阅读说明：本技术 用于烯烃异构化的方法 (Process for isomerization of olefins ) 是由 F·盖伦 F·格特纳 H-W·詹托夫 G·施托赫尼奥尔 于 2020-11-13 设计创作，主要内容包括：本发明的主题是使用包含硅-铝-混合氧化物组合物的非均相催化剂体系将具有内部双键的C4至C9烯烃异构化为具有末端双键的相应烯烃的方法。(The subject of the present invention is a process for the isomerization of C4 to C9 olefins having internal double bonds to the corresponding olefins having terminal double bonds using a heterogeneous catalyst system comprising a silicon-aluminum-mixed oxide composition.)

1. A process for isomerizing a C4 to C9 reactant olefin having an internal double bond to a product olefin having a terminal double bond using a heterogeneous catalyst, wherein the catalyst is a silicon-aluminum-mixed oxide composition having the following composition:

a) 96 to 99.99 wt.% of silicon oxide (as SiO)₂Calculating); and

b) 0.01 to 4% by weight of aluminum oxide (as Al)₂O₃Calculation).

2. The process of claim 1, wherein the catalyst has the following composition:

a) 98.5 to 99.95% by weight of silicon oxide (as SiO)₂Calculating); and

b) 0.05 to 1.5% by weight of aluminum oxide (as Al)₂O₃Calculation).

3. The method of claim 1 or 2, wherein the silicon-aluminum-mixed oxide composition has 50 to 250 m²G, preferably from 100 to 220 m²BET surface area in g.

4. The process according to any one of claims 1 to 3, wherein the catalyst consists of shaped bodies which are produced from the silicon-aluminum-mixed oxide composition with the addition of a binder and at least a temporary auxiliary in a shaping process.

5. The process according to any one of claims 1 to 4, wherein a hydrocarbon mixture is used in the isomerization, which hydrocarbon mixture comprises the reactant olefins to be isomerized and also already comprises product olefins, wherein the content of product olefins is increased by the isomerization.

6. The process according to any one of claims 1 to 5, wherein the isomerization is carried out at a temperature of from 20 ℃ to 600 ℃, preferably from 100 ℃ to 500 ℃, particularly preferably from 200 ℃ to 450 ℃.

7. The process according to any one of claims 1 to 6, wherein the gas space velocity in the isomerization is from 2000 to 8000h^-1Preferably from 2500 to 4000h^-1。

8. The process according to any one of claims 1 to 7, wherein as reactant olefin a C4 to C8 reactant olefin having an internal double bond is used, preferably a C4 to C6 reactant olefin having an internal double bond, particularly preferably a C4 reactant olefin having an internal double bond.

9. The process according to claim 8, wherein cis-and/or trans-2-butene or a hydrocarbon mixture comprising these 2-butenes is used as reactant olefin and the product olefin having a terminal double bond is 1-butene.

10. The process according to any one of claims 1 to 9, wherein the silicon-aluminum-mixed oxide composition is present predominantly or completely in the form of agglomerated primary particles.

11. The method of claim 10, wherein the silicon-aluminum-mixed oxide composition is characterized by a weight ratio of primary particles (Al) in a near-surface region₂O₃/SiO₂)_{Surface of}Less than the weight ratio (Al) in the whole primary particles₂O₃/SiO₂)_{All are}。

12. The process according to claim 10 or 11, wherein the silicon-aluminium-mixed oxide composition is present predominantly or completely in the form of agglomerated primary particles, wherein

I) Weight ratio (Al) in all primary particles₂O₃/SiO₂)_{All are}From 0.002 to 0.05, preferably from 0.003 to 0.015, particularly preferably from 0.005 to 0.01; and

II) weight ratio of primary particles in a near-surface layer having a thickness of 5nm (Al)₂O₃/SiO₂)_{Surface of}Less than in all primary particles.

13. The process of any one of claims 1 to 12, wherein the catalyst is fully crystalline, partially crystalline, or X-ray amorphous.

