WO2014009347A1

WO2014009347A1 - Method for the treatment of an output from a hydocarbon conversion by separating hydrocarbon halogenides and subsequent scrubbing

Info

Publication number: WO2014009347A1
Application number: PCT/EP2013/064449
Authority: WO
Inventors: Katharina SPUHL; Markus Schmitt; Jochen BÜRKLE; Joni JONI; Steffen Tschirschwitz; Daniel Pfeiffer; Stefan Bitterlich; Michael HÜBNER; Pawel CZAJKA
Original assignee: Basf Se; Basf Schweiz Ag
Priority date: 2012-07-11
Filing date: 2013-07-09
Publication date: 2014-01-16

Abstract

The invention relates to a method for treating an output from a hydrocarbon conversion process that is carried out in the presence of an acidic ionic liquid. Preferably, the hydrocarbon conversion process is an isomerization process. Initially, the hydrogen halogenide is removed, in a device, from a mixture obtained in the hydrocarbon conversion and containing at least one hydrocarbon and at least one hydrogen halogenide, then said mixture enriched with hydrogen halogenide is subjected to scrubbing.

Description

Process for the treatment of a hydrocarbon conversion with removal of hydrogen halides and downstream scrubbing

description

The present invention relates to a process for the treatment of a hydrocarbon conversion effluent wherein the hydrocarbon conversion is carried out in the presence of an acidic ionic liquid. The hydrocarbon conversion is preferably an isomerization. From a derived from the hydrocarbon conversion mixture containing at least one hydrocarbon and at least one hydrogen halide, the hydrogen halide is first withdrawn in a device, whereupon the hydrogen halide depleted mixture is subjected to a wash. Ionic liquids can be used in various hydrocarbon conversion processes, in particular they are suitable as catalysts for the isomerization of hydrocarbons. A corresponding use of an ionic liquid is disclosed for example in WO 201 1/069929, where a special selection of ionic liquids in the presence of an olefin is used for the isomerization of saturated hydrocarbons, in particular for the isomerization of methylcyclopentane (MCP) to cyclohexane. An analogous process is described in WO 201 1/069957, although the isomerization is not carried out in the presence of an olefin but with a copper (II) compound.

In addition to the ionic liquid can at

Hydrocarbon conversion processes, especially in Isomerisierungsprozessen, also hydrogen halides, preferably as cocatalysts are used. Frequently, the hydrogen halides are used in gaseous form. In order to make better use of the co-catalytic effect of the hydrogen halides, a partial pressure of 1-10 bar of hydrogen halide, in particular hydrogen chloride, is generally set above the reaction mixture by carrying out the isomerization. However, the hydrogen halide used is dissolved to some extent in the hydrocarbons and thus discharged from the isomerization reaction. This portion of hydrogen halide dissolved in the hydrocarbons must be removed from the hydrocarbons following isomerization, particularly due to the corrosive nature of the hydrogen halide, which is often associated with problems in practice.

US-A 201 1/0155632 discloses a process for the preparation of products with a low hydrogen halide content, wherein in at least two separation steps by stripping or distillation from a mixture which originates from a reactor and contains an ionic liquid as a catalyst, the content of hydrogen halides is reduced. In one embodiment of the process described in US-A 201 1/0155632, the ionic liquid used as a catalyst is recycled to an alkylation reactor from a downstream phase separator, from a first distillation column downstream of the phase separator is hydrogen chloride and from a further downstream second distillation column is a Isobutane-containing stream is returned to the alkylation reactor. In US-A 201 1/0155632, however, it is nowhere disclosed that a hydrogen halide, in particular hydrogen chloride, is effectively separated from a product, for example from an alkylation product or an isomerization product, in two process stages, the second process stage being a wash with an aqueous medium can be. In contrast, in the embodiments described therein, the use of two separation stages without the use of an aqueous washing medium, in particular of two distillation steps, absolutely necessary to obtain a low content of hydrogen halide in the reaction product. A meaningful disclosure as in US-A 201 1/0155632 is contained in US-A 201 1/0155640, however, the method described therein relates to a hydrocarbon conversion. US Pat. No. 3,271,467 discloses a method and an associated apparatus for maintaining the hydrogen halide concentration in a hydrocarbon conversion, using as catalyst a metal halide and the hydrogen halide as promoter. Suitable metal halides are, for example, aluminum chloride, aluminum bromide, boron trifluoride or halides of zinc, tin, antimony or zirconium, but such compounds are not ionic liquids. The hydrocarbon conversion may, for example, be an isomerization of methylcyclopentane (MCP) to cyclohexane. From the hydrocarbon-containing outlet of the hydrocarbon conversion, a stream rich in gaseous hydrogen halide is separated in a (first) stripping device and discharged from the arrangement. A second stream, enriched in hydrogen halide, is passed from the stripping apparatus to an absorber to selectively separate, on a solid absorber, the hydrogen halide contained in that stream. The thus separated hydrogen halide is removed from the solid absorber again and returned to the system.

