A copper-based catalyst, its preparation method and use

Abstract

This invention relates to the field of catalyst technology, specifically to a copper-based catalyst, its preparation method, and its application. The specific technical solution is as follows: (1) NaOH solution is slowly added dropwise to C4H6CuO4·H2O solution, and after stirring, a blue mixed solution is obtained; (2) The blue mixed solution is transferred to a reaction vessel and heated in an oven at 100-200℃ for 12-48 hours to obtain a solid-liquid mixture; (3) The solid-liquid mixture is centrifuged, washed, and dried to obtain the copper-based catalyst. This invention solves the problem of the large amount of alkaline waste salt pollutants generated by the synthesis of FDCA under alkaline conditions in existing technologies.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a copper-based catalyst, its preparation method, and its application. Background Technology

[0002] 5-Hydroxymethylfurfural (HMF), a product of glucose hydrolysis from plant cellulose and subsequent dehydration, is one of the most promising biomass-based platform compounds. It can be synthesized into 2,5-furandicarboxylic acid (FDCA) via oxidation, replacing petroleum-based terephthalic acid in the production of polymers such as polyethylene furanate (PEF). PEF is a 100% bio-based polymer widely used in the manufacture of packaging, textiles, films, and other products, thus achieving an organic link between biomass chemistry and petrochemicals.

[0003] In practice, the oxidation of HMF to FDCA typically requires alkaline conditions. The salt formed by FDCA and alkali has higher solubility in aqueous solution, and alkaline conditions promote the oxidation of hydroxyl / aldehyde groups in HMF and its intermediates, thus improving the synthesis efficiency of FDCA. However, alkaline conditions also promote side reactions of HMF, corrode equipment, and generate large amounts of alkaline waste salt pollutants. Therefore, there is an urgent need to develop an HMF oxidation system under alkaline conditions to solve these problems.

[0004] Studies have shown that oxygen as the oxidant, under the action of noble metals (Pt, Pd, Ru), can efficiently catalyze the alkali-free oxidation of HMF to FDCA. However, this process requires harsh reaction conditions (120-140℃, high oxygen pressure), and the cost of noble metals is high. Therefore, the non-noble metal-catalyzed tert-butyl peroxide oxidation system has attracted much attention in recent years due to its low cost and ability to be carried out under normal pressure.

[0005] Chinese patent CN120440855A discloses a method for preparing a hollow cobalt phosphide catalyst and a method for oxidizing 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid, but the catalyst preparation process is relatively complex. Chinese patent CN119455977A discloses a method for preparing a nano-microstructured multi-metal oxide catalyst and a method for selectively catalytically oxidizing 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid. The catalyst has advantages such as high dispersibility, strong controllability, and rapid crystallization, but it requires an alkaline oxidation system to achieve efficient and selective conversion of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a copper-based catalyst, its preparation method, and its application. This solves the problem of generating large amounts of alkaline waste salt pollutants caused by the synthesis of FDCA under alkaline conditions in existing technologies. The catalyst used for oxidation reactions has advantages such as high activity, high stability, and high selectivity.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention discloses a method for preparing a copper-based catalyst, comprising the following steps:

[0009] (1) NaOH solution was slowly added dropwise to C4H6CuO4·H2O solution and stirred to obtain a blue mixed solution;

[0010] (2) Transfer the blue mixed solution to a reaction vessel and heat it in an oven at 100-200℃ for 12-48h to obtain a solid-liquid mixture;

[0011] (3) After centrifuging, washing and drying the solid-liquid mixture, the copper-based catalyst is obtained.

[0012] Preferably, in step (1), the concentration of the C4H6CuO4·H2O solution is 0.1-5 mol / L; and the concentration of the NaOH solution is 0.5-2 mol / L.

[0013] Preferably, in step (1), the stirring time is 30-60 min.

[0014] Preferably, in step (3), the black solid after centrifugation of the solid-liquid mixture is washed 2-4 times with deionized water and ethanol, and then dried at 50-100℃ for 12-48h.

[0015] Correspondingly, a copper-based catalyst prepared by the above preparation method.

[0016] Preferably, the copper-based catalyst has a specific surface area of ​​2 m². 2 / g-10m 2 / g, pore volume is 0.01mL / g-0.10mL / g, and average pore size is 20nm-50nm.

[0017] Accordingly, the application of a copper-based catalyst prepared by the above method in the alkali-free oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid.

