Process for controlling heavies in recycle catalyst streams

Abstract

Specifically, a process for controlling heavies in a recycle catalyst stream for use in a continuous hydroformylation process in which olefins are converted with synthesis gas in the presence of a hydroformylation catalyst to form an aldehyde product stream, followed by separation of the catalyst for recycle to the hydroformylation step, comprises removing a crude product stream from a hydroformylation reaction zone, the crude product stream comprising one or more aldehyde products, one or more heavy by-products, a transition metal-organophosphorus ligand complex catalyst, one or more unconverted reactants, and one or more inert lights; providing a water stream; combining the water stream with the crude product stream into an azeotropic vaporizer; removing from the vaporizer an overhead gas stream comprising the one or more aldehyde products, the one or more unconverted reactants, the one or more inert lights, a portion of the water, and a portion of the heavy by-products; a liquid recycle catalyst stream to be sent to the reaction zone, the liquid recycle catalyst stream comprising the transition metal-organophosphorus ligand complex catalyst, a remainder of the aldehyde product, and a remainder of the heavy by-products, as a residue stream from the azeotropic vaporizer, wherein at least 25% of the aldehyde product recovered in the overhead gas stream from the condenser is removed as a water azeotrope.

Description

[Technical Field]

[0001] The present invention relates to a method for controlling heavies in a catalyst recycle stream. More particularly, the present invention relates to a two-stage process of hydroformylation and product-catalyst separation for controlling heavies in a catalyst recycle stream to a hydroformylation stage.

[0002] It is well known in the art that aldehydes can be produced by reacting olefinically unsaturated compounds with carbon monoxide and hydrogen in the presence of a metal-organophosphorus ligand complex catalyst, and that a preferred process involves continuous hydroformylation and recycling of a catalyst solution containing a metal-organophosphorus ligand complex catalyst, wherein the metal is selected from Group 8, Group 9, or Group 10. Rhodium is a preferred Group 9 metal. Such technology is exemplified by U.S. Pat. Nos. 4,148,830, 4,717,775, and 4,769,498. Aldehydes produced by such processes have wide utility, for example, as intermediates for hydrogenation to aliphatic alcohols, amination to aliphatic amines, oxidation to aliphatic acids, and aldol condensation to produce components of plasticizers.

[0003] Commercial hydroformylation of C4 or higher olefins in the presence of a rhodium-triorganophosphine ligand complex catalyst, such as a rhodium-triphenylphosphine ligand complex catalyst, is typically carried out in an integrated reaction-separation system similar to that shown in Figure 1. For example, the C4 olefins include an essentially pure 1-butene or 2-butene stream, as well as mixed C4 raffinate I and raffinate II streams containing 1-butene, 2-butene, isobutylene, and butane. Referring to Figure 1, the mixed butene-containing raffinate stream (1) is fed to a first reactor (Reactor 1) along with a stream (2) containing carbon monoxide and hydrogen (synthesis gas). A liquid product stream (3) is removed from the first reactor and fed to a second reactor (Reactor 2), while a gas stream (4) removed from the top of the first reactor may also be fed to the second reactor (Reactor 2). Each reactor contains a quantity of rhodium-triphenylphosphine ligand complex catalyst and, optionally, free triphenylphosphine ligand. The complex catalyst and optional free ligand are advantageously solubilized in liquid heavy by-products, including aldehyde condensation dimers, trimers, and higher oligomers derived from the hydroformylation of the C4 feed. The gas stream (5) exiting the last reactor can be recycled to the first reactor, combusted, or fed as fuel to a downstream process. The liquid product stream (6) exiting the last reactor is sent to a vaporizer, from which an overhead stream (7) containing one or more C5 aldehyde products, one or more unconverted C4 olefins, unconverted synthesis gas, volatile inerts (e.g., butane), and some heavy by-products is removed. The overhead stream (7) from the vaporizer is condensed at approximately 40°C and 10 psig (69 kPa), and the resulting liquid stream (8) is sent to a purification zone (unit not shown) for C5 separation and purification. A vent stream (9) removes volatiles from the condenser. These volatiles consist primarily of nitrogen, carbon monoxide, hydrogen, and less than 1 percent aldehyde products. The vent gas can be flared, sent to a vent recovery stream, or sent to a downstream plant fuel stream.A catalyst recycle stream (10) containing the rhodium-triphenylphosphine ligand complex catalyst and, optionally, free triphenylphosphine ligand dissolved in the liquid heavy by-products is obtained from the vaporizer as a liquid tail stream and is typically recycled to the first hydroformylation reactor (Reactor 1). The operating conditions of the vaporizer are adjusted so that the rate of heavies production in the reaction system is essentially equal to their removal rate in the vaporizer. The vaporizer operates at approximately 135°C and superatmospheric pressure. Under these vaporizer conditions, the rhodium-triphenylphosphine ligand complex catalyst is thermally stable. Significantly higher temperatures can result in catalyst deactivation. Furthermore, the concentration of heavies in the catalyst recycle stream to the first reactor typically remains constant, avoiding the accumulation of heavy by-products in the recycle stream to the hydroformylation reactor.

[0004] Current hydroformylation processes favor the replacement of triorganophosphine ligands with organophosphite ligands because the latter have higher activity and can produce a higher ratio of normal to branched isomer aldehyde products. The prior art describes various mono-, bis-, and poly-organophosphite ligands for use in modern hydroformylation processes. Unfortunately, organophosphite ligands tend to be less stable than triorganophosphine ligands, i.e., more susceptible to thermal decomposition. For example, rhodium-organophosphite catalysts tend to thermally decompose in the vaporizer under operating conditions suitable for rhodium-triphenylphosphine ligands. Therefore, it is desirable to operate the vaporizer at temperatures below 135°C to minimize thermal decomposition of the organophosphite ligand.

[0005] Operating the vaporizer at temperatures below 135°C with higher molecular weight olefins necessitates the use of subatmospheric pressures to remove heavies overhead to the desired extent. The amount of heavies in the tails stream from the vaporizer should be sufficient to solubilize the catalyst and optional free ligand for recycle in the liquid stream returned to the hydroformylation reactor; however, it is desirable to avoid accumulation of heavies in the recycle stream. Therefore, it is desirable to remove heavies overhead from the vaporizer at essentially the same rate as they are formed in the hydroformylation step to avoid an increase in the amount of heavies returned to the hydroformylation reactor, where they would occupy increased reactor volume and reduce productivity. Therefore, to stabilize the organophosphite catalyst and remove heavies to the desired extent, the vaporizer must be operated at temperatures below 135°C and subatmospheric pressures. Unfortunately, condensation of the overhead stream removed from the vaporizer becomes a problem at subatmospheric pressures. Condensation temperatures below 0°C require expensive refrigeration units and complicate the overall system. It would be desirable to avoid this expense and complexity by using a simple water-cooled condensing unit to condense the overhead stream from the vaporizer, but it is not clear from the prior art how to use conventional water cooling when using the desired organophosphite ligand in the hydroformylation step.

[0006] As the molecular weight of the product aldehyde increases, the boiling point of the heavies also increases dramatically, making their removal more difficult. Higher temperatures in the vaporizer may be required, but these higher temperatures may also promote ligand loss and / or the formation of more heavies, thus quickly reaching a limit where the heavies cannot be vaporized faster than their rate of formation, limiting catalyst life.

[0007] U.S. Patent No. 6,727,391 discloses a hydroformylation process using two vaporizers in series, each operating at a lower pressure than the hydroformylation reactor, with the second vaporizer operating at a lower pressure than the first. The liquid stream from the second vaporizer is sent to a packed column where it is scrubbed with the vapor stream from the second vaporizer. U.S. Patent No. 6,100,432 discloses a similar technique to U.S. Patent No. 6,727,391, but utilizes only one vaporizer.

[0008] US Pat. No. 6,610,891 discloses a hydroformylation process that minimizes heavies by minimizing the temperatures used throughout the reaction zone and catalyst / product separation zone.

[0009] No. 5,648,553 discloses several hydroformylation process schemes that utilize a gas-liquid contact column immediately following the reactor. The liquid hydroformylation product stream is countercurrently scrubbed with synthesis gas after a vaporization step.

[0010] US Pat. No. 5,917,095 discloses a hydroformylation process using a rhodium-organophosphite catalyst, along with a general discussion of catalyst-product separation by vaporization.

[0011] U.S. Patent No. 7,262,330 describes a method for removing water from a hydroformylation system prior to the primary vaporizer to reduce decomposition of the phosphite ligand. The objective of this invention is to minimize the presence of water in the vaporizer to avoid ligand hydrolysis.

[0012] British Patent No. 826763(A) uses azeotropic distillation of aldehydes in the C4-C6 range with water to separate normal and isoaldehyde products downstream of a hydroformylation process. This disclosure is silent on the issues of vaporizing the aldehyde products and removing heavies from the catalyst solution, but rather focuses on downstream isomer separation.

