The Preliminary Research On The Influence Of Residence Time Distribution On The Performance Of Reactive Distillation-Experimental Validation And Process Optimization

In the traditional reactive distillation(RD)processes,the catalyst loading distribution in the reaction section or the reaction residence time distribution at the theoretical stage(SARTD)is usually designed to be uniform,while the effect on the performance of RD if an unevenly distributed design is used has been rarely reported in the literature.This paper clarifies the effect of(SARTD)in the reaction section on the performance of RD systems by combining the experimental verification and process optimization,and provides a feasible solution to the SARTD optimization,providing guidance for the design of the internals and industrial applications of RD processes.In this paper,the process of preparing ethyl levulinate with levulinic acid and ethanol in the presence of a resin catalyst was selected as a case study for experimental validation and process simulation of the SARTD problem.Firstly,kinetic experiments of the esterification reaction of levulinic acid and ethanol were carried out in order to evaluate the catalytic performance of the macroporous cation exchange resin KRD001,and the corresponding reaction kinetic equations and chemical equilibrium equations were obtained.Then,the RD experiment was carried out for two catalyst-loading conditions(even and uneven,the uneven distribution was achieved by loading different masses of catalysts in SCPI)to illustrate the impact of SARTD on the RD process of the esterification reaction,and experimental validation work on the SARTD problem was carried out.The experimental results shows that the conversion of levulinic acid is relatively increased by 10.85% after using uneven catalyst distribution compared to the setup with even catalyst distribution,which also verifies that a reasonable catalyst loading distribution is beneficial to improve the effect of the RD process of ethyl acetate esterification reaction.Finally,a reliable steady-state reactive distillation column model was established using Aspen Plus,which was used in process optimization.Taking the minimum reboiler duty per unit product(RDP)as the optimization goal and SARDT as the operating variable,a genetic algorithm(GA)optimization code was written to realize the SARTD optimization.The optimization results show that the optimized SARTD becomes very uneven and larger SARTs are set on the theoretical stages close to the feed position;compared with the traditional uniform SARTD,the optimized SARTD can increase the conversion of levulinic acid by 3.06% and reduce the RDP by10.09%,which indicates that reasonable SARTD is beneficial to the RD process;if the performance of the RD column remains unchanged,the optimized SARTD can reduce the required residence time of the reaction section by 11.75%.Further analysis finds that the optimized SARTD results are closely related to the equilibrium state of each theoretical stage of the reaction section,the overall trend of the reaction progress factor distribution under uniform SARTD is highly consistent with that of the optimized SARTD and a new method of SARTD optimization is proposed,which can also bring some enlightenment to other chemical process optimization problems.