Pd−Ga Intermetallic Compounds as Highly Selective Semihydrogenation Catalysts

Abstract

The intermetallic compounds Pd(3)Ga(7), PdGa, and Pd(2)Ga are found to be highly selective semihydrogenation catalysts for acetylene outperforming established systems. The stability of the crystal and electronic structure under reaction conditions allows the direct relation of structural and catalytic properties and a knowledge-based development of new intermetallic catalyst systems. In the crystal structure of PdGa palladium is exclusively surrounded by gallium atoms. The alteration of the Pd coordination in PdGa leads to a strong modification of the electronic structure around the Fermi level in comparison to elemental Pd. Electronic modification and isolation of active sites causes the excellent catalytic semihydrogenation properties.

In situ study of the formation and stability of supported Pd2Ga methanol steam reforming catalysts

“…Pd and Ga can form a number of intermetallic compounds (IMC) and/or alloys; e.g., Pd 2 Ga, PdGa, Pd 3 Ga 7 , and PdGa 5 were reported in literature [20].Metallurgically prepared, unsupported intermetallic bulk materials have been studied in recent years, showing excellent catalytic properties for selective hydrogenation of acetylene in excess ethylene [21][22][23][24].…”

Crystal structure of Ga0.47(1)Sb0.53(1)Pd2

“…Taking into account the atomic environment of the palladium atoms (the shortest contacts are to the Ga and Sb atoms and the closest Pd-Pd distances, in comparison with elemental palladium, are increased significantly (2.919(2) Å and 2.74 Å, respectively), the title compound, in analogy to the binary Ga-Pd compounds [6], is a potential candidate for the catalytic application in the selective semi-hydrogenation of acetylene in the excess of ethylene.…”

The Reduction of Alkynes Over Pd-Based Catalyst Materials - A Pathway to Chemical Synthesis

“…For larger particles, for example, 1.5-1.9 nm, the reaction rate may be described as purely geometric, supposing that it takes place exclusively on the terrace sites of the nanoparticle. Murzin have proposed a model, which describes the geometrical size effects, assuming that the nanoparticle activity is determined by the ratio of step to terrace sites [76]. Recently, SilvestreAlbero et al carried out a study of model catalysts for the selective hydrogenation of butadiene [77].…”

“…Spatial separation of the sites suppresses C-C bond formation or oligomerization reactions, enhancing semi-hydrogenation selectivity. On the other hand, the strong adsorption of quinoline on the Pd surface is likely to be caused by its large delocalised π-electron areas rather than its basic properties, because adsorption energy of naphthalene is comparable to that of quinoline, but is much higher than that of pyridine [76]. Alkylamine modifiers, similarly, enhance thermodynamic factors for Pt and CoPt 3 nanoparticles -amines with carefully chosen alkyl chain length suppress alkene adsorption and thereby increase selectivity.…”