The Mechanism of the Liquid-Phase Oxidation of Paraffinic Hydrocarbons

Bashkirov, A.N.; Kamzolkin, V.V.; Sokova, K.M.; Andreyeva, Tatiana

doi:10.1016/b978-0-08-010491-1.50018-5

Cited by 10 publications

(5 citation statements)

References 6 publications

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“…In order to obtain reasonable selectivities the reaction is usually performed according to the Bashkirov method. [42] This involves aerobic oxidation in the presence of stoichiometric amounts of B 2 O 3 to give the borate ester of the cyclic alcohol product. The borate ester is subsequently hydrolyzed to the alcohol and boric acid, followed by dehydrogenation of the alcohol to the ketone.…”

Section: Radical Chain Promoter In Cycloalkane Autoxidationsmentioning

confidence: 99%

Organocatalytic Oxidations Mediated by Nitroxyl Radicals

2004

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The use of nitroxyl radicals, alone or in combination with transition metals, as catalysts in oxidation processes is reviewed from both a synthetic and a mechanistic viewpoint. Two extremes of reactivity can be distinguished: stable (persistent) dialkylnitroxyls, such as the archetypal TEMPO, and reactive diacylnitroxyls, derived from N-hydroxy imides, such as N-hydroxyphthalimide (NHPI). The different types of reactivity observed are rationalized by considering the bond dissociation energies (BDEs) of the respective N-hydroxy precursors, substrates and reaction intermediates. Reactive diacylnitroxyl radicals are generated in situ from the corresponding N-hydroxy compound. The protagonist, NHPI, catalyzes a wide variety of free radical autoxidations, improving both activities and selectivities by increasing the rate of chain propagation and/or decreasing the rate of chain termination. In the absence of metal co-catalysts improved conversions and selectivities are obtained in the autoxidation of hydrocarbons to the corresponding alkyl hydroperoxides. For example, cyclohexylbenzene afforded the 1-hydroperoxide in 97.6% selectivity at 32% conversion when the autoxidation was performed in the presence of 0.5 mol % NHPI, and the product hydroperoxide as initiator, at 100 8C. This forms the basis for a potential coproduct-free route from benzene to phenol. In combination with transition metal co-catalysts, notably cobalt, NHPI and related compounds, such as N-hydroxysaccharin NHS, afford effective catalytic systems for the effective autoxidation of hydrocarbons, e.g., toluenes to carboxylic acids, under mild conditions. In the case of the less reactive cycloalkanes, NHS proved to be a more active catalyst than NHPI which is attributed to the higher reactivity of the intermediate nitroxyl radical, resulting from the replacement of a carbonyl group in NHPI by the more strongly electron-attracting sulfonyl group. Stable dialkylnitroxyl radicals, exemplified by TEMPO, catalyze oxidations of, e.g., alcohols, with single oxygen donors such as hypochlorite and organic peracids. The reactions involve the intermediate formation of the corresponding oxoammonium cation as the active oxidant. Alternatively, in conjunction with transition metals, notably ruthenium and copper, they catalyze aerobic oxidations of alcohols. These reactions involve metal-centered dehydrogenations and the role of the TEMPO is to facilitate regeneration of the catalyst (Ru and Cu) and oxidation of the alcohol (Cu) via hydrogen abstraction or one-electron oxidation processes. Detailed mechanistic investigations, including kinetic isotope effects, revealed that oxoammonium cations are not involved as intermediates in these reactions. In contrast, oxoammonium cations are involved in the aerobic oxidation of alcohols catalyzed by the copper-dependent oxidase, laccase, in combination with TEMPO. This different mechanistic pathway is attributed to the much higher redox potential of the copper(II) in the enzyme. Similarly, N-hydroxy compounds such as ...

