Torrefaction is a thermal pretreatment used to improve the physicochemical properties of lignocellulosic biomass prior to its thermochemical conversion. In this study, aspen wood imbued with a hydrophilic ionic liquid (1-ethyl-3-methyl imidazolium trifluoromethanesulfonate) was torrefied, and the properties of the solid product were compared to those from conventional dry torrefaction. The solid products were characterized using X-ray photoelectron spectroscopy X (XPS), photoelectron energy loss spectroscopy (ESCALOSS), and X-ray excited Auger electron spectroscopy X (XAES) in order to study the biomass surface modifications due to ionic-liquid torrefaction in comparison to dry torrefaction. The results obtained show that ionic liquids led to lignin degradation while dry torrefaction mostly affected the carbon-rich extractives. Lignin degradation was monitored using ESCALOSS and XAES techniques, which unveiled reduction in sp 2 hybridized carbon forms. Finally, ionic-liquid assisted torrefaction of the main biomass components, i.e., lignin, cellulose and hemicellulose, treated individually, showed a decrease in their O/C ratio in line with improved hydrophobicity and robustness against moisture uptake by the torrefied products. The diversity of trends revealed by our surface analysis study during the torrefaction of bare or ionic-liquid-impregnated wood, especially by means of ESCALOSS and XAES, requires the pursuit of research in order to describe more in-depth the physicochemical processes involved during torrefaction.La torr efaction est un proc ed e de pr etraitement servant à am eliorer les propri et es physicochimiques de la biomasse lignocellulosique pr ec edant sa conversion thermochimique. Dans cette etude, des echantillons de bois du type peuplier faux-tremble ont et e torr efi es selon deux modes : par torr efaction sèche conventionnelle et par impr egnation avec un liquide ionique hydrophile (1-ethyl-3-m ethyl imidazolium trifluorom ethanesulfonate) suivie d'une torr efaction. Les produits solides de torr efaction ont et e caract eris es au moyen de la spectroscopie des photo electrons X, de la spectroscopie des pertes d' energie des photo electrons (ESCALOSS) et de la spectrom etrie des electrons Auger induits par rayons X (XAES) afin de d eterminer les modifications chimiques de surface induites par ces deux modes de torr efaction. Les r esultats ont montr e que la torr efaction des echantillons de bois dans un liquide ionique contribue à la d egradation de la lignine alors que la torr efaction sèche entraîne la suppression partielle des extractibles riches en carbone. La d egradation de la lignine a egalement et e suivie par ESCALOSS et XAES qui ont r ev el e une diminution de la contribution de carbones hybrid es sp 2 . Enfin, l'utilisation de liquide ionique pour la torr efaction des principaux composants de bois (h emicellulose, cellulose et lignine), pris individuellement, a montr e qu'il y a une diminution du rapport O/C sugg erant que les produits solides torr efi es dans les liquides ionique...

The treated specimens were subjected to moisture adsorption, water absorption, swelling, and mechanical properties testing. The results revealed a notable decrease in ultimate moisture content and water uptake of the samples, provided they were impregnated with a hydrophobic ionic liquid before heat treatment at temperatures less than 200 8C. However, the mechanical properties testing showed that the elastic and rupture moduli of specimens decreased with increasing treatment temperature and time irrespective of using ionic liquids. However, the impregnated samples suffered in general increased breakability which was ascribed to partial solubilization of wood components in the ionic liquid.