Hydrothermal deactivation of silica-supported cobalt catalysts in Fischer–Tropsch synthesis

Hydrothermal conditions created by high conversion in Fischer–Tropsch hydrocarbon synthesis induce cobalt–silica mixed oxide formation causing deactivation of silica-supported cobalt catalysts. The mixed oxide phase displays a distinctive needle-like morphology with a 1-nm lattice spacing and has a Co/Si atomic ratio of 1.2/1. The hydrothermal origin of the mixed oxide is confirmed by the fact that steamed catalyst samples contain the same needle-like phase with identical lattice spacing and Co/Si ratio. Reduction in 1.2 MPa H2 at ⩾400 °C decomposes the mixed oxide and recovers small metallic cobalt particles.