WO 2010/075038 discloses a process for reducing the content of organic halides in a reaction product formed as a result of a hydrocarbon conversion process in the presence of a halogen-containing acidic ionic liquid-based catalyst. The hydrocarbon conversion process is in particular an alkylation, but this process may also be an isomerization be performed. The organic halides are removed from the reaction product by washing with an aqueous alkaline solution. However, the use of hydrogen halide as cocatalyst of ionic liquids in hydrocarbon conversions such as isomerization processes and the associated removal of hydrogen halide from the isomerization product is not disclosed in WO 2010/075038.

The object underlying the present invention is to provide a novel process for the separation of hydrogen halide from a mixture obtained in a hydrocarbon conversion, in particular in an isomerization, of at least one hydrocarbon in the presence of an acidic ionic liquid.

The object is achieved by a process for the treatment of a discharge of a hydrocarbon conversion, wherein the hydrocarbon conversion in the presence of an acidic ionic liquid having the composition K1Al _n X _{(3n + 1) is} performed, wherein K1 is a monovalent cation, X is halogen and 1 <n <2.5, the discharge comprises a mixture (G1) and the mixture (G1) contains at least one hydrocarbon and at least one hydrogen halide (HX), characterized in that the process comprises the following steps:

Feeding the mixture (G1) into a device (V1), a mixture (Gi b) containing at least 50% by weight, preferably at least 70% by weight of the hydrogen halide (HX) contained in (G1), from (V1 ) is deducted,

Discharging a mixture (G2) from the apparatus (V1), the mixture (G2) containing at least one hydrocarbon and an amount of at least one hydrogen halide (HX) reduced by the mixture (Gib) compared with the mixture (G1),

Washing the mixture (G2) with an aqueous medium to obtain a mixture (G3) containing at least one hydrocarbon and not more than 100 ppm by weight, preferably not more than 10 ppm by weight of hydrogen halide (HX) (based on the total weight of (G3 )).

By means of the process according to the invention, hydrogen halide, which is contained / dissolved in the corresponding product (hydrocarbons) following a hydrocarbon conversion, in particular to an isomerization, can be removed from this product, in particular from an isomerization product, in an advantageous manner. Due to the optional feasible, at least partial return of the hydrogen halide, this can also be used in the process again.

The processes described in the two applications US-A 201 1/0155632 and US-A 201 1/0155640 are disadvantageous in particular because the object stated therein of reducing the hydrogen halide content in products obtained in hydrocarbon conversion processes, only on purely distillative Way is solved. However, at least for hydrocarbons with up to 7 carbon atoms, that for the depletion of hydrogen halide (HX) to a very low residual concentrations (<19 ppm by weight), the distillation must be carried out as a rectification in a column. This is because it is not possible to achieve an HX concentration of a few ppm by a simple evaporation in the HX-poor fraction without discharging much of the hydrocarbon introduced into the evaporation with the HX-rich fraction , which would be associated with considerable procedural and economic disadvantages.

Although the rectification allows a more selective separation of the HX in the top product as the single-stage evaporation, but is associated with a lot of effort because jacket and internals of the rectification and their bottom evaporator and top condenser must be designed so that they strong corrosive properties of the HX withstand, ie Expensive special materials have to be used, which has a disadvantageous effect especially in the case of the complex geometries of the column internals, because here the corrosion-resistant materials or coatings are either not possible or associated with high costs.

If a flash device or another simple evaporation is used as the device (V1) in the context of the method according to the invention, this is associated with the following advantages. The use of a flash device or other simple evaporation in step a) is initially less expensive and simpler in terms of apparatus, in particular compared with the use of a rectification column (due to the corrosivity of the hydrogen halide, which has a particularly disadvantageous effect on the complex geometries given in a column). The use of a flash device as device (V1) is particularly advantageous because the separation effect in the flash device is achieved only by a pressure reduction compared to the pressure selected for the hydrocarbon conversion, in particular for the isomerization. There is thus no separate input of energy necessary, the corrosivity of the hydrogen halide is thereby less relevant. The above-described advantages of the method according to the invention are even better used if, prior to step a) according to the invention, a phase separation unit, in particular a phase separator, precedes the device (V1), in particular a flash device.

In the following, the process according to the invention for the treatment of a discharge of a hydrocarbon conversion, wherein the hydrocarbon conversion is carried out in the presence of an acidic ionic liquid, is defined in more detail. Hydrocarbon conversions as such are known to those skilled in the art. Preferably, the hydrocarbon conversion is selected from alkylation, polymerization, dimerization, oligomerization, acylation, metathesis, polymerization or copolymerization, isomerization, carbonylation, or combinations thereof. Alkylations, isomerizations, polymerizations, etc. are known in the art. Particularly preferred in the context of the present invention, the hydrocarbon conversion is an isomerization.

In the context of the present invention, the hydrocarbon conversion takes place in the presence of an acidic ionic liquid having the composition K1 Al _n X _{(3n + 1)} , where K1 is a monovalent cation, X is halogen and 1 <n <2.5. Such acidic ionic liquids are known to those skilled in the art, they are disclosed (in addition to other ionic liquids), for example in WO 201 1/069929. For example, mixtures of two or more acidic ionic liquids can be used, preferably an acidic ionic liquid is used.

