Background Art] Having been known as a useful intermediate capable of being applied to various fields, 1,2, 4-butanetriol is represented by the following Formula 1 Formula 1 The above compound has been used as, for example, an intermediate of an explosive and an intermediate of polyurethane and alkyd resins or the like, and, recently, has also been used as an important intermediate in medicine and agricultural medicine fields. Many technologies for producing 1,2, 4-butanetriol have been known, and conventional methods of producing 1,2, 4-butanetriol are as

follows: U. S. Pat. No. 3,629, 341 discloses a method of producing 1, 2,4-butanetriol, in which 1-methoxy-1, 3-butadiene as organic peroxide is epoxidated and hydrated at pH 1-2 using water of about 60-100 °C for the conversion into 3,4- dihydroxybutyl aldehyde, which is then is hydrogenated in the presence of a hydrogenation catalyst (Raney nickel, Raney cobalt, platinum, palladium, or copper-chromium oxides) to produce 1,2, 4-butanetriol. However, the above patent is undesirable in an economic aspect because relatively expensive 1- methoxy-1,3-butadiene and organic peroxides are used as a starting material.

Japanese Patent Laid-Open No. Sho. 59-70632 discloses a method of producing 1,2, 4-butanetriol, in which 2-butene-1, 4-diol is epoxidated and hydrogenated using a palladium-carbon catalyst. The above technology causes environmental pollution because a considerable amount of manganese dioxide should be used to decompose the excessive hydrogen peroxide after the epoxidation is finished, and is economically disadvantageous because a costly palladium catalyst is used for hydrogenation.

U. S. Pat. No. 4,410, 744 discloses a process of producing 1,2, 4-butanetriol, in which 2, 3-epoxy-1-propanol (glycidol) is subjected to a hydroformylation using a solvent and is then reduced in the presence of a hydrogenation catalyst, such as copper chromite. However, this patent is disadvantageous in that a starting material is high-priced and a plurality of steps is needed.

Meanwhile, U. S. Pat. No. 6,479, 714 discloses a method of producing 1,2, 4- butanetriol by reducing methyl dihydroxy butyric acid ester with a sodium borohydride catalyst. However, the method is disadvantageous in that a high production cost is needed since sodium borohydride is costly and must be added stoichiometrically, and a large amount of byproducts are generated.

U. S. Pat. No. 4,973, 769 discloses a process for producing 1,2, 4-butanetriol through catalytic hydrogenation of malic ester using a copper-containing catalyst.

Furthermore, European Pat. No. 0 297 444 discloses a method of producing

1,2, 4-butanetriol, in which an aqueous 2, 3-epoxy-1, 4-butanediol solution is hydrogenated in the presence of a Raney nickel catalyst in a batch reactor under 200-300 atm. The above method is problematic in that productivity is poor because the reaction is implemented in the batch reactor, and in that costly equipment is needed to conduct the reaction using the batch reactor under 200-300 atm.

As discussed above, in the above conventional technologies, various starting materials are used to produce 1,2, 4-butanetriol. However, the conventional technologies are undesirable in terms of economic efficiency and yield. Accordingly, a solution to the above problems is keenly needed.

[Detailed description of the Invention] [Technical Problem The present inventors have conducted extensive studies into solution of the problems described above, resulting in the finding that when a nickel-based catalyst having an improved metal surface area is packed in a continuous fixed-bed reactor to produce 1,2, 4-butanetriol from 2, 3-epoxy-1, 4-butanediol through continuous hydrogenation, an environmentally friendly and economically efficient process having high yield and productivity is achieved in comparison with the conventional techniques.

[Technical Solution Accordingly, an object of the present invention is to provide a method of producing 1,2, 4-butanetriol employing continuous hydrogenation, thereby solving problems encountered in the prior arts.

