Alkyl sulfates titration

Alkyl sulfates and sulfonates Two-phase or surfactant-electrode monitored titration... 

The acid charge to the absorber is the used sulfuric acid catalyst from the alkylation settler. It usually is of about 90% titratable acidity with about 3-5% water and 3-6% conjunct polymer. The alkylation catalyst is no longer active as an alkylation catalyst when the acidity drops to about 80% due to the pick up of conjunct polymer and alkyl sulfates. However, it is still active for the absorption of propylene until substantially all of the acid is converted to alkyl sulfates. Since the formation of alkyl sulfates from olefins and sulfuric acid are equilibrium reactions, conditions should be used which will shift the equilibrium to the right, or to the dialkyl sulfate, with minimum formation of alkyl acid sulfate. 

Two-phase titration is usually less sensitive to interference from other foreign (nonsurfactant) species. When applied to anionic surfactant systems, two-phase titration is primarily used for the analysis of alkyl sulfates and sulfonates. Typical titrants in these applications are solutions of cetylpyridinium bromide, cetyltrimethylammonium bromide, and benzyldimethylalkyl (C12 or C14) ammonium chloride. The most accurate results are, however, obtained with p-tert-octyl-phenoxy-ethoxy-ethyl-dimethyl-benzylammonium chloride, also known under the commercial name of Hyamine 1622. The structure of Hyamine 1622 is shown in Fig. 11-32,a. 

A mixture of anionic surfactants (salts of fatty acids (currently named soaps), alkyl sulfates and alkyl sulfonates may be determined by three titrations. These three surfactants are titrated using dichlorofluorescein as indicator a dimidium bromide and disulfine blue mixture are used for titration of alkyl sulfates and alkyl sulfonates, while disulfine blue is used for alkyl sulfonates titration after acid hydrolysis (Cozzoli, 1993). 

Active agent content of anionics is usually determined by titration with a cationic surfactant such as benzethonium chloride. Two-phase titration is suitable for assay of alkylaryl sulfonates alkyl sulfates and hydroxysulfates, alkanesulfonates, fatty alcohol ethoxysul-fates and alkyIphenolethoxysulfates and dialkyIsulfosuccinates (4,5). The results on ma-... 

Sampling and analysis of alkyl sulfates is the subject of ASTM standard D1570 (7). It recommends determination of water by azeotropic distillation, pH on a 0.1% aqueous solution, alkalinity by sequential titration, ethanol-insolubles, unsulfated material by liquid-liquid extraction, combined alcohol by saponification and extraction, and ester SO3 by saponification and titration or gravimetric determination of sulfate. Methods for free chloride and sulfate are also specified. 

There are separate ISO standards for primary and secondary alkyl sulfates (i.e., for products made from primary or secondary alcohols). The ISO standard covering primary alkyl sulfates specifies neutral oil by extraction from ethanol/water solution, total combined alcohols by ether extraction after acid hydrolysis, pH of a 10% aqueous solution, water by titration if below 10% or by azeotropic distillation if above 5%, and chloride by titration (60). The standard covering secondary alkyl sulfates is similar, but combined alcohols are not determined. Assay is by determination of total solids after extraction of the neutral oil, corrected for the presence of other impurities (61). 

The minimum effective chain length allowing amines to be quantitatively titrated by dodecylsulfate is 12 carbons, or 10 in the case of alkyldimethylamines titrated with tetradecylsulfate. This is true of both two-phase indicator titration and one-phase potentiometric titration. If the titrant is tetraphenylborate rather than an alkyl sulfate, the effective chain length need only be 8 for tertiary symmetric amines, while all quaternaries are titrated (87). The effective chain length concept corrects for overlapping of alkyl chains, so... 

An Ion Chromatograph has been successfully automated by interfacing it to an automatic sampler (7). Continuous unattended analysis was possible, the actual number of samples analyzed being limited by the ionic capacity of the suppressor column. The automated Ion Chromatograph was used to analyze soluble sulfates, ammonia and alkyl amines in stack and automobile exhqust samples. Excellent agreement between IC and automated barium chloroanilate titration for sulfate was obtained with a relative standard deviation less than 5%. 

Alkyl sulfonate, sulfate, and fatty amine are usually tested by using dye-reagent complex formation and counter ion titration. The applications of dye-reagent complex formation and counter ion titration are mainly introduced by the following. 

ISO 6843 specifies a variation of the extraction method for determination of PEG in nonionic surfactants. In this case, an aqueous salt solution of the surfactant is extracted with 9 1 ethyl acetate/l-butanol. Almost all of the ether sulfate goes into the organic phase, leaving behind PEG, PEG sulfate, and sulfate ion, as well as a small amount of the ether sulfate. Alkyl- or alkylphenol ethoxylate and alkyl- or alkylphenol sulfate are expected to partition primarily in the organic phase. The amount of anionic surfactant remaining in the aqueous phase is determined by two-phase titration, as is the equivalent weight of the extracted material (71). 

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