[0013] U.S. Patent No. 8,404,903 and U.S. Patent Application Publication No. 20170355656 disclose stripping gas vaporizers for removing heavies with minimal catalyst damage while reducing distillation conditions. However, due to heavies accumulation, especially in high molecular weight aldehydes, the distillation temperatures are still higher than preferred to ensure longer catalyst life. It would be desirable to achieve even lower temperatures and / or higher heavies removal rates to extend catalyst life, especially for hydroformylation processes involving C4 or higher olefins.

[0014] WO2021010878A1 - This teaches a method for reducing the presence of heavies from a catalyst mixture by using a series of primary vaporizers followed by a secondary non-azeotropic short residence time vaporizer. The invention stages the vaporizers but does not mention azeotropic vaporization in the secondary vaporizer.

[0015] European Patent No. 1232008 - This reference utilizes a membrane separator as a secondary separation unit operation after the primary vaporizer to remove heavies. Similarly, U.S. Patent No. 10,017,443 has a membrane unit operation as the primary separation step, after which the permeate proceeds to a conventional vaporizer and the retentate is recycled to the reactor. A conventional non-azeotropic vaporizer thermally separates the aldehyde product, and the catalyst solution in the vaporizer tail is sent to another membrane unit that removes heavies from the system, thus requiring two membrane units.

[0016] The rate of heavies formation is a function of many variables, with temperature being a significant variable. Using the "rule of thumb" of doubling the rate for every 10°C, even a small decrease in vaporizer temperature can have a dramatic effect on the rate of ligand loss and heavies formation, and therefore potentially provide significantly longer catalyst life. The presence of water can also inhibit the formation of acetals or ester-based heavies based on Le Chatelier's law. Summary of the Invention

[0017] In one aspect, the present invention provides a process for controlling heavies in a catalyst recycle stream, the process comprising: (a) removing a crude product stream from a hydroformylation reaction zone, the crude product stream comprising one or more aldehyde products, one or more heavy by-products, a transition metal-organophosphorus ligand complex catalyst, one or more unconverted reactants, and one or more inert lights; (b) providing a water flow; (c) combining the water stream from step (b) with the stream from step (a) into a vaporizer; (d) removing an overhead gas stream from the vaporizer, the overhead gas stream including one or more aldehyde products, one or more unconverted reactants, one or more inert lights, a portion of the water, and a portion of the heavy by-products, and feeding the overhead gas stream to a condenser; (e) removing an overhead gas stream from the condenser, the overhead gas stream comprising one or more unconverted reactants, a portion of the added water, and one or more inert lights; (f) recovering a liquid stream from the condenser comprising the aldehyde product, heavy by-products, and water; (g) separating the organic components from the water from step (f) in a liquid-liquid separation zone to recover a crude aldehyde product as a top layer and an aqueous phase as a bottom layer; (h) removing as a residue stream from the vaporizer a liquid recycle catalyst stream that is passed to the reaction zone and includes the transition metal-organophosphorus ligand complex catalyst, a remainder of the aldehyde product, and a remainder of the heavy by-products, wherein at least 25% of the aldehyde product recovered in step (d) is removed as a water azeotrope.

[0018] The process of the present invention is advantageously adapted to any process that first uses an organophosphorus as a ligand in a transition metal-ligand complex catalyst in a hydroformylation reaction to produce one or more aldehyde products from one or more reactants, and second obtains a crude product stream therefrom, mixes it with water, and then feeds it to a vaporizer to separate the aldehyde products from the catalyst for recycling back to the first reaction step. For purposes of the present invention, the term "azeotropic vaporizer" is used to describe a vaporizer used to separate a crude product stream from a hydroformylation process fluid stream by adding water to the vaporization process so that at least 25% of the resulting aldehyde products are vaporized as an azeotrope. Advantageously, the process of the present invention controls the amount of heavies recycled to the reaction step compared to the increase in the amount of heavies when the process is run under similar conditions but without the use of added water. (This comparison assumes that no heavies are intentionally added to this invention of the process to maintain higher levels of heavies, e.g., for catalyst solubilization.) Thus, reactor volume remains optimally available for producing desired products, rather than being consumed by an ever-increasing volume of unproductive heavies. The process of the present invention is most advantageously adapted as a two-step process in which olefins are hydroformylated with carbon monoxide and hydrogen in the presence of a transition metal-organophosphorus ligand complex catalyst, and the resulting crude product mixture is separated in an azeotropic vaporizer to recover the catalyst for recycle to the hydroformylation step.

[0019] The advantage of an azeotropic vaporizer is that vaporization occurs at much lower temperatures compared to vaporization of the product aldehyde and / or heavies in the absence of an azeotrope. For example, the normal boiling point of 2-methylpentanal at atmospheric pressure is 118°C, but the water azeotrope boils at 88.5°C, allowing for dramatically lower temperatures to be used. Another example is valeraldehyde, which boils at 103°C; the water azeotrope lowers the boiling point to 83°C. In addition to aldehydes, heavies can also form azeotropes with water. For example, 2-ethyl-2-hexenal is an aldol condensation product ("dimer") of butyraldehyde, which boils at 176°C; the water azeotrope lowers the boiling point to 97.6°C.

[0020] In a preferred embodiment, the rate of removal of heavy by-products in the overhead gas stream from the azeotropic vaporizer is increased relative to the rate of production of heavy by-products in the hydroformylation step compared to a process without added water.

[0021] In a preferred embodiment, the rate of removal of heavy by-products in the overhead gas stream from the vaporizer is essentially equal to the rate of production of heavy by-products in the hydroformylation process. [Brief explanation of the drawings]

[0022] [Figure 1] 1 shows a conventional integrated process for hydroformylation and separation of the liquid hydroformylation product in a vaporizer, with recycle of the liquid catalyst stream to the hydroformylation. [Figure 2] 1 illustrates an integrated process of the present invention for hydroformylation and subsequent separation of the liquid hydroformylation product in an azeotropic vaporizer, with recycle of the liquid catalyst stream to the hydroformylation and recycle of the aqueous phase. [Figure 3] 1 illustrates a preferred embodiment of the present invention for hydroformylation and subsequent separation of the liquid hydroformylation product in an azeotropic vaporizer with a preliminary conventional vaporization process prior to the azeotropic vaporizer. [Figure 4]1 illustrates a preferred embodiment of the present invention for hydroformylation and subsequent separation of the liquid hydroformylation product in an azeotropic vaporizer with a pre-membrane catalyst / product separation process prior to the azeotropic vaporizer. DETAILED DESCRIPTION OF THE INVENTION

[0023] References herein to the Periodic Table of the Elements are intended to refer to the Periodic Table of the Elements as published in Nomenclature of Inorganic Chemistry: IUPAC Recommendations 2005, Royal Society of Chemistry, 2005, ed. N.G. Connelly and T. Damhus. Also, any reference to a Group is to that Group as reflected in the Periodic Table of the Elements using the IUPAC system for numbering Groups.

[0024] All percentages, preferred amounts or measurements, ranges, and their endpoints herein are inclusive, i.e., "less than about 10" includes about 10. "At least" is equivalent to "greater than or equal to," and thus "up to" is equivalent to "less than or equal to." Numbers herein do not have precision beyond that stated. Thus, "115" includes at least 114.5 to 115.49. All ranges from "at least," "greater than," "greater than or equal to," or similarly described parameters to "up to," "to," "less than," "less than or equal to," or similarly described parameters are preferred ranges, regardless of the relative degree of preference expressed for each parameter. Thus, ranges with advantageous lower limits combined with most preferred upper limits are preferred in the practice of the invention. The term "advantageous" is used to indicate a degree of preference greater than required, but less than that indicated by the term "preferably."

[0025] Except in the examples, or unless otherwise indicated, all numbers expressing quantities, percentages, properties, functionality, and the like in this specification should be understood to be modified in all instances by the term "about." Unless otherwise specified, an element, material, or step that may cause an undesirable effect is considered substantially absent with respect to the practice of the present invention if present in an amount or form that does not cause the effect to an unacceptable extent. Those skilled in the art will recognize that acceptable limits vary with equipment, conditions, applications, and other variables, but can be determined without undue experimentation in each applicable situation. In some cases, variation or deviation of one parameter may be acceptable to achieve another desired objective.

[0026] The term "comprising" is synonymous with "including," "containing," or "characterized by" and is inclusive or open-ended and does not exclude additional, unrecited elements, materials, or steps. The term "consisting essentially of" indicates that, in addition to the specified elements, materials, or steps, unrecited elements, materials, or steps are optionally present in amounts that do not unacceptably affect at least one basic and novel characteristic of the subject matter. The term "consisting of" indicates that only the recited elements, materials, or steps are present, except that unrecited elements, materials, or steps are optionally present to the extent that they have no appreciable effect or are substantially absent.

