Aerobic partial oxidation

Table 16.4 Aerobic partial oxidation of alkanes by metal oxide catalysts. 

Separation, combustion, pyrolysis, hydrogena-tion, anaerobic fermen-tation, aerobic fermen-tation, biophotolysis, partial oxidation, steam reforming, chemical hy-drolysis, enzyme hydrol-ysis, other chemical conversions, natural processes... 

Treatment process for partial oxidation of recalcitrantly biodegradable organic pollutants. Aim is to make this recalcitrantly biodegradable products biodegradable in conventional aerobic and anaerobic wastewater treatment systems... 

Acetoacetate and 3-hydroxybutyrate are known as ketone bodies. They are classified as fat fuels since they arise from the partial oxidation of fatty acids in the liver, from where they are released into the circulation and can be used by most if not all aerobic tissues (e.g. muscle, brain, kidney, mammary gland, small intestine) (Figure 7.7, Table 7.1). There are two important points (i) ketone bodies are used as fuel by the brain and small intestine, neither of which can use fatty acids (ii) ketone bodies are soluble in plasma so that they do not require albumin for transport in the blood. 

The partial oxidation of alcohols, to afford carbonyl or carboxylic compounds, is another synthetic route of high industrial interest For this, scC02 was investigated as a reaction medium for the aerobic oxidation of aliphatic, unsaturated, aromatic and benzylic acids with different catalytic systems, mainly based on the use of noble metals, both in batch [58-64] and in continuous fixed-bed reactors [65-70]. In this context, very promising results have been obtained when studying the catalytic activity of supported palladium and gold nanoparticles in the oxidation of benzyl alcohol to benzaldehyde these allowed conversions and selectivities in excess of 90% to be achieved [71-73]. 

Under anaerobic conditions, many aerobic microbes switch their metabolism and excrete partially oxidized intermediates, such as ethanol or lactic acid, to maintain redox balance. The pathway involved, the glycolysis pathway, plays a leading role in all fermentations and is outlined in Fig. 8.4. 

Fig. 3.3. Tentative mechanism of reduction of dioxygen. The scheme shows some of the more significant reaction steps at the haem iron-Cug centre of cytochrome oxidase. The reaction may be initiated by delivery of dioxygen to the reduced enzyme (in anaerobiosis top of figure). An initially formed oxy intermediate is normally extremely short-lived, but can be stabilised and identified in artificial conditions (see Refs. 92, 99,129, 134). Concerted transfer of two electrons from Fe and Cu to bound dioxygen yields a peroxy intermediate. This, or its electronic analogue, is stabilised in the absence of electron donors (ferrocytochrome a and/or reduced Cu ), and has been termed Compound C [129,130,132). It may also be observed at room temperature, and is then probably generated from the oxidised state by partial oxidation of water in the active site, in an energy-linked reversed electron transfer reaction [29] (see also Refs. 92, 99). Also the ferryl intermediate [92,99,100] has been tentatively observed in such conditions [29]. In aerobic steady states the reaction is thought to involve the cycle of intermediates in the centre of the figure (dark frames). The irreversible step is probably the conversion of g = 6 (see Refs. 98, 133) to peroxy .

In helminths alanine is an end-product of anaerobic glycolysis and may be formed from glutamine during aerobic metabolism (28). Alanine catabolism has also been demonstrated. In addition to COj, products such as lactate, acetate and ethanol are formed indicating only partial oxidation and a relatively low energy efficiency (28). 

A Pd-MOF reported by Corma [60] was also found to be active in the partial oxidation of alcohols using air to oxidize 3-phenyl-2-propen-l-ol (cinnamyl alcohol). Ciimamyl alcohol is a suitable substrate to probe the activity and chemoselectivity of a catalyst for the aerobic alcohol oxidation. With Pd-MOF as catalyst and ambient pressure air as the oxidant, total conversion of ciimamyl alcohol was observed after... 

Mallat, T., Seyler, L., Mir Alai, M., et al. (1998). Aerobic Oxidation of a-Substituted Alcohols over Promoted Platinum Metal Catalysts, in B. Hodnett, J. Clark and K. Smith (eds). Supported Reagents and Catalysts in Chemistry, 216, Royal Society of Chemistry, Cambridge, pp. 66-71, cit. in Jenzer, G., Sueur, D., Mallat, T, etal. (2000). Partial Oxidation of Alcohols in Supercritical Carbon Dioxide, Chem. Commun., 22, pp. 2247-2248. 

Gasedn J., Valenciano R., Tellez C., Herguido J. and MenendezM. (2006). A generalized kinetic model for the partial oxidation of n-butane to maleic anhydride under aerobic and anaerobic conditions, Chem. Eng. ScL, 61, pp. 6385-6394. 

Gascon, J., Valenciano, R., Tellez, C.,et al. (2006). A Generalized Kinetic Model for the Partial Oxidation of n-Butane to Maleic Anhydride under Aerobic and Anaerobic Conditions, Chem. 

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