Methods for controlling the hydroformylation process

Abstract

A method for optimizing the production rate of a hydroformylation process for producing a mixture of n-(N)aldehyde and iso(I)aldehyde is described. The process involves contacting an olefin with carbon monoxide, hydrogen, and a catalyst comprising (A) a transition metal, (B) a monophosphine, and (C) a tetraphosphine having a specific structure. The hydroformylation production rate is increased stepwise by sequentially performing at least three of the following operations: 1.) Establish an optimized H2 / CO partial pressure ratio limited to greater than 0.4:1 and less than 2.5:1. 2.) Increase the partial pressure of syngas while limiting the CO partial pressure in at least one reaction zone to 30 psi at the optimized ratio established in step 1. 3.) Increase the partial pressure of olefin in at least one reaction zone while limiting that up to 2% of the olefin feed in the first reaction zone is not lost via the purge vent flow in the final reaction zone or the alkampage flow in any olefin recovery process. 4.) Reduce the concentration of monophosphine in the reaction fluid to a lower limit of approximately 1.5% by weight. 5.) Increase the temperature in at least one reaction zone to a limit of approximately 98°C. and 6.) Increase the concentration of transition metal in the reaction fluid, but not exceeding 1200 ppmw in the reaction zone. [Formula 1] JPEG2026523050000011.jpg71170

Description

[Technical Field]

[0001] The present invention relates to a method for maintaining or increasing the hydroformylation reaction rate for a hydroformylation process comprising polyphosphine and monophosphine catalyst systems. [Background technology]

[0002] It is known in the art that aldehydes can be readily produced by reacting olefinic unsaturated compounds with carbon monoxide and hydrogen in the presence of a solubilized rhodium-phosphite ligand complex catalyst, and that preferred types of such processes involve sequential hydroformylation. For example, U.S. Patent No. 3,527,809 discloses the hydroformylation of α-olefins for the production of aldehydes at low temperature and low pressure. This process uses a specific rhodium complex to effectively catalyze the hydroformylation of olefins with hydrogen and carbon monoxide under a predetermined set of variables in the presence of a selected triorganolin ligand.

[0003] Among the catalysts described in U.S. Patent No. 3,527,809 are compounds containing rhodium and triarylphosphine ligands, particularly triarylphosphine ligands exemplified by triphenylphosphine ("TPP"). Commercial hydroformylation processes have successfully utilized rhodium-TPP catalysts for decades, and a key aspect of the operation is the use of a large excess of TPP relative to rhodium. For example, industrial propylene hydroformylation processes are often operated with TPP concentrations of 10–12 weight percent, based on the total mass of the reaction fluid. Such high concentrations of TPP are used to achieve the regioselectivity of the desired product and to improve catalyst stability. Regarding the reaction kinetics of such rhodium-monophosphine systems, there are references such as "Propylene Hydroformylation with Rhodium Carbonyls and Triphenylphosphine: II Kinetics of Butyraldehyde Formation," PCd'Oro (et.al.), La Chimica E L'Industria, v.62, 1980, 572-579, which states that for rhodium-TPP systems containing propylene, the rate is a function of propylene, rhodium, and ligand concentrations (but not CO or H2). However, U.S. Patent No. 4,277,627(A) teaches that parameters such as reactant partial pressure, ligand concentration, and temperature have limitations that can lead to catalyst deactivation and a decrease in reaction rate. These two references teach that while short-term effects on rate can be determined by kinetic studies, maintaining a stable rate over long periods is more complex.

[0004] U.S. Patent Application Publication 2021 / 0114010 teaches a catalyst composition comprising a combination of monophosphine and tetraphosphine ligands, and a hydroformylation process using the same. U.S. Patent 11,130,725 discloses that certain monophosphines stabilize tetraphosphine-based hydroformylation catalysts and / or reduce the amount of tetraphosphine used, and International Publication 2019 / 231611 teaches that the N / I ratio (described below) can be adjusted by changing the amount of monophosphine present in a mixed polyphosphine and monophosphine catalyst system.

[0005] The initial conditions for the hydroformylation process can be developed using kinetic parameters as described above, along with practical limitations based on equipment capacity (volume, pressure rating, stirring capacity, etc.), heat removal limitations, solubility, and product / catalyst separation limitations, as is known to those skilled in the art. However, it has been observed that after a certain period, catalytic activity changes from the initial optimized design. Even in the absence of an obvious degradation mechanism, catalytic activity can decrease due to several factors, including toxins introduced via the feed (e.g., sulfur or halogens), accumulation of heavy substances (i.e., accumulation of inert substances occupying the reactor volume), and entrainment losses of the catalyst in the product-catalyst separation zone (typically the vaporizer). While initial plant operating conditions may be optimized to reflect the behavior of the new catalyst, it would be desirable to have a design that allows for further optimization of parameters if apparent catalytic activity decreases. In other cases, a plant may choose to reduce production for a certain period, as market demand may decrease. When market demand returns, it is desirable to increase the rate in the most efficient way. Furthermore, a plant may be desired to increase the production rate beyond normal levels to cope with short-term spikes in demand. In such cases, it is desirable to increase the hydroformylation rate in an efficient manner to maximize economic value, and furthermore, if the change can be easily reversed, the equipment can be quickly returned to normal operation.

[0006] Unlike catalysts consisting of rhodium and a single ligand, there is no teaching on how to control process conditions to optimize the performance of mixed tetraphosphine and monophosphine systems, such as those described in U.S. Patent Application Publication 2021 / 0114010. While the above references provide examples of good operation for each ligand individually and for specific combinations of ligands, they do not provide guidance on how to modify process conditions (such as reagent partial pressure and temperature) to achieve optimal performance and best economic value.

[0007] Olefin efficiency is a critical economic consideration in industrial hydroformylation processes. As apparent catalytic activity decreases, the olefin conversion rate typically declines, potentially leading to the loss of higher levels of unconverted olefins along with the product or in reactor vents. Recovery and recycling of unconverted olefins can mitigate some of this loss. Examples of such recovery processes are described in U.S. Patent No. 6,969,777, International Publication No. 2017160956, and Chinese Patent No. 104610032. However, these systems are complex and have limited capacity, and may not be able to cope if hydroformylation catalytic activity drops significantly or if the olefin supply rate is too high.

[0008] Furthermore, the hydrogenation of olefins to alkanes is known to occur in hydroformylation systems. This conversion to undesirable by-products reduces olefin efficiency and should therefore be minimized.

[0009] In hydroformylation processes, the regioselectivity of the product is typically expressed as the ratio of the linear (or normal) product to the branched (or iso)aldehyde product. As used herein, this ratio of linear (or normal) to branched (or iso)aldehyde products is referred to as the "N / I ratio" or "N / I". While branched products have value, linear products are often preferred. The ability to vary N / I over a wide range has been described previously (see, for example, International Publication No. 2008 / 115740, U.S. Patents No. 8,741,173, 8,598,389, and 11,344,869). However, some facilities may choose to maintain a relatively constant N / I ratio to simplify the purification process and meet downstream requirements.

[0010] Optimizing the N / I ratio and target aldehyde production rate while maximizing olefin efficiency and catalyst lifetime is a crucial economic drive in industrial hydroformylation processes. Therefore, in some examples, optimal economics can be achieved at intermediate production rates with high N / I and high olefin efficiency. Given that catalyst performance may change during long-term continuous operation, it is desirable to have readily available means for optimizing the operation of polyphosphine / monophosphine catalysts so that the desired hydroformylation rate can be achieved at substantially the same N / I ratio while minimizing cost and process inefficiencies. It is preferable that such methods are reversible and allow the plant to adapt to changing market demands. [Overview of the Initiative]

[0011] The present invention relates to a method for optimizing the operation of a hydroformylation process involving a polyphosphine / monophosphine ligand catalyst. It has been found that a series of changes to certain operating parameters allows for an increase or maintenance of the hydroformylation rate while maintaining a consistent N / I ratio with minimal loss of olefin efficiency. The changes are mostly reversible and allow for a slowdown of the production rate in case of shifts in market demand.

[0012] In one embodiment, a method for optimizing the production rate of a hydroformylation process for producing a mixture of n-(N)aldehyde and iso(I)aldehyde, the process comprising contacting an olefin with carbon monoxide, hydrogen, and a catalyst, the catalyst comprising (A) a transition metal, (B) a monophosphine, and (C) a tetraphosphine having the following structure,

[0013] [ka] In the formula, each P is a phosphorus atom, and R 1 ~R 46 Each of these is independently hydrogen, a C1-C8 alkyl group, an aryl group, an alkaryl group, or a halogen, and the contact is carried out in one or more reaction zones under hydroformylation conditions that produce a blend of n-(N) aldehyde and iso(I) aldehyde in an N / I ratio, and the hydroformylation rate is determined by the following operation, i.e., 1. Establish an optimized H2 / CO partial pressure ratio, limited to greater than 0.4:1 and less than 2.5:1. 2. In the optimized ratio established in step 1, increase the partial pressure of syngas while limiting the partial pressure of CO in at least one reaction zone to 30 psi. 3. Increase the partial pressure of the olefin in at least one reaction zone to a level that does not exceed the point at which more than 2% of the olefin feed is lost via the purge vent flow in the final reaction zone or the alkampage flow of any olefin recovery process. 4. Reduce the concentration of monophosphine in the reaction fluid to a lower limit of approximately 1.5% by weight. 5. Raise the temperature in at least one reaction zone to a limit of approximately 98°C. 6. The concentration of the transition metal in the reaction fluid is increased, but the concentration in the reaction zone does not exceed 1200 ppmw. This can be increased gradually by sequentially implementing at least three of these steps.

