EP4065541A1

EP4065541A1 - Method for separating an effluent obtained in an oligomerization step

Info

Publication number: EP4065541A1
Application number: EP20804300.0A
Authority: EP
Inventors: Pierre-Alain Breuil; Nicolas ARIBERT; Olivier COTTE
Original assignee: IFP Energies Nouvelles IFPEN
Current assignee: IFP Energies Nouvelles IFPEN
Priority date: 2019-11-26
Filing date: 2020-11-17
Publication date: 2022-10-05
Also published as: AU2020393956A1; US20220402839A1; FR3103485A1; FR3103485B1; WO2021104924A1; CN114728865A; CA3154586A1; JP2023503599A; BR112022007451A2; KR20220104695A; MX2022005841A; TW202128600A

Abstract

The present invention relates to a method for treating an effluent from an oligomerization step in a vaporization step. In particular, the oligomerization step is a step of dimerizing ethylene to but-1-ene by a nickel-based catalytic system.

Description

l

PROCESS FOR SEPARATING AN EFFLUENT FROM A STAGE

OLIGOMERIZATION

Field of the invention

The present invention relates to a process for treating an effluent from an oligomerization step in a vaporization step. In particular, the oligomerization step is a step of dimerization of ethylene to 1-butene by a nickel-based catalyst system.

Prior art

The transformation of light olefins using a homogeneous catalyst based on a transition metal, in particular based on nickel, associated with a halogenated activator, for example an alkylaluminum chloride, has been studied since the 1950s. development and marketing of various processes.

For example, octenes or hexenes or nonenes are produced respectively by dimerization of butenes or oligomerization of propylene by the Dimersol ™ process from Axens (Revue de Institut Français du Pétrole, Vol. 37, No. 5, September- October 1982, p 639). The octenes can be converted in good yields by hydroformylation reaction followed by hydrogenation to isononanols. These C9 alcohols (that is to say comprising 9 carbon atoms) are used in particular for the synthesis of plasticizers of the phthalate type for PVC. Hexenes or nonenes can also be used as a base for very good octane fuel.

The development of catalytic systems capable of dimerizing olefins requires the choice of the transition metal and the suitable ligands. Among the existing catalyst systems, several nickel-based catalytic systems using different ligands have been developed. Mention may in particular be made, by way of examples, of p-allyl nickel phosphine halide complexes with Lewis acids, as described in French patent FR1410430B, nickel phosphine halide complexes with Lewis acids, as described in patent US3485881A, complexes of nickel with imino-imidazole ligands as described in French patent FR2979836B and nickel carboxylates with hydrocarbylaluminum halides, as described in patent USA3 321546A. In dimerization processes using such catalysts, it is necessary to neutralize the catalyst at the end of the reaction to prevent the reaction from continuing in an undesirable manner.

Patent FR2733497 describes a process for the production of but-1-ene comprising a separation zone in which the reaction effluent is vaporized in two stages by means of a vaporizer implemented at identical pressures followed by a vaporization stage. by means of a thin film evaporator.

Patent FR2992962B describes a process for the production and separation of hexene-1 from a mixture of products obtained from an ethylene trimerization zone. In particular, this patent describes a separation zone using a series of stepped flashes vaporizing the liquid effluent at an increasing temperature gradient ranging from 150-200 ° C to 160-220 ° C.

The Applicant in its research has developed a new process for separating a neutralized oligomerization effluent using at least two vaporization steps according to a decreasing pressure gradient. Advantageously, the process according to the invention makes it possible to remove the neutralized catalyst by vaporization at a moderate temperature. Advantageously, the implementation of at least two vaporization steps at moderate temperature according to a decreasing pressure gradient makes it possible to prevent the phenomenon of resumption of activity of the neutralized catalyst which is responsible for a decrease in the selectivity for the desired olefins. . Thus, the process according to the invention makes it possible to maximize the production of desired olefins. The method according to the invention also makes it possible to limit the costs associated with the maintenance of production units.

Summary of the invention

The present invention relates to a process for treating an effluent resulting from an oligomerization step, comprising a step of neutralizing said effluent in order to deactivate a catalytic composition followed by a step of thermal separation of the neutralized effluent comprising - a first vaporization step implemented at a pressure between 2.0 and 5.0 MPa and at a temperature between 70 and 150 ° C, making it possible to obtain a liquid fraction sent to a second vaporization step , and a gas fraction, preferably sent to a distillation section,

- said second vaporization step is carried out at a pressure between 0.5 and 3.0 MPa and at a temperature between 70 and 150 ° C, making it possible to obtain a liquid fraction and a gas fraction , preferably, said gaseous fraction is sent to the distillation section,

- wherein the pressure of the first vaporization step is greater than the pressure of the second vaporization step, preferably at least 0.5 MPa, preferably at least 1.0 MPa, preferably at least 1.5 MPa.

Thus, the thermal separation step of the process according to the invention makes it possible to remove the neutralized catalyst by vaporization at a moderate temperature. Advantageously, the implementation of at least two vaporization steps at moderate temperature according to a decreasing pressure gradient makes it possible to prevent the phenomenon of resumption of activity of the neutralized catalyst which is responsible for a decrease in the selectivity for the desired olefins. .

Another advantage of the process according to the invention is to maximize the selectivity to butene-1.

In a preferred embodiment, the first vaporization step is carried out at a pressure between 2.0 and 4.5 MPa, preferably 2.5 and 4.0 MPa and at a temperature between 80 and 140 ° C preferably between 90 and 130 ° C.

