Phenol and Acetone from Cumene 

Phenol, C₆H₅OH (hydroxybenzene), is produced from cumene by a two step process. In the first step, cumene is oxidized with air to cumene hydroperoxide. The reaction conditions are approximately 100–130°C and 2–3 atmospheres in the presence of a metal salt catalyst:

In the second step, the hydroperoxide is decomposed in the presence of an acid to phenol and acetone. The reaction conditions are approximately 80°C and slightly below atmospheric:

In this process (Figure 1.1), cumene is oxidized in the liquid phase. The oxidation product is concentrated to 80% cumene hydroperoxide by vacuum distillation.

Figure 1.1. The Mitsui Petrochemical Industries process for producing phenol and acetone from cumene: (1) autooxidation reactor, (2) vacuum tower, (3) cleavage reactor, (4) neutralizer, (5–11 ) purification train.

To avoid decomposition of the hydroperoxide, it is transferred immediately to the cleavage reactor in the presence of a small amount of H₂SO₄. The cleavage product is neutralized with alkali before it is finally purified. After an initial distillation to split the coproducts phenol and acetone, each is purified in separate distillation and treating trains. An acetone finishing column distills product acetone from an acetone/water/oil mixture. The oil, which is mostly unreacted cumene, is sent to cumene recovery. Acidic impurities, such as acetic acid and phenol, are neutralized by caustic injection. Figure 1.2 is a simplified flow diagram of an acetone finishing column, and Table 1.1 shows the feed composition to the acetone finishing column. Cumene processes are currently the major source for phenol and coproduct acetone.

Phenol is released from the sodium salt of phenol by the action of carbon dioxide or sulfur dioxide.

Figure 1.2. A simplified process flow chart of an acetone finishing column.

Table 1.1: Feed composition of acetone finishing column

Direct hydroxylation of benzene to phenol could be achieved using zeolite catalysts containing rhodium, platinum, palladium, or irridium. The oxidizing agent is nitrous oxide, which is unavoidable a byproduct from the oxidation of KA oil to adipic acid using nitric acid as the oxidant.14 Phenol is also produced from chlorobenzene and from toluene via a benzoic acid intermediate (see “Reactions and Chemicals from Toluene”).