Method for isomerizing 2, 4, 4-trimethylpent-2-ene to 2, 4, 4-trimethylpent-1-ene

Abstract

The present invention relates to a process for the isomerization of 2, 4, 4-trimethylpent-2-ene to 2, 4, 4-trimethylpent-1-ene, in particular to a process for the isomerization of 2, 4, 4-trimethylpent-2-ene to 2, 4, 4 The subject of the invention is a process for the isomerization of 2, 4, 4-trimethylpent-2-ene to 2, 4, 4-trimethylpent-1-ene on a heterogeneous catalyst based on a zeolite or on an ion exchange resin.

Description

Technical Field

[0001] The present invention relates to a process for the isomerization of 2,4,4-trimethylpent-2-ene to 2,4,4-trimethylpent-1-ene over a heterogeneous catalyst based on zeolites or ion exchange resins. Background Art

[0002] Diisobutene is an industrially relevant product obtained by dimerization of isobutene. Diisobutene consists of the isomers 2,4,4-trimethylpent-1-ene (hereinafter also referred to as: TMP1) and 2,4,4-trimethylpent-2-ene (hereinafter also referred to as: TMP2), wherein the mass distribution of TMP1:TMP2 is about 78:22 to 81:19 (equilibrium distribution). This mixture can be converted into higher-value products, especially in carbonylation processes. In particular, in carbonylation processes, such as methoxycarbonylation (the reaction product here is methyl 3,5,5-trimethylhexanoate) or hydroformylation (the reaction product here is 3,5,5-trimethylhexanal), the reactivity of the internal olefin TMP2 is significantly lower than that of the terminal olefin TMP1. Due to insufficient catalyst stability or due to economic factors (e.g. reactor size), it is usually not possible to adjust the reaction conditions or residence times in these carbonylation reactions sufficiently to completely react the terminal olefin TMP2.

[0003] Due to its reactivity, it is less suitable to use unreacted TMP2 directly. Therefore, it is recommended to convert TMP2 or a part of it into the more reactive TMP1 form by isomerization, so that it can be finally converted into valuable products.

[0004] The methods for isomerizing TMP2 to TMP1 are known in the literature. However, these methods are carried out under homogeneous catalysis and are based on strong mineral acids, such as H2SO4, H3PO4 or benzenesulfonic acid (see US2,554,251 A). However, the disadvantage of homogeneous catalytic reaction systems is that the isomerization catalyst must be separated again in an expensive manner from the resulting pure TMP1 or the resulting TMP1 / TMP2 mixture. Only in this way can they be supplied to the above-mentioned carbonylation process. Acidic systems are also usually corrosive, so high-quality materials are required. Summary of the invention

[0005] It is therefore an object of the present invention to provide a process for the isomerization of 2,4,4-trimethylpent-2-ene to 2,4,4-trimethylpent-1-ene which does not have the above-mentioned problems but at the same time should also be able to achieve high conversions by means of the process.

[0006] This object is achieved by the method according to the invention as described in independent claim 1. Preferred embodiments are given in the dependent claims.

[0007] According to the present invention, the method is a method for isomerizing 2,4,4-trimethylpent-2-ene to 2,4,4-trimethylpent-1-ene, wherein the method comprises at least the following steps:

[0008] a. providing an input stream, the input stream containing 2,4,4-trimethylpent-2-ene and 2,4,4-trimethylpent-1-ene, wherein the proportion of 2,4,4-trimethylpent-2-ene in the total stream is at least 25 mol %, based on the total input stream;

[0009] b. isomerizing the input stream using a heterogeneous catalyst based on zeolites or ion exchange resins,

[0010] The proportion of 2,4,4-trimethylpent-2-ene in the product stream is lower than that in the input stream, and the proportion of 2,4,4-trimethylpent-1-ene in the product stream is higher than that in the input stream.

[0011] The advantage of the process of the invention is the use of a heterogeneous catalyst system. Such a catalyst system does not need to be separated from the product stream, but remains in the reaction vessel or reactor. High conversion rates can also be achieved with the catalyst system of the invention based on zeolites or ion exchange resins.

