WO2014060463A1

WO2014060463A1 - Method for producing cyclohexane with pre-separation of dimethylpentanes

Info

Publication number: WO2014060463A1
Application number: PCT/EP2013/071605
Authority: WO
Inventors: Markus Schmitt; Katharina SPUHL; Jochen BÜRKLE; Stefan Bitterlich; Steffen Tschirschwitz; Michael HÜBNER; Pawel CZAJKA
Original assignee: Basf Se
Priority date: 2012-10-18
Filing date: 2013-10-16
Publication date: 2014-04-24
Also published as: EP2909158A1; CN104718178A

Abstract

The present invention relates to a method for producing cyclohexane from benzene and/or methylcyclopentane (MCP) by hydrogenation or isomerisation. Prior to cyclohexane production, the dimethylpentanes (DMP) are separated in a distillation device (D1) from a hydrocarbon mixture (KG1) which contains DMP in addition to benzene and/or MCP. If cyclohexane is already present in the hydrocarbon mixture (KG1), the cyclohexane is separated initially with DMP in conjunction with benzene and/or MCP. The already present cyclohexane can be re-separated from DMP in a subsequent distillation step and can be recycled into the process in order to produce cyclohexane.

Description

Process for the preparation of cyclohexane with a preliminary separation of dimethylpentanes

description

The present invention relates to a process for the preparation of cyclohexane from benzene and / or methylcyclopentane (MCP) by hydrogenation or isomerization. Before the cyclohexane preparation, the DMP are separated off from a hydrocarbon mixture (KG1) which, in addition to benzene and / or MCP, also contains dimethylpentane (DMP) in a distillation apparatus (D1). If cyclohexane is already present in the hydrocarbon mixture (KG1), this cyclohexane is first separated off together with DMP from benzene and / or MCP. This already existing cyclohexane can be separated off again from DMP in a subsequent distillation step and recycled to the process for cyclohexane production.

Cyclohexane is an important value product of the chemical industry, which can be produced for example by hydrogenation of benzene or by isomerization of methylcyclopentane (MCP). However, the educts (benzene or MCP) which can be used for cyclohexane preparation are generally not present in practice as pure substances, but rather as constituents of hydrocarbon mixtures. The concrete composition of the hydrocarbon mixtures can vary widely. Often, benzene and / or MCP are contained in hydrocarbon mixtures derived from a steam cracking process. As further components, dimethylpentanes (DMP) are frequently included in such hydrocarbon mixtures. In addition, these hydrocarbon mixtures may already contain the actual target product cyclohexane. However, in order to obtain a pure target product, that is specification-compliant cyclohexane, the cyclohexane must be separated from all other components present in the hydrocarbon mixture used which are still present after the hydrogenation or isomerization, ie also from DMP contained in the starting mixture. However, the separation of the DMP from the actual process product cyclohexane is technically quite demanding and expensive, especially when it is the DMP isomer 2,4-dimethylpentane (2,4-DMP). The normal boiling point of 2,4-DMP at 80.52 ° C is very similar to the normal boiling point of cyclohexane (80.78 ° C), whereas the normal boiling points of the other DMP isomers are more distant from cyclohexane (2,3-DMP has, for example, a normal boiling point of 89.88 ° C).

US-A 2,846,485 discloses a process for producing high purity cyclohexane and benzene using a mixture comprising n-hexane, benzene, MCP, Cyclohexane and DMP contains. In a first extractive distillation zone, benzene is separated from the other educt components. The benzene-substantially liberated educt is combined with a mixture containing cyclohexane and MCP and comes from the bottom of a second fractional distillation zone. The mixture thus combined is fed into a first fractional distillation zone, an MCP-containing fraction being removed overhead and a cyclohexane-containing fraction being separated from the bottom.

The overhead product of the first fractional distillation zone is first passed to an isomerization zone in which the bulk of MCP is isomerized to cyclohexane using Fried I force catalysts such as aluminum chloride, which may additionally contain HCl. The isomerization product is introduced into the second fractionating distillation zone described above to separate there n-hexane and low boilers as the top product. The bottom product from the first fractional distillation zone is transferred to a second extractive distillation zone in which a mixture containing cyclohexane from the bottom is separated from the overhead DMP.

The process described in US-A 2,846,485 is disadvantageous because it is (among other things) expensive in terms of apparatus. The separation of the actual process product cyclohexane from DMP takes place only at the end of the process, since the cyclohexane formed in the isomerization of MCP is recycled to a DMP-containing fraction. Furthermore, in this process, the benzene is first separated off to recover it as an independent product. However, the benzene separation is more expensive in terms of apparatus than the hydrogenation to cyclohexane contained in one embodiment of the present invention.

US Pat. No. 3,311,1667 relates to a process for the removal of benzene from a mixture which is subsequently fed into an isomerization of MCP to cyclohexane. In the hydrogenation, benzene is hydrogenated with hydrogen to cyclohexane in the presence of a suitable catalyst, for example a metal catalyst on kieselguhr. The isomerization of MCP to cyclohexane is carried out in the presence of metal halides such as acid-reinforced aluminum halide. In US-A 3,311 1, 667, however, it is not described that the material used for the hydrogenation or isomerization may also contain DMP. Consequently, this document also contains no information as to where DMP is separated from cyclohexane or that this separation is problematic.

EP-A 1 995 297 discloses a process and associated apparatus for the hydrogenation and decyclization of benzene and the isomerization of C ₅ -C ₆ paraffins contained in a mixture containing not more than 1% by weight. can be used, wherein the elements of the platinum group, tin or cobalt and molybdenum are suitable as metal. For the isomerization of the mixture obtained in the hydrogenation, which may contain a residual amount of benzene, in particular zeolites are used as catalyst. In the process described in EP-A 1 995 297, the parameters are set in the isomerization in such a way that an opening of the cyclohexane rings obtained in the hydrogenation of benzene to isoalkanes is achieved. Thus, this process is not primarily concerned with the production of cyclohexane but with the production of alkanes with a high degree of branching. In addition, EP-A 1 995 297 contains no information that the educt used can contain DMP or that the separation of cyclohexane and DMP is problematic.

Ionic liquids are suitable, inter alia, 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 does not take place in the presence of an olefin, but rather with a copper (III) compound.

