Lithium Imide-Modified Nickel Catalysts for Selective Hydrogenation of Acetylene

Alkali/alkaline earth metal promoters play a crucial role in optimizing catalysts for the selective hydrogenation of acetylene. This study innovatively explores the effects of different forms of lithium (Li) promoters on enhancing ethylene selectivity and successfully develops a Li 2 NH-modified Ni/MgO catalyst synthesized via liquid-ammonia impregnation method. The catalyst exhibits significantly enhanced activity and selectivity in the semihydrogenation of acetylene, outperforming the unmodified Ni/MgO catalyst and other lithium compound-modified catalysts. Comprehensive characterization not only reveals that Li 2 NH enhances Ni dispersion and facilitates H 2 activation/dissociation, but also uncovers its dual-promoting mechanism: it finely tunes adsorption strengths through the electronic modulation while utilizing its unique hydrogen storage capability to enable controlled hydrogen supply. This synergistic mechanism is unequivocally identified as the core reason for the selectivity enhancement. This work proposes a novel strategy for designing efficient Ni-based catalysts through modification with functional alkali metal imides (e.g., Li 2 NH). The revealed structure–activity relationship and controllable hydrogen supply mechanism provide important scientific foundations for developing high-performance catalysts for selective alkyne hydrogenation, with broad implications for alkyne removal processes.