Friedel-Crafts reactions commercial solid catalyst

Sulfated zirconia is a good example of a structural Lewis acid which has been chemically treated to enhance acidity. It has been extensively studied as a solid acid catalyst for vapour phase reactions and we1112 and others14 have found that a mesoporous version of this material is a particularly effective catalyst for liquid phase Friedel-Crafts alkylation reactions and to a lesser extent Friedel-Crafts benzoylations. The commercial (MEL Chemicals Ltd) material SZ999/1 shows a nitrogen isotherm characteristic of a mesoporous solid (surface area 162 m2g, pore volume 0.22 cm3g )- Whereas microporous and mesoporous materials are capable of rapidly catalysing the alkylation of benzene with various alkenes (Table 1), on reuse only the mesoporous... 

Aromatic ketones are important intermediates in the production of fine chemicals and pharmaceuticals1,2. Thus, the anti-rheumatic Naproxen is produced by the Friedel-Crafts acetylation of 2-methoxynaphthalene into 2-acetyl-6-methoxynaphthalene and subsequent Willgerodt-Kindler reaction. Commercial acylation processes involve over-stoechiometric amounts of metal chlorides (e g. AICI3) as catalysts and acid chlorides as acylating agents, which results in a substantial formation of by-products and in corrosion problems. This is why the substitution of these corrosive catalysts by solid acid catalysts and of acid chlorides by anhydrides or acids is particularly desirable. 

There are a few other references in the scientific literature (as well as a number in the patent literature) to chemically fixed supported Lewis acids. Iron(III) chloride should be reactive enough to form surface OFeCk bonds, for example, and a stable form of supported FeCl3 has been reported.121 The solid acid has been used to catalyse liquid phase Friedel-Crafts benzoylations, although the surface structure and activity on reuse of the catalyst have not been described. At least one commercial form of supported iron(III) chloride is available." Supported SbFs has also been extensively studied, although mostly for gas-phase reactions such as the skeletal isomerisation of alkanes where it exhibits high activity indicative of its strong acidity (H0 = ca. —14).122... 

Zinc oxide, an inexpensive and commercially available inorganic solid, can be utilized as an efficient catalyst in the Friedel-Crafts acylation of activated and unactivated aromatic compounds with acyl chlorides at room temperature for 5 to 120 min (Table 4.14). Acylation is claimed to occur exclusively at the para-position of the monosubstituted aromatic compounds. The catalyst can be recovered and reused, after washing with methylene chloride, for at least two further cycles, showing quite similar high yield (-90%) in the model benzoylation of anisole. Mechanistically, it seems that zinc chloride can be the true catalyst, generated in situ by the reaction of zinc oxide with hydrogen chloride. 

Alkylation of Aromatics with Liquid Catalysts. Forty years ago, ethylbenzene, cumene, and dodecyl benzenes were produced by alkylation reactions of benzene with liquid catalysts. Although some production processes still involve these catalysts, solid catalysts such as zeolites are now often the preferred catalysts. Olefins are generally employed for commercial alkylation reactions. The chemistry discussed next will involve liquid catalysts that are protonic acids or Friedel-Crafts catalysts. 

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