DE10055036A1 - Oligomerization of n-olefins by passing a single phase fluid containing the olefins over a bed of a particulate nickel based catalyst in an opposite direction to the force of gravity - Google Patents

Abstract

A process for the oligomerization of 2-6C n-olefins comprises passing a single phase fluid containing the olefins over a bed of a particulate nickel based catalyst under adiabatic conditions in an opposite direction to the force of gravity such that a vapor phase is formed due to the heat of reaction and the vapor phase is removed in cocurrent flow with the liquid from the catalyst bed. A process for the oligomerization of 2-6C n-olefins comprises (A) preparation of a single phase fluid containing the olefins (B) passing the fluid under adiabatic conditions over a bed of a particulate nickel based catalyst whereby (C) the fluid is fed to the catalyst bed in an opposite direction to the force of gravity and the pressure is chosen such a vapor phase is formed due to the heat of reaction and the vapor phase is removed in cocurrent flow with the liquid from the catalyst bed.

Description

The present invention relates to a process for oligomeri sation of n-olefins with 2 to 6 carbon atoms on nickel containing heterogeneous catalysts.

Olefins with 2 to 6 carbon atoms and their mixtures, ins special olefins with 4 carbon atoms are large Quantities from both FCC systems and steam crackers for ver addition. Oligomers produced therefrom, in particular octenes and Dodecenes are found after hydroformulation and subsequent hydration use of the corresponding alcohols on a large scale, z. B. for the production of plasticizers or surfactants.

The oligomerization of olefins on an industrial scale is either ho mogen or heterogeneously catalyzed. Homogeneous cataly Based procedures are such. B. by A. Chauvel and G. Lefebvre in Petrochemical Processes, Volume 1, Editions Technip (1989), p. 183 to 187, described in detail. With a homogeneous catalytic process Ren you have to separate the catalyst from the reaction mixture. the This separation step causes waste streams that are due to Environmental requirements have to be revised again. Finally the homogeneous catalyst cannot be regenerated. This On the other hand, there is a disadvantage with heterogeneously catalyzed olefin oligo merizations not where an olefin-containing feed via the Bed of a heterogeneous, d. H. Ka insoluble in the reaction medium talysators is headed.

The oligomerization of low molecular weight olefins is carried out by ei accompanied by a noticeable exothermic heat. It therefore exists the need to remove the heat of reaction to an uncon to avoid controlled temperature rise. Too high tempera Doors on the catalyst bed can lead to undesirable higher formation Lead oligomers and polymers. The latter prove the active waiter surface of the catalyst and deactivate it. Depending on the type of Heat dissipation is called isothermal or adiabatic Reaction.  

Under an adiabatic reaction, the technical Understood a reaction management in which, apart from through natural heat conduction and heat radiation from the reak Tor released to the environment part of the heat of reaction, the ge Whole heat of reaction is absorbed by the reaction mixture and with this is removed from the reactor.

In contrast, the isothermal reaction in technical sense, the removal of the heat of reaction from the reactor by means of cooling or thermostatting devices through the given natural heat conduction or heat radiation targeted forcing. This becomes a - if negligible smaller - part of the heat of reaction practically inevitable with the heated reaction mixture discharged.

Isothermally operated reactors, for example water-cooled Tube bundle reactors are characterized by good controllability from, but are more expensive in terms of equipment than adiabatically operated ones Reactors and thus have higher equipment investment costs on.

Various processes have been used for oligo in the prior art merization of olefins in an adiabatic reaction wrote. For example, WO 99/25668 discloses a ver drive to the production of essentially unbranched octenes and dodecenes by oligomerization of 1-butene and / or 2-butene and butane-containing hydrocarbon streams on a nickel containing heterogeneous catalyst. The older registrations DE 100 15 002.0 and 100 26 906.0 relate to certain configurations of the known method. The feed hydrocarbon mixture is liquid or in a supercritical state. It flows through the reactor from top to bottom. The adiabatic reaction ent ent that the temperature with which the Re action mixture emerges from the reactor is significantly higher than the temperature at which the feed hydrocarbon mixture enters the reactor. The inlet temperature cannot be be chosen as low as possible; it has to be sufficient to Initiate reaction on the catalyst. The resulting high The outlet temperature of the reaction mixture is problematic table, as very high pressures are required to complete the reaction keep the mixture single-phase liquid at the outlet temperature, and handling of superheated hydrocarbons safely is undesirable.

DE 195 35 505 A discloses, inter alia, a process for the oligomerization of C ₃ -C ₁₂ olefins with a secondary or tertiary C atom in a boiling reactor. The boiling reactor consists of a catalyst section through which the starting material flows and a distillation section in which the reaction mixture flowing off the catalyst section is separated into a bottom phase and into unconverted starting material as a vapor phase. Heterogeneous acidic catalysts, such as acidic ion exchangers, are described as catalysts. The reaction on the heterogeneous catalyst and the distillation are clearly spatially separated in different areas of the boiling reactor.

