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

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-Al 2 O 3, and 1%Pt/γ-Al 2 O 3 ) 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. H 2 and CO 2 were the major reforming products together with a small amount of CO and CH 4 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 H 2 /CO/CO 2 /N 2 mixture as a model bio-oil-syngas. The effects of temperature ( T ), total pressure ( P ), contact time ( W / F ), and the CO 2 /(CO + CO 2 ) 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 + CO 2 ) conversion and higher C 5+ 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 g cat ·h·mol -1 . A total carbon (CO + CO 2 ) conversion of about 36% and a C 5+ selectivity of about 44% were obtained under typical reaction conditions: T = 300 °C, P = 1.5 MPa, and W / F = 12.5 g cat ·h·mol -1 . It was also found that the CO 2 /(CO + CO 2 ) 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.