Patent GB-585850-A (GB)
Title: Improvements relating to the production of cyclohexane and benzene from petroleum naphtha or other feedstocks
IPC: C07C5/29
Filed: 1944-12-04
Abstract: Cyclohexane and benzene are produced from petroleum naphtha or other olefin-free stocks containing methyl-cyclopentane and cyclohexane by first separating a fraction containing substantially all of these constituents, fractionating this to obtain a lower boiling fraction comprising substantially all the methylcyclopentane, n-hexane, and some benzene and branched hexanes and a higher boiling fraction comprising substantially all the cyclohexane with benzene and paraffins and contacting the lower boiling fraction with an isomerization catalyst, e.g., aluminium, chloride or a liquid complex thereof with hydrocarbons, under isomerizing conditions to convert methylcyclopentane to cyclohexane, which is recovered by extractively distilling the higher boiling fraction with a polar solvent having selective solvent action to recover cyclohexane and benzene. Especially when the benzene content of the isomerization feed is high, i.e., above 10 per cent., the isomerization product, after removal of n-hexane, branched hexanes, unchanged methylcyclopentane, and high boiling products may be subjected to the extractive distillation with the higher boiling fraction.  An initial cyclohexane or so-called isoheptane fraction from an Iranian naphtha may be fractionated to give a 69 to 74-75 DEG C. fraction which is isomerized in liquid phase at 50-150 DEG C. with up to 10 per cent. by weight of hydrocarbon chloride added as activator, whereby methylcyclopentane is converted to cyclohexane, and n-hexane to methylpentanes.  A higher boiling fraction of 74-75 to about 81-85 DEG C., free of heptanes other than 2.2- and 2.4-dimethylpentanes and triptane, is extractively distilled using a high boiling solvent in a concentration of about 20-80 per cent. by weight.  In examples, aniline is the solvent used.ALSO:Cyclohexane and benzene are produced from petroleum naphtha or other olefin-free stocks containing methylcyclopentane and cyclohexane by first separating a fraction containing substantially all of these constituents, fractionating this to obtain a lower boiling fraction comprising substantially all the methylcyclopentane, n-hexane and some benzene and branched hexanes, and a higher boiling fraction comprising substantially all the cyclohexane with benzene and paraffins, contacting the lower boiling fraction with an isomerization catalyst, e.g. aluminium chloride or a liquid complex thereof with hydrocarbons, under isomerizing conditions to convert methylcyclopentane to cyclohexane which is recovered, and extractively distilling the higher boiling fraction with a polar solvent having selective solvent action to recover cyclohexane and benzene.  Especially when the benzene content of the isomerization feed is high, i.e. above 10 per cent, the isomerization product, after removal of n-hexane, branched hexanes, unchanged methylcyclopentane, and high boiling products may be subjected to the extractive distillation with the higher boiling fraction.  An initial cyclohexane or so-called isoheptane fraction from an Iranian naphtha may be fractionated to give a 69 DEG  to 74-75 DEG  C. fraction which is isomerized in liquid phase at 50-150 DEG  C. with up to 10 per cent by weight of hydrogen chloride added as activator, whereby methylcyclopentane is converted to cyclohexane, and n-hexane to methylpentanes.  A higher boiling fraction of 74-75 DEG  to about 81-85 DEG  C., free of heptanes other than 2 : 2- and 2 : 4-dimethylpentanes and triptane, is extractively distilled using a high boiling solvent in a concentration of about 20-80 per cent by weight.  In examples, aniline is the solvent used.  In an example of the isomerization stage, a fraction of 70.4-74 DEG  C. is treated with a catalyst prepared from aluminium chloride and a xylene cut, in presence of hydrogen chloride, and at 75-80 DEG  C.