GB669552A - Improvements relating to the catalytic desulphurisation of petroleum hydrocarbons - Google Patents

Abstract

The desulphurization of a naphthene-containing petroleum distillate boiling above 375 DEG C. is effected by passing it in vapour form and mixed with hydrogen over a catalyst which combines activity for dehydrogenation of naphthene molecules to aromatics with activity for the conversion of organically combined sulphur to hydrogen sulphide and which is not poisoned as a catalyst by the presence of sulphur compounds, at a temperature and pressure such that the dehydrogenation of naphthenes contained in the distillate is effected to an extent not substantially in excess of that required to produce sufficient hydrogen to convert organically combined sulphur in the distillate into hydrogen sulphide and to maintain the vapour phase in the reaction zone, a hydrogen-rich gas mixture being separated from the treated distillate and recycled to the reaction zone to constitute the whole of the hydrogen supplied to the zone. Catalysts specified are metal sulphides and oxides of the 6th group, either alone or mixed: for example chromium oxide, tungsten sulphide, a mixture of tungsten sulphide and nickel sulphide, or cobalt molybdate or thiomolybdate, on a porous support such as natural or heat-treated bauxite, which may also be used as catalysts, activated alumina and kieselguhr. The preferred catalyst is cobalt molybdate supported on alumina. Pressures of 50-200 p.s.i. and temperatures of 750-800 DEG F. are preferred. The space velocity should be 0.5-2.0 v/v/hr. and the gas recycle rate 2,000-4,000 cu.ft./bbl. of feedstock. In the example, an Iranian wax distillate is heated to 800 DEG F. and passed over cobalt molybdate supported on alumina at a pressure of 100 p.s.i., the separated gases being recycled with the feedstock to the heating zone. Specifications 653,320 and 669,551 are referred to. The Provisional Specification mentions also the use as catalyst of molybdenum oxide supported on alumina.