PROCESS FOR SIMULTANEOUS PRODUCTION OF BENZENE LEAN GASOLINE AND HIGH PURITY BENZENE FROM CRACKED GASOLINE FRACTION

摘要

Disclosed is a process for simultaneous production of benzene lean gasoline and recovery of high purity aromatics from narrow boiling light cracked gasoline fractions. The present invention provides a vacuum based two stage extractive distillation process, with pure NMP, for production of benzene lean gasoline (benzene content less than 0.4 Weight %) by recovery of high purity aromatics (purity more than 99 Weight %) from cracked gasoline fractions (boiling in the range of 40-90° C.) comprising benzene in the range of 10-30 weight % and close-boiling non-aromatic hydrocarbons like paraffins, iso-paraffins, olefins, di-olefins (including conjugated di-olefins), and naphthenes in the range of 70-90 weight % along with impurities containing but not limited to oxygenates, metals, chlorides, sulphur compounds, nitrogen compounds and organic peroxides.;The present invention provides an improved extractive distillation process for simultaneous production of benzene lean gasoline and benzene rich product from cracked gasoline fraction, with higher recovery of better quality products along with lower utility requirements and investment costs.

主权项

1. A vacuum based extractive distillation process for simultaneous production of high purity benzene (>99 wt. %) and benzene lean gasoline (benzene content <0.2 wt. %) from cracked gasoline fraction, comprising the steps of:
a) combining in an extractive distillation column (EDC-1) operating in vacuum/negative pressure
i. a preheated (up to 90% vaporization in a pressure range of −0.307 kg/cm2g to −0.247 kg/cm2g) unprocessed cracked gasoline fraction (boiling in the range of 45-95° C.) consisting of benzene concentrated unprocessed catalytically cracked gasoline fraction obtained from a fluidized catalytic cracking unit without any pre-treatment, wherein the gasoline fraction contains impurities, 10-30 weight % benzene and 70-90 weight % close-boiling non-aromatic hydrocarbons and the impurities comprise one or more of metals at a level not exceeding in ppb level, 1-400 ppm oxygenates, 0.1-3 ppm chlorides, 100-700 ppm sulphur, 0.6-14 ppm nitrogen and organic peroxides at a peroxide level of 20-50 millimoles/litre; andii. pure N-Methyl-2-Pyrrolidone (NMP) at a solvent mixture to feed material weight ratio of about 2 to about 6, and wherein the feed material is introduced into the first ED column (EDC-1) below the middle section and the solvent at about 65° C.-95° C. is introduced into the column near the top section; b) operating the EDC-1 of step (a) under vacuum and maintaining reboiler temperature in a range of 175° C. to 185° C. to obtain vapour product from top and aromatics laden solvent rich extract from the bottom; c) cooling the vapor product from EDC-1 top as obtained in step (b), at a temperature in the range of 65° C.-75° C. and then taking it to the middle section of a second refluxed extractive distillation column (EDC-2); d) operating the EDC-2 of step (c) under vacuum/negative pressure and maintaining the EDC-2 reboiler temperature in a range of 67° C.-80° C. to recover a raffinate phase containing gasoline having a benzene content of less than 0.2 weight % from top of EDC-2 and an extract phase containing aromatic hydrocarbons and solvent mixture from bottom of EDC-2 e) recycling the extract phase as obtained in step (d) to the top of EDC-1 to serve as reflux for EDC-1; f) separating the solvent mixture from the extract phase as obtained in step (b) in a refluxed Solvent Recovery Column (SRC), operating under vacuum/negative pressure without using any stripping steam or water, to obtain hydrocarbon free solvent from the bottom and benzene rich extract product from the SRC top.