Thermodynamic Analysis And Reactor Simulation Of Benzene Alkylation With Methanol

Benzene and methanol alkylation is a process in which benzene,a petrochemical product,reacts with methanol,a coal chemical product,to produce toluene and para-xylene（PX）.It is a very valuable production technology to solve the problem that the production of PX in China cannot meet the downstream manufacturing needs.However,there are still some shortcomings in the actual alkylation technology of benzene and methanol,such as low conversion of benzene and methanol,low selectivity of PX and difficulty in the separation of xylene.In response to these problems,this paper studies the effe cts of reaction conditions and reactor design on the reaction results from the perspective of thermodynamics and kinetics,and simulates and strengthens the entire process flow.In this paper,based on the Benson group contribution method,the reaction process of the alkylation of benzene and methanol is studied from the perspective of thermodynamics,the effects of temperature,molar ratio of benzene and methanol and pressure on the composition of thermodynamic equilibrium were studied in a balanced reactor with or without hydrogen.The results of thermodynamic analysis show that the product distribution is the most ideal when the temperature is less than 440℃,the molar ratio is between 0.5 and 1,and the pressure is 0.4 MPa in the absence of hydrogen.Based on the kinetics of the alkylation of benzene and methanol,the steady-state model of the plug flow fixed bed reaction was established using COMSOL Multiphysics numerical simulation software,and the influence of operating conditions on the reaction results was studied through the modules of reaction,heat and mass transfer.The simulation results show that the PX selectivity of the reaction can reach more than 99%at high space velocity;the increase of the feed temperature will help the conversion of benzene and methanol and the toluene yield,but it is not conducive to the PX selectivity;the increase in the feed ratio of benzene and methanol increases methanol utilization rate,benzene conversion rate and toluene and PX selectivity are reduced.In order to study the influence of the reactor structure on the reaction results,the reactor structure was designed on the basis of the established fixed-bed plug flow model,and the influence of different reactor structures and operating conditions on the performance of the reactor was studied.The research results show that the more reactor subsection,the more beneficial the conversion of raw materials and the production of target products,but the more sections the more investment costs and energy consumption increase;combined with various factors,it is determined that the methanol feed in four subsection is more appropriate,and optimize operating conditions.Finally,combining the research results of the previous two chapters and the traditional alkylation process,a complete process flow was designed for the alkylation reaction of benzene and methanol,and the optimal operating conditions and process parameters were optimized.The results showed that when the feed molar ratio of benzyl alcohol was 1:1,the reaction temperature was 500℃,and the space velocity was 24 h^-1,methanol was almost completely converted,and the PX selectivity reached99.6%.The research results of this paper provide certain theoretical guidance value for the design of benzene and methanol alkylation reactor and process flow.