Separate parallel zone hydroformylation reactions

Abstract

The present invention provides a process for hydroformylating olefins to produce normal (N) aldehydes and iso (I) aldehydes in an N:I ratio RA, the process comprising hydroformylating olefins with hydrogen and carbon monoxide in the presence of a ligand-metal catalyst, the hydroformylation being carried out in at least two separate, parallel hydroformylation zones, each comprising one or more hydroformylation reactors in series, each separate hydroformylation zone producing N-aldehydes and I-aldehydes in an N:I ratio different from that of the other hydroformylation zones, the process comprising: i) feeding an olefin feed stream to each separate hydroformylation zone; ii) feeding a stream comprising hydrogen and carbon monoxide to each separate hydroformylation zone; and iii) recovering an aldehyde product stream from each separate hydroformylation zone, wherein the N:I ratio RA is the overall N:I ratio contained in the aldehyde product streams.

Description

[Technical Field]

[0001] The present invention relates to a process for hydroformylating olefins to form aldehydes. In particular, the present invention relates to controlling the linear to branched aldehyde isomer ratio in a hydroformylation process using separate hydroformylation zones that produce different ratios of linear and branched aldehydes. [Background technology]

[0002] The production of aldehydes by hydroformylation of olefins is carried out on a large scale industrially. Aldehydes are typically intermediates in the production of alcohols, acids, or esters. A known process for producing such products is the LP Oxo process offered by Dow and Johnson Matthey Davy. In a typical flowsheet, hydroformylation is carried out in the liquid phase using a ligand-rhodium catalyst, as described, for example, in U.S. Pat. No. 4,148,830 or U.S. Pat. No. 5,087,763. The liquid-phase reactor effluent is removed from the hydroformylation reactor and fed to a catalyst separation unit, where a liquid catalyst solution is separated from the product aldehyde. The liquid catalyst solution is then returned to the reactor. The liquid catalyst solution typically contains the solvent, rhodium, ligand, and other components present in the reactor.

[0003] Many variations of molecules that can function as ligands are known. Commercially available ligands are often organomonophosphines such as triphenylphosphine, organomonophosphites such as trimethylolpropane phosphite or tris(2,4-di-tert-butylphenyl)phosphite, organopolyphosphites such as organobisphosphites, or mixtures of any of these. WO 2008 / 115740, WO 2011 / 087690, WO 2010 / 117391, and WO 2016 / 089602 list various ligands. Additionally, organopolyphosphines such as those disclosed in WO 2019 / 231610 can be used. Of these types of ligands, organomonophosphites are believed to be the most active, but may have the weakest ligand-rhodium interactions. For example, in the case of propylene hydroformylation, commercially available organomonophosphites typically produce aldehydes with relatively low linear to branched isomer ratios, e.g., ratios up to about 0.5 to 1. Commercially available organomonophosphines typically produce aldehydes with relatively high linear to branched isomer ratios, even somewhat higher when used in combination with organopolyphosphines. Commercially available organobisphosphites generally have the strongest ligand-to-rhodium interactions and produce aldehydes with relatively high linear to branched isomer ratios, e.g., ratios greater than about 20:1.

[0004] Because high-value downstream products, such as plasticizers, require linear compounds, a primarily high linear-to-branched isomer ratio is often desired. This can generally be achieved, for example, using organobisphosphite ligands during hydroformylation. However, for use in, for example, the production of neopentyl glycol, lower ratios of linear to branched aldehydes may also be required. In particular, the ratio lies between the optimum ratios that can be provided using organomonophosphites or organopolyphosphites alone.

[0005] WO 2008 / 115740 discloses a process for controlling the ratio of linear to branched aldehydes using various ratios of organomonophosphite to organopolyphosphite ligands in the same reaction stream. However, such methods can have limitations, especially if none of the ligand-rhodium complexes operates under its optimum performance conditions. Summary of the Invention

[0006] The present invention provides a method for hydroformylating olefins to produce normal (N) aldehydes and iso (I) aldehydes in an N:I ratio R A the process comprises hydroformylating an olefin with hydrogen and carbon monoxide in the presence of a ligand-metal catalyst; The hydroformylation is carried out in at least two separate, parallel hydroformylation zones, each hydroformylation zone comprising one or more hydroformylation reactors in series; each separate hydroformylation zone produces N-aldehydes and I-aldehydes in a different N:I ratio than the other hydroformylation zones; The process is i) feeding an olefin feed stream to each separate hydroformylation zone; ii) feeding a stream comprising hydrogen and carbon monoxide to each separate hydroformylation zone; iii) recovering an aldehyde product stream from each separate hydroformylation zone; N:I ratio R A is the total N:I ratio contained in the aldehyde product stream.

