EP2734489A1

EP2734489A1 - Reprocessing c4 hydrocarbon mixtures containing olefin

Info

Publication number: EP2734489A1
Application number: EP12723858.2A
Authority: EP
Inventors: Burkard Kreidler
Original assignee: Evonik Degussa GmbH
Current assignee: Evonik Operations GmbH
Priority date: 2011-07-22
Filing date: 2012-05-23
Publication date: 2014-05-28
Also published as: WO2013013856A1; DE102011079674A1

Abstract

The invention relates to a method for reprocessing C₄ hydrocarbon mixtures containing at least 2-butene, wherein the 2-butene is derivatized, is separated in derivatized form, and is converted to 1-butene, at least in part.

Description

Work-up of olefin-containing C ₄ -hydrocarbon mixtures

The present invention relates to a process for the workup of C ₄ - hydrocarbon mixtures containing at least 2-butene in which the 2-butene is derivatized, separated in derivatized form and at least partially converted to 1-butene.

Owing to their reactivity and diverse reaction possibilities, olefins are among the most important building blocks in organic chemistry. They form as

Primary chemicals precursors for a variety of low molecular weight compounds such as alcohols, aldehydes, ketones, carboxylic acids, ethers and halogen compounds. However, the quantitatively most significant application lies in their use as monomers for the preparation of homo- and cooligomers as well as homopolymers and copolymers. Thus, about 50% of the globally produced ethylene and propylene are used to produce polyethylene or polypropylene as bulk plastics. Of the olefins having 4 or more carbon atoms, especially 1-olefins are economically important. Thus, isobutene and 1-butene are used as starting materials for the production of polyisobutene and poly-1-butene, on a large scale

especially needed for the preparation of copolymers such as butyl rubber or ethylene-1 - butene copolymers.

Ethylene and propylene are obtained industrially by catalytic or thermal cracking of mixtures of saturated hydrocarbons from the refining of petroleum, such as liquefied petroleum gas (LPG), natural gas liquid (NGL), naphtha, or gas oil, especially steam cracking of naphtha. Considerable amounts of C ₄ olefins (1,3-butadiene, isobutene, 1-butene, 2-butenes) and to a lesser extent C ₅ and higher olefins are obtained. The proportions of the individual fractions and their composition are determined by the type of

Cracking process, the process conditions and the used

Hydrocarbon mixture influenced. C ₄ and higher olefins may further be promoted by synthesis reaction, ie

Oligomerization and cooligomerization of lower olefins, for example, by oligomerization of ethylene using Ziegler catalysts or combined ethylene oligomerization and olefin metathesis can be obtained in the SHOP process developed by Shell and its variants, as well as by dehydrogenation of

Paraffins or be obtained from alcohols by dehydration.

As a rule, these production processes result in complex product mixtures which require work-up in order to be able to provide the olefins in a sufficient degree of purity for their further use.

The C2 fraction from the cracking of a mixture of saturated hydrocarbons contains ethane and acetylene in addition to ethylene, the C3 fraction in addition to propylene propene and Allen shares and propane. By selective hydrogenation of the polyunsaturated compounds or their removal by extractive distillation, e.g. With

Dimethylformamide or N-methylpyrrolidone and subsequent distillative separation of the olefin from the corresponding saturated hydrocarbon can be obtained from the C2 or C3 fraction of ethylene and propylene in a purity of at least 99.9%, as required for polymerization purposes.

In the case of the C ₄ fraction and higher fractions, the material separation is made more difficult by the presence of a carbon number increasing number of isomers, some of which differ only slightly in their physicochemical properties. Such is the separation of a linear 1-olefin with 4 or more

Carbon atoms of its isomers with internal double bond and / or branched structure by fractional distillation due to the small difference in the boiling points often not feasible with reasonable effort, so that more efficient selective physical and chemical separation methods are used. In particular, 1-butene in technical streams is often present along with other unsaturated and saturated C ₄ hydrocarbons. Thus, the C ₄ fraction from the cracking of a mixture of saturated hydrocarbons as essential components contains the butenisomers isobutene (bp .: -6.9 ° C), 1-butene (bp .: -6.3 ° C), cis-2 Butene (bp .: 3.7 ° C) and trans-2-butene (bp.: 0.9 ° C) and the alkanes n-butane (bp.: - 0.5 ° C) and isobutane (bp. : -1 1, 7 ° C) and polyunsaturated C ₄ compounds, in particular 1, 3-butadiene (bp .: -4.4 ° C). From these mixtures 1-butene can not be separated economically by fractional distillation because of the low boiling point difference between isobutene and 1-butene and the very low separation factor.

