Method for preparing furfuryl alcohol through selective hydrogenation of furfural

Abstract

The invention belongs to the technical field of catalytic hydrogenation, and discloses a method for preparing furfuryl alcohol through selective hydrogenation of furfural. A Cu-Co bimetallic core-shell structure catalyst is used to catalyze selective hydrogenation of furfural in a reaction solvent under certain reaction pressure and reaction temperature conditions to prepare furfuryl alcohol. The Cu-Co bimetallic core-shell structure catalyst is a CuCo-NC-SiO2 catalyst, a hydrophilic SiO2 shell layer is coated on the basis of CuCo-NC, the dispersity of the catalyst in water is enhanced, full contact between reaction sites of the catalyst and water protons is promoted, meanwhile, efficient enrichment of furfural through a porous structure is achieved through the hydrophobicity of a CN framework, and the catalyst has the advantages of being simple in preparation process, low in cost and high in efficiency. Sufficient contact between furfural and active sites of the catalyst is promoted, so that the gas-liquid-solid three-phase hydrogenation process is enhanced. Under mild reaction conditions, the yield of furfuryl alcohol can reach 100%.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalytic hydrogenation, and relates to a method for the selective hydrogenation of furfural to furfuryl alcohol. Background Art

[0002] Under the profound transformation of the global energy pattern, the development of renewable carbon resources has become an inevitable choice for achieving sustainable development. As the most abundant renewable carbon carrier, biomass can be converted into high-value materials, chemicals, and fuels. Developing and utilizing biomass energy can effectively reduce the dependence on imported oil and natural gas and enhance national energy security. As one of the most important biomass platform compounds, the preparation and conversion of furfural are the core research directions in the field of biorefining. Furfural is mainly derived from the acid-catalyzed dehydration of agricultural and forestry waste (such as corncobs, bagasse, etc.). The aldehyde group and C=C double bond in its molecular structure endow multiple conversion paths: selective hydrogenation of the carbonyl group to furfuryl alcohol, decarbonylation to synthesize furan, hydrogenation cyclization to obtain cyclopentanone, hydrodeoxygenation to prepare 2-methylfuran, etc. Furfural alcohol is mainly used as the core raw material of furan resin in the foundry industry. Its high temperature and acid-base resistance characteristics can increase the bonding strength of sand cores by more than 30%; in the field of fine chemicals, it can synthesize tetrahydrofurfuryl alcohol (solvent), furfural resin (anticorrosive coating), and pharmaceutical intermediates; at the same time, it is used as a green solvent for the cleaning of electronic-grade chemicals and participates in the production of new materials such as lithium battery binders and bio-based polyesters.

[0003] The traditional production process for preparing furfuryl alcohol from furfural relies on Cu-Cr catalysts, which require high temperature and pressure and produce highly toxic waste. Patent CN119456012A discloses a catalyst of N-doped modified MOFs-derived core-shell nanoreactor for the transfer hydrogenation of α,β-unsaturated aldehydes. The core-shell structure provides a large specific surface area and rich pore structure for the catalyst on the one hand, and effectively inhibits the aggregation of MOFs during calcination on the other hand, enabling good dispersion of Co metal centers and improving the stability of the catalyst. However, the hydrogen source selects alcohol solvents, and the reaction time is more than 10h, requiring high energy consumption. According to the report in Nanoscale, 2023, 15, 4612-4619, the catalytic performance of ZIF-67-derived Co-N-C is enhanced by encapsulation with mesoporous silica. The SiO2 shell layer restriction and appropriate pyrolysis temperature endow the catalyst with rich Co-N x species and mesoporous channels, but Co-N xThe active site is an acidic site, which is not conducive to improving the selectivity to furfuryl alcohol. Patent CN110876955A discloses a highly dispersed copper-cobalt bimetal in mesoporous silica, and the confinement effect effectively inhibits the separation and agglomeration of metal centers, achieving excellent selectivity and stability of target products in the reaction of syngas to produce lower alcohols. Patent CN114733545A discloses a water-oil amphiphilic trinuclear shell nano-catalyst, which uses the synergistic effect between Cu and Co and the hydrophilic-hydrophobic property of the catalyst to achieve highly selective hydrogenation of unsaturated C═C. Ammonia borane is selected as the hydrogen source, which has a high cost and certain safety hazards. The Co-based catalyst for the conversion of furfural to furfuryl alcohol

[0004] Therefore, it is of great significance to invent a furfural hydrogenation catalyst for furfuryl alcohol preparation with mild preparation conditions, low cost, safety and greenness. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for the selective hydrogenation of furfural to furfuryl alcohol to solve the problems of long reaction time and hydrogen source in the current selective hydrogenation of furfural to furfuryl alcohol proposed in the background technology.

