Selective catalytic hydrogenation of hexynediol to 2,5-dimethyl-2,5-hexanediol

Abstract

This invention discloses a method for the selective hydrogenation of 2,5-dimethyl-3-hexyn-2,5-diol to prepare 2,5-dimethyl-2,5-hexanediol, comprising: using 2,5-dimethyl-3-hexyn-2,5-diol as a raw material and Ru / rGO as a catalyst, carrying out a catalytic reaction in a solvent under hydrogen pressure of 0.5-3 MPa and temperature of 30-120℃ to obtain 2,5-dimethyl-2,5-hexanediol; Ru / rGO comprises reduced graphene oxide support and active component Ru, and the mass ratio of active component Ru to reduced graphene oxide support is 0.9-5:100. The catalyst of this invention can effectively suppress the hydrogenolysis reaction of hydroxyl groups during the hydrogenation process, achieving a conversion rate of up to 100% and a yield of 2,5-dimethyl-2,5-hexanediol of over 99.8%, demonstrating significant industrial application value.

Description

Technical Field

[0001] This invention relates to the field of 2,5-dimethyl-2,5-hexanediol preparation technology, specifically to a method for the selective catalytic hydrogenation of hexynylene glycol to prepare 2,5-dimethyl-2,5-hexanediol. Background Technology

[0002] 2,5-Dimethyl-2,5-hexanediol is a white, flaky or powdery solid, odorless, readily soluble in water, with a melting point of 87-89℃ and a boiling point of 214-215℃. Its molecular formula is C8H12H2O. 18 O2 is an important organic chemical raw material and fine chemical product, widely used in pyrethroid pesticides, bexarotene antitumor drugs, fragrances, artificial musk, polyethylene plastic crosslinking agents, and as a basic raw material for polyether rubber and silicone rubber bis(2,5) vulcanizing agents. It is also widely used as an intermediate in plastics, rubber, adhesives, organic peroxides, and defoamers. Furthermore, it is a key monomer in the synthesis of biodegradable plastics such as polyhydroxyalkanoates and photoresists.

[0003] Currently, the main industrial production processes for 2,5-dimethyl-2,5-hexanediol include photocatalysis and acetone-hexyne condensation hydrogenation.

[0004] Photocatalysis uses noble metal-supported nano-semiconductor materials, such as Pt / TiO2, as catalysts to selectively oxidize tert-butanol to 2,5-dimethyl-2,5-hexanediol under ultraviolet or visible light irradiation. This method has advantages such as simple process and high catalyst stability, but the product yield is low (23%), making it unsuitable for industrial production.

[0005] The acetone-hexyne condensation hydrogenation process is currently the mainstream industrial production process. This process first involves the condensation of acetylene and acetone to produce 2,5-dimethyl-3-hexyne-2,5-diol (hexynediol for short), and then hydrogenation of saturated alkyne bonds under the condition of a metal catalyst to obtain the final product 2,5-dimethyl-2,5-hexanediol (hexanediol for short).

[0006] The present invention aims to develop a catalytic reaction process for the catalytic hydrogenation of 2,5-dimethyl-3-hexyne-2,5-diol to synthesize 2,5-dimethyl-2,5-hexanediol.

[0007] Patent specification CN1074209A discloses a three-stage hydrogenation reaction to obtain 2,5-dimethyl-2,5-hexanediol in a high-pressure reactor using 0.5-1 wt% Raney Ni catalyst and ethanol as solvent. The first stage has a pressure of 0-2.0 MPa, a reaction temperature of 30-150℃, and a hydrogenation time of 2-3 hours; the second stage has a pressure of 2.0-4.6 MPa, a reaction temperature of 150-160℃, and a hydrogenation time of 1-2 hours; the third stage has a pressure of 4.6-5.5 MPa, a reaction temperature of 160-180℃, and a hydrogenation time of 5-7 hours. This process is complex, produces low-quality products, and consumes a lot of energy, making it unsuitable for industrial production.

[0008] Patent specification CN114956958A discloses a method for the catalytic hydrogenation of unsaturated alcohols. The method uses 2,5-dimethyl-3-hexyne-2,5-diol and hydrogen as raw materials, Pd / C with a mass fraction of 5% and a water content of 10% as a catalyst, and isopropanol as a solvent. The catalytic hydrogenation reaction is carried out under stirring conditions at a stirring speed of 200-800 rpm, a hydrogen pressure of 0.4-2.0 MPa, and a reaction time of 1-10 h. The conversion rate of the raw materials is 99.4%, and the purity of the 2,5-dimethyl-2,5-hexanediol product is 98.5%. However, this process has a long reaction time and poor product yield.

