Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Plural component system comprising a - group i to iv metal...
Reexamination Certificate
2000-11-13
2002-10-01
Padmanabhan, Sreeni (Department: 1621)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Plural component system comprising a - group i to iv metal...
C568S431000, C568S432000, C568S434000, C568S831000, C568S833000
Reexamination Certificate
active
06458737
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a catalyst for use in the oxidation of methylbenzenes, a process for producing aromatic aldehydes by use of said catalyst, and further a process for producing cyclohexanedimethanol from the phthalaldehyde so produced. More particularly, the present invention relates to a catalyst suited for the gas-phase oxidation of a methylbenzene in the presence of molecular oxygen to give the corresponding aromatic aldehyde in high yield, a process for oxidizing a methylbenzene in gaseous phase in the presence of molecular oxygen by use of said catalyst to produce the corresponding aromatic aldehyde in high yield, and further a process for hydrogenating the phthalaldehyde so produced to give cyclohexanedimethanol.
BACKGROUND ART
Aromatic aldehydes have highly reactive aldehyde groups and, among all aromatic compounds, are particularly broad in the spectrum of applicability. Terephthalaldehyde (TPAL), in particular, which has two aldehyde groups in para-positions, is a promising material to be exploited in the production of pharmaceutical products, agrochemicals, dyestuffs, liquid crystal polymers, electrically conductive polymers, and heat resistant plastics, among other uses, and there is a demand for development of an uncostly technology for the production of TPAL.
The first attempt to produce terephthalaldehyde by the gas-phase oxidation of p-xylene dates back to a fairly long time ago. Japanese Kokoku Publication Sho-47-2086 discloses an oxide catalyst composed of W and Mo in a ratio of 1:1 to 20:1. Japanese Kokai Publication Sho-48-47830 discloses a catalyst comprising V and either Rb or Cs. U.S. Pat. No. 3,845,137 discloses a catalyst composed of the two elements of W and Mo plus at least one element selected from the group consisting of Ca, Ba, Ti, Zr, Hf, Tl, Nb, Zn and Sn. U.S. Pat. No. 4,017,547 discloses a catalyst composed of Mo oxide, either W oxide or silicotungstic acid, and Bi oxide. U.S. Pat. No. 5,324,702 describes a special catalyst comprising Fe, Zn, V, Mo and W as supported by chemical vapor deposition (CVD) on deboronized borosilicate crystal molecular sieves.
However, these catalysts are invariably unsatisfactory in the production yield of the objective product terephthalaldehyde and none have been exploited with success on a commercial scale.
Furthermore, the investigations of the inventors proved that these catalysts lead to contain impurities causing the decrease in the yield of 1,4-cyclohexanedimethanol due to its low activity and its low selectivity for the objective compounds in hydrogenation of the obtained terephthalaldehyde.
Meanwhile, cyclohexanedimethanol is an industrially useful compound as a starting material for the production of polyester series coatings, synthetic fibers and synthetic resins, among other products.
The hitherto-known production technology for 1,4-cyclohexanedimethanol includes (1) the process starting with a dialkyl terephthalate which comprises hydrogenating the benzene ring of the dialkyl terephthalate ester and further hydrogenating the resulting 1,4-cyclohexanedicarboxylate dialkyl ester, (2) the process starting with terephthalic acid which comprises hydrogenating its benzene ring in the same manner as above and further hydrogenating the resulting 1,4-cyclohexanedicarboxylic acid, (3) the process which comprises hydrogenating the benzene ring of xylylene glycol, and (4) the process which comprises hydrogenating terephthalaldehyde.
The most representative of these processes is the process (1). However, the dialkyl terephthalate used as the starting material is synthesized by oxidizing p-xylene and esterifying the resulting terephthalic acid with an alcohol and in order to obtain the objective compound, the ester must be further subjected to two steps of hydrogenation. Thus, this process requires a multiple-reaction scheme.
In the process (2), where the starting material is terephthalic acid which can be obtained by oxidizing p-xylene, no esterification reaction is required but as pointed out in Japanese Kokai Publication Sho-52-242, the hydrogenation involves the use of a large amount of alcohol as the solvent, thus causing the disadvantage of low productivity.
Furthermore, in these processes, high-temperature, high-pressure conditions are required for the hydrogenation of the benzene ring and the carboxylic acid or its ester and, hence, the use of a special reaction equipment is essential. In addition, the copper chromite catalyst used in the later-stage reaction contains chromium which is poisonous so that a disposal problem is inevitable.
In these reactions, stoichiometrically 7 moles of hydrogen is required per mole of the substrate compound and, hence, a large amount of hydrogen is consumed. Furthermore, since 2 moles of alcohol is formed as a byproduct in the process (1) and 2 moles of water in the process (2), the amounts of starting materials required for unit production are also large. Therefore, these processes cannot necessarily be considered to be satisfactory from economic points of view.
Referring to said process (3), Japanese Kokai Publication Hei-8-187432, for instance, discloses, in the section of Example 7, a process for obtaining the objective compound cyclohexanedimethanol by hydrogenating the benzene ring of xylylene glycol using a novel hydrogenation catalyst, i.e. the Raney ruthenium catalyst, under mild conditions.
In this process, however, the starting material xylylene glycol is very expensive, and an inexpensive commercial production technology remains to be established as yet.
Japanese Kokai Publication Hei-11-335311, recently laid open for public inspection, discloses a process corresponding to said process (4), that is a one-step hydrogenation reaction process, which comprises hydrogenating the aldehyde groups and the benzene ring of terephthalaldehyde concurrently using a catalyst comprising metals of the group VIII of the long-form periodic table under defined relatively mild conditions.
This process requires hydrogenation of both the aldehyde groups and the benzene ring but stoichiometrically only 5 moles of hydrogen is required per mole of the substrate and there is no by-production of alcohol or water. In addition, the process does not require a catalyst containing a poisonous component.
However, in regard of this process, too, a commercial production technology for the starting material terephthalaldehyde has not been established as yet and the above patent literature does not allude to any specific procedure for producing terephthalaldehyde.
SUMMARY OF THE INVENTION
In view of the above state of the art, the present invention has for its object to provide a novel catalyst by use of which methylbenzenes can be oxidized in gaseous phase in the presence of molecular oxygen to give the corresponding aromatic aldehydes in high yields, a process for producing an aromatic aldehyde from the corresponding methylbenzene in a high yield by use of said catalyst, and a process for producing cyclohexanedimethanol which comprises hydrogenating phthalaldehyde among the aromatic aldehydes which can be obtained as above.
The inventors of the present invention made an intensive search for a novel catalyst with which an aromatic aldehyde may be produced in high yield by oxidizing the corresponding methylbenzene in gaseous phase in the presence of molecular oxygen and found that a catalyst having the composition described hereinafter or a catalyst comprising the catalyst active species as supported on a fire-resistant inorganic carrier has excellent partial oxidizing activity and that by using this catalyst, the object aromatic aldehyde can be produced in good yield. The inventors further found that by hydrogenating phthalaldehyde in particular, among the aromatic aldehydes which can thus be obtained, cyclohexanedimethanol can be produced with high efficiency. The present invention has its base on the above findings.
DETAILED DESCRIPTION OF THE INVENTION
The term “methylbenzene” is used herein to mean any compound having one or a plurality of methyl groups directly
Hashimoto Masashi
Kishimoto Nobuji
Nagamura Yusei
Nakajima Akiyoshi
Nakamura Isao
Nippon Shokubai Co. , Ltd.
Padmanabhan Sreeni
Witherspoon Sikarl A.
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