Pine (Pinus strobus) sawdust was pyrolyzed in a fluidized-bed reactor between the temperatures of 400 and 600 °C. The fixed-bed volume and residence time were optimized to maximize the liquid yield. We report the detailed physical and chemical properties of the bio-oil fraction collected during fast pyrolysis. The liquid yield was maximized at 500 °C, whereas increased gas formation occurred at 600 °C. 13C NMR of the bio-oil fractions indicated a decrease in the carbohydrate fraction and an increase in the aromatic fraction when pyrolysis temperatures were increased from 500 to 600 °C. Over the ranges of our investigation, the effects of the fixed-bed volume and residence time were negligible on the chemical composition of the bio-oil. Toluene and ethyl acetate bio-oil extracts were analyzed by gas chromatography/mass spectrometry following chemical derivatization. At increased reaction temperatures, the process favored conversion of guaiacols to catechols.

Determination of the molecular composition of biofuels is critical to process development. Because biofuels, such as pyrolysis oil, contain hundreds of compounds, quantitative determination of the mixtures is a formidable task and is often not necessary for routine development work. 13 C and 1 H nuclear magnetic resonance (NMR) offer a reasonable trade-off between functional group identification and analytical measurement effort. However, accuracy depends upon selection of chemical-shift regions, baseline compensation, and correction for incomplete longitudinal relaxation effects. We propose chemical-shift assignments and T 1 correction factors based on 13 C and 1 H NMR measurements of over 50 compounds that have been previously identified in pyrolysis oils and several plant natural products, especially terpenes. The results are intended to allow for a semiquantitative assessment of molecular composition of bio-oils on a time scale of 1-8 h to provide feedback for process development.

Bio-oil generated by the fast pyrolysis of biomass is an unstable material, undergoing chemical and physical transformations as the oil ages at room temperature. In this study, electrostatic precipitator (ESP) pine wood-derived bio-oil, which contains less water and does not undergo phase-separation upon aging, was characterized following accelerated aging. Bulk oil properties (percent water and viscosity) were found to increase in ways similar to conventional bio-oils. The unaged and aged bio-oil samples were characterized by gel permeation chromatography (GPC), solvent fractionation, solution 13C NMR, gas chromatography/mass spectrometry (GC/MS), and chip-based nanoelectrospray ionization, liquid chromatography, quadrupole time-of-flight (nanoESI-LC-Q-TOF) MS/MS. Using the formation of the silyated derivatives to extend the range of detectable compounds, GC/MS analysis was used to identify specific compounds that showed elevated reactivity, extending the understanding of reactivity characteristics beyond the known reactivity of aldehydes and some aromatics to distinguishing the reactivity of ring-conjugated aromatics and certain polyhydroxylated benzenes, specifically the 1,3-di-, 1,2,3-tri-, and 1,2,4-trihydroxy substituted compounds. To explain the enhanced reactivity of these compounds, we propose acid-catalyzed formation of quinone methides as important intermediates. Additionally, we find significant changes to the composition of mono- and disaccharides, where specific monosaccharides (arabinose, xylose, and glucose) increased in concentration with aging and high reactivity was observed for certain sugars with furano-ring mass spectral characteristics. In contrast, we also found that three anhydrosugars (levoglucosan, mannosan, and galactosan) were largely stable with respect to aging. High mass resolution nanoESI-LC/MS/MS analyses of peracetylated samples permitted the analysis and chromatographic separation of both lignin and carbohydrate-derived oil components and were used for the identification of a putative formaldehyde–trihydroxybenzene dimer. This work provides further insights into chemically specific entities and the processes responsible for bio-oil aging.

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Three lignins: Indulin AT, LignoboostTM, and Acetocell lignin, were characterized and pyrolyzed in a continuous-fed fast pyrolysis process. The physical and chemical properties of the lignins included chemical composition, heat content, ash, and water content. The distributed activation energy model (DAEM) was used to describe the pyrolysis of each lignin. Activation energy distributions of each lignin were quite different and generally covered a broad range of energies, typically found in lignins. Process yields for initial continuous-fed fast pyrolysis experiments are reported. Bio-oil yield was low, ranging from 16 to 22%. Under the fast pyrolysis conditions used, the Indulin AT and LignoboostTM lignin yielded slightly more liquid product than the Acetocell lignin. Lignin kinetic parameters and chemical composition vary considerably and fast pyrolysis processes must be specified for each type of lignin.