1,2-hexanediol preparation using hydrotalcite-based catalysts and process for the preparation of 1,2-hexanediol in the presence of said catalysts

Abstract

The present invention relates to a hydrotalcite-based catalyst for preparing 1,2-hexanediol and a method for preparing 1,2-hexanediol in the presence of the catalyst, and more particularly, to a catalyst for converting 1,2-hexanediol in a high yield from a reactant, i.e., methylfurfural, a catalyst in which catalytically active metals in a specific combination are supported in a hydrotalcite support, and a method for preparing 1,2-hexanediol using the same.

Description

Technical Field

[0001] This invention relates to a hydrotalcite-based catalyst for the preparation of 1,2-hexanediol and a method for preparing 1,2-hexanediol in the presence of said catalyst. In particular, it relates to a catalyst for the selective preparation of 1,2-hexanediol from a reactant, namely methylfurfural, a catalyst in which hydrotalcite is selected as a support and a catalytically active metal of a specific metal combination is supported thereon, and a method for preparing 1,2-hexanediol in high yield using the catalyst. Background Technology

[0002] 1,2-hexanediol (C6H) 12 O2 is a colorless, water-soluble solid with a main chain containing six carbon atoms and hydroxyl groups on adjacent carbon atoms 1 and 2. It is used in the polymer industry as a polyester raw material and crosslinking agent, or in the cosmetics and personal care products industry as a moisturizer, antibacterial agent, and preservative. It is a high-value-added compound used in a variety of fields.

[0003] In recent years, 1,2-hexanediol has been prepared by reacting 1-hexene with hydrogen peroxide (Patent Documents 1, 2, 3). The advantage of this method is that it allows for the preparation of 1,2-hexanediol in a cost-effective and high-yield manner using hydrogen peroxide, a low-cost oxidant.

[0004] However, while 1-hexene, as a compound mainly obtained from petrochemical feedstocks, has the advantage of convenient supply, the demand for technology research and development using biomass platform compounds to replace petrochemical feedstocks has become increasingly prominent in recent years against the backdrop of intensified climate change and strengthened carbon neutrality policies. As an example, a method for preparing 1,2-pentanediol from biomass furfural as a feedstock has been reported in the presence of Rh / OMS-2 catalyst (Non-Patent Literature 1).

[0005] Currently, as an important technology for utilizing biomass, a method for preparing 1,2-hexanediol via the hydrogenation reaction of methylfurfural derived from biomass is under development, and catalysts for performing the related reaction are also being developed. However, there are no reports on the development of novel catalysts with higher selectivity for 1,2-hexanediol, or on methods for preparing 1,2-hexanediol using such catalysts, and therefore, further technological development is still needed.

[0006] Through long-term research on catalytic systems for the high-yield preparation of 1,2-hexanediol from biomass-derived feedstocks, the inventors confirmed that the reaction selectivity of 1,2-hexanediol can be improved by using a catalytic system containing a specific combination of catalytically active metals and a hydrotalcite support, thus completing this invention. Summary of the Invention

[0007] The purpose of this invention is to provide a hydrotalcite-based catalyst for the preparation of 1,2-hexanediol in high yield using methylfurfural derived from biomass as a reactant, and a method for preparing 1,2-hexanediol in the presence of said catalyst.

[0008] To address the aforementioned problems, the present invention provides a catalyst for the preparation of 1,2-hexanediol via the reaction of methylfurfural with hydrogen, characterized in that: the catalyst for the preparation of 1,2-hexanediol contains a catalytically active metal supported in a hydrotalcite of Formula 1. [Mg 1-x Al x (OH)2][(CO3 2- ) x / 2 ·nH2O [Chemical Formula 1] (In the aforementioned chemical formula 1, x satisfies 0.2≤x≤0.33, and n satisfies 0.33≤n≤1.) The catalytically active metal comprises a metal selected from the group consisting of ruthenium and nickel; and tin (Sn).