According to the technical standard, the workup of the C ₄ fraction is carried out by first removing the polyunsaturated hydrocarbons, mainly 1,3-butadiene, by extraction (-sdistillation) and / or converted by selective hydrogenation to linear butenes. For further separation of this mixture (raffinate I) is generally used in relation to its isomers higher reactivity of isobutene by isobutene is usually reacted with alcohol or water to form a derivative which can be easily separated from the rest of the hydrocarbon mixture. When methanol is used, isobutene is formed from methyl tert-butyl ether (MTBE), when using ethanol ethyl tert-butyl ether (ETBE) and when using water tert-butanol (TBA). These products can be cleaved after their separation in reversal of the formation reaction preferably heterogeneously catalyzed on acidic oxides in the gas phase at 150-300 ° C back to isobutene. However, MTBE is preferably added as such to increase knocking resistance. From the obtained after removal of the isobutene mixture (raffinate II), which contains substantially linear butenes and n-butane and isobutane, the olefins can be separated, for example by extraction distillation.

1-Butene may then be distilled off from the olefin mixture by means of a column of sufficient separation efficiency and capacity, i. separated from the 2-butenes.

The disadvantage of this procedure is that the ratio in which the individual butene isomers are given by the composition of the originally used C ₄ fraction is specified.

Therefore, processes have been developed in the past which allow effective work-up of olefin-containing C ₄ -hydrocarbon mixtures while changing the proportions of the butene isomers.

Thus, an olefin-containing C ₄ -hydrocarbon mixture with a mass fraction of less than 1% by weight of butadiene (raffinate I, C ₄ stream of fluid catalytic cracking

Processes or selectively hydrogenated C ₄ fraction from a cracking process) are simultaneously hydrogenated and isomerized. Here remaining residual butadiene is selectively hydrogenated until its mass fraction is less than 5 ppm and at the same time isomerizes 1-butene to the thermodynamically more stable 2-butenes. The equilibrium position between 1-butene and the isomeric 2-butenes is for example at 80 ° C at a ratio of 1:17. If the isomerization is carried out in a reactive distillation, a virtually 1-butene-free top stream can be separated in this way, from which pure isobutene can be obtained by further work-up. The distillation residue is an isobutene-free mixture which consists essentially of 2-butenes. However, it is disadvantageous on the one hand that the isobutene has a lower purity compared with the separation based on a derivatization by hydration or etherification and secondly that 1-butene is converted into the reaction-bearing as well as economically less attractive 2-butenes.

On the other hand, a process in which the proportion of 1-butene would be increased by isomerization of the 2-butenes, ie, with respect to the 2-butenes, would be considerably more attractive

Working up of a butadiene-poor C ₄ - hydrocarbon mixture mainly isobutene or an isobutene derivative and 1-butene would be obtained.

WO 2008/065171 describes a process for the hydroformylation of olefins in which, in order to increase the yield of linear hydroformylation products, a large part of the olefins contained in the feed used with internals Double bond to 1-olefins isomehsiert. Alumina, silica and / or aluminosilicate supports which are at least partially coated with alkali metal or alkaline earth metal oxides, lanthanides, elements of the iron group, manganese oxide and / or zirconium oxide and in the fixed bed, fluidized bed or moving bed are particularly suitable as catalysts which facilitate double bond isomerization be used. The reaction is advantageously carried out at a pressure of 3-20 bar and a

Temperature is carried out in the range of 200 to 500 ° C, with a

Double bond isomerization is ensured, side reactions such as cleavage, skeletal isomerization, dehydrogenation and oligomerization, however

be largely avoided. However, the double bond isomerization is limited by the thermodynamic equilibrium between the individual isomers, so that the maximum achievable proportion of the respective 1-olefin is fixed at a given temperature. When using raffinate II, for example, the maximum obtainable by isomerization of 2-butenes yield of 1-butene at a temperature of 250 ° C would be only 16%. Accordingly, higher conversions can only be achieved if unreacted olefins with an internal double bond have been separated off and, if appropriate, repeatedly fed to the isomerization stage.

The object of the present invention was thus to provide an efficient process comprising a few process steps for the processing of technical olefin-containing C ₄ -hydrocarbon mixtures, in particular from cracking processes, with which the predominant fraction of 2-butenes can be isomerized to 1-butane as well as isobutene or isobutene derivatives on the one hand and 1-butene on the other hand can be separated in high purity.

