Coconut Shell Pyrolysis Oil: A Dual-Pathway Approach to Antioxidants and Renewable Aromatic Biofuels

Abstract

This study investigates the dual potential of coconut shell pyrolysis oil for both antioxidant and aryl biomass oil production, with a focus on its phenolic composition and catalytic upgrading. The pyrolysis oil, derived from coconut shells at a temperature of 550°C, is found to contain key phenolic compounds such as syringol and 4-propenylsyringol, which contribute to its valuable antioxidant properties, as demonstrated in DPPH and ABTS+ radical scavenging assays. A bulk particulate β-Mo2C hydrodeoxygenation (HDO) catalyst was successfully synthesized using a novel pelletizing-thermolysis-carburization strategy and evaluated for its catalytic performance in the upgrading of both model compounds and pyrolysis oil. The M680/20 catalyst exhibited excellent HDO activity, achieving a complete hydrodeoxygenation product yield of 100% for guaiacol and 85.7% for the pyrolysis oil. Combined experimental results and DFT theoretical calculations revealed that the methoxy group present in the phenolic compounds plays a crucial role in enhancing both the antioxidant activity and the HDO efficiency of the pyrolysis oil. Additionally, the catalyst exhibits alkyl transfer activity alongside its HDO performance. The alkyl groups in the aromatic biomass oil primarily originate from methyl transfer reactions in the methoxy groups and hydrogenation reduction of the propenyl side chains. This study offers a detailed understanding of the chemical characteristics of coconut shell pyrolysis oil and its catalytic upgrading, providing valuable insights into the optimization of pyrolysis oil for antioxidant applications and biofuel production.

Keywords: Coconut Shell, Pyrolysis oil, Antioxidants, hydrodeoxygenation, Aromatic Bio-oils