Inorganic membrane elaboration using supercritical fluids

Abstract

New techniques to modify inorganic membranes have been developed using hydrolytic decomposition of titanium isopropoxide in supercritical propan-2-01. Solid anatase particles of about 30 nm sized are deposited as a thin film on the surface and in the pores of alumina supports. In the semi-continuow one flux method, a TiO₂ anatase film with thickness between 1 and 4 urn and an infiltrated zone of 15 to 40 in depth were formed. Pore size was found around 3 nm and correlatively, the permeability was divided by a factor 2 to 5. Furthermore, the He₂/N₂ selectivity of modified membranes is higher than that calculated from Knudsen diffusion model. In the two fluxes method, the effects of reactant concentration and reaction time have been investigated. The film thickness and the penetration depth increase when raising the concentration. Finally, the reaction of TiO₂ formation are shown to be heterogeneous in nature.

Key Words:

• Supercritical fluid
• Inorganic membrane
• Titanium dioxide