Separation process for producing C5 or C6 alkanediols

Abstract

C5 or C6 alkanediol, light pollutants, and C 10 Or C 12 Linear ester, or C 10 Or C 12 A process for separating C5 or C6 alkanediols from a crude product stream containing heavy contaminants including one or more of cyclic acetals or ketals is disclosed. The process includes feeding the crude product stream to a separation system including a first distillation zone to which the crude product stream is fed and from which the heavy contaminants are removed in a heavy stream withdrawn as a bottom stream, and a second distillation zone in which the C5 or C6 alkanediols are separated from a reaction product formed in the first distillation zone, containing one or more of C5 or C6 cyclic esters or C5 or C6 aldehydes, from which the C5 or C6 alkanediols are recovered in a purified product stream. The process is characterized in that the reaction product is recovered in the reaction product stream withdrawn as a side draw from either the first distillation zone or the second distillation zone, and the light contaminants are removed in a light stream withdrawn as an overhead stream from either the first distillation zone or the second distillation zone.

Description

[Technical field]

[0001] The present invention relates to a method for producing a cycloaliphatic alcohol comprising the steps of: 10 Or C 12 Linear ester, or C 10 Or C 12 The present invention relates to a process for separating C5 or C6 alkanediols from a crude product stream that contains heavy contaminants including one or more cyclic acetals or ketals.

[0002] In particular, but not exclusively, the present invention relates to a mixture of a C5 or C6 alkanediol and a C 10 Or C 12 Linear ester, or C 10 Or C 12 and heavy contaminants comprising one or more cyclic acetals or ketals. 、 For processes for separating C5 or C6 alkanediols, the crude product stream further comprises a dialkyl ester of a C5 or C6 dicarboxylic acid, or an alkyl ester of a C5 keto acid.

[0003] The present invention relates particularly, but not exclusively, to a process for separating 1,6 hexanediol from a crude product stream comprising 1,6 hexanediol and heavy contaminants including one or more of 6-hydroxyhexyl 6-hydroxyhexanoate and 6-(oxepan-2-yloxy)hexan-1-ol, and particularly, but not exclusively, to a process for separating 1,6 hexanediol from a crude product stream comprising 1,6 hexanediol and heavy contaminants including one or more of 6-hydroxyhexyl 6-hydroxyhexanoate and 6-(oxepan-2-yloxy)hexan-1-ol, wherein the crude product stream further comprises dialkyl adipate and light contaminants.

[0004] The present invention also relates to a process for producing C5 or C6 alkanediols from dialkyl esters of C5 or C6 dicarboxylic acids or alkyl esters of C5 keto acids, and particularly, but not exclusively, to a process for producing 1,6 hexanediol from dialkyl adipates. [Background technology]

[0005] Several synthetic routes to 1,6-hexanediol are known, but one process uses adipic acid as the starting material. Adipic acid is esterified with an alkanol, usually a C1-C4 alkanol such as methanol, to give the corresponding dialkyl adipates, which are then subjected to hydrogenolysis to give 1,6-hexanediol and the alkanol, which can be recycled to produce further dialkyl adipates.

[0006] Similar processes are also known for producing 1,4 pentanediol using levulinic acid as a starting material, and for producing 1,5 pentanediol using glutaric acid as a starting material. Levulinic acid can be esterified to an alkyl levulinate, which is subjected to hydrogenolysis to form 1,4 pentanediol. Glutaric acid can be esterified to a dialkyl glutarate, which is subjected to hydrogenolysis to form 1,5 pentanediol.

[0007] Hydrogenolysis also results in the formation of by-products. For example, hydrogenolysis of dialkyl adipates such as dimethyl adipate can result in the formation of caprolactone and oxepane. As a further example, hydrogenolysis of alkyl levulinates can result in the formation of γ-valerolactone and 2-methyltetrahydrofuran, and hydrogenolysis of dialkyl glutarates can result in the formation of tetrahydro-2H-pyran-2-one and tetrahydro-2H-pyran. In addition, the hydrogenolysis product mixture usually contains small amounts of the corresponding dialkyl adipates, alkyl levulinates or dialkyl glutarates; the alkanols used in the esterification (e.g., methanol); hexanol (when producing 1,6-hexanediol) or pentanol (when producing pentanediol); water and other trace impurities.

[0008] The various components and products are generally separated and purified by multiple distillation steps using conventional distillation or by the use of a dividing wall column.

[0009] US Patent No. 7,064,239, US Patent No. 6,727,395 (B1), US Patent No. 6,288,286 (B1), US Patent No. 6,008,418 (A) and US Patent No. 5,981,769 (A) disclose methods for producing 1,6-hexanediol.

[0010] US Pat. No. 7,329,330 discloses a dividing wall distillation column for the separation and purification of 1,6-hexanediol.

[0011] EP 2614056(B1) discloses a process for producing 1,6-hexanediol and highly pure e-caprolactone from a dicarboxylic acid solution (DCL), which comprises the steps of (a) esterifying the DCL with an alcohol, (b) partially catalytically hydrogenating the ester, (c) separating 1,6-hexanediol and a low-boiling fraction as the top product by distillation, and (d) cyclizing the 6-hydroxycaproic acid ester contained in the bottom fraction in the presence of an alcohol boiling at a temperature above the boiling point of caprolactone.

[0012] US Patent No. 8,513,472 discloses a distillation process, which includes four steps: a) in a first distillation step, separating water and components having a boiling point lower than that of the alcohol used in esterification from the mixture obtained by hydrogenation; b) in a second distillation step, further separating EV components having a boiling point higher than that of 1,6-hexanediol; c) in a third distillation step, further separating EV components having a boiling point lower than that of 1,6-hexanediol; and d) in a fourth distillation step, obtaining 1,6-hexanediol, in that order. US Patent No. 8,513,472 mentions that the inventors have found that if low-boiling ester value (EV) components including ε-caprolactone or 6-hydroxycaproic acid esters are separated in the third distillation step after the second distillation step, high-purity 1,6-hexanediol can be obtained in high yield. If the order of the distillation columns is reversed to separate and remove low boiling EV components such as ε-caprolactone first, low boiling EV components such as caprolactone will be produced again during the separation of high boiling EV components in the next distillation column, and 1,6-hexanediol with a low ester value cannot be obtained. The crude product stream in US Patent No. 8,513,472 results from the esterification and hydrogenation of a mixture of carboxylic acids including glucaric acid, adipic acid and 6-hydroxycaproic acid, and therefore contains C5 species such as 1,5 pentanediol. The distillation system in US Patent No. 8,513,472 is a series of columns, and the separation of EV components with boiling points lower than that of 1,6-hexanediol is carried out in the third of the four steps. The bottom stream, which mainly contains 1,6-hexanediol and esters of 1,6-hexanediol with 6-hydroxycaproic acid, is recycled to the hydrogenation from the second step.

[0013] The applicant has discovered through experiments that mixtures of 1,6-hexanediol, caprolactone, oxepane, alkanols and water undergo various reactions, as can occur during the stage of the production of 1,6-hexanediol by hydrogenolysis of dialkyl adipates, making the task of distilling these mixtures and obtaining high-purity hexanediol even more difficult by the means described in the prior art. Reactions occur during the hydrogenation and also during the distillation process, which result in the production of small amounts of heavy and light components. Examples of these are transesters, such as 6-hydroxyhexyl methyl adipate, or heavy ethers.

[0014] A significant heavy pollutant has been found to be 6-hydroxyhexyl 6-hydroxyhexanoate, which is formed from 1,6-hexanediol and caprolactone. The formation of 6-hydroxyhexyl 6-hydroxyhexanoate is an equilibrium reaction in which 6-hydroxyhexyl 6-hydroxyhexanoate can revert to hexanediol and caprolactone under certain conditions. Another significant heavy pollutant formed is the acetal, 6-(oxepan-2-yloxy)hexan-1-ol, which is heavier than 1,6-hexanediol but can revert to the aldehyde, 6-hydroxyhexanal (lighter than 1,6-hexanediol) under certain conditions.

[0015] A similar reaction can occur in the production of 1,4 pentanediol, thereby producing 4-hydroxypentyl 4-hydroxypentanoate, which can be converted back to 1,4 pentanediol and gamma-valerolactone, and / or 5-((2-methyltetrahydrofuran-2-yl)oxy)pentan-2-ol, which can be converted back to 4-hydroxypentanal. In addition, 5-hydroxypentan-2-yl 4-hydroxypentanoate can be formed, which can be converted back to 1,4 pentanediol and gamma-valerolactone. In addition, 4-((2-methyltetrahydrofuran-2-yl)oxy)pentan-1-ol can be formed, which can also be converted back to 4-hydroxypentanal. In addition, 4-((5-methyltetrahydrofuran-2-yl)pentan-1ol and / or 5-((5-methyltetrahydrofuran-2yl)oxypentan-2-ol can be formed, which can be converted back to 4-oxopentanal.

[0016] In producing 1,5 pentanediol, 5-hydroxypentyl 5-hydroxypentanoate, which can be converted back to 1,5 pentanediol and tetrahydro-2H-pyran-2-one, and / or 5-((tetrahydro-2H-pyran-2-yl)oxy)pentan-1-ol, which can be converted back to 5-hydroxypentanal, may be produced.

