SELECTIVE HYDROGENATION CATALYST AND SELECTIVE HYDROGENATION METHOD USING THE SAME

Abstract

The present invention relates to a RuPd bimetallic catalyst for use in hydrogenation of a compound, and more particularly to a catalyst prepared by loading both ruthenium and palladium on a g-C.sub.3N.sub.4 support and to a selective hydrogenation process of a pyridine group in a reaction system containing both a pyridine group and a benzene group using the catalyst.

Claims

1. A selective hydrogenation catalyst, in which ruthenium and palladium as active components are loaded on a g-C.sub.3N.sub.4 support such that a sum of weights of the active components is 0.1 to 15 wt % based on a total weight of the catalyst including the support and which is used to selectively hydrogenate a pyridine compound represented by Chemical Formula 2 below, rather than a benzene compound represented by Chemical Formula 1 below: ##STR00012## wherein, in Chemical Formulas 1 and 2, R is a hydrogen, a C.sub.1-C.sub.13 alkyl or cycloalkyl group, a C.sub.7-C.sub.13 arylalkyl group, C.sub.1-C.sub.13 alkyl alcohol, or C.sub.1-C.sub.13 alkylether.

2. The selective hydrogenation catalyst of claim 1, wherein a weight ratio (b/a) of the ruthenium (b) relative to the palladium (a) ranges from 0.25 to 10.

3. A method of preparing a selective hydrogenation catalyst, comprising: a) preparing a support solution by dispersing a g-C.sub.3N.sub.4 support in distilled water; b) preparing a catalyst precursor solution by adding the support solution with a ruthenium precursor and a palladium precursor such that a sum of weights of ruthenium and palladium as active components is 0.1 to 15 wt % based on a total weight of the catalyst including the support; and c) drying the catalyst precursor solution and then performing heat treatment in a hydrogen atmosphere.

4. The method of claim 3, wherein, in step b), a weight ratio (b/a) of the ruthenium (b) relative to the palladium (a) ranges from 0.25 to 10.

5. The method of claim 3, wherein, in step c), the heat treatment in the hydrogen atmosphere is performed at a temperature ranging from 250 to 500? C.

6. A selective hydrogenation method, comprising selectively hydrogenating a pyridine compound of Chemical Formula 2 below in a mixture of a benzene compound represented by Chemical Formula 1 below and the pyridine compound represented by Chemical Formula 2 using a RuPd/g-C.sub.3N.sub.4 catalyst in which ruthenium and palladium as active components are loaded on a g-C.sub.3N.sub.4 support so that a sum of weights of the active components is 0.1 to 15 wt % based on a total weight of the catalyst including the support and a weight ratio (b/a) of the ruthenium (b) relative to the palladium (a) ranges from 0.25 to 10: ##STR00013## wherein, in Chemical Formulas 1 and 2, R is hydrogen, a C.sub.1-C.sub.13 alkyl or cycloalkyl group, a C.sub.7-C.sub.13 arylalkyl group, C.sub.1-C.sub.13 alkyl alcohol, or C.sub.1-C.sub.13 alkylether.

7. The selective hydrogenation method of claim 6, wherein the benzene compound is at least one selected from among benzene, toluene, xylene, cyclohexyltoluene, diphenylmethane, benzyl alcohol, phenylethyl alcohol, methyl phenyl ether, and ethyl phenyl ether.

8. The selective hydrogenation method of claim 6, wherein the pyridine compound is at least one selected from among pyridine, methylpyridine, ethylpyridine, cyclohexyl methylpyridine, benzylpyridine, pyridinemethanol, pyridylethanol, methoxypyridine, and ethoxypyridine.

9. The selective hydrogenation method of claim 6, wherein a mass of the RuPd/g-C.sub.3N.sub.4 catalyst is 0.5 to 10 wt % based on a total weight of reactants that are used.

