title: Monitoring of cellulose depolymerization in 1-ethyl-3-methylimidazolium acetate by shear and elongational rheology.
abstract: The thermal stability of cellulose in the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate, [emim]OAc was investigated. For this purpose, Eucalyptus urugrandis prehydrolysis kraft pulp was first dissolved in [emim]OAc by means of a vertical kneader and then stored at three different temperatures to study the time-depended behavior of the cellulose-[emim]OAc system. Cellulose depolymerization was assessed by characterizing the precipitated cellulose and the rheological behavior of the cellulose-[emim]OAc solutions. The results show decreases in the weight average molecular mass and in the shear viscosity at temperatures exceeding 60 °C, which can be related to progressing degradation of cellulose in the IL upon storage at elevated temperature. The changes in behavior of the solutions under extensional stresses also attest the gradual depolymerization of cellulose. The degradation has been analyzed using appropriate kinetic models. Propyl gallate appeared to be an efficient stabilizer of the cellulose-[emim]OAc system during the dissolution step even though the mechanism has not been fully understood yet.
authors.affiliation: Department of Forest Products Technology, Aalto University, School of Chemical Technology, Aalto, PO Box 16300, 00076, Espoo, Finland. Electronic address: anne.michud@aalto.fi.
authors.forename: Anne
authors.initials: A
authors.lastname: Michud
authors.affiliation: Department of Forest Products Technology, Aalto University, School of Chemical Technology, Aalto, PO Box 16300, 00076, Espoo, Finland. Electronic address: michael.hummel@aalto.fi.
authors.forename: Michael
authors.initials: M
authors.lastname: Hummel
authors.affiliation: Departamento de Engenharia Quımica, CEFT, Faculdade de Engenharia da Universidade do Porto, Rua dr Roberto Frias s/n, 4200-465 Porto, Portugal. Electronic address: shaward@fe.up.pt.
authors.forename: Simon
authors.initials: S
authors.lastname: Haward
authors.affiliation: Department of Forest Products Technology, Aalto University, School of Chemical Technology, Aalto, PO Box 16300, 00076, Espoo, Finland. Electronic address: herbert.sixta@aalto.fi.
authors.forename: Herbert
authors.initials: H
authors.lastname: Sixta
keywords: Cellulose; Cellulose degradation; Ionic liquid; Rheological characterization