Method for forming metal-oxide-modified porous ceramic membranes

A process of producing a semipermeable oxide membrane on ceramic support, comprising:

• a. passing an organic precursor of tetraethyl orthosilicate and oxygen through a porous aluminum oxide support at a chemical vapor deposition temperature below about 550.degree. C. over a deposition period of about 420 minutes plus or minus about 40 minutes to form a deposited silicon oxide film, and
• b. oxidizing said deposited silicon oxide film at an oxidizing temperature at least about 50.degree. C. higher than said deposition temperature to produce a semipermeable silicon oxide membrane on said aluminum oxide support having a pore size of an effective layer of said membrane less than or equal to about 40.ANG., a selectivity higher than Knudsen selectivity and a permeance higher than about 0.5 m.sup.3 /m.sup.2 /hr/atm as measured with hydrogen at 600.degree. C.

A process of depositing a nonmetallic solid oxide film into or on a porous ceramic support through chemical vapor deposition, comprising:

• a. passing a gas stream containing an organic nonmetallic solid oxide precursor and an oxidant through the porous ceramic support at a deposition temperature below about 550.degree. C. to form a deposited film, and
• b. oxidizing said deposited film at an oxidizing temperature higher than said deposition temperature to produce a semipermeable nonmetallic solid oxide membrane on the ceramic support,
• c. thereby forming a membrane having a selectivity higher than Knudsen selectivity and a permeance higher than about 0.5 m.sup.3 /m.sup.2 /hr/atm as measured with hydrogen at 600.degree. C.