10. The selective hydrogenation method of claim 6, performed at a temperature ranging from 20 to 200? C.

11. The selective hydrogenation method of claim 6, performed at a pressure ranging from 1 to 100 bar.

12. A selective hydrogenation method, comprising selectively hydrogenating a pyridine group in a compound represented by Chemical Formula 3 below using a RuPd/g-C.sub.3N.sub.4 catalyst in which ruthenium and palladium as active components are loaded on a g-C.sub.3N.sub.4 support so that a sum of weights of the active components is 0.1 to 15 wt % based on a total weight of the catalyst including the support and a weight ratio (b/a) of the ruthenium (b) relative to the palladium (a) ranges from 0.25 to 10: ##STR00014## in Chemical Formula 3, Z represents hydrogen; a C.sub.1-C.sub.6 alkyl group; C.sub.1-C.sub.6 alkyl alcohol; C.sub.1-C.sub.6 alkylether; or ##STR00015## wherein Q is CH or N, R.sub.1 represents hydrogen, a C.sub.1-C.sub.6 alkyl group, C.sub.1-C.sub.6 alkyl alcohol, C.sub.1-C.sub.6 alkylether or ##STR00016## R.sub.2 represents hydrogen, a C.sub.1-C.sub.6 alkyl group, C.sub.1-C.sub.6 alkyl alcohol or C.sub.1-C.sub.6 alkylether, R.sub.3 represents hydrogen, a C.sub.1-C.sub.6 alkyl group, C.sub.1-C.sub.6 alkyl alcohol or C.sub.1-C.sub.6 alkylether, and X.sub.1 or X.sub.2 represents a single bond line; (CHR.sub.4).sub.n, wherein n is an integer of 1 to 3, and R.sub.4 is H, OH, or a C.sub.1-C.sub.6 alkyl group, C(?CH.sub.2), C(O); or N(R.sub.5), wherein R.sub.5 is hydrogen or a C.sub.1-C.sub.6 alkyl group.

Description

BRIEF DESCRIPTION OF DRAWING

[0040] FIG. 1 shows an electron microscopy image of a RuPd/g-C.sub.3N.sub.4 catalyst according to the present invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

[0041] Unless defined otherwise, all technical and scientific terms used in this specification have the same meanings as would be generally understood by those skilled in the related art to which the present invention pertains. In general, the nomenclature used herein is well known and commonly used in the art.

[0042] In the specification, when any portion includes any component, this means that the portion does not exclude other components but may further include other components unless otherwise stated.

[0043] According to the present invention, a selective hydrogenation catalyst is configured such that active components, namely ruthenium and palladium, are loaded on a g-C.sub.3N.sub.4 support so that the sum of weights of the active components is 0.1 to 15 wt % based on the total weight of the catalyst including the support, and exhibits activity for the selective hydrogenation of a pyridine compound represented by Chemical Formula 2 below in a mixture comprising a benzene compound represented by Chemical Formula 1 below and the pyridine compound represented by Chemical Formula 2.

##STR00005##

[0044] In Chemical Formulas 1 and 2, R is hydrogen, a C.sub.1-C.sub.13 alkyl or cycloalkyl group, a C.sub.7-C.sub.13 arylalkyl group, C.sub.1-C.sub.13 alkyl alcohol or C.sub.1-C.sub.13 alkylether.

[0045] The g-C.sub.3N.sub.4, which is an abbreviation of graphitic carbon nitride (graphite-phase carbon nitride), is a polymer material having a two-dimensional flat structure similar to graphene.

[0046] The sum of weights of ruthenium and palladium as the active components may fall in the range of 0.1 to 15 wt %, preferably 0.5 to wt %, and more preferably 2 to 8 wt % in terms of catalytic activity, based on the total weight of the catalyst including the support. If the amount of the active components is less than 0.1 wt %, active sites that show catalytic activity per unit area of the catalyst are not sufficiently exhibited. On the other hand, if the amount thereof exceeds 15 wt %, the extent of increase in the active sites due to the increase in the amount of the active components of the catalyst is insignificant, and thus an increase in the amount of loaded active components negates economic benefits.