US-A 2005/0082201 discloses a process for the preparation of gasoline with a low benzene content, wherein first in a first process step, a hydrocarbon mixture containing benzene, olefins and sulfur-containing compounds such as thiophenes, is fed to a distillation column from the overhead the low-boiling Compounds, a side draw a benzene-containing fraction and from the bottom of the column, the high boilers are separated. In a second stage of the process, the fraction recovered from the side draw is hydrogenated in the presence of a hydrogenation catalyst to convert benzene to cyclohexane and the thiophenes to hydrogen sulfide. The obtained in the second process stage cyclohexane-containing mixture is suitable for the production of gasoline with a low benzene content. An isolation of the cyclohexane contained therein or an isomerization of MCP to cyclohexane are not disclosed in US-A 2005/0082201, the same applies to a possible presence of DMP in the starting mixture.

WO 2010/027987 relates to another process for reducing the concentration of benzene in a hydrocarbon-containing mixture. In a first separation step, a benzene-containing fraction comprising benzene and other C ₆ hydrocarbons is separated from a high boiler fraction comprising carbons of seven and more carbon atoms. The benzene-containing fraction is then hydrogenated the hydrogenation of benzene is formed cyclohexane. WO 2010/027987 also contains no information that cyclohexane can be isolated from the mixture obtained in the hydrogenation; on the contrary, this process product should also be used for gasoline production. Neither does this document disclose isomerization of MCP to cyclohexane or the presence of DMP in the starting hydrogen mixture.

The carrying out of an extractive distillation for the separation of dense substances has already been known for some time and is disclosed, for example, in US Pat. No. 4,053,369, US Pat. No. 4,955,468 or WO 02/22528. In US-A 4,053,369 it is superficially about carrying out the extractive distillation as such, detached from a single concrete separation problem. As an example from a number of very many examples, the above-mentioned documents also disclose the separation of DMP and cyclohexane by means of extractive distillation. However, the production of cyclohexane from benzene and / or MCP by hydrogenation or isomerization is not disclosed in these documents.

The object underlying the present invention is to provide a novel process for the preparation of cyclohexane from a hydrocarbon mixture. Furthermore, there should be the possibility that optionally contained in the hydrocarbon mixture cyclohexane can be recovered.

The object is achieved by a process for the preparation of cyclohexane, comprising the following steps a) feed of a hydrocarbon mixture (KG1), comprising

i) benzene and / or methylcyclopentane (MCP) and

ii) dimethylpentane (DMP) in a distillation apparatus (D1), b) separating a stream (S1) containing DMP from the bottom of the distillation apparatus (D1), c) separating a stream (S2) containing benzene and / or MCP from an outlet of Distillation device (D1), wherein the outlet is arranged above the sump of (D1), d) feeding the stream (S2) into at least one device (V) which is suitable for hydrogenation and / or isomerization, wherein in the device (V) the production of the cyclohexane by hydrogenation of benzene and / or by isomerization of MCP and the distillation device (D1) upstream of the device (V) is arranged. Pure cyclohexane can be prepared from benzene and / or MCP in an advantageous manner by the process according to the invention if hydrocarbon mixtures (starting mixtures) are used for the production of cyclohexane which, in addition to benzene and / or MCP, also contain DMP. Another advantage of the method according to the invention is the fact that it can be carried out very flexibly. Depending on the composition of the hydrocarbon mixture used (KG1 / starting mixture), after DMP has been completely or at least largely separated off (KG1) ("DMP pre-separation"), hydrogenation and / or isomerization can be carried out If the starting mixture comprises MCP If both a hydrogenation and an isomerization is carried out, the order is arbitrary, preferably according to the invention first the hydrogenation and then the isomerization carried out.

Due to the preliminary separation of DMP before the actual cyclohexane production process, the extremely complex separation, in particular distillation, of DMP can be circumvented from the cyclohexane process product, in particular when the DMP is 2,4-dimethylpentane (2,4-DMP) and this is present in the starting mixture in a concentration> 100 ppm, This significantly reduces the energy and equipment expense in the production of pure or high-purity cyclohexane. By means of the process according to the invention, the DMP contained in the starting mixture can advantageously be completely or almost completely removed from the starting mixture by the preliminary separation. The process according to the invention is particularly preferably carried out in such a way that the DMP present in the starting mixture is separated completely or almost completely (up to 2% based on the amount of all DMP isomers contained in the starting mixture) from the starting mixture by DMP preliminary separation. Alternatively, an almost complete DMP removal from the starting mixture can also be defined via the amount of DMP remaining in stream (S2) with respect to MCP and / or benzene. In this approach, it is particularly preferred that the amount of DMP withdrawn overhead from stream (S2) in the distillation apparatus based on the sum of the overhead amounts of MCP and benzene is at most 0.1% by weight, The process according to the invention can be carried out independently of whether or not cyclohexane is already present in the hydrocarbon mixture used (starting mixture). If, in addition to DMP, cyclohexane itself is also present in the hydrocarbon mixtures used, this cyclohexane contained in the starting mixture is separated off in the course of the process according to the invention together with DMP via the bottom. However, the disadvantage of reducing the amount of cyclohexane product associated with this case constellation is overcompensated by the above-described reduction in the expenditure of energy and apparatus.

However, in one embodiment of the present invention, this cyclohexane contained in the starting hydrocarbon mixture can be recovered. In this embodiment, the discharged together with the DMP from the process cyclohexane is separated by distillation, preferably by an extractive or entrainer distillation of DMP again. The resulting cyclohexane, which is substantially free of DMP, can be recycled to the actual process product (cyclohexane, which is prepared by the process according to the invention) or fed into the process of the invention at another point. The advantage of this process variant over a separation from a point further back in the process (downstream), ie z. Example, from the cyclohexane product stream, it can be seen that the DMP separation is carried out by a much smaller amount of cyclohexane, since DMP is separated only from the cyclohexane contained in the starting hydrocarbon mixture and not from that in the hydrogenation and / or Isomerization formed cyclohexane, which is the actual process product. As a result, smaller devices and a smaller amount of energy are required for this separate DMP / cyclohexane separation. In the context of the present invention, distillation can be carried out in all embodiments known to the person skilled in the art (see, for example, Kirk-Othmer Encyclopedia of Chemical Technology Published Online: 2 AUG 2004, Vol. 8 p. 786 et seq.), For example also as extractive distillation, Entrainer distillation (azeotropic distillation) or rectification. The respective distillation techniques are carried out in the corresponding devices known to the person skilled in the art. For example, an extractive distillation usually comprises at least one extractive distillation column and at least one regeneration apparatus, which is preferably also designed as a column and the extractive distillation column is connected downstream. The carrying out of an extractive distillation for the separation of dense substances is as already described above, for example, described in US Pat. No. 4,053,369, US Pat. No. 4,955,468 or WO 02/22528. 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 "dimethylpentanes" (DMP) is understood as meaning all known isomers of dimethylpentane, in particular 2,2-dimethylpentane (2,2-DMP, normal boiling point: 79, 17 ° C.), 2,3-dimethylpentane (DMP). Normal boiling point: 89.88 ° C), 3,3-dimethylpentane (3,3-DMP, normal boiling point: 86.09 ° C) and 2,4-dimethylpentane (2,4-DMP; This means that at least one dimethylpentane isomer is present in the corresponding mixtures or streams of the process according to the invention, preferably mixtures of two or more dimethylpentane isomers, one of these isomers preferably being 2, 4-dimethylpentane is.