[0027] In one aspect, the present invention provides a process for controlling heavies in a catalyst recycle stream, the process comprising: (a) removing a crude product stream from a hydroformylation reaction zone, the crude product stream comprising one or more aldehyde products, one or more heavy by-products, a transition metal-organophosphorus ligand complex catalyst, one or more unconverted reactants, and one or more inert lights; (b) providing a water flow; (c) combining the water stream from step (b) with the stream from step (a) into an azeotropic vaporizer; (d) removing an overhead gas stream from the vaporizer, the overhead gas stream including one or more aldehyde products, one or more unconverted reactants, one or more inert lights, a portion of the water, and a portion of the heavy by-products, and feeding the overhead gas stream to a condenser; (e) removing an overhead gas stream from the condenser, the overhead gas stream comprising one or more unconverted reactants, a portion of the added water, and one or more inert lights; (f) recovering a liquid stream from the condenser comprising the aldehyde product, heavy by-products, and water; (g) separating the organic components from the water from step (f) in a liquid-liquid separation zone to recover a crude aldehyde product as a top layer and an aqueous phase as a bottom layer; (h) removing as a residue stream from the vaporizer a liquid recycle catalyst stream that is passed to the reaction zone and includes the transition metal-organophosphorus ligand complex catalyst, a remainder of the aldehyde product, and a remainder of the heavy by-products, wherein at least 25% of the aldehyde product recovered in step (d) is removed as a water azeotrope.

[0028] In the present invention, reference is hereinafter made to a "reaction process," "reaction fluid," or "reaction" in which one or more reactants are contacted in an organic solvent in the presence of a metal-organophosphorus ligand complex catalyst, one or more inert lights, and optionally free organophosphorus ligand to produce a crude liquid product stream comprising one or more reaction products, one or more unconverted reactants, the transition metal-organophosphorus ligand complex catalyst, optionally free organophosphorus ligand, one or more heavy by-products, and one or more inert lights. A preferred process is a hydroformylation process in which the reactants comprise at least one olefin as described herein, as well as carbon monoxide and hydrogen.

[0029] The terms "reaction fluid," "reaction medium," and "catalyst solution" are used interchangeably herein and may include, but are not limited to, a mixture containing (a) a metal-organophosphorus ligand complex catalyst, (b) free organophosphorus ligand, (c) aldehyde products formed in the reaction, (d) unreacted reactants, (e) an organic solvent for the metal-organophosphorus ligand complex catalyst and the free organophosphorus ligand, and, optionally, (f) one or more aldehyde condensation compounds formed in the reaction. Reaction fluids may include, but are not limited to, (a) fluids in a reaction zone, (b) a fluid stream en route to at least one separation zone, (c) a fluid in a separation zone, (d) a recycle stream, (e) a fluid withdrawn from a reaction zone or a separation zone, (f) a withdrawn fluid being separated in a liquid-liquid separation zone, (g) a separated fluid returned to a reaction zone or a separation zone, and (h) a fluid in an external cooler. For purposes of this invention, the term "heavies" refers to liquid by-products of the process characterized as compounds having a normal boiling point at least 25° C. higher than that of the desired product of the reaction process. In a hydroformylation reaction, for example, where the reactants include one or more olefins (olefinically unsaturated compounds) and the desired product includes one or more isomeric aldehydes, the heavy by-products include compounds having a boiling point at least 25° C. higher than that of the aldehyde product. These by-products are typically condensation products of aldehydes to form esters, alcohols, hemiacetals, and acetals (and combinations thereof), as described, for example, in U.S. Pat. Nos. 4,148,830 and 4,247,486.

[0030] For purposes of this invention, the term "lights" refers to reactants, inerts, by-products of the process, or combinations thereof, characterized by having a normal boiling point that is at least 25° C., and preferably at least 50° C., lower than the normal boiling point of the desired product of the reaction process. As used herein, the terms "inert lights" or "light inerts" refer to lights that are unreactive in the process. "Reactive lights" refer to lights that are reactive in the process. As an example, in a hydroformylation process, reactive lights include carbon monoxide and hydrogen, while inert lights include alkanes present in the olefin feed to the reaction.

[0031] In another embodiment, the process further comprises passing the crude product stream from step (a) through a pre-product / catalyst separation process prior to step (c). This pre-product / catalyst separation process may advantageously comprise a distillation or vaporization process, wherein the overhead stream is a first crude aldehyde product stream and the bottoms are the transition metal-organophosphorus ligand complex catalyst and a heavies stream, a portion of which is then fed to step (c). Alternatively, this pre-product / catalyst separation process may comprise a membrane separation process, wherein the retentate comprises the transition metal-organophosphorus ligand complex catalyst, some of the aldehyde product, and a heavies stream and is recycled to the reaction zone, and the permeate comprises the aldehyde product, at least some heavies, unconverted reactants, inert lights, and some catalyst components and is then fed to step (c). Alternatively, the liquid-liquid phase separation process can be used as a preliminary product / catalyst separation process as described in U.S. Pat. No. 5,952,530, in which case the product phase (containing trace amounts of catalyst) and / or the catalyst-containing phase (containing substantial product aldehyde) can be fed to one or more azeotropic vaporizers specific for that particular stream, as step (c) above.

[0032] Preferably, a majority of the total aldehyde product produced in the hydroformylation reaction zone is separated in a pre-product / catalyst separation zone.

[0033] In another embodiment of the invention, at least a portion of the bottom aqueous phase from step (g) is recycled to step (b).

[0034] In another embodiment of the present invention, a buffer to maintain a proper pH value is added to the water stream before it is fed to the vaporizer.

[0035] In another embodiment of the invention, the water stream in step (b) is in the form of steam.

[0036] In some embodiments, the azeotropic vaporizer is a stripping gas vaporizer.

[0037] In a preferred embodiment, the rate of removal of heavy by-products in the overhead gas stream from the azeotropic vaporizer is essentially equal to the rate of production of heavy by-products in the hydroformylation reactor. In a preferred embodiment, the rate of removal of heavy by-products in the overhead gas stream from the azeotropic vaporizer can exceed the rate of production of heavy by-products in the hydroformylation reactor.

[0038] Referring to Figure 2, which embodies the present invention in connection with a hydroformylation process with subsequent product-catalyst separation, olefin and syngas feedstocks are fed to a feed pretreatment block (11), after which the feed stream is fed to a reaction zone (12). For purposes of this invention, olefins can range from C3 to C20, so long as the aldehydes synthesized therefrom form a minimum-boiling azeotrope with water. Determining whether an aldehyde forms a minimum-boiling azeotrope can be accomplished by methods well known in the art. The reaction zone (12) can be a single reactor or a collection of reactors in series or parallel, ranging from stirred tank reactors, jet mixer reactors, plug flow reactors, bubble column reactors, or mixtures thereof.

[0039] The aldehyde product formed in the reaction zone (12) is fed into the azeotropic vaporizer (13) along with the catalyst solution. Liquid water or steam is also introduced into the azeotropic vaporizer (13) via line (14) through a water reservoir (16). The organic phase from the reaction zone (12) and the aqueous phase from line (14) can be premixed using a static in-line mixer before entering the azeotropic vaporizer (13). Alternatively, the design of the azeotropic vaporizer can include providing intimate contact between the two phases as they vaporize before or upon entering the vaporizer. The amount of water / steam added to the system depends on the concentration of the aldehyde produced, the catalyst system, and the solvent, if used. The catalyst used in the hydroformylation, whether as a Rh-ligand complex or as the ligand itself, is selected so as not to form an azeotrope with water. The amount of water entering the azeotropic vaporizer (13) has a concentration greater than the solubility limit of water in the catalyst solution / aldehyde product exiting the reaction zone (12). Therefore, a liquid-liquid contactor between water and the catalyst solution to supply water to the catalyst solution is insufficient and cannot be used as the sole water source (such a system cannot exceed the solubility limit of water in the catalyst solution). Under the correct operating conditions as taught herein, the azeotropic vaporizer vaporizes a water-oxygenation product azeotrope, which is condensed in the condenser (15). The oxygenation product is primarily the aldehyde product, but may also include heavier hydroformylation by-products, called heavies, which can form azeotropes with water. The azeotropic vaporizer (13) can be configured to operate so that the liquid and vapor phases flow simultaneously (e.g., a rising film evaporator) or countercurrently relative to each other (e.g., a falling film evaporator). It is also possible to consider an arrangement in which the azeotropic vaporizer operates in a strip gas loop ("stripping gas vaporizer"), such as that disclosed in U.S. Patent No. 8,404,903 and U.S. Patent Application Publication No. 20170355656. Another arrangement is also possible in which the azeotropic vaporizer is a distillation column.

[0040] Condensation of the vapor in condenser (15) results in two liquid phases, an organic phase and an aqueous phase, which are transferred to a liquid-liquid (LL) separator (18). The condenser and LL separator may, in some embodiments, be one unit. The bottoms of the azeotropic vaporizer containing the catalyst solution are preferably fed to a LL separator (17) to separate the liquid water from the catalyst solution, which is then recycled to the reaction zone (12) via line (23). Optionally, an extractor may be present in the catalyst recycle stream, either after the LL separator (17) (if used) or between the vaporizer and the reaction zone, as described in U.S. Pat. No. 10,131,608.

[0041] The formation of two nearly immiscible phases (organic and aqueous) in both LL separators allows for a physical separation that simplifies the separation of azeotrope-forming components. Upon separation, a crude aldehyde product is obtained from LL separator (18) via line (19).

