Title:
Process for separating oxygen-containing compounds contained in a hydrocarbon feed, employing an ionic liquid
Kind Code:
A1


Abstract:
In order to separate oxygen-containing compounds contained in a hydrocarbon feed containing 1 to 100 carbon atoms and having any distribution of chemical categories, a process is carried out in which:
    • said hydrocarbon feed is brought into contact with an extraction phase which contains at least one non-aqueous ionic liquid with general formula Q+A, the proportion of ionic liquid in the extraction phase representing at least 25% by weight; the extraction effluent is separated into said extraction phase which contains at least one ionic liquid and at least all or a portion of the oxygen-containing compounds initially present in the hydrocarbon feed, and into the hydrocarbon feed which is depleted in oxygen-containing compounds.



Inventors:
Vallee, Christophe (Villeurbanne, FR)
Biard, Adeline (Villeurbanne, FR)
Olivier-bourbigou, Helene (Saint Genis Laval, FR)
Application Number:
11/222034
Publication Date:
04/06/2006
Filing Date:
09/09/2005
Primary Class:
Other Classes:
208/292, 208/293, 208/289
International Classes:
C10G29/00; C10G21/00; C10G21/27
View Patent Images:



Primary Examiner:
BOYER, RANDY
Attorney, Agent or Firm:
MILLEN, WHITE, ZELANO & BRANIGAN, P.C. (ARLINGTON, VA, US)
Claims:
1. A process for separating oxygen-containing compounds contained in a hydrocarbon feed containing 1 to 100 carbon atoms, and with any chemical category distribution, said process being characterized in that: said hydrocarbon feed containing oxygen-containing compounds (Cox) is brought into contact in a contacter (A) with an extraction phase (Pex) which contains at least one non-aqueous ionic liquid with general formula Q+A, the proportion of ionic liquid in the extraction phase representing at least 25% by weight; the effluent from the unit (A) is separated in a decanting unit (B) into said extraction phase which contains at least one ionic liquid and at least all or a portion of the oxygen-containing compounds initially present in the hydrocarbon feed, and into the hydrocarbon feed depleted in oxygen-containing compounds (Cpur).

2. A process according to claim 1, in which the effluent from the decanting unit (B) is introduced into the separation unit (C) from which the extraction phase containing at least one ionic liquid and a minor portion of the oxygen-containing compounds, and the major portion of the oxygen-containing compounds (Cext) are separated.

3. A process according to claim 1, in which the extraction phase from the separation unit (C) is reintroduced into the contacter (A) with the hydrocarbon feed to be treated.

4. A process according to claim 1, characterized in that in the non-aqueous ionic liquid with formula Q+A, the anions A are selected from halides, nitrate, sulphate, alkylsulphates, phosphate, alkylphosphates, acetate, halogenoacetates, tetrafluoroborate, tetrachloroborate, hexafluorophosphate. trifluoro-tris-(pentafluoroethyl)phosphate, hexafluoroantimonate, fluorosulphonate, alkyl sulphonates, perfluoroalkylsulphonates, bis(perfluoroalkylsulphonyl)amides, tris-trifluoromethylsulphonyl methylide with formula C(CF3SO2)3, bis-trifluoromethylsulphonyl methylide with formula HC(CF3SO2)3, arenesulphonates, optionally substituted with halogen or halogenalkyl groups, the tetraphenylborate anion and tetraphenylhorate anions the aromatic rings of which are substituted, tetra-(trifluoroacetoxy)-borate, bis-(oxalato)-borate, dicyanamide, tricyanomethylide, and the tetrachloroaluminate anion.

5. A process according to claim 1, characterized in that cation Q+ is selected from quaternary phosphonium, ammonium, guanidinium and/or sulphonium cations.

6. A process according to claim 5, characterized in that quaternary ammonium and/or phosphonium cation Q+ has one of general formulae NR1R2R3R4+ and PR1R2R3R4+ or one of general formulae R1R2N═CR3R4+ and R1R2P═C R3R4+ in which R1, R2, R3 and R4, which may be identical or different, each represent hydrogen of a hydrocarbyl residue containing 1 to 30 carbon atoms.

7. A process according to claim 6, characterized in that R1, R2, R3 and R4 each represent an alkyl group, a saturated or non saturated group, a cycloalkyl or aromatic group or an aryl or aralkyl group, which may be substituted.