[0014] Surprisingly, it was found that both the N / I ratio and the hydroformylation rate are almost independent of the hydrogen partial pressure. However, the rate of alkane byproduct formation is highly dependent on the hydrogen-to-carbon monoxide ratio (H2 / CO ratio). In one embodiment, the present invention includes the step of optimizing the H2 / CO ratio to minimize alkane formation. Thus, the CO partial pressure is optimized to achieve a desired N / I ratio, and then the H2 partial pressure is optimized to minimize alkane formation and to accommodate any slight changes in N / I due to the H2 partial pressure. The range of the optimized H2 / CO partial pressure ratio is >0.4:1 to <2.5:1, preferably >0.6:1, most preferably >0.9:1, but less than 2.0:1, preferably less than 1.5:1, and most preferably less than 1.04:1. Surprisingly, it was found that as long as this ratio is maintained, the syngas pressure (i.e., the sum of H2 and CO) can be increased while minimizing the effect on alkane formation. While not bound by theory, an increase in CO appears to mitigate undesirable hydrogenation. Maintaining a consistent CO:H2 ratio for the hydroformylation unit also simplifies the operation of the upstream syngas unit.

[0015] Surprisingly, it was found that the hydroformylation rate of the catalyst of the present invention initially shows a positive order relationship with the CO partial pressure, and then a negative relationship at higher pressures (where the CO partial pressure is typically greater than about 30 psi). In one embodiment, a second step of the present invention involves increasing the CO gas partial pressure up to a limit of about 65 psi for the syngas. This provides an increase in the hydroformylation rate until the reaction order of CO becomes negative (typically CO below 30 psi). The higher the CO partial pressure, the lower the N / I ratio of the product tends to be, limiting the degree of rate increase that can be achieved without significantly affecting the N / I ratio. Therefore, whether the CO partial pressure should be increased or decreased depends on where the system is on the CO partial pressure versus production rate curve, and the magnitude of the pressure change is limited by at least one of (A) the negative order region reached, in which case further increases in CO partial pressure result in a decrease in the hydroformylation rate, or (B) a substantial change in N / I. In one embodiment, the upper limit of the CO partial pressure has been found to be 20-30 psi, which is the point at which the catalyst system becomes negative in CO. The H2 and CO partial pressures can be determined by methods well known in the art, such as gas chromatography, and can be measured directly in the reactor headspace or inert purge vent.

[0016] In one embodiment, a third step of the present invention includes increasing the partial pressure of the olefin. In processes where unreacted olefins in the final reactor are not recovered, the olefin pressure can be increased until the amount of olefin lost in the final reaction zone vent constitutes about 2% or less of the total olefin supplied into the first reaction zone. In one embodiment, this can be determined by measuring the partial pressure of the olefin in the exhaust stream and the flow rate of the exhaust stream. The olefin partial pressure can be determined by methods well known in the art, such as gas chromatography (GC), and can be measured directly in the reactor headspace or inert purge vent. In another embodiment, the concentration of the olefin (e.g., mol%) is measured directly in the vent stream by GC and used to calculate the olefin loss based on the flow rate of the vent stream.

[0017] Optionally, to minimize the loss of unreacted olefins from the reactor vent and / or downstream vaporizer or purification process, an olefin recovery process as described in U.S. Patent No. 6,969,777 (B2), U.S. Patent No. 10,407,372, and Chinese Patent No. 113387780 (A) can be used. In such a system, the olefin partial pressure can be increased until the amount of olefin in the alkane purge of the olefin recovery system reaches 2% of the total olefin feed to the first reaction zone.

[0018] In one aspect, the fourth step of the present invention involves reducing the concentration of monophosphine. This can be achieved by purging a portion of the process fluid. In a preferred embodiment, the monophosphine concentration decreases over time by evaporating it with the crude product. In such an embodiment, the addition of monophosphine to the process (usually done to maintain the target concentration) is interrupted until a new, lower target concentration is reached. The lower limit of the acceptable monophosphine concentration is 1.5 wt% or more, most preferably 3 wt% or more in the catalyst solution, and the overall catalyst stability and performance are maintained.

[0019] In one aspect, the fifth step of the present invention involves increasing the temperature of at least one reaction zone. A significant increase in the reactor temperature increases the formation of heavy by-products and the decomposition rate of expensive polyphosphines. In one embodiment, the upper limit of the reaction zone temperature is 98 °C.

[0020] In one embodiment, the sixth step of the process of the present invention is to increase the transition metal concentration. Rhodium is very expensive, and therefore it is well known that the addition of rhodium incurs a direct economic cost. Furthermore, the decomposition rate of the tetraphosphine ligand may depend on the transition metal concentration. The tetraphosphine concentration is typically increased even during the addition of the transition metal to maintain a tetraphosphine:transition metal molar ratio higher than 1:1. Increasing the tetraphosphine concentration also tends to increase the decomposition of the tetraphosphine ligand. However, the benefit of increasing the hydroformylation rate can often justify the cost.

[0021] Independently increasing the amount of a transition metal (e.g., rhodium) alters the tetraphosphine:rhodium and monophosphine:rhodium ratios, and therefore, the N / I behavior may be affected depending on the degree of transition metal addition. It is preferable that the tetraphosphine and / or monophosphine be added together with, or within a short period immediately thereafter, the rhodium catalyst precursor described herein (e.g., rhodium dicarbonylacetylacetonate).

[0022] Based on these factors, the upper limit for transition metal addition is the point at which the decomposition rate of the tetraphosphine ligand becomes uneconomical, and / or the concentration of the ligand and / or the resulting active (transition metal):(tetraphosphine) in the reaction fluid originating from the product:catalyst separation zone (typically the vaporizer) approaches its solubility limit. It was determined that the maximum transition metal concentration for the process of the present invention is less than 1200 ppm.

[0023] When market demand declines, a plant may choose to reduce production accordingly. This is typically done by reducing the supply of olefins to the process. Another scenario is when a shortage of raw materials necessitates a reduction in the production rate. When market demand increases or raw material availability improves, the plant will want to have the most efficient process to increase the production rate. During lower production periods, catalyst performance may have changed due to introduced impurities, accumulation of heavy materials, changes in ligand composition, or other factors. Therefore, the teachings of the present invention enable a process to recover a desired level of production in the most efficient manner.

[0024] By carrying out the process of the present invention as described herein, olefin efficiency can be optimized, a relatively consistent N / I ratio can be maintained, and the hydroformylation rate can be increased or maintained at a desired target. Each step can be performed as needed, and the time between steps can vary and is not critical to the present invention. A hypothetical example of the process of the present invention is shown in Figure 1. [Brief explanation of the drawing]

[0025] [Figure 1] This graph shows how the reaction rate and N:I ratio might hypothetically change in response to the various processes outlined herein. [Figure 2] This graph shows the results of Example 1. [Figure 3] This graph shows the results of Example 2. [Figure 4] This graph shows the results of Example 3. [Figure 5] This graph shows the results of Example 4. [Figure 6] This graph shows the results of Example 5. [Figure 7] This graph shows the results of Example 6. [Figure 8] This graph shows the results of Example 7. [Figure 9] This graph shows the results of Example 8. [Figure 10] This graph shows the results of Example 9. [Modes for carrying out the invention]

[0026] All references to the periodic table of elements and its various groups are from the version published in the CRC Handbook of Chemistry and Physics, 72nd Ed. (1991-1992), CRC Press, page I-11.

[0027] Unless otherwise stated or implied in the context, all parts and percentages are based on weight, and all test methods are as of the filing date of this application. For the purposes of U.S. patent practice, any referenced patent, patent application, or publication is incorporated by reference in its entirety (or an equivalent U.S. version thereof) particularly with respect to definitional disclosures (to the extent that they do not conflict with any definitions specifically provided herein) and general knowledge in the art.

[0028] As used herein, “a,” “an,” “the,” “at least one,” and “one or more” are interchangeable. “Comprise,” “include,” and their variations are not limited in meaning when these terms appear in the specification and claims.

[0029] Furthermore, in this specification, an enumeration of numerical ranges by endpoints includes all numbers contained within that range (for example, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.). For the purposes of the present invention, it should be understood in accordance with what a person skilled in the art will understand that a numerical range is intended to include and support all possible subranges that may be contained within that range. For example, the range 1 to 100 is intended to convey 1.01 to 100, 1 to 99.99, 1.01 to 99.99, 40 to 60, 1 to 55, etc. Also, in this specification, an enumeration of numerical ranges and / or numbers, including such statements in the claims, can be read as including the term “about”. In such cases, the term “about” refers to substantially the same numerical ranges and / or numbers as those enumerated herein.

[0030] As used herein, the terms "ppm" and "ppmw" are interchangeable and mean parts per million by weight.

