Page 2 - 81Sulfonation-Sulfation Processing Technology for Anionic Surfactant Manufacture_opt

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Sulfonation/Sulfation Processing

Technology for Anionic Surfactant Manufacture

Jesús Alfonso Torres Ortega
Universidad de La Salle
Colombia

1. Introduction
In 2008, global production of surfactants was 13 million metric tons reaching a turnover of
US$24,33 million at 2009, which means an increment of 2% from the previous year.
Moreover, it is projected a strong growth ca. 2,8% annually till 2012 and between 3,5 – 4%
thereafter (Resnik et al., 2010). Sulfonation plants are scattered around the globe in
production units with capacities varying from 3.000 to 50.000 tons/year, mainly of anionic
surfactants. At least 800 sulfonation plants are estimated to be currently in operation around
the World. However, about 20% of the global production (2.500.000 tons/year of sulfonated
anionic surfactants) is concentrated in the United States, Western Europe and Japan (Acmite
Market Intelligence, 2010).

Anionic surfactants are the key component in a detergent formulation. A molecule of
anionic surfactant is composed of a lipophilic oil soluble “tail” (typically an organic
−
molecule C 12-C 14) and a hydrophilic water soluble “head” (such as SO 3 ). Mixtures of
organic molecules, either form non-renewable resources, such as crude oil or from
renewable sources, such as vegetable oils, are currently used as raw materials for household
detergents. The cleaning process performed by anionic surfactants (active detergents) is
described in the following way (de Groot, 1991):
i. Wetting of the substrate and dirt due to reduction of surface tension;
ii. Remotion of dirt from substrate;
iii. Retaining the dirt in a stable solution or suspension.
Sulfonation is the term that identifies an electrophilic chemical reaction where a sulfonic
group SO 3H is incorporated into a molecule with the capacity to donate electrons. The
product of this chemical reaction is recognized as sulfonic acid if the electron donor
molecule is a carbon. Sulfuric anhydride reacts easily with delocalized electronic densities
as those present in aromatics groups or alkenes in general. These reactions produce a
variety of products, including derivate polysulfones. On the other hand, the sulfating
process involves the incorporation of the SO 3H molecules to an oxygen atom in an organic
molecule to form C−O−S bonds and the sulfate group (Figure 1). Sulfates acids can be
easily hydrolyzed, and for this reason an immediate neutralization is required after the
sulfate group is formed (Foster, 1997). Although sulfonation and sulfating processes are
employed industrially to obtain a wide range of products from hair dyes to pesticides and

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