Petroleum sulfonates separation

The presence of polysulfonates in petroleum sulfonates used in lube formulations has a destabilizing effect on the formulation stabiUty and function of the sulfonate in motor oils, etc. Special techniques are utilized to help reduce the carryover of residual sludge components, including the use of hydrocarbon solvents such as hexane or heptane to faciUtate separation of sludge, often with centrihigation. Other desludging procedures include water wash, H2SO4 wash, clay percolation, and filtration. 

Synthetic and petroleum sulfonates are analyzed by the same reversed-phase chromatographic system used for the analysis of alkyl ether sulfate surfactants. Similar to alkyl ether sulfates, the sulfonate mixtures are separated into three fractions inorganic salt, sulfonates, and unreacted oil. The analysis of two petroleum sulfonates, NaPS-1 and NaPS-2, is shown in Table 4. Good separation was obtained between the inorganic salt and the sul-fonated components. The oil present in NaPS-1 and NaPS-2 surfactants consisted of low-molecular-weight components, which were totally volatile under the detector operating conditions and, therefore, could not be detected. These two sulfonates are considerably different in molecular structure distribution. However, their elution characteristics were the same as those observed for the synthetic single-component sulfonates. 

Promoters or collectors provide the substances to be separated with a water-repellent air-avid coating that will adhere to air bubbles. Typical collectors for flotation of metallic sulfides and native metals are dithiophosphates and xanthates. Fatty acids and their soaps, petroleum sulfonates, and sulfonated fatty acids are widely used as collectors in flotation of fluorspar, iron ore, phosphate rock, and others. Fuel oil and kerosene are used as collectors for coal, graphite, sulfur, and molybdenite. Cationic collectors such as fatty amines and amine salts are widely used for separation of quartz, potash, and silicate minerals. 

Pope et al. (1982) observed that when a polymer was mixed with a surfactant in an oil-free solntion, there was a characteristic phase separation into an aqneons snrfactant-rich phase and an aqueons polymer-rich phase at some sufficiently high salinity (NaCl concentration). They called this the critical electrolyte concentration (CEC). They reported that CEC was independent of the polymer type, polymer concentration, and snrfactant concentration, bnt it was dependent on the nsed snrfactant. This conclnsion cannot be universally valid. Hon (1993) observed that CEC depended on polymer and snrfactant concentrations in a HPAM-petroleum sulfonate solntion. The CEC increased with increasing temperature for the anionic surfactants and decreased with increasing temperature for the nonionic surfactants. It also increased with alcohol concentration. 

Use of Solvents. Organic solvents are sometimes used commercially to purify sulfonates or sulfates. Alcohols (methanol, ethanol, isopropanol) are employed to desalt and purify sodium dodecylbenzenesulfonate, sulfated monoglycerides, sulfated long-chain alkenes, and petroleum sulfonates. Sodium sulfate is insoluble, while the sulfonate dissolves in the alcr l. In the last two cases, separation of unreacted hydrocarbon is also effected, yielding a purer product further removal of the hydrocarbon is often achieved by extraction of the alcoholic sulfcmate solution with petroleum naphtha solvent. This purification scheme has also been used commercially to produce dodecylbenzenesulfonate detergents of low residual hydrocarbon content. ... 

Petroleum Sulfonates Most of the surfactant formulations for EOR involve petroleum sulfonates. These petroleum sulfonates are prepared from selected refinery products. Among several refinery products, the furfural extract from solvent lube operations is considered an attactive feedstock for oil recovery sulfonates. Lube oil stocks are sulfonated to separate aromatic components. The petroleum sulfonate is in short supply due to the limited demand for lube oil stocks. 

Petroleum sulfonate was used to directly flotate the raw ore in laboratory. Meanwhile, fatty acid was used to reversely flotate quartz in the flotation of the raw ore. Comparison between direct and reverse flotation separations is given as follows ... 

Petroleum sulfonates contain much more unsulfonated material than other surfactants, often 25-50%. The liquid-liquid extraction methods suitable for removal of oil from other anionics give less than quantitative results for petroleum sulfonates because of emulsion formation. While extraction is suitable for special cases, column chromatography separation of the oil is universally applicable. It is prudent to check the effectiveness of the separation by inspecting the IR spectrum of the oil fraction for the absence of sulfonate absorption at 1050 and 1200 cm" (95). There is no similar method to quickly check the purity of the sulfonate fraction, although an HPLC procedure could presumably be developed. 

The amount of residual sulfonate ester remaining after hydrolysis can be determined by a procedure proposed by Martinsson and Nilsson [129], similar to that used to determine total residual saponifiables in neutral oils. Neutrals, including alkanes, alkenes, secondary alcohols, and sultones, as well as the sulfonate esters in the AOS, are isolated by extraction from an aqueous alcoholic solution with petroleum ether. The sulfonate esters are separated from the sultones by chromatography on a silica gel column. Each eluent fraction is subjected to saponification and measured as active matter by MBAS determination measuring the extinction of the trichloromethane solution at 642 nra. (a) Sultones. Connor et al. [130] first reported, in 1975, a very small amount of skin sensitizer, l-unsaturated-l,3-sultone, and 2-chloroalkane-l,3-sultone in the anionic surfactant produced by the sulfation of ethoxylated fatty alcohol. These compounds can also be found in some AOS products consequently, methods of detection are essential. 

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-... 

In ODS, sulfur compounds present in fuels are oxidized to more polar sulfones / sulfoxides to facilitate their removal by solvent extraction or adsorption. Various oxidation systems have been reported in the literature for this transformation. Among these oxidants like hydrogen peroxide (H2O2) and carboxylic acid as catalyst3"5. For the chemical industry, it becomes more and more important to develop cleaner technologies. Solvent extraction processes are used to separate sulfones / sulfoxides from oxidized fuels. These processes required suitable and selective solvents for separation of oxidized sulfur compounds from petroleum feedstocks. 

Thus -alkanes (C10-C14) separated from the kerosene fraction of petroleum (by urea complexation or absorption with molecular sieves) are now used as one source of the alkyl group. Chlorination takes place anywhere along the chain at any secondary carbon. Friedel-Crafts alkylation followed by sulfonation and caustic treatment gives a more linear alkylbenzenesulfonate (LAS) which is soft or biodegradable. The chlorination process is now the source of about 40% of the alkyl group used for the manufacture of LAS detergent. 

Analytical procedures for the isolation of the sulfide and thiophene classes of compounds from petroleum are described. The methods are based on the selective oxidation of first the sulfides to sulfoxides, followed by silica gel separation of the sulfoxides and their reduction back to sulfides. The thiophenes are then separated from the sulfide-free oil by selective oxidation to sulfones, followed by silica gel separation of the sulfones from the oil and their reduction back to thiophenes. 

For the isolation of thiophenes from petroleum and other fossil fuels, a number of methods have been reported, including chromatography on silver nitrate (23) or palladium chloride-impregnated silica gel (24), and oxidation to the more polar sulfones followed by chromatographic separation of the sulfones, their reduction back to the thiophenes and chromatographic separation of the thiophenes (25). The... 

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