K1 is preferably an unsubstituted or at least partially alkylated ammonium ion or a heterocyclic (monovalent) cation, in particular a pyridinium ion, an imidazolium ion, a pyridazinium ion, a pyrazolium ion, an imidazolinium ion, a thiazolium ion, a triazolium ion, a pyrrolidinium ion, an imidazolidinium ion or a phosphonium ion. X is preferably chlorine or bromine.

More preferably, the acidic ionic liquid contains as cation at least a partially alkylated ammonium ion or a heterocyclic cation and / or as an anion a chloroaluminum having the composition Al _n Cl _{(3n + 1)} with 1 ≦ n ≦ 2.5. Preferably, the at least partially alkylated ammonium ion contains one, two or three alkyl radicals having (each) 1 to 10 carbon atoms. If two or three alkyl substituents with the corresponding ammonium ions are present, the respective chain length can be selected independently of one another, preferably all alkyl substituents have the same chain length. Particularly preferred are trialkylated ammonium ions having a chain length of 1 to 3 carbon atoms. The heterocyclic cation is preferably an imidazolium ion or a pyridinium ion. Particularly preferably, the acidic ionic liquid contains as cation an at least partially alkylated ammonium ion and as anion a chloroalumination with the composition Al _n Cl _{(3n + 1)} with 1 <n <2.5. Examples of such particularly preferred acidic ionic liquids are trimethylammonium chloroaluminate and triethylammonium chloroaluminate.

The acidic ionic liquid used in the present invention is preferably used as a catalyst in hydrocarbon conversion, especially as an isomerization catalyst. Furthermore, in the context of the present invention, the hydrocarbon conversion is also carried out in the presence of a hydrogen halide (HX), preferably the hydrogen halide (HX) is used as cocatalyst.

In principle, all conceivable hydrogen halides can be used as hydrogen halide (HX), for example hydrogen fluoride (HF), hydrogen chloride (HCl), hydrogen bromide (HBr) or hydrogen iodide (HI). Optionally, the hydrogen halides can also be used as a mixture, but preferably only one hydrogen halide is used in the context of the present invention. Preferably, the hydrogen halide is used, the halide part of which is also contained in the above-described acidic ionic liquid (at least partially) in the corresponding anion. Preferably, the hydrogen halide (HX) is hydrogen chloride (HCl) or hydrogen bromide (HBr). Most preferably, the hydrogen halide (HX) is hydrogen chloride (HCl).

In principle, any hydrocarbons may be used in the context of the present invention, with the proviso that at least one of the hydrocarbons used in the presence of the above-described acidic ionic liquids of a hydrocarbon conversion, in particular an isomerization, can be subjected. The person skilled in the art, on the basis of his general knowledge, knows which hydrocarbons can be subjected to a hydrocarbon conversion by acidic ionic liquids, in particular which hydrocarbons are isomerizable. For example, mixtures of two or more hydrocarbons can be used, but it can also be used only one hydrocarbon. Thus, it is possible in the context of the present invention that in a mixture containing two or more hydrocarbons only one of these hydrocarbons undergoes a hydrocarbon conversion, in particular isomerized. If appropriate, compounds which are themselves non-hydrocarbon but miscible with them can also be present in such mixtures. In the hydrocarbon conversion, preference is given to using methylcyclopentane (MCP) or a mixture of methylcyclopentane (MCP) with at least one further hydrocarbon selected from cyclohexane, n-hexane, isohexanes, n-heptane, iso-heptanes, methylcyclohexane or dimethylcyclopentanes.

More preferably, a mixture of methylcyclopentane (MCP) with at least one other hydrocarbon selected from cyclohexane, n-hexane, iso-hexanes n-heptane, iso-heptanes, methylcyclohexane or dimethylcyclopentanes used.

The hydrocarbon conversion can be carried out in principle in all the skilled person for such a purpose known devices. The corresponding device is preferably a stirred tank or a stirred tank cascade. Rührkesselkaskade means that two or more, for example, three or four, stirred tanks are connected in series (in series).

As already explained above, due to the hydrocarbon conversion in the presence of an acidic ionic liquid and a hydrogen halide (HX), the chemical structure of at least one of the hydrocarbons used changes. The hydrocarbons obtained in the hydrocarbon conversion are contained in a mixture (G1). The mixture (G1) thus differs in terms of the (chemical) composition and / or amount of hydrocarbons contained therein from the corresponding hydrocarbon composition, which is present before the hydrocarbon conversion, in particular before the isomerization. Since in such hydrocarbon conversions, especially in Isomerisierungsprozessen, the hydrocarbon conversion to be carried out often does not run to 100% (ie completely), is in the product usually also the hydrocarbon with which the hydrocarbon conversion was carried out (in lesser amount than before the isomerization) contain. If, for example, MCP is to be isomerized to cyclohexane, the isomerization product frequently contains a mixture of cyclohexane and MCP (in less amount than prior to isomerization).

