Alkylbenzene sulfonates crude

The calcium tolerance of a selected group of crude alkylbenzene sulfonates is summarized in Table II. These results, while relatively imprecise, indicate that the calcium tolerance of these surfactants in dilute solutions is quite low. In general, the calcium tolerance decreases as the equivalent weight increases, and the addition of 3 wt.% n-butanol or 2-butanol does not appear to improve stability. Finally, the onset of precipitation does not appear to be very sensitive to temperature. 

Experimental Results with Purified Surfactants. A similar series of experiments was carried out with desalted and deoiled alkylbenzene sulfonates. Aside from the apparently smaller solubility of the purified surfactants, the results were essentially the same as for the crude surfactants. The calcium ion concentration necessary to initiate precipitation from SDBS solutions was about 200 ppm. For purified SPBS it was 10 to 20 ppm, and for purified TRS 10-410 it was about 5 ppm. The onset of precipitation was relatively insensitive to temperature in the range 25-60°C, and little affected by the addition of 3 wt.% of either n-butanol or 2-butanol. It should be noted that precipitation occurred in all cases in spite of the fact that the surfactant concentrations were well above the CMC. In short, fixation of calcium ions by micelles did not prevent surfactant precipitation in these experiments. 

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). 

Petroleum sulfonates are prepared by sulfonation of hydrocarbons most commercial products are actually byproducts of petroleum refining. In the case of natural petroleum sulfonates, they are produced by sulfonation of crude oil fractions. The purpose of the sulfonation is removal of a portion of the aromatics from the oil and the resulting byprod-uct/coproduct stream is a complex mixture of sulfonated aliphatic and (mainly) aromatic hydrocarbons. To complicate matters, the term petroleum sulfonates is also applied to materials produced by sulfonation of synthetic materials, such as alkylbenzenes (detergent alkylate). In this case, a higher boiling alkylbenzene feedstock is used than for the production of surfactants for household detergents. The products therefore have only limited water solubility. 

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