Highly selective solvent

The extraction method treats the filtered fermentation liquor with a highly selective solvent, tri-n-butyl phosphate in kerosene, and then recovers free citric acid by counterextraction with water. The aqueous solution, which is further concentrated and... 

For extractive distillation, extraction and absorption processes, highly selective solvents are required. The economic importance of extraction and extractive distillation processes can be recognized from the fact that the worldwide production of the BTX aromatics (benzene, toluene, xylenes, ethylbenzene) as important primary petrochemical products for the industrial manufacturing of many chemical products... 

Early methods of separation employed such solvents as oleic acid/ crude coal-tar solvent naphtha, light pyridine,5 etc. Based on the selective solution of phenanthrene by the coal-tar naphtha, and of carbazole liy the light pyridine, Clark proposed a complicated scheme for the separation and recovery of all three of these constituents. Recently, organic liquid compounds containing the furan nucleus have been found to have a highly selective solvent action on phenanthrene and carbazole." Thns, furfural while dissolving phenanthrene and carbazole does not have a marked solvent action on anthracene at low temperatures. However, at elevated temperatures it does dissolve anthracene with the result that it is possible... 

When polar solvents like methanol was used, high yield of epoxide was observed with high selectivity. Solvents like tetrahydrofuran which are good coordinating solvents are not suitable for product formation. With complex (3) high selectivity for 2-cyclohexen-l-ol is obtained in chloroform. 

Table 1 compares the results from the selective hydrogenation of citral, at a variety of pressures and temperatures in both ionic liquids and organic solvents using palladium supported on carbon (Pd/C) and platinum supported on graphite (Pt/G). It is clear that the ionic liquid systems are highly selective solvents for the reduction of C=C without any reduction of the carbonyl group over palladium and similar selectivities can be achieved for the carbonyl group over platinum. 

At first glance, one might consider the effect of compressed CO2 on the phase behavior of multi-component polymer systems to be a simple combination of the known effects of liquid solvents and hydrostatic pressure. Solvent effects are primarily enthapic in nature and typically manifest in upper critical solution behavior. Common solvents mitigate unfavorable interactions between dissimilar segments and enhance miscibility. In blends, the addition of highly selective solvents, e.g. a non-solvent for one component, can lead to precipitation of the unfavored species at high dilution. In block copolymers, the effect of selective solvents is less clear, but studies to date reveal a collection of the solvent at the domain interface, selective dilation of one phase, and stabilization of the disordered phase via depression of the UODT. The systems we have studied each exhibit a lower critical transition. For these specific systems, previous work indicates the hydrostatic pressure suppresses free volume differences between the components and expands the region of miscibility. 

LC-MS for Catharanthus alkaloid analysis is a promising approach which will be increasingly used in the future, as interfaces are improved and highly selective solvent systems become available. The metabolites and catabolites of Catharanthus alkaloids can also be identified and determined by LC-MS conveniently. 

We discuss here two examples of aggregation of diblock copolymers in solution, the formation of spherical micelles in a highly selective solvent, good for one block and poor for the other block, and the formation of ordered mesophases in a common good solvent for both blocks. 

In a dilute solution, blends of homopolymers A and B equivalent to the two blocks of the copolymers are compatible in a common good solvent contrary to what happens in a highly selective solvent, we do not expect mesophases to form in a dilute solution but only in semidilute and concentrated solutions. Mesophases formed by block copolymers in nonselective solvents have been studied many experimental groups, perhaps most recently bv Hashimoto et al. and Williams et al. The usual interpretation of experiments is based on the "dilution approximation" in which the phase diagram of a solution can be obtained from the corresponding pure copolymer phase diagram by replacing Xab AB where is the monomer volume fraction. We have seen in section... 

In a highly selective solvent intermolecular organization occurs even in the dilute regime. Micelle formation has been sudied using a Flory-type model which gives scaling laws for the critical micelle concentration and the micellar sizes. The critical micelle concentration decays exponentially with molecular weight and occurs thus in an extremely dilute solution that is hardly measurable experimentally. In more concentrated solutions micelles order and mesophases are formed. 

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