Comprehensive study of nanostructured supports with high surface area for Fischer-Tropsch synthesis

Abstract

An extensive study of Fischer-Tropsch synthesis on nanostructure supports with high surface area such as nanostructure γ-alumina, single wall carbon nanotubes (SWNTs), and the hybrid of SWNTs/nanostructure γ-alumina has been investigated. The nanostructure γ-alumina was promoted with lanthanum to obtain better performance of catalyst and 15 wt% cobalt loading was the basis of our investigation. Fischer-Tropsch synthesis was performed in a fixed bed reactor under different reaction conditions (220–240 °C, 15–25 bar, H2/CO ratio of 2, GHSV of 900–1400) in order to study the effects of temperature, pressure and gas hourly space velocity (GHSV) changes on hydrocarbon selectivity and catalyst activity. The catalysts were extensively characterized by different methods including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), inductively coupled plasma (ICP), hydrogen (H2) chemisorption and temperature-programmed reduction (TPR). The results showed that the yield of hybrid supported catalyst (55.4%) is higher than that of nanostructure γ-alumina supported catalyst (55.0%) and lower than that of SWNTs supported cobalt catalyst (71.0%). The hybrid supported catalyst showed higher reduction degree and dispersion of cobalt particles. The temperature, pressure and GHSV effects on hybrid supported catalyst were studied and results showed that higher pressure favors the chain growth and temperature increase leads to the increases in methane selectivity and CO conversion. Higher hydrocarbon selectivity and CO conversion showed positive relationship with increasing GHSV while lower hydrocarbon selectivity diminishes.