In the context of the present invention, the term "compounds having a normal boiling point of 79 to 84 ° C" means all hydrocarbons boiling at atmospheric pressure in the range of 79 to 84 ° C and the first or in the inventive process in the hydrocarbon mixture ( In the context of the process according to the invention, one or more of these compounds can be separated from one another If desired, individual or several of these compounds can also be listed separately in the following text as a constituent of mixtures or streams the other compounds with a normal boiling point of 79-84 ° C, which are not listed by name in the relevant stream or mixture (unless otherwise stated or, for example, inf olge a previous separation no longer possible) also be present in the corresponding stream or mixture. Optionally, one or more of these compounds may also fall within the definition of another selection of compounds, such as, for example, the definition of the term "C ₅ -C ₆ alkanes".

Examples of compounds having a normal boiling point of 79 to 84 ° C are cyclohexane (80.78 ° C), 2,2-DMP (79, 17 ° C), 2,4-DMP (80.52 ° C), 2, 2,3-trimethylbutane (80.87 ° C) and benzene (80.08 ° C).

The same as above for the compounds with a normal boiling point of Compounds which fall under the term "high boiler with a normal boiling point

Examples of low boilers with a normal boiling point> 84 ° C are 3,3-DMP (86,09 ° C), 2,3-DMP (89,88 ° C) and the iso-heptanes 2- Methylhexane (2-MH; 90.06 ° C), 3-methylhexane (3-MH; 91, 87 ° C) and 3-ethylpentane (3-EP, 93.45 ° C).

In the context of the present invention, the two abovementioned groups of compounds (compounds having a normal boiling point of 79 to 84 ° C. and high boilers having a normal boiling point> 84 ° C.) may, if appropriate, also be combined to form a group of compounds. In this case constellation, the compounds are described as "high boiler with a normal boiling point

> 78 ° C. "The above comments on the two individual groups apply mutatis mutandis to this group of compounds.

Hereinafter, the inventive method for the production of cyclohexane by hydrogenation of benzene and / or isomerization of MCP, wherein a preliminary separation of DMP is carried out, further defined.

In the context of the present invention, in step a) the feed of a hydrocarbon mixture (KG1), comprising i) benzene and / or methylcyclopentane (MCP) and

ii) Dimethylpentane (DMP) in a distillation apparatus (D1).

The individual components of the hydrocarbon mixture (KG1) can be present in any desired concentrations / ratios. The hydrocarbon mixture (KG1) preferably contains at least 90% by weight, preferably at least 95% by weight, of hydrocarbons having 5 to 8 carbon atoms. The hydrocarbons may be saturated or unsaturated and / or cyclic, linear or branched. In particular, the hydrocarbon mixture (KG1) contains between 10% by weight and 60% by weight, more preferably between 20% by weight and 50% by weight, MCP and / or between 1% by weight and 30% by weight. %, more preferably between 4% and 20% by weight of benzene.

In a preferred embodiment of the present invention, cyclohexane is additionally present in the hydrocarbon mixture (KG1). Preferably contains (KG1)

MCP, iv) cyclohexane and

v) optionally at least one further compound selected from olefins or C ₅ -C ₈ alkanes.

Besides linear, monounsaturated olefins, such as pentene or hexene 5 In the component v) of the hydrocarbon mixture (KG1) the term "olefin" cyclic olefins, particularly cyclohexene, and dienes and cyclic dienes. Further, in the group of C ₅ -C ₈ alkanes also contain high boilers with a normal boiling point> 84 ° C. or compounds with a standard boiling point of 79 to 10 84 ° C. If appropriate, hydrocarbons having more than eight carbon atoms and / or hydrocarbons with one can also be present in the hydrocarbon mixture (KG1) relatively low boiling point, for example, those having less than five carbon atoms.

In the distillation apparatus (D1), the DMP contained in the hydrocarbon mixture (KG1) is preferably completely or almost completely (up to 2% based on the amount of DMP contained in (KG1)) of (KG1), in particular of benzene and / or MCP (ie the main components of the stream (S2)) separated. Alternatively, an almost complete removal of DMP from the starting mixture can also be defined by the amount of DMP remaining in stream (S2) with respect to MCP and / or benzene. In this approach, it is particularly preferred that the DMP amount withdrawn overhead from stream (S2) in the distillation apparatus (S2), based on the sum of the overhead amounts of MCP and benzene, is at most 0.1% by weight is at most 5 0.02 wt .-%.

Preferably, the distillation apparatus (D 1) is a rectification column. Furthermore, it is preferred that the outlet of the distillation apparatus (D1), from which the stream (S2) is separated according to step c), is located above the inlet, with which the hydrocarbon mixture (KG1) is fed into (D1) the outlet is in the head of (D1).

Furthermore, it is preferred that the distillation apparatus (D1) contains no reaction zone in which benzene and / or MCP are hydrogenated, and / or the stream (S2) contains 35 at most 2%, preferably at most 0.5% of cyclohexane (based on the amount contained in the hydrocarbon mixture (KG1)).

In step b) of the process according to the invention, the separation of a stream (S1) comprising DMP preferably takes place from the bottom of the distillation apparatus (D 1). The specific composition of the stream (S1) depends on the specific composition of the hydrocarbon mixture (KG1) used. The current (KG1) is also cyclohexane, the stream (S1) usually contains most of the cyclohexane from (KG1), preferably> 90%.