US Pat. No. 5,190,730 describes a process for the oligomerization of C ₄ and C ₅ isoolefins, these being carried out via an acidic ion exchanger in a fixed bed. The feed enters the fixed bed reactor at the top, and the reaction liquid flows as a thin liquid film over the catalyst. Part of the reaction liquid evaporates due to the heat of reaction.

The object of the present invention is to provide a Process for the oligomerization of n-olefins with 2 to 6 Koh lenstoffatomen, which is an implementation at essentially constant Temperature without the need for a cooling or thermostatic device Permitted on the reactor.

This object is achieved by a method in which

• a) an essentially single-phase containing these olefins provides liquid supply,
• b) the feed under essentially adiabatic conditions over a bed of a particulate nickel-containing kataly sators, which is characterized in that one
• c) the inlet against the direction of gravity over the Conducts the bed of the catalyst and selects the pressure that the feed due to the heat of reaction with formation ner vapor phase partially evaporated and the vapor phase from the and in cocurrent with the liquid phase from the bed of the Ka talysators is held.

The feed contains at least one n-olefin with 2 to 6 carbons atoms of matter, and preferably at least one inert solution medium. The olefin content in the feed is preferably about 10 to 90 wt .-%, and the content of diluent is before preferably about 90 to 10 wt .-%, each based on the total mass of the inflow.  

Propene, butenes, pentenes are preferably used as n-olefins and hexenes, especially 1-butene, 2-butene, 1-pentene, 1-hexene 3-witches or mixtures thereof.

The process is particularly suitable for the reaction of olefins which are already present in a mixture with an inert diluent. A particularly suitable C ₄ hydrocarbon stream is the so-called raffinate II, that is to say a butene-containing hydrocarbon mixture, such as that obtained from the C _{4 section} of crackers after removal of more unsaturated hydrocarbons, such as diolefins, in particular 1,3-butadienes, or acetylene and subsequent separation of the isobutene contained therein is obtained.

The C ₄ hydrocarbon streams can e.g. B. in a manner known per se from DE 39 14 817 A of butadiene, sulfur-containing and oxygen-containing compounds, such as alcohols, aldehydes, ketones or ethers, by selective hydrogenation or adsorption on a molecular sieve.

Suitable diluents are, for example, saturated Koh bons. Typically, the diluent has one Boiling point, which is a maximum of about 15 ° C from that of the oligome differentiating olefins. Al are particularly suitable kanes with 2 to 6 carbon atoms, for example ethane, propane, n-butane, isobutane, the isomeric pentanes or hexanes.

"Oligomers" include dimers, trimers and higher oli understood olomers of the feed olefins. The Ver driving is particularly suitable for the production of dimers olefins. The oligomers obtained are essentially one fold ethylenically unsaturated.

The bed of the catalyst is in a suitable reactor preferably arranged in a vertical tubular reactor. A fixed bed reactor is preferably used, in which the Ka Talysator is arranged in the form of a catalyst bed. The Cross-sectional load is chosen so that the catalyst in Calm remains, so it is firmly arranged. Is the catalyst in the right Actuator arranged on several fixed beds, so the inlet can divided and fed in at several points.

Alternatively, the method according to the invention is carried out A fluidized bed reactor is also considered. In the fluid bed reactor is the cross-sectional load above the loosening point, i.e. H. the Point of beginning bed expansion, increased.

In the process according to the invention, a single-phase flow is assumed  sig existing inflow. The oligomerization of olefins is exothermic, but the inlet must have such a temperature rature that the implementation on contact with the Kataly sator gets going spontaneously. As a rule, it is therefore necessary Lich to preheat the feed brought to reaction pressure. The The temperature of the feed is chosen so that the boiling point at this pressure is just not reached. When contacting the Ka Talysator starts the reaction liquid through the at the Oli boiling released heat to boil. The one for the change The energy required for the physical state becomes the reaction liquid withdrawn. The reaction temperature corresponds to the boiling point rature of the reaction liquid. The boiling point is pressure dependent, because at the boiling point the pressure of the vapor corresponds to the external pressure speaks. An increase in pressure leads to an increase in the boiling point temperature, a decrease in pressure leads to a decrease in Boiling temperature. The reaction temperature can therefore be determined Set pressure control.

The selectivity of the catalyst is surprisingly related Lich the desired oligomers, especially dimers better if the inlet through the bed of the catalyst from bottom to top flows than in the opposite direction of flow.

