KLUSENER PETER ANTON AUGUST (NL)
SCHOON LODEWIJK (NL)
RIGUTTO MARCELLO STEFANO (NL)
KLUSENER PETER ANTON AUGUST (NL)
SCHOON LODEWIJK (NL)
WO2009079107A1 | 2009-06-25 |
US20100147746A1 | 2010-06-17 | |||
EP0719572A1 | 1996-07-03 | |||
US6398948B1 | 2002-06-04 | |||
US20090264694A1 | 2009-10-22 | |||
US5093011A | 1992-03-03 | |||
US20090264694A1 | 2009-10-22 | |||
US20100147746A1 | 2010-06-17 | |||
US4273712A | 1981-06-16 |
C L A I M S 1. A process for reducing the halogen content of a hydrocarbon product stream which is obtained by a hydrocarbon conversion process in which use is made is made of a halogen-containing acidic ionic liquid catalyst, which process comprises the steps of: (a) mixing the hydrocarbon product stream with an aqueous caustic solution in the presence of a phase transfer catalyst ; (b) separating from the mixture obtained in step (a) a hydrocarbon-rich phase and a caustic-rich phase; and (c) recovering the hydrocarbon-rich phase having a halogen content which is smaller than the halogen content of the hydrocarbon product stream. 2. A process according to claim 1, wherein in step (b) a hydrocarbon-rich phase, a caustic-rich phase, and a phase transfer catalyst-rich phase are separated from the mixture obtained in step (a) . 3. A process according to claim 1 or 2, wherein at least part of the caustic-rich phase is recycled to step (a) . 4. A process according to claim 2 or 3, wherein at least part of the phase transfer catalyst-rich phase is recycled to step (a) . 5. A process according to any one of claims 1-4, wherein the phase transfer catalyst comprises a quaternary ammonium salt and/or a quaternary phosphonium salt . 6. A process according to any one of claims 1-5, wherein the phase transfer catalyst has the general formula ( I ) : R1R2R3RQX ( I ) wherein R1-R4 are each an alkyl group comprising 1-20 carbon atoms, optionally substituted with an aromatic group; Q is N or P; and X is an anion selected from the group consisting of halogens, hydroxide, sulphate, alkyl sulphates and hydrogen sulphate. 7. A process according to any one of claims 1-6, wherein step (a) is carried out at a temperature of less than 200°C. 8. A process according to claim 7, wherein the temperature in step (a) is carried out at a temperature of less than 150°C. 9. A process according to any one of claims 8, wherein step (a) is carried out at a temperature of less than 100°C. 10. A process according to claim 9, wherein the temperature in step (a) is in the range of from 45-75°C. 11. A process according to any one of claims 1-10, wherein the concentration of caustic in step (a) is in the range of from 0.5-50wt%, based on the aqueous caustic solution and wherein the volumetric ratio of the caustic solution to the hydrocarbon product stream is less than 1. 12. A process according to any one of claims 1-11, wherein the concentration of phase transfer catalyst in step (a) is in the range of from 0.1-5wt%, based on the aqueous caustic solution. 13. A process according to any one of claims 1-12, wherein step (a) is carried out over a period of time in the range of from 0.01-1.5 hour. 14. A process according to any one of claims wherein the hydrocarbon conversion process is < alkylation process. |
Field of the invention
The present invention provides a process for
reducing the halogen content of a hydrocarbon product stream.
Background of the invention
In a variety of hydrocarbon conversion processes use is nowadays made of halogen-containing acidic ionic liquid catalysts. Although such catalysts can effectively be used to produce useful hydrocarbon products such as gasoline or gasoline components, a major disadvantage of the use of these catalysts is that the hydrocarbon products so produced may have undesirably high halogen contents. In this respect it is observed that the
presence of organic chlorides in for instance a gasoline may generate during combustion corrosive and harmful materials such as hydrogen chloride and/or dioxins . It is therefore important that hydrocarbon products intended to be used as gasolines or gasoline components only contain a very small amount of halogens.