[0047] In the active components, the weight ratio b/a of ruthenium b relative to palladium a falls in the range of 0.25 to 10, preferably 0.75 to 5, and more preferably 1 to 4, in order to maximize the selective hydrogenation activity.

[0048] If the weight ratio b/a of ruthenium relative to palladium is less than 0.25, the hydrogenation of the benzene group is still suppressed to thus induce selective hydrogenation of the pyridine group, but the absolute hydrogenation reduction rate of the pyridine group may decrease, attributable to a decrease in the activity of the catalyst. On the other hand, if the weight ratio b/a exceeds 10, the hydrogenation rate of the benzene group may increase, and thus the RuPd/g-C.sub.3N.sub.4 catalyst composite does not exhibit catalytic activity for selective hydrogenation of the pyridine group.

[0049] According to the present invention, a method of preparing the selective hydrogenation catalyst includes a) preparing a support solution by dispersing a g-C.sub.3N.sub.4 support in distilled water; b) preparing a catalyst precursor solution by adding the support solution with a ruthenium precursor and a palladium precursor so that the sum of weights of ruthenium and palladium as active components is 0.1 to 15 wt % based on the total weight of the catalyst including the support; and c) drying the catalyst precursor solution and then performing heat treatment in a hydrogen atmosphere.

[0050] In step b), the weight ratio b/a of ruthenium b relative to palladium a may range from 0.25 to 10.

[0051] The preparation of the g-C.sub.3N.sub.4 support may be performed through known methods, and is not particularly limited.

[0052] Specifically, the g-C.sub.3N.sub.4 support is dispersed in distilled water to give a support solution, after which the g-C.sub.3N.sub.4 support solution is added with a ruthenium precursor and a palladium precursor, thus preparing a catalyst precursor solution. Here, the addition temperature is not particularly limited, and may be room temperature. After the addition, the metal precursors and the g-C.sub.3N.sub.4 support may be stirred in order to realize uniform dispersion thereof.

[0053] In the active components, the kind of ruthenium precursor is not particularly limited, and is preferably selected from among ruthenium chloride, ruthenium acetylacetonate, ruthenium nitrosyl acetate, and ruthenium nitrosyl nitrate.

[0054] The kind of palladium precursor is not particularly limited, and is preferably palladium chloride or palladium nitrate, which is economical and has high loading efficiency.

[0055] Also, the aqueous solution in which the g-C.sub.3N.sub.4 support is dispersed and the palladium precursor and the ruthenium precursor are dissolved is dewatered, thereby yielding a g-C.sub.3N.sub.4 support on which the palladium precursor and the ruthenium precursor are loaded, which is then dried. Here, the drying process may be performed through heating and/or under reduced pressure, and is preferably conducted using a vacuum drying device.

[0056] Thereafter, the dried catalyst composite is subjected to heat treatment in a hydrogen atmosphere. Heat treatment is conducted in order to control the extent of dispersion of active metals and the specific surface area thereof, remove impurities from the catalyst, and enhance bonding force of the active metals and the support, and the heat treatment is preferably performed at 250 to 500? C.

[0057] In the present invention, the heat treatment in a hydrogen atmosphere is preferably carried out in a hydrogen/argon or hydrogen/nitrogen atmosphere, and the proportion of hydrogen in the hydrogen/argon or hydrogen/nitrogen gas mixture is preferably 5 to 100%. Here, 100% hydrogen means that hydrogen is used alone.

[0058] Also, the present invention pertains to a selective hydrogenation method, including selectively hydrogenating a pyridine compound represented by Chemical Formula 2 in a mixture of a benzene compound represented by Chemical Formula 1 and the pyridine compound represented by Chemical Formula 2 using the RuPd/g-C.sub.3N.sub.4 catalyst composite.

[0059] The hydrogenation rate of the pyridine group is preferably 75% or more, more preferably 80% or more, and most preferably 95% or more.

