Nb2O5 as a radical modulator during oxidative dehydrogenation and as a Lewis acid promoter in CO2 assisted dehydrogenation of octane over confined 2D engineered NiO-Nb2O5-Al2O3

Mesoporous 2D NiO-Nb2O5-Al2O3 nanorods (and, for the first time, template free ordered mesoporous alumina (OMA)) were prepared via glycol-thermal synthesis for the direct transformation of octane to octenes via CO2 assisted dehydrogenation (CO2-DH). Nb2O5 addition modified the confinement effect and metal support interaction between NiO and alumina. The catalyst with an optimal confinement effect between all metal oxides in the nanorod composite provided 6% steady state n-octane conversion with similar to 80% selectivity to C-8 aromatics and olefins. Characterisation data of the fresh and used catalysts, obtained from CO2-DH as well as reverse water gas shift (RWGS) reactions, was used to identify the possible mechanism over this catalyst. Nb2O5 addition to the NiO catalyst facilitates CO2-DH by promoting RWGS and reverse-Boudouard reactions by forming O* from CO2 dissociation. Also, application of these materials for the oxidative dehydrogenation of n-octane and propane using air revealed the contribution of a radical mechanism.