Production of cumene hydroperoxide

Cumene hydroperoxide, obtained by the oxidation of cumene, is concentrated by submitting the crude oxidate to fractional distillation, withdrawing an overhead fraction containing unreacted cumene and acid by-products and recycling this acidic fraction to the oxidation, adding "fresh cumene" (i.e. cumene which contains substantially no acid or water) to the fractionator as liquid reflux, and withdrawing concentrated cumene hydroperoxide from the still. The overhead fraction is preferably separated from aqueous liquid and washed with alkali, in order to remove acid, before it is recycled to the oxidation. In a preferred embodiment, the concentration is carried out in two stages in series, the overhead fraction from the first stage being recycled to the oxidation, and part of the overhead fraction from the second stage (i.e. dry cumene substantially free from acid) being used as reflux liquid for both stages. In an example, a cumene oxidation product containing 23,4% by weight of cumene hydroperoxide and having a pH of 9 is concentrated in two stages, both of which consist of a climbing film evaporator combined with a fractionator. The final concentrate contains 82,5% by weight of cumene hydroperoxide and has a pH of 6,5.