CO2[sbnd]Oxidative Dehydrogenation of Ethane to Ethylene over Cr/MCM-41 Nanocatalyst Synthesized via Hydrothermal/Impregnation Methods: Influence of Chromium Content on Catalytic Properties and Performance

Abstract

A series of mesoporous Cr(x)/MCM-41 nanocatalysts with 0, 2, 5, 8 and 11wt.% content of chromium were synthesized by hydrothermal/impregnation method. The effect of chromium loading on the structure and catalytic performance of Cr/MCM-41 nanocatalysts in the oxidative dehydrogenation of ethane with CO2 was investigated. The catalysts were characterized by XRD, FESEM, EDX, DRS, BET and FTIR analysis. Various chromium species including Cr6+, Cr3+ and crystalline Cr2O3 were found in the calcined Cr(x)/MCM-41 samples. Particles of crystalline α-Cr2O3 were detected in the catalyst with Cr total content above 2wt.%. The variation of Cr content indicates that the Cr6+/Cr3+ ratio of samples increased with the Cr loading up to 8wt.%. However, a decreasing trend was observed with further increase of Cr content. This can be justified by Cr surface density. It was found that there is an optimum Cr content in Cr(8%)/MCM-41 for the best catalytic activity, attributable to higher active Cr6+ species, and more uniform dispersion of chromium species with monolayer coverage on MCM-41 and also, homogeneous surface morphology with smallest particle size. It was found that this catalyst effectively dehydrogenated ethane to ethylene in the presence of CO2 at 700°C, giving 53% ethylene yield.