In situX-ray diffraction computed tomography studies examining the thermal and chemical stabilities of working Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-delta)membranes during oxidative coupling of methane

摘要

In this study we present the results from twoin situX-ray diffraction computed tomography experiments of catalytic membrane reactors (CMRs) using Ba0.5Sr0.5Co0.8Fe0.2O3-delta(BSCF) hollow fibre membranes and Na-Mn-W/SiO(2)catalyst during the oxidative coupling of methane (OCM) reaction. The negative impact of CO2, when added to the inlet gas stream, is seen to be mainly related to the C(2+)yield, while no evidence of carbonate phase(s) formation is found during the OCM experiments. The main degradation mechanism of the CMR is suggested to be primarily associated with the solid-state evolution of the BSCF phase rather than the presence of CO2. Specifically,in situXRD-CT and post-mortem SEM/EDX measurements revealed a collapse of the cubic BSCF phase and subsequent formation of secondary phases, which include needle-like structures and hexagonal Ba(6)Co(4)O(12)and formation of a BaWO(4)layer, the latter being a result of chemical interaction between the membrane and catalyst materials at high temperatures.