Use of a supported nickel-based catalyst in the selective hydrogenation of acetylenic difunctional compounds

Abstract

This invention discloses the application of a supported Ni-based catalyst in the selective hydrogenation of alkynyl difunctional compounds, belonging to the field of catalytic chemistry and organic synthesis technology. Addressing the technical problem of high cost and reliance on noble metal catalysts in existing hydrogenation processes for alkynyl difunctional compounds, this invention provides a solution using non-noble metal Ni as the active component. The alkynyl difunctional compounds have the general formula R1–C≡C–C≡C–R1, where R1 is selected from carboxyl, ester, or hydroxyl groups, specifically including adipynediic acid, adipynedi ester, and adipynediol. Under a hydrogen atmosphere, the supported Ni-based catalyst is used to catalytically hydrogenate these compounds, causing the carbon-carbon triple bond in the molecule to undergo hydrogenation transformation, resulting in highly selective formation of the corresponding saturated difunctional compounds, namely adipic acid, adipate ester, and hexanediol. Compared with existing technologies, this invention uses Ni, which is abundant in resources and low in cost, to replace precious metals. It has the advantages of low cost of catalytic materials, wide range of applicable substrates, mild reaction conditions and good process scalability. It provides an efficient and economical technical route for the construction of diyne intermediates from terminal alkyne small molecules via coupling, and then for the preparation of high-value-added C6 saturated difunctional compounds, and has good prospects for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of catalytic chemistry and organic synthesis technology, specifically relating to the application of a supported Ni-based catalyst in the selective hydrogenation of alkynyl difunctional compounds. More specifically, it relates to a method and its application for the selective hydrogenation conversion of alkynyl difunctional compounds containing carbon-carbon triple bonds under a hydrogen atmosphere, using a supported Ni-based catalyst as the catalytic material, thereby preparing the corresponding saturated difunctional compounds. Background Technology

[0002] Adipic acid, adipate esters, and hexanediol, among other C6 difunctional compounds, are important fine chemical intermediates and polymer monomers, widely used in polyesters, polyamides, polyurethanes, plasticizers, solvents, and pharmaceutical intermediates. Green Chem. Lett. Rev. , 2025, 18 (1), 2457497. Polym. Chem., 2016, 7 (46), 7039-7046.). With the development of green chemistry and sustainable synthesis, research on efficient, mild, and selective preparation methods for C6 difunctional compounds has received continuous attention. Among related synthetic routes, alkynyl difunctional compounds containing two carbon-carbon triple bonds are an important class of intermediates. These compounds usually have a regular C6 carbon skeleton and functional groups such as carboxyl, ester, or hydroxyl groups at both ends of the molecule. Since they contain both diacetylene bonds and difunctional structures, they can be directly converted into corresponding saturated difunctional compounds, such as adipic acid, adipic ester, and hexanediol, after hydrogenation. Therefore, constructing synthetic methods from unsaturated intermediates to target saturated C6 difunctional compounds through hydrogenation conversion of these diacetylene intermediates has clear application value. In addition, these alkynyl difunctional compounds containing diacetylene bonds are readily available and can be easily prepared from simple, relatively widely sourced alkynyl small molecules via coupling reactions. For example, propargyl acid or methyl propargylate can be readily converted into the corresponding C6 diacetylene intermediates, such as adackynediic acid or adackynediester, via Glaser-Hay coupling reaction. J. Org. Chem. , 2016, 81(24): 12520-4. Faraday Discuss. (2019, 220, 269-281). Therefore, starting with readily available C3 alkynyl raw materials, C6 dialkynyl skeletons are constructed by coupling, and then the corresponding saturated C6 difunctional compounds are prepared by hydrogenation conversion, which has good route connectivity and synthetic value (JP4505936B2).

