Supported metal catalysts have found numerous applications in many catalytic reactions, including Fischer-Tropsch synthesis. Metal dispersion, metal reducibility, catalytic performance and catalyst stability are usually strongly affected by the interaction of active phase and support. A strong metal support interaction has been previously reported for titania supported catalysts.In this work, a series of titania supported cobalt catalysts promoted via deposition of a layer of carbon nitride were prepared, characterized and tested in Fischer-Tropsch synthesis. The catalytic performance of freshly activated catalysts was an interplay of cobalt dispersion and reducibility. Deposition of carbon nitride on the surface of titania resulted in a noticeable enhancement of cobalt dispersion, while it hindered to some extent cobalt reducibility. The non-promoted cobalt catalysts exhibited noticeable deactivation in Fischer-Tropsch synthesis. The catalyst deactivation was due to the progressive encapsulation of cobalt active phase by TiO 2 during the reaction. A carbon nitride layer on the TiO 2 surface stabilized cobalt nanoparticles and prevented encapsulation of active sites by TiO 2 species. The stability was significantly enhanced on all titania supported cobalt catalysts promoted with carbon nitride.

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In this work, niobia supported cobalt catalysts with both high cobalt dispersion and high cobalt loading (15 wt %) were prepared through the assistance of glow discharge plasma treatment, and their catalytic performance was tested in Fischer− Tropsch synthesis (FTS). Plasma treatment on support and especially on the decomposition of the catalyst precursor leads to a noticeable enhancement of cobalt dispersion. However, in addition to the cobalt dispersion improvement, plasma assisted decomposition of the cobalt precursor also led to the formation of CoNb 2 O 5 , which was inactive in FTS; moreover, the small cobalt particles underwent severe sintering during the reaction and caused significant and contineous deactivation. Plasma treatment on nobia could modify its porosity and hydrophilicity and generate surface functional groups; these features enabled an improved cobalt-niobia interaction and better cobalt dispersion on CoN(P)-C than on CoN-C. The enhanced FTS activity and best reaction stability on the CoN(P)-C catalyst were due to the possession of a suitable cobalt particle size and moderate cobalt-niobia interaction.