[0031] For the purposes of the present invention, the term "hydrocarbon" is intended to include all acceptable compounds having at least one hydrogen atom and one carbon atom. Such acceptable compounds may have one or more heteroatoms. In a broader embodiment, acceptable hydrocarbons include aromatic and non-aromatic organic compounds, which may be substituted or unsubstituted, acyclic (with or without heteroatoms) and cyclic, branched and unbranched, carbocyclic and heterocyclic.

[0032] As used herein, the term “substituted” is intended to include all permissible substituents of an organic compound unless otherwise indicated. In broad embodiments, permissible substituents include acyclic and cyclic, branched and unbranched, carbocyclic and heterocyclic, aromatic and non-aromatic substituents of the organic compound. Exemplary substituents include, for example, alkyl, alkyloxy, aryl, aryloxy, hydroxyalkyl, aminoalkyl (which may have 1 to 20 or more carbon atoms, preferably 1 to 12), as well as hydroxy, halo, and amino. For a given organic compound, there may be one or more permissible substituents, which may be the same or different. The present invention is not intended to be limited in any way by the permissible substituents of an organic compound.

[0033] As used herein, the term "hydroformylation" is intended to include, but is not limited to, all hydroformylation processes in which a reaction containing one or more substituted or unsubstituted olefin compounds is converted into one or more substituted or unsubstituted aldehydes or a reaction mixture containing one or more substituted or unsubstituted aldehydes. The aldehydes may be asymmetric or asymmetric.

[0034] Unless otherwise specified, the terms “hydroformylation rate,” “hydroformylation production rate,” and “production rate” as used herein are interchangeable and refer to the total mass or moles of aldehyde produced per unit time. Side reactions such as hydrogenation to hydrocarbons and aldol condensation to heavy materials are not included in the calculation of the production rate. The production rate may be expressed in different units, such as the number of moles of aldehyde per liter of reaction fluid per unit time, based on convention or preference. In one embodiment, the production rate is calculated and expressed as the total number of moles of butyraldehyde produced per liter of reaction fluid per hour (moles / L / hour). This term may be further limited by the amount of a particular aldehyde isomer produced, such as “linear aldehyde production rate,” which is specific to one particular aldehyde.

[0035] As used herein, the term “olefin efficiency” is intended to include the percentage of olefin supplied to the process that is converted to the desired aldehyde product. Hydrogenation of olefins to alkanes and purging of unreacted olefins from reactor vents or olefin recovery units adversely affect olefin efficiency. Olefin efficiency is typically determined by performing a mass balance of the system. For example, if 9.8 moles of the desired aldehyde product are produced per unit time for every 10 moles of olefin supplied, an olefin efficiency of 98% is achieved.

[0036] As used herein, the term “reaction zone” is intended to include at least one hydroformylation reactor. In some embodiments, the reaction zone includes two or more reactors in series. In some embodiments, the reaction zone includes multiple continuous stirred tank reactors (CSTRs) in series.

[0037] As used herein, the terms “optimized H2 / CO ratio” and “optimized H2 / CO partial pressure ratio” are intended to refer to a mixture of hydrogen and carbon monoxide consisting of hydrogen and carbon monoxide as a molar ratio measured as partial pressure within the reaction zone, rather than as a ratio in the feed stream or a ratio of the feed stream.

[0038] As used herein, the term “optimized syngas” is intended to include a mixture of hydrogen and carbon monoxide at an optimized H2 / CO partial pressure ratio determined by the partial pressure within the reaction zone. Unless otherwise specified, the terms “H2 / CO ratio” or “H2 / CO partial pressure ratio” refer to the gas partial pressures observed within the reaction zone, not the ratio in the feed stream, which may differ. Thus, increasing the optimized syngas partial pressure involves increasing the pressures of both hydrogen and carbon monoxide at the optimized H2 / CO ratio. The terms “optimized syngas pressure” and “optimized syngas partial pressure” are intended to include only the partial pressures of H2 and CO (excluding olefins and inert substances). The partial pressures of hydrogen and CO can be determined by the total pressure and by many methods, including gas chromatography or spectroscopic techniques well known to those skilled in the art.

[0039] As used herein, the terms “optimized aldehyde production” or “optimized aldehyde rate” are used interchangeably and refer to achieving a target aldehyde production rate at an acceptable N / I with high olefin efficiency. In some cases, a facility may choose to slow production due to decreased demand or market conditions, in which case achieving high olefin efficiency and a consistent product mixture remains important. Therefore, optimized aldehyde production is not the same as the maximum hydroformylation rate.

[0040] The terms “reaction fluid,” “reaction medium,” and “catalyst solution” are used interchangeably herein and may include, but are not limited to, (a) a transition metal-monophosphine complex catalyst (e.g., rhodium-triphenylphosphine complex catalyst), (b) a transition metal-tetraphosphine complex catalyst (e.g., rhodium-tetraphosphine complex catalyst), (c) a free monophosphine (e.g., triphenylphosphine), (d) a free tetraphosphine, (e) an aldehyde product formed during the reaction, (f) unreacted reactants, (g) a solvent for the transition metal complex catalyst and the free phosphine ligand, and optionally (h) a mixture containing the decomposition products of the monophosphine ligand and the tetraphosphine ligand. The reaction fluid may include, but is not limited to, (a) the fluid in the reaction zone, (b) the fluid stream en route to the separation zone, (c) the fluid in the separation zone, (d) the recirculation stream, (e) the fluid withdrawn from the reaction zone or separation zone, and (f) the fluid in the external cooler.

[0041] The term “ligand decomposition products” is intended to include, but not be limited to, any and all compounds obtained from one or more chemical transformations of at least one of the tetraphosphine molecules and / or monophosphine molecules packed into the reaction fluid. Such compounds may include, but are not limited to, triphosphine or diphosphine compounds derived from rhodium-enhanced cleavage of the parent tetraphosphine, as well as smaller phosphine moieties obtained from such cleavage side reactions. The ligand decomposition products are also intended to include alkyldiarylphosphines known to be present in rhodium-triarylphosphine hydroformylation catalyst solutions (see, for example, U.S. Patent No. 4,297,239, column 5). The ligand decomposition products are further intended to include any and all compounds obtained from the oxidation of phosphine moieties. For example, ligand decomposition products may include phosphine oxides derived from the oxidation of monophosphine introduced into the process, the partial or complete oxidation of tetraphosphine introduced into the process, or phosphine compounds obtained from rhodium-enhanced side reactions (e.g., oxidation of triphosphine compounds derived from parent tetraphosphine).

[0042] As used herein, the terms "tetradentate phosphine" and "tetraphosphine" are interchangeable and are intended to include compounds containing four phosphine atoms bonded to three carbon atoms, respectively.

[0043] As used herein, the terms "monodentate phosphine" and "monophosphine" are used interchangeably and include compounds containing a single phosphine atom bonded to three carbon atoms.

[0044] As used herein, the terms “rhodium complex,” “rhodium complex catalyst,” and “catalytic complex” are interchangeable and are intended to include at least one rhodium atom bonded or coordinated via an electron interaction of a ligand. Examples of such ligands include, but are not limited to, monophosphines, tetradentate phosphines, carbon monoxide, olefins (e.g., propylene), and hydrogen.

[0045] As used herein, the term “free” phosphine is intended to include monophosphine molecules or tetraphosphine molecules that are not bonded to or coordinated to rhodium.

[0046] In general, the present invention relates to a method for maintaining the N / I ratio of aldehydes produced by a hydroformylation process. The catalyst composition comprises two ligands, a monophosphine, and a tetraphosphine, and the N / I ratio of the resulting aldehyde can be slightly increased or decreased by adding one or the other ligand to the reaction zone. Changes in syngas partial pressure can also shift the N / I ratio, but the goal is to maintain a nearly constant proportion of linear butyraldehyde in the product.

[0047] In one embodiment, a method for optimizing the production rate of a hydroformylation process for producing n-(N)aldehyde and iso(I)aldehyde, the process comprising contacting an olefin with carbon monoxide, hydrogen, and a catalyst, the catalyst comprising (A) a transition metal, (B) a monophosphine, and (C) a tetraphosphine having the following structure,

[0048] [ka] In the formula, each P is a phosphorus atom, and R 1 ~R 46 Each of these is independently hydrogen, a C1-C8 alkyl group, an aryl group, an alkaryl group, or a halogen, and the contact is carried out in one or more reaction zones under hydroformylation conditions that produce a blend of n-(N) aldehyde and iso(I) aldehyde in an N / I ratio, and the hydroformylation rate is determined by the following operation, i.e., 1. Establish an optimized H2 / CO partial pressure ratio, limited to greater than 0.4:1 and less than 2.5:1. 2. In the optimized ratio established in step 1, increase the partial pressure of syngas while limiting the partial pressure of CO in at least one reaction zone to 30 psi. 3. Increase the partial pressure of the olefin in at least one reaction zone to a level that does not exceed the point at which more than 2% of the olefin feed is lost via the purge vent flow in the final reaction zone or the alkampage flow in any olefin recovery process. 4. Reduce the concentration of monophosphine in the reaction fluid to a lower limit of approximately 1.5% by weight. 5. Raise the temperature in at least one reaction zone to a limit of approximately 98°C. 6. The concentration of the transition metal in the reaction fluid is increased, but not exceeding 1200 ppmw in the reaction zone. This can be increased in steps by carrying out at least three, preferably four, five, or even all six of these steps, preferably in the order listed.

