GB630487A - Improvements in and relating to the alkylation of phenols - Google Patents

Abstract

Phenol or a cresol is alkylated by treatment with an aliphatic mono-olefine in the presence of a catalyst comprising either oleum of at least 20 per cent strength or the reaction prodduct of a portion of the compound to be alkylated and concentrated sulphuric acid or oleum of less than 20 per cent strength, the compound to be alkylated, the olefine, and the said reaction product if such be used, being treated for the removal of water prior to the alkylation. Olefines containing five to eight carbon atoms especially the octenes are advantageously used and are preferably of a tertiary nature. Dimers of butylene are suitable octenes. The acidic catalyst preferably amounts to 3 to 15 per cent by weight of the phenol or cresol to be reacted. The reactants and catalyst may be dried by any convenient method, e.g. by distillation or with water-absorbing materials. It is preferred to operate at below 50 DEG C. although temperatures of 20-80 DEG C. are stated to be suitable. In examples (1) excess commercial cresylic acid is reacted with 98 per cent sulphuric acid, to form a catalyst, distilled to remove water, and dried butene dimer added at 40 DEG C. to produce a high yield of octyl cresols compared with a similar experiment in which the reactants are not dried; (2) is a repetition of (1) using mixed 2 : 4 : 4-trimethyl pentene-1 and 2 : 4 : 4-trimethyl pentene-2 as olefine with various reaction times; in (3) dry butene dimer and commercial cresylic acid are reacted at 20 DEG C. to produce octyl cresols in the presence of a catalyst prepared by treating commercial cresylic acid with 20 per cent oleum at about 90 DEG C. and in (4) 20 per cent oleum is added to excess dry commercial cresylic acid and reacted at 75 DEG C. to form a catalyst when dry butene dimer is added with the temperature at 20 DEG C. and octyl cresols obtained. In the Provisional Specification the process comprises reacting a phenol with an olefine in the presence of a strongly acid catalyst under substantially anhydrous conditions or in the presence of not more than one gram molecule of water per gram molecule of strongly acid catalyst present. Phenol, cresols and xylenols are specified p phenols and anhydrous zinc chloride, ferric chloride, aromatic or aliphatic sulphonic acids, phosphoric acid, phosphorous pentoxide and hydrogen halides are specified catalysts.