DE102012212316A1 - Sulfur adsorption before oligomerization plants - Google Patents

Abstract

The invention relates to a method for the catalytic oligomerization of hydrocarbons with the steps of providing a mixture which, in addition to the hydrocarbons to be oligomerized, contains accompanying substances; Purifying the mixture by contacting the mixture with a cleaning bed and oligomerizing the hydrocarbons by contacting the purified mixture with a catalyst. It is based on the task of finding a strong, irreversible adsorbent with a high adsorption capacity for cleaning. The object is achieved by using an adsorbent which contains at least 10% by weight of metallic nickel and which exhibits pyrophoric properties in an air atmosphere, under normal pressure and at a temperature of 20 ° C.

Description

The invention relates to a process for the catalytic oligomerization of olefinic hydrocarbons having 3 to 6 carbon atoms with the steps of providing a mixture which in addition to the hydrocarbons to be oligomerized contains impurities; Purifying the mixture by contacting the mixture with a purification bed and oligomerizing the hydrocarbons by contacting the purified mixture with the catalyst.

A method of this type is known DE3914817C2 ,

Hydrocarbons are compounds that consist exclusively of carbon and hydrogen. The nomenclature of the hydrocarbons is based on the number of carbon atoms contained per molecule of the hydrocarbon. In short notation, the prefix C _{n is} often used, where n stands for the said number.

C ₄ hydrocarbons are thus compounds consisting exclusively of carbon and hydrogen, the number of carbon atoms per molecule being four. Important representatives of the C ₄ hydrocarbons are the alkenes and alkanes with four carbon atoms.

Mixtures of C ₄ hydrocarbons are raw materials of petrochemicals. They come either from stream crackers (so-called "crack C4") or from fluid catalytic crackers (so-called "FCC C4"). There are also mixtures of C ₄ mixtures of different origin traded, so-called "C _{4 cut} ". For the purpose of recycling the individual components, the C ₄ mixtures should be broken down into their constituents as precisely as possible.

The workup of C ₄ streams from steam crackers or catalytic crackers is described in principle in K. -D. Wiese, F. Nierlich, DGMK Report 2004-3-3, ISBN 3-936418-23-3 , A detailed overall process description can be found in DE 10 2008 007 081 A1 ,

The aspects of C ₄ workup relevant to this invention are briefly outlined below.

Technical C ₄ -hydrocarbon mixtures of catalytic crackers (FCC C4) or steam crackers (crack C4) usually also contain polyunsaturated compounds in addition to saturated and monounsaturated compounds. Before individual compounds can be isolated from these mixtures, it is often necessary to remove other compounds as completely as possible. This can be achieved by physical methods such. As distillation, extractive distillation or extraction, but also by a selective chemical reaction of the components to be removed. Particular attention must be paid to the most complete possible removal of the impurities contained in the C ₄ -hydrocarbon mixture, such as oxygen-, nitrogen- and sulfur-containing components, since these, as catalyst poisons, can have negative effects on the individual process steps. While these impurities are typically only present in trace C4 crack, they may also be present in higher concentrations in FCC C4 streams.

C ₄ -hydrocarbon mixtures from steam crackers or fluidized catalytic crackers typically have the main components listed in Table 1. (Impurities not shown) component Crack C4 FCC C4 [Mass%] [Mass%] isobutane 1-3 20-40 n-butane 6-11 5-15 1-butene 14-20 10-20 2-butene 4-8 20-35 isobutene 20-28 10-20 1,3-butadiene 40-45 less 1 Table 1: Typical compositions of crack C4 and FCC C4

The composition of the raw materials can vary greatly depending on the origin of the material. The listed C ₄ components are joined still hydrocarbons having fewer or more carbon atoms, and impurities such as mercaptans, sulfides, disulfides, nitrogen and oxygen-containing compounds in small quantities.

The working up of FCC C4 can be carried out in a variant such that initially the concentration of isobutane is reduced by means of a distillation step in a distillation to a value of less than 5 mass%, particularly preferably less than 3 mass%. At the same time, the low boilers present in the mixture (for example C ₃ hydrocarbons, light oxygen, nitrogen and sulfur-containing compounds) are removed or minimized. In the next step, all high boilers (for example C ₅ hydrocarbons, heavy oxygen, nitrogen and sulfur containing compounds) in a column are removed via the bottom. In the next step isobutene is removed, z. B. by reacting it with methanol to methyl tert-butyl ether (MTBE) and this is removed by distillation. If pure isobutene is to be recovered, the methyl tert-butyl ether can subsequently be split again to give isobutene and methanol.

For further workup of the C ₄ mixture, the remaining polyunsaturated compounds must be converted by means of a selective hydrogenation process to the corresponding monounsaturated and saturated compounds. Now 1-butene and remaining isobutane can be separated by distillation in sufficient purity and the remaining 2-butenes and n-butane can be further worked up. Frequently, the 2-butenes are converted by oligomerization, more precisely, by dimerization to octenes. In this case, a molecule with eight carbon atoms is built up from two molecules with four carbon atoms each. The octenes can then be converted by hydroformylation to PVC plasticizer alcohols. The saturated C ₄ hydrocarbons remaining after the reaction of the olefins can be used in particular as propellants for aerosols.

By an oligomerization is meant a process in which from hydrocarbons having three to six carbon atoms, in particular from propene and butenes, higher alkenes having 6-20 carbon atoms are built up.

Oligomerizations are of paramount importance in the petrochemical industry. For the formation of the C-C bond either strong acids or transition metal complexes are used as catalysts. The former lead, due to the Markovnikov rule, to products with almost maximum degree of branching, which is particularly favorable for use in fuels. With transition-metal complexes, on the other hand, it is possible to produce relatively linear products that can be further processed petrochemically. One of the most common forms of processing is hydroformylation. It leads to hydrogenation of the primary aldehydes to higher alcohols, which are for example widely used in plasticizers for plastics, especially PVC. On the other hand, oxidation of the aldehydes gives rise to higher carboxylic acids which, for example, can also be used as plasticizer components or for the production of industrially important metal soaps.