[0012] The input stream used contains 2,4,4-trimethylpent-2-ene and 2,4,4-trimethylpent-1-ene, wherein the proportion of 2,4,4-trimethylpent-2-ene in the total stream is at least 25 mol %, preferably at least 28 mol %, based on the total input stream. A stream with less trimethylpent-2-ene is so close to the equilibrium distribution that it is not worth using. Such a stream may be a diisobutene stream, which can be prepared by dimerization of isobutene or isobutene-containing hydrocarbon mixtures, as disclosed, for example, in EP 1 360 160 B1. Furthermore, the stream used here can be obtained as an unreacted residual stream in a carbonylation process, for example in methoxycarbonylation or hydroformylation.

[0013] The isomerization in step b. can be carried out in principle in various suitable reactors. Isomerization can be carried out in a single reactor or in a plurality of reactors connected in parallel or in series. It can also be carried out in the form of batch or continuous operation. Isomerization is preferably carried out in one or more continuously operated reactors, which are generally used for solid / liquid contact reactions. When a continuously operated flow reactor is used, a fixed bed is generally but not exclusively used. When a fixed bed flow reactor is used, the liquid can flow upward or downward. In most cases, it is preferred that the liquid flows downward. In addition, the reactor can be operated by product recirculation or straight-through mode. A concept different from a fixed bed reactor is, for example, a reactor in which an ion exchanger or a zeolite is present in the form of suspension in a liquid phase.

[0014] The reactor used in the isomerization according to the invention is preferably a tubular reactor or a tube bundle reactor, in particular one having an inner tube diameter of 10 to 60 mm. The aspect ratio of the catalyst bed can be varied here depending on the geometric dimensions of the reactor or on its filling level. Thus, different empty tube velocities can be achieved at the same contact quantity and loading (LHSV).

[0015] Whether it is a tubular reactor or a tube bundle reactor, the heating of the reactor tubes can be carried out by steam or heat carrier oil via the reactor jacket. In particular, when a liquid heating medium is used, the construction of the jacket side should be such that there is a temperature gradient as uniform as possible on all tubes. The technical measures required for this are known to those skilled in the art and are described in the literature (installing deflection plates, annular baffle structures, feed / discharge of heat carriers, etc. at various positions of the reactor). Preferably, the reaction medium and the heat carrier are transported through the tractor tube or the reactor jacket in a parallel flow manner, more preferably from top to bottom. For example, a preferred embodiment is described in DE 102006040433 A1.

[0016] The isomerization of 2,4,4-trimethylpent-2-ene to 2,4,4-trimethylpent-1-ene occurs exothermically, ie with release of energy, which leads to an increase in the temperature of the reaction mixture. In order to limit the temperature increase, the feed stream can be diluted, for example by recycling the product.

[0017] The reactor(s) used for the isomerization can be operated adiabatically, polytropically or virtually isothermally. Virtually isothermally means that the temperature at any point in the reactor is at most 10° C. higher than the temperature at the reactor inlet. In the case of adiabatic operation of the reactors, it is generally expedient to connect a plurality of reactors in series and to provide cooling between the reactors. Suitable reactors for polytropic or virtually isothermal operation are, for example, the already mentioned tube bundle reactors as well as stirred tank reactors and loop reactors.

[0018] The process can be carried out at relatively mild temperatures. The isomerization in step b is preferably carried out at a temperature of 25°C to 90°C, preferably 30°C to 80°C, particularly preferably 35°C to 70°C.

[0019] Furthermore, the isomerization according to the invention can be carried out at a pressure equal to or greater than the vapor pressure of the input stream mixture and / or the reaction mixture at the respective reaction temperature, preferably at a pressure of less than 40 bar.

[0020] The isomerization in step b. is also preferably carried out in the liquid phase. It should be clear that in this case the pressure and temperature must be chosen so that the input stream is or can be present in the liquid phase.

[0021] In the isomerization of the present invention, the one or more reactors may also contain a variety of catalysts based on zeolites or ion exchange resins. For example, a mixture of ion exchange resins with different reactivities may be used. Similarly, the reactor may contain catalysts with different activities, which are arranged, for example, in layers. If multiple reactors are used, each reactor may be filled with the same or different (one or more) catalysts based on zeolites or ion exchange resins.

