A layered nanosheet composite material and a method for catalytic hydrogenation and hydrogenolysis of furfural to prepare furfuryl alcohol and pentanediol

Abstract

The present invention discloses a ZnCo layered nanosheet composite material derived from ZIF-8 at room temperature and a method for catalytic hydrogenation / hydrogenolysis of furfural to prepare furfuryl alcohol / pentanediol. The composite material is prepared by etching ZIF-8 using different concentrations of Co in an aqueous NaBH4 solution at room temperature. The prepared material has a high specific surface area, thin-layer nanosheets, abundant acidic sites, and abundant mesoporous structures. Using anhydrous ethanol as a solvent and furfural as a raw material, in a batch stirred autoclave, at a temperature of 160 °C and a time of 0.5 h, the substrate is completely converted, and the selectivity of furfuryl alcohol is 97%. When the time is extended to 4 h, the selectivity of pentanediol is 46.9%. This work depicts an effective strategy for constructing a non-noble metal catalyst of zinc cobalt hydroxide with heteroatom ultrathin nanosheets derived from metal-organic frameworks, which may open up a new way for the development of efficient catalysts for pentanediol production. 2+ The prepared material has a high specific surface area, thin-layer nanosheets, abundant acidic sites, and abundant mesoporous structures. Using anhydrous ethanol as a solvent and furfural as a raw material, in a batch stirred autoclave, at a temperature of 160 °C and a time of 0.5 h, the substrate is completely converted, and the selectivity of furfuryl alcohol is 97%. When the time is extended to 4 h, the selectivity of pentanediol is 46.9%. This work depicts an effective strategy for constructing a non-noble metal catalyst of zinc cobalt hydroxide with heteroatom ultrathin nanosheets derived from metal-organic frameworks, which may open up a new way for the development of efficient catalysts for pentanediol production.

Description

Technical Field

[0001] The present invention belongs to the field of fine chemicals, and particularly relates to a ZnCo layered nanosheet composite derived from ZIF-8 at room temperature and a method for catalytic hydrogenation / hydrogenolysis of furfural to prepare furfuryl alcohol / 1,2-pentanediol. Background Art

[0002] 1,2-Pentanediol is an important chemical intermediate raw material, mainly used in the synthesis of fungicide propiconazole, the production of polyesters and polyurethanes, surfactants, pharmaceutical intermediates, cosmetic intermediates, fragrances and flavors, etc. Up to now, according to the different sources of research raw materials, using n-butanal and hydrocyanic acid as raw materials, α-hydroxyvaleric acid is prepared by hydrolysis of cyanohydrin intermediate, and then hydrogenated under the action of Ru-Re based catalyst to obtain 1,2-pentanediol, and the yield can reach 66%. However, the reaction route is long, hydrocyanic acid is toxic and flammable, the reaction conditions are harsh (190 °C and 25 MPa) and noble metal catalysts are used (US20080604905A1). Using methyl 2-hydroxyvalerate as raw material to directly hydrogenate to 1,2-pentanediol, although the yield of this method can reach 95%, the raw materials are very scarce and the production cost is high (CN102627526A). At the same time, using n-pentene and cyclopentene as raw materials, 1,2-epoxypentane is prepared by epoxidation, and then hydrolyzed and ring-opened to obtain 1,2-pentanediol, but this method has problems such as easy generation of by-products, low product yield and serious equipment corrosion (CN1552684, CN104177230A, US4605795A). Using glutaric acid as raw material, it is first esterified to obtain methyl 1,5-glutarate, and then hydrogenated under the action of CuZnAl catalyst at 150-350 °C and 3-5 MPa to obtain 1,5-pentanediol. The conversion rate and selectivity of 1,5-pentanediol of this process can both be greater than 95%, but the process flow is long and the raw material cost is high (CN03137598.7, CN1565728A). Using 1,5-pentanedial as raw material, hydrogenation is carried out at 60-120 °C and 2-8 MPa through supported Ni-based catalyst (CN101225022) or Ru-based catalyst (CN101270032). This method has good selectivity and mild conditions, but the disadvantages are that the raw material resources are not rich and the price is high. To sum up, the above methods can obtain a relatively high yield of 1,2-pentanediol under optimized conditions. However, the raw materials are expensive, the sources are limited, the preparation process is complex, and the production cost is high; the reaction conditions are harsh, which is not conducive to industrial application. Therefore, the preparation of 1,2-pentanediol still urgently needs to develop new raw material sources and synthesis routes.

