Title of Invention	A PROCESS FOR THE SEPARATION OF A MIXTURE COMPRISING ETHYLENE, 1-BUTENE AND HYDROCARBON CUTS
Abstract	(57) Abstract: The present invention provides a process for the separation of a mixture comprising ethylene, a hydrocarbon cut principally comprising hydrocarbons containing 4 carbon atoms per molecule, the major portion being comprised by 1-butene and a hydrocarbon cut principally comprising hydrocarbons containing 6 carbon atoms per molecule the major portion of which being alpha-golems containing at least 6 carbon atoms per molecule, the ethylene content of said mixture being in the range 30% to 70% by weight, in which separation is effected in a distillation zone to obtain an overhead fraction comprising the major portion of the ethylene present in said mixture and between 0% and 100% by weight of the 1-butene present in said mixture the process being characterized in that said zone is also supplied with supplemental 1-butene in an amount in the range 1 to 40 times the quantity (by weight) of 1-butene present in said mixture. PRICE: THIRTY RUPEES

Title of Invention

A PROCESS FOR THE SEPARATION OF A MIXTURE COMPRISING ETHYLENE, 1-BUTENE AND HYDROCARBON CUTS

Abstract

(57) Abstract: The present invention provides a process for the separation of a mixture comprising ethylene, a hydrocarbon cut principally comprising hydrocarbons containing 4 carbon atoms per molecule, the major portion being comprised by 1-butene and a hydrocarbon cut principally comprising hydrocarbons containing 6 carbon atoms per molecule the major portion of which being alpha-golems containing at least 6 carbon atoms per molecule, the ethylene content of said mixture being in the range 30% to 70% by weight, in which separation is effected in a distillation zone to obtain an overhead fraction comprising the major portion of the ethylene present in said mixture and between 0% and 100% by weight of the 1-butene present in said mixture the process being characterized in that said zone is also supplied with supplemental 1-butene in an amount in the range 1 to 40 times the quantity (by weight) of 1-butene present in said mixture. PRICE: THIRTY RUPEES

