Cumene process

Most of the world s acetone is now obtained as a coproduct of phenol by the cumene process, which is used by 21 of 31 producing companies in North America, Western Europe, and Japan. Cumene is oxidi2ed to the hydroperoxide and cleaved to acetone and phenol. The yield of acetone is beheved to average about 94%, and about 0.60—0.62 unit weight of acetone is obtained per unit of phenol (13). 

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). 

Hydroperoxidation of m- or />Diisopropylbenzene. This is an important industrial route to resorcinol and hydroquinone. The process in principle is identical to the cumene process for the manufacturing of phenol (qv). 

Cumene process in addition, Kalama Co. (Kalama, Wash.) has a capacity of 32,000 t/yr by the toluene process. 

Cumene Process. There are several Hcensed processes to produce phenol which are based on cumene (qv) (1,8—11). AH of these processes consist of two fundamental chemical reactions cumene is oxidized with air to form cumene hydroperoxide, and cumene hydroperoxide is cleaved to yield phenol and acetone. In this process, approximately 0.46 kg of acetone and 0.75 kg of phenol are produced per kg of cumene feedstock. 

The recovery area of the plant employs fractionation to recover and purify the phenol and acetone products. Also in this section the alpha-methylstyrene is recovered and may be hydrogenated back to cumene or recovered as AMS product. The hydrogenated AMS is recycled as feedstock to the reaction area. The overall yield for the cumene process is 96 mol %. Figure 1 is a simplified process diagram. 

Table 4 shows the worldwide and U.S. production figures and prices for phenol since the mid-1980s. Because the cumene process accounts for more than 95% of the world s phenol supply, the economics of phenol production are closely tied to this production method. In the cumene process 615 kg of acetone are coproduced with each ton of phenol produced. Thus, the economics of phenol production are influenced by acetone (qv). 

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. 

Fig. 5. UOP cumene process Rx = reactor R = rectifier BC = benzene column CC = cumene column T = transalkylation.

AlCl and Hydrogen Chloride Catalyst. Historically, AIQ processes have been used more extensively for the production of ethylbenzene than for the production of cumene. In 1976, Monsanto developed an improved cumene process that uses an AIQ. catalyst, and by the mid-1980s, the technology had been successfully commercialized. The overall yields of cumene for this process can be as high as 99 wt % based on benzene and 98 wt % based on propylene (60). 

At one time the requirement for phenol (melting point 41°C), eould be met by distillation of eoal tar and subsequent treatment of the middle oil with eaustic soda to extraet the phenols. Such tar acid distillation products, sometimes containing up to 20% o-cresol, are still used in resin manufacture but the bulk of phenol available today is obtained synthetically from benzene or other chemicals by such processes as the sulphonation process, the Raschig process and the cumene process. Synthetic phenol is a purer product and thus has the advantage of giving rise to less variability in the condensation reactions. 

A third process, now the principal synthetic process in use in Europe, is the cumene process. 

Figure 10-5. A flow diagram of the UOP cumene process " (1) reactor, (2,3) two-stage flash system, (4) depropanizer, (5) benzene column, (6) clay treatment, (7) fractionator, (8) transalkylation section.

Cumene processes are currently the major source for phenol and coproduct acetone. Chapter 8 notes other routes for producing acetone. 

The most common precursor to phenolic resins is phenol. More than 95% of phenol is produced via the cumene process developed by Hock and Lang (Fig. 7.1). Cumene is obtained from the reaction of propylene and benzene through acid-catalyzed alkylation. Oxidation of cumene in air gives rise to cumene hydroperoxide, which decomposes rapidly at elevated temperatures under acidic conditions to form phenol and acetone. A small amount of phenol is also derived from coal. 

Phenol is the major source of Bakelite and phenol resins, which are utihzed in many commodities worldwide phenol is also used as reagent for syntheses of dyes, medicines and so on. The industrial demand for phenol has increased every year and its production now exceeds 7.2 megaton year 94% of the worldwide production of phenol is processed in the cumene process. The cumene process involves the reaction of benzene with propene on acid catalysts like MCM-22, followed by auto-oxidation of the obtained cumene to form explosive cumene hydroperoxide and, finally, decomposition of the cumene hydroperoxide to phenol and acetone in sulfuric acid (Scheme 10.3) [73],... 

The three-step cumene process, including the liquid-phase reactions and using sulfuric acid, is energy-consuming, environmentally unfavorable and disadvantageous for practical operation the process also produces as an unnecessary byproduct acetone, stoichiometrically. Furthermore, the intermediate, cumene hydroperoxide, is explosive and cannot be concentrated in the final step, resulting in a low one-path phenol yield, ( 5%, based on the amount of benzene initially used). Thus, direct phenol synthesis from benzene in one-step reaction with high... 

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. 

In conclusion no catalysts with good performances (>5% conversion and >50% selectivity, simultaneously) have been discovered to date. New selective catalysts for direct phenol synthesis from benzene with 02 are essential for the novel industrial process replacing the cumene process - there are many problems to be resolved. 

Phenol is an important chemical intermediate of industrial interest, used as substrate for the production of antioxidants, polymers and agrochemicals. Actually, more than of 90% of the world production is realized by the three-step cumene process that leads to the formation of acetone as by-product. 

The charge to the unit is treated refinery propane-propylene along with recycle benzene from the recycle column overhead. Make-up benzene is added to the recycle. Nitration-grade benzene is usually used so that a drag stream of benzene is not required to remove contaminants from the unit. Table IX shows the component analysis of the various streams in the cumene process. 

In the cumene process (Fig. 1), cumene is oxidized to form cumene hydroperoxide that is then concentrated and cleaved to produce phenol and acetone. By-products of the oxidation reaction are acetophenone and dimethyl benzyl alcohol, which is dehydrated in the cleavage reaction to produce alpha-methylstyrene. 

Inserting oxygen into the C-H bond of an alkane initially leads to hydroperoxides. When this reaction is performed with atmospheric oxygen it is also called autooxidation. It usually leads to a multitude of products, because of further spontaneous reactions, so this reaction is of limited synthetic use. An exception is oxidation of isobutane with oxygen, which leads to 70 % yield of tert-butyl hydroperoxide at a conversion of 80% (Table 1, entry 7). Hydrogen bromide is used, among other compounds, as an initiator [15]. tert-Butyl hydroperoxide is used as an oxidant in propylene oxide production by the Halcon process. In the formation of phenol by the cumene process cumene is oxidized into the corresponding hydroperoxide in a similar way. 

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. 

Wallace, J.W., Gimpel, H.E. The Dow-Kellogg Cumene Process, in Meyer s Handbook of Petroleum Refining Processes, McGraw-Hill, New York, USA, 2nd edn, 1997... 

Some excellent reviews exist on benzene alkylation.52 Comparison of Beta with other zeolites (USY 53 or MCM-22 and ZSM-5)54 shows that Beta seems to be the most active catalyst whereas MCM-22 shows the best overall properties combining a good activity with an excellent stability. Similar results are found for the zeolite-based cumene processes where zeolite Beta is used in the process developed by Enichem.52... 

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