Process for refining alcohols derived from the hydrogenation of aldehydes

Abstract

The present invention relates to a process for refining alcohols derived from the hydrogenation of aldehydes, comprising (a) providing a first stream from a hydrogenation unit to a first refinery, the first stream comprising alcohol and a first group of impurities and a second group of impurities; (b) removing a majority of the first group of impurities in the first refinery based on a boiling point difference between the first group of impurities and the alcohol, a majority of the first group of impurities leaving the first refinery in a second stream, and a majority of the alcohol leaving the first refinery in a third stream; (c) providing the third stream to a second refinery; (d) removing a second group of impurities in the second refinery based on a boiling point difference between the second group of impurities and the alcohol, a majority of the second group of impurities leaving the second refinery in a fourth stream, a majority of the alcohol leaving the second refinery in a fifth stream, and additional alcohol and additional impurities leaving the refinery in a sixth stream; (e) providing at least a portion of the sixth stream back to the first refinery; (f) monitoring the amount of the first group of impurities in the fifth stream; and (g) adjusting the flow rate of the sixth stream based on the amount in (f).

Description

Technical Field

[0001] The present invention relates to a process for refining alcohols, and in particular, to a process for refining alcohols derived from the hydrogenation of aldehydes. Background Art

[0002] Aliphatic C3-C 12 Alcohol, such as n-butyl alcohol, and specifically, 2-ethylhexanol has economic value. By the hydroformylation of olefins and the subsequent hydrogenation of the aldehyde formed as an intermediate (for example, propylene hydroformylation is made to form n- / isobutyraldehyde, and hydrogenation is subsequently to form n- / isobutyraldehyde), or by the aldol condensation of straight-chain aliphatic aldehydes to obtain the corresponding unsaturated aldehyde and hydrogenation subsequently (for example, n-butylaldehyde aldol condensation is made into 2-ethylhexenal, and hydrogenation is subsequently to form 2-ethylhexanol), these alcohols can be prepared. Such methods are well known in the industry.

[0003] Besides being used as a solvent, n-butanol is mainly used in paint and coating applications and for the preparation of carboxylic acid esters, specifically n-butyl acrylate and di-n-butyl phthalate (DBP). 2-Ethylhexanol is mainly required as the alcohol component for the preparation of di-2-ethylhexyl phthalate (DEHP) and 2-ethylhexyl acrylate.

[0004] For these uses, and in particular the preparation of acrylic esters, high purity alcohols are essential to meet performance specifications such as sulfuric acid color. In the industrial preparation of alcohols, purification of the alcohols is traditionally carried out by multi-stage fractional distillation. The alcohols are exposed to thermal stress over a period of several hours, typically using bottom temperatures of 150°C to 200°C. As a result, in the case of aliphatic C3-C 12 In the distillation of alcohols, such as butanol and 2-ethylhexanol, the corresponding aldehydes and other impurities are formed and can only be separated off at high cost under the conventional conditions employed in the technology.

[0005] For refining C3-C 12 The method for alcohol is known but has multiple problems. Conventional alcohol refining strategies can only achieve acceptable lower amounts of aldehydes in the alcohol product. For example, n-butyl alcohol and isobutyl alcohol are traditionally produced by hydrogenation of butyraldehyde, while n-butyl aldehyde and isobutyl aldehyde are produced by hydroformylation of propylene. The hydrogenation of butyraldehyde is usually carried out using a copper-containing or nickel-containing catalyst. The reaction is reversible and therefore never fully converted into butanol. The crude butanol from hydrogenation is sent to refining to remove light and heavy substances in order to achieve the harsh product specifications specified by butanol consumers (e.g., butyl acrylate producers).

[0006] Conventional butanol refining processes use two or three towers. The first tower may be a light matter tower to remove unconverted aldehydes and water, the second tower is a heavy matter tower to remove materials with higher boiling points than isobutanol and n-butanol, and the third tower is used to separate isobutanol from n-butanol. Although the aldehyde concentration can be reduced in the light matter tower (e.g., 5 ppmw or less), the amount of aldehyde found in the product butanol may be much higher. This indicates that aldehydes are generated somewhere in the refining tower.

[0007] One explanation is given in U.S. Pat. No. 7,790,938: Catalyst fines from upstream hydrogenation enter the refinery. In the absence of hydrogen, these catalyst particles become catalysts for dehydrogenation (converting butanol back into butyraldehyde and hydrogen). U.S. Pat. No. 7,790,938 attempts to prevent / reduce this mechanism by placing a filter between the hydrogenation unit and the refinery. By its nature, sufficiently fine particles can still pass through this filter. Therefore, the filter will reduce the passage of catalyst fines, but it cannot completely prevent its passage. The effectiveness of the filter can be improved by using a smaller mesh size, but this will result in a higher pressure drop on the filter and may require more frequent filter changes. In addition, the filter will not remove dissolved (leached) metals from the hydrogenation catalyst, which can still act as a dehydrogenation catalyst (and a heavy material forming / cracking agent).

