Facile synthesis of zirconia doped hybrid organic inorganic silica membranes

•One step synthesis of zirconia doped hybrid silica is described.•A four-fold increase in H2/CO2 selectivity is achieved by doping BTESE with zirconia.•N2 sorption data shows a densification effect on bulk samples.•Tuning of dip-sol concentration leads to optimal results.

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.