New hybrid CNT–alumina supports for Co-based Fischer–Tropsch catalysts

• CNT–alumina surface was functionalized by oxidation in H2O2.
• CNT on alumina surface promotes Co0 formation in catalyst.
• Fischer-Tropsch synthesis.
• Composites CNT-alumina is promising support for Co-catalysts.

Carbon nanotubes–alumina (CNT-Al2O3) composite was synthesized by catalytic pyrolysis of methane over Co/Al2O3 particles. Surface of the composite was further modified by oxygen-containing groups through oxidation in H2O2 solution. Resulted materials were investigated by nitrogen adsorption, scanning electron microscopy, thermal analysis and X-ray photoelectron spectroscopy. Catalysts (based on non-oxidized and oxidized composites, CNTs and alumina) obtained by Co impregnation were characterized by temperature-programmed reduction and transmission electron microscopy. As a comparative study, Co-catalysts for Fischer-Tropsch synthesis were made under ambient pressure and between 190 and 220 °C. It was observed that activity and selectivity of the catalysts are dependent on the nature of the supports. Particle size distribution of Co was found to be dependent on the structure of the support and chemical composition of the surface. CNT-Al2O3 demonstrated the highest C5 +-fraction yield while the yield decreased in a range of CNT-Al2O3 > oxidized CNTs > Al2O3 > CNTs > oxidized CNT-Al2O3.

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