[0007] Advantageously, loss of metal catalyst during the process can be reduced compared to processes such as those disclosed in WO 2008 / 115740, and the N:I ratio is controlled by using various ratios of different ligand types in the same reaction stream. This, in turn, can have benefits in reducing equipment inventory, capital costs, and running costs. Advantageously, for a particular set of operating conditions and ligand-metal catalyst in each hydroformylation zone, R A can be controlled by the relative flow rates of the aldehyde product streams from each hydroformylation zone. Thus, a further advantage of the present invention is that, unlike systems such as those disclosed in WO 2008 / 115740, where the N:I ratio is controlled by the ratio of organomonophosphite to organopolyphosphite ligand in the same reaction stream, the N:I ratio, R, can be controlled by varying the flow rates to each hydroformylation zone. A The advantage of this method is that it allows rapid variation of the N:I ratio. It will be understood that substantially the same olefin is fed to each separate hydroformylation zone. For example, the olefin feed stream may be split between the separate hydroformylation zones. Thus, the process may include splitting the olefin feed stream into feed streams for each separate hydroformylation zone. The flow rate ratio of the olefin feeds to each zone may be used as part of controlling the N:I ratio. The flow rate of the aldehyde product stream from the hydroformylation zone may be controlled by modifying the olefin feed streams, including the relative flow rates of the olefin feed stream and the carbon monoxide and hydrogen containing stream to each separate hydroformylation zone. The desired N:I ratio, R A Based on this, one skilled in the art can determine the relative feed flow rates required based on the identity of the ligand-metal catalyst used and the operating conditions in each hydroformylation zone. In one example, the olefin feed is split and fed to a first hydroformylation zone and a second hydroformylation zone in proportion to the required production capacity of each zone. A stream containing hydrogen and carbon monoxide is also preferably split to each separate hydroformylation zone in proportion to the required production capacity of each zone. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram of one embodiment of the process of the present invention. [Figure 2] FIG. 2 is a process schematic diagram of a further embodiment of the present invention. [Figure 3] 1 is a chart showing metal loss in mixed-ligand hydroformylation reactions. [Figure 4] 1 is a chart showing metal loss in a single-ligand hydroformylation reaction producing an aldehyde with a relatively low N:I ratio. [Figure 5] 1 is a chart showing metal loss in a single-ligand hydroformylation reaction producing an aldehyde with a relatively high N:I ratio. DETAILED DESCRIPTION OF THE INVENTION

[0009] The hydroformylation process, its reagents, conditions, and equipment are known, and the hydroformylation step in the present invention can be carried out according to known techniques used in conventional hydroformylation processes. The process of the present invention uses at least two, preferably two, separate, parallel hydroformylation zones. Each hydroformylation zone comprises at least one, typically at least two, and typically no more than four, e.g., two, three, or four, hydroformylation reactors in series. The hydroformylation zones are parallel in the sense that the reaction fluids in each separate hydroformylation zone do not mix. The reaction fluids include solvent, ligand-metal catalyst, free ligand, and additional components such as solubilizers and stabilizers. For example, there may be a small amount of flow bridging by passing vent air from the reactor in one hydroformylation zone to the reactor in another hydroformylation zone. The hydroformylation reactor may be a multi-stage reactor, such as described in US Pat. No. 5,763,671, in which physical barriers exist creating one or more theoretical stages per reactor vessel.

[0010] The hydroformylation process in each zone is generally carried out in a continuous manner, in which the olefin is hydroformylated with carbon monoxide and hydrogen in a liquid homogeneous reaction mixture, i.e., the reaction fluid described above. Suitable inert solvents include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, acetophenone, and cyclohexanone; aromatics such as benzene, toluene, and xylene; halogenated aromatics including o-dichlorobenzene; ethers such as tetrahydrofuran, dimethoxyethane, and dioxane; halogenated paraffins including methylene chloride; and paraffinic hydrocarbons such as heptane. Preferred solvents are aldehyde products and / or oligomers of aldehyde products with reactive olefins.