[0018] Preferably, the preparation process of the 2,5-furandicarboxylic acid is as follows: copper-based catalyst, 5-hydroxymethylfurfural, solvent, and tert-butyl hydroperoxide are added to a reactor and reacted at 60-100°C for 1-8 hours. The 2,5-furandicarboxylic acid is obtained after the reaction is completed.

[0019] Preferably, the mass ratio of the copper-based catalyst to 5-hydroxymethylfurfural is 1-20:1-20, and the volume ratio of the solvent to tert-butyl hydroperoxide is 1-40:0.1-5.

[0020] Preferably, the solvent is one of dimethyl sulfoxide, acetonitrile, tert-butanol, and water.

[0021] The present invention has the following beneficial effects:

[0022] 1. The Cu-based catalyst prepared in this invention is a low-cost and abundant non-precious metal material, which is an ideal alternative to expensive precious metals. It can maintain high catalytic activity and selectivity in alkali-free systems, drive the reaction efficiently under relatively mild conditions, and maintain high selectivity for the target product FDCA. It exhibits good catalytic performance in the HMF oxidation process.

[0023] 2. The catalyst disclosed in this invention is prepared by hydrothermal synthesis and experimental operations of centrifugation, washing and drying, and the overall steps are relatively simple.

[0024] 3. The catalyst CuO of the present invention is a non-precious metal catalyst with low cost; it has suitable surface alkalinity and a single exposed CuO (111) crystal plane, which can efficiently promote the oxidation of HMF to FDCA under alkali-free conditions.

[0025] 4. The catalyst of the present invention has high stability and can be recycled 5 to 10 times without significant reduction in activity; it has high oxidation activity and can efficiently catalyze the oxidation reaction of 5-hydroxymethylfurfural under mild reaction conditions. Attached Figure Description

[0026] Figure 1 The XRD pattern of the CuO catalyst prepared in Example 3;

[0027] Figure 2 The TEM image of the CuO catalyst prepared in Example 3;

[0028] Figure 3 The results of the recycling test of the CuO catalyst prepared in Example 3 at 80°C for 4 hours are shown. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Unless otherwise specified, the technical means used in the implementation examples are conventional means well known to those skilled in the art.

[0031] This invention provides a method for preparing a copper-based catalyst, comprising the following steps:

[0032] (1) Slowly add NaOH solution to C4H6CuO4·H2O solution and stir for 30-60 min to obtain a blue mixed solution; prepare C4H6CuO4·H2O solution with a concentration of 0.1-5 mol / L by dissolving C4H6CuO4·H2O in deionized water; prepare NaOH solution with a concentration of 0.5-2 mol / L by dissolving NaOH in deionized water.

[0033] (2) The blue mixed solution was transferred to a reaction vessel with a polytetrafluoroethylene liner and heated in an oven at 100-200℃ for 12-48h to obtain a solid-liquid mixture;

[0034] (3) Centrifuge the solid-liquid mixture to separate the black solid, wash it with deionized water and ethanol 2-4 times each, and then dry it in an oven at 50-100℃ for 12-48h to obtain a copper-based catalyst.

[0035] This invention provides a copper-based catalyst prepared by the above-described method. The copper-based catalyst has a specific surface area of ​​2 m². 2 / g-10m 2 / g, pore volume is 0.01mL / g-0.10mL / g, and average pore size is 20nm-50nm.

[0036] This invention provides an application of the copper-based catalyst prepared by the above method in the alkali-free oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid.

[0037] The preparation process of the 2,5-furandicarboxylic acid is as follows: a copper-based catalyst, 5-hydroxymethylfurfural, solvent, and tert-butylhydrogen peroxide are loaded into a batch reactor and reacted at 60-100℃ for 1-8 hours. The 2,5-furandicarboxylic acid is obtained after the reaction is complete. The solvent is one of dimethyl sulfoxide, acetonitrile, tert-butanol, and water.

[0038] The mass ratio of the copper-based catalyst to 5-hydroxymethylfurfural is 1-20:1-20, and the volume ratio of the solvent to tert-butyl hydroperoxide is 1-40:0.1-5.

[0039] The present invention will be further described below with reference to specific embodiments.

[0040] Example 1

[0041] The catalyst of this invention is CuO with exposed 111 crystal planes.