For acidic catalysis just mentioned, heterogeneous acids, such as zeolites or more generally H-form silicates, or heterogenized acids, such as the SPA (solid phosphoric acid), are typically used in the highly concentrated and therefore extremely viscous phosphoric acid in the form of a "supported liquid phase" on an inert, highly porous carrier, preferably SiO ₂ , is present spread. However, it is also possible to use two-phase systems with liquid catalysts, for example heteropolyacids. In practice, however, such systems have hardly been used industrially so far.

In the case of the transition metal complexes, almost exclusively those of the nickel, only very occasionally of the cobalt or of the palladium, are used. The oligomerization of the olefins is carried out according to generally accepted scientific opinion on hydrides and metal alkyls. In general, a co-catalyst is required for effective olefin oligomerization (except ethylene), in most cases a Lewis acid. One of the few exceptions to this rule is that proposed by Keim et al. ( Behr, Falbe, Freudenberg, Germ: 1,3-diketones as active ligands in the nickel-catalyzed linear oligomerization of olefins. Israel J. Chemistry 27 (1986), 277-279) described nickel hexafluoroacetylacetonate catalyst.

The transition metal complex catalysts can be used both homogeneously and heterogeneously. The best-known application of a homogeneous system is the DIMERSOL process developed by the Institute Francais de Petrole (IFP). The best-known heterogeneous system is used in the OCTOL ^® process, which was developed by the former Hüls AG (now Evonik Industries AG). Of the OCTOL® process is in Hydrocarbon Process., Int. Ed. (1986) 65 (2nd sect.1), pages 31 to 33 as in DE3914817 . EP1029839 and DE 10 2004 018 753 described in more detail.

Both systems - the classical organometallic, homogeneous catalyst and the complete heterogeneous catalyst of the OCTOL ^® process - seem to work on very similar principles despite all formal differences and also lead to very similar products. A further development of the DIMERSOL process is the DIFASOL process (also from the IFP). The catalyst is dissolved in a highly polar phase (here an ionic liquid), which can be separated after intensive contact with the organic phase and thus a multiple use the catalyst allows.

The feed streams used for the oligomerization have generally already reached a high degree of purity by previous processes in which contaminants have been removed again and again. However, remaining impurities can reversibly or irreversibly deactivate the catalysts. Of course, this deactivation should be reduced to a minimum for economic reasons. Therefore, as many catalyst poisons as possible should be kept away from the catalyst by further purification steps.

The various catalyst poisons present in the feed streams have a different poisoning effect. Thus, the acid catalyst systems or system components such as cocatalysts are almost exclusively poisoned by components that are themselves basic or at least release by subsequent reactions bases. A particularly typical example of such substances is acetonitrile, which can be separated as a very weak base comparatively difficult by sorption. However, it reversibly poisons strong Lewis acids. In the presence of traces of water, it hydrolyzes there via acetamide to the strong base ammonia, which irreversibly deactivates Bronsted acids by forming ammonium ions. Incidentally, a partial catalyst poison always also represents water itself, but its effect is generally reversible, provided that it does not contribute to the formation of stronger catalyst poisons by further reactions. For the nickel-catalyzed oligomerization of butenes at OCTOL ^® catalyst, a water content of about 5 ppm to measurable deactivation already leads. However, the water is added by many systems to olefins and the alcohols formed are oxidized by the usual catalyst systems via a transfer hydrogenation with hydrogenation of other unsaturated components until the thermodynamic equilibrium is reached.

The metal complex catalysts are also sensitive to basic substances. The poisoning effect takes place primarily mostly via the deactivation of the acid cocatalyst.

The metal component of the catalysts, however, is particularly strongly attacked by components such as sulfur in the form of certain compounds, which irreversibly destroys the metal hydride or the metal complex by forming sparingly soluble sulfides in certain circumstances. Since the metals are usually present in very low oxidation states, sulfur compounds are particularly effective, which are able to oxidize the metals to a relatively high oxidation state, such as di- and polysulfides. Different sulfur compounds are therefore able to act differently. For example, while disulfides react extremely well to thioethers and sulfur, which then oxidizes the metal hydrides to form sulfides, thioethers themselves initially appear to act only as Lewis bases. By further, usually in detail not known processes and reactions with other trace components of the system but they also ultimately - albeit much slower - lead to the formation of metal sulfides.

After the foregoing, therefore, the task is to protect the catalyst as effectively as possible against catalyst poisons and in particular sulfur compounds for the most economical operation of a Olefinoligomerisierung with metal complexes. This is all the stronger, the more starting material, the catalyst is present to specifically implement especially true therefore recycled to heterogeneous catalysts such as the OCTOL ^® process, or even in two phases as that of the DIFASOL process.

Acetonitrile is a component of many light olefin streams and is usually entered via washing or extraction processes. Targeted removal is difficult. However, it is known that in the synthesis of MTBE or TBA, which is usually carried out on technical acidic ion exchangers, significant amounts of which are hydrolyzed. The liberated ammonium then deactivates the ion exchanger.

