ES2540085T3 - Procedure for oligomerization of isobutene in hydrocarbon streams containing n-butene - Google Patents

Abstract

Process for oligomerization of isobutene in the presence of n-butene in a solid acidic ion exchanger, characterized in that the reaction is carried out in an ion exchanger whose acidic protons were partly exchanged for metal ions .

Description

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DESCRIPTION

Procedure for oligomerization of isobutene in hydrocarbon streams containing n-butene

The invention relates to a process for the oligomerization of isobutene in mixtures of hydrocarbons containing isobutene in a solid acidic ion exchange resin, in which the acidic ion exchange resin contains sulfonic acid groups whose protons were partly exchanged for metal ions.

A mixture of 2,4,4-trimethylpent-1-ene and 2,4,4-trimethylpent-2-ene, technically designated as diisobutene, is obtained on an industrial scale by isobutene dimerization. It is a coveted fuel component, in particular after hydrogenation to form the corresponding paraffin (isooctane, 2,4,4-trimethylpentane) due to its high octane number (a measure of the antidetonating power of the carburetor fuel). Isooctane also serves as a reference for the determination of the octane index. Mixtures of diisobutene or isooctane containing other C8 isomers or hydrocarbons with other C numbers can also be used for use as a fuel additive.

Higher purities of diisobutene are normally desired for use in synthesis. By hydroformylation of diisobutene, 3,5,5-trimethylhexanal is obtained, which can be oxidized into the corresponding carboxylic acid. The carboxylic acid finds use for the preparation of peroxides, lubricants and drying agents. In addition, diisobutene is used for the alkylation of phenols. The alkylaromatic compounds that result in this case are intermediate products for the preparation of detergents.

Diisobutene can be obtained through dimerization, in general oligomerization, of isobutene. In this case, along with the dimers (C8) oligomers of larger molar masses (mainly C12, C16) are also formed. Through transposition reactions of the main chain, the C8 dimers contain, together with diisobutene, also small portions of other C8 olefins. If isobutene is used as a precursor for oligomerization in mixtures with other olefins, co-oligomers are also formed. In the presence of 1-butene, for example, 2,2-dimethylhexenes and 2,2,3-trimethylpentenes result.

For the industrial preparation of diisobutene, either as a precursor for synthesis or as a fuel additive, several criteria have to be taken into account from mixtures of hydrocarbons containing isobutene. To them belong a high selectivity of C8, a high purity of C8 isomers, the long-term stability of the catalyst, the technical solutions for the evacuation of the heat of the resulting reaction, and in the case of using mixtures that also contain 1 -butene, a poor isomerization of 1-butene in 2-butenes.

A high selectivity of C8 is desired, among others, given that the isobutene tetramers (or co-tetramers with linear C4 olefins) or their hydrogenated derivatives are not suitable for use in carburetor fuels, since they have a boiling point that is too high. high. The formation of tetramers therefore represents, in the preparation of fuel additives, a real loss of performance. The boiling points of the trimers or of their hydrogenated derivatives are, with 170-180 ° C, in the upper part of the boiling point range for carburetor fuels; they can certainly be used proportionally in fuels, but their training must be minimized as much as possible.

A high purity of C8 isomers, that is to say a high proportion of diisobutene in the C8 fraction and only a small formation of codimers (dimers based on 1-butene and isobutene) and transposition products, is particularly desired in the preparation of diisobutene which Find use in synthesis. In addition, the formation of codimers, for example with n-butenes, should be avoided, since with this n-butenes are consumed which, otherwise, could be used differently (1-butene, for example as (co) monomer for polymers).

High long-term stability of the catalyst is not only necessary in order to minimize catalyst costs, but also in order to keep the technical complexity of the catalyst change low.

In the case of isobutene oligomerization, heat is also released in considerable quantities. If it is not sufficiently evacuated, the reaction mixture is heated. This can lead to both the worsening of selectivities and can also have a negative influence on the stability of the catalyst.

Isobutene often technically precipitates in mixtures with 1-butene. Substances cannot be separated by distillation with technically convenient complexity. Therefore, a separation is achieved by selective chemical reaction of one of the two components, for example the etherification of isobutene. In the case of the chemical reaction of isobutene, 1-butene should not, however, be transposed into 2-butenes (see K.

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Weissermel, H.J. Arpe, Industrielle Organische Chemie, Wiley-VCH, 5th edition, 1998, pages 74-82). 1-Butene is a coveted raw material, among others it is used as a comonomer in the preparation of polyolefins.

All these criteria are already described in the literature and solutions were also found in part. An essential point of the work is in the development of catalysts. The oligomerization of isobutene can be catalyzed by Lewis, Brönsted acids or coordination compounds, in particular those of nickel. Catalysts for this reaction have long been known and are the subject of numerous patents and publications.

The oligomerization can be carried out, in principle, in a homogeneous manner, that is, using soluble catalysts in the reaction mixture, or heterogeneous, that is, using insoluble catalysts in the reaction mixture. The drawback of the homogeneous procedures is that the catalyst leaves the reactor with the reaction products and the precursors that have not reacted, from which it must be separated, processed and discarded or returned.

Most of the technical procedures therefore use heterogeneous catalysts which, in addition, are arranged in the fixed bed, so that a complex separation of the catalyst is avoided. Most of the known solid catalysts belong to one of the following groups: a) mineral acids (e.g., sulfuric acid or phosphoric acid) on a support material (e.g., oxide of

aluminum or silicon dioxide) b) zeolites or other aluminosilicates with or without endowment of other metals, in particular with transition metals c) acid-ion exchange resins.

