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Pyrolysis-assisted catalytic hydrogenolysis of lignin at temperatures greater than 250 °C includes pyrolytic degradation prior to catalytic conversion. This study investigated the reactivities of various intermediate products from lignin pyrolysis using Pd/C and H 2 in anisole at 300 and 350 °C. Saturated alkyl side chains (methyl, ethyl, and propyl) were very stable, whereas side chains containing functional groups were hydrogenated and/or fragmented into saturated alkyls or unsubstituted H-, presumably by efficient adsorption onto the polar Pd surface. Specifically, unsaturated C C bonds were hydrogenated to saturated alkyls. Conjugated α-ketone changed to -CH 2 -, while conjugated aldehydes underwent deformylation through α-scission along with the above deoxydation. Deformylation also proceeded for side chains bearing OH groups. Lignin pyrolysis intermediates containing conjugated C C and C O groups had particularly high affinity for Pd/C, allowing successive transformations (e.g., coniferyl alcohol → dihydroconiferyl alcohol → ethyl guaiacol) before desorption. Therefore, the composition of side-chain alkyls of monomers, including unsubstituted ones, depends on the chemical composition of intermediates produced by pyrolysis. [Display omitted] • Pyrolysis followed by catalytic hydrogenolysis explains the composition of final product. • Pathways of guaiacol/alkyl guaiacols from lignin over Pd/C in anisole are clarified. • Saturated alkyls (methyl, ethyl, and propyl) are quite stable and final products. • Conjugated C C and C O groups are reactive, but unconjugated C O is stable. • Deformylation of alcohols and aldehydes occurs, generating reactive hydrogen in situ. [ABSTRACT FROM AUTHOR]

The fast pyrolysis of cellulose produces levoglucosan (LG), but secondary pyrolysis reactions tend to reduce the yield. The present study assessed the fast pyrolysis of cellulose by infrared (IR) heating under nitrogen flow. Because the nitrogen was not efficiently heated, gaseous LG was immediately cooled, resulting in a maximum yield of 52.7% under optimized conditions. Slow nitrogen flow and a high IR power level provided a greater gas yield by raising the temperature of the cellulose, and the formation of CO could be used as an indicator of the gasification of LG. Glycolaldehyde (GA) was the major byproduct, and the GA yield remained relatively constant under all conditions. Accordingly, GA was not a secondary product from the LG but was likely produced from the reducing ends of cellulose and other intermediate carbohydrates. The pyrolysis of cellulose proceeded within a narrow region of carbonized material that absorbed IR radiation more efficiently. The bulk of each cellulose sample could be decomposed in spite of this heterogeneous process by maintaining fast pyrolysis conditions for a sufficient length of time. This technique is a superior approach to LG production compared with other fast pyrolysis methods based on heat conduction. [ABSTRACT FROM AUTHOR]