Gold-promoted plasma-synthesized Ni-Co-Fe/C catalyst for Fischer-Tropsch synthesis

Abstract

From this study, we present results of a nanometric, gold-promoted Fischer-Tropsch synthesis (FTS) catalyst, with carbon support. A ternary 5%Ni-70%Co-25%Fe/C formulation was synthesized using induction suspension plasma spray (SPS) technology; the so-produced formulation was doped with 5%Au through the impregnation method. The catalysts (Au-Ni-Co-Fe/C and Ni-Co-Fe/C) were tested for 24 h in a continuously stirred tank reactor (CSTR) operated at 260 °C, 2-MPa pressure and H2/CO molar ratio of 2 using feed gas composition set at 0.6 L/L (60 vol%) H2 and 0.3 L/L (30 vol%) CO balanced in Ar flowing at gas hourly specific velocity (GHSV) of 3600 cm3 h−1 g−1 of catalyst. Catalyst performance was benchmarked against comparable plasma-synthesized bimetallic 80%Co-20%Fe/C and ternary 10%Ni-70%Co-20%Fe/C formulations. The bimetallic Co-Fe/C showed (a) catalytic activity of ∼40% CO conversion and (b) selectivity of ∼19% for gasoline fraction (C5–C12) and 55% towards diesel (C13–C20). Addition of 10%Ni to the Co-Fe/C improved CO conversion from 40 to 50% with enhanced selectivity for gasoline from 19 to 50%, but the diesel fraction dropped from 55 to 22%. Incorporation of 5%Au in the 5%Ni-Co-Fe/C catalyst led to 60% CO conversion. Yet, when compared to the un-promoted 5%Ni-Co-Fe/C catalyst that showed 90% CO conversion with relatively high selectivity towards the undesired CO2 (14%) and CH4 (23%), presence of Au cut H2O production by almost half and improved selectivity for gasoline fraction from 38 to 41% and for diesel from 20 to 32%. All tested catalysts’ α-values lay between 0.78 and 0.88 in the C10+ region.