[0011] The reaction is maintained at a temperature and pressure favorable to the hydroformylation of the olefin, and make-up amounts of olefin, carbon monoxide, and hydrogen are fed to the reaction medium as the reactants are exhausted. Liquid-phase reactor effluent is removed from the hydroformylation reactor in each hydroformylation zone and fed to a catalyst separation and product recovery system in each hydroformylation zone, where a liquid catalyst solution is separated from the product aldehyde. The liquid catalyst solution is then returned to the reactor. The liquid catalyst solution typically contains solvent, metal, ligand, and other components present in the reaction fluid. Typical flowsheets are described, for example, in U.S. Pat. No. 4,148,830 or U.S. Pat. No. 5,087,763.

[0012] Preferably, the olefin is a C3 to C 16 An olefin, more preferably a C3 to C 12 The olefin is preferably a monoolefin. The olefin is preferably an acyclic olefin, such as a linear olefin or a branched olefin. For example, the olefin may be propylene or normal butene. Preferably, the aldehyde has one more carbon than the olefin. Therefore, the aldehyde is preferably a C4-C 17 Aldehydes, more preferably C4-C13 The aldehyde is preferably a C4 aldehyde. For example, the aldehyde may be butyraldehyde. Those skilled in the art will understand that the aldehyde produced depends on the olefin used.

[0013] The hydrogen and carbon monoxide-containing stream can be obtained from any available source and is generally synthesis gas, known as syngas. Typically, the same source stream is used for each hydroformylation zone, which is then split into two or more individual streams and fed to the reactors of each hydroformylation zone. The molar ratio of hydrogen to carbon monoxide can range from about 1:10 to about 100:1, generally from about 1:10 to about 10:1, or from about 2:1 to about 1:2, inclusive. The feed flow rate depends on the ligand-metal catalyst, the olefin feed rate, and other operating conditions. Such flow rates are known or can be readily calculated by one skilled in the art.

[0014] The hydrogen and carbon monoxide containing stream, and the olefin feed, typically each pass through a respective purification system that serves to protect the hydroformylation catalyst system from low levels of impurities such as sulfides and chlorides; such systems are known to those skilled in the art.

[0015] The catalytic metal is generally a transition metal and is typically selected from rhodium, cobalt, iridium, ruthenium, iron, nickel, palladium, platinum, osmium, chromium, molybdenum, and tungsten, and mixtures thereof. Preferably, the metal is selected from rhodium, cobalt, iridium, and ruthenium, more preferably, rhodium, cobalt, and ruthenium, and most preferably, the metal is rhodium.

[0016] It should be understood that one hydroformylation zone operated under conditions to produce an aldehyde product stream having a higher N:I ratio than another hydroformylation zone means that the other hydroformylation zone operates to produce an aldehyde product stream having a lower N:I ratio. Each separate hydroformylation zone typically uses a different ligand-metal catalyst, which generally means that the ligand used in each zone is different. The metal is typically the same in each zone. Typically, the hydroformylation zone operated under conditions to produce an aldehyde product stream having an N:I ratio of about 2:1 or less, typically at least about 0.5:1. Generally, this zone contains a ligand-metal catalyst in which the ligand is an organomonophosphite ligand. Suitable ligands for this reaction zone are known and are described, for example, in WO 2008 / 115740, WO 2011 / 087690, WO 2010 / 117391, and WO 2016 / 089602. Typically, the hydroformylation zone, which operates under conditions to produce an aldehyde product stream having a higher N:I ratio, operates under conditions to produce an aldehyde product stream having an N:I ratio of at least about 6:1, typically no greater than about 35:1. Generally, this zone contains a ligand-metal catalyst, wherein the ligand is an organomonophosphine ligand, or an organopolyphosphite ligand, such as an organobisphosphite, or an organopolyphosphine ligand, e.g., an organotetraphosphine ligand. Suitable organomonophosphines or organopolyphosphites, e.g., organobisphosphite ligands, for this reaction zone are known and are described in WO 2008 / 115740, WO 2011 / 087690, WO 2010 / 117391, WO 2016 / 089602, and WO 2019 / 231610.

[0017] Each hydroformylation zone produces N-aldehydes and I-aldehydes at different N:I ratios, and the N:I ratio R Ais the total N:I ratio contained in the aldehyde product stream. Stated differently, the combined N:I ratios in the separate aldehyde product streams are recovered from each hydroformylation zone. Therefore, R A represents the weighted average power output of each hydroformylation zone. Thus, for a particular set of operating conditions and ligand-metal catalyst in each hydroformylation zone, R A can be controlled by the relative flow rates of the aldehyde product streams from each hydroformylation zone. Thus, a further advantage of the present invention is that, unlike systems such as those disclosed in WO 2008 / 115740, where the N:I ratio is controlled by the ratio of organomonophosphite to organopolyphosphite ligand in the same reaction stream, the N:I ratio R A can be rapidly changed by varying the flow rates to each hydroformylation zone.

