Method and apparatus for producing aldehydes

Abstract

The present invention provides a process for the production of C2n unsaturated aldehydes wherein n is in the range of from 3 to 6 and includes end values, the process comprising: (iv) passing a crude aldol stream from an aldol condensation reaction to a crude aldol distillation column operating under distillation conditions, to form a bottoms stream having an increased concentration of C2n unsaturated aldehydes, water, and heavy matter as compared to the crude aldol stream, and an overhead stream comprising unreacted Cn aldehydes, Cn-1 alkanes, Cn-1 olefins, and a reduced concentration of C2n unsaturated aldehydes, water, and heavy matter as compared to the crude aldol stream; (v) passing the overhead stream from the crude aldol distillation column to a first condenser zone configured to provide a first condensed stream comprising unreacted Cn aldehyde and water in an increased concentration compared to the overhead stream from the crude aldol distillation column and an overhead stream, the overhead stream comprising Cn-1 alkanes, Cn-1 olefins, and unreacted Cn aldehydes and water in a reduced concentration compared to the overhead stream from the crude aldol distillation column; (vi) passing the overhead stream from the first condenser zone to a second condenser zone, the second condenser zone configured to condense at least a portion of the overhead stream from the first condenser zone to provide a Cn / Cn-1 condensate; and wherein at least a portion of the Cn / Cn-1 condensate is recovered and returned upstream of the crude aldehyde distillation column or back to the crude aldehyde distillation column.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method and apparatus for the production of aldehydes. In particular, the method and apparatus according to the present invention provide for improved feedstock efficiency in the synthesis of aldehydes, more particularly in the production of 2-alkyl alkenals. BACKGROUND

[0002] Synthetic aldehydes, such as 2-alkyl alkenals, are commonly used as intermediates in the production of alcohols, such as 2-alkyl alkanols, which themselves are used for a variety of applications in the chemical industry, including as solvents, fuels, chemical intermediates in the synthesis of organic compounds, and the like. Globally, a variety of alcohols are produced annually. For certain alcohols (e.g. ethanol), biological synthesis methods such as fermentation can be suitable for the production of the alcohol. However, for longer chain alcohols and branched alcohols, synthetic production is generally required.

[0003] Existing methods for the synthetic production of aldehydes, such as 2-alkyl alkenals, include the step of hydroformylation of an olefin (also known as the "oxo" process) in the presence of a catalyst, followed by an aldol condensation. Hydroformylation introduces a formyl group into an unsaturated olefin to provide an aldehyde. Hydroformylation can be carried out by contacting the olefin with synthesis gas (a mixture of carbon monoxide and hydrogen). Once the aldehyde has been produced, hydrogenation reduces the aldehyde to provide the corresponding alcohol.

[0004] In the case where longer chain alcohols or branched alcohols are required, the method can include the step of carrying out an aldol condensation to condense two aldehydes, followed by dehydration, thereby providing an unsaturated aldehyde, such as a 2-alkyl alkenal. Such aldol condensation reaction products are commonly referred to as a, b-unsaturated aldehydes. In the case where the aldol condensation reaction is carried out between two identical aldehydes, the a, b-unsaturated aldehyde is referred to as a self-condensation product. In the case where the aldol condensation reaction is carried out between two different aldehydes, the a, b-unsaturated aldehyde is referred to as a cross-condensation product. The aldol condensation process is typically base or acid catalysed.

[0005] The unsaturated aldehyde is then reduced by hydrogenation to provide the corresponding saturated alcohol.

[0006] Given the widespread use of alcohols, particularly 2-alkyl alkanols, it is desirable to produce alcohols in a cost-effective manner with maximum yield and maximum purity on an industrial scale.

[0007] It is therefore an object of the present invention to improve feedstock efficiency and yield in the production of aldehydes, particularly 2-alkyl alkenals, produced by industrial methods. This advantage is beneficial in itself and also to the overall feedstock efficiency and yield in the production of alcohols, particularly 2-alkyl alkanols where the aldehydes are intermediates. SUMMARY

[0008] The present inventors have provided a method for the production of C nAldehydes (where n is in the range of 3 to 6 and includes the extreme values) produce C 2n Novel methods and apparatus for unsaturated aldehydes, more particularly 2-alkylenal, and even more particularly 2-propylhept-2-enal. Advantageously, the methods and apparatus of the present invention improve product yield and increase raw material efficiency.

[0009] The method and apparatus of the present invention can improve the recovery of unreacted C from the crude aldol distillation column provided after the aldol condensation reaction. n Aldehydes. The distillation column is configured to separate the reaction mixture provided by the aldol condensation step. More specifically, the invention provides a first condenser section and a second condenser section at the top of the distillation column to recover unreacted C. n The first condensate stream of aldehydes contains remaining unreacted C. n Aldehydes and C n-1 Alkanes and C n-1 C of olefins n / C n-1 Condensate, and substances containing C n-1 Alkanes and C n-1 Optional vapor feed stream of olefins. C n-1 Alkanes and C n-1 Alkenes are typically found in C14 groups used in aldol condensation reactions. n Aldehydes are present in the feed stream because they are present in the feed used for the hydroformylation reaction. Small amounts of C are typically permitted. n-1 Alkanes and C n-1 An olefin is introduced into an aldol condensation reaction to regulate the temperature at the bottom of a crude aldehyde distillation column, which is described in this paper and used to distill C... n C is at least partially separated from aldehydes n-1 Alkanes and C n-1 Alkenes. C n Aldehydes, C n-1 Alkanes and C n-1 Olefins accumulate and concentrate to high levels at the top of aldol distillation columns due to their hydrophobic properties, and are typically evacuated to limit their accumulation. This is usually achieved by partially condensing the overhead distillate from the crude aldol column in a single condensation step, for example, by cooling to approximately 80°C in the synthesis of 2-propylhept-2-enal using pentanal. This results in the feedstock C... n Loss of aldehydes.

