Alkylphenols
Authors: Lorenc John F. , Lambeth Gregory , Scheffer William 
Published: August 2004

The production of alkylphenols in 1993 exceeded 450,000 t/yr on a worldwide basis. Alkylphenols of greatest commercial importance have alkyl groups ranging in size from one to twelve carbons. The vast majority of alkylphenols are used to synthesize derivatives which have applications ranging from surfactants to pharmaceuticals. The four principal markets are nonionic surfactants, phenolic resins, polymer additives, and agrochemicals. Nonionic surfactants and phenolic resins based on alkylphenols are mature markets and only moderate growth in these derivatives is expected. Concerns over the biodegradability and toxicity of these alkylphenol derivatives to aquatic species may limit their use in the future. The use of alkylphenols in the production of both polymer additives and monomers for engineering plastics is expected to show above‐average growth as plastics continue to replace traditional building materials. Alkylphenols containing 3–12‐carbon alkyl groups are produced from the corresponding alkenes under acid catalysis. Alkylphenols containing the methyl group are produced by the alkylation of phenol with methanol. An alkylphenol is a phenol derivative wherein one or more of the ring hydrogens has been replaced by an alkyl group(s). Appropriate names of alkylphenols for abstract citations can be unambiguous and refer to a specific compound, but are lengthy and cumbersome to use. Common names are prevalent for alkylphenols commercial importance. The physical properties of alkylphenols are comparable to those of phenol and are strongly influenced by the type of alkyl substituent and its position on the ring. The solubility of alkylphenols in water falls off precipitously as the number of carbons attached to the ring increases. They are generally soluble in common organic solvents: acetone, alcohols, hydrocarbons, toluene. Alkylphenols can be synthesized by alkylation of a phenol, hydroxylation of an alkylbenzene, dehydrogenation of an alkyl‐cyclohexanol, or ring closure of an appropriately substituted acyclic compound. Alkylphenols undergo a variety of chemical transformations, involving the hydroxyl group or the aromatic nucleus that convert them to value‐added products. Alkylphenols of commercial importance are generally manufactured by the reaction of an alkene with phenol in the presence of an acid catalyst. Reactors used to produce alkylphenols are simple batch reactors, complex batch reactors, and continuous reactors. Some alkylphenol applications can tolerate “as is” reactor products, but most alkylphenols sold today require refinement, eg, distillation. Most commercially important alkylphenol production is of three types, unrefined alkylphenols, monoalkylphenols, and dialkylphenols. The toxicity of alkylphenols as a class of compounds ranges from moderately toxic to practically nontoxic and most are irritants or corrosive toward skin. Commercial uses and derivatives of alkylphenols include 4‐tert‐amylphenol, used in phenolic resins; 4‐tert‐butylphenol, used in phenolic resin applications; 2‐sec‐butylphenol, used as a polymerization inhibitor in the production of styrene, but with market growth expected to be negative because of environmental concerns; 4‐cumylphenol, used as a chain terminator for polycarbonates; 4‐dodecylphenol, used in lube oil additives; 2‐methylphenol, used in the production of novolak phenolic resins; 3‐methylphenol, used in the production of phenolic‐based antioxidants and in the production of herbicides and insecticides; 4‐methylphenol, used in the production of phenolic antioxidants; 4‐nonylphenol, used in the production of nonionic surfactants and in the production of tris(4‐nonylphenyl) phosphite (TNPP), a secondary antioxidant which protects organic materials against oxidative degradation; 4‐tert‐octylphenol, used in the production of ethoxylates and phenolic resins; and dialkylated phenols, used in the production of uv stabilizers, polyolefin films, outdoor furniture, and clearcoat automotive finishes, and in the photographic industry.