In a preferred embodiment, the second vaporization step is carried out at a pressure between 0.8 and 3.0 MPa, preferably 1.0 and 2.0 MPa and at a temperature between 80 and 140 ° C. preferably between 90 and 130 ° C.

In a preferred embodiment, the thermal separation step implements a third vaporization step into which is sent the liquid fraction resulting from the second vaporization step, said third vaporization step is carried out at a pressure between 0.1 and 1.5 MPa and at a temperature between 70 and 200 ° C, making it possible to obtain a liquid fraction and a gaseous fraction, preferably said gaseous fraction is sent to the distillation section, and pressure of the second vaporization step is greater than the pressure of the third vaporization step, preferably at least 0.5 MPa, preferably at least 0.8 MPa.

Preferably, the third vaporization step is carried out at a pressure between 0.3 and 1.2 MPa, preferably between 0.4 and 1.0 MPa and at a temperature between 80 and 140 ° C, preferably between 80 and 130 ° C.

In a preferred embodiment, the first step and / or the second step and / or the third step of thermal separation are carried out via a flash balloon, preferably coupled with a heat exchanger.

In a preferred embodiment, the gaseous fraction resulting from the first vaporization stage and / or the gaseous fraction resulting from the second vaporization stage and / or the gaseous fraction resulting from the third vaporization stage are liquefied by reducing the temperature. , so as to achieve a pressure between 2.0 and 5.0 MPa and preferably to be sent to the distillation section.

In a preferred embodiment, the temperature making it possible to liquefy the gaseous fraction (s) resulting from the vaporization stages is between 0 and 60 ° C.

In a preferred embodiment, the oligomerization step uses a catalytic composition comprising an alkylaluminum halide and optionally a nickel precursor.

In a preferred embodiment, the alkylaluminum halide has the formula [Al _m R ⁵ _n X3- _n ] _o in which

- R ⁵ is an alkyl group, linear or branched, containing from 1 to 12 carbon atoms,

- X is a chlorine or bromine atom, and preferably a chlorine atom, and

- m is chosen from 1 or 2, - n is chosen from 0, 1 or 2,

- o is chosen from 1 or 2.

In a preferred embodiment, the effluent resulting from an oligomerization step contains an alkylaluminum halide content of between 0.01 and 100,000 ppm by weight. In a preferred embodiment, the step of neutralizing the effluent resulting from the oligomerization step is carried out to deactivate a catalytic composition by bringing said effluent into contact with a neutralization system comprising:

- an alcohol of general formula R ¹ OH, in which the group R ¹ is chosen from:

* an alkyl group, linear or branched, containing from 2 to 20 carbon atoms,

* an aryl group containing from 5 to 30 carbon atoms; and or

- an amine of general formula NR ² R ³ R ⁴ , in which the groups R ² , R ³ and R ⁴ , which are identical or different, are independently chosen from:

* a hydrogen,

* an alkyl group, linear or branched, containing from 1 to 20 carbon atoms, and optionally substituted by an NH ₂ group.

In a preferred embodiment, the temperature of contacting the neutralization system and the effluent from the oligomerization step is that at which said oligomerization step takes place.

In a preferred embodiment, the neutralization system comprises an alcohol of general formula R ¹ OH and an amine of general formula NR ² R ³ R ⁴ .

In a preferred embodiment, the molar ratio of amine to alcohol is between 0.5 and 100.

Detailed description of the invention

It is specified that, throughout this description, the expression "between ... and ..." should be understood as including the limits mentioned.

In the sense of the present invention, the various embodiments presented can be used alone or in combination with each other, without limitation of combination.

In the sense of the present invention, the different parameter ranges for a given step such as the pressure ranges and the temperature ranges can be used alone or in combination. For example, within the meaning of the present invention, a preferred pressure value range can be combined with a more preferred temperature value range. The present invention relates to a process for treating an effluent resulting, preferably directly, from an oligomerization step, comprising a step of neutralizing said effluent followed, preferably directly, by a step of thermal separation of the effluent. neutralized comprising: - a first vaporization step implemented at a pressure between 2.0 and 5.0 MPa and at a temperature between 70 and 150 ° C, the liquid fraction obtained at the end of the first step of vaporization is sent to a second vaporization step, and the gaseous fraction is sent to a distillation section, - said second vaporization step is carried out at a pressure of between 0.5 and 3.0 MPa and at a temperature of between 70 and 150 ° C, the gaseous fraction resulting from the second vaporization step is sent to the distillation section,

Thus, the thermal separation step according to the invention makes it possible to remove the neutralized catalyst by vaporization at a moderate temperature. Advantageously, the implementation of at least two vaporization steps at moderate temperature according to a decreasing pressure gradient makes it possible to prevent the phenomenon of resumption of activity of the neutralized catalyst which is responsible for a decrease in the selectivity for the desired olefins. .

Another advantage of the neutralization process according to the invention is to maximize the selectivity to butene-1.

Thermal separation step The process according to the invention therefore comprises a thermal separation step, commonly called vaporization, of an effluent resulting from an oligomerization step previously neutralized to deactivate a catalytic composition, said thermal separation step comprising: - a first vaporization step implemented at a pressure between 2.0 and 5.0 MPa and at a temperature between 70 and 150 ° C, making it possible to obtain a liquid fraction sent to a second vaporization step , and a gas fraction, preferably sent to a distillation section,

Said thermal separation step advantageously makes it possible to remove the neutralized catalyst as well as the heavy by-products (C12 +) generated during the oligomerization step, and to send the desired olefins to a distillation section in order to purify them.