[0042] The preparation method specifically includes the following steps:

[0043] (1) Preparation of catalyst precursor: Dissolve 1.198 g of C4H6CuO4·H2O in 60 mL of deionized water, and then dissolve 2.4 g of NaOH in 60 mL of deionized water and stir for 20 min. Slowly add the NaOH solution to the C4H6CuO4·H2O solution and stir again for 0.5 h to obtain a blue mixed solution.

[0044] (2) Catalyst preparation: The blue mixed solution obtained in step (1) was transferred to a 250 mL high-pressure reactor lined with stainless steel and placed in an oven at 100 °C for 24 h. The black precipitate was collected, centrifuged, and washed three times each with deionized water and ethanol. Then, it was dried in an oven at 70 °C for 24 h to obtain the CuO catalyst with a specific surface area of ​​10 m². 2 / g, pore volume is 0.08 mL / g, and average pore size is 28 nm.

[0045] Example 2

[0046] The catalyst of this invention is CuO with exposed 111 crystal planes.

[0047] The preparation method specifically includes the following steps:

[0048] (1) Preparation of catalyst precursor: Dissolve 1.198 g of C4H6CuO4·H2O in 60 mL of deionized water, and then dissolve 2.4 g of NaOH in 60 mL of deionized water and stir for 20 min. Slowly add the NaOH solution to the C4H6CuO4·H2O solution and stir again for 0.5 h to obtain a blue mixed solution.

[0049] (2) Catalyst preparation: The blue mixed solution obtained in step (1) was transferred to a 250 mL high-pressure reactor lined with stainless steel and placed in an oven at 120 °C for 24 h. The black precipitate was collected, centrifuged, and washed three times each with deionized water and ethanol. Then, it was dried in an oven at 70 °C for 24 h to obtain the CuO catalyst with a specific surface area of ​​8 m². 2 / g, pore volume is 0.08 mL / g, and average pore size is 42 nm.

[0050] Example 3

[0051] The catalyst of this invention is CuO with exposed 111 crystal planes.

[0052] The preparation method specifically includes the following steps:

[0053] (1) Preparation of catalyst precursor: Dissolve 1.198 g of C4H6CuO4·H2O in 60 mL of deionized water, and then dissolve 2.4 g of NaOH in 60 mL of deionized water and stir for 20 min. Slowly add the NaOH solution to the C4H6CuO4·H2O solution and stir again for 0.5 h to obtain a blue mixed solution.

[0054] (2) Catalyst preparation: The blue mixed solution obtained in step (1) was transferred to a 250 mL high-pressure reactor lined with stainless steel and placed in an oven at 140 °C for 24 h. The black precipitate was collected, centrifuged, and washed three times each with deionized water and ethanol. Then, it was dried in an oven at 70 °C for 24 h to obtain the CuO catalyst with a specific surface area of ​​5 m². 2 / g, pore volume is 0.03 mL / g, and average pore size is 24 nm.

[0055] The XRD pattern of the prepared CuO catalyst is shown in the figure. Figure 1 As shown in the figure, the sharp and clear diffraction peaks indicate that the prepared CuO catalyst has a high degree of crystallinity. In the figure, the diffraction peaks at 2θ = 32.542, 35.523, 38.703, 48.715, 53.466, 58.318, 61.552, 66.303, 68.072, 72.419, and 75.097 are attributed to CuO (JCPDS#45-0937).

[0056] TEM image of the prepared CuO catalyst is shown below. Figure 2 As shown in the figure, the lattice fringes of the CuO crystal plane can be clearly observed, with a corresponding interplanar spacing of 2.36 nm, which is consistent with... Figure 1 The data contained in the XRD patterns are consistent.

[0057] Example 4

[0058] The catalyst of this invention is CuO with exposed 111 crystal planes.

[0059] The preparation method specifically includes the following steps:

[0060] (1) Preparation of catalyst precursor: Dissolve 1.198 g of C4H6CuO4·H2O in 60 mL of deionized water, and then dissolve 2.4 g of NaOH in 60 mL of deionized water and stir for 20 min. Slowly add the NaOH solution to the C4H6CuO4·H2O solution and stir again for 0.5 h to obtain a blue mixed solution.

[0061] (2) Catalyst preparation: The blue mixed solution obtained in step (1) was transferred to a 250 mL high-pressure reactor lined with stainless steel and placed in an oven at 160 °C for 24 h. The black precipitate was collected, centrifuged, and washed three times each with deionized water and ethanol. Then, it was dried in an oven at 70 °C for 24 h to obtain the CuO catalyst with a specific surface area of ​​3 m². 2 / g, pore volume is 0.02 mL / g, and average pore size is 22 nm.

