Effect of FSP-inserted cobalt in titania-zirconia support on Fischer-Tropsch synthesis over cobalt catalyst

Abstract

In this research, the Fischer-Tropsch synthesis (FTS) over cobalt catalysts supported on binary (Co-TiO2 and Co-ZrO2) and tertiary (Co-TiO2-ZrO2) support were studied with various amount of inserted-cobalt and TiO2-to-ZrO2 wieght ratio in range of 5 to 30% and 4:1 to 1:4, respectively. The mixed support was prepared by flame spray pyrolysis (FSP). Finally, the 20 wt. % Co was impregnated on these supports. The catalysts were characterized by several technique such as X-ray diffraction (XRD), N2-physisorption, Temperature programmed reduction (H2-TPR) and H2-chemisorption. The catalytic properties were tested by FTS. The support preparation by FSP using mixture liquid precursors can produce the mixture of metallic phases such as cobalt titanate (CoTiO3), titanium zirconate (Ti2ZrO6) and zirconium titanate (ZrTiO4). The reduction degree of Co catalysts was decreased with increasing amount of inserted-Co. Because of the addition of inserted-Co induced to strong metal-support interaction in catalysts. Cobalt metallic sites of catalysts decreased due to the increasing of metal-support interaction, except the catalyst supported on zirconia. The addition of 5% inserted-cobalt to TiO2 and ZrO2 support improved heavy hydrocarbon selectivity and rate of reaction, respectively. Role of small inserted-cobalt in modified TiO2 support disturbed the dispersion of impregnated-cobalt led to large cobalt oxide size, reflected to hydrocarbon-chain propagation. On the other hand, cobalt in modified ZrO2 support dispersed on the surface of catalyst that difference from TiO2 because of weak metal-support interaction. Increasing of cobalt dispersion enhanced rate of reaction. The addition of small inserted-cobalt in mixed TiO2-ZrO2 support with 4:1 weight ratio exhibited the best catalytic activities than other mixed support catalysts.

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