Ceramic and Metal-Composite Membranes: Synthesis, Characterization and Reaction Studies

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Abstract - Varma - 9529172 The eventual successful industrial application of inorganic membranes for simultaneous reaction and separation in membrane reactors depends on the ability to produce membranes of desired structural, catalytic and permeation properties. In many cases of practical interest, the optimal distribution of catalyst is a multiple-step function within the pellet and in the membrane. In catalytic membranes, precise distribution of the active element can be obtained using sequential slip-casting of active and inert sols. In these membranes, permeation studies indicate Knudsen flow with high fluxes. Synthesis procedures have been developed to prepare permselective metal composite membranes and microporous membranes with controlled active catalyst distributions. It has been demonstrated that for the same amount of catalyst and active surface area, nonuniform pellets have a higher overall conversion than uniform pellets. The PI plans to study metal composite and microporous ceramic membranes. For the case of metal composite membranes, he will determine the mechanism of film growth during electroless plating and osmosis, derive the deposition kinetics and develop a mathematical model based on the experimental findings. The synthesis chemistry and kinetics will be correlated with the film microstructure (using computer simulation) and membrane performance. On the basis of these results, the synthesis parameters will be optimized to yield membranes of desired properties. In the case of microporous membranes, the role of synthesis parameters (sol-gel and slip-casting characteristics) on the structure, permeation and catalytic properties of membrane materials will be determined to provide an understanding of the synthesis process. Further, methods will be developed to obtain and maintain high catalyst surface area per unit reactor volume. Finally, the stability of these membranes under the severe chemical and thermal conditions encountered in practice will also be examin ed. The performance of these membranes for reaction and separation, and that of a novel thin film composite catalytic membrane, will be evaluated using dehydrogenation (ethane to ethylene, ammonia decomposition) and partial oxidation (ethylene epoxidation) as probe reactions. A successful completion of this work will enhance the fundamental understanding of the relationship between synthesis and structure, and how the structure affects the material, permeation and reaction properties of the membrane.