Process for preparing porous ceramic membrane

Claim 1

A process for preparing a porous ceramic membrane comprising the steps of: (a) disposing on a porous ceramic substrate having capillary pores a layer of alumina sol, wherein said alumina sol is prepared by hydrolyzing an alcoholate or a chelate of aluminum, drying and burning the layer disposed on the substrate to form a porous ceramic substrate having a burnt alumina sol layer disposed thereon, (b) impregnating the burnt layer disposed on the substrate with a solution of an alcoholate or a chelate of aluminum in an organic solvent, (c) subjecting the aluminum alcoholate or chelate impregnated in the burnt layer disposed on the substrate to hydrolysis in heated steam to cause a conversion thereof to alumina sol, (d) immersing the substrate having the alumina sol impregnate burnt layer disposed thereon in an aqueous solution of sodium silicate and subjecting said substrate to a heat treatment in steam after said substrate has been removed from said solution, (e) repeating steps (a), (b), (c), and (d) to fill the capillary pores of the substrate with alumina sol at least to the extent sufficient to enable the membrane to be capable of separating condensible gases, and (f) immersing the resultant product of step (e) in an aqueous solution of sodium silicate, subjecting said product to a heat treatment in steam after said product has been removed from said solution, thereafter subjecting said product to a hot water rinse treatment to remove occluded sodium ions and drying said product to form a porous ceramic membrane.