Full Text	The present invention concerns an improved industrial process for the separation of a mixture comprising ethylene, 1 butene, alpha-olefins containing at least 6 carbon atoms per molecule and possibly heavier hydrocarbon products, the ethylene content of the mixture being in the range 30% to 70% by weight. In a preferred implementation of the process of the present invention, the mixture originates from a homogeneous liquid phase ethylene oligomerisation zone and comprises unreacted ethylene, 1-butene, 1-hexene, 1-octene, olefins containing at least 10 carbon atoms per molecule, inhibited catalyst and oligomerisation solvent. Ethylene oligomerisation is usually carried out in a generally homogeneous catalytic liquid phase process in the presence or otherwise of a solvent, using a Ziegler type catalyst which generally comprises a compound of a metal such as titanium, chromium, zirconium and an organoaluminium compound, at a temperature in the range 100°C to 200C and at a pressure in the range 0.5 MPa to 20 MPa. In a preferred implementation of the process of the present invention, the separation process follows an oligomerisation process in the presence of a solvent. The effluent from the ethylene oligomerisation step comprises unconverted ethylene and alpha-olefins, mainly 1-butene, 1-hexene, 1-octene, the oligomerisation solvent and Cio^ alpha-olefins (i.e., containing at least 10 carbon atoms per molecule). The effluent also includes catalyst. At the outlet to the oligomerisation step, the catalyst is deactivated by any compound which is known to the skilled person to inhibit an oligomerisation catalyst. The compound is generally an amine, preferably a long chain amine, i.e., containing at least six carbon atoms per molecule. Thus the feed to be separated preferably comprises essentially unconverted ethylene, 1-butene, 1-hexene, 1-octene, oligomerisation solvent, the compound resulting from deactivation of the catalyst by the inhibitor, which for impunity will be referred to as inhibited catalyst, and alpha-olefins. The separation of ethylene from alpha-olefins such as 1-butene, 1-hexene and 1-octene, and from the solvent, inhibited catalyst and alpha-olefins, suffers food a particular problem which is Nuked to the high proportion of ethylene and to the sensitivity of alpha-olefins to temperature, which imposes a bottom temperature in the distillation zone of less than 250C, preferably less than 200C. This produces a distillation column head temperature which can be achieved industrially, but at high operating cost. For example, it is often below -30C when the distillation zone consists of a distillation column with a bottom temperature of 200C, where the solvent is Roth-xylene and where the major portion of the ethylene contained in the feed is to be separated overhead. The aim of the invention is to provide a solution to the problem described above where separation must be carried out by distillation of a mixture as described above in a distillation zone which is generally a distillation column. The solution which forms the object of the invention consists of deliberately adding supplemental 1-butene to the mixture to be separated which is preferably a mixture from an ethylene oligomerisation step, either into the mixture before separation by distillation, or directly into the column, preferably to the upper plates, or a portion into the mixture and the other portion directly into the column. Thus the bottom temperature of the column is maintained at a temperature at which the alpha-olefins are stable, and an effluent which principally contains the major portion of the ethylene contained in the mixture and possibly a portion of the 1-butene contained in the mixture can be separated overhead, while a mixture comprising all or a portion of the 1-butene, the alpha-olefins containing more than 6 carbon atoms per molecule, the hydrocarbon solvent and the inhibited catalyst can be separated at the bottom. The solution described above can be generalised to any case where a mixture of the same type must be separated by distillation, in a distillation zone which is generally a distillation column. The importance of our solution is that a reasonable condensation temperature is obtained at the head of the column. The effluents obtained can be pumped into a higher pressure column in the separation train which is downstream of the distillation zone of the invention. This avoids the use of compressors which are more delicate than pumps as regards maintenance. Thus the process of the invention is a process for the separation of a mixture comprising ethylene, a C4 hydrocarbon cut, i.e., principally comprising hydrocarbons containing 4 carbon atoms per molecule, the major portion being comprised by 1-butene, a Cg hydrocarbon cut, i.e., principally comprising hydrocarbons containing 6 carbon atoms per molecule, mainly comprising alpha-olefins containing at least 6 carbon atoms per molecule and possibly hydrocarbon products containing at least 7 carbon atoms per molecule, the ethylene content of the mixture being in the range 30% to 70% by weight, preferably in the range 40% to 60% by weight, in which separation is effected in a distillation zone to obtain an overhead fraction comprising the major portion of the ethylene present in the mixture and between 0% and 100% by weight, preferably between 50% and 70% by weight, and more preferably between 55% and 65% by weight of the 1-butene present in the mixture, the process being characterized in that the zone is also supplied with supplemental 1-butene in an amount in the range 1 to 40 times the quantity (by weight) of 1-butene present in the mixture, preferably in the range 2 to 25 times the quantity, and more preferably in the range 5 to 20 times the quantity. The condensation