Mineral acids on supports are only poorly suited as catalysts, since they also determine transposition reactions in the main chain (reaction of two isobutene molecules to form other C8 isomers other than 2,4,4-trimethylpentene).

In EP 0 224 220 an oligomerization of butene is carried out in a zeolite catalyst provided with bismuth and / or lead. In this case, the C8 fraction contains more than 4% of unwanted 2,3,4-trimethylpentenes. Zeolites as catalysts are also used in US 4720600. The oligomerization of isobutene in an amorphous x-ray aluminosilicate is disclosed in EP 0 536 839. In this case, even at mild temperatures of 60-65 ° C it is not possible It can prevent a loss of 2,2,4-trimethylpentenes due to isomerization of the skeleton. The oligomerization of isobutene in an amorphous nickel aluminosilicate by X-rays is described in WO 93/06926. In this case, undiluted isobutene is reacted at 60 ° C. The product spectrum shows that C8 selectivity is not particularly high. In the case of an isobutene conversion of 1520%, the selectivity of C8 amounts to 85-86%, in the case of a conversion of 75%, only 72%. In US 3531539 isobutene, which is presented in mixtures with 1-butene, is reacted in a molecular sieve. US 3518323 discloses the isobutene reaction that occurs in mixtures with nbutenes, in a supported nickel catalyst. The selective dimerization of isobutene from mixtures of C4 monoolefins in heterogeneous nickel catalysts is also described in US 3832418. In US 4197185, the reaction of isobutene based on mixtures of C4 hydrocarbons in inorganic heterogeneous catalysts is part of the process claimed.

The reaction of isobutene in acid-exchange ion exchange resins has long been known and was also used in large-scale processes (Hydrocarbon Processing, April 1973, page 171; Erdöl, Kohle, Erdgas, Petrochem. 1974, 27, Notebook 5, page 240). Through the discussion of limiting the use of MTBE (methyl tert-butyl ether, it is obtained technically from isobutene and methanol) as a fuel additive, procedures for isobutene dimerization again find a reinforced consideration. For this reason, a current overview was published on variants of the process for the reaction of isobutene in ion exchange resins of an acidic nature; Hydrocarbon Processing, February 2002, page 81. Depending on the isobutene content of the raw material used, different process variants are used in this case, both in order to control the exotherm of the reaction, as well as to control the selectivity . Mainly, the addition of moderators and / or dilution is used to reduce the concentration of isobutene. The use of moderators that are added to the reaction in order to control the activity and selectivity of the catalyst is the subject of various patents. Typical moderators are, for example, methyl tert-butyl ether, tert-butanol or water. The main drawback of the moderators is that the moderator or the constituent products of the reaction that result from it must be separated from the product. In US 4100220 the use of water or TBA (tert-butyl alcohol) as a moderator is disclosed, WO 01/51435 describes the use of TBA. US 4375576 and US 4447668 take advantage of MTBE as moderator, GB 2325237 take advantage of ethers and primary alcohols, EP 1074534 takes advantage of tertiary alcohols, primary alcohols and ethers, EP 1074534 uses, in general, "oxygenated compounds". Since in the presence of acidic catalysts, t-butyl ether such as MTBE is formed from isobutene and

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alcohols, processes for the parallel production of isobutene ethers and oligomers are also known (US 5723687).

The use of moderators also entails disadvantages in technical operation. Catalysts used as ion exchangers that can be reduced in their activity by the addition of moderators such as water or TBA, react very slowly during the change of the reactor charge. After changing the amount of feed, the reactor needs time in order to return to a steady state. However, a stationary behavior of the reactor is advantageous for a simple and safe operation of the installation. An advantage of the use of partially neutralized ion exchangers is that the time required to achieve a stationary behavior of the reactor after a charge change is shortened.

Together with or in parallel with the use of moderators, dilution of the isobutene-containing starting material is described, in order to achieve better selectivities, but in particular also a control of exotherm (US 5877372, WO 01/51435, US 2002 / 0002316). US 5003124 describes a procedure in which the problem of heat evacuation from the reaction is addressed, working only in liquid phase at the boiling temperature of the liquid phase.

The documents US 6 274 783 and WO 01/81278 both have processes for oligomerization with simultaneous hydrogenation of the products.

In EP 0 417 407, molded bodies of strongly acidic ion exchangers are used as a catalyst for isobutene oligomerization. These ion exchangers are treated, in part, subsequently with acid in order to achieve increased acidity. The yield in dimers of 93-96% is good. However, the composition of the C8 fraction is not disclosed.

EP 0 048 893 describes a process for the preparation of C4 oligomers and alkyl tert-butyl ethers. Isobutene is reacted together with liquids in liquid phase in an acid cation exchanger that is occupied with one or more Group 7 or 8 metals of the Periodic System. In this case, metals are presented elementally.

EP 0 325 144 discloses the use of acidic ion exchangers that are partly loaded with amphoteric elements (aluminum, chromium, vanadium, titanium, zirconium, molybdenum, tungsten are preferred). These modified ion exchangers are used as catalysts in the preparation of tert-amyl alcohol (TAA) from i-amylenes. The advantage of the process lies in an increased conversion of the iamilenes and in a simultaneous repression of the oligomerization of the i-amylenes.

