Two-stage process combining N2O decomposition and ethane ODH over a MoVTeNbO-M1 catalyst

Multicomponent MoVTeNbO catalysts containing the orthorhombic M1 phase are highly active for the oxidative dehydrogenation (ODH) of ethane using O2 as oxidant, but their performance with N2O is strongly limited by the low efficiency of N2O decomposition capacity of the M1 catalyst. To overcome this limitation, we propose a strategy based on decoupling N2O decomposition from ethane oxidative dehydrogenation in a tandem reactor; in which N2O is decomposed in an upstream bed prior to contacting ethane with the M1 catalyst. Two different N2O decomposition catalysts were evaluated, i.e., CeO2 and a Cs-doped cobalt oxide (Cs- Co3O4), along with M1 catalyst. While with CeO2 the catalytic performance of the M1 catalyst was improved (by efficiently generating reactive oxygen species from N2O), with the Cs-Co3O4 we observed near-complete N2O conversion, leading to significantly higher ethane conversion and enhanced olefin yields of the subsequent M1 catalyst. In addition, different reactor configurations show that physical separation of both processes is essential to maximize performance, enabling high ethane conversion and ethylene selectivity at moderate temperatures. Characterization of fresh and spent catalysts indicates that performance is governed by the dynamic redox state of the M1 surface, strongly dependent on the oxidizing environment. These results demonstrate that decoupling oxidant generation from hydrocarbon conversion is an effective strategy for N2O valorization and selective ethane ODH.