Hydrocarbons reactivity toward oxygen

Fluorocarbons are far less reactive towards oxygen than hydrocarbons. Thus mixtures of tetrafluoromethane, hexafluoroethane, perfluoropropane... 

Porous ceramic membranes have also found application in MRs as reactant distributors, particularly for catalytic oxidative dehydrogenation reactions where the intermediate or final products are more reactive towards oxygen than the original hydrocarbons, which limits reaction selectivity. As a result, total rather than partial oxidation of the original hydrocarbon is often achieved. Systems which can control the oxygen concentration along the reactor length, such as membranes by means of an MR, can increase the reaction selectivity towards the intermediate or final products (Coronas eta/., 1995). 

Table 12.10. Relative Reactivities of Some Aromatic Hydrocarbons toward Oxygen"...

The reactivity of a series of hydrocarbons toward oxygen measured under a standard set of conditions can give some indication of the susceptibility of various structural units to autoxidation. Table 12.10 gives the results for a series of hydrocarbons. These data indicate the activating effect of alkyl, vinyl, and phenyl substituents. 

Anthracene (404) and its derivatives are reported to yield 9,10-sndoperoxides (405). No mechanistic studies were made with respect to the influence of substituents and their positions on the reactivity of the anthracenes toward oxygen, except those discussed earlier. However, substituent effects have been observed with regard to the thermal stability of the anthracene endoperoxide and its thermal transformation reactions, which either lead to quinone formation or to evolution of oxygen and reformation of the hydrocarbon (Table XIII). 

Superoxide ion is not highly reactive towards hydrocarbons (i.e., lipids) and is readily removed from biological systems by superoxide dismutase, forming hydrogen peroxide and oxygen. However, the protonated superoxide ion or hydroperoxyl radical, HO, reacts with NADH and alkanes. Although such a reactive... 

The present measurements indicate a high reactivity of the sulfide surfaces toward oxygen-containing compounds and very little toward light hydrocarbons and ammonia. 

It has been shown, however, that the oxidation of hydrocarbons is structure-sensitive, i.e. that the specific rate relative to the area of the particles is dependent on the size of the latter. These observations are explained by considering the reactivity of oxygen towards Pt crystallites. The larger the particles, the more difficult they are to oxidize. Since metallic Pt is more active than its oxide in catalyzing hydrocarbon oxidation, it is consequently easier to understand that the specific rate increases with particle size. 

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