Therefore, there is a demand for an effective diisobutene preparation or isobutene separation for the preparation of 1-butene from mixtures of C4 hydrocarbons.

Surprisingly, it was found that this problem can be solved by the oligomerization of liquid phase isobutene in an acidic ion exchange resin with sulfonic acid groups, when a part of the protons of the acidic ion exchanger is exchanged by ions of metals

Therefore, the object of the present invention is a process for oligomerization of isobutene in the presence of n-butenes in an ion exchanger of an acidic, solid character, the reaction being carried out in an ion exchanger, whose protons of an acidic nature. They were partly exchanged for metal ions.

This technique can also be used to effectively obtain 1-butene. Another object of the invention is therefore a process for the preparation of 1-butene according to claim 11.

Acid ion exchange resins are only catalysts that can be used for oligomerization of isobutene when they have a certain minimum acidity. Thus, resins with carboxylic acid groups are often not acidic enough and therefore, as a general rule, are not suitable as a catalyst. Suitable resins are those with sulfonic acid groups. Its activity in the oligomerization of isobutene can be reduced by moderators such as alcohols (TBA), ethers (MTBE) or water.

From the literature it is known to reduce the acid strength of ion exchangers with sulfonic acid groups by partial ion exchange (Structure-breaking Effect of Metal Ions influencing the Acidity of an Anhydrous Acid, C. Buttersack, H. Widdecke, J. Klein, Journal of Molecular Catalysis, 40 (1987) 23-25). However, it is surprising that an ion exchange resin modified in this way can be used

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advantageously in the preparation of fuel additives from mixtures of hydrocarbons containing isobutene.

In the processes according to the invention, solid sulfonated ion exchange resins are used in which, in particular, 0.1 to 60%, 0.1 to 50%, 0.1 to 40%, 0.1 to 30% 0.1 to 29%, preferably 0.5 to 20%, particularly preferably 5 to 15% of the acidic protons of the sulfonic acid groups have been exchanged for metal ions. As metal ions that replace protons, alkali metal, alkaline earth metal, chromium, manganese, iron, cobalt, nickel, zinc and aluminum ions can be used, as well as ions from the lanthanide group (rare earths). Preferably alkali metal ions are used, in particular sodium ions. It is also possible that the resin is charged with two or more different metal ions.

Suitable ion exchange resins are, for example, those that are prepared by sulfonating phenol / aldehyde condensates or co-oligomers of vinyl aromatic compounds. Examples of vinyl aromatic compounds for the preparation of co-oligomers are: styrene, vinyl toluene, vinyl naphthalene, vinyl ethylbenzene, methyl styrene, vinyl chlorobenzene, vinyl xylene and divinyl benzene. In particular, co-oligomers resulting from the reaction of styrene with divinylbenzene are used as a precursor for the preparation of ion exchange resins with sulfonic groups. The properties of these resins, in particular the specific surface, porosity, stability, expansion or shrinkage and exchange capacity can be varied by the preparation process. The resins can be prepared in gel, macroporous or sponge form. Strongly acidic styrene-divinylbenzene type resins are sold, among others, under the following trade names: CT 151 of the business name Purolite, Amberlyst 15, Amberlyst 35, Amberlite IR-120, Amberlite 200 of the business name Rohm & Haas, Dowex M-31 of the company name DOW, K 2611, K 2431 of the company name Bayer. The ion exchange capacity of resins completely present in the H + form is typically between 1 and 2, in particular between 1.5 and 1.9 moles of H + per liter of wet resin (commercially used) .

In the process of the invention, macroporous resins are preferably used such as, for example, K 2431 of the company name Bayer, Amberlyst 15 or Amberlyst 35 of the company name Rohm & Haas. The pore volume preferably amounts to 30 to 60 ml / g, in particular 40 to 50 ml / g (referred to resin moistened with commercially used water).

The grain size of the resin preferably ranges from 500 μm to 1500 μm, in particular between 600 μm and 1000 μm.

Granulometry can be chosen in a narrower or wider range. Thus, for example, ion exchange resins with a very unitary grain size (monodisperse resins) can be used.

It may be advantageous to use reactors, which are driven with high linear velocities, to reduce the differential pressure, use a larger grain and, in reactors that are traveled with a low linear velocity, a smaller grain to achieve optimum conversion.

Optionally, ion exchange resins can be used as molded bodies such as, for example, cylinders, rings or spheres.

In the case of using several reactors, these can be loaded with resin of a grain size (or granulometry) the same or different.

Different methods can be used for the preparation of partially neutralized ion exchange resins, which are all described in the specialized literature. If the ion exchange resin is presented in H-form, protons can be exchanged for metal ions. If the resin is presented as a metal salt, metal ions can be replaced by protons with the help of acids. In principle this ion exchange can take place both in organic suspension and in aqueous suspension. In a simple procedure, for example the ion exchange resin in the H + form is suspended with an amount of liquid such that a well agitable suspension results. To do this, a solution containing the desired ions is dosed. After the ion exchange is performed, the partially exchanged ion exchange resin is washed and dried.

The amount of solvent for the suspension of the ion exchange resin is typically in one to ten times the volume of the ion exchange resin itself. For the preparation of the solution with the desired type of ions, which is provided by dosage, it is advisable to choose a solvent that is miscible with the solvent in which the resin is suspended. It is convenient to use equal solvents.

