Tuning Supported Ni Catalysts By Varying Zeolite Beta Heteroatom Composition: Effects On Ethylene Adsorption And Dimerization Catalysis

The influence of zeolite heteroatom composition on the electron density and catalytic activity of a supported Ni cation is examined. Ni-[X]-Beta catalysts, where X = Al, Ga, Fe, or dealuminated, were synthesized and characterized with probe molecule adsorption with FTIR spectroscopy and C2H4 dimerization catalysis. It was observed via CO adsorption that supported Ni cations were increasing in electron density in the order: [Fe] > [Ga] > [Al]. C2H4 dimerization activity increased with increasing electron density of the Ni cation. Despite similarities in reported acid site strength, the acid sites on [Fe]-Beta in this work had significantly lower activity than those on [Ga]-Beta for the skeletal isomerization of linear butenes as well as C2H4 dimerization. Introducing H-2 as a reactant resulted in a decrease in dimerization activity for Ni-[Al]-Beta and Ni-[Ga]-Beta but an increase for Ni-[Fe]-Beta. The selectivity and activity of Ni-[DeAl]-Beta changed dramatically with the introduction of H-2, which subsequently converted all C2H4 with ca. 100% selectivity towards C2H6 (even with a lower space velocity relative to without H-2). These results demonstrate the ability of heteroatom composition to tune catalysis by using C2H4 dimerization catalysis as a test reaction with zeolite Beta supported Ni catalysts.