[0060] The benzene compound is preferably at least one selected from among benzene, toluene, xylene, cyclohexyltoluene, diphenylmethane, benzyl alcohol, phenylethyl alcohol, methyl phenyl ether, and ethyl phenyl ether, and the pyridine compound is preferably at least one selected from among pyridine, methylpyridine, ethylpyridine, cyclohexyl methylpyridine, benzylpyridine, pyridine methanol, pyridylethanol, methoxypyridine, and ethoxypyridine.

[0061] When the selective hydrogenation of the pyridine compound in the mixture comprising the benzene compound and the pyridine compound is carried out using the RuPd/g-C.sub.3N.sub.4 catalyst composite, the pyridine group is more selectively hydrogenated than the benzene group.

[0062] The benzene compound has high solubility with respect to the pyridine compound, and is maintained in a liquid phase at the hydrogenation temperature depending on the type of benzene compound. In the hydrogenation of the pyridine compound, the benzene compound is suitable for use as a solvent for dissolving the pyridine compound. Furthermore, the benzene compound does not contain reactive sites having high reactivity and does not cause changes in functional groups or drastic changes in chemical properties upon hydrogenation, and thus constant reaction conditions may be provided during the reaction process.

[0063] In the selective hydrogenation method, the RuPd/g-C.sub.3N.sub.4 catalyst is preferably used in an amount of 0.1 to 10 wt % based on the total weight of reactants that are used. If the amount of the RuPd/g-C.sub.3N.sub.4 catalyst is less than 0.1 wt %, the activity of the catalyst is not sufficiently exhibited. On the other hand, if the amount of the RuPd/g-C.sub.3N.sub.4 catalyst exceeds 10 wt %, economic benefits are negated in terms of enhancement of the activity of the catalyst depending on the amount of the catalyst.

[0064] The selective hydrogenation is preferably carried out at a temperature ranging from 20 to 200? C. and a pressure ranging from 1 to 100 bar.

[0065] According to the present invention, the selective hydrogenation catalyst may also be used as a catalyst for selective hydrogenation in a molecule. An embodiment of the present invention pertains to a selective hydrogenation method, including selectively hydrogenating a pyridine group in a compound represented by Chemical Formula 3 below using the RuPd/g-C.sub.3N.sub.4 catalyst.

##STR00006##

[0066] In Chemical Formula 3, Z represents hydrogen, a C.sub.1-C.sub.6 alkyl group, C.sub.1-C.sub.6 alkyl alcohol, C.sub.1-C.sub.6 alkylether or

##STR00007##

(wherein Q is CH or N), R.sub.1 represents hydrogen, a C.sub.1-C.sub.6 alkyl group, C.sub.1-C.sub.6 alkyl alcohol, C.sub.1-C.sub.6 alkylether or

##STR00008##

R.sub.2 represents hydrogen, a C.sub.1-C.sub.6 alkyl group, C.sub.1-C.sub.6 alkyl alcohol or C.sub.1-C.sub.6 alkylether, R.sub.3 represents hydrogen, a C.sub.1-C.sub.6 alkyl group, C.sub.1-C.sub.6 alkyl alcohol or C.sub.1-C.sub.6 alkylether, and X.sub.1 or X.sub.2 represents a single bond line, (CHR.sub.4).sub.n (wherein n is an integer of 1 to 3, and R.sub.4 is H, OH, or a C.sub.1-C.sub.6 alkyl group), C(?CH.sub.2), C(O), or N(R.sub.5) (wherein R.sub.5 is hydrogen or a C.sub.1-C.sub.6 alkyl group).

[0067] Upon the selective hydrogenation reaction using the RuPd/g-C.sub.3N.sub.4 catalyst, the compound represented by Chemical Formula 3 is subjected to selective hydrogenation of a pyridine group therein, thus obtaining a compound represented by Chemical Formula 4 below.

##STR00009##

[0068] When the compound of Chemical Formula 3 in which Z is

##STR00010##

and Q is N is hydrogenated using the RuPd/g-C.sub.3N.sub.4 catalyst, a compound represented by Chemical Formula 5 below may be obtained.

