Production of C4 Hydrocarbons from Modified Fischer−Tropsch Synthesis over Co−Ni−ZrO2/Sulfated-ZrO2 Hybrid Catalysts

Abstract

Fischer−Tropsch synthesis was carried out at atmospheric pressure in a fixed-bed microreactor at temperatures and weight hourly space velocities (WHSV) ranging from 513 to 533 K and 5 to 25 h-1, respectively, over hybrid catalysts (physical mixtures) containing Co−Ni−ZrO2 and sulfated-ZrO2 catalysts. The sulfated-ZrO2/Co−Ni−ZrO2 catalyst weight ratios (SZ/CN) ranged from 0 to 3, whereas sulfate concentrations in sulfated-ZrO2 catalyst (sulfate loading) ranged from 5 to 15 wt %. Fischer−Tropsch synthesis over Co−Ni−ZrO2 catalyst alone produced a maximum C4 hydrocarbon selectivity of 14.6 wt % at a temperature of 523 K and WHSV of 15 h-1. There was an impressive increase in C4 hydrocarbons selectivity to a maximum of 32.4 wt % when catalyst HB5,1 (SZ/CN of 1 and sulfate loading of 5 wt %) was used. This catalyst also gave an extremely high selectivity for isobutane (maximum of 10.6 wt % of total hydrocarbon products) as compared to 0.1 wt % obtained with Co−Ni−ZrO2 catalyst. A time-on-stream study on cataly...