DE102005026213A1 - Process for the oligomerization of olefins - Google Patents

Abstract

The present invention relates to a process for the oligomerization of C¶2¶-C¶8¶ monoolefins in the presence of an oligomerization catalyst, wherein DOLLAR A a) the C¶2¶-C¶8¶ monoolefins in at least one adsorption zone for removal of components which impair the oligomerization, with at least one adsorbent brings in contact and DOLLAR A b) the output of step a) in at least one reaction zone oligomerized, DOLLAR A characterized in that the adsorbent contains at least one capable of use as oligomerization catalyst component. Furthermore, the invention relates to the use of an adsorbent containing nickel in oxidized form for reducing the content of polyunsaturated hydrocarbons and / or oxygen, nitrogen, sulfur, phosphorus and / or halogen-containing impurities in a hydrocarbon mixture by contacting the hydrocarbon mixture with the nickel in oxidized form containing adsorbent.

Description

The present invention relates to a process for the oligomerization of C ₂ -C ₈ monoolefins in the presence of an oligomerization catalyst, wherein the C ₂ -C ₈ monoolefins are brought into contact with an adsorbent to remove components which impair the oligomerization before it reacts in a catalytic oligomerization reaction.

mixtures of longer chain linear oligomers, e.g. with 8 or more carbon atoms, are more economical Meaning, as they are z. B. as diesel fuel components and as intermediates for the preparation of functionalized, predominantly linear hydrocarbons are suitable. Thus, for example, by hydroformylation and subsequent Hydrogenation of the longer-chain linear olefin oligomers, the corresponding alcohols, in turn among other things, as starting materials for detergents and as a plasticizer be used.

For use as plasticizer alcohols, a low degree of branching of the olefins is crucial. The degree of branching is described by the ISO index, which indicates the average number of methyl branches of the respective olefin fraction. To wear z. For example, in a C ₈ fraction, the n-octenes with 0, Methylheptene with 1 and dimethylhexenes with 2 to the ISO index of the fraction at. The lower the ISO index, the greater the linearity of the molecules in each fraction. Higher linearity generally results in higher hydroformylation yields and better properties of the plasticizers made therefrom.

The above-mentioned mixtures of relatively long-chain linear oligomers are in turn obtainable from olefin mixtures with predominantly linear short-chain starting olefins. Such hydrocarbon mixtures containing short chain olefins, e.g. B. containing 2 to 8 carbon atoms, are available on a large scale. So you get z. For example, in the workup of petroleum by steam cracking or fluidized catalyst cracking (FCC) a hydrocarbon mixture referred to as C _{4 cut} having a high total content of olefins, especially of olefins having 4 carbon atoms. Such C ₄ cuts are essentially mixtures of isomeric butenes and butanes and are suitable, if appropriate after previous separation of isobutene, especially for the preparation of relatively long-chain oligomers, in particular of octenes and dodecenes.

On an industrial scale, both homogeneous and heterogeneously catalyzed processes are used for the oligomerization. Due in part to the technically complicated separation of the catalyst from the reaction mixture in homogeneous catalysis, heterogeneous catalysis is to be preferred here. The known heterogeneous catalyst systems are based essentially on nickel- and silicon-containing catalysts, which often additionally contain aluminum and / or other active components. Methods for preparing such catalysts and their use for the oligomerization of olefins are known and, for example, in the DE 43 39 713 A1 , WO 01/37989 A2, EP 0 272 970 A1 . US 5,169,824 DE-A-2051 402, DD 273 055 A1 and US 5,113,034 described.

The industrially available mixtures of short-chain olefins used for oligomerization, such as, for example, C ₄ cuts, often contain compounds which act as catalyst poisons and deactivate the abovementioned oligomerization catalysts. These catalyst poisons include, for. As alkynes and polyunsaturated hydrocarbons such as butadiene, further oxygen-containing compounds such as alcohols, aldehydes, ketones and ethers, and nitrogen-containing, sulfur-containing and halogen-containing compounds. The presence of such catalyst poisons in the oligomerization leads over time to a decrease in catalyst activity, which is often irreversible.

Out In the prior art methods are known to single, the oligomerization impairing Remove components from a hydrocarbon mixture. in this connection are the hydrocarbon mixtures usually with more or less well regenerable adsorbents brought into contact.

It is z. B. known, sulfur compounds by alkali washing and Nitrogen compounds by water washing from olefin-containing hydrocarbon mixtures, to be used for the oligomerization to remove. in this connection However, only a rough separation of the compounds in question results.

DE-A-39 14 817 describes a process for the oligomerization of olefins on a heterogeneous nickel-containing fixed-bed catalyst, wherein the hydrocarbon mixture to be used is passed before the oligomerization through a molecular sieve having a pore diameter of greater than 4 Angstroms to 15 Angstroms and removes the polyunsaturated hydrocarbons contained by selective hydrogenation. The molecular sieves used are natural and synthetic aluminum silicates, ie zeolites. However, the use of aluminum silicates for the adsorption of catalyst poison effective impurities from olefin mixtures for the catalytic oligomerization is associated with disadvantages. Thus, the surface of molecular sieves available for adsorption irreversibly decreases in the presence of water vapor. In addition, zeolites under thermal stress tend to form Lewis acidic groups which catalyze the oligomerization of olefins in undesirable manner and cause, for example, a decrease in selectivity, a broadening of the molecular weight distribution or a high degree of branching (ISO index) of the resulting oligomers.

Furthermore, describe z. For example, DE-A-20 57 269, EP 0 081 041 A1 and DE-A-1 568 542 disclose the removal of polyunsaturated olefins by selective catalytic hydrogenation to the corresponding monoolefins. Depending on the boundary conditions, a residual content of dienes of less than 50 ppm or less than 5 ppm can be achieved.

In the in the DE 198 45 857 A1 described methods for the catalytic oligomerization of short-chain monoolefins, an adsorbent is used, which is selected from alumina, alumina-containing solids, aluminum phosphates, silicas, diatomaceous earth, titanium dioxides, zirconium dioxides, phosphates, carbonaceous adsorbents, Polymeradsorbentien and mixtures thereof.

The However, these methods are only limited for removal of compounds acting as catalyst poisons. On the one hand, many can Catalyst poisons already in trace amounts the lifetime of an oligomerization catalyst on the other hand are the adsorbents used so far unable to safely retain all potential catalyst poisons. Therefore, the known methods for removing catalyst poisons are sufficient generally not looking for the oligomerization to win suitable olefin mixtures, the good ones Allow service lives of the catalysts used.

So can especially in the case of polyunsaturated olefins such as dienes already as low as less than 50 ppm or less than 5 ppm permanently lead to deactivation of the catalyst. A further depletion, e.g. to less than 1 ppm, is in the practice by means of the above selective hydrogenation not economically feasible, since this leads to significant overhydration, i.e. to the formation of alkanes, and thus to the loss of valuable Feed lead would.

It is an object of the present invention to provide a process for the catalytic oligomerization of C ₂ -C ₈ monoolefins, in which the olefin mixture used is brought into contact with an adsorbent which can be regenerated easily and substantially without decreasing the adsorption capacity, that the catalyst poisons contained therein are removed as far as possible before the oligomerization. In particular, the inventive method should ben the most complete removal of polyunsaturated hydrocarbons.

