Upgrading light naphtas for increased olefins production

Abstract

The present invention is a process to upgrade light naphthas comprising branched paraffins and their use as a feedstock in a steam cracking unit, said light naphthas consisting essentially of 90 to 100% by weight of hydrocarbons having at least 5 and up to 8 carbon atoms, said process comprising, a) optionally providing an isomerization zone recovered from the gasoline unit of an oil refinery, b) optionally providing a separation zone capable to treat an hydrocarbon stream comprising branched paraffins and normal paraffins to produce a first hydrocarbon stream having a reduced branched paraffins content and an enhanced normal paraffins content and a second hydrocarbon stream having an enhanced branched paraffins content and a reduced normal paraffins content, c) optionally providing a depentanizer, such that at least two of a), b) and c) are present, wherein, the light naphtha is sent to one of a), b) and c), streams are circulating between the various zones a), b) or c), a stream rich in normal paraffins is sent to the steam cracking unit.

1 . Process to upgrade light naphthas comprising branched paraffins and their use as a feedstock in a steam cracking unit, said light naphthas consisting essentially of 90 to 100% by weight of hydrocarbons having at least 5 and up to 8 carbon atoms, said process comprising,
 a) providing an isomerization zone recovered from the gasoline unit of an oil refinery,   b) providing a separation zone capable to treat an hydrocarbon stream comprising branched paraffins and normal paraffins to produce a first hydrocarbon stream having a reduced branched paraffins content and an enhanced normal paraffins content and a second hydrocarbon stream having an enhanced branched paraffins content and a reduced normal paraffins content,   e) optionally providing a depentanizer,   d) sending the light naphtha to the isomerization zone and operating said zone at conditions effective to produce a light naphtha having a reduced branched paraffins content and an enhanced normal paraffins content,   e) sending the withdrawn light naphtha from step d) to the separation zone to recover a first and a second hydrocarbon streams,   f) sending the first hydrocarbon stream recovered from step e) to the steam cracking unit,   g) recycling at least a part of the second hydrocarbon stream recovered from step e) at the inlet of the isomerization zone,   h) optionally, before the recycling of step g), sending the second hydrocarbon stream recovered at step e) to a depentanizer to recover a stream comprising essentially pentane and a stream having a reduced pentane content and sending at least a part of said stream comprising essentially pentane at the inlet of the isomerization zone.   
     
     
         2 . Process to upgrade light naphthas comprising branched paraffins and their use as a feedstock in a steam cracking unit, said light naphthas consisting essentially of 90 to 100% by weight of hydrocarbons having at least 5 and up to 8 carbon atoms, said process comprising,
 a) providing an isomerization zone recovered from the gasoline unit of an oil refinery,   b) providing a separation zone capable to treat an hydrocarbon stream comprising branched paraffins and normal paraffins to produce a first hydrocarbon stream having a reduced branched paraffins content and an enhanced normal paraffins content and a second hydrocarbon stream having an enhanced branched paraffins content and a reduced normal paraffins content,   c) sending the light naphtha to the separation zone to recover a first and a second hydrocarbon streams,   d) sending the second hydrocarbon stream recovered from step c) to the isomerization zone and operating said zone at conditions effective to produce a light naphtha having a reduced branched paraffins content and an enhanced normal paraffins content,   e) mixing the outlet stream of step d) with the first hydrocarbon stream recovered from step c) and sending said mixed stream to the steam cracking unit.   
     
     
         3 . Process to upgrade light naphthas comprising branched paraffins and their use as a feedstock in a steam cracking unit, said light naphthas consisting essentially of 90 to 100% by weight of hydrocarbons having at least 5 and up to 8 carbon atoms, said process comprising,
 a) providing an isomerization zone recovered from the gasoline unit of an oil refinery,   b) providing a separation zone capable to treat an hydrocarbon stream comprising branched paraffins and normal paraffins to produce a first hydrocarbon stream having a reduced branched paraffins content and an enhanced normal paraffins content and a second hydrocarbon stream having an enhanced branched paraffins content and a reduced normal paraffins content,   c) optionally providing a depentanizer,   d) sending the light naphtha to the separation zone to recover a first and a second hydrocarbon streams,   e) sending the first hydrocarbon stream recovered from step d) to the steam cracking unit,   f) sending at least a part of the second hydrocarbon stream recovered from step d) to the isomerization zone and operating said zone at conditions effective to produce a light naphtha having a reduced branched paraffins content and an enhanced normal paraffins content,   g) optionally, before sending the second hydrocarbon recovered from step h) to the isomerization zone, sending said hydrocarbon stream to a depentanizer to recover a stream comprising essentially pentane and a stream having a reduced pentane content and sending said stream comprising essentially isopentane to the isomerization zone,   i) recycling the outlet stream from step f) to the inlet of the separation zone.   
     