A process for reducing the concentration of organic halide in a product stream of an alkylation process wherein use is made of a halide-based acidic ionic liquid catalyst has been described in US 2009/0264694. In said process the concentration of organic halide is reduced by contacting at least part of the product stream with a hydrotreating catalyst in the presence of hydrogen and under hydrotreating conditions. Such a process has the drawback that hydrotreating processes are expensive because the application of high pressures and the need for equipment to recycle excess of hydrogen. Further, in US 2010/0147746 a process for reducing halide concentrations in a hydrocarbon product has been described, wherein at least a portion of the hydrocarbon is contacted with an aqueous caustic solution under conditions to reduce the halide concentration in the hydrocarbon product. A considerable disadvantage of such a caustic process is the fact that preferred conditions include temperatures of no less than 200°C or greater.
Clearly, there is a need in the art to provide an effective process for reducing the halogen content of hydrocarbon product streams that overcomes the above- mentioned disadvantages.
Summary of the invention
It has been found that the halogen content of a hydrocarbon product stream can attractively be reduced when use is made of a caustic solution in the presence of a phase transfer catalyst.
Accordingly, the present invention provides a process for reducing the halogen content of a hydrocarbon product stream which is obtained by a hydrocarbon
conversion process in which use is made is made of a halogen-containing acidic ionic liquid catalyst, which process comprises the steps of:
(a) mixing the hydrocarbon product stream with an aqueous caustic solution in the presence of a phase transfer catalyst ;
(b) separating from the mixture obtained in step (a) a hydrocarbon-rich phase and a caustic-rich phase; and
(c) recovering the hydrocarbon-rich phase having a halogen content which is smaller than the halogen content of the hydrocarbon product stream.
The combined use of a caustic solution and a phase transfer catalyst establishes a highly attractive reduction of the halogen content of a hydrocarbon product stream that is produced by means of a halogen-containing acidic ionic liquid catalyst.
Detailed description of the invention
In the process according to the invention a
hydrocarbon product stream is mixed in step (a) with an aqueous caustic solution in the presence of a phase transfer catalyst. The caustic to be used in the aqueous caustic solution can be chosen from a variety of
caustics. The caustic can be chosen from metal hydroxides and other Bronsted basic compounds, and mixtures thereof. Suitable examples of metal hydroxides include NaOH, KOH, LiOH, RbOH, FrOH, CsOH, Mg(OH) 2 and Ba(OH) 2 . Preferably, the caustic comprises NaOH or KOH. Suitably, the
concentration of caustic in step (a) can suitably be in the range of from 0.5-50 wt%, based on the aqueous caustic solution. Preferably, the concentration of caustic is in the range of from 5-45 wt%, more preferably in the range of from 10-40 wt%, based on the aqueous caustic solution. In step (a), the volumetric ratio of the aqueous caustic solution and the hydrocarbon product stream is suitably less than 10, preferably less than 1.
In step (a) use is made of a phase transfer
catalyst. Phase transfer catalysts facilitate the
migration of a reactant into a phase from which it is normally absent. A wide variety of phase transfer
catalysts can be used in accordance with the present invention. Suitable examples of phase transfer catalysts include quaternary ammonium and phosphonium salts as for instance described in US 4,273,712. Preferably, the phase transfer catalyst is a quaternary ammonium salt.