[0010] According to a first aspect of the invention, a method for producing C is provided. 2n A method for unsaturated aldehydes, wherein n is in the range of 3 to 6 and includes end values, the method comprising:

[0011] (i) will include C n-1an olefin stream of olefins is fed to a hydroformylation reactor and the olefin stream is contacted with a hydroformylation gas stream comprising hydrogen and carbon monoxide to perform a hydroformylation reaction, thereby providing a crude aldehyde stream comprising C n aldehyde, C n-1 alkanes and C n-1 olefins;

[0012] (ii) feeding the crude aldehyde stream to a crude aldehyde distillation zone operating under distillation conditions to form a bottoms stream comprising C n aldehyde, C n-1 alkanes and C n-1 olefins and an increased concentration of C n aldehyde relative to the crude aldehyde stream and an increased concentration of C n-1 alkanes and C n-1 olefins relative to the crude aldehyde stream;

[0013] (iii) feeding the bottoms stream from the crude aldehyde distillation column to an aldol condensation reactor under condensation and dehydration conditions to perform an aldol condensation reaction of C n aldehyde, thereby providing a crude aldol stream comprising aldol product C 2n unsaturated aldehyde, unreacted C n aldehyde, C n-1 alkanes, C n-1 olefins, water, and heavies;

[0014] (iv) passing the crude aldol stream to a crude aldol distillation column operating under distillation conditions to form a bottoms stream having an increased concentration of C 2n unsaturated aldehyde, water, and heavies, and an increased concentration of C n aldehyde, C n-1 alkanes, C n-1 olefins, and a decreased concentration of C 2n unsaturated aldehyde, water, and heavies relative to the crude aldol stream;

[0015] (v) passing the overhead stream from the crude aldol distillation column to a first condenser zone configured to provide a first condensed stream comprising an increased concentration of unreacted C n aldehyde and water relative to the overhead stream from the crude aldol distillation column and an overhead stream comprising C n-1 alkanes, C n-1 olefins, and a decreased concentration of unreacted C n aldehyde and water relative to the overhead stream from the crude aldol distillation column;

[0016] (vi) The overhead feed stream from the first condenser zone is fed to a second condenser zone, which is configured to condense at least a portion of the overhead feed stream from the first condenser zone to provide C. n / C n-1 Condensate; and

[0017] C n / C n-1 At least a portion of the condensate is recovered and returned upstream of the crude aldehyde distillation column or returned to the crude aldehyde distillation column.

[0018] Advantageously, the crude aldehyde distillation zone more effectively converts C n Aldehydes and C n-1 Alkanes and C n-1 Olefin separation and promotes the release of unreacted C atoms. n Aldehydes are effectively recycled back to the aldol condensation step, rather than being wastefully discharged. C323 is recovered from the crude aldehyde distillation zone. n-1 Alkanes and C n-1 Olefins also allow the feed stream to be output as a liquid rather than a low-pressure gas, thereby increasing the recovery of C. n-1 Alkanes and C n-1 The value of olefin feedstock.

[0019] In the method of the present invention, n is suitably 4, 5, or 6, typically 4 or 5, preferably 5. Therefore, the C in the olefin feed stream... n-1 The olefin may suitably be propylene or butene, preferably butene, such as but-1-ene. C n Aldehydes are suitably C4, C5, or C6 aldehydes, usually C4 or C5, preferably C5, i.e., pentanal. They undergo an aldol condensation reaction to provide the C6 carbon atom for the aldol product. 2n Most of the C in unsaturated aldehydes n Aldehydes are straight-chain aldehydes, such as valeraldehyde (pentanal). Typically, branched-chain aldehydes will be expressed as total C20. n The aldehyde may be present in an amount of up to 10 mol%, suitably up to 7.5 mol%. For example, in C n When the aldehyde is pentanal, 3-methylbutanal and 2-methylbutanal can exist. These isomers are typically formed during the hydroformylation step. 2n Unsaturated aldehydes are preferably C8 or C9. 10 Or C 12- Unsaturated aldehydes, typically C8 or C6 10 Unsaturated aldehydes, preferably C 10 C 2n The unsaturated aldehyde can be a 2-alkylenal. Preferably, C 2n The aldehyde is 2-propylhept-2-enal.

[0020] C n-1alkane can be C n-1 alkane or isomeric C n-1 mixture of alkanes. For example, where n is 5 and C n aldehyde is pentanal, C n-1 alkane includes n-butane and isobutane, typically n-butane. The C n-1 alkane can be brought into the hydroformylation step from the olefin feed and / or can be produced during hydroformylation. The C n-1 alkene can be C n-1 alkene, or isomeric C n-1 mixture of alkenes. For example, where n is 5 and C n aldehyde is pentanal, C n-1 alkene includes but-1-ene as well as cis-but-2-ene and trans-but-2-ene. The C n-1 alkene is typically brought into the hydroformylation step from the olefin feed, and can also be formed at various stages throughout the process. The C n-1 alkane and C n-1 The amount of alkene will typically depend on the nature of the olefin feed to the hydroformylation step. Other alkanes (such as C n alkane) can also be present, which will increase in concentration as C n-1 alkane and C n-1 alkene together complete the process of the present invention. In other words, the stream comprising increasing concentrations of C n-1 alkane and C n-1 alkene will also have increasing concentrations of C n alkane. Any C n alkane can be brought into the hydroformylation step from the olefin feed and / or can be produced during hydroformylation.