temperature at the head of the distillation zone at reflux is generally in tiie range -35C to +60C, preferably in the range +20C to +50C. The process of the invention comprises at least two possible implementations. In a first implementation of the process of the invention, supplemental 1-butene is added to the mixture before its entry into the distillation zone, and so the [mixture + supplemental 1-butene] ensemble is supplied to the zone. In a further implementation of the process of the invention, the supplemental 1-butene is injected directly into the distillation zone independentiy of the supply of the mixture, preferably to the upper plates of the zone. However, the scope of the invention also includes a third possibility which consists of combining the two preceding possibilities, i.e., a portion of the 1-butene is added to the mixture and the other portion is injected directly into the distillation zone. In a preferred implementation of the process of the invention, the mixture originates fi"om a homogeneous liquid ethylene oligomerisation zone and comprises unreacted ethylene, 1-butene, 1-hexene, 1-octene, olefins containing at least 10 carbon atoms per molecule, and oligomerisation solvent. Preferably, the mixture further comprises the oligomerisation catalyst which has been deactivated by an inhibitor, i.e., the inhibited catalyst. The inhibitor is generally selected from the group formed by amines, and preferably it is selected from the group formed by long chain amines, i.e., amines containing at least 6 carbon atoms per molecule. The solvent is generally selected from compounds which are known to the skilled person for the activity as a solvent for ethylene oligomerisation. However, any other solvent which is known to the skilled person to have similar boiling point(s) and comparable properties could be envisaged. The solvent is generally a hydrocarbon, but a non hydrocarbon solvent could also be used. The solvent is preferably selected from hydrocarbon solvents containing at least one aromatic nucleus. More preferably, the solvent is principally constituted by a mixture of xylenes, and more preferably again, the solvent is ortho-xylene. Within the scope of the preferred implementation of the invention, the process comprises a separation train downstream of the distillation zone, supplied by at least the major portion of the bottom product from the zone. The separation train can also be separately fed by the overhead product from the zone, especially when the overhead product includes 1-butene. The separation zone thus formed by the separation train and the distillation zone can effect different subsequent separations. Thus in a first implementation, it can produce an effluent comprising ethylene as its major portion, an effluent comprising 1-butene as its major portion, an effluent comprising 1-hexene and 1-octene as its major portion, and an effluent comprising alpha-olefins containing at least 10 carbon atoms per molecule as its major portion, along with inhibited catalyst and solvent. In a second implementation, it can produce an effluent comprising ethylene as its major portion, an effluent comprising 1-butene as its major portion, an effluent comprising 1-hexene as its major portion, an effluent comprising 1-octene as its major portion, and an effluent comprising alpha-olefins containing at least 10 carbon atoms per molecule as its major portion, along with inhibited catalyst and solvent. Finally, in a third implementation, it can produce an effiuent comprising ethylene as its major portion, an effluent comprising 1-butene as its major portion, an effluent comprising 1-hexene as its major portion, an effluent comprising 1-octene as its major portion, an effluent comprising the solvent as its major portion, and an effluent comprising alpha-olefins containing at least 10 carbon atoms per molecule as its major portion, along with inhibited catalyst. Within the context of the preferred implementation of the process of the invention and in accordance with the three variations described above, the process can produce at least one effluent comprising ethylene as its major portion, and preferably the process is such that the major portion of the portion of the effluent comprising ethylene as its major portion is recycled to the oligomerisation zone. In addition to ethylene, the portion can also comprise 0% to 20% by weight of 1-butene, preferably 3% to 10% by weight of 1-butene, i.e., it may contain no 1-butene at all or it may contain 1-butene in an amount of 0% to 20% by weight, preferably 3% to 10% by weight. Accordingly, the present invention provides a process for the separation of a mixture comprising ethylene, a hydrocarbon cut principally comprising hydrocarbons containing 4 carbon atoms per molecule, the major portion being comprised by 1-butene and a hydrocarbon cut principally comprising hydrocarbons containing 6 carbon atoms per molecule, the major portion of which being alpha-olefins containing at least 6 carbon atoms per molecule, the ethylene content of said mixture being in the range 30% to 70% by weight, in which separation is effected in a distillation zone to obtain an overhead fraction comprising the major portion of the ethylene present in said mixture and between 0% and 100% by weight of the 1-butene present in said mixture, the process being characterized in that said zone is also supplied with supplemental 1-butene in an amount in the range 1 to 40 times the quantity (by weight) of 1-butene present in said mixture. The foUowing-non limiting example illustrates the invention. EXAMPLE A mixture originating from an oligomerisation step and comprising ethylene (771 kg/h) and alpha-olefins such as 1-butene (273 kg/h), 1-hexene (206 kg/h), 1-octene (112 kg/h) and oligomers containing at least