Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
2000-06-27
2003-04-15
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C562S408000, C562S406000, C562S409000
Reexamination Certificate
active
06548698
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to the oxidative carbonylation of toluene, catalyzed by rhodium complexes in the presence of an oxidant, whereby para-toluic acid is produced at selectivities over 90%, or by iridium complexes wherein para-toluic acid is produced at somewhat lower selectivities.
TECHNICAL BACKGROUND OF THE INVENTION
The oxidative carbonylation reaction of aromatic compounds is an attractive method for the direct synthesis of aromatic carboxylic acids from arenes and carbon monoxide. In particular, oxidative carbonylation of toluene produces toluic acids that can be oxidized for manufacturing phthalic, isophthalic, and terephthalic acids employed as monomers for polyesters.
As used herein, “turnover number” (TON) means the number of molecules transformed per catalyst molecule. Higher TON's in comparable times indicate higher catalyst efficiency.
Palladium catalysts in the presence of oxidants (see, for example: Fujiwara, Y.; Kawata, I.; Sugimoto, H.; Taniguchi, H., J. Organomet. Chem. 1983, 256, C35; Jintoku, T.; Fujiwara, Y.; Kawata, I.; Kawauchi, T.; Taniguchi, H., J. Organomet. Chem. 1990, 385, 297; Ugo, R.; Chiesa, A., J. Chem. Soc., Perkin Trans. I 1987, 2625; Taniguchi, Y.; Yamaoka, Y.; Nakata, K.; Takaki, K.; Fujiwara, Y., Chem. Lett. 1995, 345) have been used, but the catalytic turnover numbers (TON) achieved for the carbonylation of toluene were low (2-8). Additionally, the para-selectivity of the reaction never exceeded 67%, normally being in the range of 40 to 55%. The TON's were increased when oxygen was used as the oxidant in the presence of a cuprous promoter, but the para-selectivity was still relatively low (about 46%).
J. J. Van Venrooy, U.S. Pat. No. 4,093,647, reported carbonylation of toluene using palladium catalyst with thallium, which was added in stoichiometric amounts and improved para-selectivity.
Rhodium catalysts have also been used for the oxidative carbonylation of toluene, improving the para-selectivity to between 63 and 94% (see, for example: Kalinovskii, I. O.; Lescheva, A. A.; Kuteinikova, M. M.; Gel'bshtein, A. I. Zh. Obshch. Khim. 1990, 60, 123, J. Gen. Chem. USSR 1990, 60, 108 (English Translation)). Relatively good TON's were obtained, but only when the reactions were run at 140° C. using CO and O
2
reactants with Cu promoter under pressures of about 150 to 250 psi and in ratios within explosive limits. F. J. Waller, U.S. Pat. Nos. 4,356,318; 4,416,801; 4,431,839; 4,463,103 to DuPont, and F. J. Waller,
Catal. Rev. Sci. Eng
. 1986, 28, 1, reported the carbonylation of toluene catalyzed with perfluorinated ion-exchange polymer/Rh composite occurring under more severe conditions, 150° C. and 2000-4000 psi of CO containing 3% O
2
. Although the CO/O
2
ratio was outside explosive limits, the TON's achieved were low (<9). Running the reaction in the presence of Cu
2+
, triflic acid and triflic anhydride resulted in slightly higher TON's (42), the reaction conditions required still being relatively drastic.
The rhodium-catalyzed process described by Kalinovskii et al., Zh. Obshch. Khim. 1990, 60, 123, J. Gen. Chem. USSR 1990, 60, 108 (English Translation); Kalinovskii, I. O.; Lescheva, A. A.; Pogorelov, V. V.; Gel'bshtein, A. I.,
Khim. Tverd. Topliva
1993, 8, gives substantial quantities of hydroxylated side-products when water is present in the reaction mixture.
SUMMARY OF THE INVENTION
The present invention discloses a para-selective process for preparing toluic acid, comprising: combining toluene, carbon monoxide, having a pressure from about 0 and about 5000 psi, and an oxidant, with a rhodium catalyst, in an acid medium.