[0003] The process of preparing linear diol pentanediol from biobased furfural has advantages such as wide raw material sources and a green and pollution-free production process compared to traditional petroleum-based routes. Therefore, a route for the selective hydrogenolysis of furfural and its semi-hydrogenated product furfuryl alcohol, and the fully hydrogenated product tetrahydrofurfuryl alcohol to synthesize pentanediol in one step under mild conditions has received extensive attention. Wang Yanqin et al. from East China University of Science and Technology developed a process route for the hydrogenation of furfural to prepare 1,5-pentanediol and 1,2-pentanediol using Pt / Co2AlO4 as a catalyst under mild conditions (140 °C, 1.5 MPa H2) (CN102134180A, Xu, W., Wang, H., Liu, X., Ren, J., Wang, Y., and Lu, G. Direct catalytic conversion of furfural to 1,5-pentanediol by hydrogenolysis of the furan ring under mild conditions over Pt / Co2AlO4 catalyst. Chem. Commun. 2011, 47, 3924–3926.), but the yields of 1,2-pentanediol and 1,5-pentanediol in this process are only 16% and 35% respectively. Chinese patent CN102872897A discloses a method for the hydrogenolysis of furfuryl alcohol to prepare 1,5-pentanediol catalyzed by hydrogen-type ultrastable zeolite (H-USY) loaded with Pt. This method can achieve a target product yield of nearly 80%, but a large amount of precious metal Pt catalyst needs to be added during the reaction, resulting in high production costs. Using Pt / Al2O3 as a catalyst, the US patent (US20140066666A1) achieved a yield of 80% for the hydrogenolysis of furfuryl alcohol to 1,2-pentanediol, but a large amount of Pt catalyst also needs to be added.The Japanese Tomishige research group reported the preparation of 1,2-pentanediol and 1,5-pentanediol by one-step hydrogenolysis using tetrahydrofurfuryl alcohol as the raw material. The single Rh / SiO2 catalyst had a relatively high selectivity for 1,2-pentanediol (up to 61.7%), but the conversion rate was only 5.7%. After adding Re and Mo promoters, the conversion rate could rise to over 90%, and the main product became 1,5-pentanediol (over 90%) (Koso, S., Furikado, I., Shimao, A., Miyazawa, T., Kunimori, K., and Tomishige, K. Chemoselective hydrogenolysis of tetrahydrofurfuryl alcohol to 1,5-pentanediol. Chem. Commun., 2009, 2035-2037. Nakagawa, Y., Tamura, M., and Tomishige, K. Catalytic Reduction of Biomass-Derived Furanic Compounds with Hydrogen. ACS Catal., 2013, 3, 2655-2668.). Hu Xun et al. from the University of Jinan developed a method using furfural as the raw material and NiFeMgAl hydrotalcite as the catalyst to react at 170 °C and 4 MPa H2 for 3 h to prepare 31% 1,5-pentanediol (Shao, Y., Wang, J., Sun, K., Gao, G., Li, C., Zhang, L., Zhang, S., Xu, L., Hu, G., and Hu, X. Selective hydrogenation of furfural and its derivative over bimetallic NiFe-based catalysts: Understanding the synergy between Ni sites and Ni–Fe alloy. Renew. Energ., 2021, 170, 1114-1128.). In summary, at present, the synthesis of pentanediol from furfural with good yields still mainly relies on noble metal oxide catalysts, and the yields of non-noble metal layered double metal hydroxide catalysts are usually low when synthesizing pentanediol. Summary of the Invention

[0004] Based on the above background, the present invention proposes a method for synthesizing high-value fine chemicals furfuryl alcohol / pentanediol by catalytic hydrogenation / hydrogenolysis of furfural in one pot using a ZIF-8-derived non-precious metal ZnCo layered nanosheet composite at room temperature. This method provides a simple, low-cost, efficient, environmentally friendly and industrially viable production method for the conversion of furfural to furfuryl alcohol / pentanediol.

