Acetone recovery and purification

Abstract

Methods and systems for the production of acetone from cumene hydroperoxide (CHP) are disclosed. The disclosed methods involve cleaving CHP to form a cleavage product stream. In some embodiments, the cleavage product stream is separated into an overhead stream and a bottoms stream. The bottoms stream is neutralized, washed, and then processed in a crude acetone column to provide a crude acetone stream. The overhead stream of the cleavage product is flashed forward in the method, bypassing neutralization, washing, and the crude acetone column, and then combined with the crude acetone stream. The combined acetone stream is provided to an acetone product column. According to some embodiments, the acetone product column includes a side draw for obtaining a recycle acetone stream, which is recycled to the cleavage reactor(s). The recycle acetone side draw can be located lower on the acetone product column than the point at which product acetone is obtained. The disclosed methods improve process efficiency.

Description

Invention Field

[0001] This application relates to methods and systems for producing acetone from cumene. More specifically, embodiments relate to improving the efficiency of acetone recovery.

[0002] introduction

[0003] Phenol and acetone are produced by various methods, the most common of which are referred to by different names such as the Hock method, the Hock and Lang method, or the cumene-to-phenol method. This method begins with the oxidation of cumene (isocumene) to form cumene hydroperoxide (CHP). The CHP is then cleaved in the presence of an acid catalyst to form a mixture of phenol, acetone, and / or α-methylstyrene (“AMS”). This mixture is subsequently neutralized and fractionated to recover the final products phenol, acetone, and / or AMS.

[0004] Although this method has been used for decades, there is still a continuous need to optimize the efficiency of product recovery in this method.

[0005] Overview

[0006] This document discloses a method for producing acetone, comprising (i) cracking cumene hydroperoxide (CHP) in at least one cracking reactor to form a cracking product stream, (ii) separating the cracking product stream into a top stream and a bottom stream, (iii) separating the bottom stream in a crude acetone column to provide a phenol-rich stream and an acetone-rich stream, (iv) feeding both the top stream from step (ii) and the acetone-rich stream from step (iii) into an acetone product column, and (v) obtaining product acetone from the acetone product column. According to some embodiments, the at least one cracking reactor comprises a first-stage cracking reactor and a second-stage cracking reactor, and cracking CHP comprises: providing CHP to the first-stage cracking reactor, contacting CHP with an acid catalyst, recycled acetone, and water to form a first-stage cracking reactor product, providing the first-stage cracking reactor product to the second-stage cracking reactor, and obtaining the cracking product stream as an effluent from the second-stage cracking reactor. According to some embodiments, separating the cracking product stream into a top stream and a bottom stream comprises flashing the cracking product stream in a flash tank to provide a top stream from the flash tank. According to some embodiments, the flash tank operates at a pressure of about 90 kPa to about 190 kPa. According to some embodiments, the top stream from the flash tank contains about 60 vol% to about 75 vol% acetone. According to some embodiments, the method further includes cooling the bottom stream of step (ii). According to some embodiments, the method further includes neutralizing the bottom stream of step (ii). According to some embodiments, feeding both the top stream of step (ii) and the acetone-rich stream of step (iii) into an acetone product column includes combining the top stream of step (ii) with the acetone-rich stream of step (iii) to form a combined stream, and feeding the combined stream into the acetone product column. According to some embodiments, the crude acetone column includes a condenser, and wherein combining the top stream of step (ii) with the acetone-rich stream of step (iii) includes feeding the top stream of step (ii) into the condenser. According to some embodiments, the method further includes recycling the acetone from the acetone product column to a pyrolysis reactor for performing step (i). According to some embodiments, the acetone product column includes a first side pump from which product acetone is obtained and a second side pump from which recycled acetone is obtained. According to some embodiments, the second side pump is located below the first side pump.

