Cumene

After ethylbenzene, cumene (isopropylbenzene) is the most important industrial derivative of benzene. Cumene is also produced by benzene alkylation recovery from the corresponding coal or petrochemical streams is uneconomical, owing to the low levels of cumene present. 

Cumene gained particular technical importance following the discovery of the phenol synthesis via the oxidation of cumene by Heinrich Hock and Shon Lang in Clausthal/Germany in 1944. Cumene had already been obtained by Cornelius Radziewanowski in 1895, by reaction of benzene and isopropyl chloride in the presence of aluminum filings and dry hydrogen chloride. A 66 % yield was 

The reaction of benzene and propylene is carried out in a similar way to the reaction of benzene and ethylene in the production of ethylbenzene. An excess of benzene is used and, in special processes, transalkylation and separation of the reaction products by distillation and subsequent recycle are included to reduce the formation of highly alkylated products. 

As in ethylbenzene production, alkylation can be performed either in the gas or in the liquid phase. Propylation of benzene in the liquid phase is achieved with sulfuric acid or aluminum chloride as catalyst at 30 to 40 °C, or with hydrogen fluoride at 50 to 70 °C, and propylene pressures up to 7 bar. The propylene used must be largely free from other olefins. A propylene/propane mixture, such as occurs in refinery gases, can be used for the reaction, since propane is not converted and can readily be stripped from the reaction products. 

Gas-phase alkylation with a benzene/propylene ratio of 5 1 takes place using phosphoric acid silicate catalysts at temperatures of 250 to 350 °C and pressures of 30 to 45 bar. The reaction is carried out in the presence of steam to achieve better control of the exothermic conversion, and at the same time to fix the phosphoric acid better to the carrier through the formation of hydrates. In order to produce one part by weight of cumene, 0.67 parts of benzene and 0.38 parts of propylene are converted. Around 0.05 parts by weight of heavy aromatics (tar) arise through polyalkylation and condensation selectivity is 96 to 97 mol %. 

In the United States, the largest producers of cumene are Flint Hills Resources in Corpus Christi, XX CITGO Petroleum in Corpus Christi, IX Georgia Gulf in Pasadena, XX Shell Chemical in Deer Park, XX Sunoco in Philadelphia, PA, and West-ville, Nl and INFOS Phenol in Port Arthur, XX. 

Cumene is chlorinated to chlorocumene to be used in synthesizing dicumyl peroxide, the major peroxide curative used by the rubber industry. Cumene is oxidized to acetone, which is reacted with aniline to produce XMQ, the highest volume antioxidant used by the rubber industry. 

Cumene is oxidized to acetone, which reacts with diphenyi amine to produce ADPA antioxidant. (Phenoi is aiso a coproduct of cumene oxidation.) 

Cumene is oxidized to phenol, which is used to produce aniline and many other rubber chemicals (see phenol). (Acetone is a byproduct of cumene oxidation as well.) 

It was realized during World War 11 that alkylated benzene molecules coirld be used to increase the octane level of aviation gasoline. The Petroleum Administration for War had asked for a high-octane synthetic aromatic component in 1941 and propyl benzene, also known as cumene, and butyl benzene were produced in the United States and the United Kingdom, respectively. In 1944, the Hock and Lang process, which produced phenol and acetone from cumene was introduced, and this industrial process became the basis of the major source of phenol throughout the world  

More recently, new processes for phenol which do not prodnce acetone by products have been described. 

As in all alkylation reactions the catalyst used to produce cumene from propylene and benzene is a strong acid and a number of processes have been introduced. The first were developed by Distillers and Hercules in 1953  

Phosphoric acid/kieselguhr with added steam or aluminum trichloride have been the most widely used catalytic processes. Excess benzene is usually added to the reaction mixture to limit the formation of di- and tri-propylbenzene and to maximize the selectivity of propylene to cumene. Pure propylene must be used to avoid the production of ethyl benzene. 