[0005] The present invention reports a facile synthesis method for etching ZIF-8-mediated ZnCo-LDH layered nanosheet composites with NaBH4 in water at room temperature, and for the first time uses it for the preparation of pentanediol by hydrogenation / hydrogenolysis of furfural in anhydrous ethanol solution. The morphology of the synthesized materials with different Co concentrations was characterized in detail by SEM characterization means. As 2+ shown. The results show that as the Co 2+ concentration increases, the ZIF-8 structure collapses and the morphology changes. The optimal morphology is ZnCo Figure 2 -LDH, showing ultrathin layered double metal hydroxides. Approximately 50% of 1,5-pentanediol was obtained under the optimal reaction conditions, and the raw materials are renewable, with the highest product selectivity in the non-precious metal system. This work proposes an effective strategy for constructing metal-organic framework-derived heteroatom ultrathin nanosheet zinc cobalt hydroxide non-precious metal catalysts, providing an excellent opportunity to better explore the structure-function relationship of catalysts and offering the possibility of developing new routes. 2+ concentration increases, the ZIF-8 structure collapses and the morphology changes. The optimal morphology is ZnCo 1.5 -LDH, showing ultrathin layered double metal hydroxides. Approximately 50% of 1,5-pentanediol was obtained under the optimal reaction conditions, and the raw materials are renewable, with the highest product selectivity in the non-precious metal system. This work proposes an effective strategy for constructing metal-organic framework-derived heteroatom ultrathin nanosheet zinc cobalt hydroxide non-precious metal catalysts, providing an excellent opportunity to better explore the structure-function relationship of catalysts and offering the possibility of developing new routes. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 It is the gas chromatogram-mass spectrum for the preparation of furfuryl alcohol / pentanediol from furfural.

[0007] Figure 2 It is the SEM diagram of the synthesis process of ZnM-LDH and the influence of metal on the ZIF-8 structure. DETAILED DESCRIPTION OF THE INVENTION

[0008] The present invention will be further described in conjunction with the implementation examples. Unless otherwise specified, the reagents and instruments used in the following examples are all commercially available products.

[0009] Preparation of ZIF-8

[0010] Take 5.94 g of Zn(NO3)2·6H2O and dissolve it in 150 mL of organic solvent to form a solution; take 6.56 g of 2-methylimidazole and dissolve it in 150 mL of methanol to form a solution. Mix the two organic solutions and stir overnight to form a precipitate. After centrifugation, wash it 5 times with organic solvent, and finally dry it in a vacuum drying oven at 60 °C for 5 h to obtain ZIF-8

[0011] All subsequent examples use the ZIF-8 prepared in this example.

[0012] Example 1

[0013] Catalyst preparation: Weigh 0.2 mol of Co(NO3)2·6H2O and dissolve it in 1 mL of water, stir for 2 h and set aside, denoted as solution A. Take 0.2 g of ZIF-8 and dissolve it in 10 mL of water, stir for 1 h and set aside, denoted as solution B. Add solution A to solution B and stir for 1 h. Then dissolve 0.1 g of NaBH4 in 1 mL of the solution, denoted as solution C. Subsequently, add solution C to the A-B mixture and stir for 1 h. Finally, wash the mixture 3 times with water and methanol respectively, and finally dry it in a vacuum drying oven at 80 °C for 12 h to obtain ZnCo 0.2 -LDH.

[0014] Reaction engineering: Mix 0.5 mmol of furfural with 0.02 g of the prepared catalyst ZnCo 0.2 -LDH in anhydrous ethanol solution; put it into a high-pressure reactor with a volume of 50 mL, heat to 140 °C, 2 MPa H2, react for 30 min. After the reaction, extract 1 mL of the reaction solution and perform qualitative analysis by gas chromatography-mass spectrometry (GC-MS, Agilent), and quantitative analysis by gas chromatography (GC, Agilent). The results are as follows: the conversion rate of furfural is 20.34%, and the selectivity of furfuryl alcohol is 11.1%.