Another object of the present invention is to provide a method of producing 1,2, 4-butanetriol, in which 2, 3-epoxy-1, 4-butanediol having an epoxide moiety is used as a starting material for producing 1,2, 4-butanetriol while adopting catalytic and operation conditions suitable for the continuous hydrogenation of said epoxide,

thereby improving yield, productivity, and economic efficiency.

In order to accomplish the above objects, an embodiment of the present invention provides a method of continuously producing 1,2, 4-butanetriol. The method comprises feeding a liquid mixture comprising 2, 3-epoxy-1., 4-butanediol and a solvent into a continuous fixed-bed reaction system in which a nickel catalyst having a metal surface area of at least 3 m2/g is packed, and continuously hydrogenating the liquid mixture in a hydrogen (gas) atmosphere at conditions in which a reaction temperature is 10-250 C, a reaction pressure is 5-300 atm, and a liquid hourly space velocity (LHSV) is 0. 1-30 hr~l.

[Advantageous Effects] The present invention is advantageous in that 2, 3-epoxy-1, 4-butanediol having an epoxide moiety is used as a starting material for producing 1,2, 4- butanetriol while adopting catalytic and reaction conditions suitable for the continuous hydrogenation of said epoxide, thereby economically producing 1,2, 4- butanetriol at high yield and productivity.

[Best Mode for Carrying Out the Invention] The present invention may be achieved by the following description.

As described above, the present invention relates to a process in which a liquid mixture of 2, 3-epoxy-1, 4-butanediol and a solvent as a starting material are fed into a continuous reaction system and continuously converted into 1,2, 4- butanetriol as a target material under hydrogen atmosphere. According to the present invention, productivity and yield to a space time are high, a catalyst is repeatedly reused without an additional treatment process, it is easy to separate a product, and a continuous fixed-bed reaction system, which is capable of significantly simplifying the process, is adopted.

In the fixed-bed reaction system, the type of reactor and feeding and flowing directions of a reactant are not specifically limited. However, it is

preferable to use a trickle-bed reactor having a device which is capable of enabling the liquid reactant and hydrogen gas to simultaneously flow from an upper part of the reactor to a lower part of the reactor and uniformly dispersing the reactant throughout the reactor so as to ensure smooth contact between the reactants. This well-known trickle-bed reactor has a characteristic in which gas/liquid flows to a lower part of the reactor through a bed having catalyst particles packed therein while the catalyst particles are fixed.

Meanwhile, 2, 3-epoxy-1, 4-butanediol, which is used as the starting material in the present invention, is typically produced from 2-butene-1, 4-diol, and the production of 2, 3-epoxy-1, 4-butanediol may be exemplified by the following Reaction equation 1 (e. g. , cis type).

Reaction equation 1 In the present invention, 2, 3-epoxy-1, 4-butanediol as the reactant is fed in the form of a liquid mixture with a solvent into the continuous fixed-bed reaction system. In this regard, it is preferable that the solvent be an organic solvent which does not react with 2, 3-epoxy-1, 4-butanediol as the reactant or with the hydrogen gas. In the present invention, the solvent may be one or more selected from the group consisting of alcohols, such as methanol, ethanol, propanol, and isopropanol, and ethers, such as tetrahydrofuran (THF), dioxane, and diglyme. In this respect, preferably, 2, 3-epoxy-1, 4-butanediol is mixed with the solvent in a concentration of about 3-50 wt%, and more preferably, about 5-30 wt% based on a weight of the liquid mixture.

Meanwhile, according to the present invention, a catalyst for hydrogenation should hydrogenate the epoxy moiety in 2, 3-epoxy-1, 4-butanediol as the reactant, thereby producing 1,2, 4-butanetriol with high selectivity. Taking the above into consideration, a nickel-based catalyst is selected. In the preferable form of the nickel-based catalyst, inorganic oxide is used as a supporter or a binder. In the supported catalyst as described above, alumina, silica, zirconia, and titania may be used alone or in combination as inorganic oxide. In the catalyst using inorganic oxide as the supporter or binder, the nickel content is not specifically limited.

