Catalysis Today, Vol.317, 50-55, 2018
Oxidative dehydrogenation of ethane using MoO3/Fe2O3 catalysts in a cyclic redox mode
Oxidative dehydrogenation (ODH) of ethane offers large reductions in energy consumption and associated greenhouse gas emissions when compared to conventional steam cracking for ethylene production; however, catalytic ODH of ethane using co-fed O-2 requires expensive air separation. As an alternative, we are investigating novel core-shell catalysts that utilize lattice oxygen (O2-) as the sole oxidant and operate in a cyclic redox mode. In this work, redox catalysts having 1, 3 and 6 monolayer (ML) equivalents of MoO3 on alpha-Fe2O3 and a stoichiometric ferric molybdate, Fe-2(MoO4)(3), were prepared, characterized by powder x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS), and temperature-programmed reduction (TPR) and evaluated for ethane ODH in a cyclic redox mode at 600 degrees C. The characterization data are consistent with a core-shell structure for the calcined MoO3/Fe2O3 catalysts with a mixed Mo-Fe oxide surface layer. H-2 and ethane TPR evidence that the shell inhibits Fe2O3 reduction and decreases the ethane combustion activity of the fully oxidized catalyst. Covering the Fe2O3 core with MoO3 also increases ODH activity and ethylene selectivity. In cyclic redox mode at 600 degrees C, ethylene selectivity was 57-62% for catalysts with 3 and 6 ML equivalents of MoO3.
Keywords:Oxidative dehydrogenation;Chemical looping;Molybdenum oxide;Iron oxide;X-ray photoelectron spectroscopy;Diffuse reflectance infrared Fourier transform spectroscopy;Temperature-programmed reduction