Ring halogenation of aromatic compounds

Details Ring halogenation of aromatic compounds Ring halogenation of aromatic compounds

2000-04-11

2001-05-01

Killos, Paul J. (Department: 1623)

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

Organic compounds

Halogen containing

C252S183110, C252S183130

Reexamination Certificate

active

06225514

ABSTRACT:

BACKGROUND OF THE INVENTLON
This invention relates to the halogenation of the ring of an aromatic compound. In particular, it relates to that halogenation using a heterogeneous catalyst that is the reaction product of a support and a dopant.
Chlorinated aromatic compounds are important intermediates for making pharmaceuticals, herbicides, fungicides, and other chemicals. The chlorination of an aromatic ring requires the presence of a catalyst. Both homogeneous (single phase) catalysts, such as various metal chlorides (e.g., aluminum trichloride) and heterogenous (more than one phase) catalysts (e.g., silica, alumina, and various zeolites) have been used for this purpose. While these catalysts are effective, they are not easy to use. Homogeneous catalysts have to be kept anhydrous, more than one equivalent of the catalyst is needed for substrates that contain Lewis base sites, and it is sometimes difficult to separate the product from the catalyst. Heterogeneous catalysts, on the other hand, tend to decompose under the reaction conditions.
SUMMARY OF THE INVENTlON
We have discovered that certain non-zeolytic heterogeneous catalysts are very effective in reactions in which an aromatic ring is halogenated. Because these catalysts are solids, separation of the liquid product can be easily accomplished by filtration or decantation and water extraction or distillation is not needed to remove the catalyst. Unlike some previous catalysts used for this reaction, the catalysts of this invention do not readily decompose in the presence of corrosive acids. The catalysts are applicable to the halogenation of many different types of aromatic ring compounds. Using these catalysts, one or more halogens can be added to an aromatic ring.
DESCRIPTlON OF THE PREFERRED EMBODIMENTS
Virtually any kind of aromatic compound having sites available on an aromatic ring (i.e., hydrogen atoms) can be halogenated according to the process of this invention. While benzene and benzene derivatives are preferred as they are commercially more important, naphthalene, anthracene, and other multiple aromatic ring structures can also be used as the substrate. Aromatic rings that are substituted with nitrile, alkyl, halogen, acid chloride, carboxylic acid, hydride, and other groups can also be halogenated according to the process of this invention. Examples of single ring aromatic compounds that can be halogenated in the process of this invention include benzene, chlorobenzene, chlorotoluene, p-chlorobenzotrifluoride, 3,4-dichlorobenzotrifluoride, p-methylbenzoylchloride, methyl p-methylbenzoate (a.k.a. methyl p-toluate (MPT)), toluene, methyl 2-chloro p-toluate, methyl 4-chloromethylbenzoate, o-xylene, m-xylene, p-xylene, benzotrifluoride, m-trifluoromethyl benzotrifluoride, p-chlorobenzonitrile, and alkyl and dialkyl benzenes. The preferred class of substrates has aromatic rings that are deactivated towards electrophilic aromatic substitution, such as benzoates, nitrites, benzotrihalides, and halogenated aromatics.
Any halogenating agent can be used, but chlorinating and brominating agents are preferred as those products are more important commercially. Examples of halogenating agents include F
2
, SF
4
, XeF
2
, I
2
, ICl, ICl
3
IBr, Br
2
, BrCl, SO
2
Cl
2
, Cl
2
, SOCl
2
, COCl
2
, C
2
O
2
Cl
4
, C
3
O
3
Cl
6
, and n-chlorosuccinimide. Chlorine and bromine are preferred as they are inexpensive and readily available. The amount of haloginating agent used should be stoichiometric with the desired product. That is, a 1 to 1 molar ratio of the halogenating agent to the substrate will add 1 halogen while a 2 to 1 molar ratio of the halogenating agent to the substrate will add 2 halogens, etc. The positions to which the halogens are added proceed in the order of the normal rules of halogen addition.