Surprisingly It was found that this task is solved when used as an adsorbent a component capable of use as an oligomerization catalyst starts.

• a) die C₂-C₈-Monoolefine in wenigstens einer Adsorptionszone zur Entfernung von Komponenten, welche die Oligomerisierung beeinträchtigen, mit wenigstens einem Adsorptionsmittel in Kontakt bringt und
• b) den Austrag aus Schritt a) in wenigstens einer Reaktionszone oligomerisiert,

dadurch gekennzeichnet, dass das Adsorptionsmittel wenigstens eine zum Einsatz als Oligomerisierungskatalysator befähigte Komponente enthält.The present invention therefore provides a process for the oligomerization of C ₂ -C ₈ monoolefins in the presence of an oligomerization catalyst in which

• a) bringing the C ₂ -C ₈ monoolefins into contact with at least one adsorbent in at least one adsorption zone to remove components which impair the oligomerization, and
• b) oligomerizing the effluent from step a) in at least one reaction zone,

characterized in that the adsorbent contains at least one component capable of being used as an oligomerization catalyst.

For the purposes of the present invention, an oligomerization catalyst is generally understood to mean a component which undergoes an oligomerization reaction of monoolefins such as C ₂ -C ₈ monoolefins to form longer-chain monoolefins, eg C ₈ , C ₁₀ , C ₁₂ monoolefins or monoolefins having more than 12 C atoms, catalyze.

For the catalytic oligomerization of monoolefin-containing hydrocarbon mixtures, it is possible to use all customary processes known to the person skilled in the art and in particular oligomerization catalysts, as described, for example, in DE-A-43 39 713, WO 01/37989 A2, US Pat. EP 0 272 970 A1 . US 5,169,824 DE-A-2051 402, DD 273 055 A1 and US 5,113,034 have been described. The oligomerization catalysts described in this prior art generally have a proportion of nickel in oxidized form as the catalytically active component. Usually, the nickel in oxidized form is present as nickel oxide (NiO), optionally as nickel aluminosilicate. In principle, however, all catalysts useful for catalyzing oligomerization reactions of C ₂ -C ₈ monoolefins are suitable as oligomerization catalysts for the process according to the invention.

When Oligomerisierungskatalysator usable components have in the Usually a content of nickel in oxidized form, calculated as NiO, of at least 0.5% by weight, and more preferably in the range of 0.5 to 90% by weight, especially in the range of 0.5 to 80% by weight, more specifically in the range of 2 to 70% by weight, more particularly in the range of 10 to 70% by weight, and more particularly in the range of 40 to 60% by weight, based on the total weight of the oligomerization catalyst, on.

The Oligomerization catalysts can supported or in the form of unsupported catalysts. suitable Support materials on which the oligomerization catalysts can be applied or with which they can be mixed are further down in the Related to carrier materials for the used according to the invention Adsorbent described. The support materials described there are basically also for the invention to be used Oligomerisierungskatalysatoren useful.

The components which can be used as oligomerization catalyst may further comprise one or more further metal oxides as active components and / or as support materials. These include in particular TiO ₂ , ZrO ₂ , SiO ₂ , Al ₂ O ₃ , Ga ₂ O ₃ , In ₂ O ₃ and the mixed oxides and mixtures thereof. In particular, an oligomerization catalyst is used which has a content of TiO ₂ and / or ZrO ₂ in the range of 5 to 30 wt .-%, especially in the range of 10 to 20 wt .-%; a content of Al ₂ O ₃ in the range of 0 to 20 wt .-%, especially in the range of 0 to 10 wt .-%; and a content of SiO ₂ in the range of 0 to 60 wt .-%, especially in the range of 10 to 50 wt .-%, each based on the total weight of the oligomerization catalyst having.

The Contain as oligomerization catalyst usable components optionally sulfur in oxidized form, the molar ratio of Sulfur atoms to nickel atoms in the oligomerization catalyst in question usually less than 1.

Preferably you put to implementation the method according to the invention the oligomerization catalysts described in WO 95/14647 one.

It goes without saying the expert, that also combinations of the aforementioned oligomerization catalysts can be used. For example, you can several identical oligomerization catalysts in parallel or be used in series reactors. Advantageous on a parallel circuit is, inter alia, that temporary power drops or OUTAGES collected in a reactor without switching off the reaction current or can be compensated. Also a combination of different oligomerization catalysts is possible.

For the purpose the method according to the invention can several different adsorbents in combination be used. In this case, it is only necessary according to the invention that at least one of the Adsorpti onsmittel used for use as an oligomerization catalyst enabled Component, e.g. one of the above-mentioned oligomerization catalysts, contains.

In a first embodiment the invention is an adsorbent, which is a for Use as an oligomerization catalyst-capable component, without other different adsorbents. Here, the contained in the adsorbent for use as an oligomerization catalyst enabled Component and the for the olefin oligomerization used oligomerization catalyst be the same, i. it will each be the same component both as an adsorbent and as an oligomerization catalyst used. Furthermore you can those contained in the adsorbent for use as oligomerization catalyst enabled Component and the oligomerization catalyst used different be. As a component capable of being used as an oligomerization catalyst are in particular the aforementioned oligomerization catalysts suitable.

In a further embodiment If one sets an adsorbent, which is one used as an oligomerization catalyst enabled Component contains together with other adsorbents. Again, the contained in the adsorbent for use as an oligomerization catalyst enabled Component and the for the olefin oligomerization used oligomerization catalyst be the same or different. For the other adsorbents it can be used both as an additional oligomerization catalyst enabled Components as well as conventional Adsorbents, as described below, without catalytic activity to olefin oligomerization. As for use as an oligomerization catalyst enabled Component are in particular the aforementioned oligomerization catalysts suitable. Unless conventional Adsorbent used, it has proved to be advantageous proved, to be oligomerized monolefins first with To bring this into contact before contacting with the for use as oligomerization catalyst capable of components or adsorbents he follows.

In a preferred embodiment The invention is used as an adsorbent and as an oligomerization catalyst the same component. If necessary, one additionally uses this or more, different from the oligomerization catalyst conventional Adsorbents as described below.

When Adsorbent, the same as the oligomerization catalyst used are basically, come all previously mentioned as usable oligomerization catalysts Components into consideration. In particular, such adsorbents, which are capable of use as oligomerization catalyst, for implementation the method according to the invention suitable containing nickel in oxidized form. This nickel in oxidized form containing adsorbent have in the Usually a content of nickel in oxidized form, calculated as NiO, of at least 0.5% by weight, and more preferably in the range of 0.5 to 90% Wt .-%, especially in the range of 0.5 to 80 wt .-%, more specifically in Range of 2 to 70 wt%, more particularly in the range of 10 to 70% by weight, and more specifically in the range of 40 to 60% by weight, respectively based on gas total weight of the nickel in oxidized form containing Adsorbent, on. About that can out Such adsorbents have the same additional active components or carrier materials, the previously for the components to be used as the oligomerization catalyst were called. This extra active components or carrier materials lie here in the same amounts in the nickel in oxidized form containing adsorbent previously for the as oligomerization catalyst specified components.

