PdTi alloys as an excellent catalyst for semi-hydrogenation reactions

Abstract

Acetylene semi-hydrogenation to ethylene is essential in industry to purify ethylene. Although Pd is the most active pure metal catalyst for this reaction, it exhibits a limited selectivity as it tends to over-hydrogenate ethylene. Inspired by previous experimental findings, in this work we study PdTi bimetallic catalysts by the combination of two complementary approaches: PdTi subnanocluster tetramers of different composition are studied when deposited on a ɣ-Al2O3 (100) surface, and a set of larger nanoparticles is explored with different core/shell motifs and PdTi mixing patterns. Our results taken together show that monometallic Pd and Ti are too reactive for the semi-hydrogenation of acetylene. At low or medium Ti proportions, however, alloying confers a beneficial effect on Pd. On the one hand, Ti shows a clear preference to be bound to the support and helps anchor the cluster, leading to more sintering resistance. On the other hand, Ti modifies the electronic structure of Pd through a charge transfer process, tuning the reactivity of Pd and producing a more selective catalyst.