Preferably, the neutralized catalyst, as well as the heavy by-products (C12 +) separated in the vaporization step and contained in the liquid fraction from the last vaporization step implemented are sent to an incinerator.

The gas fractions sent to the distillation section include unconverted ethylene, products formed during the oligomerization step and optionally solvent.

Advantageously, the first vaporization step is carried out at a pressure of between 2.0 and 5.0 MPa, preferably between 2.2 and 4.5 MPa, preferably between 2.4 and 4.0 MPa, and of preferably between 2.5 and 3.5 MPa, and at a temperature between 70 and 150 ° C between 80 and 140 ° C, preferably between 90 and 130 ° C, and preferably between 95 and 120 ° C.

Advantageously, the second vaporization step is carried out at a pressure between 0.5 and 3.0 MPa, preferably between 0.8 and 3.0 MPa, preferably 1.0 and 2.0 MPa, preferably between 1.1 and 1.8 MPa, and very preferably between 1.2 and 1.5 MPa, and at a temperature between 70 and 150 ° C, preferably between 80 and 140 ° C, preferably between 90 and 130 ° C, and preferably between 95 and 125 ° C.

Preferably, the thermal separation step implements a third vaporization step into which is sent the liquid fraction resulting from the second vaporization step, said third vaporization step is carried out at a pressure between 0.1 and 1.5 MPa and at a temperature between 70 and 150 ° C. Said third vaporization step makes it possible to obtain a liquid fraction and a gas fraction, preferably said gas fraction is sent to the distillation section.

In this case, the pressure of the second vaporization step is higher than the pressure of the third vaporization step, preferably at least 0.5 MPa, preferably at least 0.8 MPa, preferably at least 1.0 MPa, and preferably at least 1.5 MPa.

The last liquid fraction obtained at the end of the last vaporization step, either of the second or of the third vaporization step, is preferably sent to an incinerator, and the gaseous fraction obtained at the end of the last vaporization step , either the second or the third vaporization step is sent to the distillation section.

Advantageously, the third vaporization step is carried out at a pressure between 0.1 and 1.5 MPa, preferably between 0.3 and 1.2 MPa, preferably between 0.4 and 1.0 MPa, so preferred between 0.5 and 0.8 MPa, and at a temperature between 70 and 150 ° C, preferably between 80 and 140 ° C, preferably between 80 and 130 ° C, preferably between 85 and 130 ° C, preferably between 90 and 120 ° C and very preferably between 95 and 110 ° C.

Flash is understood to mean a gas / liquid separation effected by a change in pressure and / or temperature. Preferably, the first step and / or the second step and / or the third step of thermal separation are implemented by means of a flash balloon, preferably coupled with a heat exchanger or any other sequence making it possible to partially vaporize an effluent. Thus, a wide choice of technology is available for the implementation of any one of the thermal separation steps, said technologies are preferably chosen from:

- simple evaporators (or natural convection) with a double jacket, with coils or of the thermosiphon type, - more complex evaporators with horizontal, vertical (for example of the “climbing film” or “falling film” type) or inclined tubes, with forced recirculation, and

- more specific systems of thin-film evaporators (vertical conical, horizontal conical, short path) possibly coupled with different heating modes (steam, oils, molten salts, induction or others), plate evaporators.

In a preferred embodiment, the thermal separation step does not use thin film evaporators as described in patent FR2733497.

In a preferred embodiment, the gaseous fraction resulting from the first vaporization stage and / or the gaseous fraction resulting from the second vaporization stage and / or the gaseous fraction resulting from the third vaporization stage are liquefied, upstream of said vaporization. distillation section, by reducing the temperature, so as to reach a pressure between 2.0 and 5.0 MPa and preferably to be sent to the distillation section, preferably by means of a pump. Advantageously, this embodiment makes it possible to dispense with the use of a compressor, which makes it possible to limit the costs of implementing the process for treating the effluent resulting from an oligomerization step. Preferably, the temperature making it possible to liquefy the gas fraction (s) resulting from the vaporization stages is between 0 and 60 ° C, preferably between 10 and 55 ° C, and preferably between 20 and 50 ° C. Neutralization step

The method according to the invention comprises a step of neutralizing the effluent from the oligomerization step. Preferably, the neutralization step comprises bringing said effluent into contact with a neutralization system comprising, preferably consisting of:

- an alcohol of general formula R ¹ OH, in which the group R ¹ is chosen from

* an alkyl group, linear or branched, containing from 2 to 20 carbon atoms,

* an aryl group containing from 5 to 30 carbon atoms; and or

- an amine of general formula NR ² R ³ R ⁴ , in which the groups R ² , R ³ and R ⁴ , which are identical or different, are chosen independently from

* a hydrogen,

Thus, said neutralization step makes it possible to obtain an effluent in which the catalytic composition is neutralized, that is to say deactivated. In addition, said composition no longer exhibits catalytic activity for the oligomerization reaction.

Advantageously, the R ¹ group can be an alkyl group containing from 3 to 15 carbon atoms, preferably from 4 to 14 carbon atoms, preferably from 6 to 12 carbon atoms and preferably between 7 and 10 carbon atoms .

In a preferred embodiment, the group R ¹ is a branched alkyl.

In another preferred embodiment, the R ¹ group is a linear alkyl.

In a preferred embodiment, the group R ¹ is an alkyl substituted by one or more substituents chosen from a hydroxyl (-OH), or an amine (-NH ₂ ).

Advantageously, the group R ¹ can be an aryl group containing from 5 to 30 carbon atoms, preferably from 5 to 20 carbon atoms, preferably 6 to 18 carbon atoms, and preferably from 6 to 15 carbon atoms. .