[0007] This document also discloses a method for producing acetone, the method comprising (i) cracking cumene hydroperoxide (CHP) in at least one cracking reactor to form a cracking product stream, (ii) treating at least a first portion of the cracking product stream to wash and neutralize the first portion of the cracking product stream, (iii) separating the first portion of the cracking product stream in a crude acetone column to provide a phenol-rich stream and an acetone-rich stream, (iv) feeding the acetone-rich stream from step (iii) to an acetone product column, and (v) extracting product acetone from a first side of the acetone product column and extracting recycled acetone from a second side of the acetone product column. According to some embodiments, the second side is below the first side. According to some embodiments, the at least one cracking reactor comprises a first cracking reactor and a second cracking reactor. According to some embodiments, the method further comprises recycling the recycled acetone to the second cracking reactor. According to some embodiments, recycling the recycled acetone to the second cracking reactor comprises recycling a certain amount of acetone, based on the CHP provided to the at least one cracking reactor, the certain amount of acetone having a weight ratio of about 0.05 to about 0.25 of acetone to CHP. According to some embodiments, the method further includes, prior to step (ii), flashing the pyrolysis products in a flash tank to provide the first portion of the pyrolysis product stream as a bottom stream from the flash tank and to provide a top stream. According to some embodiments, the method further includes flashing the top stream forward downstream of the crude acetone column. Brief description of the attached diagram

[0009] Figure 1 This illustrates one embodiment of a system for producing acetone and phenol from cumene hydroperoxide (CHP).

[0010] Figure 2 An embodiment of an improved system for producing acetone and phenol from cumene hydroperoxide (CHP) is shown.

[0011] Detailed Explanation

[0012] Figure 1 A system 100 for producing acetone and phenol from cumene hydroperoxide (CHP) is shown. Concentrated CHP enters the system via line 102. The concentration of CHP in line 102 can be about 65-90% by weight, more generally about 80-85% by weight, for example about 82% by weight. CHP can be produced by the oxidation of cumene, for example, as described in U.S. Patent No. 8,697,917, the entire contents of which are incorporated herein by reference. Oxidation products (not shown) from the oxidation of cumene include CHP, and may also include one or more of α-methylstyrene (AMS), dimethylbenzyl alcohol (DMBA), and / or acetophenone (ACP).

[0013] Concentrated CHP is fed to a single pyrolysis reactor or two pyrolysis reactors in series, for example, as described in U.S. Patent No. 5,371,305. In the illustrated system 100, two pyrolysis reactors in series are shown. CHP is fed to a first pyrolysis reactor 104, where it undergoes acid-catalyzed pyrolysis. For example, the acid catalyst may be sulfuric acid (H₂SO₄). In the illustrated embodiment, the first pyrolysis reactor may, for example, be a remixing reactor and operates at 50°C to 80°C. In the first pyrolysis reactor, CHP is partially reacted in two reactions: i) CHP pyrolysis to form phenol and acetone, and ii) CHP partially reacts with DMBA in an equilibrium reaction to yield the intermediate dicumyl peroxide (DCP) and water. DMBA is partially dehydrated to AMS, which reacts with phenol in a continuous reaction to form high-boiling cumylphenol. AMS may also form a high-boiling dimer. Additional byproducts such as hydroxyacetone (HA), 2-methylbenzofuran (2-MBF), and isopropylidene acetone (MO) may also be produced. The pyrolysis reaction is highly exothermic, therefore recycled acetone can be supplied to the pyrolysis reactors (multiple pyrolysis reactors) to maintain an appropriate dilution, thereby minimizing the formation of unwanted byproducts. In the illustrated embodiment, recycled purified acetone is supplied to the first pyrolysis reactor via line 106. Water may also be added to obtain the optimal pyrolysis yield.

[0014] In the illustrated embodiment, the product of the first pyrolysis reactor 104 is fed to a second pyrolysis reactor 108, where three main reactions occur: i) residual CHP from the first pyrolysis reactor is pyrolyzed into phenol and acetone, ii) residual DMBA from the first pyrolysis reactor is dehydrated into AMS, and iii) DCP is converted into AMS, phenol, and acetone. The second-stage pyrolysis reactor may be a plug flow reactor, for example, a plug flow reactor operating at a temperature of about 105°C to 145°C, and may be steam-heated.

