Strategy for Extending the Stability of Bio-oil-Derived Phenolic Oligomers by Mild Hydrotreatment with Ionic-Liquid-Stabilized Nanoparticles.

The development of catalytic transformations and processes is essential to utilize bio-oil and lignin derivatives. Metal nanoparticles (M-NPs) stabilized in ionic liquids (ILs) are promising for the catalytic hydrotreatment of bio-oil because the properties of the catalyst system can be customized by combining the appropriate IL and metal nanoparticles. Herein, we demonstrate an experimental approach to stabilize lignin-derived phenolics isolated from bio-oil with ruthenium NPs stabilized by an ionic copolymer in 1-ethyl-3-methylimidazolium acetate ([C2 C1 Im][OAc]). The mild hydrotreatment of phenolic oligomers (POs) was performed with the synthesized M-NP catalyst at 100 °C for 6 h. Hydrotreatment of the POs resulted in enhanced thermal stability of the POs by as much as a factor of three, as determined by the aging index and by reducing reactive functionalities, which was also confirmed by NMR spectroscopy and GC analysis. The results support our hypothesis that M-NPs stabilized in ILs can effectively stabilize POs under mild conditions, which could be applicable to any lignin-derived phenolic.