Optimization of the Reaction Conditions for Catalytic Fast Pyrolysis of Pretreated Lignin over Zeolite for the Production of Phenol

Abstract

AbstractThe catalytic fast pyrolysis of lignin for the production of phenols over commercial zeolites was studied in‐depth. The results show that the production of phenols depended on several parameters, such as lignin pretreatment methods, pyrolysis temperature, zeolite structure and acidity, pyrolysis time, and feed‐to‐catalyst weight ratio. Lignin pretreatments had a significant influence on the liquid‐product distribution. Hydrogen chloride pretreatment of lignin increased the depolymerization of the lignin matrix, resulting in an increase of the liquid yield, as well as the phenol fraction. High temperature (e.g., 650 °C) and a fast heating rate (20 °C ms−1) were required to depolymerize lignin and increase the yield of liquid products, and large‐pore‐size zeolites (e.g., FAU) with Si/Al of approximately 15 favored the formation of phenols. A long pyrolysis time (20 s) was also beneficial for phenol to desorb from the catalyst. The medium feed‐to‐catalyst weight ratio of approximately 1:1 prevented further conversion of phenols to deoxygenated products such as aromatic hydrocarbons (benzene, toluene, and xylene).