Effect of Mo loading and support type on hydrocarbons and oxygenates produced over Fe-Mo-Cu-K catalysts supported on activated carbons

Abstract

Abstract The effects of Mo loading and type of activated-carbon (AC) support on activity, stability, and selectivities to hydrocarbons and alcohols during Fischer-Tropsch synthesis over Fe-Mo-Cu-K/AC catalysts are studied under the conditions of 310–320 o C, 2.2 MPa, 3 Nl-gcat/h and H 2 /CO = 0.9 in a fixed-bed reactor. Mo loadings of 0, 6 and 12 weight percent were used to determine the effect of Mo loading, while four different carbon supports, i.e. peat, generic wood, pecan-shell and walnut-shell derived ACs, were used to determine the effect of carbon support. Addition of Mo promoter to the Fe-Cu-K catalyst supported on peat AC leads to improved catalyst stability and improved selectivities to methane and oxygenates. The 6% Mo catalyst is more active and produces more hydrocarbons and oxygenates than the 12% Mo catalyst. Carbon-support type affects both catalyst activity and selectivity. Catalysts supported on pecan and peat ACs are the most active and produce the largest amount of hydrocarbons; the catalyst supported on pecan AC also shows the best C 5+ selectivity. The catalyst supported on walnut-shell AC shows high C 5+ selectivity too, but it is not as active. The catalyst using a wood AC support is the least active, with the smallest C 5+ hydrocarbon selectivity (least chain-growth probability) but the highest oxygenate selectivity. In all cases, hydrocarbons upto ~C 34 and alcohols upto ~C 5 , are detected, and total oxygenates make up less than 6 wt% of total products. It is hypothesized that the Mo promoter prevents active sites from agglomeration, and that textural properties, such as BET and pore volume of carbon supports, might be similarly related to catalytic performance.