Naphthalene from coal tar

In coal tar refining, rectification is used to produce a naphthalene fraction which, depending on the separation efficiency of the naphthalene column, can have a naphthalene content rising to over 90%. Table 9.1 shows the composition of a close-cut coal tar naphthalene fraction. 

Total sulfur content Total nitrogen content 6,000 ppm 750 ppm 

For the production of technical naphthalene (crystallization point 78.5 °C) a redistillation of the naphthalene oil using columns with approx. 80 trays and reflux ratios of from 7 to 10 1 is sufficient. 

Refined naphthalene, with a crystallization point above 79.6 °C, is usually obtained by crystallization or hydrogenation. The choice of process is made on economic grounds, especially the price of hydrogen, and on the required level of sulfur in the refined naphthalene. Crystallization is characterized by high naphthalene yields and favorable energy costs high yields are also favored by a high concentration of naphthalene in the feedstock. However, the sulfur content of coal-derived naphthalene cannot be reduced below 300-400 ppm by crystallization 

Hydrogenation is carried out at 400 °C under a pressure of about 14 bar with cobalt/molybdenum catalysts. Thianaphthene is thereby converted into H2S and ethylbenzene other naphthalene co-boiling materials are broken down to lower-boiling hydrocarbons, which can be separated by distillation. 

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English chemist and physician John Kidd obtains naphthalene from coal tar, pointing the way toward the use of coal as a source of many important chemicals. 

Ghoshal S, RG Luthy (1996) Bioavailability of hydrophobic organic compounds from nonaqueous-phase liquids the biodegradation of naphthalene from coal tar. Environ Toxicol Chem 15 1894-1900. 

Oxidation of naphthalene by oxygen in the presence of vanadium pentoxide destroys one ring and yields phthalic anhydride. Because of the availability of naphthalene from coal tar, and the large demand for phthalic anhydride (for example, see Secs. 30.18 and 32.7), this is an important industrial process. 

The total annual production of petroleum probably contains some 30 million t naphthalene [4, 5]. The world production of naphthalene from coal tar and from petroleum (excluding the Eastern Bloc countries) is estimated at 1 million t [36]. In contrast, as estimated earlier, the quantitaties of higher aromatics present in gas/ diesel oil are much higher. Annually, these could amount to 100 million t [5, 26] in western Europe alone, and 300- 00 million t alkylated benzenes (with more than 9 C-atoms) and - possibly alkylated - naphfiililenes and tetralines worldwide. 

Many valuable chemicals can be recovered from the volatile fractions produced in coke ovens. Eor many years coal tar was the primary source for chemicals such as naphthalene [91-20-3] anthracene [120-12-7] and other aromatic and heterocycHc hydrocarbons. The routes to production of important coal-tar derivatives are shown in Eigure 1. Much of the production of these chemicals, especially tar bases such as the pyridines and picolines, is based on synthesis from petroleum feedstocks. Nevertheless, a number of important materials continue to be derived from coal tar. 

Large-scale recovery of light oil was commercialized in England, Germany, and the United States toward the end of the nineteenth century (151). Industrial coal-tar production dates from the earliest operation of coal-gas faciUties. The principal bulk commodities derived from coal tar are wood-preserving oils, road tars, industrial pitches, and coke. Naphthalene is obtained from tar oils by crystallization, tar acids are derived by extraction of tar oils with caustic, and tar bases by extraction with sulfuric acid. Coal tars generally contain less than 1% benzene and toluene, and may contain up to 1% xylene. The total U.S. production of BTX from coke-oven operations is insignificant compared to petroleum product consumptions. 

The economics of naphthalene recovery from coal tar can vary significantly, depending on the particular processiag operation used. A significant factor is the cost of the coal tar. As the price of fuel oil increases, the value of coal tar also increases. The price history of naphthalene from 1975 to 1993 is given in Table 7. 

