Analysis through thermogravimetric analyses of the impact of torrefaction processes performed under a non-oxidative atmosphere on hydrolysis lignin samples

Abstract Hydrolysis lignin samples were torrefied in a fixed bed reactor under a nitrogen flow, under four different isothermal temperatures (225, 250, 275 or 300 °C) and during 30 or 60 min. The impact of such torrefaction conditions on the hydrolysis lignin samples was analyzed through thermogravimetric analyses performed under non-oxidative or oxidative atmospheres and under a heating rate of 5 °C/min. The thermogravimetric profile and the reactivity of the raw and torrefied samples were compared. The optimal values of the kinetic parameters were determined using the EIPR model, first determining the number of constituents to be considered, then their proportions applying Van Soest’s protocol to the raw material and adjusting them for the torrefied samples. These values of the kinetic parameters were validated through observations of the experimental and simulated mass and mass rate curves and computations of the maximal difference between these curves. The values of the kinetic parameters did not significantly vary with the isothermal temperature or with the torrefaction residence time.