Sulfonated surfactants methyl ester sulfonate

The tt-sulfo fatty acid esters represent another class of anionic surfactants. Methyl ester sulfonates (MES) are surfactants that are derived from a variety of methyl ester feedstocks such as coconut, palm kernel, palm stearin, beef tallow, and soy. Palmitic and stearic acid derivatives lead to good detergency because of the long hydrophobic residues [3, 4]. The sensitivity of MES to water hardness is similar to AOS and small compared to LAS and SAS. MES have exceptional dispersion power with respect to lime soap. They have only been used in a few Japanese detergents [3, 4]. 

However, it could be expected that the share of the latter group will rise to the same extent as the rising importance of environmental digestibility. It is very possible that in the future the C16/C18 ester sulfonates will partly replace the alkylbenzenesulfonates produced from petrochemical raw material [6,7]. N. R. Smith [8] expects the a-sulfo methyl esters to be an alternative to ethylene-based surfactants. An increase in the production of surfactants based on ethylene is problematic, because in industrial countries ethylene production is occurring at 95% of capacity and more. 

Because there are never chain length pure surfactants in technical applications, the CMC of mixtures of different ester sulfonates is important. Fabry and Giesen showed that the CMC value of C16 a-methyl ester sulfonate is lower than the value of a C16/C18 a-ester sulfonate. There is the same tendency for C16 a-disalt and C16/C18 a-disalt. For the C16/C18 mixtures the ester group has no influence on the CMC. The methyl ester has nearly the same values as the ethyl and the /-propyl ester [59]. 

Fujiwara et al. used the CMC values of sodium and calcium salts to calculate the energetic parameters of the micellization [61]. The cohesive energy change in micelle formation of the a-sulfonated fatty acid methyl esters, calculated from the dependency of the CMC on the numbers of C atoms, is equivalent to that of typical ionic surfactants (Na ester sulfonates, 1.1 kT Ca ester sulfonates, 0.93 kT Na dodecyl sulfate, 1.1 kT). The degree of dissociation for the counterions bound to the micelle can be calculated from the dependency of the CMC on the concentration of the counterions. The values of the ester sulfonates are also in the same range as for other typical ionic surfactants (Na ester sulfonates, 0.61 Ca ester sulfonates, 0.70 Na dodecyl sulfate, 0.66). 

The analytical methods for a-sulfo fatty acid esters reported in the literature deal with the determination of the surfactants in different matrices like detergents or product mixtures from the fabrication. The methyl esters of a-sulfo fatty acids can be separated from a mixture of different surfactants together with sulfonated surfactants by adsorption on an anionic exchanger resin such as Dowex 1X2 or 1X8. Desorption from the exchanger resin is successful with sodium hydroxide (2%) in a 1 1 mixture of isopropanol and water [105]. 

For a further separation of the sulfonated surfactants the latter are heated for 4 h with 2 N HC1. The methyl ester sulfonates are split into methanol and a-sulfo fatty acids, which form disodium salts after neutralization with NaOH. The product mixture from acid hydrolysis can be separated by extraction with petroleum ether. For example, the fatty alcohols formed from fatty alcohol sulfo-... 

Coco-Based Surfactants. The most important coconut oil-based surfactants are fatty alcohol sulfate, fatty alcohol ether sulfate, and fatty alcohol polyglycol ether. Two relatively new coco-based surfactants are fatty acid methyl ester sulfonate and alkyl polyglycoside, which is produced from fatty alcohol and starch or sugar, both renewable materials. 

FIG. 8.12 Detergency as a function of water hardness in methyl ester sulfonate/LAS formulations. Conditions 25°C, surfactant 270 ppm, NaiCCh 135 ppm, silicate 135 ppm. (Reproduced from Satsuki, T., in Proceedings of the 3rd World Conference on Detergents Global Perspectives, Cahn, A., Ed., AOCS Press, Champaign, IL, 1994, p. 135. With permission.)... 

The classic use of methyl esters of vegetable oils has been as intermediates in the production of fatty alcohols from vegetable oils (Peters, 1996 Ahmad et al., 2007) or esterquats and methyl ester sulfonates (Ahmad et al., 2007). Fatty alcohols and the other products are used in surfactants and cleaning supplies. Intermediates were produced from polyisobutylene (PIB) maleic anhydride and rapeseed oil methyl esters which were used to acylate polyethylene polyamines (Hancsok et al., 2006). These additives showed corrosion-inhibiting and lubricity-improving effects. 

If the central sulfur atom of the hydrophilic group is directly bonded to a carbon atom, the resulting compound is called a sulfonate. Because aromatic ring systems will easily react with sulfuric acid or sulfur trioxide, alkylbenzene sulfonates were one of the earliest types of surface-active compounds to be produced. The sulfonate group is the hydrophilic part in many surfactants in the trade. Besides alkylbenzene sulfonates, alkane sulfonates, olefine sulfonates, of-sulfo fatty acid methyl esters, taurates and isothionates should also be mentioned. 

A great deal of interest is currently focused on methyl ester sulfonates (MES) from palm and coconut derivatives with the increase in crude oil prices and the resultant increase in the prices of petrochemicals. MES offers an environment friendly and viable alternative to the old workhorse surfactant linear alkylbenzene sulfonic acid/sulfonate (LAS/LABS), which is derived from linear alkylbenzene (LAB). 

Hovda, K.D., Effect of Methyl Ester Feedstock on Sulfonate Quality, Proceedings of1994 International Seminar on Surfactants and Detergents, Xian, November 10-13,1994. 

These surfactant classes are a subset of those used in cleaning applications, and there are classes that are noticeably absent from the list above, such as alcohol sulfates, salts of fatty acids (soaps), alkanolamides, aliphatic sulfonates, betaines (amphoterics), methyl ester sulfonates and the relatively new alkyl polyglycosides. All of these have seen various applications in the petroleum industry, but perhaps lesser importance in EOR. Cost, availability and performance are the obvious issues in determining the potential use of surfactants in EOR. 

A simple yet highly effective nonbleach, two-step process had been described for purifying palm Cie ig potassium methyl ester sulfonates [54]. In the first step, water is added to the impure surfactant mixture. The temperature of the system is maintained above the Krafft point of the surfactant, so that the surfactant and associated impurities are completely solubilized. Once completely dissolved, the surfactant mixture is allowed to cool, and the potassium-neutralized methyl ester sulfonate precipitates out selectively. In the second step, the purified surfactant is recovered by gravity or pressure filtration or by centrifugation, followed by drying. 

From the practical point of view, it is important to study the detergency of technical surfactants. Ester sulfonates produced from technical starting materials have fatty acid groups of different chain lengths. Optimal washing properties are reached in the case of the methyl ester sulfonates with... 

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