ZEOLITE MEMBRANE AND A PROCESS FOR THE PRODUCTION THEREOF

The present invention is directed at a supported zeolite structure comprising substantially-sintered monolithic porous ceramic substrate having coated thereon a uniformly thin, essentially continuous zeolite crystal layer covering at least one surface and associated pores of the porous ceramic material. The zeolite crystal layer is comprised of a single layer of zeolite crystals and is free of any growth enhancing, selectivity enhancing, or reparation layer and exhibits an oriented structure whereby the crystals exhibit a substantially columnar cross-section. Preferably, the porous ceramic substrate support comprises, on an analyzed oxide basis, 10-90%, by weight alumina and exhibits a crystal phase assemblage selected from the group consisting of cordierite, mullite, alumina, and/or mixtures thereof. A method for forming a zeolite membrane disclosed herein is also provided. The method generally comprises the steps of providing porous ceramic substrate and hydrothermally treating the substrate with an aqueous solution comprising sodium oxide or sodium hydroxide and having an alumina concentration of less than about 0.01%. The pH of the solution and the treatment time and temperature are such that these reaction conditions result in partial dissolution of the alumina in the substrate and essentially no nucleation in the solution thereby resulting in growth of the zeolite which is essentially continuous over the porous support.