[0009] Patent specification CN109574806A discloses a method for catalytic hydrogenation to prepare hexanediol using a continuous flow fixed-bed reactor. This method replaces the traditional batch reactor with a fixed-bed reactor, using a supported Ni-based catalyst, water as a solvent, a reaction temperature of 60–120°C, and a hydrogen pressure of 1–3 MPa. The process efficiently converts 2,5-dimethyl-3-hexyn-2,5-diol to 2,5-dimethyl-2,5-hexanediol, achieving an optimal product yield of 92.8%. However, this process suffers from drawbacks such as cumbersome catalyst preparation and significant batch-to-batch variations in catalyst stability.

[0010] Patent specification WO2020111496A1 discloses a method for synthesizing 2,5-dimethyl-3-hexyn-2,5-diol. In a high-pressure reactor, ethyl acetate is used as the solvent, hydrogen pressure is 1 MPa, and hydrogenation is carried out at room temperature using a 1 mol% Pd / C catalyst for 12 h, yielding 84% 2,5-dimethyl-2,5-hexanediol. This process suffers from drawbacks such as high solvent cost and low product yield.

[0011] It can be seen that existing processes for the catalytic hydrogenation of 2,5-dimethyl-3-hexyne-2,5-diol to synthesize 2,5-dimethyl-2,5-hexanediol generally suffer from drawbacks such as harsh reaction conditions, high reaction temperatures, and, in particular, low reaction yields. This is mainly because, in addition to the main reaction of alkyne hydrogenation, the hydrogenation process also involves side reactions such as olefin hydrogenation and hydroxyl hydrogenolysis. The reaction mechanism diagram is shown below. Figure 1 As shown: In the catalytic hydrogenation of 2,5-dimethyl-3-hexyn-2,5-diol (I), the alkyne is first added to form an alkene, generating 2,5-dimethyl-3-hexen-2,5-diol (II). The alkene can be further hydrogenated to generate the target product 2,5-dimethyl-2,5-hexanediol (III), but the hydroxyl group may also be removed by hydrogenolysis to generate intermediate (V). Intermediate (V) can further undergo hydrogenolysis to generate intermediate (VI), the alkene can be hydrogenated alone to generate intermediate (IV), or both can occur simultaneously to generate intermediate (VII). Summary of the Invention

[0012] Based on the above mechanism, this invention develops a novel ruthenium (Ru)-based hydrogenation catalyst supported on graphene (rGO) for the selective hydrogenation of 2,5-dimethyl-3-hexyn-2,5-diol (I) to 2,5-dimethyl-2,5-hexanediol (III). Through the large π bonds of the graphene support, the substrate 2,5-dimethyl-3-hexyn-2,5-diol (I) and the intermediate 2,5-dimethyl-3-hexen-2,5-diol (II) are selectively adsorbed, forming π-π conjugation. This effectively suppresses the adsorption of hydroxyl groups around the hydrogenation active sites, thereby inhibiting the hydrogenolysis reaction and improving reaction selectivity.

[0013] This invention provides a method for the selective hydrogenation of 2,5-dimethyl-2,5-hexanediol (I) to prepare 2,5-dimethyl-2,5-hexanediol, using Ru supported on reduced graphene oxide as a catalyst, wherein the active component Ru exists in the form of nanoparticles. This catalyst can effectively suppress the hydrogenolysis of hydroxyl groups during the hydrogenation process, achieving a conversion rate of up to 100% and a yield of over 99.8% of 2,5-dimethyl-2,5-hexanediol, demonstrating significant industrial application value.

[0014] The specific technical solution is as follows: A method for selectively hydrogenating 2,5-dimethyl-3-hexyn-2,5-diol to prepare 2,5-dimethyl-2,5-hexanediol includes: using 2,5-dimethyl-3-hexyn-2,5-diol as a raw material and Ru / rGO as a catalyst, carrying out a catalytic reaction in a solvent under hydrogen pressure of 0.5-3 MPa (e.g., 0.7 MPa, 1 MPa, 1.5 MPa, 2 MPa, 2.5 MPa, etc.) and temperature of 30-120℃ (e.g., 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, etc.) to obtain 2,5-dimethyl-2,5-hexanediol; The Ru / rGO comprises a reduced graphene oxide support and an active component Ru, wherein the mass ratio of the active component Ru to the reduced graphene oxide support is 0.9-5:100, such as 1:100, 2:100, 2.5:100, 2.6:100, 2.7:100, 2.8:100, 2.9:100, 3:100, 4:100, 4.5:100, 4.8:100, 4.9:100, etc., preferably 2.9-3:100.

