Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2001-04-18
2003-06-03
Shippen, Michael L. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C502S034000, C502S053000, C502S054000, C502S055000, C568S771000
Reexamination Certificate
active
06573413
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the activation of catalysts for hydroxylation of aromatics. The present invention also relates to restoring activity of deactivated hydroxylation catalysts and to preventing the loss of activity in such catalyst.
BACKGROUND OF THE INVENTION
Introduction of a hydroxyl group onto an aromatic ring is one of the most difficult problems of organic synthesis. The simplest reaction of this type, benzene oxidation to phenol, is conducted presently by the so-called cumene process involving three stages. Numerous efforts to perform a direct benzene oxidation to phenol with molecular oxygen have not been successful. Interaction with oxygen results in a cleavage of the benzene ring and a low phenol selectivity.
The production of hydroxylated aromatics by partial oxidation of aromatics using nitrous oxide over zeolites has been demonstrated. See U.S. Pat. Nos. 5,055,623; 5,001,280; 5,110,995; and 5,756,861, the subject matter of which is incorporated herein by reference in its entirety. The most commonly utilized hydroxylated aromatic is phenol, which is used primarily in production of phenolic resins, caprolacturn, nitrophenols, chlorophenols, etc.
Various problems have been encountered in efforts to commercialize a viable aromatic hydroxylation process. One such problem lies in the activation and deactivation of catalysts utilized in such processes, in particular the activation and deactivation of zeolite catalysts. Zeolite catalysts inherently possess several drawbacks, namely low activity and gradual deactivation, leading to the eventual need to replace the catalyst.
While there are many explanations and theories as why zeolite catalysts are problematic with regard to activation and deactivation for aromatic hydroxylation reactions with accompanying solutions to such problems, no solution has been achieved that provides a noticeable improvement to existing processes. Various processes have been used to activate zeolite catalysts for aromatic hydroxylation reactions. For example, Zholobenzlo reported in
Mendeleev Commun.
(1993) No. 1, pg. 28-29, a method for phenol production using zeolite catalyst that had been activated by high temperature calcination in air (e.g., 350-1000° C.). In U.S. Pat. Nos. 5,672,777; 4,002,578; and German Patent Application No. DE 196 34 406 A1, the subject matter of which is incorporated herein in its entirety, discloses the activation zeolite catalyst for use in aromatic hydroxylation reactions by hydrothermal treatment (e.g., 350-950° C.) of the catalyst using steam in an inert gas carrier. However, the above-mentioned activation processes do not significantly increase the activation of the catalysts.
As described in U.S. Pat. Nos. 4,784,747 and 4,443,554, the entire subject matter of which is incorporated herein, the use of an inert gas in the steaming activation of zeolite catalysts (utilized for a variety of reactions) is essential. As prescribed in these patents, reducing gases are to be avoided due to the negative impact on such gases to the acidity of the catalyst, which is believed to provide catalyst activity.
Reductive treatment has been utilized for the activation of supported metal catalysts used in the reactions of ammonia synthesis or hydrogenation of various organic compounds. Sometimes such a reductive treatment is employed for zeolite catalysts to increase their activity prior to reactions proceeding in a reducing atmosphere, without the presence of an oxidant. For example, U.S. Pat. No. 4,002,578, the entire subject matter of which is incorporated herein by reference, discloses an activation method for zeolites, containing metals of the VIII group, by treatment of such zeolites in hydrogen at 250-650° C. Such treatment increases the catalytic activity of zeolites in hydrogenation reactions. In U.S. Pat. No. 4,539,305, the entire subject matter of which is incorporated herein by reference, a similar reductive treatment of zeolite catalysts is carried out to increase such catalysts activity in reforming processes. In U.S. Pat. No. 4,326,994, the entire subject matter of which is incorporated herein by reference, a zeolite activation method is described in which the zeolite is treated with water vapor and in the presence of ammonia as well. This improves the zeolite catalytic properties with regard to cracking, hydrocracking, alkylation, dealkylation, isomerization and aromatization of hydrocarbons.
However, it is not known to utilize a reductive treatment with zeolite catalysts when such catalysts are employed in oxidation reactions, since such treatment would be expected by the artisan to degrade catalytic activity for such reactions. In particular, heterogeneous catalytic oxidation reactions proceed generally in the range of rather high temperatures (above 300° C.). At such temperatures, any contact of the reduced catalyst with an oxidant would expectedly cause catalyst oxidation, thus rendering the catalyst in a state equivalent to the catalyst prior to the reductive treatment. In addition, any catalyst treatments, such as the reductive treatment followed by oxidation, would be expected to cause thermal/physical damages to the catalyst. Accordingly, for application in oxidation reactions, reductive pretreatment would be expected by the artisan to provide negligible catalyst activity improvement, and moreover, may likely damage the catalyst.
Other catalyst activation processes include the use of steam and reducing gases. See U.S. Pat. Nos. 4,150,064; 4,748,140; 5,308,822; 4,826,800; 4,547,482; 4,452,693; and 4,911,904, the entire subject matter of which is incorporated herein by reference. However, such processes treat non-zeolite catalysts that are comprised of materials and structures quite diverse from zeolite catalysts, and are accordingly, utilized for catalyzing reactions significantly different from hydroxylation reactions. Thus, activation of zeolite catalysts utilized for oxidation reactions has heretofore not included use of steam and reducing gases.
SUMMARY OF THE INVENTION
The present invention provides for a method for catalytic production of hydroxylated aromatic compounds by exposing a zeolite catalyst to an atmosphere of reducing gas to activate the catalyst, and reacting an aromatic compound with nitrous oxide in the presence of the activated catalyst. Also, the present invention concerns a method for restoring activity of a deactivated zeolite catalyst by exposing the zeolite catalyst to an atmosphere of reducing gas. Moreover, the present invention relates to a method for reducing activity loss of a zeolite catalyst during production of hydroxylated aromatics by reacting an aromatic compound with nitrous oxide in the presence of the zeolite catalyst, and exposing the catalyst during the reaction to an atmosphere of reducing gas.
DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
In accordance with the present invention, a zeolite catalyst is activated by exposing said catalyst to reducing atmosphere to thereby render the catalyst suitable for use in hydroxylation of various compounds, including aromatics and substituted aromatics. Such activated catalyst may be utilized in commercial hydroxylation of aromatics, such as in one-step hydroxylation of benzene to phenol as set forth in U.S. Pat. Nos. 4,982,013; 5,001,280; 5,055,623; 5,110,995; 5,672,777; 5,756,861; and 5,808,167, the entire subject matter of which is incorporated herein by reference.
In one embodiment of the present invention, a zeolite catalyst is activated by exposing the catalyst to a reducing gas and water vapor. The zeolite catalyst may include zeolites of various chemical compositions having a pentasyl or beta type structure, such as those set forth in U.S. Pat. Nos. 4,982,013; 5,001,280; 5,055,623; 5,110,995; 5,672,777; 5,756,861; and 5,808,167, the entire subject matter of which is incorporated herein by reference. For example, the zeolite catalyst may include ZSM-5 and ZSM-11 zeolite catalysts containing a catalytically effective amount (e.g., up to 2 wt %) of transition metal, such as one or more elemen
Chernyavsky Valery S.
Dubkov Konstantin A.
Kharitonov Alexander Sergeevich
Panov Gennady I.
Shippen Michael L.
Solutia Inc.
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