Enhanced H2/CH4 and H2/CO2 separation by carbon molecular sieve membrane coated on titania modified alumina support: Effects of TiO2 intermediate layer preparation variables on interfacial adhesion

A new CMS membrane with smaller gas pair H2/CO2 and H2/CH4 separation factor of approximately 8.3 and 726, with an H2 permeability of 600.7 Barrer, was synthesized by coating it on titanium gel-modified alumina supports. After calcination, the titanium gel provided an interconnected nano-network intermediate layer for casting dope to penetrate the support and form an interlocking matrix. By adjusting the hydrolysis-condensation rate using acid catalysts, the intermediate layer structure can be modified, which is beneficial for supporting CMS membrane with high adhesion, but not with an interlocking depth too high to increase mass-transfer resistance. Three adhesion mechanisms are proposed in this study to investigate intrinsic adhesion of the selective layer on the TiO2/Al2O3 composite support. These mechanism are mechanical interlocking, chemical bonding, and adsorption. The relationship between permselectivity and adhesion was also evaluated. An adequate/slight pore penetration with strong mechanical interlocking can enhance adhesion without sacrificing high permeance. The new CMS membrane is a promising candidate for electricity generation/hydrogen production with CO2-capture and oxygen-fuel applications.