[0021] C n-1 The amount of alkene is not particularly limited, and is not critical to the present invention. For example, a suitable olefin stream entering the hydroformylation reactor can comprise at least 50 mole % C n-1 alkene, optionally at least 60 mole % C n-1 alkene, optionally at least 70 mole % C n-1 alkene, also optionally at least 80 mole % C n-1 alkene, further optionally at least 90 mole % C n-1 alkene.

[0022] The hydroformylation reactor can suitably be operated at a C n-1 alkene single-pass conversion of at least 40%, optionally at least 50%, also optionally at least 60%. The C nThe concentration of aldehyde will depend on the level of conversion and is not critical to the present invention. The crude aldehyde stream can comprise, for example, at least 25 mole % C n aldehyde relative to the total moles of the crude aldehyde stream.

[0023] The bottoms stream from the crude aldehyde distillation column, which also provides the feed to the aldol condensation reactor, can comprise, for example, at least 70 mole % C n aldehyde, further optionally at least 80 mole % C n aldehyde, typically at least 90 mole % C n aldehyde relative to the total moles of the crude aldehyde stream.

[0024] The overhead stream from the crude aldehyde distillation column can comprise, for example, at least 95 mole % C n-1 alkane and C n-1 alkene. This stream can be output as a liquid rather than a low pressure gas, increasing the value of the recovered C n-1 alkane and C n-1 alkene stream.

[0025] The aldol condensation reaction can suitably operate at at least 50%, optionally at least 60%, further optionally at least 70% C n aldehyde single pass conversion. The crude aldol stream can comprise, for example, at least 5 mole % C 2n unsaturated aldehyde relative to the total moles of the crude aldol stream. Typically, the crude aldol stream can comprise, for example, at least 5 mole % C 2n unsaturated aldehyde. A significant amount of water can be present in this stream, for example, at least 50 mole % relative to the total moles of the crude aldol stream. The crude aldol stream will also comprise heavies. As used herein, the term "heavies" refers to organic molecules having a molecular weight greater than C 2n unsaturated aldehyde and / or a boiling point greater than C 2n unsaturated aldehyde. The crude aldol stream will also comprise unreacted C n aldehyde and C n-1 alkane and C n-1 alkene.

[0026] The bottoms stream from the crude aldol distillation column can also comprise an aqueous phase, for example, at least 80 mole % of the bottoms stream can be aqueous. For example, when a homogeneous catalyst is used, the aqueous phase typically comprises dissolved aldol condensation reaction catalyst, for example, NaOH. The aqueous phase is typically separated from an organic phase comprising C 2n unsaturated aldehyde by decantation. Alternatively, for example, when a heterogeneous catalyst is used in the aldol condensation reaction, there can be no aqueous phase to separate, and the entire bottoms stream is an organic phase. The organic phase is the stream described herein for production of C 2nThe process for the alcohol provides a feed. The process includes producing C 2n an unsaturated aldehyde, followed by step (vii): feeding the organic phase of the bottoms stream from the crude aldol distillation column to a hydrogenation zone to hydrogenate the C 2n an unsaturated aldehyde, thereby providing C 2n an alcohol.

[0027] The overhead stream from the crude aldol distillation column can include, for example, at least 15 mole % combined C n-1 alkanes, C n-1 alkenes, and unreacted C n aldehyde relative to the total moles of the overhead stream from the crude aldol distillation column. The overhead stream from the crude aldol distillation column can include at least 10 mole % unreacted C n aldehyde relative to the total moles of the overhead stream from the crude aldol distillation column. The overhead stream from the crude aldol distillation column can also include small amounts of C 2n unsaturated aldehyde, for example less than 2 mole %, typically less than 1 mole %.

[0028] The first condenser zone typically uses a heat exchanger to condense the overhead stream from the first condenser zone. Preferably, at least a portion (i.e., not all) or substantially all of the first condensed stream is recovered as a first condensed stream recycle stream and returned to the aldol condensation reactor. The first condensed stream typically includes water, and the first condensed stream is typically passed through a decanter to remove water prior to being returned to the aldol condensation reactor. In the decanter, an aqueous stream is separated from the first condensed stream to provide the first condensed stream recycle stream. The aqueous stream typically includes at least 95 mole % water relative to the total moles of the aqueous stream. After passing through the decanter, the first condensed stream recycle stream can include, for example, at least 60 mole % combined C n-1 alkanes, C n-1 alkenes, and unreacted C n aldehyde, optionally at least 80 mole % combined C n-1 alkanes, C n-1 alkenes, and unreacted C n aldehyde, and optionally less than 5 mole % water relative to the total moles of the first condensed stream. The first condensed stream can also include any small amounts of the remaining amounts of C 2n unsaturated aldehyde.

