A novel acid catalyst based on super/subcritical CO₂-enriched water for the efficient esterification of rosin

Abstract

Rosin esters are widely applied as masticatory substances and beverage stabilizers, while classical acid-catalysed processes will lead to metal residue or environmental issues. Super/subcritical CO2–enriched high temperature liquid water (HTLW) as a green acid catalyst in the esterification reaction of rosin with glycerol was investigated. The pH of CO2–H2O binary system, as calculated based on gas–liquid equilibrium, charge balance and chemical equilibrium equations, ranged from 3.49 to 3.70 depending on the reaction conditions, indicating effective acid catalysis. Response surface methodology experiments showed the optimum conditions were 3.5 h, 3.9 MPa CO2 pressure, a rosin-to-glycerol molar ratio of 1.32 and 269°C, and an enhanced esterification yield of 94.74% was achieved, which was superior to that obtained using a ZnO catalyst. It was found that the esterification kinetics was a pseudo first-order reaction, and the enthalpy and entropy of activation were calculated using the Arrhenius–Polanyi equation. The presence of super/subcritical CO2-enriched HTLW catalyst can decrease the activation energy and significantly accelerate the reaction rate.

Characteristics and Kinetics of Rosin Pentaerythritol Ester via Oxidation Process under Ultraviolet Irradiation

“…A good fit of the kinetic parameters would confirm the suitability of the mathematical model to describe the reaction [ 30 , 31 ]. An F-test was performed to assess the accuracy of the model results when F > F (m, N-m, 0.95), which denotes the 95% value of the Fisher distribution with (m, N-m) degrees of freedom.…”

“…Moreover, ∆H ≠ becomes lower with the light intensity increases; it indicates that UV irradiation could induce the formation of activated complex. ∆S ≠ is a measure of changes in the disorder of molecules in the system, and the negative value of ∆S ≠ shows that the degree of disorder of transition state was lower as compared to reactants in the ground state [ 31 ].…”

Recent Progress on Catalytic of Rosin Esterification Using Different Agents of Reactant

“…In general, room temperature annealing provided the best conditions for rosin esterification utilizing Fe 3 O 4 /MOF-5. The development of super/subcritical CO 2 and the presence of high temperature liquid water are investigated as environmentally friendly acid catalysts in the esterification process between rosin and glycerol [32]. Experiments with response surface methods revealed that CO 2 pressure affects the yield, which is higher than that produced with a ZnO catalyst.…”