Improving the selectivity of Ni-Al mixed oxides with isolated oxygen species for oxidative dehydrogenation of ethane with nitrous oxide

Abstract

Oxidative dehydrogenation (ODH) of ethane by a soft oxidant is a thermally favorable process for the valorization of ethane and the improvement of ethylene selectivity. Here, Ni-Al mixed oxides (NixAl-MO) derived from layered double hydroxides (LDH) were used for ODH of ethane by the N2O oxidant for the first time. The selectivity of ethylene improved by about 30% over Ni3Al-MO with 80 wt% NiO loading compared with that over NiO/Al2O3 with the same loading. The conversion of ethane reached 35% with the ethylene selectivity of 70% at 480 °C under complete abatement of N2O. Detailed characterizations showed that the LDH precursor facilitated the high dispersion of NiO with good incorporation of Al cations in Ni3Al-MO, which promoted the isolation of electrophilic oxygen (O−) species. The isolated O− species were favorable for selective conversion of ethane to ethylene. Furthermore, they also led to weaker adsorption of ethylene and decrease the consecutive oxidation ability compared with the adjacent O− species in NiO/Al2O3. As a result, the selectivity of ethylene increased significantly by using the Ni-Al mixed oxides.