[0015] In the illustrated system 100, the pyrolysis products from the second pyrolysis reactor 108 are cooled using a cooler 110 and directed to one or more neutralization and washing units 112. The pyrolysis effluent contains sulfuric acid, which serves as a catalyst for the pyrolysis reaction. To avoid corrosion problems in downstream equipment, one or more bases, such as sodium hydroxide, and / or one or more salt solutions must be used to extract and neutralize these acids. For example, the salt solution may be or include sodium phenolate. The salt solution can reduce or stop any further pyrolysis reaction in the pyrolysis products. Therefore, the neutralization and washing unit 112 can produce neutralized pyrolysis products. However, in the improved embodiments described below, the pyrolysis products are treated differently, as will be described.

[0016] The primary purpose of the steps following cracking and neutralization (i.e., acetone fractionation) is to purify the products (acetone and phenol) and recover byproducts and recyclable cumene. The purpose of the acetone fractionation system is to: (1) crudely separate the light and heavy components of the feed; and (2) purify the acetone product. The organic effluent from the neutralization unit (multiple neutralization units) 112 flows to the first distillation column, referred herein as the crude acetone column (CAC) 114. The function of the CAC is to separate the neutralization product into phenol and acetone fractions. Various aspects of the CAC are described in U.S. Patent No. 8,889,915, the entire contents of which are incorporated herein by reference. The vapor distillate (line 120) contains acetone, water, cumene, AMS, a small amount of phenol, and other light components from the feed. The CAC may be equipped with a CAC reboiler 116 and a CAC condenser 118. For example, the CAC reboiler 116 may be a forced-circulation exchanger heated by high-pressure steam. The phenol-rich bottom product (line 122) can be directed to the phenol fractionation unit (not shown). The top vapor (line 120) is partially condensed in the CAC condenser 118. The condensed liquid is returned to CAC 114, while the vapor distillate is sent via line 126 to the second distillation column, here referred to as the acetone product column (APC) 124.

[0017] The purpose of APC 124 is to remove light residues (primarily acetaldehyde, via line 128) from the acetone product and to separate acetone from water, cumene, AMS, and other heavy organic compounds. Several aspects of APC are described in U.S. Patent No. 4,340,447, the contents of which are incorporated herein by reference. APC is equipped with an APC reboiler 130 and an APC condenser 131. The APC reboiler 130 can be fed from a liquid trap outside the bottom tray of APC 124 and from the recirculated stream from the bottom of the column, and can be heated by low-pressure steam.

[0018] The internal volume 140 of APC 124 may be empty, partially filled with one or more packing materials, or completely filled with one or more packing materials (not shown). Exemplary packing materials may include, but are not limited to, trays, packings, or combinations thereof. As used herein, the term "tray" may include, but is not limited to, one or more types of trays that can improve the contact between the gas and liquid phases within APC 124. Exemplary trays may include, but are not limited to, perforated trays, sieve trays, bubble cap trays, floating valve trays, fixed valve trays, cylindrical trays, dual-flow trays, baffle trays, spray plate trays, chimney trays, slotted trays, or any combination thereof. As used herein, the term "packing material" or "packing" may include, but is not limited to, one or more types of structured and / or randomly shaped materials disposed within APC 124. Packing materials can increase the effective surface area within APC 124, which can improve mass transfer between the liquid and gas phases within APC 124. Packing materials can be made of any suitable material, such as metals, nonmetals, polymers, ceramics, glass, or any combination thereof. Exemplary examples of random filler materials include, but are not limited to, Raschig rings and NeXRings. TM Nutter Rings TM I-Rings TM C-Rings TM P-Rings TM R-Rings TM and S-Rings TM , ULTRA CASCADE MINI AHPP Saddle-Rings, Pall rings, SuperBlend TM2-Pac, or any combination thereof. Exemplary examples of commercially available structured fillers may include, but are not limited to, structured fillers, corrugated sheets, rolled sheets, mesh, grids, wire mesh, or any combination thereof. The filler material can improve the mass transfer and / or separation of multi-component fluids. The filler material and / or filler pattern in the internal volume 140 may include one or more structured and / or random filler materials. Two or more types of filler materials may be disposed within the internal volume 126. APC 124 may be made of one or more metallic materials that are physically and chemically compatible with the temperature, pressure, and contents of APC 124. Suitable metallic materials may include, but are not limited to, ferroalloys including carbon steel and stainless steel such as cladded carbon steel and 304 and 316 stainless steel, as well as duplex stainless steel, and combinations thereof. Furthermore, APC 124 can operate at pressures and temperatures ranging from a low value of about 40 kPa, about 50 kPa, or about 60 kPa to a high value of about 80 kPa, about 90 kPa, or about 100 kPa.

