WO2002022532A1

WO2002022532A1 - Method for separating acetone and cumene from decomposition products of cumene hydroperoxide

Info

Publication number: WO2002022532A1
Application number: PCT/US2001/028893
Authority: WO
Inventors: Steven L. Pimplaskar; Ronald K. Nilsen; Oliver Wahnschafft
Original assignee: Sunoco Inc., (R & M)
Priority date: 2000-09-18
Filing date: 2001-09-18
Publication date: 2002-03-21
Also published as: AU2001290988A1

Abstract

A distillation process wherein a feed mixture comprising phenol, acetone and cumene is fed to a point intermediate between the top and bottom of a distillation column, an overhead stream comprising acetone is withdrawn from a point adjacent to the top of the column, and a bottoms stream comprising phenol is withdrawn from a point adjacent to the bottom of the column. The improvement represented by the present invention comprises withdrawing a side stream at a point where the feed is introduced and below the top of the column to remove cumene from the column.

Description

METHOD FOR SEPARATING ACETONE AND CUMENE FROM DECOMPOSITION PRODUCTS OF CUMENE HYDROPEROXIDE

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an improved separation of cumene hydroperoxide decomposition products by distillation, the improvement being withdrawing a side stream from the distillation column above the feed to remove cumene.

Related Background Art

Products obtained from decomposition of cumene hydroperoxide include phenol, acetone, cumene, and α-methylstyrene (AMS), among others. The process of separating these products is complicated by the existence of azeotropes and immiscible regions between some of the products. Several distillation columns may be required to achieve satisfactory separation of the components to produce commercial grades of acetone and phenol, and to produce cumene that can be recycled. For example, a two-column distillation procedure typically is used just to effect an initial separation into streams rich in acetone, phenol and cumene. The first column produces an overhead stream which is largely acetone, with a small amount of water, and traces of other products, and a bottoms stream which is mostly phenol, and which also contains most of the cumene, together with small amounts of other products. The bottoms stream is fed to the second column, which produces an overhead stream containing mostly cumene and a bottoms stream containing mostly phenol.

The necessity of using multiple distillation columns results in a capital- and energy-intensive process for separating phenol, acetone, and other associated products from decomposition of cumene hydroperoxide. A simpler distillation process that could reduce capital equipment costs and energy consumption would be desirable.

SUMMARY OF THE INVENTION

The present invention is directed to a distillation process wherein a feed mixture comprising phenol, acetone and cumene is fed to a point intermediate between the top and bottom of a distillation column, an overhead stream comprising acetone is withdrawn from a point adjacent to the top of the column, and a bottoms stream comprising phenol is withdrawn from a point adjacent to the bottom of the column. The improvement represented by the present invention comprises withdrawing a side stream at a point above where the feed is introduced and below the top of the column to remove cumene from the column.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic diagram of the distillation column used in a pilot-scale distillation according to the method of this invention.

Figure 2 is a schematic diagram of the flow and control systems in the pilot-scale distillation. DETAILED DESCRIPTION OF THE INVENTION

Withdrawing a side stream above the level at which feed is introduced to a single distillation column has the unexpected benefit of providing acetone, cumene and phenol streams comparable to those obtained from a two-column separation. While further purification of any of the product streams may require additional distillation, depending on the specifications to be met by each product, the initial separation into acetone, cumene and phenol streams is greatly simplified. Single-column distillation of a cumene hydroperoxide decomposition mixture according to this process thus avoids the capital and operating costs associated with a second distillation column.

The term "adjacent," in connection with the top or bottom of the column, refers to a tray in the column which is the top or bottom tray, respectively, or one which is adjacent to the top or bottom tray, respectively. Preferably the overhead and bottoms streams are withdrawn from the top and bottom trays, respectively. The term

"intermediate" refers to a tray between the top and bottom trays. Typically, the spacings between the feed and the top, bottom and side trays are sufficient to achieve the desired separation of components. For example, the side stream and the overhead stream preferably are separated by a sufficient number of trays to reduce the level of cumene in the overhead stream to less than 1%. In an embodiment of this invention, the separation is performed in a packed column with no trays. In this case, the overhead stream is withdrawn from the column at or above the top of the packing, and the bottoms stream is withdrawn from the column at or below the bottom of the packing.