##STR00011##

[0069] In the following description of preferred embodiments of the present invention, detailed descriptions of known functions and components incorporated herein will be omitted when the same may make the subject matter of the present invention unclear.

[0070] Furthermore, descriptions of embodiments and drawings of the present invention disclosed herein are only for the purpose of illustration of the preferred embodiments of the present invention, and are not intended to represent all of the technical ideas of the present invention, and thus a variety of equivalents and modifications able to substitute therefor may be provided at the point of time of filing of the present invention.

[0071] Hereinafter, a detailed description will be given of a RuPd selective hydrogenation catalyst and a selective hydrogenation process using the same according to the present invention through the following examples and comparative examples, with reference to the appended drawing.

<Preparation Example> Preparation of RuPd/g-C.SUB.3.N.SUB.4 .Catalyst

[0072] 1) Preparation of g-C.sub.3N.sub.4 Support

[0073] 6 g of melamine and 372 mg of 2,4,6-triaminopyrimidine were mixed with 250 mL of ethanol and stirred at 100? C. for 16 hr. After stirring, vacuum drying was performed. 6 g of the dried carbon nitride precursor powder was mixed with 6.78 g of lithium chloride and 8.22 g of potassium chloride, followed by a condensation reaction using a tubular burning machine. Here, nitrogen gas was allowed to flow at a flow rate of 500 cc/min, and the temperature was elevated to 550? C. at a rate of 12? C./min and was maintained at 550? C. for 4 hr. The obtained brown powder was repetitively filtered with water at 90? C., thus removing both lithium chloride and potassium chloride. Thereby, g-C.sub.3N.sub.4 was yielded as the support.

[0074] 2) Preparation of 2.5 wt % Ru-2.5 wt % Pd/g-C.sub.3N.sub.4

[0075] 1 g of g-C.sub.3N.sub.4 was dispersed in 10 mL of distilled water. 69.7 mg of ruthenium chloride, corresponding to 2.5 wt %, and 68 mg of palladium nitrate, corresponding to 2.5 wt %, were dissolved in 2 mL of distilled water. Thereafter, the g-C.sub.3N.sub.4-dispersed solution was added with the metal precursor solution and stirred at room temperature for 30 min. Thereafter, vacuum drying was performed, followed by heat treatment in a hydrogen atmosphere using a tubular burning machine. Here, a 5 mol % hydrogen/argon gas was allowed to flow at a flow rate of 350 cc/min, and the temperature was elevated to 350? C. at a rate of 5? C./min and was then maintained at 350? C. for 3 hr. FIG. 1 shows a transmission electron microscopy image of the 2.5 wt % Ru-2.5 wt % Pd/g-C.sub.3N.sub.4 thus synthesized.

[0076] 3) Preparation of 2.5 wt % Ru-2.5 wt % Pd/Al.sub.2O.sub.3

[0077] 1 g of alumina was dispersed in 10 mL of distilled water. 69.7 mg of ruthenium chloride, corresponding to 2.5 wt %, and 68 mg of palladium nitrate, corresponding to 2.5 wt %, were dissolved in 2 mL of distilled water. Thereafter, the alumina-dispersed solution was added with the metal precursor solution and stirred at room temperature for 30 min. Thereafter, vacuum drying was performed, followed by heat treatment in a hydrogen atmosphere using a tubular burning machine. Here, a 5 mol % hydrogen/argon gas was allowed to flow at a flow rate of 350 cc/min, and the temperature was elevated to 350? C. at a rate of 5? C./min and was then maintained at 350? C. for 3 hr.

[0078] 4) Preparation of 2.5 wt % Ru-2.5 wt % Pd/C

[0079] 1 g of activated carbon was dispersed in 10 mL of distilled water. 69.7 mg of ruthenium chloride, corresponding to 2.5 wt %, and 68 mg of palladium nitrate, corresponding to 2.5 wt %, were dissolved in 2 mL of distilled water. Thereafter, the activated carbon-dispersed solution was added with the metal precursor solution and stirred at room temperature for 30 min. Thereafter, vacuum drying was performed, followed by heat treatment in a hydrogen atmosphere using a tubular burning machine. Here, a 5 mol % hydrogen/argon gas was allowed to flow at a flow rate of 350 cc/min, and the temperature was elevated to 350? C. at a rate of 5? C./min and was then maintained at 350? C. for 3 hr.

