GB639945A - Process for the dehydrogenation of hydrocarbons - Google Patents

Abstract

Hydrocarbons having 6-12 carbon atoms in a straight chain are dehydrogenated by contacting the vapour mixed with hydrogen with a dehydrogenating metal oxide at a mass velocity of at least 5 mg. of hydrocarbon per sq. cm. of cross-sectional area per second. Benzene, toluene, and xylenes may be obtained from n-hexane, heptane, and octane respectively, the corresponding mono- or di-olefins may similarly be cyclized, and naphthenes such as cyclohexane and methyl cyclohexane dehydrogenated. Gasoline fractions may be reformed. Simple dehydrogenation without cyclization may be effected using less severe conditions. Liquid space velocities are generally 0.1-20 vols. per hour per vol. of catalyst, temperatures 450-650 DEG C., pressures from 1-70 atmos., and ratios of hydrogen to hydrocarbon vapour of 0.5-40 by volume. Oxides of the elements in the left-hand columns of Groups 4, 5 and 6, preferably on supports such as oxides of aluminium, magnesia or silicon, firebrick, fuller's earth, clays, montmorillonite, bentonite, or the like, are suitable catalysts, particularly oxides of Cr, V, Mo or Ce on alumina. Products may be separated and unconverted reactants recycled. Temperatures, space velocities and other conditions may be varied along the line of flow. Examples illustrate the effect of varying the mass velocity from below 5 up to 22 mg. per sq. cm. per sec, in aromatizing a naphtha at 550 DEG C., 3.5 atmos., and 0.5 liquid space velocity, using chromia-alumina and 4 or 8 molar proportions of added hydrogen, carbon formation decreasing and ratio of aromatics to carbon increasing.