Numerical Analysis of CO2-to-DME Conversion in a Membrane Microchannel Reactor

Direct DME synthesis via CO2 hydrogenation in a membrane-integrated microchannel reactor is modeled. The proposed reactor comprises rectangular permeate and reaction channels separated by layers of sodalite membranes, permitting only H2O and H-2 transport. Reaction channels, dosed with CO2 and H-2, are washcoated with a physical mixture of methanol synthesis (Cu-ZnO/Al2O3 (CZA)) and dehydration (HZSM-5) catalysts. Pure H-2-fed permeate channels host the steam transported from reaction channels. The mathematical model of the isothermal, steady-state reactor involves conservation equations in catalyst and fluid phases, catalytic reactions, and membrane separation. The model is successfully benchmarked against literature-based experimental data. Differences between isothermal and non-isothermal models remain negligible. At 543 K, 50 bar, and H-2/CO2 = 3, cross-membrane H2O and H-2 transport increases membraneless CO2 conversion and DME yield values by more than 2-fold, i.e., up to similar to 73 and similar to 35%, respectively. Counter-current flow configuration offers more H2O separation than the co-current one. The sweep-to-reactive stream inlet velocity ratio affects cross-membrane mass transfer significantly. Reactor performance is positively correlated with the CZA/HZSM-5 mass ratio. A similar to 7 m(3)-sized reactor can transform similar to 1 x 10(3) tons/year of CO2 into 2.76 x 10(2) tons/year of DME.

Automated summary

Direct synthesis of DME via CO2 hydrogenation in a membrane-integrated microchannel reactor is investigated. The proposed reactor consists of sodalite membranes separating permeate and reaction channels, allowing only H2O and H-2 transport. The mathematical model of the reactor is successfully validated against experimental data and shows improved CO2 conversion and DME yield through cross-membrane transport.