• (i) dem Nickel in oxidierter Form, insbesondere in einer Menge im Bereich von 0,5 bis 90 Gew.-%, speziell im Bereich von 10 bis 70 Gew.-% und ganz speziell im Bereich von 40 bis 60 Gew.-%, jeweils berechnet als NiO;
• (ii) einem oder mehreren Metalloxid(en), vorzugsweise ausgewählt unter TiO₂, ZrO₂, SiO₂, Al₂O₃, Ga₂O₃, In₂O₃ und den Mischoxiden und Mischungen davon, besonders bevorzugt ausgewählt unter TiO₂, ZrO₂, SiO₂, Al₂O₃; insbesondere TiO₂ und/oder ZrO₂ in einer Menge im Bereich von 5 bis 30 Gew.-%, speziell im Bereich von 10 bis 20 Gew.-%; SiO₂ in einer Menge im Bereich von 0 bis 60 Gew.-%, speziell im Bereich von 10 bis 50 Gew.-%; Al₂O₃ in einer Menge im Bereich von 0 bis 20 Gew.-%, speziell im Bereich von 0 bis 10 Gew.-%;
• (iii) gegebenenfalls Schwefel in oxidierter Form, wobei das molare Verhältnis von Schwefelatomen zu Nickelatomen vorzugsweise weniger als 1 beträgt und insbsondere im Bereich von 0, 25 : 1 bis 0,38 : 1 liegt;

wobei sich die Anteile der einzelnen Komponenten zu 100 Gew.-% ergänzen. Der Ausdruck „im Wesentlichen" bedeutet hier, dass der Anteil anderer Komponenten üblicherweise nicht mehr als 0,5 Gew.-% beträgt. Im Allgemeinen wird dieser Anteil nicht mehr als 0,1 Gew.-% betragen.In a preferred embodiment, an adsorbent containing nickel in oxidized form is used, which consists essentially of

• (i) the nickel in oxidized form, in particular in an amount in the range from 0.5 to 90% by weight, especially in the range from 10 to 70% by weight and especially in the range from 40 to 60% by weight , each calculated as NiO;
• (Ii) one or more metal oxide (s), preferably selected from TiO ₂ , ZrO ₂ , SiO ₂ , Al ₂ O ₃ , Ga ₂ O ₃ , In ₂ O ₃ and the mixed oxides and mixtures thereof, more preferably selected from TiO ₂ , ZrO ₂ , SiO ₂ , Al ₂ O ₃ ; in particular TiO ₂ and / or ZrO ₂ in an amount in the range from 5 to 30% by weight, especially in the range from 10 to 20% by weight; SiO ₂ in an amount ranging from 0 to 60% by weight, especially in the range of 10 to 50% by weight; Al ₂ O ₃ in an amount ranging from 0 to 20% by weight, especially in the range of 0 to 10% by weight;
• (iii) optionally, sulfur in oxidized form, wherein the molar ratio of sulfur atoms to nickel atoms is preferably less than 1, more particularly in the range of 0.25: 1 to 0.38: 1;

wherein the proportions of the individual components add up to 100 wt .-%. The term "substantially" here means that the proportion of other components is usually not more than 0.5% by weight. In general, this proportion will not be more than 0.1% by weight.

to execution the method according to the invention it has proven to be advantageous to use the component of the adsorbent, which is capable of use as an oligomerization catalyst, to choose among such components containing nickel in oxidized form. In particular, you will be in In this case, the aforementioned nickel in oxidized form containing Use adsorbent. Preferably, those are used in WO 95/14647 and WO 01/37989 described nickel-containing oligomerization catalysts adsorbents containing nickel in oxidized form.

Particular preference is given to using an adsorbent, essentially consisting of nickel oxide, silicon dioxide, titanium dioxide and / or zirconium dioxide and optionally alumina, with a content, After deduction of the loss on ignition after tempering at 900 ° C, of nickel oxide, calculated as NiO, from 10 to 70 wt .-%, 5 to 30 wt .-% titanium dioxide and / or zirconia, 0 to 20 wt .-% alumina, 20 to 40% by weight of silica, and 0.01 to 1% by weight of an alkali metal oxide, with the proviso that the proportions of the individual components supplement to 100% by weight, obtainable by precipitation of an aluminum-free or a dissolved one Aluminum salt-containing nickel salt solution at a pH of 5 to 9 by adding this nickel salt solution to an alkali water glass solution containing solid titanium dioxide and / or zirconia, drying and heat treatment of the resulting precipitate at 350 to 650 ° C and in particular at 30 to 90 ° C.

Also It is particularly preferable to use an adsorbent which passes through a process is prepared in which alumina with a Nickel compound and a sulfur compound applied, and while simultaneously or first with the nickel compound and after with the sulfur compound, and the adsorbent thus obtained subsequently dried and calcined, thereby obtaining in the finished adsorbent a molar ratio of sulfur to nickel from 0.25: 1 to 0.38: 1.

The abovementioned adsorbents generally have a BET specific surface area in the range from about 10 to 2000 m ² / g, in particular in the range from 10 to 1500 m ² / g, especially in the range from 20 to 600 m ² / and completely especially in the range of 100 to 500 m ² / g.

It goes without saying the expert that contained in the aforementioned adsorbents component suitable for use as an oligomerization catalyst both in their active form as well as in the form of a precursor can be used. Such precursors become common by thermal treatment at temperatures of a few hundred Degrees, e.g. in the range of 200 to 800 ° C, converted into the respective akti ve form. Preferably if the component which is capable of being used as oligomerization catalyst is added their active form. To remove any existing Moisture can be the catalyst or its active form before carrying out the Oligomerization reaction of a treatment in a stream of nitrogen at a sufficiently high temperature, e.g. in the range of 150 to 200 ° C, subject. This drying is preferably carried out in situ.

In a special embodiment you use in addition at least one further, substantially nickel-free adsorbent. Therefor In particular, all those adsorbents come into consideration, in the prior art already for the removal of impurities from hydrocarbon mixtures used for the oligomerization of olefins are used, proposed or used. "Essentially Nickel-free "means here and below that the respective adsorbent nickel usually only in minor amounts, e.g. in traces, contains. For the purpose of In the present invention, an adsorbent agent is essentially Nickel free ", if its content of nickel is less than 0.5% by weight, based on the total weight of the adsorbent is.

such essentially nickel-free adsorbents that are suitable for the process of the invention are suitable, are common and known to those skilled so-called active aluminas. Your Production takes place z. B. starting from aluminum hydroxide, which by usual precipitation method from aluminum salt solutions available is. Also includes z. B. the commercially available Bayer aluminum hydroxide. These aluminum hydroxides can then directly by heating to temperatures of about 700 to 2100 ° C in suitable furnaces, such as z. As rotary or fluidized bed calcination, to active alumina be implemented. For the preparation of spherical activated alumina Aluminum hydroxide can be used in a vacuum or in a kick heater Be subjected to the presence of a high temperature resistant gas. This is the aluminum hydroxide for a short time, in general a few seconds, heated to temperatures of about 1100 to 1600 ° C. For the inventive method suitable active aluminas are also starting from aluminum hydroxide gels available. For the preparation of such gels z. B. precipitated aluminum hydroxide according to usual Work-up steps, such as filtering, washing and drying, activated and subsequently optionally ground or agglomerated. If desired, you can then the resulting alumina still a molding process, such as extrusion, granulation, tableting submit. As adsorbents are preferably Selexsorb ™ grades from Alcoa.

