Kinetics of glycerol and polyglycerol maleates production: Raw materials for partially bio-based concrete admixtures

Abstract

In this work, the self-catalyzed kinetics to produce glycerol, diglycerol, and polyglycerol-4 maleate esters were experimentally determined from 60 ºC to 80 °C. These esters can be used as intermediates in the production of partially bio-based admixtures that can replace petroleum-derived polycarboxylate ethers, which are traditionally used as concrete superplasticizers. The obtained experimental data were used to adjust the kinetic model parameters for the three reactions, including the effect of temperature. The model adequately predicted the behavior of the three proposed reactions, which was statistically validated using the Fisher-Snedecor test. The activation energies of glycerol, diglycerol, and polyglycerol-4 maleate were 29.5, 85.5, and 68.9 kJ/mol, respectively, with frequency constants of 7.93 × 102, 2.02 × 1011, and 4.48 × 108 min−1. The highest activation energy was obtained for the esterification of maleic anhydride (MAH) with diglycerol, indicating that this reaction is more temperature dependent. The kinetic constants at 70 °C were 2.56 × 10−2 min−1, 1.92 × 10−2 min−1, and 1.46 × 10−2 min−1 for the esterification of MAH with glycerol, diglycerol, and polyglycerol respectively, showing a greater reaction rate for the esterification with glycerol.