Fischer-Tropsch synthesis of olefin-rich liquid hydrocarbons from biomass-derived syngas over carbon-encapsulated iron carbide/iron nanoparticles catalyst

Olefins are extensively used in the chemical industry as building blocks for manufacturing a wide range of products such as polymers, drugs, cosmetics, solvents, and detergents. Traditionally, olefins have been produced from thermal or catalytic cracking of petroleum-derived hydrocarbons, but environmental and economic concerns are urging exploration of alternative routes for their production from renewable sources. Herein, we report the synthesis of olefin-rich liquid hydrocarbons from biomass-derived syngas (biosyngas) via Fischer-Tropsch reaction by using carbon-encapsulated iron carbide/iron nanoparticles (CEICINs) catalysts. The CEICINs core-shell nanostructured catalysts typically constituted iron carbide/iron-core diameters of 6-30 nm and graphite-shell thickness of 2-5 nm, where the iron carbide/iron-core consisted of alpha-Fe, theta-Fe3C and Fe15.1C. The catalytic peiformance over CEICINs at mild reaction conditions (310 degrees C, 1000 psig, 3000 h(-1)) showed that CO and H-2 conversion was similar to 87.5% and 85%, respectively. The C5+ liquid hydrocarbon selectivity was similar to 65%, similar to 44.8% of which was olefins. The liquid product formation rate was 0.12 g/(g(cat) h) during the time-on-stream of 100 h after achieving steady state. The volume percent of the oil phase in the liquid product was similar to 60%. The higher reaction temperature led to the higher selectivity towards olefins, while the effect of biosyngas pressure was not a significant factor concerning olefin selectivity. Gas hourly space velocity (GHSV) had a negative effect on the formation of olefins due to the short-time contact of the reactant gas with the CEICINs catalyst. This work demonstrated the technical feasibility of the direct synthesis of olefin-rich liquid hydrocarbons by utilizing CEICINs catalysts from biosyngas via biomass gasification, biosyngas cleaning, and Fischer-Tropsch synthesis technology. (C) 2016 Elsevier Ltd. All rights reserved.