Kinetics Of Methanol To Propene And Reactor Simulation

Propylene is an important industrial raw material,used to generate propylene,acrylonitrile and propylene oxide.At present,more than 90%of the world's propylene is produced by the oil line,mainly through the naphtha steam cracking(Steam Cracking),propane dehydrogenation and catalytic cracking(Fluid Catalyst Cracking,FCC).Because of the shortage of oil resources,methanol to propylene(MTP)which enbles the transformation of coal,natural gas and biomass gas via MTP draws more and more attention.In this thesis,the thermodynamics,reaction network and reaction kinetics of the MTP reaction on industrial ZSM-5 zeolite catalysts were studied.And the industrial six-stage fixed-bed reactor was simulated based on the obtained reaction kinetic model.The main content of this thesis is as follows:1.The thermodynamics analysis of MTP:the results showed that the methylation reaction was an irreversible exothermic reaction,and the cracking reaction of olefins was a reversible endothermic reaction.The superposition-cracking reaction was reversible reaction including bothendothermic reaction and exothermic reaction.The hydrogenation of olefins and methanol cracking reactions were also irreversible and exothermic.The equilibrium composition of olefins was limited by thermodynamic equilibrium,and affected by temperature and pressure.2.MTP process was studied experimentally in a miniature fixed bed reactor.Experiments for methanol feed only,olefin feed only,methanol and olefin co-feed were investigated respectively.The results revealed that the key reaction steps of MTP on the H-ZSM-5 zeolite included methanol methylation,C2?C5 olefins oligomerization-cracking,C6 and C7 olefins cracking.MTP involved a complex reaction network in which all steps to propylene were fast reactions while methanol cracking,ethylene conversion,aromatics and parafins generation were slow reactions.A comprehensive MTP reaction network with the kinetic model was developed.The kinetic parameters were obtained by means of data fitting through Levenberg-Marquardt method.3.Based on the obtained reaction kinetic model,the industrial six-stage fixed bed reactor was simulated.The calculated results coincided with the industrial results,and the relative errors of each component were within 7.5%.The concentration and temperature distribution in each bed were given in the thesis.The effects of catalyst particle size and contact time on the selectivity of the product were investigated,and the results suggested that the main reactions of MTP generating propylene were rapid reaction,and the hydrogen transfer reactions of olefins were slow reaction.By reducing the particle size of the catalyst,the limitation of internal diffusion could be eliminated and the propylene selectivity could be improved.Since the side reactions are irreversible,the selectivity of the side reactions could be effectively reduced by reducing the contact time,thus the selectivity of propylene increased.