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Section: Radical Chain Promoter In Cycloalkane Autoxidationsmentioning

confidence: 99%

Organocatalytic Oxidations Mediated by Nitroxyl Radicals

2004

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“…One concept that has been reported for improving alcohol selectivity in alkane oxidations is the Bashkirov process, which involves the use of boron compounds such as boric acid, boric oxide and borate esters [17][18][19]. These boron species function as Lewis acids which direct the oxidation towards the formation of alcohols, and subsequently trap the alcohols in the form of borate esters to protect them from over-oxidation [20][21][22][23][24].…”

Section: N-alkanementioning

confidence: 99%

Borate-assisted liquid-phase selective oxidation of n-pentane

Aworinde¹,

Wang²,

Lapkin³

2018

Applied Catalysis A: General

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Oxidation of n-pentane with molecular oxygen to sec-pentanols was performed in the presence of a free radical initiator (di-tert-butyl peroxide) and a boron compound (sec-butyl metaborate), with in situ adsorption of water on molecular sieve 3A. Kinetics of the reaction was studied in a laboratory-scale batch reactor over a broad range of conditions (130-150°C, 20-30 bar, 5-10 vol% O 2) in order to establish the optimum parameters for maximising the selectivity and yield of sec-pentanols. Results show that the initiator markedly improves the rate of oxidation, and hence yield, compared to thermal oxidation without an initiator, while the boron species enhances the selectivity to sec-pentanols. Under the conditions investigated, maximum secpentanol selectivity is 56% with an alcohol-to-ketone ratio of 3.6:1 for the borate-assisted oxidation compared to 33% and 1.1:1, respectively, for the oxidation without borate. This work demonstrates the feasibility of oxyfunctionalization of n-pentane with industrially relevant selectivity and yield.

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“…Selectivity improvement of the cyclohexane oxidation process means protection of the desired reaction products (olone) from further oxidation. The earliest effective solution to this problem has been application of a boron oxidation adjuvant such as metaboric acid, which forms an ester with cyclohexanol (see eq 5) that is more resistant to oxidation than II and III . − This development has led to an improved technology for accomplishing continuous LPO of cyclohexane to KA oil, based on the Bashkirov principle of using boric acid in stoichiometric amounts to produce alcohol esters and thereby gaining alcohol selectivity.…”

Section: Adipic Acid From Cyclohexane Via Conventional Two-step Oxida...mentioning

confidence: 99%

Transiting from Adipic Acid to Bioadipic Acid. 1, Petroleum-Based Processes

Bart

Cavallaro

2014

Ind. Eng. Chem. Res.

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Adipic acid, which is a very important commodity chemical, is traditionally manufactured industrially by an aged and unsustainable multistep process that involves homogeneous catalysts, aggressive oxidants (concentrated nitric acid) and the production of large quantities of the greenhouse gas nitrous oxide. Much research and development into alternative and cleaner process routes to adipic acid have been carried out over the past 70 years. Improved reaction schemes have invoked variations in fossil raw materials (from benzene and phenol to cyclohexane, cyclohexanol, cyclohexanone, cyclohexene, butadiene, and adiponitrile, etc.), oxidants (O 2 , air, H 2 O 2 , t-BuOOH, ozone), catalysts (homogeneous, heterogeneous, phase transfer, biomimetic) and reaction conditions (low temperature, atmospheric pressure, and solvent-, metal-, halide-, and corrosion-free). No single proposed alternative pathwaysome of which are purely academicsimultaneously addresses the problems of petrochemical origin, toxic starting materials or reagents, generation of environmentally incompatible byproducts, use of forcing reaction conditions, and cost in an entirely satisfactory manner, despite very intense efforts. Recently, more benign bio-based reaction pathways have been proposed starting from renewables, such as glucose or vegetable oils (which will be discussed in Part 2 of this series).

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The Mechanism of the Liquid-Phase Oxidation of Paraffinic Hydrocarbons

Cited by 10 publications

References 6 publications

Organocatalytic Oxidations Mediated by Nitroxyl Radicals

Organocatalytic Oxidations Mediated by Nitroxyl Radicals

Borate-assisted liquid-phase selective oxidation of n-pentane

Transiting from Adipic Acid to Bioadipic Acid. 1, Petroleum-Based Processes

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