GB898059A - Improvements in or relating to the separation of hydrocarbon mixtures - Google Patents

Abstract

In the regeneration of zeolitic molecular sieves which have been used to separate mixtures of adsorbable hydrocarbons with non-adsorbable hydrocarbons, non-adsorbed and surface adsorbed hydrocarbons are purged from the bed of zeolite with the vapour of a substance which is liquid at 60 DEG F. and 30 inches Hg, before desorption to recover the adsorbed fraction is effected. The purging medium may be the vapour of methyl isobutyl ketone, isooctane, cyclohexane or benzene, and may be at an elevated pressure in the range 1 to 1,000 p.s.i.g.; desorption is normally effected with a paraffin. Adsorption is generally effected at 200 DEG to 600 DEG C. using a fixed or moving zeolite bed, in the liquid or vapour phase, and is preferably discontinued before breakthrough. According to Example (1) a gas-oil fraction is contacted with a 5 molecular sieve at 380 DEG C. until 70 to 75% of the saturation weight of normal paraffins at breakthrough is obtained; purging is effected with methyl isobutyl ketone followed by 10 to 20 mm. Hg vacuum and desorption is effected at 390 DEG C. with n-heptane; (2) adsorption as in (1), purging at 390 DEG C. with iso-octane followed by nitrogen, and desorption as in (1); (3) adsorption as in (1), purging at 400 DEG C. with cyclohexane followed by nitrogen; desorption as in (1); (4) adsorption as in (1), purging at 400 DEG C. with benzene followed by nitrogen, desorption as in (1). Specification 898,058 is referred to.