The stream (S1) separated from the bottom of the distillation apparatus (D1) contains DMP and optionally further components. The other components are preferably cyclohexane, high boilers with a normal boiling point> 78 ° C and / or unsaturated compounds. Some of the unsaturated compounds can also be considered as high boilers with a normal boiling point> 78 ° C. The unsaturated compounds are preferably selected from benzene, olefins, cyclic olefins, in particular cyclohexene, dienes and cyclic dienes.

Preferably stream (S1) contains at least 98% of the DMP contained in the hydrocarbon mixture (KG1), more preferably at least 99% of the DMP. Furthermore, it is preferred that the stream (S1) separated from the bottom of the distillation apparatus (D1) contains at most 10%, preferably at most 5%, particularly preferably at most 2%, of the MCP contained in (KG1). In step c) of the method according to the invention, the separation of a stream (S2) containing benzene and / or MCP from an outlet of the distillation apparatus (D1), wherein the outlet is disposed above the sump of (D1). The specific composition of the stream (S2) depends on the specific composition of the hydrocarbon mixture (KG1) used. The stream (S2) always necessarily contains benzene or MCP, preferably benzene and MCP. If cyclohexane is also present in the hydrocarbon mixture (KG1) used, the stream (S2) generally contains only a portion of the cyclohexane from (KG1), preferably <10%. Preferably, step c) is carried out such that the stream (S2) contains at least 95%, preferably at least 98% of the hydrocarbon mixture (KG1) contained subset consisting of benzene and MCP and / or that the stream (S2) at most 0, 1 wt .-%, preferably at most 0.02 wt .-%, (based on the total amount of benzene and MCP in stream (S2)) DMP. More preferably, the stream (S2) contains at most 0.015 wt .-%, (based on the total amount of benzene and MCP in stream (S2)) 2,4-DMP.

In step d) of the process according to the invention, the current (S2) is fed into at least one device (V) which is suitable for hydrogenation and / or isomerization. In the device (V), the preparation of the cyclohexane by hydrogenation of benzene and / or by isomerization of MCP. Furthermore, the Distillation device (D1) upstream of the device (V), the device (V) is thus downstream of the distillation device (D1).

Depending on the composition of the hydrocarbon mixture (KG1) used in step a) and consequently also of the stream (S2) which is fed into at least one device (V), hydrogenation and / or isomerization are carried out according to the invention in step d). Hydrogenation is only necessary if (KG1) contains benzene and optionally cyclohexene. Again, isomerization is only required if (KG1) contains MCP. However, if (KG1) contains both benzene (and optionally cyclohexene) and MCP, according to the invention both a hydrogenation and an isomerization are carried out. The hydrogenation and the isomerization are preferably carried out spatially separated from each other in at least one separate device (V) (see also the comments below in the text). Carrying out a hydrogenation of benzene as such for the production of cyclohexane and / or carrying out an isomerization of MCP as such for the production of cyclohexane are known in principle to the person skilled in the art.

In a first embodiment of the present invention, the device (V) is at least one hydrogenation reactor (HR). In this embodiment, benzene is hydrogenated to cyclohexane in the hydrogenation reactor (HR), wherein the hydrogenation is preferably carried out using hydrogen. Furthermore, it is preferred that the hydrogenation takes place in the liquid phase and / or in the presence of a nickel-containing catalyst. This first embodiment will be further clarified in the following text.

The hydrogenation of benzene to cyclohexane is usually carried out in the presence of a suitable catalyst. Suitable catalysts are in principle all known to those skilled in the catalysts, such as a metal catalyst on diatomaceous earth according to US-A 3,311 1, 667 or metal-containing catalysts according to EP A 1 995 297, where as the metal elements of the platinum group, tin or cobalt and Molybdenum preferably be used.

Preferably, the hydrogenation is carried out in the presence of a catalyst containing as active metal (also referred to as metal component or active component) at least one element of the 8th to 10th group of the Periodic Table of the Elements (PSE), for example iron, cobalt, nickel or ruthenium (corresponds to Subgroup VIIIB of the CAS version of the PSE), in particular nickel or ruthenium. Furthermore, it is preferred that the active metal is applied to a carrier material (carrier). Suitable carriers are in principle all carriers known to the person skilled in the art, for example SiO ₂ -containing, zirconium oxide-containing or aluminum oxide-containing carriers. Particular preference is given to using a catalyst which The hydrogenation as such is carried out and operated in a manner known per se to the person skilled in the art, preferably a combination of a main reactor operated in the optionally cooled circulation (recycling of a portion of the mixture flowing out of the reactor into the mixture flowing into the reactor, where appropriate the cooling is placed before or after the said feed) and a subsequent in-line, that is operated without feedback secondary reactor. In this case, the device (V) thus comprises two hydrogenation reactors (HR).

The hydrogenation reactors (H R) are preferably designed as fixed bed reactors without internal cooling. In this case, the hydrogenation is preferably operated so that the temperature difference between incoming and exiting mixture is monitored continuously and when this value falls below a certain setpoint, the inlet temperature is raised. Furthermore, it is preferred that the hydrogenation reactors are operated in trickle mode.

Further preferably, the hydrogenation is followed by an apparatus in which is expanded to a pressure below that set in the post-reactor pressure. In this case, a gas stream is produced which contains hydrogen previously dissolved in the hydrocarbon mixture and in any case is compressed and returned to at least one of the hydrogenation reactors (HR).

The hydrogenation is preferably carried out at a temperature between 50 and 200 ° C, more preferably between 100 and 180 ° C and / or a pressure between 10 and 300 bar abs., Particularly preferably between 30 and 200 bar abs. carried out.

