Low-cost and facile fabrication of defect-free water permeable membrane for CO2 hydrogenation to methanol

Abstract

CO2 hydrogenation to methanol is a high value-added way for CO2 utilization. However, the conversion of CO2 to methanol is severely limited by the thermodynamic equilibrium. Using water permeable membranes to simultaneously remove the by-product (H2O) during the reaction can overcome this limitation, and enhance CO2 conversion and methanol yield. In this work, a defect-free NaA zeolite membrane supported on an alumina hollow fiber substrate was fabricated via a totally template-free method with the capability to scale up at a low cost in the future. Furthermore, the as-synthesized membrane can effectively separate water from other small gas molecules (H2 and CO2) under extremely harsh conditions (T ≥ 200℃ and P ≥ 20 bar), with a water flux up to 4.8 × 10-7 mol m−2 s−1 Pa−2 and superior separation factor for H2O/H2 (>10000), H2O/CO2 (>10000) and H2O/CH3OH (>300). With this remarkable separation performance, this zeolite membrane is promising to be applied in CO2 hydrogenation to methanol. Moreover, DFT analysis provides more insights to explain the water separation behavior of this membrane.