[0018] The flow rate of the aldehyde product stream from the hydroformylation zone can be controlled by modifying the olefin feed stream and the stream containing carbon monoxide and hydrogen. A Based on this, one skilled in the art can readily determine the relative feed flow rates required based on the identity of the ligand-metal catalyst used and the operating conditions in each hydroformylation zone. The process of the present invention can be performed with an N:I ratio R that is within the range in which a significant, but small, proportion of I aldehyde is required while the catalyst is operating within optimum performance conditions. A For example, R A is at least about 0.5:1 and not more than about 10:1, typically at least about 1.5:1 and not more than about 6:1. In this range, the process of the present invention can be particularly advantageous because it can result in reactor systems of similar size in each separate hydroformylation zone, which is the most economically advantageous situation.

[0019] The N:I ratio can be determined by a variety of methods. One example is analysis of either the vapor or liquid stream coming from the reactor or process stream using techniques such as gas chromatography (GC), infrared (IR), or nuclear infrared (NIR). The product N:I ratio can also be determined by flow measurements from a distillation column used to separate the N-aldehyde and I-aldehyde.

[0020] Within each hydroformylation zone, the operating conditions that typically differ from those of the other hydroformylation zones are the carbon monoxide partial pressure, temperature, metal concentration in the reaction fluid, and ligand concentration in the reaction fluid, including free ligand and ligand complexed with the metal to provide the ligand-metal catalyst. Particular ligand-metal catalysts have particularly preferred ranges for these operating conditions. Advantageously, each hydroformylation zone can be operated under conditions that are optimal for the performance of the ligand-metal catalyst used within the zone.

[0021] The concentration of metal-ligand catalyst in the reaction fluid of the hydroformylation zone need only be the minimum amount necessary to provide a metal concentration for catalyzing the desired hydroformylation process. Generally, the metal concentration is at least about 20 ppmw, typically at least about 30 ppmw. Generally, the metal concentration is 1000 ppmw or less, typically 600 ppmw or less. When organophosphine ligands, particularly organomonophosphines, are used, the metal concentration can typically be in the range of 100 to 1000 ppmw, preferably 200 to 600 ppmw, inclusive. When organomonophosphite ligands are used, the metal concentration can typically be in the range of 20 to 200 ppmw, preferably 30 to 100 ppmw, inclusive. When organopolyphosphite ligands, particularly organobisphosphites, are used, the metal content will typically be in the range 20 to 200 ppmw, preferably 30 to 100 ppmw, inclusive, where for the avoidance of doubt ppmw means parts per million by weight of the reaction fluid.

[0022] The amount of ligand in the reaction fluid, including both free and complexed forms, generally exceeds 1 molar equivalent relative to the metal, and may be present in concentrations up to the solubility limit of the ligand in the reaction fluid. The specific amount depends on the nature of the ligand. When organophosphine ligands, particularly organomonophosphines, are used, the amount of ligand is typically in the range of about 30 to about 500 molar equivalents relative to the metal, preferably about 100 to about 200 molar equivalents relative to the metal, inclusive. When organomonophosphite ligands are used, the amount of ligand is typically in the range of about 4 to about 200 molar equivalents relative to the metal, inclusive. When organopolyphosphite ligands, particularly organobisphosphites, are used, the amount of ligand is typically greater than about 1 equivalent relative to the metal, up to about 200 molar equivalents, preferably up to about 5 molar equivalents. The amounts of metal and ligand in the reaction fluid can be readily determined by known analytical methods. For example, metals can be quantified by inductively coupled plasma (ICP) techniques, and ligands can be quantified by the addition of ions to an aliquot of the reaction fluid. 31 It can be quantified by P NMR or HPLC.

[0023] The reaction conditions for the hydroformylation process in each reactor can vary widely. Generally, the hydroformylation process can be carried out at a reaction temperature above about 25°C, typically above about 50°C. The hydroformylation process can be carried out at a reaction temperature below about 200°C, typically below about 120°C. When organophosphine ligands, including organomonophosphines and organopolyphosphines, are used, it can be beneficial to carry out the hydroformylation reaction at a temperature within the range of about 60°C to about 130°C, inclusive, preferably about 75°C to about 120°C. When organomonophosphite ligands are used, it can be beneficial to carry out the hydroformylation reaction at a temperature within the range of about 50°C to about 110°C, inclusive, preferably about 65°C to about 100°C. When organopolyphosphite ligands are used, it may be beneficial to carry out the hydroformylation reaction at a temperature within the range of about 50°C to about 110°C, preferably about 60°C to about 100°C, inclusive.