It is further preferred in the hydrogenation process according to the invention that the total conversion of the benzene (and optionally other unsaturated compounds present in the stream (S2)) is at least 90%, more preferably 99%, and / or the residual content of the benzene (and optionally other im Current (S2) unsaturated compounds contained) 1 wt .-%, preferably at most 0, 1 wt .-%, particularly preferably at most 0.01 wt .-% is. In a second embodiment of the present invention, the device (V) is at least one suitable device (VAI) for carrying out an alkane isomerization. In this embodiment, in the device (VAI) suitable for carrying out an alkane isomerization, MCP is isomerized to cyclohexane, preferably in the presence of an acidic ionic liquid. This second embodiment will be further clarified in the following text. The isomerization of MCP to cyclohexane is usually carried out in the presence of a suitable catalyst. Suitable catalysts are in principle all catalysts known to those skilled in the art, for example Friedel-Crafts catalysts according to US-A 2,846,485 such as aluminum chloride, which may additionally contain HCl, or metal halides according to US-A 3,311 1, 667 such as aluminum chloride, zirconium chloride or boron trifluoride , Also suitable as catalysts are the zeolites or ionic liquids used in EP-A 1 995 297, as used, for example, in WO 201 1/069929. In the present invention, the isomerization is preferably carried out in the presence of an acidic ionic liquid having the composition K1 Al _n X _{(3n + 1)} , wherein K1 is a monovalent cation, X is halogen and 1 <n <2.5. 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) one to ten 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 one to three 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. Further, in the isomerization, in addition to the acidic ionic liquid, a hydrogen halide (HX) may also be used as a cocatalyst. When For example, hydrogen fluoride (HF), hydrogen chloride (HCl), hydrogen bromide (HBr) or hydrogen iodide (Hl). 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 whose halide moiety is also contained in the above-described acidic ionic liquid (at least partially) in the corresponding anion is used. Preferably, the hydrogen halide (HX) is hydrogen chloride (HCl) or hydrogen bromide (HBr). Most preferably, the hydrogen halide (HX) is hydrogen chloride (HCl).

10

As device (V) for carrying out the isomerization, it is possible in principle to use all devices known to the person skilled in the art for such a purpose. Preferably, the device (V) is a stirred tank or a stirred tank cascade. Rührkesselkaskade means that two or more, for example, three or four, 15 stirred tank are connected in series (in series).

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 during the isomerization is between 1 and 20 bar abs. (absolute), preferably between 2 and 10 bar abs., Is.

Carrying out an isomerization of MCP in the presence of an acidic ionic liquid as catalyst and optionally a hydrogen halide as cocatalyst is known to the person skilled in the art. Preferably, the hydrocarbons form

25 (ie cyclohexane, MCP and optionally other hydrocarbons present in the stream (S2)) and the ionic liquid in the isomerization in each case a separate phase, wherein subsets of the ionic liquid may be contained in the hydrocarbon phase and subsets of the hydrocarbons in the ionic liquid phase. If available, that will

Hydrogen halide, in particular hydrogen chloride, preferably introduced in gaseous form into the device (V) 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.

35

The isomerization in the apparatus (V) is preferably carried out such that two liquid phases and one gas phase are present 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 40-90% by weight of the hydrocarbons. The gas phase contains at least 90% by weight of at least one hydrogen halide, preferably hydrogen chloride. Possibly contains, from which the ionische liquid is formed, as for example 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.

Preferably, the process according to the invention is carried out with hydrocarbon mixtures (KG1) which contain both benzene and MCP. In this case (third embodiment of the process according to the invention), hydrogenation and isomerization of the starting mixture completely or at least substantially freed from DMP are carried out for cyclohexane preparation according to step d) after the preliminary DMP separation. It is therefore a combination of the above-described first and second embodiments according to step d), wherein the above-described explanations to the first and second embodiments apply mutatis mutandis to the present third embodiment.

Optionally, the hydrogenation and the isomerization can be performed together in a single device (V), preferably in this third embodiment of the process according to the invention, the hydrogenation and the isomerization carried out spatially separated from each other. The device (V) preferably comprises at least one hydrogenation reactor (HR) (for the hydrogenation) and at least one device (VAI) suitable for carrying out an alkane isomerization. The sequence or the number of stages is arbitrary, preferably first a hydrogenation and then an isomerization is carried out. The hydrogenation can be carried out, for example, in one or in two reactors connected in series ("two-stage") .The same applies to the isomerization, which can be carried out, for example, in a stirred tank cascade of three or more stirred tanks in succession and / or isomerization in at least one device (V) resulting cyclohexane is usually isolated from the device (V) cyclohexane in a purity of at least 98 wt .-%, preferably at least 99.5 wt.%, Particularly preferably 99 When several devices (V) are used, the isolation of the cyclohexane is preferably carried out from the mixture obtained in the last device (V), that is, the device (V) located furthest downstream. The isolation as such is carried out by methods known to those skilled in the art, for example using one or more Distillation in which in the device (V) after hydrogenation and / or isomerization contained cyclohexane-containing mixture is fed. Optionally, the device (V) designed according to the first, second, third or (subsequent) fourth embodiment comprises, in addition to the mentioned reaction apparatuses, further devices, in particular means for separating substances, eg. B. by rectification or distillation. Such devices may be used, for example, to isolate cyclohexane and / or to separate high boilers from a mixture or the target product.

FIG. 1 again illustrates the method according to the invention in accordance with a preferred embodiment of steps a) to d). CH is cyclohexane, B is benzene and the terms in parenthesis indicate the most relevant and / or major components of the particular stream for the process. Benzene and / or MCP can be present in the starting mixture (KG1) and correspondingly in the stream (S2), preferably benzene and MCP are present. The device (V) is selected according to the composition of (KG1) / the current (S2) as described above (first to third embodiments). When both benzene and MCP are present, the device (V) comprises both hydrogenation and isomerization (third embodiment). The hydrogenation is preferably carried out in at least one reactor, the isomerization preferably in a stirred tank or a stirred tank cascade, wherein the isomerization of the hydrogenation is connected downstream.

In a further preferred embodiment (fourth embodiment) of the process according to the invention, the cyclohexane optionally present in the stream (S1) is separated off from DMP, in particular by distillation in a distillation apparatus (D2). In this case, the stream (S1) is introduced into the distillation apparatus (D2), wherein in (D2) cyclohexane is separated off from DMP. The concrete composition of the stream (S1) has already been described above in connection with step b) according to the invention. The distillation or the distillation apparatus (D2) can be one-stage or multi-stage, for example two-stage or three-stage, preferably three-stage. In this context, the number of stages (stage) is the number of columns, each including ancillary apparatus such. B. bottom evaporator and condensers, understood, which together form the distillation apparatus (D2). A three-stage distillation apparatus (D2) means that a total of three columns, each including ancillary equipment such. B. bottom evaporator and condensers, in each of which a distillation process can be carried out together form the distillation apparatus (D2). Preferably, (D2) comprises an extractive distillation column.