8. A process according to claim 6, characterized in that at least one of groups R1, R2, R3 and R4 carries one or more functions selected from the following: —CO2R, —C(O)R, —OR, —C(O)NRR′, —C(O)N(R)NR′R″, —NRR′, —SR, —S(O)R, -S(O)2R, —SO3R, —CN, —N(R)P(O)R′R′, in which R, R′ and R″, which may be identical or different, each represent hydrogen or hydrocarbyl radicals containing 1 to 30 carbon atoms.

9. A process according to claim 5, characterized in that the ammonium and/or phosphonium ion is derived from a nitrogen-containing and/or phosphorus-containing heterocycles comprising 1, 2 or 3 nitrogen and/or phosphorus atoms, with general formulae embedded image in which the cycles are constituted by 4 to 10 atoms, preferably 5 to 6 atoms, and R1 and R2, which may be identical or different, are as defined above.

10. A process according to claim 5, characterized in that the quaternary ammonium or phosphonium cation has one of the following formulae:
R1R2+N═CR3—R7—R3C═N+R1R2 and R1R2+P═CR3—R7—R3C═P+R1R2 in which R1, R2 and R3, which may be identical or different, are as defined above and R7 represents an alkylene or phenylene residue.

11. A process according to claim 6, characterized in that the groups R1, R2, R3 and R4 represent methyl, ethyl, propyl, isopropyl, butyl, secondary butyl, tertiary butyl, amyl, phenyl, benzyl or 2-hydroxyethyl radicals and R7 represents a methylene, ethylene, propylene or phenylene group.

12. A process according to claim 5, characterized in that the quaternary ammonium and/or phosphonium cation Q+ is selected from the group formed by N-butylpyridinium, N-ethylpyridinium, pyridinium, 3-ethyl-1-methylimidazolium, 3-butyl-1-methylimidazolium, 3-hexyl-1-methylimidazolium, 3-butyl-1,2-dimethylimidazolium, the 1-(2-hydroxyethyl)-3-methylinidazolium cation, the 1-(2-carboxyethyl)-3-methylimidazolium cation, diethylpyrazolium, N-butyl-N-methylpyrrolidinium, N-butyl-N-methylmorpholinium, trimethylphenylammonium, tetrabutylphosphonium and tributyl-tetradecylphosphonium.

13. A process according to claim 5, characterized in that the quaternary sulphonium and/or quaternary guanidinium cations have one of the following general formulae:
SR1R2R3+ or C(NR1R2)(NR3R4)(NR5R6)+ in which R1, R2, R3, R4, R5 and R6, which may be identical or different, each representing hydrogen or a hydrocarbyl residue containing 1 to 30 carbon atoms.

14. A process according to claim 13, characterized in that R1, R2, R3, R4, R5 and R6 each represent an alkyl group, a saturated or non saturated group, a cycloalkyl or aromatic group or an aryl or aralkyl group, which may be substituted.

15. A process according to claim 13, characterized in that at least one of groups R1, R2, R3 and R4 carries hydrocarbyl radicals carrying one or more functions selected from the following: —CO2R, —C(O)R, —OR, —C(O)NRR′, —C(O)N(R)NR′R″, —NR′R″, —SR, —S(O)R, —S(O)2R, —SO3R, —CN, —N(R)P(O)R′R′, —PRR′, —P(O)RR′, —P(OR)(OR′), P(O)(OR)(OR′), in which R, R′ and R″, which may be identical or different, each represent hydrogen or hydrocarbyl radicals containing 1 to 30 carbon atoms.

16. A process according to claim 1, characterized in that the non-aqueous ionic liquid is 3-butyl-1-methylimidazolium bis(trifluoromethylsulphonyl)amide, 3-butyl-1,2-dimethylimidazolium bis(trifluoromethylsulphonyl)amide, N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulphonyl)amide, 3-butyl-1-methylimidazolium tetrafluoroborate, 3-butyl-1,2-dimethylimidazolium tetrafluoroborate, 3-ethyl-1-methylimidazolium tetrafluoroborate, 3-butyl-1-methylimidazolium hexafluoroantimonate, 3-butyl-1-methylimidazolium trifluoroacetate, 3-ethyl-1-methylimidazolium triflate, 1-(2-hydroxyethyl)-3-methylimidazolium bis(trifluoromethylsulphonyl)amide, 1-(2-carboxyethyl)-3-methylimidazolium bis(trifluoromethylsulphonyl)amide, and N-butyl-N-methylmorpholinium bis(trifluoromethylsulphonyl)amide.

