GB876702A - Process for producing gasoline of improved quality - Google Patents

Abstract

Gasoline is upgraded by distilling to separate C5 and C6 hydrocarbons from the C7 +, catalytically reforming the latter and distilling to separate from the reformate C5 and C6 products from C7 + products, passing the C5 and C6 reformate with a recycle stream through a molecular sieve adsorbent to separate normal paraffins from other hydrocarbons which latter are blended with the C7 + reformate to form the product, recovering normal paraffins from the sieve and isomerising together with at least the normal paraffins in the C5 and C6 feed hydrocarbons and returning the isomerisate to the sieve as the recycle stream. In a modification the C5 and C6 reformate may be isomerised before passing through the sieve. The total C5 + C6 feed stream may be passed to the isomerisation or it may pass first through the sieve. If desired the desorbed stream of normal paraffins from the sieve may be separated into C5 and C6 streams which are isomerised separately, the n-hexane being processed at a lower temperature. The C7 + feed stream may have an end point of up to 232 DEG C. and is reformed over a platinum catalyst, preferably in 3 or 4 reaction zones, at 427-566 DEG C., 6.8-68 atmospheres, 0.5-10 vol./vol./hr., with 0.5-20 mols of hydrogen per mol of hydrocarbons. Isomerisation may be effected over aluminium chloride or bromide, zinc chloride or ferric chloride at 10-149 DEG C. or, preferably, over platinumalumina-halogen at 93-482 DEG C., 3.5-68 atmospheres, and 0.2-10 vol./vol./hr. with 0.5-5 mols of hydrogen per mol of hydrocarbon. Sorption on the molecular sieve, which may be a zeolite of pure size 4 or 5 , may be effected in the vapour or liquid phase, and desorption effected with a heated gas, e.g. nitrogen, steam or propane at 100-900 DEG C., or with liquid butane.