The basis of the invention is, on the one hand, that the butenes present in an olefin-containing C ₄ -hydrocarbon mixture can be reacted by reaction with water according to the rule of Markovnikov essentially to secondary and tertiary alcohols, which can be separated by distillation. In this way, formed from isobutene tert-butanol can be separated in particular from 2-butanol formed from 1-butene and 2-butene material. 2-butanol can then pass through catalytic elimination reaction are reacted under non isomerizing conditions to 1 - butene. In particular, 2-butanol can be reacted by kinetically controlled dehydration under non-isomerizing conditions on a mixed oxide catalyst described in WO 2005/058485 A1 with surprisingly high selectivity of up to 98.5% to 1-butene.

The present invention therefore provides a process for working up C ₄ -hydrocarbon mixtures containing at least 2-butene, the process comprising the following steps:

By adding water to the C ₄ -hydrocarbon mixture

Reaction of at least part of the 2-butene to 2-butanol, separation of a fraction comprising 2-butanol and optionally 1 butanol from the mixture obtained under a),

Catalytic elimination of at least part of the 2-butanol contained in the separated fraction as well as the 1-butanol optionally present in the fraction to 1-butene.

In particular, the method of the invention is the workup of

olefin-containing C ₄ -hydrocarbon mixtures which are obtained in the cracking of mixtures of saturated hydrocarbons, for example in the context of the processing of crude oil or natural gas on an industrial scale. It is preferable that in the C ₄ - hydrocarbon mixture in the present process is a C ₄ fraction of a hydrocarbon mixture from a cracking process in petroleum processing.

The process of the present invention has the advantage that it allows in a simple and efficient manner at the same time an efficient separation of isomeric butenes as well as a substantial isomerization of 2-butenes to economically more significant 1-butene. In particular, for the first time a process is described with which from a C ₄ fraction advantageously both isobutene, tert-butyl alcohol (TBA) on the one hand and on the other highly highly enriched 1-butene with isomerization of

predominantly part of the 2-butene to 1-butene can be obtained in two reactive process steps, the first reactive process step also serving for the separation of isobutene and 1-butene in the form of their derivatives. Derivatives include the corresponding products of an addition reaction with water, i. to understand the corresponding isomeric butanols. A particular procedural advantage of the invention is that the fraction separated in step b) does not have to be separated further into 2-butanol and 1-butanol, since in the course of the catalytic elimination both substances are finally converted to 1-butene. It is therefore sufficient to subject the separated fraction containing 2-butanol and optionally also 1-butanol as a whole to the elimination step. Apparative overhead for the isolation of 1-butanol is therefore eliminated.

In addition to 2-butanol and 1-butanol, the separated fraction can also further

Components of the mixture obtained by the reaction of step a). Another object of the present invention is directed to the use of 1-butene obtained by the method according to the invention as a monomer or comonomer for the production of polyolefins, wherein the 1-butene may optionally be purified by distillation additionally before use. In principle, all hydrocarbon mixtures which contain at least 2-butene and essentially hydrocarbons having 4 carbon atoms, in

inventive method can be used. Unless explicitly distinguished between the cis and the trans form, the terms 2-butene and 2-butenes in the context of the present invention mean both stereoisomers in each case, ie. cis-2-butene and trans-2-butene. Analogously, the term butene (e) is the

All butene isomers, ie isobutene, 1-butene and cis- and trans-2-butene to unless expressly understood to differ from the context. The latter also applies mutatis mutandis to the butanol (e) used as generic terms. In addition to 2-butene, the hydrocarbon mixture may typically contain further linear and / or branched olefins, preferably having 4 carbon atoms. In a preferred embodiment, the C ₄ -hydrocarbon mixture used in the process according to the invention comprises, for example, in addition to 2-butene, at least one or more components selected from 1-butene, isobutene and saturated hydrocarbons. In a particularly preferred embodiment of the process according to the invention, the C ₄ -hydrocarbon mixture comprises, in addition to 2-butene, at least 1-butene, isobutene and saturated hydrocarbons. The proportion of butenes is typically at least 95% by weight, preferably at least 99% by weight, particularly preferably at least 99.5% by weight, in each case based on the total weight of the monoethylenically unsaturated compounds present in the hydrocarbon mixture. In addition to the monoethylenically unsaturated compounds, that used in the process according to the invention

Hydrocarbon mixture saturated and / or polyethylenically unsaturated hydrocarbons, preferably having 4 carbon atoms. Particular preference is given to those mixtures in which the proportion of saturated and mono- and polyethylenically unsaturated hydrocarbons with 4