[0009] As an example of the present invention, the methylfurfural can be derived from biomass.

[0010] The tin content supported in the catalyst can be less than 20 wt%, preferably less than 10 wt%, more preferably less than 5 wt%, and most preferably in the range of 1 to 5 wt%.

[0011] As an example of the present invention, the catalyst can be used by reduction without calcination in an oxidizing atmosphere.

[0012] Furthermore, the present invention can provide a method for preparing 1,2-hexanediol in the presence of the hydrotalcite-based catalyst.

[0013] The method for preparing 1,2-hexanediol is characterized in that: 1,2-hexanediol is prepared by liquid-phase reaction of methylfurfural with hydrogen in the presence of a hydrotalcite-based catalyst, wherein methylfurfural is diluted in any solvent selected from 1-propanol, isopropanol, 1-butanol, 2-butanol, and mixtures thereof and the reaction is carried out in the liquid phase.

[0014] The present invention is characterized in that: when the reaction is carried out in the presence of the hydrotalcite-based catalyst, the temperature is 120~200℃, preferably 120~140℃, and the reaction pressure is 20~40 bar, preferably 20~30 bar.

[0015] According to the present invention, when using a catalytic system comprising a catalytically active metal and a hydrotalcite-based support containing a specific metal combination, it is effective in using biomass-derived methylfurfural as a reactant and preparing 1,2-hexanediol in high yield. Detailed Implementation

[0016] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art. Generally, the nomenclature used in this specification is that which is well-known and commonly used in the art.

[0017] Throughout this specification, when a part is described as "including" a certain element, unless otherwise expressly stated to the contrary, it does not mean that other elements are excluded, but rather that other elements may be included.

[0018] Next, the preparation of 1,2-hexanediol using a hydrotalcite-based catalyst and the method for preparing 1,2-hexanediol in the presence of the catalyst will be described.

[0019] The catalyst according to the present invention for the preparation of 1,2-hexanediol by the reaction of methyl furfural with hydrogen is characterized in that a specific combination of catalytically active metals is supported in a hydrotalcite of formula 1. [Mg 1-x Al x (OH)2][(CO3 2- ) x / 2 ·nH2O [Chemical Formula 1] (In the aforementioned chemical formula 1, x satisfies 0.2≤x≤0.33, and n satisfies 0.33≤n≤1.) The catalytically active metal comprises a metal selected from the group consisting of ruthenium and nickel; and tin (Sn).

[0020] Methylfurfural can be used to prepare 1,2-hexanediol and mixtures containing 1,2-hexanediol via a single-stage direct hydrogenation reaction, and the reaction yield of 1,2-hexanediol can be adjusted according to the activity of the catalyst used.

[0021] The methyl furfural can be a compound derived from biomass, specifically from hemicellulose. The main component of hemicellulose is xylan, which is hydrolyzed into xylose, a pentose sugar. Furfural can be easily obtained by dehydrating xylose.

[0022] The tin content supported in the catalyst can be less than 20 wt%, preferably less than 10 wt%, more preferably less than 5 wt%, and most preferably in the range of 1 to 5 wt%.

[0023] The catalytically active metal is preferably a heterogeneous catalytic system supported on a support. The present invention is characterized in that: the support is hydrotalcite of the following chemical formula 1.

[0024] [Mg 1-x Al x (OH)2][(CO3 2- ) x / 2 ·nH2O [Chemical Formula 1] (In the aforementioned chemical formula 1, x satisfies 0.2≤x≤0.33, and n satisfies 0.33≤n≤1.) The loading of the catalytically active metal relative to the hydrotalcite support is 8-12 wt%, preferably 9-11 wt%. When the loading of the catalytically active metal meets the above range, the optimal effect can be achieved between catalytic activity and loading.

