METHOD OF RECOVERING BENZOIC ACID FROM LIQUID-PHASE TOLUENE OXIDATION PRODUCT

FIELD: industrial organic synthesis. SUBSTANCE: benzoic acid is recovered by rectification on periodic column at pressure 100 mm Hg. Into column, after isolation of first fraction composed of toluene and benzaldehyde, azeotropic agent, in particular acetamide, is added and second fraction composed of acetamide and diphenyl is isolated during 3.5-5.6 h at reflux-to-product ratio 57-66 and column top temperature 153.7-162 C. Intermediate fraction containing benzoic acid and acetamide is tapped from the still of column and then returned thereto together with azeotropic agent for subsequent fractionation. At last, third fraction composed of benzoic acid is isolated during 5 to 5.5 h at reflux-to-product ratio 0.8-1.2. Isolated second fraction composed of acetamide and diphenyl is extracted with water at 20-22 C to give diphenyl crystals and aqueous acetamide solution, the latter being there isolated and returned into process. EFFECT: increased recovery of benzoic acid, reduced power consumption, and obtained additional commercial product (diphenyl). 1 dwg, 3 ex