Fischer–Tropsch synthesis over LaFe 1− xCo xO 3 perovskites from a simulated biosyngas feed

Abstract

The Fischer–Tropsch synthesis reaction using a simulated gas mixture, comparable to that obtained from biomass transformation (biosyngas), was studied over LaFe 1− x Co x O 3 perovskites. The perovskites were prepared using the amorphous citrate precursor method and the FTS reaction was carried out in a stainless steel fixed bed reactor at 300 °C and 1 MPa. Nitrogen adsorption was at −196 °C. Thermal-programmed reduction (TPR), X-ray diffraction (XRD), Fourier-transform IR spectroscopy (FTIR), oxygen-temperature-programmed desorption (O 2-TPD) and scanning electron microscopy (SEM) were used as characterization methods. The perovskites were found to display two crystal systems determined by XRD patterns, orthorhombic for x Co < 0.5 and rhombohedral for x Co ≥ 0.5. The LaFe 1− x Co x O 3 perovskites, with a substitution degree x Co = 0.1, 0.2 and 1.0, displayed significant intrinsic CO conversion. This activity was probably due to the formation of Co–metal segregates on the surface, as suggested by XRD patterns. The highest CO intrinsic conversion was obtained for perovskites with a substitution degree of x Co = 0.2. The LaFe 1− x Co x O 3 perovskites presented a wide distribution of liquid hydrocarbons (C 6–C 18+) and high CH 4 formation. The liquid product distribution was related to the average size of iron particles. The increase of cobalt particle size favours the formation of hydrocarbons centred in C 8–9 chain length.