Pneumatically controlled transport and reaction in inorganic membranes

The pneumatic-control concept involves the application of a pressure gradient across a nonpermselective porous inorganic membrane to control the trans-membrane flux of a permeate while minimizing the backdiffusion of another component, In this study the concept was investigated for a series of inorganic membranes. Tubular, macroporous, sintered metal membranes were impregnated or coated with colloidal silica. Binary and ternary transport experiments reveal that the morphology can be tailored to achieve the desired trans-membrane flux with minimal backdiffusion. Simulations of the multicomponent transport in the membranes using the Dusty Gas Model are in good agreement with the data. The imposed pressure gradient creates a convective flow of the permeate across the membrane which inhibits the backdiffusion of the second component, The pneumatic-control transport was tested in a membrane reactor using the catalytic combustion of ethylene as the test reaction. A membrane reactor having catalytic pellets inside a porous tube (packed-bed membrane reactor, PB) was experimentally tested, The measured temperature rise shows the effect of distributing the oxygen along the length of the catalyst zone, Multiple steady states were observed for the PBMR. Trans-membrane pressure drop was found to have a significant effect on conversion and reactant and product partitioning between the core and shell sides of the membrane.