Effects of alkali promoters on tri-metallic Co-Ni-Cu-based perovskite catalyst for higher alcohol synthesis from syngas

© 2019 Elsevier B.V. Direct conversion of natural gas-derived syngas into higher alcohols via the Fischer-Tropsch process offers a more sustainable pathway to address fuels and chemicals demands for various industries in the near future. Large scale application of this process nonetheless relies on the availability of a highly active and selective catalyst. In this work, tri-metallic Co-Ni-Cu catalyst derived from La0.9Sr0.1Co0.8Ni0.1Cu0.1O3 perovskite precursor with two different alkali promoters were prepared and tested for higher alcohol synthesis from syngas. Active components and catalyst performances were found to vary with same weight loading of Na and K. K-promoted catalyst demonstrated the best higher alcohol formation with the higher alcohol distribution of 82.2% and alcohol chain growth probability factor of 0.53 at 325 °C, followed by the Na-promoted and non-promoted counterparts. The rationale behind the alkali addition—performance relationship is two-fold. On one hand, the addition of alkali promotes the formation of stable Co2C; resulting in high Co2C/Co ratio that enhances the higher alcohol distribution but decreases the CO conversion. On the other hand, the increased catalyst basicity obtained from alkali promotion facilitates the carbon chain propagation of alcohols, especially for the conversion of methanol to ethanol. In addition, the alkali promoters, especially K, prevent the deactivation of catalyst Co-Ni-Cu by eliminating the carbon deposition during the reaction; resulting in a stable catalyst even at 340 °C.