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The ion exchange preferably takes place in the temperature range of 10 to 100 ° C, particularly preferably 20 to 40 ° C. As a general rule, the exchange has ended after no later than 24 hours. After ion exchange, the catalyst is separated from the solution, e.g. eg, by decantation or filtration and, optionally, then washed with a solvent. It is convenient to use the same solvent in which the catalyst was suspended.

It is advantageous to dry the wet catalyst, on the one hand, in order to make it more manipulable (capable of flowing) and, on the other hand, in order to keep the impurification of the product in the first days after the reactor starts. part of the adherent solvent or its consecutive reaction products. Drying can take place in a vacuum or in a stream of inert gas, for example in a stream of nitrogen. Drying temperatures are typically between 10 and 120 ° C.

A preferred mode for the preparation of the catalysts used in the process according to the invention is the exchange of protons for metal ions in the aqueous phase, the washing of the ion exchange resin partially exchanged with water and the subsequent drying.

The ions with which the resin should be charged can be presented in the form of solutions of hydroxides or salts of organic or inorganic acids. In the case of salts of polybasic acids, salts of an acidic nature can also be used. Also, compounds with other organic radicals such as, for example, alcoholates or acetylacetonates can be used. As a source of metal ions, metal hydroxides and salts of inorganic acids are preferably used. Very particularly preferred is the use of alkali metal hydroxides (for example sodium hydroxide), alkali metal halides (for example sodium chloride), alkali metal sulfates (for example sodium sulfate), alkali metal nitrates (for example sodium nitrate), alkaline earth metal hydroxides and alkaline earth metal nitrates.

Depending on the procedure described above, different activity and selectivity catalysts can be prepared, depending on the degree of exchange, the type of ions and the resin.

A reactor in the process according to the invention may contain a mixture of resins of different reactivity. It is also possible that a reactor contains catalysts with a different activity, arranged in layers. If more than one reactor is used, the different reactors can be loaded with catalysts of the same or different activity or activities.

As starting substances, mixtures of hydrocarbons containing isobutene are used. Preferably, mixtures of isobutene with other C4 hydrocarbons (portion of components C4 greater than 95%) are used.

Technical mixtures containing isobutene are, for example, light gasoline fractions from refineries, C4 fractions of crackers (for example steam crackers, hydrocrackers, catalyst crackers), Fischer-Tropsch synthesis mixtures, butane dehydrogenation mixtures , mixtures of the isomerization of the skeleton of linear butenes and mixtures that result by olefin metathesis. These techniques are described together in the specialized literature, K. Weissermel, H.J. Arpe, Industrielle Organische Chemie, Wiley-VCH, 5th edition, 1998, pages 23-24; 65-69; 122-124.

Preferably C4 fractions of steam crackers are used (which are operated primarily for the production of ethene and propene and in which raw materials are used, for example, refinery gases, naphtha, diesel, LPG (liquefied petroleum gas ) and NGL (natural gas liquid)) or catalyst crackers. C4 cuts that result as a secondary product contain, depending on the cracking process, different amounts of isobutene. Other main components are 1,3-butadiene, 1-butene, c-2-butene, t-2-butene, nbutane and i-butane. Typical isobutene contents of the C4 fraction are found in the C4 fraction of steam crackers, in 18 to 35%, in FCC catalyst crackers in 10-20%.

For the process according to the invention it is advantageous to separate several unsaturated hydrocarbons such as 1,3-butadiene from the starting mixture. This can take place according to known procedures, for example by extraction, distillation by extraction or complex formation (see K. Weissermel, H.J. Arpe, Industrielle Organische Chemie, Wiley-VCH, 5th edition, 1998, pages 119-121). An alternative for the separation of several times unsaturated hydrocarbons is a selective chemical reaction. Thus, for example, 1,3-butadiene can be selectively hydrogenated to form linear butenes as described, e.g. eg, in EP 52 3482. Also by selective reactions of 1,3-butadiene, for example dimerization to form cyclooctadiene, trimerization to form cyclododecadiene, polymerization or telomerization reactions, 1,3-butadiene can be separated at least partly. If a C4 cut of cracking was used as raw material, in all cases a mixture of hydrocarbons remains (refined I or C4 cracking

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Hydrogenated (HCC4)) which mainly contains saturated n-butane and isobutane hydrocarbons and isobutene, 1-butene and 2-butenes olefins.

Mixtures of isobutene-containing hydrocarbons used in the process according to the invention may have the following compositions:

Typical composition of selectively hydrogenated and refined CC4 I obtained from the C4 cut of a water vapor cracker (high intensity)

HCC4

Refined I

Component

min. [%] max. [%] min. [%] max. [%]

isobutene

one 4,5 1.5 8.0

n-butane

5 8 6.0 15.0

t-butene

18 twenty-one 7.0 10

1-butene

35 Four. Five 15.0 35.0

isobutene

22 28 33.0 50.0

c-butene

5 8 4.0 7.0

1,2-butadiene

<1%

1,3-butadiene

500 ppm 2000 ppm <1%

monovinylacetylene

<1%

Typical refining composition I that is obtained from C4 cuts of catalyst crackers and steam crackers (high intensity)

Base catalyst cracker Ref. I

Water steam cracker base Ref. I (low intensity)

Component

typical [%] typical [%]

isobutane

37 3

n-butane

13 6

t-butene

12 10

1-butene

12 27

isobutene

fifteen 44

c-butene

eleven 10

1,3-butadiene

<< 1% << 1%

The refined I or HCC4 is, together with others, a mixture of hydrocarbons containing isobutene preferably used in the context of this invention. Since facilities for the treatment of C4 hydrocarbons are, as a general rule, constituted as a chain (association of several facilities), it is however possible that

10 the refining I or HCC4 goes through one or more other process steps before entering the process according to the invention. In this way, a general concept adapted individually for the treatment with the corresponding product portfolio can be realized in each case.