The catalysts of this invention, commonly known as “solid acid catalysts,” can be made by reacting a dopant with a support. The support is at least one inorganic oxide of at least one metal that is at least divalent and which forms a metal-to-oxygen matrix on calcination, such as
Supports that can be used include TiO
2
, ZrO
2
, HfO
2
, MnO
2
, Fe
2
O
3
, Fe
3
O
4
, GeO
2
, SnO
2
, TlO
3
, Nb
2
O
5
, Ta
2
O
5
, SC
2
O
3
, La
2
O
3
, SiO
2
, and mixtures thereof. The preferred supports are MnO
2
, TiO
2
, ZrO
2
, Fe
2
O
3
, Fe
3
O
4
, and mixtures thereof as they have been found to work well. The support is 51 to 99 wt % of the catalyst weight, and preferably is 80 to 96 wt % of the catalyst weight.
The dopant is a compound that can place oxy anions into the support matrix during calcination. The oxy anions comprise an element that is at least divalent bonded to at least two oxygen atoms. Examples of suitable dopants include H
2
SO
4
, (NH
4
)
2
SO
4
, (NH
4
)HSO
4
, SO
3
, WO
3
, H
2
WO
4
, H
2
MoO
4
, (NH
4
)
2
WO
4
, (NH
4
)
2
MoO
4
, Mo(NO
3
)
6
, W(NO
3
)
6
, MoO
3
, H
3
PO
4
, (NH
4
)
3
PO
4
, (NH
4
)
2
HPO
4
, (NH
4
)H
2
PO
4
, Cr
2
O
3
, and mixtures thereof. The preferred dopants are WO
3
, H
2
SO
4
, (NH
4
)
2
SO
4
, Cr
2
O
3
, and mixtures thereof as they have been found to work well. The oxy anions are 1 to 49 wt % of the catalyst weight and are preferably 4 to 20 wt % of the catalyst weight. For example, about 10 to about 15 wt % H
2
WO
4
or about 5 to about 10 wt % H
2
SO
4
is preferably present in the catalyst when the support is zirconia.
Preparation and use of these catalysts for other purposes are known. See, for example, the following literature, herein incorporated by reference: Xuemin Song et al., “Sulfated Zirconia Based Strong Acid Catalyst: Recent Progress,” Catal. Rev. Sci. Eng. 38, 329-412 (1996); K. Tanabe et al., “Design of Sulfur Promoted Solid Superacid Catalyst,” Successful Design of Catalysts, 99-110, Elsevier Science Publications, T. Inui, editor, 1988; Kazushi Arata, “Solid Superacids,” Advances in Catalysis, 37 (1990), 165-211, especially pages 177-204; Tsutomu Yamaguchi, “Recent Progress in Solid Superacids,” Applied Catalysis, 61 (1990), 1-25, especially pages 12-23; and M. Misono et al., “Solid Superacid Catalysts,” Chemtech, November 1993, 23-29, especially pages 24-25. Many of the catalysts of this invention are commercially available and have been used for the acylation of aromatics with acids and acid halides (e.g., U.S. Pat. No. 5,126,489; M. Hino et al., “Acylation of Toluene with Acetic and Benzoic Acids catalyzed by a solid superacid in a Heterogeneous System” J. Chem. Soc. Chem. Comm. 1985,112-113; and K. Arata et al., “Benzoylation of Toluene With Benzoyl Chloride and Benzoic Anhydride Catalyzed by Solid Superacids on Sulfate Supported Alumina,” Applied Catalysis, 59 (1990) 197-204). They have also been used for the oligomerization of olefins (e.g., U.S. Pat. Nos. 5,191,139; 5,113,034; and 5,304,696), the alkylation of phenol (e.g., U.S. Pat. Nos. 4,236,033 and 5,304,688), and the akylation of aromatics with olefins (e.g., U. S. Pat. Nos. 5,243,115; 5,396,011; 5,516,954; and 5,563,311). The catalysts have been used for reactions which traditionally use Bronstead acid-Lewis acid combinations as catalysts, such as carbonylation of aromatics with carbon monoxide to form aromatic aldehydes (U.S. Pat. No. 5,679,867; T. H. Clingenpeel et al., “C
13
Study of the Carbonylation of Benzene with CO on Sulfated Zirconia,” J. Am. Chem. Soc. (1997), 119(23), 5469-5470) and the alkylation of aromatics with benzyl chlorides (K. Tanabe et al., “Benzylation of Toluene with Benzyl Chloride,” Proceedings of the 8
th
International Congress on Catalysis, Vol. 5, Verlag Chemie, Berlin (1984), pg 601; S. N. Koyande et al., “Reaction Kinetics of Benzene With Benzyl Chloride on Sulfate-Treated Metal Oxide Catalysts,” Ind. Eng.Chem. Res. (1998), 37, 908-913). Zirconium containing pentasil ad. (acidic) zeolites, where part of the alumina in the aluminosilicate matrix has been replaced with zirconia, have been used to isomerize chlorinated aromatics (e.g., U.S. Pat. No. 4,935,561) and have increased lifetime as compared to the non-zirconia containing pentasil zeolites.
The catalysts can be made by co

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