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BASIL™– The first commercial process using ionic liquids |
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BASF’s innovative BASIL™ technology can significantly improve chemical processes, increasing yields and capacities. This technology involves what are known as ionic liquids, and provides an elegant solution to a challenge met in many production processes: The removal of acids that are formed as by-products. The conventional method results in the formation of solid salts, which cause problems in large-scale production. If the BASIL™ technology is used, however, the salts remain liquid and are much easier to handle.
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Acid by-products have to be removed to prevent decomposition of the desired product. Normally, tertiary amines such as triethylamine are used to scavenge the acids, but bases like these form solid salts when they react with acids, and the reaction mixture becomes a suspension.
Suspensions are easy to handle on a laboratory scale, but on the industrial scale they can cause serious problems. They usually make the reaction mixture more viscous, leading to insufficient mixing of the reactants. Heat transfer in large vessels containing suspensions is often less than satisfactory, so hot spots may occur. Furthermore, it is difficult to transport suspensions through piping, and filtration to separate the solid and liquid phases is expensive and can be time-consuming.
If an acid has to be scavenged with a base, then formation of a salt is unavoidable. But why not form a liquid salt? This is the basic idea behind the BASIL™ technology. The abbreviation stands for “Biphasic Acid Scavenging utilizing Ionic Liquids.”
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Ionic liquids have unique properties: They are salts that consist 100 percent of ions and they are liquid at temperatures below 100C. Because they are relatively polar materials, they do not mix with solvents or nonpolar product molecules. Ionic liquids have been the subject of extensive research in academic circles in recent years. BASF was quick to pick up on this and rapidly developed an effective solution for a specific production problem.
Using the BASF product 1-methylimidazole as an acid scavenger, an ionic liquid is formed: 1-methylimidazolium chloride, which has a melting point of 75C. The clear liquid phase can easily be separated and used for further reaction steps. BASIL™ is more than a technology for acid scavenging, however. The 1-methylimidazole used also acts as a catalyst and speeds up the reaction considerably. As a result, it is possible to use a narrow, continuously operated jet reactor instead of a stirring vessel. The reactor is only thumb-sized, but is able to produce hundred of tons of product. Since 2002, the BASIL™ process has been used in the routine production of alkoxyphenylphosphines, handling ionic liquids on a multi-ton scale. Alkoxyphenylphosphines are important raw materials for the production of BASF’s Lucirin® photoinitiators that are used to cure coatings and printing inks by exposure to UV light.
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