GB659787A - Improvements in or relating to oxidation of hydrocarbons - Google Patents

Abstract

Phthalic anhydride is obtained by the vapour phase oxidation, in the presence of a solid oxidation catalyst such as vanadium oxide, of a hydrocarbon fraction boiling between 165 DEG and 185 DEG C. and containing substantial amounts of indene and/or hydrindene. The said fraction may be obtained by the steam cracking of gas oil, kerosene, or naphtha feed stocks, generally at 600-800 DEG C. Certain coal tar fractions containing substantial amounts of indene and/or hydrindene can also be used as the feed stock. The catalyst may be employed in a fixed bed or the process may be of the moving bed or fluid-flow type, e.g. the technique, described in Specifications 583,032, [Group III], 633,128, [Group XII], and 634,102, [Group III], may be used. The transfer-line reactor technique described in Specification 634,102, [Group III], is particularly suitable. Specified oxidation catalysts are vanadium oxide or mixtures of vanadium oxide and other oxides, e.g. molybdenum oxide. Potassium compounds such as the sulphate may be added as promoters. The catalyst may be supported on an inert support and in the transfer-line reactor, the catalyst preferably is in the form of microspheres. The oxidation may be carried out either with or without an oxidizing gas. The latter may be pure oxygen, air, or a mixture of oxygen with an inert gas such as nitrogen. When no oxidizing gas is used catalysts such as the higher oxides of vanadium may be employed as oxygen carriers which can be enriched with reactive oxygen in a separate zone. When oxidizing gas is used it should be present in substantial excess over the hydrocarbons. The oxidation temperature may be 400-700 DEG C and especially 430 DEG to 480 DEG C. In examples phthalic anhydride is obtained by (1) contacting a mixture of air and a petroleum fraction boiling at 165-185 DEG C. containing indene and hydrindene with a vanadium oxide catalyst on a corundum support; (2) by contacting a mixture of hydrindene vapour and air with vanadium oxide on corundum promoted by potassium sulphate; (3) by contacting a mixture of indene vapour and air with the same catalyst as in (2).