[0049] Steps 1-5 can be easily reversed (i.e., the rate can be reduced by reversing the changes), but step 6 is almost irreversible. However, it should be understood that the production rate can be reduced if desired by lowering the reactor temperature after step 6 (reversing step 5). It should also be understood that combining steps (e.g., performing both steps 1 and 2 simultaneously) or skipping a single step is intended and still falls within the scope of the invention. At least three, preferably four, and more preferably all five of the first five steps should be performed in the order listed, but performing one of the steps in a different order (e.g., step 4 before step 2) is considered within the scope of the invention, although it is not expected to be optimal. The time between steps is not specified in the invention and is instead determined by the observed performance of the system.

[0050] In some embodiments, the monophosphine is one or more of the following: triphenylphosphine, tris(o-tolyl)phosphine, trinaphthylphosphine, tri(p-methoxyphenyl)phosphine, tri(m-chlorophenyl)-phosphine, trimenzylphosphine, tricyclohexylphosphine, dicyclohexylphenylphosphine, cyclohexyldiphenylphosphine, and trioctylphosphine. In some embodiments, the monophosphine is triphenylphosphine. In some embodiments, the catalyst comprises a mixture of different monophosphine species.

[0051] In some embodiments, the structure of the tetraphosphine is R 1 ~R 46 Each of these is hydrogen. In some embodiments, the catalyst comprises one or more of the following tetraphosphines.

[0052] [ka]

[0053] In some embodiments, the transition metal is rhodium, and the monophosphine is triphenylphosphine, R 1 ~R 46 Each of them is hydrogen, and the olefin contains propylene.

[0054] In some embodiments, the amount of monophosphine in the reaction zone is greater than 1.5 weight percent based on the total weight of the reaction fluid in the reaction zone. In some embodiments, the amount of monophosphine in the reaction zone is 1.5 to 13 weight percent based on the total weight of the reaction fluid in the reaction zone. In some embodiments, the amount of monophosphine in the reaction zone is 4 to 8 weight percent based on the total weight of the reaction fluid in the reaction zone. In some embodiments, the amount of tetraphosphine in the reaction zone is greater than 0.06 weight percent based on the total weight of the reaction fluid in the reaction zone. In some embodiments, the amount of tetraphosphine in the reaction zone is 0.1 to 9 weight percent based on the total weight of the reaction fluid in the reaction zone. In some embodiments, based on the total weight of the reaction fluid in the reaction zone, the amount of monophosphine in the reaction zone is greater than 1.5 weight percent, and the amount of tetraphosphine in the reaction zone is greater than 0.06 weight percent, and preferably less than 5 weight percent, 2 weight percent, or 1 weight percent, most preferably less than about 0.4 weight percent. In some embodiments, based on the total weight of the reaction fluid in the reaction zone, the amount of monophosphine in the reaction zone is 1.5 to 13 weight percent, and the amount of tetraphosphine in the reaction zone is 0.1 to 9 weight percent.

[0055] Hydrogen and carbon monoxide may be obtained from any suitable source, including petroleum cracking and refining operations.

[0056] Surprisingly, the CO partial pressure was found to be the dominant variable for both the hydroformylation rate and the N / I ratio, compared to the H2 partial pressure. Furthermore, excess hydrogen reduces olefin efficiency due to hydrogenation side reactions that form alkanes (e.g., propane). Therefore, the first step of the process of the present invention includes establishing an optimized H2 / CO partial pressure ratio to minimize alkane formation and thereby improve olefin efficiency. As found and disclosed herein, the optimized H2 / CO partial pressure ratio is preferably greater than 0.4:1, preferably greater than 0.6:1, more preferably greater than 0.7:1, most preferably greater than 0.9:1, and less than 2.5:1, preferably less than 1.5:1, and most preferably less than 1.04:1.

[0057] In commercial-scale operations, the ratio may vary depending on the limitations of the equipment and measurements, but generally the ratio is within 20% of the target value (i.e., values ​​of 0.9:1 to 1:1.3 may be observed against a target of 1.1:1.0), preferably within 10% of the target value, or most preferably within 5%. Apart from these unintended variations, the optimized H2 / CO partial pressure ratio is maintained throughout all steps of the process of the present invention.

[0058] Syngas (derived from synthesis gas) is the name given to a gas mixture containing varying amounts of CO and H2. Methods of production are well known. While hydrogen and CO are typically the main components of syngas, syngas may also contain CO2 and inert gases such as N2 and Ar. Syngas is commercially available and is often used as a fuel source or as an intermediate for producing other chemicals. In one embodiment, step 2 of the present invention involves increasing the optimized syngas partial pressure. For clarity, the partial pressures of both hydrogen and carbon monoxide are increased incidentally so that an optimized H2 / CO partial pressure ratio is maintained during step 2 of the present invention.

[0059] The ratio of H2 to CO in the syngas feed to the reaction zone can be varied by methods known in the art, including pressure swing absorption separation and membrane separation processes. In some cases, the facility may not have the ability to vary the ratio in the feed, which may limit the optimization in step 1. Some control of the headspace partial pressure is provided by reactor headspace venting. It has been found that the headspace composition may differ from the feed composition, and therefore some control of the headspace partial pressure ratio may be affected by changes in the vent flow, especially if the vent is not discarded for delivery to a downstream reactor. In a preferred embodiment, a syngas separation unit is used to deliver a CO-rich flow to the hydroformylation zone and an H2-rich flow to a downstream hydrogenation unit.

[0060] In one embodiment, step 3 of the present invention includes increasing the partial pressure of olefins in the reaction zone. In some embodiments, the partial pressure of olefins in the reaction zone is increased by increasing the rate of olefin supply to at least one reaction zone. Recognizing that partial pressure and concentration are related, the use of a higher partial pressure of olefins results in an increased proportion of olefins in the liquid catalyst fluid. It has been found and disclosed herein that the hydroformylation rate exhibited by the catalyst of the present invention has a positive order relationship with respect to olefin concentration. Thus, increasing the partial pressure of olefins in the reaction zone accelerates the hydroformylation reaction but may also increase the concentration of olefins in the “off-gas” (e.g., inert substance purge vent) of the final reaction zone. A high olefin content in the “off-gas” means lower olefin efficiency, as it may be necessary to purge a portion of the gas flow from the product recovery zone before recirculating to the liquid in order to remove inert substances (e.g., alkanes). Therefore, indiscriminately increasing the partial pressure of olefins in the reaction zone may reduce olefin efficiency and adversely impact the economics of the process. In one embodiment, step 3 of the present invention includes increasing the olefin supply rate to at least one reaction zone to a level not exceeding the point at which more than 2% of the olefin supply is lost via the purge vent flow of the final reaction zone or the alkampurge flow of any olefin recovery process. The olefin concentration in the reaction zone headspace or purge flow can be measured by one or more analytical techniques such as gas chromatography, and the flow rate of the purge flow can be measured by one or more mass flowmeters well known to those skilled in the art.

[0061] When market demand decreases and a plant reduces production by decreasing olefin supply, the amount of unreacted olefin in the final reaction zone is typically very low. If it is desired to return the plant to normal production levels, the olefin supply may be returned to its original (e.g., plant design) flow rate, which increases the partial pressure of olefin in the reaction zone. However, due to changes in the catalyst or catalyst solution composition, the system may not return to its initial performance. In this case, the process of the present invention allows the plant to return production to the design rate in a cost-effective manner.

[0062] In some embodiments, the catalyst of the present invention has been used in commercial production for approximately six months, and the observed aldehyde productivity has decreased from the initial target. The process of the present invention provides the best results for optimized plant performance when the steps are performed in a predetermined sequence. The time between each step is not critical to the present invention, but the sequence is particularly important for obtaining optimal performance.

[0063] In some embodiments, apparatus designed to recover unreacted olefins, such as propylene, from an inert material purge stream can be used (see, for example, U.S. Patent No. 6,969,777, International Publication No. 2017160956, and Chinese Patent No. 104610032). In such embodiments, the increase in olefin partial pressure is generally limited by the propylene partial pressure in the alkamp purge stream originating from a propylene recovery unit containing no more than 2% of the total olefins supplied to the first reaction zone. The olefin concentration in the olefin recovery purge stream is measured by one or more analytical techniques, such as gas chromatography.

