Extraction of phenol from wastewater

Details Extraction of phenol from wastewater Extraction of phenol from wastewater

2002-11-20

2004-11-30

Drodge, Joseph (Department: 1723)

Liquid purification or separation

Processes

Liquid/liquid solvent or colloidal extraction or diffusing...

C210S639000, C210S919000, C568S754000, C568S758000, C585S258000

Reexamination Certificate

active

06824687

ABSTRACT:

BACKGROUND
1. Field of the Invention
The present invention relates to a method for the treatment of aqueous wastes, and particularly to a method for removing phenol from waste water.
2. Background of the Art
Various chemical processes produce waste water streams which contain phenol. For example, in a commonly employed process phenol is produced by the peroxidation of cumene to cumene hydroperoxide, which is then cleaved to phenol and acetone. Alpha-methyl styrene (AMS) is also produced and can be recovered as a by-product, or hydrogenated to cumene and then recycled to the phenol process. Waste water streams from such a process contain dissolved phenol which must be removed before the waste water can be discharged into the environment.
Various methods have been used in the past to remove phenolics (phenol and cresol) from waste water streams, including chemical reaction, adsorption with resins, and liquid-liquid extraction.
In extraction processes the phenol-containing water is treated with an extractant. Typically, the extractant is a solvent which is immiscible in water, but in which the phenol preferably dissolves. The phenol is thereafter recovered from the extractant stream. Various extractants have been employed, including benzene, toluene, xylene, cumene, and other aromatic or aliphatic liquids.
For example, U.S. Pat. No. 3,963,610 to Hauschulz et al. discloses a method of removing phenol from wastewater using cumene as an extractant. The cumene is washed with aqueous sodium carbonate and then sodium hydroxide to recover the phenol as a phenate.
U.S. Pat. No. 6,071,409 to Bondy et al. discloses phenolic wastewater treatment with ethers for removal and recovery of phenolics.
In a conventional method, aqueous effluent containing phenol is treated with solvent extraction to remove phenol in a single-stage extraction method which includes recycling of the solvent. The fresh solvent is supplied from an overhead of an AMS topping column and includes cumene and other hydrocarbons. The phenol is recovered from the solvent by caustic washing and is then recycled back to the process.
More particularly, referring now to
FIG. 1
, a prior art system
10
for the recovery of phenol and acetone from the product of the oxidation and cleavage of cumene is shown. Methods and apparatus for oxidizing cumene to cumene hydroperoxide and cleaving the cumene hydroperoxide to acetone and phenol are known. Effluent
11
from the cleavage of cumene hydroperoxide contains acetone, phenol, and by-products such as cumene, AMS, and other components (e.g., benzene, toluene, ethylbenzene, butyl benzene). The effluent
11
is sent to a splitter
12
which separates by fractionation an overhead stream
13
containing acetone, cumene and AMS, and a bottoms stream
14
containing phenol and some AMS. The bottoms
14
is sent to distillation column
21
wherein AMS is separated out as an overhead stream
22
and phenol and other heavier components are separated out as a bottoms stream
23
. The bottoms stream
23
is then sent on to further purification in distillation column
24
wherein purified phenol is separated as an overhead stream
25
and heavier components are separated out as a bottoms stream
26
.
The overhead stream
13
from splitter
12
is sent to distillation system
15
wherein acetone is separated out as an overhead stream
16
, and cumene and AMS are separated out as a bottoms stream
17
. The bottoms stream
17
is sent to the distillation system
18
, which separates the cumene-AMS mixture by fractionation into an overhead stream
19
containing cumene and other components, and a bottoms stream
20
containing AMS.
The overhead from the distillation system
18
is then sent to prior known system
50
for recovery of phenol from waste water. Referring now to
FIG. 2
, waste water stream
52
is introduced into a primary dephenolation drum
51
. The waste water stream may optionally be pre-treated with acid (e.g., H
2
SO
4
) to convert any phenates in the water to phenol, which can be removed by the hydrocarbon extractant. Stream
19
containing cumene and other hydrocarbons is introduced into drum
51
and the dephenolated water is discharged via stream
53
. The hydrocarbon solvent stream, which contains a major portion of the phenol, is sent via stream
55
to caustic wash drum
56
. Caustic solution (e.g., 20% aqueous NaOH) is added to the drum via stream
57
to convert phenol back into a phenate (sodium phenate) which is preferentially soluble in water and thereafter removed in water stream
58
. A portion of stream
58
may optionally be recycled to stream
57
. The hydrocarbon stream, is removed via stream
59
. A portion of the hydrocarbon solvent is recycled via stream
54
back to stream
19
. Another portion
60
is sent on to further processing.
What is needed is an improved method for extracting phenol from a wastewater stream which can be used in conjunction with a process for producing phenol and acetone from cumene.
SUMMARY OF THE INVENTION
A method is provided herein for the extraction of phenol from a waste water stream. The method is used in conjunction with a process for producing acetone and phenol from cumene which includes an acetone finishing column and an alpha-methylstyrene recovery system downstream of the acetone finishing column. The method for extracting phenol from waste water comprises contacting a phenol-containing waste water stream with a fresh hydrocarbon solvent, the hydrocarbon solvent being a hydrocarbon portion of a bottoms stream from the acetone finishing column, to produce a dephenolated waste water stream and a spent hydrocarbon solvent; and, conveying at least some of the spent hydrocarbon solvent to the alpha-methylstyrene recovery system without recycling any portion of the spent hydrocarbon solvent to the step (a) of contacting the phenol-containing waste water. Preferably, a major portion of phenol in the spent hydrocarbon is removed, for example by caustic washing, prior to step of conveying the spent hydrocarbon solvent to the alpha-methylstyrene recovery system.
Preferably the fresh hydrocarbon stream derived from the bottoms stream of the acetone finishing column is water washed prior to contacting the phenol-containing waste water stream in order to remove any entrained phenate.
The method and system of the present invention advantageously provides significantly better phenol recovery from the waste water than the prior known method.


REFERENCES:
patent: 2807654 (1957-09-01), Grimmett et al.
patent: 3300405 (1967-01-01), Black
patent: 3446732 (1969-05-01), Gasser et al.
patent: 3963610 (1976-06-01), Hauschulz et al.
patent: 4016213 (1977-04-01), Yeh et al.
patent: 4026791 (1977-05-01), Wallace
patent: 4164469 (1979-08-01), Wagner
patent: 4179365 (1979-12-01), Sumi
patent: 4480134 (1984-10-01), Fulmer
patent: 4567304 (1986-01-01), Fulmer
patent: 4575568 (1986-03-01), Yuhas, Jr. et al.
patent: 5456806 (1995-10-01), Lorenzoni et al.
patent: 5905178 (1999-05-01), Hildreth
patent: 6071409 (2000-06-01), Bondy et al.
patent: 6720461 (2004-04-01), Taggart et al.
patent: 0 717 024 (1996-06-01), None
patent: 1459458 (1976-12-01), None
International Search Report, PCT/US03/36602 filed Nov. 14, 2003.

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