[0025] The preparation method of the catalytic system in which the catalytically active metal is supported on a hydrotalcite support can be carried out either by impregnation or by other methods after the hydrotalcite has been formed in advance, or by co-precipitating the material used to prepare the hydrotalcite and the catalytically active metal precursor at the same time.

[0026] The type of tin precursor used as the catalytically active metal is not particularly limited. As an example, Sn(NO3)2, SnCl2, SnBr2, SnI2, Sn(OH)2, SnSO4, Sn(CH3COO)2, and Sn(CH3COCHCOCH3) can be used. 2、 One or more components can be selected from SnO, SnO2, and Sn3(PO)4.

[0027] The types of ruthenium and nickel precursors used as the catalytically active metals are not particularly limited. As an example, one or more of the following can be used: halogen salts, nitrates, carbonates, sulfates, nitrosylacetates, and nitrosylnitrates.

[0028] Furthermore, the present invention can provide a method for manufacturing the catalyst for the preparation of 1,2-hexanediol. As a method for manufacturing a catalyst for the preparation of 1,2-hexanediol comprising a metal selected from the group consisting of ruthenium and nickel, and a catalytically active metal of tin (Sn) supported on a hydrotalcite of formula 1, the method includes: a) preparing a hydrotalcite support dispersion solution by dispersing the hydrotalcite support in water or an organic solvent; b) adding a precursor selected from the group consisting of ruthenium precursor and nickel precursor, and a tin precursor as active ingredients to the hydrotalcite support dispersion solution, followed by stirring; c) obtaining a dried product by drying the solution after stirring in step b); d) obtaining a calcined product by calcining the dried product; e) obtaining a catalyst for the preparation of 1,2-hexanediol comprising a metal selected from the group consisting of ruthenium and nickel as the catalytically active metal, and tin (Sn) supported on a hydrotalcite of formula 1, by reducing the calcined product.

[0029] As an example of the present invention, step a) can be changed to step a') of preparing a solution of a precursor selected from the group consisting of ruthenium precursor and nickel precursor, and a tin precursor, which is used as a catalytically active metal, and step b) can be changed to dispersing the previously prepared hydrotalcite support of Formula 1 into the solution of the precursor selected from the group consisting of ruthenium precursor and nickel precursor, and the tin precursor, that is, the order of addition of the hydrotalcite support and the catalytically active metal can be changed.

[0030] Furthermore, as another example of the present invention, steps a) and b) can be performed simultaneously, thereby simultaneously introducing the precursor of the carrier and the active ingredient metal.

[0031] Furthermore, as an example of the present invention, the precursors of steps b) and b') can be directly added to the solutions of steps a) and a'), or the solutions can be added to the solutions of steps a) and a') after the precursors of steps b) and b') are dissolved in separate solvents respectively.

[0032] Furthermore, as another example of the present invention, the calcination in step d) can be omitted, and the process can proceed directly to step e).

[0033] Furthermore, the method for preparing the catalyst for the preparation of 1,2-hexanediol according to the present invention can also be achieved by co-precipitation, in addition to the aforementioned impregnation method. Another example of the catalyst preparation method of the present invention includes: i) preparing a support and a catalytically active metal precursor solution for quantitatively dissolving a precursor used to prepare the chemical formula 1 hydrotalcite, a precursor selected from the group consisting of a ruthenium precursor and a nickel precursor, and a tin precursor, in a solvent; ii) adjusting the pH of the support and catalytically active metal precursor solution; iii) aging the solution after pH adjustment in step ii) at a specific temperature; iv) drying the aging solution after precipitate filtration and selective washing; v) calcining the dried precipitate; and vi) reducing the calcined product.

[0034] As an example of the present invention, in step i), the precursors used to prepare the hydrotalcite of Formula 1 and the precursors selected from the group consisting of ruthenium and nickel precursors for use as catalytically active metals, as well as the tin precursor, can be simultaneously added to the solvent, or the solutions in which each precursor is dissolved separately can be mixed together to prepare the support and the catalytically active metal precursor solution. As for the mixing order at this time, the precursors selected from the group consisting of ruthenium and nickel precursors for use as catalytically active metals and the tin precursor can be mixed first, followed by the mixing of the precursors used to manufacture the hydrotalcite of Formula 1, or the mixing can be performed in the reverse order.

