ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Physicochemical study of petroleum crude oil fractions. V. Reaction kinetics of oxidation

A. Tkáč and V. Kellö

Slovak Technical University, Bratislava

Abstract: cf. C.A. 54, 2706c. The reaction kinetics were studied of the oxidn. of the mixt. of hydrocarbons present in domestic crude oils and their lubricating oil distillates, chromatographic fractions of cable oils, and aromatic exts. from Saratov crude oil. Quant. spectrographic analysis of the changes in the hydrocarbon structure (which had been detd. by the n-d-mol. wt. method) shows a different character of the reaction kinetics for different compns. of the hydrocarbon mixt. The oxidn. of the alkane-naphthene fractions is affected by the rate of diffusion of O and of the oxidn. products, but this does not occur in the presence of aromatic components. The effect of diffusion was considerably reduced by exposing samples in thin layers. The oxidn. of the alkane-naphthene fractions can be expressed by the equation ΔEc-0 = k.eϕt, where ΔE is the change in the extinction; and ϕ and k are consts., corresponding to the chain mechanism of oxidn. of the degenerated branching type. With increasing concn. of aromatic fractions the oxidn. proceeds at a const. rate without induction period; and oxidn. of the alkane-naphthene fractions is inhibited. Fractions contg. a major amt. of condensed and unsym. di- and trisubstituted aromatic hydrocarbons are as much as 20 times more effective as inhibitors than complex aromatic-naphthenic systems and more highly substituted monocyclic aromatic compds. Highly active inhibitors are present in aromatic exts. of Saratov crude oil. The activation energy of the oxidn. of pure alkane-naphthene fractions is 33 kcal./mol., and in the presence of the aromatic components (5% of aromatic C) decreases to 9 kcal./mol. Polar oxidn. products of aromatic hydrocarbons are insol. in the alkane-naphthene hydrocarbons and are pptd. whereas oxidn. of the alkane-naphthene type hydrocarbons leads to the formation of carboxyl groups.

Full paper in Portable Document Format: 139a498.pdf (in Slovak)

Chemical Papers 13 (9) 498–514 (1959)