[0008] The second possibility is that the high temperature in the refinery sump or reboiler causes the decomposition of the heavies, and therefore also the formation of aldehydes. Such "heavies" are aldehyde condensation adducts and are commonly found in hydroformylation processes (see U.S. Pat. Nos. 4,138,588 and 4,148,830). In order to minimize this reaction, the temperature of the refinery can be reduced, which requires a lower operating pressure that can be applied to all towers. In the heavies tower, it is obvious that the possibility of decomposition is greatest when the concentration of heavies in the sump is the highest. The temperature of the heavies tower sump and reboiler can be reduced by allowing a higher butanol content in the bottom draw. A higher butanol content will cause greater losses or more recovery work. Several attempts have been made in the prior art to reduce the aldehydes formed by adding alkali metal hydroxides or alkaline earth metal hydroxides to the tower sump. However, alkali metal hydroxides will catalyze the conversion of newly formed aldehydes into heavier components, possibly through aldol condensation or Cannizzaro mechanism. Furthermore, these alkali or alkaline earth metal hydroxides are usually fed in aqueous solution. The conditions in the column will cause the water to evaporate slowly, so it is likely that butanol will eventually form the product.

[0009] In short, the use of filters and / or the addition of hydroxide solutions complicates the design and operation of the process, only partially solves the problems described, and introduces new problems.

[0010] Previous attempts to refine alcohols may partially or completely mitigate one or several potential sources of contaminants. However, multiple mechanisms are frequently operated, so it is preferred to have a process that can mitigate many sources of contaminants. It is desirable to have a new process for refining alcohols that avoids some or all of the problems of previous processes. Summary of the invention

[0011] The present invention provides methods for refining alcohols derived from the hydrogenation of aldehydes. In some embodiments, the concentration of impurities contained in the product alcohol is significantly reduced.

[0012] In one aspect, a method for refining alcohols derived from hydrogenation of aldehydes, the method comprising (a) providing a first stream from a hydrogenation unit to a first refinery, wherein the first stream comprises alcohols and a first set of impurities and a second set of impurities; (b) removing a majority of the first set of impurities in the first refinery based on a difference in boiling points between the first set of impurities and the alcohols, wherein the majority of the first set of impurities exits the first refinery in a second stream, and a majority of the alcohols exit the first refinery in a third stream; (c) providing the third stream to a second refinery; (d) removing a second set of impurities in the second refinery based on a difference in boiling points between the second set of impurities and the alcohols, wherein a majority of the second set of impurities exits the second refinery in a fourth stream, and a majority of the alcohols exit the second refinery in a fifth stream as a side draw. (e) providing at least a portion of the sixth stream back to the first tower; (f) monitoring the amount of the first group of impurities in the fifth stream; and (g) adjusting the flow rate of the sixth stream based on the amount of the first group of impurities in the fifth stream, wherein one of the first group of impurities and the second group of impurities has a boiling point higher than the boiling point of the alcohol, and wherein the boiling point of the other group of impurities is lower than the boiling point of the alcohol.

[0013] These and other embodiments are discussed in greater detail in the detailed description which follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A process flow diagram is shown illustrating a prior art process for refining alcohols derived from the hydrogenation of aldehydes.

[0015] Figure 2 The present invention is a process flow chart showing a method for refining alcohols derived from hydrogenation of aldehydes according to one embodiment of the present invention.

[0016] Figure 3The present invention is a process flow chart showing a method for refining alcohols derived from hydrogenation of aldehydes according to one embodiment of the present invention.

[0017] Figure 4 The present invention is a process flow chart showing a method for refining alcohols derived from hydrogenation of aldehydes according to one embodiment of the present invention. DETAILED DESCRIPTION

[0018] All references to the Periodic Table of the Elements and Groups therein are to that edition in the CRC Handbook of Chemistry and Physics, 72nd Edition (1991-1992) CRC Press, pages 1-11.

[0019] Unless stated to the contrary or implicit from the context, all parts and percentages are by weight and all test methods are current as of the filing date of this application. For purposes of U.S. patent practice, the contents of any cited patent, patent application, or publication are incorporated by reference in their entirety (or their equivalent U.S. versions are so incorporated by reference), particularly with respect to definitions (to the extent not inconsistent with any definitions specifically provided in this disclosure) and disclosure of common knowledge in the art.

[0020] As used herein, "a / an", "the", "at least one", and "one or more" are used interchangeably. When the terms "comprising", "including", and variations thereof appear in the specification and claims, these terms are not intended to be limiting. Thus, for example, an aqueous composition comprising particles of "a" hydrophobic polymer can be interpreted as referring to the composition comprising particles of "one or more" hydrophobic polymers.

[0021] As used herein, the term "ppmw" means parts per million by weight.

[0022] Oxo alcohols are synthesized by reacting olefins (usually C2-C 11) is hydroformylated to produce aldehyde. Aldehyde is then hydrogenated to the corresponding alcohol. Examples can include converting propylene to butanol, converting heptene to octenal to octanol, etc. After hydrogenation, aldehyde can undergo aldol condensation, whereby two aldehydes are combined to produce a single unsaturated aldehyde, rather than being immediately hydrogenated to alcohol. This unsaturated aldehyde is then hydrogenated to the corresponding alcohol. Examples include converting propylene to butyraldehyde to convert 2-ethyl-hexenal to 2-ethyl-hexanol, converting butenes to valeraldehyde to convert 2-propyl-heptal to 2-propyl-heptanol, etc. Alcohol is usually separated from non-desirable pollutants by refining. The pollutants in the crude alcohol stream can be unconverted aldehydes, aldol condensation products, acids, esters, acetals, hemiacetals, paraffins, ethers, etc. The present invention provides a simple and cost-effective method for refining alcohol streams from a hydrogenation unit to produce products that meet specifications.