[0024] Generally, the total gas pressure, including the olefin reactant, carbon monoxide, hydrogen, and any inert gases, in the hydroformylation zone reactors can range from about 1 psia (6.9 kPa) to about 10,000 psia (68.9 MPa). Typically, the process can be operated at a total gas pressure, including the olefin reactant, carbon monoxide, and hydrogen, of less than about 2000 psia (13,800 kPa), preferably less than about 500 psia (3450 kPa). When the total gas pressures differ between the hydroformylation zones, vent from the reactor in the hydroformylation zone operating at a higher carbon monoxide partial pressure can advantageously be passed to the reactor in another hydroformylation zone. This can increase the efficiency of utilization of the stream containing hydrogen and carbon monoxide.

[0025] When certain ligands are used, for example, when organomonophosphite ligands are used, a relatively high carbon monoxide partial pressure is desirable. This can increase the stability of the ligand system. Thus, when organomonophosphite ligands are used, the hydroformylation process is typically carried out at a carbon monoxide partial pressure ranging from about 1 bar to about 20 bar, inclusive, typically from about 3 bar to about 10 bar. When certain other ligands are used, lower carbon monoxide partial pressures can be used without significantly affecting the stability of the ligand system. This can increase the activity of the ligand without a tradeoff in stability. Thus, particularly when organomonophosphine or organopolyphosphite ligands are used, the hydroformylation process is typically carried out at a carbon monoxide partial pressure ranging from about 0.1 bar to about 5 bar, inclusive, typically from about 0.5 bar to 4 bar. The ability to provide an optimal carbon monoxide partial pressure environment for each hydroformylation zone is an advantage of the present invention. When one hydroformylation zone operates under a higher carbon monoxide partial pressure than another hydroformylation zone, but not only under these operating conditions, vent from the reactor in the hydroformylation zone operating under the higher carbon monoxide partial pressure can be fed to the reactor in the hydroformylation zone operating under the lower carbon monoxide partial pressure. Advantageously, this can increase the efficiency of utilization of the feed stream containing hydrogen and carbon monoxide.

[0026] After the hydroformylation reaction, the aldehyde product streams can be combined for further processing, or they can be further processed individually. Further processing can include catalyst recovery and separation of the aldehyde from unreacted olefins and other impurities using processes known in the art, such as those described in WO 2017 / 158315. An advantage of the present invention is that downstream processes using increased carbon monoxide partial pressure during catalyst separation or carbon monoxide strip gas, as disclosed in WO 2016 / 089602 and WO 2020 / 240194, are not required to maintain catalyst stability throughout the process stream. Such processes can be implemented on a small scale only in the hydroformylation zones where they are needed, such as zones where organomonophosphite ligands are used. After such further processing, N and I isomer separation can then be performed on either the individual aldehyde product streams recovered from each separate hydroformylation zone, or on the combined stream. Thus, the process involves feeding each separate aldehyde product stream to a single N and I isomer separation zone to separate N:I isomers in an N:I ratio, R A High N:I ratio fluids containing aldehydes with N:I ratios greater than 1000 and N:I ratios R A and recovering a low N:I ratio stream containing aldehydes having an N:I ratio less than 1:1. Alternatively, the process may further include feeding each separate aldehyde product stream to separate N and I isomer separation zones, each containing an isomer column, and recovering from each separate N and I isomer separation zone a high N:I ratio stream containing aldehydes having an N:I ratio greater than the N:I ratio in the aldehyde product stream fed to the zone, and a low N:I ratio stream containing aldehydes having an N:I ratio less than the N:I ratio in the stream fed to the zone. Low N:I ratio streams typically have an N:I ratio less than about 1:90, preferably less than about 1:99. High N:I ratio streams typically have an N:I ratio greater than about 90:1, preferably greater than about 99:1. The N and I isomer separation zone comprises one or more separation vessels known in the art, typically distillation columns, for example as described in WO 2017 / 182780.