If the distillation apparatus (D2) comprises an extractive distillation column, (Extractive adjuvant). Extractive auxiliaries as a rule compounds are used, for which the following formula (1) applies:

With

YDMP, E ^~ activity coefficient of 2,4-dimethylpentane in the extractive aid at infinite dilution,

YcH, E ₌ activity coefficient of cyclohexane in the extractive auxiliary at infinite

Dilution, n = preferably 1, 1, particularly preferably 1, 3. As extractive auxiliaries, preference is given to using oxygen-containing open-chain or cyclic organic compounds having a boiling point of at least 5 K above that of cyclohexane (81 ° C.), especially those which contain an amide function R-CO-NR'R "as structural element R, R 'and R "(independently of one another) are preferably selected from C ₃ -C 30 -alkyl or H. Particularly suitable extractive aids are N-methylpyrrolidone, N-formylmorpholine. However, compounds such as sulfolane, dimethyl sulfoxide or other compounds known to the skilled person as non-protic polar solvents are also suitable. Also suitable are mixtures of several of the compounds mentioned with one another or with water. Preferably, the cyclohexane / DMP separation comprises the following steps i) to iii) and optionally step iv), wherein the distillation apparatus (D2) is formed by the three components (D2-1) to (D2-3): i) a rectification column (D2-1), in which the majority of the high boiler with a normal boiling point> 84 ° C (based on the amount in the feed to (D2-1) over

Sump and most of the cyclohexane and other compounds with a normal boiling point of 79 to 84 ° C (based on the amount in the feed to D2-1) are removed overhead, ii) an extractive distillation column (D2-2), in the top product of (D2-1) is combined with an extractive aid and distilled in such a way that the majority of the extractive aid and the cyclohexane over sump and most of the other compounds contained in the top product of (D2-1) iii) a regeneration column (D2-3), in which the majority of the cyclohexane contained in the bottom stream from (D2-2) is overhead and the major part is at a normal boiling point of 79-84 ° C the extractive aid contained in the bottom stream from (D2-2) are withdrawn via bottom and iv) optionally a hydrogenation apparatus, in which the top product from (D2-3) is performed.

In the above embodiment, the term "majority" (unless stated otherwise) means at least 50% by weight, preferably at least 80% by weight, more preferably at least 95% by weight, in particular at least 99% by weight (the values are to be understood as proportions of the respective feed stream).

The optional step iv) contained in the above embodiment is usually carried out only if the stream (S1) contains unsaturated compounds which are thus also fed to the distillation apparatus (D2) and which, moreover, do not pass through the bottom of the rectification column ( D2-1) are removed from the process. The hydrogenation according to optional step iv) can be carried out analogously to the hydrogenation according to the first embodiment described above, preferably it is carried out in one stage.

Optionally, the preferred embodiment of cyclohexane / DMP separation described above can also be carried out without a rectification column (D2-1) as a compulsory constituent. In this variant, the cyclohexane / DMP separation is carried out only by using the two columns (D2-2) and (D2-3) mutatis mutandis, optionally also a hydrogenation device can be downstream. This variant is preferably carried out, provided that in the stream (S1) no or only a small proportion of high boilers with a normal boiling point> 84 ° C are included. If these high boilers are present, they are for the most part withdrawn together with the other compounds with a normal boiling point of 79 to 84 ° C overhead (D2-2). The above-described preferred embodiment using the extractive distillation column (D2-2) is preferably carried out and operated such that the DMP-containing stream withdrawn overhead from (D2-2) is less than 50% by weight, preferably less than 10% by weight. - contains% cyclohexane. Furthermore, the cyclohexane-containing stream withdrawn via overhead regeneration column (D2-3) preferably contains less than 1% by weight, more preferably less than 10 ppm by weight of extractive assistant and / or less than 1% by weight, preferably less than 300 ppm Dimethylpentane, more preferably less than 150 weight ppm of 2,4-dimethylpentane.

Furthermore, it is preferred that cyclohexane in a purity of at least 98 wt .-%, in particular at least 99.5 wt .-%, from (D2) is isolated. With regard to carrying out the isolation of the cyclohexane, the same considerations apply as stated above in connection with the isolation of the cyclohexane from the device (V). Alternatively, the cyclohexane derived from the distillation apparatus (D2) according to the fourth embodiment may be combined with the cyclohexane prepared in the apparatus (V) according to the first to third embodiments.

The fourth embodiment of the present invention described above is additionally illustrated below in a preferred embodiment in conjunction with FIG. In FIG. 2, the abbreviations, arrows and other symbols have an analogous meaning, which has been described above for FIG. 1 or in the description of this preferred embodiment. In the embodiment according to FIG. 2, a distillation apparatus (D2) consisting essentially of three columns ((D2-1) to D2-3)) is used, which is followed by a hydrogenation apparatus. The individual columns may also include ancillary equipment such as sump evaporators or condensers, which are not shown in Figure 2 for clarity. HV means hydrogenation device, EHM means extractive aid, S> 84 means low boiler with a normal boiling point> 84 ° C, 24DMP means 2,4-dimethylpentane and the bracketed terms give the most relevant and / or major components of the respective stream at. 24DMP is exemplified as the preferred component of (other) compounds with a normal boiling point of 79-84 ° C. The extractive aid used is preferably N-methyl-2-pyrrolidone (NMP).

The stream (S1), preferably from the bottom of the distillation apparatus (D1), which contains DMP, cyclohexane, unsaturated compounds and, if appropriate, high boilers having a normal boiling point> 78 ° C., is fed into the rectification column (D2-1). The unsaturated compounds are preferably selected from benzene, olefins, cyclic olefins, in particular cyclohexene, dienes and cyclic dienes. In (D2-1), the concentration of the cyclohexane present in the stream (S1) takes place, the stream (S1) first being rectified in a component which boils heavier than cyclohexane (ie, for example, 3,3-DMP and other high boilers having a normal boiling point) 84 ° C or correspondingly boiling unsaturated compounds) enriched stream 15 and a heavier than cyclohexane boiling components other compounds having a boiling point of 79 to 84 ° C, at least a portion of the unsaturated compounds and a residual amount of high boilers having a normal boiling point> 84 ° C) is separated. Stream 15 may, for example, be fed to a steam cracking process as cofeed or used as part of fuel blends.