[0042] The aqueous phase from LL separators (17) and / or (18) can be recycled to the water reservoir (16) via lines (21) and (20), respectively, to reduce water usage. An optional water purge stream (22) from LL separator (17) can be used to purge any undesirable species that accumulate in the aqueous phase. Make-up water can be added to the water reservoir (16) to replace any water lost from the system.

[0043] Olefinically unsaturated compounds suitable for use in the process of the present invention are those capable of participating in a hydroformylation process to produce the corresponding aldehyde product and capable of being separated from the crude liquid hydroformylation product stream by vaporization and subsequent decantation. For purposes of the present invention, "olefin" is defined as an aliphatic organic compound containing at least carbon and hydrogen atoms and having at least one carbon-carbon double bond (C=C). Preferably, the olefin contains one or two carbon-carbon double bonds, more preferably one carbon-carbon double bond. The double bond can be located at a terminal position along the carbon chain (alpha olefins) or at any internal position along the chain (internal olefins). Optionally, the olefin can contain elements other than carbon and hydrogen, including, for example, nitrogen, oxygen, and halogens, preferably chlorine and bromine. The olefin can also be substituted with functional substituents, including, for example, hydroxy, alkoxy, and alkyl substituents. Preferably, the olefins used in the process of the present invention include substituted or unsubstituted olefins having a total of 3 to 20 carbon atoms, most preferably 4 to 18 carbons. Exemplary olefins suitable for the process of the present invention include, but are not limited to, propylene and isomers of the following monoolefins: butene, pentene, hexene, heptene, octene, nonene, and decene; specific non-limiting examples include 1-butene, 2-butene, 1-pentene, 2-pentene, and 1-hexene, 2-hexene, 3-hexene, as well as heptene, octene, nonene, and decene. Other non-limiting examples of suitable olefins include 2-methylpropene (isobutylene), 2-methylbutene, cyclohexene, isoprene, 2-ethyl-1-hexene, styrene, 4-methylstyrene, 4-isopropylstyrene, 4-tert-butylstyrene, alpha-methylstyrene, 3-phenyl-1-propene, 1,4-hexadiene, and 1,7-octadiene.

[0044] Preferably, the olefin stream used in the process of the present invention comprises a C4 Raffinate I or C4 Raffinate II isomeric mixture containing butene-1, butene-2, isobutylene, butane, and optionally butadiene. The C4 Raffinate I stream contains 15 to 50 weight percent isobutylene and 40 to 85 weight percent normal butenes, with the remainder to 100 percent being primarily n-butane and isobutane. Normal butenes are generally a mixture of butene-1 and butene-2 ​​(cis and trans). The relative proportions of the stream components will depend on the composition of the petroleum feed, the conditions used in the steam cracking or catalytic cracking operation, and in subsequent process steps from which the C4 stream is derived. The C4 raffinate II stream comprises about 15 to 55 volume percent 1-butene, about 5 to about 15 volume percent 2-butene (5 to 35 volume percent trans-2-butene), about 0.5 to about 5 volume percent isobutylene, and about 1 to about 40 volume percent butane.

[0045] Other embodiments include higher molecular weight olefin starting materials, such as C5 to C20 olefins, as defined herein. For example, in embodiments, when the olefin starting material is mixed C8 olefins, the mixed C8 olefins include a mixture such as can be obtained via the dimerization of mixed butenes, including 1-butene, cis- and trans-2-butene, and optionally isobutene. In one embodiment, a stream containing mixed octenes derived from the dimerization of raffinate II is used; such a mixture can be produced, for example, by the Axens Dimersol process (Institut Français du Petrole, Review, Vol. 37, No. 5, September-October 1982, p. 639) or the Huls AG Octol process (Hydrcarbon Processing, February 1992, p. 45-46). It is understood that the olefin mixture used in the process of the present invention may also contain a certain amount of linear alpha-olefins.

[0046] In some embodiments, the olefin starting material is a mixed C9 olefin as defined herein. Such a mixture may be available from a variety of sources and may be produced, for example, by the process described in Johan A. Martens, Wim H. Verrelst, Georges M. Mathys, Stephen H. Brown, Pierre A. Jacobs, "Tailored Catalytic Propene Trimerization over Acidic Zeolites with Tubular Pores," Angewandte Chemie International Edition, Angewandte Chemie International Edition 2005, Volume 44, Issue 35, pages 5687-5690.

[0047] It should be understood that embodiments of the present invention are designed for use in processes in which the olefin starting material is a C3-20 olefin, such as those described above. In some embodiments, the olefin starting material is primarily mixed C8 olefins or mixed C9 olefins, and may include either mixed C8 olefins or mixed C9 olefins. However, it should also be understood that in processes designed for the hydroformylation of mixed C8 olefins, small amounts of mixed C9 olefins may also be present in the olefin starting material. Similarly, it should also be understood that in processes designed for the hydroformylation of mixed C9 olefins, small amounts of mixed C8 olefins may also be present in the olefin starting material.

[0048] Hydrogen and carbon monoxide are also required for the hydroformylation process of the present invention. These gases may be obtained from any available source, including petroleum cracking and refining operations. A synthesis gas mixture is preferably used. The H:CO molar ratio of gaseous hydrogen to carbon monoxide may preferably range from about 1:10 to about 100:1, with a more preferred H:CO molar ratio being from about 1:10 to about 10:1, and even more preferably from about 1:10 to about 1:2.

[0049] Transition metal-ligand complex catalysts that can be used in the hydroformylation process of the present invention, as well as methods for their preparation, are well known in the art. Generally, such catalysts can be preformed or formed in situ and consist essentially of a transition metal complexed with an organophosphorus ligand, preferably an organophosphite ligand. Suitable transition metals for forming the metal-ligand complex include Groups 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. Preferred metals are rhodium, cobalt, iridium, and ruthenium, more preferably rhodium, cobalt, and ruthenium, and most preferably rhodium. Other suitable metals include Group 6 metals selected from chromium (Cr), molybdenum (Mo), tungsten (W), and mixtures thereof. Mixtures of metals from groups 6, 8, 9 and 10 may also be used in the present invention.

[0050] Preferred organophosphorus ligands that make up the metal-organophosphorus ligand complex and free organophosphorus ligand include mono-, di-, tri-, and higher order organophosphites, as described in detail in U.S. Patent No. 8,404,903. Mixtures of such ligands may be used in the metal-organophosphite ligand complex catalyst and / or the free ligand, if desired, and such mixtures may be the same or different.

[0051] The most preferred organophosphorus ligands are triorganophosphite ligands such as tris-2,4-di-tert-butylphenyl)phosphite represented by formula W.

[0052] [ka]

[0053] A second preferred triorganophosphite ligand comprises tris(2-t-butyl-4-methylphenyl)phosphite, represented by formula X.

[0054] [ka]

[0055] In a preferred embodiment of the present invention, the organophosphorus ligand comprises an organobisphosphite ligand.

[0056] Another class of preferred organophosphorus ligands that make up the metal-organophosphorus ligand complex and the free organophosphorus ligand includes nonionic triarylphosphines, as described in detail in U.S. Patent No. 3,527,809. Mixtures of such triarylphosphine ligands can be used in the metal-organophosphorus ligand complex catalyst and / or the free ligand, if desired. A preferred triarylphosphine is triphenylphosphine.

[0057] As used herein and in the claims, the term "complex" refers to a coordination compound formed by the binding of one or more electron-rich molecules or atoms with one or more electron-poor molecules or atoms. For example, organophosphorus ligands usable herein possess one or more phosphorus donor atoms, each with one available or unshared electron pair, which can independently or cooperatively (e.g., via chelation) form coordinate covalent bonds with the metal. Carbon monoxide may also be present and can form a complex with the metal. Complex catalysts may also contain additional ligands, such as hydrogen or anions, to fill the coordination sites or nuclear charge of the metal. Exemplary additional ligands include, for example, halogens (Cl, Br, I), alkyl, aryl, substituted aryl, acyl, CF, C2F5, CN, (R)2PO, and RP(O)(OH)O (where each R is the same or different and is a substituted or unsubstituted hydrocarbon radical, e.g., alkyl or aryl), acetate, acetylacetonate, SO4, PF4, PF6, NO2, NO3, CHO, CH2=CHCH2, CH3CH=CHCH2, C2H5CN, CH3CN, NH3, pyridine, (C2H5)3N, mono-, di- and tri-olefins, tetrahydrofuran, and the like.

[0058] The number of available coordination sites on the transition metals mentioned above is well known in the art. The catalytic species may include a complex catalyst mixture of monomeric, dimeric, and / or higher nuclear forms, and is preferably characterized by at least one organophosphorus-containing molecule complexed per molecule of transition metal, e.g., rhodium. The catalytic species of the preferred catalyst used in the hydroformylation reaction may be complexed with carbon monoxide and hydrogen in addition to the organophosphorus ligand, in view of the carbon monoxide and hydrogen gases used in the hydroformylation reaction.