[0023] The present invention relates to a process for refining alcohols derived from the hydrogenation of aldehydes. In some embodiments, the alcohol is C3-C 12 Alcohols and may be linear or branched. In some embodiments, the method of the present invention is particularly suitable for refining C4-C 10 Alcohols. Some examples of these alcohols include n-butanol, 2-ethylhexanol, and 2-propylheptanol. In some embodiments, at least 70% by weight of the alcohols in the stream provided to the first refinery in the process of the present invention are C4 to C12 alcohols, based on the total weight of the alcohols in the first stream. In some embodiments, at least 80% by weight of the alcohols in the stream provided to the first refinery in the process of the present invention are C4 to C12 alcohols, based on the total weight of the alcohols in the first stream. In some embodiments, at least 90% by weight of the alcohols in the stream provided to the first refinery in the process of the present invention are C4 to C12 alcohols, based on the total weight of the alcohols in the first stream. In some embodiments, at least 95% by weight of the alcohols in the stream provided to the first refinery in the process of the present invention are C4 to C12 alcohols, based on the total weight of the alcohols in the first stream.

[0024] In one embodiment, a method for refining an alcohol derived from the hydrogenation of an aldehyde comprises:

[0025] (a) providing a first stream from a hydrogenation unit to a first refining column, wherein the first stream comprises alcohol and a first set of impurities and a second set of impurities;

[0026] (b) removing a majority of the first group of impurities in the first refinery based on a difference in boiling points between the first group of impurities and the alcohol, wherein the majority of the first group of impurities exits the first refinery in a second stream and a majority of the alcohol exits the first refinery in a third stream;

[0027] (c) providing the third stream to a second refining column;

[0028] (d) removing a second group of impurities in the second refinery based on a difference in boiling points between the second group of impurities and the alcohol, wherein a majority of the second group of impurities exits the second refinery in a fourth stream, wherein a majority of the alcohol exits the second refinery as a side draw in a fifth stream, and wherein additional alcohol and additional impurities from the first group of impurities exit the refinery in a sixth stream;

[0029] (e) providing at least a portion of the sixth stream back to the first column;

[0030] (f) monitoring the amount of the first group of impurities in the fifth stream; and

[0031] (g) adjusting the flow rate of the sixth stream based on the amount of the first group of impurities in the fifth stream,

[0032] wherein one of the first group of impurities and the second group of impurities has a boiling point higher than the boiling point of the alcohol, and wherein the boiling point of the other group of impurities is lower than the boiling point of the alcohol.

[0033] In some embodiments, a majority of the sixth stream (50% to less than 100% of the sixth stream exiting the second refining column) is provided back to the first column.

[0034] In some embodiments, the first group of impurities has a boiling point higher than the boiling point of the alcohol, and the second group of impurities has a boiling point lower than the boiling point of the alcohol. In some of these embodiments, the fourth stream comprising a majority of the second group of impurities is provided to a hydrogenation unit.

[0035] In some embodiments, wherein the boiling point of the first group of impurities is lower than the boiling point of the alcohol, and wherein the boiling point of the second group of impurities is higher than the boiling point of the alcohol. In some of these embodiments, the second stream comprising a majority of the first group of impurities is provided to a hydrogenation unit.

[0036] In some embodiments, the present methods further comprise providing the second stream from the first refinery to a third refinery, wherein a seventh stream comprising a portion of the alcohol from the first stream is provided from the third refinery to the first refinery, and wherein an eighth stream is removed from the third refinery.

[0037] In some embodiments, the second refinery comprises at least two trays, and wherein the side draw is positioned above the first tray in the column, wherein the bottom tray is tray 1. Preferably, the side draw is at least two trays above the bottom tray. Preferably, in embodiments where the second refinery is a heavies column to remove impurities having a boiling point higher than that of the product alcohol, the feed to the second refinery is above the sump, and the side draw is at at least one tray above the feed tray.

[0038] According to some embodiments, a crude alcohol stream is provided from a hydrogenation unit to a first refinery from which a first group of impurities has been removed. The first group of impurities may include aldehydes and water. The stream containing most of the alcohol entering the first refinery is then provided to a second refinery. In the second refinery, a bottom extract rich in heavy substances is removed from the bottom, a stream containing mainly product alcohols is removed using a side draw, and an overhead extract containing aldehydes, alcohols and / or other light substances is removed from the top of the tower. Aldehydes prepared in or fed to the second refinery may be concentrated in the top of the tower. At least a portion of the overhead extract, if not all, is returned to the first refinery.

[0039] With respect to the side draw of the removal of product alcohol, in some embodiments, the side draw is higher than the height at which the feed from the first refinery is provided, and is several trays below the top tray of the second refinery. The feed from the first refinery enters the second refinery at a tray that is typically about half of the tower or lower, so as to allow the heavy materials to concentrate in the trays below the feed point. The side draw should be at a sufficient number of trays above the feed tray to minimize short circuiting (i.e., the feed passes through to the side draw without achieving a steady state in the vapor-liquid equilibrium), and is sufficiently higher than the feed tray so that the heavy materials in the side draw reach a desired lower concentration. Therefore, the aldehydes fed to the second refinery or produced in the second refinery will move upward and concentrate at the top of the tower, thereby passing through the side draw.

