Conversion of syngas into olefins with high hydrogen atom economy.

In synthesizing olefins from syngas, low hydrogen atom economy (HAE), the fraction of reactant hydrogen in the hydrocarbon product, arises from hydrogen loss in water by-product. We report a sodium-modified FeCx@Fe3O4 core-shell catalyst coupling water-gas shift (WGS) with syngas-to-olefins (STO) to convert water into hydrogen in situ. HAE reaches about 66 to 83%, exceeding that of methanol-to-olefins (MTO, 50% upper limit). The approximately 95% carbon monoxide conversion and >75% olefin selectivity were simultaneously obtained. The coupling effect was validated by isotope tracing with deuterium oxide and blocking the WGS pathway, and the contribution of WGS was quantitatively evaluated. These results, using lower hydrogen to carbon monoxide ratios, implied that reducing steam consumption in the WGS reaction and reducing the overall output of carbon dioxide and wastewater enabled a sustainable STO process for potential industrialization.