Investigation of Mixtures of a Co-Based Catalyst and a Cu-Based Catalyst for the Fischer-Tropsch Synthesis with Bio-Syngas: The Importance of Indigenous Water

A series of different mechanical mixtures of a narrow-pore Co/c-Al2O3 catalyst and a Cu-based WGS-catalyst has been investigated in the low-temperature Fischer-Tropsch synthesis (483 K, 20 bar) with a model bio-syngas (H-2/CO = 1.0) in a fixed-bed reactor. The higher the fraction of WGS-catalyst in the mixture, the lower is the Co-catalyst-time yield to hydrocarbons. This is ascribed to a strong positive kinetic effect of water on the Fischer-Tropsch rate of the Co-catalyst, showing the importance of the indigenously produced water, especially in fixed-bed reactors where the partial pressure of water is zero at the reactor inlet. A preliminary kinetic modeling suggests that the reaction order in P-H2O is 0.3 for the Co/c-Al2O3 catalyst in the range of the studied reactor-average partial pressures of water (i.e., 0.04-1.2 bar).