Density functional theory applied to thermochemical calculations for phenol reactions

Phenol recovery from wastewaters is a crucial task in the chemical process area, for both economical and environmental reasons, since phenol is a high added value product but, also, highly toxic. Reactive distillation is being proposed as an alternative process for eliminating phenol from water. However, before studying the process, it is necessary to derive a suitable phenol reaction and, also, to calculate its equilibrium constants, since no such values are reported in the open literature. In this work, Benson's method and molecular modeling are applied to calculate thermochemical values for phenol reactions with acetic acid (phenol acylation) and with acetic anhydride (phenol esterification). However, Benson's method presented limitation for calculation of the thermochemical values for the proposed reactions, because some of the additivity groups are not found in published tables. Using molecular modeling, calculations were carried out at several temperatures. Results from density functional theory (DFT) indicate that the equilibrium constant for phenol esterification is greater than the one for phenol acylation and, thus, the former reaction is more suitable in terms of consumption of phenol. Moreover, it was observed that the acylation reaction reaches high conversions only at high temperatures.