Sulfur-containing toxins are usually removed in the candidate propene and butene streams by an alkaline wash. Hydrogen sulfide and mercaptans react particularly well. In general, the alkaline washing solutions are regenerated by oxidation with air, such as in the MEROX ^® process of the UOP. The mercaptans are oxidized in the aqueous washing solution to di- and polysulfides, which are separated as an oily phase. However, a small portion of these di- and polysulfides remains dissolved or suspended in the aqueous alkali, and it is often not possible to quantitatively remove this residue prior to recycling in the laundry by washing this aqueous phase with a wash oil or the like, so that Although the mercaptans largely removed, but on the other hand, small amounts of di- and polysulfides are re-entered into the stream. These are, as just mentioned, sulfur components which convert the metal hydrides essential for the reaction into sparingly soluble metal sulfides and thereby irreversibly deactivate the catalyst. Typically, for example, the streams of FCC C ₄ contain about 100 to 200 ppm sulfur. After the MEROX ^® scrubbing this content is up to a value of below 10 ppm then reduced conventionally, the sulfur compounds then mainly consist of the di- and polysulfides.

Other acid catalysts present in the processing stages prior to oligomerization, which may also include alumina carriers from certain hydrogenation catalysts, may also convert mercaptans to thioethers. Thioethers are relatively inert and are difficult to remove adsorptively. Notably, thioethers are barely acting as catalyst poisons, and if anything, initially primarily as Lewis bases. However, the reverse reaction of the formation of thioethers by addition of olefins to mercaptans is an equilibrium reaction. Accordingly, thioethers can release much more reactive compounds again by the simple reverse reaction or further subsequent reactions under appropriate reaction conditions.

In practice, some of the poisons can also be directed into fractions by clever arrangement of separation operations, such as distillations, in which they no longer come into contact with sensitive catalysts. Often, however, this is not possible to the extent that appears desirable in view of the purity of the streams, so that upstream of the catalyst beds adsorber must be preceded to ensure the required purity.

In the case of the adsorbers, it is generally necessary to distinguish between those which can be regenerated and those which irreversibly convert or chemically bind the catalyst poisons.

Molecular sieves and zeolites are frequently used as regenerable adsorbers. Examples of the use of reversible adsorbers for the purification of hydrocarbon streams prior to oligomerization can be found in DE3914817C2 and in the DE19845857A1 , The regenerable adsorbents bind the adsorbate with only moderate strength, because regeneration - albeit under other conditions, such as higher temperatures and lower pressures - requires that they also be able to leave the adsorber. This condition results in a relatively small capacity until breakthrough. In addition, high operating costs often arise due to freeing and flushing of the beds as well as the provision and disposal of the regeneration gases or the liquid streams.

• • Sie müssen eine hohe Adsorptionskapazität aufweisen
• • Sie müssen möglichst viele verschiedene Stoffe binden
• • Sie müssen relativ preisgünstig erhältlich sein.

In general chemistry, irreversibly working adsorbers are known, which can have distinct advantages over reversible adsorbers, provided that they fulfill three essential conditions:

• • They must have a high adsorption capacity
• • You need to bind as many different substances as possible
• • They must be available at relatively low cost.

Concrete examples of the use of irreversible adsorbers prior to oligomerization have not previously been disclosed in the literature.

• • das unterschiedliche Schwefelkomponenten möglichst vollständig aus dem Gemisch entfernt,
• • das kostengünstig, einfach und ohne permanente Zufuhr zusätzlicher Betriebsstoffe wie beispielsweise Wasserstoff zu betreiben ist,
• • das eine möglichst hohe Bindungskapazität für Schwefel hat,
• • das einen Verlust an Olefinen durch Nebenreaktionen wie Oligomerisierung, Isomerisierung und Hydrierung vermeidet,
• • und das den Strom nicht seinerseits mit Komponenten kontaminiert, die in den nachgeschalteten Prozessen, insbesondere in Oligomerisierungen, stören.

In view of this prior art, the object of the invention is to find an irreversible adsorbent for the purification of a hydrocarbon mixture intended for oligomerization,

• • removes the different sulfur components as completely as possible from the mixture,
• • which is inexpensive, easy to operate without permanent supply of additional supplies such as hydrogen,
• • which has the highest possible binding capacity for sulfur,
• • which avoids loss of olefins by side reactions such as oligomerization, isomerization and hydrogenation,
• • and that does not in turn contaminate the stream with components that interfere with the downstream processes, especially in oligomerization.

This object is achieved in that an adsorbent is used which contains at least 10 wt .-% of metallic nickel and which exhibits pyrophoric properties in air atmosphere, under atmospheric pressure and at a temperature of 20 ° C.

• a) Bereitstellen eines Gemisches, welches neben den zu oligomerisierenden Kohlenwasserstoffen Begleitstoffe enthält;
• b) Reinigen des Gemisches durch Kontaktieren des Gemisches mit einem Reinigungsbett;
• c) Oligomerisieren der Kohlenwasserstoffe durch Kontaktieren des gereinigten Gemisches mit dem Katalysator;
• d) bei welchem das Reinigungsbett ein festes Adsorptionsmittel umfasst, welches zu mindestens 10 Gew.-% metallisches Nickel enthält und welches an Luftatmosphäre, unter Normaldruck und bei einer Temperatur von 20°C pyrophore Eigenschaften zeigt.

The invention therefore provides a process for the catalytic oligomerization of hydrocarbons with the following steps:

• a) providing a mixture which in addition to the hydrocarbons to be oligomerized contains impurities;
• b) purifying the mixture by contacting the mixture with a cleaning bed;
• c) oligomerizing the hydrocarbons by contacting the purified mixture with the catalyst;
• d) in which the cleaning bed comprises a solid adsorbent which contains at least 10 wt .-% of metallic nickel and which exhibits pyrophoric properties in air atmosphere, under atmospheric pressure and at a temperature of 20 ° C.

It has been found that such adsorbents, if they are in a pyrophoric state, ie ignite spontaneously under normal ambient conditions, react well with sulfur compounds even without the supply of hydrogen. Particularly fast and complete they react with di- and polysulfides.

Therefore, this type of cleaning is particularly suitable for being turned on after a MEROX ^® scrubbing as a police filter into the stream.