Further for the inventive method suitable substantially nickel-free adsorbents are still alumina-containing solids. These include z. B. the so-called Clays which also contain aluminum oxides as the main constituent, and mixtures of at least one alumina and at least another of the aforementioned adsorbents.

If desired, the aluminum oxides or aluminum oxide-containing solids used according to the invention may additionally comprise at least one alkali metal and / or alkaline earth metal compound. To For this purpose, the alumina or alumina-containing solid, for example, a soaking step with an appropriate solution and optionally further conventional process steps, such as drying and / or calcination, are subjected. Preferably, this modification of the adsorbent takes place after molding. Preferably, the alumina or the alumina-containing solid has an alkali metal and / or alkaline earth metal content of at most 1 wt .-%, z. In a range of about 0.0001 to 1.0% by weight based on the total weight of the substantially nickel-free adsorbent. The aluminum oxides or aluminum oxide-containing solids used according to the invention preferably contain the alkali metals and / or alkaline earth metals in the form of their oxides.

Of Further for the inventive method suitable substantially nickel-free adsorbents are aluminum phosphates.

Farther for the inventive method suitable substantially nickel-free adsorbents are silicas, the e.g. by drainage and activation of silica gels. Another procedure for the production of silica is the flame hydrolysis of silicon tetrachloride, whereby by suitable variations the reaction parameters, e.g. the stoichiometric Composition of the educt mixture and the temperature, the desired surface properties of the resulting silica varies widely can be.

Farther suitable essentially nickel-free adsorbents are diatomaceous earth, which also contain silicas as the main constituent. To counts, e.g. the diatomaceous earth obtained from silica sediments.

Farther suitable substantially nickel-free adsorbents are titanium dioxides and zirconium dioxides, as described, for. B. in Römpp, Chemie Lexikon, 9th ed. (Paperback), Vol. 6, p. 4629f. and pp. 5156f. and the one quoted there Literature are described. This is here in full reference taken.

Farther suitable substantially nickel-free adsorbents are still Phosphates, in particular condensed phosphates, such as. B. melting or incandescent phosphates, the one big one have active surface. Suitable phosphates are, for. B. in Römpp, Chemie Lexikon, 9th ed. (Paperback), Vol. 4, p. 3376f. and the literature cited therein. This is hereby fully incorporated by reference.

Farther suitable substantially nickel-free adsorbents are carbonaceous Adsorbents, preferably activated carbon. Activated carbon is understood here generally carbon with a porous structure and high internal Surface. For the production of activated carbon are plant, animal and / or mineral carbonaceous raw materials, eg. With dehydrating agents, such as zinc chloride or phosphoric acid, heated or charred by dry distillation and then oxidative activated. This can be z. As the charred material at elevated temperatures from about 700 to 1000 ° C treat with steam, carbon dioxide and / or mixtures thereof.

The Essentially nickel-free adsorbents are preferred Titanium dioxides, zirconium dioxides, silicon dioxides, kieselguhr, Aluminas, alumina-containing solids, aluminum phosphates, natural and synthetic aluminosilicates, phosphates, carbon-containing Adsorbents and mixtures thereof, more preferably under alumina and alumina-containing solids. Very particularly preferred are aluminum oxides and alumina-containing solids that are at least having an alkali metal and / or alkaline earth metal. Preferably is the alkali metal and / or alkaline earth metal content at most 1% by weight, e.g. in the Range of 0.0001 to 1 wt .-%, based on the total weight of essentially nickel-free adsorbent.

The essentially nickel-free adsorbents generally have a BET specific surface area in the range from about 10 to 2000 m ² / g, in particular in the range from 10 to 1500 m ² / g and especially in the range from 20 to 600 m ² / g, up.

The essentially nickel-free adsorbents used according to the invention generally have no catalytic activity for the oligomerization of olefins. An oligomer formation of not more than 0.2% by weight, in particular not more than 0.1% by weight, based on the total amount of monoolefin in the oligomerization mixture used, is observed in a novel adsorbent (so-called 1st cycle) according to the invention hydrocarbon mixture. Advantageously, this tendency to oligomer formation substantially does not increase even with regenerated adsorbents (2nd to nth cycle). Furthermore, the inventively used substantially Nickel-free adsorbent advantageously no tendency to a significant isomerization tion of unbranched monoolefins.

Provided in addition to adsorbents, one for use as an oligomerization catalyst capable component included, in addition conventional Adsorbents are used, so is the weight ratio of the former to the latter usually in the range of 10: 90 to 90: 10 and in particular in the range of 30: 70 to 70: 30. Preferably one of the above is used Nickel-containing oligomerization catalysts as adsorbents, the one capable of use as an oligomerization catalyst component contains one. As conventional Adsorbents preferably find the above-described nickel-free Adsorbent use. In a special embodiment Thus, nickel-containing and nickel-free adsorbents are used, the weight ratio from nickel-containing to nickel-free adsorbents in the range from 10:90 to 90:10 and especially in the range of 30: 70 until 70: 30.

The used according to the invention Adsorbents can prior to their use a conventional molding process such as pelleting, tableting or extruding. In particular, the adsorbents are in the form of extrudates, e.g. strands, in particular cylindrical Strands, or Used bullets. strand-shaped Adsorbents preferably have a length in the range of 0.1 to 2 mm and more preferably in the range of 0.2 to 1 mm and a Diameter in the range of about 0.5 to 10 mm and more preferred in the range of 1 to 5 mm. Point spherical adsorbents preferably a diameter in the range of about 0.1 to 5 mm and more preferably in the range of 1 to 5 mm.

Furthermore, before being used, the adsorbents can be applied to optionally inert and / or non-porous carrier materials, as known from the prior art. These include, for example, quartz (SiO ₂ ), porcelain, magnesium oxide, silicon carbide, titanium dioxide, alumina (Al ₂ O ₃ ), aluminum silicate, steatite (magnesium silicate), zirconium silicate or mixtures of these support materials. The shape of the support material is generally not critical. For example, carrier materials in the form of spheres, rings, tablets, spirals, tubes, extrudates or chippings can be used. The dimensions of these support materials correspond to the dimensions usually set in the production of adsorbents used as solid phase and overflowed by a gas phase. The abovementioned carrier materials can also be mixed into the adsorbents in powder form.

to cupped Coating of the carrier materials with the inventively used Adsorbents can known methods of the prior art are used. To the Example can the adsorbent-containing suspensions in a coating drum or in a fluid bed coater, optionally at elevated temperature, on the support materials sprayed become. In a suspension or slurry of a powder of the invention used Adsorbents in water or in an organic solvent, e.g. higher Alcohols, polyhydric alcohols, e.g. Ethylene glycol, 1,4-butanediol or glycerol, dimethylformamide, dimethylacetamide, dimethyl sulphoxide, N-methylpyrrolidone or cyclic ureas, e.g. N, N'-dimethyl ethylene or N, N'-dimethylpropyleneurea, or mixtures of these organic solvents with water, organic Binders such as copolymers dissolved or such binders can advantageously in the form of an aqueous Dispersion can be added. In this case, binder contents are generally in the range of 10 to 20% by weight, optionally in the range of 1 to 10 wt .-%, based on the solids content of the suspension or slurry set. Suitable binders are e.g. Vinyl acetate / vinyl laurate, Vinyl acetate / acrylate, styrene / acrylate, vinyl acetate / maleate or Vinyl acetate / ethylene copolymers.

at the coating of the support materials with the inventively used Adsorbents are generally temperatures in the range from 20 to 500 ° C applied, wherein the coating in the coating apparatus under atmospheric pressure or under reduced pressure. When using binders For coating, these should be made by thermal treatment at temperatures from over 200 up to 500 ° C, where the binders decompose and / or burn out the applied layer are removed, e.g. as part of a conditioning pretreatment.

