Molecular Sieve Silica Membranes For H2/CO Separation

Membranes have been used for gas separation for quite some time but have seen major growth during the 90’s [1]. For many industrial applications involving gas streams, it is important that membranes resist high temperatures and corrosive environments. As in Table 1, organic membranes are not heat resistant at high temperatures while zeolite membranes have pore sizes too large to separate gases of small kinetic diameters. Out of the technologies listed in Table 1, many research groups [2-8] are developing metallic (palladium) and ceramic (silica based) membranes for H2 fuel technology. Palladium membranes are expensive but have infinite H2 selectivity. Hence, palladium membranes are ideal candidates for those applications in which a high purity of H2 is required. On the other hand, Armor [10] summarised the main features of various membranes and pointed out the following impractical aspects of palladium membranes over silica membranes: • Specific alloy compositions needed for specific reactions • Permeability affected by CO, S and other impurities • Phase changes of Pd cause deterioration of membrane • High temperature regeneration required