Cresols, industrial source

Although coal tar is still an industrial source of phenol and the three cresols (methylphenols), e.g. m-cresol (2), and the dimethyl derivatives (xylenols), synthetically manufactured material predominates. 

Until the late 1890s, coumarin was obtained commercially from only natural sources by extraction from tonka beans and deer tongue. Then synthetic methods of preparation and industrial manufacturing processes were discovered and developed starting principally from o-cresol, phenol, and sahcylaldehyde. Various methods can be used to obtain coumarin from each of these starting materials. 

Sources of Raw Materials. Coal tar results from the pyrolysis of coal (qv) and is obtained chiefly as a by-product in the manufacture of coke for the steel industry (see Coal, carbonization). Products recovered from the fractional distillation of coal tar have been the traditional organic raw material for the dye industry. Among the most important are ben2ene (qv), toluene (qv), xylene naphthalene (qv), anthracene, acenaphthene, pyrene, pyridine (qv), carba2ole, phenol (qv), and cresol (see also Alkylphenols Anthraquinone Xylenes and ethylbenzenes). 

Cresols have been identified as components of automobile exhaust (Hampton et al. 1982 Johnson et al. 1989 Seizinger and Dimitriades 1972), and may volatilize from gasoline and diesel fuels used to power motor vehicles. Vehicular traffic in urban and suburban settings provides a constant source of cresols to the atmosphere. Hence, urban and suburban populations may be constantly exposed to atmospheric cresols. Cresols are also emitted to ambient air during the combustion of coal (Junk and Ford 1980), wood (Hawthorne et al. 1988, 1989), municipal solid waste (James et al. 1984 Junk and Ford 1980), and cigarettes (Arrendale et al. 1982 Novotny et al. 1982). Therefore, residents near coal- and petroleum-fueled electricity- generating facilities, municipal solid waste incinerators, and industries with conventional furnace operations or large-scale incinerators may be exposed to cresols in air. People in residential areas where homes are heated with coal, oil, or wood may also be exposed to cresols in air. 

A number of years ago. coal tar was the primary, if not the sole, source lor hundreds of important organic chemicals and derivatives, notably the phenols, cresols, naphthalene, and anthracene, as well as other important coal lar end-prralucls, such as solvent naphtha and pitch. In recent years, synthetic processes Tor the production of phenol, the cresols and later the xylcnols. have been developed and thus, to a large extent, have pushed coal lar into the background as a source of feedstocks for (he chemical industry. 

Traditionally, the source of benzene and toluene has been coal. Coke is produced for use in the steel industry and a by-product of this process is coal tar which, when distilled, provides benzene, toluene, xylenes, phenol and cresols (methylphenols), and naphthalene, the most abundant single component. 

Biosensors based on a Clark oxygen electrode, coupled to tyrosinase immobilized by three different methods, were investigated for the determination of phenol in real matrices, such as water of various natural sources, industrial wastes and oil press. The feasibility study included direct use of the biosensors and in situ analysis. An integrated system, incorporating SPE, desorption, fractionation and biosensor detection, was validated for screening phenolic compounds in water. Two types of electrode were tested, solid graphite and CPE incorporating tyrosinase. Correct analyses were found for river water samples spiked with phenol (10 p.gL ), p-cresol (25 p.gL ) and catechol (1 A mul-... 

Meeting the need for a comprehensive source addressing every aspect of cresol production, analysis, and impact, this detailed reference offers the most up-to-date account of cresols and their downstream derivatives—written by an internationally renowned consultant in the fine chemicals industry. 

Mixed cresols, also known as cresylic acids, the lowest among the alkyl phenols, were primarily produced as by-products from coal carbonization plants or recovered from the petroleum refinery caustic washes. These cresols obtained from natural sources were known to the chemical industry for the last 75 years and had limited uses. Production of synthetic cresols from toluene opened up new avenues for these products... 

In 1865 just prior to Kekule s synthesis of phenol, Joseph Lister (1827-1912) was experimenting with carbolic acid as an aid to antiseptic surgery which he had pioneered. A mixture of crystallised carbolic acid and shellac (lac plaster) was employed in the finally adopted mode of application. The requirement of phenol for the manufacture of picric acid during the Boer war and other uses resulted in a demand which soon outstripped the resources of phenol/cresols available from coal distillation. Synthetic phenol thus became a potentially important intermediate. The lengthy processing involved in the separation of phenol and the isomeric cresols led to the desirability for specific syntheses. In 1978 of the world production of phenol only 3% came from coal sources by extraction of the mixed phenols (about 1.5% in coal tar) with 10% sodium hydroxide, acidification with carbon dbxide and separation. Phenolic compounds are also formed during catalytic cracking processes in the petroleum industry. There are historically six industriai processes for the production of synthetic phenol, variously from benzene and toluene, some of which are also applicable to the cresols and the dihydric phenols. 

Toluene. Toluene resembles benzene in being well suited to the partial-pressure distillation procedure for sulfonation. This process is used industrially for producing sulfonate converted to cresols. Sulfone formation is low and the yield is maximum these results are essential for volume production in competition with sources for cresols not employing sulfonation. Toluenesulfonate for other uses is made to some extent with SOa, Yield loss is incurred from sulfone formation, but there are compensating processing advantages, as shown in Table 7-3. 

As might be expected, the type of feedstock chemical and industrial process play a key role in determining the presence of phenols in wastewater. For example, the nitration of benzene and toluene to produce nitrobenzene and dinitrotoluene also leads to the incidental formation of nitrophenol, dinitrophenol, and dinitro-o-cresol. Similarly, alkylphenols and methyl-phenols may be produced during alkylation and solvent extraction of toluene, xylene, and Cg-Q alkylphenols. Wise and Fahrenthold (1981) suggested that most industrial processes were not sources of priority pollutants because the processes do not involve critical precursor/process combinations. In addition, synthetic production methods generally lead to an increase in complexity of priority pollutant molecules. These in turn exhibit variable toxicity and persistance, which may be comparable to related priority pollutants. 

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