Ruthenium nanoparticles encapsulated inside porous hollow carbon spheres: A novel catalyst for Fischer-Tropsch synthesis

Two novel Ru Fischer-Tropsch (FT) catalysts were made that were supported on the inside of two hollow carbon spheres that differed in terms of their shell porosity. Mesoporous Stober spheres were made and Ru deposited on the silica. The Ru/silica spheres were encapsulated with carbon deposited by CVD (toluene) or from resorcinol/formaldehyde. Removal of the silica gave Ru@HCS (d(Ru) = 5.5) and Ru@MHCS (3.2 nm) that had carbon shells (d = ca. 20 nm) with different physicochemical properties as evidenced by the TEM, nitrogen adsorption-desorption, TGA, Raman spectroscopy and XRD measurements. FT studies were performed on the two catalysts (10 bar; 190/220/250 degrees C; 2/1 ratio H-2/O-3). Classical Fischer-Tropsch data was obtained indicating that the catalysts could access the reactants and that FT products could escape from the inside of the spheres (acting as a nanoreactor). Activity data indicated diffusion control of CO/H-2 into the nanoreactor and selectivity data indicated an alpha value of 0.74-0.78 (220 degrees C). Typical product selectivity associated with small Ru particles was observed and the methane content increased with reaction temperature. No substantial Ru sintering occurred below 220 degrees C. It is thus seen that the porosity of the two hollow carbon architectures is suitable for the FT polymerization reaction. (C) 2016 Elsevier B.V. All rights reserved.