Page 16 - 81Sulfonation-Sulfation Processing Technology for Anionic Surfactant Manufacture_opt

Sulfonation/Sulfation Processing Technology for Anionic Surfactant Manufacture 283

diffusivities of reagents are estimated from the Wilke-Chang equations and diffusivities in
the mixture are estimated through the Vignes equation (Vignes, 1966). Generally, in methyl
ester sulfonation the amount of intermediate III in the final product varies from 10-20%
(Foster, 2004), but this amount can be reduced by a long and heated digestion (aging stage).
An experimental apparatus showed in Figure 16 was utilized by Torres (2009) for
researching the parameters of film SO 3-sulfonation of methyl ester derived from
hydrogenated stearin palm, this apparatus was designed by Chemical Engineering
Laboratory from Universidad Nacional de Colombia (Bogotá, Colombia).

Fig. 16. Experimental apparatus for methyl ester sulfonation using a falling film reactor and
SO 3 stripped from 65% oleum with dried air process

High degree of sulfonation is obtained in the aging step controlling simultaneously the
temperature and residence time. At higher temperatures it is feasible to obtain higher
conversion levels, whereas at low temperatures (below 80°C) the time required to reach high
conversions is considerably long. These reactions are highly exothermic in order of 150 – 170
kJ/mole (including 25 kJ/mole of the absorption heat of gaseous SO 3). A kinetic model has
been development by Roberts (2007) based on the proposal that two major intermediates are
involved in aging (Figure 17).

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