Studies On Cobalt Supported On The Carbon Titania Composite Materials For Application In Fischer-tropsch Synthesis

Fischer-Tropsch synthesis （FTS） is an important technological process forindirectly producing liquid fuels and chemicals by coal, natural gas and biomass.Catalyst support is one of the significant parameters affecting the performance ofcatalysts in FTS. Many supports such as SiO₂, Al₂O₃, TiO₂and C have beenextensively studied for supported Co catalysts for years. Titania itself has differentcrystalline phases such as anatase, brookite and rutile phase. Differences in crystallinephases may result in changes in physical and chemical properties of titania. Thus,different crystalline phase compositions of titania could play an important role on thecatalytic performance of titania supported Co catalysts during CO hydrogenation aswell. The Co/TiO₂catalyst has strong metal support interaction （SMSI） whichsignificantly affects the cobalt dispersion and reduction of the catalyst. Cobaltnanoparticles have been covered by a few atomic layers thick TiO_x after reductiontreatment of a Co/TiO₂, leading to the loss in FTS catalytic activity. Novel carbonmaterials provide new possibilities to tune the metal–support interactions. Theordered porous channels in mesoporous carbons may also exert a confinement effect,resulting in unique catalytic properties. Different functional groups（e.g., carboxylicacid groups） can also be introduced onto carbon surfaces, which are useful forimmobilization of catalytically active sites or cause additional catalytic functions. Asa result, carbon-titania composite and ordered mesoporous carbon will be promisingFT catalyst supports.In this work, carbon-titania composite has been synthesized by hydrothermaltreatment. Ordered mesoporous carbon has been synthesized using SBA-16as a hardtemplate. The catalyst activity for FTS was measured in a fixed bed reactor. Thechemical and structure properties of the support significant affect the catalytic activityand product selectivity of Co catalysts which has been discussed in detail.1. The catalytic performance of carbon-titania composite supported cobalt catalystshowed a high CO coversion and selectivity to C₅₊. Because different functionalgroups （e.g., carboxylic acid groups） onto carbon surfaces, are useful forimmobilization of catalytically active sites.2. Titania was calcined at450℃,550℃, and650℃at N2atmosphere respectively.The titania （calcined at450℃） supported cobalt catalyst showed high activitytoward CO hydrogenation. The occurrence of more rutile decrease the number of cbalt active sites on the surface of the catalyst, resulting in the decrease inFTS activity.3. Compared to active carbon supported cobalt catalyst, ordered mesoporouscarbon supported cobalt catalyst showed lower selectivity toward CH4.Interaction between the ordered mesoporous carbon and the Co precursor isweaker relatively, which can promote the reduction of Co precursor. As a result,the cobalt particles size get bigger, which can produce less CH4.