The term "stage" is used to designate a theoretical, or ideal separation step in the distillation process. Since an actual distillation column operates at less than 100% efficiency, the number of trays required to achieve a given separation is greater than the theoretical number of stages calculated in a simulation.

The distillation of the present invention preferably is conducted at about atmospheric pressure, most preferably in the range from about 10 psia (70 kPa) to about 25 psia (170 kPa), most preferably from atmospheric pressure to about 18 psia (124 kPa). The side stream is withdrawn at a temperature suitable for removing an azeotrope of cumene with acetone, water or other components, preferably in the range from about 90 °C to about 130°C. The feed mixture is introduced into the column at a point below the side stream, preferably at least at stage five, counting from the top of the column. While the temperature of the feed is not believed to be critical because the heat content of the feed is a small fraction of the total heat input to the column, it is typically in the range from about 50°C to about 100°C. Preferably, the part of the column from which the bottoms stream is withdrawn is at a temperature in the range from about 125°C to about 196°C. In one preferred embodiment of the invention, the temperature is from about 150°C to about 196°C; in another preferred embodiment, the temperature is from about 125°C to about 140°C. Preferably, the part of the column from which the overhead stream is withdrawn is in a range from about 55°C to about 75°C, most preferably from about 55°C to about 65°C.

Typically, the side stream withdrawn from the column will contain less than 10% acetone. Preferably, the side stream will also contain less than 0.5% AMS. Typically, both the overhead and bottoms streams contain less than 1% cumene. Therefore, the method of this invention achieves separation of relatively high purity cumene, acetone and phenol in a single distillation column.

The following Examples are intended solely to illustrate certain preferred embodiments of the invention, and not to limit the invention.

EXAMPLES

COMPARATIVE EXAMPLE 1: Simulation of Two-Column Separation of Acetone, Cumene and Phenol.

A two-column separation system was modeled using ASPENPLUS software (available from Aspen Technology, Inc.) with a theoretical basis of 10,000 pounds/hr. of feed. The feed to the first column had the following composition and component mass flow rates:

The first column had a packing height of 40 feet (12 m), and had 40 stages, with the feed being introduced at stage 10, the overhead stream removed from stage 1, and the bottoms stream from stage 40. The feed temperature was 60°C. The pressure at stage 1 was 17.253 psia (118.96 kPa), and at stage 14 was 17.553 psia (121.02 kPa). The temperature at stage 1 was 60.9°C, and at stage 14 was 175.3°C. Heat was removed by the condenser at a rate of 10⁶ BTU/Hr. and added to the reboiler at a rate of 1.7x10⁶ BTU/Hr. The reflux ratio at the top of the column was 0.25. The overhead stream had the following composition and flow rates:

The bottoms stream had the following composition and flow rates, and comprised the feed for the second column:

The second column had 38 stages, with the feed being introduced at stage 23, the overhead stream removed at stage 1, and the bottoms stream at stage 38. The pressure at stage 1 was 3.53 psia (24.3 kPa), and at stage 38 was 10.57 psia (72.88 kPa). The temperature at stage 1 was 72.3 °C, and at stage 38 was 167.8°C. Heat was removed by the condenser at a rate of 1.15x10⁶ BTU/Hr. and added to the reboiler at a rate of l.OOxlO⁶ BTU/Hr. The reflux ratio at the top of the column was 5.22. The overhead stream had the following composition and flow rates:

The bottoms stream had the following composition and flow rates:

EXAMPLE 1 : Simulation of One-Column Separation of Acetone, Cumene and Phenol.

A one-column separation system was modeled using ASPENPLUS software (available from Aspen Technology, Inc.) with a theoretical basis of 10,000 pounds/hr. of feed. The feed to the column had the following composition and component mass flow rates:

The column had 38 stages, with the feed being introduced at stage 27, the overhead stream removed from stage 1, the bottoms stream from stage 38, and the side stream from stage 6. Heat was removed by the condenser at a rate of 2.44xl0⁶ BTU/Hr. and added to the reboiler at a rate of 2.52x10⁶ BTU/Hr. The temperature at stage 1 was 60.9°C, and at stage 38 was 186.2°C. The pressure at stage 1 was 17.253 psia (118.96 kPa), and at stage 38 was 17.553 psia (121.02 kPa). The reflux ratio at the top of the column was 2.05. The overhead stream had the following composition and flow rates:

The side stream had the following composition and flow rates:

The bottoms stream had the following composition and flow rates:

Comparison of the results obtained from the one-column separation of this Example with those from the two-column separation of Comparative Example 1 shows that the one-column separation produces acetone, cumene and phenol streams of comparable purity.