[0029] The overhead stream from the first condenser zone can typically include, for example, at least 50 mole % combined C n-1 alkanes, C n-1alkenes and unreacted C n aldehydes. The overhead stream from the first condenser zone can comprise, for example, at least 10 mole % C n aldehydes. The overhead stream from the first condenser zone can also comprise residual water.

[0030] In the second condenser zone, C n / C n-1 The condensate can be produced in a single condensation step or in multiple condensation steps. In each condensation step or the condensation step, a heat exchanger can be used to condense the overhead stream from the first condenser zone. Alternatively or additionally, in each condensation step or the condensation step, the overhead stream from the first condenser zone can be condensed by washing with a process stream that is cooler than the overhead stream from the first condenser zone. If desired, such a process stream can be actively cooled so that it is cooler than the overhead stream from the first condenser zone. A suitable process stream is at least a portion of the first condensation stream recycle stream. In this case, the remainder of the first condensation stream recycle stream can still be returned to the aldol condensation reactor. Another suitable process stream is a portion of the crude aldehyde stream. In this case, the remainder of the crude aldehyde stream is still fed to the crude aldehyde distillation zone. Another suitable process stream is a portion of the bottoms stream from the crude aldehyde distillation column. In this case, the remainder of the bottoms stream from the crude aldehyde distillation column is still fed to the aldol condensation reactor. Such washing further increases the recovery of any remaining C n aldehydes and improves feedstock efficiency.

[0031] A portion (i.e. not all) or substantially all of the overhead stream from the first condenser zone can be condensed. In the alternative where not all of the stream is condensed, a vapor stream will be produced by the second condenser zone, which can be vented. The vapor stream suitably comprises an increased concentration of C n-1 alkanes and C n-1 alkenes. The vapor stream can comprise, for example, at least 90 mole % C n-1 alkanes and C n-1 alkenes, optionally at least 95 mole % C n-1 alkanes and C n-1 alkenes. At least a portion (i.e. not all) or substantially all of the C n / C n-1 The condensate is recovered and returned upstream of the crude aldehyde distillation column or to the crude aldehyde distillation column. C n / C n-1 The condensate can suitably comprise, for example, at least 10 mole % C n / C n-1at least 50 mole % of the total moles of condensate of C n-1 alkanes, C n-1 olefins and C n aldehydes. C n / C n-1 The condensate can comprise, for example, relative to C n / C n-1 at least 15 mole % of the total moles of condensate of C n aldehydes. C n / C n-1 The condensate can further comprise residual water. In this case, a decanter can be used to remove the water. In the decanter, the water-containing stream is separated from C n / C n-1 The condensate is separated. Typically, at least 20 mole %, optionally at least 50 mole %, further optionally at least 90 mole % of C n / C n-1 The condensate is recovered as a recycle stream. Typically, at least 95 mole % of C n / C n-1 The condensate is returned to upstream of the crude aldehyde distillation column or to the crude aldehyde distillation column. Advantageously, such recycling can be performed without the need for expensive compression, which would otherwise be necessary due to the crude hydroxy aldehyde distillation column typically being operated at a lower pressure than the crude aldehyde distillation column, since the recycling is provided in liquid form.

[0032] The temperature in the first condenser zone will typically be higher than the condensation temperature in the second condenser zone, for example at least 10 °C higher. The temperature in the first condenser zone can typically be in the range of 50 °C to 110 °C, optionally 70 °C to 90 °C. The condensation temperature in the second condenser zone can typically be in the range of 2 °C to 50 °C, optionally 35 °C to 45 °C, further optionally 35 °C to 40 °C.

[0033] According to a second aspect of the application, there is provided a device for producing C 2n an unsaturated aldehyde, wherein n is in the range of 3 to 6, the device comprising:

[0034] a hydroformylation reactor configured to contact an olefin stream comprising an olefin with hydrogen and carbon monoxide to perform a hydroformylation reaction on the olefin, thereby providing a stream comprising C n aldehydes, C n-1 alkanes, and C n-1 an olefin;

[0035] a crude aldehyde distillation column configured to receive a crude aldehyde stream and to provide an overhead stream and a bottoms stream;

[0036] an aldol condensation reactor configured to receive the crude aldol stream and provide a crude aldol stream, wherein the crude aldol stream comprises aldol product C 2n unsaturated aldehyde, unreacted C n aldehyde, C n-1 alkane, C n-1 alkene, water, and heavies;

[0037] a crude aldol distillation column configured to receive the crude aldol stream and provide an overhead stream and a bottoms stream;

[0038] a first condenser zone configured to cool the first overhead stream to provide a first condensed stream and an overhead stream;

[0039] a second condenser zone in fluid communication with the first condenser zone, wherein

[0040] the second condenser zone is configured to cool the first overhead stream to provide a condensate and an optional vapor stream;

[0041] wherein the second condenser zone is in fluid communication with the crude aldol distillation column or upstream of the crude aldol distillation column, such that at least a portion of the condensate is returned to the crude aldol distillation column or upstream of the crude aldol distillation column;

[0042] wherein the first condenser zone is optionally in fluid communication with the aldol condensation reactor, such that at least a portion of the first condensed stream is returned to the aldol condensation reactor. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 A schematic diagram illustrating a conventional process for the industrial production of aldehydes is shown.

[0044] Figure 2 A schematic process for the industrial production of aldehydes according to the present application is shown.

[0045] Figure 3 A schematic process for the industrial production of aldehydes according to the present application is shown.