17. A process for separating oxygen-containing compounds contained in a hydrocarbon feed according to claim 1, in which the contacter (A) and the decanting unit (B) are combined in a single piece of equipment.

18. A process according to claim 1 comprising separating oxygen-containing compounds contained in a hydrocarbon cut composed mainly of olefins and paraffins.

19. A process according to claim 18 comprising separating oxygen-containing compounds contained in a hydrocarbon cut containing 0 to 50% by weight of olefins and 50% to 100% by weight of paraffins.

20. A process according to claim 1 comprising separating oxygen-containing compounds contained in Fischer-Tropsch synthesis effulents, said oxygen-containing compounds containing 1 to 50 carbon atoms.

Description:

FIELD OF THE INVENTION

The present invention relates to the field of purifying hydrocarbon feeds. In particular, the present invention relates to separating oxygen-containing compounds contained in a hydrocarbon cut. The present invention is of particular application in separating alcohols and acids contained in a hydrocarbon cut mainly composed of paraffins and olefins. More particularly still, the present invention is highly suitable to separating alcohols and acids contained in an effluent from the Fischer-Tropsch reactor.

Separating oxygen-containing compounds contained in effluents from the Fischer-Tropsch reactor is necessary as said oxygen-containing compounds inhibit or reduce the activity of catalysts used for treating and upgrading such cuts.

The present invention concerns a process for separating oxygen-containing compounds contained in any hydrocarbon cut using ionic liquids. More particularly, the invention is applicable to the treatment of effluents from the Fischer-Tropsch synthesis.

PRIOR ART

In the Fischer-Tropsch process, synthesis gas (mixture of CO+H2) is catalytically transformed into oxygen-containing products and into essentially linear hydrocarbons, the length of the carbon chain possibly being from 1 to more than 100.

Said Fischer-Tropsch synthesis effluents are generally free of heteroatomic impurities such as sulphur, nitrogen or metals. They also contain few or practically no aromatics, naphthenes and more generally cyclic compounds, in particular in the case of a cobalt catalyst.

In contrast, such effluents may contain a non negligible amount of oxygen-containing products which, expressed as a percentage by weight, is generally less than 20% in total, and also an amount of unsaturated compounds (generally olefinic compounds) which is generally less than 50% by weight.

In the case of effluents from the Fischer-Tropsch synthesis, the oxygen-containing compounds are more particularly alcohols and acids.

Chemical conversion of synthesis gas into hydrocarbons using the Fischer-Tropsch process, commonly known as the Fischer-Tropsch synthesis, is carried out in the presence of a catalyst based on at least one group VIII metal.

The catalysts used may be of different natures, but usually contain bulk or supported iron or cobalt.

The supports used are generally based on silica, alumina or titanium oxide.

The Fischer-Tropsch synthesis is generally operated at temperatures in the range 200° C. to 300° C., and at pressures in the range 1 MPa to 8 MPa.

Using a Fe/Mn/Zn catalyst at a pressure of 3 to 6 MPa can result in high selectivities for olefins and oxygen-containing compounds (principally alcohols) with a chain length of 2 to more than 30. The invention is thus particularly suitable for the treatment of that type of Fischer-Tropsch synthesis effluents.

U.S. Pat. No. 4,686,317 discloses a process for eliminating oxygen-containing impurities contained in a light hydrocarbon cut (C2 to C9). It comprises extracting oxygen-containing compounds using a heavy polar organic solvent, washing the hydrocarbons with water to recover the dissolved solvent, and mixing the phase derived from the extraction and the wash water to recover the heavy polar organic solvent. That process does not consider recovering the extracted oxygen-containing compounds.

US-A-2004/0044263 discloses a process for separating oxygen-containing compounds from a hydrocarbon mixture containing paraffins, olefins and oxygen-containing compounds. It uses liquid-liquid extraction with a polar solvent and an apolar organic counter-solvent. However, that process suffers from a number of disadvantages. Firstly, it is limited to C8 and higher hydrocarbons and to C4 and higher alcohols, and secondly, it necessitates separating the olefins and paraffins from the apolar organic solvent by distillation.

The present invention concerns a process for separating oxygen-containing compounds contained in any hydrocarbon cut (in particular a cut which may contain hydrocarbons containing less than 8 carbon atoms, and alcohols containing less than 4 carbon atoms) using ionic liquids.

