Study On Catalytic Oxidation Of M-Xylene To M-Methylbenzoic Acid And Process Intensification

M-methylbenzoic acid(MTA)is a common organic chemical raw material and pesticide intermediate.The oxidation process for producing m-toluic acid has harsh reaction conditions,much by-products and difficulty in product operation and separation.The domestic production technology is relatively imperfect,the production capacity is low,and a large amount of foreign imports are required.In this paper,combined with the domestic and foreign experimental research on m-toluic acid,using m-xylene(MX)as the raw material,air as the oxidant,and cobalt naphthenate as the catalyst,the following three aspects of research are carried out:oxidation in a tank reactor process and kinetics research,oxidation process research in microchannel reactor,numerical simulation of gas-liquid mixing process in stirred tank reactor,bubble column and microchannel.The MX catalytic oxidation to MTA is a reaction initiated by free radicals.The effects of four different factors on the reaction were investigated in a stirred tank reactor.The experimental results showed that at a reaction temperature of 130℃,a catalyst dosage of 13.87 g,a pressure of 0.6 MPa,an air flow rate of 3 L/min,and a reaction time of 8 hours,Under the optimized conditions,the conversion rate of MX was 56.91%,and the yield of MTA was 51.56%.Investigate the influence of different pressures and temperatures on the kinetic parameters of MX oxidation to MTA,and fit the corresponding kinetic equations.The process conditions of MX oxidation to MTA in the microchannel reactor were studied,and the influence of five different factors on the microchannel reactor on the reaction was investigated.The optimal reaction eonditions to obtain the reaction on the microchannel reactor are:M(Co3+):M(MX)=1.73‰,reaction temperature 120℃,gas-liquid ratio 25:0.2,reaction time 60 min,reaction pressure 0.8 MPa;The conversion of m-xylene was 19.42%,and the selectivity of m-toluic acid was 90.1%.Computational fluid dynamics(CFD)method was used to study the gas-liquid mixing process on different types of reactors.According to the aeration conditions,the stirring blade is designed as a three-layer combined blade structure stirred tank reactor,the bottom blade is a semicircular tube turbine blade,and the upper two layer blades are a wide blade oblique blade blade.Studies have shown that when the stirring speed is 60 rpm and 120 rpm,when the speed is 60 rpm,the bottom turbine blade has poor gas dispersion effect,poor overall carrier gas performance,and short gas residence time;At 120 rpm,the bottom turbine blade has a short gas residence time.The dispersion effect of the gas is good,and the gas is more evenly distributed in-the circulation zone,which is beneficial to the full transfer and reaction of the gas and the reaction material.In the bubble column reactor,the dynamic distribution of the gas holdup in the system and the local air/water flow field distribution in the system are studied.The research results have a good guiding effect on the feeding of the bubble column and the industrial design.In a microchannel reactor,a T-tube is used as a model to establish a grid to study the flow state of the gas phase in the liquid phase,and investigate the volume fraction of the gas phase in the liquid phase.