Preferably, the phase transfer catalyst has the general formula ( I ) : R1R2R3R4QX (I) wherein R1-R4 are each an alkyl group comprising 1-20 carbon atoms, optionally substituted with an aromatic group; Q is N or P; and X is an anion selected from the group consisting of halogens, hydroxide, sulphate, alkyl sulphates and hydrogen sulphate. Preferably, R1-R4 are each an alkyl group comprising 1-14 carbon atoms. R1-R4 can each be substituted with an aromatic group. A
suitable example of an aromatic group is a phenyl group. Preferably, Q is N. Preferably, X is an anion selected from the group consisting of halogens and hydroxide. More preferably, X is hydroxide. Suitable phase transfer catalysts include tetrabutylammonium chloride,
tetrabutylammonium bromide, tetrabutylammonium hydroxide, benzyl triethylammonium chloride, benzyl triethylammonium bromide, benzyl triethylammonium hydroxide, benzyl trimethylammonium chloride, benzyl trimethylammonium bromide, benzyl trimethylammonium hydroxide, methyl trioctylammonium chloride (Aliquat336) , methyl
trioctylammonium hydroxide, butyl trioctylammonium chloride, butyl trioctylammonium hydroxide,
tetraoctylammonium chloride, tetraoctylammonium
hydroxide, tributyl octylammonium chloride, tributyl octyl ammonium hydroxide, cetyl trimethylammonium
chloride, cetyl trimethylammonium bromide, cetyl
trimethylammonium hydroxide, triethyl octylammonium chloride, triethyl octylammonium hydroxide, benzyl tributylammonium chloride, methyl trioctylammonium chloride, tetradecyl trimethylammonium bromide, dodecyl trimethylammonium chloride, phenyl trimethylammonium chloride, cetyl dimethyl benzylammonium bromide and cetyl dimethylbenzylammonium chloride. Especially tetrabutylammonium chloride, tetrabutylammonium bromide and tetrabutylammonium hydroxide are suitable phase transfer catalysts to be used in accordance with the present invention.
The concentration of the phase transfer catalyst in step (a) can suitably be in the range of from
0.01-10 wt%, based on the aqueous caustic solution.
Preferably, the concentration of phase transfer catalyst in step (a) is in the range of from 0.1-5 wt%, based on the aqueous caustic solution.
Step (a) can suitably be carried out at a
temperature of up to 300 °C. Preferably, step (a) is carried out at a temperature of less than 200 °C, more preferably less than 150 °C, in particular less than
100 °C, and most preferably at a temperature in the range of from 45-75 °C.
Suitably, step (a) is carried out over a period of time in the range of from 0.0002-2 hours. Preferably, step (a) is carried out over a period of time in the range of from 0.01-1.5 hours.
Suitably, efficient mixing can be established by using appropriate mixing means. Examples of suitable mixing means include, for instance, dynamic and static mixers and stirred reactors. Turbulent flows can also be applied to establish effective mixing of the hydrocarbon product stream, the aqueous caustic solution and the phase transfer catalyst. A mixture of the aqueous caustic solution and the phase transfer catalyst can be mixed with the hydrocarbon product stream in step (a) or the aqueous caustic mixture can first be mixed with the hydrocarbon product stream after which the phase transfer catalyst is mixed with the mixture of the hydrocarbon product stream and the aqueous caustic solution so obtained. In another embodiment the phase transfer catalyst is first mixed with the hydrocarbon product stream after which the aqueous caustic solution is mixed with the mixture of the hydrocarbon product stream and the phase transfer catalyst so obtained.
In step (b) of the process according to the present invention at least a hydrocarbon-rich phase and at least a caustic-rich phase are separated from the mixture obtained in step (a) . Preferably, in step (b) a
hydrocarbon-rich phase, a caustic-rich phase, and a phase transfer catalyst-rich phase are separated from the mixture obtained in step (a) .
In a preferred embodiment of the present process at least part of the caustic-rich phase is recycled to step
(a) . Preferably, before recycling at least part of the caustic-rich to step (a) , caustic, preferably fresh caustic, is added to the caustic-rich phase to maintain the caustic concentration in step (a) at a sufficient level.
In a preferred embodiment of the present process at least part of the phase transfer catalyst-rich phase is recycled to step (a) . Preferably, before recycling at least part of the phase transfer catalyst-rich phase to step (a) , phase transfer catalyst, preferably fresh phase transfer catalyst, is added to the phase transfer
catalyst-rich phase to maintain the concentration of the phase transfer catalyst in step (a) at a sufficient level .
