Abstract
In this work, we report alumina-supported metal-metalloid alloy nanoparticles (Pd(2)B/Al(2)O(3)) as highly efficient alkyne semi-hydrogenation catalysts. The mentioned catalysts contain orthorhombically distorted hcp Pd(2)B nanoparticles and were prepared by in situ transformation of Pd/Al(2)O(3) with borane dimethylamine complex by a solvothermal method. The synthesized Pd(2)B/Al(2)O(3) demonstrated greatly enhanced semi-hydrogenation performance. Under reaction conditions of 30 °C, 0.1 MPa of H(2) and a substrate/Pd molar ratio of 1000/1, the conversions of 3-hexyne-1-ol could reach 99.8% in 15 min with a yield of cis-3-hexen-1-ol of 93.3%. Importantly, the alkene and cis- to trans-alkene selectivity only slightly decreases with an extended reaction time, showing the inhibition of deep hydrogenation. Experimental studies and density functional theory calculations indicate that the catalytic enhancement is originated from the formation of Pd(2)B alloy, which alters the electronic and geometric properties of surface species, thus suppressing the deep hydrogenation with the enhanced alkene selectivity.