Carbon atoms together at least 90 wt.%, Preferably at least 95 wt.%, Particularly preferably at least 99 wt.%, Particularly preferably at least 99.5 wt.% Based on the total weight of the C ₄ - hydrocarbon mixture used. The proportion of saturated hydrocarbons in the total weight of the hydrocarbon mixture is preferably at most 60% by weight, particularly preferably at most 40% by weight and very particularly preferably at most 20% by weight. The hydrocarbon mixture used in the process according to the invention is preferably a large-scale olefin-containing C ₄ - Hydrocarbon mixture. Suitable industrially available olefin-containing C ₄ -hydrocarbon mixtures result primarily from the cracking of mixtures of saturated hydrocarbons in petroleum processing,

for example by catalytic cracking, for example in fluid catalytic cracking (FCC) or hydrocracking with subsequent dehydrogenation, but especially by thermal cracking processes, especially in the presence of water vapor

(Steam splitting, steam cracking). The use mixtures used in these processes are primarily liquefied petroleum gas (LPG), natural gas liquid (NGL), naphtha or gas oil. In a particularly preferred embodiment of the process according to the invention, the hydrocarbon mixture used is a C ₄ fraction from a hydrocarbon mixture from a cracking process in the

Petroleum processing. Such C ₄ fractions are obtainable, for example, by fluid catalytic cracking or steam cracking of gas oil or by steam cracking of naphtha. C ₄ -hydrocarbon mixtures which can be used in the process of the present invention can furthermore also be carried, for example, by

Catalytic dehydrogenation of LPG and NGL, by dimerization of ethylene using Ziegler catalysts or olefin metathesis in the SHOP process developed by Shell and its variants, as well as by dehydration of C ₄ alcohols win. The large-scale production of olefin-containing C ₄ -hydrocarbon mixtures by means of one of the abovementioned options is possible by customary methods known to the person skilled in the art (see, for example, K. Weissermehl, J. Arpe, Industrielle Organische Chemie, 4th edition, VCH Verlag, Weinheim, 1994). , The exact chemical composition of the C ₄ -hydrocarbon mixture is influenced by the type of cleavage process, the process conditions and the feed mixture.

A C ₄ fraction from naphtha steam cracking suitable for use in the process according to the invention has, for example, a composition containing several or all of the following components:

From 10 to 60% by weight of 1,3-butadiene,

10 to 40% by weight of isobutene, 5 to 30% by weight of 1-butene,

From 2 to 15% by weight of trans-2-butene,

From 2 to 15% by weight of cis-2-butene,

1 to 10% by weight of n-butane,

0.5 to 5% by weight of isobutane,

in total not more than 5% by weight of vinylacetylene, ethylacetylene and 1,2-butadiene, and also trace gases such as propene, propane, cyclopropane, allenes, methylcyclopropane, pentenes, pentanes etc. with a maximum proportion of 1% by weight and a maximum of 5% by weight .% where all salary information is based on the total weight of the

Refer hydrocarbon mixture.

A C ₄ -hydrocarbon mixture from a fluid catalytic cracking (FCC) process can preferably also be used in the process according to the invention, which typically has a composition which contains several or all of the following components:

15 to 40% by weight, preferably 20 to 35% by weight, isobutane,

From 2 to 15% by weight, preferably from 4 to 10% by weight, of n-butane,

5 to 25% by weight, preferably 12 to 17% by weight, 1-butene,

From 15 to 45% by weight, preferably from 20 to 35% by weight, of 2-butenes,

From 10 to 30% by weight, preferably from 18 to 25% by weight, of isobutene,

less than 2% by weight, preferably less than 1% by weight, of 1, 3-butadiene,

in total less than 10% by weight, preferably less than 5% by weight, of C ₅ -hydrocarbons, and in total less than 2% by weight, preferably less than 1% by weight, of C ₃ -hydrocarbons, all of the contents being based on

Total weight of the hydrocarbon mixture relate.

The content of oxygen-containing, sulfur-containing, nitrogen-containing and / or halogen-containing compounds in the C ₄ -hydrocarbon mixture used is preferably not more than 500 ppm by weight, preferably not more than 100 ppm by weight, particularly preferably not more than 10% by weight. ppm, and more preferably not more than 1 ppm by weight, based in each case on the total weight of the mixture. At higher starting content, such compounds can be substantially removed by treating the C ₄ -hydrocarbon mixture with a suitable adsorbent, such as with a molecular sieve in an upstream step. Sulfur-containing impurities such as mercaptans can be removed, in particular by extraction with alkaline aqueous solution, optionally under catalytic oxidation. Suitable, known in the art such

For example, the Merox processes of UOP and the fiber film processes of Merichem are desulfurization processes. If the C ₄ -hydrocarbon mixture contains polyunsaturated hydrocarbons, such as 1,3-butadiene, vinylacetylene, ethylacetylene and 1,2-butadiene, these can preferably be present in one or more of these several of the processing according to the invention upstream process steps are removed by extraction and / or extraction distillation and / or by selective hydrogenation in monounsaturated

Hydrocarbons are transferred. For example, 1, 3-butadiene forms with

Copper ammonium acetate [Cu (NH ₃ ) ₂ ] OAc reversible Complexes, which can be separated by extraction from a C ₄ -hydrocarbon mixture. In particular, the separation of the main amount of polyunsaturated compounds from the C ₄ hydrocarbon mixture, ie in particular of 1, 3-butadiene, but by extraction distillation done. Extraction solvents suitable for this purpose are, for example, dimethylformamide, dimethylacetamide, acetonitrile or N-methylpyrrolidone.