14. The method of claim 13, wherein the catalyst is X-ray amorphous.

Technical Field

The present invention relates to a process for the isomerization of C4 to C9 olefins having internal double bonds to the corresponding olefins having terminal double bonds using a heterogeneous catalyst system comprising a silicon-aluminum-mixed oxide composition.

Background

In isomerization (also referred to as rearrangement in the case of intramolecular processes), the starting molecule is converted into a molecule which is unchanged by empirical formula but which has a changed atomic order, atomic arrangement or bond arrangement. Isomers generally have comparable bond energies, so that relatively free interconversion can occur. A distinction is made according to the type of conversion, for example bond isomerization where double bonds are rearranged, for example between C-C bonds (but where the person skilled in the art is also aware of many bond isomerizations involving heteroatoms such as O, N, P or S), skeletal isomerization where linear compounds are rearranged into branched compounds, hydroisomerization where alkanes are rearranged into isomeric alkanes via olefinic intermediate bodies in the presence of hydrogen, or cis/trans isomerization where substituents of double bonds are rearranged. The isomerization is usually accelerated by acidic/basic catalysts. The nature of the catalyst, such as the strength of the acid/base centers, determines to a large extent which isomerization takes place in the molecule. The isomerization required here is bond isomerization.

Olefins having terminal double bonds, so-called α -olefins (e.g.1-butene, 1-hexene or 1-octene), are important starting materials for many processes in the chemical industry, for example hydroformylation, oligomerization or polymerization for the preparation of aldehydes. The advantage of olefins having terminal double bonds compared with olefins having internal double bonds (e.g.2-butene, 2-hexene or 2-octene) is that they are in large part significantly more reactive in industrially operated processes. Furthermore, olefins having terminal double bonds are significantly more expensive than the corresponding olefins having internal double bonds. In contrast, however, there is also a need in the chemical industry for olefins having internal double bonds.

The corresponding olefins having terminal or internal double bonds may be provided by various processes, such as cracking processes. Another possibility is the catalytic isomerization of olefins having internal double bonds to the corresponding olefins having terminal double bonds. Reverse isomerization to olefins with internal double bonds is also possible. The degree of conversion is in each case limited by thermodynamic equilibrium. Catalytic isomerization to olefins with terminal double bonds is known, for example, from EP 0718036 a 1.

Catalysts used in the prior art for the isomerization to olefins having a terminal double bond are generally catalysts having acid/base functionality and transition metal-containing catalysts (the latter are mostly in the presence of hydrogen, which corresponds to the so-called hydroisomerization). In the case of acid/base catalysts, alkali and alkaline earth metal-doped aluminosilicates are used, corresponding to exchanged zeolites or pure basic oxides (e.g. MgO).

A general problem with isomerization reactions is that the olefin to be isomerized is a reactive molecule due to its double bond and therefore side reactions may occur. One example is oligomerization, which can take place over acidic catalyst systems and, in the case of corresponding use of acidic catalysts, as a side reaction in the isomerization. In order to prevent oligomerization of the olefins when isomerizing to olefins having a terminal double bond, preference is given to using basic catalyst systems or catalysts doped with alkali metals or alkaline earth metals.

Disclosure of Invention

Surprisingly, it has been found that, in contrast to this, it is also possible to use SiO-based materials with a certain proportion of (weakly) acidic aluminum oxide₂That is to say, for example, catalysts based on the silicon-aluminium-mixed oxide compositions described herein, which provide high activity for isomerization and have good product selectivity. In addition, oligomerization as a side reaction did not occur or hardly occurred.

The process according to the invention is therefore a process for isomerizing C4 to C9 reactant olefins having an internal double bond, preferably C4 to C8 reactant olefins having an internal double bond, furthermore preferably C4 to C6 reactant olefins having an internal double bond, particularly preferably C4 reactant olefins having an internal double bond, to product olefins having a terminal double bond using a heterogeneous catalyst, wherein the catalyst comprises a silicon-aluminum-mixed oxide composition.

