Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Reexamination Certificate
2001-11-08
2004-08-24
Price, Elvis O. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
C570S101000, C570S143000, C570S144000, C570S151000, C570S190000, C570S202000
Reexamination Certificate
active
06781021
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a catalyst composition and a method for isomerizing halogenated aromatics. Particularly, the present invention relates to a catalyst and a method for isomerizing halogenated aromatics such as dichlorobenzene (DCB), chlorotoluene (CT) or dichlorotoluene (DCT), etc., for increasing m-DCB, m-CT, 2,6-DCT or 3,5-DCT.
DCB, one of halogenated aromatics, can be obtained by chlorinating benzene. However, since this reaction is strong in o-orientation and p-orientation, isomerization must be used when the m-isomer is necessary. Furthermore, the ratio of demand for respective DCB isomers is often different from the ratio of the respective isomers produced by chlorination. Therefore, also for effective utilization of DCB, a DCB isomerization method has an important technical significance.
When any one of respective DCB isomers or the m-DCB produced by isomerization is used alone, it must be separated.
Distillation as a method for separating isomers requires many rectifying columns since the respective isomers are close to each other in boiling point. Recently, Japanese Patent Publication (Tokko Hei) Nos. 1-12732 and 7-86092 disclose an adsorption separation method and a method of using adsorption separation and distillation in combination.
It is economically very important that the DCB isomers remaining after separating and removing the intended DCB isomer are re-used for isomerization reaction, to increase the concentration of the intended isomer. Subsequently the intended DCB isomer is separated and removed again, to repeat the cycle.
As a method for such isomerization reaction, Japanese Patent Publication (Tokko) No. 64-9972, etc. disclose a method of using acid type mordenite or a zeolite, the aperture of the largest pore of which comprises the 10-membered oxygen ring, as a catalyst. However, also for this method, it is industrially important to further improve isomerization activity.
CT can be obtained by chlorinating toluene. However, since this reaction is strong in o-orientation and p-orientation, isomerization must be used when the m-isomer is necessary. Furthermore, the ratio of demand for CT isomers is often different from the ratio of respective CT isomers produced by chlorination. Therefore, also for effective utilization of CT, a CT isomerization method has an important technical significance.
When any one of CT isomers or the m-CT produced by isomerization is used alone, it must be separated.
Distillation as a method for separating the isomers requires an ultraprecise rectifying column since the respective isomers are close to each other in boiling point, and cannot be said to be an industrial method. Recently, Japanese Patent Publication (Tokko) Nos. 63-24495 and 63-64412 disclose an adsorption separation method and a method of using adsorption separation and distillation in combination.
It is economically very important that the CT isomers remaining after separating and removing the intended CT isomer are subjected to isomerization reaction, to increase the concentration of the intended isomer again. Subsequently the intended CT isomer is separated and removed again, to repeat the cycle.
As a method for such isomerization reaction, Japanese Patent Publication (Tokko) No. 62-15050 discloses a method of using a zeolite, the aperture of the largest pore of which comprises the 10-membered oxygen ring, as a catalyst. However, also for this method, it is industrially important to further improve the isomerization activity.
Furthermore, in general, DCT is obtained by dichlorination of toluene. This reaction is a strongly oriented reaction, and the production ratio of the obtained isomers is 20 to 35% of 2,4-DCT: 25 to 55% of 2,5-DCT: 5 to 35% of 2,6-DCT: 8 to 12% of 2,3-DCT: 5 to 12% of 3,4-DCT. This reaction does not yield 3,5-DCT, and to obtain 3,5-DCT, DTC must be isomerized.
When any one of DCT isomers or 3,5-DCT produced by isomerization is used alone, it must be separated.
These isomers cannot be separated by distillation since they are close to each other in boiling point. So, for example, as disclosed in Japanese Patent Publication (Tokko) Nos. 1-45457 and 1-40016, the separation can be effected by an adsorption separation method or a method of using adsorption separation and distillation in combination.
It is very economically important that the DCT isomers remaining after separating and removing the intended DCT isomer are subjected to isomerization reaction again, to increase the concentration of the intended isomer. Subsequently the intended DCT isomer is separated and removed again, to repeat the cycle.
As a method for such isomerization reaction, Japanese Patent Publication (Tokko) Nos. 4-37054 and 37055 disclose a method of using a mordenite type zeolite (hereinafter called “mordenite”). However, also for this method, it is industrially important to further improve the isomerization activity.
If a zeolite-containing catalyst is used for isomerizing halogenated aromatics, the catalyst generally declines in performance with the lapse of time. So, the catalyst must be replaced by a new catalyst or regenerated by calcination, etc. at a proper time, and it is industrially very advantageous to prolong the life or regeneration period.
If these conventionally known isomerization catalysts can be further improved in activity, the reaction temperature can be lowered. If a catalyst is used for reaction, the catalytic activity declines, and it is generally practiced that to compensate the decline of activity, the reaction temperature is raised. Therefore, if the reaction temperature can be lowered, the catalyst can be used in a wider temperature range, and as a result, the catalyst life can be prolonged.
From the above points of view, the inventors studied intensively on the method for improving the catalytic activity, and as a result, found that if the maximum diameter of secondary particles of a zeolite in a formed catalyst is reduced, the catalytic activity in the reaction to isomerize halogenated aromatics can be improved, to achieve the present invention.
Furthermore, the inventors found that if the primary particle size of mordenite used as a zeolite for isomerizing DCT is reduced, the catalytic activity in the DCT isomerization reaction can be improved, to achieve the present invention.
Moreover, the inventors investigated the method for isomerizing halogenated aromatics, and as a result, found that if halogenated aromatics with a dissolved oxygen content of 15 wt ppm or less are used, the deactivation of the zeolite-containing catalyst can be inhibited, to prolong the life of the catalyst, for allowing efficient isomerization of halogenated aromatics.
OBJECTS OF THE INVENTION
An object of the present invention is to provide a catalyst composition with high halogenated aromatics isomerization activity.
Another object of the present invention is to provide a method for isomerizing halogenated aromatics, which can prolong the life or regeneration period of the catalyst.
Further other objects of the present invention will be clarified in the following description.
BRIEF DESCRIPTION OF THE INVENTION
The present invention achieves the above objects. The catalyst composition for isomerizing halogenated aromatics of the present invention is a catalyst composition for isomerizing halogenated aromatics, characterized in that the maximum diameter of secondary particles of the zeolite in the formed catalyst is 5 microns or less. The isomerizing catalyst composition of the present invention includes the following preferable embodiments.
(a) Said halogenated aromatics are compounds represented by the following general formula (I).
(where X1 stands for a halogen atom; X2, a hydrogen atom or halogen atom; and X3, a halogen atom or lower alkyl group).
(b) With a halogen atom selected as X1, a hydrogen atom as X2 and a halogen atom or methyl group as X3 in the general formula (I), the aperture of the largest pore of the zeolite comprises the 10-membered oxygen ring.
(c) Said halogenated aromatics are dichlorobenzene and chl
Iwayama Kazuyoshi
Kato Hajime
Kato Masashi
Okino Hirohito
Yamakawa Shinobu
Piper Rudnick LLP
Price Elvis O.
Toray Industries Inc.
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