BASIL process

Nobody would have predicted this application, but this shows that ILs can be smart and simple solutions to complex problems including chemistry, process engineering, and separation technology. 

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

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. 

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. 

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. 

Fig. 9-4 Today the BASIL process is run in a small jet reactor that has a capacity of 690 000 kg h". BASF Aktiengesellschaft 2002.

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. 

From an engineering point of view, ILs offer a huge potential (similar to the aqueous variants as described in Chapter 2) for separating reaction products and recycling the catalyst. New reactors may be smaller than in conventional homogeneous catalysis (e.g., the Difasol or Basil processes), which contributes to making processes environmentally friendlier . 

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. 

BASF s Basil process uses ILs as functional materials and not as a solvent The IL (e.g., methylimidazolium chlorhydrate) is formed during the chemical reaction while scavenging acid byproducts (e.g., HCl). The generation of IL leads to the formation of two clear phases in the reactor, thus solving the problem of separation of byproduct and the elimination of solid formation. This leads to an increase in reaction rate and productivity and a decrease in reactor volume. 

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. 

The use of BASF s BASIL process for scavenging hydrochloric adds in the chemical synthesis of phosphorus compounds like 02POR or 0P (OR)2 by reaction of 02PC1 (or 0PCI2) and ROH offers significant advantages over the conventional system (Figure 3.8). 

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). 

Fig. 20.15 BASIL process with a much smaller jet reactor. Image copyright from BASF—The Chemical Company...

A significant commercial application of Bronsted acidic ILs has been by BASF with their range of BASIL processes, which involve ILs in industrial processes. These include the PIL [HMImjCl, where the PIL is produced from using 1-methylimidazolium as an acid scavenger of HCl, and the Bronsted acidic AIL [EMIm]HS04, used in liquid-liquid extraction. In 2003, Rogers and Seddon reported that, for one particular BASIL process, the productivity had been increased by a factor of 80 000 compared to the conventional process ... 

BASF—BASIL process, 2007 http //www2.basf.de/en/intermed/nbd/ products/ionio liquids. 

ILs are known [35,36]. Two prominent examples are the BASIL process from BASF [37] and the dissolution of cellulose to make high-value fibers out of it [38]. 

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