Silicon-aluminum mixed oxide compositions used as catalysts can be prepared by means of flame hydrolysis according to the methods disclosed in particular in DE 19847161 a1 or EP 0850876 a 1. In the so-called "co-pyrolysis (co-fumed) process", volatile silicon compounds and aluminum compounds, for example silicon tetrachloride and aluminum trichloride, are injected into a detonation gas flame consisting of hydrogen and oxygen or air, whereby the silicon compounds and aluminum compounds are hydrolyzed by means of water produced in the detonation gas flame and form a mixed oxide composition.

An alternative method, which is also disclosed in said document, is the so-called doping method. In this method, on the one hand, the oxide, in this case, for example, silicon oxide, is produced from its volatile compounds (for example silicon tetrachloride) in a gas flame by flame hydrolysis, and furthermore an aerosol containing the salt of the element to be doped (for example, aluminum in this case) is fed into the detonation gas flame, and the corresponding mixed oxide is thus formed. The silicon-aluminum mixed oxide compositions thus produced by flame hydrolysis are predominantly to completely amorphous.

The silicon-aluminum mixed oxide compositions prepared by means of the preparation methods mentioned by way of example are characterized by their high chemical purity and preferably have the following composition:

a) 96 to 99.99% by weight of silicon oxide, preferably 98.5 to 99.95% by weight of silicon oxide (as SiO)₂Calculating); and

b) 0.01 to 4% by weight of alumina, preferably 0.05 to 1.5% by weight of alumina (as Al)₂O₃Calculation).

In a preferred embodiment of the invention, the silicon-aluminum-mixed oxide composition also comprises alkali metal oxides and/or alkaline earth metal oxides, particularly preferably in an amount of up to 1% by weight, based on the total composition. For the introduction of alkali metal oxides or alkaline earth metal oxides, the mixed oxide compositions prepared by flame hydrolysis may be treated with aqueous solutions of alkali metal hydroxides or alkaline earth metal hydroxides. This can be carried out, for example, by impregnating or impregnating the mixed oxide compositions prepared by flame hydrolysis with alkali metal salt solutions and/or alkaline earth metal salt solutions. The treated mixed oxide composition is then washed with water, dried at 100 to 150 ℃ and calcined at 300 to 600 ℃, preferably 450 to 550 ℃. Silicon and aluminum oxides may also already contain traces of alkali or alkaline earth metals and are not considered here.

The silicon-aluminum-mixed oxide composition of the invention can also be treated with an acidic aqueous solution having a source of phosphorus. As phosphorus source, use may be made of phosphoric acid, phosphonic acid, phosphinic acid, polyphosphoric acid or dihydrogen phosphate, preferably phosphoric acid. For this purpose, the mixed oxide composition is first suspended in water and the resulting suspension is then mixed with a phosphorus source, preferably to a pH of from 0 to 6, furthermore preferably from 1 to 2.5, particularly preferably from 2 to 2.5. The treated mixed oxide composition is then washed with water, dried at 100 to 150 ℃ and calcined at 300 to 600 ℃, preferably 450 to 550 ℃.

In a preferred embodiment, the silicon-aluminum-mixed oxide composition according to the invention is present predominantly (i.e. > 70%) or completely in the form of agglomerated primary particles. The silicon-aluminum mixed oxide composition is characterized in particular by the weight ratio of primary particles (Al) in the near-surface region₂O₃/SiO₂)_{Surface of}Less than the weight ratio (Al) of the whole primary particles₂O₃/SiO₂)_{All are}. The term "near-surface region" refers herein to the region from the surface up to a depth of 5 nm. The difference in the weight ratios means that the alumina concentration at the surface is less than the alumina concentration in the entire composition. The total primary particles include silica and alumina moieties in the near-surface region.

