Ionic prices

Ionic liquid synthesis in a commercial context is in many respects quite different from academic ionic liquid preparation. While, in the commercial scenario, labor-intensive steps add significantly to the price of the product (which, next to quality, is another important criterion for the customer), they can easily be justified in academia to obtain a purer material. In a commercial environment, the desire for absolute quality of the product and the need for a reasonable price have to be reconciled. This is not new, of course. If one looks into the very similar business of phase-transfer catalysts or other ionic modifiers (such as commercially available ammonium salts), one rarely finds absolutely pure materials. Sometimes the active ionic compound is only present in about 85 % purity. However, and this is a crucial point, the product is well specified, the nature of the impurities is known, and the quality of the material is absolutely reproducible from batch to batch. 

A compromise between coloration and economics in commercial ionic liquid production is therefore necessary. Since chromatographic decoloration steps are known and relatively easy to perform (see Section 2.2.3), we would not expect there to be a market for a colorless ionic liquid, if the same substance can be made in a slightly colored state, but at a much lower price. 

For commercial ionic liquid synthesis, quality is a key factor. FFowever, since availability and price are other important criteria for the acceptance of this new solvent concept, the scaling-up of ionic liquid production is a major research interest too. 

The price of ionic liquids is determined by many parameters, such as personnel, overheads, and real production costs. One can imagine that production on a small scale would be mostly determined by the personnel cost and little by the material cost. On a large scale, the material cost should become more important and mainly determine the price of an ionic liquid. This means that the price of a large-scale commercial ionic liquid should be dictated by the price of the cation and anion source. 

The future price of ionic liquids will also reflect intellectual property considerations. While the currently most frequently requested ionic liquids, the tetrafluoroborate and hexafluorophosphate ionic liquids, are all patent-free, many recently developed, new ionic liquid systems are protected by state of matter patents. Table 2.2-2 gives an overview of some examples published after 1999. 

If the ionic liquid can be recycled and if its lifetime is proven to be long enough, then its initial price is probably not the critical point. In Difasol technology, for example, ionic liquid cost, expressed with respect to the octene produced, is lower than that of the catalyst components. 

The cost of the ionic liquid is still a limiting factor. However, the commercial availability of these liquids has improved considerably over the last few years and prices have already gone down significantly [20], This development can be expected to continue as ionic liquids continue to make their transition from curiosities to commodities [79]. In any case the cost of the ionic liquid has to be weighed against that of current chemicals or catalysts. If the ionic liquid can be recycled and if its lifetime proved to be long enough, then its initial price is probably not the critical point. 

The ionic liquid investment could be further reduced if future research enables the application of ammonium based alkylsulfate or arylsulfonate ionic liquids. For these systems bulk prices around 15 /kg are expected. Ammonium based alkylsulfate or arylsulfonate ionic liquids usually show melting points slightly above room temperature but clearly below the operating temperature of the hydroformylation reaction. Therefore these systems may be less suitable for the liquid-liquid biphasic process in which the ionic liquid may be involved in process steps at ambient temperature (e.g. phase separation or liquid storage). In contrast, for the SILP catalyst a room temperature ionic liquid is not necessarily required as long as the film becomes a liquid under the reaction conditions. Assuming an ammonium based SILP catalyst, the capital investment for the ionic liquid for the industrial SILP catalyst would add up to 105,000 . 

On the base of a Rh-price of about 20,000 /kg and a ligand price of about 1000 /kg it becomes quite obvious that the loss of the ionic liquid would only be a minor part of the overall cost arising from the case of complete SILP-catalyst deactivation. It should be noted that a deactivated SILP catalyst may still offer some options for regeneration (e.g. extraction with scC02 to remove heavies). However, these options are not yet developed and their efficiency is unclear at this point. 

Surfactants belong to a group of products where a low price is crucial, and therefore they are usually synthesized from coarsely defined mineral oil fractions or vegetable oils both of which represent (sometimes complex) mixtures (Fig. 11.25). Cationic and anionic surfactants are readily detected by ESI, but it also serves well for the detection of non-ionic surfactants which tend to form [MH-alkali]" or [M-H] ions, respectively. [124-128]... 

Cost and commercial availabiUty More and more lab suppliers and a few large-scale suppliers offer ionic Uquids. For a more frequent use of these solvents the commercially available variety has to be increased and cost should be reduced. There is good reason that cost reductions will be possible in the near future because at least some of the ionic liquids will potentially find use in very large apphcations besides catalysis. They are discussed for fuel desulfurization, separations, hquefication, gasification and chemical modification of sohd fuels, as electrolytes or in connection with synthesis and apphcation of new materials. Also apphcations such as azeotrope-breaking liquids, thermal fluids or lubricants are under consideration. Because of economy of scale in combination with such apphcations, the price of the solvent will decrease significantly. 

Saboungi ML, Price DL,Mao G, Fernandez-Perea R, Borodin O, Smith GD, Armand M, Howells WS (2002) Solid State Ionics 147 225... 

The great technical and economic Tmportance of this product group was reached despite its higher price only because of its special properties. Due to the ionic sulfate group and the adjacent ether groups, ether sulfates combine the classical elements of ionic and nonionic surfactants in one molecule. This provides a number of properties, one of which, the Krafft-Point, is of special importance for the technical application of these compounds. 

Scheme 2.2-1 Typical ions making up ionic liquids, ordered according to their rough price on an industrial scale.

Because of the high price of TPAP, research is being made in order to develop new protocols and modified reagents that allow the recovery of perruthenate—present as TPAP or in other compounds—after oxidation of alcohols. Proposed alternatives include employing TPAP in the presence of ionic salts,62 on an Amberlist anion exchange resin63 or on a silicate.69b,c,d... 

Section 4.3 is devoted to electrodeposition in a special class of deep eutectic solvents/ionic liquids which are based on well-priced educts such as e.g. choline chloride. The impressive aspect of these liquids is their easy operation, even under air, as well as their large-scale commercial availability. One disadvantage has to be mentioned the choline chloride-based liquids especially are currently not yet... 

The motivation of this chapter was to show that despite the enormous prospects of ionic liquids in electrodeposition some troublesome aspects have to be expected. Apart from the purity and price of ionic liquids the optimum temperature for any process has to be found. Furthermore, suitable additives for electrodeposition will have to be developed and cation/anion effects that can strongly alter the morphology of deposits have to be expected. Finally, the electrochemical window alone is not the only factor that needs to be considered for the deposition of reactive metals. Suitable precursors will have to be tailor-made and it is our personal opinion that the electrodeposition of metals like Mg, Ti, Ta and Mo may not be possible from metal halides but rather metal bis(trifluoromethylsulfonyl)amide salts and other ones may be more suitable. 

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