[0006] To achieve the above object, the present invention provides a method for the selective hydrogenation of furfural to furfuryl alcohol, using a Cu-Co bimetal core-shell structure catalyst. The CuCo@NC@SiO2 catalyst exhibits superior performance to CuCo@NC and other Co-based catalysts supported on traditional materials, having a large specific surface area and a rich pore structure. Nitrogen doping can provide Co-Nx active sites. In addition, the addition of an appropriate amount of Cu enhances the interaction between Cu and Co, changes the adsorption configuration of the metal active center to FAL, and avoids over-hydrogenation reactions. Under the reaction solvent and certain hydrogen pressure and reaction temperature, furfural is catalytically hydrogenated selectively to obtain furfuryl alcohol.

[0007] The technical solution of the present invention:

[0008] A method for the selective hydrogenation of furfural to furfuryl alcohol, using a Cu-Co bimetal core-shell structure catalyst, catalytically hydrogenates furfural selectively to prepare furfuryl alcohol under the reaction solvent and certain reaction pressure and reaction temperature conditions; the Cu-Co bimetal core-shell structure catalyst is a CuCo@NC@SiO2 catalyst;

[0009] The steps are as follows:

[0010] (1) Dissolve cobalt salt, copper salt and cetyltrimethylammonium bromide in deionized water and record it as solution A, dissolve 2-methylimidazole in deionized water and record it as solution B. Quickly drip solution A into solution B, stir at room temperature, centrifuge and wash the obtained mixture, and dry it overnight to obtain CuCo-ZIF;

[0011] (2) Add the CuCo-ZIF obtained in step (1) to deionized water. After ultrasonic dispersion until uniform, add sodium hydroxide solution, continue ultrasonic oscillation, add cetyltrimethylammonium bromide, stir for 0.5 h, then slowly dropwise add tetraethyl orthosilicate methanol solution, stir at room temperature for 0.5 h, filter the obtained mixture, wash with deionized water until the pH = 7, and dry overnight to obtain the CuCo-ZIF precursor with SiO₂ coated on the surface;

[0012] (3) Calcinate the CuCo-ZIF precursor with SiO₂ coated on the surface obtained in step (2) under an inert atmosphere to obtain the CuCo@NC@SiO₂ catalyst;

[0013] (4) Dissolve the CuCo@NC@SiO₂ catalyst obtained in step (3) in a reaction solvent, and carry out the catalytic selective hydrogenation of furfural to prepare furfuryl alcohol in a high-pressure reactor.

[0014] In step (1), the cobalt salt is cobalt nitrate hexahydrate, and the active metal Co accounts for 20 - 30% of the total mass of the catalyst; the copper salt is copper nitrate trihydrate, and the active metal Cu accounts for 0 - 9% of the total mass of the catalyst; control the mass ratio of the cobalt salt to the copper salt to be 1:(0 - 0.72).

[0015] In step (1), the mass ratio of 2-methylimidazole to the cobalt salt is 1:(0.03 - 0.06);

[0016] In step (1), the stirring time at room temperature is 0.5 - 1 h;

[0017] In step (2), the concentration of the sodium hydroxide solution is 0.1 - 0.2 mol / L, and it is used to adjust the pH of the dispersion to 8 - 9;

[0018] In step (2), the mass ratio of CuCo-ZIF to cetyltrimethylammonium bromide is 1:(0.1 - 0.5);

[0019] In step (2), the mass ratio of tetraethyl orthosilicate to CuCo-ZIF is 1:(0.6 - 3);

[0020] In step (2), the drying temperature is 60 - 80 °C;

[0021] In step (3), the calcination temperature is 500 - 800 °C, the heating rate is 2 - 5 °C / min; the cooling rate is 1 - 10 °C / min; the inert atmosphere is nitrogen or argon.

[0022] In step (4), the reaction pressure is 0.25 - 2 MPa; the reaction temperature is 90 - 150 °C.

[0023] In step (4), the reaction time is 120 - 180 min; the reaction solvent is deionized water.

[0024] Advantages of the present invention:

[0025] (1) The catalyst of the present invention is based on CuCo@NC coated with a hydrophilic SiO2 shell layer, which enhances the dispersion of the catalyst in water, promotes the full contact between the reaction sites of the catalyst and water protons, and at the same time utilizes the hydrophobicity of the CN skeleton to achieve efficient enrichment of furfural in the porous structure, promoting the full contact between furfural and the active sites of the catalyst, thereby enhancing the gas-liquid-solid three-phase hydrogenation process.