In addition to the hydrocarbons, the mixture (G1) contains at least one hydrogen halide (HX) and optionally further components. The hydrogen halide (HX) contained in the mixture (G1) is usually the same hydrogen halide as that used in the hydrocarbon conversion (preferably as cocatalyst) because the hydrogen halide normally does not change in its chemical structure due to the hydrocarbon conversion however, partial replacement of the anion portion of the hydrogen halide used with other halide ions in the process may occur. As another Component in the mixture (G1) is preferably the ionic liquid described above. The mixture (G1) contains between 10 and 99 wt .-%, preferably between 50 and 95 wt .-% acidic ionic liquid (the amounts are based on the total weight of hydrocarbons and hydrogen halide in the mixture (G1)).

Preferably, the mixture contains (G1) as a hydrocarbon -so as a product of the hydrocarbon conversion- cyclohexane. More preferably, the mixture (G1) contains as cyclohexane cyclohexane or a mixture of cyclohexane with at least one further hydrocarbon selected from methylcyclopentane (MCP), n-hexane, iso-hexanes, n-heptane, iso-heptanes, methylcyclohexane or dimethylcyclopentanes.

The mixture (G1) particularly preferably contains as hydrocarbon a mixture of cyclohexane, MCP and at least one further hydrocarbon. Preferably, the further hydrocarbon is selected from n-hexane, iso-hexanes, n-heptane, iso-heptanes, methylcyclohexane or dimethylcyclopentanes. If the hydrocarbon conversion is carried out as isomerization, the proportion of branched hydrocarbons in the mixture (G1) is preferably less than 10% by weight (based on the sum of all the hydrocarbons present in the mixture (G1)).

In a preferred embodiment of the present invention, the mixture (G1) i) contains as hydrocarbon a mixture of cyclohexane with at least one further hydrocarbon selected from methylcyclopentane (MCP), n-hexane, iso-hexanes, n-heptane, iso-heptanes, Methylcyclohexane or dimethylcyclopentanes, ii) hydrogen chloride (HCl) and iii) an acidic ionic liquid containing as cation an at least partially alkylated ammonium ion and as the anion a chloroaluminum having the composition Al _n Cl _{(3n + 1)} with 1 <n <2.5 having.

In a further preferred embodiment of the present invention, the hydrocarbons present in the mixture (G1) have at least 80% by weight of at least 5 carbon atoms per molecule. These hydrocarbons particularly preferably have at least 6 carbon atoms per molecule.

The mixture (G1) is initially in the apparatus in which the hydrocarbon conversion is carried out. In the context of the method according to the invention, the mixture (G1) is discharged from this device as a discharge. In other words, this means that the discharge comprises the mixture (G1) and the discharge or mixture (G1) after it has been the device for Carrying out the hydrocarbon conversion has been subjected to the inventive steps (a) to c) (defined below in the text).

In the context of the present invention, if the hydrocarbon conversion is an isomerization, the isomerization is preferably carried out as follows. Carrying out an isomerization of hydrocarbons in the presence of an ionic liquid as catalyst and a hydrogen halide as cocatalyst is known to the person skilled in the art. Preferably, the hydrocarbons and the ionic liquid each form a separate phase in the isomerization, wherein subsets of the ionic liquid in the hydrocarbon phase and subsets of the hydrocarbons may be contained in the ionic liquid phase. The hydrogen halide, in particular hydrogen chloride, is preferably introduced in gaseous form into the device for carrying out the isomerization. The hydrogen halide may, at least in part, be contained in the two aforementioned liquid phases, preferably the hydrogen halide forms a separate gaseous phase.

The isomerization is preferably carried out at a temperature between 0 ° C and 100 ° C, more preferably at a temperature between 30 ° C and 60 ° C. Furthermore, it is preferred that the pressure in the isomerization between 1 and 20 bar abs. (absolute), preferably between 2 and 10 bar abs., Is.

Preferably, the isomerization is carried out in the apparatus so that there are two liquid phases and one gas phase in a stirred tank or a stirred tank cascade. The first liquid phase contains at least 90% by weight of the acidic ionic liquid and the second liquid phase contains at least 90% by weight of the hydrocarbons. The gas phase contains at least 90% by weight of at least one hydrogen halide, preferably hydrogen chloride. Optionally, there may also be a solid phase containing components in solid form from which the ionic liquid is formed, such as AICI ₃ . In this case, the pressure and composition of the gas phase are adjusted so that the partial pressure of the gaseous hydrogen halide, in particular of HCl gas, in the gas phase between 1 and 20 bar abs., Preferably between 2 and 10 bar abs. is. In step a) of the process according to the invention, the mixture (G1) is fed into a device (V1), a mixture (Gi b) containing at least 50% by weight of the hydrogen halide (HX) contained in (G1) being selected from ( V1) is subtracted. Preferably, the mixture (Gi b) is withdrawn from the device (V1) partially or completely gaseous, particularly preferably completely gaseous. At least 50%, more preferably at least 70% of the hydrogen halide introduced with the mixture (G1) are preferably removed with mixture (Gi b). Preferably, a partial or complete return of the mixture (Gi b) takes place in the apparatus for carrying out the hydrocarbon conversion, optionally with pressure increase by means of a suitable device such as a jet, piston, turbo or screw compressor. Preferably, the mixture (Gi b) is completely recycled to the apparatus for carrying out the hydrocarbon conversion. If no complete return of the mixture (Gi b) is carried out, the excess amounts of mixture (Gi b) are carried out from the process according to the invention and discarded or fed to a further process step.