The present invention also discloses a para-selective process for preparing toluic acid, comprising: combining toluene, carbon monoxide, and an oxidant, with an iridium catalyst, in an acid medium.
Another disclosure of this invention is a process for preparing a mixture of p-toluic and m-toluic acids, comprising: combining toluene, carbon monoxide, and an oxidant, under oxidizing conditions, with a suitable rhodium or an iridium catalyst, in an acid medium, wherein the mixture of p-toluic and m-toluic acids may be oxidized to make terephthalic and isophthalic acids suitable for use, without separation, in the formation of polyester materials.
DETAILED DESCRIPTION OF THE INVENTION
This invention relates to a process for the selective catalytic synthesis of para-toluic acid by reacting toluene in the presence of carbon monoxide (CO) and an oxidant in strong acid medium and in the presence of a rhodium catalyst. Examples of oxidants include, but are not limited to K
2
S
2
O
8
, oxygen and air, which by definition comprises oxygen. Although K
2
S
2
O
8
is a preferred persulfate, other persulfates of the formula M
x
M′
y
S
2
O
8
.zH
2
O can be used. An example of strong acid medium includes, but is not limited to, trifluoroacetic acid. In the formula M
x
M′
y
S
2
O
8
.zH
2
O, M and M′ are cations selected from the group consisting of Li, Na, K, Rb, Cs, and H, x+y=2, and z is any number from 0 to about 10. If K
2
S
2
O
8
is used the process can be carried out at temperatures that are about or slightly above room temperature. The desired p-toluic acid is produced at greater than 90% selectivity. If oxygen gas (O
2
) or air is used the process can be carried out at temperatures up to about 120° C. or above with CO/O
2
or CO/air ratios below the explosive limit. The desired p-toluic acid is produced in about or above 65% selectivity. By either method, the p-toluic acid produced may subsequently be used to make terephthalic acid. The terephthalic acid can be used as a monomer in a variety of polymerization reactions, including the production of polyesters.
When O
2
or air is used as the oxidant and the reaction is run at elevated temperatures for example, at about 120° C. or above, significant amounts of m-toluic acid are formed in addition to the p-toluic acid. This mixture of p- and m-toluic acids may be used subsequently to make mixed terephthalic and isophthalic acids, which can be used for making polyester materials.
This invention also relates to a process for the selective catalytic synthesis of para-toluic acid by reacting toluene in the presence of carbon monoxide (CO) and an oxidant (for example, K
2
S
2
O
8
, oxygen or air) in mild acid (for example, acetic acid) medium in the presence of an iridium catalyst. If K
2
S
2
O
8
is used the process can be can be carried out at temperatures at or above about 100° C. When iridium catalyst is used the para-selectivity is generally less than about 80% selectivity, which is lower than that observed for rhodium catalyst. Any iridium compound capable of dissolving in the reaction medium under the reaction conditions described is suitable. Specific compounds are described below. Mixtures of p- and m-toluic acids may also be formed using these iridium catalysts, and, as described above, may be used to make mixed terephthalic and isophthalic acids, which in turn can be used for making polyester materials.
Reaction Media:
A mixture of trifluoroacetic acid and toluene is used as the reaction medium. Although other fluorinated carboxylic acids can be used (e.g., perfluorobutyric acid) trifluoroacetic acid was used mostly in the examples below. The trifluoroacetic acid:toluene ratio may vary in a broad range. Most experiments using K
2
S
2
O
8
oxidant and rhodium catalyst were carried out in 1:1, volume/volume (v/v) trifluoroacetic acid:toluene. When oxygen gas or air is used as the oxidant with rhodium catalyst the trifluoroacetic acid:toluene ratio is smaller, from as little as about 1:100 up to about 1:5 (v/v), and the addition of trifluoroacetic anhydride results in improved yield of toluic acids.
When K
2
S
2
O
8
is used as the oxidant, the reaction readily occurred in the presence of small amounts of water, although evidence has been obtained for the water gas shift reaction taking place when H
2
O is present. When water was present in small amounts no significant
Grushin Vladimir
Thorn David Lincoln
Barts Samuel
E. I. du Pont de Nemours and Company
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