Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2002-06-28
2003-04-22
Richter, Johann (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S832000
Reexamination Certificate
active
06552235
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method for producing cyclohexanol, and, more particularly, to an industrially useful improvement of the method for producing cyclohexanol by hydrating cyclohexene using a solid acid as a catalyst.
PRIOR ART
As methods for producing cycloalkanols by hydrating cycloolefins such as cyclohexene, methods which use solid acid catalysts such as strongly acidic ion exchange resins and zeolites as catalysts have been well known. A feature of these methods is that removal of the catalysts is easier as compared with removal of homogeneous system catalysts such as mineral acids, but these methods suffer from the problem of low yield. In order to improve the yield, it has been proposed to add various organic solvents or organic additives.
For example, JP-A-58-194828 proposes to add organic solvents such as alcohols of 1-10 carbon atoms, halogenated hydrocarbons, ethers, acetone and methyl ethyl ketone. JP-A-62-120333 and JP-A-62-126141 propose addition of phenols, JP-A-64-13044 proposes addition of fluoro-alcohols, JP-A-1-254634, JP-A-1-313447 and JP-A-4-247041 propose addition of aliphatic carboxylic acids, and JP-A-5-255162 proposes addition of benzoic acids. Moreover, JP-A-8-176041 proposes addition of benzoic acids having a substituent selected from the group consisting of alkoxy groups, aryloxy groups, alkylcarbonyl groups, arylcarbonyl groups, alkyloxycarbonyl groups, aryloxycarbonyl groups, aryl groups and arylalkyl groups. JP-A-9-263558 proposes addition of aromatic heterocyclic carboxylic acids. JP-A-7-247232 reports an effect exhibited by the coexistence with cycloalkanones, specifically, cyclohexanone. Furthermore, JP-A-9-249601 discloses a method in which a material having an action to enhance the distribution ratio of cycloalkenes into water is added alone or is allowed to coexist together with a material having an action to enhance the distribution ratio of cycloalkanols to organic layers, and it proposes addition of an alkylsulfonic acid or a heteropoly-acid in the former case and addition of an aromatic carboxylic acid, a phenol or a cyclic saturated carboxylic acid in the latter case. Moreover, in “Journal of Japan Chemical Society”, 1989, (3), p.521-527, it is reported that the reaction rate and equilibrium conversion rate increase due to the presence of phenol, benzyl alcohol and methyl ethyl ketone.
However, these methods of adding various organic additives still have various problems in industrial working, and none of these methods can solve all of the problems. In many cases, there are problems that the yield is still insufficient even when the organic additives are used, and the use of solvents (organic additives) in large amounts is necessary for the improvement of the yield. Further problems are that the organic additives react with the starting material cyclohexene or the product cyclohexanol in the hydration reaction system, and the organic additives per se are not stable under the hydration reaction conditions, whereby by-products resulting from the organic additives are produced so as to cause loss of the organic additives and reduction in purity of the product cyclohexanol.
For example, use of the benzoic acid proposed in JP-A-5-255162, etc. has the problem that an esterification reaction takes place with the product cyclohexanol. Another problem is that purification of the reaction mixture by distillation is difficult to perform owing to the sublimation of benzoic acid.
In the case of using acetic acid proposed in JP-A-1-313447, since cyclohexyl acetate is produced in a large amount, a method for recovering each of cyclohexene, cyclohexanol and acetic acid is separately needed, which is disadvantageous for industrial working.
Although the phenols proposed in JP-A-62-120333, JP-A-62-126141, etc. are effective as solvents for improving the yield of cyclohexanol, since the cyclohexanol produced and the phenol form an azeotropic composition (maximum azeotropic point), there is a problem that distillation separation of cyclohexanol and phenol is impossible in industrial working, and, furthermore, there is a problem that since the solubility of phenol in water is high, namely, 8.5%, a loss of solvent increases in industrial working as mentioned hereinafter.
Benzyl alcohol disclosed in “Journal of Japan Chemical Society”, 1989, (3), p.521-527 as a material having the effects of improving reaction rate and equilibrium conversion rate readily causes a hydration reaction under the hydration reaction conditions and is converted to dibenzyl ether, and, thus, the loss of solvent is great in industrial working. In addition, the above solvent effects cannot be obtained by dibenzyl ether and the effect of improving the conversion rate cannot be obtained.
Since cyclohexanone proposed in JP-A-7-247232 is somewhat lower in boiling point than the cyclohexanol to be produced, there will be a problem in distillation separation from cyclohexanol in industrial working. Furthermore, since cyclohexanone is also high in solubility in water, namely, 8.7%, there is a problem of an increase in loss of solvent in industrial practice.
On the other hand, new proposals have been made against these problems. For example, JP-A-9-286745 proposes to use a benzoic acid having a substituent on at least the 2-position as the organic additive to control esterification of the benzoic acid and the starting material cyclohexene. However, according to the examples in this patent publication, even when 2,6-dimethylbenzoic acid is used, complete inhibition of esterification thereof was not realized, and, further, the yield of cyclohexanol was only 14.7% by a batch reaction of 120° C.×1 hour using the additive in an amount of as large as 23 parts by weight. Thus, it cannot be said that a sufficient yield can be obtained.
JP-A-9-286746 proposes a method of using as an additive a cyclohexanecarboxylic acid having at least one substituent on the 1-, 2- or 6-position. According to the examples given therein, it is reported that the esterification can be inhibited by using 2-isopropylcyclohexanecarboxylic acid, but the yield of cyclohexanol is also only 13.6% by a batch reaction of 120° C.×1 hour using the additive in an amount of as large as 23 parts by weight. Thus, it cannot be said that a sufficient yield is obtained. Moreover, the organic additives used in these methods are extremely special ones.
On the other hand, for inhibiting deterioration of activity and for not deteriorating the performance of separation from the catalyst, JP-A-9-227429 and JP-A-9-227430 propose a method of feeding a solid organic additive in the molten state or as a solution to a reactor and a method of first contacting an aqueous slurry containing a solid acid catalyst with an organic additive in the presence of a cycloolefin. That is, in other words, it is suggested that the presence of the solid organic additive used in these methods has adverse effects of causing deterioration in catalyst activity with lapse of time and deterioration in separability of the catalyst in ordinary usage.
As mentioned above, the prior technologies as to the method of improving the yield of cyclohexanol by the addition of organic additives or solvents involve any one of the following problems in industrial practice.
1. The yield is still insufficient even when organic additive is used. Alternatively, a large amount of organic additive is necessary for improving the yield.
2. Impurities resulting from organic additive are produced in the hydration reaction system and the organic additive is lost with lapse of time, and, furthermore, the organic additive reacts with the starting material cyclohexene or the product cyclohexanol.
3. It is difficult to perform distillation separation between the organic additive per se or by-products resulting from the organic additive and the product cyclohexanol.
4. Deterioration of the activity of the hydration reaction catalyst is accelerated by the organic additive per se or by-products resulting from the organic additive.
5. The organic additive per se o
Kaneshima Tokitaka
Takamatsu Yoshikazu
Asahi Kasei Kabushiki Kaisha
Birch & Stewart Kolasch & Birch, LLP
Price Elvis O.
Richter Johann
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