Stream 16 is fed to an extractive distillation column (D2-2). In the extractive distillation column (D2-2) at a point above the feed of stream 16, a at least one extractive aid (EHM) containing stream 17 is performed. At a location also above the inlet of stream 16, preferably above the inlet of stream 17, z. B. at the top of the column or after the top condenser of the column, a stream 18 is taken, which is compared to stream 16 at other compounds with a normal boiling point of 79 to 84 ° C, in particular to 2,4-DMP, enriched. Preferably, the stream 18 contains a majority of the other compounds contained in the stream 16 with a normal boiling point of 79 to 84 ° C, in particular to 2,4-DMP. Via a point below the inlet of stream 16, preferably via the bottom of the column, a stream 19 is taken, containing the extractive aid, cyclohexane and the unsaturated compounds, wherein in stream 19 the concentration ratio cyclohexane / other compounds with a normal boiling point of 79 to 84 ° C, especially 2,4-DMP, is higher than in the stream 16.

The extractive distillation column (D2-2) is preferably carried out and operated so that stream 18 contains at most 100 ppm by weight, preferably at most 10 ppm by weight, more preferably at most 1 ppm by weight of extractive auxiliary. This can be achieved by the highest feed of an EHM-containing stream at least 5, preferably at least 10 theoretical plates (according to the definition of the skilled worker) below the head and / or (D2-2) with a reflux ratio of at least 5, preferably at least 10 is operated. Stream 19 is passed, optionally after preheating, into the regeneration column (D2-3). From the regeneration column (D2-3) is compared to stream 19 to cyclohexane enriched stream 20 and a stream 19 against cyclohexane depleted stream 21 (stream 21 contains superficially the extractive aid, a subset of cyclohexane and (optionally) a residual amount of other Stripped compounds with a normal boiling point of 79 to 84 ° C, in particular to 2,4-DMP). From stream 21, a discharge stream (purge stream) 21 a is branched off, which preferably accounts for at most 5%, particularly preferably at most 1%, of the amount of stream 21. The remaining stream is, if appropriate after cooling (which can also take place in the heat network with preheating of stream 19) at least partially fed to the stream 17 and / or returned in the vicinity of the stream 16 in the extractive distillation column (D2-2). Stream 20 is optionally passed into the hydrogenation device (HV) along with a hydrogen-containing stream in which the unsaturated compounds selected from benzene, olefins, cyclic olefins, especially cyclohexene, dienes and cyclic dienes, are hydrogenated with the aid of a suitable catalyst. However, hydrogen can also be introduced separately from stream 20 in (HV), as shown in FIG. The stream 22 obtained in the hydrogenation contains cyclohexane as the main constituent and may, if appropriate, be worked up further, for example specification-compliant (high-purity) cyclohexane can be isolated from stream 22. Optionally, the stream 22 can also be combined with the cyclohexane or a cyclohexane-containing stream which is prepared in the process according to the invention in the device (V) (according to the first to third embodiments).

In the present invention, a combination of the third and fourth embodiments described above is preferably performed.

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

For the simulation calculation the BASF own software Chemasim is used (using the commercially available software Aspen Plus (manufacturer: Aspen Tech, Burlington / Massachusetts, USA) one would get the same results). The following rough composition of the hydrocarbon mixture (KG1) is used (for detailed composition, see Table 1):

Benzene 9.6% by weight

Methylcyclopentane (MCP) 32.0% by weight

Dimethypentane (DMP) 0.8% by weight

Other hydrocarbons 57.6% w / w

In the device (V), in the following Examples 1 and 2, first a hydrogenation and then an isomerization is carried out. The relevant parameters for this are as follows:

1 . Hydrogenation: Ni fixed bed catalyst

36 bar H ₂

Reaction temperature: 140-160 ° C

2. Isomerization: Hydrocarbon conversion in the presence of an ionic

Liquid (trimethylammoniumheptachlorodialumate)

Reaction pressure: 3.5 bara HCl In the two examples, the distillation apparatus D1 is arranged once before the apparatus V (Example 1) and once after the apparatus V (Comparative Example 2). 1st example with pre-separation of DMP

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

Said hydrocarbon mixture KG1 (for detailed composition, see Table 1) is introduced into a distillation apparatus D1 (rectification column). In this, the DMP contained in KG1 is separated off via the bottom of D1 (S1) in such a way that stream S2 still contains at most 0.1% by weight, based on benzene and MCP, of DMP (see S2 Table 1). Stream S2 is withdrawn as distillate from D1 and contains the corresponding benzene and MCP. Subsequently, this is placed in a device V, in which cyclohexane is prepared by hydrogenation of benzene and by isomerization of MCP. The cyclohexane produced leaves device V with a purity of at least 99.9% by weight (see CH Table 1).

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

Column D1

Number of steps 80

Return ratio 4.159

Evaporator power [kW] 2003

Capacitor power [kW] 2005

To ensure the separation of the DMP in the column D1 to 80 stages with an evaporator power of about 2 MW are required.

2nd comparative example with post-separation of DMP

Comparative Example 2 is shown schematically in FIG. Unless otherwise indicated, in FIG. 3 the abbreviations and symbols have the same meanings as described above for FIGS. 1 or 2.

The said hydrocarbon mixture KG1 (detailed composition see Table 1) is in this case fed first to the device V, in which cyclohexane is prepared by hydrogenation of benzene and by isomerization of MCP. The DMP is not separated in an upstream column. The stream S2 ^* , coming from the hydrogenation or isomerization stage, is now placed in a distillation apparatus (rectification column). In this, the DMP contained in S2 ^* is removed via the bottom as stream S1 ^* , so that a purity of 98% by weight is given for CH in the distillate. The detailed compositions of the individual streams are in Table 2.

