Cumene Cumyl hydroperoxide

Hock and Kropf [253] studied cumene oxidation catalyzed by Pb02. They proposed that Pb02 decomposed cumyl hydroperoxide (ROOH) into free radicals (R0 , R02 ). The free radicals started the chain oxidation of cumene in the liquid phase. Lead dioxide introduced into cumene was found to be reduced to lead oxide. The reduction product lead oxide was found to possess catalytic activity. The following tentative mechanism was proposed. 

The effect of jumping of the maximal hydroperoxide concentration after the introduction of hydrogen peroxide is caused by the following processes. The cumyl hydroperoxide formed during the cumene oxidation is hydrolyzed slowly to produce phenol. The concentration of phenol increases in time and phenol retards the oxidation. The concentration of hydroperoxide achieves its maximum when the rate of cumene oxidation inhibited by phenol becomes equal to the rate of hydroperoxide decomposition. The lower the rate of oxidation the higher the phenol concentration. Hydrogen peroxide efficiently oxidizes phenol, which was shown in special experiments [8]. Therefore, the introduction of hydrogen peroxide accelerates cumene oxidation and increases the yield of hydroperoxide. 

The experiments on emulsion cumene oxidation with AIBN as initiator proved that oxidation proceeds via the chain mechanism inside hydrocarbon drops [17]. The presence of an aqueous phase and surfactants compounds does not change the rate constants of chain propagation and termination the ratio (fcp(2fct)-1/2 = const in homogeneous and emulsion oxidation (see Chapter 2). Experiments on emulsion cumene oxidation with cumyl hydroperoxide as the single initiator evidenced that the main reason for acceleration of emulsion oxidation versus homogeneous oxidation is the rapid decomposition of hydroperoxide on the surface of the hydrocarbon and water drops. Therefore, the increase in the aqueous phase and introduction of surfactants accelerate cumene oxidation. 

The kinetic study of cumyl hydroperoxide decomposition in emulsion showed that (a) hydroperoxide decomposes in emulsion by 2.5 times more rapidly than in cumene (368 K, [RH] [H20] = 2 3 (v/v), 0.1 N Na2C03) and (b) the yield of radicals from the cage in emulsion is higher and close to unity [19]. The activation energy of ROOH decomposition in cumene is Ed = 105 kJ mol-1 and in emulsion it is lower and equals Ed 74 kJ mol 1 [17]. 

FIGURE 11.1 The kinetic curves of cumyl hydroperoxide formation in emulsion oxidation of cumene [8] at T — 358 K, H20 RH — 3 l (v/v) 1 N Na2C03 with input of 0.015mol L 1 H202 in the moments designated by arrows (curve 1), after 8 h (curve 2), and after 4 h (curve 3). 

These reactions produce free radicals, as follows from the fact of consumption of free radical acceptor [42]. The oxidation of ethylbenzene in the presence of thiophenol is accompanied by CL induced by peroxyl radicals of ethylbenzene [43]. Dilauryl dithiopropionate induces the pro-oxidative effect in the oxidation of cumene in the presence of cumyl hydroperoxide [44] provided that the latter is added at a sufficiently high proportion ([sulfide]/[ROOH] > 2). By analogy with similar systems, it can be suggested that sulfide should react with ROOH both heterolytically (the major reaction) and homolytically producing free radicals. When dilauryl dithiopropionate reacts with cumyl hydroperoxide in chlorobenzene, the rate constants of these reactions (molecular m and homolytic i) in chlorobenzene are [42]... 

The CLD methods for HPLC using isoluminol (190) with microperoxidase catalysis, for determination of lipid hydroperoxides in clinical fluids, have been reviewed. Determination of phospholipids hydroperoxides by luminol (124) CL has been reviewed . A fast RP-HPLC method (retention times 1 to 2 min) for determination of hydroperoxides and other peroxide compounds includes UVD, which is not always effective, and CLD, attained on injection of luminol (124), the CL reagent (Scheme 3), hemin (75a), a catalyst, and NaOH to raise the pH of the solution. A FLD cell may act as CLD cell if the excitation source is turned off. The selectivity of CLD is of advantage over UVD in industrial analysis thus, for example, UVD of a sample from a phenol production line based on cumene oxidation (equation 13) shows peaks for cumyl hydroperoxide (27), unreacted cumene, cumyl alcohol and acetophenone, whereas CLD shows only the 27 peak. The... 

FIGURE 11.1 The kinetic curves of cumyl hydroperoxide formation in emulsion oxidation of cumene [8]... 

Cumyl hydroperoxide, Cumene hydroperoxide, see 2-Phenyl-2-propyl hydroperoxide, 3160... 

Substituted thietanes 102 and 132-134 are inhibitors of the cumene oxidation to cumyl hydroperoxide. These properties result from the termination of the radical oxidation chain process as well as from the catalysis of the hydroperoxide degradation <2001RJAC114>. 

Cumyl hydroperoxide, 80% with cumene 2116 No ingition No propagation... 

SYNS CUMEENHYDROPEROXYDE pUTCH) CUMENE HYDROPEROXIDE pOT) CUMENE HYDROPEROXIDE, TECHNICALLY PURE pop CUMENT HYDROPEROXIDE CUMENYL HYDROPEROXIDE CUMOLHYDROPEROXID (GERMAN) CUMYL HYDROPEROXIDE O-CUMYL mT)ROPEROXIDE CUMYL HYDROPEROXIDE, TECHNICAL PURE pop o,a-DIMETHYLBENZYL HYDROPEROXIDE (MAK) HYDROPEROXYDE de CUMENE (FRENCH) HYDROPEROXYDE de CUMYLE (FRENCH) IDROPEROSSIDO di CUMENE (ITALIAN)... 

