Kinetic modelling of the solventless synthesis of solketal with a sulphonic ion exchange resin

Abstract

Synthesis of solketal from acetone and glycerol is approached in this work through a batch process in the absence of solvents. A heterogeneous catalysis approach was employed using the resin Lewatit GF101 as catalyst after selection from a few other sulphonic ion exchange resins. An initial study of the external mass transfer revealed that a stirring rate of 750rpm sufficed for the external mass transfer not to be the rate limiting step. Similarly, a study of the internal mass transfer showed that for particle sizes of 190μm the maximum reaction rate was achieved. Once the optimal stirring and particle size conditions were determined, a series of kinetic runs was conducted varying temperature (30–40°C), initial molar excess of acetone to glycerol (3–12) and catalyst load (0.5–1% w/w) for this reaction in equilibrium. Different kinetic models based on potential laws and Eley–Rideal (ER) and Langmuir–Hinshelwood–Hougen–Watson (LHHW) equations were proposed to fit to the experimental data obtained. After physical and statistical discrimination, an ER accounting for the direct and reverse reaction was selected, with activation energies of 124.0±12.9kJmol−1 and 127.3±12.6kJmol−1 for the direct and reverse reaction, respectively, and enthalpy of adsorption of 128.0±21.4kJmol−1 for the adsorption constant of water.