Production of biocrudes from biomass in a fixed-bed tubular reactor: product yields and compositions

Fixed-bed pyrolysis in a tubular reactor were conducted on three biomass samples, Euphorbia rigida, sunflower (Helianthus annuus L.) pressed bagasse and hazelnut (Corylus avellana) shells, to determine the possibility of each being a potential source of renewable fuels and chemical feedstocks. The effects of pyrolysis temperature and sweep gas (N2) flow rate on the pyrolysis yields and chemical compositions of the biocrudes obtained were investigated. The maximum biocrude yield of 45.7 wt% was obtained from sunflower pressed bagasse in N2 atmosphere at a pyrolysis temperature of 823 K and fixed heating rate of 7 K min−1. However, this biocrude yield can be compared with the biocrude of Euphorbia rigida (31.5 wt%) at optimum conditions. The biocrude yield of sunflower pressed bagasse increased by 26.4% as the final temperature was increased from 673 to 823 K whereas the biocrude yield of Euphorbia rigida increased by 30.8% more than sunflower pressed bagasse when the final temperature was increased from 673 to 823 K. The pyrolysis products were characterized by elemental analysis, high performance size exclusion chromatography (HPSEC) and 1H NMR spectroscopy, and also compared with the currently utilized transport fuels by simulated distillation. The pentane subfractions of biocrudes were analyzed for the quantification of hydrocarbons by gas chromatography. The chemical characterizations have shown that the biocrudes obtained from Euphorbia rigida, sunflower pressed bagasse and hazelnut shells were quite similar to crude oil and shale oil.