[0015] The preferred mass ratio of 2,5-dimethyl-3-hexyn-2,5-diol to Ru / rGO is 1:0.002-0.05, such as 1:0.005, 1:0.01, 1:0.02, etc.

[0016] The solvent preferably includes water and / or an alkaline low-carbon alcohol. The alkaline preferably includes KOH. The low-carbon alcohol preferably includes methanol. The mass concentration of the alkaline in the alkaline low-carbon alcohol is preferably 0.2%.

[0017] The preferred mass ratio of the solvent to 2,5-dimethyl-3-hexyn-2,5-diol is 3-19:1, for example, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, etc.

[0018] The preferred time for the catalytic reaction is 1-12 h, such as 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, etc.

[0019] Furthermore, the conversion rate of the catalytic reaction is 100%, and the yield of 2,5-dimethyl-2,5-hexanediol is above 99.8%.

[0020] The preferred method for preparing Ru / rGO includes: adding RuCl3 and NaBH4 to an aqueous dispersion of graphene oxide, stirring until fully reacted, allowing it to stand, then separating the solid and liquid, washing and drying the solid to obtain Ru / rGO.

[0021] In the preparation method of Ru / rGO, the molar ratio of NaBH4 to RuCl3 is preferably 49~51:1.

[0022] In the Ru / rGO preparation method, the temperature for thorough stirring and reaction is room temperature, such as 25°C, and the time is 7-9 h, such as 8 h.

[0023] The graphene oxide in the aqueous dispersion is preferably prepared by a modified Hummers method, which specifically includes: adding graphite powder, K2S2O7 and P2O5 sequentially to sulfuric acid under reflux and stirring at 80-90℃, keeping the mixture warm and stirring for 4-6 hours (e.g., 4.5 hours), then naturally cooling to room temperature, adding deionized water for dilution, letting it stand overnight, separating the solid and liquid, washing and drying the solid to obtain graphene oxide.

[0024] In the modified Hummers process, preferably, the sulfuric acid contains H2SO4 with a mass concentration of 98% or higher.

[0025] In the modified Hummers process, the preferred mass ratio of graphite powder, K2S2O7, and P2O5 is 1:(0.8-1):(0.8-1), and more preferably 1:0.84:0.84.

[0026] In the modified Hummers process, the volumetric amount of sulfuric acid used, based on the mass of graphite powder, is preferably 4-5 mL·g. -1 More preferably 4 mL·g -1 .

[0027] Compared with the prior art, the beneficial effects of this invention are as follows: (1) The raw materials used in the preparation of the catalyst in this invention are abundant and reasonably priced. The chemical method used to prepare graphene oxide is mature, simple and easy to operate. The graphene oxide is reduced by co-precipitation to obtain Ru-supported graphene catalyst Ru / rGO. The Ru nanoparticles are small and uniformly distributed, resulting in good catalytic effect.

[0028] (2) Thanks to the selective π-π adsorption of alkynes and alkenes on the graphene surface, the hydrogenolysis reaction was well suppressed, and Ru / rGO showed good catalytic activity: the reaction conversion rate can reach 100%, and the yield of 2,5-dimethyl-2,5-hexanediol is over 99.8%, which has great industrial application value.

[0029] (3) Compared with traditional Raney Ni catalyst, Ru / rGO also has many advantages such as low reaction temperature and pressure and short reaction time. Attached Figure Description

[0030] Figure 1 The main reaction and side reaction mechanisms are shown in the diagram for the catalytic hydrogenation synthesis of 2,5-dimethyl-2,5-hexanediol from 2,5-dimethyl-3-hexyn-2,5-diol. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Operating methods not specifically specified in the following embodiments are generally performed under conventional conditions or as recommended by the manufacturer.

[0032] Example 1: Preparation of graphene oxide: Graphene oxide was prepared using a modified Hummers method: 400 mL of concentrated sulfuric acid (98% H2SO4) was added to a 5000 mL round-bottom flask, refluxed, and mechanically stirred. 100 g of graphite powder, 84 g of K2S2O7, and 84 g of P2O5 were added sequentially at 80 °C, and the mixture was stirred until homogeneous. The reaction was carried out at 80 °C for 4.5 h. Heating was stopped, and the mixture was allowed to cool naturally to room temperature. Then, 2500 mL of deionized water was slowly added to the flask for dilution. The mixture was allowed to stand overnight, vacuum filtered, and the filter cake was collected. The cake was washed with deionized water until neutral and dried at 60 °C to obtain 98 g of graphene oxide.