In this context, a police filter is to be understood as meaning a second cleaning entity which is arranged behind a first cleaning entity and whose function is to definitively keep residual amounts of the catalyst poisons not detected by the first cleaning entity away from the oligomerization or in the event of a malfunction in the first Instance to exclude immediate damage to the oligomerization.

As the first cleaning instance preferably a MEROX serves ^® wash, which separates most of the catalyst poisons in advance in large quantities. Only the mercaptans and not covered by the MEROX ^® scrubbing especially the then present in the mixture di- and polysulfides are then retained in the adsorption bed according to the invention. In the event of a malfunction in the MEROX ^® plant, the adsorber takes over its full cleaning function and protects the oligomerization from immediate irreversible damage. Since the police filter absorbs only a small amount of adsorbate in the normal operating state, it may be designed capacitively much smaller than a MEROX ^® wash. Accordingly, he is exhausted in a major accident. The appropriate sizing of the police filter depends on how quickly the inflowing mixture can be diverted.

Thioethers as a relatively unreactive substances are not removed in MEROX ^® washes practical. In order to avoid excessive concentrations at the inlet into the adsorber bed, they are preferably separated off at a suitable point in the process sequence upstream of the adsorbent bed as high boilers in a distillation.

The adsorber bed is preferably switched directly in front of the reactors of the oligomerization. The embodiment makes little special claims, since no heat of reaction has to be removed or supplied during operation. Depending on the circumstances, usually residence times between 0.01 and 0.2 hours are provided, but if necessary also beyond. Since the operation at elevated temperature accelerates the Abreaktion and increases the sulfur capacity, it is advantageous to arrange them for the most prevailing preheaters. An operating temperature of at least 60 ° C., particularly advantageously above 80 ° C., is advantageous.

The adsorbent is usually delivered in a pre-reduced state stabilized by oxidation of the surface, which allows handling at room temperature in air. After filling the reactors, the adsorbers must be reactivated by a Nachreduktion, and after use, the catalysts must be re-stabilized by careful oxidation with air to remove them in the same way from the reactor can.

For the materials used, a mixture of nitrogen with 0.5 to 10% of hydrogen, which has been preheated to at least 170 ° C., preferably above 200 ° C., is generally used for the after-reduction the temperature in the reactor can be regulated by the hydrogen content. At a high reaction rate, one will therefore rather drive through less hydrogen, the further the oxide layer is degraded, one will increase the hydrogen content. In an analogous manner, one proceeds in the necessary before opening the reactor stabilization, except that here the gas is cooled to ambient temperature or even lower and nitrogen is driven under continuous increase in the air content, even with pure air no significant heating occurs. The material can then be handled in the air.

The containers for the adsorber should preferably be designed so that they can also be reduced before use and stabilized after use. In order to achieve a particularly effective cleaning and to avoid interruptions of operation by changing the adsorbent, it is advisable to use several containers, which can be connected in series in such a way that always the container with the highest and at the exit always with the lowest load is arranged. At least one container can, without interrupting the power to be cleaned, taken out and flushed the material contained in it, passivated and removed, then done in a similar manner, the refilling and Nachreduktion.

The use of material with a high nickel surface area is advantageous because the rate of adsorption and conversion reaction correlates with it and these materials also have a higher adsorption capacity.

• • bindet den Schwefel aus verschiedensten Schwefelverbindungen nahezu vollständig,
• • benötigt lediglich eine Aktivierung im Wasserstoffstrom, ansonsten keine zusätzlichen Betriebsstoffe,
• • benötigt keine periodischen Reinigungs- und Desorptionsströme, da es sich um ein irreversibles Adsoptionsmittel handelt;
• • kann in einem einfachen Behälter untergebracht werden, der einfach vom dem Gemisch durchströmt wird, vorzugsweise bei leicht erhöhter Temperatur, wie sie typischerweise oft ohnehin für die Speisung von Reaktoren erforderlich ist,
• • verursacht praktisch keine Nebenreaktionen der Olefine wie Oligomerisierung, Isomerisierung und Hydrierung und damit auch keine Verluste
• • setzt keinerlei Stoffe in Konzentrationen frei, die irgendeinen Einfluss auf die nachfolgenden Verarbeitungsstufen haben,
• • ist angesichts der bei typischen Schwefelkonzentrationen unter 5 ppmw und eine Kapazität von mindestens 5 Gew.-% Schwefel langen Lebensdauer sehr kostengünstig im Betrieb, auch wenn es nicht direkt regeneriert werden kann, sondern nach Erschöpfung der Kapazität nur noch einer rohstofflichen Verwertung zugeführt werden kann.

The invention solves the problem convincingly. The adsorbent

• • almost completely binds sulfur from various sulfur compounds
• • only requires activation in the hydrogen stream, otherwise no additional consumables,
• • does not require periodic purges and desorption streams because it is an irreversible adsorbent;
• • can be accommodated in a simple container which simply flows through the mixture, preferably at a slightly elevated temperature, which is typically often required anyway for the supply of reactors,
• • causes virtually no side reactions of the olefins such as oligomerization, isomerization and hydrogenation and thus no losses
• • does not release any substances in concentrations that have any influence on subsequent processing stages,
• • is in view of the typical sulfur concentrations below 5 ppmw and a capacity of at least 5 wt .-% sulfur long life in a very cost-effective operation, even if it can not be directly regenerated, but after exhaustion of the capacity can only be fed to a raw material recovery ,

Preferably, the adsorbent has a metallic nickel surface of at least 3 m ² / g, preferably 9 m ² / g, based on its nickel content. This favors the adsorption effect and at the same time causes the pyrophoric properties. The surface is measured by hydrogen chemisorption.

The adsorbent is preferably a composite comprising a porous inorganic framework material coated with metallic nickel on its surface, the nickel content of the adsorbent being 10 to 70% by weight.

