Benzene industrial source

An alkene mixture of industrial source (equal amounts of C9-C13 alkenes and alkanes) was used in the alkylation of benzene on three Nafion-silica catalysts with 5%, 13%, and 20% loadings.195 20% Nafion-silica showed high and stable activity and its performance exceeded that of a Y-zeolite-based material. The selectivity to 2-phenylalkanes (25%) was higher than in the Detal process using fluorinated silica-alumina but decreased somewhat with increasing Nafion content. 

Figure 2.28 Industrial aromatic alkylations and breakdown of benzene used in the chemical industry. Source adapted from Perego and Ingallina [221],...

For the chlorinated benzenes, a very similar distribution within the sediment core is observed as for some PAHs, e.g. benzo[a]pyrene. An elevated large-scale industrial activity related to these compounds can be deduced for the time between 1947 and 1955. We attribute the decrease in contamination towards the top layers to a reduction of emissions as a result of more efficient sewage treatment plants (Fig. 1A,B) as well as a modified array of products. The concentration profile of HCB (Fig. 6C) and all lower chlorinated benzenes (Tab. 2) suggests the dominance of industrial sources responsible for the contamination as contrasted to agricultural emission derived from pesticide usage. It should be noted that the contamination level of 1,4-dichlorobenzene was elevated in the time period between 1975 and 1980, comparable with concentration levels determined in Rhine river sediments 1982/83. The extensive use of 1,4-dichlorobenzene as an odorous ingredient of toilet cleaners contributed additionally to the contamination via sewage effluents (LWA, 1987/1989). 

ORIGIN/INDUSTRY SOURCES/USES component of benzene hexachloride, bhc a former insecticide small amounts may come from isomerization of lindane upon exposure to sunlight... 

The Cg alkylaromatics fraction is formed by ethylbenzene and the three xylene isomers. Ethylbenzene is used as a raw material to produce styrene by dehydrogenation, or oxidative dehydrogenation. Para-xylene and ortho-xylene are catalytically oxidized to give terephthalic and phthalic acid. The meta-xylene isomer can also be oxidized to give isophthalic acid. The major industrial source of these products is the catalytic reforming of naphthas. The Cyclar process, can also produce xylenes from propane and butane. However, using this process, xylenes are formed less selectively than toluene or benzene in the BTX. 

Benzene was prepared from coal tar by August W von Hofmann m 1845 Coal tar remained the primary source for the industrial production of benzene for many years until petroleum based technologies became competitive about 1950 Current production IS about 6 million tons per year m the United States A substantial portion of this ben zene is converted to styrene for use m the preparation of polystyrene plastics and films... 

The Clean Air Act Amendments of 1990 limit the amount of benzene in gasoline in the United States to 1% (7). Initially there was some concern that this would dismpt the benzene supply and demand balance in the chemical industry because at that time gasoline contained benzene above 1%. If refiners had to extract all of the benzene above 1%, substantial additional benzene would be produced. However, only modest increases in the quantity of benzene produced from reformer sources is expected as most refiners can adjust the composition of reformer feed and reformer severity to produce less benzene. 

Friedel-Crafts alkylation using alkenes has important industrial appHcations. The ethylation of benzene with ethylene to ethylbenzene used in the manufacture of styrene, is one of the largest scale industrial processes. The reaction is done under the catalysis of AlCl in the presence of a proton source, ie, H2O, HCl, etc, although other catalysts have also gained significance. 

Estimates based on published and industry infomiation sources for production of linear alkyl (C 2) benzene alkylate sulfonic acid andlauryl-3 mol ethoxy... 

Until the 1940s light oil obtained from the destmctive distillation of coal was the principal source of benzene. Except for part of the World War 11 period, the quantity of benzene produced by the coal carbonization industry was sufficient to supply the demand even when a large portion of benzene was used for gasoline blending. 

After 1950, benzene in motor fuel was largely replaced by tetraethyllead but the demand for benzene in the chemical industry persisted and soon exceeded the total production by the coal carbonization industry. To meet this growing demand, methods for producing benzene directiy from petroleum sources were developed. 