[0017] In prior art distillation systems for separating 1,6 hexanediol, these heavy contaminants can fractionate into the bottom of a conventional or dividing wall column. In the high temperature and residence time regions of the column reboiler and sump, heavy contaminants such as 6-hydroxyhexyl 6-hydroxyhexanoate or 6-(oxepan-2-yloxy)hexan-1-ol can react to reform lighter components, including caprolactone or 6-hydroxyhexanal, which can then travel back up the column and contaminate the product when the overhead or side-draw product is removed.

[0018] In addition, 6-hydroxyhexanal can form in the sump of the column in the presence of oxygen due to air ingress in a vacuum operated column. This aldehyde is light and will contaminate the 1,6 hexanediol product in prior art distillation systems configured to take an overhead or side-draw product.

[0019] Contamination of products containing caprolactone or 6-hydroxyhexanal can cause quality problems in downstream polymer processes. 6-hydroxyhexanal is also prone to the formation of peroxides, such as 7-hydroperoxyoxepan-2-ol or 1-hydroperoxyhexane-1,6-diol, when in contact with air, which also causes quality problems in polymer processes.

[0020] For example, in a dividing wall configuration such as that described in U.S. Pat. No. 7,329,330, vapors from the sump of the column contain light components from the reaction of the heavy components in the sump. These light components can migrate to the product side of the dividing wall and contaminate the product draw with light components. This is not true for components in a non-reactive mixture where complete removal of the light components from the product draw is typically expected. Although the prior art system of U.S. Pat. No. 8,513,472 proposes a solution to the problem of ε-caprolactone formation in the sump of the column, the linear chaining of columns in U.S. Pat. No. 8,513,472 may not provide the most cost-effective solution and efficient overall process.

[0021] Applicant has also determined that some of the lighter components, such as esters (including unreacted dialkyl adipates), lactones and aldehydes, which may be treated as ester value contaminants by prior art systems, can be further hydrogenated to useful 1,6-hexanediol products, and therefore it would be beneficial to recover these components. However, to do so economically, it is necessary to efficiently separate these components from the 1,6-hexanediol product and from other unusable by-products, such as light contaminants. Such separation can be carried out in a long chain of columns, but such a scheme can be an expensive solution. A more cost-effective configuration is needed.

[0022] Applicants have determined that similar contamination problems and opportunities may occur in the production of other C5 or C6 alkanediols, such as 1,4 pentanediol or 1,5 pentanediol.

[0023] There is a continuing demand for the production of high purity 1,6-hexanediol and other C5 or C6 alkanediols, such as 1,4 pentanediol or 1,5 pentanediol, at low cost. It is therefore desirable to provide improved processes for producing C5 or C6 alkanediols, such as 1,6-hexanediol, particularly processes that reduce losses, increase yields, and make efficient use of utility and feedstock. There is also a need for improved separation systems for purifying crude C5 or C6 alkanediol streams, such as crude 1,6 hexanediol streams. Summary of the Invention

[0024] According to a first aspect of the present invention, a C5 or C6 alkanediol, a light pollutant, and a C 10 Or C 12 Linear ester, or C 10 Or C 12A process for separating a C5 or C6 alkanediol from a crude product stream containing heavy contaminants including one or more cyclic acetals or ketals is provided, the process comprising: feeding the crude product stream to a separation system comprising a first distillation zone to which the crude product stream is fed and from which the heavy contaminants are removed in a heavy stream withdrawn as a bottom stream; and a second distillation zone in which the C5 or C6 alkanediol is separated from a reaction product formed in the first distillation zone, the reaction product comprising one or more of a C5 or C6 cyclic ester, or a C5 or C6 aldehyde, from which the C5 or C6 alkanediol is recovered in a purified product stream, characterized in that the reaction product is recovered in a reaction product stream withdrawn as a side draw from either the first distillation zone or the second distillation zone, and the light contaminants are removed in a light stream withdrawn as an overhead stream from either the first distillation zone or the second distillation zone.

[0025] A purified product stream is recovered from the second distillation zone. Preferably, the reaction product stream and the lights stream are removed from the same distillation zone.

[0026] Preferably, the first and second distillation zones are contained within a single column, the second distillation zone being separated from the first distillation zone by a baffle beginning at the bottom of the column and extending above both a feed point where a crude product stream is fed to the first distillation zone and a recovery point where a purified product stream is recovered from the second distillation zone. Preferably, the reaction product stream is removed as a side draw above the top of the baffle.

[0027] The first and second distillation zones may be in separate columns. Preferably, the separate columns include a primary column and a secondary column, the first intermediate stream connects the overhead outlet of the secondary column to a side inlet of the primary column, the light stream is recovered as an overhead stream from the primary column, and the reaction product stream is taken from the primary column as a side draw above the side inlet of the primary column. Preferably, the second intermediate stream connects the side outlet of the primary column to a side inlet of the secondary column, the side outlet of the primary column being below the side inlet of the primary column to which the first intermediate stream connects. Preferably, the primary column includes a condenser and the secondary column does not include a condenser. Preferably, the condenser included in the primary column is used to vaporize a feed stream used in the production of C5 or C6 alkanediols, such as an alkanol stream used in an upstream esterification.

[0028] Preferably, the crude product stream further comprises unreacted feed comprising a dialkyl ester of a C5 or C6 dicarboxylic acid or an alkyl ester of a C5 keto acid, which unreacted feed is recovered in the reaction product stream.

[0029] Preferably, the C5 or C6 alkanediol is a compound according to formula I:

[0030] [ka] wherein either R1 is H and n is 3 or 4; or R1 is CH3 and n is 2.

[0031] Preferably, C 10 Or C 12 The linear ester is a compound according to formula II:

[0032] [ka] wherein either R1 and R2 are H and n is 3 or 4; or R1 and R2 are CH3 and n is 2.

[0033] Preferably, C 10 Or C 12 The cyclic acetal or ketal is a compound according to formula III:

[0034] [ka] wherein either R1 and R2 are H and n is 3 or 4; or R1 and R2 are CH3 and n is 2.

[0035] Preferably, the C5 or C6 cyclic ester is a compound according to formula IV:

[0036] [ka] wherein either R1 and R2 are H and n is 3 or 4; or R1 and R2 are CH3 and n is 2.

[0037] Preferably, the C5 or C6 aldehyde is a compound of formula V:

[0038] [ka] wherein either R1 is H and n is 3 or 4; or R1 is CH3 and n is 2.

[0039] Preferably, the unreacted feed material is a compound according to formula VI:

[0040] [ka] In the formula, R3 is a C1 to C5 alkyl group, preferably a C1 to C3 alkyl group, most preferably methyl or ethyl, and in the formula, n is 2 and R4 is CH3; or n is 3 or 4, R4 is R5-O-, and R5 is a C1 to C5 alkyl group, preferably a C1 to C3 alkyl group, most preferably methyl or ethyl.

[0041] One of the following is preferred: a) the C5 or C6 alkanediol is 1,6 hexanediol, each of which, when present, is 10 Or C 12 The linear ester is 6-hydroxyhexyl 6-hydroxyhexanoate, C 10 Or C 12 The cyclic acetal or ketal is 6-(oxepan-2-yloxy)hexan-1-ol, the C5 or C6 cyclic ester is caprolactone, the C5 or C6 aldehyde is 6-hydroxyhexanal, and the unreacted feed material is a dialkyl adipate, preferably dimethyl adipate.

[0042] b) the C5 or C6 alkanediol is 1,5 pentanediol, each of which, when present, is 10 Or C 12 The linear ester is 5-hydroxypentyl 5-hydroxypentanoate, C 10 Or C 12 The cyclic acetal or ketal is 5-((tetrahydro-2H-pyran-2-yl)oxy)pentan-1-ol, the C5 or C6 cyclic ester is tetrahydro-2H-pyran-2-one, the C5 or C6 aldehyde is 5-hydroxypentanal, and the unreacted feed material is a dialkyl glutarate, preferably dimethyl glutarate.

[0043] c) the C5 or C6 alkanediol is 1,4 pentanediol, each of which, when present, is 10 Or C 12 The linear ester is 4-hydroxypentyl 4-hydroxypentanoate, C 10 Or C 12 The cyclic acetal or ketal is 5-((2-methyltetrahydrofuran-2-yl)oxy)pentan-2-ol, the C5 or C6 cyclic ester is gamma valerolactone, the C5 or C6 aldehyde is 4-hydroxypentanal, and the unreacted feed material is an alkyl levulinate, preferably methyl levulinate.

[0044] Heavy pollutants are C 10 Or C 12 Branched esters, especially C 10 It may further comprise a branched ester, which may occur particularly when the C5 or C6 alkanediol is 1,4 pentanediol, in which case the branched ester may be 5-hydroxypentan-2-yl 4-hydroxypentanoate.

[0045] Heavy pollutants are those with two or more C 10 Or C 12 In some embodiments, the heavy contaminants may include cyclic acetals or ketals. 10 Or C 12 Cyclic acetals and C 10 Or C 12 In some embodiments, the heavy contaminants may include two or more C cyclic ketals. 10 Or C 12 In some embodiments, the heavy pollutants may include two or more C 10 Or C 12 In some embodiments, the heavy contaminant may comprise two or more C 10 Or C 12 Cyclic acetals and two or more C 10 Or C 12 In particular, when the C5 or C6 alkanediol is 1,4 pentanediol, the heavy pollutants may include one or more, two or more, three or more, or all four of 5-((2-methyltetrahydrofuran-2-yl)oxy)pentan-2-ol, 4-((2-methyltetrahydrofuran-2-yl)oxy)pentan-1-ol, 4-((5-methyltetrahydrofuran-2-yl)pentan-1ol, and 5-((5-methyltetrahydrofuran-2yl)oxypentan-2-ol.

