Intermetallic Compounds as Potential Alternatives to Noble Metals in Heterogeneous Catalysis: The Partial Hydrogenation of Butadiene on γ-Al4Cu9(1 1 0).

Recently, non-noble intermetallic compounds have shown promising catalytic performances in the partial hydrogenation of alkynes and alkenes. In this work, the properties of γ-Al₄Cu₉(1 1 0) toward the gas-phase hydrogenation of butadiene were investigated at total pressures of 2-20 mbar and temperatures of 110-180 °C. The model catalyst is active and 100 % selective to butenes. Moreover, although less active than Al₁₃Fe₄(0 1 0), which was evaluated previously for the same reaction, it is more selective and more stable. The combination of catalytic tests with pre- and postreaction Auger electron spectroscopy measurements and comparative tests with Cu(1 1 0) shows that Cu governs the reaction on γ-Al₄Cu₉(1 1 0). However, the lower activity of the (more Cu-rich) sputtered Al₄Cu₉ surface with respect to the annealed one and the differences between Al₄Cu₉ and Cu surfaces in terms of butene isomer distribution, butene conversion kinetics, and sensitivity to poisons, demonstrate the unique character of the intermetallic compound. [ABSTRACT FROM AUTHOR]