Fingerprinting Bio-Oils from Lignocellulose and Comparison with Fossil Fuels

摘要

Positive and negative electrospray ionization-mass spectrometry, gas chromatography—mass spectrometry and Fourier transform infrared spectroscopy were used as complementary "fingerprinting" techniques for an initial evaluation of bio-oils from lignocellulose with different origins and degrees of upgrading and also for a comparison with petroleum based fuels. The tabulated spectra and chromatograms were interpreted using principal component analysis (PCA). The samples were crude fast pyrolysis oils from different wood feedstock, bio-oils made by liquefaction of lignin (lignin-to-liquid, LtL), hydrodeoxygenated (HDO) and more extensively hydrotreated (HT) fast pyrolysis oils and some petroleum based fuels. The major trend is that the crude pyrolysis oils from different laboratories and feedstock are relatively similar in composition, and different from the LtL, HDO and HT oils and the petroleum based fuels. However, pyrolysis oils made of mixtures of spruce, bark and needles are particularly influenced by the presence of needles, the latter gives relatively more low-molecular weight compounds. The different LtL oils are relatively similar in composition and similar to fast pyrolysis oils stabilized by moderate hydrodeoxygenation, although there are two groups of LtL oils depending on whether ethanol or water was used as a reaction medium. Significant upgrading of the crude pyrolysis oils is required to reach fuel quality. Also, the LtL and HDO oils require further upgrading. It is recommended that further fuel specific analyses are carried out after further upgrading and subsequent fractionation of the upgraded bio-oils into for example gasoline and diesel fractions.