• • Nickel 15 bis 65 Gew.-%, bevorzugt 45 Gew.-%;
• • Zinkoxid 0 bis 40 Gew.-%, bevorzugt 28 Gew.-%;
• • mindestens ein Oxid der Gruppe umfassend Siliciumoxid, Titandioxid, Aluminiumoxid 5 bis 75 Gew.-%, bevorzugt 25 Gew.-%;
• • Graphit weniger als 5 Gew.-%, bevorzugt 2 Gew-%;
• • sonstige Komponenten weniger als 40 Gew.-%, bevorzugt 0 Gew-%.

Most preferably, the adsorbent has the following 100% complementary composition:

• Nickel 15 to 65% by weight, preferably 45% by weight;
• Zinc oxide 0 to 40% by weight, preferably 28% by weight;
• At least one oxide of the group comprising silicon oxide, titanium dioxide, aluminum oxide 5 to 75% by weight, preferably 25% by weight;
• Graphite less than 5% by weight, preferably 2% by weight;
• Other components less than 40% by weight, preferably 0% by weight.

The purification of the mixture before the oligomerization is conveniently carried out at a temperature of 30 ° to 150 ° C, preferably at 80 ° C in the liquid phase by contacting with a cleaning bed, which consists of a bed of adsorbent having a bulk density of 0.7 to 1.5 kg / dm ³ , preferably 1.15 kg / dm ³ consists.

It is important for the purposes of the present invention that the adsorbent has no essential catalytic activity for the oligomerization of olefins. The oligomerization of the hydrocarbons to be oligomerized should take place exclusively on the catalyst, but not in the purification bed. The oligomerization catalyst is therefore outside the cleaning bed in another apparatus.

To activate the adsorbent, the cleaning bed is to be flushed with a stream of hydrogen at a temperature of 150 ° C to 400 ° C, preferably 180 ° C to 280 ° C, especially 200 ° C to 240 ° C prior to use. During operation, no further energy input is required.

The process according to the invention is suitable in principle for the oligomerization of all olefins, preferably those without branching of the carbon chain on the double bond. As technically relevant are to be considered thereof e.g. Ethene, propene, n-butenes, n-pentenes, hexenes, neo-witches, etc. Of these, propene and butenes occupy the absolutely most important position. Propene as a pure compound is relatively easy to work up and separate from the saturated component propane. This is no longer the case with butenes and butanes. The present description of the process focuses on the technically most relevant case of butenes, but without excluding an application for other olefins.

• • 1-Buten 0.2 bis 45 Gew.-%, bevorzugt 12 Gew.-%;
• • trans-2-Buten 15 bis 50 Gew.-%, bevorzugt 38 Gew.-%;
• • cis-2-Buten 20 bis 25 Gew.-%, bevorzugt 23 Gew.-%;
• • n-Butan 25 bis 30 Gew.-%, bevorzugt 27 Gew.-%;
• • Wasserstoff 0 bis 1 Gew.-%, bevorzugt weniger als 0.5 Gew.-%;
• • Wasser 0 bis 0.01 Gew.-%, bevorzugt weniger als 0.0005 Gew.-%;
• • Verunreinigungen weniger als 0.5 Gew.-%.

The adsorbent according to the invention can be used particularly advantageously for purifying mixtures which have the following composition which is 100% complementary:

• 1-butene 0.2 to 45% by weight, preferably 12% by weight;
• Trans-2-butene 15 to 50% by weight, preferably 38% by weight;
• Cis-2-butene 20 to 25% by weight, preferably 23% by weight;
• N-butane 25 to 30% by weight, preferably 27% by weight;
• • hydrogen 0 to 1 wt .-%, preferably less than 0.5 wt .-%;
• • water 0 to 0.01 wt .-%, preferably less than 0.0005 wt .-%;
• Impurities less than 0.5% by weight.

These mixtures are typical C ₄ hydrocarbon streams in a workup state just prior to the oligomerization of the butenes contained therein. The "impurities" includes in addition to the sulfur-containing compounds and bases such as amines or nitriles, which are, however, below the detection limit.

The method is particularly well applicable to such mixtures because it removes well as poisons for the heterogeneous, aluminum, silicon or nickel containing oligomerization catalysts acting impurities. The catalyst poisons are, in particular, sulfur-containing hydrocarbons. Therefore, the method is preferably applied to those streams comprising sulfur-containing hydrocarbons as impurities whose proportion in the mixture is between 0.1 and 20 ppmw, calculated as sulfur.

• i) Bereitstellen des C₄-Kohlenwasserstoffstromes;
• ii) zumindest teilweise Abtrennung von mindestens einer im C₄-Kohlenwasserstoffstrom enthaltenen Komponente, wobei die abgetrennte Komponente ausgewählt ist aus der Gruppe umfassend Isobutan, 1.3-Butadien, Isobuten, 1-Buten, Wasser.

Such a mixture is obtained by working up a C ₄ -hydrocarbon stream, ie by the following working steps:

• i) providing the C ₄ hydrocarbon stream;
• ii) at least partially separating at least one component contained in the C ₄ hydrocarbon stream, wherein the separated component is selected from the group comprising isobutane, 1,3-butadiene, isobutene, 1-butene, water.

The separation of the organic value components isobutane, 1,3-butadiene, isobutene, 1-butene are industrially practiced recovery steps in the C ₄ chemistry.

The separation of the water is due to a different motivation: Since homogeneously dissolved water in the mixture slightly weakens the effect of the adsorber, the stream is preferably dried before it enters the adsorbent bed, for example by azeotropic distillation (drying distillation).

In the C ₄ hydrocarbon stream may be either a C ₄ hydrocarbon stream from a fluid cracker (FCC) or from a steam cracker (Crack-C4) or mixtures thereof act (C4-section).

