Tuning the Metal-Support Interaction and Enhancing the Stability of Titania-Supported Cobalt Fischer-Tropsch Catalysts via Carbon Nitride Coating

Supported metal catalysts have found numerous applications in many catalytic reactions, including Fischer-Tropsch (FT) synthesis. Metal dispersion, metal reducibility, catalytic performance, and catalyst stability are usually strongly affected by the interaction of the 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 the deposition of a layer of carbon nitride were prepared, characterized, and tested in FT synthesis. The catalytic performance of freshly activated catalysts was an interplay of cobalt dispersion and reducibility. The deposition of carbon nitride on the surface of titania resulted in a noticeable enhancement of cobalt dispersion, whereas it hindered cobalt reducibility to some extent. The nonpromoted cobalt catalysts exhibited a noticeable deactivation in FT synthesis. The catalyst deactivation was due to the progressive encapsulation of the cobalt active phase by TiO2 during the reaction. A carbon nitride layer on the TiO2 surface stabilized cobalt nanoparticles and prevented the encapsulation of active sites by the TiO2 species. The stability was significantly enhanced on all titania-supported cobalt catalysts promoted with carbon nitride.