[0019] The net bottom stream 132 from APC 124 can be fed to a portion of the crude AMS (not shown). The product acetone can be obtained from side pump 134. A portion of the APC 124 reflux from reflux condenser 131 can be recycled to the cracking reactor portion via line 106, for example, to the first cracking reactor 104 as described above. Note that the recycled acetone (line 106) can also be part of the acetone product side pump 134. The amount of recycled acetone can be determined based on the proportion of CHP feed to the cracking reactor. For example, the amount of acetone recycled to the cracking reactor (multiple cracking reactors) with an acetone to CHP weight ratio can be from about 0.05 to about 0.25 based on the CHP feed to the cracking reactor (multiple cracking reactors).

[0020] APC 124 may be provided with one or more caustic alkali addition points 136 for adding caustic alkali materials such as sodium hydroxide (NaOH). For example, caustic alkali addition points (multiple caustic alkali addition points) 136 may be located between the feed stream 126 and the product side drawer 134.

[0021] It will be understood that some aspects and devices of system 100, which are not specifically related to the content of this disclosure, but are implemented in the actual operation of such a system, are not mentioned herein. Such aspects and devices are known in the art and can be described in the foregoing incorporated references.

[0022] The inventors have discovered that the efficiency of system 100 can be improved. Figure 2 System 200 for the production of acetone and / or phenol from CHP is described, and system 200 is similar in some respects to system 100. Figure 1 Similar to [the previous system], but including several improved features. A first additional aspect of system 200 is a flash tank 202, which is equipped to receive effluent from the pyrolysis reactor stage, such as effluent from the second pyrolysis reactor 108. As can be seen from the above discussion, the second pyrolysis reactor operates at high temperatures, for example, ranging from a low of about 105°C, about 110°C, about 115°C to a high of about 135°C, about 140°C, or about 145°C. In system 200, the effluent (containing acetone vapor) is supplied to the flash tank 202 via line 204. The flash tank can operate at pressures ranging from a low of about 90 kPa or about 100 kPa to a high of about 180 kPa or about 190 kPa. The liquid bottoms contained in the flash tank 202 are supplied to the neutralization cooler 110 via line 206. Acetone-containing vapor from flash tank 202 is “forward flashed” in this method via line 208, bypassing neutralization units 112 and CAC114. The temperature of this acetone-containing vapor ranges from a low of about 85°C or about 90°C to a high of about 115°C or about 120°C. This forward flashed stream contains acetone and may contain water, cumene, AMS, and phenol. Line 208 may contain about 60 vol% or about 65 vol% of acetone (lowest) to about 70 vol% or about 75 vol% (highest). Line 208 may contain about 3.5 vol% or about 4.0 vol% of cumene (lowest) to about 5.0 vol% or about 5.5 vol% (highest). Line 208 may contain about 21 vol% or about 23 vol% of water (lowest) to about 27 vol% or about 29 vol% (highest). Line 208 may contain a low of about 0.3 vol% or about 0.32 vol% to a high of about 0.38 vol% or about 0.40 vol% of AMS. Line 208 may contain a low of about 0.8 vol% or about 1.0 vol% to a high of about 1.3 vol% or about 1.5 vol% of phenol. The forward flash vapor stream 208 may be combined with the top stream 120 of CAC 114. For example, stream 208 may be added to the feed to APC 124 upstream (208a) or downstream (208b) of CAC condenser 118. Providing the forward flash stream 208 upstream of CAC condenser 118 (via stream 208a) or using another partial condenser (not shown) may reduce the phenol content of the net vapor stream before it is sent to APC 124. CAC condenser 118 can be cooled by air, by cooling water, by tempering water, or by the cumene feed stream to the oxidizer, as described in U.S. Patent No. 8,889,915.