Workplace exposure limits for benzene have been regulated to levels as low as 0.5 ppm (43). Industrial emissions affecting the pubHc ate now low enough that the EPA considers that a greater hazard exists from mosdy indoor sources such as smoking, automobile exhausts, and consumer products (44). 

Until the mid-1950s the main raw material source for the European plastics industry was coal. On destructive distillation coal yields four products coal tar, coke, coal gas and ammonia. Coal tar was an important source of aromatic chemicals such as benzene, toluene, phenol, naphthalene and related products. From these materials other chemicals such as adipic acid, hexamethylenedia-mine, caprolactam and phthalic anhydride could be produced, leading to such important plastics as the phenolic resins, polystyrene and the nylons. 

With each succeeding year in the 1950s and 1960s there was a swing away from coal and vegetable sources of raw materials towards petroleum. Today such products as terephthalic acid, styrene, benzene, formaldehyde, vinyl acetate and acrylonitrile are produced from petroleum sources. Large industrial concerns that had been built on acetylene chemistry became based on petrochemicals whilst coal tar is no longer an indispensable source of aromatics. 

The generation of caibocations from these sources is well documented (see Section 5.4). The reaction of aromatics with alkenes in the presence of Lewis acid catalysts is the basis for the industrial production of many alkylated aromatic compounds. Styrene, for example, is prepared by dehydrogenation of ethylbenzene made from benzene and ethylene. 

Also of importance to the industry is the demand for aromatic products. The high octane reformate, which is rich in aromatics, is a major source of aromatics for petrochemical operations. Powerformers can produce aromatics such as benzene and toluene. 

Fumaric acid is used in the plastics industry, in the food industry and as a source of malic add. Although demand has increased rapidly over the last 30 years its production from fermentation has been totally replaced by a chemical method. It is now produced far more cheaply by the catalytic oxidation of hydrocarbons, particularly benzene. With the continuing uncertainties concerning the availability and cost of petroleum, however, fermentation may yet be a viable alternative. 

The Cio fraction in reformates has been considered a likely petroleum source for obtaining durene (9). However, there are 28 kinds of isomeric arenes in the fraction, and the durene content is only 5-9%. Therefore, the isolation of durene from such a complicated mixture is inefficient, and some complicated techniques are required for it. In contrast, 1,2,4-trimethyl-benzene (pseudocumene) can be easily isolated simply by the distillation of the Cg fraction of the reformates, and a high-purity pseudocumene has been produced on an industrial scale. 

Why start out with benzene The obvious answer is that benzene is one of the handRil of basic building blocks in the petrochemicals industry along with ethylene, propylene, and a few others. The more subde reason is that benzene, more than any of those other chemicals, comes from a broader b e- steel mill coking, petroleum refining, and olefins plants. For that reason, the benzene network, the sources and the uses, is more complex than any of the others. 

The large demand for benzene is due to its use as a starting material in the production of polystyrene, acrylonitrile styrene butadiene rubber, nylons, polycarbonates and linear alkyl benzene detergent. All of these final chemical products that are suitable to form into consumer goods have multiple chemical transformations in various industrial processes to obtain them from benzene. Because the production of benzene does not involve a liquid adsorptive process on a zeolite, these processes are not described here but can be found in other sources. However, it is important to note that benzene is typically a large byproduct from an aromatics... 

Phenol is the major source of Bakelite and phenol resins, which are utihzed in many commodities worldwide phenol is also used as reagent for syntheses of dyes, medicines and so on. The industrial demand for phenol has increased every year and its production now exceeds 7.2 megaton year 94% of the worldwide production of phenol is processed in the cumene process. The cumene process involves the reaction of benzene with propene on acid catalysts like MCM-22, followed by auto-oxidation of the obtained cumene to form explosive cumene hydroperoxide and, finally, decomposition of the cumene hydroperoxide to phenol and acetone in sulfuric acid (Scheme 10.3) [73],... 

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