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Fast pyrolysis of pinewood sawdust and two of its major components, namely lignin and cellulose was carried out using a laboratory scale induction-heating reactor. The effect of five different temperatures (500°, 550°, 600°, 650° and 700 °C) was tested on the product yield and quality. The products were characterized to evaluate the water content, elemental composition, chemical composition and energy content. The char yield decreased with temperature for all of the biomasses. The maximum liquid yield of 55.28% was achieved at 600 °C for pine sawdust, and the highest liquid yields for cellulose and lignin were obtained at 500 °C. Water content in the liquid fraction decreased as reaction temperature increased. The GC-MS revealed that the bio-oil from cellulose was rich in anhydrosugars while majority of the liquid from lignin had high phenolic contents. Analysis of the gas fraction shows that as the temperature increases the gas yield increases, which, when paired with the declining char masses, showed an increase in the biomass breakdown at higher temperatures. Liquid fraction from pine sawdust has the highest HHV with a peak at 550 °C.

The unique decomposition pathways of hydrolytic lignin (HL) dissolved in an acetone/water mixture (9:1) and dispersed by a droplet evaporation technique under nitrogen gas flow has been investigated in a conventional reactor at atmospheric condition, a temperature region of 400–550 °C, and a residence time of 0.12 s. The results validate the fact that dispersion of the lignin into the gas phase by decreasing the sample size (as well as “minimizing the char area to avoid catalytic contact” of molecular products/radicals with the surface) may open new perspectives in understanding the chemistry of the depolymerization of lignin. Using Laser Desorption Ionization-Time of Flight-Mass Spectrometry (LDI-TOF-MS) the intrinsic ion m/z = 550, as the major MS peak from fresh HL dissolved in an acetone/water mixture before pyrolysis, was detected. Surprisingly, the expected phenolic compounds after pyrolysis were in trace amounts at less than 15% conversion of lignin. Instead, oligomeric intermediate substances with low (<550 Da) and high molecular weight (>550 Da) containing lignin-substructures (trapped on quartz wool located at the end of the reactor at ∼300 °C) were detected as major products using LDI-TOF-MS. The hypothesis about a largely disputed key question on lignin pyrolysis as to whether the phenolic compounds or oligomers (dimers, trimers, etc.) are the primary products is discussed. Additionally, a focus on the free-radical mechanism of depolymerization of solid lignin by formation of free intermediate radicals from initial lignin macromolecules as well as from inherent, low molecular weight oligomer molecules is developed based on the Low Temperature Matrix Isolation (LTMI) EPR technique.

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