[0040] The concentration of aldehydes in the alcohol side draw is determined by the type of aldehyde, the aldehyde feed, the number of trays between the side draw and the top of the column, and the overhead draw flow rate. Assuming that the pressure in the second refinery is fixed, the temperature of the sump of the second refinery can be controlled by adjusting the sump draw (i.e., if the temperature is too high, the sump flow rate is increased and vice versa). A constant temperature of the sump is likely to produce a constant decomposition of heavies and thus a constant formation of aldehydes; therefore, it is preferred to keep this parameter constant. Many of the above parameters (e.g., type of aldehyde, number of trays, refining conditions, etc.) are fixed. However, the present invention advantageously allows the flow rate of the overhead draw to be varied to control the purity of the alcohol side draw.

[0041] The concentration of aldehydes in the top of the second refinery column can be controlled by adjusting the overhead draw flow rate (i.e., the higher the recycle flow rate, the lower the aldehyde concentration). This small recycle flow enables the process to maintain a lower aldehyde concentration in the alcohol side draw so that the product alcohol specification of maximum aldehydes can be met. In some embodiments, this can be advantageously accomplished without the need or addition of hydroxide solution or excessive losses due to purge because the overhead is recycled.

[0042] In an alternative embodiment, the order of the refinery can be reversed, and the refinery for heavy material impurities (i.e., impurities with a boiling point higher than the boiling point of the alcohol) is placed upstream of the refinery for light material impurities (i.e., impurities with a boiling point lower than the boiling point of the alcohol). In this embodiment, any lighter impurities produced in the feed or in the refinery will be separated from the alcohol in the second refinery. However, these embodiments will still lead to potential problems with the formation of heavy materials. If any heavy materials are sent from the heavy material column (in this embodiment, the first refinery) or made in the light material column (in this embodiment, the second refinery), the heavy materials will accumulate at the bottom of the light material column. Because heavy materials can be formed in the light material column (now placed after the heavy material column), these heavy materials will be generated at the bottom of the second refinery. Therefore, in this embodiment, a side distillate of the product alcohol stream can be provided on the second refinery for removing product alcohol without heavy materials. In these embodiments, the side draw may be on at least one tray above the sump in the second refinery and below the feed tray (where the stream from the first refinery is provided to the second refinery). The distance above the sump may be selected to promote a desired lower concentration of heavies in the side draw. The heavies will accumulate in the sump of the second refinery, and a small amount of the sump extract may be returned to the heavies column (in this embodiment, the first refinery).

[0043] Now turning to the diagram, Figure 1 The process flow diagram for refining alcohols derived from the hydrogenation of aldehydes is shown. In this process, the design utilizes two refining columns, wherein the first column (4) is a "lights column" and the second column (7) is a "heavys column". An aldehyde-containing stream (e.g., from a hydroformylation process) is fed to a hydrogenation unit (2) via stream (1). The resulting crude alcohol is fed to a "lights column" (4) via stream (3), wherein lower boiling impurities are removed via a purge stream (5). Optionally, some or all of this purge, which may contain aldehydes, may be diverted back to the hydrogenation unit (2) via stream (5a). The bottom stream from column (4) contains product alcohol and heavies (stream (6)). This stream (6) is sent to a "heavys column" (7), wherein the product alcohol is removed from the top as stream (8) and the heavies are purged via line (9). Stream (9) may be further reprocessed and recycled as needed to recover alcohol and aldehydes. However, such further processing requires additional equipment, such as complete refining columns, reboilers, vacuum sources, etc., which is capital intensive and increases the footprint of the refining unit.

[0044] Figure 2 A method for refining alcohols derived from hydrogenation of aldehydes according to one embodiment of the present invention is shown. In this embodiment, the method is similar to Figure 1The method of claim 1, wherein the first refinery (4) is a light matter column because it removes impurities having a boiling point lower than that of the product alcohol, and the second refinery (7) is a heavy matter column because it removes impurities having a boiling point higher than that of the product alcohol. The second refinery (7) has a side draw, wherein a stream (8) of product alcohol is removed from the second refinery (7). The side draw is positioned at a few (e.g., two or more) trays below the top tray of the second refinery (7) and above the tray where the stream (6) is provided to the second refinery (7). A small amount of the overhead stream (10) from the second refinery (7) is returned to a position prior to the first refinery (4), preferably prior to the feed stream (3) provided to the first refinery (4). The flow rate in the overhead stream (10) can be adjusted to obtain an acceptable concentration of light substances (e.g., aldehydes and / or water) in the refined alcohol removed in stream (8). Because stream (10) is not sent back to the hydrogenation unit (2), the refining and hydrogenation units are independent, so that the concentration of water in the hydrogenation unit (2) does not increase. The amount of water sent back to the hydrogenation unit (2) via optional line (5a) can also be controlled as in prior art designs (usually via decantation).

[0045] Figure 3 A method for refining alcohols derived from hydrogenation according to another embodiment of the present invention is shown. Figure 2 The embodiment shown in switches the order of the refineries. That is, the first refinery (7) after the hydrogenation unit (2) is a heavy matter column because it removes impurities with boiling points higher than the boiling point of the product alcohol, and the second refinery (4) is a light matter column because it removes impurities with boiling points lower than the boiling point of the product alcohol. The crude alcohol stream (3) from the hydrogenation unit (2) enters the first refinery ("heavy matter column") (7), and the heavy materials are removed via stream (9). The first refinery (7) is operated to remove most of the heavy materials entering via stream (3), and is therefore a simple distillation column, preferably operated at reduced pressure (e.g., using Figure 3Optional condenser and vacuum source not shown in Figure 2). The overhead stream (16) leaving the first refinery (7) contains product alcohol (optionally trace amounts of heavy and lighter impurities), which is sent to the second refinery ("lights column") (4). Stream (16) is provided at a few trays below the top tray of the second refinery (4). Lighter impurities are removed at the top of the column via stream (15). If necessary, an optional recycle line (15a) can be used to return a portion of this overhead stream to the feed of the hydrogenation unit (2). A side draw is used to obtain refined product alcohol as stream (8). The side draw is located below the feed tray of stream (16) and above the bottom sump tray of the second refinery (4), allowing a small amount of heavy matter recycle stream (11) to be removed and recycled back to the first refinery ("heavy matter column") (7). The flow of streams (11) and (15) can be controlled to obtain higher purity product alcohol.

[0046] Figure 4 A method for refining alcohols derived from hydrogenation according to another embodiment of the present invention is shown. Figure 4 for Figure 3 A further enhancement of the process shown in , because it utilizes a third refining column (17). Figure 4 In some embodiments, the heavy material stream (9) (from the bottom of the first refinery (7)) is further reprocessed and recycled to recover alcohols and aldehydes. The third refinery (17) can subject the heavy material stream (9) to vigorous distillation. In some embodiments, the resulting alcohols and possible aldehydes from the top of the third refinery (17) are returned to the refinery process via stream (20). In other embodiments, the resulting alcohols and possible aldehydes from the top stream (19) of the third refinery (17) are returned to the hydrogenation unit (2) via stream (21). In some embodiments, a portion of the top stream (19) from the third refinery (17) is returned to the refinery process at stream (20) and a portion is returned to the hydrogenation unit (2) via stream (21). Based on the aldehyde content of stream (19), it may be desirable to provide at least a portion of the top stream (19) to the hydrogenation unit (2). The final purge is to purge the non-recoverable heavy materials from the third refinery (17) via stream (18).

[0047] Figure 4The third refinery (17) is operated under more stringent conditions and is preferably independent of the refinery (7) so that many of the acetals and esters in the heavies are cracked back to alcohols and aldehydes, but without fouling due to the accumulation of very high molecular weight organic heavies (which may be mixed with hydrogenation catalyst fines and leached metals). Because the third refinery (17) is not in the direct product production path, it can be shut down for cleaning and purging by diverting stream (9) directly to stream (18) with minimal impact on the main refining process (columns (7) and (4)). By separating the presence of heavies, including metal contaminants, from the main product stream, the presence and generation of impurities in the final distillation step is reduced. Because the third refinery (17) processes much smaller flows than the main columns (7) and (4), it can be much smaller and does not need to contain a large number of trays, thus providing a lower capital design.

[0048] Unlike previous designs of first refining columns that required operation with a specific content of heavy materials, Figure 3 The first refinery (7) in can be operated under a wider range of conditions because there is a recycle process for both effluent streams. For example, trace amounts of heavies in stream (16) will be removed and recycled back for reprocessing via stream (11), even though the content in stream (16) may already be above the target specification for product alcohol. In addition, the use of a side draw to remove the alcohol product via stream (8) will allow these heavies to be removed at the bottom of the second refinery (4). After the primary mechanism that promotes the formation of heavies in the second refinery (4) has been removed, the amount of additional heavies formed is reduced, so that the amount of total heavies to be removed remains low. Conversely, when operating the tower (7) with very low heavies content in stream (16), the higher alcohol content in stream (9) will be recovered and recycled in the third refinery (17) via stream (19).

[0049] In each of the above embodiments of the invention, the first refinery in series need not achieve complete removal of a particular impurity, since it is assumed that more impurities will be produced in the next refinery, and mitigation measures are taken to dispose of carryover from the first and second refineries as long as the total amount does not exceed that of the second refinery. For example, where the formation of impurities varies over time (e.g., from an aged hydrogenation catalyst or higher levels of catalytic metal leaching), the recycle rate can be adjusted as needed.

[0050] In any case, the first refinery is operated under conditions to achieve separation of the product alcohol from the first group of impurities such that the cracking or pyrolysis of the heavies supplied to the first refinery via stream (3) is less than 20 wt%, preferably less than 10 wt% and most preferably less than 5 wt% of the incoming heavies. If extensive pyrolysis is desired, it should be carried out under conditions such as Figure 4The reaction is carried out in a separate column shown in FIG. 1 (using a third refinery (17)) which maintains the bulk of the material in the first refinery under milder conditions and minimizes other side reactions.

[0051] The amount of impurities carried over from the first refinery and / or produced in the second refinery is readily determined by conventional means (e.g., gas chromatography or tandem infrared spectroscopy). Figure 2 Analysis of midstream (8) can readily detect increased levels of aldehydes, which can be used as a basis for increasing the flow of stream (10) to reduce the aldehyde content in the product alcohol stream (8). In the case of a continuously operated production facility, the impurity profile does not typically change rapidly; therefore, simple daily adjustments should be sufficient once stable operation is achieved.

[0052] Figure 3 The embodiment shown in may be particularly useful for hydrogenation catalysts that tend to produce fines or leach their metals. These impurities can be removed in the first refinery (7) as part of the heavies purge in stream (9), and are therefore not present in the second downstream refinery (4) to catalyze dehydrogenation or heavies formation. This embodiment removes Figure 2 The examples shown in are compared to these earlier catalyst fragments and thus mitigate any side reactions they may cause prior to final refining.

[0053] The use of smaller recycle loops (streams (10) and (11)) can surprisingly significantly improve product quality with minimal capital cost or change in normal refinery operations. In addition, in some embodiments, the refinery process of the present invention may have no impact on upstream units and can be operated independently of the hydrogenation unit.

[0054] All aspects of refinery column design (e.g., number of columns, selection of condensers and reboilers, number and type of trays, feed trays, alcohol side draw trays and reboiler duty, tray design, operating pressure, etc.) can be readily determined by one of ordinary skill in the art based on the teachings herein.

[0055] Light Material Tower( Figure 2-4 The actual number of trays in column (4)) may be between 1 and 200, between 30 and 80 in other embodiments, or between 40 and 60 in other embodiments.

[0056] Heavy Material Tower( Figure 2-4 The actual number of trays in column (7)) may be between 1 and 200, in some embodiments between 30 and 80, or in other embodiments between 40 and 60.

[0057] In e.g. Figure 2In the embodiment shown in , the refined alcohol extract tray (for side-draw distillate) in the second refinery (7) is in some embodiments 1 to 15 trays below the top tray, or in some embodiments 3 to 10 trays below the top tray. Figure 2 In the embodiments shown in , the feed tray in the second refinery (7) is, in some embodiments, at least one tray below the refinery alcohol extract tray (for side-drawing distillate), in some embodiments, greater than 6 trays below the extract tray, or in some embodiments, greater than 15 trays below the extract tray.

[0058] In e.g. Figure 3 In the embodiment shown in FIG. 1 , the refined alcohol extract trays (for side-draw distillate) in the second refinery (4) are, in some embodiments, 1 to 15 trays above the sump, or in some embodiments, 2 to 5 trays above the sump. Figure 3 In the embodiments shown in , the feed tray in the second refinery (4) is, in some embodiments, at least 1 tray above the refinery alcohol extract tray (for side-drawing distillate), in some embodiments, greater than 6 trays above the extract tray, or in some embodiments, greater than 20 trays above the extract tray.

[0059] The tray functionality may be provided by any means to contact the liquid phase with the vapor phase to effectively act as a theoretical tray or plate (e.g., a sieve tray or valve tray or structured packing or random packing) using techniques known to those of ordinary skill in the art based on the teachings herein.

[0060] Other equipment may be installed between the first refinery and the second refinery, such as filters, pumps, condensers, hydrogenation reactors (e.g., polishing hydrogenators), oxidation reactors, degassing stations, scrubbers, and other appropriate contactors. These additions may help produce a refined alcohol product without altering the invention, provided that a recycle stream from the second refinery is returned to the first refinery (or prior to the first refinery), and this recycle stream is taken from a sump or overhead from the second refinery, and a product alcohol draw is taken from a side draw on the second refinery.

[0061] Based on the teachings herein, one of ordinary skill in the art can easily determine the feed locations to the refinery and the product extraction locations within the refinery based on the impurity content. Figure 3 and Figure 4 In the case of a product stream (8), for example, the product stream (8) may be removed in gaseous form to minimize heavies in the liquid phase of the stream. Figure 2In the embodiment of the present invention, the product stream (8) can be considered as the liquid phase from the tray to allow the light materials to pass to the next tray. The number of trays between the feed and extraction ports can be easily determined by a person skilled in the art, and in some cases, the feed and extraction port locations may be different. Figure 2-4 The location shown in .

[0062] The recycle stream from the second refinery to the first refinery (e.g. Figure 2 The flow in (10) and Figure 3-4 The stream (11) in the first refining column can be returned to the feed line of the first refining column. In some embodiments, these recycle streams (e.g. Figure 2 The flow in (10) and Figure 3-4 Stream (11) in (2) can be directly returned to the first refinery on the same tray as stream (3) from hydrogenation unit (2) or any other tray. One of ordinary skill in the art can determine the optimal tray for providing these streams to the first refinery based on the teachings herein.

[0063] Optionally, the light materials column ( Figure 2 Stream 5a or Figure 3-4 Some or all of the purge stream of stream 15a) in the hydrogenation unit (2) is provided to recover unreacted aldehyde. In some embodiments, the recycle stream or a portion thereof may be further returned upstream of the hydrogenation step (e.g., if there is a large amount of unreacted olefin, then returned to the hydroformylation step).

[0064] For purposes of the present invention, the phrase "different boiling point relative to the alcohol" refers to the boiling point of the impurity being higher or lower than the product alcohol. Thus, when one stream has a higher boiling point than the product alcohol, the other stream will have a lower boiling point. Alternatively, if the first stream has a lower boiling point than the product alcohol, the second stream will have a higher boiling point. Because the product alcohol can be a mixture of isomers, the boiling point difference is relative to the alcohol isomer that is closest to the boiling point of the impurity.

[0065] In some embodiments, the difference in boiling points between the impurities and the product alcohol should be greater than 5°C, in some embodiments greater than 10°C, in some embodiments greater than 20°C, and in some embodiments greater than 30°C, each at the pressure of the distillation.