     
         4 . Process to upgrade light naphthas comprising branched paraffins and their use as a feedstock in a steam cracking unit, said light naphthas consisting essentially of 90 to 100% by weight of hydrocarbons having at least 5 and up to 8 carbon atoms, said process comprising,
 a) providing an isomerization zone recovered from the gasoline unit of an oil refinery,   b) providing a deisopentanizer,   c) sending the light naphtha to a deisopentanizer to recover a stream comprising essentially isopentane and a stream having a reduced isopentane content,   d) sending the stream having a reduced isopentane content recovered from step c) to the steam cracking unit,   e) sending the stream comprising essentially isopentane recovered from step c) to the isomerization zone and operating said zone at conditions effective to produce a light naphtha having a reduced branched paraffins content and an enhanced normal paraffins content,   f) recycling the outlet of step e) to the inlet of the deisopentanizer.   
     
     
         5 . Process according to  claim 1  wherein the isomerization zone operates under the presence of hydrogen. 
     
     
         6 . Process according to  claim 1  wherein the light naphtha to be upgraded is a C5 cut comprising, the total being 100 w %, 100 to 95% of a mixture of pentane and isopentane and 0 to 5% of cyclopentane. 
     
     
         7 . Process according to  claim 1  wherein the light naphtha to be upgraded is a C5/C6 cut comprising, the total being 100 w %,
 0 to 10% of C7+, 
 0 to 10% of C4, 
 80 to 100% of a mixture of normal and branched C5 and C6. 
 
     
     
         8 . Process according to  claim 7  wherein the light naphtha to be upgraded is a C5/C6 cut comprising, the total being 100 w %,
 0 to 5% of C7+, 
 0 to 5% of C4, 
 90 to 100% of a mixture of normal and branched C5 and C6. 
 
     
     
         9 . Process according to  claim 8  wherein the light naphtha to be upgraded is a C5/C6 cut comprising, the total being 100 w %,
 0 to 2% of C7+, 
 0 to 5% of C4, 
 93 to 100% of a mixture of normal and branched C5 and C6. 
 
     
     
         10 . Process according to  claim 7  wherein in the light naphtha to be upgraded the C7+ is a C7. 
     
     
         11 . Process according to  claim 7  wherein in the light naphta to be upgraded the proportion of NaftC5+NaftC6 is less than 7 w %, preferably less than 5%. 
     
     
         12 . Process according to  claim 7  wherein in the light naphta to be upgraded the proportion of Aromatics C6 is less than 5 w %. 
     
     
         13 . Process according to  claim 12  wherein in the light naphta to be upgraded the proportion of Aromatics C6 is less than 2 w %. 
     
     
         14 . Process according to  claim 13  wherein in the light naphta to be upgraded the proportion of Aromatics C6 is less than 1.5 w %. 
     
     
         15 . Process according to  claim 4  wherein the light naphtha to be upgraded is a C5 cut comprising, the total being 100 w %,
 0 to 10 % of C7+, 
 0 to 10% of C4, 
 80 to 100% of C5, said C5 is essentially a mixture of iC5 and nC5. 
 
     
     
         16 . Process according to  claim 15  wherein in the light naphta to be upgraded the C7+ is a C6+. 
     
     
         17 . Process according to  claim 15  wherein the light naphtha to be upgraded is a C5 cut comprising, the total being 100 w %,
 0 to 5% of C6+, 
 0 to 5% of C4, 
 90 to 100% of C5, said C5 is essentially a mixture of iC5 and nC5. 
 
     
     
         18 . Process according to  claim 17  wherein the light naphtha to be upgraded is a C5 cut comprising, the total being 100 w %,
 0 to 3% of C6+, 
 0 to 3% of C4, 
 94 to 100% of C5, said C5 is essentially a mixture of iC5 and nC5. 
 
     
     
         19 . Process according to  claim 16  wherein in the light naphta to be upgraded the C6+ is a C6. 
     
     
         20 . Process according to  claim 15  wherein in the light naphta to be upgraded the C5 mixture comprises less than 5 w % of NaftC5 (C5 napthenics). 
     
     
         21 . Process according to  claim 20  wherein in the light naphta to be upgraded the C5 mixture comprises less than 3 w % of NaftC5 (C5 napthenics)