Overview

Chlorosulfonic acid was first prepared by Williamson1 in 1854 by the action of phosphorus pentachloride on concentrated sulfuric acid and later2 by the direct action of hydrochloric acid on sulfur trioxide. Other methods of preparation include: distillation of fuming sulfuric acid (oleum) with phosphorus pentoxide in a stream of gaseous hydrogen chloride; the action of phosphorus trichloride or oxychloride, chlorine, thionyl chloride, or sulfur monochloride on concentrated or fuming sulfuric acid; passing a mixture of sulfur dioxide and chlorine into glacial acetic acid; or reaction of carbon tetrachloride with fuming sulfuric acid.3

Chlorosulfonic acid is also named chlorosulfuric acid in Chemical Abstracts, but Chlorosulfonic acid is the commercial name by which it is more widely known. Other names are: sulfuric chlorohydrin, sulfuric acid chlorohydrin, monochlorosulfuric acid, monochlorosulfonic acid, chlorohydrated sulfuric acid and sulfuryl hydroxychloride.4

1 Manufacture

Modern chemical plants manufacture Chlorosulfonic acid by the direct union of equimolar quantities of sulfur trioxide and dry hydrogen chloride gas.4 The process is a continuous flow operation and, since it is highly exothermic, heat removal is essential to maintain the reaction temperature at 50 80 C. The sulfur trioxide may be used in the form of 100% liquid or as a dilute gaseous mixture from a contact sulfuric acid plant. Likewise, the hydrogen chloride may be 100% gas or in a diluted form. The chemical reactor may be a packed column cooled by a water-cooled condenser to moderate the vigour of the reaction and hence avoid decomposition of the product. The chemical plant...