The extraction solvent is usually passed in countercurrent to the fully vaporized C ₄ -hydrocarbon mixture in an extraction column from below, whereby the solvent is charged with the more soluble polyunsaturated compounds. Components of dissolved monounsaturated compounds can be driven off by feeding polyunsaturated compounds at the lower end of the extraction column. At the top of the extraction column is obtained in this way a hydrocarbon mixture which is substantially free of polyunsaturated compounds. The residual content of polyunsaturated

Total of compounds is at most 1% by weight, preferably less than 0.2% by weight, based on the total weight of the butadiene-poor C _{4 obtained} . Hydrocarbon mixture. By selective hydrogenation, for example, according to the procedure described in EP 81 041 or DE 15 68 542, the proportion of polyunsaturated compounds can further to a residual content of less than 10 ppm by weight, preferably not more than 5 ppm by weight and completely more preferably not more than 1 ppm by weight, based on the total weight of the C ₄ -

Hydrocarbon mixtures are reduced. The use of, for example, accessible in the above manner butadiene-poor C ₄ hydrocarbon mixtures with a

Residual content of at most 0.5% by weight, preferably less than 0.2% by weight, more preferably less than 0.1% by weight, very particularly preferably less than 10 ppm of 1,3-butadiene is particularly preferred in the process according to the invention , A C ₄ - fraction from a hydrocarbon mixture from a cracking process in petroleum processing, which has largely been freed, for example in the above-described manner of polyunsaturated compounds, in particular 1, 3-butadiene is

commonly referred to as raffinate I.

A raffinate I, which preferably as C ₄ hydrocarbon mixture in

according to the invention can be used, e.g. usually a composition containing several or all of the following components:

From 1 to 10% by weight, preferably from 2 to 5% by weight, isobutane,

From 5 to 15% by weight, preferably from 7 to 12% by weight, of n-butane,

15 to 40% by weight, preferably 25 to 35% by weight, 1-butene,

From 5 to 12% by weight, preferably from 7 to 10% by weight, of trans-2-butene,

From 2 to 8% by weight, preferably from 4 to 6% by weight, of cis-2-butene,

30 to 55 wt.%, Preferably 40-50 wt.%, Isobutene, and

not more than 0.5% by weight, preferably less than 0.3% by weight, more preferably less than 0.1% by weight, of 1,3-butadiene,

all salary data are based on the total weight of the

Refer hydrocarbon mixture. The C ₄ -hydrocarbon mixture, from which optionally as described above oxygen, sulfur, nitrogen and / or halogen-containing compounds and / or polyunsaturated compounds were removed, water is added in step a) to react the butenes to butanols.

The subject matter of the present invention is thus directed to a process for working up C ₄ -hydrocarbon mixtures containing at least 2-butene, the process comprising the following steps:

(a).

(a) by adding water to the C ₄ -hydrocarbon mixture, reacting at least part of the 2-butene to 2-butanol,

(b) separation of a fraction containing 2-butanol and optionally 1 -

Butanol from the mixture obtained under a),

(c) Catalytic elimination of at least a portion of the separated one in the

Fraction containing 2-butanol and optionally contained in the fraction 1-butanol to 1-butene.

The reaction with water in step a) of the process according to the invention can be carried out in particular by acid catalysis. As acidic catalysts are suitable

equally diluted mineral acids, e.g. Sulfuric acid, hydrochloric acid or

Nitric acid, as well as acidic ion exchangers. Also Lewis acids such as e.g.

Aluminum halides, BF ₃ or SnCl ₄ can be used as catalysts in process step a) of the process according to the invention.

In the reaction in process step a) is formed in accordance with the rule of Markovnikov from linear butenes, ie 2-butene and optionally present 1-butene, by addition reaction with water, essentially 2-butanol while isobutene contained in any of the C ₄ - hydrocarbon mixture analogously tert tert. Butanol results. The proportion of 1-butanol formed in the reaction is low, typically <10% by weight with respect to the total amount of butanol formed. The reaction of the butenisomers with water over acidic catalysts is well known to those skilled in the art. As early as 1926, Benjamin T. Brooks in Chem. Rev., 1926, 2, 369-394 summarized that the isomeric butenes under identical

Reactivate conditions to tert-butanol and secondary 2-butanol.