[0059] The amount of transition metal-ligand complex catalyst present in the hydroformylation step is the minimum amount necessary to provide the necessary metal concentration to catalyze the selected hydroformylation process. Generally, metal concentrations, e.g., rhodium concentrations, in the range of about 10 ppm to about 1000 ppm, calculated as free metal in the hydroformylation reaction stream, are sufficient for most processes, although it is generally preferred to use about 10 to 500 ppm metal, more preferably 25 to 350 ppm metal.

[0060] Optionally, free ligand (i.e., ligand not complexed with the metal) may also be present in the hydroformylation reaction fluid. The free ligand may correspond to any of the organophosphorus ligands described above. The hydroformylation process of the present invention may advantageously comprise from about 0.1 to about 300 moles of free organophosphorus ligand per mole of metal in the hydroformylation reaction fluid. Preferably, the hydroformylation is carried out in the presence of from about 1 to about 50 moles of organophosphite ligand, more preferably from about 1.1 to about 4 moles of organophosphite ligand, per mole of metal present in the reaction fluid, the amount of ligand being the sum of both the amount of bound ligand complexed with the metal present and the amount of free (uncomplexed) ligand present. When a triarylphosphine is used, the organophosphorus to rhodium ratio is typically much higher, typically comprising 5 to 20 weight percent of the reaction fluid, which typically corresponds to 30 to 300 moles of triarylphosphine per mole of catalyst metal. Make-up or additional ligand can be fed to the hydroformylation process at any time and in any suitable manner as needed, for example to maintain a predetermined level of free ligand in the reaction fluid.

[0061] The reaction conditions for the hydroformylation process can vary widely. For example, the H:CO molar ratio of gaseous hydrogen to carbon monoxide can advantageously range from about 1:10 to 100:1 or more, with a more preferred hydrogen to carbon monoxide molar ratio being from about 1:10 to about 10:1. Advantageously, the hydroformylation process can be carried out at a reaction temperature above about -25°C, more preferably above about 50°C. Advantageously, the hydroformylation process can be carried out at a reaction temperature below about 200°C, preferably below about 120°C.

[0062] Advantageously, the total gas pressure, including the olefin reactant, carbon monoxide, hydrogen, and any inert lights, can range from about 1 psia (6.8 kPa) to about 10,000 psia (68.9 MPa). Preferably, the process is operated at a total gas pressure, including the olefin reactant, carbon monoxide, and hydrogen, of less than about 2,000 psia (6,895 kPa), more preferably less than about 500 psia (34.5 kPa). Advantageously, the carbon monoxide partial pressure varies from about 1 psia (6.8 kPa) to about 1000 psia (6,800 kPa), preferably from about 3 psia (20.7 kPa) to about 800 psia (5,516 kPa), more preferably from about 15 psia (103.4 kPa) to about 100 psia (689 kPa), while the hydrogen partial pressure preferably varies from about 5 psia (34.5 kPa) to about 500 psia (3,450 kPa), more preferably from about 10 psia (68.0 kPa) to about 300 psia (2,070 kPa).

[0063] The synthesis gas (CO+H) feed flow rate can vary widely over any operable flow rate sufficient to achieve the desired hydroformylation process. The synthesis gas feed flow rate depends on the specific form of catalyst, the olefin feed flow rate, and other operating conditions. Similarly, the vent flow rate from the oxo reactor can be any operable flow rate sufficient to achieve the desired hydroformylation process. The vent flow rate depends on the reactor size and the purity of the reactants and synthesis gas feed. Suitable synthesis gas feed and vent flow rates are described in the following reference: "Process Economics Program Report 21D: Oxo Alcohols 21d," SRI Consulting, Menlo Park, California, published December 1999, which is incorporated herein by reference. Other synthesis gas and vent flow rates may be appropriate depending on the process design, as determined by one skilled in the art.

[0064] The crude liquid output from the hydroformylation reactor system can be fed directly to an azeotropic vaporizer. Optionally, the crude liquid output from the hydroformylation reactor system can first be fed to a flash column or "knock-out pot" to reduce pressure and remove a small vent stream of low molecular weight volatiles (lights) such as carbon monoxide, hydrogen, N2, and other inert lights, after which the remaining bulk liquid product is removed from the bottom of the flash column and fed to the azeotropic vaporizer.

[0065] In a preferred embodiment, the crude liquid output from the hydroformylation reaction system or flash column can be fed to a pre-catalyst / product separation process to remove some of the product or some of the catalyst before feeding the azeotropic vaporizer. For example, in a preferred embodiment as shown in FIG. 3, a conventional vaporizer (24) (non-azeotropic) is first used to remove as much crude aldehyde product as possible via line (28), after which at least a portion of the pre-vaporizer residue is sent via line (25b) to the azeotropic vaporizer (13). This concentrates the heavies, thus strengthening the heavy ends azeotrope. The pre-vaporizer (24) is a conventional vaporizer or stripping gas vaporizer that uses thermal energy to vaporize the product aldehyde and retain the catalyst solution in liquid form. The vaporized aldehyde is condensed in condenser (27), which optionally provides a majority of the total crude aldehyde produced via line (28). Preferably, this is the primary product removal process for the system. Provision can be made to feed only a slip stream (25b) of the pre-vaporizer (24) residue to the secondary azeotropic vaporizer (13), with the remainder recycled to the reaction zone via lines (25a) and (23). This slip stream option reduces the amount of water and steam required to operate the azeotropic vaporizer, reduces its size, and reduces the stress on the total ligand inventory due to the stripping requirements in the azeotropic distillation to remove heavies. As described herein, conventional pre-vaporizers (24) and azeotropic vaporizers (13) can be configured so that the liquid and vapor phases flow simultaneously (e.g., rising film evaporators), countercurrently to each other (e.g., falling film evaporators), or operate in different modes. The crude product from the azeotropic vaporizer (via (19)) can be combined with the crude product (28) from the pre-vaporizer or processed separately.

[0066] Alternatively, the crude liquid output from the hydroformylation reactor system can be fed to an intermediate product-catalyst separation process to remove and recycle a portion of the catalyst before feeding the resulting material to an azeotropic vaporizer (13). An example of such an intermediate product-catalyst separation process is a membrane separation unit, such as that described in U.S. Pat. No. 10,017,443. This preferred scheme is shown in FIG. 4, where the primary mode of catalyst and product separation is a membrane unit instead of a vaporizer. In FIG. 4, this is represented by membrane unit (30), while other unit operations remain the same. Here, membrane unit (30) selectively splits the organic stream from the reaction zone (12) into a retentate stream (31) and a permeate stream (32) based on membrane characteristics. Generally, the membrane is selective toward retaining the catalyst solution in the retentate and pushing heavies into the permeate. However, in most cases, both the catalyst and heavies are present in certain amounts in the permeate and retentate, respectively. Thus, the catalyst-rich retentate (31) can be fed back to the reactor, and the permeate (32), containing product, heavies, and a portion of the catalyst, can be fed to an azeotropic vaporizer (13), which is a secondary separation unit operation and performs the same function as described above with respect to FIG.

[0067] The advantages of using a pre-product / catalyst separation process followed by a secondary azeotropic vaporizer include: (1) The feed-to-tail ratio (F / T), the ratio of the stream entering the vaporization system compared to the catalyst recycle stream to the reaction zone, can be increased compared to a single vaporizer system. When using only one conventional vaporizer, the amount of aldehyde and heavies vaporized is limited by the vaporizer temperature. The upper limit of this temperature is determined by the catalyst deactivation temperature. This limits the F / T ratio or recycle ratio and reduces the overall productivity of the system. When using a secondary azeotropic vaporizer, additional aldehyde can be vaporized with the aid of water (forming an azeotrope). Therefore, the overall plant productivity can be increased by vaporizing additional aldehyde by increasing the overall F / T ratio without increasing the operating severity. A higher F / T ratio generally results in a longer residence time in the reactor and therefore a higher olefin conversion. (2) This system requires less water and less energy than simply using an azeotropic vaporizer as the primary vaporizer. Because the amount of water (and steam required to vaporize that water) is greater to produce the azeotrope of higher olefins, this scheme reduces the amount of water required and is therefore more suitable for higher molecular weight olefins. In general, the higher the molecular weight of the oxygenated compound, the greater the amount of water required to form the azeotrope. (3) Removal of heavies in the azeotropic vaporizer may be sufficient to eliminate / reduce the heavies purge stream and eliminate / reduce the load on the subsequent catalyst recovery process from the purge stream. If the organic feed to the azeotropic vaporizer is from a pre-separation unit operation, this stream will contain a higher concentration of heavies because either the aldehydes have been vaporized in the pre-vaporizer or the heavies have been selectively separated in a membrane separator. Higher concentrations of heavies tend to form azeotropes with water, which have a higher selectivity for vaporization of heavies compared to the lower concentration heavy stream. Aldehydes are still the primary product vaporized from the azeotropic vaporizer. (4) Reduced severity of the primary vaporizer: With a secondary azeotropic vaporizer that vaporizes some of the aldehydes in addition to vaporizing the heavies, the primary vaporizer can be operated at milder conditions, helping to extend catalyst life and reduce ligand degradation. By decoupling the product and heavies removal processes, each process can be optimized for its specific task, rather than a compromise between them when only a single product / catalyst separation process is used.