[0046] Figure 4 A schematic process for the industrial production of aldehydes according to the present application is shown. DETAILED DESCRIPTION

[0047] The present application will now be described in detail with reference to the following non-limiting examples and drawings. While the present application is generally described with reference to the production of 2-propylhept-2-enal, it will be appreciated by those skilled in the art that the present application can be applied to the production of any other C 2n production of unsaturated aldehydes.

[0048] The 2-alkyl propanols described herein are preferably formed via hydrogenation of an a,b-unsaturated aldehyde, wherein the a,b-unsaturated aldehyde is a self-condensation product. Preferably, the a,b-unsaturated aldehyde is a self-condensation product of pentanal. Preferably, the a,b-unsaturated aldehyde is 2-propylhept-2-enal.

[0049] The following Scheme 1 shows a general process for the production of 2-propylhept-2-enal and 2-propylheptanol.

[0050]

[0051] Scheme 1 : General process for the production of 2-propylheptanol from butene .

[0052] A process for the production of 2-propylhept-2-enal and 2-propylheptanol will now be described with reference to the above Scheme 1 and Figure 1 .

[0053] With reference to Figure 1 , a C n-1 alkene (e.g. but-1-ene) and a C n-1 alkane (e.g. an isomer of butane) and a C n-1 alkene (e.g. but-1-ene, cis-but-2-ene and trans-but-2-ene) is provided to a hydroformylation reactor 5. The alkene stream 1 can be provided as a crude cracking product stream from industrial cracking of hydrocarbons. The person skilled in the art will be familiar with industrial cracking processes. The crude cracking product stream can undergo one or more enrichment steps, for example by passing the crude cracking product stream through one or more distillation columns to increase the concentration of C n-1 alkenes in the alkene stream 1 provided to the hydroformylation reactor 5.

[0054] In the hydroformylation reactor 5, the C n-1 alkenes are contacted with carbon monoxide and hydrogen provided via a synthesis gas stream 3 in the presence of a liquid catalyst solution to provide C n aldehydes, more particularly pentanal. This hydroformylation process is also known as the “oxo process”. A typical flow diagram is described in, for example, US 4,148,830 or US 5,087,763, which are incorporated herein by reference. The hydroformylation liquid catalyst system typically comprises a solvent, rhodium, a ligand and other components, but can be any suitable catalyst system for hydroformylation. Typical organic phosphine and organic phosphite ligands are described in, for example, WO2008 / 115740, WO2011 / 087690, WO2010 / 117391 and WO2016 / 089602, which are incorporated herein by reference.

[0055] The hydroformylation provides a crude aldehyde stream 7, which comprises C n-1 alkanes, Cn-1 olefins and C n mixtures of aldehyde hydroformylation products (e.g., pentanal and, in the case of pentanal, isomers 2-methylbutanal and 3-methylbutanal).

[0056] Crude aldehyde stream 7 is passed to a crude aldehyde distillation zone 9 to increase the concentration of C n aldehyde in the aldol condensation reactor feed stream 13 provided to aldol condensation reactor 15. Distillation zone 9 can be a single distillation column or a multi-column distillation apparatus, provided that a bottoms stream 13 is produced that contains C n aldehyde, C n-1 alkanes and C n-1 olefins, where the concentration of C n aldehyde is increased relative to the crude aldehyde stream, and an overhead stream 11 that contains an increased concentration of C n-1 alkanes and C n-1 olefins relative to the crude aldehyde stream. Stream 11 can be output as a liquid rather than a low pressure gas, increasing the value of the recovered C n-1 alkanes and C n-1 olefins stream. Additionally, some streams can be recycled to hydroformylation to convert additional C n aldehyde.

[0057] Any suitable components can be used in the distillation zone, and the skilled person can determine, for example, what tray internals and conditions suitable for the desired separation are used. Further enrichment steps can be included between crude aldehyde distillation column 9 and aldol condensation reactor 15, but are not necessary. For example, the distillation column increases the amount of linear aldehyde.

[0058] Stream 13 is provided to aldol condensation reactor 15. The aldol condensation reaction is carried out in aldol condensation reactor 15 under condensation and dehydration conditions to carry out the aldol condensation reaction of C n aldehyde (e.g., pentanal) to provide a crude aldol stream containing aldol product C 2n unsaturated aldehyde (e.g., 2-propylhept-2-enal) and unreacted C n aldehyde, C n-1 alkanes, C n-1 olefins, water, and heavies. The heavies include trace amounts of aldol condensation reaction catalyst, such as sodium hydroxide and salts (such as sodium pentanoate).

[0059] Such aldol condensation steps are known in the art and are described, for example, in US 5,434,313 and US 6,340,778, which are incorporated herein by reference. Suitable reagents for carrying out the aldol condensation reaction in the aldol condensation reactor 15 include suitable bases or acids. The aldol condensation reaction is preferably carried out in the liquid phase (i.e. the feed) and the reagents are in the liquid phase. The skilled person will know such suitable acids and bases for liquid phase reactions, but can be selected from inorganic bases (e.g. NaOH), organic bases (e.g. NEt3), inorganic acids (e.g. H2SO4) and organic acids (e.g. F3CCOOH). Alternatively, a heterogeneous catalyst can be used and the skilled person will know suitable such catalysts. During the aldol condensation reaction, water is produced as a by-product (dehydration). In order to carry out the aldol condensation reaction, the aldol condensation reactor 15 is typically maintained at a temperature of 80 °C to 140 °C. The skilled person is able to determine suitable conditions for operating the aldol condensation reaction to achieve the desired first pass conversion of the aldehyde. n Conditions for first pass conversion of aldehyde.