<Examples 1 to 3 and Comparative Examples 1 to 4> Selective Pyridine Reduction Depending on the Type of Catalyst

[0080] Selective pyridine reduction was conducted after adding 81.9 mmol pyridine, 81.9 mmol benzene, and a metal-loaded catalyst into a high-pressure reactor, without additional additives. As such, the amount of the metal-loaded catalyst was set such that the total mol of the metals in the catalyst was 0.4 mol % based on the total mol of benzene and pyridine.

[0081] The temperature was elevated to 150? C. for 45 min at a hydrogen pressure of 10 bar. After 45 min, the hydrogen pressure was increased to 40 bar and the reaction was carried out for 2 hr.

[0082] Table 1 below shows the results of measurement of hydrogenation conversion depending on the type of catalyst used for selective pyridine hydrogenation.

TABLE-US-00001 TABLE 1 conversion (%) Catalyst composition Pyridine Benzene Example 1 4 wt % Ru1 wt % Pd/g-C.sub.3N.sub.4 >99 5.4 Example 2 2.5 wt % Ru2.5 wt % Pd/g-C.sub.3N.sub.4 98.8 2.4 Example 3 1 wt % Ru4 wt % Pd/g-C.sub.3N.sub.4 75.7 2.0 Comparative 5 wt % Ru/g-C.sub.3N.sub.4 97.5 95.1 Example 1 Comparative 5 wt % Pd/g-C.sub.3N.sub.4 49.3 4.9 Example 2 Comparative 2.5 wt % Ru2.5 wt % Pd/Al.sub.2O.sub.3 85.6 33.7 Example 3 Comparative 2.5 wt % Ru2.5 wt % Pd/C >99 54.2 Example 4

[0083] As is apparent from Table 1, when comparing the results of hydrogenation conversion of Examples 1 to 3 with those of Comparative Examples 1 to 4, the selective hydrogenation rate of pyridine was increased under the condition that both Ru and Pd were loaded on g-C.sub.3N.sub.4. The reactivity varied depending on the wt % of RuPd. The total hydrogenation rate was increased with an increase in the amount of loaded ruthenium (Ru). The hydrogenation rates of pyridine and benzene were increased with an increase in the amount of loaded ruthenium, but the extent of increase thereof was W different, and thus the maximum selective hydrogenation rate of pyridine relative to benzene was present.

<Comparative Examples 5 to 8> Comparison with Commercially Available Catalyst Upon Selective Pyridine Hydrogenation

[0084] Selective hydrogenation was carried out using a commercially available catalyst under the same reaction conditions as in Example 1.

[0085] Table 2 below shows the results of measurement of hydrogenation conversion depending on the type of catalyst used for selective pyridine hydrogenation.

TABLE-US-00002 TABLE 2 Conversion (%) Catalyst composition Pyridine Benzene Example 1 2.5 wt % Ru2.5 wt % Pd/g-C.sub.3N.sub.4 98.8 2.4 Comparative 5 wt % Ru/Al.sub.2O.sub.3 >99 46.1 Example 5 Comparative 5 wt % Pd/Al.sub.2O.sub.3 0 0 Example 6 Comparative 5 wt % Ru/C >99 57.4 Example 7 Comparative 5 wt % Pd/C 45.2 1 Example 8

[0086] As is apparent from Table 2, the commercially available ruthenium (Ru) catalyst considerably facilitated the hydrogenation of benzene, thus significantly deteriorating the selective hydrogenation effect of the pyridine group compared to the present invention. Also, the palladium (Pd) catalyst was varied in reactivity depending on the type of support. The alumina support did not catalyze the hydrogenation, and the carbon support was allowed to selectively hydrogenate only pyridine, but exhibited low conversion.

[0087] Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.