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 specifically, embodiments relate to improving the purity of the produced acetone.

[0002] [Introduction] Phenol and acetone are produced in various ways, and the most common method is variously known as, inter alia, the Hock process, the Hock-Lang process, or the cumene-phenol process. This process begins by oxidizing 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 of phenol, acetone, and / or AMS.

[0003] Such methods have been used for decades, but there continues to be a need to optimize the purity of the aldehydes produced.

[0004] [Summary] This specification discloses a method for purifying acetone in an acetone production process. The method comprises supplying 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 located above the first feed point; supplying the transferred portion of the crude acetone fraction to a caustic treatment tank; supplying an alkaline aqueous solution to the caustic treatment tank; returning the bottom flow from the caustic treatment tank 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. According to some embodiments, the crude acetone fraction is obtained as a top flow from a crude acetone column (CAC) upstream of the APC. According to some embodiments, the crude acetone fraction contains acetone, water, cumene, alpha-methylstyrene (AMS), phenol, methanol, and aldehydes. According to some embodiments, the crude acetone fraction contains 60 to 1000 ppm (vol) of aldehydes, which include acetaldehyde and / or propionaldehyde. According to some embodiments, the crude acetone fraction contains 50 to 500 ppm (vol) of methanol. According to some embodiments, the alkaline aqueous solution contains an oxide, hydroxide, or phenate of an alkali or alkaline earth metal. According to some embodiments, the alkaline aqueous solution contains sodium hydroxide. According to some embodiments, the sodium hydroxide has a concentration of about 0.1 to about 15%. According to some embodiments, the caustic treatment tank has a temperature of about 45 to about 75°C. According to some embodiments, the caustic treatment tank does not have internal components. According to some embodiments, the caustic treatment tank has fixed internal components for mixing. According to some embodiments, the caustic treatment tank has a stirrer. According to some embodiments, the caustic treatment tank has a circulation pump. According to some embodiments, the caustic treatment tank provides a residence time of about 3 to about 60 minutes.According to some embodiments, the method further comprises contacting a portion of the crude acetone fraction with a zeolite adsorbent to remove methanol from the portion of the crude acetone fraction before supplying the portion of the crude acetone fraction to a caustic treatment tank. According to some embodiments, the purified acetone contains less than about 20 ppmwt of aldehydes in total. According to some embodiments, the purified acetone has a permanganate time of more than 12 hours. According to some embodiments, the purified acetone contains less than 100 ppm(wt) of methanol.

[0005] This specification also discloses a system for recovering purified acetone. The system comprises a crude acetone column (CAC) configured to separate the products of a cumene hydroperoxide cleavage reaction into a top fraction containing crude acetone and a bottom fraction containing phenol, and an acetone purification column (APC), wherein crude acetone is received at a first feed point in the APC, and the crude acetone is separated into purified acetone and residual heavy compounds. In the first side draw located above the first supply point Purified acetone to provide The system comprises an acetone purification column (APC) configured to feed, and a caustic treatment tank configured to receive a portion of crude acetone drawn from a second side draw of the APC located above a first feed point of the APC and below a first side draw, receive a supply of an alkaline aqueous solution, mix the portion of crude acetone with the alkaline aqueous solution, and return the contents of the caustic treatment tank to the second feed point of the APC, the second feed point of the caustic treatment tank located between the first feed point and the second side draw. According to some embodiments, the crude acetone fraction contains acetone, water, cumene, alpha-methylstyrene (AMS), phenol, methanol, and aldehydes. According to some embodiments, the alkaline aqueous solution contains sodium hydroxide. According to some embodiments, the caustic treatment tank provides a residence time of about 3 to about 60 minutes. According to some embodiments, the caustic treatment tank does not have internal components. According to some embodiments, the caustic treatment tank includes one or more fixed internal components for mixing, a stirrer, or a circulation pump. [Brief explanation of the drawing]

[0006] [Figure 1] Figure 1 shows an embodiment of a system for producing acetone and phenol from cumene hydroperoxide (CHP). [Figure 2] Figure 2 shows an improved system for purifying acetone, in which a portion of the generated acetone reacts with a caustic substance in a caustic reaction vessel. [Figure 3] Figure 3 shows an improved system for purifying acetone, in which a portion of the generated acetone is passed through an adsorbent tank to remove alkyl alcohols from the generated acetone. [Figure 4] Figure 4 shows a further embodiment of an improved system for purifying acetone, in which a portion of the generated acetone is passed through an adsorbent tank to remove alkyl alcohols from the generated acetone. [Modes for carrying out the invention]

[0007] [Detailed explanation] Figure 1 shows 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 herein but are 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 incorporated references above.

