Multi-objective optimization of non-isothermal simulated moving bed reactor: Methyl acetate synthesis

Abstract

Simulated moving bed reactor (SMBR) increases conversion of a reversible chemical reaction by introducing continuous counter-current in-situ adsorptive separation of reactants and/or products. Effects of temperature variance among different operating zones on the performance of a 4-column SMBR for reaction in the form of A↔B+C were evaluated based on multi-objective optimization. This article is focused on the model system of methyl acetate synthesis. A total of five representative cases with different temperature distributions in the range of 308–323 K were compared for six optimization problems with two or three objective functions along with practical constraints in terms of product purity, yield, unit throughput and solvent consumption. Pareto solutions were obtained for each problem. Under optimal conditions, a major fraction (over 85%) of the fed acid is converted in feed-section. For a given purity requirement, Cases 1 and 2 with 323 K in the feed section have similar unit throughput, higher than those of the other cases studied by about 10–40%. Compared with isothermally operated Case 1, Case 2 with a temperature gradient exhibited reduced solvent consumption (defined as the ratio of desorbent flowrate to maximum flowrate) by about 20% at 313 K. The superiority of non-isothermal operation resulting on reduced solvent consumption becomes more significant with decreased purity requirement and/or decreased unit throughput.