• • Isobutan 35 bis 40 Gew.-%, bevorzugt 37 Gew.-%;
• • n-Butan 10 bis 15 Gew.-%, bevorzugt 13 Gew.-%;
• • 1-Buten 10 bis 14 Gew.-%, bevorzugt 12 Gew.-%;
• • Isobuten 12 bis 17 Gew.-%, bevorzugt 15 Gew.-%;
• • cis-2-Buten 9 bis 20 Gew.-%, bevorzugt 14 Gew.-%;
• • trans-2-Buten 5 bis 15 Gew.-%, bevorzugt 9 Gew.-%;
• • 1.3-Butadien 0 bis 1 Gew.-%, bevorzugt 0.8 Gew.-%;
• • Wasser 0 bis 1 Gew.-%, bevorzugt weniger als 0.5 Gew.-%;
• • Verunreinigungen, insbesondere Schwefel enthaltende Kohlenwasserstoffe von weniger als 0.5 Gew.-%, bevorzugt zwischen 0.01 und 0.2 Gew.-%.

If FCC-C4 is used, the C ₄ hydrocarbon stream to be worked up will have approximately the following composition:

• Isobutane 35 to 40 wt .-%, preferably 37 wt .-%;
• N-butane 10 to 15% by weight, preferably 13% by weight;
• 1-butene 10 to 14% by weight, preferably 12% by weight;
• Isobutene 12 to 17% by weight, preferably 15% by weight;
• Cis-2-butene 9 to 20% by weight, preferably 14% by weight;
• Trans-2-butene 5 to 15% by weight, preferably 9% by weight;
• • 1,3-butadiene 0 to 1 wt .-%, preferably 0.8 wt .-%;
• • water 0 to 1 wt .-%, preferably less than 0.5 wt .-%;
• Contaminants, in particular sulfur-containing hydrocarbons of less than 0.5 wt .-%, preferably between 0.01 and 0.2 wt .-%.

• • Isobutan 0.6 bis 8 Gew.-%, bevorzugt 7 Gew.-%;
• • n-Butan 0.5 bis 8 Gew.-%, bevorzugt 5 Gew.-%;
• • 1-Buten 9 bis 25 Gew.-%, bevorzugt 13 Gew.-%;
• • Isobuten 10 bis 35 Gew.-%, bevorzugt 22 Gew.-%;
• • trans-2-Buten 3 bis 7 Gew.-%, bevorzugt 5 Gew.-%;
• • cis-2-Buten 2 bis 8 Gew.-%, bevorzugt 4 Gew.-%;
• • 1.3-Butadien 25 bis 70 Gew.-%, bevorzugt 44 Gew.-%;
• • Wasser 0 bis 1 Gew.-%, bevorzugt weniger als 0.5 Gew.-%;
• • Verunreinigungen, insbesondere Schwefel enthaltene Kohlenwasserstoffe weniger als 0.5 Gew.-%, bevorzugt zwischen 0.01 und 0.2 Gew.-%.

If crack C4 is used, the C ₄ hydrocarbon stream to be worked up will have approximately the following composition:

• Isobutane 0.6 to 8 wt .-%, preferably 7 wt .-%;
• N-butane 0.5 to 8% by weight, preferably 5% by weight;
• 1-butene 9 to 25% by weight, preferably 13% by weight;
• Isobutene 10 to 35% by weight, preferably 22% by weight;
• Trans-2-butene 3 to 7% by weight, preferably 5% by weight;
• Cis-2-butene 2 to 8% by weight, preferably 4% by weight;
• 1,3-butadiene 25 to 70% by weight, preferably 44% by weight;
• • water 0 to 1 wt .-%, preferably less than 0.5 wt .-%;
• Contaminants, in particular sulfur-containing hydrocarbons less than 0.5 wt .-%, preferably between 0.01 and 0.2 wt .-%.

In the course of the process according to the invention, olefinic hydrocarbons having four carbon atoms in the liquid phase are particularly preferably oligomerized on a heterogeneous, aluminum, silicon or nickel-containing catalyst at from 0 to 200 ° C. and at absolute pressures of from 1 to 70 bar. Most preferably, butenes are dimerized to octenes.

The adsorbent used is preferably an available product. Surprisingly, it has been found that the H 10126 rs catalyst available from Evonik Industries AG is an excellent adsorber for the realization of the present invention.

• x) Bereitstellen eines porösen Gerüstmaterials aus Siliciumoxid und/oder Titandioxid und/oder Aluminiumoxid und/oder Graphit;
• y) Vermengen des Gerüstmaterials mit Nickeloxid und Zinkoxid;
• z) Reduktion des Nickeloxids zu metallischem Nickel.

If the adsorbent is not to be purchased, its production can basically be carried out by the following steps:

• x) providing a porous framework of silica and / or titanium dioxide and / or alumina and / or graphite;
• y) mixing the framework with nickel oxide and zinc oxide;
• z) reduction of the nickel oxide to metallic nickel.

The preparation of the adsorbent essentially corresponds to the preparation of catalysts of similar composition. The porous framework material preferably consists of silicon oxide and graphite. Since a basic discovery of the invention is that a commercially available catalyst is suitable as an irreversible adsorbent for the purification of mixtures before entering into an oligomerization, the preparation of the adsorber is also the subject of the invention.

