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

Abstract

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.

Cobalt catalysts on carbon-based materials for Fischer-Tropsch synthesis: a review

“…This, not only improved catalysts activity, but also increased catalyst resistance to deactivation. In a recent study, Hong et al [153] improved the reducibility and stability of Co/TiO2 catalyst by tuning MSI via carbon nitride coating. In addition, the presence of a carbon nitride layer on the TiO2 surface inhibited the encapsulation of Co 0 particle by the TiO2 support during FTS [153].…”

“…In a recent study, Hong et al [153] improved the reducibility and stability of Co/TiO2 catalyst by tuning MSI via carbon nitride coating. In addition, the presence of a carbon nitride layer on the TiO2 surface inhibited the encapsulation of Co 0 particle by the TiO2 support during FTS [153]. The impact of catalyst pretreatment on deactivation in FTS was also evaluated by Aluha et al [79] using plasma synthesized Co/C catalysts.…”

Direct observation of the evolving metal–support interaction of individual cobalt nanoparticles at the titania and silica interface

“…14 In the most basic sense, when CoNPs interact weakly with the support surface, migration occurs, leading to aggregation and a lowering of the cobalt dispersion and apparent reaction activity as the number of surface active sites decreases. 15,16 Alternatively when the interaction between CoNPs and the support is intimate or strong they have been observed to become encapsulated by a TiO x (x < 2) overlayer ($few atomic layers thick) particularly aer reduction. 9,[16][17][18] The encapsulation by TiO x actually was also reported in other TiO 2 supported metal NPs such as Au, Pt and Rh.…”

“…15,16 Alternatively when the interaction between CoNPs and the support is intimate or strong they have been observed to become encapsulated by a TiO x (x < 2) overlayer ($few atomic layers thick) particularly aer reduction. 9,[16][17][18] The encapsulation by TiO x actually was also reported in other TiO 2 supported metal NPs such as Au, Pt and Rh. [19][20][21][22] Interestingly it has been reported that the amorphous TiO x suboxide layer around CoNPs can be tuned and broken by sequential treatments in reducing/oxidising gases, resulting in signicantly improved catalytic activity.…”

Impact of Coordination Features of Co(II)-Glycine Complex on the Surface Sites of Co/SiO2 for Fischer–Tropsch Synthesis

“…Thus, varying Co species exist in the impregnation solution, which makes the drying and calcination process less controllable and results in the inhomogeneous Co oxide particles over the support due to the different thermal decomposition behavior and the interaction with the support of the Co species. Although the obtained catalysts have a higher catalytic activity, they usually exhibit a high deactivation rate due to the inhomogeneous Co particle size distributions, which leads to the sintering of small cobalt particles through Ostwald ripening [23][24][25][26][27]. Therefore, exploring controllable methods for the synthesis of highly dispersed Co-supported catalyst with homogenous size distribution of Co is crucial for development of high-performance FT catalysts in industry.…”