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In this work for the first time Ion-Jelly® membranes were developed and characterized. Ion-Jelly® is a new green and sustainable gel material, obtained by addition of an ionic liquid to gelatine. Three different ionic liquids ([EMIM][DCA], [BMIM][DCA] and [BMPyr][DCA]), were used to study the difference in the membrane properties introduced by changes in the ionic liquid cation. The physical properties of the membranes were characterized by traction, contact angles, and SEM. These membranes were further tested in separation processes using supercritical carbon dioxide for the fractionation of a model mixture made of oleic acid and squalene and for the separation of biodiesel products and reagents. The permeability to pure gases (H2, N2, O2, CO2 and CH4) was also determined and ideal selectivities calculated.

Fractionation of a mixture of oleic acid/squalene using room temperature ionic liquids as the extracting agent has been investigated for a range of imidazolium and phosphonium based ionic liquids. The partition coefficient of oleic acid to the ionic liquid phase varied from 0.85 for [C 2 ][NTf2] to 2.96 for [EMIM][MDEGSO 4 ]. It was observed that the fractionation of the oil mixture could be tuned by appropriately choosing the combination of the anion and cation type. This effect could be explained by the change in the polarity of the ionic liquid.

Six different membranes were tested at 18.0 MPa and 313 K for their performance to fractionate a model mixture of squalene/oleic acid with supercritical carbon dioxide. A significant enrichment of squalene in the permeate side was achieved with a 10 μm-coating layer polydimethyl siloxane (PDMS) membrane at the tested conditions although with the drawback of a lower total permeate flux. Additional fractionation experiments of the same model mixture were carried out in a countercurrent packed column at 18.0 MPa of pressure and 313 and 323 K of temperature. At a solvent-to-feed mass flow ratio of ca. 40 an extraction efficiency of 88% of the total mass of squalene fed to the column was obtained at 18.0 MPa/313 K. The raffinate and extract streams obtained at these conditions had a squalene content of 10 and 63.5 wt%, respectively. An optimized combination of supercritical extraction and membrane separation could be used to increase the purity of the extract stream in squalene.

A non-isothermal dynamic simulation model of a countercurrent supercritical fluid extraction column with structured packing is presented. The model incorporates momentum and energy balances in the packed bed. The two countercurrent fluid phases and the structured packing are assumed to be in local thermal equilibrium, a reasonable assumption given the high surface area of the packing. The dynamic model is validated by comparing predicted results with experimental data for the fractionation of the binary mixture squalene + methyl oleate with supercritical carbon dioxide. Good agreement is obtained between measured and predicted temperature and composition profiles of gas and liquid phases along the packed bed. The dynamic model is further employed to determine optimal extraction conditions that maximize squalene recovery subjected to purity constraints in the raffinate stream.

Vapor−liquid equilibrium data are reported for the ternary system oleic acid + squalene + carbon dioxide in the temperature range of (313 to 333) K and in the pressure range of (14 to 22) MPa. Experiments were performed in a continuous-type equilibrium apparatus where a static mixer promotes the equilibrium between the gas and liquid phases. A low selectivity of carbon dioxide toward squalene was obtained, indicating that the separation is poor. Oleic acid was of technical grade containing other fatty acids in minor quantities. Distribution coefficients of major fatty acids were evaluated in the range described. Equilibrium data were correlated using the Peng−Robinson equation of state with a reasonably good agreement. The interaction parameters of the equation were optimized by minimizing the deviations between the calculated and experimentally determined vapor and liquid-phase compositions and distribution coefficients of each component.

A dynamic model of a supercritical fluid extraction (SFE) process was developed and applied to the fractionation of the binary mixture squalene/methyl oleate by supercritical carbon dioxide. The model combines a mathematical model for each main piece of equipment of the SFE process, namely, the countercurrent packed extraction column, the separation column for oil recovery and solvent regeneration, the heat exchanger for heating fresh CO2, and the make-up of solvent in the process plant. Experimental tests were performed in a pilot-plant SFE apparatus where perturbations on prespecified operating parameters were induced and their effect on main process variables determined. A good agreement was obtained between experimental and predicted results. In addition, the dynamic model of the packed extraction column was applied to other SFE case studies where sufficient experimental data is available. The dynamic model was found to correctly predict the outlet streams composition profiles of all the case studies. © 2007 American Institute of Chemical Engineers AIChE J, 2007