The method according to the invention is essentially adiaba conditions. Below that is an operating understood wisely in which the exothermic reaction is free amount of heat largely from the reaction mixture in the reak Tor added and no cooling by cooling devices turns. It goes without saying that a purely adiabati reaction management in the theoretical-academic sense of Be handles "adiabatic" technically only with uneconomically high Effort could be accomplished as a - albeit neglected loosely smaller - part of the free in the exothermic reaction the amount of heat practically through heat conduction and heat radiation is released to the environment. In a technical sense, the half under an adiabatic reaction or operation wise understood such a, apart from that by natural heat conduction and heat radiation from the reactor to the Environment released part of the heat of reaction, the total reacti onswärme absorbed by the reaction mixture and with this from the Reactor is discharged. Synonymous with adiabatic response In the technical sense, the term "qua si-adiabatic "reaction control used. The measure of a essentially adiabatic reaction, as in the applied the present invention, corresponds to one  Adiabatic reaction control in the techni explained above senses.

The procedure is carried out so that at least a small part the reaction liquid evaporates during the reaction, others complete evaporation of the reaction liquid is avoided. In addition to controlling the pressure, this can in particular especially by controlling the cross-sectional load of the kata analyzer and / or a variation in the composition of the olefin containing inflow can be achieved. So you can by sharing inert diluent the concentration of olefins in the feed reduce and thus limit the maximum expected heat Zen.

If the diluent is the lowest boiling component is, it is preferably evaporated during the reaction. By Use a sufficiently large amount of diluent can complete evaporation of the reaction liquid ver be avoided. The warming tone and consequently that during the order Vaporized portion of the reaction liquid can set by varying the cross-sectional load of the catalyst bed tes are influenced, with an increase in cross-sectional load generally exothermic heat leads.

The oligomerization reaction preferably takes place at 30 to 280 ° C and in particular at 30 to 140 ° C and very particularly preferred at 40 to 130 ° C instead. The corresponding pressures are in usually in the range of 5 to 70 bar, in particular 8 to 30 bar and very particularly preferably in the range from 10 to 20 bar.

The method according to the invention is preferably carried out in in particular through a suitable choice of the cross-sectional load and / or the composition of the feed that the concentration of oligo in the liquid phase leaving the bed of the catalyst in the range of about 5 to 80% by weight, preferably about 10 to 50 wt .-% and in particular about 15 to 25 wt .-%, based on the Liquid phase. Too high an oligomer concentration works adversely affect the selectivity, if the oligo is too low the process becomes uneconomical.

After leaving the catalyst bed, the structures are formed ten oligomers in a manner known per se from the unreacted ten olefins and the inert diluent separated. The The oligomers are separated by a method known per se ren, e.g. B. by fractional distillation.  

The reaction discharge freed from the oligomers formed, the essentially from unreacted olefins and inert ver there is some or all of the fertilizer in front of the bed of the Catalyst are recycled. Since the returned current is ge is olefin-depleted compared to the primary feed mixture by varying the quantity returned control the inflow.

As catalysts, there are generally known ones, a small one Branching nickel-containing catalysts in Be garb as they z. B. by O'Connor et al in Catalysis Today, 6, 329 (1990), particularly on pages 336-338 and in the DE-43 39 713 A references cited from the prior art are described, so that to the sites found there explicit reference is made.

Examples of such nickel-containing oligomerization catalysts - in which the nickel is usually present in oxidic form - are:

• - nickel on silicon dioxide,
• - nickel on silica-alumina,
• - Nickel on silica-alumina layered silicates, such as Mica and clays, especially montmorillonite,
• - Nickel on zeolite supports, such as mordenite, faujasite, zeolite X, zeolite Y, zeolite ZSM-5 or other zeolites of the ZSM type, Zeolites with MCM-41 structure or CZS-1 structure,
• - Nickel on aluminum oxide, optionally together with anions especially inorganic acid, such as sulfur, phosphorus, boron acid,
• - nickel on zirconium oxide, which is mixed with acids such as sulfuric acid, Phosphoric acid or boric acid is treated,
• - NiO / ZrO ₂ / SO ₄ / SiO ₂ systems,
• - Nickel on sulfated titanium dioxide.

According to a preferred embodiment of the Ver driving one uses the kata described in DE 43 39 713 catalysts. The catalysts described there consist in their essentially catalytically active mass, d. H. without consideration contamination caused by initial or process checks chemicals are brought in during catalyst production, made of nickel oxide, silicon dioxide, titanium oxide and / or zirconium dioxide and optionally aluminum oxide containing Nic keloxide from 10 to 70 wt .-%, 5 to 30 wt .-% titanium oxide and / or Zirconium dioxide, 0 to 20 wt .-% aluminum oxide and the rest of to 100 wt .-% silicon dioxide and are by precipitation of the catalyst Contain door mass at pH 5 to 9 by adding a nickel nitrate  tending aqueous solution to an alkali water glass solution, the Ti contains tandioxide and / or zirconium dioxide, filtering, drying and annealing at 350 to 650 ° C, available.