As device (V1) for carrying out the gaseous removal (separation) of the hydrogen halide (HX) from the mixture (G1) it is possible in principle to use all devices known to the person skilled in the art for such a purpose, preferably an evaporation device, a rectification column, a device for flash evaporation (Flash device) or a stripping device. More preferably, V1 is a flash device. By the device (V1) should be carried out in the context of the inventive method, preferably a separation of the hydrogen halides of the hydrocarbons. In the context of the present invention, step a) is to be understood such that when using a flash device as the device (V1), a corresponding flash process (flashing) is carried out with the mixture (G1). The same applies to the other embodiments of the device (V1) listed above, such as stripping apparatus or rectification column.

In the context of the present invention, the term "evaporation", which is carried out in a corresponding evaporation apparatus, the following understood: For the evaporation is characteristic that evaporated from the liquid mixture to be separated under heat, a part, and condensed after separation from the residual liquid mixture Thus, a vapor phase is generated for the original liquid phase in which the lower-boiling mixture components accumulate.

In the context of the present invention, the term "rectification" which is carried out in a corresponding rectification column (rectification apparatus), also called a rectification column or rectification apparatus, is understood as follows: In the rectification, the steam produced by distillation is passed in a rectification column in countercurrent to a In this way, more volatile components in the overhead and heavier volatile in the bottom product of the rectification are enriched. In the context of the present invention, the term "flashing", which is carried out in a corresponding flash device and can also be referred to as flash evaporation, means the following: In the case of flash evaporation (flashing), a liquid mixture is introduced into a suitable device (flash device) ), for example, in a vapor-liquid separation vessel (ie, on a suitable device such as a valve, a reduction of the pressure takes place, which is sufficient to spontaneously evaporate a portion of the liquid mixture) The liquid mixture can, for example, operated at a higher pressure reaction stage However, it may also be preheated in a preheater, for example at boiling temperature, wherein the pressure in the preheater must be higher than the pressure in the downstream precipitation vessel higher proportion of lower-boiling components. The flash evaporation thus provides for a partial separation of the incoming mixture, wherein the separator can act as a single theoretical separation stage. However, the flashing can also be combined with a heat input into the liquid mixture remaining during the flash process, for example by means of a circulation evaporator connected to the separation vessel.

In the context of the present invention, the term "stripping", which is carried out in a corresponding stripping apparatus, means the following: during stripping, the depletion of one or more lower-boiling components takes place from a liquid, this being carried out, preferably in a countercurrent column, is contacted with gases such as nitrogen, air or water vapor, so that as a result of the gas caused by the reduction of the partial pressure of the lower-boiling components in the gas phase, their solubility in the liquid decreases.

Further information on the above terms distillation, rectification, evaporation, flashing and / or stripping can be found in the following textbooks: Sattler, Thermal Separation Methods, VCH, 1988; Perry's Chemical Engineers' Handbook, 7th Edition; RH Jerry, DW Green, 1997, McGraw Hill. In step b) of the process according to the invention, the discharge of a mixture (G2) from the device (V1), wherein the mixture (G2) at least one hydrocarbon and compared to the mixture (G1) to the mixture (Gi b) reduced amount of at least a hydrogen halide (HX). For example, the mixture (G2) may contain at least 50% reduced amount of at least one hydrogen halide (HX). Preferred is in Mixture (G2) containing an over the mixture (G1) by at least 70% reduced amount of at least one hydrogen halide (HX) included.

In step c) of the process according to the invention, the mixture (G2) is washed with an aqueous medium to obtain a mixture (G3) containing at least one hydrocarbon and not more than 100 ppm by weight, preferably not more than 10 ppm by weight of hydrogen halide (HX ) (based on the total weight of (G3)). In the context of the process according to the invention, it is preferred that the mixture (G3) obtained in process step c) (washing step c) completely or at least substantially with respect to the composition and / or amount of the hydrocarbons contained therein with the mixtures (G1) and (G2) matches. In this context, the term "broad agreement" is to be understood as meaning that at least 90% by weight, preferably at least 95% by weight, in particular at least 99% by weight, of the hydrocarbons contained in the mixture (G1) The mixture (G3) particularly preferably contains no further components apart from at least one hydrocarbon and not more than 100 ppm by weight, preferably not more than 10 ppm by weight of hydrogen halide.

The method step c) is preferably carried out such that the laundry according to step c) comprises at least two washing steps, wherein c1) in a first washing step the aqueous medium used has a pH> 9, preferably> 12, c2) in a second washing step used aqueous medium has a pH between 5 and 9, preferably between 6 and 8, having.

