Noncatalyzed Liquefaction of Celluloses in Hydrothermal Conditions: Influence of Reactant Physicochemical Characteristics and Modeling Studies

Abstract

This paper reports a fundamental study on the hydrothermal liquefaction of cellulose into light products. First it aimed at comparing the noncatalyzed intrinsic reactivity of model celluloses such as Avicel and Sigmacell with various physicochemical characteristics (degree of polymerization, crystallinity, particle size, morphology). This information is of importance to dissociate the chemophysical phenomenon from the catalytic one in the case of catalytic liquefaction to better evaluate the added-value of a catalyst. Under various conditions (3–70 g·L–1, 175–200 °C, 0–120 h) despite a higher degree of polymerization Sigmacell reacted faster compared to Avicel and formed a higher amount of light products. The reactivity was preferentially influenced by the initial morphology of cellulose. The liquefaction in the absence of catalyst was never complete and led to insoluble hydrochar formation (20–30 wt %). Then a model was built based of three reaction pathways with kinetics and thermodynamic investigation....