Study of an iron-manganese Fischer-Tropsch synthesis catalyst promoted with copper

The metal-silica interaction and catalytic behavior of Cu-promoted Fe-Mn-K/SiO2 catalysts were investigated by temperature-programmed reduction/desorption (TPR/-TPD), differential thermogravimetric analysis, in situ diffuse reflectance infrared Fourier transform analysis, and Mossbauer spectroscopy. The Fischer-Tropsch synthesis (FTS) performance of the catalysts With Or Without copper Was Studied in a slurry-phase continuously stirred tank reactor. The characterization results indicate that several kinds of metal oxide-silica interactions are present oil Fe-MnK/SiO2 catalysts with or Without copper, which include iron-silica, copper-silica, and potassium-silica interactions. In addition to the well-known effect of Cu promoter on casing the reduction of iron-based FTS catalysts, it is found that Cu promoter call increase the rate of carburization, but does not vary the extent of carburization during the steady-state FTS reaction. The basicity of the Cu and K co-promoted catalyst is greatly enhanced, as demonstrated by CO2-TPD results. In the FTS reaction, Cu improves the rate of catalyst activation and shortens the induction period, whereas the addition of Cu has no apparent influence on the steady-state activity Of the catalyst. Promotion of Cu strongly affects hydrocarbon selectivity. The product distribution shifts to heavy hydrocarbons, and the olefin/paraffin ratio is enhanced on the catalyst due to the indirect enhancement of surface basicity by the copper promotion effect. (c) 2005 Elsevier Inc. All rights reserved.