[0046] Most preferably, the C5 or C6 alkanediol is 1,6 hexanediol, each when present being 10Or C 12 The linear ester is 6-hydroxyhexyl 6-hydroxyhexanoate, C 10 Or C 12The cyclic acetal or ketal is 6-(oxepan-2-yloxy)hexan-1-ol, the C5 or C6 cyclic ester is caprolactone, the C5 or C6 aldehyde is 6-hydroxyhexanal, and the unreacted feed is a dialkyl adipate, preferably dimethyl adipate.There is then provided, according to a preferred form of the first aspect of the present invention, a process for separating 1,6 hexanediol from a crude product stream comprising 1,6 hexanediol, light contaminants, and heavy contaminants comprising one or more of 6-hydroxyhexyl 6-hydroxyhexanoate and 6-(oxepan-2-yloxy)hexan-1-ol, the process comprising a first distillation zone to which the crude product stream is fed and from which the heavy contaminants are removed in a heavy stream withdrawn as a bottom stream, and a second distillation zone formed in the first distillation zone. and a second distillation zone in which 1,6 hexanediol is separated from a reaction product comprising one or more of caprolactone and 6-hydroxyhexanal from which 1,6 hexanediol is recovered in a purified product stream, characterized in that the reaction product is recovered in a reaction product stream withdrawn as a side draw from either the first distillation zone or the second distillation zone, and light contaminants are removed in a lights stream withdrawn as an overhead stream from either the first distillation zone or the second distillation zone. Preferred and advantageous features of the first aspect of the invention, including those described above, are now described in more detail with reference to a process in which the C5 or C6 alkanediol is 1,6 hexanediol and the other compounds are as listed in (a) above. Such a process may be particularly advantageous as a process producing high purity, low cost 1,6 hexanediol is particularly desirable. However, given the above information, one skilled in the art will understand how the following discussion can be applied more generally to the first aspect, as well as to processes using other C5 or C6 alkanediols, particularly those compounds described in (b) and (c) above.

[0047] Removal of heavy contaminants in the heavy stream taken as a bottom stream from the first distillation zone, which is the zone fed with the crude product stream, advantageously means that the reaction products formed by the decomposition of 6-hydroxyhexyl 6-hydroxyhexanoate and 6-(oxepan-2-yloxy)hexan-1-ol in the first distillation zone can be separated from 1,6-hexanediol in the second distillation zone. Since 6-hydroxyhexyl 6-hydroxyhexanoate and 6-(oxepan-2-yloxy)hexan-1-ol have already been removed, they are not present to react in the second distillation zone, and a high-quality 1,6-hexanediol purified product stream can be obtained. Advantageously, the present invention also uses the first and second distillation zones to separate light contaminants and reaction products. Separation of the reaction product stream advantageously means that useful lighter components produced in the reaction in the first distillation zone can be recycled, typically to upstream hydrocracking. By removing the reaction product stream as a side draw from either the first or second distillation zone, that stream may also contain reaction products from the first distillation zone which, although undesirable in the purified product stream, may still have value if recycled upstream in the process. Moreover, recovery of these valuable components is accomplished without additional expensive distillation columns.

[0048] It will be appreciated that when the 1,6-hexanediol in the crude product stream is produced from the hydrocracking of a dialkyl adipate, the crude product stream may also contain unreacted dialkyl adipate. It is advantageous to recycle the unreacted dialkyl adipate to the hydrocracking, particularly in the reaction product stream, so as to avoid the capital costs of a separate recycle stream. Thus, preferably, the crude product stream further comprises a dialkyl adipate, which is recovered in the reaction product stream.

[0049] Preferably, the reaction product stream and the light stream are removed from the same distillation zone. Thus, the reaction product stream may be removed as a side draw from the first distillation zone, and the light stream may be removed as an overhead stream from the first distillation zone. The reaction product stream may be removed as a side draw from the second distillation zone, and the light stream may be removed as an overhead stream from the second distillation zone. By removing the reaction product stream and the light stream from the same distillation zone, the two distillation zones can be sized most efficiently. In particular, the size, and therefore the equipment costs, of the distillation zone from which the reaction product stream and the light stream are not removed can be reduced. Furthermore, in some embodiments, the distillation zone may be thermally integrated with other distillation zones, thus saving further equipment costs.

[0050] In a particularly preferred configuration, the first and second distillation zones may be contained within a single column, with the second distillation zone separated from the first distillation zone by a baffle that begins at the bottom of the column and extends above both the feed point where the crude product stream is fed to the first distillation zone and the recovery point where the purified product stream is withdrawn from the second distillation zone. Unlike prior art dividing wall columns that share the same bottom volume, by providing a baffle that begins at the bottom of the column and extends above both the feed point where the crude product stream is fed to the first distillation zone and the recovery point where the purified product stream is withdrawn from the second distillation zone, the present invention advantageously prevents contamination of the purified product stream with products formed by reaction of heavy components withdrawn in the heavies stream from the first distillation zone. For example, 6-hydroxyhexyl 6-hydroxyhexanoate and 6-(oxepan-2-yloxy)hexan-1-ol entering the feed will travel downward within the first distillation zone as the baffle extends above the feed point. When 6-hydroxyhexyl 6-hydroxyhexanoate and 6-(oxepan-2-yloxy)hexan-1-ol react to form caprolactone and 6-hydroxyhexanal at the bottom of the first distillation zone, caprolactone and 6-hydroxyhexanal move up the first distillation zone to the top of the baffle. Caprolactone and 6-hydroxyhexanal are lighter than 1,6-hexanediol. Therefore, as 1,6-hexanediol moves down the second distillation zone to the collection point where the purified product stream is collected from the second distillation zone, it is not contaminated with caprolactone and 6-hydroxyhexanal, as in the prior art dividing wall column where caprolactone and 6-hydroxyhexanal move up the column and pass through the collection point for the purified product stream. Preferably, the top of the baffle is positioned to allow 1,6-hexanediol to pass through the top of the baffle, but not 6-hydroxyhexyl 6-hydroxyhexanoate and 6-(oxepan-2-yloxy)hexan-1-ol.

[0051] Preferably, the reaction product stream is removed as a side draw from above the top of the baffle. Applicant has realized that the reaction products formed from 6-hydroxyhexyl 6-hydroxyhexanoate and 6-(oxepan-2-yloxy)hexan-1-ol are undesirable in the refinery product stream, but are still valuable if recycled upstream in the process. By removing the reaction product stream as a side draw from above the top of the baffle, components formed in the bottom of the first distillation zone, such as caprolactone and 6-hydroxyhexanal, can be removed in the reaction product stream. Similarly, if the crude product stream contains dialkyl adipate (which is also lighter than 1,6-hexanediol), it can also pass through the top of the baffle and be recovered in the reaction product stream. The reaction product stream is preferably recycled, for example, to upstream hydrocracking.

[0052] The first and second distillation zones may advantageously be arranged in separate columns. Preferably, the separate columns include a primary column and a secondary column, with the first intermediate stream connecting the overhead outlet of the secondary column to the side inlet of the primary column. The secondary column may thus process a particular part of the separation, with the lighter components in the secondary column being sent to the primary column for separation. The reaction product stream may be taken from the secondary column, the light components returned to the primary column, for example as part of an integrated reflux useful to the secondary column, and then the light stream is recovered from the primary column. However, preferably, both the reaction product stream and the light stream are recovered from the primary column. Thus, the light stream is preferably recovered as an overhead stream from the primary column, and the reaction product stream is preferably taken from the primary column as a side draw above the side inlet of the primary column. Such an arrangement may reduce the size and cost of the secondary column and the overall process, since the design and operation of the secondary column may be focused on a particular separation.

[0053] For example, the secondary column may be a first distillation zone, with a heavy stream being separated from the bottom of the second column and the remaining material being sent to the primary column for separation of the light, reaction product and purified product streams. In this manner, the size and cost of the secondary column may be kept low and focused on removing the heavy streams, particularly the reactive 6-hydroxyhexyl 6-hydroxyhexanoate and 6-(oxepan-2-yloxy)hexan-1-ol, which in this embodiment are advantageously removed prior to separation of the purified product stream in the primary column containing the second distillation zone. Such a configuration offers the advantage of removing 6-hydroxyhexyl 6-hydroxyhexanoate and 6-(oxepan-2-yloxy)hexan-1-ol in the first distillation zone, but minimizing the cost of an additional column containing that first distillation zone.

[0054] Preferably, the second intermediate stream connects a side outlet of the primary column to a side inlet of the secondary column, the side outlet of the primary column being below the side inlet of the primary column to which the first intermediate stream connects.

[0055] Such a connection between the primary and secondary columns can be advantageous in several ways. For example, in some embodiments, the secondary column can be a second distillation zone. In these embodiments, the heavy, light and reaction product streams are preferably removed in the primary column. Preferably, in these embodiments, the secondary column processes material from the intermediate section of the primary column to separate the purified product stream from the lighter components, which are returned in a first intermediate stream to the primary column where they are separated into the reaction product stream and the light stream. The second intermediate stream advantageously recovers material from the intermediate section of the primary column for further separation in the secondary column. Such a configuration can allow the most difficult separation between 1,6-hexanediol in the purified product stream and the reaction products in the reaction product stream, such as 6-hydroxyhexanal or caprolactone, to be performed in a secondary column specifically designed for that purpose. For example, by returning an overhead stream from the secondary column to the primary column rather than recovering the reaction product stream from the secondary column, the secondary column does not have to handle the separation of the light stream from the reaction product stream. Therefore, the size and operating conditions of the secondary column can be optimized to make the separation of 1,6-hexanediol and reaction products in the purified product stream as cost-effective as possible.

