GB573340A - Improvements relating to the production of an aviation or motor fuel or an aviation or motor fuel constituent - Google Patents

Abstract

Cyclopentane is produced by the hydrogenation of cyclopentadiene in the presence of a temperature-moderating diluent, for example hydrogen in excess of that used as reactant, benzol or cyclopentane or mixtures thereof. Benzol forerunnings of coal tar distillates may be treated to polymerize the cyclopentadiene to dicyclopentadiene, the crude concentrate obtained which boils at about 75-175 DEG C. being freed from carbon disulphide and topped to remove light ends, boiling range 78-80 DEG C., consisting of benzene, with some unsaturated hydrocarbons and sulphur compounds. The residue is mainly dicyclopentadiene. Conversion to dimer may also be effected by contact with acid and pure dimer obtained by fractionation under vacuum. The dicyclopentadiene or residue containing it is depolymerized, for example in a column packed with iron or steel turnings or wool at 200-300 DEG C., the overhead product at a column head temperature of 40-42 DEG C. being sulphur-free cyclopentadiene. The rates of feed and distillation are adjusted to the rate of hydrogenation in the subsequent hydrogenation unit to reduce formation of higher polymers. Hydrogenation may be effected in the vapour phase at 400 DEG C. and 200 lbs./sq. in. with a 5 per cent molybdenum oxide on alumina catalyst and an oil feed rate of 1.0 vol./vol./hr. with a hydrogen recycle rate of 5000-6000 c. ft. per barrel of oil feed. The feed is advantageously diluted with the previously removed light ends when the benzene is refined in the same operation and the complete preliminary removal of carbon disulphide is unnecessary. The mixture of cyclopentane and benzene obtained, after removal of the small amount of high boiling residue produced, may be used as an aviation spirit blending constituent. Where sulphur-sensitive catalysts are used, such as Raney nickel, materials must be sulphur-free and hydrogenation may be effected in the liquid phase with a nickel catalyst at 50-100 DEG C. using cyclopentane as diluent. In examples: (1) benzene is distilled from the crude concentrate of benzol fore-runnings and the residue heated to 160-180 DEG C. to distil cyclopentadiene which is diluted with four times its volume of the light ends and hydrogenated, using molybdenum oxide-alumina as above. The product is used as diluent in subsequent hydrogenations, the cyclopentadiene content in the feed being always 20 per cent by volume, and the final product contains 60 per cent cyclopentane; (2) the crude material is dropped into a flask heated to 240-250 DEG C. and the vapours passed through an iron tube packed with steel wool. The properties of the product at different temperatures and rates of feed are tabulated. The product is hydrogenated as before to give cyclopentane and refined benzol.