Naphthalene (qv) from coal tar continued to be the feedstock of choice ia both the United States and Germany until the late 1950s, when a shortage of naphthalene coupled with the availabihty of xylenes from a burgeoning petrochemical industry forced many companies to use o-xylene [95-47-6] (8). Air oxidation of 90% pure o-xylene to phthaUc anhydride was commercialized ia 1946 (9,10). An advantage of o-xylene is the theoretical yield to phthaUc anhydride of 1.395 kg/kg. With naphthalene, two of the ten carbon atoms are lost to carbon oxide formation and at most a 1.157-kg/kg yield is possible. Although both are suitable feedstocks, o-xylene is overwhelmingly favored. Coal-tar naphthalene is used ia some cases, eg, where it is readily available from coke operations ia steel mills (see Steel). Naphthalene can be produced by hydrodealkylation of substituted naphthalenes from refinery operations (8), but no refinery-produced napthalene is used as feedstock. Alkyl naphthalenes can be converted directiy to phthaUc anhydride, but at low yields (11,12). 

Replacing one carbon atom of naphthalene with an a2omethene linkage creates the isomeric heterocycles 1- and 2-a2anaphthalene. Better known by their trivial names quinoline [91-22-5] (1) and isoquinoline [119-65-3] (2), these compounds have been the subject of extensive investigation since their extraction from coal tar in the nineteenth century. The variety of studies cover fields as diverse as molecular orbital theory and corrosion prevention. There is also a vast patent Hterature. The best assurance of continuing interest is the frequency with which quinoline and isoquinoline stmctures occur in alkaloids (qv) and pharmaceuticals (qv), for example, quinine [130-95-0] and morphine [57-27-2] (see Alkaloids). 

In the late nineteenth century and up to World War II coal was the major starting material for the organic chemical industry. When coal is heated in the absence of oxygen, coke and volatile by-products called coal tars are created. All sorts of organic chemicals can be isolated from coal tar - benzene, toluene, xylenes, ethylbenzene, naphthalene, creosotes, and many others (including Hofmann and Perkin s aniline). The organic chemical industry also draws upon other natural products, such as animal fats and vegetable oils, and wood by-products. 

Until 1959, all the phthalic anhydride was made from coal tar naphthalene, the double-benzene ring compound also shown in Figure 18—3 was easily oxidized directly to phthalic acid. But with phthalic anhydride being only a small share of coal oil, and with the demand for phthalic anhydride escalating rapidly, coal tar became an inadequate source. The frantic search for an alternative route led to the development of the recovery process for ortho-xylene from refinery aromatics streams discussed in Chapter 3 and the... 

Seventeen priority pollutant compounds can be classified as polynuclear aromatics (PNA). These compounds consist of two or more benzene rings that share a pair of carbon atoms. They are all derived from coal tar, with naphthalene being the largest constituent. Naphthalene derivatives such as alpha-naphthylamine and alpha-naphthol are used in some pesticide processes therefore, naphthalene is by far the most prevalent PNA priority pollutant in the industry. Acenaphthene, anthracene, fluorene, fluoranthene, and phenathrene are found as raw material impurities. Acenaphthene is found in one pesticide process as a raw material. The remaining ten PNAs are not suspected to be present in pesticide processes. 

In 1983 about 72% of the phthalic anhydride made in the United States came from the reaction of o-xylene with air. The rest was made from naphthalene, which was isolated from coal tar and petroleum. In 1989 all plants used o-xylene. 

Benzene, naphthalene, toluene, and the xylenes are naturally occurring compounds obtained from coal tar. Industrial synthetic methods, called catalytic reforming, utilize alkanes and cycloalkanes isolated from petroleum. Thus, cyclohexane is dehydrogenated (aromatization), and n-hexane(cycli> zation) and methylcyclopentane(isomerization) are converted to benzene. Aromatization is the reverse of catalytic hydrogenation and, in the laboratory, the same catalysts—Pt, Pd, and Ni—can be used. The stability of the aromatic ring favors dehydrogenation. 

Two or more benzene rings fused together form a number of polycyclic benzenoid aromatic compounds, naphthalene, anthracene and phenanthrene, and their derivatives. All these hydrocarbons are obtained from coal tar. Naphthalene is the most abundant (5%) of all constituents of coal tar. 

