PRELIMINARY STUDIES ON THE POTENTIAL FOR GAS SEPARATION BY MESOPOROUSCERAMIC OXIDE MEMBRANES SURFACE-MODIFIED BY ALKYL PHOSPHONIC-ACIDS

A composite ceramic-organic membrane has been prepared by chemical gra fting of organo-phosphate molecules to the surface of an aluminium-oxi de membrane. Gas-transport mechanism through the initial mesoporous me mbrane with pore size of 5 nm is essentially based on Knudsen diffusio n and so does not give significant separation factors between gases of similar molecular weights. Modification of membrane surface propertie s allows control of the relative contribution of differing transport m echanisms. Modified membranes have been tested for various gas permeat ions (methane, ethane, propane, hydrogen, nitrogen and carbon dioxide) at room temperature. The modified membranes display high permeability and high selectivity coefficient for propane/nitrogen separation. The chemical, physical and geometrical properties of the modifying molecu les can be chosen in order to improve the performances of any specific application.