Preferably, the aqueous medium according to the first washing step contains an alkali metal hydroxide, more preferably NaOH. Preferably, the aqueous medium according to the second washing step is water, more preferably demineralized water. If appropriate, method step c) can be carried out such that step c2) can be carried out before step c1). Thus, in this process variant, washing is first carried out with an aqueous medium having a lower pH, followed by washing with an aqueous medium having a higher pH. Furthermore, it is also possible to carry out several steps c1) and several steps c2) one behind the other, if necessary in an alternating sequence. Preferably, in the context of the present invention, the washing step c) is carried out in two stages, with step c1) first, followed by step c2). In one embodiment of the present invention, only a one-step washing step c) is carried out, wherein the aqueous medium has a pH of 5 to 9, preferably between 6 and 8, and is particularly preferably demineralized water. In this embodiment, washing step c) is preferably carried out in a countercurrent extraction column or mixer-settler arrangement.

Furthermore, it is preferred in the context of the present invention that step c) is carried out using at least one dispersing and phase separation unit or at least one extraction column per wash step. Preferably, the dispersing and phase separation unit is a mixer-settler apparatus (combination of a stirred tank with a subsequent phase separator), a combination static mixer with phase separator or a combination of mixing pump with phase separator. Furthermore, in the context of the present invention it is preferred that in the case of a multistage, in particular two-stage scrubbing, the mixture (G2) is conducted in countercurrent to the aqueous medium. In the context of the present invention, the mixture (G2) discharged from the device (V1) is particularly preferably washed without intermediate steps with the aqueous medium (according to step c)).

In another embodiment, the washing step c) is carried out in a, preferably in countercurrent, multistage mixer-settler apparatus or it is extracted in a countercurrent extraction column with water. In the case of the mixer-settler apparatus or extraction column, in the direction of flow of the mixture (G 2) (containing the hydrocarbons), this is preferably followed by a further washing stage, which is fed with fresh water. In its aqueous outlet there is a device for the continuous measurement of the pH or the electrical conductivity so as to monitor the complete removal of the non-hydrocarbon components, in particular HCl.

Preferably, the steps a) and b) according to the invention are carried out according to at least one, more preferably according to all three variants i) to iii) listed below, wherein i) the mixture (G2) discharged from the device (V1) is at least 95% by weight liquid (in step b)), the mixture (Gi b) withdrawn from the device (V1) amounts to at least 95% by weight is gaseous (in step a)), the discharged mixture (G2) by at most 150 K, preferably at most 100 K, is warmer than the withdrawn mixture (Gi b) (in step b)). In a particularly preferred embodiment of the present invention, a one-stage evaporation, in particular a one-stage flash evaporation, takes place in the device (V1) and the mixture (G2) discharged from the device (V1) is washed with the aqueous medium without intermediate steps. In Figure 1, the inventive method is illustrated again according to a preferred embodiment. In this embodiment, an at least partial return of the in step a), preferably gaseous, separated mixture (Gi b) is performed. R1 represents the device in which the hydrocarbon conversion, in particular an isomerization, is carried out. This is preferably a stirred tank or a stirred tank cascade. The device (V1) is preferably an evaporator, in particular a flash device. By coming out of the device (V1) and pointing upward arrow is shown that optionally in the context of the inventive method, only a partial return of the separated in step a) mixture (Gi b) can be performed or that the mixture (Gi b ) is fed to a further process step, preferably a substance separation. This is particularly advantageous when (V1) is performed as stripping. In this case, in the process step, complete or partial separation of the hydrogen halide from the stripping gas employed may be carried out and the hydrogen halide-enriched stream thus obtained may be wholly or partly recycled to the apparatus for carrying out the hydrocarbon conversion. According to FIG. 1, the mixture (G2) discharged from the device (V1) is washed without intermediate steps with the aqueous medium (according to step c)). The washing step c) according to FIG. 1 can be one-stage or multi-stage as described above, preferably a multi-stage, in particular two-stage washing of the mixture (G2) in countercurrent to aqueous medium is carried out and / or a dispersing and phase separation unit, in particular a mixer-settler apparatus, is used. In a further preferred embodiment of the present invention, the mixture (G1) as discharge from the device in which the hydrocarbon conversion is carried out, discharged, passed through a phase separation unit, in particular in a phase separator, and then fed into the device (V1). In other words, this means that following the implementation of the hydrocarbon conversion and before carrying out the inventive step a), an intermediate step is carried out. In this intermediate step, the acidic ionic liquid contained in the mixture (G1) is preferably completely or at least partially separated from the mixture (G1), whereupon the mixture (G1) depleted of acidic ionic liquid is fed into the device (V1).

Preferably, at least 90%, preferably at least 99%, of the acidic ionic liquid is separated from the mixture (G1) in the phase separation unit and, if appropriate, recycled to the apparatus in which the hydrocarbon conversion is carried out. Particularly preferably, the acidic ionic liquid separated from the mixture (G1) in the phase separation unit is completely or partially returned to the device for carrying out the hydrocarbon conversion, in particular for carrying out an isomerization.

