Catalytic Depolymerization of Lignin in Ionic Liquid Using a Continuous Flow Fixed-Bed Reaction System

Abstract

The catalytic depolymerization of alkali lignin dissolved in a mixed solvent of ionic liquid (N-allylpyridinium chloride, [Apy]Cl) and water, with ZrO2/SO42– or Pt-ZrO2/SO42– catalyst, were performed in a continuous flow fixed-bed reaction system at low temperature (from 150 to 210 °C). The yields (carbon-based) of total products and phenolic compounds catalyzed by ZrO2/SO42–, which increased with increasing temperature, were 30.6% and 13.4% at 210 °C, respectively. Furthermore, the addition of platinum to the ZrO2/SO42– catalyst enhanced the depolymerization of alkali lignin. In the case of Pt-ZrO2/SO42–, the yields (carbon-based) of total products and phenolic compounds reached 44.9% and 18.7%, respectively, at 210 °C. Additionally, [Apy]Cl readily dissolved lignin and served as a medium for lignin depolymerization, which improved the reactivity of lignin for the use in the continuous flow system at low temperature.