Catalytic cracking of Etek lignin with zirconia supported metal-oxides for alkyl and alkoxy phenols recovery

Alkyl and alkoxy phenols are desirable products from the catalytic depolymerisation of lignin. In this work, ex-situ catalytic pyrolysis of Etek lignin in presence of Na, Ce, NiCe, MgCe, Fe and FePd on ZrO₂ was studied. The largest combined yield of monomeric phenolics and alkylphenols was produced by Na/ZrO₂ catalysts. A parametric study of the most promising Na/ZrO₂ then resulted in using a catalyst:lignin ratio of 3:1 at 500 °C as the best option, enhancing at 17.5 wt% the recovery of total phenolics including 6 wt% alkyl phenols, which is equivalent to 27.8 wt% and 9.5 wt% of the starting lignin in Etek lignin waste. The study of the catalyst basicity indicates that the mild basicity of Na/ZrO₂ was mostly responsible for the enhanced mono phenols recovery. Due to formation of thermally stable Na₂CO₃ during pyrolysis, successful Na/ZrO₂ regeneration requires temperature of 900 °C or higher.