GB610187A - Process for the adsorptive separation of straight chain from branch chain paraffins - Google Patents

Abstract

Paraffins having a straight chain are separated from those of branched structure by selective adsorption with activated coconut shell charcoal. Activation is preferably effected with activating agents such as carbon dioxide and steam. Hydrocarbon mixtures of 3-12, preferably 6-10 carbon atoms are first separated into fractions of a boiling range less than 200, preferably less than 25 DEG F. and adsoprtion effected at - 60 DEG to 285 DEG F., preferably 32 DEG to 125 DEG F., and atmospheric pressure or above. The amount of charcoal is generally about 100-1000 lbs. per barrel. Normal heptane may be adsorbed from its admixture with isooctane, normal hexane or pentane separated from the branched isomers, and normal C5-C7 paraffins from associated branched paraffins. Narrow boiling fractions of an alkylate may be separately treated and the branched paraffins combined. Aromatics and some naphthenes, if present, may be adsorbed with the normal paraffins. Desorption may be effected with a solvent, preferably a hydrocarbon of lower boiling range than the feed, e.g. iso-pentane, butane, propane or hexanes, although other compounds such as ethers, aldehydes, ketones, alcohols, acids, amines, CO2, CS2 and SO2 may be used. Thus, the carbon with adsorbed heptane is regenerated with about 3 volumes of isopentane, the heptane being liberated and, if desired, converted to branched hydrocarbons. The adsorbent, wetted with iso-pentane, may be re-used as such or first purged with an inert-gas or by heating. When treating a feed containing other hydrocarbons in addition to paraffins, different adsorbents may be used therefor, e.g. activated alumina to remove aromatics. In examples, a mixture of equal volumes of iso-octane and n-heptane is passed through a bed of Columbia activated carbon (coconut shell charcoal).ALSO:Paraffins having a straight chain are separated from those of branched structure by selective adsorption with activated coconut shell charcoal. Activation is preferably effected with activating agents such as carbon dioxide and steam. Hydrocarbon mixtures of 3-12, preferably 6-10 carbon atoms are first separated into fractions of a boiling range less than 200 DEG , preferably less than 25 DEG F., and adsorption effected at -60 DEG to 285 DEG , preferably 32 DEG to 125 DEG F., and atmospheric pressure or above, preferably with the feed in the liquid phase. The amount of charcoal is generally about 100-1000 lbs. per barrel. Normal heptane may be adsorbed from its admixture with iso-octane, normal hexane or pentane separated from the branched isomers, and normal C5-C7 paraffins from associated branched paraffins. Narrow boiling fractions of an alkylate may be separately treated and the branched paraffins combined. Aromatics and some naphthenes, if present, may be adsorbed with the normal paraffins. Desorption may be effected with a solvent, preferably a hydrocarbon of lower boiling range than the feed, e.g. iso-pentane, butane, propane or hexanes, although other compounds such as ethers, aldehydes, ketones, alcohols, acids, amines, CO2, CS2 and SO2 may be used. Thus, the carbon with adsorbed heptane is regenerated with about 3 volumes of isopentane, the heptane being liberated and, if desired, converted to branched hydrocarbons. The adsorbent, wetted with isopentane, may be re-used as such or first purged with an inert gas or by heating. The hydrocarbon feed may be agitated with the charcoal which is then separated, either in batch or continuous operation, the feed may percolate a bed of adsorbent, or the two may be fed continuously in countercurrent. The separated branched paraffins may be used as fuels. When treating a feed containing other hydrocarbons in addition to paraffins, different adsorbents may be used therefor. Thus, to improve a virgin naphtha fraction, activated alumina is used to remove aromatics, the normal paraffins adsorbed with activated coconut charcoal, and the desorbed aromatics blended with the residual isoparaffins. In examples, a mixture of equal volumes of iso-octane and n-heptane is passed, in liquid or vapour phase, through a bed of Colombia activated carbon (coconut shell charcoal).