Hydroformylation Process

Abstract

The present disclosure relates to a continuous hydroformylation process. In one aspect, the continuous hydroformylation process comprises: (a) reacting CO, H in a reaction fluid in at least two reaction zones in the presence of a hydroformylation catalyst under hydroformylation conditions sufficient to form at least one aldehyde product. 2 and at least one olefin, wherein the hydroformylation catalyst comprises a catalytic metal and a ligand, and the reaction temperature in the first reaction zone is controlled using a first heat exchanger, and (b) recovering at least a portion of the hydroformylation catalyst from a product stream and recycling at least a portion of the recovered hydroformylation catalyst through the first reaction zone. By diverting a portion of the olefin feed stream and / or a portion of the recycled hydroformylation catalyst from the first reaction zone to a downstream reaction zone, the reaction rate in the first reaction zone is reduced and the reaction rate in the downstream reaction zone is increased to reduce heat generation in the first reaction zone, to ensure that sufficient heat removal capacity remains in the heat exchanger in the first reaction zone to ensure stable control of the reaction at a target reaction temperature.

Description

[Technical Field]

[0001] The present invention relates generally to a continuous hydroformylation process. [Background technology]

[0002] Introduction It is known that aldehydes can be produced by a continuous process involving reacting an olefinically unsaturated compound with carbon monoxide and hydrogen in the presence of a metal-organophosphorus ligand complex catalyst. This process is disclosed, for example, in U.S. Patent Nos. 4,148,830, 4,717,775, and 4,769,498. Reaction temperature is an important hydroformylation process variable for several reasons.

[0003] It is generally recognized that stable, controlled operation of commercial-scale hydroformylation plants is highly desirable. It is also clear that accurate temperature control is crucial for catalyst life. The problem of temperature control in commercial-scale hydroformylation reactions has long been recognized. Section 1.2.4 of J. Falbe (ed.), "New Syntheses with Carbon Monoxide" (Springer-Verlag, NY 1980), provides an overview of the problem using diagrams of anomalous temperature behavior. A more detailed analysis is provided in E.P. Van Elk, P.C. Borman, J.A.M. Kuipers, and G.F. Versteeg; Chemical Engineering Science 56 (2001) 1491-1500), which discusses the complexities of stability and dynamic behavior. The rhodium hydroformylation reaction is characterized by complex kinetics, mass flow problems, and its highly exothermic nature (28-35 kcal (118-147 kJ) / mol olefin), all of which make temperature control quite challenging.

[0004] U.S. Patent No. 4,277,627 teaches several routes to catalyst deactivation, including intrinsic deactivation. Operating conditions are designed to minimize loss of activity from phosphine-based catalysts. Temperature is a key variable controlling the rate of catalyst deactivation.

[0005] In addition to its effect on catalyst stability, temperature control can have a significant impact on the efficiency of the process. Lower temperatures result in lower reactivity and olefin losses throughout the system. As taught in U.S. Pat. No. 4,148,830, higher temperatures result in greater ligand decomposition due to unavoidable aldol formation and a higher rate of heavies formation. Other temperature-related effects, such as greater hydrogenation (to alkanes or alcohols) and greater fluctuations in the linear to branched ("N:I") product ratio, can also adversely affect plant productivity.

[0006] Generally speaking, to control temperature, one must control the rate of heat generation and / or the rate of heat removal. At steady state, the two are equal. The rate of heat generation is generally determined by factors such as the desired plant production rate (i.e., olefin feed rate), the nature of the olefins (ethylene is more reactive, followed by primary olefins, then secondary olefins), and catalyst concentration, to name a few. The production rate and olefins used are generally not changed because they would adversely affect plant economics. Therefore, historically, temperature control has focused mostly on heat removal.

[0007] The removal of heat from a heat exchanger is traditionally described by the following equation: Heat removal=A*U*ΔT (1) (where "U" is the heat transfer coefficient which depends on conditions on both the process and refrigerant sides of the equipment (viscosity, sensible heat, flow rate, presence of bubbles, etc.), "A" is the surface area available for heat transfer, and ΔT is the temperature difference between the product fluid and the refrigerant).

[0008] The surface area of ​​the heat exchanger is generally constant. Because large internal cooling coils inside the reactor occupy valuable reactor space, it is common practice to use external heat exchangers in reactors that require significant heat removal. See, for example, WO 2012 / 008717(A2), U.S. Pat. Nos. 4,523,036, 8,389,774, and 5,367,106. Increasing the size of the heat exchanger to have a very large surface area generally provides better stability, but is expensive, increases the plant footprint, and increases maintenance costs.

[0009] There are disclosures aimed at controlling reactor temperature through manipulation of operating conditions. For example, in the highly active phosphite-based Rh catalyst system disclosed in U.S. Pat. No. 5,744,650, optimizing the temperature difference ΔT between the process side and the coolant side of the heat exchanger is critical for stable temperature control. U.S. Pat. No. 5,744,650 provides a good overview of the actual heat exchanger design used to control a hydroformylation reactor, but focuses on the coolant side of the heat exchanger. Unfortunately, controlling the temperature of the cooling water increases the complexity and operation of the plant, resulting in additional costs. Furthermore, process control response is significantly delayed in that it takes time to change the cooling water temperature, and then the changed cooling water must reestablish its temperature in the heat exchanger, which then must establish a new ΔT to take effect in the reactor. The large masses involved in an industrial-scale hydroformylation process significantly increase response time.

[0010] Traditionally, other means for heat removal are based on varying the refrigerant mass flow rate within a heat exchanger. Varying the refrigerant side flow has been considered the preferred route because the piping and equipment on the refrigerant side is generally much smaller than on the process side, e.g., 6 inch versus 20 inch pipes, and involves less expensive metals, e.g., carbon steel, compared to stainless steel on the process side.

[0011] It is also known that reaction kinetics, which are influenced by temperature, have a significant impact on process stability. U.S. Patent No. 5,763,679 teaches that deactivation of metal-organophosphorus ligand complex catalysts caused by inhibiting or poisoning phosphorus compounds can be reversed or reduced by conducting a hydroformylation process in a reaction zone where the hydroformylation reaction rate is negative or inverse order in carbon monoxide. The presence of both positive and negative CO order kinetics (and various levels of inhibitors) makes it very difficult to control these highly active catalysts using conventional process control strategies.

[0012] U.S. Patent No. 5,362,917 discloses a method for controlling the stability of a hydroformylation process by varying the flow rate of synthesis feed gas or vent gas to maintain a predetermined constant carbon monoxide partial pressure in the hydroformylation process. Because the product isomer (N:I) ratio is dependent on the CO partial pressure, attempting to maintain the CO partial pressure can stabilize the N:I ratio, but cannot simultaneously stabilize the reaction rate because other reagents may vary as well.

