Unlocking enhanced selectivity of Pd/Al2O3 in semihydrogenation of alkynes by in situ ligand‐reduction strategy

Abstract

AbstractThe partial hydrogenation of alkynes into alkenes constitutes a pivotal chemical transformation in the synthesis of fine chemicals, pharmaceuticals, and polymers. Nevertheless, the extant industrial catalyst falls short of achieving a felicitous equilibrium between its catalytic potency and selectivity. Herein, triphenylphosphine (PPh3) modified Pd/Al2O3 catalysts are fabricated through a “one‐pot” process, which achieve highly selective hydrogenation of alkynes at room temperature. PPh3 plays a dual role—as a reducing agent and a ligand. Kinetic and characterization studies reveal PPh3 alters H2 activation from homolytic to heterolytic cleavage, which facilitate the formation of alkene. Moreover, PPh3 can also optimize the reaction microenvironment, achieving the reduced self‐poisoning of alkyne and promoted desorption of alkene. In the realm of alkyne hydrogenation, our philosophy encompasses a global optimization of active sites, ligand systems, and reaction microenvironmental. This method steers the course of catalyst development for other reactions beyond the field of alkyne hydrogenation.