Structural changes of chars produced from fast pyrolysis of lignin at 100–300 °C

A Review on Lignin Liquefaction: Advanced Characterization of Structure and Microkinetic Modeling

“…205,206,258,259 In literature, the terms "coke" or "soot", in contrast to "char", more typically describe downstream gas-phase formation/deposition of solid carbonaceous products. 260 Broadly, it has been shown that lower temperatures tend to yield higher amounts of char, [201][202][203]205,261 while lower pressure 30,42,207 and vapor residence time tend to yield lower amounts of char. 38,210,212 Higher pressure and correspondingly longer vapor residence time results in reduced mass transfer and an increase in secondary intraparticle charforming reactions.…”

“…265 It has been broadly shown that low molecular-weight (THF-soluble) portion of lignin undergoes pyrolytic decomposition reactions into volatiles and polymerization reactions into high molecular weight products (that are THF insoluble). 261 The main reactions happening during repolymerization are aldol condensation, rearrangement reactions, demethoxylation, hydrogenation, and hydrodeoxygenation (Table 8) and are responsible for further increasing the molecular weight of intermediate products via overall increase in the average degree of polymerization of these products. In the coal pyrolysis CPD model, 65 a simple one-step Arrhenius rate expression is used to describe cross-linking, accounting for the reattachment of intermediate molecules (liquid) to the infinite char matrix.…”

“… ,,, In literature, the terms “coke” or “soot”, in contrast to “char”, more typically describe downstream gas-phase formation/deposition of solid carbonaceous products . Broadly, it has been shown that lower temperatures tend to yield higher amounts of char, − ,, while lower pressure ,, and vapor residence time tend to yield lower amounts of char. ,, Higher pressure and correspondingly longer vapor residence time results in reduced mass transfer and an increase in secondary intraparticle char-forming reactions . Bai et al emphasize the importance of reoligomerization on char formation, especially at temperatures less than 500 °C, where the extent of condensation reactions exceeds that of secondary C–C cracking reactions .…”

“…The self-condensation capacity of lignin is typically accelerated in acid environments . It has been broadly shown that low molecular-weight (THF-soluble) portion of lignin undergoes pyrolytic decomposition reactions into volatiles and polymerization reactions into high molecular weight products (that are THF insoluble) . The main reactions happening during repolymerization are aldol condensation, rearrangement reactions, demethoxylation, hydrogenation, and hydrodeoxygenation (Table ) and are responsible for further increasing the molecular weight of intermediate products via overall increase in the average degree of polymerization of these products.…”

A Review on Biomass Gasification: Effect of Main Parameters on Char Generation and Reaction

“…Chua et al 106 investigated the interactions between low-and highmolecular-weight portions of lignin during fast pyrolysis at 100−300 °C, indicating that the interactions made char structures more condensed due to the polymerization reactions of oxygenated functional groups and aromatic structures with fused 2−5 rings. Chua et al 107 further found that the lowmolecular-weight portion was largely decomposed into volatiles and the high-molecular-weight portion intended to initiate polymerization reactions. Besides, high temperature (>1000 °C) is also used to study the intrinsic gasification kinetics of biomass char with CO 2 , steam, or their mixtures.…”