• α) es handelt sich bei dem Adsorptionsmittel um einen festen Verbundstoff, welcher ein poröses anorganisches Gerüstmaterial umfasst, das an seiner Oberfläche mit metallischem Nickel belegt ist,
• β) das Adsorptionsmittel weist die, sich zu 100 % ergänzende Zusammensetzung auf: • Nickel 40 bis 50 Gew.-%, bevorzugt 45 Gew.-%; • Zinkoxid 25 bis 31 Gew.-%, bevorzugt 28 Gew.-%; • Siliciumoxid 23 bis 28 Gew.-%, bevorzugt 25 Gew.-%; • Graphit 1.8 bis 2.2 Gew.-%, bevorzugt 2 Gew.-%; • Verunreinigungen 0 bis 1 Gew.-%, bevorzugt 0 Gew.-%;
• χ) die metallische Nickeloberfläche auf dem Adsorptionsmittel beträgt mindestens 3 m²/g, bevorzugt 9 m²/g, bestimmt nach Wasserstoff-Chemiesorption;
• δ) das Adsorptionsmittel zeigt an Luftatmosphäre, unter Normaldruck und bei einer Temperatur von 20°C pyrophore Eigenschaften;

als Polizeifilter zur Entschwefelung von Gemischen unmittelbar vor Oligomerisierung im Gemisch enthaltener Kohlenwasserstoffe.The invention also relates to the use of the adsorbent having the following properties:

• α) the adsorbent is a solid composite comprising a porous inorganic framework material coated with metallic nickel on its surface,
• β) the adsorbent has the, to 100% complementary composition: • Nickel 40 to 50 wt .-%, preferably 45 wt .-%; Zinc oxide 25 to 31% by weight, preferably 28% by weight; Silicon oxide 23 to 28% by weight, preferably 25% by weight; Graphite 1.8 to 2.2% by weight, preferably 2% by weight; Impurities 0 to 1% by weight, preferably 0% by weight;
• χ) the metallic nickel surface on the adsorbent is at least 3 m ² / g, preferably 9 m ² / g, determined by hydrogen chemisorption;
• δ) the adsorbent shows in air atmosphere, under normal pressure and at a temperature of 20 ° C pyrophoric properties;

as a police filter for the desulfurization of mixtures immediately before oligomerization in the mixture contained hydrocarbons.

The adsorbent used in combination with the first cleaning agent as a police filter prior to oligomerization is obtainable by the above-described manufacturing method. Alternatively, an existing product is used, preferably Catalyst H 10126 rs from Evonik Industries AG.

example

The invention will now be explained in more detail by way of example.

The adsorbent used is the commercial catalyst H 10126 rs from Evonik Industries AG, containing about 45% by weight of Ni, about 28% by weight of ZnO, about 25% by weight of SiO ₂ and about 2% by weight of graphite of cylindrical dome tablets 5 × 5 mm, filled with a measured by hydrogen chemisorption nickel surface of 9 m ² / g in three reaction tubes with 3 cm diameter and 10 kg each content. The bulk density is about 1.15 kg / dm ³ . The adsorbent is reactivated in a nitrogen-hydrogen stream at about 220 ° C, depending on the heat of reaction first 1% by volume of hydrogen, at the end of 50% by volume of hydrogen are added. Thereafter, the catalyst beds are cooled in a stream of nitrogen. The tubes are then connected in series with a sampling valve between the reactors and at each end. The beds are brought by heating the tube walls to a temperature of 80 ° C and flowed through with a mixture containing about 12% by weight of 1-butene, about 38% by weight of trans-2-butene, about 23% by weight cis-2-butene and about 27% by weight of n-butane. As an impurity, the material contains on average 5 mg / kg of sulfur predominantly in the form of dimethyl disulfide. The load of the adsorber beds is 85 kg / h, the sulfur input thus about 425 mg / h.

According to the analyzes, the sulfur is first quantitatively removed from the mixture in the first reactor. From an operating time of 3300 hours, the sulfur content at the outlet of the first reactor rises rapidly. This sharp breakthrough corresponds to an adsorbed amount of sulfur of about 1400 g or a sulfur uptake of the adsorber of about 14 wt .-%. Breakthrough after the second reactor occurs after about 6800 hours, after the third reactor after about 9500 hours. The cleaning beds have taken up at this time a total of about 4.05 kg of sulfur, corresponding to an average intake of 13.45 wt .-% based on the freshly charged adsorbent.

After the end of this experiment, the beds are rinsed with warm nitrogen and then carefully oxidized with a cold nitrogen-air mixture until no significant evolution of heat occurs in pure air. The adsorbent can be removed substantially intact and with sufficient strength.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 3914817 C2 [0002, 0029]
• DE 102008007081 A1 [0006]
• DE 3914817 [0017]
• EP 1029839 [0017]
• DE 102004018753 [0017]
• DE 19845857 A1 [0029]

Cited non-patent literature

• K. -D. Wiese, F. Nierlich, DGMK Report 2004-3-3, ISBN 3-936418-23-3 [0006]
• Behr, Falbe, Freudenberg, Germ: 1,3-diketones as active ligands in the nickel-catalyzed linear oligomerization of olefins. Israel J. Chemistry 27 (1986), 277-279). [0016]
• OCTOL® process is in Hydrocarbon Process., Int. Ed. (1986) 65 (2nd section 1), pages 31 to 33 [0017]

Claims (15)