[0003] In existing technologies, the hydrogenation conversion of alkynes or alkyne-functionalized compounds typically employs noble metal catalysts such as Pd, Pt, and Ru. ACS Catal., 2024, 14(4), 2463-72. Dalton Trans. (2017, 46, 12381-12403.). These catalysts typically exhibit high catalytic activity, but they also suffer from scarce metal resources, high prices, and significant costs for industrial application. For alkynyl difunctional compounds with a diyne structure and polar functional groups at both ends, the hydrogenation process involves not only the stepwise transformation of the carbon-carbon triple bond to a saturated carbon chain but also requires consideration of the stability of functional groups such as carboxyl, ester, or hydroxyl groups. Therefore, high demands are placed on the activity, selectivity, and applicability of the catalyst. Nat Commun ., 2025, 16, 9543.).

[0004] Ni, as a transition metal with abundant reserves and relatively low price, has a good foundation for application in hydrogenation reactions. Supported Ni-based catalysts have attracted attention in various hydrogenation systems due to their relatively mature preparation methods, low cost, and ease of scale-up. Coord. Chem. Rev. , 2024, 507: 215716. Sci. Adv., 2023, 9(48), eadj8225.). However, current research on selective hydrogenation of alkynyl difunctional compounds, especially substrates containing both dialkynyl bonds and difunctional structures, remains relatively limited. Differences in the electronic effects and adsorption behavior of functional groups in different substrates may lead to significant variations in hydrogenation activity, reaction rate, and product distribution. Therefore, it is still necessary to develop Ni-based catalytic systems and their application methods suitable for such substrates. In addition, alkynyl difunctional compounds can serve as important intermediates obtained by coupling alkynyl small molecules, and subsequent hydrogenation steps can be used to construct corresponding saturated C6 difunctional products, demonstrating good route connectivity and process expansion value.

[0005] In summary, developing a supported Ni-based catalyst system suitable for the selective hydrogenation of alkynyl difunctional compounds is of great significance for expanding non-precious metal catalytic hydrogenation technology, reducing the cost of catalytic materials, and enriching the preparation routes of related difunctional compounds. Summary of the Invention

[0006] The purpose of this invention is to provide an application of a supported Ni-based catalyst in the selective hydrogenation of alkynyl difunctional compounds, in order to solve the problems of the existing technology, such as strong dependence on noble metal catalysts, high catalytic cost, and relative lack of non-noble metal catalytic systems applicable to substrates containing diacetylene bonds and difunctional groups.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: The application described in this invention involves the catalytic hydrogenation reaction of alkynyl difunctional compounds having the following general formula under a hydrogen atmosphere using a supported Ni-based catalyst, resulting in the hydrogenation transformation of the carbon-carbon triple bonds in the molecule to obtain the corresponding saturated difunctional compounds: R1 is selected from carboxyl (-COOH), ester (-COOR), or hydroxyl (-CH2OH).

[0008] In this invention, the alkynyl difunctional compound is selected from at least one of adadiyndiic acid, adadiyndiate ester, or adadiyndiol.

[0009] The supported Ni-based catalyst is prepared by co-precipitation, impregnation, or deposition-precipitation. The catalyst support is selected from at least one of alumina, silica, titanium dioxide, zirconium oxide, mesoporous molecular sieves, activated carbon, carbon nanotubes, or graphitic carbon nitride. The Ni precursor is selected from at least one of nickel nitrate, nickel acetate, nickel sulfate, or their hydrates.

[0010] The supported Ni-based catalyst has a Ni loading of 0.5 wt.% to 40 wt.%. In one specific embodiment of the present invention, the Ni loading is 10 wt.%.

[0011] The hydrogenation reaction is carried out in a solvent selected from at least one of water, methanol, ethanol, isopropanol, tetrahydrofuran, ethyl acetate, or toluene.

[0012] The hydrogenation reaction temperature is 80~160℃, the hydrogen pressure is 0.2~8 MPa, and the reaction time is 0.5~48 h. In one specific embodiment of the present invention, the hydrogenation reaction temperature is 100℃ and the hydrogen pressure is 2 MPa.

[0013] Using the above method, when the substrate is adipynediic acid, the product obtained is adipic acid; when the substrate is adipynediate, the product obtained is adipate; and when the substrate is adipynediol, the product obtained is hexanediol.