Preferably, the alcohol of general formula R ¹ OH is chosen from 1-propanol, 2-propanol, iso-propanol, 1-butanol, 2-butanol, iso-butanol, sec- butanol, tert- butanol, 1-pentanol, 2-pentanol, 3-pentanol, 1-hexanol, 2-hexanol, 3-hexanol, 1-heptanol, 2-heptanol, 3-heptanol, 4- heptanol, 1-octanol, 2-octanol, 3- octanol, 4-octanol, 2-ethyl-1-hexanol, 2-methyl-3-heptanol, 1-decanol, 2-decanol, 3-decanol, 4-decanol, 5-decanol, 1-undecanol, 2-undecanol, 7-methyl-2- decanol, 1-docecanol, 2-dodecanol, 2-ethyl-1 -decanol, phenol, 2-methylphenol, 2,6-dimethylphenol, 2,4,6-trimethylphenol, 4-methylphenol, 2-phenylphenol, 2,6-diphenylphenol, 2,4,6 -triphenylphenol, 4-phenylphenol, 2-tert-butyl-6-phenylphenol, 2,4-ditertbutyl-6-phenylphenol, 2,6-diisopropylphenol, 2,6-ditert-butylphenol, 4-methyl -2,6-ditert-butylphenol, taken alone or as a mixture. Preferably, the alcohol of general formula R ¹ OH is 2-ethyl-1-hexanol.

Preferably, the groups R ² , R ³ and R ⁴ , which are identical or different, are chosen independently from a hydrogen, an alkyl group, linear or branched, containing from 2 to 20 carbon atoms, preferably from 4 to 14 carbon atoms. carbon, preferably 6 to 12 carbon atoms and more preferably 7 to 10 carbon atoms.

In a preferred embodiment, at least one of the groups R ² , R ³ and R ⁴ is chosen from hydrogen.

In an even more preferred embodiment, at least two of the groups R ² , R ³ and R ⁴ are chosen from hydrogen.

In a particular embodiment, the amine is a poly-amine such as a diamine. In other words at least one of the groups R ² , R ³ and R ⁴ is substituted by an amino group (-NH ₂ ). Preferably, one of the groups R ² , R ³ and R ⁴ is substituted by an amino group (-NH ₂ ).

Preferably, the amine of general formula NR ² R ³ R ⁴ is chosen from 1-propylamine, 2-propylamine, iso-propylamine, 1-butylamine, 2-butylamine, iso-butylamine, sec-butylamine, tert-butylamine, 1-pentylamine, 2-pentylamine, 3-pentylamine, 1-hexylamine, 2-hexylamine, 3-hexylamine, 1-heptylamine, 2-heptylamine, 3-heptylamine, 4-heptylamine, 1-octylamine, 2-octylamine, 3-octylamine, 4-octylamine, 2-ethyl-1-hexylamine, 2-methyl-3-heptylamine, 1 -decylamine, 2-decylamine, 3-decylamine, 4-decylamine, 5-decylamine, 1-undecylamine, 2- undecylamine, 7-methyl-2-decylamine, 1-dodecylamine, 2- dodecylamine, 2-ethyl-1-decylamine, taken alone or as a mixture. In a preferred embodiment, the neutralization system comprises an alcohol of general formula R ¹ OH and an amine of general formula NR ² R ³ R ⁴ .

Advantageously, the use of an alcohol R ¹ OH and an amine NR ² R ³ R ⁴ as a neutralization system makes it possible to deactivate the catalytic composition while overcoming the problems associated with corrosion and the recovery of activity of said system which results in a decrease in selectivity.

In fact, the use of an alcohol and an amine makes it possible synergistically to prevent the resumption of activity of the neutralized catalytic composition during the subsequent stages of purification of the effluent while limiting the associated corrosion phenomena. in the presence of the used catalytic composition.

When the neutralization system comprises an alcohol and an amine, the effluent from the oligomerization step is contacted according to one embodiment, successively with the amine and then with the alcohol.

In another embodiment, the effluent from the oligomerization step is advantageously contacted with a mixture of alcohol and amine.

In another embodiment, the effluent resulting from the oligomerization step is advantageously brought into contact simultaneously with an alcohol of formula R ¹ OH and with an amine of formula NR ² R ³ R ⁴ .

Advantageously, the molar ratio of amine to alcohol is between 0.5 and 100, preferably between 1.0 and 90, preferably between 1.1 and 80, preferably between 1.5 and 70, preferably between 2.0 and 60, and preferably between 2.2 and 50. In a preferred embodiment, the molar ratio of amine to alcohol is between 0.5 and 40, preferably between 1, 0 and 30, preferably between 1.1 and 20, preferably between 1.5 and 15, preferably between 2.0 and 10, and more preferably between 2.2 and 5.0. Advantageously, the molar ratio of the neutralization system to the alkylaluminum halide is between 0.5 and 100, preferably between 1.0 and 90, preferably between 1.5 and 80, preferably between 2.0 and 70, preferably between 3.0 and 60, preferably between 3.5 and 50. In a preferred embodiment, the molar ratio of the neutralization system to the alkylaluminum halide is between 0.5 and 50, preferably between 1.0 and 40, preferably between 1.5 and 30, preferably between 2.0 and 20, preferably between 3.0 and 15, preferably between 3.5 and 10.0.

