Reactions Involved in Cumene Peroxidation Process:
C6H5CH (CH3) + O2 → C6H5C (CH3)2OOHC6H5C (CH3)2OOH + H2SO4 ↔ C6H5OH + CH3COCH3
(Cumeneperoxide) (Phenol) (Acetone)
Material Requirements:
The raw materials that are required for the manufacture of phenol involve the following materials.
- Cumene
- Air
- Sulfuric acid
- Sodium hydroxide
Co-product: Acetone
A Short Process Description for Phenol Manufacturing:
The cumene peroxidation process for the manufacture of phenol involves the liquid phase air oxidation of cumene to cumene peroxide, which in turn is decomposed to phenol and acetone by the action of an acid.
The cumene (isopropylbenzene) may be manufactured by either liquid or vapor phase alkylation of benzene with propylene. In the liquid phase, the alkylation catalyst is usually sulfuric acid; in the vapor phase, it is phosphoric acid absorbed on a carrier. Purified cumene is mixed with purified recycled cumene and fed to the oxidation vessel along with a dilute soda ash solution, to maintain the pH between 6.0 and8.0, the mixture is contacted with air and held at 110 and 115°C until 20 to 25% of the cumene is converted to the cumene peroxide. Yields of cumene peroxide may be improved by operating at lower temperatures (100 to 110°C) and accepting lower conversions. In one modified process sequence of three to four reactors is operated at a successively lower temperature.
The crude mixture from the oxidizer is concentrated to about 80% cumene peroxide and fed to a reactor in which the cumene peroxide is cleaved to phenol and acetone. The reaction is usually carried out under conditions of mild temperature (70 to 80°C) and pressure and in the presence of a small amount of sulfuric acid. Numerous non-oxidizing inorganic acids, e.g. sulphuric dioxide are used. The cleavage mechanism is an example of a 1, 2 shift from carbon to oxygen.
Such 1, and 2 cleavages shouldn't occur during the oxidation stage because phenols are potent inhibitors of free radical oxidation. Therefore, it is essential that no acidic materials must interfere with the oxidation process.
The resulting product mixture consists following compositions of the products
COMPOUND (wt %)
|
%COMPOSITION
|
Phenol
|
14
|
Cumene
|
76
|
Acetone
|
8
|
Acetophenone
|
0.4
|
ά methyl styrene
|
1.6
|
 |
| Phenol by Cumene Process |
The products are separated by distillation. Acetone is removed overhead in the first column and further purified by distillation. The bottoms from this column are then vacuum distilled to send unreacted cumene and by-product a methyl styrene overhead. If this impure cumene were recycled as such, the methyl styrene must be purified. This can be done by catalytic hydrogenation of the ά methyl styrene to cumene, by careful fractionation. In the latter case, methyl styrene is available as a by-product. The bottoms from the vacuum still are further distilled to separate acetophenone and cumene from phenol. Phenol is the overhead product obtained with a yield of 90 to 92%.
