Ga-Doped MgAl2O4 Spinel as an Efficient Catalyst for Ethane Dehydrogenation to Ethylene Assisted by CO2

A series of Ga-doped MgAl2O4 spinels was prepared via a simple coprecipitation method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption, X-ray photoelectron spectroscopy (XPS), and thermogravimetry (TG) techniques. Their acidity and basicity were measured by NH3-temperature-programmed desorption (TPD) and CO2-TPD, respectively. These spinel catalysts exhibit good catalytic performance toward ethane dehydrogenation after Ga-doping either in the absence or in the presence of CO2. Their dehydrogenation activity is positively associated with the amount of surface acid sites of medium-strong strength, confirming that the coordinatively unsaturated Ga3+ cations are the active species in the reaction. The introduction of CO2 shows an obvious promoting effect on the dehydrogenation activity of the catalysts because of their high activity for the reverse water-gas shift reaction along with an improved catalyst stability, as a result of the coexisting Boudouard reaction. An ethane conversion of 43% and ethylene selectivity of 92% can be achieved, and the activity and selectivity of this type of catalysts can be fully recovered by regeneration through calcination in flowing air.