Enhanced C3+ alcohol synthesis from syngas using KCoMoSx catalysts: effect of the Co-Mo ratio on catalyst performance

K-Co-MoS catalysts varying in Co content were prepared to investigate the role of Co in this catalyst formulation for the synthesis of C3+ alcohols from syngas. The Co-MoS precursors and the best performing K-doped version were characterized in detail and the amount of active cobalt sulfide and mixed metal sulfide (Co-Mo-S) phases were shown to be a function of the Co content. The catalysts were tested in a continuous set-up at 360 °C, 8.7 MPa, a GHSV of 4500 mL g h and a H/CO ratio of 1. The highest alcohol selectivity of 47.1%, with 61% in the C3+ range, was obtained using the K-Co-MoS catalyst with a Co/(Co + Mo) molar ratio of 0.13. These findings were rationalized considering the amount and interactions between cobalt sulfide and Co-Mo-S or MoS phases. Process studies followed by statistical modeling gave a C3+ alcohol selectivity of 31.0% (yield of 9.2%) at a CO conversion of 29.8% at optimized conditions.