[0033] Example 2: 10 g of graphene oxide prepared in Example 1 was weighed and added to 2000 mL of deionized water and dispersed by sonication at 25 kHz for 30 min. 0.20 g of RuCl3 was weighed and added to the dispersion, along with 1.82 g of NaBH4. The mixture was stirred at room temperature (25℃) for 8 h and then allowed to stand for 24 h. The product was separated by centrifugation, washed several times with water, and then freeze-dried to obtain Ru / rGO, with a Ru loading of approximately 1 wt%. The 1 wt% Ru / rGO loading used in the following examples refers to the catalyst prepared in Example 2.

[0034] Example 3: The only difference from Example 2 is that the amount of RuCl3 is changed to 0.60 g and the amount of NaBH4 is changed to 5.46 g; all other aspects are the same, resulting in a Ru / rGO with a Ru mass loading of approximately 3 wt%. The 3 wt% Ru / rGO loading used in the following examples refers to the catalyst prepared in Example 3.

[0035] Example 4: The only difference from Example 2 is that the amount of RuCl3 is changed to 1.00 g and the amount of NaBH4 is changed to 9.10 g; all other aspects are the same, resulting in a Ru / rGO with a Ru mass loading of approximately 5 wt%. The 5 wt% Ru / rGO loading used in the following examples refers to the catalyst prepared in Example 4.

[0036] Example 5: 120 g of 2,5-dimethyl-3-hexyn-2,5-diol, 480 g of 0.2 wt% KOH methanol solution, and 6 g of 5 wt% Pd / C (53 wt% water content) catalyst were added to a reactor. The reaction temperature was set at 100 °C and the hydrogen pressure at 2 MPa. After 12 h of reaction, the reactor was opened and a gas phase was analyzed. The conversion rate of 2,5-dimethyl-3-hexyn-2,5-diol was 99.7%, and the yield of 2,5-dimethyl-2,5-hexanediol was 12.0%.

[0037] Examples 6 to 10: While keeping other reaction conditions unchanged, the Pd / C catalyst in Example 5 was replaced with 5 wt% Pt / C (63 wt% water content), 5 wt% Ru / C (56 wt% water content), 5 wt% Ru / rGO (prepared according to the catalyst obtained in Example 4, with a water content of 59 wt%), 5 wt% Rh / C (57 wt% water content), and Raney Ni.

[0038] Comparing Examples 5-10, the experiment using Ru / rGO as a catalyst had the highest yield, while the experiments using Pd / C and Pt / C as catalysts had the lowest yield. See Table 1 for details. In Table 1, hexynediol refers to 2,5-dimethyl-3-hexynediol, and hexanediol refers to 2,5-dimethyl-2,5-hexanediol.

[0039] Table 1

[0040] This invention further optimizes the effect of Ru / rGO on the catalytic hydrogenation of 2,5-dimethyl-3-hexyne-2,5-diol by adjusting substrate concentration, reaction temperature, reaction pressure, catalyst dosage (relative to substrate), and catalyst loading. Specific examples are shown below. The Ru / rGO catalyst used in the following examples was prepared according to Examples 2-4 and formulated with a water content of 59 wt%.

[0041] Example 11: 120 g of 2,5-dimethyl-3-hexyn-2,5-diol, 480 g of 0.2 wt% KOH methanol solution, and 6 g of 1 wt% Ru / rGO (59 wt% water content) catalyst were added to a reactor. The reaction temperature was set at 60 °C and the hydrogen pressure at 3 MPa. After 3 h of reaction, the reactor was opened and a gas phase analysis was performed. The conversion rate of 2,5-dimethyl-3-hexyn-2,5-diol was 95.6%, and the yield of 2,5-dimethyl-2,5-hexanediol was 93.5%.

[0042] Examples 12 to 25: Examples 12 to 25 are based on Example 11 (i.e., unless otherwise specified, they are the same as Example 11). Specific parameters and conditions are shown in Table 2. In Table 2, hexynediol refers to 2,5-dimethyl-3-hexynediol, hexanediol refers to 2,5-dimethyl-2,5-hexanediol, catalyst amount = catalyst mass / 2,5-dimethyl-3-hexynediol mass, substrate concentration = 2,5-dimethyl-3-hexynediol mass / (2,5-dimethyl-3-hexynediol mass + solvent mass).