[0064] In one embodiment, a fourth step of the process of the present invention includes reducing the concentration of monophosphine. In one embodiment, a catalyst solution containing rhodium, one equivalent or more of tetraphosphine, and monophosphine is subjected to catalyst-product separation zone conditions that volatilize at least some of the free monophosphine along with the aldehyde product. In some embodiments, the monophosphine removed along with the product is replenished to maintain a nearly constant concentration of monophosphine in the process fluid. Such monophosphine addition can be carried out in batches or continuously. Surprisingly, a negative order relationship has been found between the monophosphine concentration and the hydroformylation rate. In other words, reducing the monophosphine concentration in the reaction fluid by volatilization (e.g., vaporization) and pausing the addition of monophosphine increases the observed production rate. Although tetraphosphine and transition metal catalysts are high molecular weight compounds with very low volatility, the volatility of monophosphine is known, and its ability to control its concentration in the reaction fluid is known to those skilled in the art. For example, U.S. Patent No. 5,110,990 describes a method for minimizing the volatilization of monophosphine in a reaction fluid, such that those skilled in the art will understand that the volatilization of monophosphine in the reaction fluid can be accelerated by not performing the procedure described in this patent. The lower limit of the monophosphine concentration in the process of the present invention is ≤1.5% by weight. The monophosphine concentration can be measured by one or more analytical techniques, such as high-performance liquid chromatography (HPLC).

[0065] In one embodiment, the process of step 2 can be repeated while step 4 is being performed. It has been found that as the monophosphine level decreases and the production rate increases, the N / I ratio also tends to increase. As mentioned above, an unintended consequence of step 2 (i.e., the increase in CO partial pressure) was a potentially low N / I ratio. Therefore, step 2 can be used to offset the higher N / I ratio from step 4.

[0066] In one embodiment, a fifth step of the process of the present invention includes increasing the temperature of at least one reaction zone. It is known to those skilled in the art that the hydroformylation rate generally increases with increasing temperature. It is also known that higher temperatures often have unintended negative consequences, including, but not limited to, increased formation of heavy byproducts, accelerated ligand decomposition rates, and shortened catalyst lifetime. Increased tetraphosphine decomposition has adverse effects on the economics of the process. In the process of the present invention, it has been determined and disclosed herein that the temperature of the reaction zones should not be raised above 98°C.

[0067] In another embodiment, a sixth step of the process includes increasing the transition metal concentration in the reaction fluid, subject to the above-described restrictions on ligand decomposition rate, tetraphosphine:metal molar ratio, and solubility. The maximum transition metal concentration in the process of the present invention is 1200 ppmw.

[0068] Advantageously, a solvent is used in the hydroformylation process. Any suitable solvent that does not excessively interfere with the hydroformylation process may be used. Examples of suitable solvents for rhodium-catalyzed hydroformylation processes include those disclosed in U.S. Patents 3,527,809, 4,148,830, 5,312,996, and 5,929,289. In rhodium-catalyzed hydroformylation processes, it may be desirable to use an aldehyde compound as the main solvent that corresponds to the aldehyde product to be produced and / or a higher boiling point aldehyde liquid condensation byproduct that may be produced in situ during the hydroformylation process, for example, as described in U.S. Patents 4,148,830 and 4,247,486. The main solvent typically ultimately contains both the aldehyde product and higher boiling point aldehyde liquid condensation by-products ("heavy products"), due to the nature of the continuous process. The amount of solvent is not particularly important and only needs to be sufficient to provide the desired amount of transition metal concentration in the reaction medium. Typically, the amount of solvent ranges from about 5% to about 95% by weight, based on the total weight of the reaction fluid. A mixture of solvents may also be used.

[0069] The catalyst of the present invention comprises a transition metal, a monophosphine, and a tetraphosphine. In certain useful embodiments, the catalyst comprises rhodium, a monophosphine, and a tetraphosphine. The most desirable catalyst is halogen-free, such as metal-bonded chlorine, and contains at least one of the monophosphine and tetraphosphine that complex with hydrogen, carbon monoxide, and rhodium metal, thereby producing a catalyst that is soluble in the above liquid phase and stable under reaction conditions.

[0070] As the transition metal, Group 8, 9, and 10 metals selected from rhodium (Rh), cobalt (Co), iridium (Ir), ruthenium (Ru), iron (Fe), nickel (Ni), palladium (Pd), platinum (Pt), osmium (Os), and mixtures thereof can be mentioned. Preferred metals are rhodium, cobalt, iridium, and ruthenium, more preferably rhodium, cobalt, and ruthenium, particularly rhodium.

[0071] The number of available coordination sites on such metals is well-known in the art. Thus, the catalyst species that can include the complex catalyst mixture can include monomeric, dimeric, or higher nuclearity forms, preferably being a metal, for example, at least one complex-forming organophosphine-containing molecule per molecule of rhodium. For example, the catalyst species of the preferred catalyst used in the hydroformylation reaction is considered to be able to form a complex with carbon monoxide and hydrogen gas in addition to tetraphosphine and / or organophosphine ligands from the perspective of carbon monoxide and hydrogen gas used by the hydroformylation reaction. The exact structure of the catalyst complex is not known, and as described above, two or more active catalyst structures or resting states may exist.

[0072] In certain preferred embodiments, the transition metal is rhodium. Rhodium can be introduced into the liquid phase as a preformed catalyst, for example, a stable crystalline solid, rhodium hydridocarbonyl-tris(triphenylphosphine), RhH(CO)(PPh3)3. Rhodium can be introduced into the liquid bulk as a precursor form that is converted to the catalyst in the system. Examples of such precursor forms are rhodium carbonyltriphenylphosphine acetylacetonate, Rh2O3, Rh4(CO) 12 , Rh6(CO) 16 , and rhodium dicarbonyl acetylacetonate. Both the catalyst compounds that provide the active species in the reaction medium and their preparation are known in the art. See Brown et al., Journal of the Chemical Society, 1970, pp. 2753-2764.

[0073] The rhodium complex catalyst may be in a homogeneous or heterogeneous form. For example, a pre-formed rhodium hydride-carbonyl-phosphine ligand catalyst may be prepared and introduced into the hydroformylation reaction mixture. More preferably, the rhodium-phosphine ligand complex catalyst may be derived from a rhodium catalyst precursor that can be introduced into the reaction medium for the formation of an active catalyst in situ. For example, rhodium dicarbonylacetylacetonate, Rh2O3, Rh4(CO) 12 , Rh6(CO) 16 Rhodium catalyst precursors such as Rh(NO3)3 can be introduced into the reaction mixture along with monophosphine and / or tetraphosphine for the formation of an active catalyst in situ. In a preferred embodiment, rhodium dicarbonylacetylacetonate is used as the rhodium precursor and is combined with at least one of monophosphine and / or tetraphosphine in the solvent and introduced into the reactor along with syngas for the formation of an active catalyst in situ. Additional monophosphine and / or tetraphosphine may be added as needed to achieve and maintain the desired concentration. In any case, carbon monoxide, hydrogen, monophosphine and tetraphosphine are all ligands that can complex with metals, and under the conditions used for the hydroformylation reaction, it is sufficient for at least one active metal-ligand catalyst to be present in the reaction mixture.

[0074] In some embodiments, the catalyst composition is formed in a mixing tank by combining a rhodium catalyst precursor with monophosphine and / or tetraphosphine. If the rhodium catalyst precursor is combined with only one of the two ligands before being added to the reactor, the other ligand may be added separately to the reactor to form the catalyst composition in the reactor.

[0075] The amount of rhodium complex catalyst present in the reaction fluid only needs to be the minimum amount necessary to produce the desired production rate. Generally, a rhodium concentration in the range of 50 ppmw to 1200 ppmw, calculated as free metal in the reaction fluid within the hydroformylation reactor, should be sufficient for most processes, but generally, it is generally preferable to use 150 to 800 ppmw of metal, more preferably 150 to 500 ppmw of rhodium.

[0076] In some embodiments, the catalyst composition (whether fully formed in the mixing tank or in the reactor) contains at least 40 moles of monophosphine per mole of transition metal (preferably rhodium). In some embodiments, the catalyst composition contains 40 to 350 moles of monophosphine per mole of transition metal (rhodium). In some embodiments, the catalyst composition contains at least 1 mole of tetraphosphine per mole of transition metal (rhodium). In some embodiments, the amount of tetraphosphine in the catalyst composition contains 1 to 10 moles of tetraphosphine per mole of transition metal (rhodium). As described in the examples, the molar amounts of monophosphine or tetraphosphine are measured by high-performance liquid chromatography (HPLC). Typical methods are calibrated to weight percentages, but often the level of phosphine ligands is reported as weight percentages because it can be easily converted to moles based on molecular weight to evaluate the ligand:transition metal ratio. The molar amounts of transition metals such as rhodium can be easily measured by analytical techniques such as atomic absorption spectrometry, inductively coupled plasma chromatography, or X-ray fluorescence.

[0077] While the tetraphosphine ligand may decompose into one or more monophosphine compounds, the amount of monophosphines in the catalyst composition and reaction fluid according to embodiments of the present invention is far greater than what would be expected to potentially appear through decomposition. In other words, the majority of monophosphines in the catalyst composition or reaction fluid are added to or filled into the catalyst composition or reaction fluid to provide a specific amount (for example, not derived from tetraphosphines present in the catalyst composition or reaction fluid).

[0078] In commercial operations, ligand concentrations are typically maintained by periodic or continuous addition. To do so, the ligand concentration in the reaction fluid is routinely measured by one or more analytical techniques. High-performance liquid chromatography (HPLC) is typically preferred. Unless otherwise indicated herein, when referring to the amount of ligand in a reaction, the ligand concentration is determined by HPLC as described in the examples. Ligand concentrations in such analyses are often reported as weight percentages, and therefore, these units are often convenient for use in continuous operations.

