Recent developments in inorganic membrane technology have led to the possibility of performing chemical reactions in reactors with permeable walls that allow the selective removal of products or feeding of reactants. In particular, oxygen may be transported with complete selectivity through mixed-conducting solid-oxide membranes. Computer simulations are presented of the use of O-2-permeable membrane reactors for three reactions of interest in waste recovery and reduction : (1) the removal of product oxygen to increase conversion in the reversible thermal decomposition of waste CO2; (2) the removal of product oxygen to prevent an undesired consecutive reaction to NO2 in the catalytic decomposition of NO; and (3) the gradual supply of reactant oxygen along the reactor length to control temperature excursions and thus improve selectivity to desired products, in the partial oxidation of o-xylene to phthalic anhydride. The simulation results suggest that further developments in oxygen-permeable membrane materials will be needed to obtain stable membranes under low oxygen partial pressures, with high oxygen fluxes at moderate reaction temperatures, before significant advantages will be obtained using membrane reactors.