Page 59 - Chemical and process design handbook

Speight_Part 1_S&V 11/7/01 3:01 PM Page 1.45

SULFONATION 1.45
tion above the desired value. Azeotropic removal of the water of reaction in
the sulfonation of benzene can be achieved by using an excess of vaporized
benzene.
.
The use of oleum (H SO SO ) for maintaining the necessary sulfur triox-
3
4
2
ide concentration of a sulfonation mixture is a practical procedure.
Preferably the oleum and organic compound should be added gradually
and concurrently to a large volume of cycle acid so as to take up the water
as rapidly as it is formed by the reaction. Sulfur trioxide may be added
intermittently to the sulfonation reactor to maintain the sulfur trioxide con-
centration above the value for the desired degree of sulfonation.