Phenol, from benzene

Iron impregnated on activated carbon was used as catalyst for the direct synthesis of phenol from benzene. The effect of Sn addition to the catalyst was studied. The prepared catalysts were characterized by BET, SEM and XRD analysis. The catalyst 5.0Fe/AC showed good activity in the conversion of benzene and addition of Sn seemed to improve the selectivity of phenol in the reaction. 

Examples for necessary process improvements through catalyst research are the development of one-step processes for a number of bulk products like acetaldehyde and acetic acid (from ethane), phenol (from benzene), acrolein (from propane), or allyl alcohol (from acrolein). For example, allyl alcohol, a chemical which is used in the production of plasticizers, flame resistors and fungicides, can be manufactured via gas-phase acetoxylation of propene in the Hoechst [1] or Bayer process [2], isomerization of propene oxide (BASF-Wyandotte), or by technologies involving the alkaline hydrolysis of allyl chloride (Dow and Shell) thereby producing stoichiometric amounts of unavoidable by-products. However, if there is a catalyst... 

Raschig (2) Also called Raschig-Hooker. A two-stage regenerative process for making phenol from benzene. The benzene is first chlorinated with hydrochloric acid in the presence of air, at 200 to 260°C, over a copper catalyst on an alumina base ... 

Since zeolite catalysts are successfully introduced in the refining and petrochemical industries, it is not surprising that most of the recent advances concern incremental improvements of existing processes with the development of new generations of catalysts (e.g., dewaxing, ethylbenzene and cumene synthesis). The number of newer applications is much more limited, for example, direct synthesis of phenol from benzene and aromatization of short-chain alkanes, etc. However, both the improvement and development of processes contribute significantly to environmental advances. 

Problem 19.9 Devise practical laboratory syntheses of the following phenols from benzene or toluene and any inorganic or aliphatic compounds (a) m-iodophenol, (b) 3-chloro-4-methylphenol, (c) 2-bromo-4-methylphenol. 

The aim of the project was to investigate different gas-phase reactions. In particular, alternative routes for the synthesis of propylene oxide [101,102] and the synthesis of phenol from benzene and N20 [103] should be found. As a first milestone a throughput of approximately 15-20 molProduct kgCat 1 h 1 was targeted. 

The radical "OH in surface waters is quickly consumed by organic compounds, bicarbonate, carbonate, and nitrite. It has a typically low steady-state concentration of around 10"16 M. For this reason it cannot be directly detected, and quantification in laboratory experiments is usually carried out by means of reactions of known kinetics. The formation of phenol from benzene, of 4-hydroxybenzoic from benzoic acid, and the disappearance of nitrobenzene are suitable systems if intermediate monitoring is carried out by liquid chromatography, while the disappearance kinetics of butyl chloride is suitable for headspace sampling and gas-chromato-graphic analysis [64]. 

Although significant improvements have been made in the synthesis of phenol from benzene, the practical utility of direct radical hydroxylation of substituted arenes remains very low. A mixture of ortho-, meta- and para-substituted phenols is typically formed. Alkyl substituents are subject to radical H-atom abstraction, giving benzyl alcohol, benzaldehyde, and benzoic acid in addition to the mixture of cresols. Hydroxylation of phenylacetic acid leads to decarboxylation and gives benzyl alcohol along with phenolic products [2], A mixture of naphthols is produced in radical oxidations of naphthalene, in addition to diols and hydroxyketones [19]. 

The electro-Fenton method (or EFR) was initially used for synthetic purposes considering the hydroxylation of aromatics in the cathodic compartment of a divided cell. Thus, the production of phenol from benzene (Tomat and Vecchi 1971 Tzedakis et al. 1989), (methyl)benzaldehydes and (methyl)benzyl alcohols from toluene or polymethylbenzenes (Tomat and Rigo 1976,1979,1984,1985) by adding Fe3+ to generate Fe2+ via reaction (19.13), as well as benzaldehyde and cresol isomers from toluene or acetophenone and ethylphenol isomers from ethylbenzene (Matsue et al. 1981) with direct addition of Fe2+, have been described. Further studies have reported the polyhydroxylation of salicylic acid (Oturan et al. 1992)... 

