Hydroformylation process of short-chain olefins in the gas phase

Abstract

The present invention relates to a process for the hydroformylation of short-chain olefins, in particular C2-C5 olefins, in which the catalyst system is immobilized on a support consisting of a porous ceramic material and in which synthesis gas or carbon monoxide is passed through the reactor during the idle time of the process.

Description

Technical Field

[0001] The project related to this patent application is funded by the European Union (EU) research and innovation program "Horizon 2020" (grant agreement number 869896). The present invention relates to a process for the hydroformylation of short-chain olefins, in particular C2-C5 olefins, in which the catalyst system is immobilized on a support consisting of a porous ceramic material, and to a process in a reactor in which synthesis gas or carbon monoxide is passed through the reactor during process shutdown.

Background Art

[0002] Hydroformylation, with an annual world production capacity of millions of tons, is one of the most important reactions in industrial chemistry. In this process, an alkene (olefin) is converted using a catalyst with a mixture of carbon monoxide and hydrogen (also known as synthesis gas or syngas) to form aldehydes, which are important and valuable intermediates in the production of bulk chemicals such as alcohols, esters, and plasticizers. Hydroformylation is carried out almost exclusively with homogeneous catalysts on an industrial scale. Soluble transition metal catalyst systems are usually cobalt- or rhodium-based and are often used for the hydroformylation of short-chain olefins together with phosphorus-containing ligands such as phosphines or phosphites.

[0003] Known methods have various problems, especially related to the fact that rhodium, cobalt, and their compounds are relatively expensive. To avoid catalyst loss during the hydroformylation process as much as possible, a great deal of energy and process engineering are required, including extremely complex processes such as a catalyst recycling step. Furthermore, the product purification process to ensure that as little catalyst residue remains in the product as possible has become more complex. A further problem with known homogeneous catalyst processes is the stability of the ligands that must withstand the conditions of hydroformylation such as temperature, pressure, pH value, etc., and the consumption of the solvent used in the process, which must be replenished by subsequent dosing.

[0004] To avoid the above problems in hydroformylation with homogeneous catalysts, hydroformylation processes have been developed that heterogenize the catalyst system, particularly by immobilization on a support material. Thus, the terms "heterogenization" and "immobilization" are understood to mean that the catalyst is immobilized by forming a thin liquid film on the surface and / or in the pores of a solid support material using an ionic liquid, and there is no reaction solution in the conventional sense in which the catalyst is uniformly dissolved. Hydroformylation processes in which the catalyst is heterogenized on a support material are disclosed, for example, in Patent Documents 1 to 4.

[0005] When carrying out hydroformylation with a heterogeneous catalyst, problems may arise when there is an idle time, for example during maintenance work or for other production-related reasons. In the context of the present invention, idle time (downtime, stop time) means that during this time the feed mixture cannot be passed through the reactor and thus hydroformylation cannot be carried out. After such an idle time, the performance of the reaction is usually lower, i.e., the conversion and selectivity are lower. This is probably due to the formation of high-boiling substances and the destruction of the catalyst. To avoid the formation of high-boiling substances, the product mixture is usually purged with nitrogen from the reaction space during the idle time. Nevertheless, it has been found that the performance of the reactor still deteriorates afterwards.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

[0007] Therefore, the problem of the present invention is to provide a hydroformylation process of olefins that does not exhibit the above problems and can, in particular, resume operation more rapidly and without loss of catalytic activity after an idle time. [Means for Solving the Problems]

[0008] This problem is achieved according to claim 1 of the present application in that the reactor is purged with synthesis gas or carbon monoxide during the idle time. Thus, product residues are purged from the reaction space and the catalyst complex is protected by a high CO partial pressure. [Modes for Carrying Out the Invention]

[0009] Accordingly, the present invention is a process for hydroformylating C2-C8 olefins in a reaction zone using a heterogeneous catalyst system, the process comprising feeding a gaseous feed mixture comprising C2-C8 olefins, together with synthesis gas, onto a support consisting of a porous ceramic material in which a hydroformylation catalyst system comprising a Group 8 or 9 metal of the Periodic Table, at least one organophosphorus-containing ligand and a stabilizer is immobilized, wherein the support is in the form of a monolith, i.e., a block of ceramic material, or in the form of powder, granules or a shaped body, and the support consists of a hydrocarbon-based, hydrogen nitride-based, silicide-based material or a mixture thereof, wherein there is an idle time during which the gaseous feed mixture does not pass through the reactor, and during the idle time the reactor is purged with the synthesis gas or carbon monoxide, thereby providing a process.

