Glycerol Valorization as Biofuel: Thermodynamic and Kinetic Study of the Acetalization of Glycerol with Acetaldehyde

Abstract

The work reported in this article is a thermodynamic and kinetic study of the acetalization reaction between acetaldehyde and glycerol to produce glycerol ethyl acetal (GEA). A catalyst screening was performed allowing for the choice of Amberlyst-15 wet resin as the most suitable catalyst for this reaction. Through the study of the reaction thermodynamic equilibrium, it was possible to determine the value of the equilibrium constant as a function of temperature, ln­(<i>K</i>) = 1.419 + 1055/<i>T</i>, and the corresponding thermodynamic parameters Δ<i>H</i>_298 K⁰ = −8.77 kJ·mol^–1 and Δ<i>G</i>_298 K⁰ = −12.3 kJ·mol^–1. Additionally, the standard enthalpy and Gibbs free energy of formation of GEA were also obtained, as −584.4 and −387.0 kJ·mol^–1, respectively. The Langmuir–Hinshelwood–Hougen–Watson model considering internal mass-transfer limitations presented the best fitting of the reaction kinetic behavior. The parameters estimated for this model were <i>k</i>c (mol·g_cat^–1·s^–1) = 3.13 × 10⁹ – 6223/<i>T</i> and <i>K</i>_S,W = 1.82 × 10^–3 exp­(2361/<i>T</i>). The acetalization of glycerol with acetaldehyde presents an activation energy of 51.7 kJ·mol^–1