[0014] Compared with the prior art, the present invention has the following significant advantages: First, this invention uses Ni, which is abundant and inexpensive, as the catalytic active component, replacing traditional precious metal catalysts such as Pd, Pt, and Ru, which significantly reduces the cost of catalytic materials and has good prospects for industrial application.

[0015] Secondly, the supported Ni-based catalyst provided by this invention exhibits good hydrogenation activity and extremely high selectivity (>99%) for diyne substrates containing different polar functional groups (carboxyl, ester, hydroxyl). It has a wide range of applicable substrates and can prepare high-value-added C6 saturated difunctional compounds (adipic acid, adipic ester, hexanediol) in one step.

[0016] Third, by optimizing the catalyst support, Ni precursor and reaction conditions (temperature, pressure and solvent), this invention can achieve efficient hydrogenation conversion under relatively mild conditions (such as 100°C, 2 MPa H2), with mild reaction conditions and strong process scalability.

[0017] Fourth, the alkynyl difunctional substrates involved in this invention can be easily prepared from widely available terminal alkyne molecules (such as propargyl acid and methyl propargyl ester) through coupling reactions, thus constructing a synthetic route from inexpensive raw materials to high-value products, which has the advantages of readily available raw materials, clear route and good process integration. Attached Figure Description

[0018] Figure 1 The images show electron micrographs of Ni-based catalysts on different supports, including a-Ni / ZrO2, b-Ni / SiO2, c-Ni / SBA-15, d-Ni / C, and e-Ni / g-C3N4. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0020] In the following examples, all reagents and raw materials used were commercially available products or could be prepared according to literature methods. Catalyst loadings refer to mass percentages (wt.%). Qualitative and quantitative analyses of the products were performed using gas chromatography (GC), high-performance liquid chromatography (HPLC), and nuclear magnetic resonance spectroscopy (NMR).

[0021] Example 1 Preparation method of supported Ni / Al2O3 catalyst Nickel nitrate hexahydrate was dissolved in deionized water to prepare an impregnation solution containing a Ni precursor. Alumina (Al₂O₃) support was weighed according to the set Ni loading amount and added to the impregnation solution. The solution was stirred and impregnated at room temperature for 12 h. After impregnation, the solution was dried at 80 °C for 24 h to obtain a solid precursor. The obtained precursor was then calcined at 400 °C for 6 h in air, followed by reduction at 300 °C for 2 h in hydrogen atmosphere to obtain a supported Ni / Al₂O₃ catalyst.

[0022] Example 2 Preparation method of supported Ni / SiO2 catalyst This embodiment illustrates the application of silica support in this invention. The preparation steps are basically the same as in Example 1, except that the alumina (Al2O3) support in Example 1 is replaced with a silica (SiO2) support to obtain a supported Ni / SiO2 catalyst.

[0023] Example 3 Preparation method of supported Ni / TiO2 catalyst This embodiment illustrates the application of titanium oxide support in this invention. The preparation steps are basically the same as in Example 1, except that the alumina (Al2O3) support in Example 1 is replaced with a titanium oxide (TiO2) support to obtain a supported Ni / TiO2 catalyst.

[0024] Example 4 Preparation method of supported Ni / ZrO2 catalyst This embodiment illustrates the application of the zirconia support in this invention. The preparation steps are essentially the same as in Example 1, except that the alumina (Al2O3) support in Example 1 is replaced with a zirconia (ZrO2) support, resulting in a supported Ni / ZrO2 catalyst.

[0025] Example 5 Preparation method of supported Ni / SBA-15 catalyst This embodiment illustrates the application of mesoporous molecular sieve support in this invention. The preparation steps are basically the same as in Example 1, except that the alumina (Al2O3) support in Example 1 is replaced with a mesoporous molecular sieve support. In this embodiment, the mesoporous molecular sieve used is SBA-15, resulting in a supported Ni / SBA-15 catalyst.

