Recently, a joint research team led by Professor Yongfeng Zhou, Associate Professor Jun Li, and Researcher Yuanhai Su from Shanghai Jiao Tong University published a research paper titled "Cobalt hydride-mediated photocatalytic semihydrogenation of acetylene impurities for continuous-flow production of polymer-grade ethylene" in the journal Nature Catalysis. This research achievement reports a metal-catalyzed hydrogen atom transfer pathway that facilitates photocatalytic semihydrogenation of acetylene through the rapid formation of cobalt hydride. By employing a continuous-flow strategy, the photocatalytic efficiency is significantly enhanced, enabling the continuous production of polymer-grade ethylene (with acetylene content less than 5 ppm).

Article abstract:

The semihydrogenation of acetylene impurities in crude ethylene streams to produce polymer-grade ethylene is important for the polyethylene industry. Photocatalytic reduction offers a promising solution in terms of sustainability. However, the current state of photocatalytic acetylene semihydrogenation systems has shown limited activity. Here we report a metal-catalysed hydrogen atom transfer pathway to promote photocatalytic acetylene semihydrogenation via rapid formation of cobalt hydride species. Applying a N,N′-bis(salicylidene)ethylenediamine cobalt catalyst with an electron-donating ligand that energetically favours cobalt hydride formation in pure acetylene yields excellent acetylene-to-ethylene reduction performance with near-unity selectivity, a turnover number of 29,401, and a turnover frequency of 2.14 s⁻¹. Most importantly, we engineered a continuous-flow photoreactor, by which crude ethylene containing 1.10 vol% acetylene can be steadily converted into polymer-grade ethylene continuously over 50 h.