LAboratoire de Spectrochimie Infrarouge et Raman – UMR 8516
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Soutenance de thèse de Ivan Vyalov

Molecular dynamics simulation of dissolution of cellulose in supercritical fluids and mixtures of cosolvents/supercritical fluids

Cellulose is insoluble in neat supercritical CO2 and the main objective of this work was to investigate mixtures of scCO2 with polar cosolvents for the development of new processing technologies for the cellulose dissolution. The objective is achieved by studying the dissolution process of monomer of cellulose and its various polymorphs. The effect of the thermodynamic parameters on the dissolution process was analyzed by molecular dynamics simulation. We started by analyzing the structure of pure supercritical fluids and the mixtures of supercritical fluids/cosolvents using Voronoi tesselations and nearest neighbours approach. The thermodynamic integration method was used to to analyze the thermodynamics of the mixtures of scCO2/cosolvents (the energy, entropy and free energy of mixing ) and to check the validity of the potential models used in our simulations.

To analyze the dissolution of cellulose, we started from studying the solvation free energy of cellobiose (cellulose monomer) which was calculated from molecular dynamics simulations using free energy perturbation method. The influence of conformational degrees of freedom on solvation free energy of cellobiose was also analyzed using the metadynamic approach.

Finally, the direct dissolution of cellulose nanocrystal polymorphs in 1-ethyl-3-methylimidazolium chloride, in carbon dioxide and ammonia at supercritical conditions and in the mixture of supercritical CO2 and various solvents (ethanol, acetone). It was found that various mixtures of CO2 with cosolvents do not dissolve cellulose but they can considerably affect its crystalline structure whereas ammonia fluid can dissolve cellulose and this process is significantly influenced by the thermodynamic conditions (temperature, pressure and density).

La soutenance aura lieu le 09.12.2011 à 10h00
Université Lille 1, Bâtiment Sup, Amphi 13 rez-de-chaussée
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