ten carbon atoms per molecule (167 kg/h) was separated; the oligomerisation solvent was ortho-xylene (3712 kg/h) and the catalyst had been deactivated by the addition of dodecylamine. The distillation zone consisted of a distillation column in which the bottom temperature needed to be 2(X)C. A pressure of 10.5 bars (1.05 MPa) and a condensation temperature at reflux of -50.3C were requirements for practically all of the ethylene contained in the feed to be separated. A pressure of 3.5 bars (0.35 MPa) and a condensation temperature at reflux of -73C were requirements for a mixture of olefins containing 2 to 8 carbon atoms per molecule to be separated. The two calculated condensation temperatures at reflux are hardly economical on an industrial scale. Further, it was desired to produce a head temperature of 40C in the column, which was compatible with the use of a water condenser. Thus with the solution of the invention, which consisted of introducing 12 times the quantity of 1-butene contained in the mixture from the oligomerisation step into that mixture, the optimal pressure of the column was 29 bars (2.9 MPa) and the molar ratio of 1-butene in the overhead fraction was of the order of 50%. WE CLAIM: 1. A process for the separation of a mixture comprising ethylene, a hydrocarbon cut principally comprising hydrocarbons containing 4 carbon atoms per molecule, the major portion being comprised by 1-butene and a hydrocarbon cut principally comprising hydrocarbons containing 6 carbon atoms per molecule, the major portion of which being alpha-loafs containing at least 6 carbon atoms per molecule the ethylene content of said mixture being in the range 30% to 70% by weight, in which separation is effected in a distillation zone to obtain an overhead fraction comprising the major portion of the ethylene present in said mixture and between 0% and 100% by weight of the 1-butene present in said mixture, the process being characterized in that said zone is also supplied with supplemental 1-butene in an amount in the range 1 to 40 times the quantity (by weight) of 1-butene present in said mixture. 2. The process according to claim 1, in which the mixture additionally comprises hydrocarbon products containing at least 7 carbon atoms per molecule. 3. The process according to claim 1 or claim 2, in which the supplemental 1-butene is added to said mixture before its entry into the distillation zone, so that the [mixture + supplemental 1-butene] ensemble is supplied to said zone. 4. The process according to claim 1 or claim 2, in which the supplemental 1-butene is injected directly into the distillation zone independently of the supply of said mixture. 5. The process according to claim 1 or claim 2, in which a portion of the 1-butene is added to the mixture and the other portion of the 1-butene is injected directly into the distillation zone independently of the supply of said mixture. 6. The process according to any one of claims 1 to 5, in which the mixture originates from a homogeneous liquid ethylene oligomerisation zone and comprises unreacted ethylene, 1-butene, 1-hexene, 1-octene, alpha-olefins containing at least 10 carbon atoms per molecule, the oligomerisation catalyst which has been deactivated by an inhibitor, i.e., inhibited catalyst, and the oligomerisation solvent. 7. The process according to claim 6, in which a separation train is provided downstream of the distillation zone, said separation train being supplied with the major portion of the product from the bottom of said zone, the separation zone thus constituted by said separation train and said distillation zone producing an effluent comprising ethylene as its major portion, an effluent comprising at least 10 carbon atoms per molecule as its major portion, along with inhibited catalyst and solvent. 8. The process according to claim 6, in which a separation train is provided downstream of the distillation zone, said separation train being supplied with the major portion of the product from the bottom of said zone, the separation zone thus constituted by said separation train and said distillation zone being capable of producing an effluent comprising ethylene as its major portion, an effluent comprising 1-butene as its major portion, an effluent comprising 1-hexene as its major portion, an effluent comprising 1-octene as its major portion, and an effluent comprising compounds containing at least 10 carbon atoms per molecule as its major portion, along with inhibited catalyst and solvent. 9. The process according to claim 6, in which a separation train is provided downstream of the distillation zone, said separation train being supplied with the major portion of the product from the bottom of said zone, the separation zone thus constituted by said separation train and said distillation zone producing an effluent comprising ethylene as its major portion, an effluent comprising 1-butene as its major portion, an effluent comprising 1-hexene as its major portion, an effluent comprising 1-octene as its major portion, an effluent comprising the solvent as its major portion, and an effluent comprising alpha-olefins containing at least 10 carbon atoms per molecule as its major portion, along with inhibited catalyst. 10. The process according to any one of claims 6 to 9, in which a major portion of the portion of the effluent comprising ethylene as its major portion is recycled to the oligomerisation zone. 11. The process according to claim 10, in which said portion comprises 0% to 20% by weight of 1-butene in addition to the ethylene. 12. A process for the separation of a mixture comprising ethylene, a hydrocarbon cut comprising 4 carbon atoms, 1-butene, a hydrocarbon cut comprising 6 carbon atoms and heavier hydrocarbon products substantially as herein described and exemplified.