[0079] R in the tetraphosphine shown above 1 ~R 46 However, in some embodiments where each is hydrogen, the amount of tetraphosphine in the reaction fluid in the reactor of the hydroformylation process is 0.1 to 5 weight percent based on the total weight of the reaction fluid in the reactor. Exemplarily, a preferred catalyst precursor composition essentially consists of a solubilized rhodium complex precursor, at least one of monophosphine and tetraphosphine, and a solvent. Monophosphine and tetraphosphine readily substitute for one of the carbonyl ligands of the rhodium acetylacetonate complex precursor, as seen by the generation of carbon monoxide gas. By introducing the catalyst precursor composition into the reactor, additional monophosphine or tetraphosphine may then be optionally added to achieve the target concentration in the reaction fluid.

[0080] Therefore, the rhodium-ligand complex catalyst in the reaction fluid of the hydroformylation reactor advantageously comprises rhodium that complexes with carbon monoxide and at least one of monophosphine and tetraphosphine. In one embodiment, a mixture of rhodium-ligand complexes is used. For example, the catalyst further comprises rhodium that complexes with carbon monoxide and tetradentate phosphine in a chelated and / or non-chelated manner. The catalyst further comprises rhodium that complexes with one or more monophosphine molecules and carbon monoxide. The exact structure of the catalyst complex is unknown, and as described above, two or more active catalyst structures or static states may exist.

[0081] In addition to the rhodium complex catalyst, free monophosphines (i.e., monophosphines that have not complexed with the metal) are also present in the reaction fluid and, depending on the specific configuration, may be present in the catalyst composition before being supplied to the reactor. The importance of free ligands is taught in U.S. Patent No. 3,527,809, UK Patent Application No. 1,338,225, and Brown et al. (previously cited), pp. 2759-2761. In some embodiments, the hydroformylation process of the present invention may involve 1.5 weight percent or more of free monophosphine in the reaction medium. The reaction fluid may also contain free tetradentate phosphine. In some such embodiments, the concentration of free tetradentate phosphine may range from 0.1 to 5 moles per mole of rhodium.

[0082] In embodiments of the present invention, the monophosphine compound that can function as a ligand is the compound of formula I.

[0083] [ka] In the formula, P is a phosphorus atom, and Y 1 ~Y 3Each of these is independently an aryl group, an alkaryl group, a cycloalkyl group, a benzyl group, a C3-C8 alkyl group, an alkoxy group of 1-8 carbon atoms, an aryloxy group, or a halogen. Exemplary examples include, but are not limited to, triphenylphosphine, tris(o-tolyl)phosphine, trinaphthylphosphine, tri(p-methoxyphenyl)phosphine, tri(m-chlorophenyl)phosphine, tripenzylphosphine, tricyclohexylphosphine, dicyclohexylphenylphosphine, cyclohexyldiphenylphosphine, and trioctylphosphine. In some embodiments, the monophosphine compound may be a sterically hindered phosphine, such as those described in U.S. Patents 4,283,562 and 5,741,945. For example, in some such embodiments, Y in formula I 1 ~Y 3 These can independently be a substituted or unsubstituted C3-C8 alkyl group, a substituted or unsubstituted C5-C8 cycloalkyl group, or a substituted or unsubstituted C6-C12 aryl group.

[0084] In some embodiments, a mixture of monophosphines may be used.

[0085] In embodiments of the present invention, the tetraphosphine compound that can function as a ligand is the compound of formula II.

[0086] [ka] In the formula, each P is a phosphorus atom, and R 1 ~R 46 Each of these is independently hydrogen, a C1-C8 alkyl group, an aryl group, an alkaryl group, a haloalkyl group, or a halogen. In a preferred embodiment, R 1 ~R 46 Each of them is hydrogen. Other examples of tetraphosphine that may be used in some embodiments are described elsewhere in this specification.

[0087] In some embodiments, a mixture of tetraphosphines may be used.

[0088] The hydroformylation process and its operating conditions are well known. In a typical embodiment, an olefin (e.g., propylene) is hydroformylated in a continuous or semi-continuous manner, the product is separated in a separation zone, and the concentrated catalyst solution is recycled to one or more reactors. The recycling procedure generally involves continuously or intermittently withdrawing a portion of the liquid reaction medium containing the catalyst and aldehyde product from the hydroformylation reactor, i.e., the reaction zone, and, if necessary, recovering the aldehyde product therefrom in one or more stages under atmospheric pressure, reduced pressure, or high pressure in a separate distillation zone using a composite membrane as disclosed in U.S. Patents 5,430,194 and 5,681,473, or by a more conventional and preferred method of distilling the aldehyde product, i.e., by vapor separation, and the non-volatile metal catalyst residue is recycled to the reaction zone as disclosed, for example, in U.S. Patent 5,288,918. The condensation of volatile materials, and their separation and further recovery by, for example, further distillation, can be carried out in any conventional manner, the crude aldehyde product can be passed through for further purification and isomer separation as needed, and any recovered reactants (e.g., olefinic starting materials and syngas) can be recycled to the hydroformylation zone (reactor) in any desired manner. The recovered metal catalyst containing the retaining liquid of such membrane separation, or the recovered non-volatile metal catalyst containing the residue of such vaporization separation, can be recycled to the hydroformylation zone (reactor) in any desired conventional manner.

[0089] In a preferred embodiment, the hydroformylation reaction fluid comprises at least a certain amount of five main components or constituents, namely, a solvent, an aldehyde product, a free triphenylphosphine ligand, a free tetraphosphine ligand, and a rhodium catalyst complex comprising rhodium and one or more of tetraphosphine and monophosphine. The hydroformylation reaction mixture composition may, and usually, contain additional components, such as those intentionally used in the hydroformylation process or formed in situ during the process. Examples of such additional components, if used, include unreacted olefin starting materials, carbon monoxide and hydrogen gas, as well as by-products formed in situ, ligand decomposition compounds, and high-boiling point liquid aldehyde condensation by-products, and other inert co-solvent type materials or hydrocarbon additives.

[0090] The hydroformylation process may be carried out using one or more suitable reactors, such as a continuous-stirred tank reactor (CSTR), a Venturi reactor, a bubble column reactor, or a slurry reactor. The optimal size and shape of the reactor depends on the type of reactor used. The reaction zone used may be a single vessel or comprise two or more separate vessels. The separation zone used may be a single vessel or comprise two or more separate vessels. The reaction zone(s) and separation zone(s) used herein may be located in the same vessel or in different vessels. For example, reaction separation techniques such as reaction distillation and reaction membrane separation may occur within the reaction zone(s).

[0091] The hydroformylation process may be carried out by recycling unused starting materials, if necessary. The reaction may be carried out sequentially or in parallel within a single reaction zone or multiple reaction zones. The reaction steps may be influenced by gradually increasing the addition of one of the starting materials to the other. Alternatively, the reaction steps may be combined by the simultaneous addition of the starting materials. The starting materials may be added to each or all of the sequential reaction zones. If complete conversion is not desired or cannot be achieved, the starting materials may be separated from the product, for example, by distillation, and then recycled back into the reaction zone.

[0092] The hydroformylation process may be carried out in either glass-lined stainless steel or similar type of reaction equipment. To control excessive temperature fluctuations or to prevent any possible "runaway" reaction temperatures, one or more internal and / or external heat exchangers may be installed in the reaction zone.

[0093] The hydroformylation process of the present invention may be carried out in one or more steps or stages. The exact number of reaction steps or stages depends on the best compromise between capital cost and the high catalyst selectivity, activity, lifetime, and ease of operation achieved, as well as the inherent reactivity of the starting materials in question, and the stability of the starting materials and the desired reaction product under reaction conditions.

[0094] In one embodiment, the hydroformylation process useful in the present invention may be carried out in a multi-step reactor, such as the one described in U.S. Patent No. 5,728,893. Such a multi-step reactor may be designed with internal physical barriers that create two or more theoretical reaction steps per vessel.

[0095] The hydroformylation process is generally preferred to be carried out in a continuous manner. Continuous hydroformylation processes are well known in the art. The continuous process may be carried out in a single-pass mode, i.e., a vapor mixture containing unreacted olefinic starting material and the vaporized aldehyde product are removed from the liquid reaction mixture, the aldehyde product is recovered from the liquid reaction mixture, and supplemental olefinic starting material, carbon monoxide, and hydrogen are supplied to the liquid reaction medium for the next single pass-through without recirculating the unreacted olefinic starting material. Such recirculation procedures are well known in the art and may involve, for example, liquid recirculation of a metal-organophosphorus complex catalyst fluid separated from the desired aldehyde reaction product, as disclosed in U.S. Patent No. 4,148,830, or gas recirculation procedures, as disclosed in U.S. Patent No. 4,247,486, and may be a combination of both liquid and gas recirculation procedures as needed. The most preferred hydroformylation process involves a continuous liquid catalyst recirculation process. Suitable liquid catalyst recirculation procedures are disclosed, for example, in U.S. Patents No. 4,668,651, No. 4,774,361, No. 5,102,505 and No. 5,110,990.