[0068] The feed to the azeotropic vaporizer includes the organic phase and the aqueous phase (14) from the hydroformylation reaction zone (12) described above, as shown in FIG. 2. The water added to form the azeotropic mixture in the azeotropic vaporizer can be added to the crude liquid output from the hydroformylation reactor system before being fed to the azeotropic vaporizer, added as a separate stream, or both. Water from the water reservoir (16) can be premixed with the organic phase using a static in-line mixer or actively mixed before entering the azeotropic vaporizer (13). In the former case, the two streams need to be as mixed as possible before entering the reactor, even though the mixture will not be homogeneous. Mixing ensures a more uniform distribution of the two phases into the azeotropic vaporizer, which results in a more stable system. In this case, water is preferably added as a liquid to the organic liquid phase and is preferably preheated to the reaction zone temperature and the azeotropic vaporizer temperature, or a temperature therebetween.

[0069] Alternatively, the design of the azeotropic vaporizer can include providing intimate contact between the two phases as they vaporize before or upon entering the azeotropic vaporizer (13). If water is introduced separately from the raw liquid output, the water can be liquid water or vapor.

[0070] The water reservoir (16) in Figure 2 may be a tank or other suitable device for supplying water to the system and may incorporate heating and degassing capabilities. The reservoir may also be mixed with optional additives prior to introduction into the azeotropic vaporizer (13). Such additives include, but are not limited to, weakly basic amines, such as those described in U.S. Patent No. 10,131,608.

[0071] The amount of water / steam added to the system depends on the concentration of the aldehyde produced, the catalyst system, and the solvent, if used. The amount of water entering the azeotropic vaporizer (13) is greater than the solubility limit of water in the catalyst solution / aldehyde product exiting the reaction zone (12). The azeotropic vaporizer (13), under operating conditions as taught herein, vaporizes the water-oxygenation product azeotrope, which is condensed in condenser (15).

[0072] The amount of water added is the amount needed to maintain azeotropic distillation in the azeotropic vaporizer. Insufficient water results in lower productivity and higher temperatures, while too much water potentially results in higher steam usage and higher water flow in the optional LL separator (17). There are two convenient ways to determine the optimal amount of water to add in step (c). 1. Compare the amounts of water and organic phase obtained in step (g) with the amounts of water and organic phase predicted from offline experiments that show what the azeotrope values ​​should be, and adjust the amount of water added to match the predicted values. 2. A properly operating azeotropic vaporizer operating at high azeotropic distillation levels (above 90%) should have at least some water remaining in the bottoms of the azeotropic vaporizer tails, and therefore measuring the amount of water present in the bottoms of the azeotropic vaporizer (e.g., the tails stream from step (i)) should ensure that at least some water is present to ensure that the entire azeotropic vaporizer was operated under azeotropic conditions. If an LL separator (17) is not used, the water level should be at least the saturation limit (typically 0.1 wt%) at the azeotropic vaporizer bottoms temperature, but can be higher if an LL separator is used to minimize liquid water transfer to the reaction zone.

[0073] The composition of the azeotrope used in the first method for controlling the amount of water added can be determined by means well known in the art and is illustrated in our examples. Based on the flow of organic phase (19) and aqueous phase (20) while maintaining a constant total liquid level in LL separator (18) and a constant water / organic interface level, the relative amounts of the organic and aqueous phases can be determined and compared to the ratio predicted by offline experiments as shown in the examples of this invention. Excess water flow in stream (21) (when LL separator (17) is used) also indicates that excess water is being added.

[0074] Similarly, measurement of the water content of the liquid recycle catalyst stream from the bottom of the azeotropic vaporizer (13) can be performed by conventional means such as Karl Fischer analysis or by on-line methods such as infrared or near-infrared (IR) analytical techniques, including Fourier transform IR (FTIR) and Raman spectroscopy.

[0075] Regardless of the method used to determine the amount of water added and the conditions in the azeotropic vaporizer, the amount of water added back to the reaction zone in the catalyst recycle stream (23) should be low enough so as not to form a significant separate aqueous phase within the reactor. This is preferably accomplished using an LL separator (17). A separate aqueous phase under the reaction conditions in the reaction zone (12) represents non-productive volume because the catalyst and olefins are not soluble in the aqueous phase. The concentration of water dissolved in the catalyst solution at the reaction zone temperature can be readily determined by conventional means, and the presence of an aqueous phase should be less than 1 wt. % of the total liquid phase in the reaction zone.

[0076] The azeotropic vaporizer (13) is of conventional design, as known to those skilled in the art. It is advantageously designed as a vertical tubular heat exchanger equipped with heating means. The dimensions of the azeotropic vaporizer (number, diameter, and length of tubes) are determined by the equipment capacity and are limited only by the vendor's manufacturing plant capabilities. Typically, there are no internals other than a liquid and gas distributor incorporated into the inlet head of the heat exchanger to ensure good distribution of the feed. A crude liquid product stream containing one or more products, one or more heavy by-products, the transition metal-organophosphorus ligand complex catalyst, one or more unconverted reactants, one or more reactive lights, and optionally one or more inert lights is advantageously fed to the top third, preferably the top head, of the azeotropic vaporizer at a temperature and pressure appropriate to obtain a desired overhead gas stream containing a portion of the heavy by-products and a liquid recycle residue stream containing the remainder of the heavy by-products and the transition metal-organophosphorus ligand complex catalyst. In a preferred embodiment of the present invention, the input is a liquid hydroformylation product stream containing one or more aldehyde products, one or more heavy by-products, one or more unconverted olefin reactants, a transition metal-organophosphorus ligand complex catalyst, optionally free organophosphorus ligand, carbon monoxide, hydrogen, and inert lights, and the azeotropic vaporizer is operated at a temperature high enough to remove at least a portion of the heavies in the gas overhead stream but low enough to ensure stability of the catalyst and organophosphorus ligand in the azeotropic vaporizer. Preferably, the azeotropic vaporizer temperature is greater than about 80°C, more preferably greater than about 90°C. Preferably, the azeotropic vaporizer temperature is less than about 130°C, more preferably less than about 120°C. The pressure in the azeotropic vaporizer is advantageously greater than about 14 psia (96.5 kPa), preferably greater than about 20 psia (138 kPa). The pressure in the azeotropic vaporizer is advantageously less than about 100 psia (689 kPa), preferably less than about 60 psia (414 kPa). The azeotropic vaporizer is advantageously operated at a crude liquid product feed to liquid residue mass ratio ranging from about 2 / 1 to about 5 / 1, preferably from about 2.0 / 1 to about 3.0 / 1.

[0077] Preferably, for the azeotropic vaporizer, a stripping gas vaporizer is used, as described in U.S. Patent No. 8,404,903 and U.S. Patent Application Publication No. 20170355656. The mass ratio of crude liquid product feed to recycle gas feed to the vaporizer is preferably greater than about 0.1 / 1, more preferably greater than about 0.5 / 1, but preferably less than 2 / 1, more preferably less than about 1 / 1.

[0078] The overhead gas stream from the azeotropic vaporizer is fed to a condenser (15). The condenser advantageously uses conventional water cooling; no special refrigeration unit is required. Water is the preferred cooling liquid for operating temperatures ranging from above freezing (i.e., above 10°C) to about 50°C, preferably from about 34°C to about 45°C. The condensed liquid is sent to a liquid-liquid separator (18), and the uncondensed gas is either vented (not shown in FIG. 2) or recycled to the azeotropic vaporizer as part of the stripping gas (not shown in FIG. 2) as described in U.S. Pat. No. 8,404,903 and U.S. Patent Application Publication No. 20170355656.

[0079] The condensate from the condenser is separated into an organic layer and an aqueous layer in a liquid-liquid separation zone (18). The design of such a separation device is not strictly critical to the present invention, is well known to those skilled in the art, and is typically operated below the condenser cooling temperature and below the condenser pressure. The organic phase, containing the product aldehyde, heavies, and trace amounts of water and other materials, is removed via line (19) for further processing (e.g., purification, hydrogenation, aldol condensation). Given the high molecular weight of the aldehyde product and heavies, the solubility of water in the organic phase is typically very low; therefore, very little water is lost in the crude aldehyde product stream. This water can be recovered in downstream processing and recycled as needed. The aqueous layer is preferably recycled via line (20) back to the azeotropic vaporizer as part of the water introduced into the azeotropic vaporizer for azeotropic distillation to unit (16). A purge on line (20) may also be present (not shown in FIG. 2).

[0080] In one preferred embodiment, the aqueous stream from the bottom of unit (18), as part of the condensation process in unit (15), is sent through a cross heat exchanger on its way to unit (16), maximizing heat integration within the plant and minimizing steam costs.

