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【正文】 ation or anion, were used. An example is the use of [3(triphenylphosphonium) propanesulfonic acid][tosylate tosylate[Gr.,=without water], chemical pound formed by removing water, H2O, from another pound。and ethanoic anhydride anhydridenoderivatives of the imidazolium cation, ., 4(3methylimidazolium) butanesulfonic acid [35]. This last approach could be used to enable the ionic liquid to catalyze esterification, transesterification, and specifically biodiesel forming reactions. Also, it is possible to design the ionic liquid in such a way that it can be recovered intact at the end of a reaction, thus not creating any ionic liquid waste, and recycled (one of the issues with ionic liquids is that they can be more expensive than some of the simpler catalysts, and somewhat more expensive than conventional solvents).Esterification reactions in ionic liquids Esterification reactions readily occur in certain ionic liquids. A simple example is reactions catalyzed by the Franklin basic [36,37] 1butylpyridinium ionic liquid, [C4py]ClAlCl3 [38,39]. Unfortunately, the ionic liquid is consumed in the reaction. It is known that the [[]]anion dissociates to phosphate and fluoride ions under aqueous conditions, and this could lead to catalyst being turned into an inactive fluoride salt [40]. Despite this, Tang et al. used the 1methylimidazolium tetrafluoroborate ionic liquid ([Hmim][[]]) as a solvent and catalyst for the reaction [41]. Another example is the reaction of primary, secondary, and tertiary alcohols that were ethanoylated with ethanoic acidethor both of the ionic liquids acidic or basic (either Lewis or Bronsted) [34]. Specific examples of ionic liquids which exhibit Bronsted acidity due to functionalized cations include sulfonic acid sulfonic acid(?n`ī39。ī`?n), atom or group of atoms carrying a positive charge. The charge results because there are more protons than electrons in the cation. ..... Click the link for more information.is a viable method, but this involves large volumes of water [7].Table 1 lists Bronsted acidic and basic catalysts, lipase catalysts, and supercritical alcohol catalysts. In regards to Lewis basic and acidic catalysts, there are several examples in the literature [2428].What role can ionic liquids play? Ionic liquids have been used in a large number of chemical reaction types. Examples can be found in the twovolume book by Wasserscheid and Welton [29] and a review on the industrial applications of ionic liquids [30]. The principal reasons for attempting reactions in ionic liquids is that these solvents are involatile except at low pressures and high temperatures [31], and their properties can be designed to suit a particular need (designer solvents) [32]. An example of design is to alter the structure of ionic liquid such that it phase separates from the product of a reaction, making product isolation easier [33]. Another approach is to make either the cationcationalcohol was shown to have a higher reaction rate than transesterification when using the same supercritical alcohol [7].
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