Xylenol from phenol

Triaryl phosphates are produced by reaction of phosphoms oxychloride with phenoHc compounds at 100—200°C with magnesium or aluminum chloride catalyst. Past use of cresols and xylenols from coal tar or petroleum is replaced for lower toxicity and cost by synthetic phenoHcs, primarily isopropyl phenol, /-butyl phenol, and phenol itself A range of viscosities is achieved by selection and proportioning of the phenols and their isomers used for the starting material. 

These are thermoset polymers made from phenol or, less commonly, phenolic-type compounds such as the cresols, xylenols, and resorcinol, together with formaldehyde. They had been known for some time - G.T (later Sir Gilbert) Morgan discovered them in the early 1890s when attempting (unsuccessfully) to make artificial dyestuffs by reaction of phenol with formaldehyde. But this knowledge had not been exploited before 1907, the year in which Leo... 

The Lurgi gasifiers used by Sasol operate at "low" temperatures and consequently phenols, and "tars" are "distilled" from the coal at the top of the gasifier, and carried out with the raw gas. On condensation two liquid phases are formed, "tar" and "gas liquor" (water). The "tar acids" (phenol, cresols etc) are dissolved in the "gas liquor" which is fed to the Phenosolvan unit where the acids are recovered by counter current extraction with butyl acetate or diisopropyl ether. The crude tar acids are fractionated to yield phenol, ortho, meta and para cresol and xylenols. The phenol is further refined to produce a high purity, colourless and stable product. Phenol is used mainly in the production of formaldehyde resins while the cresols are used as flotation frothers and in the manufacture of pesticides etc. 

Other Organic Processes. Solvent extraclion has found application in the coal-tar industry for many years, as for example in the recovery of phenols from coal-tar distillates by washing with caustic soda solution. Solvent extraction of I any and resimic acitl from tall oil has been reported. Dissociation extraclion is used in separate ffr-cresol from p-crcsol and 2,4-xylenol from 2.5-xylenol, Solvent extraclion can play a role in the direct manufacture of chemicals from coal, treatment of industrial effluents, biopolymer extraction, and difficult separations. 

The method used by Yorkshire Water Authority [42] for determining phenols in potable waters has a criterion of detection of 3-70pg depending on the phenol. It is capable of determining phenols and cresols, xylenols, dihydric phenols, monochlorophenols, dichlorophenols and trichlorophenols. The phenols are extracted from the water sample with ethyl acetate using a liquid-liquid extractor. After drying, the extract is concentrated to a small volume then treated with... 

Traditionally, phenol is produced from benzene, cresols from toluene and xylenols from xylenes. There are three isomers of xylenes, namely, / -xylene, o-xylene, and m-xylenes. Accordingly, there are six isomers of xylenols which have been mentioned earher vide 1.1. Some of the properties of various xylenols have also been mentioned. Commercially, xylenols have assumed great significance. In some cases, xylenols can be used as substitutes of cresols. However, some of the individual xylenol isomers have importance in organic chemical synthesis. 

Methylation of phenol with methanol to produce o-cresol and 2,6-xylenol, and 2,4-xylene from p-cresol and 2,3-xylenol and 2,5-xylenol from m-cresol has been reported [1,47,48]. 

In the A stage, simple PF resins are readily soluble in alcohol, esters, ketones, phenols, and some ethers, and insoluble in hydrocarbons and oils. As a class, resols tend to be more soluble in alcohols and water, and novolaks tend to be more soluble in hydrocarbons. In the early stages of condensation, resols are often soluble in water, owing to the presence of methylolphenols, especially polyalcohol. This is more pronounced with resols that are derived from phenol. Cresilic resols are less soluble, and xylenolic resols are almost insoluble in water. The solubility of A-stage resins in dilute aqueous sodium hydroxide or in mixtures of water and alcohols follows the same trend. 

Soncek and Jelinkova have also used this differential principle to determine in polypropylene two antioxidants (2,6-ditert-butyl-4-methylphenol and 4-substituted 2,6-xylenol) which have virtually identical ultraviolet absorption spectra in the absence of alkali (method 7). The antioxidants can be distinguished in alkaline medium, where 4 substituted 2,6-xylenol forms phenolate readily, thus allowing the utilisation of the bathochromic shift for its determination. The use of derivative spectroscopy reduces light scattering and matrix interferences when extracts from polypropylene samples are measured. 

Brooks has shown that o, m, and p cresols can be separated from each other and from phenol and the xylenols by gas chromatography. He used... 

Triaryl phosphates are produced from the corresponding phenols (usually mixtures) by reaction with phosphoms oxychloride, usually in the presence of a catalyst (94—96). They are subsequently distilled and usually washed with aqueous bases to the desired level of purity. Tricresyl phosphate was originally made from petroleum-derived or coal-tar-derived cresyflc acids, ie, cresols, variously admixed with phenol and xylenols. Discovery of the toxicity of the ortho-cresyl isomers led manufacturers to select cresols having very Httle ortho-isomer. 

Alkylated phenol derivatives are used as raw materials for the production of resins, novolaks (alcohol-soluble resins of the phenol—formaldehyde type), herbicides, insecticides, antioxidants, and other chemicals. The synthesis of 2,6-xylenol [576-26-1] h.a.s become commercially important since PPO resin, poly(2,6-dimethyl phenylene oxide), an engineering thermoplastic, was developed (114,115). The demand for (9-cresol and 2,6-xylenol (2,6-dimethylphenol) increased further in the 1980s along with the growing use of epoxy cresol novolak (ECN) in the electronics industries and poly(phenylene ether) resin in the automobile industries. The ECN is derived from o-cresol, and poly(phenylene ether) resin is derived from 2,6-xylenol. 