[0056] Another advantage of the second intermediate stream providing such a connection between the primary and secondary columns is that beneficial heat integration between the primary and secondary columns is possible. This can be beneficial whether the first distillation zone is in the primary column and the second distillation zone is in the secondary column, or vice versa. In particular, the primary column may provide reflux for the secondary column, thus eliminating the need for a condenser on the secondary column. This reduction in the number of devices can advantageously reduce the cost of the process.

[0057] Preferably, the purified product stream comprises at least 98% by weight 1,6-hexanediol; more preferably at least 99% by weight; even more preferably at least 99.5% by weight; even more preferably at least 99.9% by weight.

[0058] The crude product stream may contain from 1 wt% to 20 wt% caprolactone, preferably from 5 wt% to 15 wt% caprolactone. The composition and amount of the reaction product stream may vary based on factors such as the age of the hydrocracking catalyst that affect the conversion of dialkyl adipate.

[0059] The amount of the reaction product stream may rise, for example, to about 20 wt% of the plant capacity over the catalyst life. Thus, the mass flow rate of the reaction product stream may range from 5 wt% to 30 wt% of the process capacity. Preferably, the reaction product stream contains 20 wt% or less, more preferably 15 wt% or less, and most preferably 10 wt% or less of caprolactone. Preferably, the reaction product stream contains at least 1 wt%, more preferably at least 2 wt% or at least 5 wt% of caprolactone. Preferably, the reaction product stream contains 90 wt% or less, more preferably 80 wt% or less of dialkyl adipate. Preferably, the reaction product stream comprises at least 10 wt%, more preferably at least 50 wt% of dialkyl adipate. Similar amounts and compositions may apply to the corresponding compounds for processes using other C5 or C6 alkanediols as described above.

[0060] Each of the first and second distillation zones may be operated at a pressure of about 0.05 to about 1 bar absolute, preferably about 0.05 to about 0.1 bar absolute. Thus, the first and second distillation zones are preferably vacuum distillation zones. The first distillation zone is preferably operated at a bottom temperature, i.e. at the bottom of the first distillation zone, of about 190°C to about 220°C. The first distillation zone is preferably operated at a top temperature, i.e. at the top of the first distillation zone, of about 170°C to about 190°C. The second distillation zone is preferably operated at a bottom temperature of about 180°C to about 200°C. The second distillation zone is preferably operated at a top temperature of about 80°C to about 160°C, more preferably at a top temperature of about 80°C to 120°C. The above temperatures for the first and second distillation zones may be particularly advantageous when the alkanediol is 1,6-hexanediol, but may also be applicable to processes using other C5 or C6 alkanediols as described above. The first and second distillation zones may be trayed or may use structured packing, preferably structured packing. The first and second distillation zones may each contain from 10 to 100 theoretical plates, preferably from 15 to 60 theoretical plates.

[0061] According to a second aspect of the present invention, there is provided a process for producing C5 or C6 alkanediols from a feedstock comprising a dialkyl ester of a C5 or C6 dicarboxylic acid or an alkyl ester of a C5 keto acid, the process comprising a hydrocracking step in which the feedstock undergoes hydrocracking to C5 or C6 alkanediols; and a separation step in which the C5 or C6 alkanediols, light contaminants, and C 10 Or C 12 Linear ester, or C 10 Or C 12A crude product stream comprising heavy contaminants including one or more of cyclic acetals or ketals is separated into a heavy stream comprising the heavy contaminants, a refined product stream comprising C5 or C6 alkanediols, a light stream comprising light contaminants, and a reaction product stream comprising reaction products comprising one or more of C5 or C6 cyclic esters or C5 or C6 aldehydes formed in the separation step, where the refined product stream is recovered and the reaction product stream is recycled to the hydrocracking step.

[0062] It will be appreciated that the separation process of the second aspect of the invention may be carried out in accordance with the first aspect of the invention described above and may benefit from the advantages described above in relation to that first aspect.

[0063] Preferably, the feedstock is produced by esterification of a C5 or C6 dicarboxylic acid or a C5 keto acid with an alkanol. The alkanol is preferably ethanol or methanol, most preferably methanol. The alkanol is preferably in the vapor phase due to the esterification, providing an opportunity for heat integration with other parts of the process. In particular, the separation step preferably includes one or more distillation zones, typically with one or more condensers, for concentrating the overhead stream. Heat recovered from the overhead stream can be used to vaporize the alkanol by feeding the liquid alkanol to one or more of these condensers for vaporization. In this way, the overall efficiency and heat consumption of the process is improved. Thus, preferably, at least a portion of the alkanol is vaporized in the separation step by heat exchange with a hot stream. Preferably, at least a portion of the alkanol is vaporized in the separation step by heat exchange in a condenser.

[0064] Preferably, the C5 or C6 alkanediol is a compound according to formula I:

[0065] [ka] wherein either R1 is H and n is 3 or 4; or R1 is CH3 and n is 2.

[0066] Preferably, C 10 Or C 12 The linear ester is a compound according to formula II:

[0067] [ka] wherein either R1 and R2 are H and n is 3 or 4; or R1 and R2 are CH3 and n is 2.

[0068] Preferably, C 10 Or C 12 The cyclic acetal or ketal is a compound according to formula III:

[0069] [ka] wherein either R1 and R2 are H and n is 3 or 4; or R1 and R2 are CH3 and n is 2.

[0070] Preferably, the C5 or C6 cyclic ester is a compound according to formula IV:

[0071] [ka] wherein either R1 and R2 are H and n is 3 or 4; or R1 and R2 are CH3 and n is 2.

[0072] Preferably, the C5 or C6 aldehyde is a compound of formula V:

[0073] [ka] wherein either R1 is H and n is 3 or 4; or R1 is CH3 and n is 2.

[0074] Preferably, the feed material is a compound according to formula VI:

[0075] [ka] In the formula, R3 is a C1 to C5 alkyl group, preferably a C1 to C3 alkyl group, most preferably methyl or ethyl, and in the formula, n is 2 and R4 is CH3; or n is 3 or 4, R4 is R5-O-, and R5 is a C1 to C5 alkyl group, preferably a C1 to C3 alkyl group, most preferably methyl or ethyl.

[0076] Preferably, the C5 or C6 dicarboxylic acid or C5 keto acid is a compound according to formula VII:

[0077] [ka] In the formula, either R6 is OH and n is 3 or 4, or R6 is CH3 and n is 2.

[0078] One of the following is preferred: a) the C5 or C6 alkanediol is 1,6 hexanediol, each of which, when present, is 10 Or C 12 The linear ester is 6-hydroxyhexyl 6-hydroxyhexanoate, C 10 Or C 12 The cyclic acetal or ketal is 6-(oxepan-2-yloxy)hexan-1-ol, the C5 or C6 cyclic ester is caprolactone, the C5 or C6 aldehyde is 6-hydroxyhexanal, the feedstock is a dialkyl adipate, preferably dimethyl adipate, and the C5 or C6 dicarboxylic acid or C5 keto acid is adipic acid. b) the C5 or C6 alkanediol is 1,5 pentanediol, each of which, when present, is 10 Or C 12The linear ester is 5-hydroxypentyl 5-hydroxypentanoate, C 10 Or C 12 The cyclic acetal or ketal is 5-((tetrahydro-2H-pyran-2-yl)oxy)pentan-1-ol, the C5 or C6 cyclic ester is tetrahydro-2H-pyran-2-one, the C5 or C6 aldehyde is 5-hydroxypentanal, the feedstock is a dialkyl glutarate, preferably dimethyl glutarate, and the C5 or C6 dicarboxylic acid or C5 keto acid is glutaric acid. c) the C5 or C6 alkanediol is 1,4 pentanediol, each of which, when present, is 10 Or C 12 The linear ester is 4-hydroxypentyl 4-hydroxypentanoate, C 10 Or C 12 The cyclic acetal or ketal is 5-((2-methyltetrahydrofuran-2-yl)oxy)pentan-2-ol, the C5 or C6 cyclic ester is gamma valerolactone, the C5 or C6 aldehyde is 4-hydroxypentanal, the feedstock is an alkyl levulinate, preferably methyl levulinate, and the C5 or C6 dicarboxylic acid or C5 keto acid is levulinic acid.