[0026] Example 6 Preparation method of supported Ni / C catalyst Nickel nitrate hexahydrate was dissolved in deionized water to prepare an impregnation solution containing a Ni precursor. Activated carbon support was weighed according to the set Ni loading amount and added to the impregnation solution. The solution was stirred and impregnated at room temperature for 12 h. After impregnation, the solution was dried at 80 °C for 24 h to obtain a solid precursor. The obtained precursor was then calcined at 300 °C for 6 h in an argon (Ar) atmosphere, followed by reduction at 300 °C for 2 h in a hydrogen atmosphere to obtain a supported Ni / C catalyst.

[0027] Example 7 Preparation method of supported Ni / CNTs catalysts This embodiment illustrates the application of carbon nanotube supports in this invention. The preparation steps are essentially the same as in Example 6, except that the activated carbon support in Example 6 is replaced with a carbon nanotube (CNT) support, resulting in a supported Ni / CNT catalyst.

[0028] Example 8 Preparation method of supported Ni / g-C3N4 catalyst This embodiment illustrates the application of graphite-phase carbon nitride support in this invention. The preparation steps are basically the same as in Example 6, except that the activated carbon support in Example 6 is replaced with a graphite-phase carbon nitride (g-C3N4) support, resulting in a supported Ni / g-C3N4 catalyst.

[0029] Example 9 Application of supported Ni / Al2O3 catalysts in the hydrogenation reaction of dimethyl adipynediate Dimethyl adipoxydimethyl ester (0.5 mmol) substrate, 1 mL solvent, and a supported Ni catalyst (equivalent to 1 mol% of the substrate molar amount) were added to a high-pressure reactor, with methanol as the solvent. After sealing the reactor, the air was replaced with an inert gas, followed by hydrogen purging. Hydrogen was then introduced to 2 MPa, and the reaction was carried out at 100 °C for 8 h. After the reaction was complete, the reactor was cooled to room temperature, the residual gas was released, the catalyst was separated by filtration, and the reaction liquid was collected. The reaction products were qualitatively and quantitatively analyzed by gas chromatography and nuclear magnetic resonance, and the results are listed in Table 1.

[0030] Examples 10-16 Application of supported Ni catalysts with different supports in the hydrogenation reaction of dimethyl adipynediate This set of examples illustrates the application of the supported Ni-based catalyst in the hydrogenation reaction of dimethyl adipynediol and compares the performance of different supported catalysts.

[0031] Dimethyl adipoxydimethyl ester (0.5 mmol) substrate, 1 mL solvent, and 1 mol% of supported Ni catalyst (using Ni / SiO2, Ni / TiO2, Ni / ZrO2, Ni / SBA-15, Ni / C, Ni / CNTs, and Ni / g-C3N4 from Examples 2-8, corresponding to Examples 10-16) were added to a high-pressure reactor, with methanol as the solvent. After sealing the reactor, the air was replaced with an inert gas, followed by hydrogen, and then hydrogen was introduced to 2 MPa. The reaction was carried out at 100°C for 8 h. After the reaction was completed, the reactor was cooled to room temperature, the residual gas was released, the catalyst was separated by filtration, the reaction liquid was collected, and the reaction products were qualitatively and quantitatively analyzed by gas chromatography and nuclear magnetic resonance. The results are listed in Table 1.

[0032] Examples 17-24 Application of supported Ni catalysts with different supports in the hydrogenation reaction of adipynediic acid This set of examples illustrates the application of the supported Ni-based catalyst in the hydrogenation reaction of adipynediic acid and compares the performance of different supported catalysts.

[0033] Adipynediic acid (0.5 mmol) substrate, 1 mL solvent, and 1 mol% of supported Ni catalyst (equivalent to 1 mol% of substrate molar amount) were added to a high-pressure reactor. The supported Ni catalysts were Ni / Al₂O₃, Ni / SiO₂, Ni / TiO₂, Ni / ZrO₂, Ni / SBA-15, Ni / C, Ni / CNTs, and Ni / g-C₃N₄ prepared in Examples 2-8, corresponding to Examples 17-24. Methanol was used as the solvent. After sealing the reactor, air was replaced with an inert gas, followed by hydrogen. Hydrogen was then introduced to 2 MPa, and the reaction was carried out at 100°C for 8 h. After the reaction, the reactor was cooled to room temperature, the remaining gas was released, the catalyst was separated by filtration, and the reaction liquid was collected. The reaction products were qualitatively and quantitatively analyzed by gas chromatography, liquid chromatography, and nuclear magnetic resonance. The results are listed in Table 1.

