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Order-Induced Selectivity Increase of Cu60Pd40 in the Semi-Hydrogenation of Acetylene
Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Straße 40, 01187 Dresden, Germany
Centre for Energy Research, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary
Fritz-Haber-Institute of the Max-Planck-Society, Faradayweg 4-6, 14195 Berlin, Germany
* Author to whom correspondence should be addressed.
Received: 22 May 2013; in revised form: 26 June 2013 / Accepted: 13 July 2013 / Published: 16 July 2013
Abstract: The two structural modifications of Cu60Pd40 were synthesized as bulk powders and tested as unsupported model catalysts in the semi-hydrogenation of acetylene. The partly ordered low-temperature modification (CsCl type of structure) showed an outstanding ethylene selectivity of >90% over 20 h on stream while the disordered high-temperature modification (Cu type of structure) was 20% less selective, indicating an influence of the degree of order in the crystal structure on the catalytic properties. The results are supported by XRD and in situ XPS experiments. The latter suggest the existence of partly isolated Pd sites on the surface. In situ PGAA investigations proved the absence of metal hydride formation during reaction. Quantum chemical calculations of the electronic structure of both modifications using the CPA-FPLO framework revealed significant differences in their respective density of states, thus still leaving open the question of whether the degree of structural order or/and the electronic hybridization is the decisive factor for the observed difference in selectivity.
Keywords: Cu60Pd40; intermetallic compound; alloy; semi-hydrogenation; phase transition
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Friedrich, M.; Villaseca, S.A.; Szentmiklósi, L.; Teschner, D.; Armbrüster, M. Order-Induced Selectivity Increase of Cu60Pd40 in the Semi-Hydrogenation of Acetylene. Materials 2013, 6, 2958-2977.
Friedrich M, Villaseca SA, Szentmiklósi L, Teschner D, Armbrüster M. Order-Induced Selectivity Increase of Cu60Pd40 in the Semi-Hydrogenation of Acetylene. Materials. 2013; 6(7):2958-2977.
Friedrich, Matthias; Villaseca, Sebastián A.; Szentmiklósi, László; Teschner, Detre; Armbrüster, Marc. 2013. "Order-Induced Selectivity Increase of Cu60Pd40 in the Semi-Hydrogenation of Acetylene." Materials 6, no. 7: 2958-2977.