[0010] The feature of the present invention is to purge the reactor with synthesis gas and carbon monoxide during the idle time. Thereby, after the idle time, it becomes possible to achieve a higher conversion rate and yield compared to other purge gases, and thus the reactor can be returned to normal operation more quickly. The temperature during the purge with synthesis gas or carbon monoxide is preferably in the range of 20 to 200 °C, more preferably in the range of 22 to 175 °C, and even more preferably in the range of 85 to 150 °C. Further, during the idle time, the reactor is preferably maintained at a maximum of 10 °C lower than the reaction temperature. This is to avoid cooling. The pressure during the purge is not so important, but it should not exceed the pressure during hydroformylation.

[0011] The feed mixture used may be any mixture containing C2 - C8 olefins as reactants, preferably C2 - C5 olefins, especially ethene, propene, 1 - butene, 2 - butene, 1 - pentene or 2 - pentene. The amount of olefin in the feed mixture should, of course, be an amount sufficient to operate the hydroformylation reaction economically. Examples of feed mixtures that can be used in the process according to the invention include, in particular, industrial mixtures from the petrochemical industry, such as raffinate streams (raffinate I, II or III) or crude butane. According to the invention, crude butane contains 5 - 40% by mass of butene, preferably 20 - 40% by mass of butene (the butene consists of 1 - 20% by mass of 1 - butene and 80 - 99% by mass of 2 - butene) and 60 - 95% by mass of butane, preferably 60 - 80% by mass of butane.

[0012] The method according to the invention is carried out in at least one reactor in which the hydroformylation according to the invention takes place. The carrier with the heterogeneous catalyst system is arranged in at least one reactor. In a further embodiment of the invention, the process may also be carried out in a plurality of reactors which may be connected in parallel or in series. Preferably, in this case, the reactors are connected in parallel and used alternately.

[0013] Hydroformylation is preferably carried out under the following conditions: The temperature of the hydroformylation is in the range of 65 to 200 °C, preferably 75 to 175 °C, more preferably 85 to 150 °C. The temperature may be set by a suitable cooling device, such as a cooling jacket. The pressure in the hydroformylation is desirably not exceeding 35 bar, preferably 30 bar, particularly preferably 25 bar. The molar ratio of the synthesis gas to the feed mixture should be 6:1 to 1:1, preferably 5:1 to 3:1. In some cases, the feed mixture may be diluted with an inert gas, such as an alkane present in an industrial hydrocarbon stream.

[0014] The catalyst system used in the hydroformylation process according to the present invention preferably comprises a transition metal of Group 8 or Group 9 of the Periodic Table of the Elements, particularly iron, ruthenium, iridium, cobalt or rhodium, more preferably cobalt and rhodium, or particularly preferably rhodium, at least one organophosphorus-containing ligand and a stabilizer.

[0015] The stabilizer is preferably an organic amine compound, more preferably of the following formula (I):

[0016]

Chemical formula

[0017] In a particularly preferred embodiment of the present invention, the stabilizer is of the following formulae (I.1), (I.2), (I.3), (I.4), (I.5), (I.6), (I.7) and (I.8):

[0018]

Chemical formula

[0019]

Chemical formula

[0020]

Chemical formula

[0021]

Chemical formula

[0022] For all film - forming components, i.e., in this case the stabilizer, the gas solubility of the reactants should be better than that of the product. This alone can achieve a partial separation between the reactant olefin used and the product aldehyde formed. In principle, other film - forming substances can also be considered for this purpose, but care should be taken so that no high - boiling - point formation occurs and / or the resupply of the reactant olefin is surely restricted.

