Performance evaluation of the ASOG method for predicting liquid-liquid equilibria in lipid technology

Author(s)

Carlos Eduardo Sampaio Dantas

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Química
• Defense date: 2018-07-30

Examining board members

Roberta Ceriani; Reginaldo Guirardello; Eduardo Augusto Caldas Batista

• Advisor: Roberta Ceriani

Abstract

Acquiring experimental data and modeling of liquid-liquid equilibrium (LLE) of fatty (lipid) systems have been constantly under study in the past two decades, motivated by increasing biodiesel production, and processing of glycerol and edible oils/fats. Industrial production involves mixtures composed of carboxylic acids, fatty acids, fatty acid alkyl esters, alcohols (mainly methanol and ethanol), glycerol, aldehydes, acylglycerol, water, and other organic compounds. During processing, purification steps are extremely important, because they affect directly final product quality, and knowledge of LLE for mixtures of these compounds, present throughout biodiesel production, is very relevant. Conversely, liquid-liquid extraction represents a mild alternative for the current way of purification of fatty acids. Besides being naturally complex due to high non-linearity of equations, LLE calculation by means of group contribution methods still has several limitations, hampering projects of process improvements. In this context, this work aimed at evaluating the group contribution method ASOG (Analytical Solution of Groups) - still unexplored for systems of the lipid technology - along with the recently published method Solution Structure of Isoactivity Equations to perform predictive calculation of LLE. Subroutines were created using the Matlab®. The evaluation was carried out for a total of 440 mixtures (3.018 tie lines) taken from literature, composed by those aforementioned substances, typical of this industrial segment. Interactions between groups CH3xCOOH, OHxCOOH, COOxCOOH, H2OxCH3, H2OxCOO, H2OxCOOH, COHxCH3,COHxCOO, OHxCOO e CH3xC=C were readjusted in an optimization routine also created in Matlab®, which improved solubility prediction of acids, water, and aldehydes in organic and alcoholic phases, except in systems containing small chain carboxylic acids and long chain alcohols. The Solution Structure of the Isoactivity Equations offered a simpler way to perform LLE calculation, but it showed convergence problems, which could be overcome by increasing the number of initial estimations to initialize the method, demanding more time of simulation (AU)

• FAPESP's process: 16/06853-3 - Performance evaluation of the ASOG method for predicting liquid-liquid equilibria in lipid technology
• Grantee: Carlos Eduardo Sampaio Dantas
• Support Opportunities: Scholarships in Brazil - Master