The use of static mixers as alternative contacting devices for supercritical fluid separation processes has been proposed recently. Here, we present new data that addresses the hydrodynamic behavior and mass transfer kinetics of a Kenics-type static mixer under high pressure conditions. The gas pressure drop and the mass transfer coefficient for the fractionation of an oil mixture by supercritical carbon dioxide were measured for several operating conditions of pressure, temperature, feed composition and gas to liquid mass flowratio. Based on the experimental data, a correlation was developed for the pressure drop and the mass transfer coefficient as a function of dimensionless numbers. The extraction efficiency of the static mixer was compared with the extraction yield obtained with a countercurrent packed column, for the same system. The oil loading in carbon dioxide was the same for both contacting devices. Whereas the yield of extraction was higher for the packed column, the static mixer presented the higher extraction efficiency per transfer unit.

Vapor–liquid equilibrium data are reported for the ternary system methyl oleate–squalene–carbon dioxide in the temperature range of 313–343 K and in the pressure range of 11–21 MPa. Experiments were performed in a continuous-type equilibrium apparatus by using a static mixer ensemble to promote the equilibrium between the gas and liquid phases. High selectivity of carbon dioxide towards methyl oleate was obtained. Equilibrium data were correlated using the Soave–Redlich–Kwong equation of state with the Mathias–Klotz–Prausnitz mixing rule. The binary interaction parameters were optimized by minimizing the deviations between the calculated and experimentally determined vapor and liquid phase compositions and distribution coefficients of each substance. A fairly good correlation of the data could be obtained with an average absolute deviation (AAD) of 1.3×10−2.

A mixture that partially resembles the distillates obtained from the deodorization process of olive oils was used as a case study to test and develop mass-transfer models valid for supercritical fluid processes. Such models are useful engineering tools that provide a theoretical background for the scale-up of industrial plants. In the first part of this series of papers, the fractionation performance of the model mixture squalene/methyl oleate by supercritical carbon dioxide in a countercurrent packed column containing a corrugated gauze-type structured packing was presented. This second part presents a general correlation for predicting the mass-transfer efficiency of the high-pressure packed column. Several correlations taken from the literature were used and their results compared with the experimentally determined mass-transfer coefficients and holdup. A model formerly developed for distillation columns was found to be valid for our high-pressure system. It was found that the area of the gauze packing...

The design of countercurrent packed columns operating under high-pressure conditions requires knowledge of their hydrodynamic and mass transfer behavior. A laboratory-scale continuous supercritical fluid extraction apparatus was developed with the purpose of obtaining data needed for such designs. The current work is part of a study to assess the feasibility of supercritical carbon dioxide in fractionating a mixture of squalene and methyl oleate. This mixture partly emulates the residues obtained from the olive oil refining process. Phase equilibrium data were previously measured to evaluate the best operating conditions. Here, we examine the continuous fractionation of two different feeds, with 40 and 70 wt % of squalene, under various extraction conditions. An extraction yield as high as 90 wt % of squalene in the raffinate phase was achieved. The selectivity and extraction efficiency were determined as functions of the oil-to-carbon dioxide flow ratio as well as the reflux ratio. In a subsequent paper ...

The transesterification reaction of n -butyl acetate by 1-hexanol catalyzed by Novozym 435 (immobilized Candida antarctica lipase B from Novo Nordisk) suspended in near-critical carbon dioxide, near-critical ethane, and compressed propane at 35°C and 100 bar was studied. Separate equilibration of the solvents with mixtures of salt hydrates known to give a certain water activity ( a w ) allowed us to convert water concentration into water activity. In all the solvents, the catalytic activity of Novozym was nearly insensitive to a w up to saturation. Reaction rates were higher in propane and ethane than in CO 2 , possibly due to the direct adverse effect of CO 2 already observed with other enzymes. By sieving the enzyme preparation into different size series, it was possible to verify the existence of internal diffusion limitations. These were significantly more severe in propane than in the other two solvents which can be explained by the fact that propane behaves like a conventional liquid in this study whereas CO 2 and ethane are closer to the critical point. An increase in temperature at constant pressure activated the enzyme in the three solvents. This effect was most pronounced in CO 2 and comparable in ethane and propane. In propane, activation by temperature was almost negligible when the whole enzymatic preparation was used which should reflect the existence of more severe mass transfer limitations in this solvent. Experiments at fixed density showed that the activation of Novozym in ethane was solely a temperature effect whereas in CO 2 , this effect was combined with one mediated by changes in solvation.