Preferably, the effluent resulting directly from an oligomerization step contains an alkylaluminum halide content of between 0.01 and 100,000 ppm by weight, preferably between 0.1 and 10,000 ppm by weight, preferably between 1, 0 and 1000 ppm by weight, preferably between 2.0 and 600 ppm, preferably between 3.0 and 400 ppm, preferably between 5.0 and 200 ppm, preferably between 6.0 and 100 ppm, preferably between 8.0 and 50 ppm, preferably between 10 and 40 ppm and preferably between 12 and 30 ppm by weight relative to the total weight of said effluent.

Preferably, the effluent resulting directly from an oligomerization step contains an alkylaluminum chloride, at a content such that the chlorine content of between 0.1 and 100,000 ppm by weight, preferably between 1.0 and 10,000 ppm. weight, preferably between 2.0 and 1000 ppm weight, preferably between 3.0 and 600 ppm, preferably between 4.0 and 400 ppm, preferably between 5.0 and 200 ppm, preferably between 8.0 and 100 ppm, preferably between 10 and 80 ppm, preferably between 12 and 70 ppm and preferably between 15 and 60 ppm by weight relative to the total weight of said effluent.

The neutralization system is preferably brought into contact with the effluent resulting from the oligomerization step at a temperature between -40 and 250 ° C, preferably between -20 ° C and 150 ° C, preferably between 20 ° C and 100 ° C, preferably between 30 to 80 ° C and very preferably between 40 and 60 ° C. Advantageously, the temperature of contacting the neutralization system and the effluent from the oligomerization step is that at which said oligomerization step takes place.

Advantageously, the alcohol of general formula R ¹ OH and / or the amine of general formula NR ² R ³ R ⁴ can be used in an identical or different solvent. Said solvent may be chosen from any solvent capable of diluting or dissolving the amine and / or alcohol.

Advantageously, said solvent can be chosen from one or more solvents as described above for the catalytic composition.

"Optional" oligomerization step

Advantageously, the effluent treated in the process according to the invention is obtained at the end of an oligomerization step, preferably ethylene in olefin using a catalytic composition comprising an alkylaluminum halide, and preferably a metal precursor, in particular a nickel precursor, said step making it possible to obtain said effluent treated in the process according to the invention, preferably in liquid form and comprising unconverted ethylene, the products formed during the oligomerization step, said catalytic composition and optionally solvent.

Preferably, the olefins obtained at the end of the oligomerization step are but-1-ene, but-2-ene, hex-1-ene and / or oct-1-ene, alone or in combination.

The oligomerization step is preferably carried out in the presence of said catalytic composition preferably comprising an alkylaluminum halide and a nickel precursor, with a nickel concentration advantageously between 10 ¹² and 1.0 mol / L, and preferably between 10 ⁹ and 0.4 mol / L.

The oligomerization step is advantageously carried out at a pressure between 0.1 and 20.0 MPa, preferably between 0.1 and 15.0 MPa, and preferably between 0.5 and 8.0 MPa , and at a temperature between -40 and 250 ° C, preferably between -20 ° C and 150 ° C, preferably between 20 ° C and 100 ° C, and preferably between 30 to 80 ° C.

Preferably, the oligomerization step is a step of dimerization of ethylene into but-1-ene and / or into but-2-ene, of trimerization of ethylene into hex-1-ene, or of tetramerization of ethylene to oct-1-ene.

Advantageously, the oligomerization step can be carried out continuously or discontinuously.

In a preferred embodiment, the constituents of the catalytic composition are injected into a reactor stirred by conventional mechanical means or by external recirculation, in which the olefin reacts, preferably with temperature control. In another embodiment, the alkylaluminum halide and a solution comprising the nickel precursor and optionally a ligand are injected into a reactor stirred by conventional mechanical means or by external recirculation, in which the olefin reacts, of preferably with temperature control. Catalytic composition

The effluent treated in the process according to the invention therefore results from a step of oligomerization of ethylene to olefin using a catalytic composition comprising an alkylaluminum halide and preferably a nickel precursor.

Preferably, the nickel precursor is chosen from nickel (II) chloride, nickel (II) chloride (dimethoxyethane), nickel bromide (II), nickel (II) bromide (dimethoxyethane), fluoride nickel (ll), nickel iodide (ll), nickel sulphate (ll), nickel carbonate (ll), nickel dimethylglyoxime (ll), nickel hydroxide (ll), nickel (ll) hydroxyacetate, nickel (ll) oxalate, nickel (ll) carboxylates such as for example nickel 2-ethylhexanoate, nickel (ll) phenates, nickel (ll) naphthenates , nickel acetate (ll), nickel trifluoroacetate (ll), nickel triflate (ll), nickel stearate (ll), nickel formate (ll), nickel acetylacetonate (ll) , nickel hexafluoroacetylacetonate (ll), TT-allylnickel (ll) chloride, TT-allylnickel (ll) bromide, methallylnickel (ll) chloride dimer, h ³ - allylnickel (ll) hexafluorophosphate ), r hexafluorophosphate | ³ -methallylnickel (II) and 1,5-cyclooctadienyl of nickel (II), in their hydrated form or not, taken alone or as a mixture.

Preferably, the nickel precursor is chosen from nickel sulfate (II), nickel carbonate (II), nickel dimethylglyoxime (II), nickel hydroxide (II), nickel hydroxyacetate ( II), nickel oxalate (II), nickel carboxylates (II) such as for example nickel 2-ethylhexanoate, nickel phenates (II), nickel naphthenates (II), nickel acetate nickel (ll), nickel trifluoroacetate (ll), nickel triflate (ll), nickel acetylacetonate (ll), nickel hexafluoroacetylacetonate (ll), TT-allylnickel (ll) chloride, TT-allylnickel (II) bromide, methallylnickel (II) chloride dimer, q ³ -allylnickel (I) hexafluorophosphate, r | ³ -methallylnickel (II) and 1,5-cyclooctadienyl of nickel (II), in their hydrated form or not, taken alone or as a mixture.