[0079] Most preferably, the C5 or C6 alkanediol is 1,6 hexanediol, each when present being 10 Or C 12 The linear ester is 6-hydroxyhexyl 6-hydroxyhexanoate, C 10 Or C 12The cyclic acetal or ketal is 6-(oxepan-2-yloxy)hexan-1-ol, the C5 or C6 cyclic ester is caprolactone, the C5 or C6 aldehyde is 6-hydroxyhexanal, the feedstock is a dialkyl adipate, preferably dimethyl adipate, and the C5 or C6 dicarboxylic acid or C5 keto acid is adipic acid. Then, according to a preferred form of the second aspect of the present invention, there is provided a process for producing 1,6 hexanediol from dialkyl adipate, the process comprising: a hydrocracking step in which the dialkyl adipate undergoes hydrocracking to 1,6 hexanediol; and a separation step in which a crude product stream comprising 1,6 hexanediol, light contaminants, and heavy contaminants comprising one or more of 6-hydroxyhexyl 6-hydroxyhexanoate and 6-(oxepan-2-yloxy)hexan-1-ol is separated into a heavy stream comprising the heavy contaminants, a refined product stream comprising 1,6 hexanediol, a light stream comprising the light contaminants, and a reaction product stream comprising reaction products formed in the separation step comprising one or more of caprolactone and 6-hydroxyhexanal, wherein the refined product stream is recovered and the reaction product stream is recycled to the hydrocracking step. Preferred and advantageous features of the second aspect of the present invention, including those mentioned above, are now described in more detail with reference to a process in which the C5 or C6 alkanediol is 1,6 hexanediol and the other compounds are as listed in (a) above. Such a process may be particularly advantageous, since a process that produces high purity, low-cost 1,6 hexanediol is particularly desirable. However, given the above information, one skilled in the art will understand how the following discussion can be applied more generally to the second aspect, processes using other C5 or C6 alkanediols, particularly processes using compounds described in (b) and (c) above.

[0080] Such a process advantageously recognizes that the reactions occurring in the separation system are not simply a problem to be addressed in producing a high purity refined product stream, but also an opportunity to recover useful materials from the heavy by-products produced in hydrocracking. Recovery and recycling of reaction products advantageously reduces losses from the process, increasing efficiency and reducing costs.

[0081] Preferably, any unreacted feed in the crude product stream, such as unreacted dialkyl adipate, is also recycled in the reaction product stream. Recycle of the unreacted feed from the separation step along with the useful reaction product allows all valuable components to be recycled in a single unit stream, thus advantageously reducing the cost of the process.

[0082] The separation step preferably includes one or more distillation zones. Preferably, there is an alkanol removal step between the hydrocracking step and the separation step. For example, the reactor effluent may be recovered from the hydrocracking step and sent to the alkanol removal step. In the alkanol removal step, the alkanol, preferably methanol, is removed from the reactor effluent, preferably by distillation. The alkanol-removed reactor effluent is a crude product stream. Preferably, 90% by weight, more preferably 95% by weight, even more preferably 99% by weight, of the alkanol is removed from the reactor effluent in the alkanol removal step. Preferably, water is also removed from the reactor effluent in the alkanol removal step. Preferably, 90% by weight, more preferably 95% by weight, even more preferably 99% by weight, of the water is removed from the reactor effluent in the alkanol removal step.

[0083] As such, it is a particularly particularly advantageous aspect of the present invention that the first and second distillation zones are provided within a single column, the second distillation zone being separated from the first distillation zone by a baffle beginning at the bottom of the column and extending above both the feed point at which the crude product stream is fed to the first distillation zone and the recovery point at which the purified product stream is recovered from the second distillation zone. Such a system may be advantageous for efficiently producing a high purity purified product stream of 1,6-hexanediol, or other C5 or C6 alkanediol, regardless of whether the reaction products from the separation are recovered in the reaction product stream. Thus, according to a third aspect of the present invention, a method for producing a high purity purified product stream of 1,6-hexanediol, or other C5 or C6 alkanediol, and a high purity purified product stream of 1,6-hexanediol, or other C5 or C6 alkanediol, is provided. 10 Or C 12 Linear ester, or C 10 Or C 12 A process for separating a C5 or C6 alkanediol from a crude product stream containing heavy contaminants including one or more cyclic acetals or ketals can be provided, the process comprising a first distillation zone to which the crude product stream is fed and from which the heavy contaminants are removed in a heavy stream removed as a bottom stream, and a second distillation zone in which the C5 or C6 alkanediol is separated from a reaction product formed in the first distillation zone, the reaction product comprising one or more of a C5 or C6 cyclic ester, or a C5 or C6 aldehyde. and a second distillation zone from which a C5 or C6 alkanediol, preferably 1,6 hexanediol, is separated and recovered in a purified product stream, characterized in that the first and second distillation zones are contained within a single column, the second distillation zone being separated from the first distillation zone by a baffle that begins at the bottom of the column and extends above both a feed point at which the crude product stream is fed to the first distillation zone and a recovery point at which the purified product stream is recovered from the second distillation zone.

[0084] Preferably, the C5 or C6 alkanediol is a compound according to formula I:

[0085] [ka] wherein either R1 is H and n is 3 or 4; or R1 is CH3 and n is 2.

[0086] Preferably, C 10 Or C 12 A linear ester is a compound according to formula II:

[0087] [ka] wherein either R1 and R2 are H and n is 3 or 4; or R1 and R2 are CH3 and n is 2.

[0088] Preferably, C 10 Or C 12 The cyclic acetal or ketal is a compound according to formula III:

[0089] [ka] wherein either R1 and R2 are H and n is 3 or 4; or R1 and R2 are CH3 and n is 2.

[0090] Preferably, the C5 or C6 cyclic ester is a compound according to formula IV:

[0091] [ka] wherein either R1 and R2 are H and n is 3 or 4; or R1 and R2 are CH3 and n is 2.

[0092] Preferably, the C5 or C6 aldehyde is a compound of formula V:

[0093] [ka] wherein either R1 is H and n is 3 or 4; or R1 is CH3 and n is 2.

[0094] One of the following is preferred: a) the C5 or C6 alkanediol is 1,6 hexanediol, each of which, when present, is 10 Or C 12 The linear ester is 6-hydroxyhexyl 6-hydroxyhexanoate, C 10 Or C 12 The cyclic acetal or ketal is 6-(oxepan-2-yloxy)hexan-1-ol, the C5 or C6 cyclic ester is caprolactone, and the C5 or C6 aldehyde is 6-hydroxyhexanal. b) the C5 or C6 alkanediol is 1,5 pentanediol, each of which, when present, is 10 Or C 12 The linear ester is 5-hydroxypentyl 5-hydroxypentanoate, C 10 Or C 12 The cyclic acetal or ketal is 5-((tetrahydro-2H-pyran-2-yl)oxy)pentan-1-ol, the C5 or C6 cyclic ester is tetrahydro-2H-pyran-2-one, and the C5 or C6 aldehyde is 5-hydroxypentanal. c) the C5 or C6 alkanediol is 1,4 pentanediol, each of which, when present, is 10 Or C 12 The linear ester is 4-hydroxypentyl 4-hydroxypentanoate, C 10 Or C 12 The cyclic acetal or ketal is 5-((2-methyltetrahydrofuran-2-yl)oxy)pentan-2-ol, the C5 or C6 cyclic ester is gamma valerolactone, and the C5 or C6 aldehyde is 4-hydroxypentanal.

[0095] Most preferably, the C5 or C6 alkanediol is 1,6 hexanediol, each when present being 10 Or C 12The linear ester is 6-hydroxyhexyl 6-hydroxyhexanoate, C 10 Or C 12 The cyclic acetal or ketal is 6-(oxepan-2-yloxy)hexan-1-ol, the C5 or C6 cyclic ester is caprolactone, and the C5 or C6 aldehyde is 6-hydroxyhexanal. In accordance with a preferred form of the third aspect of the present invention, there is then provided a process for separating 1,6 hexanediol from a crude product stream comprising 1,6 hexanediol and heavy contaminants including one or more of 6-hydroxyhexyl 6-hydroxyhexanoate and 6-(oxepan-2-yloxy)hexan-1-ol, the process comprising a first distillation zone to which the crude product stream is fed and from which heavy contaminants are removed in a heavy stream withdrawn as a bottom stream, and a second distillation zone to which the caprolactone and 6-hydroxyhexanal formed in the first distillation zone are fed. and a second distillation zone in which 1,6 hexanediol is separated from the reaction product, including one or more of the alkoxyhexanal, from which 1,6 hexanediol is recovered in a purified product stream, characterized in that the first and second distillation zones are contained within a single column, and the second distillation zone is separated from the first distillation zone by a baffle, the baffle beginning at the bottom of the column and extending above both the feed point where the crude product stream is fed to the first distillation zone and the recovery point where the purified product stream is recovered from the second distillation zone. Preferred and advantageous features of the third aspect of the invention, including those described above, are now described in more detail with reference to the process in which the C5 or C6 alkanediol is 1,6 hexanediol and the other compounds are as listed in (a) above. Such a process may be particularly advantageous, since a process for producing high purity, low cost 1,6 hexanediol is particularly desirable. However, given the above information, one skilled in the art will understand how the following discussion can be applied more generally to the third aspect, and to processes using other C5 or C6 alkanediols, particularly those compounds described in (b) and (c) above.