A process for the catalytic oligomerization of olefinic hydrocarbons having 3 to 6 carbon atoms, comprising the following steps: a) providing a mixture which contains accompanying substances in addition to the hydrocarbons to be oligomerized; b) purifying the mixture by contacting the mixture with a cleaning bed; c) oligomerizing the hydrocarbons by contacting the purified mixture with the catalyst; characterized in that d) that the cleaning bed comprises a solid adsorbent, which contains at least 10 wt .-% of metallic nickel and which shows pyrophoric properties in air atmosphere, under normal pressure and at a temperature of 20 ° C. A method according to claim 1, characterized in that the adsorbent has a metallic nickel surface of at least 3 m ² / g, preferably 9 m ² / g, determined by means of hydrogen chemisorption. A method according to claim 1 or 2, characterized in that the adsorbent is a composite comprising a porous, inorganic framework material coated on its surface with metallic nickel, the nickel content of the adsorbent being 10 to 70% by weight. % is. A method according to claim 3, characterized in that the adsorbent has the following, to 100% complementary composition: • nickel 15 to 65 wt .-%, preferably 45 wt .-%; Zinc oxide 0 to 40% by weight, preferably 28% by weight; At least one oxide of the group comprising silicon oxide, titanium dioxide, aluminum oxide 5 to 75% by weight, preferably 25% by weight; Graphite less than 5% by weight, preferably 2% by weight; Other components less than 40% by weight, preferably 0% by weight. Method according to one of claims 1 to 4, characterized in that when cleaning the mixture at a temperature of 30 ° to 150 ° C, preferably at 80 ° C, is contacted in liquid phase with the cleaning bed, wherein the cleaning bed from a bed of Adsorbent having a bulk density of 0.7 to 1.5 kg / dm ³ , preferably 1.15 kg / dm ³ consists. Method according to one of claims 1 to 5, wherein the adsorbent having no essential catalytic activity for the oligomerization of olefins, in particular that the oligomerization takes place exclusively on the catalyst, but not in the cleaning bed. Method according to one of claims 1 to 6, characterized in that the adsorbent prior to use in the cleaning bed with a hydrogen stream at a temperature of 150 ° C to 400 ° C, preferably 180 ° C to 280 ° C, in particular 200 ° C to 240 ° C is activated. Method according to one of claims 1 to 7, characterized in that the provided mixture before the cleaning has the following, to 100% complementary composition: • 1-butene 0.2 to 45 wt .-%, preferably 12 wt .-%; Trans-2-butene 15 to 50% by weight, preferably 38% by weight; Cis-2-butene 20 to 25% by weight, preferably 23% by weight; N-butane 25 to 30% by weight, preferably 27% by weight; • hydrogen 0 to 1 wt .-%, preferably less than 0.5 wt .-%; • water 0 to 0.01 wt .-%, preferably less than 0.0005 wt .-%; Impurities less than 0.5% by weight. A method according to claim 8, characterized in that the impurities comprise sulfur-containing hydrocarbons, wherein the proportion of sulfur-containing hydrocarbons in the mixture between 0.1 and 20 ppmw calculated as sulfur. A method according to claim 8 or 9, characterized in that the provision of the mixture comprises the steps of: i) providing a C ₄ hydrocarbon stream; ii) at least partially separating at least one component contained in the C ₄ hydrocarbon stream, wherein the separated component is selected from the group comprising isobutane, 1,3-butadiene, isobutene, 1-butene, water. A method according to claim 10, characterized in that the C ₄ -hydrocarbon stream has the following, to 100% complementary composition: • isobutane 35 to 40 wt .-%, preferably 37 wt .-%; N-butane 10 to 15% by weight, preferably 13% by weight; 1-butene 10 to 14% by weight, preferably 12% by weight; Isobutene 12 to 17% by weight, preferably 15% by weight; Cis-2-butene 9 to 20% by weight, preferably 14% by weight; Trans-2-butene 5 to 15% by weight, preferably 9% by weight; • 1,3-butadiene 0 to 1 wt .-%, preferably 0.8 wt .-%; • water 0 to 1 wt .-%, preferably less than 0.5 wt .-%; Impurities, in particular sulfur-containing hydrocarbons of less than 0.5 wt .-%, preferably between 0.01 and 0.2 wt .-%; or that the C ₄ hydrocarbon stream has the following, 100% complementary composition: isobutane 0.6 to 8 wt .-%, preferably 7 wt .-%; N-butane 0.5 to 8% by weight, preferably 5% by weight; 1-butene 9 to 25% by weight, preferably 13% by weight; Isobutene 10 to 35% by weight, preferably 22% by weight; Trans-2-butene 3 to 7% by weight, preferably 5% by weight; Cis-2-butene 2 to 8% by weight, preferably 4% by weight; 1,3-butadiene 25 to 70% by weight, preferably 44% by weight; • water 0 to 1 wt .-%, preferably less than 0.5 wt .-%; Contaminants, in particular sulfur-containing hydrocarbons less than 0.5 wt .-%, preferably between 0.01 and 0.2 wt .-%. Process according to at least one of claims 1 to 11, characterized in that olefinic hydrocarbons having four carbon atoms in the liquid phase on a heterogeneous, aluminum, silicon or nickel-containing catalyst at temperatures of 0 to 200 ° C and at absolute pressures of 1 to 70 is oligomerized, in particular that butenes are dimerisiert to Oktenen. Process for the preparation of an adsorbent comprising the following steps: x) providing a porous framework of silica and / or titanium dioxide and / or alumina and / or graphite; y) mixing the framework with nickel oxide and zinc oxide; z) reduction of the nickel oxide to metallic nickel. Use of an adsorbent having the following properties: α) the adsorbent is a solid composite comprising a porous inorganic framework material coated with metallic nickel on its surface, β) the adsorbent has the following characteristics: 100% additional composition: nickel 40 to 50 wt .-%, preferably 45 wt .-%; Zinc oxide 25 to 31% by weight, preferably 28% by weight; Silicon oxide 23 to 28% by weight, preferably 25% by weight; Graphite 1.8 to 2.2% by weight, preferably 2% by weight; Impurities 0 to 1% by weight, preferably 0% by weight; χ) the metallic nickel surface on the adsorbent is at least 3 m ² / g, preferably 9 m ² / g, determined by means of hydrogen chemisorption; δ) the adsorbent shows in air atmosphere, under normal pressure and at a temperature of 20 ° C pyrophoric properties; as a police filter for the desulfurization of mixtures immediately prior to oligomerization in the mixture of contained olefinic hydrocarbons having three to six carbon atoms. Use according to claim 14, characterized in that the adsorbent was prepared according to claim 13.