UNIFAC Evaluation of the Liquid–Liquid Phase Equilibrium during Lipase-Catalyzed Peracidation of Different Carboxylic Acids.

Abstract

Carboxylic peroxy acids are organic oxidants of relevance in the cosmetic, food and agrochemical industries, used as intermediaries in the Baeyer-Villiger reaction and the Prileschajew epoxidation. The peroxy acids synthesis (peracidation) consists of a reversible reaction between a carboxylic acid and a hydrogen peroxide molecule to give a peroxy acid and water. This reaction is usually carried out in situ in a two-liquid-phase system (liq-liq): a continuous organic phase, where the substrates to be epoxidized are dissolved in, and a disperse phase of aqueous nature, as a supply of hydrogen peroxide molecules. The non-ideality and dynamic character of reactive biphasic systems entails the difficulty in the estimation of the distribution of species between both phases, which in turn determines its kinetic description. Then, a thermodynamic model that describes the phase behavior, with acceptable precision, is required. Therefore, the aim of this work was to evaluate the UNIFAC model’s performance to predict the phase distribution of peroxy carboxylic acid, carboxylic acid and hydrogen peroxide through non-reacting as well as from reacting systems. The immobilized lipase from Candida Antarctica B was used as the catalyst of the reaction. The systems also varied according to the type of carboxylic acids used - lauric, octanoic or acetic - and the type of solvent used - diisopropyl ether, toluene, hexane or heptane. UNIFAC showed suitable estimations of some of the component solubilities, especially with toluene systems, presenting some limitations in the description of interactions of asymmetric compounds such as hydrogen peroxide and hexane.