A sinter resistant Co Fischer-Tropsch catalyst promoted with Ru and supported on titania encapsulated by mesoporous silica

One of the pathways responsible for the deactivation of Fischer-Tropsch catalysts is the loss of active metal surface area due to nanoparticle agglomeration. To combat this effect efforts have been made to increase the interaction between the metal nanoparticles and the support using materials like silica. In this study, the supported metal particles were covered with a highly porous layer of silica to stabilize the Co nanoparticles on a titania support both during reduction and under reaction conditions. Co3O4 nanoparticles (size range: 8-12 nm) supported on titania were stabilized by coating them with a thin layer of mesoporous silica (similar to 4 nm) to make Fischer-Tropsch catalysts that are less prone to sintering (Co/TiO2@mSiO(2)). To mitigate the strong metal support interactions brought about by the titania and silica a Ru promoter was loaded together with the cobalt nanoparticles onto the titania (CoRu/TiO2@mSiO(2)). Temperature programmed XRD studies on the evolution of the Co metal nanoparticles showed that there was no significant particle size growth under reduction conditions in the temperature range from 30 to 600 degrees C. Chemisorption studies following reduction under hydrogen at 350 degrees C and 450 degrees C gave results consistent with the in situ XRD data when compared to the Co/TiO2. Fischer-Tropsch synthesis on the Co/TiO2@mSiO(2) and CoRu/TiO2@mSiO(2) catalysts encapsulated inside the mesoporous silica shell exhibited good catalytic performance without any display of significant mass transport limitations that might arise due to a silica shell coating of the active sites. For these two catalysts the Fischer-Tropsch activity increased with reduction temperature without any significant negative changes in their selectivity due to sintering, while the activity on Co/TiO2 decreased due to Co nanoparticle sintering.