Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2002-05-02
2004-03-16
Richter, Johann (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S861000
Reexamination Certificate
active
06706932
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for producing a diol mixture. More particularly, the present invention is concerned with a method for producing a diol mixture comprising 1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol, which comprises: (A) providing a dicarboxylic acid mixture comprising succinic acid, glutaric acid and adipic acid and having a nitric acid content which does not exceed a specific value, wherein the dicarboxylic acid mixture is prepared by denitrating an aqueous by-product solution obtained in an adipic acid production process, and (B) subjecting the dicarboxylic acid mixture to hydrogenation in the presence of water, hydrogen gas and a hydrogenation catalyst containing an active metal species comprising ruthenium and tin, to thereby obtain a hydrogenation reaction mixture comprising a diol mixture comprising 1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol. The method of the present invention for producing a diol mixture is advantageous not only in that an aqueous by-product solution (containing a dicarboxylic acid mixture comprising succinic acid, glutaric acid and adipic acid) obtained in an adipic acid production process can be used as a raw material for a useful diol mixture, but also in that a diol mixture comprising 1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol can be produced stably for a long period of time directly from the dicarboxylic acids by hydrogenation thereof, not through esterification thereof.
2. Prior Art
Diols are very important compounds which are widely used as raw materials for polyester resins, urethane foams, urethane coating materials, adhesives and the like in various industrial fields. Diols are commercially produced in large amounts. The production of diols is conducted mainly by a method which comprises subjecting a dicarboxylic diester to hydrogenation. Hereinbelow, an explanation is made with respect to the production of diols by this method involving hydrogenation of a dicarboxylic diester, taking production of 1,4-butanediol as an example.
As a method for producing 1,4-butanediol, a method is known in which two hydroxyl groups are introduced into n-butane to thereby produce 1,4-butanediol. This method is very disadvantageous from an economical view-point. Therefore, at present, it is virtually impossible to produce 1,4-butanediol on a commercial scale by the above-mentioned method. For this reason, at present, 1,4-butanediol is produced from n-butane by a method comprising: subjecting n-butane to air oxidation to produce succinic acid, maleic acid, succinic anhydride or maleic anhydride, especially maleic acid or maleic anhydride: and producing 1,4-butanediol from the thus produced acid or acid anhydride.
In general, a dicarboxylic acid, such as maleic acid, can be easily converted to a diol by a reduction reaction. In the reduction reaction, generally, an appropriate reducing agent is used. Usually, the reduction reaction of a dicarboxylic acid requires the use of a strong reducing agent having extremely high reactivity, such as lithium aluminum hydride. Special care must be taken in the handling and storage of such a strong reducing agent. Therefore, such a strong reducing agent is not suitable for use in the commercial scale production of a diol.
On the other hand, the so-called hydrogenation reaction, i.e., a reduction reaction performed using hydrogen gas as a reducing agent in the presence of an appropriate catalyst, is suitable for practice on a commercial scale. However, usually, the hydrogenation reaction cannot be applied to the reduction of a dicarboxylic acid. This is because the conventional catalyst used for hydrogenation is soluble in a dicarboxylic acid, so that the catalytic activity of the catalyst cannot be maintained in the presence of a dicarboxylic acid.
Therefore, at present, the production of 1,4-butanediol is performed by a method in which maleic acid or maleic anhydride obtained by air oxidation of n-butane is reacted with an appropriate alcohol to obtain a maleic diester, and the obtained maleic diester is subjected to a hydrogenation reaction in the presence of a copper-containing catalyst under high temperature and high pressure conditions, to thereby convert the diester to 1,4-butanediol.
The method for producing an alcohol by the hydrogenation of an ester in the presence of a copper-containing catalyst under high temperature and high pressure conditions is described in, for example, Japanese Patent Application prior-to-examination Publication (Kohyo) No. 2000-510837 (corresponding to U.S. Pat. No. 6,100,410), Japanese Patent Application prior-to-examination Publication (Kohyo) No. 2000-510475 (corresponding to U.S. Pat. No. 6,077,964), Japanese Patent Application prior-to-examination Publication (Kohyo) No. 2000-506134 (corresponding to U.S. Pat. No. 5,981,769), Unexamined Japanese Patent Application Laid-Open Specification No. 7-196558 (corresponding to U.S. Pat. No. 5,414,159) and U.S. Pat. No. 5,334,779.
However, in any of the methods of these patent documents, three steps (i.e., production of a dicarboxylic acid, esterification of the produced dicarboxylic acid, and hydrogenation of the produced ester) are required, so that the process for producing an alcohol inevitably becomes complicated. The complicated process poses a problem in that the process needs a number of apparatuses, such as an apparatus for the esterification of the dicarboxylic acid and an apparatus for separating, recovering and recycling an alcohol which is by-produced in the step for hydrogenation of the ester, wherein the alcohol is that which has been used in the esterification of the dicarboxylic acid.
As is understood from the above, the production of a diol by the hydrogenation of a diester is disadvantageous from the viewpoint of the production cost and the like. Therefore, various studies have been made with respect to the method for simplifying the process for producing a diol.
As an example of such a method, there can be mentioned a method in which a dicarboxylic acid (but not an ester thereof) is directly subjected to hydrogenation using a catalyst which can maintain its catalytic activity even in the presence of an acid, to thereby obtain a diol.
In this method, a diol can be obtained by a two-step process, i.e., a process comprising the steps of producing a dicarboxylic acid and then hydrogenating the produced dicarboxylic acid. In this method, esterification of a dicarboxylic acid (such esterification is required in the conventional process) is not required, so that an apparatus for the esterification is not required. Further, since this method does not involve esterification, this method is free from the problem that an alcohol (used in the esterification) is by-produced in the hydrogenation of the ester, and therefore this method does not need an apparatus for recovering and recycling the by-produced alcohol. As a result, the process for producing a diol can be simplified, and plant and equipment required for practicing the process can also be considerably simplified.
A number of proposals have been made with respect not only to catalysts for use in the hydrogenation of a dicarboxylic acid to produce a diol and but also to methods for producing a diol using such catalysts. Some of these proposals are concerned with technologies for producing 1,4-butanediol by the direct hydrogenation of succinic acid or maleic acid. In these technologies, usually, the hydrogenation is performed in the presence of water. Only the catalyst systems used in these technologies are enumerated below.
A catalyst comprising a ruthenium-iron oxide (U.S. Pat. No. 4,827,001);
a catalyst comprising a porous carbon having carried thereon ruthenium-tin, wherein the BET specific surface area (as determined by the application of the Brunauer-Emmett-Teller adsorption isotherm) of the porous carbon is 2,000 m
2
/g or more (Unexamined Japanese Patent Application Laid-Open Specification No. 5-246915);
a catalyst comprising silica having carried thereon ruthenium and tin,
Konishi Mitsuo
Ueno Eizaburou
Yokota Koshiro
Asahi Kasei Kabushiki Kaisha
Birch & Stewart Kolasch & Birch, LLP
Price Eluis O.
Richter Johann
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