Development of Rare-Earth Promoted Cobalt-Based Fischer-Tropsch Synthesis Catalysts with High Activity and Selectivity

Development of Rare-Earth Promoted Cobalt-Based Fischer-Tropsch Synthesis Catalysts with High Activity and Selectivity

Leilei He,†  Maohong Fan†µ*                                                                                             

†Department of Chemical and Petroleum Engineering, University of Wyoming, Laramie, Wyoming 82071

µSchool of Energy Resources, University of Wyoming, Laramie, Wyoming 82071

The objective of this research is to find an optimal ratio of rare earth elements (RE), lanthanum (La) and cerium (Ce), as promoters of Co-based Fischer-Tropsch synthesis (FTS) to achieve maximal diesel yield.  Synthesized rare-earth promoted catalysts were characterized with Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), X-ray diffraction (XRD) and hydrogen temperature programmed reduction (H₂-TPR). The effects of La/Ce molar ratio on the FTS performance of silica gel supported cobalt based catalysts were investigated in a fixed bed reactor at the temperature of 220 and 240 °C. The evaluation tests show that the catalysts promoted by composited rare-earth (CRE) with appropriate molar ratio La to Co have better FTS performance than unpromoted and individual rare-earth (IRE) promoted catalysts. The results show that the CRE promoted FTS catalysts are promising. The CO conversion is increased significantly and the selectivity of methane and C₂-C₄ is decreased while the selectivity of long chain hydrocarbons is greatly increased (C₅⁺ increased from 70.36% to 80.25% at 220 °C and from 69.94 % to 78.02 % at 240 °C, respectively). Among all CRE modified catalysts, based on the result of distribution of C₁₂-C₁₈ (weight % of hydrocarbons), Co-1La2Ce/S.G (n RE: n Co = 0.1 and n La: n Ce = 1: 2) is proven as a highly efficient catalyst for production of diesel rich synthetic oil from coal-derived syngas.