[0060] The aldol condensation reaction provides a crude aldol stream 17 comprising C 2n unreacted C n aldehyde, C n-1 alkane, C n-1 alkene, water and heavies. The aldol condensation reaction is typically operated continuously, such that the crude aldol stream 17 is removed from the aldol condensation reactor 15 during the aldol condensation reaction.

[0061] The crude aldol stream 17 is subjected to an enrichment step by passing the crude aldol stream 17 to a crude aldol distillation column 19 to increase the concentration of C 2n unsaturated aldehyde in a bottoms stream 21, which can be decanted to remove water, and then the organic phase is provided to a hydrogenation reactor (not shown) to produce C 2n alcohol (e.g. 2-propyl heptanol).

[0062] More specifically, the aldol distillation step comprises passing the crude aldol stream 17 to a crude aldol distillation column 19 operated under distillation conditions to form a bottoms stream 21 having an increased concentration of C 2n unsaturated aldehyde, water and heavies, and a bottoms stream 21 comprising unreacted C n aldehyde, C n-1 alkane, C n-1 alkene and a reduced concentration of C 2nan unsaturated aldehyde, water and heavies. Any suitable means can be used for distillation, and the skilled person can determine, for example, what internals to use and conditions suitable for the required separation. Distillation is described, for example, in US 5,434,313, which is incorporated herein by reference.

[0063] Figure 1 The crude aldol distillation column 19 comprised in the conventional industrial process for the production of 2-propylhept-2-eneal is exemplified. The overhead stream 23 is passed to a condenser zone 25 configured to provide a condensed stream 29 comprising an increased concentration of C n aldehyde and water and a vapour stream 27 containing mainly C n-1 alkanes and C n-1 alkenes. The condensed stream 29 also contains C n-1 alkanes and C n-1 alkenes and any C 2n unsaturated aldehyde present in the first overhead stream. The condenser zone 25 comprises a heat exchanger for cooling the overhead stream 23 to a temperature of 70 to 90 °C, preferably to about 80 °C, especially in the case of the production of 2-propylhept-2-eneal from pentanal. This stream 29 is passed through a decanter 31 which separates an aqueous stream 33 and a recycle stream 35 which recycles the organics back to the aldol condensation reactor 15. To mitigate pressure build-up within the crude aldol distillation column 19, a vapour stream 27 is simply purged during distillation. The vapour stream 27 typically contains some C n aldehyde and C n-1 alkanes and C n-1 alkenes, thus C n aldehyde is lost from the process in the purge.

[0064] Figure 2 is a schematic representation of the process according to the present application, wherein a first condenser zone 25 and a second condenser zone 37 are present at the top of the crude aldol distillation column.

[0065] The first condenser zone 25 comprises a first heat exchanger. The overhead stream 23 from the crude aldol distillation column is cooled in the heat exchanger, for example by a cold water stream. According to Figure 1 the process of the present application, at least a portion of the first condensed stream 29 is decanted and recycled to the aldol condensation reactor 15. Typically, the first overhead stream 23 is cooled in the heat exchanger 25 to a temperature of 70 to 90 °C, preferably to about 80 °C, especially in the case of the production of 2-propylhept-2-eneal from pentanal.

[0066] The overhead stream 27 from the first condenser zone is sent to a second condenser zone 37, rather than being vented according to the conventional process of Figure 1 the present application. The second condenser zone is configured to provide Cn / C n-1 Condensed stream 41 comprising increased concentration of C n aldehydes, e.g., pentanal, compared to second overhead stream 27. Optionally, a vapor stream 39 is also provided comprising increased concentration of C n-1 alkanes and C n-1 alkenes, e.g., isomers of butane and but-1-ene, cis-but-2-ene and trans-but-2-ene.

[0067] The second condenser zone includes a heat exchanger to provide C n / C n-1 condensed stream 41. Second overhead stream 27 is cooled in the second heat exchanger, typically by a cold water stream. Preferably, second overhead stream 41 is cooled in the second heat exchanger 37 to about 2°C to 50°C, optionally 35°C to 45°C, further optionally 35°C to 40°C, e.g., to about 38°C, particularly in the case of production of 2-propylhept-2-enal from pentanal. C n / C n-1 Condensate 41 passes through a decanter 43 which separates an aqueous stream 45 and a recycle stream 47 which recycles the organics back to crude aldehyde distillation column 9. The distillation column more efficiently separates C n aldehydes from C n-1 alkanes and C n-1 alkenes, and facilitates efficient recycle of unreacted C n aldehydes back to the aldol condensation step, rather than wasting them by venting. Recovery of C n-1 alkanes and C n-1 alkenes from the crude aldehyde distillation column as a liquid rather than a low pressure gas, thereby increasing the value of the recovered C n-1 alkanes and C n-1 alkenes stream.

[0068] Figure 3 is a schematic of another method according to the invention in which there is a first condenser zone 25 and a second condenser zone 37 at the top of the crude aldol distillation column. In this method, a recycle stream 35, which is cooler than the overhead stream 27, is used to wash the overhead stream 27 and condense the stream to provide C n / C n-1 condensate stream 41, rather than using a heat exchanger. Stream 41 is passed through a decanter 43 to provide a recycle stream 47 which recycles the organics back to crude aldehyde distillation column 9. A vapor stream 39 containing C n-1 alkanes and C n-1 alkenes is optional.

