Toluene Liquid Phase Air Oxidation Method Benzaldehyde Conditions Study

This paper studied the process for production of benzaldehyde, benzoic acidoand benzoic alcohol by catalytic oxidation of toluene with air in the liquid phase. The optimal process conditions of batch operation were obtained by single factoroexperiments.The effects of catalyst, catalyst promoter, ratio and amount of catalyst and catalyst promoter, temperature, reaction time and pressure on the selectivity and yield of benzaldehyde have been investigated. The results indicated that: (1) the selectivity and yield of benzaldehyde was high with cobalt naphthenate as catalyst; (2) ammonium bromide as cocatalyst could greatly curtail induction period and increase the selectivity of benzaldehyde; (3) the reaction rate would be low with too small amount of the catalyst, and the selectivity of benzaldehyde would decrease with too large amount of the catalyst; (4) long reaction time would reduce the selectivity and yield of benzaldehyde; (5) high pressure would increase the reaction rate. The following reaction conditions were found to be suitable: cobalt naphthenate 1.5 (by weight of toluene), mole ratio of Br to Co (Br/Co) 1.5; reaction temperature150 ~C, reaction time 4h, pressure 7MPa. Under the optimal conditions, the selectivity of benzaldehyde was 40.1% and the yield of it was 10.6% and the reaction mixture contains 8% benzaldehyde.It was pointed out that the catalytic oxidation of toluene to benzaldehyde free- -of chloride by air in the liquid phase has a bright prospect for industrialization.