The further preferred embodiment of the present invention described above is additionally illustrated in FIG. In FIG. 2, the abbreviations, arrows and other symbols have a meaning corresponding to that stated above for FIG. 1; PT means phase separation unit, IL means acidic ionic liquid.

From the mixture (G3), cyclohexane is preferably isolated in the context of the present invention. Methods and apparatus for the separation of cyclohexane from the mixture (G3) are known in the art.

Hereinafter, the present invention will be illustrated by way of examples.

BASF's own Chemasim software was used for the simulation calculation (the same results would be obtained using the commercially available software Aspen Plus (manufacturer: AspenTech, Burlington / Massachusetts, USA)). The following substances or mixtures are used for the example calculation: a) hydrocarbon mixture (A) with the composition

2-methyl-pentane 0.66% by weight

3-methyl-pentane 1, 95% by weight

N-hexane 28.85% by weight Methyl cyclopentane! 51, 02% by weight

Cyclohexane 17.44% by weight

2,3-dimethyl-butane I 0.05% by weight

Other hydrocarbons 0.03% by weight b) Hydrogen chloride gas (B)

c) ionic liquid (IL), it is trimethylammonium heptachlorodialuminate (TMA-I L)

For the examples described, (A) and (B) are mixed so that the resulting mixture after phase separation G1 (-I L) has an HCl content of 1.5% by weight.

Example 1 with HCI separation or recirculation via flash device (V1) and subsequent washing with an aqueous medium

Example 1 is carried out according to the embodiment schematically illustrated in FIG.

In a device R1 is an isomerization of a hydrocarbon mixture (A) in the presence of an ionic liquid (trimethylammonium heptachlorodialuminate - TMA-I L), which serves as a catalyst, instead. This isomerization preferably refers to the reaction of methylcyclopentane to cyclohexane. The volume ratio of ionic liquid to organic phase is 5. Furthermore, hydrogen chloride gas (B) for stabilizing the IL and the recirculation streams Gi b from a flash device V1 and IL from a phase separation PT supplied. For device R1, an operating pressure of 3.5 bar (abs) and a temperature of 50 ° C are assumed. The resulting mixture G1 is passed into a phase separation device PT. For simplicity, it is assumed that the TMA-IL is completely separated and recycled as a pure IL phase. The organic phase G1 (-I L) is passed into the flash device V1, where it is expanded to an operating pressure of 1 bar (abs). The resulting gas fraction Gi b is returned to the device R1. The liquid mixture G2 is discharged from V1 and the organic stream G2 is further depleted in a subsequent step W by washing (multi-stage) with an aqueous medium of hydrogen chloride.

The calculated properties and compositions of the streams are shown in Table 1.

Table 1: Properties and composition of the streams from Example 1

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2nd Comparative Example with distillative HCl separation

Comparative Example 2 is shown schematically in FIG. In contrast to example 1, however, no washing step c) is carried out, but instead a distillation column (K1) is used instead of the device (V1). In a device R1, isomerization of a hydrocarbon mixture (A) takes place in the presence of an ionic liquid (trimethylammonium chloroaluminate - TMA-IL), which serves as a catalyst. This isomerization preferably refers to the reaction of methylcyclopentane to cyclohexane. The volume ratio of ionic liquid to organic phase is 5 l / l. Furthermore, hydrogen chloride gas (B) is supplied to stabilize the IL. For device V1, an operating pressure of 3.5 bar (abs) and a temperature of 50 ° C are assumed. The resulting mixture G1 is passed into a phase separation device PT. For simplicity, it is assumed that the TMA-IL is completely separated and recycled as a pure IL phase. The resulting organics G1 (-IL) is passed into a distillation column K1. The hydrogen chloride contained in G1 is removed by distillation in this, wherein the residual content of hydrogen chloride in the organic bottom product should be less than 10 wt ppm. The gaseous distillate is returned to the apparatus R1.

The calculated properties and compositions of the streams are shown in Table 2.

Table 2: Properties and composition of the streams from Comparative Example 2

For K1 a grade number of 9 is used. The heat output for the evaporator is 0.88 kW.

3. Results of the simulation calculation

The results show that the relatively costly, distillative separation (heat requirement for the evaporator and special material requirements for the column da corrosive condition) of the hydrogen chloride from the organics (alos the hydrocarbons) by a simple relaxation in a Flash apparatus with downstream laundry with a neutral medium to be replaced. In this case, the desired reduction of hydrogen chloride in the organic less than 10 ppm by weight can be maintained.

The use of a flash device is more cost-effective compared to the distillative process and simpler in terms of apparatus, since due to less complex geometries less susceptible to corrosion and also no separate energy input is necessary.