[0027] A commercially important downstream product is an alcohol prepared by hydrogenation of the aldehyde produced by the present process, e.g., butanol prepared from a propylene feed via N-butyraldehyde. Another commercially important downstream product is an alkyl alcohol, typically a 2-alkyl alkanol, prepared by aldol condensation of the normal aldehyde prepared by the process of the present invention, followed by dehydration and hydrogenation. For example, the production of 2-ethylhexanol from N-butyraldehyde (from a propylene feedstock) and the production of 2-propylheptanol from N-valeraldehyde (from a butylene feedstock). Other alkyl alcohols, such as neopentyl glycol, can be prepared using an aldol condensation reaction with an additional aldehyde, in the case of neopentyl glycol, where the aldehyde is formaldehyde, followed by dehydration and hydrogenation. The production of neopentyl glycol uses I-butyraldehyde.

[0028] Thus, the present invention also provides a process for preparing alcohols, which process comprises an N:I ratio R A and then hydrogenating at least a portion of the aldehydes to provide an alcohol. Prior to hydrogenation, N and I aldehyde isomer separation can be performed as described above, such that high N:I ratio or low N:I ratio streams are hydrogenated. Alternatively, the aldehydes can be hydrogenated without aldehyde isomer separation. The hydrogenation process can be operated under any suitable conditions, for example, as described in WO 2019 / 197831.

[0029] The present invention also provides a process for preparing alkyl alkanols, typically 2-alkyl alkanols such as 2-ethylhexanol or 2-propylheptanol, as well as more substituted alkyl alkanols such as neopentyl glycol. This process involves generating a high N:I ratio stream and a low N:I ratio stream using the process described above, and then performing an aldol condensation reaction on one of the high N:I ratio stream or the low N:I ratio stream, followed by a dehydration and hydrogenation step to provide the alkyl alcohol. Typically, when a 2-alkyl alcohol, such as 2-ethylhexanol or 2-propylheptanol, is prepared, a high N:I ratio stream, typically having an N:I ratio greater than about 99:1, is used. In the case of neopentyl glycol, a low N:I ratio stream, typically having an N:I ratio less than about 1:99, is used.

[0030] Such process steps are known in the art and can operate under any suitable conditions, for example, aldol condensations and dehydrations as described in U.S. Pat. Nos. 5,434,313, 6,340,778, and 9,006,495, and hydrogenations as described in WO 2018 / 069714.

[0031] The invention will now be described with reference to the accompanying drawings and by way of example of the hydroformylation of propylene and synthesis gas to produce I- and N-butyraldehydes. It will be understood that the invention is equally applicable to the production of other aldehydes from suitable alternative olefin feedstocks. Those skilled in the art will appreciate that the drawings are schematic and that in a commercial plant, additional items of equipment may be required, such as reflux drums, pumps, vacuum pumps, compressors, gas recycle compressors, temperature sensors, pressure relief valves, control valves, flow controllers, level controllers, etc. The provision of such equipment accessories does not form part of the present invention and is in accordance with conventional chemical engineering practice.

[0032] A schematic illustrating the overall concept of the process of the present invention is shown in Figure 1. The process has two parallel hydroformylation zones, each with a different ligand-metal catalyst system. The ligand-metal catalyst system in zone 1 produces a low N:I aldehyde product ratio (typically about 1:1), while the ligand-metal catalyst system in zone 2 produces a high N:I aldehyde product ratio (typically about 30:1). The propylene 1 and syngas 2 feeds each pass through their respective purification systems 3 and 4. Following feedstock purification, the feeds are split and fed to zones 1 and 2 in proportion to the required production capacity of each zone. Propylene is split into stream 5A to zone 1 and stream 5B to zone 2, and syngas is split into stream 6A to zone 1 and stream 6B to zone 2.

[0033] Reactors 7 and 8 of hydroformylation zone 1, in this case two in series, operate at temperature and pressure conditions optimized for the first zone ligand-metal catalyst system. The reaction temperature is typically the same in reactors 7 and 8 of zone 1, and the pressure in reactor 8 is slightly lower to allow for easy transfer of fluids from reactor 7 to reactor 8. Liquid 7L and vapor 7V streams are typically fed separately from reactor 7 to reactor 8. Reactors 9 and 10 of hydroformylation zone 2 operate in a similar manner but typically operate at different temperature and pressure conditions than zone 1, which are optimized for the second ligand-metal catalyst system.