In addition to 2-butene, the C ₄ -hydrocarbon mixture used in the process according to the invention comprises at least one or more

Components selected from 1-butene, isobutene and saturated hydrocarbons, so usually in step a) optionally present 1-butene is at least partially reacted to 2-butanol and optionally also to 1-butanol and optionally to at least partially tert isobutene . Butanol reacted. In a particularly preferred embodiment of the process according to the invention, the C ₄ -hydrocarbon mixture comprises, in addition to 2-butene, at least 1-butene, isobutene and saturated hydrocarbons, to which water is added in step a) for reaction, at least part of the 2-butene being added to 2 Butanol, 1-butene at least in part to 2-butanol and optionally also to 1-butanol and isobutene is at least partially reacted to tert-butanol.

In conventional procedure, the reaction in step a) of

process according to the invention at a temperature in the range of 30-80 ° C, preferably from 50-70 ° C, and at a pressure in the range of 5-25 bar absolute, preferably from 10-15 bar absolute. Water can be in the water

Be used and supplied to the olefin-containing hydrocarbon mixture in the presence of the catalyst in a reactor in countercurrent.

The mixture obtained from process step a) is subsequently separated by material. In principle, all physical / chemical separation processes with which an effective separation of the 2-butanol formed in step a) from any tert-butanol formed, on the one hand, and from the unreacted hydrocarbons, on the other hand, can be regarded as suitable for use in the context of the present invention , Suitable embodiments usable

physical-chemical separation processes such as condensation, freezing, distillation, Absorption and / or adsorption can, for. B. Ullmann's Encyclopedia of Industrial Chemistry, Verlag Chemie, Weinheim, 4th ed., Volume 2, page 489 ff.

Preferably, however, the separation in process step b) is carried out by distillation, preferably by means of fractional distillation. The fraction to be subjected to the catalytic elimination, containing 2-butanol and optionally also 1-butanol is preferably withdrawn from the stripping section of the distillation column. When

The distillation column may in this case be any distillation column known to the person skilled in the art, e.g. a bubble tray column, packed column, packed column or

Dividing wall column can be used. The distillation can at a pressure of 1 to 50 bar absolute, preferably from 2 to 40 bar absolute and more preferably from 5 to 20 bar absolute setting a temperature in the bottom of the distillation column in the range of 40 to 250 ° C, in particular in the range 50 to 200 ° C and especially in the range of 60 to 140 ° C are performed.

By means of fractional distillation, the mixture obtained from process step a) can be separated into at least two fractions, namely a fraction comprising 2-butanol, at least partly formed by reaction of 2-butene with water, and a low-boiling fraction. For the purposes of the present invention, the term low-boiling fraction is to be understood as meaning a fraction of chemical compounds which have boiling points which are at least 30 K, preferably at least 50 K and particularly preferably at least 70 K lower than the boiling point of 2-butanol it is mainly hydrocarbons unconverted in process step a), ie saturated hydrocarbons, e.g. n-butane, isobutane, propane or pentenes or unreacted unsaturated hydrocarbons, i. especially butenes act. All within the scope of the present invention

The boiling point data used here refer to atmospheric pressure, as long as no deviating information is given. The fraction comprising 2-butanol, if present in the mixture to be separated, often also contains 1-butanol. Contains the mixture to be separated from process step a) tert-butanol from the

Addition reaction of isobutene with water, it is desirable this in one or separate several additional fractions. For this purpose, it can be exploited that the boiling point of the tert-butyl alcohol is lower than that of the corresponding n-butyl and 2-butyl alcohols. Includes the C ₄ used in the process according to the invention

Hydrocarbon mixture in addition to 2-butene at least one or more

Components selected from 1-butene, isobutene and saturated hydrocarbons, so that in step a) optionally present 1-butene at least in part to 2-butanol and optionally also to 1-butanol and optionally present isobutene at least in part to tert.- Butanol is reacted, the resulting mixture in process step b) can thus be separated by distillation

a low boiler fraction containing unreacted butenes and / or saturated hydrocarbons,

- A fraction containing 2-butanol and optionally 1-butanol and optionally a fraction containing tert-butanol.

The boiling points of 2-butanol (bp.: 99 ° C), 1-butanol (bp.: 1 18 ° C) and tert-butanol (bp. 82 ° C) are significantly higher than the boiling points in the zu separating mixture of hydrocarbons present, ie in particular of isobutene (bp .: - 6.9 ° C), 1-butene (bp.: -6.3 ° C), cis-2-butene (bp.: 3.7 ° C ) and trans-2-butene (bp.

