Isomerising light hydrocarbons - by separate isomerisn of pentanes and hexanes to products of higher octane number

摘要

Hydrocarbons which are contaminated by cpds. of O, S, S cpds., N cpds. and/or unsatd. hydrocarbons are isomerised by (a) hydrogenating the hydrocarbons over a catalyst resistant to the impurities, and recovering a 5-6C isomerisable hydrocarbon, (b) sepng. this 5-6C hydrocarbon mixt. into a 5C isomerisable hydrocarbon and a 6C isomerisable hydrocarbon, (c) contacting the 6C hydrocarbon with H2 in presence of an isomerisation catalyst at 93-204 degrees C, (d) recovering is ohexane from the prod. and recycling the remaining prod. to step (c), (e) contacting the 5C isomerisable hydrocarbon with H2 in presence of an isomerisation catalyst at 149-371 degrees C, and (f) recovering isopentane from the prod. and recycling the prod. to step (e). Conversion and selectivity are improved. Optimum conditions can be maintained in each isomeriser. The prods. are hydrocarbons of higher octane number.