Abstract
On the basis of kinetic data of 4-phenyl-o-xylene and 4-phenyl-o-tolunitrile ammoxidation, formation mechanism of the products was analyzed and generalized. It has been shown that dissociative adsorption of a substrate and mononitrile occurs on the centers with high heats of adsorption of oxygen and as a consequence, completely covered with it, competitive adsorption of NH3 and O2 occurs on the centers with low heats of adsorption of the latter; mononitrile and dinitrile are formed correspondingly from adsorbed fragments of both substrate and NH3, and tolunitrile and NH3; surface interaction of adsorbed fragments of substrate and O2 with low heat of adsorption gives imide and CO2; hydrolysis of dinitrile into imide occurs on centers completely covered with ammonia; imide decarboxylation occurs on the centers covered with it; oxidative destruction of tolunitrile occurs on centers covered with substrate and mononitrile.
Highlights
In papers [1] [2] kinetic regularities of vapor phase catalytic ammoxidation of both a substrate-4-phenyl-o-xylene and an intermediate 4-phenyl-o-tolunitrile were studied
The old analog wearing a patent character [5] exists in this field; the kinetic regularities of 4-phenyl-o-xylene ammoxidation on V2O5-CrO3/γ-Al2O3 catalyst have not been studied
The phenyl group is related to substituent of the third kind [13], which may show both electron-donating and electron-withdrawing properties and, taking into account lack of a significant role of conjugation, i.e. electron-donating property of the phenyl group, due to the fact that resonance constants of phenyl and methyl groups, located at the para-position, are not significantly different [14] [15], should be noted that the phenyl group in 4-phenyl-o-xylene molecule reveals the electron-withdrawing character
Summary
In papers [1] [2] kinetic regularities of vapor phase catalytic ammoxidation of both a substrate-4-phenyl-o-xylene and an intermediate 4-phenyl-o-tolunitrile were studied. (2015) Mechanism of the Products Formation in the Vapor Phase Ammoxidation Reaction of 4-Phenyl-o-Xylene. In paper [6] the main routes of catalytic oxidative conversions of some methyl derivatives of biphenyl in the gas phase, including 3,4-dimethylbiphenyl (4-phenyl-o-xylene) ammoxidation, were studied. The ammoxidation on many oxide catalysts is the exothermic catalytic reaction of o-xylene accompanied by the formation of major products, nitrites and imides. As a result of own study, it has been found that on the V-Sb-Bi-Zr/γAl2O3-oxide catalyst, at high conversion of the starting 4-phenyl-o-xylene in single process [8] [9], ammoxidation gives 80 mol% of 4-pfenylftalonitrile. In contrast to the single process, conducting of process with recirculation reduces quantity of the formed by-products, the share of deep oxidation and increases selectivity on a 4- phenyl phthalonitrile to 97.72% [8]
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