Selective production of C4 hydrocarbons from syngas in a dual reactor using Co-Ni/ZrO2 and SO42-/ZrO2 catalysts

The product stream from the Fischer-Tropsch (FT) reaction using a Co-Ni/ZrO2 catalyst was modified by SO42-/ZrO2 catalyst (solid acid catalyst) in a dual fixed-bed microreaction system. While the operating conditions for the first reactor containing the FT catalyst was fixed at 523 K and 1 atm, the effects of operating variables such as the second reactor temperature, the Co-Ni/ZrO2:SO42-/ZrO2 catalyst ratio and weight hourly space velocity (WHSV) on the steady-state product distribution were investigated. In this process, high selectivity (33 wt %) toward the total C-4 hydrocarbons was achieved when the second reactor was operated at 423 K, with a catalyst ratio of 1:1.5 and at a WHSV of 15 h(-1). This selectivity is much higher compared to a maximum selectivity of 14 wt % obtained using a single reactor with a Co-Ni/ZrO2 catalyst. Catalyst characterization using temperature-programmed desorption of NH3 and H-1 MAS NMR showed that this high selectivity toward total C-4 hydrocarbons was due to the strong acidity of the SO42-/ZrO2 catalyst. However, this catalyst deactivated rapidly which was due to coke deposition on the SO42-/ZrO2 catalyst. Under these experimental conditions, external and intraparticle mass transfer effects were found to be negligible. On the basis of the product distribution in a dual-reaction system, a reaction pathway has been proposed.