Typical acid catalysts are not regenerable and particularly in the case of aluminium trichloride can lead to disposal problems, so zeolites are now increasingly used as active catalysts. Early problems were encountered with relatively fast deactivation or the formation of ethyl benzene and butyl benzene from metathesis (disproportionation) reactions. These were overcome when Dow introduced a dealuminated mordenite catalyst (3DDM— three-dimensional dealumi-nated mordenite) that was both stable over 18 months of testing and regenera-ble. Yields with the mordenite catalyst are greater than 99% and purity is almost 100%. ENI in Italy used a selective S-zeolite catalyst and process improvements led to an increased plant capacity of 30-40%. 

Drypoinl Specific gravity of liquiil at MV60 F 0J84S Tsn 0.885 

PROPERTIES RESEARCH GRADE PURE GRADE techrical GRADE 

Isopropylbmzifif and .2,4-Trimt(hylbtnnne art Mmetimet ttabili/td with 2,6-ditertiarv butyl-4-mathyiphanol which can be rtmovad by distillation. 

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Benzene was first isolated by Faraday in 1825 from the liquid condensed by compressing oil gas. It is the lightest fraction obtained from the distillation of the coal-tar hydrocarbons, but most benzene is now manufactured from suitable petroleum fractions by dehydrogenation (54%) and dealkylation processes. Its principal industrial use is as a starting point for other chemicals, particularly ethylbenzene, cumene, cyclohexane, styrene (45%), phenol (20%), and Nylon (17%) precursors. U.S. production 1979 2-6 B gals. 

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. 

Because the protonation of ozone removes its dipolar nature, the electrophilic chemistry of HOs, a very efficient oxygenating electrophile, has no relevance to conventional ozone chemistry. The superacid-catalyzed reaction of isobutane with ozone giving acetone and methyl alcohol, the aliphatic equivalent of the industrially significant Hock-reaction of cumene, is illustrative. 

The thermal decomposition of thia2ol-2-yl-carbonyl peroxide in benzene, bromobenzene, or cumene affords thiazole together with good yields of 2-arylthiazoles but negligible amounts of esters. Thiazol-4-ylcarbonyl peroxide gives fair yields of 4-arylthiazoles, but the phenyl ester is also a major product in benzene, indicating reactions of both thiazol-4-yl radicals and thiazol-4-carbonyloxy radicals. Thiazole-5-carbonyl peroxide gives... 

Treating 2-bromothiazole with copper at 170°C in cumene as solvent affords the 2.2 -bisthiazole (Scheme 9) (69). The 2-halogenothiazoles can... 

PROPENE The major use of propene is in the produc tion of polypropylene Two other propene derived organic chemicals acrylonitrile and propylene oxide are also starting materials for polymer synthesis Acrylonitrile is used to make acrylic fibers (see Table 6 5) and propylene oxide is one component in the preparation of polyurethane polymers Cumene itself has no direct uses but rather serves as the starting material in a process that yields two valuable indus trial chemicals acetone and phenol... 

Cumene (isopropylbenzene) is a relatively inexpensive com mercially available starting material Show how you could prepare m-isopropyl nitrobenzene from cumene... 

From cumene Almost all the phenol produced in the United States is prepared by this method Oxi dation of cumene takes place at the benzylic posi tion to give a hydroperoxide On treatment with dilute sulfuric acid this hydroperoxide is converted to phenol and acetone... 

The most widely used industrial synthesis of phenol is based on isopropylbenzene (cumene) as the starting material and is shown m the third entry of Table 24 3 The eco nomically attractive features of this process are its use of cheap reagents (oxygen and sulfuric acid) and the fact that it yields two high volume industrial chemicals phenol and acetone The mechanism of this novel synthesis forms the basis of Problem 24 29 at the end of this chapter... 

One of the mdustnal processes for the preparation of phenol discussed in Section 24 6 includes an acid catalyzed rearrangement of cumene hydroperoxide as a key step This reaction proceeds by way of an intermediate hemiacetal... 

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