Active site tuning based on pseudo-binary alloys for low-temperature acetylene semihydrogenation.

ABSTRACT

The development of an efficient catalytic system for low-temperature acetylene semihydrogenation using nonnoble metals is important for the cost-effective production of polymer-grade pure ethylene. However, it remains challenging owing to the intrinsic low activity. Herein, we report a flexibly tunable catalyst design concept based on a pseudo-binary alloy, which enabled a remarkable enhancement in the catalytic activity, selectivity, and durability of a Ni-based material. A series of (Ni1-xCux)3Ga/TiO2 catalysts exhibiting L12-type pseudo-binary alloy structures with various Cu contents (x = 0.2, 0.25, 0.33, 0.5, 0.6, and 0.75) were prepared for active site tuning. The optimal catalyst, (Ni0.8Cu0.2)3Ga/TiO2, exhibited outstandingly high catalytic activity among reported 3d transition metal-based systems and excellent ethylene selectivity (96%) and long-term stability (100 h) with near full conversion even at 150 °C. A mechanistic study revealed that Ni2Cu hollow sites on the (111) surface weakened the strong adsorption of acetylene and vinyl adsorbate, which significantly accelerated the hydrogenation process and inhibited undesired ethane formation.