[0096] Combining the first and second distillation zones in a single column advantageously eliminates many of the costs associated with separate columns. There is only one column for production, transport and introduction, no separate columns need to be connected, and the two distillation zones are thermally integrated with each other. These advantages can be realized especially in the purification of a crude product stream containing 1,6-hexanediol, because the most difficult separation is between 1,6-hexanediol and components such as caprolactone and 6-hydroxyhexanal that are undesirable in the purified product stream. The separation of 6-hydroxyhexyl 6-hydroxyhexanoate and 6-(oxepan-2-yloxy)hexan-1-ol from 1,6-hexanediol in the bottom of the column is simpler, which means that the lower part of the column can be divided into two parts using a baffle, without significantly increasing the size of the column, and there is space in the lower part of the column to contain the second distillation zone. Thus, the first and second distillation zones can be provided in a column of a similar size in this case as would be required to accommodate only the first distillation zone. It will be appreciated that such a configuration can advantageously result in cost savings. Unlike prior art dividing wall columns sharing the same bottom volume, by providing a baffle beginning at the bottom of the column and extending above both the feed point where the crude product stream is fed to the first distillation zone and the recovery point where the purified product stream is recovered from the second distillation zone, the present invention advantageously accommodates the first and second distillation zones in a single column while still ensuring the advantage of preventing contamination of the purified product stream with products formed by reaction of the heavy components removed in the heavy stream from the first distillation zone. For example, 6-hydroxyhexyl 6-hydroxyhexanoate and 6-(oxepan-2-yloxy)hexan-1-ol entering the feed will travel downwards in the first distillation zone as the baffle extends above the feed point.When 6-hydroxyhexyl 6-hydroxyhexanoate and 6-(oxepan-2-yloxy)hexan-1-ol react to form caprolactone and 6-hydroxyhexanal at the bottom of the first distillation zone, caprolactone and 6-hydroxyhexanal move up the first distillation zone to the top of the baffle. Caprolactone and 6-hydroxyhexanal are lighter than 1,6-hexanediol. Therefore, as 1,6-hexanediol moves down the second distillation zone to the collection point where the purified product stream is collected from the second distillation zone, it is not contaminated with caprolactone and 6-hydroxyhexanal, as in the prior art dividing wall column where caprolactone and 6-hydroxyhexanal move up the column and pass through the collection point for the purified product stream. Preferably, the top of the baffle is positioned to allow 1,6-hexanediol to pass through the top of the baffle, but not 6-hydroxyhexyl 6-hydroxyhexanoate and 6-(oxepan-2-yloxy)hexan-1-ol.

[0097] The single column preferably comprises two reboilers, one connected to the first distillation zone and one connected to the second distillation zone. The provision of two reboilers can advantageously allow independent control of the bottom temperatures of the first and second distillation zones.

[0098] Those skilled in the art will appreciate that features of the invention described in relation to one aspect of the invention may be equally applicable in another aspect of the invention. For example, it will be appreciated that the advantages described above in relation to the third aspect of the invention may be equally applicable to the use of the third aspect of the invention by itself, or to the use of the third aspect of the invention in the first or second aspects of the invention. It will be appreciated that some features of the invention may not be applicable to some aspects of the invention and may be excluded from some aspects of the invention. [Brief description of the drawings]

[0099] The invention will now be described, by way of example only, with reference to the following drawings: [Figure 1] 1 is a process according to an embodiment of the present invention. [Diagram 2] 1 is a process according to an embodiment of the present invention. [Diagram 3] 1 is a process according to an embodiment of the present invention. [Figure 4] 1 is a process according to an embodiment of the present invention. [Diagram 5] 1 is a process according to an embodiment of the present invention. [Figure 6] 1 is a process according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0100] In FIG. 1, crude product stream 1 is fed to a first distillation zone A1 contained in a secondary column. Crude product stream 1 comprises a mixture containing hexanediol, caprolactone, oxepane, dimethyl adipate, hexanol, methyl hydroxyhexanoate, transesters (e.g., 6-hydroxyhexyl methyl adipate), ethers (e.g., hydroxyhexyl-methyl ether or other heavy ethers), 6-hydroxyhexyl 6-hydroxyhexanoate, 6-(oxepan-2-yloxy)hexan-1-ol, 6-hydroxyhexanol, other trace impurities, and light contaminants such as residual alkanols, and / or water. In some embodiments, a recycle stream 7 containing heavy components from a second distillation zone B1 contained in a separate primary column may also be fed to the first distillation zone A1, preferably at the same feed point or further down the first distillation zone A1. Heavy components from crude stream 1 and recycle stream 7 are concentrated in the lower section of first distillation zone A1 and removed in heavies stream 2. First distillation zone A1 includes reboiler H2.

[0101] The heavy components include 6-hydroxyhexyl 6-hydroxyhexanoate, which reacts in the sump of the first distillation zone A1 to form 1,6-hexanediol, and caprolactone. 6-(oxepan-2-yloxy)hexan-1-ol also reacts in the sump to form 6-hydroxyhexanal, with additional 6-hydroxyhexanal being formed in the presence of oxygen from the admission of air to the first distillation zone A1. The caprolactone and 6-hydroxyhexanal are then lighter and rise back up to the first distillation zone A1. The heavy components, including 6-hydroxyhexyl 6-hydroxyhexanoate and 6-(oxepan-2-yloxy)hexan-1-ol, decrease in composition in the upper section of the first distillation zone A1, decreasing the heavy component content in the overhead vapor draw 3 and / or the overhead liquid draw 4a. The overhead vapor draw 3 and the overhead liquid draw 4a are examples of a first intermediate stream connecting the overhead outlet of the secondary column containing the first distillation zone A1 with the side inlet of the primary column containing the second distillation zone B1. The condenser H1 is provided at the top of the first distillation zone A1 and can be a partial or full condenser to provide a reflux return 4b to the first distillation zone A1. If the condenser H1 is a partial condenser, the overhead vapor draw 3 is fed to the second distillation zone B1. In that case, the overhead liquid draw 4a may also be sent to the second distillation zone B1. If the condenser H1 is a full condenser, there is no overhead vapor draw 3 and the overhead liquid draw 4a is fed to the second distillation zone B1. The condenser H1 can be cooled conventionally by cooling water or by usefully recovering heat for the overall process, for example by raising steam or by vaporizing an alkanol such as methanol fed to the process. Caprolactone and 6-hydroxyhexanol from the reaction of 6-hydroxyhexyl 6-hydroxyhexanoate with 6-(oxepan-2-yloxy)hexan-1-ol in the sump appear in overhead vapor draw 3 and / or overhead liquid draw 4a.Other lighter components such as dimethyl adipate, methyl hydroxyhexanoate, hydroxyhexyl methyl ether, hexanol, residual alkanols, oxepane, and water from the feed also appear in overhead vapor draw 3 and / or overhead liquid draw 4a.

[0102] The second distillation zone B1 includes a condenser H3 that provides reflux 5b to distillation zone B. Condenser H3 can be conventionally cooled by cooling water or by usefully recovering heat for the overall process, for example by raising steam or by vaporizing an alkanol such as methanol that is fed to the process. The second distillation zone B1 further includes a reboiler H4. 1,6-hexanediol can be recovered as a side-draw refined product stream 6 or a bottom refined product stream 6a from the bottom section of the second distillation zone B1. This combination removes the light and heavy components in the crude product stream 1 and the light components produced by reaction in the sump of the first distillation zone A1, reducing the composition in the refined product stream 6 or 6a. If a bottom refinery product stream 6a is taken, any additional aldehydes formed in the presence of oxygen due to the ingress of air into the sump of the second distillation zone B1, which are light compared to the product 1,6-hexanediol, will migrate to the top of the second distillation zone B1, reducing the tendency of contaminating the bottom refinery product stream 6a. Taking a side refinery product stream 6 allows the purge of heavies 7 to be recycled to the first distillation zone A1. Taking a side-draw refinery product stream 6 also reduces any heavy contamination of the refinery product stream 6, in the event that additional heavy components are produced in the sump of the second distillation zone B1. The light components are concentrated in the upper section of the second distillation zone B1. The light contaminants are removed in the light stream 5a. The reaction product stream 8, which comprises dimethyl adipic acid ester and methyl hydroxyhexanoate, and reaction products from the first distillation zone, such as caprolactone and 6-hydroxyhexanal, is recovered as a side-draw from the second distillation zone B1. The reaction product stream can be recycled to the hydrocracking step in the overall 1,6-hexanediol production process to produce more 1,6-hexanediol. Adjustment of the lights stream 5a maximizes the removal of light contaminants and minimizes the loss of esters, caprolactones, and aldehydes. This allows for efficient recycling and hydrogenation of unconverted ester material and reaction products from the first distillation zone A1, improving the efficiency of 1,6-hexanediol production.A purge 9 can be removed from the reaction product stream 8 to remove other intermediate boilers that cannot be converted to 1,6-hexanediol and would otherwise contaminate the 1,6-hexanediol product.

[0103] In FIG. 2, where the same items are numbered the same and will not be described again, a thermally integrated arrangement of a secondary column including a first distillation zone A1 and a primary column including a second distillation zone B1 is used. The roles of condensers H1 and H3 in FIG. 1 can be combined in condenser H3 in FIG. 2, saving the number of installed equipment. The overhead vapor draw 3 from the first distillation zone A1 is the first intermediate stream connecting the overhead outlet of the secondary column with the side inlet of the primary column. The liquid side draw 4 is taken from the second distillation zone B1 and provides reflux to the first distillation zone A1. The liquid side draw 4 is thus the second intermediate stream connecting the side outlet of the primary column with the side inlet of the secondary column, the side outlet of the primary column being below the side inlet of the primary column to which the first intermediate stream, the overhead vapor stream 3, connects.

[0104] In Figure 3, crude product stream 1, having the same composition as in Figures 1 and 2, is fed to a first distillation zone A2 contained in a primary column. In some embodiments, a recycle stream 17 containing heavy components from a second distillation zone B2 contained in a separate secondary column may also be fed to the first distillation zone A2, preferably at the same feed point or further down the first distillation zone A2. The heavy components from crude product stream 1 and recycle stream 17 are concentrated at the bottom of the first distillation zone A2 and removed in heavy stream 12. The first distillation zone A2 includes a reboiler H12.