Typical steps of the process that may be preceded by the process according to the invention are water washing, adsorber purification, selective hydrogenation, TBA synthesis and other reactions.

15 selective, drying, hydroisomerization and distillation.

Water wash

By washing with water, hydrophilic components can be separated in whole or in part from the mixture of hydrocarbons containing isobutene, for example nitrogen components. Examples of nitrogen components are acetonitrile or N-methylpyrrolidone (which may, for example, come from an extractive distillation of 1.3

20 butadiene). Oxygenated compounds (eg, acetone from FCC crackers) can also be separated, in part by washing with water. The hydrocarbon stream containing isobutene is saturated with water after washing with water. In order to avoid the existence of two phases in the reactor, the reaction temperature should be approx. 10 ° C above the temperature of the water wash.

Adsorber

25 Adsorbers are used to separate impurities. This can be advantageous, for example, when noble metal catalysts are used in one of the process stages. Nitrogen or sulfur compounds are often separated through pre-adsorbed adsorbers. Examples of adsorbers are aluminum oxides,

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molecular sieves, zeolites, activated carbon, clays impregnated with metals. The adsorbers are marketed for various social reasons, for example for the social name Alcoa (Selexsorb®).

Selective hydrogenation

Unsaturated compounds several times still contained in small amounts, in particular 1,3-butadiene, may continue to be eventually reduced by additional selective hydrogenation steps (see EP 081041; Erdöl, Kohle, Erdgas, Petrochem. 1986, 39, 73). (Pentanal, 2-methylbutanal) can be separated by distillation.

TBA synthesis

Parts of the isobutene can be reacted with water to form tert-butanol (TBA). Procedures for the preparation of TBA from mixtures of hydrocarbons containing isobutene are known in the art (see, for example, Erdöl, Erdgas, Kohle, 1987, 103, 486). TBA is used, for example, as a solvent, but it is also used by retro-dissociation in isobutene and water for the preparation of very pure isobutene.

Drying

Water possibly contained in the mixture of hydrocarbons containing isobutene, which can proceed, for example, from washing with water or the synthesis of TBA, can be separated by known methods for drying. Suitable procedures are, for example, separation by distillation of water as an azeotrope. In this case, an azeotrope with contained C4 hydrocarbons can often be used or entrainment agents are added. The water content of the isobutene-containing hydrocarbon mixture should amount, after drying, to approx. 10-50 ppm.

Hydroisomerization

With the hydroisomerization process, the position of the double bonds in the molecule can be shifted. A classic example is the hydroisomerization of 1-butene to give 2-butenes. At the same time, several unsaturated compounds are hydrogenated (for example radicals in 1,3-butadiene) to give simple olefins. Hydroisomerization processes are state of the art and, for example, part of patent applications GB 2057006, US 3764633 and DE 2223513. If, by means of hydroisomerization before the process according to the invention, the ratio of the portions of 1- is shifted. butene / 2-butene in the feed, then this has consequences on the formation of the codimers that result in the process according to the invention. In this way, it is possible, for example, from mixtures of isobutene-containing hydrocarbons in which the 1-butene content was reduced by hydroisomerization processes to near thermodynamic equilibrium, by dimerization in partially neutralized ion exchangers, generating products containing 2,2-dimethylhexenes (isobutene and 1-butene codomers) is possible, for example, from mixtures of hydrocarbons containing isobutene in which the 1-butene content was reduced by procedures From hydroisomerization to near thermodynamic equilibrium, by dimerization in partially neutralized ion exchangers, generate products in which 2,2-dimethylhexenes (isobutene and 1-butene codimers) are contained in a proportion less than 1%. From mixtures of this type, very pure diisobutene can be separated by distillation with a purity of> 98.5%.

Hydroisomerization has become particularly important because in the case of a broad isomerization of 1-butene to give 2-butene, the isobutene can be separated by distillation of the remaining C4 hydrocarbons with the 1-butene moieties and eventually together with isobutane By means of a skillful combination of distillation and hydroisomerization, for example in a reactive distillation, currents with isobutene content can be created that are largely free of n-butenes. These currents are also adapted as raw material for the process according to the invention. (EP 1 184 361 describes the use of a raw material created in this way for oligomerization of isobutene, the oligomerization being carried out as reactive distillation). The oligomerization product in the partially neutralized ion exchanger is then largely free of C8 coders.

Distillation

Mixtures of hydrocarbons containing isobutene can be decomposed by distillation into fractions with different concentrations of isobutene. This can take place both directly with the refined I

either the HCC4, or after having gone through one or several other stages of the process (see the

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hydroisomerization). By direct distillation of refining I or HCC4, for example, a separation can be obtained in a fraction depleted in 2-butenes and n-butane and enriched in isobutene.

