Naphthalene, oxidation kinetics

An alternative route to phthalic anhydride is the partial oxidation of naphthalene. The heat of reaction is — 430 kcal/mol. This reaction can be performed using a promoted V2O5 catalyst on silica, much like that considered in Example 9.1. Suppose In(fik) = 31.6800—19,100/T for the naphthalene oxidation reaction and that the subsequent, complete oxidation of phthalic anhydride follows the kinetics of Problem 9.3. Suppose it is desired to use the same reactor as in Example 9.1 but with a,>, = 53g/ m. Determine values for and T aii that maximize the output of phthalic anhydride from naphthalene. 

Kinetics of naphthalene and substituted naphthalenes oxidation by stoich. RuOy CCl to phthalic acids suggest an initial second-order reaction giving a complex with a naphthalene-0-Ru(Vl) bond, followed by a slower decomposition of this intermediate involving C-H bond cleavage [371]. 

The kinetics of the naphthalene oxidation obviously depend on the properties of the catalyst used, but some general statements can be made for the majority of V205-based catalysts. 

Peterson, T. L, Kinetics and mechanism of naphthalene oxidation by nonlinear estimation, Chem. Eng. Sci., 17, 203-219 (1962). 

The observations that the pH-independent reactions of deuterium-labeled 5-met-hoxyindene oxide and 6-methoxy-1,2,3,4-tetrahydronaphthalene-1,2-oxide show significant primary kinetic deuterium isotope effects for the ketone-forming reactions, whereas the pH-independent reactions of deuterium-labeled naphthalene oxide and benzene oxide do not, are quite puzzling. Clearly, more work needs to be done to fully understand why transition-state structures for rearrangement of arene oxides to phenols differ from those for rearrangement of benzylic epoxides to ketones. 

C. Kinetics of Naphthalene Oxidation over Vanadium Oxide. 470... 

Ioffe and Sherman (149) studied the kinetics of naphthalene oxidation to phthalic anhydride on a more complex vanadium-potassium-sulfate catalyst over a wide range of conversions and temperatures. The naphthalene oxidation was found to be independent of naphthalene concentration. This reaction is first order with respect to oxygen concentration and is inhibited with reaction products. 

Certain information on the kinetics of naphthalene oxidation over various vanadium catalysts is given in the review by Dixon and Long-field (110). This reaction was found to vary from zero to first order with respect to naphthalene, and be close to first order for oxygen. 

ITie kinetics of naphthalene oxidation can be represented by the following equation, with constant oxygen partial pressure ... 

Fluidised catalysts are also used in the synthesis of high-grade fuels from mixtures of carbon monoxide and hydrogen, obtained either by coal carbonisation or by partial oxidation of methane. An important application in the chemical industry is the oxidation of naphthalene to phthalic anhydride, as discussed by Riley(131). The kinetics of this reaction are much slower than those of catalytic cracking, and considerable difficulties have been experienced in correctly designing the system. 

A kinetic study of nitrous acid-catalyzed nitration of naphthalene with an excess of nitric acid in aqueous mixture of sulfuric and acetic acids (Leis et al. 1988) shows a transition from first-order to second-order kinetics with respect to naphthalene. (At this acidity, the rate of reaction through the nitronium ion is too slow to be significant the amount of nitrous acid is sufficient to make one-electron oxidation of naphthalene as the main reaction path.) The reaction that initially had the first-order in respect to naphthalene becomes the second-order reaction. The electron transfer from naphthalene to NO+ has an equilibrium (reversible) character. In excess of the substrate, the equilibrium shifts to the right. A cause of the shift is the stabilization of cation-radical by uncharged naphthalene. The stabilized cation-radical dimer (NaphH)2 is just involved in nitration ... 

Aromatic hydrocarbons which have methyl side chains mainly behave like toluene and form aldehydes, while combustion is stimulated and selective oxidation of the nucleus is repressed. The oxidation of methyl-naphthalene, for example, exhibits a low selectivity with respect to phtha-lic anhydride formation, combustion and maleic acid formation being the dominating reactions. Durene is a special case because it resembles o-xy-lene. The oxidation of durene over a V—W—O catalyst at 420° C is reported to produce pyromellitic dianhydride, phthalic and maleic anhydride, although combustion dominates (Geiman et al. [122]). 1,2,4-Trimethyl-benzene yields dimethylbenzene and trimellitic acid if oxidized on a Sn— V—O catalyst. Kinetic data have been measured by Balsubramanian and Viswanath [37]. 

The cerium(IV) oxidation of lactyllactic acid49 and of 4-oxopentanoic acid50 in aqueous nitric acid solutions shows first-order dependence of the reaction on both cerium(IV) and substrate. A 1 1 complex formation between manganese(III) and amine, which later decomposes in the rate-limiting step, best explains the kinetics of oxidation of aliphatic amines by cerium(IV) in nitric acid medium in the presence of manganese(II).51 The kinetics of oxidation of naphthalene, 2-methyhiaphthalene, and a-naphthol with cerium(IV) in perchloric acid solutions have been studied.52 Use of a 50-fold molar excess of cerium(IV) perchlorate results in complete oxidation of fluorophenols to CO2, HCO2H, and HF in 48 h at 50 °C.53... 

Kinetic models for UV/H202 were developed based on known chemical and photochemical principles by Glaze et al. (1992), who examined the oxidation of nitrobenzene, naphthalene, and pentachlorophenol to illustrate some features of the UV/H202 process. The model took into account the effects of... 

Significant characteristics of the porphyrin iron monoxide are seen in the chemical reactivity. Naphthalene is converted initially to the corresponding arene oxide on treatment with P 450 (19), consistent with a molecular mechanism of oxygen transfer from an iron monoxide to the aromatic nucleus. Retention of stereochemistry in the P-450 catalyzed hydroxylation of d ethylbenzene also supports the molecular mechanism. The unusually large kinetic isotope effect observed for the P-450 oxidation of dideutero 1,3-diphenylpropane, kJkD = 11, demonstrates that C—H cleavage is involved in the rate determining step (20), probably in a very unusual environment, not incompatible with a molecular mechanism. 

Similar tests of the fiuidized-bed method have been successful with a variety of molecular adsorbates and catalysts (other zeolites, supported oxides, naphthalene, pyridine, methanol, alkanes, alkenes, acetonitrile, ammonia, etc.) (25). We believe that this fiuidized-bed method is a major step forward for measurements of working catalysts with UV Raman spectroscopy. It should also be a useful method for measurements of catalytic kinetics by reducing heat and mass transfer effects that arise when catalysts are used in the form of pellets. In the limit of low conversions... 

There have been several recent investigations into the mechanism of photo-cyanation of aromatic hydrocarbons. The process with naphthalene, biphenyl, and phenanthrene has been subjected to a kinetic analysis the reactions in dry or aqueous methyl cyanide are shown to involve two transient species, the first of which is an ionic complex formed from a triplet excimer of the arene, or, in the presence of an electron acceptor, from a triplet exciplex. Reaction of the transient complex with the cyanide ion yields the radical ArHCN, and in aqueous methyl cyanide this second transient reacts with itself to produce dihydrocyano- and cyano-compounds. In dry methyl cyanide the radical species is oxidized to the cyano product. 

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