[0035] Furthermore, as another example of the invention, the precursors selected from the group consisting of ruthenium and nickel precursors, and the precursors for manufacturing the hydrotalcite of Formula 1, can be mixed first, and a tin precursor can be mixed therein; or the precursors for manufacturing the hydrotalcite of Formula 1, and the tin precursors, can be mixed therein, and a precursor selected from the group consisting of ruthenium and nickel precursors can be mixed therein; variations of other mixing sequences are also possible. However, in the case where step i) is not a single step but a sequential mixing, the pH adjustment in step ii) can be performed after the sequential mixing, and the aging in step iii) can be performed after the final mixing, or after the mixing of each step.

[0036] Furthermore, as another example of the present invention, the calcination step of v) can be omitted, thereby directly performing the reduction step of vi).

[0037] The ripening process in step iii) can be carried out by placing the food in a heated state or by placing it in a state without heating it separately.

[0038] The pH adjustment in step ii) can be performed using alkaline or acidic substances, preferably NaOH.

[0039] Furthermore, in step iv), the reduction step can be performed in the liquid phase using reducing agents such as hydrazine or NaBH4, or by performing a heat treatment process in a hydrogen environment. This is to control the dispersion and specific surface area of ​​the catalytically active metal, remove impurities from the catalyst itself, and improve the bonding force between the catalytically active metal and the support. Preferably, the treatment is carried out in a temperature range from room temperature to 500°C.

[0040] In the reduction step (vi), the metal present as a catalytically active metal may be completely reduced, or only partially reduced. For example, when ruthenium and tin are used as active metals, ruthenium may exist in a reduced metallic state, while a portion of tin may not be reduced, but rather exist in a state combined with oxygen, i.e., Sn. 2+ Sn 4+ They exist in states such as ruthenium and nickel. Furthermore, metals selected from the group consisting of ruthenium and nickel, which are catalytically active metals, can form alloys with each other.

[0041] Furthermore, the method for producing 1,2-hexanediol according to the present invention is characterized in that it is prepared by reacting methyl furfural with hydrogen in the presence of a catalyst containing a metal selected from the group consisting of ruthenium and nickel, and a catalytically active substance of tin, supported in a hydrotalcite carrier.

[0042] The methyl furfural can be a compound derived from biomass, specifically from hemicellulose. The main component of hemicellulose is xylan, which can be hydrolyzed into xylose, a pentose sugar. Methyl furfural can be easily obtained by dehydrating xylose.

[0043] The amount of hydrotalcite-based catalyst used in the preparation of 1,2-hexanediol is preferably 1 to 15 wt% relative to methylfurfural. If the catalyst content is less than 1 wt%, sufficient catalytic activity may not be achieved, while if the catalyst content exceeds 15 wt%, it may result in poor economic efficiency in terms of the catalytic activity improvement effect based on the catalyst content.

[0044] The reaction, carried out in the presence of the catalyst, can be performed in the liquid phase or the gas phase, preferably in the liquid phase.

[0045] As an example, the reaction temperature during the reaction in the presence of the catalyst is 120–200°C, preferably 120–140°C, and the hydrogen pressure is 20–40 bar, preferably 20–30 bar. If the hydrogen pressure is less than 20 bar, the reaction rate may be too slow, while if the hydrogen pressure exceeds 40 bar, the yield of 1,2-hexanediol may decrease as the yield of byproducts increases.

[0046] The reaction of the present invention can be carried out in the liquid phase, in which case methylfurfural reacts under conditions that maintain the liquid phase.