Full Text

The present invention concerns an improved industrial process for the separation of a mixture comprising ethylene, 1 butene, alpha-olefins containing at least 6 carbon atoms per molecule and possibly heavier hydrocarbon products, the ethylene content of the mixture being in the range 30% to 70% by weight. In a preferred implementation of the process of the present invention, the mixture originates from a homogeneous liquid phase ethylene oligomerisation zone and comprises unreacted ethylene, 1-butene, 1-hexene, 1-octene, olefins containing at least 10 carbon atoms per molecule, inhibited catalyst and oligomerisation solvent.
Ethylene oligomerisation is usually carried out in a generally homogeneous catalytic liquid phase process in the presence or otherwise of a solvent, using a Ziegler type catalyst which generally comprises a compound of a metal such as titanium, chromium, zirconium and an organoaluminium compound, at a temperature in the range 100°C to 200C and at a pressure in the range 0.5 MPa to 20 MPa. In a preferred implementation of the process of the present invention, the separation process follows an oligomerisation process in the presence of a solvent.
The effluent from the ethylene oligomerisation step comprises unconverted ethylene and alpha-olefins, mainly 1-butene, 1-hexene, 1-octene, the oligomerisation solvent and Cio^ alpha-olefins (i.e., containing at least 10 carbon atoms per molecule). The effluent also includes catalyst. At the outlet to the oligomerisation step, the catalyst is deactivated by any compound which is known to the skilled person to inhibit an oligomerisation catalyst. The compound is generally an amine, preferably a long chain amine, i.e., containing at least six carbon atoms per molecule. Thus the feed to be separated preferably comprises essentially unconverted ethylene, 1-butene, 1-hexene, 1-octene, oligomerisation solvent, the compound resulting from deactivation of the catalyst by the inhibitor, which for impunity will be referred to as inhibited catalyst, and alpha-olefins.

The separation of ethylene from alpha-olefins such as 1-butene, 1-hexene and 1-octene, and from the solvent, inhibited catalyst and alpha-olefins, suffers food a particular problem which is Nuked to the high proportion of ethylene and to the sensitivity of alpha-olefins to temperature, which imposes a bottom temperature in the distillation zone of less than 250C, preferably less than 200C. This produces a distillation column head temperature which can be achieved industrially, but at high operating cost. For example, it is often below -30C when the distillation zone consists of a distillation column with a bottom temperature of 200C, where the solvent is Roth-xylene and where the major portion of the ethylene contained in the feed is to be separated overhead.
The aim of the invention is to provide a solution to the problem described above where separation must be carried out by distillation of a mixture as described above in a distillation zone which is generally a distillation column. The solution which forms the object of the invention consists of deliberately adding supplemental 1-butene to the mixture to be separated which is preferably a mixture from an ethylene oligomerisation step, either into the mixture before separation by distillation, or directly into the column, preferably to the upper plates, or a portion into the mixture and the other portion directly into the column. Thus the bottom temperature of the column is maintained at a temperature at which the alpha-olefins are stable, and an effluent which principally contains the major portion of the ethylene contained in the mixture and possibly a portion of the 1-butene contained in the mixture can be separated overhead, while a mixture comprising all or a portion of the 1-butene, the alpha-olefins containing more than 6 carbon atoms per molecule, the hydrocarbon solvent and the inhibited catalyst can be separated at the bottom. The solution described above can be generalised to any case where a mixture of the same type must be separated by distillation, in a distillation zone which is generally a distillation column.