[0013] Similarly, U.S. Patent No. 7,446,231 addresses reaction control by manipulating the total pressure of the reactor. This patent attempts to simultaneously handle several gaseous reagents that affect kinetics. Instead of setting a fixed CO partial pressure, the total pressure is maintained at a constant propylene feed rate, based on the observation that CO and H partial pressures are self-regulating and the expectation that a more stable process will result. As shown in Figure 1 of U.S. Patent No. 7,446,231, the optimal operating region is at the peak of the hydroformylation rate vs. CO partial pressure plot, where the fastest rates and highest N:I performance are observed. Unfortunately, operation at this peak is inherently unstable because the kinetic model does not consider changes in reaction order (including the zeroth order at the peak itself). Therefore, the technology of U.S. Patent No. 7,446,231 is applicable only in the negative CO order region.

[0014] Therefore, hydroformylation reactors typically operate in an inherently unstable regime and rely on reactor control systems to maintain stable process control. Conventional hydroformylation reactor temperature control systems have controlled the reactor liquid temperature by adjusting the cooling water inlet temperature, the cooling water flow rate, or a combination of these. Historically, this control scheme has worked reasonably well, primarily because the reaction rates of first-generation commercial hydroformylation catalysts are relatively slow—e.g., less than 1.5 gmol (aldehyde) / liter (reactor volume) / hour—and therefore relatively little heat of reaction is generated per unit time / volume. However, recently commercialized next-generation hydroformylation catalysts have significantly faster reaction rates than existing catalysts. Faster reaction rates translate into greater heat generation in the hydroformylation reactor per unit time. Conventional reactor temperature control schemes are too slow to effectively control the reactor temperature for reactions using new hydroformylation catalysts.

[0015] The design of heat exchangers is well known in the art, and the above-mentioned issues must be considered in the design of a heat exchanger to ensure that it has sufficient capacity to remove heat generated in the system at the rate at which heat is generated, including the above-mentioned variables. As used herein with respect to a heat exchanger, the term "capacity" refers to the maximum amount of heat energy (often measured in BTUs, kilojoules, kilowatts, etc.) that can be removed per unit time when the heat exchanger is operating in its maximum heat removal mode. As noted in equation (1) above, there are numerous factors, such as U, A, and ΔT, that affect the heat removal rate and, therefore, the capacity of the heat exchanger. Generally, the process or coolant flow (U) and ΔT (coolant temperature) are the primary drivers of capacity. These must be balanced against the amount of heat generated by the hydroformylation reaction, as well as some additional capacity to accommodate variations in olefin purity, cooling water fluctuations (e.g., seasonal variations), etc. The hydroformylation production rate (total olefin feed) is assumed to be held constant so that the plant production rate remains constant.

[0016] It has been found that traditional heat exchanger designs can become inadequate over time, especially with more active catalysts and / or more reactive olefins. Examples include dramatic changes in olefin composition in the feed, fouling, and changes in catalyst activity. The latter is particularly concerning when retrofitting older equipment with more active catalysts, such as those mentioned above. Higher activity catalysts convert more olefins in the first reactor than older, less active catalysts, meaning more heat is generated in the first reactor than in the original plant design. Older designs typically lack the rapid response required for similarly negative-order catalysts. Simply lowering reactor temperature to reduce reaction rate also reduces the ΔT across the heat exchanger, thereby reducing heat exchanger capacity. This effect magnifies heat exchanger capacity constraints, as newer, more reactive catalysts tend to be more sensitive to higher temperatures and operate at lower temperatures while still exhibiting higher olefin conversion. To alleviate this problem requires replacing the existing heat exchangers or adding more cooling capacity, which is expensive and increases the plant's footprint and maintenance costs.

[0017] Therefore, it would be desirable to have an improved reactor temperature control process for a hydroformylation reactor that balances the heat removal requirements of the reactor using existing heat exchangers that have limited heat removal capacity. Summary of the Invention

[0018] The present invention generally relates to a continuous hydroformylation process that provides improved thermal reactor temperature control. In some aspects, the continuous hydroformylation process is particularly advantageous in processes using active hydroformylation catalysts that generate more heat in the reactor than conventional hydroformylation catalysts. In some aspects, such processes can facilitate the use of heat exchangers to sufficiently remove heat from the reactor using newer, more active hydroformylation catalysts, provided that such heat exchangers have the heat removal capacity designed for reactions using conventional hydroformylation catalysts. For example, some embodiments of the continuous hydroformylation process of the present invention may be useful for converting a hydroformylation process operating with a particular hydroformylation catalyst (e.g., a conventional catalyst) to a process using a more active (more reactive) hydroformylation catalyst without the need to replace the heat exchanger(s) associated with the hydroformylation reactor.

[0019] In one embodiment, the continuous hydroformylation process of the present invention comprises: (a) contacting CO, H, and at least one olefin in the presence of a hydroformylation catalyst in a reaction fluid in at least two reaction zones under hydroformylation conditions sufficient to form at least one aldehyde product, wherein the hydroformylation catalyst comprises a catalytic metal and a ligand, and the reaction temperature in a first reaction zone is controlled using a first heat exchanger; and (b) recovering at least a portion of the hydroformylation catalyst from the product stream and recycling at least a portion of the recovered hydroformylation catalyst through the first reaction zone, wherein: (1) a portion of the olefin feed stream is recycled to a reaction zone downstream from the first reaction zone; and / or (2) varying the concentration of the catalytic metal in the first reaction zone by adjusting the amount of recycled hydroformylation catalyst diverted from the first reaction zone to a downstream reaction zone, thereby decreasing the reaction rate in the first reaction zone and increasing the reaction rate in a downstream reaction zone to ensure sufficient heat removal capacity remains in the heat exchangers in the first reaction zone to ensure stable control of the reaction at a target reaction temperature.

[0020] These and other embodiments are described in more detail in the detailed description. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a process flowsheet showing a conventional reaction train having three reactors (reaction zones) in series that are fed to a product / catalyst separation zone where crude product is removed and the catalyst is recycled back to the first reactor. [Figure 2]1 is a process flowsheet illustrating the diversion of a portion of the olefin feed from a first reactor (reaction zone) to a second reactor (reaction zone) to adjust or control the amount of reaction occurring in the first reactor, according to one embodiment of the present invention. [Figure 3] 1 is a process flowsheet illustrating the diversion of a portion of catalyst recycled from a product / catalyst separation zone from a first reactor (reaction zone) to a second reactor (reaction zone) to vary the catalyst concentration in the first reactor, thereby controlling the amount of reaction occurring in the first reactor, according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present disclosure generally relates to reducing heat generation in a first reaction zone in a continuous hydroformylation process by decreasing the reaction rate in the first reaction zone and increasing the reaction rate in downstream reaction zones to ensure sufficient heat removal capacity remains in the heat exchangers within that first reaction zone to ensure stable reaction control at a target reaction temperature. The process described herein is a continuous process for producing aldehydes by hydroformylation of alpha-olefins. The aldehydes produced by such processes have a wide range of utility, for example, as intermediates for hydrogenation to aliphatic alcohols, amination to aliphatic amines, oxidation to aliphatic acids, and aldol condensation to produce plasticizers.

