M.E. Araújo

Improving phase equilibrium calculation with the Peng–Robinson EOS for fats and oils related compounds/supercritical CO2 systems

Abstract Several predictive methods for normal boiling point, critical temperature, critical pressure, and acentric factor, applied to fatty acids and fatty acid esters of high molecular weight were evaluated. The properties estimated by the selected methods were used to analyze the ability of the Peng–Robinson equation of state (EOS) to predict the vapor–liquid equilibria of binary and ternary systems of fats and oils related compounds with CO 2 . Van der Waals mixing rules with the combining rules proposed by Kwak and Mansoori and Park et al. were used. For fatty acids, the method of Constantinou and Gani was selected for the prediction of the critical temperature and that of Somayajulu for the prediction of the critical pressure when experimental boiling temperatures were available. In the absence of experimental data, the method of Constantinou and Gani was selected for the prediction of critical and boiling temperatures, as well as for the critical pressure. For fatty acid esters, the method of Joback and Reid was chosen for the prediction of the critical and boiling temperatures, and that of Constantinou and Gani was selected for the prediction of the critical pressure. The indirect method of Tu was preferred for the prediction of the acentric factors of high molecular weight fatty acids. The correlation of Vetere was chosen for the prediction of the acentric factors of low molecular weight fatty acid esters, and the indirect method of Tu was selected for the prediction of the acentric factors for the methyl ester family. The results for the phase equilibria suggest that the Peng–Robinson equation, with the quadratic mixing rules for the three combining rules tested, is capable of predicting vapor–liquid equilibrium with quality comparable to the results obtained with the mixing rules for more complex models like MHV1 and LCVM.

Supercritical extraction of pupunha (Guilielma speciosa) oil in a fixed bed using carbon dioxide

The pupunha (Guilielma speciosa) is the fruit of a palm tree typical of the Brazilian Northern region, whose stem is used as a source of heart of palm. The fruit, which is about 65% pulp, is a source of oil and carotenes. In the present work, an analysis of the kinetics of supercritical extraction of oil from the pupunha pulp is presented. Carbon dioxide was used as solvent. The extractions were carried out at 25 MPa and 323 K and 30 MPa and 318 K. The chemical composition of the extracts in terms of fatty acids was determined by gas chromatography. The amount of oleic acid, a saturated fatty acid, in the CO2 extracts was larger than that in the extract obtained with hexane. The overall extraction curves were modeled using the single-parameter model proposed in the literature to describe the desorption of toluene from activated coal.

A mass transfer model applied to the supercritical extraction with CO2 of curcumins from turmeric rhizomes (Curcuma longa L)

Increasing restrictions on the use of artificial pigments in the food industry, imposed by the international market, have increased the importance of raw materials containing natural pigments. Of those natural substances with potential applications turmeric rhizomes (Curcuma longa L), are one of the most important natural sources of yellow coloring. Three different pigments (curcumin, desmetoxycurcumin, and bis-desmetoxycurcumin) constitute the curcuminoids. These pigments are largely used in the food industry as substitutes for synthetic dyes like tartrazin. Extraction of curcuminoids from tumeric rhizomes with supercritical CO2 can be applied as an alternative method to obtain curcuminoids, as natural pigments are in general unstable, and hence degrade when submitted to extraction with organic solvents at high temperatures. Extraction experiments were carried out in a supercritical extraction pilot plant at pressures between 25 and 30 MPa and a temperature of 318 K. The influence of drying pretreatment on extraction yield was evaluated by analyzing the mass transfer kinetics and the content of curcuminoids in the extracts during the course of extraction. The chemical identification of curcuminoids in both the extract and the residual solid was performed by spectrophotometry. Mass transfer within the solid matrix was described by a linear first-order desorption model, while that in the gas phase was described by a convective mass transfer model. Experimental results showed that the concentration profile for curcuminoids during the supercritical extraction process was higher when the turmeric rhizomes were submitted to a drying pretreatment at 343 K.

Fractional Distillation of Organic Liquid Compounds Produced by Catalytic Cracking of Fats, Oils, and Grease

This work aims to investigate the fractional distillation of organic liquid products (OLP) obtained by catalytic cracking of palm oil (Elaeis guineensis Jacq.) at 450°C, 1.0 atm, with 5, 10, and 15% (wt) Na 2 CO 3 , using a stirred tank reactor of 143 L. The fractional distil‐ lations of OLP were carried out in laboratory scale with and without reflux using col‐ umns of different heights, and a pilot‐packed distillation column with internal reflux. OLP and distillation fractions (gasoline, kerosene, light diesel, and heavy diesel) were physicochemically characterized for density, kinematic viscosity, acid value, saponi‐ fication value, refractive index, flash point, and copper strip corrosion. The OLP and light diesel fractions were analyzed by Fourier transform infrared spectroscopy (FT‐IR) and gas chromatography‐mass spectrometry (GC‐MS). For the experiments in labora‐ tory scale, the yields of distillates decrease along with column height, with and without reflux, while those of bottoms products increase. The yields of distillates and gas increase with increasing Na 2 CO 3 content, while those of bottoms products decrease. The densities of gasoline, kerosene, and light diesel produced in laboratory scale with reflux superpose exactly those of kerosene, light diesel, and heavy diesel produced in laboratory scale without reflux. The kinematic viscosity decreases with increasing column height for the experiments in laboratory scale. The acid values of distillation fractions decrease along with the column height for the experiments with and without reflux. The FT‐IR of distil‐ lation fractions in pilot and laboratory scales identified the presence of aliphatic hydro‐ carbons and oxygenates. The GC‐MS analysis identified OLP composition of 92.84% (area) hydrocarbons and 7.16% (area) oxygenates. The light diesel fraction contains 100% hydrocarbons with an acid value of 0.34 mg KOH/g, proving the technical feasibility of OLP de‐acidification by the fractional distillation process.