Green solvents in cellulose derivatization: kinetics of cellulose acylation in mixtures of ionic liquid and DMSO

• Grant number: 13/16694-1
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Effective date (Start): October 01, 2013
• Effective date (End): October 31, 2014
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Organic Chemistry
• Principal Investigator: Omar Abou El Seoud
• Grantee: Thais Cordeiro Teixeira
• Host Institution: Instituto de Química (IQ). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 10/03629-9 - Green solvents: chemistry and applications of ionic liquids in catalysis, colloid chemistry and derivatization of biopolymers, AP.TEM

Abstract

Industrially, the transformation of cellulose into derivatives is carried out under heterogeneous conditions. As each glucose anhydrous unit posses three hydroxyl groups, the maximum degree of substitution (DS) is three. In the heterogeneous process it is not possible to get directly products with intermediates values of DS, for example, 2, due to the heterogeneity of the products. Industrially, the cellulose is transformed into its tri-ester (DS ~ 3) followed by partial controlled hydrolysis until the average DS required. Also, there is, the route, subject of this project, to realize all reactions under homogeneous conditions. The cellulose is dissolved in a solvent and the reaction is carried out with the biopolymer dissolved. Among the solvents employed for physical dissolution of cellulose, i.e., without the formation of covalent bonds, are ionic liquids, ILs. Among the problems of the use of ionic liquids are their high cost and high viscosity of cellulose solution observed with some ILs (mainly, the chlorides). Though the mixtures of aprotic dipolar solvent/IL solves, in principle, both problems, there are few information about the interactions in these systems, including between the two components of the binary mixture; among each one and cellulose, and about the dependence of DS on the solvent composition. Chemical kinetics offers quantitative answers about such relationships. The objectives of the present project are to determine the relationship between the medium composition and its efficiency in the acylation of cellulose (microcrystalline and fibroses). This objective can be reached through determination of rate constants as a function of IL concentration, nature of the anhydride employed, and calculation of reaction activation parameters.