Study On The Kinetics Of Liquid Phase Oxidation Of Toluene And The Simulation And Optimization Of Reactor Network

Both benzoic acid and benzaldehyde are important organic raw materials in the industry. Liquid-phase oxidation of toluene by air is a green process to produce benzoic acid and benzaldehyde because of mild reaction condition, high yield and safety.This work was to study the kinetics characteristics of liquid-phase air oxidation of toluene in a stirred tank reactor by using cobalt/manganese/nickel in naphthenic acid as catalyst and benzaldehyde as initiator. In order to clarify the reaction mechanism of liquid-phase oxidation of toluene, the initiation and transfer of chain reaction, and effects of intermediate product on oxidation reaction, it is necessary to study the reaction kinetics of toluene oxidation. The experiments were carried out at different stirred rate, reaction temperature and addition amount of benzaldehyde. The variation of reactant and product concentration with reaction time under reaction temperature of 155,160,165,170℃ was obtained. A suitable reaction network and kinetics model of liquid-phase oxidation of toluene was proposed and the kinetics paramerters were determined based on the experimenral results.A reactor model for gas-liquid two-phase bubble column of toluene oxidation was built on the kinetics model and reactor flow model. The established model predicts the conversion, selectivity and yield of the industrial process with the relative differences less than 5%, which indicate that the established model is reliable and could be used to predict the outcome. Then the influence of the operating parameters such as toluene flux, operating temperature, operating pressure, temperature of input air and input toluene on the production index (the conversion, the selectivity and the yield) was investigated. The toluene flux, operating temperature, operating pressure are the remarkable factors.Finally, a superstructure model of reactor network was proposed on the basis of continuous stirred-tank reactors (CSTR) and plug-flow reactors (PFR). A multilevel-hierarchical approach to the mixed non-linear programming synthesis of process flowsheets was applied to obtain the global optimal solutions. As a result, a better structure of the reactor network as well as the reactor type and size in the network were gained, which fulfilled the design and optimization target of improving the yield of benzoic acid and producing benzaldehyde meanwhile.