Copper Single-Atom-Covered Pt Nanoparticles for Selective Hydrogenation of Phenylacetylene

Abstract

The selective hydrogenation of alkynes to alkenes is very important for both industry and scientific investigation, and overhydrogenation of alkynes to alkanes is the biggest problem to be solved. Suppressing the catalytic hydrogenation of alkenes to alkanes and keeping the efficient conversion from alkynes to alkenes at the same time is a viable solution, but the slight difference in structure between alkynes and the corresponding alkenes causes great difficulty in realizing such a target. The Pt/C–Cu bimetallic catalysts are used to catalyze the selective hydrogenation of phenylacetylene (PA) to styrene (ST). High-resolution STEM and EXAFS results show that the prepared Pt/C–Cu catalysts are composed of copper single atoms and Pt nanoparticles. In particular, Pt/C–Cu is a catalyst in which copper single atoms cover the surface of Pt nanoparticles. The experimental results reveal that the selectivity of ST strongly depends on the coverage of Cu single atoms over Pt nanoparticles in Pt/C–Cu, so selective hydrogenation of PA is a structure-sensitive reaction. The selectivity of ST can reach 94.4% at a PA conversion of 100% in the selective hydrogenation of PA over Pt/C–0.5Cu, an optimized Pt–Cu bimetallic catalyst; after selective removal of PA in ST from 100 to 30 ppm over the same catalyst, the yield of ST reaches 99.97%. The chemisorption results of H2 and probe molecule ethene (C2H4) over the Pt–Cu/C catalysts reveal that Cu single atoms covering on the surface of Pt nanoparticles weaken the Pt–H and Pt–C2H4 interactions, so the catalytic hydrogenation of the carbon–carbon double bond over Pt/C–0.5Cu can be tremendously suppressed. The added Cu single atoms over Pt nanoparticles are not poisonous sites because they can also act as the active centers to activate hydrogen and the carbon–carbon double bond.