[0026] (2) The catalyst provided by the present invention exhibits excellent catalytic activity when used for the selective hydrogenation of furfural to prepare furfuryl alcohol. Under relatively mild reaction conditions, the yield of furfuryl alcohol can reach 100%. Moreover, the CuCo@NC@SiO2 catalyst used in the present invention has simple preparation conditions, low loadings of Co and Cu, and good dispersion.

[0027] (3) Compared with the traditional Cu-Cr catalyst, the Cu-Co bimetallic catalyst of the present invention exhibits more excellent catalytic activity and selectivity, and has stronger environmental friendliness. Compared with the nitrogen-doped carbon support directly calcined from ZIF-67, the core-shell structure of the present invention can significantly improve the catalytic activity by using the confinement effect.

[0028] (4) Adjusting the addition amounts of copper salt and cobalt salt in the catalyst of the present invention results in different molar ratios of Co to Co. Co-based catalysts have high hydrogenation ability, but usually require high reaction temperatures and reaction pressures, which are prone to cause over-hydrogenation reactions. The introduction of the second metal Cu enhances the activity and selectivity of the resulting catalyst by promoting the binding of the O atom on C=O to the metal surface or polarizing the C=O bond in furfural as a weak acid site. Description of the drawings

[0029] Figure 1 XRD patterns of Examples 1-4 and Comparative Example 1.

[0030] Figure 2 Scanning electron microscope images of Example 1 and Comparative Example 1, where a) is Cu2Co8@NC and b) is Cu2Co8@NC@SiO2.

[0031] Figure 3 Transmission electron microscope images of Example 1 and Comparative Example 1, where a) is Cu2Co8@NC, b) is Cu2Co8@NC@SiO2, and c) is Cu2Co8@NC@SiO2.

[0032] Figure 4 N2 physical adsorption-desorption isotherms of Example 1 and Comparative Example 1.

[0033] Figure 5Contact angle test diagrams of water and furfural for Example 1 and Comparative Example 1, where a) is the contact angle of Cu2Co8@NC with water, b) is the contact angle of Cu2Co8@NC@SiO2 with water, c) is the contact angle of Cu2Co8@NC with furfural, and d) is the contact angle of Cu2Co8@NC@SiO2 with furfural. Detailed implementation manners

[0034] The following further illustrates the detailed implementation manners of the present invention in conjunction with the accompanying drawings and technical solutions.

[0035] Example 1

[0036] Preparation of Cu2Co8@NC@SiO2 catalyst

[0037] Step 1: Dissolve 0.9312 g of Co(NO3)2·6H2O, 0.1932 g of Cu(NO3)2·3H2O, and 30 mg of CTAB in 40 mL of deionized water, denoted as solution A. Dissolve 18.16 g of 2-methylimidazole in 280 mL of deionized water, denoted as solution B. Rapidly drip solution A into solution B, stir at room temperature for 0.5 h, centrifuge and collect the obtained mixture, wash it three times with deionized water and anhydrous ethanol respectively, and dry it overnight at 80 °C to obtain Cu2Co8-ZIF.

[0038] Step 2: Weigh 0.3 g of Cu2Co8-ZIF and add it to 120 mL of deionized water. Ultrasonic for 15 min to fully disperse CuCo-ZIF in deionized water, then sequentially add 4.8 mL of NaOH aqueous solution (0.12 mol / L) and 3 mL of CTAB aqueous solution (25 mg / mL), and stir for 0.5 h. After adding 0.4 mL of TEOS to 3 mL of methanol, slowly drip it into the above solution. After stirring for 0.5 h, filter and collect the obtained purple precipitate, wash it with deionized water until the pH = 7, and dry it overnight at 80 °C to obtain Cu2Co8-ZIF@SiO2.

[0039] Step 3: Calcinate Cu2Co8-ZIF@SiO2 in a tube furnace at 600 °C for 2 h under a nitrogen atmosphere, and set the heating rate to 2 °C·min -1 , and finally obtain Cu2Co8@NC@SiO2.

[0040] Example 2

[0041] Preparation of Cu1Co9@NC@SiO2 catalyst

[0042] This example is a variant of Example 1. Other implementation conditions are the same as those in Example 1, and the difference lies in that 1.0476 g of Co(NO3)2·6H2O and 0.0966 g of Cu(NO3)2·3H2O are added in Step 1.