[0023] The organophosphorus - containing ligand for the catalyst system according to the present invention can be selected from any ligand known in hydroformylation. A number of suitable ligands are known to those skilled in the art from patent and technical literature, for example, mono - or biphosphite ligands. The organophosphorus - containing ligand preferably has the following general formula (II): R’ - A - R” - A - R”’ (II) (wherein R’, R’’, and R’’’ are each an organic group, provided that R’ and R’’’ are not the same, A is a - O - P(-O)2 - group for each of the two cross - links, and two of the three oxygen atoms - O - are each bonded to the group R’ and the group R’’’ respectively) There is a biphosphite structure represented by the following formula. The organic groups R’, R’’, and R’’’ preferably do not have a trialkoxysilane group at the terminal.

[0024] In a preferred embodiment, R', R'' and R''' in the compound of formula (VI) are preferably selected from substituted or unsubstituted 1,1'-biphenyl groups, 1,1'-binaphthyl groups and ortho-phenyl groups, particularly from substituted or unsubstituted 1,1'-biphenyl groups, provided that R' and R''' are not the same. More preferably, the substituted 1,1'-biphenyl group has an alkyl group and / or an alkoxy group, particularly a C1-C4 alkyl group, more preferably a tert-butyl and / or methyl group, and / or preferably a C1-C5 alkoxy group, more preferably a methoxy group, at the 3,3' and / or 5,5' positions of the 1,1'-biphenyl basic structure.

[0025] According to the present invention, the above catalyst system is present in a heterogeneous form on a carrier made of a porous ceramic material. The term "heterogeneous on a carrier" in the context of the present invention is understood to mean that the catalyst system is immobilized by a stabilizer to form a thin solid or liquid film on the inner surface and / or outer surface of the solid carrier material. This film may be solid at room temperature and liquid under the reaction conditions. More specifically, the inner surface of the carrier includes the inner surface of the pores. The concept of immobilization includes both the case where the catalyst system and / or the catalytically active species are dissolved in a solid or liquid film, and the case where the stabilizer acts as an adhesion promoter or the catalyst system is adsorbed on the surface but not chemically / covalently bonded to the surface. Therefore, according to the present invention, the catalyst system is dispersed on the surface of the carrier and / or in the pores, rather than in a reaction solution in the conventional sense where the catalyst is uniformly dissolved.

[0026] The porous support material is preferably selected from the group consisting of nitride ceramics, carbide ceramics, silicide ceramics and mixtures thereof, such as carbonitride materials. The nitride ceramic is preferably selected from silicon nitride, boron nitride, aluminum nitride, and mixtures thereof. The carbide ceramic is preferably selected from silicon carbide, boron carbide, tungsten carbide, or mixtures thereof. It may be a mixture of a carbide ceramic and a nitride ceramic known as a carbonitride. The silicon nitride ceramic (silicide ceramic) is preferably molybdenum disilicide (molybdenum silicide). The carrier according to the invention to which the catalyst system is applied preferably consists of a carbide ceramic, particularly preferably silicon carbide. In this case, the carrier may be present as a carrier, i.e., a block of ceramic material, or in the form of a powder, in the form of a granular material, or in the form of a shaped body. If the carrier is a monolith, the carrier consists of a block of porous ceramic material (a three-dimensional object). The block may be single-piece or may be composed of a plurality, i.e., at least two, individual parts, which can be joined to each other to form the block and / or may be fixed to each other or connected to each other in a detachable manner.

[0027] The carrier made of a porous ceramic material is preferably a three-dimensionally extending component, and in principle, its cross-section may be of any geometric shape, for example, circular, angular, square, or a similar shape. In a preferred embodiment, the three-dimensionally extending component that can be used as the carrier has the main flow direction (the direction in which the feed mixture and the synthesis gas flow from the inlet to the outlet of the reactor) as the longitudinal direction (the direction of the longest extension).

[0028] The carrier monolith of the porous ceramic material formed in this way has at least one continuous flow path (channel) in the main flow direction. However, the channels are not completely continuous and may be designed to terminate at the end opposite to the inlet of the reactor or to be closed towards this end. The carrier monolith may have at least two or more flow paths. The diameter of the channel may range from 0.25 to 50 mm, preferably from 1 to 30 mm, more preferably from 1.5 to 20 mm, and particularly preferably from 2 to 16 mm. When there are a plurality of channels, the diameters of the channels may be the same or different from each other. The diameter of the channel is selected in comparison with the diameter of the whole carrier or one of the diameters, especially so as not to impair the mechanical stability.