The above carrier materials and coating methods are in principle also suitable for the invention Oligomerization.

According to the invention to be oligomerized C ₂ -C ₈ monoolefins are in at least one adsorption zone with or brought into contact and the adsorbents in at least one reaction zone oli gomerisiert. An adsorption zone is understood here to mean the spatial area which is claimed by one or more usually solid adsorbents and by which the educt mixture, usually a gaseous mixture with a high content of C ₂ -C ₈ monoolefins, can be flowed through. A reaction zone is understood here to mean the spatial area which is claimed by one or more usually solid oligomerization catalysts and can be flowed through by the educt mixture after it has been discharged from the adsorption zone.

It will be understood by those skilled in the art that the specific configuration and arrangement of the adsorption and reaction zone (s) may be in any known manner. It is preferable to arrange the adsorption and reaction zone (s) spatially separated from one another, ie to structurally separate from one another by the apparatus design. For this purpose, for example, a relatively small-sized apparatus (for example of the order of a few m ³ , usually in the range of 1 to 20 m ³ and often not more than 25 m ³ ) can be provided as the adsorption zone and a comparatively larger-sized apparatus (eg in of the order of about 100 m ³ , usually in the range of 50 to 250 m ³ and often more than 25 m ³ ) as a reaction zone. It has proved to be advantageous for carrying out the process according to the invention if the volume ratio of adsorption to reaction zone is chosen such that it is in the range from 1: 1 to 1: 500 and in particular in the range from 1: 2 to 1: 100. If available, in each case the total adsorption zones or reaction zones are to be calculated together and then related to one another.

Provided If one uses different adsorbents, one can e.g. provide a first adsorption zone in a first reactor, the contains a first adsorbent, and separately, so apparative separated from it, e.g. in a second reactor, a second adsorption zone, which contains a second adsorbent. Here, the first and / or the second adsorbent at least one used contain as component capable of oligomerization.

Advantageously, at least two adsorption zones will be arranged so that the C ₂ -C ₈ monoolefins to be oligomerized in the first adsorption zone are contacted with a conventional adsorbent, eg a substantially nickel-free adsorbent as described above, and in the second adsorption zone with an adsorbent containing at least one capable of use as an oligomerization catalyst component, are brought into contact. The latter may be, for example, an adsorbent containing nickel in oxidized form, as described above.

In a further embodiment, a substantially nickel-free adsorbent together with a nickel adsorbed in oxidized form in a single adsorption zone, for example in superimposed form, mixed in the form of a random distribution or in the form of a gradient bed. The use in mixed form optionally allows better control of the temperature. In the case of a gradient bed, linear and nonlinear gradients can be used. It may be advantageous in this case to carry out the distribution within the bed in such a way that the C ₂ -C ₈ monoolefins to be oligomerized are first brought into contact with the substantially nickel-free adsorbent before they are mixed with the adsorbent containing the nickel in oxidized form Contact us.

It goes without saying the expert that the illustrated different variants for the design of the adsorption and reaction zones in each case also can be applied in the way that you ever two or more identically designed adsorption and / or Reaction zones arranged in parallel and / or behind one another. Especially a configuration is advantageous in which at least two separate similar adsorption zones are provided, which are parallel to each other can be operated. This allows temporary power losses or failures collected in a reactor without switching off the reaction current or be compensated. This is e.g. achieved by that one the Adsorption zones operates so that both with different from each other Amounts of catalyst poisons are loaded. Preferably one arranges two adsorption zones in parallel and operates them alternately, e.g. alternately during a given period of time. Particularly preferred In such an approach, the switching from one to the other adsorption zone, respectively, after a loading of the adsorbent with a predetermined maximum quantity was reached at catalyst poisons. This maximum amount may be e.g. out a specific product specification. In particular, will this maximum amount be sized so that the catalytic activity of the oligomerization catalyst at an economically acceptable level. It has e.g. proved to be advantageous, such an aforementioned switching respectively when in the stream leaving the adsorber Content of potential catalyst poisons as described below are from 0.001% by weight (10 ppm by weight) reached or exceeded becomes.

In the process according to the invention, generally customary monoolefin-containing hydrocarbon mixtures which contain C ₂ -C ₈ -monoolefins can be used as starting materials. Such hydrocarbon mixtures have one or more types of monoolefins having 2 to 8 carbon atoms, in particular having 2 to 6 carbon atoms. In particular, mixtures with a high proportion of monoolefins, for example in the range from 10 to 90% by weight, based on the total weight of the mixture, are suitable. Of these, especially suitable are those which contain, in particular, aliphatic and / or cycloaliphatic C ₄ monoolefins and / or C ₅ -C ₆ monoolefins. The hydrocarbon mixtures used advantageously contain a high proportion, for example in the range from 10 to 90% by weight, based on the total weight of the mixture, of unbranched monoolefins. The use of an oligomerization catalyst which leads to low-branched oligomers in good yield thus allows according to the invention to obtain oligomers with high linearity, ie with a low ISO index.

For the process according to the invention, it is possible to use, for example, a hydrocarbon mixture obtained on an industrial scale. These include, for example, the C ₄ cuts obtained in the processing of crude oil by steam cracking or fluidized catalyst cracking (FCC). In a specific embodiment, a so-called raffinate II is used. In a further specific embodiment, a hydrocarbon mixture comprising C ₂ -C ₈ monoolefins, which consists of a, for example, according to the DE 198 59 911 olefin metathesis was carried out used.

In a further specific embodiment, a large-scale C _{4 cut is} used which contains essentially 10 to 90% by weight of butenes and 10 to 90% by weight of butanes, the butene fraction containing the following hydrocarbons: 1 to 99 Wt% trans-2-butene; From 1 to 50% by weight of 1-butene; From 1 to 50% by weight of cis-2-butene; and 1 to 5% by weight of isobutene; and wherein the proportion of the butene and the butane fraction add up to 100 wt .-%. The term "essentially" here means that the proportion of further components is generally not more than 1% by weight and in particular not more than 0.1% by weight.