Non-aqueous ionic liquids with general formula Q+A, initially developed by electrochemists, are now being used ever more widely as solvents and catalysts for catalytic or enzymatic organic reactions, as solvents for liquid-liquid separations, or for the synthesis of novel materials (see, for example, H Olivier-Bourbigou, L Magna, J Mol Catal A, Chem 2002, vol 182, p 419).

The popularity of that novel class of solvents is due to their physico-chemical properties in that they can be modulated by changing the nature of the anion and the cation and their very low vapour tension, to produce alternative solvents which are better for the environment than conventional volatile organic solvents.

Because of their completely ionic nature and their polar nature, such ionic liquids have proved to be very good solvents for ionic or polar compounds, a property which in particular allows easy separation of oxygen-containing compounds from hydrocarbon cuts.

US-A-2003/0125599 uses ionic liquids to separate the olefins contained in a mixture of non olefinic compounds such as paraffins, aromatics or oxygen-containing compounds. However, this technique requires a metal salt in addition to an ionic liquid, for example a copper or silver salt. Further, that technique cannot separate alcohols from an olefin-paraffin mixture.

WO-A-02/074718 describes the use of ionic liquids as third parties (also known as entrainers) for the separation of azeotropic mixtures or compounds with similar boiling points. However, that extractive distillation method requires a temperature equal to or above the boiling point of the most volatile compound, which leads to a high energy cost. Further, it is not applicable to separating alcohols contained in a hydrocarbon feed as it is essentially based on separation as a function of boiling point.

WO-A-03/070667 concerns a process for liquid-liquid extraction using ionic liquids, but does not describe the separation of oxygen-containing compounds contained in a mixture of hydrocarbons.

BRIEF DESCRIPTION OF THE FIGURE

FIG. 1 shows a flow diagram of the process of the invention in which the optional unit (C) is shown in dotted lines.

Units (A) and (B) may be distinct or combined.

BRIEF DESCRIPTION OF THE INVENTION

The invention concerns a process for separating oxygen-containing compounds contained in any hydrocarbon feed, which uses an extraction phase containing at least one ionic liquid. The term “any” means that the hydrocarbon feed may contain 1 to 100 carbon atoms with a distribution of chemical categories (paraffins, olefins, acetylenes, naphthenes and aromatics) which may itself be of any type (i.e. each chemical family may represent any percentage in the mixture).

The term “extraction phase” means the phase containing at least one ionic liquid which, at the end of the extraction process, will recover all or a portion of the oxygen-containing compounds initially present in the hydrocarbon feed.

Oxygen-containing compounds which may generally be encountered in a hydrocarbon feed are alcohols, ethers, aldehydes or ketones, acetals, acids or esters, water or a mixture of these compounds.

In the case of Fischer-Tropsch synthesis effluents, said oxygen-containing compounds are more particularly alcohols and acids.

Within the context of the invention, the oxygen-containing compounds will contain 1 to 100 carbon atoms, preferably 1 to 50 carbon atoms, and more preferably 1 to 20 carbon atoms.

The separation process of the present invention may briefly be described in connection with FIG. 1 as follows:

    • the hydrocarbon feed containing oxygen-containing compounds (Cox) is brought into contact in a contacting unit (or contacter) (A) with an extraction phase (Pex) which contains at least one non-aqueous ionic liquid with general formula Q+A, the proportion of ionic liquid in the extraction phase representing at least 25% by weight;
    • the effluent from the unit (A) is separated in a decanting unit (B) into said extraction phase, which contains at least one ionic liquid and: at least all or a portion of the oxygen-containing compounds initially present in the hydrocarbon feed, and into the hydrocarbon feed depleted in oxygen-containing compounds (Cpur).

In a variation of the process of the invention, said extraction phase from the decanting unit (B) may be introduced into the separation unit (C) from which the extraction phase containing at least one ionic liquid and a minor portion of the oxygen-containing compounds, and the major portion of the oxygen-containing compounds (Cext) are separated.

In a further variation of the process of the invention, the extraction phase from the separation unit (C) may be reintroduced into the contacter (A) with the hydrocarbon feed to be treated.

Finally, in a further variation of the process of the invention, the contacter unit (A) and the decanting unit (B) may be combined in a single piece of equipment, for example in a liquid-liquid extraction column operating in counter-current mode.