Zeolites have been used as (acid) catalysts in hydration/dehydration reactions. A pertinent example is the Asahi process for the hydration of cyclohexene to cyclo-hexanol over a high silica (Si/Al>20), H-ZSM-5 type catalyst [57]. This process has been operated successfully on a 60000 tpa scale since 1990, although many problems still remain [57] mainly due to catalyst deactivation. The hydration of cyclohexanene is a key step in an alternative route to cyclohexanone (and phenol) from benzene (see Fig. 2.19). The conventional route involves hydrogenation to cyclohexane followed by autoxidation to a mixture of cyclohexanol and... 

Resorcinol, dihydroxy benzene, and naphthols both a and P, are the most important hydroxy-aromatics having wide applications and are produced from benzene and naphthalene, respectively, using similar technologies as in production of synthetic phenol from benzene or cresols from toluene. It may be relevant to discuss briefly about these products. 

Processes that have been commercialized for production of cresois from toluene have been mostly an adaptation and extension of those used for manufacture of phenol, from benzene. As in the case of phenol the three most important processes for manufacture of cresois from toluene (nitrate grade) are based on... 

It has been recently announced that technology for separation of para- and meto-cymenes is offered by Chiyoda Corporation in Yokohama, Japan through Kellog. As in the case of phenol from benzene via cumene, acetone is obtained as a co-product during production of cresols from toluene via cymenes. 

Bai et al. [330] found a remarkable selectivity (88% in the steady-state reaction and 94% in the pulse reaction) in the direct synthesis of phenol from benzene with molecular oxygen over a Re/zeolite catalyst prepared by chemical vapor deposition (Figure 3.62). However, stable performances could be obtained only by continuous feeding of relatively high concentrations of NH3 (around 30%), which is necessary to stabilize the active complex containing interstitial N atoms (see the model of the complex in... 

Figure 2.62 Direct synthesis of phenol from benzene using molecularoxygen on rhenium complexes in ZSM-5. Source adapted from Iwasawa et al. [330],...

Bianchi, D., Bortolo, R., Buzzoni, R., Cesana, A., Dalloro, L. and D Aloisio, R. (2004) Integrated process for the preparation of phenol from benzene with recycling of by-products. Furopean Patent FP 1424320 to Polimeri Furopa. 

M. Li, X. Jian, T. M. Han, L. Liu, Y. Shi, Reaction-controlled phase-transfer catalyst K3PV4024 for synthesis of phenol from benzene. Chin. J. Catal. 25 (2004) 681. 

With worldwide phenol consumption exceeding 5 million tons in 1995, optimizing production routes of this essential chemical becomes very important. As an alternative to the traditional cumene process, a one-step-synthesis of phenol from benzene is highly desirable. With a ZSM5 type zeolite in its acid form as catalyst and nitrous oxide as oxidant, benzene may be directly oxidized to phenol [1-4] ... 

The catalytic effect of the nitric acid gas has been attributed to (a) increase in the concentration of active oxygen and (b) greater oxidizing power of nitrogen peroxide.27 The formation of phenol from benzene by electrochemical oxidation has been explained on the basis of atomic oxygen,18 a hypothesis that may hold in this case. A mechanism for the catalytic effect of nitrogen peroxide based on the conclusion that it is readily activated by the absorption of radiation over a relatively wide range of frequencies is as follows ... 

These processes perform the oxidation of hydrochloric add in situ. Their principle is similar to the one implemented to produce phenol from benzene by the Hooker/Raschig process (see Section 10.1.3). The first industrial ethylene oxychlorination plant was built by Dow in the United States in 1955. 

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