甲苯液相氧化反应过程的动力学研究

Kinetics of Liquid- Phase Oxidation of Toluene to Benzoic Acid by Air

在直径Φ48mm 的鼓泡床反应器中对以醋酸钴(CO^(2+))水溶液为催化剂的甲苯液相空气氧化反应动力学进行了研究。结果表明,反应体系的活性时间随催化剂的用量的增大而线性增大,当 Co 含量大于2×10^(-2)%(mass)时,对反应影响较小。甲苯液相空气氧化反应的甲苯消耗动力学分别与甲苯浓度和氧溶解在甲苯中的浓度成一级反应.其宏观动力学活化能约为41 kJ/mol。氧在液相主体消耗的本征动力学活化能为57 kJ/mol,指前因子53.34m^3/(mol·s)。通过 Ha 数和效率因子η对反应动力学控制步骤进行分析,结果表明,Ha 小于0.1,η为0.606～0.728。反应主要发生在液相主体,受动力学控制,但传质仍对反应有影响。

Liquid-phase oxidation of toluene by air was a green technology for producing benzoic acid. In φ48mm bubble column reactor, kinetics of liquid-phase oxidation was investigated under conditions close to commercial operation. Experimental catalyst concentration was 2. 0×10^-2% （mass）. Oxidation was first order both toluene and oxygen concentration in toluene. The apparent activation energy of toluene consumption was estimated to be 41 kJ/mol from 418K to 448K. The intrinsic activation energy estimated was 57 kJ/mol and the pre-exponential factor estimated was 53.34 m^3·mol^-1·s^-1 on oxygen consumption in liquid-phase zone. According to film theory, mass transfer parameters were calculated under reaction conditions, and Hatta Number Hα was less than 0. 1 and the gas-liquid reaction effectiveness factor η was the range of 0. 606 - 0. 728. It was suggested t hat oxidation was mainly controlled by reaction kinetics in liquid-phase zone. The influences of mass transfer on oxidation process were slight.