Cumene, acidity

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. 

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... 

Until World War 1 acetone was manufactured commercially by the dry distillation of calcium acetate from lime and pyroligneous acid (wood distillate) (9). During the war processes for acetic acid from acetylene and by fermentation supplanted the pyroligneous acid (10). In turn these methods were displaced by the process developed for the bacterial fermentation of carbohydrates (cornstarch and molasses) to acetone and alcohols (11). At one time Pubhcker Industries, Commercial Solvents, and National Distillers had combined biofermentation capacity of 22,700 metric tons of acetone per year. Biofermentation became noncompetitive around 1960 because of the economics of scale of the isopropyl alcohol dehydrogenation and cumene hydroperoxide processes. 

This procedure may result in a concentration of cumene hydroperoxide of 9—12% in the first reactor, 15—20% in the second, 24—29% in the third, and 32—39% in the fourth. Yields of cumene hydroperoxide may be in the range of 90—95% (18). The total residence time in each reactor is likely to be in the range of 3—6 h. The product is then concentrated by evaporation to 75—85% cumene hydroperoxide. The hydroperoxide is cleaved under acid conditions with agitation in a vessel at 60—100°C. A large number of nonoxidising inorganic acids are usehil for this reaction, eg, sulfur dioxide (19). 

Anaerobic stmctural adhesives are typically formulated from acryhc monomers such as methyl methacrylate [80-62-6] C Hg02, and methacrylic acid [79-41-4] (see Acrylic ester polymers). Very often, cross-linking agents such as dimethacrylates are also added. A peroxide, such as cumene... 

Acryhc stmctural adhesives have been modified by elastomers in order to obtain a phase-separated, toughened system. A significant contribution in this technology has been made in which acryhc adhesives were modified by the addition of chlorosulfonated polyethylene to obtain a phase-separated stmctural adhesive (11). Such adhesives also contain methyl methacrylate, glacial methacrylic acid, and cross-linkers such as ethylene glycol dimethacrylate [97-90-5]. The polymerization initiation system, which includes cumene hydroperoxide, N,1S7-dimethyl- -toluidine, and saccharin, can be apphed to the adherend surface as a primer, or it can be formulated as the second part of a two-part adhesive. Modification of cyanoacrylates using elastomers has also been attempted copolymers of acrylonitrile, butadiene, and styrene ethylene copolymers with methylacrylate or copolymers of methacrylates with butadiene and styrene have been used. However, because of the extreme reactivity of the monomer, modification of cyanoacrylate adhesives is very difficult and material purity is essential in order to be able to modify the cyanoacrylate without causing premature reaction. 

Propylation of benzene with propylene, catalyzed by supported phosphoric acid (or related catalysts such as AlCl ), gives cumene [98-82-8] in another important industrial process. Cumene (qv), through the intermediacy of cumene hydroperoxide, is used in the manufacture of phenol (qv). Resorcinol similarly can be made from y -diisopropylbenzene (6). 

Synthetic phenol capacity in the United States was reported to be ca 1.6 x 10 t/yr in 1989 (206), almost completely based on the cumene process (see Cumene Phenol). Some synthetic phenol [108-95-2] is made from toluene by a process developed by The Dow Chemical Company (2,299—301). Toluene [108-88-3] is oxidized to benzoic acid in a conventional LPO process. Liquid-phase oxidative decarboxylation with a copper-containing catalyst gives phenol in high yield (2,299—304). The phenoHc hydroxyl group is located ortho to the position previously occupied by the carboxyl group of benzoic acid (2,299,301,305). This provides a means to produce meta-substituted phenols otherwise difficult to make (2,306). VPOs for the oxidative decarboxylation of benzoic acid have also been reported (2,307—309). Although the mechanism appears to be similar to the LPO scheme (309), the VPO reaction is reported not to work for toluic acids (310). 

Diisopropjibenzenes (DIPB) are readily obtained via Eriedel-Crafts alkylation of benzene or cumene by propylene. This reaction inhquid phase has not evolved drastically since 1980 with the exception of the large variety of heterogeneous acid catalysts that are now being used, mainly zeoHtes, type HZSM-12, giving a para/meta ratio = 0.7 (4). In fact, propylene can also be replaced by isopropyl alcohol coming from the hydrogenation of acetone that... 

The cumene oxidation route is the lea ding commercial process of synthetic phenol production, accounting for more than 95% of phenol produced in the world. The remainder of synthetic phenol is produced by the toluene oxidation route via benzoic acid. Other processes including benzene via cyclohexane, benzene sulfonation, benzene chlorination, and benzene oxychl orin ation have also been used in the manufacture of phenol. A Hst of U.S. phenol production plants and their estimated capacities in 1994 are shown in Table 2, and worldwide plants and capacities are shown in Table 3. 

Oxidation of cumene to cumene hydroperoxide is usually achieved in three to four oxidizers in series, where the fractional conversion is about the same for each reactor. Fresh cumene and recycled cumene are fed to the first reactor. Air is bubbled in at the bottom of the reactor and leaves at the top of each reactor. The oxidizers are operated at low to moderate pressure. Due to the exothermic nature of the oxidation reaction, heat is generated and must be removed by external cooling. A portion of cumene reacts to form dimethylbenzyl alcohol and acetophenone. Methanol is formed in the acetophenone reaction and is further oxidized to formaldehyde and formic acid. A small amount of water is also formed by the various reactions. The selectivity of the oxidation reaction is a function of oxidation conditions temperature, conversion level, residence time, and oxygen partial pressure. Typical commercial yield of cumene hydroperoxide is about 95 mol % in the oxidizers. The reaction effluent is stripped off unreacted cumene which is then recycled as feedstock. Spent air from the oxidizers is treated to recover 99.99% of the cumene and other volatile organic compounds. 

