Phenol, atmosphere

Physical properties. All solid except m -cresol, CH3CJH4OH, which is a liquid. All colourless when pure, but frequently slightly coloured due to atmospheric oxidation. All have in varying degrees a characteristic odour of carbolic acid. Phenol, the cresols and resorcinol have a caustic action on the skin. 

The process is carried at moderate (slightly above atmospheric) pressures, but at very high temperatures that reach a maximum of 1900°C. Even though the reaction time is short (0.6—0.8 s) the high temperature prevents the occurrence of any condensable hydrocarbons, phenols, and/or tar in the product gas. The absence of Hquid simplifies the subsequent gas clean-up steps. 

Sta.rting from Phenol. Phenol can be selectively oxidized into -benzoquinone with oxygen. The reaction is catalyzed by cuprous chloride. At low catalyst concentration, the principal drawback of this method is the high pressure of oxygen that is required, leading to difficult safety procedures. It appears that a high concentration of the catalyst (50% of Cu(I)—phenol) allows the reaction to proceed at atmospheric pressure (58). 

The second processing step, in which benzoic acid is oxidized and hydrolyzed to phenol, is carried out in two reactors in series. In the first reactor, the benzoic acid is oxidized to phenyl benzoate in the presence of air and a catalyst mixture of copper and magnesium salts. The reactor is operated at 234°C and 147 kPa gauge (1.5 kg/cm g uge). The phenyl benzoate is then hydrolyzed with steam in the second reactor to yield phenol and carbon dioxide. This occurs at 200°C and atmospheric pressure. The overall yield of phenol from benzoic acid is around 88 mol %. Figure 2 shows a simplified diagram for the toluene—benzoic acid process. 

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. 

Low temperature tars contain 30—35 wt % non aromatic hydrocarbons, ca 30% of caustic-extractable phenols in the distillate oils, and 40—50% of aromatic hydrocarbons. The latter usually contain one or more alkyl substituent groups. On atmospheric distillation, coke-oven tars yield 55—60% pitch, whereas CVR tars give 40—50% pitch. The pitch yield from low temperature tars is in the 26—30% range. 

Eor many polymeri2ations, MEHQ need not be removed instead, polymeri2ation initiators are added. Vinyhdene chloride from which the inhibitor has been removed should be refrigerated in the dark at —10° C, under a nitrogen atmosphere, and in a nickel-lined or baked phenolic-lined storage tank. If not used within one day, it should be reinhibited. 

Procedures for shipping boric acid esters depend on the particular compound. Aryl borates produce phenols when in contact with water and are therefore subject to shipping regulations governing such materials and must carry a Corrosive Chemical label. Lower alkyl borates are flammable, flash points of methyl, ethyl, and butyl borates are 0, 32, and 94°C, respectively, and must be stored in approved areas. Other compounds are not hazardous, and may be shipped or stored in any convenient manner. Because borate esters are susceptible to hydrolysis, the more sensitive compounds should be stored and transferred in an inert atmosphere, such as nitrogen. 

One 1-ml aliquot is added to 1.0 ml of freshly-distilled 1,2-dibromo-ethane (bp 132°C) in an oven-dried flask which contains a static atmosphere of nitrogen or argon. After the resulting solution has been allowed to stand at 25°C for 5 min, it Is diluted with 10 rat of water and titrated for base content (residual base) to a phenolphthalein endpoint with standard 0.100 M hydrochloric acid. The second 1-mL aliquot is added cautiously to 10 ml of water and then titrated for base content (total base) to a phenol phthalein endpoint with standard aqueous 0.100 M hydrochloric acid. The methyllithium concentration is the difference between the total base and residual base concentrations.2 Alternatively, the methynithiura concentration may be determined by titration with a standard solution of sec-butyl alcohol employing 2,2 -bipyridyl as an indicator. 

Because phenols are weak acids, they can be freed from neutral impurities by dissolution in aqueous N sodium hydroxide and extraction with a solvent such as diethyl ether, or by steam distillation to remove the non-acidic material. The phenol is recovered by acidification of the aqueous phase with 2N sulfuric acid, and either extracted with ether or steam distilled. In the second case the phenol is extracted from the steam distillate after saturating it with sodium chloride (salting out). A solvent is necessary when large quantities of liquid phenols are purified. The phenol is fractionated by distillation under reduced pressure, preferably in an atmosphere of nitrogen to minimise oxidation. Solid phenols can be crystallised from toluene, petroleum ether or a mixture of these solvents, and can be sublimed under vacuum. Purification can also be effected by fractional crystallisation or zone refining. For further purification of phenols via their acetyl or benzoyl derivatives (vide supra). 

