Carbon nanotube-supported catalysts prepared by a modified photo-Fenton process for Fischer–Tropsch synthesis

Abstract

We demonstrate the use of a green catalyst precursor and oxidant in a modified photo-Fenton process for synthesis of efficient Fischer–Tropsch catalysts. The process yields small, stable, and well-dispersed catalyst nanoparticles (Fe or Co) on carbon nanotubes (CNTs) that do not require calcination due to the absence of foreign components (nitrate, chloride, or acetate) that must be removed during postsynthesis treatment. The synthesized catalysts were characterized by X-ray diffraction (XRD), N2 physisorption, H2 temperature-programmed reduction (H2 TPR), Raman spectroscopy, transmission electron microscopy (TEM), and inductively coupled plasma (ICP) spectroscopy. Results showed high catalyst dispersion and smaller catalyst particles with narrow particle-size distributions in comparison to catalysts synthesized by incipient wetness impregnation (IWI). Performance of CNT-supported catalysts (CO conversion, C5+ selectivity, and catalyst lifetime) prepared by the photo-Fenton process was evaluated during Fischer–Tropsch synthesis (FTS) and compared with that of CNT- and SiO2-supported catalysts synthesized via IWI. In general, a CNT-based Fe or Co catalyst, prepared by the photo-Fenton process, shows a higher performance at a lower FTS reaction temperature (200 °C for Co and 250 °C for Fe) and a decreased potential for catalyst sintering in comparison with that of conventional catalysts (synthesized via IWI). In particular, a Co catalyst obtained from the photo-Fenton process shows high CO conversion (∼80%) and outstanding selectivity for liquid hydrocarbons (C5+; ∼70%). The process demonstrates a new synthesis route for exploiting outstanding material properties of CNTs in catalysis.