[0105] As noted above, the heavy components include 6-hydroxyhexyl 6-hydroxyhexanoate, which reacts in the sump of the first distillation zone A2 to form 1,6-hexanediol, and caprolactone. 6-(oxepan-2-yloxy)hexan-1-ol also reacts in the sump to form additional 6-hydroxyhexanal, which is formed in the presence of oxygen from the entry of air into the first distillation zone A2. Caprolactone and 6-hydroxyhexanal are then lighter and rise back up into the first distillation zone A2. The heavy components, including 6-hydroxyhexyl 6-hydroxyhexanoate and 6-(oxepan-2-yloxy)hexan-1-ol, decrease in composition above the feed point of crude product stream 1 to the first distillation zone A2, decreasing the heavy component content in the side draw 13. Sidedraw 13 is a second intermediate stream connecting the side outlet of the primary column to the side inlet of the secondary column. Condenser H11 is provided at the top of the first distillation zone A2 to provide reflux 15b to the first distillation zone A2. Condenser H11 can be conventionally cooled by cooling water or by usefully recovering heat for the overall process, for example by raising steam or by vaporizing an alkanol such as methanol that is fed to the process. Caprolactone and 6-hydroxyhexanal from the reaction of 6-hydroxyhexyl 6-hydroxyhexanoate with 6-(oxepan-2-yloxy)hexan-1-ol in the sump appear in sidedraw 13. This sidedraw 13 can be taken from above the feed point of crude product stream 1. Other light components (e.g. dimethyl adipate), methyl hydroxyhexanoate, hydroxyhexyl-methyl ether, hexanol, oxepane, and residual alkanols, as well as light contaminants such as water from crude product stream 1 may also appear in side draw 13. These are removed in second distillation zone B2 and returned to first distillation zone A2 via first intermediate stream 14, which connects the overhead outlet of the secondary column comprising second distillation zone B2 to the side inlet of the primary column comprising first distillation zone A2.The side outlet through which side draw 13 is removed is below the side inlet through which first intermediate stream 14 is fed. Reflux for the second distillation apparatus B2 may be provided by partial condenser H13. The product 1,6-hexanediol may be removed as side-draw refined product stream 16 or bottoms refined product stream 16a. The second distillation zone B2 includes a reboiler H14.

[0106] This process removes the light and heavy components in feed 1 and the light components produced by the reaction in the sump of the first distillation zone A2, reducing the composition in the purified product stream 16 or 16a. With the side purified product stream 16 removed, a purge of heavies can then be recycled to the first distillation zone A2 via recycle stream 17. The light components are concentrated in the upper section of the first distillation zone A2. The light contaminants are removed in the overhead lights stream 15a. The reaction product stream 18 is removed as a side draw from the first distillation zone A2. The reaction product stream 18 includes esters, dimethyl adipate, and methyl hydroxyhexanoate, and includes reaction products from the sump of the first distillation zone A2, such as caprolactone, which can be recycled to hydrogenation in the overall 1,6-hexanediol production process to produce more 1,6-hexanediol. A purge 19 can be removed from reaction product stream 18 to eliminate other intermediate boilers that cannot be converted to 1,6-hexanediol and would otherwise contaminate purified product stream 16 or 16a.

[0107] In FIG. 4, where the same items are numbered the same and will not be described again, a thermally integrated arrangement of a primary column comprising a first distillation zone A2 and a secondary column comprising a second distillation zone B2 is used. The roles of the condensers H11 and H13 in FIG. 3 can be combined in the condenser H11 in FIG. 4, saving the number of installed equipment. The condenser H11 can be conventionally cooled by cooling water or by usefully recovering heat for the entire process, for example by raising steam or by vaporizing an alkanol such as methanol that is fed to the process. The side draw 13 from the first distillation zone A2 is a second intermediate stream that connects the side outlet of the primary column to the side inlet of the secondary column. The first intermediate stream 14 connects the overhead outlet of the secondary column comprising the second distillation zone B2 with the side inlet of the primary column comprising the first distillation zone A2. The side outlet of the primary column is below the side inlet of the primary column to which the first intermediate stream 14 connects. In this embodiment, the secondary column containing the second distillation zone B2 effectively acts as an additional distillation zone for material from the intermediate section of the primary column containing the first distillation zone A2, which is recovered in a side draw 13 and separated in the second distillation zone B2 focusing on the most difficult separation between the purified product streams 16, 16a and the reaction product stream 18, any light contaminants and reaction products are returned to the first distillation zone A2 by the first intermediate stream 14 and separated and recovered in the lights stream 15a and the reaction product stream 18, and the purified product stream 16 or 16a is recovered from the second distillation zone B2.

[0108] FIG. 5 shows another configuration of the first distillation zone A3 and the second distillation zone B3. As shown in FIG. 5, the first distillation zone A3 and the second distillation zone B3 may advantageously be combined into a single column by using a sealed separation baffle 20 that extends completely to the bottom of the column. The baffle 20 extends up the column to a point above the feed point of the crude product stream 1 to the first distillation zone A3, which has the same composition as in the previous figure. The baffle 20 also extends above the recovery point of the purified product streams 26, 26a from the second distillation zone B3. The single column includes two reboilers H22 and H24. The heavy stream 22 is taken from the bottom of the first distillation zone A3, while the heavy purge stream 27 may be recycled from the second distillation zone B3 to the first distillation zone A3 at or below the feed point of the crude product stream 1, especially if the purified product stream 26 is taken as a side draw. Alternatively or additionally, purified product stream 26a may be taken off as a bottom stream. The advantages of purified product streams 26 and 26a are as described above for purified product streams 6 and 6a. In fact, the operation of FIG. 5 with respect to separation is very similar to that of FIGS. 1 and 2, and FIG. 5 benefits from being a single column and being fully thermally integrated. Thus, the reaction products from the sump of the first distillation zone A3 are recovered in reaction product stream 28, along with possible purge 29, as in reaction product stream 8. Light contaminants are recovered in lights stream 25a in the same manner as in lights stream 5a, and reflux stream 25b is provided by condenser H23, as in reflux stream 5b and condenser H3. High purity 1,6-hexanediol is obtained in purified product streams 26, 26a, as the reaction products rise up baffle 20 and then continue to rise in the second distillation zone B3 until removed in reaction product stream 28. Therefore, they do not descend through the second distillation zone B3 and contaminate the purified product streams 26, 26a.Combining the first and second distillation zones A3 and B3 in a single column, as in Figure 5, is particularly advantageous for the separations described herein, since the diameter of the column required for the role of the combined first distillation zone A3 and the lower section of the second distillation zone B3 (separated by baffle 20) is similar to the diameter required for the upper section of the second distillation zone B3 above the baffle 20. Thus, by combining the roles in a single column, the column required is similar in size to the primary column containing the second distillation zone B1 of Figure 1 or Figure 2, resulting in significant savings in equipment costs.

[0109] In Figure 6, adipic acid 101 is fed to esterification unit 201 and esterified with an alkanol, such as methanol. The alkanol includes recycle alkanol 102 from downstream alkanol and water removal step 203, and make-up alkanol 103. The product of esterification unit 201 includes dialkyl adipates 104. The alkanol used in esterification unit 201 may be vaporized using heat from a product separation process 204, for example, according to the first or third aspects of the invention, or from the processes described in relation to Figures 1-5 above. Product separation process 204 may thus include distillation zones as described above, and heat from these distillation zones may be used to vaporize the liquid alkanol 105. For example, the liquid alkanol may be fed to a condenser, such as condenser H1, H3 or H11 in Figures 1-5 above, where it may be subjected to heat exchange with a stream passing through the condenser to cool the stream and vaporize the liquid alkanol 105, which may then be fed back to the esterification unit 201 as alkanol vapor 106. The dialkyl adipate 104, along with recycled ester 108, is fed to hydrogenation 202 and hydrogenated to 1,6 hexanediol, which is removed in reactor effluent 109. The alkanol and water are removed by distillation in alkanol and water removal step 203, and the remaining crude product stream 110 is fed to product separation process 204. 1-5, in separation process 204, crude product stream 110 is separated into a purified product stream (111) comprising 1,6 hexanediol, a heavies stream (112), a lights stream 113, and a reaction product stream 108 which may comprise esters and / or caprolactone and 6-hydroxyhexanal formed in product separation process 204. A purge 114 may be removed from reaction product stream 108.

[0110] The above embodiment is such that the C5 or C6 alkanediol is 1,6 hexanediol, each when present, 10 Or C 12The linear ester is 6-hydroxyhexyl 6-hydroxyhexanoate, C 10 Or C 12 Although the examples relate to those in which the cyclic acetal or ketal is 6-(oxepan-2-yloxy)hexan-1-ol, the C5 or C6 cyclic ester is caprolactone, the C5 or C6 aldehyde is 6-hydroxyhexanal, the feed or unreacted feed is a dialkyl adipate, preferably dimethyl adipate, and the C5 or C6 dicarboxylic acid or C5 keto acid is adipic acid, one of ordinary skill in the art, given the teachings elsewhere herein, will understand how to apply the features of those examples to processes using other C5 and C6 alkanediols and their corresponding compounds described elsewhere herein.