The process of the invention is applicable to separating oxygen-containing compounds contained in a hydrocarbon cut primarily composed of olefins and paraffins. More particularly, it may be applicable to separating oxygen-containing compounds contained in a hydrocarbon cut containing 0 to 50% by weight of olefins and 50% to 100% by weight of paraffins.

Finally, the process of the invention is particularly suitable for separating oxygen-containing compounds contained in Fischer-Tropsch synthesis effluents, said oxygen-containing compounds containing 1 to 100 carbon atoms, preferably 1 to 50 carbon atoms, and more preferably 1 to 20 carbon atoms.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a process for separating oxygen-containing compounds contained in any hydrocarbon feed, said process being characterized in that:

    • said hydrocarbon feed containing oxygen-containing compounds is brought into contact with an extraction phase which contains at least one non-aqueous ionic liquid with general formula Q+A, the proportion of ionic liquid in the extraction phase representing at least 25% by weight; and
    • in that said extraction phase, which contains at least one ionic liquid and at least all or a portion of the oxygen-containing compounds initially present in the hydrocarbon feed, is separated from the hydrocarbon feed depleted in oxygen-containing compounds.

In a variation of the present invention, the extraction phase, which contains at least one ionic liquid and all or a portion of the oxygen-containing compounds initially present in the hydrocarbon feed, may be regenerated.

In this case, said extraction phase is eliminated at least partially from the oxygen-containing compounds it contains and said extraction phase is re-used by bringing it again into contact with the hydrocarbon feed. Further, all or part-of the oxygen-containing compounds contained in the extraction phase may be recovered.

One of the aims of the present invention is to reduce the amount of oxygen-containing compounds in a hydrocarbon feed which may comprise all chemical categories: paraffins, olefins, acetylenes, naphthenes and aromatics in any proportions.

The present invention is particularly advantageous when the hydrocarbon feed comprises at least some olefins, as said olefins are not modified during said process.

The separation process of the invention does not cause any olefin isomerization, in particular no isomerization of alpha olefins to internal olefins.

The present invention is particularly advantageous when the hydrocarbon feed is constituted at least in part by olefins and paraffins, as the proportion of olefins with respect to the paraffins is not significantly modified.

The present invention is also particularly advantageous in that, because of the non volatile nature of ionic liquids, it is very easy to recover the oxygen-containing compounds extracted by distillation or stripping the extraction phase. This point constitutes a distinct advantage over processes in which the solvent has to be recovered by expensive distillation.

In the non-aqueous ionic liquid with formula Q+Aemployed in the extraction phase, the anions A are preferably selected from halides, nitrate, sulphate, alkylsulphates, phosphate, alkylphosphates, acetate, halogenoacetates, tetrafluoroborate, tetrachloroborate, hexafluorophosphate, trifluoro-tris-(pentafluoroethyl)phosphate, hexafluoroantimonate, fluorosulphonate, alkyl sulphonates (for example methylsulphonate), perfluoroalkylsulphonates (for example trifluoromethylsulphonate), bis(perfluoroalkylsulphonyl)amides (for example bis-trifluoromethylsulphonyl amide with formula N(CF3SO2)2), tris-trifluoromethylsulphonyl methylide with formula C(CF3SO2)3, bis-trifluoromethylsulphonyl methylide with formula HC(CF3SO2)3, arenesulphonates, optionally substituted with halogens or halogenalkyl groups, the tetraphenylborate anion and tetraphenylborate anions the aromatic rings of which are substituted, tetra-(trifluoroacetoxy)-borate, bis-(oxalato)-borate, dicyanamide, tricyanomethylide, and the tetrachloroaluminate anion.

Cations Q+ are preferably selected from the group formed by quaternary phosphonium, quaternary ammonium, quaternary guanidinium and/or quaternary sulphonium. In the formulae below, R1, R2, R3, R4, R5 and R6 represent hydrogen (with the exception of the NH4+ cation NR1R2R3R4), preferably a single substituent representing hydrogen, or hydrocarbyl radicals containing 1 to 30 carbon atoms, for example alkyl groups, saturates or unsaturates, cycloalkyls or aromatics, aryls or aralkyls, which may be substituted, containing 1 to 30 carbon atoms.

