Preparation and properties of hydrothermally stable gamma-alumina membranes

Supported mesoporous gamma -Al2O3 membranes deteriorate and blister in stea m-containing environments at high temperatures. This deterioration led us t o the development of a new type of supported gamma -Al2O3 membrane with sig nificantly improved stability under hostile conditions. Two measures were t aken to achieve this result. First, the gamma -Al2O3 itself was stabilized by an addition of 6 mol % La2O3 to suppress pore growth of the mesoporous s tructure. Second, the adherence of the gamma -Al2O3 membrane to the alpha - Al2O3 support was significantly improved by application of phosphate bondin g between the membrane layer and the support, using an Al(H2PO4)(3) precurs or solution. Membranes applied without phosphate bonding were separated fro m the alpha -Al2O3 support during high-temperature steam treatment, resulti ng in complete loss of separative properties. The newly developed membranes could be operated for 100 h at 600 degreesC in H2O/CH4 = 3/1 (bg volume) a t 2.5 MPa total pressure with no delamination or cracking in the membrane-s upport interface and with no significant pore growth in the gamma -Al2O3 me mbrane.