[0015] Example 2

[0016] According to the method of catalyst preparation and reaction engineering in Example 1, only the molar mass of Co(NO3)2·6H2O is 0.5 mol, and the catalyst ZnCo 0.5 -LDH is prepared. The results of the reaction are as follows: the conversion rate of furfural is 32.4%, and the selectivity of furfuryl alcohol is 14.4%.

[0017] Example 3

[0018] According to the method of catalyst preparation and reaction engineering in Example 1, only the molar mass of Co(NO3)2·6H2O is 1.5 g, and the catalyst ZnCo 1.5 -LDH is prepared. The results of the reaction are as follows: the conversion rate of furfural is 100%, and the selectivity of furfuryl alcohol is 90.3%.

[0019] Example 4

[0020] According to the method of catalyst preparation and reaction engineering in Example 1, only the molar mass of Co(NO3)2·6H2O is 3.0 g, and the catalyst ZnCo 3.0-LDH. The results obtained from the reaction were as follows: the conversion rate of furfural was 100%, and the selectivity of furfuryl alcohol was 86.5%.

[0021] Example 5

[0022] According to the method for preparing the catalyst and the reaction engineering of Example 1, only the molar mass of Co(NO3)2·6H2O was 4.5 mol, and the catalyst ZnCo 4.5 -LDH was prepared. The results obtained from the reaction were as follows: the conversion rate of furfural was 100%, and the selectivity of furfuryl alcohol was 84.5%.

[0023] Example 6

[0024] According to the method for preparing the catalyst and the reaction engineering of Example 3, only the reaction temperature was 160 °C. The results obtained from the reaction were as follows: the conversion rate of furfural was 100%, and the selectivity of furfuryl alcohol was 99.9%.

[0025] Example 7

[0026] According to the method for preparing the catalyst and the reaction engineering of Example 6, only the reaction time was 240 min, the hydrogen pressure was 4 MPa. The results were as follows: the conversion rate of furfural was 100%. The selectivity of furfuryl alcohol was 0%, the selectivity of tetrahydrofurfuryl alcohol was 19.1%, the selectivity of 1,2-pentanediol was 8.1%, and the selectivity of 1,5-pentanediol was 46.8%.

[0027] Comparing Comparative Examples 1-4, it can be seen that when 1.5 mol of Co(NO3)2·6H2O etched ZIF-8, the highest selectivity of furfuryl alcohol was at 140 °C, 2 MPa H2, 30 min. Combining the scanning electron microscopy of ZIF-8 etched with different molar masses of Co(NO3)2·6H2O, it can be concluded that ZnCo lamellar nanosheet structures were obtained by etching ZIF-8 with 1.5 mol of Co(NO3)2·6H2O. Comparing Example 3 and Example 6, it can be seen that the highest selectivity of furfuryl alcohol was 97.9%, indicating that 160 °C was the optimal reaction temperature. Comparing Example 6 and Example 7, it can be seen that extending the reaction time and increasing the hydrogen pressure increased the selectivity of tetrahydrofurfuryl alcohol, 1,2-pentanediol, 1,5-pentanediol, etc., and the selectivity of furfuryl alcohol was 0%, further indicating that furfuryl alcohol was an intermediate. According to the results of the above specific implementation cases, it shows that the catalyst provided by the present invention can be effectively used for the production of pentanediol from furfural. Under the optimal conditions, that is, the reaction temperature is 160 °C, the reaction time is 30 min, the substrate conversion rate is 100%, and the selectivity of furfuryl alcohol is close to 100%. Keeping other conditions unchanged and further extending the reaction time to 4 h, the selectivity of pentanediol can reach 50%.

[0028] The specific embodiments of the present invention are merely for the purpose of exemplary illustration, and the catalyst is applicable to the hydrogenation / hydrogenolysis conversion of biomass-derived furan compounds into cyclic alcohols and linear alcohols. It does not limit the protection scope of the present invention in any way. Those skilled in the art can make improvements or transformations according to the above description, and all such improvements and transformations shall fall within the protection scope of the appended claims of the present invention.

