Promotion of Metal–Organic-Framework-Derived Co@C Catalysts for Fischer–Tropsch Reaction by Physical Mixing of Aluminum Isopropoxide

The cobalt-catalyzed Fischer–Tropsch reaction is used industrially to convert syngas (CO + H2) into long-chain (C5+) hydrocarbons, and the enhancement of catalytic performance by the judicious introduction of additives and promoters has drawn wide interest. Previously, we showed that cobalt-based metal–organic frameworks (MOFs) can be used as sacrificial templates to prepare carbon-supported Co materials (Co@C) with high activity and selectivity for C5+ hydrocarbons. Here, we demonstrate that aluminum-promoted Co catalysts with excellent activity, selectivity, and stability can be readily obtained by simple mechanical mixing of a Co-MOF precursor with aluminum isopropoxide prior to pyrolysis. Under optimized conditions, CO conversions of 80% and C5+ selectivities of 82% could be attained at 2.9 MPa, 300 °C, 0.3 L/gcat./min space velocity and H2/CO = 2. In contrast, analogous materials prepared by impregnation of the same Co-MOF with aluminum nitrate were completely inactive due to the extensive formation of poorly reducible CoAl2O4 spinel. A combination of characterization techniques evinces a blocking effect served by the Al additives, which inhibits the aggregation of incipient cobalt nanoparticles during thermal decomposition. Overall, our findings could help guide the large-scale production of active Co catalyst systems.