InPd₃ and InPd₂Cu IntermetallicCatalysts for Selective Hydrogenation Catalysis

The selective hydrogenation of unsaturated hydrocarbons is a critical process in industrial catalysis. Hydrogenating linear alkenes while avoiding the adsorption or hydrogenation of aromatics is important to some petroleum refinery processes. This study investigates the performance of InPd_3–<i>x</i>Cu_<i>x</i> ternary intermetallic compounds for hydrogenation catalysis, combining density functional theory (DFT) and microkinetic modeling (MKM). The substitution of Pd by Cu at the 2<i>b</i> site in the InPd₃ lattice alters the geometric and electronic properties of the surface active sites. Structural and thermodynamic analyses, supported by CALPHAD modeling, confirmed Cu’s preference for the 2<i>b</i> site. Surface energy calculations identified the (112) facet as the most stable surface for both InPd₃ and InPd₂Cu. DFT-based adsorption studies showed that Cu substitution significantly reduces benzene adsorption while maintaining a moderate ethylene binding energy. Reaction energy barriers and sensitivity analyses from MKM revealed that Cu incorporation reduces the likelihood of aromatic poisoning, while slightly increasing activation barriers for ethylene hydrogenation. DFT energetics calculated at varying coadsorbate coverages were used with MKM to demonstrate improved resistance to benzene poisoning in InPd₂Cu compared to InPd₃. Ternary intermetallics can offer a wide range of compositions to tune the hydrogenation active site geometric and electronic structure.