For oligomerization according to the invention

Various variants are possible for the technical realization of the reaction of the hydrocarbon mixtures containing isobutene. The reaction can be carried out in batches or, preferably, in continuously operating reactors that are usually used in the case of solid / liquid contact reactions. In the case of using flow reactors that work continuously, most of the time, but not exclusively, a fixed bed is used. Another concept as fixed bed reactors are, for example, reactors in which the ion exchanger is present suspended in a liquid phase (see "Bayer Procedure", Erdöl und Kohle, Erdgas, Petrochemie, 1974, 27, Notebook 5, page 240). When a fixed bed flow reactor is used, the liquid can flow up or down. Most of the time a downward flow of the liquid is preferred. A cooling liquid that runs through the reactor may eventually have an equal or opposite flow direction. In addition, it is possible to operate the reactor under product return or in a direct step.

In the case of using tube reactors, the ratio of length to diameter of the catalyst charge can be varied, either by the geometric measurements of the reactor or by its degree of loading. In the case of an equal amount of contact and load (LHSV), different speeds of the empty tubes can therefore be achieved.

The reaction of isobutene-containing hydrocarbon mixtures in acid ion exchangers takes place under the release of energy, which leads to heating of the reaction mixture. For the limitation of the temperature increase, in the case of employing non-partially neutralized ion exchangers, moderators that reduce the activity of the catalyst are often necessary. As moderators, for example, alcohols (TBA), ethers (MTBE) or water are used. A disadvantage of the use of moderators is that they must be separated from the product stream (see Hydrocarbon Processing, February 2002, page 81). Only when they are contained in a low concentration, can they eventually remain in the product.

Another effective means to limit the increase in temperature is the dilution of the hydrocarbon mixtures containing isobutene, for example by product return or by the addition of inert hydrocarbons, for example diisobutane. Through the activity of the catalyst reduced by partial neutralization, the reaction rates per catalyst volume are lower than in the case of the use of non-exchanged ion exchange resins. With the lower conversion, the resulting amount of heat is also smaller. With this, with a corresponding reactor concept, the heat can be evacuated to a sufficient extent and the use of moderators can be waived. In a preferred embodiment of the methods according to the invention, therefore, moderators are not added.

The reactors used in the technical process can be operated in an adiabatic, polytropic or practically isothermal way. Practically isothermal means that the temperature in an arbitrary place of the reactor is at most 10 ° C higher than the temperature at the inlet of the reactor. In the case of adiabatic operation of the reactors it is convenient, as a general rule, to connect several reactors in series and cool between the reactors. Reactors that are suitable for polytropic or practically isothermal operation are, for example, tube bundle reactors, boiler with stirrer and loop reactors. The reactor can also be operated in the form of a reactive distillation containing catalytic packages with partially neutralized ion exchangers. Examples of catalytic packaging can be indicated Katapack® of the business name Sulzer, and Multipack® of Montz GmbH.

It is possible to combine several reactors, also of different construction types. In this case, after each of the reactors an optional distillation separation of reaction products can take place. In addition, it is possible to operate the reactors under the product return.

The temperatures at which the oligomerization is operated range from 5 to 160 ° C, preferably between 40 and 110 ° C.

The reaction can take place with and without the addition of an additional solvent. Saturated hydrocarbons, in particular C4, C8 or C12 hydrocarbons, are preferably used as solvents. Very particularly preferred is the use of isooctane. In the case of the addition of solvents, their proportion amounts to 0 to 60% by weight, preferably 0 to 30% by weight.

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The reaction according to the invention can be carried out at a pressure equal to or greater than the vapor pressure of the starting hydrocarbon mixture at the respective reaction temperature, preferably at a pressure below 40 bar, that is, the mixtures Hydrocarbons containing isobutene occur during oligomerization, in whole or in part, in the liquid phase. When the reaction is to be carried out completely in the liquid phase, the pressure should be 2 to 4 bars above the vapor pressure of the reaction mixture, in order to avoid evaporation problems in the reactors.

Also when the reaction is operated at a pressure at which the reaction mixture is not completely present in liquid form (for example in a reactive distillation or in the case of process variants analogous to US 5003124), the oligomerization has place according to the process according to the invention, nevertheless, in the liquid phase, that is, in a "wet" catalyst, that is to say moistened with liquid.

The total conversion to isobutene can be adjusted through the type and quantity of the catalyst used, the adjusted reaction conditions and the number of reaction steps. In principle, it is possible to react the isobutene in mixtures of hydrocarbons containing isobutene almost quantitatively. In the case of the presence of other olefins, that is, for example, in the case of the use of refining I as a raw material, the formation of isobutene codomers with other olefins can be greatly increased. Therefore, it is advantageous to limit the conversion of isobutene to 95%, even better to 90%.

The oligomerization output product according to the invention can be made differently. Preferably, the oligomerization exit product is separated into C8 olefins, that is, mainly diisobutene, and C4 olefins, that is, unreacted olefin such as isobutene, 1-butene and / or 2-butene and inert butanes. .

A preferred way of separating these fractions is distillation separation. In this case, firstly unreacted isobutene is separated together with other low boiling compounds (fraction (A), hydrocarbons with less than 7 carbon atoms) from the oligomers. If refining I is used as a raw material in the process according to the invention, then a mixture is obtained in distillation as fraction (A) which in its composition resembles what is often defined as refining II. Isobutene residues that have not reacted can be separated, if desired, from this mixture according to known methods, for example by etherification with alcohols (DE 2853769; Ullmann's Encyclopledia, sixth edition, Electronic Version, Production of methyl-tert-butyl- ether).

