Ionic liquids BASIL process

Biphasic Acid Scavenging Utilising Ionic Liquids (BASIL ) process, 26 899, 900 Biphenyls... 

In 2002 BASF established the first dedicated industrial-scale ionic liquid-based process [7]. The so-called BASIL process (BASIL = Biphasic Acid Scavenging utilizing Ionic Liquids) is used for the synthesis of alkoxyphenylphosphines, which are important raw materials in the production of BASF s Lucirines (Scheme 9-3), substances that are used as photoinitiators to cure coatings and printing inks by exposure to UV light. 

In the BASF BASIL process that utilizes A-methylimidazole to scavenge HCl byproduct, the acidic ionic liquid A-methylimidazolium chloride [HMIMJCl was formed, with a melting point of 75°C (13,102). Recently, the group of Bronsted acidic ionic liquids with the same cation was extended to include other anions, such as BFF, TfO , and TsO . The melting point of the salt is between 30 and 109°C. Strong hydrogen bonding in the tosylate salt was characterized by IR spectroscopy. 

BASF s BASIL process [15] and the Dimersol process [16] have both been commercialized. The former uses the ionic liquid as a phase transfer catalyst to produce alkoxyphenylphosphines which are precursors for the synthesis of photoinitiators used in printing inks and wood coatings. The imidazole acts as a proton scavenger in the reaction of phenyl-chlorophosphines with alcohols to produce phosphines. The Dimersol process uses a Lewis acid catalyst for the dimerization of butenes to produce Cs olefins which are usually further hydroformylated giving C9 alcohols used in the manufacture of plasticizers. Several other processes are also at the pilot plant scale and some ionic liquids are used commercially as additive e.g. binders in paints. 

BASIL [Biphasic Acid Scavenging utilizing Ionic Liquids] A range of catalytic processes for synthetic organic chemistry. These processes use ionic liquids as solvents, from which it is easy to recover the catalysts. Developed by BASF from 2002 and first commercialized in 2004 for the synthesis of alkoxyphenyl phosphines. Awarded the Entec Medal for safety and environmental innovation in 2005. 

The BASIL process economically avoids the problems resulting from solids generation by making use of ionic liquids to scavenge acids. Instead of using a tertiary amine, 1-alkylimidazole is used to scavenge the produced acids. As the imidazole reacts with the acid, an alkylimidazolium salt is formed that is an ionic liquid at the reaction temperature. As a liquid, the alkylimidazolium salt can be easily removed by a liquid-liquid phase separation. 

Alkylimidazole acts also as a nucleophilic catalyst, thereby improving reaction rates, and increasing yields and selectivities. The IL liquid in the BASIL process thus acts as co-catalysts and scavenger for by-products. The space-time yield was increased from 8kgm h using the old process (without ionic liquid) to 690 000 kg m h using the BASIL process an 80 000-fold increase in productivity. 

Of course, the intrinsic presence of neutral molecules in pure ionic liquids becomes more and more relevant if the equilibrium constant is less and less in favor of the ionic compound. For the N-protonated l-alkyUmidazolium salts the amount of neutral, unprotonated alkylimidazole is obviously a function of the anion s basicity. Here, the wide range of potential anion basicities has provoked the question as to whether these systems should at all be considered as ionic liquids. However, some convincing applications of these substances in catalysis [28] and organic synthesis [29] (see BASIL process in Chapter 9) and physical measurements [30] have led to the now widely accepted view that at least combinations of 1-alkylimidazoles with strong acids can be regarded as ionic liquids. 

Figure 3 The BASIL process. After the reaction two clear liquid phases are obtained the upper one is the pure product and the lower is the ionic liquid HMIMCI ( BASF Aktiengesellschaft 2002).

During 2003 we saw the first published process based on ILs [6], In its BASIL process (see Section 5.3.2), BASF has disclosed the involvement of an imidazolium-based ionic-liquid in the production of alkoxyphenylphosphines. This constitutes an impressive demonstration that IL technology can result in significant financial savings. Another process said to be poised for licensing is the French Petroleum Institute s butene dimerization process, the Difasol process (see Section 5.3.1). Besides these, some more promising applications are currently under investigation, and are hoped to be disclosed in the near future. Notable examples of research areas are in electrochemistry (batteries), biocatalysis, and the application of ILs in extraction processes, e.g., the deep desulfurization of diesel oil. 

Using the BASIL process (the acronym stands for Biphasic Add Scavenging utilizing Ionic Liquids), BASF was the first company to transfer ionic liquids from laboratory to commercial dimensions, and the BASIL process became the first large-scale industrial process worldwide that uses ionic hquids. 

After the reaction, there are two clear liquid phases that can easily be worked up by a simple phase separation. The upper phase is the pure product and no reaction solvent is needed. The lower phase is the pure Ionic Liquid and can be deprotonated with sodium hydroxide, regenerating the methylimidazole (Fig. 20.13). Comparing to the conventional method (Fig. 20.14a), BASIL process uses a much smaller reactor (Fig. 20.14b). 

Maase M, Massonne K, Uerdingen E, Vagt U (2006) BASIL - BASF s processes based on ionic liquids. Aldrich Chem Files 6(9) 3... 

Protic ionic liquids are technically attractive because they represent a range of materials that may be readily prepared simply by mixing a suitable proton acceptor and a Bronsted acid. Because of the reversibility of protonation, the conponent acid and base may, in principle, be separated, purified and the salt subsequently reformed, a route to recovery and recycle not generally available for fully allq lated ionic liquids. Indeed, the ionic liquid, 1-methylimidazolium chloride, a vital conponent of the BASIL process, is attractive for this very reason. 

The first industrial process to involve ionic liquids was introduced by BASF in 2002. Called BASIL", this technology addresses the problem of HCl formed as a byproduct in the synthesis of alkoxyphenylphosphanes (eq. 9.86). Before the advent of ionic liquids, HCl was scavenged by a tertiary amine, forming a solid [RsNHJCl salt which was separated by filtration. On a commercial scale, this operation is expensive. BASF now uses 1-methylimidazole to scavenge HCl (eq. 9.87). 1-Methylimidazolium chloride is an ionic liquid (mp 348 K) which is immiscible with the reaction solvent. Separation of the two liquid phases is achieved at a lower cost than the filtration previously needed. Deprotonation of the 1-methylimidazolium cation regenerates imidazole which is recycled. 

Basil A trademark used by BASF for their range of processes using ionic liquids, which includes BASIL. Basset See DR. 

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