The effect of sulfur on supported cobalt Fischer-Tropsch catalysts

TiO2- and SiO2-supported, 10% by mass cobalt Fischer-Tropsch (F-T) catalysts, loaded with low concentrations of sulfur (100-2000 ppm) from different sources ((NH4)(2)S, (NH4)(2)SO4, and (NH4)(2)SO3), have been synthesized and characterized using DRIFTS and TPR. CO adsorption and FT reaction, monitored by DRIFTS, revealed that small amounts of sulfur (100 ppm) increased the strength of most types of metal-CO interactions and enhanced F-T catalyst activity, as reflected by more intense metal-CHx infrared intensities relative to the unsulfided catalyst. Sulfur concentrations between 200 and 2000 ppm gave infrared spectra with decreased intensity of the absorbance peaks due to adsorbed hydrocarbons. It was found that the presence of sulfur resulted in a slight increase in the reduction temperature of the titania-supported catalysts. Sulfur on the surface of the silica supported catalysts decreased the intensity of the TPR peak related to a reducible silicate. (C) 1999 Elsevier Science B.V. All rights reserved.