[0034] Propylene and synthesis gas feeds pass through the reactors in both hydroformylation zones. A portion of the synthesis gas feed can bypass the first reactor in each zone (Streams 6C and 6D) and be fed to the second reactor. Vent gas from second reactor Streams 8V and 10V is cooled in respective vent condensers 11 or 12 to maximize butyraldehyde product recovery, and vent gas streams 11V and 12V are purged from the system to limit the accumulation of inerts. Crude reactor products from hydroformylation Zone 1, Streams 8L and 11L, are then passed to Zone 1 product recovery system 13, where butyraldehyde is vaporized and condensed under optimal conditions to separate it from the catalyst, and concentrated catalyst solution Stream 15 is recycled back to Zone 1 reactors 7 and 8. Typically, increased carbon monoxide partial pressure, or carbon monoxide strip gas, is used during catalyst separation in this zone, as disclosed in WO 2016 / 089602 and WO 2020 / 240194.

[0035] Similarly, crude reactor product streams 10 L and 12 L from zone 2 are passed to zone 2 product recovery system 14, which vaporizes and condenses the butyraldehyde to separate it from the catalyst, and recycles concentrated catalyst solution stream 16 back to the reactor in zone 2. Advantageously, increased carbon monoxide partial pressure, or carbon monoxide strip gas, is not required in this zone, thus reducing the overall equipment required and associated costs compared to processes in which aldehydes having similar N:I ratios are produced in a single reaction zone using multiple ligand-metal catalysts in the same zone.

[0036] The crude butyraldehyde products from Hydroformylation Zone 1, Stream 17, and Hydroformylation Zone 2, Stream 18, can then be combined and passed to Stabilization Column 19, equipped with an associated reboiler and condenser, where lights such as propylene, propane, and any dissolved gases are removed in overhead Stream 21, before Crude Butyraldehyde Stream 20 is passed to Isomer Column 22, equipped with an associated reboiler and condenser. The isomer column separates the crude butyraldehyde into N-Butyraldehyde Stream 23 and I-Butyraldehyde Stream 24 products.

[0037] In Figure 2, synthesis gas-rich vent gas stream 11V is passed from zone 1 to the reactor in zone 2 via reactor 9. Thus, a portion of the remaining hydrogen and carbon monoxide can be used in the hydroformylation synthesis in zone 2. In this case, zone 1 needs to be operated at a slightly higher pressure than zone 2. This use of vent gas can increase the efficiency of use of the hydrogen and carbon monoxide-containing stream. [Example]

[0038] Low and high N:I ratio flowsheets, as well as a mixed-ligand comparative example reflecting the process disclosed in WO 2008 / 115740, were independently tested using a continuously operated miniplant with three hydroformylation reactors. Each reactor had an independent synthesis gas feed and vent, allowing for single or multiple reactor testing. The unit was also equipped with product separation and catalyst recycle for long-term continuous testing.

[0039] The catalyst solution is dissolved in butyraldehyde or another suitable solvent (e.g., toluene, texanol) and then introduced into the reactor system. Syngas and propylene are then introduced to begin continuous operation. Process parameters are modified to optimize temperature, pressure, ligand-metal catalyst concentration, and throughput. Various analytical techniques known to those skilled in the art are used to determine the composition of all gas and liquid streams. All analytical and field equipment is verified through periodic equipment calibrations or checks. This data is then used to determine selectivity information about the process. Examples were performed using conditions optimized for each individual catalyst system, as described above.

[0040] Comparative example of mixed ligand system The reactor was charged with rhodium metal and organomonophosphite ligand (ligand A) and organobisphosphite ligand (ligand B). The system was operated for a total of 140 days at conditions primarily optimized for Ligand B with a desired N:I ratio of 3. The reactor system was operated at a mixed butyraldehyde production rate of 3.0 g mol / hr, with the required N:I ratio butyraldehyde achieved in two distinct segments of operation (days 0-70 and days 120-130). The decrease in rhodium concentration over these segments, both measured via ICP, was 0.151 μg Rh loss per gram of butyraldehyde produced during these two periods. The rhodium concentration over time is shown in Figure 3.

[0041] Parallel Zone Example The hydroformylation of propene to butyraldehyde with a desired N:I ratio of 3 was carried out in two separate reaction zones, a low N:I zone and a high N:I zone. The desired N:I ratio in each zone and the volume required in each zone are shown in Table 1 below.

[0042] [Table 1] * bal = butyraldehyde

[0043] Low N:I Zone The reactor was charged with rhodium metal and organomonophosphite ligand (ligand A). The system was operated for a total of 100 days at conditions optimized for ligand A. The N:I ratio in this example was kept constant at about 1.4. The decrease in rhodium concentration measured via ICP was 0.073 μg Rh loss per gram of butyraldehyde produced. The change in rhodium concentration over time is shown in Figure 4.