However, it is preferably at least about 5 wt%, and more preferably, about 5-80 wt%, based on the total weight of the catalyst.

According to the present invention, a metal surface area of the nickel-based catalyst is at least 3 m2/g, and preferably, at least 5 m2/g. When the metal surface area is less than 3 m2/g, it is unsuitable as a continuous hydrogenation catalyst because reactivity and selectivity are reduced. Herein, the"metal surface area" may be measured by a hydrogen adsorption method, which is disclosed in Journal of Catalysis 197, 210-219 (2001), which is incorporated in the present invention as a reference.

The catalyst may have any shape, including a sphere, cylinder, or granule.

However, it is preferable that the catalyst be formed in the shape of a sphere or cylinder so as to have desirable mechanical properties.

Meanwhile, the liquid reactant as described above is fed into the reaction system and then converted into 1,2, 4-butanetriol in the hydrogen atmosphere through hydrogenation. In this regard, it is important to control operation conditions so as to maximally suppress the generation of by-products and the reduction of conversion efficiency. Accordingly, it is preferable that reaction conditions be set to a temperature of about 10-250'C, a reaction pressure of about 5-300 atm, and a weight space velocity of about 0.1-30 her'1 (liquid mixture).

More preferably, the conversion is implemented under conditions of a reaction temperature of about 50-150 °C, a reaction pressure of about 10-200 atm, and a

weight space velocity of about 0.5-10 her 1 (liquid mixture). Most preferably, the conversion is implemented under conditions of a reaction temperature of about 60- 130°C, a reaction pressure of about 10-200 atm, and a weight space velocity of about 0.5-8 hr-1 (liquid mixture).

Furthermore, a molar ratio of hydrogen to 2, 3-epoxy-1, 4-butanediol is adjusted to at least 1 or more, and preferably, to about 1-10 in consideration of economic efficiency of the process.

The present invention is advantageous in that it is possible to separate products, which are exhausted from the fixed-bed reaction system after they are hydrogenated, using only a distillation operation without an additional catalyst filtration to recover desired target products, thus a recovery of the products is simplified after the reaction is finished.

[Mode for Carrying Out the Invention J A better understanding of the present invention may be obtained through the following examples and comparative examples which are set forth to illustrate, but are not to be construed as the limit of the present invention.

EXAMPLES 1 TO 4 AND COMPARATIVE EXAMPLE 1 4g of Na2WO4 2H20 was dissolved in 30 g of water, and mixed with 300 g of 2-butene-1, 4-diol. The 2-butene-1, 4-diol solution was agitated, and 390 g of aqueous hydrogen peroxide solution (concentration of 30 wt%) was slowly added thereto. The temperature was maintained at 60°C, and the reaction continued for 8 hours to produce 724 g of aqueous 2, 3-epoxy-1, 4-butanediol. solution.

724 g of the aqueous 2, 3-epoxy-1, 4-butanediol solution thus produced was mixed with 2200 g of isopropanol solvent to produce a reactant solution. The reactant solution was fed into a continuous fixed-bed reactor (manufactured by the inventors), in which a nickel/silica catalyst (nickel content of 30 wt%) having a

metal surface area of 24 m2/g was packed, and hydrogenated under conditions of a reaction temperature of 120 C, a reaction pressure of 90 atm, a liquid hourly space velocity (LHSV) of 4.0 hr-1, and a gas hourly space velocity (GHSV) of 500 hr-1, thereby being converted into 1,2, 4-butanetriol (Example 1).

Furthermore, the same reactant was hydrogenated under the same conditions except that the metal surface areas of the nickel-based catalyst were 11 m2/g (Example 2), 5 m2/g (Example 3), 4 m2/g (Example 4), and 2 m2/g (Comparative Example 1).

