Revealing the ameliorating effect of chromium oxide on a carbon nanotube catalyst in propane oxidative dehydrogenation

Oxygenized multi-walled carbon nanotubes were modified with chromium oxide and applied in propane oxidative dehydrogenation. A propylene selectivity of 84.0% was obtained at a propane conversion of 19.8% on a Cr-1.5 wt% sample. The beneficial effect of chromium was studied by integrated techniques. X-ray photoelectron spectroscopy, and FT-IR results show that surface oxygen groups were greatly optimized as a result of chromium doping. It was also revealed that chromium improves the oxygen chemisorption properties of the catalyst, whereas the propylene desorption ability was enhanced. The superior catalytic performance was ascribed to the synergistic effect between chromium and CNTs. Moreover, as signaled from in situ FT-IR experiments, surface carbonyl (C=O) groups were detected to be the active sites in PODH reaction and the presence of chromium greatly facilitates C=O restoration, which as a whole determines the catalytic performance.