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

ABSTRACT

Extra-heavy olefins (C12+=), 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 C12+=, though there is a trade-off between enhancing C-C coupling and suppressing further hydrogenation of olefins. Herein, we achieve selective production of C12+= via the overall conversion of CO and water, denoted as Kölbel-Engelhardt synthesis (KES), in polyethylene glycol (PEG) over a mixture of Pt/Mo2N and Ru particles. KES provides a continuously high CO/H2 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 CO2 to hydrocarbons reaches the theoretical minimum, and the C12+= yield reaches its maximum of 1.79 mmol with a selectivity (among hydrocarbons) of as high as 40.4%.