The Origin of the Special Surface and Catalytic Chemistry of Ga-Rich Ni3Ga in the Direct Dehydrogenation of Ethane

Synthesis of kinetically trapped, alumina-supported Ni3Ga nanoparticles with particle surface composition partially controlled by off-stoichiometric Ni:Ga loading ratios enabled active, highly selective, and stable catalysts to be developed for the direct dehydrogenation of ethane to ethylene. Experimental studies indicated a direct correlation between superstoichiometric Ga loading and ethylene selectivity yet an inverse correlation with ethane conversion. A catalyst with a 1:1 Ni:Ga loading ratio exhibited a good balance between activity (TOF 5.0 x 10(-2) s(-1)), selectivity (94%), and stability (94 to 90% over the 32-h test). The catalyst could also be easily regenerated using an oxidation and reduction cycle. DFT calculations and in situ DRIFTS CO adsorption confirm that surface reactivity is attenuated as Ga concentration at the particle surface increased.