[0023] Using a forward flash configuration, as shown in system 200, results in improved system efficiency. Specifically, by bypassing CAC 114, some of the work of CAC reboiler 116 is offloaded. For example, this improved approach can reduce the energy input to the CAC by 20% to 30%, such as 25%, depending on the operating parameters.

[0024] Further improvements to System 200 involve how a portion of acetone is recycled from APC 124 back to the cracking reactor (multiple cracking reactors). Recall System 100 ( Figure 1 In a discussion, a portion of the purified acetone was recycled to the first-stage pyrolysis reactor 104 via pipeline 106. Figure 2 In system 200, circulating acetone (line 210) is side-pumped below acetone product line 134. The inventors have recognized that the energy used at the top of the APC is primarily consumed in the separation of acetone from water and other light impurities. The inventors have also recognized that the energy from the reflux condenser 131 (e.g., Figure 1 The recycled acetone provided by the purified acetone from the product acetone extract 134 is purer than that required to promote the pyrolysis reaction. Therefore, lowering the point on the column from which the recycled acetone is extracted provides significant energy savings by the APC 124. The distance DH below the product acetone extract from which the recycled acetone is extracted will be determined based on the specific implementation by balancing energy savings (a larger DH provides greater energy savings) and the required purity and / or dryness of the recycled acetone. For example, extracting the recycled acetone too low on the column carries the risk of caustic contamination of the recycled acetone. Those skilled in the art are capable of determining the optimal position of the recycled acetone extract 210 for a particular injection based on these considerations. As described above, the amount of acetone recycled to the pyrolysis reactor (multiple pyrolysis reactors) can be determined based on the proportion of the CHP feed to the pyrolysis reactor (multiple pyrolysis reactors). For example, the weight ratio of recycled acetone to CHP feed can be from about 0.1 to about 0.5.

[0025] As shown in the table below, the two improvements described herein—(1) flashing the acetone-rich portion of the pyrolysis product forward in the method, bypassing the CAC, and (2) obtaining recycled acetone from a lower side of the APC—each result in higher efficiency. Flashing the acetone-rich portion of the pyrolysis product forward (Embodiment 1) improves the efficiency of the method by reducing the energy that must be input to the CAC reboiler. Obtaining recycled acetone from a lower side of the APC (Embodiment 2) improves efficiency by reducing the energy that must be input to the APC reboiler. It should be noted that although the illustrated system 200 includes both embodiments described above, each embodiment individually contributes to an increase in efficiency. Therefore, methods and systems including any one of the described embodiments, individually or in combination, are within the scope of this disclosure.

[0026] A comparative study of system 100 and the improved system 200 was conducted using method simulations. For this study, a CHP stream 102 containing approximately 82 wt% CHP and 18 wt% cumene, directed to the first cracking reactor 104, was used as the feed stream. In both systems, the flow rate of circulating acetone to the first cracking reactor 104 was kept constant. The comparative results of this study are shown in Table 1.

[0027] Table 1

[0028]

[0029] This study shows that using Implementation Scheme 1 reduces the energy to CAC by 25%, while Implementation Scheme 2 reduces the energy to APC 124 by 30%. When both schemes are implemented, the total energy of the entire acetone treatment system is reduced by approximately 26%.

