Title : Fischer-Tropsch synthesis catalyzed by small TiO2 supported cobalt nanoparticles prepared by sodium borohydride reduction
Fischer-Tropsch Synthesis (FTS) is considered a key process of the XTL technologies (biomass-to-liquid, BTL, gas-to-liquid, GTL, and solid-to-liquid, STL) since through this catalytic reaction, syngas (a mixture of H2 and CO) can be transformed into clean fuels. One of the main challenges in Fischer-Tropsch is the design of highly active catalysts and for this purpose, the particle size of the active phase is probably one of the most relevant parameters for the optimization of the catalyst productivity.
In the present work, the synthesis of well-defined small cobalt nanoparticles and its catalytic evaluation in the Fischer-Topsch synthesis is described. Cobalt nanoparticles in the range of 1.7–7 nm were synthesized in water using sodium borohydride as reducing agent and subsequently immobilized on TiO2. Both colloidal and TiO2 supported NPs were characterized by TEM, XRD, HRTEM, XPS, TGA, ICP techniques and their catalytic performance of the supported catalysts evaluated in the Fischer–Tropsch synthesis. As a general trend, an increase in activity and TOF was observed when the particle size decreased. These results were rationalized by the higher reducibility of the catalysts bearing the smaller nanoparticles. The unconventional stability of these relatively small CoNPs in FTS was attributed to the promoting effect of boron on the stability of the cobalt nanocrystals.