Cresylic acid extraction

Naphthenic acids and cresylic acid, which are extracted from certain crude oil fractions, are briefly reviewed at the end of the chapter. 

Cresylic acid is a commercial mixture of phenolic compounds including phenol, cresols, and xylenols. This mixture varies widely according to its source. Properties of phenol, cresols, and xylenols are shown in Table 4-5 Cresylic acid constitutes part of the oxygen compounds found in crudes that are concentrated in the naphtha fraction obtained principally from naphthenic and asphaltic-based crudes. Phenolic compounds, which are weak acids, are extracted with relatively strong aqueous caustic solutions. 

However, cresylic acid is still obtained to a lesser extent from petroleum fractions, especially cracked gasolines, which contain higher percentages of phenols. It is also extracted from coal liquids. 

Strong alkaline solutions are used to extract cresylic acid. The aqueous layer contains, in addition to sodium phenate and cresylate, a small amount of sodium naphthenates and sodium mercaptides. The reaction between cresols and sodium hydroxide gives sodium cresylate. 

It should be noted that the extraction of cresylic acid does not create an isolation problem with naphthenic acids which are principally present in heavier fractions. Naphthenic acids, which are relatively stronger acids (lower pKa value), are extracted with less concentrated caustic solution. 

Duosol Process. The Duosol process developed by the Max B. Miller Co. (28) is an outstanding example of commercial adoption of a double solvent extraction process. Patents (27) for this process date from May 1933 and cover numerous aspects of the problem including a variety of paraffinic solvents (ethane, propane, butane, petroleum ether) and naphthenic solvents (wood tar acids, cresols, creosote, and phenol). Present commercial application utilizes propane and Selecto (a mixture of phenol and cresylic acid, normally ranging in composition from 20 to 80% phenol). 

Solvent extraction has become the most widely used method of refining lubricating oils. Selective solvents which extract the less desirable constituents include phenol, furfural, dichloroethyl ether, mixtures of cresylic acid and propane, and liquid sulfur dioxide. Liquid propane precipitates asphaltic constituents and wax and retains the more desirable oil components in solution. Dewaxing may also be accomplished by other solvents such as mixtures of benzene and methyl ethyl ketone. 

The extracted mixture of phenolic compounds, usually referred to by the trade designation of cresylic acids, was essentially free of fatty acids but contained appreciable quantities of thiophenols. Several methods were found effective in minimizing the content of sulfur-containing impurities. 

Solvent Extraction Performance in Organic Chemicals Industry (Cresylic acid Recovery Subcategory) Using Extractor (Spray Column Contactor and Stripping Column) and Solvent (Isobutylene)... 

Cresylic Acids. Cresylic acids, or petroleum phenols, are obtained from cracked distillates, such as heavy catalytic naphtha and cracked heating oil. They usually exist in these distillates in amounts up to about 0.2% and are removed by extraction with a 10 to 40% sodium hydroxide solution (77). The extract is subsequently steamed, then... 

It has been found that catalytic naphthas contain about ten times as much cresylic acid as do thermal naphthas (32). The cresylic acid may easily be recovered by treatment with dilute caustic soda to give a product containing 20% phenol, 25% xylenols, 45% cresols, and 10% impurities. Removal of sulfur from this extract to give marketable cresylic acid is a problem, being solved by air blowing, partial neutralization, distillation, or a combination thereof. 

The Shell benzene recovery process uses phenol or, in special cases, other solvents such as cresylic acids or sulfolanes, to separa te benzene from nonaromatics by extractive distillation. This process has been described by Dunn and Lieholm 22), and others 63). 

Tar acids are produced by the extraction of the oils with aqueous caustic soda at a temperature sufficient to prevent naphthalene from crystallizing. The phenols react with the sodium hydroxide to give the corresponding sodium salts as an aqueous extract known variously as crude sodium phenate, sodium phenolate, sodium carbolate, or sodium cresylate. The extract is separated from the phenol-free oils, which are then taken for naphthalene recovery. 

PPG-40 diethylmonium chloride ore flotation agent, copper extraction Cresylic acid ore flotation collector Bis-hexamethylenetriamine ore leaching additive Dihexyl sodium sulfosuccinate ore processing... 

Double-solvent Processes Propane-cresylic acid -f- phenol (Duo-SoP (extractive and precipitative refining). 

Duo-Sol Process. This is the only double-solvent process that has been used extensively. One solvent (propane) dissolves paraffinic hydrocarbons, and the other (cresylic acid or Selecto O dissolves naphthenic hydrocarbons. The two solvents are used in a countercurrent system of How, and the feed is introduced at an intermediate point in the flow system (see Fig. 11-5). In one end of the extraction system the outgoing cresylic acid solution is stripped of paraffinic material by pure propane,... 

Dualayer Distillate A process for extracting organic acids from petroleum fractions, using an aqueous solution of sodium cresylate. Developed by the Mobil Oil Company in the 1950s. 

After hydrolysis by 2N methanol solution of H2SO4, the product was neutralized with KOH to pH=5 and methanol evaporated. The dry residue was expected to be poly(allilamine), polymethacrylic acid, and K2SO4. Indeed, after extraction with anhydrous methanol and acetone, poly(allilamine) was identified by NMR and IR spectrometries. After evaporation, solvent from the methanol part of the extract insoluble in chloroform part was obtained. After esterification by diazomethane the product was identified as polyfmethyl methacrylate) on the basis of IR and H-NMR spectroscopy. IR spectroscopy was applied in order to examine the copolymerization of multimethacrylate (p-cresyl-formaldehyde oligomers with methacrylic groups) with st3rrene. It was found that double bond peak at 1650 cm disappeared during the process and it was absent in the product of polymerization. Polymerization and... 

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