Partial carbon encapsulation synthesis of separated Ni-Ag catalyst for efficient selective hydrogenation of acetylene: Synergizing hydrogen spillover and steric hindrance

Abstract

The selective hydrogenation of acetylene is a vital process to for the purification of crude ethylene in petroleum industry. Achieving high activity and selectivity simultaneously over Ni-based catalysts is still challenging. Herein, a partial encapsulation strategy is proposed by fabricating carbon-encapsulated Ag nanoparticles and un-encapsulated Ni nanoparticles on Al2O3 surface (Ni-Ag@C/Al2O3) toward the enhanced selectivity without loss of activity. In particular, the Ni-Ag@C/Al2O3 exhibits higher ethylene selectivity of 81% at the complete acetylene conversion along with excellent stability for 30-h, in sharp with the Ni/Al2O3 (6%) and Ni-Ag/Al2O3 (54%) catalyst. The enhanced selectivity is attributed to the promotion of hydrogen spillover by the carbon species on Al2O3 surface and the inhibition of oligomer formation by a steric hindrance formed by the carbon layer on the Ag surface. This study provides a new structural design avenue of bifunctional bimetallic catalyst for selective hydrogenation reaction.