Production of phenol

Details Production of phenol Production of phenol

1999-03-25

2001-01-02

Padmanabhan, Sreeni (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Oxygen containing

C568S385000, C568S485000, C568S741000, C568S754000, C568S768000

Utility Patent

active

06169215

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the production of phenol and more particularly to a process for producing phenol and acetone from cumene hydroperoxide.
2. Description of the Prior Art
Phenol is an important organic chemical with a wide variety of industrial uses. It is used, for example, in the production of phenolic resins, bisphenol-A and caprolactam. A number of processes are currently in use for the production of phenol but the single process providing the largest proportion of the total production capacity is the cumene process which now accounts for over three quarters of the total U.S. production. The basic reaction involved in this process is the cleavage of cumene hydroperoxide into phenol and acetone:
C
6
H
5
C(CH
3
)
2
OOH=C
6
H
5
OH+(CH
3
)
2
CO
The reaction takes place under acid conditions with the yield of both phenol and acetone generally being 40 percent or more.
On an industrial scale, the cumene hydroperoxide is usually treated with dilute sulphuric acid (5 to 25 percent concentration) at a temperature of about 50 to 70° C. After the cleavage is complete, the reaction mixture is separated and the oil layer distilled to obtain the phenol and acetone together with cumene, alpha-methylstyrene, acetophenone and tars. The cumene may be recycled for conversion to the hydroperoxide and subsequent cleavage. The phenol produced in this way is suitable for use in resins although further purification is required for a pharmaceutical grade product.
Although the process described above is capable of producing both phenol and acetone in good yields, it would be desirable to find a process which would reduce the need for the product separation and purification steps which are inherent in a homogeneous process and would avoid the need for environmentally hazardous liquid acids.
The heterogeneous cleavage of cumene hydroperoxide (CHP) over various solid acid catalysts has already been reported. For example, U.S. Pat. No. 4,490,565 discloses the use of zeolite beta in the cleavage of cumene hydroperoxide, whereas U.S. Pat. No. 4,490,566 discloses the use of a Constraint Index 1-12 zeolite, such as ZSM-5, and EP-A-492807 discloses the use of faujasite in the same process. The use of smectite clays in the acid-catalyzed decomposition of cumene hydroperoxide is described in U.S. Pat. No. 4,870,217.
U.S. Pat. No. 4,898,995 discloses a process for the coproduction of phenol and acetone by reacting cumene hydroperoxide over a heterogeneous catalyst consisting of either an ion exchange resin having sulfonic acid functionality or a heteropoly acid, such as 12-tungstophosphoric acid, on an inert support, such as silica, alumina, titania and zirconia. Such heteropoly acid catalysts are generally used as their hydrates, and as such are inherently unstable at temperatures in excess of 350° C.
None of the solid-acid catalysts currently proposed for cumene hydroperoxide cleavage exhibit the required combination of activity and selectivity to provide an acceptable replacement for sulfuric acid.
SUMMARY OF THE INVENTION
The present invention is directed to a process for producing phenol and acetone from cumene hydroperoxide, wherein the process comprises the step of contacting cumene hydroperoxide with a solid-acid catalyst produced by calcining a source of a Group IVB metal oxide with a source of an oxyanion of a Group VIB metal at a temperature of at least 400° C.
The process of the invention can achieve at or near 100% conversion of cumene hydroperoxide at long on-stream times with high selectivity to phenol and acetone and with extremely low coproduction of impurities such as 4-cumylphenol, 2,4-diphenyl-4-methyl-1-pentene, and mesityl oxide.
Preferably, said temperature is at least 600° C. and more preferably is 700-850° C.
Preferably, Group IVB metal oxide is selected from zirconia and titania.
Preferably, said Group VIB metal oxyanion is selected from oxyanions of chromium, molybdenum and tungsten.
Preferably, said solid acid catalyst also contains a further metal selected from Group IB, VIIB and VII metals, and preferably selected from iron, manganese and copper.
Preferably, said contacting step is conducted at a temperature of 20 to 150° C. and a pressure of atmospheric to 1000 psig and more preferably at a temperature of 40 to 120° C. and a pressure of atmospheric to 400 psig.
DESCRIPTION OF SPECIFIC EMBODIMENTS
The process of the invention uses a solid acid catalyst comprising an oxide of a Group IVB metal modified with an oxyanion or oxide of a Group VIB metal by calcination of the oxide species at a temperature of at least 400° C. The modification of the Group IVB metal oxide with the oxyanion of the Group VIB metal imparts acid functionality to the material. The modification of a Group IVB metal oxide, particularly, zirconia, with a Group VIB metal oxyanion, particularly tungstate, is described in U.S. Pat. No. 5,113,034; and in an article by K. Arata and M. Hino in
Proceedings
9
th International Congress on Catalysis
, Volume 4, pages 1727-1735 (1988).
For the purposes of the present disclosure, the expression, Group IVB metal oxide modified with an oxyanion of a Group VIB metal, is intended to connote a material comprising, by elemental analysis, a Group IVB metal, a Group VIB metal and oxygen, but with more acidity than a simple mixture of separately formed Group IVB metal oxide mixed with a separately formed Group VIB metal oxide or oxyanion. Such enhanced acidity is believed to result from an actual chemical interaction between the Group IVB metal oxide and the Group VIB metal oxyanion.
In the aforementioned article by K. Arata and M. Hino, when discussing the generation of acidity of sulfated Group IVB metal oxides, it is suggested that solid superacids are formed when sulfates are reacted with hydroxides or oxides of certain metals, e.g., Zr. These superacids are said to have the structure of a bidentate sulfate ion coordinated to the metal, e.g., Zr. In this article, it is further suggested that a superacid can also be formed when tungstates are reacted with hydroxides or oxides of Zr. The resulting tungstate modified zirconia materials are theorized to have an analogous structure to the aforementioned superacids comprising sulfate and zirconium, wherein tungsten atoms replace sulfur atoms in the bidentate structure. It is further suggested that tungsten oxide combines with zirconium oxide compounds to create superacid sites at the time a tetragonal phase is formed.
Although it is believed that the present catalysts may comprise the bidentate structure suggested in the aforementioned article by Arata and Hino, the particular structure of the catalytically active site in the present Group IVB metal oxide modified with an oxyanion of a Group VIB metal has not yet been confirmed, and it is not intended that this catalyst component should be limited to any particular structure.
The present catalysts may have calculated mole ratios, expressed in the form of XO
2
/YO
3
, where X is at least one Group IVB metal (i.e., Ti, Zr, and Hf) and Y is at least one Group VIB metal (i.e., Cr, Mo, or W), of up to 1000, e.g., up to 300, e.g., from 2 to 100, e.g., from 4 to 30, although it is to be appreciated that these forms of oxides, i.e., XO
2
and YO
3
, may not actually be present in the catalyst of the invention. It is to be appreciated that mixtures of Group IVB metals and/or mixtures of Group VIB metals may be present in the catalyst of the invention.
The Group IVB metal oxide is preferably selected from titania, zirconia and hafnia, with zirconia being most preferred, while the Group VIB metal oxyanion is preferably selected from oxyanions of chromium, moybdenum and tungsten, with oxyanions of tungsten being most preferred. The Group IVB and Group VIB metal species present in the final catalyst are not limited to any particular valence state and may be present in any positive oxidation value possible for the respective species. For example, when the catalyst contains tungsten, subjecting the catalyst to reducing condit

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