Avaliação de métodos de contribuição de grupos na predição do equilíbrio de fases de misturas presentes na produção de biodiesel utilizando a Equação de Peng-Robinson

Abstract

The increase in energy consumption associated with population growth has been worrying global governments, as a result the search for the development of renewable energy is increasing. Biodiesel appears as a strong candidate among them, being formed by a mixture of long chain fatty acid alkyl esters and industrially produced by the transesterification of animal fats or vegetable oils with short-chain alcools. Understanding the phase equilibrium behavior for systems involved in biodiesel production is fundamental for designing and optimizing processes involving the separation, production, storage and combustion of compounds in biodiesel production. The objective of this dissertation was to evaluate the predictive performance of the Peng-Robinson equation, classical van der Waals mixing rule, and contribution methods indicated in the literature to determine the critical properties of pure substances, to model the liquid-vapor equilibrium systems present in biodiesel production. The work was divided in four case studies, the first evaluates the performance of three different critical properties of different oleic acid + ethanol systems, at high pressures, was considered the possible esterification reaction between the acid and the alcohol forming ester and alcohol. The other studies evaluated the performance for the systems containing ethyl ester + ethanol, biodiesel + alcohol and soybean oil + methanol/ethanol/n-hexane, at subatmospheric pressures. It was verified that for the subatmospheric systems the predictive modeling was efficient presenting deviations less than 5%, except for systems containing soybean oil. For the ethanol + oleic acid system it was possible to identify the influence of the reaction on the bubble point curve.