DE10361638A1 - Production of polyisobutene, used e.g. as intermediate for lubricating oil and fuel additives, involves polymerization using boron trifluoride catalyst with cyanide or nitrile as moderator and/or contacting product with inorganic adsorbent - Google Patents

Abstract

Production of polyisobutene with number average molecular weight Mn 400-50000 and over 50 mole-% methylidene groups by polymerization of a reaction mixture containing isobutene in the presence of a catalyst containing boron trifluoride, is carried out at least partly in the presence of hydrogen cyanide or a cyanide or nitrile as moderator (I) and/or the reaction mixture is contacted with an inorganic adsorbent after polymerization in the presence of (I).

Description

The The invention relates to a process for the preparation of highly reactive polyisobutenes with low fluorine content.

beschrieben wird, in der "Polymer" für den um eine Isobuteneinheit verkürzten Polyisobutenrest steht. Die Methylidengruppen zeigen die höchste Reaktivität, wohingegen die weiter im Inneren der Makromoleküle liegenden Doppelbindungen je nach ihrer Lage im Makromolekül keine oder nur eine geringere Reaktivität bei Funktionalisierungsreaktionen zeigen. Der Anteil an Methylidengruppen im Molekül ist daher das wichtigste Qualitätsmerkmal der Polyisobutene. Hochreaktive Polyisobutene werden unter anderem als Zwischenprodukte zur Herstellung von Additiven für Schmier- und Kraftstoffe verwendet.The so-called highly reactive polyisobutenes are polyisobutenes having a high content of methylidene groups. For the purposes of the present application, methylidene groups are understood as meaning those double bonds whose position in the polyisobutene macromolecule is represented by the general formula

is described in the "polymer" stands for truncated by an isobutene polyisobutene. The methylidene groups show the highest reactivity, whereas the double bonds lying further inside the macromolecules, depending on their position in the macromolecule, show no or only a lower reactivity in functionalization reactions. The proportion of methylidene groups in the molecule is therefore the most important quality feature of the polyisobutenes. Highly reactive polyisobutenes are used inter alia as intermediates for the preparation of additives for lubricants and fuels.

highly reactive Polyisobutenes can obtained by polymerization of isobutene under boron trifluoride catalysis become.

at However, the catalysis with boron trifluoride occurs as a side reaction for the addition of fluorine to the polyisobutene or for the formation of and middle molecular fluorine-containing by-products, such as tert-butyl fluoride, diisobutyl fluoride or triisobutyl fluoride contaminating the polyisobutene.

If technical C ₄ -hydrocarbon streams, such as the so-called raffinate I, are used as the isobutene source, which in addition to isobutene contain relatively large amounts of linear butenes, in particular 1-butene, higher polyisobutenyl fluorides are also observed. The latter are difficult to remove from the formed polyisobutene and lead to a significant increase in the fluorine content.

In order to put the isobutene-depleted C ₄ hydrocarbon streams, besides the polyisobutene, to industrial reuse, it is desirable to reduce the isobutene content to 2% by weight or less. However, if the polymerization is driven close to quantitative conversions, polyisobutenes of lower reactivity (lower methylidene group content) are generally obtained. Extensive isobutene depletion without loss of reactivity can be achieved using reactors connected in series (main reactor and postreactor). However, the formation of undesired isobutene oligomers generally increases in the postreactor.

The EP-A 1 081 165 describes a possibility for reducing the halogen content of polyisobutene by it is treated under conditions with alumina, the double bond isomerization largely prevent. The treatment takes place z. B. on an alumina fixed bed. It is postulated that at the alumina surface a Cleavage of the halogenated polyisobutene molecules with the formation of vinylidene groups he follows. Since this reaction is not thermodynamically favored, it will probably take place only to a small extent.

• – eine Verringerung des Fluorgehalts des erhaltenen Polyisobutens;
• – bei hohem Methylidengruppengehalt,
• – hohem Isobutenumsatz und
• – reduzierter Bildung unerwünschter Isobutenoligomere erlaubt.

The invention is based on the object to provide a method which

• A reduction in the fluorine content of the resulting polyisobutene;
• At high methylidene group content,
• High isobutene conversion and
• - Reduced formation of undesired isobutene oligomers allowed.

