(144b) Catalytic Depolymerization and Liquefaction of Lignin in Ionic Liquid By SO42?/ZrO2 in a Flow through System

Lignin has been considered as a promising sustainable feedstock for high value-added aromatic chemical production. Here, we proposed a novel and efficient process for alkali lignin depolymerization and liquefaction in a flow through system with pretreatment unit, reaction unit and separation unit. In pretreatment unit, lignin was dissolved in N-allyl pyridinium chloride ([Apy]Cl) and SO₄^2−/ZrO₂ was used as the catalyst in reaction unit. The effects of different reaction temperatures (150, 170, 190, 210 ℃) on the yields of carbon and monomer (on the lignin intake) were investigated, the yields of carbon and monomers appear to be minimized (17.888% and 3.278% respectively) at 150 ℃ and increased to 39.179% and 20.254% at 210 ℃ respectively. The structural evolution of the alkali lignin was intensively investigated via comparative characterization of raw and residues using FT-IR. The structures of residues were changed with temperature increased, and coke had probably been formed.The thermal stability of [Apy]Cl and regenerated [Apy]Cl were studied. According to the results, during the pretreatment process the β–O–4 linkages were partially cleaved, and in reaction process, SO₄^2−/ZrO₂ mainly cleaved the β–O–4, α–O–4，α–O–γ and C–C linkages in lignin and produced phenolic products and their derivatives. Proposed [Apy]Cl pretreatment mechanism of lignin and depolymerization liquefaction mechanism of lignin in [Apy]Cl catalyzed by SO₄^2−/ZrO₂ were speculated.