[0096] In one embodiment, the aldehyde product mixture may be separated from the other components of the crude reaction mixture by any suitable method, such as solvent extraction, crystallization, distillation, evaporation, wipe film evaporation, drip film evaporation, phase separation, filtration, or any combination thereof. It may be desirable to remove the aldehyde products from the crude reaction mixture, as they are formed through the use of scavengers, as described in International Publication No. 88 / 08835. One method for separating the aldehyde mixture from the other components of the crude reaction mixture is by membrane separation, which is described, for example, in U.S. Patents Nos. 5,430,194 and 5,681,473.

[0097] As described above, the desired aldehyde may be recovered from the reaction mixture. For example, recovery techniques disclosed in U.S. Patents No. 4,148,830 and No. 4,247,486 can be used. For example, in a continuous liquid catalyst recirculation process, a portion of the liquid reaction mixture (containing aldehyde products, catalyst, etc.), i.e., the reaction fluid, removed from the reaction zone can be sent to a separation zone, e.g., a vaporizer / separator, and the desired aldehyde product can be separated from the liquid reaction fluid by distillation under atmospheric pressure, reduced pressure, or high pressure in one or more steps, condensed, and collected in a product receiver, and further purified if desired. The remaining non-volatile catalyst containing the liquid reaction mixture can then be recycled to the reactor as much as possible, together with hydrogen and carbon monoxide dissolved in the liquid reactants, after separating any other volatile materials (e.g., unreacted olefins) from the condensed aldehyde product, for example by distillation in any conventional manner, if desired.

[0098] More specifically, the distillation and separation of the desired aldehyde product from the metal-organophosphorus complex catalyst containing the reaction fluid can occur at any preferred temperature. Generally, such distillation is preferably carried out at relatively low temperatures, e.g., below 150°C, and more preferably in the range of 50°C to 140°C. In one embodiment, such aldehyde distillation is carried out under reduced pressure, e.g., under a total gas pressure substantially lower than the total gas pressure used during hydroformylation, if low-boiling aldehydes (e.g., C4 to C6) are involved, or under vacuum if high-boiling aldehydes (e.g., C7 or higher) are involved. For example, a common practice is to subject the liquid reaction product medium removed from the hydroformylation reactor to reduced pressure in order to vaporize a substantial portion of the unreacted gas dissolved in a liquid medium containing a much lower synthesis gas concentration than present in the reaction medium, to a distillation zone, e.g., a vaporizer / separator (where the desired aldehyde product is distilled). Generally, distillation pressures ranging from vacuum to a total gas pressure of up to 340 kPa should be sufficient for most purposes. These separation processes typically include a process purge vent to remove excess syngas, as well as inert substances such as hydrocarbons including N2 and hydrogenated olefins.

[0099] In one embodiment, a fluidized gas may be used within the separation zone to facilitate aldehyde distillation. Such a strip gas vaporizer is described, for example, in U.S. Patent No. 8404903.

[0100] The increased concentration, high temperature, and low partial pressure that occur in the separation zone can adversely affect the catalyst, both in terms of catalyst deactivation and / or increased ligand decomposition.

[0101] Exemplary non-optically active aldehyde products of the hydroformylation process according to embodiments of the present invention depend on the olefin used as a reactant and may include, for example, n-butyraldehyde, isobutyraldehyde, n-barrelaldehyde, 2-methyl-1-butyraldehyde, hexanal, hydroxyhexanal, 2-methyl-1-heptanal, nonanal, 2-methyl-1-octanal, decanal, adipoaldehyde, 2-methylglutaraldehyde, 2-methyladipaldehyde, 3-hydroxypropionaldehyde, and the like.

[0102] In some embodiments where propylene is an olefin undergoing hydroformylation, the product is a mixture of n-butyraldehyde and 2-methylpropionaldehyde. As described above, the ratio of a linear (N) isomer to a branched (I) isomer, such as the ratio of n-butyraldehyde to 2-methylpropionaldehyde (isobutyraldehyde), is conventionally referred to as the N / I ratio or simply N / I. In the case of long-chain olefins, the ratio of the terminal aldehyde to the sum of the branched (internal) aldehydes is referred to herein as the N / I ratio.

[0103] As shown in the table below, each step of the process of the present invention can be effectively carried out within the range defined by the lower and upper limits. Except for #6, all steps can be easily reversed, and it should be understood that the effects will be in the opposite direction as shown below. Furthermore, in #6, some of the other variables, such as #5 (temperature), can be reduced. The time between each step is a function of the specific catalyst and system performance and is not critical to the operation of the present invention.

[0104] [Table 1]

[0105] Since rhodium is very expensive, and therefore implies high working capital costs, step 6 (varying the rhodium concentration) is almost always the least desirable option. Furthermore, it has been found that the decomposition rate of tetraphosphine ligands is higher with increasing transition metal concentrations, which implies another cost disadvantage. However, in systems where catalytic purging is used to remove heavy components, and / or systems where inherent rhodium loss (e.g., due to encombination) may be high, the aforementioned rhodium replenishment can allow for a timely reversal of step 6.

[0106] In some embodiments, after step 6, the process can be repeated starting from step 1 or another subsequent step. As described above, step 2 can be repeated in or during step 4. The time between each step is not important to the operation of the present invention and can be considerable.

[0107] Some embodiments of the present invention will be described in more detail in the following examples. [Examples]

[0108] All parts and percentages in the following examples are by weight unless otherwise indicated. The concentration of ligand A is expressed as a weight percentage of the solution or as equivalents (i.e., moles of ligand A per mole of rhodium). Pressures in the following examples are given in pounds per square inch gauge unless otherwise indicated. Unless otherwise indicated, all operations, such as the preparation of catalyst solutions, are carried out under an inert atmosphere. Comparative experiments are not embodiments of the present invention.

[0109] The gas composition (mol%) is measured by gas chromatography (GC), and the partial pressure is then calculated based on the total pressure using Raul's law. The terms "PPH2", "PPCO", and "PPC3=" refer to the partial pressures of H2, CO, and propylene, respectively.

[0110] The tetradentate phosphine concentration is measured by high-pressure liquid chromatography (HPLC). To prevent oxidation during analysis, the phosphine is derivatized to a stable sulfur phosphine by mixing it with a sulfur-saturated diluent (50:50 volume acetonitrile, THF saturated with elemental sulfur).

[0111] External standard HPLC analysis is performed on an Agilent 1200 Infinity series HPLC with a UHPLC SB-C8 3.0 mm, 1.8 μm guard column, followed by a Zorbax SB-C8 analytical column (3.0 × 150 mm). The solvent gradient is 55% water and the remainder acetonitrile for 4 minutes, then adjusted to 20:80 water:acetonitrile for 22 minutes, and finally back to the original composition for the remainder of the 35-minute run. The solvent flow rate is 1.00 mL / min overall, and the column temperature is maintained at 40°C. Two microliters of sample are injected into the system, and the multi-wavelength UV detector is set to 240 nm.

[0112] Preparation of ligand A The tetradentate phosphine compound ligand A used in these examples is prepared as described in International Publication No. 2019 / 231611 and has the following structure.

[0113] [ka]

[0114] Ligand B is triphenylphosphine (TPP).

[0115] General procedure A: A liquid recirculation reactor system is used, consisting of two 1-liter stainless steel stirred-tank reactors connected in series. Each reactor is equipped with a stirrer, sparger, silicone oil shell, and pneumatic level control. Reactors 1 and 2 are further connected via lines to allow the transfer of unreacted gases and the pumping of a portion of the liquid solution containing the aldehyde product and catalyst from reactor 1 to reactor 2. Thus, the unreacted olefin in reactor 1 can be further hydroformylated in reactor 2. Reactor 2 has a vent for removing unreacted gases. A portion of the solution in reactor 2 is continuously pumped to a catalyst separation zone, which includes two consecutive vaporizers. Each vaporizer consists of a heated zone followed by a container (separator) for vapor / liquid separation. The vaporized components are condensed and collected in a product receiver. The non-volatile liquid effluent from the second vaporizer, containing the catalyst, is recirculated to reactor 1. The pressure and temperature of the vaporizers are varied to achieve the desired product separation. The pneumatic level controller maintains the liquid level in each separator. The reaction product rate is expressed as the number of moles of aldehyde produced per unit time per volume of catalyst solution (moles / L-hour). Product selectivity is expressed as N / I.

[0116] General Procedure B- A continuous reaction system is used, including a 90 mL Fisher-Porter tube equipped with a mass flow controller for precise control of the gas flow. The catalyst solution is filled into the tube, and the gas is continuously introduced through a sparger at the bottom of the reactor. The off-gas is sent to a process analyzer to enable quantification of the components. This reactor design is described in detail in U.S. Patent No. 5,731,472, the teachings of which are incorporated by reference.

[0117] Example 1: Follow general procedure A except that a single reactor and vaporizer (temperature = 110-135°C and 11 psig) is used. The catalyst solution contains 304 ppm Rh, 5.5 wt% TPP, and an average of 0.31 wt% ligand A. Establish partial pressures of 20 psi CO and 82 psi propylene. Keep all parameters constant except for the H2 partial pressure. Measure the production rate under each condition, and the results are shown in Figure 2.