[0043] Table 2

[0044] Comparing Examples 11-13, the change in substrate concentration had virtually no impact on the experimental hydrogenation effect; the conversion rate was 100% in all examples, and the yields were similar. Considering that higher substrate concentration leads to higher yield, a substrate concentration of 25 wt% was preferred.

[0045] Comparing Examples 14 and 25, the catalyst loading had little effect on the yield of hexanediol; the conversion rates in both experiments were 100%, and the yields were not significantly different.

[0046] Comparative Examples 14-17 show that the higher the temperature, the faster the reaction rate and the shorter the reaction time, but the yield gradually decreases. Therefore, the preferred temperature is 30 °C.

[0047] Comparing Examples 17, 18, 19, 20, and 23, the experimental yield was significantly lower at a reaction pressure of 0.5 MPa than at other pressures. From the perspective of production safety and production cycle, the preferred reaction pressure is 0.7 MPa.

[0048] Comparative Examples 22-25 show that when the catalyst dosage is 0.2 wt%, 0.5 wt%, 1 wt%, and 2 wt%, the product yield ranges from 92.1% to 98.1%. Considering the catalyst cost, the preferred catalyst dosage is 0.5 wt%.

[0049] In Example 19, the highest yield of 2,5-dimethyl-2,5-hexanediol was 99.8%, corresponding to a substrate concentration of 25 wt%, a catalyst loading of 3 wt%, a catalyst dosage of 0.5 wt%, a reaction temperature of 30°C, and a reaction pressure of 0.7 MPa.

[0050] Catalyst repeatability tests were conducted under the process conditions of Example 19. The specific procedures were as follows: Catalyst was recovered after each use; considering losses during recovery, 10% of the initial catalyst mass was added each time to continue the reaction.

[0051] Specific implementation examples are shown below.

[0052] Example 26: 120 g of 2,5-dimethyl-3-hexyn-2,5-diol, 480 g of water, and 0.6 g of 3 wt% Ru / rGO (59 wt% water content) catalyst were added to the reactor. The reaction temperature was set to 30℃ and the hydrogen pressure to 0.7 MPa. After 3 h of reaction, the reactor was opened and samples were taken for gas phase analysis.

[0053] Examples 27 to 35: While keeping other reaction conditions unchanged, the Ru / rGO catalyst recovered after the reaction in the previous embodiment (Example 27 used the catalyst recovered after the reaction in Example 26, and so on) was added each time at a rate of 10% relative to the initial catalyst mass to continue the reaction.

[0054] Table 3 presents the catalyst repeatability comparison data. In Table 3, hexynediol refers to 2,5-dimethyl-3-hexyne-2,5-diol, and hexanediol refers to 2,5-dimethyl-2,5-hexanediol. Comparing Examples 26 to 35, the yield of 2,5-dimethyl-3-hexyne-2,5-diol remained relatively stable with increasing catalyst usage. At the 10th use, the feed conversion rate was 99.8%, and the product yield still maintained at 98.0%. Table 3 shows that although the Ru / rGO catalyst has a higher cost, its stability is good, making it suitable for industrial production processes.

[0055] Table 3

[0056] In summary, the catalyst of this invention exhibits excellent catalytic performance in the selective hydrogenation of 2,5-dimethyl-3-hexyne-2,5-diol to prepare 2,5-dimethyl-2,5-hexanediol. It operates under mild reaction conditions, low energy consumption, and short reaction time, significantly improving production efficiency and product yield, and thus has promising prospects for industrial application.

[0057] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for selectively hydrogenating 2,5-dimethyl-3-hexyne-2,5-diol to prepare 2,5-dimethyl-2,5-hexanediol, characterized in that, include: Using 2,5-dimethyl-3-hexyn-2,5-diol as a raw material and Ru / rGO as a catalyst, the reaction was carried out in a solvent under hydrogen pressure of 0.5-3 MPa and temperature of 30-120℃ to obtain 2,5-dimethyl-2,5-hexanediol. The Ru / rGO comprises a reduced graphene oxide support and an active component Ru, wherein the mass ratio of the active component Ru to the reduced graphene oxide support is 0.9-5:

100.

2. The method for selective hydrogenation of 2,5-dimethyl-3-hexyne-2,5-diol to prepare 2,5-dimethyl-2,5-hexanediol according to claim 1, characterized in that, The mass ratio of 2,5-dimethyl-3-hexyn-2,5-diol to Ru / rGO is 1:0.002-0.05, preferably 1:0.