[0022] The isomerization of the present invention uses a catalyst based on a zeolite or an ion exchange resin as a heterogeneous catalyst. The corresponding zeolites and ion exchange resins are widely available and known to those skilled in the art. It has been found that the Si:Al ratio of the zeolite-based catalyst is preferably 40:1 to 200:1. In addition, styrene-divinylbenzene types, preferably in the H form and in a partially neutralized form, are very suitable as catalysts based on ion exchange resins.

[0023] When the catalyst is a zeolite, some zeolites have proven to be particularly advantageous, such as β-zeolite and γ-zeolite. Therefore, the zeolite is preferably selected from Z-β-H-25, Z-β-H-38, Z-β-H-360, Z-Mor-H-20, ZYH-60, ZYH-80, Z-β-H, Z-CFG-1, Z-β-ammonium-38, Z-CBV 760CY (1.6), Z-CBV 780CY (1.6), CP 814E CY (1.6), CBV500CY (1.6), H-CZB-150 and mixtures thereof.

[0024] The ion exchange resin used can be, for example, an ion exchange resin prepared by sulfonation of a phenol / aldehyde condensate or by sulfonation of a cooligomer of an aromatic vinyl compound. Examples of aromatic vinyl compounds used to prepare cooligomers are: styrene, vinyltoluene, vinylnaphthalene, vinylethylbenzene, methylstyrene, vinylchlorobenzene, vinylxylene and divinylbenzene. It is particularly preferred to use an ion exchange resin prepared by sulfonation of a cooligomer formed by the reaction of styrene and divinylbenzene for isomerization. The ion exchange resin can be made into a gel-like, macroporous or spongy state. It is well known that the properties of these resins, in particular the specific surface area, porosity, stability, expansion or contraction and exchange capacity, can be changed by the preparation process.

[0025] Preferred ion exchange resins of the styrene-divinylbenzene type are sold, inter alia, under the following trade names: CT 151 and CT 275 from Purolite, 15. 35. IR-120, 200, Dowex M-31 from Dow, Lanxess K 2621, K-2431.

[0026] The pore volume of the ion exchange resins which can be used as catalysts, in particular preferably ion exchange resins of the styrene-divinylbenzene type, is preferably 0.3 to 0.9 ml / g, more preferably 0.5 to 0.9 ml / g. The pore volume can be determined, for example, by adsorption techniques. The particle size of the ion exchange resin is preferably 0.3 mm to 1.5 mm, more preferably 0.5 mm to 1.0 mm. Narrower or wider particle size distributions can be selected. Thus, for example, ion exchange resins with very uniform particle sizes (monodisperse resins) can be used.

[0027] The ion exchange resins which can be used as catalysts for the isomerization can be present as partially neutralized ion exchange resins. For this purpose, the ion exchange resins can be treated with acids or bases, as described in EP 1360160B1.

[0028] The isomerization in step b. then results in a product stream in which the proportion of 2,4,4-trimethylpent-2-ene is lower than in the input stream and the proportion of 2,4,4-trimethylpent-1-ene is higher than in the input stream. In a preferred embodiment of the invention, the proportion of 2,4,4-trimethylpent-1-ene in the product stream is from 60 to 80 mol %, preferably from 65 to 80 mol %. The proportion of 2,4,4-trimethylpent-2-ene in the product stream is then from 20 to 40 mol %, preferably from 20 to 35 mol %. DETAILED DESCRIPTION

[0029] The present invention is described below by way of examples. These examples are for illustration only and do not limit the subject matter of the present invention.

[0030] Example

[0031] Example 1

[0032] 2.4 g of the catalyst according to the invention (Purolite CT 275, partially neutralized, 0.9 eq / L) are charged into a tubular reactor with a diameter of 0.6 cm. 2,4,4-trimethylpent-2-ene (>99%) is fed into the reactor. The isomerization is carried out at a temperature of 55° C. and ambient pressure. After leaving the reactor, the distribution of 2,4,4-trimethylpent-2-ene to 2,4,4-trimethylpent-1-ene is determined (2,4,4-trimethylpent-2-ene:2,4,4-trimethylpent-1-ene in the input stream 99:1). The analysis is carried out by gas chromatography. The peak areas are evaluated by external calibration.