The process should be particularly suitable for the use of technical C ₄ hydrocarbon streams, which in addition to isobutene linear butenes, such as 1-butene, cis- or trans 2-butene.

These Task is solved by a process for producing polyisobutene having a number average Molecular weight of 400 to 50,000 and a content of methylidene groups of more than 50 mol% by polymerization of an isobutene-containing Reaction mixture in the presence of a boron trifluoride-containing catalyst, wherein the polymerization at least temporarily in the presence of a Among cyanide, cyanides and nitriles selected moderator performs and / or the reaction mixture after completion of the polymerization in the presence of the moderator with an inorganic adsorbent brings into contact.

The term "content of methylidene groups" refers to the percentage of polyisobutene molecules with methylidene group, based on the number of all olefinically unsaturated polyisobutene molecules in a sample. It can be determined by ¹ H-NMR and / or ¹³ C-NMR spectroscopy, as is known in the art. The content of methylidene groups is more than 50 mol%, preferably at least 60 mol%, particularly preferably at least 75 mol%.

The according to the inventive method Polyisobutene obtained has a number average molecular weight Mn from 400 to 50,000, preferably 500 to 5,000, especially 700 up to 2500. The dispersibility (D = Mw / Mn) typically less than 2.5, preferably less than 2.0 and in particular less than 1.8.

in the inventive method Hydrogen cyanide, cyanides or nitriles are also used, which is the reactivity of the boron trifluoride catalyst control and therefore for the purposes of the present application are referred to as "moderators". In contrast to other measures for controlling the catalyst activity, such. B. lowering of temperature, allow the moderators of the invention high isobutene conversions, the formation of undesirable Isobutenoligomere and fluorinated compounds is pushed back. In the embodiments of the invention in which the reaction mixture after completion of the polymerization for removing or cleaving fluorinated products with an adsorbent is treated, the presence of a moderator prevents one undesirable Double bond isomerization of the polyisobutenes and / or activation / structural change of the adsorbent.

When Moderators in the process according to the invention Hydrogen cyanide (hydrocyanic acid) or organic nitriles are suitable of the general formula R-CN, in which R is alkyl, alkenyl, alkynyl, Alkaryl or aralkyl preferably having up to 12 carbon atoms stands. Preferably, the moderator is acetonitrile, propionitrile, acrylonitrile and benzonitrile selected.

Besides Also suitable are inorganic cyanides, in particular alkali metal and / or alkaline earth metal cyanides, such as sodium cyanide or potassium cyanide. The cyanides can expediently on inert insoluble carrier be applied, which are suspended in the reaction mixture.

Of the Moderator is generally used in an amount of 1 to 25 mol%, preferably 5 to 15 mol%, based on the boron trifluoride, to Given reaction mixture.

Suitable starting materials for the process according to the invention are both isobutene itself and also isobutene-containing C ₄ hydrocarbon streams, for example C ₄ raffinates, C ₄ cuts from isobutane dehydrogenation, C ₄ cuts from steam crackers, FCC crackers (fluid catalyst Cracking), provided they are largely exempt from 1,3-butadiene contained therein. C ₄ hydrocarbon streams suitable according to the invention generally contain less than 1000 ppm, preferably less than 200 ppm of butadiene. Typically, the concentration of 1-butene, cis-, and trans-2-butene in the C ₄ hydrocarbon streams is in the range of 40 to 60 weight percent. Such C ₄ hydrocarbon streams are preferred feedstocks for the process of the present invention. When C ₄ cuts are used as feedstock, the hydrocarbons other than isobutene play the role of an inert diluent.

Due to the high viscosity of the polyisobutenes, the polymerization takes place in the presence of a diluent. For the process according to the invention, those diluents or mixtures are suitable which are inert to the reagents used. Suitable diluents are saturated or unsaturated aliphatic, cycloaliphatic and aromatic hydrocarbons, for example saturated hydrocarbons, such as butane, pentane, hexane, heptane, octane, for example n-hexane, i-octane, cyclopentane, cyclohexane, methylcyclohexane, toluene or ethylbenzene; halogenated hydrocarbons such as methyl chloride, dichloromethane or trichloromethane and mixtures of the abovementioned compounds. Isobutene itself can also be used as diluent if the polymerization is operated only to a partial conversion. Preferably, the diluents prior to their use in the method of Verun purified such as water, carboxylic acids or mineral acids, for example by adsorption on solid adsorbents, such as activated carbon, molecular sieves or ion exchangers.