[0023] All references to the Periodic Table of the Elements and the various groups therein are to the version published in the CRC Handbook of Chemistry and Physics, 72nd Ed. (1991-1992) CRC Press, pages I-10.

[0024] Unless otherwise stated or implicit from the context, all parts and percentages are by weight and all test methods are as of the filing date of this application. For purposes of U.S. patent practice, the contents of any referenced patent, patent application, or publication are incorporated by reference in their entirety (or the U.S. equivalent thereof is so incorporated by reference), particularly with respect to the disclosure of definitions (to the extent not inconsistent with any definitions specifically provided in this disclosure) and general knowledge in the art.

[0025] As used herein, "a," "an," "the," "at least one," and "one or more" are used interchangeably. "Comprise," "include," and variations thereof do not have a limiting meaning when these terms appear in the specification and claims. Thus, for example, an aqueous composition comprising particles of "a" hydrophobic polymer can be interpreted to mean that the composition comprises particles of "one or more" hydrophobic polymers.

[0026] Also herein, the recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.). For purposes of the present invention, it should be understood that numerical ranges are intended to include and support all possible subranges subsumed within that range, consistent with what one of ordinary skill in the art would understand. For example, a range of 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.

[0027] As used herein, the term "ppmw" means parts per million by weight.

[0028] For purposes of this invention, the term "hydrocarbon" is intended to include all permissible compounds having at least one hydrogen atom and one carbon atom. Such permissible compounds may also contain one or more heteroatoms. In a broad aspect, permissible hydrocarbons include acyclic (with or without heteroatoms) and cyclic, branched and unbranched, carbocyclic and heterocyclic, aromatic and non-aromatic organic compounds, which may be substituted or unsubstituted.

[0029] As used herein, the term "substituted" is contemplated to include all permissible substituents of organic compounds, unless otherwise indicated. In a broad aspect, the permissible substituents include acyclic and cyclic, branched and unbranched, carbocyclic and heterocyclic, aromatic and nonaromatic substituents of organic compounds. Illustrative substituents include, for example, alkyl, alkyloxy, aryl, aryloxy, hydroxyalkyl, aminoalkyl (which can range from 1 to 20 or more carbon atoms, preferably 1 to 12 carbon atoms), as well as hydroxy, halo, and amino. The permissible substituents can be one or more and the same or different for appropriate organic compounds. This invention is not intended to be limited in any manner by the permissible substituents of organic compounds.

[0030] As used herein, the term "hydroformylation" is intended to include, but is not limited to, all permissible asymmetric and non-asymmetric hydroformylation processes, including the conversion of one or more substituted or unsubstituted olefinic compounds, or a reaction mixture containing one or more substituted or unsubstituted olefinic compounds, to one or more substituted or unsubstituted aldehydes, or a reaction mixture containing one or more substituted or unsubstituted aldehydes.

[0031] As used herein, the terms "reaction fluid," "reaction medium," and "catalyst solution" are used interchangeably and may include, but are not limited to, (a) the metal-organophosphorus ligand complex catalyst, (b) the free organophosphorus ligand, (c) the aldehyde product formed in the reaction, (d) any unreacted reactants, (e) a solvent for the metal-organophosphorus ligand complex catalyst and the free organophosphorus ligand, and, optionally, (f) one or more ligand decomposition products, such as oxides or phosphate compounds, formed in the reaction (which may be homogeneous or heterogeneous, including those deposited on surfaces of process equipment). Reaction fluids may include, but are not limited to, (a) fluids within the reactor, (b) fluid streams en route to the separation zone, (c) fluids within the separation zone, (d) recycle streams, (e) fluids withdrawn from the reaction zone or separation zone, (f) withdrawn fluids that are being treated with an aqueous buffer, (g) treated fluids returned to the reaction zone or separation zone, (h) fluids within an external cooler, and (i) ligand decomposition products and their salts.

[0032] As used herein, the terms "reactor" and "reaction zone" refer to a separate unit where conditions are such that the hydroformylation reaction occurs. These conditions include the presence of olefin, synthesis gas, and catalyst in solution at a temperature high enough to generate a detectable amount of heat. The terms "reactor" and "reaction zone" are used interchangeably except when the reactor body has multiple zones, in which case the term "reaction zone" is explicitly used (e.g., a second reaction zone within a single reactor body). A reaction zone may comprise more than one reactor in series, or may be a reactor having several separate reaction zones or stages within the reactor body, such as those described in U.S. Pat. No. 5,728,893. The terms "downstream reaction zone" or "downstream reactor" are used interchangeably herein to refer to the primary process flow of a reaction train, from the first reaction zone where olefin is first introduced into the reaction zone series, to the product of this reaction zone being fed to the second (downstream) reaction zone, then to the third reaction zone (if present), and so on, until the final reaction zone in the series is connected to a product / catalyst separation zone.

[0033] A "hydrolyzable organophosphorus ligand" is a trivalent phosphorus ligand containing at least one PZ bond, where Z is oxygen, nitrogen, chlorine, fluorine, or bromine. Examples include, but are not limited to, phosphites, phosphino-phosphites, bisphosphites, phosphonites, bisphosphonites, phosphinites, phosphoramidites, phosphino-phosphoramidites, bisphosphoramidites, fluorophosphites, and the like. The ligand may contain a chelating structure and / or may contain multiple PZ moieties, such as polyphosphites, polyphosphoramidites, and mixed PZ moieties, such as phosphite-phosphoramidites, flurophosphite-phosphites, and the like.

[0034] As used herein, the term "complex" refers to a coordination compound formed by the binding of one or more electron-rich molecules or atoms (i.e., ligands) with one or more electron-poor molecules or atoms (i.e., transition metals). For example, organophosphorus ligands usable herein possess one phosphorus(III) donor atom with one unshared electron pair, which can form a coordinate covalent bond with the metal. Polyorganophosphorus ligands usable herein possess two or more phosphorus(III) donor atoms, each with one unshared electron pair, each of which can form a coordinate covalent bond independently or possibly in concert with the transition metal (e.g., via chelation). Carbon monoxide may also be present and can form a complex with the transition metal. The final composition of the complex catalyst may also contain additional ligand(s), such as hydrogen, monoolefins, or anions, to fill the coordination sites or nuclear charge of the metal, as described above.

[0035] The number of coordination sites available on a transition metal is well known in the art and depends on the particular transition metal selected. The catalytic species may include complex catalyst mixtures in monomeric, dimeric, or higher nuclei forms, which are preferably characterized by at least one organophosphorus-containing molecule complexed per molecule of metal, e.g., rhodium. For example, it is believed that the catalytic species of a preferred catalyst used in hydroformylation reactions may be complexed with carbon monoxide and hydrogen in addition to one or more organophosphorus ligand(s).

