Abstract
In this study we present the results from two in situ X-ray diffraction computed tomography experiments of catalytic membrane reactors (CMRs) using Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) hollow fibre membranes and Na-Mn-W/SiO2 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 C2+ 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 situ XRD-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 Ba6Co4O12 and formation of a BaWO4 layer, the latter being a result of chemical interaction between the membrane and catalyst materials at high temperatures.
Highlights
Wang et al.[17] studied the OCM reaction using a catalytic membrane reactor with a Ba0.5Sr0.5Co0.8Fe0.2O3Àd tubular membrane and a La–Sr/CaO catalyst packed-bed
We presented in situ X-ray diffraction computed tomography (XRD-CT) studies of two catalytic membrane reactors consisting of BSCF hollow fibre membranes and a Na–Mn–W/SiO2 catalyst
The spatially-resolved diffraction patterns obtained under operating conditions coupled with laboratory mass spectrometry (MS) measurements and scanning electron microscopy (SEM)/energy dispersive X-ray analysis (EDX) post-reaction measurements revealed that there are several challenges that need to be addressed before the BSCF membrane can be used for the industrial application of the OCM process
Summary
Wang et al.[17] studied the OCM reaction using a catalytic membrane reactor with a Ba0.5Sr0.5Co0.8Fe0.2O3Àd tubular membrane and a La–Sr/CaO catalyst packed-bed. The packed-bed catalytic membrane reactor and the catalytic membrane reactor (i.e. membrane only) configurations were tested using similar OCM conditions. Both configurations showed similar performance for CH4 conversion and C2+ yield, the packed-bed catalytic membrane reactor led to significantly higher C2H4/C2H6 ratio (12.5 as opposed to 1 for the catalytic membrane reactor). Czuprat et al.[18] investigated the Na–Mn–W/SiO2 catalyst packed inside the hollow fibre BaCoxFeyZrzO3Àd (x + y + z = 1) membrane. A C2+ yield of 17% and C2H4/C2H6 ratio of 4 was obtained for a CH4 conversion of 18964 | Phys.
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