Method for efficiently recovering low-content benzoic acid through melt crystallization

Abstract

The invention belongs to the field of chemical purification, and particularly relates to a method for efficiently recovering low-content benzoic acid through melt crystallization. The method comprises the following steps: (1), performing liquid-phase feeding: adding a solid benzoic acid coarse material with the mass percentage of 40-85% into a layered melt crystallizer, and performing melting at a melting temperature until the solid benzoic acid coarse material is molten into a liquid state; (2), performing cooling and crystallizing: cooling the liquid benzoic acid coarse material with the mass percentage content of more than or equal to 40% at the cooling rate of 1-30K / h, the final cooling temperature being 70-80 DEG C; and keeping the temperature constant for 0.5 h; (3), performing heating and sweating: after the uncrystallized mother liquor is discharged, sweating the crystal at the heating rate of 1-20 K / h, performing eating to 110-125 DEG C, keeping the temperature for 0.5 h, and discharging the sweating liquid; and (4), melting the materials. The method provided by the invention is suitable for the benzoic acid crude product with the mass percentage content of more than or equal to 40%, preferably more than or equal to 50%, is free of additional solvents, reduces the operation cost, simplifies the operation, is environment-friendly, does not produce three wastes, and can obtain benzoic acid with the purity of more than 93%.

Description

technical field [0001] The invention belongs to the field of chemical purification, and relates to a method for efficiently recovering low-content benzoic acid through melt crystallization. Background technique [0002] Benzoic acid is an aromatic acid organic compound and the simplest aromatic acid. It appears as white needle-like or scale-like crystals. It exists widely in nature in the form of free acid, ester or its derivatives. It is mainly used in the preparation of sodium benzoate preservatives, and in the synthesis of drugs and dyes; it is also used in the production of plasticizers, mordants, fungicides and spices. Therefore, the commercial value of benzoic acid is huge, so if it is possible to recover low-content benzoic acid, it is of great value to obtain a high-purity product. [0003] Initially, benzoic acid was obtained by dry distillation of benzoin gum or hydrolysis of alkaline water, and also by hydrolysis of hippuric acid. In industry, toluene, o-xylene ...

AI Technical Summary

Problems solved by technology

However, this method does not indicate the purity of raw materials, and the amount of solvent dissolved is limited, and the process is more cumbersome and requires more equipment