worin

• – L¹ für Wasser, einen Halogenkohlenwasserstoff, ein primäres C₁-C₅-Alkanol, ein sekundäres C₃-C₅-Alkanol, ein Phenol und/oder einen tert-Butylether steht,
• – L² für wenigstens einen Aldehyd und/oder ein Keton steht,
• – L³ für einen von einem tert-Butylether verschiedenen Ether mit wenigstens 5 Kohlenstoffatomen, ein sekundäres Alkanol mit wenigstens 6 Kohlenstoffatomen, ein primäres Alkanol mit wenigstens 6 Kohlenstoffatomen und/oder ein tertiäres Alkanol steht,
• – das Verhältnis b:a im Bereich von 0,9 bis 3,0, vorzugsweise 1,1 bis 2,5, liegt,
• – das Verhältnis c:a im Bereich von 0 bis 0,5, vorzugsweise 0 bis 0,3, liegt,
• – das Verhältnis d:a im Bereich von 0 bis 1,0, vorzugsweise 0,1 bis 1, insbesondere 0,1 bis 0,6, liegt.

As catalysts boron trifluoride complex catalysts are preferred. This is understood to mean catalysts of boron trifluoride and at least one cocatalyst. Suitable cocatalysts are usually oxygen-containing compounds. The catalyst preferably has the composition:

wherein

• L ^{1 represents} water, a halogenated hydrocarbon, a primary C ₁ -C ₅ -alkanol, a secondary C ₃ -C ₅ -alkanol, a phenol and / or a tert-butyl ether,
• L ^{2 represents} at least one aldehyde and / or one ketone,
• L ^{3 is} an ether other than a tert-butyl ether having at least 5 carbon atoms, a secondary alkanol having at least 6 carbon atoms, a primary alkanol having at least 6 carbon atoms and / or a tertiary alkanol,
• The ratio b: a is in the range from 0.9 to 3.0, preferably 1.1 to 2.5,
• The ratio c: a lies in the range from 0 to 0.5, preferably 0 to 0.3,
• The ratio d: a is in the range from 0 to 1.0, preferably 0.1 to 1, in particular 0.1 to 0.6.

The starters L ¹ are compounds with an abstractable hydrogen atom without significant steric hindrance. They are called "starters" because their active hydrogen atom is incorporated at the beginning of the growing polyisobutene chain. In addition, tert-butyl ethers, such as tert-butyl methyl ether, which readily form a tert-butyl cation, phenols, such as phenol or cresols, or halogenated hydrocarbons, such as dichloromethane or trichloromethane are suitable. As L ¹ , for example, water, methanol, ethanol, 2-propanol and / or 1-propanol are suitable. Of these, methanol is most preferred.

Aldehydes and / or ketones, which usually comprise one to 20, preferably 2 to 10, carbon atoms and in which preferably functional groups other than the carbonyl group are absent, may also be used as regulator L ² . As L ² , for example, formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, acetone, methyl ethyl ketone and diethyl ketone are suitable. Acetone is the most preferred.

The solubilizers L ³ have a solubilizing effect and increase the solubility of the catalyst complex in the feedstock. These are ethers having at least 5 carbon atoms, which are different from tert-butyl ethers, or long-chain and / or sterically hindered alcohols which provide shielding against the access of isobutene molecules. It is preferable to use dialkyl ethers having 5 to 20 carbon atoms, a secondary alkanol having 6 to 20 carbon atoms, a primary alkanol having 6 to 20 carbon atoms, and / or a tertiary C _{4 to} C ₂₀ alkanol. When primary alkanols are used, they preferably have a β-branch, ie, a branch on the adjacent carbon atom to the carbon atom bearing the hydroxyl group. Suitable representatives are, for example, di-n-butyl ether, di-n-hexyl ether, dioctyl ether, 2-ethylhexanol, 2-propylheptanol, the oxo alcohols of di-, tri- and tetramerpropylene and di- and trimerbutene, linear 1-alcohols (z B. are obtainable by the Alfol ^® method), if they are liquid under reaction conditions, such as n-hexanol or n-octanol, and selected tert-butanol. Of these, 2-ethylhexanol is most preferred.