Conversion of 2, 3-epoxy-1, 4-butanediol and selectivity of 1,2, 4-butanetriol according to the hydrogenation are described in the following Table 1.

Table 1 Ni surface area of Conversion (%) Selectivity (%) the catalystim/g) Example 1 24 100. 0 96. 0 Example 2 11 95. 0 94. 5 Example 3 5 85. 3 92. 1 Example 4 4 80. 2 90. 4 Com. Exam. 1 2 70. 4 87. 1 From Table 1, it can be seen that larger nickel surface area of the catalyst brings about higher conversion of 2, 3-epoxy-1, 4-butanediol and higher selectivity of 1,2, 4-butanetriol. Particularly, when the nickel surface area is less than 3 m2/g (Comparative Example 1), the conversion is rapidly lowered and the selectivity is reduced relative to Examples 1 to 4.

EXAMPLES 5 AND 6 Hydrogenation was conducted through the same procedure as Example 1 except that ethanol (Example 5) and tetrahydrofuran (Example 6), respectively, were used as a solvent, and the results are described in the following Table 2.

Table 2 Example Solvent Conversion (%) Selectivity (%) Isopropanol 100. 0 96. 0 5 Ethanol 100. 0 95. 5 6 Tetrahydrofuran 100. 0 94. 5.

COMPARATIVE EXAMPLE 2 10 g of aqueous 2, 3-epoxy-1, 4-butanediol solution produced as in Example 1, 33 g of isopropanol, and 0.6 g of Raney-nickel were placed into a high pressure batch reactor, and then hydrogenated at a reaction temperature of 120 °C and a hydrogen pressure of 90 atm for 6 hours to produce 1,2, 4-butanetriol. The analysis results were that the conversion of 2, 3-epoxy-1, 4-butanediol was 100 % while the selectivity of 1, 2,4-butanetriol was 84 %.

COMPARATIVE EXAMPLE 3 10 g of aqueous 2, 3-epoxy-1, 4-butanediol solution produced as in Example 1,33 g of isopropanol, and 0.6 g of palladium-carbon (Pd content: 5 wt%) were placed into a high pressure batch reactor, and then hydrogenated at a reaction temperature of 120 °C and a hydrogen pressure of 90 atm for 5 hours to produce 1,2, 4-butanetriol. The analysis results were that the conversion of 2, 3-epoxy-1, 4- butanediol was 99.5 % and the selectivity of 1,2, 4-butanetriol was 70 %.

From the results of Comparative Examples 2 and 3, it can be seen that when 2, 3-epoxy-1, 4-butanediol having an epoxide moiety is used as the reactant, the conventional hydrogenation catalyst for producing 1,2, 4-butanetriol provides low selectivity, and thus it is difficult to apply to a commercial process. On the other hand, it can be seen that the nickel-based catalyst (particularly, the nickel- based catalyst having a metal surface area of at least 3 m2/g) according to the present invention exhibits excellent performance.

EXAMPLE 7 Hydrogenation was conducted through the same procedure as Example 1 except that a reaction temperature and a liquid hourly space velocity were respectively set to 90 °C and 3.0 hr-1, thereby producing 1,2, 4-butanetriol. The analysis results were that the conversion of 2, 3-epoxy-1, 4-butanediol was 100 % and the selectivity of 1,2, 4-butanetriol was increased to 99 %.

Industrial Applicability] As described above, the present invention is advantageous in that 2,3- epoxy-1, 4-butanediol having an epoxide moiety is used as a starting material for producing 1,2, 4-butanetriol while adopting catalytic and operation conditions suitable for the continuous hydrogenation of said epoxide, thereby economically producing 1, 2,4-butanetriol at high yield and productivity.

It should also be understood that the foregoing relates only to the scope of the invention as defined by the appended claims rather than by the description preceding them, and all changes that fall within scopes and bounds of the claims, or equivalence of such scopes and bounds are therefore intended to be embraced by the claims.