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. 

Currently, almost all cumene is produced commercially by two processes ( /) a fixed-bed, kieselguhr-supported phosphoric acid catalyst system developed by UOP and (2) a homogeneous AlCl and hydrogen chloride catalyst system developed by Monsanto. 

SPA Catalyst. The sohd phosphoric acid (SPA) catalyst process has been the domiaant source of cumene siace the 1930s. This process accounts for more than 90% of cumene operating capacity (59). A simplified process flow diagram is given ia Figure 5. 

Gymene. Methyhsopropylben2ene [25155-15-1] can be produced over a number of different acid catalysts by alkylation of toluene with propylene (63—66). Although the demand for cymene is much lower than for cumene, one commercial plant was started up in 1987 at the Yan Shan Petrochemical Company in the People s RepubHc of China. The operation of this plant is based on SPA technology offered by UOP for cumene. The cymene is an intermediate for the production of y -cresol (3-methylphenol) [108-59-4]. 

Catalysts. Nearly aU. of the industrially significant aromatic alkylation processes of the past have been carried out in the Hquid phase with unsupported acid catalysts. For example, AlCl HF have been used commercially for at least one of the benzene alkylation processes to produce ethylbenzene (104), cumene (105), and detergent alkylates (80). Exceptions to this historical trend have been the use of a supported boron trifluoride for the production of ethylbenzene and of a soHd phosphoric acid (SPA) catalyst for the production of cumene (59,106). 

Because of their initial commercial success and the industry s growing awareness of environmental issues, soHd acid catalysts are expected to ultimately replace Hquid acid catalysts. Several pubHcations describe the use of soHd acid catalysts for the production of cumene and detergent alkylates (62,85-87,109). 

Process. As soHd acid catalysts have replaced Hquid acid catalysts, they have typically been placed in conventional fixed-bed reactors. An extension of fixed-bed reactor technology is the concept of catalytic distillation being offered by CR L (48). In catalytic distillation, the catalytic reaction and separation of products occur in the same vessel. The concept has been appHed commercially for the production of MTBE and is also being offered for the production of ethylbenzene and cumene. 

Gumylphenol. -Cumylphenol (PGP) or 4-(1-methyl-l-phenylethyl)phenol is produced by the alkylation of phenol with a-methylstyrene under acid catalysis. a-Methylstyrene is a by-product from the production of phenol via the cumene oxidation process. The principal by-products from the production of 4-cumylphenol result from the dimerization and intramolecular alkylation of a-methylstyrene to yield substituted indanes. 4-Cumylphenol [599-64-4] is purified by either fractional distillation or crystallization from a suitable solvent. Purification by crystallization results in the easy separation of the substituted indanes from the product and yields a soHd material which is packaged in plastic or paper bags (20 kg net weight). Purification of 4-cumylphenol by fractional distillation yields a product which is almost totally free of any dicumylphenol. The molten product resulting from purification by distillation can be flaked to yield a soHd form however, the soHd form of 4-cumylphenol sinters severely over time. PGP is best stored and transported as a molten material. 

Benzoic Acid. Ben2oic acid is manufactured from toluene by oxidation in the liquid phase using air and a cobalt catalyst. Typical conditions are 308—790 kPa (30—100 psi) and 130—160°C. The cmde product is purified by distillation, crystallization, or both. Yields are generally >90 mol%, and product purity is generally >99%. Kalama Chemical Company, the largest producer, converts about half of its production to phenol, but most producers consider the most economic process for phenol to be peroxidation of cumene. Other uses of benzoic acid are for the manufacture of benzoyl chloride, of plasticizers such as butyl benzoate, and of sodium benzoate for use in preservatives. In Italy, Snia Viscosa uses benzoic acid as raw material for the production of caprolactam, and subsequendy nylon-6, by the sequence shown below. 

Oxidation of butyraldehyde to butyric acid [107-92-6]is most commonly carried out employing air or oxygen as the oxidant. Alternatively, organic oxidants, eg, cumene hydroperoxide, can also be employed effectively to give high yields of butyric acid, (4). 

Homogeneous Oxidation Catalysts. Cobalt(II) carboxylates, such as the oleate, acetate, and naphthenate, are used in the Hquid-phase oxidations of -xylene to terephthaUc acid, cyclohexane to adipic acid, acetaldehyde (qv) to acetic acid, and cumene (qv) to cumene hydroperoxide. These reactions each involve a free-radical mechanism that for the cyclohexane oxidation can be written as... 

Cumene as a pure chemical intermediate is produced in modified Friedel-Crafts reaction processes that use acidic catalysts to alkylate benzene with propylene (see Alkylation Friedel-CRAFTSreactions). The majority of cumene is manufactured with a soHd phosphoric acid catalyst (7). The remainder is made with aluminum chloride catalyst (8). 

More than 95% of the cumene produced is used as feedstock for the production of phenol (qv) and its coproduct acetone (qv). The cumene oxidation process for phenol synthesis has been growing in popularity since the 1960s and is prominent today. The first step of this process is the formation of cumene hydroperoxide [80-15-9]. The hydroperoxide is then selectively cleaved to phenol [108-95-2] and acetone [67-64-1/ in an acidic environment (21). 

These enable temperature control with built-in exchangers between the beds or with pumparound exchangers. Converters for ammonia, 80.3, cumene, and other processes may employ as many as five or six beds in series. The Sohio process for vapor-phase oxidation of propylene to acrylic acid uses hvo beds of bismuth molybdate at 20 to 30 atm (294 to 441 psi) and 290 to 400°C (554 to 752°F). Oxidation of ethylene to ethylene oxide also is done in two stages with supported... 

---