The importance of our solution is that a reasonable condensation temperature is obtained at the head of the column. The effluents obtained can be pumped into a higher pressure column in the separation train which is downstream of the distillation zone of the invention. This avoids the use of compressors which are more delicate than pumps as regards maintenance.
Thus the process of the invention is a process for the separation of a mixture comprising ethylene, a C4 hydrocarbon cut, i.e., principally comprising hydrocarbons containing 4 carbon atoms per molecule, the major portion being comprised by 1-butene, a Cg hydrocarbon cut, i.e., principally comprising hydrocarbons containing 6 carbon atoms per molecule, mainly comprising alpha-olefins containing at least 6 carbon atoms per molecule and possibly hydrocarbon products containing at least 7 carbon atoms per molecule, the ethylene content of the mixture being in the range 30% to 70% by weight, preferably in the range 40% to 60% by weight, in which separation is effected in a distillation zone to obtain an overhead fraction comprising the major portion of the ethylene present in the mixture and between 0% and 100% by weight, preferably between 50% and 70% by weight, and more preferably between 55% and 65% by weight of the 1-butene present in the mixture, the process being characterized in that the zone is also supplied with supplemental 1-butene in an amount in the range 1 to 40 times the quantity (by weight) of 1-butene present in the mixture, preferably in the range 2 to 25 times the quantity, and more preferably in the range 5 to 20 times the quantity.
The condensation temperature at the head of the distillation zone at reflux is generally in tiie range -35C to +60C, preferably in the range +20C to +50C.
The process of the invention comprises at least two possible implementations. In a first implementation of the process of the invention, supplemental 1-butene is added to the mixture before its entry into the distillation zone, and so the [mixture + supplemental 1-butene] ensemble is supplied to the

zone. In a further implementation of the process of the invention, the supplemental 1-butene is injected directly into the distillation zone independentiy of the supply of the mixture, preferably to the upper plates of the zone. However, the scope of the invention also includes a third possibility which consists of combining the two preceding possibilities, i.e., a portion of the 1-butene is added to the mixture and the other portion is injected directly into the distillation zone.
In a preferred implementation of the process of the invention, the mixture originates fi"om a homogeneous liquid ethylene oligomerisation zone and comprises unreacted ethylene, 1-butene, 1-hexene, 1-octene, olefins containing at least 10 carbon atoms per molecule, and oligomerisation solvent. Preferably, the mixture further comprises the oligomerisation catalyst which has been deactivated by an inhibitor, i.e., the inhibited catalyst. The inhibitor is generally selected from the group formed by amines, and preferably it is selected from the group formed by long chain amines, i.e., amines containing at least 6 carbon atoms per molecule.
The solvent is generally selected from compounds which are known to the skilled person for the activity as a solvent for ethylene oligomerisation. However, any other solvent which is known to the skilled person to have similar boiling point(s) and comparable properties could be envisaged. The solvent is generally a hydrocarbon, but a non hydrocarbon solvent could also be used. The solvent is preferably selected from hydrocarbon solvents containing at least one aromatic nucleus. More preferably, the solvent is principally constituted by a mixture of xylenes, and more preferably again, the solvent is ortho-xylene.
Within the scope of the preferred implementation of the invention, the process comprises a separation train downstream of the distillation zone, supplied by at least the major portion of the bottom product from the zone. The separation train can also be separately fed by the overhead product from the zone, especially when the overhead product includes 1-butene. The separation zone thus formed by

