title: Structural changes in microcrystalline cellulose in subcritical water treatment.
abstract: Subcritical water is a high potential green chemical for the hydrolysis of cellulose. In this study microcrystalline cellulose was treated in subcritical water to study structural changes of the cellulose residues. The alterations in particle size and appearance were studied by scanning electron microscopy (SEM) and those in the degree of polymerization (DP) and molar mass distributions by gel permeation chromatography (GPC). Further, changes in crystallinity and crystallite dimensions were quantified by wide-angle X-ray scattering and (13)C solid-state NMR. The results showed that the crystallinity remained practically unchanged throughout the treatment, whereas the size of the remaining cellulose crystallites increased. Microcrystalline cellulose underwent significant depolymerization in subcritical water. However, depolymerization leveled off at a relatively high degree of polymerization. The molar mass distributions of the residues showed a bimodal form. We infer that cellulose gets dissolved in subcritical water only after extensive depolymerization.
authors.affiliation: Department of Forest Product Technology, School of Chemical Technology, Aalto University, Helsinki, Finland. lasse.tolonen@aalto.fi
authors.forename: Lasse K
authors.initials: LK
authors.lastname: Tolonen
authors.forename: Gerhard
authors.initials: G
authors.lastname: Zuckerstätter
authors.forename: Paavo A
authors.initials: PA
authors.lastname: Penttilä
authors.forename: Walter
authors.initials: W
authors.lastname: Milacher
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Habicht
authors.forename: Ritva
authors.initials: R
authors.lastname: Serimaa
authors.forename: Andrea
authors.initials: A
authors.lastname: Kruse
authors.forename: Herbert
authors.initials: H
authors.lastname: Sixta
mesh_terms: D002236:Carbohydrate Conformation; D002482:Cellulose / Q000737:chemistry*; D003460:Crystallization; D007700:Kinetics; D010316:Particle Size; D013499:Surface Properties; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D002482:Cellulose