[0036] In one embodiment, the continuous hydroformylation process of the present invention comprises: (a) contacting CO, H, and at least one olefin in the presence of a hydroformylation catalyst in a reaction fluid in at least two reaction zones under hydroformylation conditions sufficient to form at least one aldehyde product, wherein the hydroformylation catalyst comprises a catalytic metal and a ligand, and the reaction temperature in the first reaction zone is controlled using a first heat exchanger; and (b) recovering at least a portion of the hydroformylation catalyst from the product stream and recycling at least a portion of the recovered hydroformylation catalyst through the first reaction zone. In such embodiments, the heat generation in the first reaction zone is reduced by (1) varying the olefin partial pressure in the first reaction zone by diverting a portion of the olefin feed stream from the first reaction zone to a downstream reaction zone and adjusting the amount of the olefin feed stream diverted, and / or (2) varying the catalytic metal concentration in the first reaction zone by diverting a portion of the recycled hydroformylation catalyst from the first reaction zone to a downstream reaction zone and adjusting the amount of the recycled hydroformylation catalyst diverted, thereby reducing the reaction rate in the first reaction zone and increasing the reaction rate in the downstream reaction zone to ensure sufficient heat removal capacity remains in the heat exchangers in the first reaction zone to ensure stable reaction control at the target reaction temperature. In some embodiments, the reaction temperature in the first reaction zone is maintained within 1°C of the target reaction temperature. Some processes of the present invention further include measuring the olefin concentration in the headspace of the first reaction zone and adjusting the amount of the olefin feed stream diverted to the downstream reaction zone based on the measurement. In some embodiments, the reaction rate is greater than 1.5 gmol aldehyde / liter reactor volume / hour. In some embodiments, the reaction rate is greater than 2.0 gmol aldehyde / liter reactor volume / hour. In some embodiments, the ligand used in the hydroformylation reaction is a hydrolyzable organophosphorus ligand. In some embodiments, the catalytic metal is rhodium. In some embodiments, the reaction temperature is 100° C. or less.

[0037] As described above, the hydroformylation process of the present invention comprises contacting CO, H, and at least one olefin in a reaction fluid in at least two reaction zones in the presence of a hydroformylation catalyst comprising a catalytic metal and a ligand under hydroformylation conditions sufficient to form at least one aldehyde product. Optional process components include amines and / or water, such as those described in U.S. Patent Nos. 5,288,918, 5,731,472, and 5,741,944.

[0038] The hydrogen and carbon monoxide may be obtained from any suitable source, including petroleum cracking and refining operations. Syngas mixtures are the preferred source of hydrogen and CO.

[0039] Syngas (from synthesis gas) is the name given to a gas mixture containing varying amounts of hydrogen (H) and carbon monoxide (CO). Methods of production are well known. Hydrogen and CO are typically the primary components of syngas, but syngas may also contain CO and inert gases such as N and Ar. The molar ratio of H to CO can vary widely but generally ranges from 1:100 to 100:1, preferably 1:10 to 10:1. Syngas is commercially available and is often used as a fuel source or as an intermediate for producing other chemicals. The most preferred H:CO ratio is 3:1 to 1:3, more preferably about 1:2 to 2:1.

[0040] Substituted or unsubstituted olefinically unsaturated reactants that may be used in the hydroformylation process include both optically active (prochiral and chiral) and optically non-active (achiral) olefinically unsaturated compounds, in some embodiments containing from 2 to 40 carbon atoms, in some embodiments from 3 to 20 carbon atoms, and in some embodiments from 3 to 5 carbon atoms. Such compounds are well known in the art and are described in detail in U.S. Patent Application Publication No. 2010 / 006980. Such olefinically unsaturated compounds may be terminally or internally unsaturated and may be of linear, branched, or cyclic structure, as well as mixtures of olefins such as those obtained from the oligomerization of propene, butene, isobutene, and the like (e.g., so-called dimer, trimer, or tetramer propylene, as disclosed in U.S. Pat. Nos. 4,518,809 and 4,528,403).

[0041] Prochiral and chiral olefins useful in asymmetric hydroformylation that can be used to produce enantiomeric aldehyde mixtures include those of the formula:

[0042] [ka] [In the formula, R 1 , R 2 , R 3 , and R 4 are the same or different (provided that R 1 is R 2 or R 3 is R 4substituted alkyl, wherein the substitution is selected from dialkylamino, such as benzylamino and dibenzylamino; alkoxy, such as methoxy and ethoxy; acyloxy, such as acetoxy, halo, nitro, nitrile, thio, carbonyl, carboxamide, carboxaldehyde, carboxyl, and carboxylic acid ester; aryl, including phenyl; substituted aryl, including phenyl, wherein the substitution is alkyl, amino, including alkylamino and dialkylamino, such as benzylamino and dibenzylamino, hydroxy; alkoxy, such as methoxy and ethoxy; acyloxy, such as acetoxy;

[0023] Prochiral and chiral olefins of this definition are also understood to include those selected from substituted aryl selected from siloxy, halo, nitrile, nitro, carboxyl, carboxaldehyde, carboxylic acid ester, carbonyl, and thio; acyloxy such as acetoxy; alkoxy such as methoxy and ethoxy; amino including alkylamino and dialkylamino such as benzylamino and dibenzylamino; acylamino and diacylamino such as acetylbenzylamino and diacetylamino; nitro; carbonyl; nitrile; carboxyl; carboxamide; carboxaldehyde; carboxylic acid ester; and alkylmercapto such as methylmercapto.

[0024] Prochiral and chiral olefins of this definition also include molecules of the above general formula in which the R groups are bonded to form a ring compound, such as 3-methyl-1-cyclohexene.

[0043] Illustrative optically active or prochiral olefinic compounds useful in asymmetric hydroformylation are described, for example, in US Pat. Nos. 4,329,507, 5,360,938, and 5,491,266.

[0044] In some embodiments, a mixture of olefins may be used, and the composition of this mixture may change over time. As the composition of the olefin mixture changes, the reactivity of the hydroformylation process may change as well, sometimes rapidly. For example, changing from a polymer-grade propylene feedstock to a refinery-grade propylene feedstock with a significant ethylene content can result in a dramatic change in the behavior of the reaction system.

[0045] Advantageously, a solvent is used in the hydroformylation process. Any suitable solvent that does not excessively interfere with the hydroformylation process can be used. Illustrative examples of suitable solvents for rhodium-catalyzed hydroformylation processes include those disclosed in U.S. Pat. Nos. 3,527,809, 4,148,830, 5,312,996, and 5,929,289. Non-limiting examples of suitable solvents include saturated hydrocarbons (alkanes), aromatic hydrocarbons, water, ethers, aldehydes, ketones, nitriles, alcohols, esters, and aldehyde condensation products. Specific examples of solvents include tetraglyme, pentane, cyclohexane, heptane, benzene, xylene, toluene, diethyl ether, tetrahydrofuran, butyraldehyde, and benzonitrile. The organic solvent may also contain dissolved water up to the saturation limit. Exemplary preferred solvents include ketones (e.g., acetone and methyl ethyl ketone), esters (e.g., ethyl acetate, di-2-ethylhexyl phthalate, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate), hydrocarbons (e.g., toluene), nitrohydrocarbons (e.g., nitrobenzene), ethers (e.g., tetrahydrofuran (THF)), and sulfolane. In rhodium-catalyzed hydroformylation processes, it may be desirable to employ as the primary solvent an aldehyde compound corresponding to the aldehyde product desired to be produced and / or to a high-boiling aldehyde liquid condensation by-product that may be produced in situ during the hydroformylation process, as described, for example, in U.S. Pat. Nos. 4,148,380 and 4,247,486. The primary solvent typically ultimately contains both the aldehyde product and higher-boiling aldehyde liquid condensation by-products ("heavies") due to the nature of the continuous process. The amount of solvent is not particularly critical and need only be sufficient to provide the desired transition metal concentration in the reaction medium. Typically, the amount of solvent ranges from about 5 weight percent to about 95 weight percent, based on the total weight of the reaction fluid. Mixtures of solvents may also be used.

