Characteristics of Bio-Oil-Syngas and Its Utilization in Fischer−Tropsch Synthesis

• Published in: Energy & fuels 2007-07, Vol.21 (4), p.2421-2432
• Main Authors: Wang, Zhao Xiang, Dong, Ting, Yuan, Li Xia, Kan, Tao, Zhu, Xi Feng, Torimoto, Youshifumi, Sadakata, Masayoshi, Li, Quan Xin
• Format: Article
• Language: English
• Subjects: Applied sciences; Biomass; Energy; Exact sciences and technology; Fuel processing. Carbochemistry and petrochemistry; Fuels; Gas processing; Natural energy
• ISSN: 0887-0624; 1520-5029
• DOI: 10.1021/ef0700275

The Fischer−Tropsch synthesis (FTS) using bio-oil-syngas has been investigated as a potential approach to obtaining clean liquid bio-fuels. Bio-oil-syngas, defined as the syngas obtained from bio-oil steam reforming, was generated via the catalytic steam reforming of homemade bio-oil. Bio-oil reforming performances including the hydrogen yield, carbon conversion, and main composition of the bio-oil-syngas have been investigated over three different catalysts (C12A7/15%Mg, 12%Ni/γ-Al2O3, and 1%Pt/γ-Al2O3) in a fixed-bed flow reactor. It was found that the most important parameters for steam reforming of the bio-oil were the temperature, the molar ratio of steam to carbon fed (S/C), and the reforming catalyst types. H2 and CO2 were the major reforming products together with a small amount of CO and CH4 in the effluent gaseous products of bio-oil steam reforming. The new catalyst C12A7/15%Mg exhibited high reforming activity under the optimum steam reforming conditions. The hydrogen yield of about 71% with a carbon conversion over 93% was obtained over the C12A7/15%Mg catalyst under reforming conditions of T = 750 °C, S/C = 6.0, and gas hourly space velocity (GHSV) = 26 000 h-1. Furthermore, FTS was performed in a fixed-bed flow reactor by using the H2/CO/CO2/N2 mixture as a model bio-oil-syngas. The effects of temperature (T), total pressure (P), contact time (W/F), and the CO2/(CO + CO2) ratio (r) on the FTS performance were investigated over the coprecipitated iron catalyst of Fe/Cu/Al/K. To obtain a higher total carbon (CO + CO2) conversion and higher C5+ selectivity, it was found that the optimum FTS conditions over the Fe/Cu/Al/K catalyst are T = 280∼300 °C, P = 1.0∼2.0 MPa, and W/F> 12.5 gcat·h·mol-1. A total carbon (CO + CO2) conversion of about 36% and a C5+ selectivity of about 44% were obtained under typical reaction conditions:  T = 300 °C, P = 1.5 MPa, and W/F= 12.5 gcat·h·mol-1. It was also found that the CO2/(CO + CO2) ratio of the syngas has a remarkable effect on FTS performance, and r < 0.5 is more suitable for FTS in our investigated range. The characteristics of steam reforming catalysts and the FTS catalyst were also investigated by various characterization measurements.