[0047] The methylfurfural can be diluted in a solvent capable of dissolving methylfurfural, and the solvent preferably comprises in the range of 25 to 100 wt% relative to the methylfurfural. Without limitation, the solvent can be an alcohol, GBL (gamma-butyrolactone), water, or mixtures thereof. The solvent is preferably an alcohol, more preferably 1-propanol, isopropanol, 1-butanol, 2-butanol, or mixtures thereof.

[0048] The alcohol solvent has high solubility for methylfurfural and does not contain highly reactive reaction sites, thus avoiding functional group changes or drastic chemical property changes due to reaction with hydrogen, thereby providing stable reaction conditions during the reaction process.

[0049] When the catalyst of the present invention, which contains a metal selected from the group consisting of ruthenium and nickel, and a catalytically active metal of tin (Sn) supported in a hydrotalcite support of the chemical formula 1, is used to perform the reaction of methylfurfural with hydrogen, the reaction yield of 1,2-hexanediol can be improved.

[0050] The reaction yield of the 1,2-hexanediol is preferably 75% or more, more preferably 85% or more, and most preferably 90% or more.

[0051] Next, preferred embodiments of the present invention will be described. For reference, the following embodiments are merely illustrative of one or more preferred embodiments of the present invention, and the present invention is not limited to these embodiments. Various modifications can be made within the scope of the present invention in the following embodiments.

[0052] <Example 1: Preparation of 10wt% 1Ni-1Sn / Hydrotalcite catalyst> Hydrotalcite was purchased and used from Sigma-Aldrich. The molar ratio of Ni to Sn was 1:1, and Ni(NO3)2·6H2O and SnCl4·5H2O were quantitatively loaded into hydrotalcite by impregnation after the total mass of Ni and Sn was 10 wt%. This yielded 1Ni-1Sn / hydrotalcite.

[0053] <Example 2: Preparation of 4.66wt% 1Ru-1Sn / Hydrotalcite catalyst> Except that RuCl3 was used instead of Ni(NO3)2·6H2O in Example 1, 1Ru-1Sn / hydrotalcite was prepared by the same method.

[0054] <Comparative Example 1: Preparation of 10wt% 1Ni-1Sn / ZnO catalyst> Except that ZnO was used instead of hydrotalcite in Example 1, 1Ni-1Sn / ZnO was prepared using the same method.

[0055] <Comparative Example 2: Preparation of 4.66wt% 1Ru-1Sn / ZnO catalyst> Except that RuCl3 was used instead of Ni(NO3)2·6H2O in Comparative Example 1, 1Ru-1Sn / ZnO was prepared by the same method.

[0056] <Experimental Example: Preparation of 1,2-hexanediol using the catalysts of the Examples and Comparative Examples> After preparing a 20 mL batch reactor system equipped with a temperature regulator, pressure regulator, and magnetic stirrer, 1.5 g (10 wt% of the feed) of the hydrotalcite-based catalyst of Examples 1 and 2, which had been reduced at 500°C for 6 hours prior to the reaction, or the ZnO-based catalyst of Comparative Examples 1 and 2, was added to a reactor containing 15 g of feed with an MF concentration of 10% (isopropanol (IPA) as solvent). After sealing the reactor system and heating it to a temperature of 120–140°C under an H2 pressure of 20–30 bar, the reaction was started while stirring at 500 rpm. The reaction was considered complete when the MF peak disappeared. The yield of the products, i.e., the reaction results, was determined by gas chromatography (GC) and recorded in Table 1 below.

[0057] Table 1

[0058] Referring to Table 1, the results of the methylfurfural conversion reaction performed in the presence of the Ni-Sn / hydrotalcite catalyst of Example 1 showed that the highest 1,2-hexanediol (1,2-HDO) yield was achieved at a stable pressure of 20 bar and a temperature of 130°C. Furthermore, when the pressure was increased to 30 bar to perform the methylfurfural conversion reaction in the presence of the Ni-Sn / hydrotalcite catalyst of Example 1, the reaction time was reduced by 11%, but the yield showed an equivalent or greater increase (0.6% p).