[0046] The hydroformylation catalyst used in the hydroformylation process comprises a catalytic metal and a ligand. The ligand is typically an organophosphorus ligand. Exemplary metal-organophosphorus ligand complexes that can be used in such hydroformylation reactions include metal-organophosphorus ligand complex catalysts. These catalysts, as well as methods for their preparation, are well known in the art and include those disclosed in the patents referenced herein. Generally, such catalysts, which may be preformed or formed in situ, comprise a metal complexed with an organophosphorus ligand, carbon monoxide, and optionally hydrogen. The ligand complex species may exist in mononuclear, binuclear, and / or higher nuclear forms. However, the exact structure of the catalyst is unknown.

[0047] The metal-organophosphorus ligand complex catalyst may be optically active or non-optically active. The catalytic metal may include a Group 8, 9, or 10 metal selected from rhodium (Rh), cobalt (Co), iridium (Ir), ruthenium (Ru), iron (Fe), nickel (Ni), palladium (Pd), platinum (Pt), osmium (Os), and mixtures thereof. Preferred metals are rhodium, cobalt, iridium, and ruthenium, more preferably rhodium, cobalt, and ruthenium, especially rhodium. Mixtures of these metals may also be used. Acceptable organophosphorus ligands that comprise the metal-organophosphorus ligand complex and the free organophosphorus ligand include mono-, di-, tri-, and higher polyorganophosphorus ligands. Mixtures of ligands may be used in the metal-organophosphorus ligand complex catalyst and / or the free ligand, and such mixtures may be the same or different.

[0048] Organophosphorus compounds that can function as ligands for metal-organophosphorus ligand complex catalysts and / or free ligands can be of the achiral (optically inactive) or chiral (optically active) type and are well known in the art. Achiral organophosphorus ligands are preferred.

[0049] Among the organophosphorus ligands that can function as ligands in metal-organophosphorus ligand complex catalysts are triarylphosphines, monoorganophosphites, diorganophosphites, triorganophosphites, organophosphites, organomonophosphoramidite and organopolyphosphoramidite compounds, as well as other hydrolyzable organophosphorus compounds. Such organophosphorus ligands and / or methods for their preparation are well known in the art.

[0050] Triarylphosphines that can be used in the processes of the present disclosure include any organic compound containing one phosphorus atom covalently bonded to three aryl or arylalkyl radicals, or combinations thereof. Mixtures of triarylphosphine ligands may also be used. Representative organomonophosphines include those of the formula:

[0051] [ka] [In the formula, each R 29 , R 30 , and R 31 and R may be the same or different and represent a substituted or unsubstituted aryl radical containing 4 to 40 or more carbon atoms. Such triarylphosphines can be found described in more detail, for example, in U.S. Pat. No. 3,527,809, the disclosure of which is incorporated herein by reference. Exemplary triarylphosphine ligands are triphenylphosphine, trinaphthylphosphine, tritolylphosphine, tri(p-biphenyl)phosphine, tri(p-methoxyphenyl)phosphine, tri(m-chlorophenyl)phosphine, pN,N-dimethylaminophenylbis-phenylphosphine, and the like. Triphenylphosphine, i.e., where each R 29 , R 30 , and R 31 Compounds of formula I in which is phenyl are examples of preferred organomonophosphine ligands. The hydroformylation reaction is preferentially carried out in a liquid containing an excess of free triarylphosphine.

[0052] Representative monoorganophosphites, diorganophosphites, triorganophosphites, and organopolyphosphites (containing two or more tertiary (trivalent) phosphorus atoms) can include those having the following formula, which are described in detail in WO 2012 / 14541:

[0053] [ka]

[0054] As a further option, any organophosphoramidite ligand may be used as an organophosphorus ligand or in combination with any other organophosphorus ligand, and any organopolyphosphoramidite ligand may be used as an organophosphorus ligand or in combination with any other organophosphorus ligand. Organophosphoramidite ligands are known and are used in the same manner as organophosphite ligands. Representative organophosphoramidite ligands are of formulas (X-XII):

[0055] [ka]

[0056] Organophosphoramidites are further described, for example, in U.S. Patent No. 7,615,645. As used herein, "organophosphorus ligand" and similar terms include organomonophosphoramidite ligands and organopolyphosphoramidite ligands, unless specifically stated otherwise.

[0057] Illustrative examples of such organophosphorus ligands include 2-t-butyl-4-methoxyphenyl(3,3'-di-t-butyl-5,5'-dimethoxy-1,1'-biphenyl-2,2'-diyl)phosphite, methyl(3,3'-di-t-butyl-5,5'-dimethoxy-1,1'-biphenyl-2,2'-diyl)phosphite, 6,6'-[[3,3'-bis(1,1-dimethylethyl)-5,5' -dimethoxy-[1,1'-biphenyl]-2,2'-diyl]bis(oxy)]bis-dibenzo[d,f][1,3,2]dioxaphosphepine, 6,6'-[[3,3',5,5'-tetrakis(1,1-dimethylethyl)-1,1'-biphenyl]-2,2'-diyl]bis(oxy)]bis-dibenzo[d,f][1,3,2]dioxaphosphepine, (2R,4R)-di[2,2'-(3,3 2,4-pentyldiphosphite, (2R,4R)di[2,2'-(3,3'-di-tert-butyl-5,5'-dimethoxy-1,1'-biphenyl)]-2,4-pentyldiphosphite, 2-[[2-[[4,8,-bis(1,1-dimethylethyl),2,10-dimethoxydibenzo-[d,f][1,3,2]dioxophosphite [sphepin-6-yl]oxy]-3-(1,1-dimethylethyl)-5-methoxyphenyl]methyl]-4-methoxy, methylenedi-2,1-phenylenetetrakis[2,4-bis(1,1-dimethylethyl)phenyl] ester of phosphorous acid, and [1,1'-biphenyl]-2,2'-diyltetrakis[2-(1,1-dimethylethyl)-4-methoxyphenyl] ester of phosphorous acid.