Claims

claims

1 . A method for treating a Austrage a hydrocarbon conversion, wherein the hydrocarbon conversion in the presence of an acidic ionic liquid with the composition K1Al _s X _{(3n + 1)} is performed, where K1 is a monovalent cation, X is halogen and 1 <n <2.5, the discharge comprises a mixture (G1) and the mixture (G1) contains at least one hydrocarbon and at least one hydrogen halide (HX), characterized in that the process comprises the following steps: a) feeding the mixture (G1) into a device (V1 ), wherein a mixture (Gi b) containing at least 50% by weight, preferably at least 70% by weight of the hydrogen halide (HX) contained in (G1), is taken off from (V1), b) discharge of a mixture (G2 ) from the device (V1), wherein the mixture (G2) at least one hydrocarbon and compared to the mixture (G1) to the mixture (Gi b) reduced amount of at least one

Hydrogen halide (HX), c) washing the mixture (G2) with an aqueous medium to obtain a mixture (G3) containing at least one hydrocarbon and not more than 100 ppm by weight, preferably not more than 10 ppm by weight of hydrogen halide

(HX) (based on the total weight of (G3)).

2. The method according to claim 1, characterized in that the mixture contained in the mixture (G1) hydrocarbons to at least 80 wt.%, Preferably at least 95 wt .-%, at least 5, preferably at least 6, carbon atoms per molecule.

3. The method according to claim 1 or 2, characterized in that the hydrocarbon conversion is selected from an alkylation, a polymerization, a dimerization, an oligomerization, an acylation, a metathesis, a polymerization or copolymerization, an isomerization, a carbonylation or combinations thereof ,

4. The method according to claim 3, characterized in that the hydrocarbon conversion is an isomerization, preferably a

Isomerization of methylcyclopentane (MCP) to cyclohexane. Method according to one of claims 1 to 4, characterized in that the device (V1) is an evaporator, a rectification column, a flash device or a stripping device, in particular (V1) is a flash device

Method according to one of claims 1 to 5, characterized in that i) the mixture (G2) discharged from the device (V1) is at least 95% by weight liquid, ii) the mixture (Gi b ) to at least 95 wt.% Is gaseous and / or iii) the discharged mixture (G2) by at most 150 K, preferably at most 100 K, is warmer than the withdrawn mixture (Gi b).

Process according to any one of Claims 1 to 6, characterized in that the hydrogen halide (HX) is hydrogen chloride (HCl).

Method according to one of claims 1 to 7, characterized in that the laundry according to step c) comprises at least two washing steps, wherein c1) in a first washing step, the aqueous medium used has a pH> 9, preferably> 12, and most preferably contains NaOH .

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c2) in a second washing step, the aqueous medium used has a pH between 5 and 9, preferably between 6 and 8, and, more preferably, demineralized water, optionally step c2) can be carried out prior to step c1).

30

9. The method according to any one of claims 1 to 7, characterized in that the aqueous medium has a pH of 5 to 9, preferably between 6 and 8, and is particularly preferably demineralized water.

10. The method according to any one of claims 1 to 9, characterized in that in the device (V1) a single-stage evaporation, in particular a single-stage flash evaporation, takes place and the device (V1) discharged mixture (G2) without intermediate steps with the aqueous medium is washed.

40 1 1. Process according to one of Claims 1 to 10, characterized in that hydrogen halide (HX) withdrawn via the mixture (Gi b) in step a) is completely or partially recycled to the apparatus in which the hydrocarbon conversion, in particular the isomerization is carried out.

12. The method according to any one of claims 1 to 1 1, characterized in that 5 the mixture (G1) as a hydrocarbon cyclohexane or a mixture of cyclohexane with at least one further hydrocarbon selected from methylcyclopentane (MCP), n-hexane, iso-hexanes , n-heptane, iso-heptanes, methylcyclohexane or dimethylcyclopentanes.

10. The method according to any one of claims 1 to 12, characterized in that the acidic ionic liquid as a cation at least partially alkylated ammonium ion or a heterocyclic cation and / or anion as a chloroalumination having the composition Al _n CI _{(3n + 1)} with 1 <n <2.5.

15. The method according to any one of claims 1 to 13, characterized in that the mixture (G1) additionally contains between 10 and 99 wt .-%, preferably between 50 and 95 wt.% Acidic acidic acid.

15. The method according to any one of claims 1 to 14, characterized in that 20 the mixture (G1) discharged as a discharge from the device in which the hydrocarbon conversion is performed, passed through a phase separation unit, in particular in a phase separator, and then in the device (V1) is fed.

25. The method according to claim 15, characterized in that separated in the phase separation unit from the mixture (G1) at least 90%, preferably at least 99% of the acidic ionic liquid and optionally in the apparatus in which the hydrocarbon conversion is carried out, is returned ,

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17. The method according to any one of claims 1 to 16, characterized in that step c) is carried out as a single- or multi-stage wash using at least one dispersing and phase separation unit or at least one extraction column per Wäschwstufe.

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18. The method according to claim 17, characterized in that the dispersing and phase separation unit is a mixer-settler apparatus, a combination static mixer with phase separator or a combination of mixing pump with phase separator.

40 A method according to claim 17 or 18, characterized in that in a multi-stage washing the mixture (G2) is conducted in countercurrent to the aqueous medium.

A method according to any one of claims 1 to 19, characterized in that from the mixture (G3) cyclohexane is isolated.