Fractionation, fats solvent

The aromatics-laden or fat solvent is fractionated in a distillation column. The widely different boiling points of the solvent and aromatics make the separation relatively easy and clean. The solvent is recycled back to the beginning of the process. The arorhatic extract, called crude benzene, is usually passed through a clay treater to remove any olefins that sometimes get created in the process and then distilled once again to produce high purity benzene. 

Phase separated polymer mixtures are important in many practical applications, such as confectionery and low-fat foods. Values of the fraction (x) of a component can be replaced by those of the fraction of solvent (Sx) associated with polymer (Morris, 1998) so that Figure 6-22 may be used also to understand the role of solvent partitioning. A key assumption is that there is complete separation of the two polymers in to their respective phases, so that the relative phase volumes (hence, the polymer concentration in each phase) may be characterized by the p-factor, defined as ... 

The principle of oil fractionation is based on the difference in solubility of the component TAGs. The difference in solubility is directly related to the types of TAGs in the fats and oils. Three major processes are employed commercially to produce value-added fractionated fats and oils (1) dry fractionation, (2) solvent fractionation, and (3) aqueous detergent fractionation. 

The major control objective is to recover the specified fraction of the carbon dioxide in the feed gas. This is achieved by controlling the composition of CO2 in the off-gas at 1.3 mol% by manipulating the flow rate of the lean solvent to the absorber. The removal of CO2 from the fat solvent fed to the stripper is achieved by controlling the temperature in the stripper reflux drum at 363 K by manipulating the heat input to the stripper reboUer. 

Fractional crystallization may be accompHshed on a batch, continuous, or semicontkiuous basis. Oil is chilled continuously while passkig through the unit and is then passed over a continuous belt filter which separates soHd fat from the Hquid oil. The process gives poorer separation compared to solvent fractionation because oils are viscous at crystallization temperatures and are entrained to a significant extent ki the soHd fraction. The Hquid fraction, however, is relatively free of saturated material. 

Solubility Properties. Fats and oils are characterized by virtually complete lack of miscibility with water. However, they are miscible in all proportions with many nonpolar organic solvents. Tme solubiHty depends on the thermal properties of the solute and solvent and the relative attractive forces between like and unlike molecules. Ideal solubiHties can be calculated from thermal properties. Most real solutions of fats and oils in organic solvents show positive deviation from ideaHty, particularly at higher concentrations. Determination of solubiHties of components of fat and oil mixtures is critical when designing separations of mixtures by fractional crystallization. 

The enantioselective determination of 2,2, 3,3, 4,6 -hexachlorobiphenyl in milk was performed by Glausch et al. (21). These authors used an achiral column for an initial separation, followed by separation of the eluent fraction on a chiral column. Fat was separated from the milk by centrifugation, mixed with sodium sulfate, washed with petroleum ether and filtered. The solvent was evaporated and the sample was purified by gel permeation chromatography (GPC) and silica gel adsorption chromatography. Achiral GC was performed on DB-5 and OV-1701 columns, while the chiral GC was performed on immobilized Chirasil-Dex. 

Schemes for recrystallisation from melts are similar to those for solutions, although a solvent is not normally added. Usually, simple sequences of heating (melting) and cooling (partial crystallisation) are followed by separation of the purified crystals from the residual melt. Selected melt fractions may be mixed at intervals according to the type of scheme employed, and fresh feed-stock may be added at different stages if necessary. As Bailey1114 reports, several such schemes have been proposed for purification of fats and waxes.

Most existing methods are based on instrumental analysis involving exhaustive sample pretreatment and preconcentration steps, followed by purification and fractionation before final chromatographic separation and detection. For fat and oil samples, dissolving the lipids in an appropriate solvent is usually the first treatment. This has been achieved by melting the fat at 90°C followed by LLE or direct solid liquid extraction (SEE) with an apolar solvent [37], column extraction with a mixture of apolar solvents after drying of the sample with anhydrous Na2S04, Soxhlet extraction and/or sonication with apolar solvents. Typically, sample intake is between 0.5 g and 1 g and quantitative recoveries >60% have been reported. 

Reports a standardized method for direct determination of TBA value in oils, fats, and lipid extracts. Unlike distillation and extraction methods, this technique determines total reactive substances without previous isolation of the volatile fraction. Furthermore, the solvent of choice is organic (l-butanol) rather than aqueous. This protocol is reported as the official (AOCS) method to determine TBA value (direct method) of animal and vegetable fats and oils, fatty acids and their esters, partial glycol esters, and similar materials. 

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