The BF ₃ concentration in the reactor is generally in the range of 0.005 to 1 wt .-%, based on the liquid reaction phase, in particular in the range of 0.01 to 0.7 wt .-% and especially in the range of 0, 02 to 0.5 wt .-%.

The Boron trifluoride complexes can in separate reactors prior to their use in the process of the invention be preformed, stored after their formation and depending on Demand be metered into the polymerization.

A Another, preferred variant is that the boron trifluoride complexes generated in situ in the polymerization apparatus or an inlet. In this procedure, the respective cocatalyst is optionally together with a solvent fed to the polymerization or the feed and Boron trifluoride in the required amount in this mixture of Reactants dispersed. This is the boron trifluoride and the cocatalyst to boron trifluoride complex to. Instead of an additional solvent For example, in situ generation of the boron trifluoride catalyst complex, the reaction mixture from unreacted isobutene and polyisobutene as a solvent act.

The Polymerization of isobutene is preferably carried out in a continuous Method. activities for the continuous polymerization of isobutene in the presence of boron trifluoride-containing Catalysts in inert organic solvents to give polyisobutene are known per se. In a continuous process is continuously part of the resulting in the polymerization reactor Reaction mixture discharged. An amount corresponding to the discharge Feedstock becomes continuous to the polymerization reactor supplied and mixed with a circulating amount. The ratio of circulating volume to inflow is usually in the range of 1: 1000: 1 to 1: 1, preferably in Range of 500: 1 to 5: 1 and in particular in the range of 20: 1 to 100: 1 v / v. The mean residence time of the isobutene to be polymerized in the polymerization reactor, by reaction volume and feed rate is determined may be 5 seconds to several hours. residence from 1 to 30 minutes, especially 2 to 20 minutes are preferred.

The Polymerization generally occurs at a temperature in the range from -60 ° C to +40 ° C, preferably less than 0 ° C, more preferably in the range of -5 ° C to -40 ° C and especially in the range of -10 ° C to -30 ° C. The heat of polymerization is according to a cooling device dissipated. These can be liquid, for example Ammonia as a coolant operate. Another way, the polymerisation derive, is the Siedekühlung. This is the heat released by evaporation of the isobutene and / or other volatile Components of the isobutene feedstock or possibly volatile solvent dissipated.

The Polymerization of the isobutene is carried out in the usual manner for the continuous polymerization Reactors, such as stirred kettles, Tube, tube bundle and loop reactors, wherein loop reactors, d. H. Tube (bundle) reactors with circulation and turbulent flow or internals such as static mixers, d. H. with stirred tank characteristics, are preferred. Very cheap are in low-viscosity reaction mixtures loop reactors with Pipe cross-sections leading to turbulent flow; in high-viscosity reaction mixtures larger pipe cross sections with static mixing elements.

In preferred embodiments you lead the polymerization in at least two consecutive reactors by, at least the first reactor in some areas backmixed is, with the moderator at least in the second and / or further Metered reactor. In preferred embodiments, one doses a first subset of the moderator in the first reactor and at least another subset in the second or further reactor. Of the Proportion of the metered in the first reactor subset of the total is presenter preferably 40 to 90%.

in the first reactor is the supplied Isobutene in general up to a partial conversion of up to 95%, preferably 50 to 90%, more preferably 70 to 90%, based on the introduced into the first reactor isobutene, polymerized. The discharge from the first reactor is preferably without further Workup in the second reactor or from a previous one passed into the subsequent reactor. Here is the more Polymerization without addition of fresh isobutene.

The Residence time of the reaction mixture in the first reactor is in the Adjustment of an isobutene conversion of 50 to 90% usually 5 to 60 minutes, but may be shorter or longer, depending on whether one very active or less active catalyst is used. in the second reactor is generally a residence time of 1 to 180, preferably set from 2 to 120 minutes. Generally in the Last reactor of isobutene conversion adjusted so that the total sales of isobutene is 90 to 99.5%.