[0030] Although specific embodiments of the invention have been shown and described, it should be understood that the foregoing discussion is not intended to 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. Therefore, the invention is intended to cover substitutions, modifications, and equivalents that fall within the spirit and scope of the invention as defined in the claims.

Claims

1. A method for manufacturing acetone, the method comprising: (i) Cracking cumene hydroperoxide (CHP) in at least one cracking reactor to form a cracking product stream, (ii) Separate the pyrolysis product stream into a top stream and a bottom stream. (iii) Separate the bottom stream in the crude acetone column to provide a phenol-rich stream and an acetone-rich stream. (iv) Feed both the top stream from step (ii) and the acetone-rich stream from step (iii) into the acetone product column, and (v) Obtain acetone from the acetone product column. in: (A) Separating the pyrolysis product stream into a top stream and a bottom stream involves flashing the pyrolysis product stream in a flash tank. (B) Obtaining product acetone from the acetone product column includes recycling the recycled acetone from the acetone product column to step (i), or (C) The combination of (A) and (B).

2. The method of claim 1, wherein the at least one pyrolysis reactor comprises a first-stage pyrolysis reactor and a second-stage pyrolysis reactor, and wherein pyrolysis of CHP comprises: CHP is supplied to the first-stage pyrolysis reactor. CHP is contacted with an acid catalyst, recycled acetone, and water to form the products of the first-stage cracking reactor. The product from the first-stage pyrolysis reactor is fed to the second-stage pyrolysis reactor, and The pyrolysis product stream is obtained as the effluent from the second-stage pyrolysis reactor.

3. The method of claim 1, wherein the flash tank operates at a pressure of 90 kPa to 190 kPa.

4. The method of claim 1, wherein the top stream from the flash tank comprises 60% to 75% acetone.

5. The method of claim 1, further comprising cooling the bottom stream of step (ii).

6. The method of claim 1, further comprising neutralizing the bottom stream of step (ii).

7. The method of claim 1, wherein feeding both the top stream of step (ii) and the acetone-rich stream of step (iii) into the acetone product tower comprises combining the top stream of step (ii) with the acetone-rich stream of step (iii) to form a combined stream, and feeding the combined stream into the acetone product tower.

8. The method of claim 7, wherein the crude acetone column includes a condenser, wherein combining the top stream of step (ii) with the acetone-rich stream of step (iii) includes feeding the top stream of step (ii) into the condenser.

9. The method of claim 1, wherein the acetone product column comprises a first side pump from which product acetone is obtained and a second side pump from which recycled acetone is obtained.

10. The method of claim 9, wherein the second side drawer is located below the first side drawer.

11. A method for manufacturing acetone, the method comprising: (i) Cracking cumene hydroperoxide (CHP) in at least one cracking reactor to form a cracking product stream, (ii) Flashing the pyrolysis product stream in a flash tank to provide a first portion of the pyrolysis product stream as a bottom stream from the flash tank and to provide a top stream; (iii) Processing at least the first portion of the pyrolysis product stream to wash and neutralize the first portion of the pyrolysis product stream. (iv) Separating the first portion of the pyrolysis product stream in a crude acetone column to provide a phenol-rich stream and an acetone-rich stream. (v) Feed the acetone-rich stream from step (iv) into the acetone product column, and (vi) Obtain product acetone from the first side of the acetone product column and obtain recycled acetone from the second side of the acetone product column.

12. The method of claim 11, wherein the second side drawer is below the first side drawer.

13. The method of claim 11, wherein the at least one pyrolysis reactor comprises a first pyrolysis reactor and a second pyrolysis reactor.

14. The method of claim 13, further comprising recycling acetone to a second pyrolysis reactor.

15. The method of claim 14, wherein recycling acetone to the second pyrolysis reactor comprises recycling a certain amount of acetone based on the CHP supplied to the at least one pyrolysis reactor, the certain amount of acetone having a weight ratio of 0.05 to 0.25 of acetone to CHP.

16. The method of claim 11, further comprising flashing the top stream forward downstream of the crude acetone column.

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