Propene cumene hydroperoxidation

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],... 

Combining thianthrene radical ion(l+) with free radicals to produce thianthrenium salts has also been achieved. Decomposition of various cumene hydroperoxides (83MI6) and of azobis(2-phenoxy-2-propane) (85MI1) gave 5-arylthianthrenium ions together with 5-(propen-2-yl)thianthrenium perchlorate in the latter case. 

The autoxidation of alkylbenzenes constitutes the industrial route for the production of the corresponding hydroperoxides. The two well-known examples are the production of 1-phenylethyl hydroperoxide in the Shell and ARCO processes for the co-production of styrene and propene oxide, and the production of cumene hydroperoxide for the production of phenol via the Hock process (1,2) A disadvantage of the Hock-process is the co-production of acetone. One possible alternative involves the use of cyclohexylbenzene (CHB) in Scheme 1. 

Phenol and acetone are produced from benzene and propene by the cumene route, which can be divided into cumene process and cumene oxidation process [1]. Benzene and propene react to cumene in the cumene process. In the cumene oxidation process, cumene is oxidized to cumene hydroperoxide (CHP), which is converted into phenol and acetone in a successive reaction, the so-called cleavage. The oxidation of cumene to CHP is described in detail in the following sections. 

From Cumene Hydroperoxide. This process illustrates industrial chemistry at its best. Overall, it is a method for converting two relatively inexpensive organic compounds—benzene and propene—into two more valuable ones—phenol and acetone. The only other substance consumed in the process is oxygen from air. Most of the worldwide production of phenol is now based on this method. The synthesis... 

The mechanism of each of the reactions in the synthesis of phenol from benzene and propene via cumene hydroperoxide requires some comment. The first reaction is a familiar one. The isopropyl cation generated by the reaction of propene with the acid (H3PO4) alkylates benzene in a typical Friedel-Crafts electrophilic aromatic substitution ... 

Phenol production is typically carried out by add induced conversion of cumene hydroperoxide to phenol and acetone (Hock process). Cumene hydroperoxide is obtained by oxidation of cumene. The cumene feedstock for the latter reaction is provided by Friedel-Crafts alkylation of benzene with propene. Alternative routes (chlorobenzene hydrolysis, cydohexanol dehydrogenation, oxidative decarboxylation of benzoic acid) exist but are of much lower industrial relevance. 

Finally, it is noted that the direct epoxidation of propene with molecular oxygen is potentially more economically attractive than all of the coproduct processes currently in operation. It is indeed a holy grail in oxidation chemistry. Notwithstanding the extensive research on this topic in the last three decades, an industrially viable method for the direct epoxidation of propene has not been forthcoming. Sumitomo has recently announced [67] that they will commercialize a coproduct free route to PO but this probably involves an alkyl hydroperoxide e.g. cumene) oxidant with recycling of the alcohol coproduct [68]. 

Alkylation of benzene with propene to isopropylbenzene (cumene), oxidation of cumene to the corresponding tert-hydroperoxide and cleavage to phenol and acetone (Hock process). 

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. 

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) ... 

We turned our attention next to the autoxidation of ethylbenzene (EB) to the corresponding hydroperoxide (EBHP) which constitutes the first step in the SMPO (styrene monomer propene oxide) process for the co-production of styrene and propene oxide from ethylbenzene and propene (Scheme 7). The overall selectivity to propene oxide obviously depends on the selectivity to EBHP in the first step, which is believed to be 80-85% in the commercial process. This is lower than for cumene as a result of secondary (in the case of EB) versus tertiary (in the case of cumene) C-H bond oxidation. The main byproduct in the autoxidation of ethylbenzene is acetophenone (16). From an economic viewpoint die production of acetophenone should be kept as low as possible. 

We have developed an effective method for the selective autoxidation of alky-laromatic hydrocarbons to the corresponding benzylic hydroperoxides using 0.5 mol% NHPI as a catalyst and the hydroperoxide product as an initiator. Using this method we obtained high selectivities to the corresponding hydroperoxides, at commercially viable conversions, in the autoxidation of cyclohexylbenzene, cumene and ethylbenzene. The highly selective autoxidation of cyclohexylbenzene to the 1-hydroperoxide product provides the basis for a coproduct-free route to phenol and the observed inq)rovements in ethylbenzene hydroperoxide production provide a basis for in roving the selectivity of the SMPO process for styrene and propene oxide manufacture. 

In the cumene process, benzene is first converted, via the action of propene, to isopropylbenzene (cumene) in a Friedel-Crafts type reaction. Catalysts such as AICI3, sulfuric acid, or phosphoric acid are necessary. Treating cumene with oxygen results in the formation of a hydroperoxide at the tertiary C atom, and this can be decomposed to phenol and acetone. 

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