Cobalt supported on mesoporous silicas for the Fischer-Tropsch synthesis

Abstract: This thesis deals with the study of several catalysts for the Fischer-Tropsch synthesis in the Biomass-To-Liquid process. In this work two groups of catalysts were tested. On the one hand, two series of catalysts with cobalt loadings of 6 and 12 wt% over SiO2 and some of them containing 5wt% of TiO2 were tested. One the other hand, other two series of mesoporous short channel SBA-15, all of them with cobalt loadings of 12wt% and some with 5wt% of titania. The first series was supported on SBA-15 DeWitte and the second one on SBA-15 Martinez. On the one hand, the influence of water addition to the feed, titania content and cobalt loading to the catalyst and was studied, as well as the consequences of a GHSV. The FT reaction was carried out along 5 periods of 24 hours each, in which conditions such as feed and water content were modified, enabling the study of these parameters. It was found that water provokes an increase of the CO conversion and has a positive kinetic effect on the rate to hydrocarbons. However, this fact reaction is followed by a quick deactivation, enhanced by high water partial pressures. Most of that deactivation is irreversible since it is not completely recovered after water removal. On the other hand, differences between the supports were studied. Some SBA-15 supported catalysts show CO diffusion limitations at longer channel lengths than what applies for conventional 3D porous supports. Titania grafting increases the rate to hydrocarbons, showing positive results for FT catalysts development.