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

[0009] The concentrated CHP is supplied 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. CHP is supplied 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-mixing reactor and may be operated between 50°C and 80°C. In the first cleavage reactor, CHP partially reacts in two reactions: i) CHP is cleaved to produce phenol and acetone, and ii) CHP partially reacts with DMBA in an equilibrium reaction to produce the intermediate product dicumyl peroxide (DCP) and water. DMBA is partially dehydrated to AMS. AMS reacts with phenol in a sequential reaction to produce high-boiling cumylphenol. Furthermore, AMS may produce high-boiling point dimers. Additional by-products such as hydroxyacetone (HA), 2-methylbenzofuran (2-MBF), and mesityl oxide (MO) may also be produced. Since the cleavage reaction is highly exothermic, recycled acetone may be supplied to the cleavage reactor to continue appropriate dilution and thereby minimize the formation of undesirable by-products. In the illustrated embodiment, recycled acetone is supplied 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 take place: i) residual CHP from the first cleavage reactor is cleaved into phenol and acetone; ii) residual DMBA from the first cleavage reactor is dehydrated to AMS; and iii) DCP is converted to AMS, phenol, and acetone. The second cleavage reactor may be a plug flow reactor with a temperature of, for example, about 105°C to 145°C, and may be heated by steam.

[0011] In the illustrated system 100, the cleavage product from the second cleavage reactor 108 is cooled using a condenser 110 and led to one or more neutralization and washing units 112. The effluent after cleavage 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 with one or more bases, such as sodium hydroxide, and / or one or more salt solutions. For example, the salt solution may be or contain sodium phenate. The salt solution can reduce or stop the cleavage reaction continuing in the cleavage product. Thus, the neutralization and washing unit 112 can produce neutralized cleavage product.

[0012] The steps following cleavage and neutralization (i.e., acetone fractionation) are primarily aimed at purifying the products (acetone and phenol) and recovering by-products and recyclable cumene. The acetone fractionation system is for (1) crude separation of light and heavy components in the fractionation feed, and (2) purification of the acetone product. The organic effluent from the neutralization unit 112 flows through line 113 to the first distillation column, which is referred herein to 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. Embodiments of the CAC are described in U.S. Patent No. 8,889,915, the full 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 substances 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 bottom material (line 122) rich in phenol may be led to a phenol fractionation unit (not shown). The top 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 herein as the acetone product column or acetone purification column (APC) 124. According to some embodiments, the vapor fraction supplied 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) of aldehydes in total.

[0013] APC124 is for removing lighter components (primarily acetaldehyde, via line 128) from acetone products and for separating acetone from water, cumene, AMS, and other heavy organic matter. Embodiments of the APC are described in U.S. Patent No. 4,340,447 ("'447 Patent"), which are incorporated by reference. The APC comprises an APC reboiler 130 and an APC condenser 131. Supply to the APC reboiler 130 may be from a liquid trap outside the bottom tray of the APC124, or from a recirculating flow from the bottom of the column, and the APC reboiler 130 may be heated by low-pressure steam.

[0014] The internal volume 140 of the APC 124 may be empty, or it 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 a combination thereof. As used herein, the term “tray” may include, but are not limited to, one or more trays that can increase 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 float trays, baffle trays, shower deck trays, chimney trays, slit trays, or any combination thereof. As used herein, the term “packing material” or “packing” may include, but are not limited to, one or more regularly and / or irregularly shaped materials placed within the APC 124. The filler material can increase the effective surface area within the APC124, thereby improving mass transfer between the liquid and gas phases within the APC124. The filler material can be made from any suitable material, such as metals, nonmetals, polymers, ceramics, glass, or any combination thereof. Specific examples of irregular fillers include Raschig Ring and NeXRing. TM Nutter Rings TM I-Rings TMC-Rings TM P-Rings TM R-Rings TM and S-Rings TM Intalox® ULTRA, IMTP®, HY-PAK®, CASCADE MINI RINGS®, FLEXIRING®, AHPP Saddle Rings, Pole Rings, SuperBlend TM 2-Pac, or any combination thereof, may be included, but is not limited to these. Specific examples of commercially available structured packing may be included, but is not limited to structured packing, corrugated sheets, crimped sheets, wire mesh, grids, or any combination thereof. The packing material may improve mass transfer and / or separation of multi-component fluids. The packing material and / or packing pattern within the internal volume 140 may include one or more structured and / or irregular packing materials. Two or more types of packing materials may be placed within the internal volume 126. APC124 can be made from one or more metallic materials that are physically and chemically compatible with the temperature, pressure, and contents of APC124. Suitable metallic materials may be included, but are not limited to, iron alloys including carbon and stainless steel such as clad carbon steel, 304 stainless steel, and 316 stainless steel, duplex stainless steel, and combinations of these metallic materials. Furthermore, the APC124 can operate in a range of pressures and temperatures from a minimum of approximately 40kPa, 50kPa, or 60kPa to a maximum of approximately 80kPa, 90kPa, or 100kPa.

