A MOF-supported Pd1–Au1 dimer catalyses the semihydrogenation reaction of acetylene in ethylene with a nearly barrierless activation energy

Abstract

The removal of acetylene from ethylene streams is key in industry for manufacturing polyethylene. Here we show that a well-defined Pd1–Au1 dimer, anchored to the walls of a metal–organic framework (MOF), catalyses the selective semihydrogenation of acetylene to ethylene with ≥99.99% conversion (≤1 ppm of acetylene) and >90% selectivity in extremely rich ethylene streams (1% acetylene, 89% ethylene, 10% H2, simulated industrial front-end reaction conditions). The reaction proceeds with an apparent activation energy of ∼1 kcal mol–1, working even at 35 °C, and with operational windows (>100 °C) and weight hourly space velocities ($$66{,}000\,{\mathrm{ml}}\,{\mathrm{g}}^{-1}_{\mathrm{cat}}\,{\mathrm{h}}^{-1}$$ 66 , 000 ml g cat − 1 h − 1 ) within industrial specifications. A combined experimental and computational mechanistic study shows the cooperativity between both atoms, and between atoms and support, to enable the barrierless semihydrogenation of acetylene.

Carburization in the Crystalline Structure of the Metal Ag for Efficient Selective Hydrogenation of Acetylene

“…Invariably, a trace amount of acetylene (0.3–2%) is inevitably generated as a byproduct in ethylene production, which would poison the Ziegler–Natta catalysts for ethylene polymerization, consequently reducing the quality of produced polyethylene. − Selectively hydrogenating trace acetylene to desired ethylene is widely acknowledged as a highly effective and economically viable method to remove the acetylene impurities from the ethylene stream, thereby ensuring a net gain in ethylene production. Pd-based catalysts are commonly employed for the selective hydrogenation of acetylene due to their high H 2 dissociation ability, − in which the Al 2 O 3 -supported Pd–Ag catalysts are commercially used in the petrochemical industry . However, ethylene formation is strongly dependent on the acetylene conversion, resulting in the markedly accelerated formation of undesired ethane at a high acetylene conversion .…”