Usually the abovementioned hydrocarbon mixtures contain catalyst poisons, i.e. Components which impair the oligomerization, by deactivating the oligomerization catalyst. For this counting oxygenates such as water, alcohols, e.g. methanol, Ethanol, isopropanol, n-propanol, n-butanol, sec-butanol, isobutanol, tert -butanol, ether, e.g. Diethyl ether, methyl tert-butyl ether, aldehydes, e.g. Formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, ketones, e.g. Acetone, methyl ethyl ketone, etc. Other commonly used catalyst poisons are nitrogen-containing compounds such as amines and sulfur-containing Compounds such as hydrogen sulfide, thio alcohols, thioethers, e.g. Dimethyl sulfide and dimethyl disulfide, carbon sulfide, etc. If necessary included on an industrial scale Hydrocarbon mixtures used for olefin oligomerization even more production-related catalyst poisons. These include e.g. Halogen compounds, Traces of usual Extractants, e.g. Acetonitrile or N-methylpyrrolidone etc., as well optionally organic phosphorus and arsenic compounds.

Of the Content of the aforementioned catalyst poisons in the process according to the invention used hydrocarbon mixtures is not limiting in principle Factor for the use of the invention described above to be used Adsorbent. With increasing content of the catalyst poison decreases However, the required volume of adsorbent per Time unit and hydrocarbon throughput too. Therefore, it is optional more economically, the hydrocarbon mixtures used for olefin oligomerization prior to contacting with the adsorbents described above, in particular, prior to contacting with those previously described essentially nickel-free adsorbents of a coarse cleaning to undergo known from the prior art methods. So it is generally favorable the content of the aforementioned catalyst poisons in the hydrocarbon mixtures in contact with the adsorbents used according to the invention, if necessary, by usual Procedure at most about 0.5 wt .-% (5000 ppm by weight), preferably at most 0.2 wt .-% (2000 ppm by weight), in particular at the most 0.1 wt.% (1000 wt. Ppm). Suitable procedures too Such a rough purification of hydrocarbon mixtures are z. In DE-A-39 14 817 and the literature cited therein, to which reference is made in its entirety.

In a preferred embodiment, a hydrocarbon mixture containing the C ₂ -C ₈ monoolefins prior to contacting with adsorbents containing nickel in oxidized form is contacted with nickel-free adsorbent such that the content of oxygen, nitrogen, sulfur -, phosphorus and / or halogen-containing impurities in the hydrocarbon mixture to at most 0.001 wt .-% and in particular to at most 0.0001 wt .-%, based on the total weight of the hydrocarbon mixture is reduced.

The contain hydrocarbon mixtures used for the oligomerization furthermore usually multiple monoethylenically unsaturated Hydrocarbons and / or alkynes. Thus, e.g. a typical one Raffinate II has a content of butadiene of the order of several thousand Ppm by weight. It has to carry out the method according to the invention proved to be advantageous, the content of such impurities prior to oligomerization by selective hydrogenation to the corresponding To reduce monoolefins. Suitable methods for selective hydrogenation are e.g. in DE-A-20 57 269, EP-A-0 081 041 and DE-A-15 68 542 which is incorporated herein by reference in its entirety. In particular, one will carry out a hydrogenation so that the obtained in the inventive method to be used hydrocarbon mixture has a content of several times unsaturated Hydrocarbons and / or alkynes of at most 0.01% by weight (100 ppm by weight), especially 0.005% by weight (50 ppm by weight) and especially 0.001% by weight (10 ppm by weight). Optionally, this selective hydrogenation even after bringing the hydrocarbon mixture into contact with a substantially nickel-free adsorbent, however prior to contacting with the nickel in oxidized form Adsorbent done.

In a preferred embodiment the discharge from step a), i. after exiting the adsorption zone and before entering the reaction zone, a content of several times unsaturated Hydrocarbons of less than 0.001 wt .-%, based on the Total weight of the discharge, on.

According to the invention, an adsorbent is used in at least one adsorption zone, which contains at least one component capable of being used as an oligomerization catalyst. While the essentially nickel-free adsorbents, as stated above, usually do not have any significant catalytic activity for the oligomerization of olefins, this naturally does not apply to the adsorbent component which contains the component which is suitable for use as an oligomerization catalyst. In particular, this relates to nickel in oxidized form containing adsorbent or components. In this connection, it is advantageous to use an identical or similar component both as oligomerization catalyst and as adsorbent containing the component capable of use as oligomerization catalyst, since in this case the olefin products already formed in the adsorption zone by oligomerization in the reaction zone formed olefin products in terms of selectivity and quality. It has been found that this also applies if the adsorption is carried out under conditions in which generally only a small amount, for example less than 20% by weight of the C ₂ -C ₈ monoolefins used, are oligomerized. Conditions for controlling the conversion of the oligomerization reaction are known in principle to the person skilled in the art and can easily be determined by him in routine experiments. It has further been found that by using lower temperatures than those typically used for the oligomerization reaction, for example, when adjusting temperatures below 50 ° C and especially below 30 ° C, the catalytic oligomerization activity of the adsorbents used as the oligomerization catalyst contain able component, can be greatly reduced; on the other hand, the adsorption capacity for potential catalyst poisons is essentially retained.

In general, the process according to the invention is carried out under reaction conditions (temperature, pressure, throughput, etc.) in which less than 50% by weight, in particular less than 20% by weight and especially less than 10% by weight of C ₂ -C ₈ monoolefins, in each case based on the total weight of the C ₂ -C ₈ monoolefins used, are oligomerized in step a). To achieve this purpose, in particular a control of the temperature of the adsorption zone (s) into consideration. Usually, the adsorption is carried out at a temperature of less than 50 ° C, in particular less than 40 ° C and especially less than 30 ° C. At a temperature of less than 30 ° C in the adsorption usually only a small amount of oligomerization occurs (eg in the order of 0.1 to 5 wt .-% of C ₂ -C ₈ monoolefins used), the absolute extent However, among other things by the olefin concentration and the state and the load of the catalyst is influenced. At a temperature of less than 10 ° C in the adsorption zone, oligomerization can be almost completely eliminated. It is possible to carry out the adsorption at a temperature of more than 50 ° C. In this case, however, the heat of reaction caused by the significantly occurring oligomerization reaction is reliably removed from the adsorption zone, ie, from the catalyst bed, resulting in a qualitatively comparable olefin product as in the oligomerization reaction carried out in the reaction zone.

The process according to the invention is preferably carried out in such a way that the temperature in the adsorption zone containing nickel-free adsorbents is in the range from 0 to 150 ° C., more preferably in the range from 5 to 100 ° C. and most preferably in the range from 10 to 50 ° C. The temperature in the adsorption zone containing nickel-containing adsorbent is preferably in the range of 0 to 50 ° C, more preferably in the range of 5 to 40 ° C and most preferably in the range of 10 to 30 ° C. If nickel-free and nickel-containing adsorbent are used in combination in the same adsorption zone, the temperatures mentioned above for the nickel-containing adsorbent are advantageously chosen.

Usually, the C ₂ -C ₈ monoolefins or a hydrocarbon mixture containing them at a pressure in the range of about 1 to 200 bar, in particular in the range of about 1 to 100 bar, especially in the range of about 1 to 50 bar and very specifically in the range of about 10 to 30 bar, brought into contact with the adsorbent.

