Etherification of Pine Wood and Sawdust Pyrolysis Oils for Fuel Applications

Abstract

This study investigates the etherification of pyrolysis oils derived from pinewood (PWPYO) and sawdust (SWPYO) as a strategy to reduce their high acidity and improve their compatibility with fuel blends. Three etherification procedures were evaluated using potassium carbonate and ethyl iodide (Procedure 1), and ethyl iodide or sec-butyl iodide under phase-transfer catalytic conditions (Procedures 2 and 3, respectively). The upgraded oils were characterized by potentiometric titration, FTIR spectroscopy, and GC × GC–TOF–MS to assess acidity reduction and compositional changes. Significant decreases in acid value were achieved, particularly with Procedure 1, which reduced the acid value of PWPYO from 68.83 to 0.63 mgKOH g–1 and that of SWPYO from 84.78 to 1.38 mgKOH g–1. FTIR and chromatographic analyses confirmed the transformation of phenolic hydroxyl groups into ether functionalities. Medium-scale experiments using Procedure 1 successfully reproduced the acidity reduction and ether formation observed at laboratory scale, although mixing and mass-transfer limitations affected process efficiency. Solubility tests revealed limited miscibility with hydrocarbon fuels but stable blends with short-chain alcohols. Etherification proved to be an effective pretreatment to mitigate acidity in phenol-rich pyrolysis oils, although further optimization is required to improve fuel compatibility and scale-up performance.