The Concentration of the isobutene in the liquid reaction phase in the main reactor is usually in the range of 0.2 to 50 wt .-%, preferably in the range of 0.5 to 20 wt .-% and in particular in the range of 1 to 10 wt .-%, based on the liquid reaction phase. In the Preparation of polyisobutenes with number average molecular weights Mn in the range of 500 to 5000 is preferably carried out at an isobutene concentration in the range of 1 to 20 wt .-% and in particular in the range of 1.5 to 10% by weight. In the production of polyisobutenes with a Number average molecular weight Mn of more than 5000 works preferably at an isobutene concentration in the range of 4 to 50 Wt .-%. In preferred embodiments In the first reactor, an isobutene concentration of 3% by weight does not below.

At the Leaving the last reactor, the reaction mixture usually contains 2% by weight or less of isobutene. Preferably, an isobutene concentration of 0.5 wt .-% not fallen below.

The polymerization process according to the invention is preferably carried out at least in the main reactor under isothermal conditions, ie the temperature of the liquid reaction mixture in the polymerizate Onsreaktor has a steady value and does not change during operation of the reactor or only to a small extent. If desired, the polymerization in the second reactor may be at a lower polymerization temperature than in the first reactor; it then usually requires further activation by the addition of fresh boron trifluoride or a regulator, such as an aldehyde or ketone, z. Acetone. However, it is preferred to operate the second or further reactor at a slightly higher temperature to complete the isobutene conversion by thermal activation. Since the polymerization is exothermic, one can operate for this purpose the second or further reactor under substantially adiabatic conditions, ie the reactor is not actively cooled or heated and the heat of polymerization is absorbed by the reaction mixture.

The discharged from the polymerization reactor reaction mixture still contains active catalyst. As a result, this can occur in the polymerization reactor formed polyisobutene disadvantageous in terms of molecular weight, Change molecular weight distribution and end group content. Around Therefore, to prevent further reaction usually becomes polymerization terminated by deactivation of the catalyst. The deactivation For example, by adding water, alcohols, acetonitrile, Ammonia or aqueous solutions from mineral bases or by discharging into one of the the aforementioned media are effected. The deactivation is preferred with water, preferably at temperatures in the range of 1 to 60 ° C (water temperature) carried out becomes. At lower temperatures, it is recommended to stop by Addition of acetonitrile; the deactivated discharge can expediently for pre-cooling be used of the inlet, z. B. in a countercurrent heat exchanger.

The Boron trifluoride complex catalysts can also largely from the discharge separated and recycled to the polymerization reaction. The separation and recycling of Catalyst from the discharge of the polymerization reaction is out WO 99/31151, to which reference is made in its entirety becomes. Used to separate the catalyst from the discharge it prefers limited soluble Boron trifluoride complex catalysts and / or the reaction mixture is cooled Temperatures of, for example, 5 to 30 Kelvin below reactor temperature, preferably 10 to 20 Kelvin below reactor temperature. at the separation of the catalyst from the reactor output recommends it is, before the isobutene concentration in the discharge to values below 2 wt .-%, preferably 1 wt .-% and in particular below 0.5 wt .-%, based on the discharge, lower.

Of the Catalyst falls in the form of finely divided droplets which, as a rule, rapidly change into a coherent phase. The complex droplets or the coherent one Phase have a significantly higher Density as the polymer solution. You can therefore usually with the help of separators, separators or other collection containers separated from the polymer-rich, catalyst-poor product phase become. The thereby separated polymer-rich product phase is in Generally homogeneous and contains only small amounts more soluble Catalyst shares. These are in the manner described above, preferably with water, deactivated.

Around To reduce the fluorine content (further) brings you in preferred embodiments the reaction mixture after completion of the polymerization in contact with an inorganic adsorbent. The inorganic adsorbent is preferably among alumina, zeolites and combinations selected from it.

To the Contacting the reaction mixture with the adsorbent are all conceivable discontinuous and continuous processes suitable. So you can the polyisobutene in portions with the adsorbent offset, preferably with mechanical movement, and after sufficient Separate residence time, z. B. by filtration, decantation or another suitable method. Conveniently, the adsorbent in a fixed bed ago, in an adsorption column is arranged, is passed through the reaction. The adsorption column is preferably arranged vertically and is the material flow in Direction of gravity or preferably against gravity flows through. It can also used several cascaded adsorption columns become.