R1, R2, R3, R4, R5 and R6 may also represent hydrocarbyl radicals carrying one or more functions selected from the following: —CO2R, —C(O)R, —OR, —C(O)NRR′, —C(O)N(R)NR′R″, —NRR′, —SR, —S(O)R, —S(O)2R, —SO3R, —CN, —N(R)P(O)R′R′, —PRR′, —P(O)RR′, —P(OR)(OR′), —P(O)(OR)(OR′) in which R, R′ and R″, which may be identical or different, each represent hydrogen or hydrocarbyl radicals containing 1 to 30 carbon atoms.

The quaternary sulphonium and quaternary guanidinium cations preferably have one of the following general formulae:
SR1R2R3+ or C(NR1R2)(NR3R4)(NR5R6)+
in which R1, R2, R3, R4, R5 and R6, which may be identical or different, are as defined above.

The quaternary ammonium and/or phosphonium ions Q+ preferably have one of general formulae NR1R2R3R4+ and PR1R2R3R4+ or one of general formulae R1R2N═CR3R4+ and R1R2P═CR3R4+ in which R1, R2, R3 and R4, which may be identical or different, are as defined above.

The ammonium and/or phosphonium cations may also be derived from nitrogen-containing and/or phosphorus-containing heterocycles comprising 1, 2 or 3 nitrogen and/or phosphorus atoms, with general formulae: embedded image
in which the cycles are constituted by 4 to 10 atoms, preferably 5 to 6 atoms, R1 and R2, which may be identical or different, being as defined above.

The quaternary ammonium or phosphonium cation may also have one of the following formulae:
R1R2+N═CR3—R7—R3C═N+R1R2 and R1R2+P═CR3—R7—R3C═P+R1R2
in which R1, R2 and R3, which may be identical or different, are defined as above and R7 represents an alkylene or phenylene radical.

Particular groups R1, R2, R3 and R4 which may be mentioned are methyl, ethyl, propyl, isopropyl, primary butyl, secondary butyl, tertiary butyl, amyl, phenyl or benzyl radicals; R7 may be a methylene, ethylene, propylene or phenylene group.

Preferably, the ammonium and/or phosphonium cation Q+ is preferably selected from the group formed by N-butylpyridiniun, N-ethylpyridinium, pyridinium, 3-ethyl-1-methylimidazolium, 3-butyl-1-methylimidazolium, 3-hexyl-1-methylimidazolium, 3-butyl-1,2-dimethylimidazolium, the 1-(2-hydroxyethyl)-3-methylimidazolium cation, the 1-(2-carboxyethyl)-3-methylimidazolium cation, diethylpyrazolium, N-butyl-N-methylpyrrolidinium, N-butyl-N-methylmorpholinium, trimethylphenylammonium, tetrabutylphosphonium and tributyl-tetradecylphosphonium.

Examples of salts which may be used in the invention that can be cited are 3-butyl-1-methylimidazolium bis(trifluoromethylsulphonyl)amide, 3-butyl-1,2-dimethylimidazolium bis(trifluoromethylsulphonyl)amide, N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulphonyl)amide, 3-butyl-1-methylimidazolium tetrafluoroborate, 3-butyl-1,2-dimethylimidazolium tetrafluoroborate, 3-ethyl-1-methylimidazolium tetrafluoroborate, 3-butyl-1-methylimidazolium hexafluoroantimonate, 3-butyl-1-methylimidazolium trifluoroacetate, 3-ethyl-1-methylimidazolium triflate, 1-(2-hydroxyethyl)-3-methylimidazolium bis(trifluoromethylsulphonyl)amide, 1-(2-carboxyethyl)-3-methylimidazolium bis(trifluoromethylsulphonyl)amide, and N-butyl-N-methylmorpholinium bis(trifluoromethylsulphonyl)amide. These salts may be used alone or as a mixture.

In the present invention, the proportion of ionic liquid with formula Q+A in the extraction phase represents at least 25% by weight.

The extraction phase may also contain ionic liquid(s), one or more polar organic solvents with a relative dielectric constant of more than 5, or organic compounds contained in the hydrocarbon feed and partially or completely soluble in the ionic liquid.

The oxygen-containing compounds present in the hydrocarbon feed may be alcohols, ethers, aldehydes or ketones, acetals, acids or esters, water or a mixture of said compounds. Preferably, the oxygen-containing compounds will contain 1 to 100 carbon atoms, more preferably 1 to 50 carbon atoms, and still more preferably 1 to 20 carbon atoms.

