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

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