the separation train and the distillation zone can effect different subsequent separations. Thus in a first implementation, it can produce an effluent comprising ethylene as its major portion, an effluent comprising 1-butene as its major portion, an effluent comprising 1-hexene and 1-octene as its major portion, and an effluent comprising alpha-olefins containing at least 10 carbon atoms per molecule as its major portion, along with inhibited catalyst and solvent. In a second implementation, it can produce an effluent comprising ethylene as its major portion, an effluent comprising 1-butene as its major portion, an effluent comprising 1-hexene as its major portion, an effluent comprising 1-octene as its major portion, and an effluent comprising alpha-olefins containing at least 10 carbon atoms per molecule as its major portion, along with inhibited catalyst and solvent. Finally, in a third implementation, it can produce an effiuent comprising ethylene as its major portion, an effluent comprising 1-butene as its major portion, an effluent comprising 1-hexene as its major portion, an effluent comprising 1-octene as its major portion, an effluent comprising the solvent as its major portion, and an effluent comprising alpha-olefins containing at least 10 carbon atoms per molecule as its major portion, along with inhibited catalyst.
Within the context of the preferred implementation of the process of the invention and in accordance with the three variations described above, the process can produce at least one effluent comprising ethylene as its major portion, and preferably the process is such that the major portion of the portion of the effluent comprising ethylene as its major portion is recycled to the oligomerisation zone. In addition to ethylene, the portion can also comprise 0% to 20% by weight of 1-butene, preferably 3% to 10% by weight of 1-butene, i.e., it may contain no 1-butene at all or it may contain 1-butene in an amount of 0% to 20% by weight, preferably 3% to 10% by weight.

Accordingly, the present invention provides a process for the separation of a mixture comprising ethylene, a hydrocarbon cut principally comprising hydrocarbons containing 4 carbon atoms per molecule, the major portion being comprised by 1-butene and a hydrocarbon cut principally comprising hydrocarbons containing 6 carbon atoms per molecule, the major portion of which being alpha-olefins containing at least 6 carbon atoms per molecule, the ethylene content of said mixture being in the range 30% to 70% by weight, in which separation is effected in a distillation zone to obtain an overhead fraction comprising the major portion of the ethylene present in said mixture and between 0% and 100% by weight of the 1-butene present in said mixture, the process being characterized in that said zone is also supplied with supplemental 1-butene in an amount in the range 1 to 40 times the quantity (by weight) of 1-butene present in said mixture.

The foUowing-non limiting example illustrates the invention.
EXAMPLE
A mixture originating from an oligomerisation step and comprising ethylene (771 kg/h) and alpha-olefins such as 1-butene (273 kg/h), 1-hexene (206 kg/h), 1-octene (112 kg/h) and oligomers containing at least ten carbon atoms per molecule (167 kg/h) was separated; the oligomerisation solvent was ortho-xylene (3712 kg/h) and the catalyst had been deactivated by the addition of dodecylamine. The distillation zone consisted of a distillation column in which the bottom temperature needed to be 2(X)C.
A pressure of 10.5 bars (1.05 MPa) and a condensation temperature at reflux of -50.3C were requirements for practically all of the ethylene contained in the feed to be separated. A pressure of 3.5 bars (0.35 MPa) and a condensation temperature at reflux of -73C were requirements for a mixture of olefins containing 2 to 8 carbon atoms per molecule to be separated. The two calculated condensation temperatures at reflux are hardly economical on an industrial scale.
Further, it was desired to produce a head temperature of 40C in the column, which was compatible with the use of a water condenser. Thus with the solution of the invention, which consisted of introducing 12 times the quantity of 1-butene contained in the mixture from the oligomerisation step into that mixture, the optimal pressure of the column was 29 bars (2.9 MPa) and the molar ratio of 1-butene in the overhead fraction was of the order of 50%.

WE CLAIM:
1. A process for the separation of a mixture comprising ethylene, a hydrocarbon cut principally comprising hydrocarbons containing 4 carbon atoms per molecule, the major portion being comprised by 1-butene and a hydrocarbon cut principally comprising hydrocarbons containing 6 carbon atoms per molecule, the major portion of which being alpha-loafs containing at least 6 carbon atoms per molecule the ethylene content of said mixture being in the range 30% to 70% by weight, in which separation is effected in a distillation zone to obtain an overhead fraction comprising the major portion of the ethylene present in said mixture and between 0% and 100% by weight of the 1-butene present in said mixture, the process being characterized in that said zone is also supplied with supplemental 1-butene in an amount in the range 1 to 40 times the quantity (by weight) of 1-butene present in said mixture.
2. The process according to claim 1, in which the mixture additionally comprises hydrocarbon products containing at least 7 carbon atoms per molecule.
3. The process according to claim 1 or claim 2, in which the supplemental 1-butene is added to said mixture before its entry into the distillation zone, so that the [mixture + supplemental 1-butene] ensemble is supplied to said zone.
4. The process according to claim 1 or claim 2, in which the supplemental 1-butene is injected directly into the distillation zone independently of the supply of said mixture.
5. The process according to claim 1 or claim 2, in which a portion of the 1-butene is added to the mixture and the other portion of the 1-butene is injected directly into the distillation zone independently of the supply of said mixture.