Advantageously, the alkylaluminum halide corresponds to the formula [Al _m R ⁵ _n X _3.n ] ₀ in which

- X is a chlorine or bromine atom, and preferably a chlorine atom, and - m is chosen from 1 or 2,

- n is chosen from 0, 1 or 2,

- o is chosen from 1 or 2

When m is equal to 2, the R ⁵ groups can be identical or different. Preferably, R ⁵ is chosen from a linear or branched alkyl group containing from 2 to 10 carbon atoms, preferably from 2 to 6 carbon atoms, and preferably from 2 to 4 carbon atoms.

Preferably, R ⁵ is an alkyl group chosen from methyl, ethyl, propyl, i-propyl, isopropyl, n-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl. Preferably, R ⁵ is an alkyl group chosen from ethyl, propyl, i-propyl, isopropyl, n-butyl, and tert-butyl.

Advantageously, the alkylaluminum halide is chosen from the group formed by methylaluminum dichloride (MeAICI ₂ ), ethylaluminum dichloride (EtAICI ₂ ), ethylaluminum sesquichloride (Et ₃ Al ₂ CI ₃ ), chloride of diethylaluminum (Et ₂ AICI), diisobutylaluminum chloride (iBu ₂ AICI), isobutylaluminum dichloride (iBuAICI ₂ ), taken alone or as a mixture.

The molar ratio of the alkylaluminum halide to the nickel precursor, denoted Al / Ni, is preferably greater than or equal to 5, more preferably greater than or equal to 6, and preferably less than or equal to 30, preferably less than or equal to 25, more preferably less than or equal to 20.

Advantageously, the catalytic composition can also comprise a ligand chosen from a phosphine.

In another embodiment, the catalytic composition comprises a ligand chosen from a phosphine of formula PR ⁶ R ⁷ R ⁸ in which the groups R ⁶ , R ⁷ and R ⁸ , identical or different to each other, linked or not to each other, are chosen

- from substituted or unsubstituted aromatic groups which may or may not contain heteroelements,

- And / or from cyclic or unsubstituted alkyl groups, substituted or unsubstituted and containing or not containing heteroelements. Advantageously according to the invention, the catalytic composition comprises at least one phosphine ligand of formula PR ⁶ R ⁷ R ⁸ in which the groups R ⁶ , R ⁷ and R ⁸ are identical to one another.

The aromatic groups R ⁶ , R ⁷ and R ⁸ of the phosphine ligand PR ⁶ R ⁷ R ⁸ are preferably chosen from the group formed by the phenyl, o-tolyl, m-tolyl, p-tolyl, mesityl, 3,5 groups. -dimethylphenyl, 4-n-butylphenyl, 4-methoxyphenyl, 2-methoxyphenyl, 3- methoxyphenyl, 4-methoxyphenyl, 2-isopropoxyphenyl, 4-methoxy-3,5-dimethylphenyl, 3,5-di-tert-butyl-4 -methoxyphenyl, 4-chlorophenyl, 3,5-di (trifluoromethyl) phenyl, benzyl, naphthyl, bisnaphthyl, pyridyl, bisphenyl, furanyl, thiophenyl.

The R ⁶ , R ⁷ and R ⁸ alkyl groups of the phosphine ligand PR ⁶ R ⁷ R ⁸ advantageously comprise 1 to 20 carbon atoms, preferably 2 to 15 carbon atoms, preferably between 3 and 10 carbon atoms. Preferably, the alkyl groups R ⁶ , R ⁷ and R ⁸ of the phosphine ligand PR ⁶ R ⁷ R ⁸ are chosen from the group formed by the methyl, ethyl, propyl, isopropyl, n-butyl, tert-butyl, cyclopentyl groups, cyclohexyl, benzyl, adamantyl.

Advantageously, the molar ratio between the phosphine ligand of formula PR ⁶ R ⁷ R ⁸ and the nickel precursor is between 5 and 25, preferably between 5 and 20, more preferably between 5 and 15. Preferably, this ratio molar is between 6 and 30, preferably between 6 and 25, more preferably between 6 and 20, even more preferably between 6 and 15, and even more preferably between 7 and 14.

In a preferred embodiment, each constituent or mixture of constituents of the catalytic composition can be used in a solvent.

The solvent (s) are advantageously chosen from

- ethers, alcohols, halogenated solvents and hydrocarbons, saturated or unsaturated, cyclic or not, aromatic or not, comprising between 1 and 20 carbon atoms, preferably between 1 and 15 carbon atoms and preferably between 4 and 15 carbon atoms,

- ionic liquids.

Preferably, the solvent is chosen from pentane, hexane, cyclohexane, methylcyclohexane, heptane, butane or isobutane, cycloocta-1,5-diene, benzene, toluene, ortho-xylene, mesitylene, ethylbenzene, diethyl ether, tetrahydrofuran, 1,4-dioxane, dichloromethane, dichloroethane, chlorobenzene, dichlorobenzene, methanol, ethanol, pure or as a mixture and ionic liquids.

In the case where the solvent is an unsaturated hydrocarbon, it can be advantageously chosen from the products of the oligomerization reaction.

