A greener process for isosorbide production: Kinetic study of the catalytic dehydration of pure sorbitol under microwave

In the context of a more environmentally friendly and economical process development, the use of microwaves has many advantages such as reduced energy consumption and reduced reaction time. The work presented here focuses on the dehydration of sorbitol to isosorbide in the presence of an acid catalyst in a solvent-free system and under microwave heating. The obtained yield is up to 70%. Different optimization parameters of the reaction are investigated as the temperature, the presence of an inert gas, the influence of the pressure, the agitation speed and the catalyst loading. Several species such as intermediate anhydro-hexitol are identified and quantified and a simplified reaction scheme is proposed. A kinetic study is carried out between 120 degrees C and 160 degrees C using different catalyst loadings. Several models considering first order reactions or Langmuir-Hinshelwood type equations are studied. The kinetic parameters obtained are evaluated and discussed. We conclude that the kinetics of the reaction is only correctly described by a Langmuir-Hinshelwood type model, including the adsorption-desorption equilibrium of sorbitol on the catalyst. (C) 2013 Elsevier B.V. All rights reserved.