Ti-MOR promoted the ring hydroxylation of toluene, ethylbenzene and xylenes with negligible oxidation of the ethyl side chain [59]. In the same study, however, and in contrast to earlier ones, a similar result was also reported for TS-1. No oxidation of benzylic methyls was observed. Cumene yielded mainly the decomposition products of cumyl hydroperoxide. The oxidation of t-butylbenzene was negligibly low. The reachvity order, toluene > benzene > ethylbenzene > cumene, reflects the reduced steric constraints in the large pores of mordenite. Accordingly, the rate of hydroxylation ofxylene isomers increased in the order para < ortho < meta, in contrast to the sterically controlled one, ortho < meta para, shown on TS-1. It is worth menhoning that the least hindered p-xylene exhibited the same reactivity on either catalyst. 

Such reactions take place with p-xylene [28], ethylbenzene [28], and especially readily with isopropylbenzene (cumene) [29], where the intermediate free radical is stabilized not only by the aromatic ring but also by the two adjacent methyl groups. The oxidation of cumene to cumyl hydroperoxide (equation 162) followed by acid treatment is a basis for the large-scale production of phenol. 

Autoxidation is one of the key steps in the industrial synthesis of phenol and acetone from benzene and propylene. In the second step of this synthesis, cumene (isopropylbenzene) is autoxidized to give cumyl hydroperoxide. 

The most important industrial processes are (i) the oxidation of cumene to cumyl hydroperoxide, (ii) the oxidation of cyclohexane to cyclohexanol and cyclohexanone,... 

Alternative routes that do not produce sizeable quantities of coproducts and that do not use chlorine-based chemistry have already been, or will be, implemented at the commercial level. In April 2003, Sumitomo Chemical commercialized the first PO-only plant in Japan, which produces PO by oxidation of propene with cumyl hydroperoxide (the latter being obtained by hydroperoxidation of cumene) without a significant formation of coproducts. Nowadays, the plant located at the Chiba factory, a joint venture between Nihon Oxirane Co and Lyondell, produces around 200 000 tons of PO/year. A second plant was started in May 2009 in Saudi Arabia, a joint project with Saudi Arabian Oil Co. 

Oxidation, where cumene is oxidized in air to obtain cumyl hydroperoxide (CHP). 

The cumene process, sometimes referred to as the Hock process, was made possible by the discovery of cumyl hydroperoxide and of its cleavage to phenol and acetone [1]. Shortly after World War II the reaction was developed into an industrial process by the Distillers Co. (BP Chemicals) in the United Kingdom and Hercules in the USA. The first commercial plant was started in Montreal, Canada, in 1952 by M.W Kellogg. 

The process is based upon three different reactions (i) Friedel-Crafts alkylation of benzene with propene to afford cumene (isopropylbenzene) (ii) cumene oxidation with oxygen to give cumyl hydroperoxide and (iii) cleavage of cumyl hydroperoxide in acidic medium to afford phenol and acetone (Equation 13.2) ... 

The oxidation is mostly carried out in traditional bubble column reactors series of two to six reactors, up to 20 m high, are common in industry. The reaction is exothermic 120kJ are released per mole of produced hydroperoxide, and must be removed by cooling. The final reaction mixture, containing 20-30% of cumyl hydroperoxide, is then concentrated by distilling off some unreacted cumene to obtain a 65-85% hydroperoxide to be fed to the cleavage step (Figure 13.2). 

Cumyl hydroperoxide is eventually cleaved in the presence of an acid catalyst, to yield phenol and acetone, together with minor amounts of by-products such as a-methylstyrene, arising from dehydration of 2-phenyl-2-propanol, and dicumyl peroxide. a-Methylstyrene can be recovered to cumene in a hydrogenation stage. 

The method is based on the research of Hock and Lang (1944) concerning the splitting of cumyl hydroperoxide into phenol and acetone. Only in 1932, however, after experiencing a number of development problems, did the first industrial plant built by Hercules-Power produce phenol regularly. Despite the advent of new techniques on the market, which temporarily appeared to threaten the virtual monopoly of the cumene method, the industry continues to demonstrate considerable confidence in this method. 

The cumene feed must be free of oxidation propagation chain splitters, especially sulfur compounds, styrene, aniline and phenol. Since the reaction rate is extremely sensitive to these impurities, special care is taken to remove them. Phenol can be removed by treatment with caustic soda. However, its effect is less harmful than it appears, because it exerts an even more inhibitory action on side reactions, leading for instance to acetophenone or 2-phenyl 2-propanol, than on the main hydroperoxidation reaction, and because, in small amounts (10 to 1000 ppm), and combined with the sodium salt of cumyl hydroperoxide, its effect enhances tbe final yield ofthe operation. 

The selective oxidation of hydrocarbons into hydroperoxides, primary products of oxidation is the most difficult problem because of the high catalytic activity of the majority of applied catalysts in ROOH decomposition. At the same time, the problem of selective oxidation of alkylarens (ethylbenzene and cumene) with molecular 02 in ROOH, is of current importance from the practical point of view in connection with ROOH use in large-tonnage productions such as production of propylene oxide and styrene (a-phenylethylhydroperoxide, PEH), or phenol and acetone (cumyl hydroperoxide) [1],... 

---