[0034] Examples 25-32 Application of supported Ni catalysts with different supports in the hydrogenation reaction of hexynediol This set of examples illustrates the application of the supported Ni-based catalyst in the hydrogenation reaction of hexynediol and compares the performance of different supported catalysts.

[0035] A substrate of hexanediol (0.5 mmol), 1 mL of solvent, and a supported Ni catalyst (equivalent to 1 mol% of the substrate molar amount) were added to a high-pressure reactor. The supported Ni catalysts were Ni / Al₂O₃, Ni / SiO₂, Ni / TiO₂, Ni / ZrO₂, Ni / SBA-15, Ni / C, Ni / CNTs, and Ni / g-C₃N₄, prepared in Examples 2-8, corresponding to Examples 25-32. Methanol was used as the solvent. After sealing the reactor, the air was replaced with an inert gas, followed by hydrogen. Hydrogen was then introduced to 2 MPa, and the reaction was carried out at 100°C for 8 h. After the reaction, the reactor was cooled to room temperature, the remaining gas was released, the catalyst was separated by filtration, and the reaction liquid was collected. The reaction products were qualitatively and quantitatively analyzed by gas chromatography and nuclear magnetic resonance. The results are listed in Table 1.

[0036] Table 1 Results of hydrogenation reactions in Examples 9-32 As shown in Table 1, the supported Ni catalysts prepared in this invention exhibit good catalytic hydrogenation activity for all three alkynyl difunctional substrates, with selectivity for all products exceeding 99%. The catalyst activity varies for different substrates. For example, Ni / Al₂O₃ and Ni / g-C₃N₄ show the best activity for dimethyl adipynediol; Ni / SiO₂ shows the highest conversion rate for adipynediol; and Ni / C and Ni / SBA-15 exhibit the most outstanding activity for adipynediol.

[0037] Examples 33-37 Effect of different reaction temperatures on hydrogenation reaction Dimethyl adipoxydiacetic acid was used as the substrate and a supported Ni / Al₂O₃ catalyst was used as the catalyst. The hydrogenation reaction was investigated at 80℃, 100℃, 120℃, 140℃, and 160℃ under the same substrate amount, catalyst amount, hydrogen pressure, reaction time, and solvent conditions. The products were analyzed after the reaction, and the results are listed in Table 2.

[0038] Table 2 Effect of reaction temperature on the hydrogenation performance of dimethyl adipynedianoate As shown in Table 2, reaction temperature has a significant impact on catalytic activity. At 80℃, the conversion rate is relatively low and the selectivity is slightly poor; when the temperature rises to 100℃, the conversion rate increases significantly to over 98%, and the selectivity reaches over 99%. Further increasing the temperature slightly improves the conversion rate, but the change is not substantial. Considering both energy consumption and reaction efficiency, 100℃ is the most suitable reaction temperature.

[0039] Examples 38-42 Effect of different hydrogen pressures on hydrogenation reaction Dimethyl adipoxydiacetic acid was used as the substrate and a supported Ni / Al₂O₃ catalyst was used as the catalyst. Under the same substrate amount, catalyst amount, reaction temperature, reaction time, and solvent conditions, the hydrogenation reaction was investigated at hydrogen pressures of 0.2 MPa, 1 MPa, 2 MPa, 4 MPa, and 8 MPa. The products were analyzed after the reaction, and the results are listed in Table 3.