[0029] Furthermore, the carrier monolith made of the ceramic material is porous, that is, it has pores. In particular, the catalyst system according to the present invention is also arranged in these pores in the solid or liquid film. The pore diameter preferably ranges from 0.9 nm to 30 μm, more preferably from 10 nm to 25 μm, and particularly preferably from 70 nm to 20 μm. The pore diameter can be determined by nitrogen adsorption or mercury porosimetry in accordance with DIN 66133 (June 1993 edition).

[0030] In a preferred embodiment, the carrier monolith has at least partially continuous pores extending from the surface to the channels and / or from one channel to the nearest channel. A plurality of pores may be connected to each other and thus form a single continuous pore.

[0031] According to the present invention, the carrier may exist in the form of powder, granules, or in the form of shaped bodies such as pellets, rings, spheres. The average particle size (d50) of the carrier may be 0.1 mm to 7 mm, preferably 0.3 mm to 6 mm, particularly preferably 0.5 mm to 5 mm. The average particle size can be measured by an imaging method, particularly the methods defined in ISO 13322-1 (as of December 1, 2004) and ISO 13322-2 (as of November 1, 2006). The production of the carrier in the form of powder, granules or shaped bodies can be carried out according to methods known to those skilled in the art. For example, it can be carried out by mechanically crushing a monolith of carbide, nitride, silicide material or a mixture thereof, such as with a jaw crusher, and adjusting the particle size of the obtained crushed granules by sieving.

[0032] Similar to the carrier monolith, the particles of the ceramic material in the form of powder, granules or shaped bodies are porous, i.e., they have pores. In particular, the catalyst system according to the present invention is also arranged in these pores in the solid or liquid film. The pore diameter is preferably in the range of 0.9 nm to 30 μm, more preferably in the range of 10 nm to 25 μm, particularly preferably in the range of 70 nm to 20 μm. The pore diameter can be measured by nitrogen adsorption or mercury porosimetry according to DIN 66133 (version of June 1993).

[0033] The production of the carrier, whether it is a monolith, powder, granules or shaped body, is carried out as described below: The provided powder, granules or pellets of ceramic material serving as a carrier can further have applied thereto a so-called washcoat, which consists of the same or a different ceramic material, preferably silicon oxide, from the ceramic material to which it is applied. The washcoat itself can be porous or non-porous, preferably it is non-porous. The particle size of the washcoat is preferably from 5 nm to 3 μm, more preferably from 7 nm to 700 nm. The washcoat is used to introduce or generate a desired pore size and / or to increase the surface area of the support. The washcoat can be applied, in particular, by dipping (dip coating) the carrier into a washcoat solution containing the ceramic material of the washcoat (optionally as a precursor). The amount of the washcoat on the carrier is ≤20% by mass, preferably ≤15% by mass, particularly preferably ≤10% by mass, based on the total amount of the carrier. However, in a preferred embodiment of the present invention, the carrier has no washcoat. The catalyst system is applied to the carrier regardless of the presence or absence of the washcoat.

[0034] The catalyst system is applied to the carrier with or without using a washcoat. For this purpose, first a catalyst solution is prepared by mixing, in particular at room temperature and ambient pressure, the catalyst solution containing at least one organophosphorus-containing ligand, at least one metal precursor, for example a chloride, oxide, carboxylate of each metal, at least one stabilizer and at least one solvent. Optionally, an ionic liquid can be used in the preparation of the catalyst system, but the catalyst solution can also be prepared without using an ionic liquid. In particular, the catalyst solution is prepared in an inert environment, for example in a glove box. The "inert environment" in this case means an atmosphere containing as little water and oxygen as possible. The solvent can be selected from all solvent classes (protic, aprotic, polar or non-polar). Prerequisites for the solvent are the solubility of the catalyst system (ligand, metal precursor, stabilizer and optionally the ionic liquid), and preferably also the high boiling point formed in hydroformylation. The solubility can be increased by heating during the immobilization step.

[0035] The solvent is preferably an aprotic and polar or aprotic polar solvent such as acetonitrile or ethyl acetate, or an aprotic non-polar solvent such as THF or diethyl ether. Also, a chlorinated hydrocarbon such as dichloromethane or an aldehyde may be used as the solvent.