In the case where the solvent is an ionic liquid, it is advantageously chosen from N-butyl-pyridinium hexafluorophosphate, N-ethyl-pyridinium tetrafluoroborate, pyridinium fluorosulphonate, butyl-3-methyl-1 tetrafluoroborate -imidazolium, butyl-3-methyl-1-imidazolium bis-trifluoromethane-sulfonyl amide, triethylsulfonium bis-trifluoromethane-sulfonyl amide, butyl-3-methyl-1-imidazolium hexafluoro-antimonate , butyl-3-methyl-1-imidazolium hexafluorophosphate, butyl-3-methyl-1-imidazolium trifluoroacetate, butyl-3-methyl-1-imidazolium trifluoromethylsulfonate, trimethylphenylammonium hexafluorophosphate and trimethylphenylammonium hexafluorophosphate tetrabutylphosphonium, tetrabutylphosphonium chloride, N-butylpyridinium chloride, ethylpyridinium bromide, butyl-3-methyl-1-imidazolium chloride, diethylpyrazolium chloride, pyridinium hydrochloride, trim etethylphenylammonium chloride chloride of butylmethylpyrrolidinium.

Separation step in an "optional" distillation section

Typically, olefins from the ethylene oligomerization step have a higher molecular weight than unreacted ethylene. In general, unreacted ethylene has a lower boiling point than that of oligomers resulting from the oligomerization step, such as but-1-ene, but-2-enes. , hex-1-ene or oct-1-ene.

According to the invention, any separation means known to those skilled in the art making use of these differences in volatility and molecular weight between the products to be separated can be used in the separation step. Advantageously according to the invention, the separation means used are distillation columns of any type.

The process according to the invention optionally comprises a separation step advantageously comprising a distillation section. Preferably, according to the process of the invention, the gas fractions resulting from the thermal separation step, comprising in particular the unconverted ethylene, the products formed and the solvent, are sent in mixed gas / liquid form to the distillation section.

The distillation section advantageously comprises at least three distillation columns, preferably at least four distillation columns. According to a preferred variant of the invention, the distillation section comprises four distillation columns.

The following examples illustrate the invention without limiting its scope.

Examples

Implementation of the oligomerization step

93 mL of n-heptane are introduced into a reactor, previously dried under vacuum and placed under an ethylene atmosphere, then 6 mL of a solution containing the nickel precursor Ni (2-ethylhexanoate) ₂ (noted Ni (2- EH) ₂ , 40 pmol and tricyclohexylphosphine (PCy ₃ ) (400 pmol). Between 1 and 2 g of ethylene are then dissolved in the reactor, stirring is started and the temperature programmed at 40 ° C. After degassing of the Reactor, the temperature is programmed at 45 ° C. (test temperature). 1 mL of an ethylaluminum dichloride solution (600 pmol) is then introduced. The reactor is brought to the test pressure (2 MPa). L The stirring is started, the reaction is carried out under pressure control, the supply of ethylene making it possible to maintain the pressure at the test pressure. After having reached the desired consumption of ethylene, the supply of ethylene is then cut off. liquid effluent is neutralized by a neutralization system. In the following examples, the effluent The gaseous elements are quantified and qualified by gas chromatography (GC), the liquid phases are weighed and qualified by GC.

Example 1: thermal separation step with 2 vaporization steps in series (according to the invention) The neutralized effluent obtained at the end of the oligomerization step as described above is compressed to a pressure of 3, 25 MPa then partially vaporized by heating in a heat exchanger to a temperature of 115 ° C. The gas fraction is then separated from the liquid fraction in a flask. The gas fraction is sent to a distillation section and the liquid fraction is sent to a second flash. The liquid fraction resulting from the first flash is expanded to a pressure of 1.35 MPa. Said expanded liquid fraction is then partially vaporized by heating in a heat exchanger to a temperature of 117 ° C. The gas fraction is then separated from the liquid fraction in a flask. The gas fraction is sent to the distillation section and the liquid phase comprising the neutralized catalyst is sent to an incinerator.

Table 1 below shows the conditions at the different stages as well as the composition of each stream. The last liquid effluent from the second flash comprises the hetero-elements from the catalytic system and from the inhibitor (s) (Ni, P, Al, Cl, O, N, etc.) as well as their associated organic part.

It appears that the implementation of a thermal separation step comprising two flashes in series makes it possible to separate the neutralized catalyst from the products of interest by maximizing the quantity of olefins of interest (but-1-ene noted B1 and but-2-ene denoted B2) sent to a distillation section, which maximizes the productivity of the oligomerization process.

In addition, no isomerization problem is observed during said thermal separation step, which makes it possible to send more than 99% of the butenes formed during the oligomerization step to the distillation section without degradation of selectivity.

Table 1: Operating conditions and compositions of the incoming and outgoing streams of the spent catalyst separation section

Example 2: thermal separation step with 3 vaporization steps in series (according to the invention) The neutralized effluent obtained at the end of the oligomerization step as described above is compressed to a pressure of 3, 25 MPa then partially vaporized by heating in a heat exchanger to a temperature of 115 ° C. The gas fraction is then separated from the liquid fraction in a flask. The gas fraction is sent to a distillation section and the liquid fraction is sent to a second flash. The liquid fraction resulting from the first flash is expanded to a pressure of 1.3 MPa. Said expanded liquid fraction is then partially vaporized by heating in a heat exchanger to a temperature of 107 ° C. The gas fraction is then separated from the liquid fraction in a flask. The gas fraction is sent to the distillation section and the liquid fraction is sent to a third flash. The liquid fraction resulting from the second flash is expanded to a pressure of 0.5 MPa. Said expanded liquid fraction is then vaporized by heating in a heat exchanger to a temperature of 98 ° C.