Preferably, the oxygen-containing compounds will be alcohols or acids.

Preferably, the alcohols will represent 1% to 20% by weight of the hydrocarbon feed, and the acids will represent 0 to 50% by weight of oxygen-containing compounds.

In the hydrocarbon feed, the hydrocarbons may be paraffins, olefins, aromatics, acetylenics, naphthenes or any mixture of said compounds.

Preferably, the hydrocarbons will contain between 1 and 100 carbon atoms, preferably between 1 and 50 carbon atoms, and more preferably between 1 and 20 carbon atoms.

Preferably, the hydrocarbons are primarily constituted by olefins and paraffins.

Preferably, the olefins will represent 0 to 50% by weight of the hydrocarbon feed, and the paraffins will represent 50% to 100% by weight of the hydrocarbon feed, the sum or the two values being equal to 100.

The present invention will be particularly advantageous in the case in which the hydrocarbon feed is constituted by the effluent from a Fischer-Tropsch synthesis reactor.

The contact of the hydrocarbon feed with the extraction phase containing at least one ionic liquid may be made continuously or in a fractionated manner.

Separating the extraction phase containing at least one ionic liquid from the hydrocarbon feed depleted in oxygen-containing compounds may be carried out continuously, semi-continuously or batchwise.

Advantageously, contact and separation of the hydrocarbon feed and the extraction phase containing at least one ionic liquid may be carried out using an industrial liquid-liquid extraction apparatus.

Examples which may be cited are mixer-decanters (with gravity decanting and/or by coalescence and/or electrostatically), column extractors (baffle columns, plate columns, packed columns, mechanically, pressurized or agitated stirred column), or centrifugal extractors (staged or continuous differentials).

In a variation of the process of the invention, the extraction phase containing at least one ionic liquid may be regenerated after the contact and separation steps.

In a variation of the process of the invention, the compounds extracted from the hydrocarbon feed, in particular oxygen-containing compounds, may be recovered.

Regeneration of the extraction phase containing at least one ionic liquid and recovery of the compounds extracted from the hydrocarbon feed, in particular oxygen-containing compounds, may be carried out by distillation, stripping, extraction, precipitation or any other separation method known to the skilled person.

Preferably, regeneration of the extraction phase containing at least one ionic liquid and recovery of the compounds extracted from the hydrocarbon feed, in particular oxygen-containing compounds, are carried out by distillation or stripping.

The diagram in FIG. 1 describes the most common implementation of the process of the invention. However, the scope of the invention is not limited thereto.

The hydrocarbon feed containing the oxygen-containing compounds to be treated (Cox in FIG. 1) is introduced via line 1 into a contacter (A) where it is mixed with an extraction phase containing at least one ionic liquid (Pex) in FIG. 1) introduced via line 2.

The effluent from the contacter (A) is sent to the decanting unit (B) via line 3 The fraction containing the hydrocarbon feed depleted in oxygen-containing compounds (Cpur) is separated from the extraction phase. This fraction Cpur is evacuated via line 4.

In an optional embodiment, the fraction containing the extraction phase is sent via a line 5 to the separation unit (C).

The compounds extracted from the hydrocarbon feed, in particular oxygen-containing compounds, are separated and evacuated via line 7.

The regenerated extraction phase is recycled via line 6.

It should be noted that the contacter (A) and decanting unit (B) may be combined into a single device, for example a liquid-liquid extraction column operating in counter-current mode.

The following examples illustrate the invention without limiting its scope.

EXAMPLE 1

Oxygen-containing compounds were extracted from a hydrocarbon feed using different ionic liquids (in accordance with the invention).

The hydrocarbon feed was obtained by distillation of a Fischer-Tropsch synthesis effluent. The hydrocarbon feed was composed of C6 to C10 olefins and paraffins and C3 to C7 alcohols.

The composition of said feed was obtained by gas chromatography and Karl-Fischer analysis and is shown in Table I.

TABLE I
ComponentsMolar content
Alcohols 6.2%
Olefins38.4%
(of which α-olefins)(32.5%)
Paraffins55.3%
Water1700 ppm

The extraction tests were carried out in a small jacketed glass reactor (40 cm3) provided with an argon inlet to maintain it under an inert atmosphere. The temperature was regulated by a heat conducting fluid which circulated inside the jacket. All of the tests were carried out at a temperature of 30° C.

The ionic liquids were synthesized in a laboratory in accordance with conventional protocols described in the literature.

