Phenol chlorobenzene processes

In the chlorobenzene process, benzene is chlorinated at 38 to 60°C in the presence of ferric chloride (FeCl3) catalyst. The chlorobenzene is hydrolyzed with caustic soda at 400°C and 11,000 psi (2.56 kPa) to form sodium phen-ate. The impure sodium phenate reacts with hydrochloric acid to release the phenol from the sodium salt. 

Phenol Processes by Manufacturers ° Chlorobenzene Process In 1000 tons per yr. 

Historically, phenol was produced by the distillation of coal tar. Today, phenol is prepared by one of several synthetic methods, such as the fusion of sodium benzenesulfonate with sodium hydroxide followed by acidification the hydrolysis of chlorobenzene by dilute sodium hydroxide at high temperature and pressure to give sodium phenate, which on acidification liberates phenol (Dow process) or the catalytic vapor-phase reaction of steam and chlorobenzene at 500°C (Raschig process). 

Utility charges are highest for the chlorobenzene process chiefly because of the charge for power for electrolysis. Here the producrion,of chlorine and chlorobenzene is considered as an integral part of thO phenol process. If the chlorobenzene had to be bought, or acquired by intraplant transfer at most favorable market prices, the competitive position of this process would not appear so attraetiye. The Rascli process is the faiE t ste ... 

The chlorobenzene processes for the production of phenol have lost then-importance since the 1970 s. Occasionally, the toluene oxidation process, also developed by Dow is still used. In the first stage of this process, toluene is oxidized to benzoic acid with air in the liquid phase at 150 to 170 °C and 5 to 10 bar, in the presence of cobalt salts, with 90% selectivity. By-products are methylbiphenyls, benzyl alcohol, benzaldehyde and esters. Following the purification of the crude product by distillation or crystallization, the benzoic acid is transformed into phenol in the presence of copper (II) salts with air and steam at 230 to 250 °C, and 2 to 10 bar, by way of the intermediate compounds copper benzoate, benzoyl-salicylic add and phenyl benzoate. The recovered crude phenol is refined by distillation. The molar yield of phenol is around 85 to 90%. 

Figure 10.50 Aniline is obtained from either nitrobenzene (Process 1), phenol (Process 2), or chlorobenzene (Process 3)...

Obtained synthetically by one of the following processes fusion of sodium ben-zenesulphonate with NaOH to give sodium phenate hydrolysis of chlorobenzene by dilute NaOH at 400 C and 300atm. to give sodium phenate (Dow process) catalytic vapour-phase reaction of steam and chlorobenzene at 500°C (Raschig process) direct oxidation of cumene (isopropylbenzene) to the hydroperoxide, followed by acid cleavage lo propanone and phenol catalytic liquid-phase oxidation of toluene to benzoic acid and then phenol. Where the phenate is formed, phenol is liberated by acidification. 

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 most widely used process for the production of phenol is the cumene process developed and Hcensed in the United States by AHiedSignal (formerly AHied Chemical Corp.). Benzene is alkylated with propylene to produce cumene (isopropylbenzene), which is oxidized by air over a catalyst to produce cumene hydroperoxide (CHP). With acid catalysis, CHP undergoes controUed decomposition to produce phenol and acetone a-methylstyrene and acetophenone are the by-products (12) (see Cumene Phenol). Other commercial processes for making phenol include the Raschig process, using chlorobenzene as the starting material, and the toluene process, via a benzoic acid intermediate. In the United States, 35-40% of the phenol produced is used for phenoHc resins. 

Raschig developed the first commercial oxychlorination process in 1928 to make chlorobenzene which was then hydrolyzed to phenol The Durez plant in North Tonawanda, New York, put on-stream in 1937, used this process. 

The Dow Chemical Company in the mid-1920s developed two processes which consumed large quantities of chlorobenzene. In one process, chlorobenzene was hydrolyzed with ammonium hydroxide in the presence of a copper catalyst to produce aniline [62-53-3J. This process was used for more than 30 years. The other process hydrolyzed chlorobenzene with sodium hydroxide under high temperature and pressure conditions (4,5) to product phenol [108-95-2]. The LG. Earbenwerke in Germany independentiy developed an equivalent process and plants were built in several European countries after World War II. The ICI plant in England operated until its dosing in 1965. 

