Objective Zeolites are microporous crystalline alumino-silicates, having cage-like structures of precise geometry with pores of uniform shape; zeolites are capable of molecular sieving. The objective of this research is to develop zeolite membranes that are capable of highly selective H 2 separation from other light gases (CO, CO 2 and CH 4 ) for use in catalytic membrane reactor applications related to coal conversion and gasification. These zeolite membranes have the potential to operate over

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... a wide temperature and pressure range and in chemically challenging environments where existing technologies are inefficient or unable to operate. Accomplishments to Date To obtain high selectivity for H 2 separation at elevated temperatures over other light gases, the membranes must be able to discriminate between molecules that are approximately 0.3-0.4 nm in size and 0.1 nm or less in size difference. To date, zeolite membranes have not been made very successful to achieve this sieving because the membranes synthesized either have zeolite pores too big for H 2 separation or contains too many defects. To decrease the zeolite pore size and/or the number of defects within the zeolite membranes, we used silylation reaction to post-treat the as-synthesized zeolite membranes. In this reaction, methyldiethoxysilane (MDES) was firstly chemisorbed onto the acid sites within the zeolite membrane, then catalytically cracked on sites and oxidized. As a result, additional silicon atoms were added to the original zeolite structures, and the effective pore opening size of the defects and/or zeolite pores was decreased. Two different types of zeolite membranes have been silylated: medium pore MFI membranes with ten-membered ring structure and small pore SAPO-34 membranes with eight-membered ring structure. The silylation reaction could reproducibly improve the hydrogen separation performance for both types of zeolite membranes. For MFI type zeolite membranes with plenty of acid sites, MDES could penetrate into the medium-sized zeolite pores. Thus, after silylation, the zeolite pores were partially blocked. As a result, hydrogen selectivity over other light gases (CO 2 , CO, CH 4 , N 2 , O 2 ) all increased. The H 2 /CO 2 ideal selectivity can be as high as 235 for the silylated MFI membranes, as compared with only 1.8 for the original membrane. The H 2 permeance however, decreased more than an order of magnitude. For H 2 /CO 2 , and H 2 /CH 4 binary mixtures, The H 2 /CO 2 separation selectivity at 473 K increased from 1.4 to 37, whereas the H 2 /CH 4 separation selectivity increased from 1.6 to 33. The membranes became 2. Submitted Light gas separations though silylated zeolite membranes, M. Hong, R.D. Noble, J.L. Falconer, 3 rd international zeolite membrane meeting, July 25-28, 2004, Breckenridge, CO Awards Received as a Result of Supported Research Modification of MFI zeolite membranes by silylation for H 2 separation, M. Hong,