The following were introduced into the jacketed glass reactor:

    • 2 ml of ionic liquid; and
    • 4 ml of hydrocarbon feed.

The mixture was then stirred at 1200 rpm using a magnetic bar, for 1 h. At the end of this period, stirring was stopped and the mixture was decanted for 15 minutes. The upper hydrocarbon phase was then removed and analyzed.

The results obtained are shown in Table II and are given as the molar percentage.

The following abbreviations are used:

n.d.=not determined

[BMI]: 1-butyl-3-methylimidazolium

[BMMI]: 1-butyl-2,3-dimethylimidazolium

[BMPyrr]: N-butyl-N-methylpyrrolidinium.

[(HOCH2CH2)MI]: (2-hydroxyethyl)-1-methyl-3-imidazolium

[BMMorph]: N-butyl-N-methylmorpholinium

[NTF2]: bis-trifluoromethylsulphonylamide

TABLE II
Extraction solventAlcoholOlefins (of which α-olefins)ParaffinsWater
[BMI][NTF2]3.9%38.1% (32.6%)57.9%nd
[BMMI][NTF2]3.0%38.3% (32.4%)58.7%nd
[BMPyrr][NTF2]3.0%38.7% (33.0%)58.3%nd
[BMI][BF4]4.7%37.9% (32.1%)57.4%nd
[BMMI][BF4]4.9%38.4% (32.8%)56.7%nd
[EMI][BF4]5.1%38.3% (32.5%)56.6%nd
[BMI][SbF6]3.6%38.5% (32.7%)57.8%nd
[BMI][CF3CO2]0.4%39.0% (33.6%)60.6%275 ppm
[EMI][CF3SO3]2.0%39.3% (33.6%)58.8%nd
[(HOCH2CH2)MI][NTF2]4.1%38.5% (32.9%)57.3%nd
[BMMorph][NTF2]4.6%37.9% (32.9%)57.5%nd

EXAMPLE 2

The possibility of reducing the alcohol content in the hydrocarbon feed by successive extraction with the ionic liquid [BMI] [NTF2] was studied.

The following were introduced into a jacketed glass reactor:

    • 2 ml of [BMI][NTF2]; and
    • 4 ml of hydrocarbon feed.

The mixture was then stirred at 1200 rpm using a magnetic bar, for 1 h. At the end of this period, stirring was stopped, and the mixture was decanted for 15 minutes.

The upper hydrocarbon phase was removed, analyzed and brought into contact with 2 ml of “fresh” [BMI][NTF2] for a further extraction.

The results obtained are shown in Table III and are given as a molar percentage.

TABLE III
Olefins
Extraction noAlcohol(of which, α-olefins)Paraffins
13.7%38.6% (33.0%)57.6%
21.1%38.6% (33.8%)60.3%
30.5%37.3% (32.1%)62.2%

EXAMPLE 3

The possibility of regenerating the extraction phase was studied in the case of [BMI][CF3CO2]. The non volatile nature of the ionic liquids allowed the extraction phase to be regenerated very easily using the following protocol:

The following were introduced into a jacketed glass reactor:

    • 1.5 ml of [BMI][C.F3CO2]; and
    • 6 ml of hydrocarbon feed.

The mixture was then stirred at 1200 rpm using a magnetic bar, for 1 h. At the end of this period, stirring was stopped, and the mixture was decanted for 15 minutes. The upper hydrocarbon phase was removed and analyzed. The lower liquid phase was taken off under vacuum (10−1 mbar) for 2 hours at ambient temperature.

A new volume (6 ml) of hydrocarbon feed was then added to the ionic liquid phase for a new extraction.

The results obtained are shown in Table IV and are given as a molar percentage.

TABLE IV
Olefins
(of which α-
Extraction noAlcohololefins)ParaffinsWater
10.7%40.1% (34.8%)59.1%162 ppm
2 (1st recycle)0.8%39.0% (33.8%)60.1%157 ppm
3 (2nd recycle)1.2%38.8% (33.6%)59.9%170 ppm

Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.

In the foregoing and in the examples, all temperatures are set forth uncorrected in degrees Celsius and, all parts and percentages are by weight, unless otherwise indicated.

The entire disclosures of all applications, patents and publications, cited herein and of corresponding French application No. 04/09.660, filed Sep. 10, 2005 are incorporated by reference herein.

The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.