Environmental phenol hydrogenation

Analytical methods used for determining DNOC in environmental samples are given in Table 6-2. Most of the methods for products, waters, soils, and sludges rely on extraction of DNOC from an acidified matrix acidification minimizes dissociation of the phenolic hydrogen and thus facilitates extraction into an organic solvent or adsorption onto a solid phase extraction medium. The influence of pH on the adsorption of DNOC to humic materials in coal waste waters has been studied (Porschmann and Stottmeister 1993) and significant adsorption was found to occur at pH 7 but not... 

Benzene Oxychlorin tion. In the benzene oxychlorination process, also known as the Raschig Hooker process, benzene is oxychlorinated with hydrogen chloride, air, and with the presence of iron and copper chloride catalyst to form chlorobenzene. The reaction occurs at 200—260°C and atmospheric pressure. The chlorobenzene is hydrolyzed at 480°C in the presence of a suitable catalyst to produce phenol and chloride. The yield of phenol is - 90 mol% of theoretical. These plants have been shut down for environmental and economic reasons. 

The dissociation of water coordinated to exchangeable cations of clays results in Brtfnsted acidity. At low moisture content, the Brrfnsted sites may produce extreme acidities at the clay surface-As a result, acid-catalyzed reactions, such as hydrolysis, addition, elimination, and hydrogen exchange, are promoted. Base-catalyzed reactions are inhibited and neutral reactions are not influenced. Metal oxides and primary minerals can promote the oxidative polymerization of some substituted phenols to humic acid-like products, probably through OH radicals formed from the reaction between dissolved oxygen and Fe + sites in silicates. In general, clay minerals promote many of the reactions that also occur in homogenous acid or oxidant solutions. However, rates and selectivity may be different and difficult to predict under environmental conditions. This problem merits further study. 

The polymerization of phenols or aromatic amines is applied in resin manufacture and the removal of phenols from waste water. Polymers produced by HRP-catalyzed coupling of phenols in non-aqueous media are potential substitutes for phenol-formaldehyde resins [123,124], and the polymerized aromatic amines find applications as conductive polymers [112]. Phenols and their resins are pollutants in aqueous effluents derived from coal conversion, paper-making, production of semiconductor chips, and the manufacture of resins and plastics. Their transformation by peroxidase and hydrogen peroxide constitutes a convenient, mild and environmentally acceptable detoxification process [125-127]. 

Reductive dehalogenation of chlorinated phenols to phenol, cyclohexanol and other chlorine-free compounds takes place rapidly with hydrogen gas and Pd/C in an aqueous system or under solvent-free conditions. Thus, pentachloro phenol was able to be completely dechlorinated within 20 min (Scheme 4.45). This methodology enables a facile route for rapid and complete detoxification of highly toxic polychlorinated aromatic hydrocarbons and environmental remediation71,72. 

Although cyclohexane oxidation dominates the market, because of cheaper raw materials, the hydrogenation of phenol remains competitive, offering better selectivity with fewer environmental and safety problems. In addition, this process allows efficient valorization of phenol-rich wastes from coal industries. Recently built plants make use of this technology, as reported by the engineering group Aker-Kvaerner (www.kvaerner.com, 2004). The availability of low-price phenol is the most important element for profitability. Besides the well-known cumene process, a promising route is the selective oxidation of benzene with N20 on iron-modified ZSM-5 catalyst [12]. In this way, the price of phenol may become independent of the market of acetone. 

After closing the material and heat balances, we will examine the potential environmental impact (PEI) of the design. The basic information is the stream report. Table 5.16 shows material- and heat-balance data for a fresh feed of 150kmol/h phenol and 350kmol/h hydrogen, in total 14822.5kg/h. The products are cyclohexanone 9618.9 and 5017.9 cyclohexanol in the molar ratio 2 1. After simulation it is found that the amount of waste is 150.6 kg/h lights and 80 kg/h heavies. These data lead to a global yield of raw materials of 98.75%. 

The significance of the reaction of phenol with hydrogen has a number of important facets. First, the selective hydrogenation of phenol yields cyclohexanone, which is a key raw material in the production of both caprolactam for nylon 6 and adipic acid for nylon 6 . Second, due to the fact that phenol is an environmental toxin and phenolic waste has a variety of origins from industrial sources including oil refineries, petrochemical units, polymeric resin manufacturing and plastic units , catalytic hydrogenation of phenol is nowadays the best practicable environmental option . ... 

Peroxidases are ubiquitous, haem containing enzymes that are present in plants, in some animal tissues and in micro-organisms. They catalyse a variety of biosynthetic and degradative oxidations of phenols and amines by hydrogen peroxide or hydroperoxides. Horseradish peroxidase (HRP) and other peroxidases, particularly those present in white rot fungus Phanerochaete chrysosporium, have also been studied as potential catalysts for the oxidative degradation of aqueous solutions of azo dyes and phenolic environmental pollutants. ... 

Soaps and detergents are surfactants used in cleaning.260 Soaps are salts of fatty acids (e.g., sodium stearate). Detergents are salts of sulfonic acids, quaternary ammonium salts, tertiary amine oxides, ethylene oxide adducts of alcohols, and phenols.261 Their use in cleaning to replace chlorinated solvents262 was covered in Chap. 3, Sec. VII. (See also the use of hydrogen peroxide,263 ethyl lactate,264 and ultrasound265 to clean process equipment.) Some other environmental aspects of their use will be covered here briefly. 

With AMS hydrogenation, 1.31 tons of cumene will produce 1 ton of phenol and 0.616 tons of acetone. This high-yield process produces very high-quality phenol and acetone products with very little heavy and light-end byproducts. With over 40 years of continuous technological development, the Kellogg Brown Root (KBR) phenol process features low cumene and energy consumptions, coupled with unsurpassed safety and environmental systems. 

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