[0043] Example 3

[0044] Preparation of Cu3Co7@NC@SiO2 catalyst

[0045] This example is a variant of Example 1. Other implementation conditions are the same as those in Example 1, and the difference lies in that 0.8148 g of Co(NO3)2·6H2O and 0.2898 g of Cu(NO3)2·3H2O are added in Step 1.

[0046] Example 4

[0047] Preparation of Cu4Co6@NC@SiO2 catalyst

[0048] This example is a variant of Example 1. Other implementation conditions are the same as those in Example 1, and the difference lies in that 0.6984 g of Co(NO3)2·6H2O and 0.3864 g of Cu(NO3)2·3H2O are added in Step 1.

[0049] Example 5

[0050] Preparation of Co@NC@SiO2 catalyst

[0051] This example is a variant of Example 1. Other implementation conditions are the same as those in Example 1, and the difference lies in that 1.1640 g of Co(NO3)2·6H2O is added in Step 1, and copper nitrate trihydrate is not added.

[0052] Comparative Example 1

[0053] Preparation of Cu2Co8@NC catalyst

[0054] This example is a variant of Example 1. Other implementation conditions are the same as those in Example 1, and the difference lies in that zinc salt is not added in Step 2, and acid etching treatment is not carried out in Step 3.

[0055] XRD patterns of Examples 1 - 4 and Comparative Example 1 are as Figure 1 shown. The characteristic diffraction peaks of Examples 1 - 4 and Comparative Example 1 correspond to Cu-Co bimetal. At 2θ = 43.3°, it corresponds to the characteristic diffraction peak of Cu 0 (1 1 1), and at 2θ = 44.3°, it corresponds to the characteristic diffraction peak of Co 0 (1 1 1), proving the successful preparation of the Cu-Co bimetal catalyst.

[0056] Scanning electron microscope images of Example 1 and Comparative Example 1 are asFigure 2 As shown in Figure 2 a, it can be seen that after direct calcination treatment of Cu2Co8-ZIF, Cu2Co8@NC is a rough cubic structure with a particle size of about 280 nm. Figure 2 b, it can be seen that after coating with SiO2 and calcination, the cubic structure is still maintained, the surface becomes smooth, and the particle size is about 330 nm.

[0057] The transmission electron microscope images of Example 1 and Comparative Example 1 are as shown in Figure 3 As shown. From Figure 3 a, it can be seen that the Cu2Co8@NC@SiO2 catalyst with a core-shell structure was successfully prepared. The thickness of the SiO2 shell layer is about 24 nm, and the prepared Cu-Co bimetal has good dispersion. Figure 3 b, it can be seen that the metal nanoparticles in Cu2Co8@NC of Comparative Example 1 are dispersed in the C-N substrate. Figure 3 c, two lattice spacings of the metal nanoparticles were measured to be 0.205 nm and 0.208 nm, respectively, which belong to the Cu(111) and Co(111) crystal planes, consistent with the XRD results.

[0058] The specific surface area and pore size distribution of Example 1 and Comparative Example 1 were measured by nitrogen physical adsorption method. Figure 4 As shown, both Cu2Co8@NC and Cu2Co8@NC@SiO2 show typical Type IV isotherms. After calcination and reduction of Cu2Co8-ZIF at 600 °C, a carbon carrier doped with nitrogen is formed, and the specific surface area is small. The SiO2 shell layer increases the specific surface area of the catalyst from 175 cm 2 g -1 to 447 cm2 / g, and large mesopores appear. It can be clearly seen that the pore size becomes larger after introducing the mesoporous SiO2 shell layer. -1

[0059] The contact angle tests were carried out on Example 1 and Comparative Example 1. As shown in Figure 5 a and c, the hydrophilicity of the catalyst increases after coating with SiO2. As shown in Figure 5 b and d, the affinity for furfural increases after coating with SiO2. Due to the excellent dispersion of the SiO2 shell layer in water, the full contact between the reaction sites of the catalyst and water protons is promoted, thus enhancing the gas-liquid-solid three-phase hydrogenation process.