Table 2 below shows the conditions at the different stages as well as the composition of each stream. The last liquid effluent from the third flash comprises the hetero-elements from the catalytic system and from the inhibitor (s) (Ni, P, Al, Cl, O, N, etc.) as well as their associated organic part.

Advantageously in this embodiment of the separation, no isomerization of the desired olefins is observed, which makes it possible to maximize the recovery of the products of interest.

Table 2: Operating conditions and compositions of the incoming and outgoing streams of the spent catalyst separation section

Example 3: Neutralization step

Neutralization step The effluent obtained at the end of the oligomerization step as described above is brought into contact with a neutralization system comprising 2-ethylhexylamine and 2-ethylhexanol, at a temperature of 50 ° C. at different molar ratios of amine and alcohol to ethylaluminum dichloride (noted Al). The results obtained are presented in the table below. Isomerization is followed by CPG.

Table 3: Conditions during the neutralization step nd:: not detected

Thus the neutralization system according to the invention, and preferably the neutralization system comprising an alcohol and an amine, makes it possible to ensure the neutralization of the mixture while retaining the selectivity for the desired olefins resulting from the oligomerization step and by preventing corrosion problems linked to the presence of chlorine.

Claims

1. A method of treating an effluent resulting from an oligomerization step, comprising a step of neutralizing said effluent to deactivate a catalytic composition followed by a step of thermal separation of the neutralized effluent comprising: a first vaporization step implementation at a pressure of between 2.0 and 5.0 MPa and at a temperature of between 70 and 150 ° C, making it possible to obtain a liquid fraction sent to a second vaporization step, and a fraction gaseous, preferably sent to a distillation section, said second vaporization step is carried out at a pressure between 0.5 and 3.0 MPa and at a temperature between 70 and 150 ° C, making it possible to obtain of a liquid fraction and a gaseous fraction, preferably said gaseous fraction is sent to the distillation section, in which the pressure of the first vaporization stage is greater than the pressure of the second stage d e vaporization, preferably at least 0.5 MPa, preferably at least 1.0 MPa, preferably at least 1.5 MPa.

2. Method according to claim 1 wherein the first vaporization step is carried out at a pressure between 2.0 and 4.5 MPa, preferably 2.5 and 4.0 MPa and at a temperature between 80 and 140 ° C preferably between 90 and 130 ° C.

3. Method according to any one of the preceding claims wherein the second vaporization step is carried out at a pressure between 0.8 and 3.0 MPa, preferably 1.0 and 2.0 MPa and at a temperature. between 80 and 140 ° C, preferably between 90 and 130 ° C.

4. Method according to any one of the preceding claims wherein the thermal separation step implements a third vaporization step in which is sent the liquid fraction from the second vaporization step, said third vaporization step is put into operation. works at a pressure between 0.1 and 1.5 MPa and at a temperature between 70 and 200 ° C, allowing the production of a liquid fraction and a gaseous fraction, preferably said gaseous fraction is sent to the distillation section, and the pressure of the second vaporization step is greater than the pressure of the third vaporization step, preferably at least 0.5 MPa, preferably at least 0.8 MPa.

5. Method according to the preceding claim wherein the third vaporization step is carried out at a pressure between 0.3 and 1.2 MPa, preferably between 0.4 and 1.0 MPa and at a temperature between 80 and 140 ° C, preferably between 80 and 130 ° C.

6. Method according to any one of the preceding claims wherein the first step and / or the second step and / or the third thermal separation step are implemented by means of a flash balloon, preferably coupled with a heat exchanger.

7. Method according to any one of the preceding claims wherein the gaseous fraction resulting from the first vaporization step and / or the gaseous fraction resulting from the second vaporization step and / or the gaseous fraction resulting from the third vaporization step are liquefied by decreasing the temperature, so as to reach a pressure between 2.0 and 5.0 MPa and preferably to be sent to the distillation section.

8. The method of claim 7 wherein the temperature for liquefying the gas fraction (s) resulting from the vaporization steps is between 0 and 60 ° C.

9. A method according to any preceding claim wherein the oligomerization step uses a catalytic composition comprising an alkylaluminum halide and optionally a nickel precursor.

10. The method of claim 9 wherein the alkylaluminum halide has the formula [Al _m R ⁵ _n X3- _n ] ₀ wherein

- X is a chlorine or bromine atom, and preferably a chlorine atom, and

- m is chosen from 1 or 2,

- n is chosen from 0, 1 or 2,

- o is chosen from 1 or 2.

11. A method according to any one of claims 9 and 10 wherein the effluent from an oligomerization step contains an alkylaluminum halide content of between 0.01 and 100,000 ppm by weight.

12. Method according to any one of the preceding claims wherein the step of neutralizing the effluent from the oligomerization step is carried out by contacting said effluent with a neutralization system comprising:

* an alkyl group, linear or branched, containing from 2 to 20 carbon atoms,

* an aryl group containing from 5 to 30 carbon atoms; and / or - an amine of general formula NR ² R ³ R ⁴ , in which the groups R ² , R ³ and

R ⁴ , identical or different, are independently chosen from:

* a hydrogen,

13. The method of claim 12 wherein the temperature of contacting the neutralization system and the effluent from the oligomerization step is that at which said oligomerization step takes place.

14. A method according to any one of claims 12 to 13 wherein the neutralization system comprises an alcohol of general formula R ¹ OH and an amine of general formula NR ² R ³ R ⁴ .

15. The method of claim 14 wherein the molar ratio of amine to alcohol is between 0.5 and 100.