The Treatment with the adsorbent is generally carried out at a temperature of 5 to 100 ° C, preferably 40 to 95 ° C.

Preferably, the adsorbent comprises a zeolite having average pore sizes of 5 to 15 Å. The mean pore size is determined by the crystal structure of the zeolite and z. B. are determined from X-ray structure data. In zeolites with smaller mean pore sizes, the fluorinated by-products can diffuse poorly and are therefore insufficiently split / adsorbed. Zeolites with larger mean pore sizes can lead to increased double bond isomerization of the polyisobutene, in particular if they are activated by traces of hydrogen fluoride or water.

preferred Zeolites are among zeolite A, zeolite L, zeolite X and zeolite Y selected. Sodium zeolite A or sodium zeolite A, in which the sodium ions completely or partially replaced by magnesium and / or calcium ions are particularly preferred.

Of the Zeolite is preferably substantially free from acid to excessive double bond isomerization the terminal methylidene double bonds of the polyisobutene to thermodynamic to avoid more stable double bonds in the interior of the macromolecule. It is therefore preferable to use non-activated zeolites, i. H. those for charge compensation of the negative framework charge do not contain protons.

at The zeolite treatment will probably be the halogenated by-products split and the halogenated fission products, such as hydrogen fluoride, adsorbed on the zeolite or chemically bound by the cations. To an undesirable To prevent activation and / or structural alteration of the zeolite is it prefers that contained in the reaction and / or in the Cleavage of the halogenated polyisobutenes formed hydrogen halide by addition of an acid scavenger, z. B .: an amine or a nitrile to bind.

It is advantageous, the reaction after the catalyst deactivation and before the zeolite treatment to dry and entrained traces of water largely to remove z. B. to less than 5 ppm, preferably less than 3 ppm. Preferably, the reaction is treated Suitably, for the coalescence of the water phase still contained to promote, z. B. by filtration over a coalescing filter. To further reduce the water content, you can see the polyisobutene with a zeolite of an average Pore size of 4 Å or less bring in contact, preferably at a temperature of less as 40 ° C, z. B. 5 to 35 ° C.

In a preferred embodiment Therefore, one brings the Reaktionsautrag after the catalyst deactivation successively with (i) a first zeolite of an average Pore size of 4 Å or less, preferably at a temperature of 5 to 35 ° C, and (ii) a second zeolite an average pore size of 5 up to 15 Å, preferably at a temperature of 40 to 100 ° C, in contact.

In a particularly preferred embodiment one brings the polyisobutene successively with (i) alumina, (ii) a first zeolite having an average pore size of 4 Å or less and (iii) a second average pore size zeolite of 5 to 15 Å in Contact. The alumina may be mixed with a base such as an alkali metal or alkaline earth metal hydroxide, or an alkali or Erdalkalicyanid be doped.

After the adsorbent treatment, the diluent and optionally the unreacted isobutene are separated, usually by distillation. The distilled-off diluent can be recycled to the polymerization reactor, preferably without further treatment. If a C ₄ -hydrocarbon stream is used as the isobutene source for the process according to the invention, the isobutene-depleted stream is preferably not recycled, but rather reused, e.g. As a hydroformylation of the linear butenes contained therein to butyraldehyde supplied.

To Separation of the diluent becomes the residue, the desired one Contains polyisobutene, in usual Way worked up. fugitive Oligomers of isobutene together with diluent residues according to usual Methods removed by distillation, z. B. at temperatures up to 230 ° C in a vacuum. Circulation evaporators, falling-film evaporators, thin-film evaporators, Sambay evaporator, annular gap evaporator and the like.

The Invention is further illustrated by the following examples.

Examples 1 to 3

A reactor was used, which consisted of a stainless steel pipe (V4A) of 7.1 m length and an inner diameter of 6 mm, over which a gear pump circulated 1000 l / h of reactor contents. The tube and pump had a volume of about 200 ml. The tube and pump head were in a cooling bath of -25 ° C (cryostat). The feed was passed through a capillary with 2 mm internal diameter 700 g / h Raffinate I of the following composition, which had been dried on molecular sieve 3 Å at a contact time of 10 minutes to less than 3 ppm of water and pre-cooled to -25 ° C.

boron trifluoride, Methanol, ethylhexanol and optionally acetonitrile were added directly fed to the circulation on the suction side of the circulation pump (see Table 1). At an internal reactor temperature of -18 ° C a stationary one Isobutene concentration.