[0060] The performance investigation of the catalytic selective hydrogenation of furfural to furfuryl alcohol for the examples and comparative examples includes the following steps:

[0061] 50 mg of the catalyst, 2 mmol of furfural, and 15 mL of deionized water were added to a 100 mL stainless-steel autoclave with a glass liner. After the autoclave was sealed, the air inside the autoclave was replaced with N2 three to five times, and finally 1 MPa of H2 was charged. The stirring speed of the autoclave was set at 750 rpm and heated to 100 °C within 15 min. After the reaction was completed for 3 h, the autoclave was quickly cooled to room temperature using ice water, and the suspension after the reaction was filtered to separate the liquid product from the catalyst. The liquid product was analyzed by gas chromatography, and the results are shown in Table 1.

[0062] Table 1 Cu with different Cu / Co ratios x Co y @NC@SiO2 and Cu2Co8@NC Catalytic Results for Furfural Hydrogenation

[0063] Number Catalyst Conversion rate (%) Selectivity of furfuryl alcohol (%) Example 1 <![CDATA[Cu2Co8@NC@SiO2]]> 93.5％ 100 Example 2 <![CDATA[Cu1Co9@NC@SiO2]]> 81.2 100 Example 3 <![CDATA[Cu3Co7@NC@SiO2]]> 62.4 100 Example 4 <![CDATA[Cu4Co6@NC@SiO2]]> 22.4 100 Example 5 <![CDATA[Co@NC@SiO2]]> 97.5 90.5 Comparative Example 1 <![CDATA[Cu2Co8@NC]]> 40.6 100

[0064] It was found that the conversion rate of the Co8@NC@SiO2 catalyst in Example 5 was as high as 97.5%, but the conversion rate was 90.5%. With the incorporation of Cu, it interacted with Co. When the molar ratio of Cu to Co was in the range of 1:9, 2:8, 3:7, and 4:6, the catalytic activity first increased and then decreased, and the selectivity remained 100%. Among them, the catalytic activity was the highest when the Cu-Co molar ratio was 2:8.

[0065] As mentioned above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should all be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A method for preparing furfuryl alcohol by selective hydrogenation of furfural, characterized in that: Here are the steps: (1) Dissolving cobalt salt, copper salt and hexadecyltrimethylammonium bromide in deionized water as solution A, dissolving 2-methylimidazole in deionized water as solution B, rapidly dropping solution A into solution B, stirring at room temperature, centrifuging and washing the obtained mixed solution, and drying overnight to obtain CuCo-ZIF; (2) adding the CuCo-ZIF obtained in step (1) to deionized water, and after ultrasonic dispersion, adding sodium hydroxide solution, continuing ultrasonic oscillation, adding hexadecyltrimethylammonium bromide, stirring for 0.5 h, and then slowly adding tetraethyl orthosilicate methanol solution dropwise, stirring at room temperature for 0.5 h, filtering the obtained mixed solution, washing with deionized water to pH = 7, and drying overnight to obtain a CuCo-ZIF precursor with SiO2 coated on the surface; (3) calcining the CuCo-ZIF precursor with SiO2 coated on the surface obtained in step (2) under an inert atmosphere to obtain a CuCo@NC@SiO2 catalyst; (4) The CuCo@NC@SiO2 catalyst obtained in step (3) is used in a high-pressure reactor to catalyze the selective hydrogenation of furfural to prepare furfuryl alcohol.

2. The method according to claim 1, characterized in that In step (1), the cobalt salt is cobalt nitrate hexahydrate, and the active metal Co accounts for 20-30% of the total mass of the catalyst; the copper salt is copper nitrate trihydrate, and the active metal Cu accounts for 0-9% of the total mass of the catalyst; and the mass ratio of the cobalt salt to the copper salt is controlled to be 1:(0-0.72).

3. The method according to claim 1, characterized in that: In step (1), The mass ratio of 2-methylimidazole to cobalt salt is 1:(0.03-0.06); The stirring time at room temperature is 0.5-1 h.

4. The method according to claim 1, characterized in that In step (2), The concentration of sodium hydroxide solution is 0.1-0.2 mol / L, and is used to adjust the pH of the dispersion to 8-9; The mass ratio of CuCo-ZIF to hexadecyltrimethylammonium bromide is 1:(0.1-0.5); The mass ratio of tetraethyl orthosilicate to CuCo-ZIF is 1:(0.6-3); The drying temperature is 60-80℃.

5. The method according to claim 1, characterized in that In step (3), The calcination temperature is 500-800°C, the heating rate is 2-5°C / min, the cooling rate is 1-10°C / min, and the inert atmosphere is nitrogen or argon.

6. The method according to claim 1, characterized in that In step (4), The reaction pressure is 0.25-2MPa; the reaction temperature is 90-150℃; The reaction time is 120-180 min; the reaction solvent is deionized water.

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