[0036] The catalyst solution thus produced is brought into contact with a support (which may include a washcoat in some cases) by, for example, immersion (dip coating) or by filling a pressure vessel, for example, by direct injection into the reactor (in-situ impregnation). When applying the catalyst solution outside the reactor, it is necessary to remove the solvent and then reinstall the support in the reactor. Preferably, the catalyst solution is applied directly to the support together with the washcoat inside the reactor. This can avoid potentially time-consuming installation and removal steps as well as potential contamination of the catalyst.

[0037] The injection of the catalyst solution into the reactor can be carried out from a normal inlet or outlet, for example, using a pump. The liquid distributor or nozzle inside the reactor can ensure uniform distribution of the catalyst liquid and, in some cases, can control the existing pressure loss equipment and injection rate.

[0038] After applying the catalyst system, the solvent is separated. First, the catalyst solution is discharged from the outlet of the reactor. The solvent remaining in the reactor is vaporized by adjusting the pressure or increasing the temperature. In other embodiments, the pressure can be adjusted while simultaneously increasing the temperature. Depending on the solvent, the temperature can be set between 20 and 150 °C. For some solvents, a high vacuum (10 -3 ~10 -7 mbar) can be set, but depending on the solvent and temperature, an overpressure of several mbar to several bar may also be acceptable.

[0039] The stabilizer and, if present, the ionic liquid are immobilized on the support together with the catalyst composed of a transition metal, especially cobalt or rhodium, and the organophosphorus-containing ligand. The catalyst system can be applied to the carrier either by direct injection into the reactor (including in-situ impregnation) or outside the reactor. When applying the catalyst system outside the reactor, the carrier must always be transported in a state without air, which can be achieved, for example, with a nitrogen countercurrent. In a preferred embodiment of the present invention, the catalyst system is applied directly into the reactor, i.e., in-situ. After separating the solvent, the reactor can be immediately used to fill the feed mixture. This has the advantage that it does not require time-consuming installation and removal steps that would shut down the reactor for a long time. Furthermore, the size of the carrier is no longer restricted in that a suitable space, which is an inert environment, can be utilized in a specific size. The size of the carrier can be freely selected according to the design of the reactor.

[0040] Once the catalyst system has been applied to the carrier and the solvent has been separated, the system, more specifically the reactor, can be started using a two-stage or multi-stage start-up procedure. That is, it can be put into operation. Suitable start-up procedures are disclosed, for example, in European Patent Application No. 3632887.

[0041] From the reaction zone in which the hydroformylation according to the present invention is carried out, a gaseous effluent containing at least a portion of the formed product aldehyde and at least a portion of the unreacted olefin is continuously removed. The gaseous effluent can be subjected to one or more physical separation steps, in which the gaseous effluent is separated into at least one phase rich in unreacted olefin and at least one phase rich in product aldehyde. The separation of substances can be carried out using known substance separation processes such as condensation, distillation, centrifugation, nanofiltration or some combination thereof, preferably condensation or distillation. In the case of multi-stage separation, the product aldehyde-rich phase formed during the first separation can be fed to a second separation, in particular to the downstream aldehyde separation, where the product aldehyde is separated from other substances present in this phase, often generally alkanes and the reactant olefins. The phase rich in unreacted olefins can be returned to the hydroformylation process or, in the case of a multi-stage configuration, to one of the hydroformylation steps in order to hydroformylate the olefins contained therein to the product aldehyde.

[0042] In addition to the above phases, during the separation of substances, it is also possible to remove a purge gas stream having at least a similar or identical composition to the phase rich in unreacted olefins. The purge gas stream can be led to a second substance separation or aldehyde separation in order to separate the product aldehyde contained therein and remove impurities (e.g., nitrogen in synthesis gas) or inert substances (e.g., alkanes in the feed mixture) from the system. Impurities or inert substances can usually be removed, for example, at the top of a column, during the second separation of substances as volatile substances.