[0081] The liquid overhead stream from liquid-liquid separator (18) comprises primarily one or more aldehyde products, a portion of the unconverted olefin reactant, water, a portion of the inert lights, and a portion of the heavy by-products. Advantageously, the overhead liquid stream (19) comprises from about 10 to about 95 weight percent aldehyde products, from about 8 to about 28 weight percent unconverted olefin reactant, from about 6 to about 26 weight percent inert lights, primarily inert alkanes, 0.1 to 10 weight percent water, and from about 0.01 to about 0.2 weight percent heavy by-products.

[0082] At any given unit time, the heavy by-products exiting the condenser from the tails stream from (15) in stream (19) comprise a small portion of the liquid stream from the condenser, but this output of heavies serves to reduce the accumulation of heavy by-products in the hydroformylation step. Preferably, the rate of heavies in (19) per unit time is essentially equal to the rate of heavy by-products produced in the hydroformylation process per the same unit time. In this case, the heavies are removed from the reaction system at essentially the same rate as they are produced. Thus, there is no undesirable increase in heavies recycled to the hydroformylation step, and the heavies recycled to the hydroformylation step can remain essentially steady with only the desired amount needed to solubilize the catalyst. The reduced azeotropic vaporizer temperature made possible by the use of a water azeotrope improves heavies removal and potentially reduces ligand loss and the formation of additional heavies in azeotropic vaporizer (13).

[0083] The partial pressure of carbon monoxide in the azeotropic vaporizer and condenser overhead gas can vary dramatically depending on the conditions in the azeotropic vaporizer, as described in U.S. Patent No. 8,404,903 and U.S. Patent Application Publication No. 20170355656. The partial pressures of carbon monoxide, hydrogen, or other inert gases are not strictly critical to the present invention, but will contribute to the total pressure of the system, which is typically controlled by a vent on the condenser (not shown in FIG. 2) and / or as part of a recycle loop as taught in U.S. Patent No. 8,404,903 and U.S. Patent Application Publication No. 20170355656.

[0084] Referring to Figure 2, the liquid residue stream from (13) obtained from the azeotropic vaporizer contains primarily heavies and the transition metal-organophosphorus ligand complex catalyst, and may further contain one or more aldehyde products and / or free organophosphorus ligand. Generally, this liquid residue stream (referred to as the liquid catalyst recycle stream) contains about 40 to about 88 weight percent heavy by-products and about 7 to about 27 weight percent aldehyde products, excluding the weight of the transition metal-organophosphorus ligand complex catalyst, any free organophosphorus ligand, and possibly water. This stream may also contain small amounts of unconverted olefin reactant and inert alkanes. Obviously, the complex catalyst and ligand are not volatile, and therefore, essentially all of the catalyst and ligand are recycled to the hydroformylation reactor in the liquid catalyst recycle stream. The aqueous stream (21) consists of about 85 to 99.99% water and about 0.01 to 15% organics from the organic stream. Overall, the split between the aqueous and organic streams ((21)+(22)) / (23) ratio) may range from about 0.5 to 100.

[0085] Typically, the liquid residue stream from the azeotropic vaporizer is cooled before being sent back to the reaction zone to partially reduce ligand degradation and heavies formation during its passage. In some embodiments, the cooled azeotropic vaporizer residue stream is sent to a liquid-liquid separator, shown as unit (17) in FIG. 2. Liquid water is separated and preferably recycled via line (21) to water / steam generator unit (16) for reuse in the azeotropic distillation. This prevents the accumulation of an unproductive aqueous phase in the reaction zone. The organic phase from (17) is returned to the reaction zone via line (23).

[0086] The water used for the azeotropic distillation in unit (13) can be liquid water or vapor and is supplied by unit (16) as described above. Preferably, the majority of the water is recycled from liquid-liquid separators (17) and (18). Depending on the solubility of water in the crude aldehyde stream, the amount of water purge removed from unit (16) via line (22), and / or water losses during venting, make-up water to unit (16) may be required. The water should be obtained from a degassing (oxygen-free) and desalination process, distillation, or reverse osmosis or similar pretreatment system and should be halide-free. Additives such as buffers can be used to maintain an appropriate pH value (preferably between 4.5 and 9, most preferably between 6.0 and 7.5). Buffers suitable for this application are preferably non-salts to avoid fouling the azeotropic vaporizer; therefore, the water-soluble, weakly basic amine buffers used in U.S. Pat. No. 10,131,608 are preferred. The buffering agent can advantageously be premixed and added to the water (e.g., in unit (16)) before introduction into the azeotropic vaporizer or as a separate stream.

[0087] The amount of optional weakly basic amine to be added can be calculated based on the pH drop observed in the water feed to the azeotropic vaporizer (13) (i.e., stream (14)) compared to the pH of the water exiting the LL separator (17) in either stream (21) or (22). A pH drop of more than 0.5 units indicates that significant acid is being removed, and therefore the feed needs to be increased. A drop of less than 0.1 units suggests that the feed can be reduced to save on the cost of the amine additive.

[0088] In a preferred embodiment, a water purge (22) can also be used to remove water-soluble impurities from the system, such as acids, halides (from the raw material feed), etc. In a preferred embodiment, a weakly basic amine is present in the water from reservoir (16), and therefore the purge removes acidic impurities that have been neutralized by the amine additive. The flow rate of stream (22) is generally low and can be used to mitigate the pH drop observed between streams (14) and (21). Due to environmental considerations, this stream is preferably sufficient to maintain the pH drop noted above at less than 0.5 pH units, without the use of excessive amounts of amine additive.

[0089] When the process of the present invention is carried out as described above, a catalyst recycle stream having a controlled, preferably reduced, amount of heavies is obtained compared to a baseline process (comparison process) identical to the process of the present invention except that no water is added to the azeotropic vaporizer. For the baseline process, see FIG. 1, which shows the crude product feed to the vaporizer, the overhead gas stream from the vaporizer to the condenser, and the gas overhead output from the condenser, in which no additional water is used to form an azeotrope in the vaporizer, any portion of which is recycled back to the vaporizer. In the baseline process, particularly if the vaporizer temperature must be lowered to accommodate the lower stability of the transition metal-organophosphorus ligand complex catalyst and the free organophosphorus ligand, the heavies do not exit the vaporizer in sufficient quantities, and therefore a larger amount of heavy by-products is recycled to the hydroformylation step in a harmful form. The process of the present invention removes more heavy by-products in the azeotropic vaporizer overhead gas stream, allowing for beneficial operation of the vaporization process at lower temperatures for catalyst life and the use of a conventional water-cooled condenser without expensive refrigerants and cooling equipment. The present invention also allows for the vaporization process to operate at lower temperatures, which can slow the formation of heavies without reducing the aldehyde vaporization rate due to the need to operate at lower temperatures or require lower system pressures.

[0090] The optional use of a weak amine additive in the water added to the azeotropic distillation process mitigates the problem of any acid-catalyzed phosphite decomposition and acid-catalyzed heavies formation during the vaporization process. Neutralizing and removing these acids should reduce these side reactions.

[0091] When using triarylphosphines, a lower temperature in the azeotropic vaporizer can reduce the amount of triarylphosphines that volatilize from the reaction fluid. Triarylphosphines, such as triphenylphosphine, have a low but significant vapor pressure and therefore may volatilize during the vaporization of high molecular weight aldehydes (see WO2022180394). Triarylphosphines do not appear to form azeotropes, and therefore the present invention can reduce the vaporization temperature required to remove aldehyde heavies while reducing the loss of triarylphosphine ligands. Triarylphosphine ligands can have a detrimental effect on downstream liquid-phase hydrogenation systems, so reducing volatilization can provide downstream benefits. [Example]

[0092] The objects and advantages of the present invention are further illustrated by the following examples, which also further clarify the present invention. The particular materials and amounts thereof, as well as other conditions and details recited in these examples, should not be used to limit the present invention. Rather, they are intended to be illustrative of the invention as a whole. Furthermore, other embodiments of the present invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. Examples of the present invention are numbered, while comparative samples that are not examples of the present invention are designated alphabetically.

[0093] Example 1C9 For aldehyde mixture: Azeotrope experiments were conducted in batch mode, with both the organic and aqueous phases simultaneously mixed and heated. For the experiment, 150 g of organic phase and 50 g of distilled water were placed in a reboiler. The organic phase consisted of the rhodium-ligand catalyst, C8 olefins, C9 aldehydes, C9 aldehyde dimers, trimers, and heavier by-products (collectively referred to as heavies), as well as trace amounts of C4–C7 olefins and alkanes. The ligand used in this experiment was approximately 0.25 wt% tris-(2,4-ditertbutylphenyl)phosphite. The flask was placed on a heating mantle, and the experimental pressure was set to 1 atmosphere absolute. The reboiler was connected to a spinning band column, and the overhead of the spinning band column was connected to a condenser, with the condenser cooling medium circulating at 5°C. Agitation of the organic and aqueous phase mixture begins while the reboiler is heated to 100-110°C, a temperature slightly above the azeotropic temperature of the aldehyde-water system, measured at approximately 99°C. An overhead condensate is collected as the liquid mixture in the reboiler is heated and separated using a separatory funnel to contain both organic and aqueous phases, after which the phases are weighed and analyzed to understand the composition of the condensate.

