfonamide according to the present invention seems to be more advantageous in that the collected mother liquors are cooled to 18 to 22 [deg.] C. while moving in 8 to 25 hours, whereupon the o-toluenesulfonamide is separated. from the mother liquor, preferably by sedimentation and filtration.

The invention is based on the knowledge of the kinetics of solid phase excretion in relation to the amount of simultaneously impurities impurities. Only under the conditions of the invention (final temperature, cooling rate) an acceptable content of impurities close to the crude o-toluenesulfonamide can be achieved, which can be further reprocessed.

By treating the mother liquors with the process according to the invention, the yield of the whole process is increased by 3 to 5% when converted to pure o-toluenesulfonamide. The additionally obtained o-toluenesulfonamide has a composition corresponding to the crude amide and is therefore added to the main process stream. before crystallization of the crude o-toluenesulfonamide.

The term cooling for the purposes of the present invention is understood to mean a decrease in the temperature of the mother liquor, which, depending on the particular conditions, can also be achieved by heating or spontaneous temperature drop, always in order to maintain the desired rate of temperature of the mother liquor.

In the practice of this invention, after centrifuging the crystallized o-toluenesulfonamide, the mother liquors are charged to a collection vessel where they are cooled from about 35 ° C to about 20 ° C with stirring over a period of 8 to 25 hours. Upon reaching the lower temperature 3e, stirring was stopped and the precipitated o-toluenesulfonamide was allowed to settle.

The clarified solution (ethyl alcohol-water) is withdrawn into the reservoir of the distillation station, the remainder of the mother liquor with the separated solid phase is stirred and discharged to suction, where the crystals of crude o-toluenesulfonamide are separated. The remaining mother liquors and drain.

Exemplary embodiment

After centrifuging the crystals of pure o-toluenesulfonamide and 1,000 kg of mother liquor at 35 ° C, the mother liquors were charged into a 4 m < 3 > tank. During the temperature decrease ae precipitated a solid phase. After reaching 20 ° C, stirring was stopped and the suspension was allowed to sediment for 1 hour. 920 kg of the clarified solution was pumped to a distillation station for alcohol recovery. The rest was drained. 48.2 kg of solid phase were obtained which contained 5.4 kg of moisture and 42.8 kg of 73.6% o-toluenesulfonamide, which was returned to crystallization of the crude amide.

Claims (1)

Process for the treatment of mother liquors from the production of o-toluenesulfonamide, characterized in that the collected mother liquors are cooled while moving to a temperature of Ifi / 22 ° C over 8 to 25 hours, whereupon the precipitated o-toluenesulfonamide is separated from the mother solution, preferably by sedimentation and filtration.