In the 1930s, the Raschig Co. in Germany developed a different chlorobenzene-phenol process in which steam with a calcium phosphate catalyst was used to hydrolyze chlorobenzene to produce phenol (qv) and HCl (6). The recovered HCl reacts with air and benzene over a copper catalyst (Deacon Catalyst) to produce chlorobenzene and water (7,8). In the United States, a similar process was developed by the BakeHte Division of Union Carbide Corp., which operated for many years. The Durez Co. Hcensed the Raschig process and built a plant in the United States which was later taken over by the Hooker Chemical Corp. who made significant process improvements. 

Although Dow s phenol process utilized hydrolysis of the chlorobenzene, a reaction studied extensively (9,10), phenol production from cumene (qv) became the dominant process, and the chlorobenzene hydrolysis processes were discontinued. 

The chlorobenzene operations in the United States were developed primarily for the manufacture of phenol, aniline, and DDT. However, with the process changes in the production of phenol and aniline, the phase-out of DDT production, and changes in the herbicide and solvent markets, the U.S. production of chlorinated benzenes has shmnk by more than 50% since the total production peaked in 1969. U.S. production of monochlorobenzene peaked in the 1960s and decreased to a low of 101 million kg in 1986 with an 11% and 9% increase, respectively, in 1988 and 1989. 

Phenol was manufactured for many years by the Dow process, in which chlorobenzene reacts with NaOH at high temperature and pressure (Section 16.S). Now, however, an alternative synthesis from isopropylbenzene, commonly called... 

Vardanyan [65,66] discovered the phenomenon of CL in the reaction of peroxyl radicals with the aminyl radical. In the process of liquid-phase oxidation, CL results from the disproportionation reactions of primary and secondary peroxyl radicals, giving rise to trip-let-excited carbonyl compounds (see Chapter 2). The addition of an inhibitor reduces the concentration of peroxyl radicals and, hence, the rate of R02 disproportionation and the intensity of CL. As the inhibitor is consumed in the oxidized hydrocarbon the initial level of CL is recovered. On the other hand, the addition of primary and secondary aromatic amines to chlorobenzene containing some amounts of alcohols, esters, ethers, or water enhances the CL by 1.5 to 7 times [66]. This effect is probably due to the reaction of peroxyl radicals with the aminyl radical, since the addition of phenol to the reaction mixture under these conditions must extinguish CL. Indeed, the fast exchange reaction... 

The Dow Process utilizes an elimination/addition reaction to convert chlorobenzene to phenol. The proposed mechanism for this reaction is shown in Figure 8-3. The high-temperature reaction begins with chlorobenzene and aqueous sodium hydroxide. Note that this mechanism starts with the hydroxide attacking as a base, beginning dehydrohalogenation to form benzyne. The second hydroxide ion attacks as a nucleophile to form a carbanion intermediate, which behaves as a base in the last step to yield the final product. 

While some phenol is produced by the nucleophilic substitution of chlorine in chlorobenzene by the hydroxyl group (structure 17.17), most is produced by the acidic decomposition of cumene hydroperoxide (structure 17.18) that also gives acetone along with the phenol. Some of the new processes for synthesizing phenol are the dehydrogenation of cyclohexanol, the decarboxylation of benzoic acid, and the hydrogen peroxide hydroxylation of benzene. 

Chlorobenzene. Chlorobenzene is an important solvent and intermediate in the production of chemicals and dyes. Its use in phenol manufacture, however, was superseded by the introduction of the cumene process. 

The reactivities of aryl halides, such as the halobenzenes, are exceedingly low toward nucleophilic reagents that normally effect displacements with alkyl halides and activated aryl halides. Substitutions do occur under forcing conditions of either high temperatures or very strong bases. For example, chlorobenzene reacts with sodium hydroxide solution at temperatures around 340° and this reaction was once an important commercial process for the production of benzenol (phenol) ... 

In time of war the industries of a country strive to produce as much toluene as possible. The effort results in the production also of increased quantities of other aromatic hydrocarbons, particularly of benzene, and these become cheaper and more abundant. Every effort is made to utilize them profitably for military purposes. As far as benzene is concerned, the problem has been solved through chlorobenzene, which yields aniline and phenol by the Dow process, and hence picric acid, and which gives dinitro-chlorobenzene on nitration which is readily convertible, as will be described later, into picric acid and tetryl and several other... 

Steam and silica gel to produce phenol from chlorobenzene, the Dow process with steam and a copper salt catalyst, etc. 

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