[0069] Figure 4is a schematic representation of a further method according to the application in which there is a first condenser zone 25 and a second condenser zone 37 at the top of the crude hydroxy aldehyde distillation column. In this method, a portion of the crude aldehyde stream 7 is used to wash the overhead stream 27 and condense this stream to provide a C n / C n-1 condensate stream 41 rather than using a heat exchanger. If desired, the wash stream is cooled in a cooling stage (not shown). The stream 41 is passed through a decanter 43 to provide a recycle stream 47 which recycles the organics back to the crude aldehyde distillation column 9. The vapour stream 39 containing C n-1 alkanes and C n-1 alkenes is optional. A portion of the crude hydroxy aldehyde stream 7 is still fed to the crude aldehyde distillation zone 9.

[0070] The crude hydroxy aldehyde distillation column from Figures 1 to 4 can then be used to provide a crude hydroxy aldehyde stream 7 which is fed to the crude aldehyde distillation column 9. The crude hydroxy aldehyde stream 7 contains C 2n alkenes and C 2n alkanes. The bottoms stream 21 from the crude hydroxy aldehyde distillation column containing an increased concentration of C 2n unsaturated aldehydes (e.g. 2-propyl hept-2-enal) is decanted to remove the aqueous phase and the organic phase is then provided to a hydrogenation reactor (not shown). Under hydrogenation conditions, the C 2n unsaturated aldehydes undergo hydrogenation to provide C 2n alcohols, e.g. 2-propyl heptanol. Suitable hydrogenation processes are known in the art and are disclosed in, for example, WO2018 / 069714, which is incorporated herein by reference. The hydrogenation reactor can be operated under any suitable conditions. Typically a catalyst will be used. Any suitable catalyst can be used. Typically the active component of the catalyst will be based on a metal from Group VI to Group X. Suitable examples include copper, nickel, manganese, zinc, cobalt, palladium, ruthenium and iron. The catalyst can be supported. Any suitable support can be used. Suitable supports include alumina, silica or diatomite. A particularly suitable catalyst can be a supported copper chromite catalyst. The catalyst can also include a promoter to enhance selectivity.

[0071] The hydrogenation can be carried out in the liquid phase or the gas phase. Any suitable configuration can be used and the reactor can be operated under any suitable conditions. Although the specific conditions chosen will depend on the catalyst selected, the hydrogenation can be carried out at a temperature of from about 100°C to about 200°C and a pressure of from atmospheric pressure to about 15 MPa.

[0072] Where a liquid phase hydrogenation is to be used, the liquid phase hydrogenation can be carried out in any suitable manner. In one arrangement, the liquid phase hydrogenation can be carried out as a downflow over a packed bed of catalyst. A large recycle of cooled product can be mixed with the feed to remove the heat of reaction. One example of a suitable process is described in GB1362071, which is incorporated herein by reference. In an alternative arrangement, one or more heat exchangers can be used to remove the heat of reaction.

[0073] The C-containing compounds can then be purified through one or more purification steps. 2n A crude alcohol stream (e.g., 2-propylheptanol) is used to provide a purified alcohol stream. For example, the crude alcohol stream may undergo one or more distillation and purification steps, as described in WO2018 / 069714.

[0074] Examples

[0075] The following examples demonstrate that the method and apparatus according to the invention allow for the large-scale recovery of unreacted C5 aldehydes, which would otherwise be wasted. The following examples utilize... Figure 2 The computational model of the system, schematically illustrated, uses the AVEVA PROII simulator and known properties (e.g., boiling point, density, etc.) of known components (e.g., water, butene, pentaldehyde) in each feed stream, as well as gas-liquid equilibrium data. The data demonstrate that, using the method and apparatus of this invention, it is possible to obtain C n / C n-1 A large number of useful small organic molecules are recovered from the condensed material stream 41.

[0076] The results of the simulation analysis are provided in the table below.

[0077]

[0078] *Average molecular weight of the stream based on the mole percent of the components in the relevant stream.

[0079] These data show that Figure 3 The device advantageously allows for the large-scale recycling of C. 5- Aldehydes, which can be recycled to a crude aldehyde distillation column and re-enter the aldol condensation reaction, while C4 alkanes and alkenes are separated and recovered. As shown in the mass flow rate, using the method of the present invention, a large portion of the overhead feed 27 in conventional methods is converted as C4 alkanes and alkenes. n / C n-1 Recyclable organic matter in the condensate stream 41 is recovered.

[0080] Compared to use Figure 1 The device in Figure 2 The apparatus was calculated to increase the yield of 2-propylheptanol by approximately 1% after hydrogenation of the produced 2-propylheptanol.

[0081] The following shows the temperature of the second heat exchanger in the method and apparatus of the present invention relative to C. n / C n-1 The effect of the mass flow rate of the condensate flow 41.