Suitable for the contacting of the C ₂ -C ₈ monoolefins or of a hydrocarbon mixture containing them with the adsorbents described above, which may be pressure-resistant, are known to the person skilled in the art. These include the commonly used reactors for gas / solid reactions and liquid / solid reactions. Preferably, a fixed bed reactor or a moving bed reactor is used. The adsorbent may, as stated above, be used in the form of a single or in the form of multiple adsorption zones (also referred to as contact zones). Here, each of these zones may comprise one or more of the adsorbents described above. Adsorption and oligomerization can be carried out in different reactors or in successive zones in one reactor. In this case, if appropriate, the zones for the adsorption and the zones for the oligomerization are operated under different reaction conditions, in particular at different temperatures.

The bringing into contact of the hydrocarbon mixture containing the C ₂ -C ₈ monoolefins with the adsorbents is generally carried out by passing over. In this case, the hydrocarbon mixture can be brought into contact, for example, in gaseous, liquid or supercritical phase with the adsorbents. The linear velocity is preferably in a range of about 1 to 200 cm / min.

The Regeneration of the invention used Adsorbent, in particular the substantially nickel-free Adsorbent, usually by treatment with oxygen, oxygen-containing gas mixtures, e.g. Air, oxygen supplying compounds, nitrogen oxides or Mixtures thereof. The temperature during the regeneration is in the Usually in the range of about 100 to 800 ° C and especially in the range from 200 to 600 ° C.

The Regeneration of the invention used Nickel-containing adsorbent is preferably carried out by the nickel used in oxidized form containing adsorbent, its adsorption capacity as a result of use in one of the above-described methods has substantially completely regenerated by that the nickel-containing adsorbent with an oxygen-containing Gas, air, nitrogen oxides or a mixture thereof at a temperature of at least 300 ° C, e.g. in the range of 300 to 600 ° C, treated.

advantageously, can the invention used Adsorbent frequently be regenerated without the adsorption capacity in significant Way wears off. They are suitable for a simple and economical oxidative thermal regeneration, as described above. This is also after a variety of Regeneration cycles essentially no increase in the through the Adsorbent catalyzed oligomerization observed. in the Generally can Cycle numbers of at least 2, especially at least 20, especially at least 200, and especially at least 2000.

The adsorbents described above are suitable not only for use in a process for the catalytic oligomerization of monoolefinic hydrocarbon mixtures, but more generally for the treatment of olefins or olefin mixtures for reducing the content of potential catalyst poisons. The invention therefore also relates to a process for the preparation of pure olefins or olefin mixtures, for example of C ₂ -C ₃₀ monoolefins or olefin mixtures containing them, which is characterized in that olefins or olefin mixtures, for example C ₂ -C ₃₀ monoolefins or containing these olefin mixtures, with at least one of the previously described adsorbent containing at least one capable of use as oligomerization catalyst component in contact.

One Another object of the invention is the use of a nickel oxidized adsorbent as described above, for reducing the content of polyunsaturated hydrocarbons and / or oxygen, nitrogen, sulfur, phosphorus and / or Halogen-containing impurities in a hydrocarbon mixture by contacting the hydrocarbon mixture with the nickel in oxidized form containing adsorbent.

The The invention will be further illustrated by the following non-limiting examples.

When Eduktgemisch containing the olefins to be oligomerized, a raffinate II was used. The reactions were continuous using a thermostated fixed bed reactor (30 mm clear Width) under increased compared to the intrinsic pressure of the raffinate II pressure (20 bar) performed. The adsorption of catalyst poisons was carried out in an analogous reactor (30 mm clear width), which is connected upstream of the reactor with the oligomerization catalyst was and in A / B execution was present. In such an A / B embodiment, two similar Reactors are connected in parallel, so that during operation of one Reactor the other expanded, ex situ regenerated and then again can be installed without interrupting the current Procedure is necessary. The pressure was via a reactor feed pump generated before the first reactor and a pressure holding device regulated according to the second reactor.

In each case, a similar pretreatment of the catalyst and the adsorbent was carried out. For this purpose, each 250 ml of catalyst or 500 ml of adsorbent were charged into the reactor and 24 h at 160 ° C and under normal pressure in a dry stream of N ₂ (1500 Nl / h) conditioned. It was then cooled to 20 ° C. There was a metered addition of raffinate II and an increase in the pressure to 20 bar by means of the pump or pressure holding device. Subsequently, an increase in temperature in the reaction zone was optionally carried out.

I. butadiene adsorption on a Ni-containing adsorbent

It a raffinate II was used, consisting of 3.1% i-butane, 15.3 % n-butane, 29.8 1-butene, 2.1% i-butene, 31.7% trans-2-butene, 17.8 % cis-2-butene, 0.2% i-pentane, and 100 ppm of 1,3-butadiene. At a catalyst load of 2 kg / l · h was the butadiene-containing feed raffinate II at 20 ° C over a Period of 20 days over a nickel-containing oligomerization catalyst as described in Ex. 2 of DE-A-43 39 713, passed. By means of off-line GC analysis was regularly the Butadiene content in the discharge examined. Based on the specified Period of 20 days, butene turnover was less than 5% by weight. the butene used. There could be no butadiene at the reactor outlet be detected (<1 ppm or <0.0001 wt .-%, based on the total weight of the discharge). This shows that the used as adsorbent Ni-containing oligomerization catalyst effectively a restraint of olefins such as butadiene.

II. Long-term test with adsorbent according to DE-A-198 45 857 and regeneration of Ni-containing catalysts (comparative experiment)

A raffinate II was used, average consisting of 3% i-butane, 23% n-butane, 26% 1-butene, 1% i-butene, 31% trans-2-butene, 16% cis-2-butene, and as trace components 10 ppm of dienes, 30 ppm of water, 20 ppm of alcohols, 5 ppm of aldehydes and 20 ppm of ketones (all data as ppm by weight). At a catalyst loading of 2 kg / lh, this butadiene-lean feedstock raffinate II was first passed over a period of 180 days over a first fixed-bed reactor thermostated at 20 ° C. This first reactor was filled with 500 ml of active Al ₂ O ₃ (3 mm spheres, Selexsorb CD from Alcoa) and was available in duplicate for driving in A / B mode. Subsequently, the discharge from the first reactor was passed through a second thermostated fixed bed reactor. This second reactor was filled with 250 ml of nickel-containing oligomerization catalyst, as described in Ex. 2 of DE-A-43 39 713. The purified olefin stream discharged from the adsorber was examined regularly for trace components by GC analysis. After reaching the breakthrough capacity (defined here as more than 10 ppm by weight or 0.001% by weight catalyst poisons) was switched to the other adsorber. The spent adsorbent was blown dry by flushing the adsorbent with N ₂ , then removed and replaced with ex situ regenerated adsorber. The ex situ regeneration was carried out by burning in air at 400-500 ° C and cooling under N ₂ , with a flow of 500 Nl _gas / h / kg _{adsorber was} set. The reaction temperature was adjusted so that over the period considered a butene conversion between 40-50% of the butenes used was achieved.

