Flame Spray Pyrolysis Synthesized Co and Co/Ru Based Catalysts for the Thermochemical GTL : Fischer Tropsch Process

The Gas-to-Liquid Fischer-Tropsch process is an industrial process that converts syngas, a mixture of H2/CO characterized by a molar ratio equal to 2, into hydrocarbons in the range C1-C100 [1]. A monometallic 10%wtCo and bimetallic 10%wtCo - 0.1%wtRu based catalysts supported on silica were prepared by Flame Spray Pyrolysis (FSP), chatacterized by BET, SEM, TEM, TPR, XRD and tested at different temperature in a FT bench scale plant using a Packed Bed Reactor (PBR). FSP technique allows to obtain single or mixed metal oxides with an high surface area and high thermal stability thanks to the dispersion, vaporization and flame-decomposition (pyrolysis) of the precursors solution [2]. The solution is composed of Co(CH3COO)2·4H2O (Fluka), Si(OC2H5)4 (Fluka) dissolved in a 1/1 mixture of CH3CH2COOH (Fluka)/C8H10 (Sigma Aldrich). The synthesis of the bimetallic catalyst starts with FSP followed by the addition of an impregnation step of Ru using Ru3(CO)12 (Sigma Aldrich) as a precursor. Selectivity T(ᵒC) %CO C2+ CO2 CH4 <C7 >C7 Co 245 255 260 23.4 60.7 98.8 20.4 54.0 82.0 1 1 6 12 10 11 10 10 10 77 79 73 Co-Ru 225 230 245 55.8 73.2 94.5 50.2 65.1 77.5 1 2 6 9 9 12 18 17 14 72 72 68 The TPR profiles (Figure 1) of both samples show two different peaks; the first one at T= 320-360°C is related to the transition Co3O4CoO and the second at T= 700-800°C is attributable to the reduction step CoOCo [3]; Figure 1 also highlight that the insertion of Ru decrease both peaks temperatures of about 20°C. The samples have been reduced in situ at T= 400°C and then tested at different temperature in the range T= 225-260°C at P= 2.0 MPa, H2/CO= 2 with sl/h/gcat= 3.0. The catalytic results summarized in Table 1 show that the bimetallic catalyst is more active in therms of CO conversion and C2+yeld if compared with the monometallic one, nevertheless the unpromoted catalyst shows selectivity to >C7 higher respect to the Ru-doped catalyst. Finally, the selectivity toward the reaction products is not largely influenced in the range of temperature tested. Reference [1] Q. Zhang, J. Kang, Wang Y, Chem. Cat. Chem. 2010, 2, 1030. [2] H. Jang, C. Seong, Y. Suh, H. Kim, C. Lee C, Sci. and Tech. 2004, 38, 1027. [3] C. Pirola, C.L. Bianchi, A. Di Michele, S. Vitali, V. Ragaini, Cat. Comm. 2009, 10, 823.