[0111] Those skilled in the art will appreciate that the above embodiments are described by way of example only, and that variations and modifications are possible within the scope of the present invention. For example, the single column configuration of Figure 5 is advantageous even when reaction product stream 28 is not recovered separately from lights stream 25a.

Claims

1. C ５ or C ６ alkanediol, light contaminants, and C １０ or C １２ linear ester, or C １０ or C １２ heavy contaminants containing one or more of cyclic acetals or ketals, from the crude product stream, the C ５ or C ６ A process for separating alkanediol, comprising a first distillation zone into which the crude product stream is fed and from which the heavy contaminants are removed in a heavy stream taken as the bottoms, and a second distillation zone in which the C ５ or C ６ cyclic ester, or C ５ or C ６ aldehyde, from the reaction product containing one or more of which the C ５ or C ６ alkanediol is separated, and from which the C ５ or C ６ alkanediol is recovered in a purified product stream, the process comprising feeding the crude product stream to a separation system including the second distillation zone, wherein the reaction product is recovered in a reaction product stream taken as a side draw from either the first distillation zone or the second distillation zone, and the light contaminants are removed in a light stream taken as an overhead from either the first distillation zone or the second distillation zone.

2. The process according to claim 1, wherein the reaction product stream and the light stream are withdrawn from the same distillation zone.

3. The process according to claim 1, wherein the first and second distillation zones are housed within a single column, the second distillation zone is separated from the first distillation zone by a baffle, the baffle starts at the bottom of the column and extends above both the feed point where the crude product stream is fed to the first distillation zone and the recovery point where the purified product stream is recovered from the second distillation zone.

4. The process according to claim 3, wherein the reaction product stream is withdrawn as a side draw above the top of the baffle.

5. The process according to claim 1, wherein the first and second distillation zones are in separate columns.

6. The process according to claim 5, wherein the separate columns include a primary column and a secondary column, a first intermediate stream connects the overhead outlet of the secondary column to the side inlet of the primary column, the light stream is recovered as an overhead stream from the primary column, and the reaction product stream is withdrawn as a side draw from the primary column above the side inlet of the primary column.

7. The process according to claim 6, wherein a second intermediate stream connects the side outlet of the primary column to the side inlet of the secondary column, and the side outlet of the primary column is below the side inlet of the primary column to which the first intermediate stream is connected.

8. The process according to claim 7, wherein the primary column includes a condenser and the secondary column does not include a condenser.

9. wherein the crude product stream comprises ５ or ６ a dialkyl ester of a dicarboxylic acid or an alkyl ester of ５ a keto acid and further comprises an unreacted feed material, and the unreacted feed material is recovered in the reaction product stream, the process according to claim 1.

10. C ５ Or C ６ Dialkyl ester of dicarboxylic acid or C ５ C from a feed containing an alkyl ester of a keto acid ５ Or C ６ 1. A process for producing an alkanediol, comprising: ５ Or C ６ a hydrocracking step in which the alkanediol undergoes hydrocracking to an alkanediol; and a separation step, ５ Or C ６ Alkanediols, light pollutants, and C １０ Or C １２ Linear ester, or C １０ Or C １２ A crude product stream containing heavy contaminants including one or more cyclic acetals or ketals is separated from a heavy stream containing the heavy contaminants, ５ Or C ６ a purified product stream comprising an alkanediol, a lights stream comprising said light contaminants, and ５ Or C ６ Cyclic ester, or C ５ Or C ６ a purified product stream comprising reaction products comprising one or more of the aldehydes, said purified product stream being recovered and said reaction product stream being recycled to said hydrocracking step.

11. The process according to claim 10, wherein the separation step is carried out according to the process of claim 1.

12. The feedstock is produced by esterification of C with an alkanol ５ or C ６ a dicarboxylic acid or C ５ a ketonic acid, according to the process of claim 10.

13. The process according to claim 12, wherein at least a portion of the alkanol is vaporized by heat exchange in a condenser in the separation step.

14. C ５ or C ６ alkanediol, and C １０ or C １２ linear ester or C １０ or C １２ one or more of cyclic acetals or ketals, from a crude product stream containing heavy contaminants, separating said C ５ or C ６ alkanediol, a process comprising: a first distillation zone to which said crude product stream is fed and from which said heavy contaminants are removed in a heavy stream taken as bottoms; a second distillation zone from which said C ５ or C ６ cyclic ester, or C ５ or C ６ aldehyde, one or more of which is separated from a reaction product containing said C ５ or C ６ alkanediol, and from which said C ５ or C ６ alkanediol, preferably 1,6 - hexanediol, is recovered in a purified product stream, said process comprising feeding said crude product stream to a separation system comprising said first and second distillation zones, said first and second distillation zones being housed within a single column, said second distillation zone being separated from said first distillation zone by a baffle which extends above both a feed point at which said crude product stream is fed to said first distillation zone and a recovery point at which said purified product stream is recovered from said second distillation zone, characterized in that.

15. Said C ５ or C ６ The alkanediol is a compound according to formula I: 【Chemical 1】 wherein, R １ is H, and n is 3 or 4; or R １ is CH ３ and n is 2, either of these; said C １０ or C １２ The linear ester is a compound according to formula II: 【Chemical 2】 wherein, R １ and R ２ are H, and n is 3 or 4; or R １ and R ２ are CH ３ and n is 2, either of which; said C １０ or C １２ The cyclic acetal or ketal is a compound according to formula III: 【Chemical Formula 3】 wherein, R １ and R ２ are H, and n is 3 or 4; or R １ and R ２ are CH ３ and n is 2, either of which; said C ５ or C ６ The cyclic ester is a compound according to formula IV: 【Chemical 4】 wherein, R １ and R ２ are H, and n is 3 or 4; or R １ and R ２ are CH ３ and n is 2, either of which; said C ５ or C ６ the aldehyde is a compound according to formula V: [Chemical Formula 5] wherein, R １ is H, and n is 3 or 4; or R １ is CH ３ and n is 2, either of which is true: When present, the feedstock or the unreacted feedstock is a compound according to formula VI: 【Chemical Formula 6】 wherein, R ３ is C １ to C ５ alkyl group, preferably C １ to C ３ alkyl group, most preferably methyl or ethyl; wherein n is 2 and R ４ is CH ３ ; or n is 3 or 4 and R ４ is R ５ -O- and R ５ is C １ to C ５ alkyl group, preferably C １ to C ３ alkyl group, most preferably methyl or ethyl, either of which; If present, said C ５ or C ６ dicarboxylic acid or C ５ keto acid is a compound according to formula VII: 【Chemical Formula 7】 wherein R ６ is OH, n is 3 or 4, or R ６ is CH ３ and n is 2, in any of the cases; the process according to any one of claims 1 to 14.

16. a. The C ５ or C ６ alkanediol is 1,6 - hexanediol, and the C １０ or C １２ linear ester is 6 - hydroxyhexyl 6 - hydroxyhexanoate, and the C １０ or C １２ cyclic acetal or ketal is 6-(oxepan - 2 - yloxy)hexan - 1 - ol, and the C ５ or C ６ cyclic ester is caprolactone, and the C ５ or C ６ aldehyde is 6 - hydroxyhexanal, and when present, the feedstock or the unreacted feedstock is a dialkyl adipate, preferably dimethyl adipate, and the C ５ or C ６ dicarboxylic acid is also C ５ the keto acid is adipic acid. b. said C ５ or C ６ the alkanediol is 1,5 - pentanediol, and when each is present, said C １０ or C １２ the linear ester is 5 - hydroxypentyl 5 - hydroxypentanoate, said C １０ or C １２ the cyclic acetal or ketal is 5 - ((tetrahydro - 2H - pyran - 2 - yl)oxy)pentan - 1 - ol, said C ５ or C ６ the cyclic ester is tetrahydro - 2H - pyran - 2 - one, said C ５ or C ６ the aldehyde is 5 - hydroxypentanal, and when present, said feedstock or said unreacted feedstock is a dialkyl glutarate, preferably dimethyl glutarate, said C ５ or C ６ the dicarboxylic acid or C ５ the keto acid is glutaric acid c. said C ５ or C ６ the alkanediol is 1,4 - pentanediol, and when each is present, said C １０ or C １２ the linear ester is 4 - hydroxypentyl 4 - hydroxypentanoate, said C １０ or C １２ the cyclic acetal or ketal is 5 - ((2 - methyltetrahydrofuran - 2 - yl)oxy)pentan - 2 - ol, said C ５ or C ６ the cyclic ester is γ - valerolactone, said C ５ or C ６ the aldehyde is 4 - hydroxypentanal, and when present, the feedstock or the unreacted feedstock is an alkyl levulinate, preferably methyl levulinate, said C ５ or C ６ the dicarboxylic acid or C ５ the keto acid is levulinic acid. The process according to any one of claims 1 to 14, which is any of the following.

17. Said C ５ or C ６ alkanediol is 1,6 - hexanediol, said C １０ or C １２ linear ester is 6 - hydroxyhexyl 6 - hydroxyhexanoate, said C １０ or C １２ cyclic acetal or ketal is 6 - (oxepan - 2 - yloxy)hexan - 1 - ol, said C ５ or C ６ cyclic ester is caprolactone, said C ５ or C ６ aldehyde is 6 - hydroxyhexanal, and when present, said feedstock is a dialkyl adipate, preferably dimethyl adipate, said C ５ or C ６ dicarboxylic acid or C ５ keto acid is adipic acid, The process according to any one of claims 1 to 14.

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