[0094] [Table 1]

[0095] [Table 2]

[0096] The vaporized heavies / vaporized aldehyde ratio for the azeotrope is 0.69 / 45.96 or about 0.015 g / g, which is higher than the heavies production rate of about 0.001-0.005 g / g, and therefore the removal of heavies is higher than the production rate.

[0097] Example 2C9 For aldehyde mixture: This experiment was carried out in a similar manner to Example 1, except that 100 g of organic phase and 100 g of aqueous phase were added to the reboiler. The pressure was set to 0.53 atmospheres absolute and the reboiler was heated to 82-88°C to test azeotrope formation under reduced pressure.

[0098] [Table 3]

[0099] [Table 4]

[0100] The ratio of vaporized heavies / vaporized aldehyde in the azeotropic case is 1.38 / 79.17 or about 0.023 g / g, which is higher than in Example 1, and the rate of heavy product production is about 0.001-0.005 g / g, so the removal of heavy products is higher than the rate of production.

[0101] Example 3: C9 aldehyde mixture with higher heavies: This experiment was conducted in a similar manner to Example 1, except that 100 g of organic phase and 300 g of aqueous phase were added to the reboiler. The organic phase in this case contained more heavies and represented a typical stream from a primary separation unit operation after separating the aldehyde product. The pressure was set to 1 atmosphere absolute, and the reboiler was heated to 100-110°C, slightly above the azeotropic temperature of the aldehyde-water system, which should be 99°C.

[0102] [Table 5]

[0103] [Table 6]

[0104] The ratio of vaporized heavies / vaporized aldehydes in the azeotropic case was 5.16 / 42.25, or approximately 0.12 g / g, which is higher than in Examples 1 and 2. The heavy product production rate was approximately 0.001-0.005 g / g, and therefore heavy product removal was higher than production rate. As the heavy product content increased in the hydroformylation fluid, the azeotropic vaporizer was able to remove more heavies under the same conditions due to the higher inlet heavy product concentration (i.e., the heavy product azeotrope was strengthened). C9 aldehydes were still the main product from the azeotropic vaporizer; therefore, such a configuration could also increase the F / T ratio in the system.

[0105] The following table provides insight into the amount of water required to vaporize the aldehydes / total heavies from the three examples above.

[0106] [Table 7]

[0107] The ratio between water and organic phase (aldehyde or heavies) calculated in the above table refers to the amount of water evaporated per unit mass of evaporated organics. In the case of aldehydes, as can be seen from Examples 1 and 2, the water / aldehyde ratio remains in the range of 2.15 to 2.24, given similar starting aldehyde feed compositions. In Example 3, the water / aldehyde ratio is 5.4, since more water is required at lower aldehyde concentrations compared to Examples 1 and 2. This ratio varies with parameters such as temperature, pressure, varying carbon length, feed composition, and aldehyde branching, to name a few.

[0108] In the case of heavies, the water / heavies ratio varies significantly between Examples 1, 2, and 3. Between Examples 1 and 2 with similar feed compositions, the lower operating pressure in Example 2 favors a lower water-to-heavies ratio of 128.28 compared to 142.68 in Example 1. Increasing the heavies composition as shown in Example 3 compared to Examples 1 and 2 further reduces the water-to-heavies ratio to 44.19. This reduces the amount of water required in the overall process and makes the azeotropic vaporizer well suited to accepting the concentrated heavy stream from the pre-separation unit operation. This also highlights the fact that, as with aldehydes, higher heavies concentrations reduce the amount of water required for the azeotrope, and vice versa. Also, as with aldehydes, the water / heavies ratio depends on temperature, pressure, varying carbon length, feed composition, and branching in the aldehyde, to name a few.

[0109] Example 3 also demonstrates that the present invention is well suited to highly concentrated catalyst streams, such as those generated from conventional purge streams where the purged stream is treated in a focused distillation process before being sent for precious metal recovery. The present invention can facilitate the operation of focused distillations (e.g., wiped film evaporators) by facilitating recovery of residual aldehyde products, reducing viscosity, and providing an internal stripping gas. In this scheme, referring to Figure 3, the purge stream is stream (25b), and there may be no recycle line from the azeotropic vaporizer back to the reactor.

[0110] In a continuous azeotropic vaporizer, the amount of water required to achieve a particular F / T and aldehyde production rate is adjusted according to the water / aldehyde ratio described above for a particular system. This ratio is the minimum amount of water required in the azeotropic vaporizer, with any excess water remaining in the tails stream. Based on the amount of water, the amount of vaporized heavies can be calculated from the water / heavies ratio. If the heavies removal rate from the azeotropic vaporizer is higher than the heavies production rate, the heavies concentration in the reactor will decrease. This decrease reduces the heavies concentration entering the azeotropic vaporizer, reducing the heavies removal rate. This process occurs until the heavies removal rate equals the production rate.

[0111] In summary, it can be seen that the process of the present invention provides greater heavies removal in the vaporizer overhead gas stream at a lower vaporizer operating temperature for higher catalyst stability, while controlling the amount of heavies in the liquid recycle stream to the hydroformylation step.

Claims

1. 1. A process for controlling heavies in a catalyst recycle stream, said process comprising: (a) removing a crude product stream from a hydroformylation reaction zone, the crude product stream comprising one or more aldehyde products, one or more heavy by-products, a transition metal-organophosphorus ligand complex catalyst, one or more unconverted reactants, and one or more inert lights; (b) providing a water flow; (c) combining the water stream from step (b) with the stream from step (a) into an azeotropic vaporizer; (d) removing an overhead gas stream from the vaporizer, the overhead gas stream comprising one or more aldehyde products, one or more unconverted reactants, one or more inert lights, a portion of the water, and a portion of the heavy by-products, and feeding the overhead gas stream to a condenser; (e) removing an overhead gas stream from said condenser, the overhead gas stream comprising one or more unconverted reactants, a portion of the added water, and one or more inert lights; (f) recovering a liquid stream from the condenser comprising the aldehyde product, heavy by-products, and water; (g) separating organic components from the water from step (f) in a liquid-liquid separation zone to recover a crude aldehyde product as a top layer and an aqueous phase as a bottom layer; (h) removing a liquid recycle catalyst stream from the vaporizer that is passed to the reaction zone and comprises the transition metal-organophosphorus ligand complex catalyst, a remainder of the aldehyde product, and a remainder of the heavy by-products, wherein at least 25% of the aldehyde product recovered in step (d) is removed as a water azeotrope.

2. 10. The process of claim 1, wherein the crude product stream from step (a) is passed through a pre-product / catalyst separation process prior to step (c).

3. 3. The process of claim 2, wherein the preliminary product / catalyst separation process comprises a vaporization process, wherein an overhead stream comprises a first crude aldehyde product stream and a bottoms stream comprises a transition metal-organophosphorus ligand complex catalyst and heavies, and at least a portion of the bottoms stream is then fed to step (c).

4. 3. The process of claim 2, wherein the preliminary product / catalyst separation process comprises a membrane separation process resulting in a retentate portion and a permeate portion, the retentate comprising the transition metal-organophosphorus ligand complex catalyst, which can be recycled to the reaction zone, some aldehyde product, and a heavies stream, and the permeate comprising the aldehyde product, at least some heavies, unconverted reactants, inert lights, and some catalyst components, at least a portion of which is then fed to step (c).

5. 5. The process of any one of claims 1 to 4, wherein at least a portion of the bottom aqueous phase from step (g) is recycled to step (b).

6. 5. The process of any one of claims 1 to 4, wherein the residue stream from step (h) is cooled and passed to a liquid-liquid separation zone to recover a catalyst-containing organic phase as a top layer and an aqueous phase as a bottom layer which can be recycled to the reaction zone.

7. 7. The process of claim 6, wherein at least a portion of the bottom aqueous phase is recycled to step (b).

8. 5. The process of claim 3 or 4, wherein a majority of the total aldehyde product is separated in a pre-product / catalyst separation zone.

9. 3. The process of claim 1 or 2, wherein at least 90% of the product recovered in step (d) was removed as a water azeotrope.

10. 3. The process of claim 1 or 2, wherein the amount of product removed as an azeotrope is controlled by adjusting the amount of water added in step (c).

11. The process of any one of claims 1 to 4, wherein a buffering agent is added to the water feed of step (b).

12. 12. The process of claim 11, wherein the buffering agent is a weakly basic amine.

13. The process of any one of claims 1 to 4, wherein the water is added as steam.

14. The process of any one of claims 1 to 4, wherein the water is added as liquid water.

15. The process of any one of claims 1 to 4, wherein the azeotropic vaporizer is a stripping gas vaporizer.

16. The transition metal-organophosphorus ligand complex catalyst is an organic phosphite: a) Methyl [3,3'-di-t-butyl-5,5'-dimethoxy-1,1'biphenyl-2,2'-diyl]phosphite represented by formula W: 【Chemistry 1】 and (b) tris-(2,4-di-tert-butylphenyl)phosphite represented by formula X: 【Chemistry 2】 The process according to any one of claims 1 to 4, comprising one or more of:

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