The isobutene still present in the C4 olefin-containing fraction can optionally be etherified in at least one other reaction step with an alcohol. Preferably, methanol or ethanol is used for this, obtaining MTBE or ETBE

The reaction of the remaining isobutene with alcohols to give ethers can also take place before distillation. A corresponding procedure is described in DE 2944457. The oligomerization output product is reacted with alcohols, preferably methanol, in acid catalysts. In this case, a tert-butyl ether is formed from the isobutene still contained. From this mixture, it can then be separated by distillation, for example, a refining II, which eventually still contains quantities of alcohol, and subsequently processed. As refined II, which already has only small amounts of isobutene, 1-butene of high purity can be obtained (Ullmann’s Encyclopedia, sixth edition, Electronic Version, Butenes - Upgrading of Butenes). Other possibilities of use for refining II are the oligomerization of the butenes contained, for example in heterogeneous nickel catalysts. In this case, di-n-butene is obtained, among others, which can be prepared after hydroformylation, hydrogenation and esterification, plasticizers (eg, diisononyl phthalate) for synthetic materials.

After the separation of isobutene together with other low boiling compounds (fraction (A), hydrocarbons with less than 7 carbon atoms) a fraction is obtained that mainly contains C8 hydrocarbons. This contains, along with diisobutene, also the higher coders and oligomers (C12, C16). This fraction may continue to be fractionated in subsequent distillation stages. Thus, it is possible, for example, to separate a fraction with very pure diisobutene in order to use it separately, for example for chemical synthesis. For use as a carburetor fuel component it may be necessary to separate high boiling components (preferably boiling point> 220 ° C).

It is also possible to hydrogenate the entire fraction containing C8 olefins, in whole or in part, to form saturated hydrocarbons.

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If, before the separation of the low boiling compounds, an etherification of the still-contained isobutene is carried out, then the fraction with the oligomers of the isobutene also contains, together with the oligomers, ethers and alcohol moieties. This mixture can be distilled off according to methods known in individual fractions (containing, for example, as the main components ether or alcohol or oligomer). A

or several of these fractions (Cn) can be used, for example, as a fuel additive.

For use as a fuel component of the carburetor, it may be advantageous to hydrogenate the olefinic double bonds of the oligomers in whole or in part. Methods for the hydrogenation of oligomerization products to give the corresponding paraffins are sufficiently known to those skilled in the art. Common methods for the hydrogenation of olefins are described, for example, in F. Asinger, "CHEMIE UND TECHNOLOGIE DER MONOOLEFINE", AKADEMIE VERLAG, BERLIN, 1957, pages 626-628 or document DE 197 19 833.

In a preferred embodiment, the hydrogenation is carried out in a liquid phase in a heterogeneous hydrogenation catalyst. As hydrogenation catalysts, Pt, Pd and Ni are preferably used on inorganic support materials. The temperature at which hydrogenation is carried out is preferably in the range of 10 to 250 ° C, the pressure between 1 bar and 100 bars.

After hydrogenation, other fractions can be obtained by distillation. From these and from non-hydrogenated fractions, fuel additives of certain properties can be obtained by mixing.

The following Examples should explain the invention in greater detail, but not limit its range of application resulting from the claims.

Examples

Example 1

Preparation of a partially neutralized catalyst, adjustment of acid capacity

The ion exchanger used by the company name Rohm und Haas (Amberlyst 15) had an original acid capacity of 1.43 mol H + / l. To adjust the desired activity, 50% of the acid centers were neutralized.

For this, 1000 ml of the ion exchange resin was suspended in 1000 ml of demineralized water and, under intense stirring, a solution based on 28.6 g of sodium hydroxide (0.715 mol) and 500 ml was added dropwise of demineralized water in one hour in the temperature range of 20 to 40 ° C. Stirring was continued for 5 min and then the ion exchange resin was washed to neutrality three times with 1000 ml of demineralized water. Subsequent measurement of the capacity of the partially neutralized ion exchanger provided 0.715 +/- 0.03 mol H + / l. The catalyst was dried for 15 h at 70 ° C.

The preparation of other partially neutralized ion exchange resins takes place analogously to Example 1, by reacting the ion exchange resin, suspended in water, with the calculated amount of an aqueous solution of alkali metal hydroxide.

The oligomerization tests (Examples 2 to 6) were carried out in a laboratory tube reactor with a jacket, 2 m long and 6 mm internal diameter. With the help of a heat support oil, which was pumped through the reactor envelope, the reactor could be tempered. In all tests, an isobutane-isobutene mixture was oligomerized at 22 bar.

Examples 2 to 4

In the case of Tests 2 to 4, 54 ml of a partially neutralized ion exchanger with Namber (drying) of the Amberlyst 15 type were used in each case. The degree of exchange of the protons was examined in each case by determining the ion exchanger capacity.

The oligomerization of isobutene took place in each case in a 200 cm long tube reactor (spiral wound), internal diameter 6 mm, in which the catalyst was charged. The reactor was frightened from the outside by an oil bath. The raw material is transported through a pump through the reactor; at the reactor outlet the pressure is regulated by maintaining the pressure at 22 constant bars.

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The operating conditions of the individual tests, analysis of the input product and output product are indicated in the following Table. In this case, the temperature was adjusted so that comparable isobutene conversions result.