[0015] The final bottom flow 132 from APC124 may be supplied to a crude AMS washing section (not shown). The product, acetone, may be obtained from a side draw 134. A portion of the reflux from APC124 may be recycled to a cleavage reactor section, e.g., first cleavage reactor 104, via line 106, as described above. The amount of acetone recycled may be determined as a ratio based on the amount of CHP supplied 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 supplied to the cleavage reactor.

[0016] The APC124 is provided with a caustic addition point 136 for adding a caustic substance. The caustic substance may be, for example, an oxide, hydroxide, or phenate of an alkali or alkaline earth metal. An example of a suitable caustic substance is sodium hydroxide. The caustic addition point 136 is located between the feed stream 126 and the product side draw 134. The caustic substance is added to the APC124 to reduce the amount of aldehydes in the acetone product. The aldehydes undergo an aldol condensation reaction in the presence of the caustic substance to produce heavy ketones, thereby purifying the acetone product. The use of a caustic substance in the APC124 to reduce the amount of aldehydes in the acetone product is described in the incorporated '447 patent.

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

[0018] In embodiments such as those shown in Figure 1 and described in the '477 patent, the extent to which aldehydes and other reducing substances are removed by reaction with caustic substances in the APC column is limited by the contact time of the caustic substances with the aldehydes in the column. Aldol condensation depends on the contact time between the aldehydes on the distillation tray of the APC and the caustic substances. The residence time on the distillation tray may be short, for example, a few minutes. Therefore, aldol condensation of aldehydes may not be complete, and this condensation is highly dependent on the operating load of the column.

[0019] The inventors realized that the contact time between aldehydes and caustic substances could be improved by using System 200, as shown in Figure 2. In Figure 2, similar numbers represent components similar to those in System 100 shown in Figure 1. Figure 2 shows CAC 114 and APC 124, both of which are similar to the corresponding equipment in System 100 (Figure 1). System 200 also includes the upstream equipment shown in Figure 1, namely the cleavage reactors (104, 108), the cooler (110), and the neutralization and washing unit (112), but such equipment is omitted from Figure 2 for clarity. Similar to System 100 (Figure 1), in System 200 (Figure 2), organic effluent from the neutralization unit flows to CAC 114 via line 113. The vapor fraction from the CAC (referred herein to as the "crude acetone fraction") is supplied to the APC 124 via line 126, and the phenol-rich bottom material exits the CAC via line 122. According to some embodiments, the crude acetone fraction supplied 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) of aldehydes in total. More specifically, the crude acetone fraction may contain about 60 to 1000 ppm(vol) of aldehydes, which include acetaldehyde and / or propionaldehyde.

[0020] The internal volume portion 140 of the APC 124 of the system 200 is as described above. The APC 124 of the system 200 includes a side draw 202 that enables the acquisition of a portion of the material in the column and the supply thereof to the caustic treatment tank 204. The side draw may be configured at any position on the APC 124. However, according to most embodiments, as shown in FIG. 2, it is configured between the inflow line 126 from the CAC and the acetone product line 134. The caustic substance is supplied to the caustic treatment tank 204 via the line 206. Similar to the system 100 (FIG. 1), the caustic substance may be, for example, an oxide, hydroxide, or phenate of an alkali or alkaline earth metal. An example of a suitable caustic substance is sodium hydroxide. The bottoms flow from the caustic treatment tank 204 is returned to the APC 124 via the line 208. The line 208 is also generally configured to supply the APC at a position between the line 126 and the line 134.

[0021] By taking out a portion of the substance from the APC, reacting it with the caustic substance in the caustic treatment tank 204, and then returning the contents of the caustic treatment tank to the APC, the contact time with the caustic substance is lengthened. As a result, compared with the system 100 (FIG. 1), aldehydes are more efficiently removed from the acetone product. In addition, the system 200 can handle a crude acetone feed in the form of vapor (i.e., the feed entering the APC via the line 126) even if it contains a larger amount of aldehydes. The high concentration of aldehydes may be caused by 1) a high concentration of impurities in the cumene feed supplied 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 the system 200, the stream to be caustic-treated (i.e., the stream 202) does not contain phenol and has a low concentration of other organic impurities such as cumene and AMS.