Preference is therefore given to silicon-aluminum mixed oxide compositions which are present predominantly or completely in the form of agglomerated primary particles, where

I) Weight ratio (Al) in all primary particles₂O₃/SiO₂)_{All are}From 0.002 to 0.05, preferably from 0.003 to 0.015, particularly preferably from 0.005 to 0.01; and

II) weight ratio of primary particles in the near-surface region (Al)₂O₃/SiO₂)_{Surface of}Less than in all primary particles.

Weight ratio on surface (Al)₂O₃/SiO₂)_{Surface of}Can be determined, for example, by X-ray induced photoelectron spectroscopy (XPS analysis) of the powder. Further information about the surface composition can be determined by energy dispersive X-ray analysis (TEM-EDX analysis) of the individual primary particles. Weight ratio (Al) in all primary particles₂O₃/SiO₂)_{All are}Can be determined by chemical or physicochemical methods, such as X-ray fluorescence analysis of the powder.

The silicon-aluminum-mixed oxide composition used as a catalyst in the present invention may be X-ray amorphous, have crystalline portions (partially crystalline) or be completely crystalline. The silicon-aluminum-mixed oxide composition used as catalyst is preferably amorphous by X-ray. X-ray amorphous in the sense of the present invention means that the X-ray amorphous substance does not show a crystal structure in the X-ray diffraction pattern up to the detection limit of 5 nm.

Said composition according to the invention, in particular having the above-mentioned composition, and in particular having said weight ratio (Al)₂O₃/SiO₂) The differential silicon-aluminum-mixed oxide composition preferably has a thickness of 50 to 250 m²G, preferably from 100 to 200 m²BET surface area in g (determined to DIN ISO 9277 (up to: 2014-01)).

Furthermore, it may be advantageous when the silicon-aluminum-mixed oxide composition has a dibutyl phthalate value of 300 to 350, which is given in g dibutyl phthalate (DBP)/100 g of the mixed composition. The DBP value is a measure of the agglomerate structure. A low value corresponds to a low structure and a high value corresponds to a high structure. The range of 300 to 350 described for the mixed oxide composition according to the invention corresponds to a high structure. In DBP absorption, the force absorption or torque (given in Nm) of the rotating blades of a DBP measuring instrument is measured with the addition of a defined amount of DBP. In this case, for silicon-aluminum-mixed oxide compositions, a clearly defined maximum is preferably produced, which subsequently decreases with the addition of a certain amount of DBP. Dibutyl phthalate absorption can be measured, for example, with an instrument RHEOCORD 90 from Haake, Karlsruhe. For this purpose, 12 g of silicon-aluminum mixed oxide powder are filled into the kneading chamber, closed with a lid and dibutyl phthalate is metered in at a predetermined metering rate of 0.0667 ml/s via a hole in the lid. The kneader is operated with a motor speed of 125 revolutions per minute. After the maximum torque has been reached, the kneader and the DBP metering are automatically switched off. The DBP absorption was calculated from the DBP consumption and the weighed amount of particles according to the following formula: DBP value (g/100 g) = (DBP consumed (g)/powder weighed in (g)) x 100.

For industrially operated isomerization using a catalyst comprising a silicon-aluminium-mixed oxide composition, preference is given to the reaction mode in one or more fixed-bed reactors (Reaktionsfurung). For liquid phase reactions, slurry or trickle bed reactors may also be used. Other reactor types, such as fluidized bed reactors or moving bed reactors, may also be used. For this purpose, the aforementioned mixed oxide compositions prepared by flame hydrolysis or pyrolysis have to be shaped, in particular in the form of pellets, pellets or shaped bodies, such as tablets, cylinders, spheres, strand extrudates or rings, by means of shaping methods known to the person skilled in the art, with the addition of binders. Suitable binders are known to the person skilled in the art, for example using clays (Tonerde), ceramic clays (keramische Tonen), colloidal or amorphous zeolites.