In a very preferred embodiment, the catalyst is present from about 50% by weight of nickel oxide, about 13% by weight of titanium dioxide, about 34 wt% silica and about 3 wt% alumina.

According to a further preferred embodiment of the fiction According to the method, a Ka is used for the oligomerization analyzer, in which aluminum oxide with a nickel compound, such as nickel nitrate, and a sulfur compound such as ammonium sul fat or sulfuric acid, acted on simultaneously or first with the nickel compound and then with the sulfur compound bond, and then drying the catalyst thus obtained and calcined, in this way in the finished catalyst a molar ratio of sulfur to nickel of 0.25: 1 to 0.38: 1.

The Ni catalysts used according to the invention are as above mentioned, preferably arranged in a fixed bed and have the semi preferably lumpy shape: z. B. tablets (5 mm × 5 mm, 5 mm × 3 mm, 3 mm × 3 mm), rings (7 mm × 7 mm × 3 mm, 5 mm × 5 mm × 2 mm, 5 mm × 2 mm × 2 mm) or strands or star strands (1.5 mm diameter, 3 mm diameter, 5 mm diameter). The The above sizes and molded body types are only exemplary and do not limit the present Er invention.

The process according to the invention is described in the following examples illustrated in more detail.

Examples

A raffinate II with the following composition was used:
i-butane: 2% by weight
n-butane: 10% by weight
i-butene: 2% by weight
1-butene: 32% by weight
trans 2-butene: 37% by weight
cis 2-butene: 17% by weight.

A material that was produced according to DE 43 39 713 A in the form of tablets with 5 mm × 5 mm served as catalyst I. The composition in% by weight of the active components was: 50% NiO, 13% TiO ₂ , 34% SiO ₂ and 3% Al ₂ O ₃ .

The same material was used as catalyst II, but in the form of Star strands with a cross section of 3 mm.

The catalyst was either from the bottom up (swamp risk flows) or from top to bottom (trickle mode). The reaction discharge was analyzed by gas chromatography.

example 1

The oligomerization was carried out in a laboratory reactor with an inside diameter of 6 mm and a length of 1500 mm in a straight line Run performed. The preheated to 80 ° C was used Raffinate II and catalyst I (filling quantity: 27.5 g). Further Test parameters and the results of the tests are in Ta belle 1 compiled. At the specified pressure, the released heat of reaction for partial evaporation of the reak tion mixture with formation of gas bubbles.

Table 1

Example 2

The oligomerization was carried out in a laboratory reactor with an inside diameter of 6 mm and a length of 1500 mm in a straight line Run performed. The preheated to 80 ° C was used Raffinate II and Catalyst II (filling quantity: 6.5 g). Further Test parameters and the results of the tests are in Ta belle 2 compiled. At the specified pressure, the released heat of reaction for partial evaporation of the reak tion mixture with formation of gas bubbles.

Table 2

The results show that the swamp way of doing better Selek activities than the trickle mode.

Claims (7)

1. A process for the oligomerization of n-olefins having 2 to 6 carbon atoms, in which

• a) provides an essentially monophase liquid feed containing these olefins,
• b) conducts the feed under essentially adiabatic conditions over a bed of a particulate nickel-containing catalyst, characterized in that
• c) conducts the inlet against the direction of gravity over the bed of the catalyst and selects the pressure so that the inlet partially evaporates due to the heat of reaction to form a vapor phase and the vapor phase of and in cocurrent with the liquid phase from the bed of Catalyst is discharged.

2. The method according to claim 1, characterized in that one used as n-olefins with 4 to 6 carbon atoms. 3. The method according to claim 1 or 2, characterized in that you choose the pressure in step c) so that a Re action temperature from 30 to 280 ° C. 4. The method according to any one of claims 1 to 3, characterized records that the feed is also an inert dilution contains medium. 5. The method according to any one of the preceding claims, characterized characterized in that the concentration of oligomers in the liquid phase in the bed leaving the catalyst is from 5 to 80 wt .-%. 6. The method according to any one of the preceding claims, characterized characterized in that as a nickel-containing catalyst NEN catalyst used as the main active Be constituents 10 to 70 wt .-% nickel oxide, 5 to 30 wt .-% Tita noxide and / or zirconium oxide, 0 to 20 wt .-% aluminum oxide and contains the rest of silicon dioxide.   7. The method according to any one of claims 1 to 5, characterized records that one uses a catalyst for whose Production of aluminum oxide with a nickel compound and a sulfur compound, the Ka thus obtained Talysator then dries and calcined, with this way a molar ratio in the finished catalyst sulfur to nickel from 0.25: 1 to 0.38: 1.