Mathematical modeling of pervaporation membrane reactor for comparison of the performances between continuously-stirred and plug flow modes for esterification reactions

Abstract

The performances of pervaporation membrane reactors with different modes of operation are discussed in this thesis. For the synthesis of methyl acetate (MeOAc) from methanol (MeOH) and acetic acid (HOAc) in pervaporation membrane reactors (PVMRs), three modes of PVMR operation: i.e. semi-batch (SB-PVMR), plug-flow (PF-PVMR) and continuous stirred tank (CS-PVMR) are considered. Mathematical models for different PVMR modes are developed using the kinetic parameters of the reaction over Amberlyst-15 and permeation parameters for a polyvinyl alcohol (PVA). Both of the reaction and permeation rates are expressed in terms of activities. The PVA membrane shows high separation factors for HOAc and MeOAc but very low for MeOH. The simulation results of SB-PVMR mode show quite good agreement with the experimental results. The study focuses on comparing PVMR performances between two modes of continuous flow operation for various dimensionless parameters, such asDamkohler number (Da), the rate ratio (delta), the feed composition and the membrane selectivity. Flow characteristic within the reactors arisen from different operation modes affects the reactor performance through its influences on the reaction and permeation rates along the reactor. There are only some ranges of operating conditions where CS-PVMR is superior to PF-PVMR. The study is extended to consider the case with a general form of esterification reaction, A + B -- C + water. The analysis shows that superiority of PVMR compared to conventional reactors is pronounced for the case with low values of equilibrium constant. For all levels of equilibrium constant, PF-PVMR is a favorable mode of operation as long as the operating conditions can be adjusted at a suitable condition. However, if the reactor is operated at relatively high value of delta, CS-PVMR is more suitable for the operation compared to PF-PVMR.