0.9 ° C), n-butane (bp: -0.5 ° C) and isobutane (bp .: -1 1, 7 ° C). The hydrocarbons can therefore be effectively separated from the alcohols by fractional distillation and pass as low boiler fraction at the top of the distillation column. 1 - Butanol and 2-butanol are withdrawn together from the stripping section. While the isomeric butenes, in particular isobutene and 1-butene, can not be separated by distillation at reasonable expense owing to similar boiling points, the hydration of the butenes thus permits unproblematic and economical distillative separation of the isomeric butenone-derived derivatives, ie the isomeric butanols, from one another. In a preferred embodiment of the process according to the invention, at least part of the low-boiling fraction is recycled to process step a). This measure can serve to increase the total turnover of the butenes, provided that they are reacted only in part during a single reactor pass of the reaction with water. Preferably, any existing saturated

Hydrocarbons from the low boiler fraction after their separation in

Process step b) e.g. separated by a subsequent fractional distillation and the remaining portion containing the unsaturated compounds, then

Process step a) fed to the reaction again. In process step b) optionally separated tert-butanol is converted in a particular embodiment of the method according to the invention at least in part by reversing the respective formation reaction, ie elimination of water, to isobutene. For this purpose, the tert-butanol-containing fraction, optionally after further purification, usually in the gas or liquid phase of heterogeneous acidic oxide catalysts such as SiO ₂ -modified Al ₂ O 3 catalysts in a

Temperature in the range of 80-150 ° C (liquid phase) or from 150 to 370 ° C and a pressure of 5-20 bar (gas phase) implemented. The isobutene formed in this way can by distillation without much effort to isobutene of

Polymer quality with a purity of at least 99.0 wt.%, In particular of at least 99.5 wt.% To be purified.

The fraction comprising 2-butanol and optionally 1-butanol is used after any further purification in step c) of the process according to the invention, in which a catalytic elimination of at least part of the separated 2-butanol to 1-butene takes place. According to the invention, 1-butanol optionally present in a mixture with the 2-butanol can likewise be reacted to give 1-butanol. In the context of the present invention, catalytic elimination is to be understood as meaning a catalytic elimination of water (dehydration). The catalytic elimination in

Process step c) is preferably carried out on a mixed oxide catalyst comprising zirconium dioxide, yttrium oxide (Y 2 O 3) and at least one alkali and / or Erdalkalinnetalloxid. The catalyst comprises, in particular, a proportion of zirconium dioxide of 80 to 99 parts by mass, preferably of 93 to 96 parts by mass, a proportion of yttrium oxide (Y.sub.2O.sub.3) of 0.5 to 10, preferably 3.5 to 6 parts by mass, and a proportion of alkali metal oxide. and / or alkaline earth metal oxide of 0.1 to 3, preferably from 0.5 to 2, particularly preferably from 0.5 to 1 parts by mass. It may contain one or more oxide (s) from the group of alkali or alkaline earth metals, in particular a

Alkali metal oxide selected from potassium oxide and sodium oxide. The preparation of the catalyst can be carried out as described in WO 2005/058485, page 6, line 21 to page 8, line 16 and examples 1 and 2.

The elimination, mainly with the above-mentioned mixed oxide catalyst, is preferably carried out at a temperature in the range of 200 to 450 ° C, especially 280 to 380 ° C. It is preferably carried out in the gas phase. The catalyst may in this case be suspended in the reactor or arranged in lumps in the fixed bed and the catalyst loading in grams of starting material per gram of catalyst per hour, 0.01 to 15 h ^"1 , preferably 0.5 to 5 h ^{" 1} . The pressure under which the elimination of water is carried out, is in a range of 0.1 to 25 bar absolute, preferably from 0.2 to 10 bar absolute and more preferably between 1 and 5 bar absolute.

In general, in the elimination of 2-butanol with elimination of water, 1-butene (Hofmann product) and / or 2-butene (Saytzev product) can be formed as primary products. 2-Butene is thermodynamically more stable than the isomeric 1-butene and therefore predominates in the product mixture under equilibrium conditions. In contrast, the mixed oxide catalyst preferably used in the process according to the invention comprising zirconium dioxide, yttrium oxide (Y 2 O 3) and at least one alkali metal and / or alkaline earth metal oxide permits selective kinetically controlled elimination to 1-butene as the desired product, especially when 2-butanol is used. Under the selected reaction conditions is also a subsequent

Isomerization of the 1-butene to the thermodynamically more stable 2-butenes avoided. The elimination is carried out in process step c) usually only up to a partial conversion, for example up to a conversion of 50 to 95% based on the total

Amount of substance to -so each available-2-butanol and 1-butanol. This serves to avoid unwanted side reactions such as a progressive

Equilibration. However, the total conversion can advantageously be increased by separating off at least part of the 1-butene by distillation after process step c) and, preferably, at least part of the 2-butanol unreacted in process step c), optionally mixed with 1-butanol, again the

Elimination according to step c) is supplied. Is also formed as a by-product in the elimination step formed butanone by distillation from the resulting

Separated product mixture, then hydrogenated to 2-butanol and the elimination again fed, in process step c) 1-butene in some particular

preferred embodiments with a selectivity of 95 to 98.5% are obtained.

