Chemistry

Ion-Transfer Technology products fall into two categories, Solvent Extraction (SX) and Phase Transfer Catalysis (PTC). Both rely on the same concept, transporting chemical species from one phase to another and back again.

Solvent Extraction. In SX, the objective is to isolate a desired component or impurity(s) by moving it from a crude aqueous organic phase and then recovering it from, or regenerating, the organic phase by transferring that component(s) into a second aqueous phase.

Thus in SX, a desired species is either isolated and/or concentrated in the second aqueous phase, or the crude aqueous phase is purified by having undesirable components removed. From the first aqueous phase all of the Ion-Transfer Technology products, the Alamine^® and/or Aliquat^® Reagents, accomplish the SX process by forming ion pairs with the component(s) to be transported.

For this reason the component(s) must have a net negative charge. This can be accomplished by having a native negative charge as is the case of ionized acids, or by forming a complex which has a net negative charge as in the case of uranium production, UO₂(SO₄)₂^2- .

In either case, the negatively changed species forms an ion pair with the protonated form of amine (in this example Alamine^® 336) reagents. Of necessity, the environment must be acidic, i.e. pH 3 or below in order for the amine to be protonated. By this we mean that the amine associates itself with a proton (a hydrogen ion) to become a quaternary ammonium structure with a net positive charge.

Conversely, the Aliquat^® Reagents are already in the quaternary form and can form ion pairs in neutral or alkaline environments because they have a permanent positive charge. The component(s) to be transported still need to have a net negative charge in either case.

All product types, the Alamine^® and Aliquat^® Reagents have large organic ligands, and are thus capable of forming oil soluble ion pairs with water-soluble anions. To recover the desired component or regenerate the reagent, the organic phase is treated in some way so as to break the oil soluble ion pair and to transfer the target component(s) into a second aqueous phase or precipitate it from the organic phase.

In either case, the organic phase containing the reagent is regenerated and can be recycled to extract more target component(s) from the crude aqueous phase.

Cognis Alamine^® Products are tertiary amines with three straight chain C₈ to C₁₂ ligands, depending on the product.

Phase Transfer Catalysis. In the PTC process, the same concept applies, that of transporting ionic species from one phase to another. The difference lies in the fact that with PTC, a chemical reaction is promoted and nothing is “isolated” or “purified" during the reaction process. Instead, PTC promotes organic synthesis reactions by transferring mutually insoluble reactants into a common phase.

Contrary to common perception, PTC is not limited to systems with aqueous and organic soluble reactants. PTC is sometimes employed in liquid/solid and liquid/gas reactions. As the name implies, one or more of the reactants are transported into a second phase, which contains the other reactants. In this way, the reaction is not only accomplished, but promoted.

By using a PTC process, one can achieve faster reactions, obtain higher conversions or yields, make fewer byproducts, eliminate the need for expensive or dangerous solvents which dissolve all the reactants in one phase, eliminate the need for expensive raw materials and/or minimize waste problems.

Phase Transfer Catalysts generally fall into three types:

1. Quaternary Ammonium Compounds such as the Aliquats^® 100, 138 and 175.

2. Quaternary Phosphonium Compounds such as the Aliquat^® HT products.

3. Complexants, which are generally polyethers of complex structure, such as Aliplex^® 186DB, a crown ether.

Each PTC product in the Ion-Transfer Technology line is selected for its particular ability to be the best catalyst for specific processes.

There is also a third group of ITT products, the Aloxime^® Chelating Reagents. Currently, three different Aloxime^® Reagents are available from Cognis. Each is designed for a specific chelation property. Aloxime^® 500 is a b-diketone, Aloxime^® 800 is a phenolic aldoxime and Aloxime® 840 is a phenolic ketoxime. In all cases, their intended use is to solubilize metal ions in organic media.

For further information about Ion-Transfer Technology or for technical assistance, please contact Mike Virnig

Alamine^®, Aliquat^®, Aliplex^® and Aloxime^® are registered trademarks of Cognis Corporation.