Chemical intermediate, benzene release

First, points of release of benzene were identified petroleum refining and coke oven operations (production and extraction releases), use as a chemical intermediate (transportation, storage, use, and waste releases), use in gasoline (use-related release), and use in finished products (use-related release). Benzene also can be a contaminant of most of the derivatives made from it and its use as a solvent was substantial before health concerns arose. The complexity of the chemical systems dependent on benzene is shown in Figure 6. A list of potential releasing products appears in Table II. 

Next, various quantitative techniques were used to estimate releases by type of use. For use of benzene as an intermediate, we relied on the "emission factor" technique, which estimates the ratio of benzene release to total derivative production and then applies this ratio to the production rate at specific locations. Emissions factors were estimated from crude engineering assessments of the chemical processes entailed (such as open versus closed systems, continuous versus batch, and so on). 

Hydroprocessing, in petroleum refining, 18 654-657 Hydropulping, 10 535 Hydropyrolysis, coal liquefaction, 6 854 Hydroquinolines, 21 198-199 Hydroquinone (HQ) from benzene, 3 620 as a black-and-white chemical reducing agent, 19 205-206 in bleaching preparations, 7 847 clathrates, 14 160 dye releaser, 19 291-292 inclusion compounds in, 14 172, 174 intermediate used in oxidation hair dyes, 7 858t... 

Addition reactions proceed typically at unsaturated bonds such as C=C, C=0, C=N, C=N or carbon-carbon triple bonds. A molecule is added to the substrate and the product forms without release of any another molecule. With all substrates becoming part of the product, the atom economy of addition reactions is very favorable. Because today s chemical technology is largely based on unsaturated base chemicals obtained in the steam cracker process (e.g., ethylene, propylene, butenes, benzene, see Chapter 6.6), addition reactions are of the highest relevance in the whole petrochemistry. Scheme 2.2.2 shows as one important example, namely, the addition of hydrogen to benzene to form cyclohexane, a key intermediate in the production of, for example, adipinic acid or caprolactam (nylon). 

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