Page 8 - 81Sulfonation-Sulfation Processing Technology for Anionic Surfactant Manufacture_opt

Sulfonation/Sulfation Processing Technology for Anionic Surfactant Manufacture 275

Figure 7 shows a diagram of film SO 3-sulfonation along with an additional step
(bleaching) than could be required depending of the feedstock and characteristic of the
final product. Depending on the type of organic feedstock and consequent organic acid,
further reaction steps may be required before neutralization. Sulfonic acids of LABS are
one of those materials that no require an aging step to reach full conversion. Moreover, a
hydrolysis or stabilization step is required to convert anhydrides form during the
sulfonation process. Alcohol and alcohol ethoxylate sulfonic acids, as well as FAMES,
must be neutralized immediately after a delayed aging to avoid undesired by-products
formed in side reactions.

Fig. 7. Process diagram for film SO 3-sulfonation

After aging and hydrolysis a stable product is obtained, then the neutralization stage can be
carried out with many alkaline chemicals like caustic, ammonia and sodium carbonate.
Neutralization with diluted caustic is recognized as instantaneous and highly exothermic it
may form gel at high temperatures or undesired reactions may occur if micro-dispersion of
organic acid in the diluted caustic phase fails. Various loop-type reactors, consisting of a
circulation pump, homogenizer (where the acid is introduced in the circulating alkaline
paste), and heat exchanger, are used for the complex neutralization step (Foster, 1997).

4. Phenomenological description of film sulfonation
Organic liquid flow through of the reactor wall in laminar regimen, the high flow of the gas
phase by gravitational effects intensifies the formation of random waves all along the gas-
liquid interface. Depending on the flow rate of organic liquid and gas stream the thickness
of the film can increase or decrease up to twice its average value in the zone where the
waves are present (Díaz, 2009). This induced turbulence affects the local values of
concentration and temperature in the regions where appears, hence altering the mass
transfer and temperature profiles in the film. Mathematical models which describe the
sulfonation of tridecylbenzene in FFRs have been developed by Akanksha et al. (2007),
Davis et al., (1979), and Johnson & Crynes, (1974), while Dabir et al. (1996), Gutiérrez et al.
(1988) and Talens (1999) focused on dodecylbenzene sulfonation. Nevertheless, these
models have been subject of debate due to the assumption that either the chemical reaction
is limited to the gas liquid interface, the mass transfer of the sulfonating reagent in the gas
phase is the rate determining step, and/or the flow profiles in the film are neatly laminar,
neglecting the effects of the waves formed at the gas-liquid interface.
Recently Torres et al. (2009b) proposed a model for the methyl esters sulfonation that is
appropriate for both laminar and turbulent films and it considers effects of wavy film

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