6. The process according to any one of claims 1 to 5, in which the mixture originates from a homogeneous liquid ethylene oligomerisation zone and comprises unreacted ethylene, 1-butene, 1-hexene, 1-octene, alpha-olefins containing at least 10 carbon atoms per molecule, the oligomerisation catalyst which has been deactivated by an inhibitor, i.e., inhibited catalyst, and the oligomerisation solvent.
7. The process according to claim 6, in which a separation train is provided downstream of the distillation zone, said separation train being supplied with the major portion of the product from the bottom of said zone, the separation zone thus constituted by said separation train and said distillation zone producing an effluent comprising ethylene as its major portion, an effluent comprising at least 10 carbon atoms per molecule as its major portion, along with inhibited catalyst and solvent.
8. The process according to claim 6, in which a separation train is provided downstream of the distillation zone, said separation train being supplied with the major portion of the product from the bottom of said zone, the separation zone thus constituted by said separation train and said distillation zone being capable of producing an effluent comprising ethylene as its major portion, an effluent comprising 1-butene as its major portion, an effluent comprising 1-hexene as its major portion, an effluent comprising 1-octene as its major portion, and an effluent comprising compounds containing at least 10 carbon atoms per molecule as its major portion, along with inhibited catalyst and solvent.

9. The process according to claim 6, in which a separation train is provided
downstream of the distillation zone, said separation train being supplied with
the major portion of the product from the bottom of said zone, the separation
zone thus constituted by said separation train and said distillation zone
producing an effluent comprising ethylene as its major portion, an effluent
comprising 1-butene as its major portion, an effluent comprising 1-hexene as
its major portion, an effluent comprising 1-octene as its major portion, an
effluent comprising the solvent as its major portion, and an effluent comprising
alpha-olefins containing at least 10 carbon atoms per molecule as its major
portion, along with inhibited catalyst.
10. The process according to any one of claims 6 to 9, in which a major portion of
the portion of the effluent comprising ethylene as its major portion is recycled
to the oligomerisation zone.
11. The process according to claim 10, in which said portion comprises 0% to 20%
by weight of 1-butene in addition to the ethylene.
12. A process for the separation of a mixture comprising ethylene, a hydrocarbon
cut comprising 4 carbon atoms, 1-butene, a hydrocarbon cut comprising 6
carbon atoms and heavier hydrocarbon products substantially as herein
described and exemplified.

Documents:

1288-mas-96 others.pdf

1288-mas-96 abstract.pdf

1288-mas-96 claims.pdf

1288-mas-96 correspondence others.pdf

1288-mas-96 correspondence po.pdf

1288-mas-96 description (complete).pdf

1288-mas-96 form-1.pdf

1288-mas-96 form-26.pdf

1288-mas-96 form-4.pdf

1288-mas-96 petition.pdf

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Patent Number

220382

Indian Patent Application Number

1288/MAS/1996

PG Journal Number

30/2008

Publication Date

25-Jul-2008

Grant Date

28-May-2008

Date of Filing

19-Jul-1996

Name of Patentee

INSTITUT FRANCAIS DU PETROLE

Applicant Address

Inventors:

#	Inventor's Name	Inventor's Address
1	HUGUES FRANCOIS
2	BOUCOT PIERRE
3	CHODORGE JEAN -ALAIN
4	CLAIZE YVES
5	FORESTIERE ALAIN

PCT International Classification Number

C 07 C 7/04

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA