Method for producing acetone with low aldehyde content

Abstract

A method and system for producing acetone from cumene hydroperoxide (CHP) is disclosed. The method and system include an acetone purification column configured to separate acetone from other components in a product / reactant stream. The acetone purification column is equipped with a side draw configured to send a portion of the column contents to a caustic treater, where the contents are reacted with a dilute aqueous alkaline solution to remove aldehydes from the acetone product. The caustic treater contents are then returned to the acetone purification column. The use of a separate caustic treater for aldehyde removal increases the contact time between the acetone product and the alkaline solution, thereby allowing for greater removal of aldehydes.

Description

Detailed Description of the Invention

[0001] [Field of the Invention] This application relates to methods and systems for producing acetone from cumene. More particularly, embodiments relate to improving the purity of the produced acetone.

[0002] [Introduction] Phenol and acetone are produced by a variety of methods, the most common of which are variously known as the Hock process, the Hock-Lang process, or the cumene-phenol process. This process begins with the oxidation of cumene (isopropylbenzene) to produce cumene hydroperoxide (CHP). CHP is then cleaved in the presence of an acid catalyst to produce a mixture of phenol, acetone, and / or alpha-methylstyrene ("AMS"). The mixture is subsequently neutralized and fractionated to recover the final products, phenol, acetone, and / or AMS.

[0003] Although such methods have been used for decades, there is a continuing need to optimize the purity of the aldehydes produced.

[0004] [overview] Disclosed herein is a method for purifying acetone in an acetone production process. The method includes feeding a crude acetone fraction to a first feed point in an acetone purification column (APC), transferring a portion of the crude acetone fraction from the APC via a first side draw of the APC located above the first feed point, feeding the transferred portion of the crude acetone fraction to a caustic treatment vessel, feeding an alkaline aqueous solution to the caustic treatment vessel, returning a bottoms stream from the caustic treatment vessel to the APC via a second feed point located between the first feed point and the first side draw, and obtaining purified acetone from a second side draw located above the first side draw. In some embodiments, the crude acetone fraction is obtained as an overhead stream from a crude acetone column (CAC) upstream of the APC. In some embodiments, the crude acetone fraction includes acetone, water, cumene, alpha-methylstyrene (AMS), phenol, methanol, and aldehydes. In some embodiments, the crude acetone fraction contains 60 to 1000 ppm (vol) of aldehydes, including acetaldehyde and / or propionaldehyde. In some embodiments, the crude acetone fraction contains 50 to 500 ppm (vol) of methanol. In some embodiments, the alkaline aqueous solution contains an alkali or alkaline earth metal oxide, hydroxide, or phenate. In some embodiments, the alkaline aqueous solution contains sodium hydroxide. In some embodiments, the sodium hydroxide has a concentration of about 0.1 to about 15%. In some embodiments, the caustic treatment tank has a temperature of about 45 to about 75°C. In some embodiments, the caustic treatment tank has no internal parts. In some embodiments, the caustic treatment tank has fixed internal parts that provide mixing. In some embodiments, the caustic treatment tank includes an agitator. In some embodiments, the caustic treatment tank includes a circulation pump. According to some embodiments, the caustic treatment vessel provides a residence time of about 3 to about 60 minutes.In some embodiments, the method further comprises contacting the decanted portion of the crude acetone fraction with a zeolite adsorbent to remove methanol from the decanted portion of the crude acetone fraction prior to feeding the decanted portion of the crude acetone fraction to the caustic treatment vessel. In some embodiments, the purified acetone contains less than about 20 ppmwt total aldehydes. In some embodiments, the purified acetone has a permanganate time of greater than 12 hours. In some embodiments, the purified acetone contains less than 100 ppm (wt) methanol.

[0005] Also disclosed herein is a system for recovering purified acetone, comprising: a crude acetone column (CAC) configured to separate the products of a cumene hydroperoxide cleavage reaction into an overhead fraction containing crude acetone and a bottom fraction containing phenol; an acetone purification column (APC) configured to receive the crude acetone at a first feed point in the APC, separate the crude acetone into purified acetone and remaining heavy compounds, and supply the purified acetone at a first side draw located above the first feed point; and a caustic treatment vessel configured to receive a portion of the crude acetone withdrawn from a second side draw of the APC located above the first feed point and below the first side draw, receive a feed of an aqueous alkaline solution, mix the portion of the crude acetone with the aqueous alkaline solution, and return the contents of the caustic treatment vessel to the second feed point of the APC, the second feed point being located between the first feed point and the second side draw. According to some embodiments, the crude acetone fraction comprises acetone, water, cumene, alpha-methylstyrene (AMS), phenol, methanol, and aldehydes. According to some embodiments, the aqueous alkaline solution comprises sodium hydroxide. According to some embodiments, the caustic treatment vessel provides a residence time of about 3 to about 60 minutes. According to some embodiments, the caustic treatment vessel does not include internals. According to some embodiments, the caustic treatment vessel includes one or more of fixed internals that provide mixing, an agitator, or a circulation pump. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 shows an embodiment of a system for producing acetone and phenol from cumene hydroperoxide (CHP). [Figure 2] FIG. 2 illustrates an embodiment of an improved system for purifying acetone in which a portion of the produced acetone is reacted with caustic in a caustic reactor. [Figure 3] FIG. 3 illustrates an embodiment of an improved system for purifying acetone in which a portion of the produced acetone is passed through an adsorbent tank to remove alkyl alcohols from the produced acetone. [Figure 4] FIG. 4 illustrates a further embodiment of an improved system for purifying acetone in which a portion of the produced acetone is passed through an adsorbent tank to remove alkyl alcohols from the produced acetone. DETAILED DESCRIPTION OF THE INVENTION

[0007] [Detailed explanation] 1 illustrates a system 100 for producing acetone and phenol from cumene hydroperoxide (CHP). It should be understood that some features and equipment of system 100 (and other systems described herein) that are not particularly relevant here but that may be implemented in the actual operation of such systems are not described herein. Such features and equipment are known in the art and may be described in the above-incorporated references.

[0008] The concentrated CHP enters the system via line 102. The concentration of CHP in line 102 may be about 65-90 wt%, more typically about 80-85 wt%, for example, up to about 82 wt%. CHP may be produced by the oxidation of cumene, for example, as described in U.S. Pat. No. 8,697,917, the entire contents of which are incorporated herein by reference. The oxidation products from the oxidation of cumene (not shown) include CHP and may also include one or more of alpha-methylstyrene (AMS), dimethylbenzyl alcohol (DMBA), and / or acetophenone (ACP).

[0009] The concentrated CHP is fed to one or two cleavage reactors in series, as described, for example, in U.S. Patent No. 5,371,305. In the illustrated system 100, two cleavage reactors in series are shown. The CHP is fed to the first cleavage reactor 104, where it is cleaved by an acid catalyst. The acid catalyst may be, for example, sulfuric acid (H2SO4). In the illustrated embodiment, the first cleavage reactor may be, for example, a back-mixed tank reactor and may be operated at a temperature between 50°C and 80°C. In the first cleavage reactor, the CHP is partially reacted in two reactions: i) the CHP is cleaved to produce phenol and acetone, and ii) the CHP partially reacts with DMBA in an equilibrium reaction to produce the intermediate products dicumyl peroxide (DCP) and water. The DMBA is partially dehydrated to AMS, which reacts with phenol in a sequential reaction to produce high-boiling cumylphenol. AMS may also produce higher-boiling dimers. Additional by-products, such as hydroxyacetone (HA), 2-methylbenzofuran (2-MBF), and mesityl oxide (MO), may also be produced. Because the cleavage reaction is highly exothermic, recycled acetone may be fed to the cleavage reactor to maintain adequate dilution, thereby minimizing the formation of undesirable by-products. In the illustrated embodiment, recycled product acetone is fed to the first cleavage reactor via line 106. Water may be added to optimize the cleavage yield.

[0010] In the illustrated embodiment, the product of the first cleavage reactor 104 is fed to the second cleavage reactor 108, where three main reactions occur: i) the cleavage of residual CHP from the first cleavage reactor into phenol and acetone, ii) the dehydration of residual DMBA from the first cleavage reactor to AMS, and iii) the conversion of DCP to AMS, phenol, and acetone. The second-stage cleavage reactor may be a plug flow reactor at a temperature of, for example, about 105° C. to 145° C., and may be heated with steam.

[0011] In the illustrated system 100, the cleavage product from the second cleavage reactor 108 is cooled using a cooler 110 and directed to one or more neutralization and wash units 112. The cleavage effluent contains sulfuric acid, which was used as a catalyst for the cleavage reaction. To prevent corrosion problems in downstream equipment, the acid must be extracted and neutralized using one or more bases, such as sodium hydroxide, and / or one or more salt solutions. For example, the salt solutions can be or include sodium phenate. The salt solutions can reduce or stop the ongoing cleavage reaction in the cleavage product. Thus, the neutralization and wash units 112 can produce a neutralized cleavage product.

[0012] The step following cleavage and neutralization (i.e., acetone fractionation) is primarily aimed at purifying the product (acetone and phenol) and recovering by-products and recyclable cumene. The acetone fractionation system is intended to (1) roughly separate light and heavy components in the fractionation feed and (2) purify the acetone product. The organic effluent from the neutralization unit 112 flows via line 113 to a first distillation column, referred to herein as the crude acetone column (CAC) 114. The function of the CAC is to separate the neutralization product into a phenol fraction and an acetone fraction. Aspects of the CAC are described in U.S. Pat. No. 8,889,915, the entire contents of which are incorporated herein by reference. The vapor fraction (line 120) contains acetone, water, cumene, AMS, small amounts of phenol, and other light materials in the feed. The CAC may include a CAC reboiler 116 and a CAC condenser 118. The CAC reboiler 116 may be, for example, a forced circulation heat exchanger heated by high-pressure steam. The phenol-rich bottoms material (line 122) may be directed to a phenol fractionation unit (not shown). The overhead vapor (line 120) is partially condensed in the CAC condenser 118. The condensed liquid is returned to the CAC 114, and the vapor fraction is sent via line 126 to a second distillation column, referred to herein as the acetone product column or acetone purification column (APC) 124. According to some embodiments, the vapor fraction fed to the APC 124 via line 126 may contain about 7 to about 12 vol.% cumene, about 0.1 to about 0.2 vol.% phenol, about 40 to about 50 vol.% acetone, about 1 to about 2 vol.% AMS, about 200 to about 500 ppm (vol) methanol, and about 100 to about 1000 ppm (vol) total aldehydes.

[0013] The APC 124 removes light components (primarily acetaldehyde via line 128) from the acetone product and separates the acetone from water, cumene, AMS, and other heavy organics. Aspects of the APC are described in U.S. Pat. No. 4,340,447 (the "'447 patent"), the contents of which are incorporated by reference. The APC includes an APC reboiler 130 and an APC condenser 131. The APC reboiler 130 may be fed from a liquid trap external to the bottom tray of the APC 124 and from a recycle stream from the bottom of the column, and may be heated by low-pressure steam.

[0014] The interior volume 140 of the APC 124 may be empty or may be partially or completely filled with one or more fill materials (not shown). Specific fill materials may include, but are not limited to, trays, packing, or combinations thereof. As used herein, the term "tray" may include, but is not limited to, one or more tray types that may enhance contact between the gas phase and the liquid phase within the APC 124. Specific trays may include, but are not limited to, perforated trays, sieve trays, bubble cap trays, floating valve trays, fixed valve trays, cartridge trays, dual flow trays, baffle trays, shower deck trays, chimney trays, slit trays, or any combination thereof. As used herein, the terms "packing material" or "packing" may include, but are not limited to, one or more regularly and / or irregularly shaped materials disposed within the APC 124. The packing material can increase the effective surface area within the APC 124, thereby improving mass transfer between the liquid and gas phases within the APC 124. The packing material can be made of any suitable material, such as, for example, metal, non-metal, polymer, ceramic, glass, or any combination thereof. Examples of random packing materials include Raschig rings, NeXRings, and the like. TM , Nutter Rings TM , I-Rings TM, C-Rings TM , P-Rings TM , R-Rings TM and S-Rings TM , Intalox® ULTRA, IMTP®, HY-PAK®, CASCADE MINI RINGS®, FLEXIRING®, AHPP saddle rings, pawl rings, SuperBlend TM The packing may include, but is not limited to, 2-Pac, or any combination thereof. Commercially available examples of structured packing may include, but are not limited to, structured packing, corrugated sheets, crimped sheets, wire gauze, grid, wire mesh, or any combination thereof. The packing may enhance mass transfer and / or separation of multi-component fluids. The packing material and / or packing pattern within the interior volume 140 may include one or more ordered packing materials and / or random packing materials. Two or more types of packing materials may be disposed within the interior volume 126. The APC 124 may be made of one or more metallic materials that are physically and chemically compatible with the temperature, pressure, and contents of the APC 124. Suitable metallic materials may include, but are not limited to, iron alloys, including carbon and stainless steels such as clad carbon steel, 304 stainless steel, 316 stainless steel, duplex stainless steel, and combinations of these metallic materials. Additionally, the APC 124 can operate at pressures and temperatures ranging from a low of about 40 kPa, about 50 kPa, or about 60 kPa to a high of about 80 kPa, about 90 kPa, or about 100 kPa.

[0015] The final bottoms stream 132 from the APC 124 may be fed to a crude AMS wash section (not shown). Product acetone may be obtained from a side draw 134. A portion of the reflux stream from the APC 124 may be recycled to the cleavage reactor section, e.g., the first cleavage reactor 104, via line 106, as described above. The amount of acetone recycled may be proportionally determined based on the amount of CHP fed to the cleavage reactor. For example, the amount of acetone recycled to the cleavage reactor may be about 0.1 to about 0.5 by weight based on the amount of CHP fed to the cleavage reactor.

[0016] The APC 124 is provided with a caustic addition point 136 for adding caustic. The caustic may be, for example, an alkali or alkaline earth metal oxide, hydroxide, or phenate. One example of a suitable caustic is sodium hydroxide. The caustic addition point 136 is provided between the feed stream 126 and the product side draw 134. The caustic is added to the APC 124 to reduce the amount of aldehydes in the acetone product. In the presence of the caustic, the aldehydes undergo an aldol condensation reaction to produce heavier ketones, thereby purifying the acetone product. The use of caustic in the APC 124 to reduce the amount of aldehydes in the acetone product is described in the incorporated '447 patent.

[0017] As known in the art, a test for determining the purity of an acetone product is the permanganate time (PMT) test. This test involves adding a small amount of potassium permanganate to an acetone sample and measuring the time it takes for the color to disappear. A longer PMT indicates a sample containing fewer reducing substances, such as aldehydes, and a higher quality acetone. The process described in the '477 patent can produce acetone with a PMT of about 4 hours, which corresponds to about 60 to about 120 ppm (vol) of total aldehyde impurities.

[0018] In embodiments such as those shown in FIG. 1 and described in the '477 patent, the extent to which aldehydes and other reducing substances are removed by reaction with the caustic in the APC column is limited by the time the caustic is in contact with the aldehydes in the column. Aldol condensation depends on the contact time between the aldehydes and the caustic on the distillation trays of the APC. The residence time on the distillation trays can be short, e.g., a few minutes. As a result, aldol condensation of the aldehydes may not be complete, and the condensation is highly dependent on the operating throughput of the column.

[0019] The inventors have realized that the contact time between the aldehydes and the caustic can be improved by using system 200 as shown in FIG. 2. In FIG. 2, like numbers represent similar components to system 100 shown in FIG. 1. FIG. 2 shows CAC 114 and APC 124, both of which are similar to the corresponding equipment in system 100 (FIG. 1). System 200 also includes the upstream equipment shown in FIG. 1, namely, cleavage reactors (104, 108), cooler (110), and neutralization and wash unit (112), but such equipment has been omitted from FIG. 2 for clarity. As with system 100 (FIG. 1), in system 200 (FIG. 2), organic effluent from the neutralization unit flows to CAC 114 via line 113. A vapor fraction from the CAC (referred to herein as the "crude acetone fraction") is fed to the APC 124 via line 126, and a phenol-rich bottoms material exits the CAC via line 122. According to some embodiments, the crude acetone fraction fed to the APC 124 via line 126 may contain about 12 vol.% cumene, about 0.1 to about 0.2 vol.% phenol, about 40 to about 50 vol.% acetone, about 1 to about 2 vol.% AMS, about 50 to about 500 ppm (vol) methanol, and about 60 to about 1000 ppm (vol) total aldehydes. More specifically, the crude acetone fraction may contain about 60 to 1000 ppm (vol) aldehydes, including acetaldehyde and / or propionaldehyde.

[0020] The interior volume 140 of the APC 124 of system 200 is as described above. The APC 124 of system 200 includes a side draw 202 that allows for the capture of a portion of the material within the column and feeding it to a caustic treatment vessel 204. The side draw may be configured anywhere on the APC 124, but according to most embodiments, it is configured between the inlet line 126 from the CAC and the acetone product line 134, as shown in FIG. 2. Caustic material is fed to the caustic treatment vessel 204 via line 206. As with system 100 (FIG. 1), the caustic material may be, for example, an alkali or alkaline earth metal oxide, hydroxide, or phenate. An example of a suitable caustic material is sodium hydroxide. The bottoms stream from the caustic treatment vessel 204 is returned to the APC 124 via line 208. Line 208 is also typically configured to feed the APC at a location between lines 126 and 134.

[0021] By removing a portion of the material from the APC and reacting it with caustic in caustic treatment vessel 204 before returning the contents of the caustic treatment vessel to the APC, contact time with the caustic is increased. This results in more efficient removal of aldehydes from the acetone product compared to system 100 (FIG. 1). System 200 is also capable of handling higher aldehyde concentrations in the crude acetone feed in vapor form (i.e., the feed entering the APC via line 126). High aldehyde concentrations can be due to 1) high impurity concentrations in the cumene feed to the plant and / or 2) the presence of a recycled acetone stream from other processing units that use acetone downstream of the phenol plant. In system 200, the caustic-treated stream (i.e., stream 202) is phenol-free and low in cumene and other organic impurities, such as AMS.

[0022] Caustic treatment vessel 204 may, for example, be a vessel without any internals. In some embodiments, mixing may occur within caustic treatment vessel 204 because the streams being combined are two liquid phases: stream 202 is an organic phase primarily containing acetone, cumene, and AMS, and stream 206 is an aqueous phase. Mixing may be achieved, for example, using stationary mixing internals installed within the vessel, an agitator installed with the vessel, and / or a circulation pump to facilitate mixing and contact of the two phases. In some embodiments, the residence time of the contents within the caustic treatment vessel may be from about 3 to about 60 minutes, for example, from about 5 to 30 minutes.

[0023] According to some embodiments, the concentration of caustic material in the caustic treatment vessel 204 may be about 0.1 to about 15% caustic. According to some embodiments, the temperature in the caustic treatment vessel is about 45 to about 75°C, for example, 50 to 65°C. According to some embodiments, the temperature in the caustic treatment vessel is maintained by the heat of the material transferred from the APC, and no additional heating is required. Alternatively, additional heat may be supplied to the caustic treatment vessel, for example, by steam heating.

[0024] As mentioned above, the caustic treated stream is returned to the APC via line 208. This stream may enter the APC, for example, just above the steam feed line 126. Phenol in the APC is converted to sodium phenate due to the presence of free caustic in the caustic feed from the caustic treater. Residual aldehydes are also converted to heavy ketones on the trays of the APC along with the phenol / sodium phenate reaction. Other heavier organic impurities, such as cumene and AMS, are removed from the acetone as the vapor ascends the column.

[0025] The inventors have found that the disclosed methods and systems, such as system 200, can produce acetone containing a total amount of aldehydes of about 5 to about 40 ppm (wt). According to some embodiments, the aldehyde content is less than 40 ppm (wt), less than 20 ppm (wt), or less than 10 ppm (wt). The resulting acetone can achieve a permanganate time of about 12 to about 24 hours, which is a significant improvement over prior art systems. For example, according to some embodiments, the permanganate time is greater than 12 hours, greater than 18 hours, or greater than 24 hours.

[0026] Figures 3 and 4 show further embodiments for purifying acetone in an APC. In Figures 3 and 4, only the APC and associated equipment are shown. It should be understood that systems 300 (Figure 3) and 400 (Figure 4) include the upstream equipment shown in Figures 1 and 2, respectively, but such equipment has been omitted from Figures 3 and 4 for clarity. In Figures 3 and 4, like numbers represent similar components to systems 100 and 299 shown in Figures 1 and 2, respectively.

[0027] As shown in Figures 3 and 4, the inventors have realized that acetone purified by the APC 140 can be further purified to remove alkyl alcohols such as methanol by passing a portion of the APC contents through an adsorbent, such as a zeolite, e.g., a molecular sieve material. Referring to Figure 3, the APC 140 includes a first side draw 202 through which a portion of the APC contents is passed to a caustic treatment vessel 204, similar to system 200 (Figure 2). The APC 140 also includes an additional side draw 302 through which a portion of the APC contents is passed to an adsorbent vessel 304. The adsorbent vessel 304 is configured to contain an adsorbent, such as a zeolite molecular sieve material. Examples of suitable zeolite molecular sieve materials include molecular sieves having pore sizes of about 4 to about 5 Å. The contents from the adsorbent vessel 304 are then fed via line 306 to the caustic treatment vessel 204. The aldehydes are removed in the caustic treatment vessel 204 as described above. The effluent stream from the caustic treatment vessel is returned via line 208 to the APC 140 as described above for system 200 (FIG. 2).

[0028] FIG. 4 illustrates another embodiment of system 400, which includes an APC 140 equipped with an adsorbent vessel 304 containing an adsorbent, such as a molecular sieve material, for removing alkyl alcohols from acetone. System 400 differs from system 300 (FIG. 3) in that all of the APC contents routed from APC 140 to caustic treatment vessel 204 pass through adsorbent vessel 304. In other words, a portion of the APC contents is routed to adsorbent vessel 304 via line 302. The contents of adsorbent vessel 304 are then routed to caustic treatment vessel 204 via line 306. There is no other side draw, such as side draw 202 (FIG. 3), to directly supply the APC contents to caustic treatment vessel 204. In other respects, systems 300 (FIG. 3) and 400 are identical. The inventors have found that systems such as system 300 (FIG. 3) and system 400 (FIG. 4) can produce acetone with an aldehyde content of less than 20 ppm (wt) or less than 10 ppm (wt), permanganate times of greater than 12 hours, greater than 18 hours, or greater than 24 hours, and a methanol content of less than 100 ppm (wt) or less than 50 ppm (wt).

[0029] While particular embodiments of the present invention have been shown and described, it should be understood that the above discussion does not limit the invention to these embodiments. It will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the present invention is intended to cover alternatives, modifications, and equivalents that may be included within the spirit and scope of the invention as defined by the claims.

Claims

1. A method for purifying acetone in an acetone production process, comprising: feeding a crude acetone fraction to a first feed point in an acetone purification column (APC); transferring a part of the crude acetone fraction from the APC via a first side draw of the APC located above the first feed point; feeding the transferred part of the crude acetone fraction to a caustic treatment tank; feeding an alkaline aqueous solution to the caustic treatment tank; returning a bottoms stream from the caustic treatment tank to the APC via a second feed point located between the first feed point and the first side draw; obtaining purified acetone from a second side draw located above the first side draw; and a method comprising the above steps.

2. The method according to claim 1, wherein the crude acetone fraction is obtained as a top stream from a crude acetone column (CAC) upstream of the APC.

3. The method according to claim 1, wherein the crude acetone fraction contains acetone, water, cumene, alpha-methylstyrene (AMS), phenol, methanol, and aldehydes.

4. The method according to claim 1, wherein the crude acetone fraction contains 60 to 1000 ppm (vol) of aldehydes, and the aldehydes include acetaldehyde and / or propionaldehyde.

5. The method according to claim 1, wherein the crude acetone fraction contains 50 to 500 ppm (vol) of methanol.

6. The method according to claim 1, wherein the alkaline aqueous solution contains an oxide, hydroxide, or phenate of an alkali or alkaline earth metal.

7. The method according to claim 4, wherein the alkaline aqueous solution contains sodium hydroxide.

8. The method according to claim 7, wherein the sodium hydroxide has a concentration of 0.1 to 15%.

9. The method according to claim 1, wherein the caustic treatment tank has a temperature of 45 to 75°C.

10. The method according to claim 1, wherein the caustic treatment tank is without internal components.

11. The method according to claim 1, wherein the caustic treatment tank is provided with fixed internal components for mixing.

12. The method according to claim 1, wherein the caustic treatment tank is provided with a stirrer.

13. The method according to claim 1, wherein the caustic treatment tank is provided with a circulation pump.

14. The method according to claim 1, wherein the caustic treatment tank provides a residence time of 3 to 60 minutes.

15. The method according to claim 1, further comprising contacting a portion of the transferred crude acetone fraction with a zeolite adsorbent to remove methanol from the portion of the transferred crude acetone fraction before feeding the portion of the transferred crude acetone fraction to the caustic treatment tank.

16. The method according to claim 1, wherein the purified acetone contains less than 20 ppm (wt) of aldehydes in total.

17. The method according to claim 1, wherein the purified acetone has a permanganate time of more than 12 hours.

18. The method according to claim 1, wherein the purified acetone contains less than 100 ppm (wt) of methanol.

19. A system for recovering purified acetone, a crude acetone column (CAC) configured to separate the product of the cumene hydroperoxide cleavage reaction into an overhead fraction containing crude acetone and a bottom fraction containing phenol, an acetone purification column (APC), receiving the crude acetone at a first feed point in the APC, separating the crude acetone into purified acetone and residual heavy compounds, the acetone purification column (APC) configured to supply the purified acetone at a first side draw located above the first feed point, a caustic treatment tank, receiving a portion of the crude acetone drawn from a second side draw of the APC located above the first feed point and below the first side draw in the APC, receiving a supply of an alkaline aqueous solution, mixing the portion of the crude acetone and the alkaline aqueous solution, configured to return the contents of the caustic treatment tank to a second feed point of the APC, the second feed point being the caustic treatment tank located between the first feed point and the second side draw, a system comprising.

20. The system according to claim 19, wherein the overhead fraction contains acetone, water, cumene, alpha-methylstyrene (AMS), phenol, methanol, and aldehydes.

21. The system according to claim 19, wherein the alkaline aqueous solution contains sodium hydroxide.

22. The system according to claim 19, wherein the caustic treatment tank provides a residence time of 3 to 60 minutes.

23. The caustic treatment tank is the system according to claim 19, which does not have internal components.

24. The caustic treatment tank is the system according to claim 19, which comprises one or more of fixed internal components for mixing, a stirrer, or a circulation pump.

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