Sulfate-Modified NiAl Mixed Oxides as Effective C-H Bond-Breaking Agents for the Sole Production of Ethylene from Ethane

The oxidative dehydrogenation (ODH) of alkanes with N2O or CO2 is an attractive pathway to produce alkenes and decrease environmental issues. However, the sole production of alkenes from the ODH process is significantly important but remains a great challenge due to the uncontrollable oxygen species for overoxidized products. Here, we report a sulfate-modified NiAl mixed oxide derived from layered double hydroxide that exhibits similar to 100% ethylene selectivity at 10% ethane conversion using N2O as a representative soft oxidant, which surpasses the previously reported catalysts. Extensive characterizations and theoretical calculations demonstrate that the sulfate modifier favors the formation of more species Ni3+ and promotes the isolation of electrophilic oxygen (O-) species through electronic and steric effects. Different from the conventional cognition of electrophilic oxygen species leading to overoxidation, we identify that the increase of the proportion of isolated electrophilic oxygen species determines the higher selectivity of ethylene. The isolated oxygen species are favorable for the effective breakage of C-H bonds of ethane to selectively produce ethylene with facile desorption, while the adjacent ones strongly bind ethylene and excessively break the C-H bonds to overoxidation. More importantly, the sulfate-modification strategy for increasing ethylene selectivity can be extendable to not only the CO2-assisted ODH reaction but also to other catalysts.