Sinergies between organic-matrix combustion synthesis and Pt-promotion on the performances of Co-based FT catalysts

Ninety years after its discovery, Fischer–Tropsch Synthesis (FTS) is recently receiveing new interest as the key-process to convert synthesis gas derived from natural gas, coal and biomass, into high quality transportation fuels. While most of the original FTS processes relied on high-temperature bulky Fe-based catalysts, the attention today has shifted toward low-temperature Co-based supported catalysts, which exhibit higher activity and selectiv-ity. Due to the constant turnover frequency of cobalt crystallites bigger than 6 nm, the activity of cobalt catalyst linearly depends on the number of metallic active sites located on the support. In turn, the number of Co-metal centers is determined by the Co particle size (i.e. cobalt dispersions), the Co loading, and the Co reduction degree. Understanding the role of these parameters and controlling such parameters during the synthesis rep-resent one of the most significant challenge in view of the development of highly active catalysts to be used within intensified FTS reactors. The synthesis of highly active catalysts has been recently reported by both academic and industrial research groups. With respect to conventional supported FTS catalysts, which are prepared by incipient wetness impregnation, highly active catalysts have been obtained either by adding PGM as promoters or by adopting new synthesis routes, such as the organic matrix combustion, OM. PGM have been found able to favor cobalt reduction, thus increasing the fraction of cobalt which takes part to the reaction. OM, which consists in the addition of an organic material to the precursors-containing solution and in the combus-tion/decomposition of such compound during a fast calcination step, has been found effective in the synthesis of small and stable (with respect to sintering) Co-crystallites, at least in the case of SiO2 supported catalysts. How-ever, small crystallites are known to be much more resilient to reduction then bigger Co-aggregates. In this work, we investigated for the first time the synergies between the OM method, using urea as fuel, and the adoption of PGM, platinum in particular, as reduction promoter.