Reference, herein to a hydrocarbon-rich phase is to a phase comprising more than 50 mol% of hydrocarbons, based on the total moles of hydrocarbon, caustic and phase transfer catalyst. Reference, herein to a caustic- rich phase is to a phase comprising more than 50 mol% of caustic, based on the total moles of caustic, hydrocarbon and phase transfer catalyst. Reference, herein to a phase transfer catalyst-rich phase is to a phase comprising more than 50 mol% of phase transfer catalyst, based on the total moles of phase transfer catalyst, caustic and hydrocarbon. Due to the low affinity of the hydrocarbon product for aqueous solutions and the difference in density between the hydrocarbon product and the aqueous caustic solution, the hydrocarbon product and the aqueous caustic solution will separate into an upper
predominantly hydrocarbon product phase and lower
predominantly aqueous caustic solution phase. The phase transfer catalyst facilitates the migration of halogen present in the hydrocarbon product phase into the
caustic-rich phase. Depending on the concentration of the phase transfer catalyst part of the phase transfer catalyst will be in the upper predominantly hydrocarbon product phase and part of the phase transfer catalyst will be in the lower predominantly aqueous caustic solution phase and/or a separate predominantly phase transfer catalyst phase will be formed in between the upper predominantly hydrocarbon product phase and the lower predominantly aqueous caustic solution phase.
Preferably, a separate predominantly phase transfer catalyst phase is formed in between the upper
predominantly hydrocarbon product phase and the lower predominantly aqueous caustic solution phase. These phases can be separated using any suitable liquid/liquid separator. Such liquid/liquid separators are known to the skilled person and include cyclone and centrifugal separators . Examples of hydrocarbon conversion processes from which the hydrocarbon product stream is obtained include alkylation of paraffins, alkylation of aromatics,
( co ) polymerisation, oligomerisation, dimerisation, isomerisation, acetylation, olefin hydrogenation, metatheses, and hydroformylation . Preferably, the
hydrocarbon conversion process is an alkylation process. Preferably, an alkylation process of paraffins or
aromatics. Hence, the hydrocarbon product stream to be treated in accordance with the present invention is preferably an alkylate-comprising stream obtained from an alkylation process, more preferably a high octane
alkylate stream.
Ionic liquids are known in the art for their ability to catalyse alkylation reactions. A wide variety of halogen-containing acidic ionic liquid catalysts can be used in alkylation processes. The ionic liquid catalyst can suitably be a composite ionic liquid comprising cations derived from a hydrohalide of an alkyl-containing amine, imidazolium or pyridine. Preferably, the cations comprise nitrogen atoms, which are saturated with four substituents , among which there is at least one hydrogen atom and one alkyl group. More preferably, the alkyl substituent is at least one selected from methyl, ethyl, propyl, butyl, amyl, and hexyl groups. Examples of suitable cations include triethyl-ammonium (NEt3H + ) and methyl- diethyl-ammonium cations (MeNEt 2 H + ) or
The anions of the composite ionic liquid are
preferably aluminium based Lewis acids, in particular aluminium halides, preferably aluminium (III) chloride. Due the high acidity of the aluminium chloride Lewis acid it is preferred to combine the aluminium chloride, or other aluminium halide, with a second or more metal halide, sulphate or nitrate to form a coordinate anion, in particular a coordinate anion derived from two or more metal halides, wherein at least one metal halide is an aluminium halide. Suitable further metal halides, sulphates or nitrates, may be selected from halides, sulphates or nitrates of metals selected from the group consisting of Group IB elements of the Periodic Table, Group IIB elements of the Periodic Table and transition elements of the Periodic Table. Examples or suitable metals include copper, iron, zinc, nickel, cobalt, molybdenum, or platinum. Preferably, the metal halides, sulphates or nitrates, are metal halides, more preferably chlorides or bromides, such as copper (I) chloride, copper (II) chloride, nickel (II) chloride, iron (II) chloride. Preferably, the molar ratio of the aluminium compound to the other metal compounds in the range of from 1:100-100:1, more preferably of from 1:1-100:1, or even more preferably of from 2:1-30:1.
In accordance with the present invention hydrocarbon product streams can be obtained having a halogen content of less than 20 ppm by weight. Examples
The invention is illustrated by the following non- limiting examples.