For shaping, 1 to 20% by weight of the silicon-aluminum mixed oxide composition is first mixed with one of the above-mentioned binders and additionally with temporary auxiliaries, such as water, aqueous solutions, water substitutes (Wasserersatzstoffen) such as diols and polyglycols, and optionally further auxiliaries, such as fixing agents, for example cellulose ethers, and/or plasticizers, for example polysaccharides, and/or pressing aids, for example nonionic wax dispersions. The process can be carried out in apparatuses known to the person skilled in the art, for example in kneaders or intensive mixers. The actual shaping is then carried out by shaping methods, for example granulation, extrusion or dry pressing. The shaped bodies/bodies are calcined at a temperature in the range from 200 to 700 ℃ before being charged into one or more fixed-bed reactors, whereby at least the temporary auxiliary is removed.

The silicon-aluminum mixed oxide composition can be applied to a support that is inert to isomerization, for example a metal support, a plastic support or a ceramic support. If the silicon-aluminum mixed oxide composition is applied to an inert support, the mass and composition of the inert support are not taken into account in determining the composition of the silicon-aluminum mixed oxide composition.

The process according to the invention is carried out with the above-described silicon-aluminum-mixed oxide composition as catalyst to isomerize a C4 to C9 reactant olefin having an internal double bond, preferably a C4 to C8 reactant olefin having an internal double bond, furthermore preferably a C4 to C6 reactant olefin having an internal double bond, particularly preferably a C4 reactant olefin having an internal double bond, to a product olefin having a terminal double bond.

The olefins are not necessarily used in pure form but as industrially available hydrocarbon mixtures. Thus, the content of product olefins in the hydrocarbon mixture is increased by the isomerization and at the same time the content of reactant olefins is reduced.

The C5 olefins are contained in the light gasoline fraction from a refinery or cracker. Commercial mixtures comprising linear C4 olefins are light gasoline fractions from refineries, C4 fractions from FC crackers or steam crackers, mixtures from fischer-tropsch synthesis, mixtures from butane dehydrogenation, and mixtures produced by metathesis or from other commercial processes. For example, a mixture of linear butenes suitable for use in the process according to the invention can be obtained from the C4 fraction of a steam cracker. In this case, butadiene is removed in the first step. This is achieved by extraction (extractive distillation) of butadiene or its selective hydrogenation. In both cases, a C4 fraction containing almost no butadiene, the so-called raffinate I, was obtained. In a second step, MTBE is prepared, for example, by reaction with methanol, from C₄Isobutylene was removed from the stream. The now isomentless and butadiene-free C4 fraction, the so-called raffinate II, comprises linear butenes and optionally butanes. If even at least a portion of the 1-butene contained is also separated therefrom, a so-called raffinate III is obtained.

In a preferred embodiment, the stream comprising C4 olefins is fed as a hydrocarbon mixture in the process according to the invention. Suitable streams containing C4 olefins are, for example, crude butane or C4 raffinate III. Crude butane is produced as a by-product, in particular in the oligomerization of C4 olefins. However, a crude butane in the sense of the present invention is any C4 hydrocarbon stream which, in addition to a high proportion of saturated C4 hydrocarbons (typically more than 50 wt%), also comprises linear butenes, with a 1-butene content of less than 10% of the linear butenes. C4 raffinate III in the sense of the present invention is produced after separation of at least 1, 3-butadiene, isobutene and 1-butene from the C4 fraction of a steam cracker or FCC cracker.

According to the invention, the reactant olefins are olefins having an internal double bond which are at least partially converted by isomerization into product olefins, i.e. olefins having a terminal double bond (alpha-olefins). In a preferred embodiment, the reactant olefin is cis and/or trans 2-butene or a hydrocarbon mixture comprising cis and/or trans 2-butene, which is converted to 1-butene by isomerization according to the present invention. This enables enrichment of 1-butene in the previous 1-butene-depleted hydrocarbon mixture, so that said mixture can be value-utilized, for example for further processing in processes preferably with high 1-butene concentrations (for example oligomerization or oxydehydrogenation to butadiene), for obtaining 1-butene or for hydroformylation to valeraldehyde.

