GB756408A - Improvements in the manufacture of phenol and cresols - Google Patents

Abstract

In the decomposition of iso-propylbenzene hydroperoxide or of a cymene hydroperoxide with sulphuric acid to produce phenol or a cresol and acetone, the sulphuric acid in the crude decomposition mixture is neutralised by the addition of an aqueous alkaline solution containing from 10 to 60 per cent by weight of the alkali-metal salt of the phenol produced in the decomposition, prior to fractional distillation of the mixture to obtain the phenolic products. The aqueous alkaline solution may contain in addition up to 20 mol. per cent of free alkali-metal hydroxide, based on the total alkali-metal present in the solution. An excess of the aqueous alkaline solution over that required for neutralisation of the sulphuric acid may be used but the alkali-metal hydroxide content should not be more than 20 mol. per cent of that required for the complete neutralization of the acid. The alkali-metal specified is sodium. The alkali-metal sulphate formed by the neutralization is removed by filtration prior to fractionation. The process may be a batch one or continuous. In examples: (1) cumene hydroperoxide was decomposed with sulphuric acid in acetone, the acid neutralized with 10 percent sodium phenate solution, the mixture filtered, acetone, isopropylbenzene and a -methyl-styrene removed by distillation and phenol obtained by fractionation; (2) in a continuous process the a -methyl-styrene-phenol azeotrope fraction from the distillation of the decomposition product of cumene hydroperoxide was extracted with sodium hydroxide solution to give sodium phenate solution containing free alkali; the acetophenone-phenol azeotrope fraction was similarly treated and the phenate solutions combined and used to neutralize the acid catalyst in a further decomposition reaction mixture which was filtered and distilled to recover phenol, plus an acetophenone-phenol azeotrope and an a -methyl-styrene azeotrope which were then recycled; (3) the neutralization of a cumene hydroperoxide decomposition mixture with sodium phenate is compared with neutralizations using calcium hydroxide, sodium carbonate (anhydrous), sodium bicarbonate, sodium carbonate solution and sodium hydroxide; (4) neutralization of a cymene hydroperoxide decomposition mixture with sodium p-cresylate is described and compared with a similar neutralization using sodium hydroxide.