EXAMPLE 2: Pilot-Scale Test Run of One-Column Separation of Acetone, Cumene and Phenol.

An 8" diameter stainless steel column was packed with FLEX PAC^® 1.4Y structured packing material for a length of 43.2 feet, as shown in Figure 1. The packing was arranged in four beds with collectors/distributors above each bed of packing. The feed point was at 19.5 feet of packing above the reboiler. One side draw point (F3) was seven feet of packing from the top of the packing, and the other (F2) was 10.5 feet of packing from the top.

Figure 2 shows the flow scheme for the test run. For continuous operation each product stream was continuously routed back to the feed tank. The primary control loops are as shown. The column vapor loading, as measured by the condenser duty and/or the reflux plus distillate flow, was set via the reboiler duty, which was controlled by the reboiler oil temperature. The reboiler oil flow was maintained as high as practical to minimize the reboiler temperature gradient. The distillate draw rate was cascaded from a column temperature controller for Nozzle N23 temperature.

The bottoms system was jacketed and/or traced with heat transfer oil (HTO) and also included a small heat exchanger to cool the bottoms before returning to the feed tank. The feed tank was jacketed as well, which was used to regulate the feed tank temperature. The feed temperature entering the column was controlled with a HTO heated heat exchanger in the feed line.

The following test conditions were evaluated until the column lined-out, and then complete sets of profile samples were obtained in duplicate.

Column operating data were logged periodically to a printer from the DIOGENES control system and also stored as trend data on the RS3 control system. At the time when the profile samples were obtained, the normal printed log reports were directed and captured as text files on a PC. Samples were analyzed by gas chromatography (GC). Column operating data and sample analyses were obtained. The operating data are for only the time period when profile samples were obtained. For each test condition, the data were averaged over the profile sample time for each measured operating variable. The averaged results are shown in Table 1. Analytical results for each of the specification compositions are also included in Table 1.

The compound AMS continually decreased in feed, presumably because of being reacted to a higher boiling compound. At various times AMS was spiked in the feed and fresh feed charged to the system to bring the AMS concentration back up and to reduce the amount of high boilers in the feed. The rate of AMS loss decreased significantly after the kettle level was lowered prior to LEAC6. TABLE 1

Condition PIC-24 DPI-28 C-QCA C-QB2 TIC100 FIC-32 TIC-37 FIC-7 TIC-9

Number COL OH COL DP COND E-3 RB OEL COOLNT COOLNT FEED FEED

PRES RCLFLW DUTY DUTY T OUT FLOW TEMP FLOW TEMP

MMHG MMHG KBTU/H KBTU/H Temp LB MIN DEG F LB/MIN DEG F

LEAC1 890.0 12.7 93.8 175.0 422.5 120.0 83.8 9.00 195.0

LEAC2 889.8 11.7 87.6 155.4 422.5 119.9 85.5 8.99 192.7

LEAC3 889.6 14.9 106.3 185.2 425.6 119.9 83.7 9.00 194.0

LEAC4 890.1 10.9 89.2 171.5 428.1 120.0 82.7 9.01 194.2

LEAC5 890.2 10.1 87.9 167.6 427.9 119.9 82.6 9.00 195.9

LEAC6 889.9 13.0 90.0 185.9 426.0 119.9 83.7 9.03 149.7

LEAC7 890.1 13.4 87.6 198.1 426.1 119.9 83.3 9.05 153.6

Notes - Data in italics was obtained from RS3 control system trend files, all other data averaged over profile time period. - The distillate rate has been corrected from the post-test meter calibration (measured .935 = actual)