[0058] The metal-organophosphorus ligand complex catalyst can be in homogeneous or heterogeneous form. For example, a preformed rhodium hydride-carbonyl-organophosphorus ligand catalyst can be prepared and introduced into the hydroformylation reaction mixture. More preferably, the rhodium-organophosphorus ligand complex catalyst can be derived from a rhodium catalyst precursor that can be introduced into the reaction medium to form the active catalyst in situ. For example, rhodium dicarbonyl acetylacetonate, Rh2O3, Rh4(CO) 12 , Rh6(CO) 16A rhodium catalyst precursor, such as Rh(NO3)3, can be introduced into the reaction mixture along with an organophosphorus ligand to form the active catalyst in situ. In a preferred embodiment, rhodium dicarbonyl acetylacetonate is used as the rhodium precursor and reacted with the organophosphorus ligand in the presence of a solvent to form a catalytic rhodium-organophosphorus ligand complex precursor, which is introduced into the reactor along with an excess of (free) organophosphorus ligand to form the active catalyst in situ. In either case, carbon monoxide, hydrogen, and the organophosphorus ligand are all ligands capable of forming complexes with the metal, and it is sufficient that an active metal-organophosphorus ligand catalyst be present in the reaction mixture under the conditions used in the hydroformylation reaction. The carbonyl and organophosphorus ligands can form complexes with rhodium either prior to the hydroformylation process or in situ during the process.

[0059] For example, a preferred catalyst precursor composition consists essentially of a solubilized rhodium carbonyl organophosphorus ligand complex precursor, a solvent, and optionally free organophosphorus ligand. A preferred catalyst precursor composition can be prepared by forming a solution of rhodium dicarbonyl acetylacetonate, an organic solvent, and the organophosphorus ligand. The organophosphorus ligand readily displaces one of the carbonyl ligands of the rhodium acetylacetonate complex precursor, as evidenced by the evolution of carbon monoxide gas.

[0060] Thus, the metal-organophosphorus ligand complex catalyst advantageously comprises a metal complexed with carbon monoxide and an organophosphorus ligand, the ligand binding (complexing) to the metal in a chelating and / or non-chelating manner.

[0061] Mixtures of catalysts can be used. The amount of metal-organophosphorus ligand complex catalyst present in the reaction stream need only be the minimum amount necessary to provide the desired concentration of metal used, e.g., an amount sufficient to provide at least the catalytic amount of metal plus base required to catalyze the particular hydroformylation process involved, as disclosed in the above-referenced patents. Generally, concentrations of catalytic metal, e.g., rhodium, in the range of 10 ppmw to 1000 ppmw, calculated as free metal in the reaction medium, are sufficient for most processes, although it is generally preferred to use 10 to 500 ppmw of metal, more preferably 25 to 350 ppmw of metal.

[0062] In addition to the metal-organophosphorus ligand complex catalyst, free organophosphorus ligand (i.e., ligand not complexed with the metal) may also be present in the reaction medium. The free organophosphorus ligand may correspond to any of the organophosphorus ligands discussed above and defined above. Preferably, the free organophosphorus ligand is the same as the organophosphorus ligand of the metal-organophosphorus ligand complex catalyst used. However, such ligands need not be the same in any given process. The hydroformylation process of the present invention may require from 0.1 mole or less to 100 moles or more of free organophosphorus ligand per mole of metal in the reaction medium. Preferably, the hydroformylation process is carried out in the presence of 1 to 50 moles of free organophosphorus ligand per mole of metal present in the reaction medium. More preferably, in the case of organopolyphosphites, 0.1 to 4 moles of free organopolyphosphite ligand per mole of metal are used. If necessary, for example, to maintain a predetermined level of free ligand in the reaction medium, additional organophosphorus ligand may be provided to the reaction medium of the hydroformylation process at any time and in any suitable manner.

[0063] Hydroformylation processes are well known and widely practiced commercially. See, for example, U.S. Patent Nos. 4,148,830, 5,237,106, 5,763,679, 5,741,945, 5,767,321, 7,446,231, 7,906,688, and 7,863,487. The reaction conditions for the hydroformylation process can include any suitable type of hydroformylation conditions previously used to produce optically active and / or non-optically active aldehydes. The hydroformylation reaction conditions used depend on the type of aldehyde product desired. For example, the total gas pressure of hydrogen, carbon monoxide, and olefin starting compound for the hydroformylation process can range from 1 to 69,000 kPa. However, it is generally preferred to operate the process at a total gas pressure of hydrogen, carbon monoxide, and olefin starting compounds of less than 14,000 kPa, more preferably less than 3,400 kPa. The minimum total pressure is primarily limited by the amount of reactants required to achieve the desired reaction rate. More specifically, the carbon monoxide partial pressure in the hydroformylation process is preferably 1 to 6,900 kPa, more preferably 21 to 5,500 kPa, and the hydrogen partial pressure is preferably 34 to 3,400 kPa, more preferably 69 to 2,100 kPa. Generally, the molar ratio of gaseous H2:CO can range from 1:10 to 100:1 or more, with a more preferred molar ratio being 1:10 to 10:1. Generally, the hydroformylation process can be carried out at any operable reaction temperature. Advantageously, the hydroformylation process is carried out at a reaction temperature of -25°C to 200°C, preferably 50°C to 120°C. Advantageously, the reaction temperature is below 100° C. in the reactor or reaction zone that is cooled by the process of the present invention.

[0064] Newer hydroformylation catalysts (typically based on hydrolyzable organophosphorus ligands) have faster reaction rates (e.g., greater than 1.5 gmol aldehyde / liter reactor volume / hour or greater than 2.0 gmol aldehyde / liter reactor volume / hour) compared to older catalysts. The reaction rates also exhibit complex kinetics (e.g., positive and negative orders with respect to CO). These catalysts typically operate at lower reaction temperatures, e.g., 60–80°C, to minimize catalyst degradation. Lower operating temperatures reduce the ΔT between the cooling medium and the reaction medium, thereby reducing the heat removal capacity of the heat exchanger. These factors make the design of an appropriate temperature control system more complex than for traditional processes using slower-reacting catalysts.

[0065] It should be understood that the nature of the catalyst is not critical to the present invention. Nevertheless, the present invention may be particularly useful for catalysts that exhibit high reactivity (greater than 1.5 gmol aldehyde / liter reactor volume / hour in the reactor or greater than 2.0 gmol aldehyde / liter reactor volume / hour in the reactor). As discussed further below, in some embodiments, the hydroformylation process may be useful for converting a hydroformylation process that uses an older catalyst to a process that uses a newer catalyst with faster reaction rates.