The process according to the invention therefore makes it possible to obtain 2-butenes contained in the originally used C ₄ -hydrocarbon mixture overall

Intermediate the alcohol derivative largely to 1-butene to isomerize and this at the same time effectively separated by distillation. The proportion of the economically significant 1-butene, which can be obtained from the olefin-containing C ₄ hydrocarbon mixture used, can thus be significantly increased. In particular, can be obtained by the present invention advantageously in a process comprising a few steps at the same time isobutene and 1-butene as important (co) monomers in high purity, wherein the proportion of 1-butene is significantly increased by the isomerization of 2-butene.

Thus, by working up a C ₄ -hydrocarbon mixture according to the invention, 1-butene having a content of 2-butene of less than 10% by weight, based on the

Total mass of 1-butene and 2-butene can be obtained. In particular, the 1-butene is preferably obtained in a purity of at least 95% by weight, preferably at least 97% by weight. From a Roh-1-Butt of such quality can be by distillation with relatively few separation stages in comparison to the distillation of polymer grade raffinate II 1 -buten, ie a purity of at least 99.0

% By weight, preferably of at least 99.5% by weight.

The 1-butene obtained by means of the process according to the invention can be used as monomer or comonomer for the preparation of polyolefins, it being possible for the 1-butene optionally to have been additionally purified by distillation before use.

Claims

claims:

1 . A process for the workup of C ₄ -hydrocarbon mixtures containing

at least 2-butene, characterized in that the method comprises the following steps:

(a) adding at least part of the 2-butene to 2-butanol by adding water to the C ₄ -hydrocarbon mixture,

(b) separation of a fraction comprising 2-butanol and optionally 1-butanol from the mixture obtained under a),

(c) Catalytic elimination of at least a portion of the separated one in the

2. The method according to claim 1, characterized in that the C ₄ - hydrocarbon mixture is a C ₄ fraction from a hydrocarbon mixture from a cracking process in petroleum processing.

3. The method according to any one of the preceding claims, characterized in that the C ₄ hydrocarbon mixture polyunsaturated

Contains hydrocarbons and these are removed in one or more upstream process steps by extraction and / or extraction distillation and / or converted by selective hydrogenation in monounsaturated hydrocarbons.

4. The method according to any one of the preceding claims, characterized in that the reaction with water in process step a) takes place acid catalysed and / or the separation in process step b) is carried out by distillation.

5. The method according to any one of the preceding claims, characterized in that the C ₄ hydrocarbon mixture in addition to 2-butene at least one or more components selected from 1-butene, isobutene and saturated Hydrocarbons comprises, wherein in process step a) optionally present 1-butene is reacted at least in part to 2-butanol and optionally also to 1-butanol and optionally present isobutene is reacted at least in part to tert-butanol.

A method according to claim 5, characterized in that the mixture in process step b) is separated by distillation

a fraction containing 2-butanol and optionally 1-butanol, and optionally a fraction containing tert-butanol

A method according to claim 6, characterized in that at least a part of the low boiler fraction is returned in step a).

A method according to claim 6, characterized in that the separated tert-butanol is reacted at least in part with elimination of water to isobutene.

Method according to one of the preceding claims, characterized in that the catalytic elimination in process step c) on a mixed oxide catalyst comprising zirconia, yttria (Y2O3) and at least one alkali and / or alkaline earth metal oxide, preferably at a temperature in the range of 200 to 450 ° C, is performed.

Method according to one of the preceding claims, characterized in that after step c) at least a portion of the 1-butene separated by distillation, and, preferably, at least a portion of the unreacted in step c) 2-butanol again the elimination according to step c) becomes.

1 . Method according to one of the preceding claims, characterized in that after process step c) 1-butene with a content of 2-butene less than 10 wt.% Based on the total mass of 1-butene and 2-butene, preferably 1 - butene in one Purity of at least 95 wt.%, Particularly preferably of at least 97 wt.% Is obtained.

2. Use of according to the method of any one of claims 1 to 1 1st

1-butene obtained as a monomer or comonomer for the preparation of polyolefins, wherein the 1-butene is optionally additionally distilled by distillation before use.