Condition FIC-49 FIC-50 FIC-XX TIC-1 TIC-88 TIC-95 TI-4 T2305A T2306A T2306B

Number DIST SIDE BTMS F TANK M OIL LO OIL KET LQ N2V N3V N4V

FLOW FLOW FLOW TEMP T OUT T OUT TEMP TEMP TEMP TEMP

LB/MIN LB/MIN LB/MIN DEG F DEG F DEG F DEG F DEG F DEG F DEG F

LEAC1 2.53 0.95 5.75 217.0 143.2 329.8 368.1 361.9 343.6

LEAC2 2.11 1.08 5.59 215.6 142.1 331.8 368.9 364.5 348.5

LEAC3 3.41 0.962 4.50 217.2 142.8 331.1 369.7 364.2 338.9

LEAC4 2.78 0.984 5.34 153.2 217.1 141.1 334.9 371.3 369.8 358.8

LEAC5 2.73 0.964 5.41 156.2 217.6 143.0 333.5 371.3 371.2 369.4

LEAC6 2.86 1.01 5.05 148.2 158.7 124.5 328.6 365.3 355.1 345.1

LEAC7 2.86 1.02 5.19 150.9 163.2 127.4 326.8 363.9 353.7 343.3

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CM CM CS

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CO cs vo CO CM 00 o cs

H OΛ 00 00 OΛ 00 00 M CM cs s M cs

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Condition T2323A T2324A T2324B T2325A T2326A TE2245 TE2246 Distillate

Number N21V N22V N23V N24V NF4V COND COND Cumene

TEMP TEMP TEMP TEMP TEMP IN OUT

DEG F DEG F DEG F DEG F DEG F DEG F DEG F wt%

LEAC1 272.3 265.6 166.6 141.0 143.9 84.1 97.7 0.84

LEAC2 270.3 266.4 166.5 141.1 143.9 85.5 98.1 0.84

LEAC3 261.5 259.6 169.1 141.1 144.1 83.7 99.3 0.73

LEAC4 264.0 255.5 160.7 141.1 143.4 82.7 95.6 0.22

LEAC5 264.1 255.4 160.4 141.1 143.2 82.6 95.4 0.59

LEAC6 262.5 251.6 168.0 141.8 143.9 83.8 96.9 0.80

LEAC7 264.8 259.1 174.5 144.1 146.1 83.1 96.3 0.89

Condition Side Draw Side Draw Bottoms Reflux

Number Acetone AMS Cumene Ratio (1) wt% wt% wt%

LEAC1 1.80 0.00 0.10 1.50

LEAC2 1.96 0.16 0.02 1.80

LEAC3 2.34 0.06 0.08 1.10

LEAC4 2.51 0.14 0.02 1.17

LEAC5 2.70 0.06 0.01 1.17

LEAC6 2.77 0.33 0.01 1.12

LEAC7 2.88 4.69 0.01 1.07

(1) Determined from the condenser duty and using a latent heat of vaporization of 247 BTU/lb.

The preceding Examples are intended to describe certain preferred embodiments of the present invention. It should be appreciated, however, that obvious additions and modifications of the invention will be apparent to one skilled in the art. The invention is not limited except as set forth in the claims.

Claims

WHAT IS CLAIMED IS:

1. In a distillation process wherein a feed mixture comprising phenol, acetone and cumene is fed to a point intermediate between the top and bottom of a distillation column, an overhead stream comprising acetone is withdrawn from a point adjacent to the top of the column, and a bottoms stream comprising phenol is withdrawn from a point adjacent to the bottom of the column; the improvement which comprises withdrawing a side stream at a point above where the feed is introduced and below the top of the column to remove cumene from the column.

2. The process of claim 1 in which pressure in the column is from about 10 psia (70 kPa) to about 25 psia (170 kPa).

3. The process of claim 2 in which column temperature at the point where the side stream is withdrawn is in a range from about 90°C to about 130°C.

4. The process of claim 3 in which the feed mixture is introduced into the column at least five stages from the top of the column.

5. The process of claim 4 in which the side stream contains less than 10% acetone.

6. The process of claim 5 in which column temperature at the point where the bottoms stream is withdrawn is in a range from about 125°C to about 196°C.

7. The process of claim 6 in which column temperature at the point where the overhead stream is withdrawn is in a range from about 55°C to about 75°C.

8. The process of claim 7 in which each of the bottom stream and the overhead stream contains less than 1% cumene.

9. The process of claim 8 in which pressure in the column is from atmospheric pressure to about 18 psia (124 kPa).

10. The process of claim 9 in which the side stream contains less than 0.5% α- methylstyrene.

11. The process of claim 10 in which column temperature at the point where the overhead stream is withdrawn is in a range from about 55°C to about 65°C.

12. The process of claim 11 in which column temperature at the point where the bottoms stream is withdrawn is in a range from about 150°C to about 196°C.

13. The process of claim 11 in which column temperature at the point where the bottoms stream is withdrawn is in a range from about 125°C to about 140°C.