Table 2: Properties and composition of the streams

Comparative Example 2

Current: KG1 S2 * S1 * CH

topology

from apparatus V D1 D1 to apparatus V D1

Phase River River River

Properties Unit act. Value act. Value act. Value act. value

Temperature ° C 25 40 93, 12315 80,307801

Pressure bar 1 1, 1 1 1

Enthalpy kW 67 66 33 11 1

Mass flow kg / h 5000 3178 580 2598

Concentrations MolM. Unit act. Value act. Value act. Value act. value

CYCLOPENTANE 70.135 g / g 0.09493 0.00000 0.00000 0.00000

2-M-PENTANE 86.179 g / g 0.06739 0.00000 0.00000 0.00000 3-M-PENTANE 86.179 g / g 0.04333 0.00000 0.00000 0.00000

HEXAN 86.179 g / g 0.14666 0.00000 0.00000 0.00000

M-CY-PENTANE 84.163 g / g 0.32621 0.00046 0.00000 0.00056

CYCLOHEXAN 84.163 g / g 0.08849 0.81202 0.00673 0.99178

HEPTAN 100.21 g / g 0.02436 0.03828 0.20977 0.00000

2-M-HEXAN 100.21 g / g 0.02875 0.05125 0.28085 0.00000

C13DMCPENTAN 98.19 g / g 0.00938 0.00733 0.04017 0.00000

M-CYCLOHEXAN 98.19 g / g 0.00689 0.03048 0, 16702 0.00000

BENZOL 78.1 15 g / g 0.09628 0.00000 0.00000 0.00000

2,4DM-PENTAN 100,21 g / g 0,00608 0,00254 0,00000 0,0031 1

3-M-HEXAN 100.21 g / g 0.02582 0.04143 0.22705 0.00000

2.2DM PENTAN 100.206 g / g 0.00237 0.00372 0.00000 0.00455

To ensure the purity of 98 wt .-% of CH, 200 columns with an evaporator capacity of about 13 MW is required for the column D1.

3. Results of the simulation calculation

The results show that the separation of the high boilers (DMP) allows a higher purity of the cyclohexane with significantly lower investment (80 steps vs. 200 steps) and variable costs (2 MW vs. 13 MW).

Claims

claims

Process for the preparation of cyclohexane, comprising the following steps: a) Feed of a hydrocarbon mixture (KG1) comprising

i) benzene and / or methylcyclopentane (MCP) and

ii) dimethylpentane (DMP)

in a distillation apparatus (D1), b) separating a stream (S1) containing DMP from the bottom of the distillation apparatus (D1), c) separating a stream (S2) containing benzene and / or MCP from an outlet of the distillation apparatus (D1), wherein the outlet above the

D) feeding the stream (S2) into at least one device (V) which is suitable for hydrogenation and / or isomerization, wherein in the device (V) the preparation of the cyclohexane by hydrogenation of benzene and or by isomerization of MCP and the distillation device (D1) upstream of the device (V) is arranged. 2. The method according to claim 1, characterized in that from the device (V) cyclohexane in a purity of at least 98 wt .-%, preferably of at least 99.5 wt .-%, particularly preferably of at least 99.9 wt. % is isolated.

Process according to Claim 1 or 2, characterized in that hydrocarbon mixture (KG1) additionally contains cyclohexane (KG1)

i) benzene,

ii) MCP,

iii) DMP,

iv) cyclohexane and

v) optionally at least one further compound selected olefins or C ₅ -C ₈ alkanes. 4. The method according to any one of claims 1 to 3, characterized in that the stream (S2) at least 95%, preferably at least 98% of im Benzene and MCP and / or that the stream (S2) contains at most 0.1% by weight, preferably at most 0.02% by weight (based on the total amount of benzene and MCP in stream (S2)) DMP, particularly preferably the stream (S2) contains at most 0.015% by weight (based on the total amount of benzene and MCP in stream (S2)) 2,4-DMP.

5. The method according to any one of claims 1 to 4, characterized in that the distillation apparatus (D1) is a rectification column and that the outlet of the distillation apparatus (D1) from which according to step e) the stream (S2) is separated, above the Zulaufs is located, with the

Hydrocarbon mixture (KG1) is fed into (D1), preferably the outlet is in the head of (D1).

6. The method according to any one of claims 1 to 5, characterized in that the distillation apparatus (D1) contains no reaction zone in which benzene and / or MCP are hydrogenated, and / or the stream (S2) at most 2%, preferably at most 0, Contains 5% of cyclohexane (based on the amount contained in the hydrocarbon mixture (KG1)). 7. The method according to any one of claims 1 to 6, characterized in that the from the bottom of the distillation apparatus (D1) separated stream (S1) contains DMP, preferably at least 98% of the DMP contained in the hydrocarbon mixture (KG1) and / or that the stream (S1) separated from the bottom of the distillation apparatus (D1) is at most 10%, preferably at most 5%, particularly preferably at most 2% of the weight in

(KG1) contained in MCPs.

8. The method according to any one of claims 3 to 7, characterized in that the stream (S1) is introduced into a distillation apparatus (D2), wherein in (D2) cyclohexane is separated from DMP, preferably (D2) comprises a

Extractive distillation column and / or cyclohexane is preferably in a purity of at least 98 wt .-%, in particular at least 99.5 wt .-%, isolated from (D2). 9. The method according to claim 8, characterized in that the cyclohexane / DMP separation comprises the following steps i) to iii) and optionally step iv), wherein the distillation device (D2) by the three components (D2-1) to (D2 -3) is formed: a rectification column (D2-1), in which a large part of the high boiler with a NormalsiedeDunkt> 84 ° C (bezoaen on the Menae in the inlet to Compounds with a normal boiling point of 79 to 84 ° C (based on the amount in the feed to D2-1) are separated overhead, an extractive distillation column (D2-2), in which the top product of (D2-1) with an extractive aid is collected and distilled in such a way that the majority of the extractive aid and the cyclohexane over the bottom and most of the other compounds contained in the top product of (D2-1) with a normal boiling point of 79 to 84 ° C from the top (D2-2) are withdrawn, a regeneration column (D2-3), in which most of the cyclohexane contained in the bottom stream from (D2-2) overhead and most of the extractive aid contained in the bottom stream (D2-2) are withdrawn via bottom and optionally a hydrogenation device into which the overhead product from (D2-3) is guided.

Process according to claim 8 or 9, characterized in that cydohexane originating from the distillation apparatus (D2) is combined with the cyclohexane prepared in the apparatus (V).

1 1. Method according to one of claims 1 to 10, characterized in that, the device (V) is at least one hydrogenation reactor (HR) and / or the

Device (V) is at least one device suitable for carrying out an alkane isomerization (VAI).

12. The method according to claim 1 1, characterized in that in the hydrogenation reactor (HR) benzene is hydrogenated to Cydohexan, preferably in

Presence of a nickel-containing catalyst.

13. The method according to claim 1 1 or 12, characterized in that in the device suitable for carrying out an alkane isomerization (VAI) MCP is isomerized to cyclohexane, preferably in the presence of an acidic ionic liquid.