Phenol selective synthesis

Sales demand for acetophenone is largely satisfied through distikative by-product recovery from residues produced in the Hock process for phenol (qv) manufacture. Acetophenone is produced in the Hock process by decomposition of cumene hydroperoxide. A more selective synthesis of acetophenone, by cleavage of cumene hydroperoxide over a cupric catalyst, has been patented (341). Acetophenone can also be produced by oxidizing the methylphenylcarbinol intermediate which is formed in styrene (qv) production processes using ethylbenzene oxidation, such as the ARCO and Halcon process and older technologies (342,343). 

In this section, we discuss the high performance of the Rejo cluster/HZSM-5 catalyst, its active structure and dynamic structural transformation during the selechve catalysis, and the reaction mechanism for direct phenol synthesis from benzene and O2 on this novel catalyst [73, 107]. Detailed characterization and determination of active Re species have been conducted by XRD, Al solid-state MAS NMR, conventional XAFS and in situ time-resolved energy dispersive XAFS, which revealed the origin and prospects of high phenol selectivity on the novel Re/HZSM-5 catalyst [73]. 

The catalytic reaction rate was first order with respect to O2 pressure in the po2 range 0-12 kPa at 12kPa the phenol selectivity was maximized. The activation energy for the phenol synthesis was estimated to be 24 kj mol" . 

The three-step cumene process, including the liquid-phase reactions, is energyconsuming, environmentally unfavorable and disadvantageous for practical operation. The process also produces the unnecessary by-product acetone stoichio-metrically. Furthermore, the intermediate, cumene hydroperoxide, is explosive and cannot be concentrated in the final step, resulting in low phenol yield ( 5%, based on the amount of benzene initially used). Thus, direct phenol synthesis from benzene in a one-step reaction with high benzene conversion and high phenol selectivity is most desirable from the viewpoints of environment-friendly green process and economical efficiency. 

Impregnation and physically mixed Re catalysts were much less active and much less selective for the phenol synthesis (Table 2.4). The CVD catalyst was almost 18 times more active than the conventional impregnation catalyst. In the physically mixed and impregnated catalysts, the Re7 + precursors partly aggregated as ReOx like Re02 in the presence of the NH3 reductant and such ill-defined Re aggregates decreased both activity and phenol selectivity as shown in Table 2.4. 

Molecular oxygen was the active oxidant for the phenol synthesis and the maximum phenol selectivity (93.9%) was achieved on the N-interstitial Re cluster supported on HZSM-5. Molecular oxygen was activated in the space between the two Re6 octahedral cores of the Re10 cluster and benzene concertedly reacted on the activated 02 with the very low activation energy of 24 kj mol-1. The pore size of HZSM-5 is 5.5 A, which is similar to the size of the Re6-octahedral cluster framework,... 

Kvaerner Process Technology Cyclohexanone/cydohexanol Phenol/hydrogen Synthesis of KA oil with high selectivity to cyclohexanone 2 1998... 

Isoprenylation of phenols. The reaction of phenols and isoprene with this combination of AlCl, and CsHsOK (prepared in situ from phenol and K pellets) provides a highly selective synthesis of 2,2-dimethylchromanes (equation I). No other combinations of a phenoxide and a Lewis acid were found to be comparable with respect to selectivity and yield. ... 

Carboxylation of Oiganic Substrates. Selective Synthesis of 4-OH-Benzoate from Phenol and Carbon Dioxide Catalyzed by a "Supported Enzyme. ... 

Thus, to obtain a selective synthesis of phenol via direct oxidation of benzene, suitable strategies have to be envisaged to slow dovm the undesired consecutive reactions and to allow phenol to accumulate. The first step in this direction was made by George Olah, who used extremely concentrated (98%) hydrogen peroxide in a... 

Improvements of already existing oxidation processes are continuously made (in MAA manufacture, with the riser reactor by DuPont, or in oxychlorination, by Montecatini Technologic and ICI). In addition, and still more clearly demonstrating the dynamism of industrial catal5rtic oxidation, completely new catalysts are discovered, especially with the titanium silicalite which permits the synthesis of hydroquinone from phenol, selective epoxidations, oxidations of alcohols to aldehydes, and the manufacture of cyclohexanoneoxime. 

The benzylic ester resin 20 derived from Merrifield resin was described in the 1970s by Leznoff and coworkers for the selective synthesis of monotrityl ethers of symmetrical aliphatic diols, phenols and porphyrins [66-68]. More recently, the... 

Keywords Hydroialciie-likc compounds Hydroxylation of Phenol Selective oxidation Structure-activity relationships In situ powder X-ray diffraction In situ DRIFT FT-IR spectroscopy Thermal analysis (TGA-DTA-EGA-TPRO) Synthesis methodology Influence of reaction parameters Ordered network Synergism... 

Transfer of selectivity from the lower to the upper rim is the most useful method for the selective synthesis of partially functionalized calixarenes at the upper rim. Indeed, one can exploit the different reactivity of aryl ethers compared to phenols to introduce, regioselectively, additional functional groups at the upper rim of partially alkylated calixarenes. Moreover, if l,3-dialkoxy-/ -r rt-butylcalix[4]arenes are submitted to the reverse Friedel-Crafts reaction, the tert-hwiyX groups are detached only from the para position of the phenolic nuclei, obtaining compounds where only two diametral aromatic rings are available for further functionalization. 

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). 

Since a few protective groups cannot satisfy all these criteria for elaborate substrates, a large number of mutually complementary protective groups are needed and, indeed, are becoming available. In early syntheses the chemist chose a standard derivative known to be stable to the subsequent reactions. In a synthesis of callistephin chloride the phenolic —OH group in 1 was selectively protected as an acetate. In the presence of silver ion the aliphatic hydroxyl group in 2 displaced... 

In an early synthesis a methyl carbonate, prepared by reaction of a phenol with methyl chloroformate, was cleaved selectively in the presence of a phenyl ester. ... 

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