FIELD: chemistry.
SUBSTANCE: invention relates to a method for isomerisation of starting material containing paraffins, having 5 to 6 carbon atoms in which at least 15 wt % of the starting material is linear paraffins, to obtain an isomerisation product containing isomerised paraffins, where the method involves: (a) isomerisation of the starting material under isomerisation conditions, including presence of an isomerisation catalyst, reactor temperature from 40°C to 250°C, operating absolute pressure in the reactor from 100 kPa to 10 MPa and volume rate for supply of liquid ranging from 0.2 to 25 l of the isomerised hydrocarbon material in h/l of catalyst volume, so as to obtain an isomerisation product containing linear paraffins, but in concentration less than in the starting material, (b) distillation of at least a portion of the isomerisation product to obtain a low-boiling fraction containing linear paraffins and a high-boiling fraction containing normal hexane, cyclohexane, methylpentanes and methylcycloheptane, (c) bringing at least a portion of the fraction containing normal hexane from step b) into contact with the inlet side of selectively permeable membrane to obtain a retained fraction with low concentration of methylcycloheptane to as to obtain a fraction diffused through the membrane at the outlet side of the membrane, where the said fraction has high concentration of normal hexane and methylpentanes and contains at least 75 wt % normal hexane in the fraction containing normal hexane in contact with the membrane; (d) removal of the retained fraction from step c).
EFFECT: reduced operational costs for the deisohexaniser without adverse effect on octane number of the overhead fraction from the deisohexaniser.
11 cl, 1 dwg