[0059] Furthermore, to compare the catalytic activity based on the type of hydrotalcite support, the conversion reaction was performed at 130°C and 30 bar in the presence of any one of the catalysts in Examples 1 and 2 and Comparative Examples 1 and 2. The catalysts of Examples 1 and 2, using hydrotalcite as the support, exhibited superior 1,2-hexanediol (1,2-HDO) yields compared to Comparative Examples 1 and 2, which used conventional ZnO-based supports. Moreover, the catalyst of Example 1, using Ni-Sn as the active metal, showed a higher 1,2-hexanediol (1,2-HDO) yield compared to the catalyst of Example 2, using Ru-Sn.

[0060] Furthermore, the gas chromatography (GC) results after the reaction was carried out under the aforementioned reaction conditions with the H2 pressure stably maintained at 20 bar and the temperature range of 120 to 200 °C are shown in Table 2 below.

[0061] Table 2

[0062] Referring to Table 2, the results of the reaction of the catalyst of Example 1 at a certain H2 pressure of 20 bar and a temperature range of 120~200°C showed that the highest yield of 1,2-hexanediol (1,2-HDO) was observed at a temperature of 130°C. From 130°C onwards, although the reaction time shortened as the reaction temperature increased, the yield of 1,2-hexanediol (1,2-HDO) showed a gradual decreasing trend.

[0063] In the foregoing description, the embodiments illustrated in the specification or accompanying drawings have been used to illustrate the present invention. However, these are merely exemplary embodiments, and those skilled in the art should understand that the invention can be implemented through various modifications and equivalent embodiments. Therefore, the scope of protection of the present invention should be defined in accordance with the appended claims.

Claims

1. A hydrotalcite-based catalyst for the preparation of 1,2-hexanediol, characterized in that: As a catalyst for the preparation of 1,2-hexanediol via the reaction of methylfurfural with hydrogen, The catalyst for the preparation of 1,2-hexanediol contains a catalytically active metal supported in a hydrotalcite of Formula 1. [Mg 1-x Al x (OH)2][(CO3 2- ) x / 2 ·nH2O [Chemical Formula 1] (In the aforementioned chemical formula 1, x satisfies 0.2≤x≤0.33, and n satisfies 0.33≤n≤1.) The catalytically active metal comprises a metal selected from the group consisting of ruthenium and nickel; and tin (Sn).

2. The water-based talc catalyst for the preparation of 1,2-hexanediol according to claim 1, characterized in that: The methylfurfural is derived from biomass.

3. The hydrotalcite-based catalyst for the preparation of 1,2-hexanediol according to claim 1, characterized in that: The tin content supported in the catalyst is 1~5wt%.

4. The hydrotalcite-based catalyst for the preparation of 1,2-hexanediol according to claim 1, characterized in that: The catalyst is used without calcination in an oxidizing atmosphere.

5. A method for preparing 1,2-hexanediol in the presence of a hydrotalcite-based catalyst, characterized in that: Under the condition that the preparation of 1,2-hexanediol according to any one of claims 1 to 4 is carried out in the presence of a hydrotalcite-based catalyst. 1,2-Hexanediol is prepared by the liquid-phase reaction of methylfurfural with hydrogen, wherein methylfurfural is diluted in any solvent selected from 1-propanol, isopropanol, 1-butanol, 2-butanol, and mixtures thereof and the reaction is carried out in the liquid phase.

6. The method for preparing 1,2-hexanediol in the presence of a hydrotalcite-based catalyst according to claim 5, characterized in that: The reaction temperature is 120~200℃, and the reaction pressure is 20~40 bar.

7. The method for preparing 1,2-hexanediol in the presence of a hydrotalcite-based catalyst according to claim 6, characterized in that: The reaction temperature is 120~140℃ and the reaction pressure is 20~30 bar.

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