[0044] High N:I Zone The reactor was charged with rhodium metal and an organobisphosphite ligand (ligand B). The system was operated for 90 days at conditions primarily optimized for ligand B. The N:I ratio in this example was maintained at approximately 30:1. The decrease in rhodium concentration measured via ICP was 0.002 μg Rh loss per gram of butyraldehyde produced. The change in rhodium concentration over time is shown in Figure 5.

[0045] conclusion Through the use of parallel hydroformylation zones for N:I and the relative volumes illustrated in Table 1 above, the mixed ligand system has a predicted Rh loss of 0.151 μg Rh loss per gram of butyraldehyde produced (Comparative Example), while the combined parallel zone system has a predicted Rh loss of 0.042 μg Rh loss per gram of butyraldehyde produced.

Claims

1. The olefin is hydroformylated to produce normal (N) aldehydes and iso (I) aldehydes in an N:I ratio R Ａ 1. A process for producing a olefin of formula (I), comprising hydroformylating an olefin with hydrogen and carbon monoxide in the presence of a ligand-metal catalyst; the hydroformylation is carried out in at least two separate, parallel hydroformylation zones, each hydroformylation zone comprising one or more hydroformylation reactors in series; each separate hydroformylation zone produces N-aldehydes and I-aldehydes in a different N:I ratio than the other hydroformylation zones; The process comprises: i) feeding an olefin feed stream to each separate hydroformylation zone; ii) feeding a stream comprising hydrogen and carbon monoxide to each separate hydroformylation zone; iii) recovering an aldehyde product stream from each separate hydroformylation zone; The N:I ratio R Ａ is the total N:I ratio contained in the aldehyde product stream.

2. The N:I ratio R Ａ 2. The process of claim 1, wherein the ratio of hydroxybenzoates to hydroxybenzoates is less than about 10:

1.

3. The N:I ratio R Ａ 3. The process of claim 1 or 2, wherein the ratio of hydroxybenzoates to hydroxybenzoates is at least about 0.5:

1.

4. The process of any one of claims 1 to 3, wherein the hydroformylation is carried out in two separate, parallel hydroformylation zones.

5. 5. The process of any one of claims 1 to 4, wherein one hydroformylation zone operates under conditions to produce an aldehyde product stream having an N:I ratio of about 2:1 or less.

6. 6. The process of claim 5, wherein the hydroformylation zone comprises a ligand-metal catalyst, the ligand being an organomonophosphite ligand, operated under conditions to produce an aldehyde product stream having an N:I ratio of about 2:1 or less.

7. 7. The process of any one of claims 1 to 6, wherein one hydroformylation zone operates under conditions to produce an aldehyde product stream having an N:I ratio of at least about 6:

1.

8. 8. The process of claim 7, wherein the hydroformylation zone comprises a ligand-metal catalyst, the ligand being an organomonophosphine ligand, operated under conditions to produce an aldehyde product stream having an N:I ratio of at least about 6:

1.

9. 9. The process of claim 7 or 8, wherein the hydroformylation zone, operating under conditions to produce an aldehyde product stream having an N:I ratio of at least about 6:1, comprises a ligand-metal catalyst, the ligand being an organopolyphosphite ligand.

10. 10. The process of any one of claims 1 to 9, wherein vent from the reactor in the hydroformylation zone operating under a higher carbon monoxide partial pressure is fed to the reactor in the hydroformylation zone operating under a lower carbon monoxide partial pressure.

11. Each separate aldehyde product stream is fed to a single N and I isomer separation zone, with the N:I ratio R Ａ High N:I ratio streams containing aldehydes having an N:I ratio greater than Ａ 11. The process of any one of claims 1 to 10, further comprising recovering a low N:I ratio stream comprising aldehydes having an N:I ratio of less than

12. 12. A process for preparing an alkyl alcohol, the process comprising generating a high N:I ratio stream and a low N:I ratio stream using the process of claim 11, and then performing an aldol condensation reaction on one of the high N:I ratio stream or the low N:I ratio stream, followed by a dehydration and hydrogenation step to provide the alkyl alcohol.

13. 13. The process of any one of claims 1 to 12, wherein the olefin is propylene and the aldehyde is butyraldehyde.

14. A process for preparing alcohols, said process comprising reacting N-aldehydes and I-aldehydes in an N:I ratio R using the process of any one of claims 1 to 11. Ａ and then hydrogenating at least a portion of said aldehyde to provide said alcohol.

15. 15. The process of claim 14, wherein the alcohol is butanol.

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