CERAMIC BILAYER MEMBRANES FOR HIGH TEMPERATURE OXIDATION OF METHANE

摘要

Membranes of mixed conducting oxides with perovskite structure exhibit excellent permeability for oxygen ions but are often not stable under reducing conditions. The stability can be enhanced with a dense, protective coating that is stable against reduction at low oxygen partial pressures. We have studied the oxygen permeation and methane oxidation of bilayer membranes made of La_(0.5)Sr_(0.5)CoO_(3-δ) with a coating of samarium-doped ceria. The membranes showed significant oxygen fluxes under an air/helium gradient at 930℃. No signs of degradation were found when the coated side of the membrane was exposed to a gas stream containing 5.5 vol-% methane. The main reaction of methane at the membrane is deep oxidation to CO_2 and H_2O. Finely dispersed platinum deposited on the ceria surface accelerated the methane oxidation and significant amounts of the partial oxidation products CO and H_2 were detected.