[0118] The small changes in reaction product rate and N / I suggest that H2 partial pressure is not a critical variable in the hydroformylation rate, and therefore the H2 / CO partial pressure ratio should be optimized to limit propane production, which adversely affects olefin efficiency (Step 1 of the present invention).

[0119] Example 2: Follow the procedure of Example 1, except for the catalyst concentrations (290 ppm Rh, 5.9 wt% TPP, and an average of 0.24 wt% ligand A). Establish partial pressures of 24 psi H2 and 79 psi propylene. Keep all parameters constant except for the CO partial pressure. The results are shown in Figure 3.

[0120] The data clearly show that PPCO affects the hydroformylation rate and N / I ratio. Furthermore, it has been shown that propane selectivity increases at higher H2 / CO partial pressure ratios. In other words, it appears that the higher the partial pressure of CO, the more inhibited propane formation is, and therefore, when both H2 and CO increase at an optimized H2 / CO partial pressure ratio, the benefits of a higher CO partial pressure mitigate the adverse effects of a higher H2 partial pressure on propane formation.

[0121] Example 3: Using the data from Examples 1, 2, and 5 below, the relationship between the syngas partial pressure ratio (H2 / CO) and propane selectivity can be established. The results are shown in Figure 4.

[0122] As shown in Figure 3, increasing H2 minimizes the increase in the hydroformylation rate, but the data in Figure 5 shows that higher H2 / CO ratios have a strong undesirable effect on propane selectivity. Therefore, it is important to optimize the H2 / CO partial pressure ratio (Step 1 of the Method of the Invention). The optimized syngas partial pressure can be changed as long as the H2 / CO partial pressure ratio is maintained within the range indicated in Step 1 (Step 2 of the Process of the Invention).

[0123] Example 4: Following general procedure A, all parameters were kept constant except for the H2 / CO ratio. The hydroformylation rate was determined under each condition, and the results are shown in Figure 5. The reaction rate was positive order with respect to CO until PPCO reached approximately 20 psi (the reaction rate increased with increasing PPCO), and then became slightly negative order at higher PPCO levels. Examples 1 and 2 show that increasing the H2 partial pressure has little effect on the production rate and N / I, so any changes may be due to fluctuations in the CO partial pressure.

[0124] The data indicate that PPCO is a critical variable for both the hydroformylation rate and the N / I ratio. If a higher reaction rate is required and the partial pressure of CO is less than approximately 20 psi, the partial pressure of syngas should be increased while maintaining the optimized syngas ratio.

[0125] Example 5: The procedure of Example 1 was followed, except that the partial pressure of CO was kept constant at 12 psi and the partial pressure of H2 at 14 psi while varying the partial pressure of propylene. The results are shown in Figure 6.

[0126] The data show a direct correlation between the formation rate and the propylene concentration, as well as a loose correlation with the N / I ratio and olefin partial pressure, but no significant correlation with alkane formation.

[0127] Example 6: General procedure A is used. The catalyst solution consists of 305 ppm rhodium, 5.2 wt% TPP, and ligand A (0.39 wt%). This solution further contains 53% n-butyraldehyde, 2% isobutyraldehyde, 0.65% butyraldehyde dimer, 16% butyraldehyde trimer, and 5.9 wt% heavier components, which are common in sequential propylene hydroformylation. The hydrogen partial pressure is 13.9 psi on average, and the CO partial pressure is 13.7 psi on average. The TPP concentration is initially kept constant by periodic addition. After 320 days, TPP addition is discontinued. All other conditions are kept constant. The TPP concentration slowly decreases due to evaporation and / or oxidation over the next 110 days. On day 430, TPP addition is resumed. The results are shown in Figure 7.

[0128] As the TPP concentration decreases, the reaction rate increases. When the TPP concentration recovers, the reaction rate returns to its original value.

[0129] Example 7: Follow general procedure A except that the reactor temperature was increased from 92°C to 102°C on day 140 and then returned to 90°C on day 160. The effect of higher reactor temperatures on the decomposition of ligand A is shown in Figure 8.

[0130] The effect of temperature on the utilization rate of polyphosphine ligands is significant and represents an economic disadvantage (e.g., tripling the cost associated with polyphosphine ligands). This highlights the importance of the upper temperature limit in step 5.

[0131] Example 8: Follow the procedure of Example 6, except that the reactor temperature is changed. The results are shown in Figure 9.

[0132] Increasing the temperature increases the selectivity for heavy materials, which leads to undesirable inefficiencies (for example, approximately 0.08% more heavy materials are formed at 100°C compared to 90°C).

[0133] Example 9: Follow general procedure A. The rhodium concentration was initially 328 ppm, then increased to 438 ppm on day 195 (a 27% increase). The results are shown in Figure 10.

[0134] The production rate increased by 29%, and there was no direct effect on the use of ligand A, propane formation, or heavy material formation. However, the addition of rhodium represents a direct capital cost and cannot be easily reversed if a lower production rate is acceptable later on.

[0135] Examples 10a-f: Hydroformylation is carried out using general procedure B. A solution containing tetraglyme (20 mL) and ligand A (0.45 wt%) is added to the reactor. The solution further contains ligand B and rhodium at various concentrations as shown in Table 2. The initial reaction conditions are established by the target H2 / CO partial pressure ratio, as shown in Example 10a in Table 2. The obtained catalyst performance is measured, and then the conditions for Example 10b are established while keeping other variables constant. This series of process changes and performance measurements is continued sequentially through each of Examples 10c-10f. The results are summarized in Table 2.

[0136] [Table 2]

[0137] By implementing this scheme, if the performance of the initial catalyst deteriorates, or if an increase in productivity is desired to meet short-term market demand, these changes can provide an increase in the production rate of nearly 90% while maintaining the N / I ratio with minimal formation of additional heavy materials and propane.

Claims

1. A method for optimizing the production rate of a hydroformylation process for producing a mixture of n-(N)aldehyde and iso(I)aldehyde, the process comprising contacting an olefin with carbon monoxide, hydrogen, and a catalyst, wherein the catalyst comprises (A) a transition metal, (B) a monophosphine, and (C) a tetraphosphine having the following structure. 【Chemistry 1】 In the formula, each P is a phosphorus atom, and R １ ~R ４６ Each of these is independently hydrogen, a C1-C8 alkyl group, an aryl group, an alkaryl group, or a halogen, and the contact is carried out in one or more reaction zones and under hydroformylation conditions that produce a blend of n-(N) aldehyde and iso(I) aldehyde in an N / I ratio, and the rate of the hydroformylation is determined by the following operation, i.e., 1. Optimized H, restricted to a ratio greater than 0.4:1 and less than 2.5:1 ２ / To establish the CO partial pressure ratio, 2. In the optimized ratio established in step 1, increase the partial pressure of syngas while limiting the partial pressure of CO in at least one reaction zone to 30 psi.

3. Increase the partial pressure of the olefin in at least one reaction zone to a level that does not exceed the point at which more than 2% of the olefin feed is lost via the purge vent flow in the final reaction zone or the alkampage flow in any olefin recovery process.

4. Reduce the concentration of monophosphine in the reaction fluid to a lower limit of approximately 1.5% by weight.

5. Raise the temperature in at least one reaction zone to a limit of approximately 98°C.

6. A method of gradually increasing the concentration of the transition metal in the reaction fluid by sequentially performing at least three of the following steps, such that the concentration does not exceed 1200 ppmw in the reaction zone.

2. The optimized logic ２ The method according to claim 1, wherein the CO partial pressure ratio is limited to more than 0.6:1 and less than 2.0:

1.

3. The optimized logic ２ The method according to claim 1, wherein the CO partial pressure ratio is limited to more than 0.7:1 and less than 1.5:

1.

4. Target H in the reaction zone ２ The method according to claim 1, wherein the CO partial pressure ratio is 0.9 to 1.

04.

5. The method according to claim 1, wherein the monophosphine is triphenylphosphine.

6. The method according to claim 1 or claim 2, wherein the transition metal comprises rhodium.

7. R １ ~R ４６ The method according to any one of claims 1 to 6, wherein each of them is hydrogen.

8. The method according to any one of claims 1 to 7, wherein the olefin is propylene.

9. The method according to any one of claims 1 to 8, wherein the amount of monophosphine in the reaction zone is 0.5% by weight or more and 18% by weight or less, more preferably 1.5% by weight or more and 13% by weight or less, or most preferably 3.5% by weight or more but 7% by weight or less, based on the total weight of the reaction fluid in the reaction zone.

10. The process according to claims 1 to 9, wherein at least four of the first five steps are used in a specific order.

11. The process according to claims 1 to 10, wherein two or more of the above steps are combined together.

12. The process according to claim 1, wherein all six steps are performed in the order listed.

13. The method according to any one of claims 1 to 12, wherein the amount of tetraphosphine in the reaction zone is 0.1% to 0.4% by weight.

14. The method according to any one of claims 1 to 13, wherein the amount of tetraphosphine in the reaction zone is more than 1.0 mole of tetraphosphine ligand per mole of transition metal.

15. The method according to any one of claims 1 to 14, wherein the hydroformylation process is operated for at least six months before the series of steps described in claim 1 is initiated.

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