Direct synthesis of extra-heavy olefins from carbon monoxide and water.

Wang, Chuanhao; Du, Junjie; Zeng, Lin; Li, Zhongling; Dai, Yizhou; Li, Xu; Peng, Zijun; Wu, Wenlong et al. · Nat Commun · 2023

basic_science · Level V

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Abstract

Extra-heavy olefins (C<sub>12+</sub><sup>=</sup>), feedstocks to synthesize a wide range of value-added products, are conventionally generated from fossil resources via energy-intensive wax cracking or multi-step processes. Fischer-Tropsch synthesis with sustainably obtained syngas as feed-in provides a potential way to produce C<sub>12+</sub><sup>=</sup>, though there is a trade-off between enhancing C-C coupling and suppressing further hydrogenation of olefins. Herein, we achieve selective production of C<sub>12+</sub><sup>=</sup> via the overall conversion of CO and water, denoted as Kölbel-Engelhardt synthesis (KES), in polyethylene glycol (PEG) over a mixture of Pt/Mo<sub>2</sub>N and Ru particles. KES provides a continuously high CO/H<sub>2</sub> ratio, thermodynamically favoring chain propagation and olefin formation. PEG serves as a selective extraction agent to hinder hydrogenation of olefins. Under an optimal condition, the yield ratio of CO<sub>2</sub> to hydrocarbons reaches the theoretical minimum, and the C<sub>12+</sub><sup>=</sup> yield reaches its maximum of 1.79 mmol with a selectivity (among hydrocarbons) of as high as 40.4%.