Formation regulation of various rosin esters and intensification mechanism using pressurized CO2

Abstract

The esterification of rosin with pentaerythritol (PE) was studied, using pressurized CO2 as an intensified additive to high-temperature water (HTW), which formed the various esters with different soften points to meet industrial applications. A multiple linear regression model was established to determine the dependence of independent variables (CO2 pressure, temperature, PE-to-rosin mass ratio and reaction time) on rosin conversion, where the elasticity of the logarithm of CO2 pressure was 0.13, indicating pressurized CO2-HTW can effectively enhance this esterification. The conversion of rosin could be improved either by increasing the PE-to-rosin mass ratio or the reaction time, but products were monoester and triesters, respectively, thus the process regulation for the formation of various esters can be achieved through operating conditions. A corresponding stepwise esterification was proposed. Furthermore, the catalytic mechanism of pressurized CO2-HWT for this esterification were identified to be the acid catalysis of carbonic acid and the enhancemennt of CO2.