Depolymerization of Technical Lignins in Supercritical Ethanol: Effects of Lignin Structure and Catalyst - Archive ouverte HAL Access content directly
Journal Articles Energy & Fuels Year : 2021

Depolymerization of Technical Lignins in Supercritical Ethanol: Effects of Lignin Structure and Catalyst

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Abstract

Three complementary Kraft lignins and a Soda lignin were characterized by NMR (31P, 13C, and HSQC) and GPC. Their theoretical yield in monomers (TMY) assuming a complete cleavage of all β-O-4 linkages was calculated based on these analyses. The most recalcitrant Kraft lignin according to the TMY criteria was depolymerized in supercritical ethanol (250 °C, H2, 110 bar) with Pt/C, Ni/C, and Ru/C catalysts. All catalysts present an important effect on monomers (analyzed by GC/MS), oligomers (by UV fluorescence), and char yields. They promote cracking reactions and the stabilization of the broken bonds by H-transfers. The hydrogenation of the side chains of the monomers is also promoted to notably produce propyl-guaiacol. We show that an oligomeric pool prevails for all catalysts. Then, the effect of lignin structure on the depolymerization mechanism was studied by comparing the 4 lignins with the least precious catalyst (Ni/C). The S/G ratio of monomers is well related to the S/G ratio of lignins. Under our conditions, the β-O-4 content and the TMY do not control the yields in monomers. They are not relevant indicators for the depolymerization of these recalcitrant technical lignins. Future work should focus on novel catalysts and processes to improve the selective conversion of C–C bonds if monomers remain the targeted product.
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Dates and versions

hal-03469055 , version 1 (07-12-2021)

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Cite

Erika Bartolomei, Yann Le Brech, Roger Gadiou, Frédérique Bertaud, Sebastien Leclerc, et al.. Depolymerization of Technical Lignins in Supercritical Ethanol: Effects of Lignin Structure and Catalyst. Energy & Fuels, 2021, 35 (21), pp.17769-17783. ⟨10.1021/acs.energyfuels.1c02704⟩. ⟨hal-03469055⟩
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