Facile synthesis of zirconia doped hybrid organic inorganic silica membranes

Hybrid organic inorganic silica membranes are interesting candidates for gas-separation applications due to their excellent hydrothermal stability. However, up to now these membranes lack the separation performance required to separate hydrogen from carbon dioxide. In this work a procedure for doping zirconia into the hybrid silica matrix is reported, resulting in an improved H₂/CO₂ permselective membrane compared with non-doped hybrid silica membranes. Zirconia doped 1,2-bis(triethoxysilyl)ethane (Zr-BTESE) was synthesized by sol-gel chemistry, using zirconyl nitrate as the zirconium source. By optimization of the sol reaction conditions (i.e. reaction time and temperature) a homogenous sol was obtained. Defect-free membranes were obtained by adjusting the concentration of the dip-coating solution. The doped membranes showed a slight decrease in hydrogen permeance from 4.4 × 10^-7 to 1.8 × 10^-7 mol m^-2 s^-1 Pa^-1 as compared to an undoped BTESE membrane, but a large increase in H₂/CO₂ (from 4 to 16) and H₂/N₂ (from 12 to 100) permselectivity was observed.