The solubihty of alkylphenols in water falls off precipitously as the number of carbons attached to the ring increases. They are generally soluble in common organic solvents acetone, alcohols, hydrocarbons, toluene. Solubihty in alcohols or heptane follows the generalization that "like dissolves like." The more polar the alkylphenol, the greater its solubihty in alcohols, but not in ahphatic hydrocarbons likewise with cresols and xylenols. The solubihty of an alkylphenol in a hydrocarbon solvent increases as the number of carbon atoms in the alkyl chain increases. High purity para substituted phenols, through Cg, can be obtained by crystallization from heptane. 

Most coal chemicals are obtained from high temperature tar with an average yield over 5% of the coal which is carbonized. The yields in coking are about 70% of the weight of feed coal. Tars obtained from vertical gas retorts have a much more uniform chemical composition than those from coke ovens. Two or more coals are usually blended. The conditions of carbonization vary depending on the coals used and affect the tar composition. Coal-tar chemicals include phenols, cresols, xylenols, benzene, toluene, naphthalene, and anthracene. 

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. 

Many of the phenols which are used in household and other commercial disinfectant products are produeed from the tar obtained by distillation of coal or more recently petroleum. They are known as the tar acids. These phenols are separated by fractional distillation according to their boiling point range into phenol, cresols, xylenols and high boiling point tar acids. As the boiling point increases the properties of the products alter as shown ... 

Musculoskeletal Effects. A case of muscle pain and weakness was described in an individual after intermittent chronic inhalation and dermal exposure to vapors and solutions of phenol, cresol, and xylenol (Merliss 1972). The symptoms lessened when the subject was removed from exposure. 

Phenol methylation to 2,6-xylenol has been widely studied for the past few deeades owing to the room for improvisation from the viewpoint of product selectivity. Generally during phenol methylation to 2,6-xylenol, occurs via sequential methylation of phenol to o-cresol to 2,6-xylenol, various reaction parameters mediate the selectivity between the two. For instance, when the reaetants stoichiometry of methanol to phenol molar ratio > 2, and significant residence time of o-cresol may favor 2,6-xylenol selectivity. However, excess methanol is often used, sinee some amount of methanol tend to undergo oxidation into various reformate produets [71] under vapor phase condition. Similarly, reaction temperature, catalyst acid-base property, and space velocity of the reaetant are the parameters that govern the selectivity to 2,6-xylenol. 

Figure 8. Comparison of phenol conversion and ortho products selectivity performance of Cul-xCoxFe204 catalysts at 3250C, TOS = 3h (right panel) and atomic ratio of Cu/(Co+Fe) (or Co/Fe) on Cu-containing (Cu-less) catalysts (left panel). Note the large production of desired 2,6-xylenol and Cu/(Co+Fe) = 0.9 at x = 0.5 composition on spent catalyst. Reprinted from Journal of Catalysis, 210, Mathew T., et al., 2002, 405-417 with permission from Elsevier.

Further, adsorption of methylated phenols (o-cresol and 2,6-xylenol) has given very weak and broad spectral features that were correlated to their weak interaction with the catalyst. Among the ortho-methylated phenols, 2,6-xylenol desorbs fast from the surface at 200 C than o-cresol. These methylated phenols, unlike phenol, desorbed from the catalyst above 200°C that was well below the actual reaction temperature (350°C). Hence, the desorption susceptible nature of the methylated phenols above 200°C facilitated the efficient methylation at 350°C [74]. In contrast to the Cu-containing ferrospinels, CoFc204 shows little interaction [74] of phenol with methanol, when they are co-adsorbed and this might be a limiting factor to the overall reaction. 

The most common waste stream from drying and sweetening operations is spent caustic. The spent caustic is characterized as phenolic or sulfidic, depending on which is present in the largest concentration this in turn is mainly determined by the product stream being treated. Phenolic spent caustics contain phenol, cresols, xylenols, sulfur compounds, and neutral oils. Sulfidic spent caustics are rich in sulfides, but do not contain any phenols. These spent caustics have very high BOD and COD. The phenolic caustic streams are usually sold for the recovery of phenolic materials. 

As regards organic contaminants, leachates from semi-coke contain compounds such as phenols, for example, cresols, resorcinols, and xylenols, which occur at mg/L concentrations. Indeed, Kahru et al. (2002) found total phenols at concentrations up to 380 mg/L in semi-coke dump leachates. Phenols also volatilize from such leachates, depending on temperature and pH (Kundel Liblik 2000). Atmospheric phenol concentrations of 4-50 xg/m3 have been observed in the proximity of leachate ponds (Koel 1999). Generally, aliphatic hydrocarbons, carboxylic acids, and organo-nitro and organo-sulpho compounds do not occur at elevated concentrations in leachates from Estonian semi-coke (Koel 1999). 

Table IV shows that the total tar acid yield increases with decreasing carbon content of the coal. Of the total tar acids for all the coals of Table IV, except the Pittsburgh bed coal, about 50% distill below 235° C. (458° F.) at atmospheric pressure. About 70% of the total tar acids from Pittsburgh bed coal distill below 235° C. (458° F.). These lower boiling tar acids are chiefly phenol, cresols, and xylenols, and they are present in the proportion 1 to 4 to 5, respectively. This proportion does not vary much with the carbon content of the coal. Data (86) on the character of the tar acids boiling above 235° (458° F.) show that ethylphenols and indanols are present in amounts of the same order of magnitude as that of the phenol in the > 235° C. (458° F.) fraction.

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