General procedure
A series of experiments has been carried out using three different Methods A-C, which will each be discussed hereinbelow. In a number of these experiments use is made of a feedstock mimicking a hydrocarbon product stream obtained from a hydroconversion process using a halogen- containing acidic ionic liquids catalyst. In these experiments use is made of a solution containing n- octane, 1 , 1-dichloroethane and 1 , 1 , 1-trichloroethane . In a number of experiments use is made of an alkylate sample which was obtained from an alkylation process wherein use is made of a halogen-containing acidic ionic liquid catalyst. In the experiments use is made of a phase transfer catalyst that comprises tetrabutylammonium chloride or tetrabutylammonium hydroxide.
Method A (experiments up to 105 °C)
A 100 mL round bottom flask was loaded with a solution of sodium hydroxide (50 wt%) in water, and with a solution of 1 , 1-dichloroethane and 1,1,1- trichloroethane in n-octane. 0-2 wt% (on caustic basis) of a phase transfer catalyst and a magnetic stirring bar were added to the bottom flask. The flask was equipped with a reflux condenser and an overpressure of 10 mbar nitrogen was applied to obtain a more or less closed system. The oil bath was heated to the desired
temperature and the mixture stirred for several hours. The mixture was allowed to cool down to room temperature and stirring was stopped to allow the mixture to settle in 2 phases, a 1 mL sample was taken from the organic (top) layer for analysis by Gas Chromatography-Mass Spectroscopy (GC-MS) .
In case a sample was taken, the oil bath was removed and replaced by an ice-bath to cool the mixture down quickly. Stirring was stopped to allow the mixture to settle in two phases and a 1 mL sample was taken from the organic (top) layer. The reaction was continued by replacing the hot oil bath.
Method B (experiments above 105 °C)
A 100 mL autoclave (Hastelloy C) with magnetic stirring bar or a 60 mL autoclave with mechanical stirrer, was loaded with a solution of sodium hydroxide in water and with a solution of 1 , 1-dichloroethane and 1 , 1 , 1-trichloroethane in n-octane. 0-2 wt% (on caustic basis) of a phase transfer catalyst was added. The autoclave was closed and heated to reaction temperature and the mixture was stirred for several hours. The reaction was stopped by cooling down the mixture to room temperature. Stirring was stopped, the autoclave opened and the mixture was allowed to settle in phases and a 1 mL sample was taken from the organic (top) layer for analysis by GC-MS.
Methods C (experiments above 105 °C)
A 60 mL autoclave (Hastelloy C) with magnetic stirring bar or a 60 mL autoclave with mechanical stirrer, was loaded with a solution of sodium hydroxide in water and with a solution of 1 , 1-dichloroethane and 1 , 1 , 1-trichloroethane in n-octane. 0-2 wt% (on caustic basis) of a phase transfer catalyst was added. The autoclave was closed and heated to reaction temperature and the mixture was stirred for several hours. The reaction was stopped by cooling down the mixture to room temperature. Stirring was stopped, the autoclave opened and the mixture was allowed to settle in phases and a 1 mL sample was taken from the organic (top) layer for analysis by GC-MS.
GC-MS method
GC-MS analyses were performed with a Trace GC Ultra chromatograph from Interscience equipped with a 50 m x 0.2 mm x 0.5 μπι RTX-1 PONA column and equipped with a DSQII mass-selective EI detector.
The following temperature profile was used in the GC-MS for measuring the components. The oven started at 35 °C for the first 5 min, then increased with 10 °C/min to 250 °C followed by a hold time of 10 min at 250 °C. The data used for composition determination is from the FID signal. The MS signal was used for identification of the products.
Data interpretation
The peak areas from the GC-MS were filled in an excel sheet and converted into conversion percentages of the organic chlorides, using the internal standard
( cyclohexane ) and the response factors. Response factors of the organic chlorides and octane were determined experimentally .
The results of Experiments 1-26 are shown in Tables
Table 1
* comparative experiment based on aqueous solution
Table 2
* comparative experiment
based on aqueous solution
Table 3
* comparative experiment
** based on aqueous solution
It will be clear from the results shown in Tables 1- that the experiments in accordance with the present invention (Experiment Nos. 1, 3, 6, 7, 9-14, 16, 17, 19, 20 and 22-26) clearly bring about a considerable
improvement in the reduction of chlorides when compared with comparative experiments (Experiment Nos. 2, 4, 5, 8 15, 18 and 21) .
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