Phenomenological kinetic model of the synthesis of glycerol carbonate assisted by focused beam reflectance measurements

• Synthesis of glycerol carbonate using inexpensive catalysts was studied.
• The reacting system is a liquid–liquid mixture evolving into a monophasic system.
• The evolution of the dispersion was observed by FBRM.
• The change in the phase regime affects the catalytic behaviour.
• Phenomenological kinetic models were proposed, fitted and verified.

In this paper, the synthesis of glycerol carbonate from glycerol and dimethyl carbonate is studied. First, operating conditions and a catalyst were selected after screening of different alkali metal salts, resulting K2CO3 the most active species. Afterwards, given the low degree of miscibility between the reactants, a study of the phase change from a liquid–liquid emulsion to a monophasic sample throughout the reaction was successfully performed with the aid of a focused beam reflectance probe. This change took place at a conversion of approximately 0.30. With the findings of this study, distinct kinetic models were proposed and fitted to the experimental data obtained after the completion of a series of kinetic runs varying temperature (66–70 °C), molar ratio of dimethyl carbonate to glycerol (1.5–3) and catalyst load (0.75–1.25% w/w). A model composed of two potential equations was proposed with activation energy of 179.2 ± 3.7 kJ mol−1. The model was capable of describing the initial biphasic stage and the monophasic regime correlated best to the experimental data, with errors below 6.8%.

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