Hydroxy-induced cobalt oxides for syngas to light olefins

Light olefins—ethylene, propylene and butylene (C 2 = –C 4 = )—are essential building blocks in the chemicals industry and are traditionally produced by thermal or catalytic cracking of hydrocarbon feedstocks. Directly converting syngas (CO and H 2 ) into light olefins under mild conditions is attractive but challenging 1 , 2 , 3 , 4 . Prismatic cobalt carbide (Co 2 C) and associated hydrophobic modifications have shown potential for selective light-olefin synthesis under mild conditions 5 , 6 . Here we show another hydrophilic-promotion strategy in which a set of hydroxy promoters, exemplified by hydroxyapatite (Ca 5 (PO 4 ) 3 (OH), HAP), fumed silica (SiO 2 (F)) and amorphous boehmite (AlO(OH), AB), is physically mixed with a Co 2 MnO 4 precursor, inducing synergistic cobalt–manganese (Co–Mn) oxides and Co 2 C for syngas conversion. The induced anorthic Co–Mn oxides may serve as active phase for adsorbed-hydrogen-assisted CO dissociation to CH x /CH x O intermediates, whereas induced Co 2 C or the Co 2 C–oxide interface may mediate C–C coupling of these intermediates to form light olefins. This design achieved 70–82% CO conversion with light-olefins selectivity of more than 60% at 250–260 °C, 0.1 MPa with H 2 /CO ratios of 1–2, giving light-olefins carbon utilization efficiency up to 13%, among the highest reported for syngas to light olefins. This simple hydrophilic strategy for facilitating CO activation may provide useful insights for improving industrial Fischer–Tropsch processes.