The conversion of one or more reactant olefins to product olefins is limited upward by, inter alia, the temperature-dependent location of the chemical equilibrium of the isomerization reaction. The advantage obtained by using the catalyst according to the invention is that the conversion corresponds to or is only slightly lower than the thermodynamic equilibrium conversion over a broader temperature range. This also applies to the isomerization of 2-butene to 1-butene, which is limited by the thermodynamic equilibrium of the n-butene isomers. The thermodynamic equilibrium of a mixture comprising 2-butene and 1-butene is shifted towards 1-butene by the high temperature. The thermodynamic equilibrium of 1-butene is about 24% to 25% at a temperature of 400 ℃ and about 29% at a temperature of 500 ℃.

For the isomerization process according to the invention, preferably at least one fixed bed reactor is used. Other reactor types, such as fluidized bed reactors, moving bed reactors, slurry reactors, or trickle bed reactors, may also be used.

The process according to the invention can be carried out at atmospheric pressure. However, higher reaction pressures may also be employed. The pressure-operated mode in the process according to the invention is useful, for example, when the product olefins from the isomerization process according to the invention are fed to a further separation step which is likewise operated under pressure. Thus, after isomerization of 2-butene to 1-butene, the hydrocarbon mixture can be fed to a further separation step in which 1-butene and 2-butene are separated from one another by distillation under pressure.

The isomerization of 2-butene to 1-butene according to the invention is preferably carried out at temperatures of from 20 ℃ to 600 ℃, furthermore preferably from 100 ℃ to 500 ℃ and particularly preferably from 200 ℃ to 450 ℃. The gas-space velocity (gas space velocity) = GHSV) may be 2000 to 8000h^-1Preferably from 2500 to 4000h^-1. The selectivity of the isomerization according to the invention with respect to the product olefins is preferably greater than 80%, furthermore preferably greater than 82%, particularly preferably greater than 85%.

In the event that the activity and selectivity of the catalyst according to the invention are reduced by carbon deposits on the catalyst, the catalyst is conveniently regenerated. An advantageous method of catalyst regeneration is to burn off the carbon deposits on the deactivated catalyst in an oxygen-containing gas, preferably in air. It may be convenient here to dilute the air with nitrogen. The catalyst regeneration is generally carried out at a temperature of from 350 to 600 c, preferably from 400 to 450 c. The initial activity and the initial selectivity of the catalyst according to the invention can thus generally be regained in a simple manner.

The invention is described below with the aid of examples. This example serves to illustrate the invention without limiting the subject matter of the invention.

Detailed Description

Example 1 isomerization of 2-butene to 1-butene

A tubular reactor having a diameter of 0.6mm was filled with 0.2g of catalyst according to the invention (Aerosil MOX170, about 1% by weight of alumina, BET surface area of 140 to 200 m²In terms of/g). To the reactor was added crude butane having the following composition:

1-butene	Cis-2-butene	Trans-2-butene	Isobutene	N-butane	Isobutane	Other hydrocarbons
							1.56	8.87	20.18	0	67.9	0.53	0.86

Here, the crude butane was conducted through the reactor at different volume flows. The isomerization is carried out at a temperature of 380 ℃ and at a pressure in the reactor of 5.7 to 6 bara (bar, absolute). At the reaction, the conversion of 2-butene and the selectivity to 1-butene were determined. Analysis was performed by gas chromatography. Evaluation was performed by the internal standard method according to the peak area. N-butane was used as internal standard.

TABLE 1 conversion and selectivity of example 1

Volume flow of crude butane [ g/h]	Conversion of 2-butene [% ]]	Selectivity for 1-butene [% ]]
			7.5	24.91	87.82
15.2	21.91	90.66
			25.2	20.51	94.44

The results show that the catalyst according to the invention is very well suited for the isomerization.