Study on Selective Preparation of Phenolic Products from Lignin over Ru–Ni Bimetallic Catalysts Supported on Modified HY Zeolite

Abstract

The catalytic depolymerization of organic solvent lignin with the prepared catalyst 2.5Ru–10Ni/Al-HY was investigated in a high-pressure reactor. Effects of different catalysts, temperature, time, recyclability for catalyst, and solvents on the catalytic performance were explored. The optimal reaction conditions were reaction time 5 h and temperature 280 °C in ethanol solvent. As a result, the highest yield of phenolic monomers was 20.2 wt %, the yield of solid residue was only 4.8 wt %, and the gas products were CH4, C2H6, and CO mainly. With the increase of cycle times, the catalyst had no obvious deactivation, indicating a unique cycle stability. Through NMR characterization of lignin and depolymerization products, it was found that the signals of the original structures (A, B, and C) in lignin disappeared after reaction. According to the analysis of the reaction path, the depolymerization of lignin mainly included the depolymerization of lignin into reaction intermediates and the formation of phenolic compounds by breaking chemical bonds. This research showed a method for preparing phenolic products by the molecular sieve catalyzed depolymerization of lignin.