Oxidations in liquid phase

Gold NPs deposited on carbons are active and selective for mild oxidations in liquid phase although they exhibit almost no catalytic activity in the gas phase. Examples are aerobic oxidation of mono-alcohols, diols, glycerol, glucose, alkenes and alkanes. 

At the same time, N20 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 N20 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. 

The noncatalytic oxidation of 4,7-dihydro-l,3-dioxepin 46a with nitrous oxide in liquid phase at 220 °C produces 1,3-dioxepan-5-one however, the conversion is very slow <2004ASC268>. 

Similarly, the oxidation in liquid phase at about 25°C. of ethanal and of benzaldehyde catalyzed by a cobalt salt, seems to involve the... 

N.M. Emanuel, B.T. Denisov, Z.K. Meizus Chain reactions of hydrocarbon oxidation in liquid phase. Moscow "NaukcC (1965), 375 (in Russian). 

N. M. Emanuel, E. T. Denisov and Z. K. Maizus, Chain Reactions of Hydrocarbon Oxidation in Liquid Phase, Moscow, Nauka, 1965. 

In another of the commercial processes, cumene is also oxidized in liquid phase with oxygen at 105-135 C in the absence of any added catalyst. Steam is used in the gas-vapor zone of the reactor to prevent explosions. 

The radical chain reactions are described in detail in, for example, [15-17]. The scheme of oxidation in liquid phase by molecular oxygen comprises the steps initiation, propagation, and termination. 

Toluene is oxidized in liquid phase to benzoic acid, which is subsequently hydrogenated to cyclohexane carboxylic acid. Reaction of this acid with nitrosylsulfuric acid in oleum then results directly in the formation of caprolactam sulfate by a mechanism that entails simultaneous nitrosation, decarboxylation, and rearrangement of the formed oxime. 

Mokrii, EN. Intensification of the processes of aldehyde oxidation in liquid phase [in Russian], Vishaya Shcola, Lvov, 1984. 

Figure 9. Antioxidant activity of "bio oil" (extract B) and a reference commercial antioxidant (BHT 6-ditertbutyl-4-methylphenol)-) against oxidation of DBS (2,6-di-tertbuthylo-4-methylophenol). Concentration of DBS oxidation products versus time of oxidation in liquid phase at 150°C in the presence of various antioxidants ("bio oil" and BHT) under investigation.

Herm/es/Djnamit JS obe/Process. On a worldwide basis, the Hercules Inc./Dynamit Nobel AG process is the dorninant technology for the production of dimethyl terephthalate the chemistry was patented in the 1950s (67—69). Modifications in commercial practice have occurred over the years, with several variations being practiced commercially (70—72). The reaction to dimethyl terephthalate involves four steps, which alternate between liquid-phase oxidation and liquid-phase esterification. Two reactors are used. Eirst, -xylene is oxidized with air to -toluic acid in the oxidation reactor, and the contents are then sent to the second reactor for esterification with methanol to methyl -toluate. The toluate is isolated by distillation and returned to the first reactor where it is further oxidized to monomethyl terephthalate, which is then esterified in the second reactor to dimethyl terephthalate. 

Finally, atmospheric chemical transformations are classified in terms of whether they occur as a gas (homogeneous), on a surface, or in a liquid droplet (heterogeneous). An example of the last is the oxidation of dissolved sulfur dioxide in a liquid droplet. Thus, chemical transformations can occur in the gas phase, forming secondary products such as NO2 and O3 in the liquid phase, such as SO2 oxidation in liquid droplets or water films and as gas-to-particle conversion, in which the oxidized product condenses to form an aerosol. 

Modified hotocatalysts were prepared using commercial and synthesized Ti02. The modification was carried out in two different methods, i.e. platinization with H2PtCl6 solution and metallization with leached solution from wasted catalytic converter. They were characterized by UV-DRS, BET, and XRD and tested their catalytic performance for decomposition and oxidation of TCE in liquid phase. 

TS-1-catalyzed processes are advantageous from the environmental point of view as the oxidant is aqueous hydrogen peroxide, which turns into water, and the reactions are operated in liquid phase under mild conditions, showing very high selectivity and yields, thus reducing problems and the costs of by-product treatments. Confinement of the metal species in the well-defined MFl pore system endows TS-1 with shape selectivity properties analogous to enzymes. For these features the application of the terms mineral enzyme or zeozyme to TS-1 is appropriate [42]. 

Au/C was established to be a good candidate for selective oxidation carried out in liquid phase showing a higher resistance to poisoning with respect to classical Pd-or Pt-based catalysts [40]. The reaction pathway for glycerol oxidation (Scheme 1) is complicated as consecutive or parallel reactions could take place. Moreover, in the presence of a base interconversion between different products through keto-enolic equilibria could be possible. 

CoSalen Y carries oxygen as a cargo.72 The catalytic properties of the zeolite-encapsulated metal complexes depend mainly on the complexed metal atoms, which are used usually as oxidation catalysts but other applications are also beginning to emerge. The zeolite-encapsulated catalysts can be regarded as biomimetic oxidation catalysts.73 In liquid-phase oxidation reactions catalyzed... 

In liquid phase aerobic oxidation of p-xylene in acetic acid to terephthalic acid, it is important to eliminate the inherent hazards of this fuel-air mixture. Effects of temperature, pressure and presence of steam on the explosive limits of the mixture have been studied. 

Catalysis by Transition Metal Ions and Complexes in Liquid-Phase Oxidation of Hydrocarbons and Aldehydes by Dioxygen... 

CL is weak in liquid-phase hydrocarbon oxidation and can be intensified. To increase the CL, activators are added to the oxidized hydrocarbon [17,220,223]. The activator takes an excess of energy from the excited ketone molecule and emits light in high yield ... 

GF Fedorova. The Study of Chemiluminescence in Liquid-Phase Oxidation of Hydrocarbons. Thesis Dissertation, Institute of Chemical Physics, Moscow, 1979, pp 1-30 [in Russian]. 

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