Sulfonation by SO3

Aromatic compound can be sulfonated directly with SO3 in commercially available continuous and batch equipment. Conventionally sulfonation is done by sulphuric acid or oleum. But with SO3 sulfonation process has the following advantages. It is more direct and considerably faster than the present process. It requires fewer man hours and, therefore, is more economical. Conditions can be varied to give a wide range of products having different solubility characteristics and combined SO3 content. Since the reaction, batch or continuous, is stoichiometric, no waste products are formed, thus eliminating any pollution problems. In sulfonation processes sulfur trioxide is vaporized and is brought into contact with the aromatic compound in the presence of a gaseous diluent such as air, nitrogen or an inert hydrocarbon. It has been thought necessary to utilize such diluent carrier gases to reduce the intensity of the reaction between the sulfur trioxide and the material being sulfated and thereby suppress unwanted side reactions. The purpose of admixing the sulfur trioxide vapour with a diluent gas is to reduce the partial pressure of the sulfur trioxide, so that the chance of a single molecule of the material being sulfated or sulfonated contacting several molecules of Sulfur trioxide is reduced. Aromatic compound is sulfonated by sulfur trioxide in sulfonation reactor.