[0066] For purposes of this invention, the terms "lights" and "heavies" refer to materials having lower or higher boiling points (respectively) than the product alcohol at the distillation pressure. These are considered impurities and may include aldehyde dimers or trimers, hydrogenated olefins, unreacted olefins, unreacted aldehydes, esters, ethers, and catalyst decomposition materials.

[0067] The crude aldehyde product to be refined in the process of the present invention may be derived directly from the hydroformylation reactor or may be obtained from a mixture of Cn Aldehydes are coupled to produce C 2n The aldol condensation process of unsaturated aldehydes (enones) is derived. In some cases, the output of the aldehyde unit can have the presence of C n Aldehyde and C 2n unsaturated aldehydes. The resulting hydrogenation process will thus produce C n Alcohol and C 2n Alcohol both.

[0068] When the temperature is high, especially in the presence of aldehydes, heavy materials may be produced in the refining tower. According to some embodiments, the operating pressure can be set to maintain an acceptable temperature for the refining tower. For butanol, this will generally produce an operating pressure of the light material and heavy material towers (the first and second refining towers) that is higher than atmospheric pressure. Heavier product alcohols (such as 2-ethyl-hexanol or 2-propyl-heptanol) may require a tower pressure lower than atmospheric pressure to maintain an acceptable temperature. Lower pressures will produce a wider tower diameter. Therefore, it is foreseeable that the tower pressure can be set to a commercially acceptable high to maintain an acceptable high tower temperature. For the refining of relatively light alcohol products, the formation of light materials in the refining is likely to make Figure 2 type of refining process is desirable, and for the refining of relatively heavy product alcohols, the formation of heavies may make Figure 3 Or 4 types of refining processes are desirable.

[0069] In some embodiments, the methods of the present invention may be combined with the addition of metal hydroxides (as described in U.S. Pat. Nos. 2,889,375 and 6,117,277 and U.S. Patent Publication No. 2004 / 0092780) or oxygen (as described in U.S. Pat. No. 7,358,404).

[0070] Some embodiments of the present invention will now be described in detail in the following examples.

[0071] Examples

[0072] The following examples were generated using Analog Science Pro / II 8.2 modeling software, which can be readily obtained from Schneider Electric Software using known or easily determined physical properties. The conditions and parameters for Example 4 were similar to the operating equipment using these conditions.

[0073] Example 1 (Comparison)

[0074] The butanol refining process was simulated using the first refining column as a light column with 40 theoretical trays and the second refining column as a heavy column with 40 theoretical trays. A crude butanol stream at 1000 kg / h (containing 99.00 wt% of normal and isobutanol, 0.10 wt% of normal and isobutyraldehyde, 0.60 wt% of C 12 % C8 oxygenates, 0.20 wt. % C8 oxygenates, the remainder being lighter components) are fed to a first refinery (removing overhead light materials from crude butanol) operating at 1.3 bar. The bottom stream, which mainly contains butanol with heavier components and is almost free of butyraldehyde, is fed to a second refinery. In the second refinery, operating at 1.5 bar, refined butanol is obtained at the top of the tower and a heavy material stream is obtained from the bottom. The extraction of the heavy material stream is controlled to achieve a bottom temperature of 140° C., resulting in a butanol concentration of about 50 wt. %. The refined butanol contains almost no butyraldehyde. This example confirms that modeling reflects ideal refining performance.

[0075] Example 2 (Comparison)

[0076] Use something like Figure 1 The process shown in performs a simulated butanol refining process similar to Example 1. To simulate the formation of butyraldehyde in the second refining column, a second stream of 1.78 kg / h is fed to the bottom of the second column containing 100% butyraldehyde. Since butyraldehyde is lighter than butanol, the butyraldehyde fed to the second refining column with the second feed stream will leave the column together with the refined butanol. Therefore, 99.8% of the fed butyraldehyde is obtained in the refined butanol, resulting in a butyraldehyde concentration of 1818 ppm wt. This example illustrates the problem to be solved.

[0077] Example 3

[0078] Simulate Figure 2 The butanol refining process shown in . The process is similar to that of Example 2, except that the refined butanol stream in the second refinery (stream (8)) is now obtained from the side draw of the seven trays below the top tray. A flow of 1.78 kg / h of the liquid reflux from the second refinery is recycled (via stream (10)) to the first refinery (4), where it is fed at the same tray as the first feed (stream (3)). The concentration of butyraldehyde in the refined butanol stream (8) is now 629 ppm wt. Example 3 shows that recycling a very small stream (0.2 wt%) results in a significant improvement in purity without a net loss of product.

[0079] Example 4

[0080] Simulate Figure 2The butanol refining process shown in . The process is similar to that of Example 2, except that the refined butanol stream in the second refinery (stream (8)) is now obtained from the side draw distillate of the seven trays below the top tray. A flow of 3.61 kg / h of liquid reflux from the second refinery is recycled (via stream (10)) to the first refinery (4), where it is fed at the same tray as the first feed (stream (3)). The concentration of butyraldehyde in the refined butanol stream (8) is now 452 ppm wt. Example 4 shows that recycling a very small stream (0.4 wt%) causes a significant improvement in purity without a net loss of product. The flow in stream (10) can be varied as needed to match the amount of light materials (e.g., aldehydes) present from the previous column or generated in situ during the refining process.