Of the Reaction was immediately after leaving the circulation with aliquots of water quenched in a mixing pump. After the phase separation the organic phase was dried over 3 Å zeolite. The further work-up was carried out by distilling off the volatile constituents.

Of the Fluorine and Restisobutengehalt of the reaction mixture and the properties of the obtained polyisobutene are shown in Table 1.

Table 1

Examples 4 to 7

The The plant described above was modified so that the discharge after leaving the circulation, if necessary after adding another Acetonitrile, through a stainless steel tube provided with static mixing elements with 12 mm inner diameter and 50 cm length (postreactor 1) led.

In Examples 6 and 7, a second post-reactor was used, wherein the discharge after passing the postreactor 1 in a isolated but uncooled dwell (Nachreaktor 2) led, in which by means of a movable dip tube an average residence time of 10 minutes was set. A nitrogen stream of 20 l / h to the gas phase of the residence time provided a constant Gas volume in the headspace of the container.

Of the Reaction termination and the workup were carried out optionally after the first and second post-reactor, respectively, as described above.

The Results are given in Table 2.

Table 2

Example 8

example 1 was repeated. The reactor was charged with 8.55 mmol / h boron trifluoride, Feed 15.75 mmol / h of methanol and 0.43 mmol / h of ethylhexanol.

After the reaction had been quenched with water, the organic phase was passed over Al ₂ O ₃ coated with 2% by weight KCN (10 ° C., residence time 6 minutes), then admixed with 100 ppm acetonitrile over zeolite 3 Å (10 ° C.) Residence time 4 minutes) and finally at 75 ° C. over zeolite 10 Å, which had been previously doped with 1% by weight acetonitrile (residence time 20 minutes).

Claims (10)

Process for the preparation of polyisobutene with a number average molecular weight of 400 to 50,000 and a Content of methylidene groups of more than 50 mol% by polymerization an isobutene-containing reaction mixture in the presence of a Bortrifluorid-containing catalyst, wherein the polymerization at least temporarily in the presence of a hydrogen cyanide, cyanides and nitriles selected Moderator performs and / or the reaction mixture after completion of the polymerization in the presence of Moderator in contact with an inorganic adsorbent brings. The method of claim 1, wherein the moderator is under Acetonitrile, propionitrile, acrylonitrile and benzonitrile. A method according to claim 1 or 2, wherein the moderator in an amount of 1 to 25 mol%, based on the boron trifluoride, to the reaction mixture. Method according to one of the preceding claims, wherein the polymerization in at least two successive reactors performs, of which at least the first reactor is remixed at least in some areas are, with the moderator at least in the second and / or dosed further reactor. Process according to claim 4, wherein in the first reactor an isobutene concentration of 3 wt .-% not below. A method according to claim 4 or 5, wherein the second or another reactor under essentially adiabatic conditions operates. Method according to one of the preceding claims, wherein the inorganic adsorbent under alumina, zeolites and combinations thereof is. A process according to any one of the preceding claims wherein the catalyst comprises the composition:

in which L ^{1 is} water, a halogenated hydrocarbon, a primary C ₁ -C ₅ -alkanol, a secondary C ₃ -C ₅ -alkanol, a phenol and / or a tert-butyl ether, L ^{2 is} at least one aldehyde and / or a ketone, - L ^{3 is} an ether other than a tert-butyl ether having at least 5 carbon atoms, a secondary alkanol having at least 6 carbon atoms, a primary alkanol having at least 6 carbon atoms and / or a tertiary alkanol, - the ratio b: a is in the range of 0.9 to 3.0, - the ratio c: a is in the range of 0 to 0.5, - the ratio d: a is in the range of 0 to 1.0. The process of claim 1 wherein L ^{1 is selected} from water, methanol, ethanol, 2-propanol and 1-propanol. A process as claimed in claim 7, wherein L ³ is di-n-butyl ether, di-n-hexyl ether, di-octyl ether, 2-ethylhexanol, 2-propylheptanol, the oxoalcohols of di-, tri- and tetramerpropylene and di- and trimerbutene and Tert-butanol is selected.