Claims

1. A ZnCo layered nanosheet composite derived from ZIF-8 at room temperature, characterized in that, The catalyst is composed of Zn and Co species; the active component of the catalyst is the transition metal Co species; It is prepared by the method of the following steps: In the first step, Zn(NO3)2·6H2O is taken and dissolved in an organic solvent to form a solution; 2-methylimidazole is taken and dissolved in an organic solvent to form a solution; the two organic solutions are mixed and stirred overnight to form a precipitate, centrifuged, washed with an organic solvent, and finally dried in a vacuum drying oven to obtain ZIF-8; In the second step, ZIF-8 is dissolved in water, stirred and then added to an aqueous solution of CoCl2·2H2O, and stirred; In the third step, a solution containing NaBH4 is quickly added to the second step and stirred; the mixture is washed with water and an organic phase, and finally dried in a vacuum drying oven overnight to obtain ZnCo-LDH; Among them: in the first step, 0.02-0.08 mol of Zn(NO3)2·6H2O is taken and dissolved in 150 mL of methanol to form a solution; 0.08-0.32 mol of 2-methylimidazole is taken and dissolved in 150 mL of methanol to form a solution; In the second step, 0.2-0.8 g of ZIF-8 is dissolved in 50 mL of deionized water, and the aqueous solution concentration of CoCl2·2H2O is 0.2-4.5 mmol / ml; In the third step, an aqueous solution of NaBH4 with a concentration of 10-50% is quickly added to the second step.

2. The composite material according to claim 1, characterized in that: In the first step, 0.02 mol of Zn(NO3)2·6H2O is taken and dissolved in 150 mL of methanol to form a solution, 0.08 mol of 2-methylimidazole is taken and dissolved in 150 mL of methanol to form a solution, the two solutions are mixed and stirred for 12 h to form a white precipitate, the obtained white precipitate is centrifuged, washed 3 times with water and methanol respectively, and finally dried in a 60 °C vacuum drying oven for 5 h to obtain ZIF-8.

3. The composite material according to claim 1, characterized in that: In the second step, the aqueous solution concentration of CoCl2·2H2O is 1.5 mmol / ml.

4. The composite material according to claim 1, wherein: In the second step, ZIF-8 is dissolved in deionized water and stirred for 2 h, and then added to an aqueous solution of CoCl2·2H2O. 0.5-4.5 mmol of CoCl2·2H2O is dissolved in 2 mL of deionized water for the aqueous solution of CoCl2·2H2O.

5. The composite material according to claim 1, characterized in that: In the second step, the addition amount of ZIF-8 is 0.2 g.

6. The composite material according to claim 1, wherein: In the third step, an aqueous solution of NaBH4 with a concentration of 10% is quickly added to the second step and stirred at room temperature for 1 h; the mixture is washed 3 times with water and methanol, and finally dried in a 60 °C vacuum drying oven for 12 h to obtain ZnCo-LDH.

7. Use of the composite material according to any one of claims 1 to 6 in the catalytic hydrogenation / hydrogenolysis of furfural to prepare furfuryl alcohol / pentanediol.

8. A method for preparing furfuryl alcohol / pentanediol by catalytic hydrogenation / hydrogenolysis of furfural with a ZIF-8-derived ZnCo layered nanosheet composite material at room temperature, which is characterized in that, Using furfural as a substrate and the composite material according to any one of claims 1 to 6 as a catalyst, furfuryl alcohol or pentanediol is obtained by reaction.

9. The method according to claim 8, wherein Furfural, a solvent and a metal catalyst are added to a batch-type closed high-pressure reactor, and a catalytic selective hydrogenation / hydrogenolysis reaction is carried out under stirring.

10. The method according to claim 9, wherein The ratio of the furfural to the solvent is 0.5 mmol: 5 - 10 ml, the solvent is absolute ethanol, the dosage of the catalyst is 0.25 to 0.75 times the mass of the furfural, the initial hydrogen pressure is 1 - 2 MPa, the reaction temperature is 140 to 160 °C, and the reaction time is 0.5 h to 4 h.

11. The method according to claim 10, characterized in that When the reaction temperature is 160 °C and the reaction time is 0.5 h, furfuryl alcohol is obtained, and the selectivity of furfuryl alcohol is close to 100%; or when the reaction temperature is 160 °C and the reaction time is 4 h, pentanediol is obtained, and the selectivity of the pentanediol reaches 50%.

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