[0082]

Claims

1. A process for the production of C 2n unsaturated aldehydes, wherein n is in the range of 3 to 6, inclusive, the process comprising: (i) feeding a stream comprising C n-1 An olefin stream is fed to a hydroformylation reactor and the olefin stream is contacted with a hydroformylation gas stream comprising hydrogen and carbon monoxide to carry out a hydroformylation reaction, thereby providing a crude aldehyde stream comprising C n aldehyde, C n-1 alkane, and C n-1 olefin; (ii) feeding the crude aldehyde stream to a crude aldehyde distillation zone operating at distillation conditions to form a stream comprising the C n aldehyde, the C n-1 alkane, and the C n-1 alkene and comprising an increased concentration of the C n aldehyde relative to the crude aldehyde stream and a bottoms stream comprising an increased concentration of the C n-1 alkane and C n-1 alkene relative to the crude aldehyde stream; (iii) feeding the bottoms stream from the crude aldehyde distillation column to an aldol condensation reactor under condensing and dehydrating conditions to perform the C n aldol condensation reaction of aldehyde, thereby providing an aldol product C 2n unsaturated aldehyde, unreacted C n aldehyde, C n-1 alkane, C n-1 olefin, water, and heavies crude aldol stream; (iv) passing the crude aldol stream to a crude aldol distillation column operating under distillation conditions to form a crude aldol stream having an increased concentration of the C 2n unsaturated aldehyde, the water, and the heavies, and a bottoms stream comprising unreacted C n aldehyde, C n-1 alkane, C n-1 alkene, and a reduced concentration of the C 2n unsaturated aldehyde, the water, and the heavies; (v) passing the overhead stream from the crude aldol distillation column to a first condenser zone configured to provide a first condensed stream and an overhead stream, the first condensed stream comprising an increased concentration of unreacted C n aldehyde and water compared to the overhead stream from the crude aldol distillation column, the overhead stream comprising C n-1 alkane, C n-1 alkene, and a decreased concentration of unreacted C n aldehyde and water compared to the overhead stream from the crude aldol distillation column; (vi) passing the overhead stream from the first condenser zone to a second condenser zone, the second condenser zone configured to condense at least a portion of the overhead stream from the first condenser zone to provide C n / C n-1 condensate; and wherein the C n / C n-1 At least a portion of the condensate is recovered and returned upstream of the crude glycerol distillation column or to the crude glycerol distillation column.

2. The method according to claim 1, wherein at least a portion of the first condensate stream is recovered as a first condensate stream recirculation stream and returned to the aldol condensation reactor.

3. The method of claim 1 or claim 2, wherein the second condenser zone is configured to condense substantially all of the overhead feed stream from the first condenser zone.

4. The method according to any of the preceding claims, wherein at least a portion of the overhead feed stream from the first condenser zone is condensed by washing with process feed stream.

5. The method according to any of the preceding claims, wherein a heat exchanger is used to condense at least a portion of the overhead feed stream from the first condenser zone.

6. The method according to any of the preceding claims, wherein the temperature of the first condenser zone is higher than the condensation temperature of the second condenser zone.

7. The method according to any of the preceding claims, wherein n is 3, 4 or 5.

8. The method of claim 7, wherein the C 2n The unsaturated aldehyde is a 2-alkylalkenal.

9. The method of claim 8, wherein the C 2n The unsaturated aldehyde is 2-propylhept-2-enal.

10. The method of any preceding claim, wherein the C n The aldehyde is pentanal.

11. The process of any preceding claim, wherein the crude carbonyl distillation zone comprises a single crude carbonyl distillation column operating at distillation conditions to form a bottoms stream comprising C n aldehyde, C n-1 alkane, and C n-1 alkene and a heads stream comprising increased concentrations of C n aldehyde relative to the crude carbonyl stream and C n-1 alkane, and C n-1 alkene relative to the crude carbonyl stream.

12. A process for the production of C 2n alcohols, the process comprising producing C 2n unsaturated aldehydes according to the process of any preceding claim, followed by step (vii): feeding the organic phase of the bottoms stream from the crude aldol distillation column to a hydrogenation zone to hydrogenate the C 2n unsaturated aldehydes, thereby providing the C 2n alcohols.

13. A process for producing C 2n unsaturated aldehyde, wherein n is in the range of 3 to 6, the process comprising: a hydroformylation reactor configured to contact an olefin stream comprising an olefin with hydrogen and carbon monoxide to perform a hydroformylation reaction on the olefin, thereby providing a C n aldehyde, C n-1 alkane, and C n-1 olefin feed stream; A crude aldehyde distillation column, the crude aldehyde distillation column being configured to receive the crude aldehyde feed stream and provide a top stream and a bottom stream; a hydroxy aldehyde condensation reactor configured to receive the column bottoms stream from the crude aldehyde distillation column and provide a crude hydroxy aldehyde stream, wherein the crude hydroxy aldehyde stream comprises hydroxy aldehyde product C 2n unsaturated aldehyde, unreacted C n aldehyde, C n-1 alkane, C n-1 olefin, water, and heavies; A crude hydroxyl distillation column, the crude hydroxyl distillation column being configured to receive the crude hydroxyl feed stream and provide a top stream and a bottom stream; A first condenser zone, configured to cool a first overhead feed stream to provide a first condensate stream and an overhead feed stream; A second condenser zone, which is in fluid communication with the first condenser zone, is configured to cool the first overhead feed stream to provide condensate and, optionally, a vapor stream. The second condenser zone is in fluid communication with the crude aldehyde distillation column or its upstream section, so that at least a portion of the condensate is returned to the crude aldehyde distillation column or its upstream section. Optionally, the first condenser zone is in fluid communication with the aldol condensation reactor so that at least a portion of the first condensate stream is returned to the aldol condensation reactor.

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