Lewis acids industrial applications

The field of reaction chemistry in ionic liquids was initially confined to the use of chloroaluminate(III) ionic liquids. With the development of neutral ionic liquids in the mid-1990s, the range of reactions that can be performed has expanded rapidly. In this chapter, reactions in both chloroaluminate(III) ionic liquids and in similar Lewis acidic media are described. In addition, stoichiometric reactions, mostly in neutral ionic liquids, are discussed. Review articles by several authors are available, including Welton [1] (reaction chemistry in ionic liquids), Holbrey [2] (properties and phase behavior), Earle [3] (reaction chemistry in ionic liquids), Pagni [4] (reaction chemistry in molten salts), Rooney [5] (physical properties of ionic liquids), Seddon [6, 7] (chloroaluminate(III) ionic liquids and industrial applications), Wasserscheid [8] (catalysis in ionic liquids), Dupont [9] (catalysis in ionic liquids) and Sheldon [10] (catalysis in ionic liquids). 

Later on, this concept was extended to precursors containing both elements of the desired material already connected by a chemical bond in a single molecule. Such precursors are mainly referred to as single source precursors. Their potential application for the deposition of thin films of the corresponding binary materials by MOCVD processes could be demonstrated. In particular Lewis acid-base adducts R3M—ER3 and four- and six-membered heterocycles [R2MER x (Fig- 1) have been in the focus of research groups both in industry and university. Consequently, the development of powerful synthetic pathways for the preparation of such precursors has been forced. 

The aluminum trihalides are particularly important Lewis acids in the chemical industry. They promote or catalyze a large variety of reactions. One of the most important applications is the Friedel-Crafts reaction, in which two molecules combine, forming a new C—C bond. For example, aluminum chloride or some other Lewis acid catalyzes the reaction between an acid chloride and benzene to form acetophenone ... 

An application of industrial importance of Lewis acidic metal salts is the condensation of carboxylic diacids and diols to give polyesters. This is an acid catalysed reaction that in the laboratory is usually catalysed by protic acids. For this industrial application salts of manganese, nickel, or cobalt and the like are used. From a chemical point of view this chemistry may not be very exciting or complicated, the large scale on which it is being carried out makes it to an important industrial reaction [29],... 

Zeolites and other mesoporous materials are excellent catalysts for industrial and laboratory applications. Favourable characteristics are their capacity to immobihze homogenous catalysts rendering them heterogeneous, their thermal stability, and the ease of separation from the reaction products and reuse in hquid- and gas-phase conditions. The pore size and Brpnsted and Lewis acidic properties are determinant for their use as catalyst in the Beckmann rearrangement. Recently, a review on the use of zeolites and mesoporous materials in the Beckmann rearrangement was published. ... 

Main-group metal alkyls and aryls are valuable tools in preparative organic and inorganic chemistry, and many industrial applications are known for these reactive substances. In addition, they have attracted considerable attention from a more fundamental and theoretical point of view, because the high Lewis acidity at the metal center is the source of singular structures and bonding (1-3). 

Conceptually new multifunctional asymmetric two-center catalysts, such as the Ln-BINOL derivative, LnMB, AMB, and GaMB have been developed. These catalysts function both as Brpnsted bases and as Lewis acids, making possible various catalytic, asymmetric reactions in a manner analogous to enzyme catalysis. Several such catalytic asymmetric reactions are now being investigated for potential industrial applications. Recently, the catalytic enantioselective opening of meso epoxides with thiols in the presence of a heterobimetallic complex has... 

Traditionally, industrial isomerization processes involve the use of Bronsted and Lewis acids, such as HjSO, and AICI3 that are uneconomical to recycle for most of the chemical applications. Replacement of such bulk chemicals with recyclable zeolites is a very attractive... 

Transalkylation of alkylbenzenes, polyalkylbenzenes and other arenes can be brought about by a variety of catalysts including Lewis acids, Brpnsted acids and various zeolites and silicates with or without being doped with various transition metals or their oxides. There has been a particularly explosive growth in the volume of literature pertaining to the use of various natural and modified zeolites. Recent developments include the study and applications of shape-selective catalysis by zeolites. Much of the work is patented, and largely applies to industrial processes. 

Another well known example of successful application of Beta zeolite is the substitution of AICI3 for Friedel-Crafts acylation. This reaction is an important industrial process, used for the preparation of various pharmaceuticals, agrochemicals and other chemical products, since it allows us to form a new carbon-carbon bond onto an aromatic ring. Friedel-Crafts acylations generally require more than one equivalent of for example, AICI3 or BF3. This is due to the strong complexation of the Lewis acid by the ketone product. 

Significant advances resulting from the use of aluminosilicate solids were made during the last few years [3-6] and the first industrial application of zeolites in large scale Friedel-Crafts acylations was reported very recently [7]. However, most of the efforts devoted so far focused on the acylation of aromatic compounds. To the best of our knowledge, recourse to heterogeneous aluminosilicate catalysts for the acylation of alkenes has not yet been reported. Conventional methods for alkene acylation [8] involve the use of Br0nsted or Lewis acids such as sulfuric acid [9], boron trifluoride [10], zinc chloride [11], or... 

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