Acetylene Semi‐Hydrogenation at Room Temperature over Pd−Zn Nanocatalyst

Abstract

AbstractA reaction of fundamental and commercial importance is acetylene semi‐hydrogenation. Acetylene impurity in the ethylene feedstock used in the polyethylene industry poisons the Ziegler‐Natta catalyst which adversely affects the polymer quality. Pd based catalysts are most often employed for converting acetylene into the main reactant, ethylene, however, it often involves a tradeoff between the conversion and the selectivity and generally requires high temperatures. In this work, bimetallic Pd−Zn nanoparticles capped by hexadecylamine (HDA) have been synthesized by co‐digestive ripening of Pd and Zn nanoparticles and studied for semi‐hydrogenation of acetylene. The catalyst showed a high selectivity of ~85 % towards ethylene with a high ethylene productivity to the tune of ~4341 μmol g−1 min−1, at room temperature and atmospheric pressure. It also exhibited excellent stability with ethylene selectivity remaining greater than 85 % even after 70 h on stream. To the best of the authors’ knowledge, this is the first report of room temperature acetylene semi‐hydrogenation, with the catalyst effecting high amount of acetylene conversion to ethylene retaining excellent selectivity and stability among all the reported catalysts thus far. DFT calculations show that the disordered Pd−Zn nanocatalyst prepared by a low temperature route exhibits a change in the d‐band center of Pd and Zn which in turn enhances the selectivity towards ethylene. TPD, XPS and a range of catalysis experiments provided in‐depth insights into the reaction mechanism, indicating the key role of particle size, surface area, Pd−Zn interactions, and the capping agent.