Carburization in the Crystalline Structure of the Metal Ag for Efficient Selective Hydrogenation of Acetylene

The selective hydrogenation of acetylene to ethylene plays a pivotal role in the petrochemical industry. Metal Ag catalysts always show a high ethylene selectivity in acetylene hydrogenation, while the low hydrogen dissociation ability limits its application in hydrogenation reactions. Herein, a new silver carbide-like active phase (AgxC) was prepared through a crystalline phase transformation method, which is achieved by reducing silver acetylide to AgxC with H2. Surprisingly, the AgxC-containing catalyst exhibits an outstanding hydrogenation activity and selectivity simultaneously, achieving an acetylene conversion of 100% and an ethylene selectivity of 88.7% with exceptional long-term stability over at least 30 h. Density functional theory calculations reveal that the AgxC phase significantly lowers the activation barrier of H2 dissociation, leading to a substantially higher hydrogenation activity compared to the metal Ag catalyst. Furthermore, the excellent ethylene selectivity is attributed to the facile ethylene desorption rather than overhydrogenation. The results presented here encourage the pursuit of an Ag-based catalytic system for hydrogenation reactions.