[0033]

[0034] a After 80 hours of testing time.

[0035] The results show that the catalyst of the present invention is very suitable for isomerization.

[0036] Example 2

[0037] 2.0 g of the catalyst according to the invention (CBV760) are charged to a tubular reactor with a diameter of 0.6 cm. 2,4,4-trimethylpent-2-ene (>99%) is fed to the reactor. Here, 2,4,4-trimethylpent-2-ene is conducted through the reactor at a volume flow rate of 0.12 g / min. The isomerization is carried out at a temperature of 55° C. and ambient pressure. After leaving the reactor, the distribution of 2,4,4-trimethylpent-2-ene to 2,4,4-trimethylpent-1-ene is determined (2,4,4-trimethylpent-2-ene:2,4,4-trimethylpent-1-ene in the input stream 99:1). The analysis is carried out by gas chromatography. The peak areas are evaluated by external calibration.

[0038]

[0039] a After 24 hours of experimental time.

[0040] The results show that the catalyst of the present invention is very suitable for isomerization.

Claims

1. A method for isomerizing 2,4,4-trimethylpent-2-ene to 2,4,4-trimethylpent-1-ene, wherein the method comprises at least the following steps: a. providing an input stream, the input stream containing 2,4,4-trimethylpent-2-ene and 2,4,4-trimethylpent-1-ene, wherein the proportion of 2,4,4-trimethylpent-2-ene in the total stream is at least 25 mol %, based on the total input stream; b. isomerizing the input stream using a heterogeneous catalyst based on zeolites or ion exchange resins, The proportion of 2,4,4-trimethylpent-2-ene in the product stream is lower than that in the input stream, and the proportion of 2,4,4-trimethylpent-1-ene in the product stream is higher than that in the input stream.

2. The process according to claim 1 or 2, wherein the proportion of 2,4,4-trimethylpent-1-ene in the product stream is 60 to 80 mol %, preferably 65 to 80 mol %.

3. The process according to any one of claims 1 to 3, wherein the proportion of 2,4,4-trimethylpent-2-ene in the product stream is from 20 to 40 mol %, preferably from 20 to 35 mol %.

4. The process according to any one of the preceding claims, wherein the isomerization in step b is carried out at a pressure of less than 40 bar.

5. The process according to any one of the preceding claims, wherein the isomerization in step b is carried out at a temperature of 25 to 90°C, preferably 30 to 80°C, particularly preferably 35 to 70°C.

6. A process according to any one of the preceding claims, wherein the zeolite has a Si:Al ratio of from 40:1 to 200:

1.

7. The process according to any one of the preceding claims, wherein the zeolite is selected from the group consisting of β-zeolite and γ-zeolite.

8. A process according to any one of the preceding claims, wherein the catalyst is a zeolite and is selected from the group consisting of Z-β-H-25, Z-β-H-38, Z-β-H-360, Z-Mor-H-20, ZYH-60, ZYH-80, Z-β-H, Z-CFG-1, Z-β-ammonium-38, Z-CBV 760CY(1.6), Z-CBV 780CY(1.6), CP 814E CY(1.6), CBV 500CY(1.6), H-CZB-150 and mixtures thereof.

9. The process according to claim 1, wherein the ion exchange resin used is an ion exchange resin which has been prepared by sulfonation of phenol / aldehyde condensates or by sulfonation of cooligomers of aromatic vinyl compounds.

10. The process according to any one of the preceding claims, wherein the aromatic vinyl compound used to prepare the cooligomer is selected from styrene, vinyltoluene, vinylnaphthalene, vinylethylbenzene, methylstyrene, vinylchlorobenzene, vinylxylene and divinylbenzene.

11. A process according to any one of the preceding claims, wherein the ion exchange resin used is an ion exchange resin prepared by sulfonation of cooligomers formed by the reaction of styrene with divinylbenzene.

12. The process according to any one of the preceding claims, wherein the ion exchange resin used is a partially neutralized ion exchange resin.

13. The process according to any one of the preceding claims, wherein the isomerization is carried out in the liquid phase.

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