At the beginning of the long-term test, the temperature was 60 ° C, after 180 days at 100 ° C. The partially deactivated catalyst after this period was removed and subjected to extensive analysis. It was found that the catalyst located at the reactor inlet has significant amounts of nitrogen- and halogen-containing residues (100-500 ppm nitrogen or 30-40 ppm halogen), while these components are virtually undetectable at the reactor outlet. The carbon content is above the total The catalyst bed at about 2 wt .-%, with a tendency decrease towards the reactor outlet out. Rapid tests were performed to verify the performance of the degraded catalysts in a thermostated micro bed reactor 10 mm in diameter and 20 cm in length. For this purpose, in each case 10 g of the removed catalyst were conditioned in accordance with the above catalyst pretreatment. Subsequently, the catalysts were regenerated in situ for 2 h at 400-500 ° C by means of passage of air (5 Nl / h) and cooling under N ₂ . Once again, "rapid tests" were carried out over a period of 3 days and the results are shown in Table 1.

Table 1: Rapid test (1 kg / l · h raffinate II, 60 ° C reactor temperature, p = 20 bar)

you clearly recognizes that the upgraded catalyst compared to the fresh Catalyst was deactivated. In addition, one recognizes the much stronger Deactivation of the expansion catalyst at the reactor inlet, presumably caused by the additional Adsorption of nitrogen- and halogen-containing catalyst poisons. After all shows the treatment in hot Air flow, that the deactivation is reversible.

Example 1 (according to the invention)

Adsorber and catalyst Ni-based according to DE-A-43 39,713

The procedure was as in the experiment described under II., However, where fresh nickel-containing oligomerization catalyst, as described in Ex. 2 of DE-A-43 39 713, was also used as an adsorbent. The reaction temperature was adjusted so that again a butene conversion between 40-50 wt .-% of the butenes used was achieved over the period considered. At the beginning of the long-term test, the temperature was 60 ° C, after 180 days at only 75 ° C. Compared to the use of Al ₂ O ₃ as adsorbent deactivation is thus significantly reduced.

Example 2 (according to the invention)

Ni-based adsorbers according to WO 01/37989 and Ni-based catalyst according to DE-A-43 39 713

The procedure was as in the experiment described under II., But as the adsorber fresh nickel-containing oligomerization catalyst, as in Ex. EK4 of WO 01/37989, Ex. EK4, was used. The reaction temperature was adjusted so that again a butene conversion between 40-50 wt .-% of the butenes used was achieved over the period considered. At the beginning of the long-term test the temperature was 60 ° C, after 180 days only 80 ° C. Compared to the use of Al ₂ O ₃ as adsorbent deactivation is thus again significantly reduced.

Claims (19)

A process for the oligomerization of C ₂ -C ₈ monoolefins in the presence of an oligomerization catalyst, comprising: a) contacting the C ₂ -C ₈ monoolefins in at least one adsorption zone to remove oligomerization-affecting components with at least one adsorbent and b) the feed from step a) is oligomerized in at least one reaction zone, characterized in that the adsorbent contains at least one component capable of being used as an oligomerization catalyst. Method according to one of the preceding claims, characterized in that the adsorbent contained in the used as Oligomerisierungskatalysator capable component and the used Oligomerisierungskatalysator are the same. Method according to one of the preceding claims, characterized characterized in that at least one of the adsorbents is nickel contains in oxidized form. A method according to claim 3, characterized in that the adsorbent containing nickel in oxidized form consists essentially of (i) the nickel in oxidized form; (ii) one or more metal oxide (s), preferably selected from TiO ₂ , ZrO ₂ , SiO ₂ , Al ₂ O ₃ , Ga ₂ O ₃ , In ₂ O ₃ and the mixed oxides and mixtures thereof; (iii) optionally sulfur in oxidized form, wherein the molar ratio of sulfur atoms to nickel atoms is preferably less than 1; wherein the proportions of the individual components add up to 100 wt .-%. Method according to claim 4, characterized in that that the nickel in oxidized form containing adsorbent at least 0.5 wt .-%, based on the total weight of the nickel in oxidized form containing adsorbent, on nickel oxide contains. Method according to one of claims 3 to 5, characterized that at least one other, nickel-free adsorbent used becomes. Method according to Claim 6, characterized that the nickel-free adsorbent is selected from titanium dioxides, Zirconium dioxides, silicas, diatomaceous earth, aluminas, Alumina-containing solids, aluminum phosphates, natural and synthetic aluminosilicates, phosphates, carbon-containing Adsorbents, polymer adsorbents and mixtures thereof. Method according to one of the preceding claims, characterized characterized in that the adsorption and the reaction zone (s) spatially from each other are arranged separately. Method according to one of the preceding claims, characterized characterized in that the volume ratio of adsorption to reaction zone in the range of 1: 1 to 1: 500. Method according to one of claims 6 to 9, characterized that the nickel-free adsorbent together with the nickel in oxidized form containing adsorbent in a single Adsorption zone is used in the form of a gradient bed. Method according to one of the preceding claims, characterized characterized in that the components which the oligomerization affect polyunsaturated Hydrocarbons and / or oxygen, nitrogen, sulfur, Phosphorus and / or Include halogenated impurities. A method according to claim 11, characterized in that the C ₂ -C ₈ monoolefins are present in a hydrocarbon mixture having a content of polyunsaturated hydrocarbons of at most 0.01 wt .-%, based on the total weight of the hydrocarbon mixture. A method according to claim 12, characterized in that the hydrocarbon mixture comprises substantially aliphatic and / or cycloaliphatic C ₄ monoolefins and / or C ₅ -C ₆ monoolefins. A process according to any one of claims 6 to 13, characterized in that a hydrocarbon mixture comprising the C ₂ -C ₈ monoolefins is contacted with nickel-free adsorbent before being brought into contact with adsorbents containing nickel in oxidized form Content of oxygen, nitrogen, sulfur, phosphorus and / or halogen-containing impurities in the hydrocarbon mixture is reduced to at most 0.001 wt .-%, based on the total weight of the hydrocarbon mixture. Method according to one of the preceding claims, characterized characterized in that the adsorption at a temperature of less than 50 ° C carried out becomes. Method according to one of the preceding claims, characterized in that less than 50 wt .-%, based on the total weight of the C ₂ -C ₈ monoolefins used, are oligomerized in step a). Method according to one of the preceding claims, characterized in that the discharge from Step a) has a polyunsaturated hydrocarbon content of less than 0.001% by weight, based on the total weight of the effluent. Method according to one of claims 3 to 17, characterized that the nickel used in oxidized form containing adsorbent, its adsorption capacity as a result of use in a method according to one of claims 3 to 17 has substantially completely regenerated by that the nickel-containing adsorbent with an oxygen-containing Gas, air, nitrogen oxides or a mixture thereof at a temperature of at least 300 ° C treated. Use of a nickel containing oxidized form Adsorbent as defined in any one of claims 3 to 18, for Reduction in the content of polyunsaturated hydrocarbons and / or oxygen, nitrogen, sulfur, phosphorus and / or Halogen-containing impurities in a hydrocarbon mixture by contacting the hydrocarbon mixture with the nickel in oxidized form containing adsorbent.