Naphthalene is produced from coal tar or petroleum. It is made from petroleum by dealkylation of methylnaphthalenes in the presence of hydrogen at high temperature and pressure. Petroleum was a major source of naphthalene until the 1980s, but now most naphthalene is produced from coal tar. The pyrolysis of bituminous coal produces coke and coke oven gases. Naphthalene is condensed by cooling the coke gas and then separated from the gas. Naphthalene production in the United States is slightly greater than 100,000 tons annually. 

In some blackpowder type mixtures, especially those for mining purposes, charcoal is partially or wholly replaced by carbon black, brown coal, pitch from coal tar, coal tar itself, naphthalene, paraffin, wood bark, cellulose or wood meal, starch, resin etc. Thus mixtures are obtained with properties similar to blackpowder. Generally, however, they bum more slowly and are more difficult to ignite. 

Total nameplaoe capacity for all U.S. naphthalene producers in 1993 was 124 x 103 t, with 114 103 t produced from coal tar and 10 x 103 from petioleum... 

H 11.18% col pltlts(from benz or AcOH), giving a violet-red fluorescent color in soln, mp 25 0°, bp 448°, d 1.274 sol in hot benz or hot AcOH diffc sol in cold eth, CS2, AcOH or benz derived from coal-tar fractions boiling above 360° also produced by the cracking of petroleum fractions at 630-80° using catalysts, or by heating indene at 500-700° with catalysts, and by passing naphthalene coumarone thru a red-hot tube (Refs 1 to 4). Other props methods of prepn are given in the Refs... 

Crude naphthalene obtained from coal tar may contain up to 5% benzo[6]thiophene which is only partially removed by selective sulfonation.43-45 Several improvements45-51 make this process more efficient. Other chemical methods of separation include oxidation with peracetic acid, which converts benzo[6]thiophene into its readily separated 1,1-dioxide,52 and treatment with ozone, which selectively... 

Naphthalene is the most abundant pure hydrocarbon obtained from coal tar. It takes on three nitro groups readily, and four under vigorous conditions, but ordinarily yields no product which is suitable by itself for use as an explosive. Nitrated naphthalenes, however, have been used in smokeless powder and, when mixed with ammonium nitrate and other materials, in high explosives for shells and for blasting. 

Naphthalene (C qHq) is a condensed aromatic compound obtained from coal tar. It has a relatively low melting point (80.2°C b.p. 217.9 )i sublimes readily on warming, and exerts sufficient vapor pressure at room temperature to be readily detectable by its characteristic odor. It is a chemical intermediate or feedstock in the synthesis of a large number of derivatives (e.g., phthalic, anthranilic, hydroxy-, amino- and sulfonyl-), compounds used in the production of the coal tar dyes. 

Naphthalene is produced from coal tar. In the coal tar process, coal tar is processed through a tar-distillation step where approximately the first 20 wt % of distillate (chemical oil) is removed. The chemical oil, which contains practically all the naphthalene present in the tar, is reserved for further processing, and the remainder of the tar is distilled further to remove additional creosote oil fractions until a coal-tar pitch of desirable consistency and properties is obtained. The chemical oil is processed to remove the tar acids by contacting with dilute sodium hydroxide and, in a few cases, is next treated to remove tar bases by washing with sulfuric acid. 

Phthalic anhydride (melting point 131.6°C, boiling point 295°C with sublimation) can be made from the reaction of o-xylene with air and also from naphthalene (Fig. 1), which is isolated from coal tar and from petroleum. 

The raw materials used to synthesize organic dyes are commonly referred to as dye intermediates. Largely, they are derivatives of aromatic compounds obtained from coal tar mixtures. The majority of these derivatives are benzene, naphthalene, and anthracene based compounds. This section provides an overview of the chemical reactions used to prepare the key intermediates employed in dye synthesis. In this regard, emphasis is placed on halogenated, aminated, hydroxy-lated, sulfonated, and alkylated derivatives of benzene, naphthalene, and anthraquinone. 

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