[0022] The caustic treatment tank 204 may, for example, be a tank without any internals. According to some embodiments, mixing may be performed within the caustic treatment tank 204. This is because the streams to be mixed are two liquid phases. That is, stream 202 is an organic phase mainly containing acetone, cumene, and AMS, and stream 206 is an aqueous phase. Mixing may be carried out, for example, using fixed internals of the type that perform mixing installed in the tank, a stirrer installed together with the tank, and / or a circulation pump for promoting two-phase mixing and contact. According to some embodiments, the residence time of the contents in the caustic treatment tank 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 the caustic substance in the caustic treatment tank 204 may be from about 0.1 to about 15% caustic. According to some embodiments, the temperature in the caustic treatment tank is from about 45 to about 75 °C, for example from 50 to 65 °C. According to some embodiments, the temperature in the caustic treatment tank is maintained by the heat of the substance transferred from the APC and no further heating is required. Alternatively, additional heat may be supplied to the caustic treatment tank, for example by steam heating.

[0024] As described above, the caustic-treated stream is returned to the APC via line 208. This stream may enter the APC, for example, directly above the steam supply line 126. The phenol in the APC is converted to sodium phenolate due to the presence of free caustic substances in the caustic supply from the caustic treatment tank. Residual aldehydes are also converted to heavy ketones together with the phenol / sodium phenolate reaction on the trays of the APC. Other heavier organic impurities such as cumene and AMS are removed from the acetone as the steam rises up the column.

[0025] The inventors have found that acetone containing a total amount of aldehydes of about 5 to about 40 ppm(wt) can be produced by the disclosed method and system 200, etc. 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 permanganation time of about 12 to about 24 hours, which is a significant improvement compared to prior art systems. For example, according to some embodiments, the permanganation time is more than 12 hours, more than 18 hours, or more than 24 hours.

[0026] Figures 3 and 4 show further embodiments for purifying acetone in an APC. Figures 3 and 4 show only the APC and associated equipment. 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, similar numbers represent components similar to those in systems 100 and 299 shown in Figures 1 and 2, respectively.

[0027] As shown in Figures 3 and 4, the inventors discovered that the acetone purified in APC 140 could be further purified and alkyl alcohols such as methanol removed by passing a portion of the APC contents through an adsorbent such as zeolite, e.g., molecular sieve material. Referring to Figure 3, APC 140 is equipped with a first side draw 202, through which a portion of the APC contents is sent to the caustic treatment tank 204, similar to system 200 (Figure 2). APC 140 is also equipped with a further side draw 302, through which a portion of the APC contents is sent to the adsorbent tank 304. The adsorbent tank 304 is configured to contain an adsorbent such as zeolite molecular sieve material. Examples of suitable zeolite molecular sieve materials include molecular sieves with a pore size of approximately 4 to 5 Å. The contents from the adsorbent tank 304 are then supplied to the caustic treatment tank 204 via line 306. Aldehydes are removed in the caustic treatment tank 204 as described above. The flow of effluent from the caustic treatment tank is returned to the APC 140 via line 208, as described above for system 200 (Figure 2).

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

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

Claims

1. A method for purifying acetone in the acetone production process, The crude acetone fraction is supplied to the first feed point in the acetone purification column (APC), A portion of the crude acetone fraction is transferred from the APC via the first side draw of the APC located above the first supply point. The portion of the crude acetone fraction to which the crude acetone fraction has been transferred is supplied to the caustic treatment tank. The alkaline aqueous solution is supplied to the caustic treatment tank, The bottom flow of the tower is returned from the caustic treatment tank to the APC via a second supply point located between the first supply point and the first side draw. Purified acetone is obtained from the second side draw located above the first side draw, A method for providing this.

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

3. The method according to claim 1, wherein the crude acetone fraction comprises 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 does not have internal components.

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

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

13. The method according to claim 1, wherein the caustic treatment tank is equipped 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 the step of bringing the portion of the crude acetone fraction to be transferred into contact with a zeolite adsorbent to remove methanol from the portion of the crude acetone fraction transferred before supplying the portion 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 products of the cumene hydroperoxide cleavage reaction into a top fraction containing crude acetone and a bottom fraction containing phenol, Acetone purification column (APC), The crude acetone is received at the first supply point in the APC. The crude acetone is separated into purified acetone and residual heavy compounds. The acetone purification column (APC) is configured such that the purified acetone is obtained from a first side draw located above the first supply point, A caustic treatment tank, A portion of the crude acetone drawn from the second side draw of the APC, which is located above the first supply point and below the first side draw of the APC, is received. Receiving a supply of alkaline aqueous solution, A portion of the crude acetone is mixed with the alkaline aqueous solution. The contents of the caustic treatment tank are configured to be returned to the second supply point of the APC. The second supply point is located between the first supply point and the second side draw, A system equipped with these features.

20. The system according to claim 19, wherein the top fraction of the column comprises 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 caustic treatment tank provides a residence time of 3 to 60 minutes, according to the system of claim 19.

23. The caustic treatment tank is provided without internal components, according to claim 19.

24. The system according to claim 19, wherein the caustic treatment tank comprises one or more of the following: a fixed internal component for mixing, a stirrer, or a circulation pump.

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