[0040] Table 3 Effect of hydrogen pressure on the hydrogenation performance of dimethyl adipynediate As shown in Table 3, hydrogen pressure is a key factor affecting the reaction rate. At a low pressure of 0.2 MPa, the conversion rate is less than 20%. As the pressure increases to 2 MPa, the conversion rate rapidly increases to over 98%. Further increasing the pressure to 4 MPa or 8 MPa slightly improves the conversion rate, but places higher demands on the equipment. Therefore, 2 MPa is a suitable pressure that balances reaction efficiency and equipment cost.

[0041] Examples 43-48 Effect of different solvents on hydrogenation reaction Dimethyl adipoxydiacetic acid was used as the substrate and a supported Ni / Al₂O₃ catalyst was used as the catalyst. Under the same substrate amount, catalyst amount, reaction temperature, hydrogen pressure and reaction time, methanol, ethanol, isopropanol, tetrahydrofuran, ethyl acetate and toluene were used as reaction solvents for hydrogenation reactions. The products were analyzed after the reaction, and the results are listed in Table 4.

[0042] Table 4. Effects of different solvents on the hydrogenation performance of dimethyl adipynedioxyate. As shown in Table 4, solvent polarity has a significant impact on the hydrogenation reaction. In protic solvents such as methanol, ethanol, and isopropanol, the reactivity is high, with methanol showing the best effect. However, in nonpolar or weakly polar solvents such as tetrahydrofuran, ethyl acetate, and toluene, the conversion rate decreases significantly. This may be because polar solvents are more conducive to the dissolution of substrates and intermediates, as well as their interaction with the catalyst surface.

[0043] In summary, this invention provides an application of a supported Ni-based catalyst in the selective hydrogenation of alkynyl difunctional compounds. By constructing a supported Ni-based catalyst and optimizing conditions such as the support, reaction temperature, hydrogen pressure, and solvent, efficient and highly selective hydrogenation of substrates such as adipynediic acid, adipynediester, and adipynediol can be achieved under mild conditions, yielding high-value-added adipic acid, adipate ester, and hexanediol, respectively. This method features low-cost catalytic materials, a wide range of applicable substrates, and mild reaction conditions, demonstrating promising prospects for industrial application.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. The application of a supported Ni-based catalyst in the selective hydrogenation of alkynyl difunctional compounds, characterized in that, The alkynyl difunctional compounds have the following general formula: R1 is selected from carboxyl, ester, or hydroxyl groups; Under a hydrogen atmosphere, the supported Ni-based catalyst catalyzes the hydrogenation conversion of -C≡C- in the alkynyl difunctional compound to generate the corresponding saturated difunctional compound.

2. The application according to claim 1, characterized in that, The alkynyl difunctional compound is selected from one or more of hexadiynediol, hexadiynediester, or hexadiynediol.

3. The application according to claim 1, characterized in that, The supported Ni-based catalyst is prepared by co-precipitation, impregnation or deposition precipitation, and its support is selected from one or more of alumina, silica, titanium dioxide, zirconium oxide, mesoporous molecular sieve, activated carbon, carbon nanotubes or graphitic carbon nitride.

4. The application according to claim 1, characterized in that, The precursor of Ni in the supported Ni-based catalyst is selected from one or more of nickel nitrate, nickel acetate, nickel sulfate, or their hydrates.

5. The application according to claim 1, characterized in that, The Ni-based catalyst has a Ni loading of 0.5 wt.% to 40 wt.%.

6. The application according to claim 5, characterized in that, The Ni loading is 10 wt.%.

7. The application according to claim 1, characterized in that, The hydrogenation reaction is carried out in a solvent selected from at least one of water, methanol, ethanol, isopropanol, tetrahydrofuran, ethyl acetate, or toluene.

8. The application according to claim 1, characterized in that, The hydrogenation reaction temperature is 80~160℃, the hydrogen pressure is 0.2~8 MPa, and the hydrogenation reaction time is 0.5~48 h.

9. The application according to claim 8, characterized in that, The hydrogenation reaction temperature is 100℃ and the hydrogen pressure is 2MPa.

10. The application according to any one of claims 1 to 9, characterized in that, The saturated difunctional compound is adipic acid, adipic ester, or hexanediol.

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