Low pressure vapor–liquid equilibria modeling of biodiesel related systems with the Cubic–Plus–Association (CPA) equation of state

Abstract

Fatty acid esters have a wide range of applications in various chemical industries, such as pharmaceutical, cosmetic, food and, most recently, in the biodiesel production. Being able to predict the phase equilibria at reduced pressures of systems composed either only of fatty acid esters as well as also of their mixtures with alcohols, is of major relevance for the design, optimization and operation of industrial facilities producing these compounds, or their use as fuels.In the present work, the Cubic–Plus–Association Equation of State (CPA EoS) was applied to predict the isobaric vapor–liquid equilibria of six binary systems composed of ethyl/methyl fatty acid esters from laurate to linoleate in the pressure range 0.5–13.3kPa, and the isothermal phase equilibria of the binary systems tetradecane+ethyl caproate/ethyl myristate at temperatures from 373.15 to 453.15K.The predictive ability of the CPA EoS was further evaluated in the description of multicomponent biodiesel systems with associating compounds. Using binary interaction parameters computed from fatty acid ester carbon number correlations previously established the equation was able to provide excellent predictions for the low pressure vapor–liquid equilibria of the systems soybean methylic biodiesel+methanol, soybean ethylic biodiesel+ethanol, Jatropha curcas methylic biodiesel+methanol, Jatropha curcas ethylic biodiesel+ethanol, in the pressure range 6.7–66.7kPa.