The series clearly demonstrates that by partially neutralizing the ion exchanger with comparable conversions, clearly improved selectivities can be obtained with respect to C8 products.

Test No. 2 3 4

Ion exchanger A15 A15 A15 Exchange rate, metal 0% 10%, Na 40%, Na Temp. [° C] 40.0 51.2 110.0 Input product [kg / h] 0.502 0.526 0.510

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Analysis of the iso-butane input product [%] 2.20 4.09 2.88 n-butane [%] 9.56 12.16 8.98 trans-butene [%] 9.17 8.74 8.71

20 1-butene [%] 27.71 26.56 28.33 iso-butene [%] 44.76 41.99 45.14 cis-butene [%] 6.12 5.98 5.46 remainder [%] 0.49 0.46 0.49

25 Analysis of the iso-butane output product [%] 2.57 4.31 3.28 n-butane [%] 10.90 13.68 10.22 trans-butene [%] 10.43 10.14 10, 43 1-Butene [%] 31.68 29.22 30.79

30 iso-butene [%] 37.03 35.07 37.93 cis-butene [%] 6.88 7.06 6.87 remainder [%] 0.52 0.50 0.48

Iso-butene conversion 27.4% 25.8% 26.2%

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Selectivities Sel C8 [%] 84.9 88.68 92.66 Sel C12 [%] 11.6 9.8 7.1 Sel C18 + [%] 3.5 1.31 0.07

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2.4, -TMP in C8 94.9 95.4 95.7

Examples 5 and 6

In Tests 5 and 6, a mixture with isobutene content based on C4 hydrocarbons was used as raw material in each case. The composition is reproduced in the following Table.

Test No.

5 6

Ion exchanger

A15 A15

Degree of exchange, metal

40%, Na 0%, Na

Input product analysis

iso-butane

[%] 0.01 0.03

n-butane

[%] 9.25 10.82

trans-butene

[%] 19.25 17,16

1-butene

[%] 11.79 14.45

iso-butene

[%] 50.72 49.55

cis-butene

[%] 8.83 7.96

rest

[%] 0.15 0.05

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In the case of Test 5, 54 ml of a partially neutralized ion exchanger with sodium ions up to 40% of the Amberlyst 15 type were used, in Test 6, 54 ml of an Amberlyst 15 non-neutralized ion exchanger (in each case dried ion exchangers). The degree of exchange of the protons in Test 5 was examined by determining the capacity of the ion exchanger.

5 The tests were carried out analogously to Examples 2 to 4. In the case of an input product quantity of 500 g / h, the conversion of isobutene (I-beno conversion) was modified by varying the temperature of reaction between 50 and 120 ° C. Together with the conversion, the selectivity of C8 hydrocarbons (C8-Sel) and the proportion of 2,4,4-trimethylpentenes (2,4,4-TMP) in the C8 fraction were determined by gas chromatography.

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Balance Nº Conversion I-beno [%] C8-Sel [%] 2,4,4-TMP [%]

5-a 57.69 85.33 93.60 5-b 63.82 81.71 93.47 5-c 74.36 77.23 93.81

Balance Nº Conversion I-beno [%] C8-Sel [%] 2,4,4-TMP [%]

6-a 57.49 78.79 94.30 6-b 63.76 76.30 93.50 20 6-c 74.66 71.61 90.43

It is demonstrated that in the case of comparable isobutene conversions, clearly better C8 selectivities can be achieved with the partially neutralized ion exchanger.

Claims (10)

1. Process for oligomerization of isobutene in the presence of n-butene in a solid acidic ion exchanger, characterized in that the reaction is carried out in an ion exchanger whose acidic protons were partly exchanged for ions of metals. Method according to claim 1, characterized in that 0.1 to 30% of the acidic protons were exchanged for metal ions. 3. Method according to claim 1 or 2, characterized in that for the oligomerization a mixture containing isobutene, 1-butene, 2-butene and butanes is used. 4. Method according to one of claims 1 to 3, characterized in that the metal ions are ions of the alkali metals, alkaline earth metals and / or rare earths.

5.

Process according to one of claims 1 to 4, characterized in that the hydrocarbon mixtures containing isobutene during oligomerization are present, at least in part, in the liquid phase.

6.

 Process according to one of claims 1 to 5, characterized in that the oligomerization is carried out at 5 to 160 ° C.

Method according to one of claims 1 to 6, characterized in that less than 5 mol% of the 1butene present in the oligomerization is isomerized in 2-butene. Method according to one of claims 1 to 7, characterized in that the oligomerization output product is divided into C8 olefins and C4 olefins. 9. Method according to claim 8, characterized in that the isobutene contained in the fraction containing C4 olefins is etherified in at least one other reaction step with an alcohol.

10.

Process according to claim 8, characterized in that the fraction containing C8 olefins is hydrogenated to form saturated hydrocarbons.

eleven.

Process for the preparation of 1-butene from a mixture of C4 hydrocarbons containing isobutene, 1-butene, 2-butene and butanes, characterized in that the mixture of C4 hydrocarbons is reacted

25 for the oligomerization of isobutene in the presence of n-butene in a solid, acidic ion exchanger, whose acidic protons were exchanged, at least in part, by metal ions, and the 1butene is distilled off from the product of reaction. 12. Method according to claim 11, characterized in that 0.1 to 30% of the acidic protons were exchanged for metal ions. 30 14