Synthesis of ultrathin zeolite Y membranes and their application for separation of carbon dioxide and nitrogen gases.

Synthesis of zeolite Y membranes from submicrometer (>100 nm) and nano seed (<100 nm) crystals on alumina supports was examined and the separation characteristics of these membranes for CO(2) and N(2) were studied. Two secondary growth solutions were examined, one for a rapid growth (hours) and one for a slower growth process (days). Membranes formed from the rapid growth solution resulted in 2-2.5 microm thickness, while for the slower growth solution, a dense membrane of 350-600 nm thickness was formed, covered by a 25 microm porous zeolite layer. With the nano seeds as the seeding layer, no membrane was formed. A mechanism involving seed dissolution to initiate membrane formation is concluded. The separation characteristics of membranes for CO(2)/N(2) separation were similar, with very high selectivities for separation (alpha(CO(2),N(2)) > 500). The thicker membrane had lower permeance. By investigating both single gas and mixed gas permeances, strong evidence for a percolative type separation process is obtained.