Non-catalyzed and Pt/γ-Al2O3-catalyzed hydrothermal cellulose dissolution–conversion: influence of the reaction parameters and analysis of the unreacted cellulose

Abstract

Hydrothermal dissolution and/or conversion of cellulose Avicel^® occurred at 190 °C under 5 MPa of H₂ in the absence of catalyst. This reaction is temperature and time dependent. A dissolution–conversion ratio of 35% was obtained after 24 h of reaction and glucose and HMF were detected as monomeric products in a global yield of less than 5%, indicating that the majority of the products are composed of soluble oligo- and polysaccharides. The unreacted cellulose was analyzed using XRD, ¹³C solid state NMR, TGA-DTA and SEM and compared to the initial cellulose. We showed that although morphology changes occurred during the reaction, no modification of the crystallinity was observed and that hydrothermal treatment did not affect a specific part of the cellulose polymer. The presence of Pt/γ-Al₂O₃ increased the initial rate of dissolution–conversion significantly as well as the distribution of the monomeric products. Pt and H₂ atmosphere were seen to increase the dissolution–conversion ratio however their role has not been yet well established.