Catalytic behavior of Co/(Nanoβ-Zeolite) bifunctional catalysts for Fischer–Tropsch reactions

Cobalt supported on Beta zeolite catalysts were prepared by impregnation of metal salts in aqueous solution and were tested for the Fischer Tropsch reaction. The support consisted of a Beta zeolite composed by crystallites of nanometric dimensions and a SiO2/Al2O3 molar ratio of about 50. This support was impregnated with Co(NO3)2 aqueous solution using different metal loads of 7.5, 10, 15 and 20 wt% Co. These materials were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), N2 adsorption (BET), thermal programmed reduction (TPR) and FTIR of adsorbed pyridine (i.e., surface acid sites distribution). All the catalysts showed a significant catalytic activity for the F–T reaction from synthesis gas (CO + 2H2), in a continuous fixed bed reactor system. The catalysts presented a bifunctional character with a maximum of activity at a specific concentration of metal and particle size. In contrast, the selectivity patterns were strongly influenced by the support acid function, which promote the formation of isoparaffins from about 220 °C, which differ with most of conventional zeolites that show a relatively low activity for isomerization at this temperature, thus indicating an effect of the small Beta zeolite crystallites size over the catalytic activity of Co/Nanoβ-Zeolite.