Improved Performance of a PBM Reactor for Simultaneous CO2 Capture and DME Synthesis

The use of nonideal zeolite membranes for the in situ H2O removal in a packed-bed membrane reactor (PBMR) during the synthesis of dimethyl ether (DME) allows the recovery of CO2 but unexpectedly reduces DME yield by 50% in comparison to a packed-bed reactor (PBR) as previously reported [Diban et al. Chem. Eng. J. 2013, 234, 140]. Due to the advantageous performance of PBMR, the present work aims to the theoretical analysis and optimization of the working conditions and system configuration that enhance both DME yield and CO2 recovery. Here, the previously developed mathematical model able to predict the mass transport rate of all the components present in the reactive system through zeolite membranes has been modified and accounts for the sweep gas recirculation. The influence of the sweep gas flow-rate in the range 0.061.80 mol(COx) h(-1) (laboratory scale) and sweep gas recirculation factor (0 < alpha < 1) has been analyzed. Sweep gas flow-rates >0.18 mol(CO)x h(-1) favored CO2 conversion but only partial recirculation of the sweep gas promoted DME yields beyond those obtained in a PBR due to the synergism between effective H2O removal and MeOH retention in the feed side. Although energetically challenging, these results show promising prospects to apply the existing zeolite membranes for the chemical transformation of CO2 into DME on a large scale.