Non-Catalytic Oxidations by

Studies in this field are just beginning, and the number of publications hardly exceeds a dozen. The most interesting results were obtained by the research groups of Yamada [160-162], Neumann [163,164] and Kozhevnikov [165,166]. Using various type catalysts (Ru porphyrene complexes, polyoxometalates, supported metals), the authors conducted selective oxidations of various types. These include epoxidation of alkenes, oxidation of alcohols, oxidation of alkylaromatics, oxidation and aromatiza-tion of dihydroanthracenes, and some other reactions. The experiments were typically conducted at 373-423 K under 1.0 MPa pressure of nitrous oxide. 

All the authors concluded that N2O provides a very high selectivity, which is higher than generally achieved with H2O2 or O2. In some cases, a virtually quantitative yield of the target product was obtained. This can be exemplified by the N 2O epoxidation of cholesteryl benzoate [162]  

The reaction was conducted with 0.20 mmol of cholesteryl benzoate and 5.0 mol % Ru(TMP)(0)2 catalyst in fluorobenzene solvent. At the reaction temperature of 413 K and under 1.0 MPa N2O pressure, the catalyst provided a 99% yield with 99% 

At the same time, N2O proved to be a poor ligand and quite an inert oxidant. It resulted in a low reaction rate and needs a high reaction temperature. The lack of catalysts that could provide an effective activation of N2O is the main factor limiting a widespread use of nitrous oxide in liquid-phase oxidations. The development of such catalysts is an important target in this field. 

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The behaviour of hydrogen peroxide alone (Fig. 5.42, curve 3) is in agreement with this explanation the catalytic reduction obeys Eq. (5.7.8) at potentials more positive than the non-catalytic oxidation. The voltammetric curve obtained is characterized by a continuous transition from the anodic to the cathodic region. The process occurring at negative potentials is then... 

Catalysts. The non-catalytic oxidation of naphthalene either in the liquid phase under pressure or in the vapor phase at atmospheric pressure, results in the formation of complete combustion products if temperatures high enough to give good reaction rates are used or else results in die formation of complex tars by condensations and polymerizations of intermediates if such low temperatures are used as to necessitate the use of long times of contact to obtain appreciable reaction. Hence, to obtain valuable products from the oxidation in commercial yields it is essential that catalysts be used. 

Sucb a reaction obviously proceeds more slowly than in aqueous or other polar media, but much faster than does thermal hydroperoxide decomposition. This results in a sharp drop of the steady-state concentration of the hydroperoxide in the hydrocarbon oxidation in the presence of a transition metal salt. Here, a decrease of hydroperoxide concentration will be compensated by an increase of its specific rate of decomposition so that the maximum oxidation rate will remain the same as in non-catalytic oxidations. In effect, the maximum rate... 

Among such oxidations, note that liquid-phase oxidations of solid paraffins in the presence of heterogeneous and colloidal forms of manganese are accompanied by a substantial increase (compared with homogeneous catalysis) in acid yield [3]. The effectiveness of n-paraffin oxidations by Co(III) macrocomplexes is high, but the selectivity is low the ratio between fatty acids, esters, ketones and alcohols is 3 3 3 1. Liquid-phase oxidations of paraffins proceed in the presence of Cu(II) and Mn(II) complexes boimd with copolymers of vinyl ether, P-pinene and maleic anhydride (Amberlite IRS-50) [130]. Oxidations of both linear and cyclic olefins have been studied more intensively. Oxidations of linear olefins proceed by a free-radical mechanism the accumulation of epoxides, ROOH, RCHO, ketones and RCOOH in the course of the reaction testifies to the chain character of these reactions. The main requirement for these processes is selectivity non-catalytic oxidation of propylene (at 423 K) results in the formation of more than 20 products. Acrylic acid is obtained by oxidation of propylene (in water at 338 K) in the presence of catalyst by two steps at first to acrolein, then to the acid with a selectivity up to 91%. Oxidation of ethylene by oxygen at 383 K in acetic acid in... 

Due to the rich development of oxidation reactions in recent years there was a need for a book covering the area. The purpose of this book on Modem Oxidation Methods is to fill this need and provide the chemistry community with an overview of some recent developments in the field. In particular some general and synthetically useful oxidation methods that are frequently used by organic chemists are covered. These methods include catalytic as well as non-catalytic oxidation reactions in the science frontier of the field. Today there is an emphasis on the use of environmentally friendly oxidants ( green oxidants) that lead to a minimum amount of waste. Examples of such oxidants are molecular oxygen and hydrogen peroxide. Many of the oxidation methods discussed and reviewed in tliis book are based on the use of green oxidants. 

Broer, S. and Hammer, T. (2000) Selective catalytic reduction of nitrogen oxides by combining a non-thermal plasma and a V205-W03/Ti02 catalyst, Appl. Catal. B Env. 28, 101-11. 

Fig. 28.1. Results (symbols) and simulations (lines) of an experiment at 25 °C by Liger et al. (1999 their Fig. 6) in which uranyl was oxidized by ferrous iron in the presence of nanoparticulate hematite, which served as a catalyst. Vertical axis is amount of NaHCCE-extractable uranyl, which includes uranyl present in solution as well as that sorbed to the nanoparticles in the experiment, nearly all the uranyl was sorbed. Broken line shows results of a simulation assuming uranyl forms a single surface complex, >Fe0U020H, which is catalytically active solid line shows simulation in which a non-catalytic site of this stoichiometry is also present. Inset is an expanded view of the first few hours of reaction.

DeVOx A catalytic oxidation process for destroying volatile organic compounds in effluent gases. The catalyst contains a non-noble metal and can easily be regenerated. Typical operating temperatures for 95 percent VOC conversion are 175 to 225°C for oxygenates, and 350°C for toluene. Developed in 1995 by Shell, Stork Comprimo, and CRI Catalysts. First installed in 1996 at Shell Nederland Chemie s styrene butadiene rubber facility at Pemis. 

Kel-Chlor [Kellogg Chlorine] A non-catalytic version of the Deacon process for making chlorine by oxidizing hydrochloric acid, in which nitrosyl sulfuric acid and nitrosyl chloride are intermediates and concentrated sulfuric acid is used as a dehydrating agent ... 

SNCR [Selective non-catalytic reduction] A generic term for processes which remove oxides of nitrogen from flue-gases by non-catalytic chemical reactions. These include the reaction with ammonia at high temperature (1,300 to 1,900°C), and the reaction with urea. See NOxOut, SCR. 

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