[0066] The rate of the hydroformylation reaction is a function of catalyst concentration and, in most cases (but not all), also of olefin concentration. Embodiments of the present invention contemplate reducing the reaction by (1) varying the olefin partial pressure in the first reaction zone by diverting a portion of the olefin feed stream from the first reaction zone to a downstream reaction zone and adjusting the amount of diverted olefin feed stream, and / or (2) varying the catalytic metal concentration in the first reaction zone by diverting a portion of the recycled hydroformylation catalyst from the first reaction zone to a downstream reaction zone and adjusting the amount of diverted recycled hydroformylation catalyst. The first approach (option (1)—diverting a portion of the olefin feed) may be most effective when the reaction order of the olefins involved in the hydroformylation reaction is positive, and in some embodiments, is at least 0.3, in some embodiments, 0.5 or greater, and in some embodiments, 0.7 or greater. The lower the reaction order, the less effective the first approach (option (1)) is. For example, the second approach (option (2)—bypassing a portion of the recycled hydroformylation catalyst) may be desirable when the olefin reaction order is less than 0.5. In some embodiments, both approaches (option (1) and option (2)) can be implemented. Means for determining reaction kinetics and reaction order are well known to those skilled in the art.

[0067] It should also be understood that while the amount of syngas fed to each reactor or reaction zone will vary, the CO and H partial pressures are preferably maintained to ensure that the N:I ratio (the ratio of linear aldehydes to branched aldehydes produced by the hydroformylation reaction) remains optimal and to ensure catalyst stability. The total amount of olefin and syngas fed to the process should not change significantly just as it is added. Small changes (if any) in the N:I ratio using the above approaches (option (1) and / or option (2)) to control reaction rate can, in most cases, be offset by changing the CO partial pressure or ligand concentration, as will be understood by those skilled in the art based on the teachings herein.

[0068] The amount of total aldehyde produced ideally does not change significantly using processes according to some embodiments of the present invention, as opposed to conventional methods of controlling excess reaction systems by reducing the total olefin feed. It should be understood that if a slight decrease in overall conversion is observed, process parameters in downstream reaction zones can be modified to increase the conversion in such downstream reactors. Examples of such parameters include reaction temperature, CO and / or H partial pressure, etc. Generally, the amount of reaction occurring in downstream reaction zones is much less than that in the first reaction zone, so that these downstream reaction zones are more easily controlled using conventional means.

[0069] When more than one hydroformylation reactor or reaction zone is used for a given olefin, the hydroformylation reactors or reaction zones downstream of the first reactor or reaction zone in the series may operate at faster reaction rates under some scenarios, but the amount of available olefin will have been significantly reduced by the time the reaction fluid reaches the downstream reactor / zone, so the amount of heat generated will be low enough that conventional cooling schemes can be used for the downstream reactors.

[0070] In one embodiment, not more than 30% of the total olefins fed to the hydroformylation process are diverted to a downstream reactor to maintain the amount of heat removed in the heat exchanger used to remove heat from the first reaction zone. The diverted olefins are typically fed to a second reactor or reaction zone in the reaction train. In some embodiments, at least 1% of the total olefins fed to the hydroformylation process are diverted to a downstream reactor to maintain the amount of heat removed in the heat exchanger used to remove heat from the first reaction zone. In some embodiments, at least 5% of the total olefins fed to the hydroformylation process are diverted to a downstream reactor to maintain the amount of heat removed in the heat exchanger used to remove heat from the first reaction zone. In some embodiments, at least 10% of the total olefins fed to the hydroformylation process are diverted to a downstream reactor to maintain the amount of heat removed in the heat exchanger used to remove heat from the first reaction zone. In some embodiments, 1% to 30% of the total olefins fed to the hydroformylation process are diverted to a downstream reactor to maintain the amount of heat removed in the heat exchanger used to remove heat from the first reaction zone. In some embodiments, 5% to 30% of the total olefins fed to the hydroformylation process are diverted to a downstream reactor to maintain the amount of heat removed in the heat exchanger used to remove heat from the first reaction zone. In some embodiments, 10% to 30% of the total olefins fed to the hydroformylation process are diverted to a downstream reactor to maintain the amount of heat removed in the heat exchanger used to remove heat from the first reaction zone.

[0071] In one embodiment, an existing hydroformylation reaction system can be converted to one that uses a more reactive catalyst system or more reactive olefins using the process of the present invention. Such conversion may be particularly desirable if the heat exchangers used in the first reactor or first reaction zone designed for the existing hydroformylation system do not have sufficient heat removal capacity when a more reactive catalyst system and / or olefins are used instead. By diverting a portion of the olefin and / or catalyst to the second reactor / reaction zone according to the process of the present invention, the overall heat load is redistributed so that the heat exchangers of the first reactor can handle the heat load. Controlling the proportion of the diverted flow allows for stable control of such a retrofit system.

[0072] Both approaches (bypassing a portion of the olefin feedstock and bypassing a portion of the recycled hydroformylation catalyst) can balance the requirements of the first reactor or reaction zone to control reactivity to avoid excessive temperatures, thermal cycling, and similar control issues. For example, in monophosphite-based catalyst systems, excessive reaction can cause CO depletion, which can lead to rhodium losses. The ability to adjust the reactivity in the first reactor by increasing the reactivity in the second reactor can allow time to make other adjustments, such as lowering the temperature of the first reactor, but these alternative processes can be slow and limited by cooling water constraints.

[0073] Option (1) (diverting a portion of the olefin feed stream) can, in some embodiments, provide faster response times for controlling the first reactor and be easier to implement (i.e., bypass of the propylene (or other olefin) feed can be adjusted based on the temperature in the first reactor or reaction zone without the need to measure rhodium content). One possible approach is to monitor the first reactor's heat exchanger control valve and, when it approaches 90% open, divert a portion of the olefin feed stream and / or a portion of the hydroformylation catalyst recycle stream to reduce the reaction (heat load) in the first reactor. In effect, this can act as an "emergency valve." Because the first reactor is over-reacted, there is little olefin left to react in the second reactor, and therefore, shifting the reaction from the overloaded first reactor to the underutilized second reactor does not affect overall conversion.

[0074] Option (2) (bypassing a portion of the recycled hydroformylation catalyst) can have the advantage that the rhodium content in the downstream reactors can be much higher than in the first reactor, thereby increasing (or at least maintaining) the overall conversion through more forced reactivity. In some embodiments, the residence time from the second reactor to the product / catalyst separation zone is shorter than starting from the first reactor, so the amount of catalyst decomposition that occurs at higher concentrations can be mitigated by the shorter contact time. Option (2) can be easily implemented using the ratio of flow rate controls on the tails of the vaporizers feeding the first reactor and the downstream reactor, or by using online rhodium measurement techniques (e.g., XRF, GC (e.g., for triarylphosphine-based systems), or HPLC techniques).

[0075] It should be understood that any combination of the above embodiments may be used.

[0076] The hydroformylation process of the present invention can be implemented using readily commercially available process control hardware and software, as known to those skilled in the art in light of the teachings herein. The improved reactor control and stability of the process of the present invention provides a useful basis for the effective implementation of advanced process control (APC) techniques, such as multivariable model predictive control (MMPC), dynamic matrix control (DMC), real time optimization (RTO), or advanced control and optimization (AC&O). Advanced process control techniques are well known to those skilled in the art (see, for example, https: / / en.wikipedia.org / wiki / Advanced_process_control) and can be implemented using techniques known to those skilled in the art based on the teachings herein.