Aminophenol [95-55-6] M 109.1, m 175-176 , pKj 4.65, pKj 9.75. Purified by soln in hot water, decolorised with activated charcoal, filtered and cooled to induce crystn. Maintain an atmosphere of N2 over the hot phenol soln to prevent its oxidation [Charles and Preiser J Am Chem Soc 74 1385 7952]. Can also be crystd from EtOH. 

Draper and Pollard [Science 109 448 1949] added 12% water, 0.1% aluminium (can also use zinc), and 0.05% NaHC03 to phenol, and distd at atmospheric pressure until the azeotrope was removed. The phenol was then distd at 25mm. Phenol has also been dried by distn from the benzene soln to remove the water- benzene azeotrope and the excess benzene, followed by distn of the phenol at reduced pressure under nitrogen. Processes such as this are probably adequate for analytical grade phenol which has as its main impurity water. Phenol has also been crystd from pet ether/ benzene or pet ether (b 40-60°). Purified material is stored in a vacuum desiccator over P2O5 or CaS04. 

A frequently cited example of protection from atmospheric corrosion is the Eiffel Tower. The narrow and, for that age, thin sections required a good priming of red lead for protection against corrosion. The top coat was linseed oil with white lead, and later coatings of ochre, iron oxide, and micaceous iron oxide were added. Since its constmction the coating has been renewed several times [29]. Modern atmospheric corrosion protection uses quick-drying nitrocellulose, synthetic resins, and reaction resins (two-component mixes). The chemist Leo Baekeland discovered the synthetic material named after him, Bakelite, in 1907. Three years later the first synthetic resin (phenol formaldehyde) proved itself in a protective paint. A new materials era had dawned. 

The reaction mixture is heated and allowed to reflux, under atmospheric pressure at about 100°C. At this stage valve A is open and valve B is closed. Because the reaction is strongly exothermic initially it may be necessary to use cooling water in the jacket at this stage. The condensation reaction will take a number of hours, e.g. 2-4 hours, since under the acidic conditions the formation of phenol-alcohols is rather slow. When the resin separates from the aqueous phase and the resin reaches the requisite degree of condensation, as indicated by refractive index measurements, the valves are changed over (i.e. valve A is closed and valve B opened) and water present is distilled off. 

Furfural is a colourless liquid which darkens in air and has a boiling point of 161.7°C at atmospheric pressure. Its principal uses are as a selective solvent used in such operations as the purification of wood resin and in the extraction of butadiene from other refinery gases. It is also used in the manufacture of phenol-furfural resins and as a raw material for the nylons. The material will resinify in the presence of acids but the product has little commercial value. 

Paints based on phenolic resins are oil modified to permit drying at ambient temperatures. They are very suitable for most industrial atmospheres. Paints with a higher standard of chemical resistance are required for equipment that is splashed by corrosive process liquors. 

Phenol, CeHsOH (hydroxybenzene), is produced from cumene by a two-step process. In the first step, cumene is oxidized with air to cumene hydroperoxide. The reaction conditions are approximately 100-130°C and 2-3 atmospheres in the presence of a metal salt catalyst ... 

In the second step, the hydroperoxide is decomposed in the presence of an acid to phenol and acetone. The reaction conditions are approximately 80°C and slightly below atmospheric ... 

An alternative way to produce aniline is through ammonolysis of either chlorobenzene or phenol. The reaction of chlorobenzene with aqueous ammonia occurs over a copper salt catalyst at approximately 210°C and 65 atmospheres. The yield of aniline from this route is also about 96% ... 

Atmospheres polluted by oxidising agents, e.g. ozone, chlorine, peroxide, etc. whose great destructive power is in direct proportion to the temperature, are also encountered. Sulphuric acid, formed by sulphur dioxide pollution, will accelerate the breakdown of paint, particularly oil-based films. Paint media resistant both to acids, depending on concentration and temperature, and oxidation include those containing bitumen, acrylic resins, chlorinated or cyclised rubber, epoxy and polyurethane/coal tar combinations, phenolic resins and p.v.c. 

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