Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2003-05-21
2004-01-20
Shippen, Michael L. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
Reexamination Certificate
active
06680413
ABSTRACT:
The present invention relates to a process for the recovery of phenol and biphenol by-products from solutions containing them.
In particular, the present invention relates to a process for the recovery of phenol and biphenol by-products from their homogeneous mixtures containing benzene, sulfolane and water.
Phenol is a useful product in the preparation of synthetic resins, insecticides and antioxidants.
In industry, phenol is normally prepared by means of benzene alkylation with propylene to give isopropyl benzene, oxidation to the corresponding tert-hydroperoxide and subsequent cleavage to phenol and acetone in the presence of an acid catalyst.
The reaction mixture, after neutralization of the residual acid, is subjected to a series of subsequent distillations for the separation of products and by-products from the non-converted reagents which are recycled to the reaction.
A process has recently been proposed for the production of phenol by means of the direct oxidation of benzene with hydrogen peroxide, in the presence of titanium silicalite, which operates in liquid phase in the presence of sulfolane, as reaction solvent (U.S. Pat. No. 6,133,487).
The process which allows the oxidation of benzene to phenol to be obtained with high yields, is always accompanied by subsequent reactions which lead to the formation poly-hydroxylated products (mainly biphenols), in concentrations varying according to the reaction conditions.
The reaction effluent consequently contains the sulfolane solvent, non-converted benzene, the water formed and that introduced with the diluted hydrogen peroxide, in addition to the phenol, biphenols and tars produced.
In this case, the application of the traditional purification process, which includes the sequential distillation of the various components, is not suitable as, after the separation of the most volatile products (benzene, water and phenol), the distillation of the sulfolane would be required for removing the by-products having a higher boiling point than the solvent.
This solution, in addition to being uneconomical, does not allow the separation of the biphenols—such as catechol, for example—which together with sulfolane form an azeotropic mixture with the highest temperature.
In the present case, it is not even possible to resort to simple extraction with soda in water solution (U.S. Pat. No. 5,338,453), as sulfolane is miscible with water in all proportions.
It has now been found that it is possible to overcome the above-mentioned drawbacks of the known technique by means of the process of the present invention which is based on the use of an alkaline solution and benzene for the separation of biphenols from sulfolane, after the removal of the benzene, H
2
O and phenol contained in the reaction effluent.
The process of the present invention allows the recovery of the biphenol by-products dissolved in sulfolane, directly obtaining the purified solvent containing the benzene necessary for the feeding to the reactor for the direct oxidation of benzene, in addition to biphenols dissolved in water and pure phenol.
In accordance with the above, an objective of the present invention is a process for the recovery of phenol and biphenols from their homogeneous mixtures containing benzene, sulfolane and water, which comprises the following steps:
(a) feeding the reaction mixture containing benzene, water, phenol, sulfolane and the reaction by-products (biphenols), to a distillation unit consisting of two or more columns, to obtain one or more products at the head, essentially consisting of the benzene-water azeotropic mixture and phenol, and a product at the bottom, consisting of sulfolane, residual phenol and reaction by-products;
(b) feeding the benzene-water azeotropic mixture to a condensation system consisting of one or more condensers in series in which, after de-mixing, an aqueous phase and a benzene phase are separated. The latter is partially sent back to the distillation unit as reflux, whereas the aqueous phase is totally collected;
(c) feeding the bottom product coming from the distillation unit of step (a), a basic water solution and benzene to one or more mixers and separators (D
311
) to effect the salification of the biphenols in order to obtain the demixing of the system into an organic phase consisting of benzene and sulfolane and an aqueous phase consisting of water, biphenol salts and a part of sulfolane;
(d) feeding the aqueous phase coming from the mixer/separator (D
311
) and benzene to a liquid/liquid extraction column (C
310
) to obtain, at the head, an organic extract saturated with water containing benzene and sulfolane and, at the bottom, a refined product containing phenoL salts in water solution;
(e) feeding the organic phases coming from steps (c) and (d) and water to a mixing/de-mixing system (D
312
) to obtain an organic stream containing sulfolane, benzene and water and an aqueous stream, saturated with organic products, which is sent to the extraction column C
310
;
(f) feeding the organic phase coming from step (e) to a distillation column C
320
wherein the heterogeneous benzene-water azeotropic mixture with the highest pressure separates at the head, and a product consisting of sulfolane, benzene and residual water separates at the bottom;
(g) feeding the azeotropic mixture obtained in step (f) to a condensation system consisting of one or more condensers wherein an aqueous phase separates and is completely removed and used for preparing the basic aqueous solution to be adopted for the salification of phenols and a benzene phase which is sent back to the column as reflux;
(h) feeding the refined product leaving the extraction column C
310
to a mixer and acidifying with an inorganic acid or CO
2
to release phenols from their salts;
(i) feeding the aqueous saline solution obtained in step (h) and an extracting agent to an extraction column C
410
to obtain an extract containing biphenols, at the head, and a refined product consisting of saline water containing residues of the extracting agent, at the bottom;
(l) feeding the refined product to a distillation column C
430
to obtain the residual extracting agent together with water, at the head, and the saline solution, at the bottom, which is sent for disposal or recovery;
(m) feeding the extract leaving the column C
410
and the head product of column C
430
to a distillation column C
420
, obtaining the heterogeneous H
2
O-extraction solvent azeotropic mixture at the head and a solution containing water and biphenols at the bottom;
(n) feeding the head product to a condensation system consisting of one or more condensers wherein an aqueous phase is obtained which is sent as reflux to column C
420
of step (m) together with an organic phase containing the extracting agent;
(o) feeding a portion of the organic phase coming from the condenser to a distillation column C
440
to obtain a benzene-water mixture at the head, which is recycled to step (a) and the extracting agent at the bottom, which is directly fed to the separation column C
410
.
According to an embodiment of the present invention, the process comprises:
(a) feeding the reaction mixture containing benzene, water, phenol, sulfolane and reaction by-products to a first distillation column C
210
to obtain product at the head, consisting of the benzene-water azeotropic mixture and a product at the bottom, including the residual benzene and water, sulfolane, phenol and by-products;
(b) feeding the benzene-water azeotropic mixture to a condensation system consisting of one or more condensers in series in which, after de-mixing, an aqueous and a benzene phase are separated. The latter is partially sent back to the distillation column as reflux, whereas the aqueous phase is totally collected;
(c) feeding the bottom product leaving the column C
210
to a second distillation column C
220
, to obtain a head product—containing benzene, water and traces of phenol—which is recycled to step (a), and a tail product consisting of phenol, sulfolane and biphenols;
(d) feeding the tail product coming from the distillatio
Bianchi Daniele
Bortolo Rossella
Carnelli Lino
Moscotti Daniele
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Polimeri Europa S.p.A.
Shippen Michael L.
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