Friedel-Crafts Alkylation of Aromatics with Alcohols and Transalkylation Reactions: From Solid Acid Catalysts to Green Ionic Liquids

The Friedel-Crafts alkylation is a powerful substitution reaction to synthesize alkylphenols. Substitution by an alkyl group results from attack on the aromatic hydrocarbon by a cation (carbonium ion), a neutral fragment (free radical) or an anion (carbanion). The use of alcohol as alkylating agent for Friedel-Crafts reaction gives the benefit of a long stable life of the catalyst and ease of storage and transportation. The alkylphenols prepared from the alkylation of aromatics with alcohol has industrial applications in the production of high-octane gasoline and synthetic rubbers, fibres, detergents, and plastics. The yield of desired alkylphenols is further enhanced by transalkylation of the side products, di-alkylphenols, with similar or dissimilar molecules. This review details the progress of alkylation and transalkylation of aromatics with alcohols over tailor-make zeolite molecular sieves and room temperature ionic liquids to get a high yield and selectivity for a particular reaction of interest.