[0043] A further object of the present invention is also that the present invention relates to a plant comprising a reactor capable of carrying out the process according to the present invention and in particular in which the hydroformylation process according to the present invention is carried out. Furthermore, the plant can include a substance separation unit in which the gaseous effluent of the hydroformylation step is separated into at least one phase rich in unreacted olefins and at least one phase rich in product aldehyde, and the substance separation unit is arranged downstream of the hydroformylation according to the present invention. Downstream of the first substance separation unit, there may be a second substance separation unit, in particular an aldehyde separation unit, in which the product aldehyde is separated.

[0044] Even without further explanation, it is considered that those skilled in the art can make the most of the above description. Therefore, the preferred embodiments and examples should be construed merely as descriptive disclosure and should in no way be construed as limiting disclosure. The present invention will be described in more detail below with reference to examples. Alternative embodiments of the present invention are available in a similar manner.

Examples

[0045] [Examples 1 - 4] Purge with different gases during the idle time of the system. The starting material used for the carrier was SiC pellets (SiC3 - E2 - HP). These SiC pellets were placed in a circular reactor sleeve with a length of 20 cm and a diameter of 1 inch (about 2.54 cm), and glass beads of a similar size were filled above and below the pellets accordingly. These SiC pellets were exposed to a catalyst solution containing Rh(acac)(CO)2, bisphos (ligand), bis(2,2,6,6 - tetramethyl - 4 - piperidyl) sebacate (stabilizer), and dichloromethane as a solvent. For this purpose, after flushing (purging) the reactor with nitrogen, the catalyst solution was introduced into the reactor at a slight overpressure. After extracting and evaporating the solvent from the reactor, the catalyst system homogenized on the carrier granulate was used for hydroformylation. A hydrocarbon stream with the following composition was used as the feed mixture:

[0046]

Table 1

[0047]

Table 2

Claims

1. A process for hydroformylating C2-C8 olefins in a reaction zone using a heterogeneous catalyst system, the process comprising supplying a gaseous feed mixture containing C2-C8 olefins together with synthesis gas onto a carrier made of a porous ceramic material on which a hydroformylation catalyst system containing a metal of Group 8 or 9 of the periodic table, at least one organophosphorus-containing ligand, and a stabilizer is heterogeneously arranged, wherein, The carrier exists as a monolith, i.e., a block of ceramic material, or in the form of powder, granules, or a molded body, and the carrier consists of hydrocarbon-based, hydrogen nitride-based, silicide-based materials, or mixtures thereof, where, There is an idle period during which the gaseous supply mixture does not pass through the reactor, and during the idle period the reactor is purged with the synthesis gas or carbon monoxide. process.

2. The process according to claim 1, wherein no wash coat is applied to the carrier and the carrier is used without the wash coat.

3. The organophosphorus-containing ligand of the hydroformylation catalyst system is given by the following general formula (II): R'-A-R''-A-R''' (II) (In the formula, R', R'' and R''' are each organic groups, however R' and R''' are not identical, and both A are bridging -O-P(-O)) ２ (It is a - group, and two of the three oxygen atoms -O- are bonded to groups R' and R''' respectively.) The process according to claim 1, as represented by the statement.

4. The stabilizer is given by the following formula (I) 【Chemistry 1】 The process according to claim 1, wherein the organic amine compound comprises at least one 2,2,6,6-tetramethylpiperidine unit.

5. The process according to claim 1, wherein the carrier is a nitride ceramic, the nitride ceramic being selected from silicon nitride, boron nitride, aluminum nitride and mixtures thereof; or a carbide ceramic, the carbide ceramic being selected from silicon carbide, boron carbide, tungsten carbide and mixtures thereof; or a silicide ceramic, the silicide ceramic being molybdenum silicide.

6. The process according to claim 5, wherein the carrier is the carbide ceramic.

7. The process according to claim 6, wherein the carrier is silicon carbide.

8. The process according to claim 1, wherein the hydroformylation is carried out at a temperature in the range of 65 to 200°C, 75 to 175°C, or 85 to 150°C.

9. The process according to claim 1, wherein the pressure during hydroformylation is 35 bar or less, 30 bar or less, or 25 bar or less.

10. The process according to claim 1, wherein the hydroformylation catalyst system does not contain an ionic liquid.

11. The process according to claim 1, wherein a C4 olefin is used in the hydroformylation step.

12. The process according to claim 1, wherein the metal of group 8 or group 9 of the periodic table is rhodium.

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