005.

3. The method for selective hydrogenation of 2,5-dimethyl-3-hexyne-2,5-diol to prepare 2,5-dimethyl-2,5-hexanediol according to claim 1, characterized in that, The catalytic reaction was carried out in a solvent under hydrogen pressure of 0.7 MPa and temperature of 30 °C.

4. The method for selective hydrogenation of 2,5-dimethyl-3-hexyne-2,5-diol to prepare 2,5-dimethyl-2,5-hexanediol according to claim 1, characterized in that, The solvent includes water and / or an alkaline low-carbon alcohol; The alkali includes KOH; The lower alcohols include methanol; The alkali-containing low-carbon alcohol has an alkali mass concentration of 0.2%.

5. The method for selective hydrogenation of 2,5-dimethyl-3-hexyne-2,5-diol to prepare 2,5-dimethyl-2,5-hexanediol according to claim 1, characterized in that, The mass ratio of the solvent to 2,5-dimethyl-3-hexyne-2,5-diol is 3-19:

1.

6. The method for selective hydrogenation of 2,5-dimethyl-3-hexyne-2,5-diol to prepare 2,5-dimethyl-2,5-hexanediol according to claim 1, characterized in that, The catalytic reaction takes 1-12 hours, preferably 3 hours.

7. The method for selective hydrogenation of 2,5-dimethyl-3-hexyne-2,5-diol to prepare 2,5-dimethyl-2,5-hexanediol according to claim 1, characterized in that, The mass ratio of the active component Ru to the reduced graphene oxide support is 2.9-3:

100.

8. The method for selective hydrogenation of 2,5-dimethyl-3-hexyne-2,5-diol to prepare 2,5-dimethyl-2,5-hexanediol according to claim 1, characterized in that, The conversion rate of the catalytic reaction was 100%, and the yield of 2,5-dimethyl-2,5-hexanediol was above 99.8%.

9. The method for selective hydrogenation of 2,5-dimethyl-3-hexyne-2,5-diol to prepare 2,5-dimethyl-2,5-hexanediol according to claim 1, characterized in that, The preparation method of Ru / rGO includes: adding RuCl3 and NaBH4 to an aqueous dispersion of graphene oxide, stirring to react fully and then allowing it to stand, then separating the solid and liquid, washing and drying the solid to obtain Ru / rGO.

10. The method for selective hydrogenation of 2,5-dimethyl-3-hexyne-2,5-diol to prepare 2,5-dimethyl-2,5-hexanediol according to claim 9, characterized in that, In the preparation method of Ru / rGO, the molar ratio of NaBH4 to RuCl3 is 49~51:

1.

11. The method for selective hydrogenation of 2,5-dimethyl-3-hexyne-2,5-diol to prepare 2,5-dimethyl-2,5-hexanediol according to claim 9, characterized in that, In the Ru / rGO preparation method, the temperature for thorough stirring and reaction is room temperature, and the reaction time is 7-9 h.

12. The method for selective hydrogenation of 2,5-dimethyl-3-hexyne-2,5-diol to prepare 2,5-dimethyl-2,5-hexanediol according to claim 9, characterized in that, The graphene oxide in the aqueous dispersion was prepared by a modified Hummers method, which specifically includes: adding graphite powder, K2S2O7 and P2O5 sequentially to sulfuric acid under reflux and stirring at 80-90℃, keeping it at the temperature and stirring for 4-6 hours, then naturally cooling to room temperature, adding deionized water for dilution, letting it stand overnight, separating the solid and liquid, washing and drying the solid to obtain graphene oxide.

13. The method for selective hydrogenation of 2,5-dimethyl-3-hexyne-2,5-diol to prepare 2,5-dimethyl-2,5-hexanediol according to claim 12, characterized in that, The sulfuric acid contains H2SO4 at a mass concentration of over 98%.

14. The method for selective hydrogenation of 2,5-dimethyl-3-hexyne-2,5-diol to prepare 2,5-dimethyl-2,5-hexanediol according to claim 12, characterized in that, The mass ratio of graphite powder, K2S2O7, and P2O5 is 1:(0.8-1):(0.8-1), preferably 1:0.84:0.

84.

15. The method for selective hydrogenation of 2,5-dimethyl-3-hexyne-2,5-diol to prepare 2,5-dimethyl-2,5-hexanediol according to claim 12, characterized in that, The volumetric amount of sulfuric acid used is 4-5 mL·g based on the mass of the graphite powder. -1 .

Images