[0081] Example 5 (Comparison)

[0082] The 2-ethylhexanol (2EH) refining process was simulated using the first refinery as a heavy material column with 24 theoretical trays and the second refinery as a light material column with 30 theoretical trays. A crude 2EH stream was provided to the first refinery at a rate of 1000 kg / h and contained 94.0 wt% 2EH, 3.6 wt% C 12 Oxygen-containing compounds, 0.42 wt% C 16 Oxygen-containing compounds, the rest are lighter components. The first refining tower is operated at 90 mbar to remove heavy substances in the residue. The top stream from the first refinery, which mainly contains 2EH with lighter components and almost no heavy components, is fed to the second refining tower. In the second refining tower, operating at 480 mbar, refined 2EH is obtained from the bottom and a light material stream is obtained from the top of the tower. The extraction of the light material stream is controlled to achieve a reflux ratio of 15, resulting in a loss of about 10% by weight of 2EH in the top stream. The refined 2EH contains almost no C 12 and C 16 Oxygen-containing compounds.

[0083] Example 6 (Comparison)

[0084] A 2EH refining process similar to that of Example 5 was simulated, except that a stream simulating the formation of heavy materials in the second refining column was added. A stream of 3.22 kg / h was fed to the bottom of the second column and contained 45 wt% C 12 Oxygen-containing compounds and 55 wt% C 16 Oxygenated compounds. C in refined 2EH in the overhead stream 12 and C 16 The concentration of oxygenates is now 3452 ppmwt.

[0085] Example 7

[0086] Simulations based on e.g. Figure 3 The 2EH refining process of an embodiment of the present invention is shown in FIG. The process is similar to that of Example 6, except that the refined 2EH stream in the second refinery (stream (8)) is now obtained from the side draw of five trays above the bottom tray. A flow of 2.26 kg / h of the bottom residue from the second refinery is recycled (via stream (11)) to the first refinery (7), where it is fed at the same tray as the first feed (stream (3)). C in the refined 2EH stream (8) is 0.1447 W / m. 12 and C 16 The concentration of oxygenates is now 1039 ppm wt.

[0087] Example 8

[0088] The simulation of Example 7 was repeated, but a flow of 2.90 kg / h of the bottoms from the second refinery (4) was recycled via stream (11) to the first refinery (7) where it was fed at the same tray as the first feed (stream (3)). 12 and C 16 The concentration of oxygenates is now 347 ppm wt. This example shows that very small recycle flows (<0.4 wt. % of total feed) can result in significant improvements in purity.

[0089] Examples 7 and 8 show that significant improvements in purity are easily achieved through very minor recycles within the refinery process. This small amount of recycle stream will not significantly affect the heat balance or steam requirements within the refinery process, and therefore represents a very low operating cost. The flow of the recycle stream can be related to the rate of formation of heavies in a particular refinery column (based on the observed rate of formation of heavies in the column), and therefore is easily adjusted to maximize production and quality while minimizing product losses, steam usage, and other utility costs.

Claims

1. A process for refining alcohols derived from the hydrogenation of aldehydes, the process comprising: (a) providing a first stream from a hydrogenation unit to a first refining column, wherein the first stream comprises alcohol and a first set of impurities and a second set of impurities; (b) removing a majority of the first group of impurities in the first refinery based on a difference in boiling points between the first group of impurities and the alcohol, wherein the majority of the first group of impurities exits the first refinery in a second stream and a majority of the alcohol exits the first refinery in a third stream; (c) providing the third stream to a second refining column; (d) removing a second group of impurities in the second refinery based on a difference in boiling points between the second group of impurities and the alcohol, wherein a majority of the second group of impurities exits the second refinery in a fourth stream, wherein a majority of the alcohol exits the second refinery as a side draw in a fifth stream, and wherein additional alcohol and additional impurities from the first group of impurities exit the second refinery in a sixth stream; (e) providing at least a portion of the sixth stream back to the first refining column; (f) monitoring the amount of the first group of impurities in the fifth stream; as well as (g) adjusting the flow rate of the sixth stream based on the amount of the first group of impurities in the fifth stream, wherein one of the first group of impurities and the second group of impurities has a boiling point higher than the boiling point of the alcohol, and wherein the boiling point of the other group of impurities is lower than the boiling point of the alcohol.

2. The process of claim 1, wherein a majority of the sixth stream is provided back to the first refining column.

3. A method according to claim 1 or claim 2, wherein the boiling point of the first group of impurities is higher than the boiling point of the alcohol, and wherein the boiling point of the second group of impurities is lower than the boiling point of the alcohol.

4. The process of claim 3, wherein the fourth stream comprising a majority of the second group of impurities is provided to a hydrogenation unit.

5. The method of claim 1 or claim 2, wherein the boiling point of the first group of impurities is lower than the boiling point of the alcohol, and wherein the boiling point of the second group of impurities is higher than the boiling point of the alcohol.

6. The method of claim 5, wherein the second stream comprising a majority of the first group of impurities is provided to a hydrogenation unit.

7. The process of claim 1 or 2, further comprising providing the second stream from the first refinery to a third refinery, wherein a seventh stream comprising a portion of the alcohol from the first stream is provided from the third refinery to the first refinery, and wherein an eighth stream is removed from the third refinery.

8. The process of claim 1 or 2, wherein at least 70 weight percent of the alcohols in the first stream are C4 to C12 alcohols, based on the total weight of the alcohols in the first stream.

9. The process of claim 1 or 2, wherein the second refining column comprises at least two trays, and wherein the side draw is positioned above a first tray in the column.

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