[0077] Any suitable process equipment can be used. The design and construction, including the selection of suitable materials of construction, of hydroformylation process equipment is well known to those skilled in the art. In one embodiment of the present invention, the heat exchanger in the first reactor or reaction zone has a flow rate of at least 75 kW / m 3 (reactor volume) can be removed from the stream.

[0078] Compared to prior art processes, some embodiments of the hydroformylation process of the present invention can provide a more rapid response to changes in reaction rate. For example, if an increase in reactor temperature is detected, the reaction rate can be rapidly reduced by reducing the flow rate of either recycled catalyst or fresh olefin feed to the first reactor. The catalyst or olefin is diverted to the second reaction zone, thereby maintaining the overall plant production rate.

[0079] Some embodiments of the present invention are described in more detail in the following examples. [Example]

[0080] All parts and percentages in the following examples are by weight unless otherwise indicated. Pressures are given as absolute pressures unless otherwise indicated.

[0081] The following examples are given to illustrate the present invention and should not be construed as limiting the scope of the invention.

[0082] Comparative Example A (CEA) (not an embodiment of the invention) A simulation was performed to illustrate the operation of a conventional hydroformylation reactor control scheme. The process flowsheet shown in Figure 1 is the basis for this simulation. The reaction kinetics are modeled using a highly reactive hydroformylation catalyst (a commonly used bisphosphite) and propylene. The catalytic reaction rate is determined by conventional means similar to the technique taught in Rush, et al., "Kinetics and Mechanism of Propylene Hydroformylation Catalyzed by Rhodium Complexes with a Diphosphate Ligand," Kinetics and Catalysis, 2009, Vol. 50 (#4), pp. 557-566. A three-reactor train was used in the model, and reaction parameters for steady-state, stable operation using AspenPlus Dynamics software, available from AspenTech, are listed in Table 1 (CEA). Typical initial process conditions used in the model are listed in Table 1.

[0083] The effect of the modifications taught in this invention is then illustrated in Inventive Examples 1-4 (IE1-4), which use the same system as CEA (except as noted below) and apply heat duty and overall olefin conversion without any other optimization. The total amount of olefin feed is held constant to evaluate any changes in overall plant conversion (measured as "stabilizer tail," which represents the crude aldehyde product after removal of unreacted syngas, olefins, and hydrocarbons).

[0084] Example 1 (IE1) of the present invention The same parameters as used in the CEA are used, except that 10% of the propylene (C3H6) feed is diverted to the second reactor. This diversion of a portion of the propylene feed to the second reactor is illustrated by the process flowsheet in Figure 2. The reactor temperature and syngas partial pressure are kept as constant as possible.

[0085] Example 2 of the present invention (IE2) The same parameters as used in the CEA are used, except that 25% of the recycled catalyst from the product / catalyst separation zone is diverted to the second reactor. This diversion of a portion of the recycled catalyst to the second reactor is illustrated by the process flowsheet in Figure 3, and the same process flowsheet is also used in the following inventive examples 3 and 4. The reactor temperature and syngas partial pressure are kept as constant as possible.

[0086] Example 3 of the present invention (IE3) The same parameters as used in the CEA are used, except that 50% of the recycled catalyst from the product / catalyst separation zone is diverted to the second reactor. The reactor temperature and synthesis gas partial pressure are kept as constant as possible.

[0087] Example 4 of the present invention (IE4) The same parameters as used in the CEA are used, except that 80% of the recycled catalyst from the product / catalyst separation zone is diverted to the second reactor. The reactor temperature and synthesis gas partial pressure are kept as constant as possible.

[0088] [Table 1]

[0089] Inventive Example 1 shows that by diverting 10% of the olefin (propylene) to the second reactor, the load on the heat exchanger of the first reactor was reduced by approximately the same amount (9%), and the overall plant conversion was reduced very slightly (97.2% compared to 97.4% for CEA). The small reduction in overall plant conversion could be easily corrected by a small increase in process parameters in the downstream reactors, such as syngas partial pressure or temperature.

[0090] Inventive Examples 2-4 demonstrate that a large shift in the amount of recycled catalyst diverted to the second reactor moderately shifted the reactor load in the first reactor. The amount of reaction does not change linearly because the resulting unconverted olefin concentration increases while the catalyst concentration decreases, partially offsetting the two effects. This means that adjusting the amount of recycled catalyst provided to the first reactor (diverted to the second reactor) allows for a moderate and controlled shift in reactivity (and thus load shift) in the first reactor. Shifting 50% of the recycled catalyst (Inventive Example 3) did not result in a detectable change in plant productivity, but provided a comparable amount of control (a 10% reduction in the heat load in the first reactor) as seen in Inventive Example 1. Diverting 80% of the recycled catalyst to the second reactor (Inventive Example 4), reducing the load on the first reactor by 43%, only reduced the overall plant conversion by 0.3%. Small decreases in overall plant conversion could be easily corrected by small increases in process parameters in downstream reactors, such as syngas partial pressure or temperature.

Claims

1. (a) reacting CO, H in the presence of a hydroformylation catalyst in a reaction fluid in at least two reaction zones under hydroformylation conditions sufficient to form at least one aldehyde product; ２ and at least one olefin, wherein the hydroformylation catalyst comprises a catalytic metal and a ligand, and the reaction temperature in the first reaction zone is controlled using a first heat exchanger; (b) recovering at least a portion of said hydroformylation catalyst from the product stream and recycling at least a portion of said recovered hydroformylation catalyst through said first reaction zone; Including, 1. A continuous hydroformylation process comprising: (1) varying the olefin partial pressure in the first reaction zone by diverting a portion of an olefin feed stream from the first reaction zone to a downstream reaction zone and adjusting the amount of the olefin feed stream diverted; and / or (2) varying the concentration of the catalytic metal in the first reaction zone by diverting a portion of recycled hydroformylation catalyst from the first reaction zone to a downstream reaction zone and adjusting the amount of recycled hydroformylation catalyst diverted, thereby slowing the reaction rate in the first reaction zone and increasing the reaction rate in downstream reaction zones to ensure that sufficient heat removal capacity remains in the heat exchanger in the first reaction zone to ensure stable control of the reaction at a target reaction temperature.

2. 10. The process of claim 1, wherein the reaction temperature in the first reaction zone is maintained within 1°C of the target reaction temperature.

3. 3. The process of claim 1 or claim 2, further comprising measuring an olefin concentration in the headspace of the first reaction zone and adjusting the amount of the olefin feed stream diverted to the downstream reaction zone based on the measurement.

4. 4. The process of claim 1, wherein the reaction rate is greater than 1.5 gmol aldehyde / liter reactor volume / hour.

5. The process of any one of claims 1 to 4, wherein the ligand is a hydrolyzable organophosphorus ligand.

6. The process of any one of claims 1 to 5, wherein the catalytic metal is rhodium.

7. The process of any one of claims 1 to 6, wherein the reaction temperature is 100°C or less.

8. 8. The process of any one of claims 1 to 7, wherein at least one advanced process control technique is used to control the hydroformylation process.

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