GB409312A - Improvements in the dehydrogenation of hydrocarbons - Google Patents

Abstract

The catalytic dehydrogenation of hydrocarbons containing a substantial portion of normally liquid hydrocarbons saturated with hydrogen without substantial splitting of carbon linkages and formation of hydrocarbons of higher molecular weight is carried out by heating the compounds at a temperature between 200 DEG and 500 DEG C., preferably between 300 DEG and 500 DEG C. in the presence of a halogen compound of a metal or of the non-metallic elements selenium, tellurium, arsenic, antimony, silicon, carbon and hydrogen. Suitable metal halides are those of copper, silver, zinc, cadmium, thallium, lead, tin, titanium, zirconium, vanadium, bismuth, molybdenum, tungsten, uranium, manganese, rhenium, iron, nickel or cobalt and they may be arranged on carriers such as active carbon, active silica, aluminium hydroxide or chromium hydroxide. Other catalysts, especially those having a dehydrogenating action such as the sulphides, oxides or hydroxides of metals of the 5th and 6th groups, may be added, e.g. tungsten sulphide. Suitable volatile halogen compounds which may be used instead of or in addition to the solid catalysts include ethylene chloride, ethylene bromide, brombenzene or hydrogen chloride. Halogen compounds of non-metals include phosphorus trichloride, phosphorus tribromide, phosphorus diiodide, sulphur monochloride, selenium monochloride, selenium tetrachloride, selenium monobromide and tetrabromide and these bodies may also be added to solid halide catalysts. Compounds, such as boron fluoride, which exert a splitting or condensing action on hydrocarbons are preferably employed only in small concentration, together with other catalysts specified. The process may be carried out in the liquid phase, but preferably in the gaseous phase and gases such as nitrogen, carbon dioxide and water vapour, which serve as heat carriers or set up partial pressures favourable for the reaction, may be added. Such partial pressure should decrease with increasing molecular weight of the hydrocarbons. Increased, atmospheric or reduced pressure may be employed, and the process may be made cyclic. The time of reaction is approximately one-quarter minute to one minute, decreasing with increasing molecular weight of the hydrocarbons. p Suitable initial material include tars, mineral oils or fractions such as benzine or naphthenes, destructive hydrogenation products of coals, tars, mineral oils and fractions thereof. The process may be combined with the distillation of substances containing benzine, e.g. the fractions boiling above 80 DEG C. may be led over the catalysts previously described in the vapour phase. According to examples: (1) cyclohexane is treated at 430 DEG C. in the presence of active carbon impregnated with iron chloride. The products comprise benzene, unchanged cyclohexane and a gas containing 97 per cent. of hydrogen. Active carbon impregnated with silver iodide may also be used; (2) a middle oil from German petroleum is converted into benzine by treatment with hydrogen under pressure at 450 DEG C. in the presence of tungsten sulphide. The fraction boiling between 100 DEG and 190 DEG C. is led at 440 DEG C. together with ethylene chloride over a catalyst prepared by drenching active carbon from peat with 5 per cent of copper bromide. The product is equal to a mixture of the original benzine with 25 per cent of benzene in its knocking behaviour. The copper bromide may be replaced by molybdenum or tungsten bromide, vanadium chloride or an equimolecular mixture of lead and cadmium chlorides; (3) a mineral oil fraction boiling between 200 DEG and 300 DEG C. and of specific gravity 0.855 is passed at 420 DEG C. over a catalyst obtained by impregnating active carbon with aqueous stannous bromide solution, drying and then impregnating with aluminium chloride dissolved in methyl alcohol. The product is an oil of specific gravity 0.878 and may be used for production of non-knocking benzines by catalytic destructive hydrogenation.