[0062] Example 5

[0063] The catalyst of this invention is CuO with exposed 111 crystal planes.

[0064] The preparation method specifically includes the following steps:

[0065] (1) Preparation of catalyst precursor: Dissolve 1.198 g of C4H6CuO4·H2O in 60 mL of deionized water, and then dissolve 2.4 g of NaOH in 60 mL of deionized water and stir for 20 min. Slowly add the NaOH solution to the C4H6CuO4·H2O solution and stir again for 0.5 h to obtain a blue mixed solution.

[0066] (2) Catalyst preparation: The blue mixed solution obtained in step (1) was transferred to a 250 mL high-pressure reactor lined with stainless steel and placed in an oven at 180 °C for 24 h. The black precipitate was collected, centrifuged, and washed three times each with deionized water and ethanol. Then, it was dried in an oven at 70 °C for 24 h to obtain the CuO catalyst with a specific surface area of ​​2 m². 2 / g, pore volume is 0.01 mL / g, and average pore size is 24 nm.

[0067] Example 6

[0068] The catalyst of this invention is CuO with exposed 111 crystal planes.

[0069] The preparation method specifically includes the following steps:

[0070] (1) Preparation of catalyst precursor: Dissolve 1.198 g of C4H6CuO4·H2O in 60 mL of deionized water, and then dissolve 1.2 g of NaOH in 60 mL of deionized water and stir for 20 min. Slowly add the NaOH solution to the C4H6CuO4·H2O solution and stir again for 0.5 h to obtain a blue mixed solution.

[0071] (2) Catalyst preparation: The blue mixed solution obtained in step (1) was transferred to a 250 mL high-pressure reactor lined with stainless steel and placed in an oven at 140 °C for 24 h. The black precipitate was collected, centrifuged, and washed three times each with deionized water and ethanol. Then, it was dried in an oven at 70 °C for 24 h to obtain the CuO catalyst with a specific surface area of ​​8 m². 2 / g, pore volume is 0.09 mL / g, and average pore size is 45 nm.

[0072] Example 7

[0073] The catalyst of this invention is CuO with exposed 111 crystal planes.

[0074] The preparation method specifically includes the following steps:

[0075] (1) Preparation of catalyst precursor: Dissolve 1.198 g of C4H6CuO4·H2O in 60 mL of deionized water, and then dissolve 4.8 g of NaOH in 60 mL of deionized water and stir for 20 min. Slowly add the NaOH solution to the C4H6CuO4·H2O solution and stir again for 0.5 h to obtain a blue mixed solution.

[0076] (2) Catalyst preparation: The blue mixed solution obtained in step (1) was transferred to a 250 mL high-pressure reactor lined with stainless steel and placed in an oven at 140 °C for 24 h. The black precipitate was collected, centrifuged, and washed three times each with deionized water and ethanol. Then, it was dried in an oven at 70 °C for 24 h to obtain the CuO catalyst with a specific surface area of ​​4 m². 2 / g, pore volume is 0.02 mL / g, and average pore size is 25 nm.

[0077] Comparative Example 1: Preparation of 2,5-furandicarboxylic acid (FDCA)

[0078] A control experiment was conducted by loading 12.6 mg HMF, 2 mL dimethyl sulfoxide, and 550 μL tert-butyl hydrogen peroxide into a batch reactor and reacting at 80 °C for 4 h. After the reaction was completed, samples were taken for analysis, and the conversion rate of HMF and the yield of FDCA were 38.41% and 0.92%, respectively.

[0079] Comparative Example 2: Preparation of 2,5-furandicarboxylic acid (FDCA)

[0080] The CuO catalyst prepared in Example 3, 12.6 mg of HMF, and 2 mL of dimethyl sulfoxide were loaded into a batch reactor for a control experiment, and the reaction was carried out at 80 °C for 4 h. After the reaction was completed, samples were taken for analysis, and the conversion rate of HMF and the yield of FDCA were 3.51% and 0.02%, respectively.

[0081] Example 8 Preparation of 2,5-furandicarboxylic acid (FDCA)

[0082] The CuO catalyst prepared in Examples 1-7, 12.6 mg HMF, 2 mL dimethyl sulfoxide, and 550 μL tert-butyl hydrogen peroxide were respectively packed into a batch reactor and reacted at 80 °C for 4 h. After the reaction was completed, samples were taken for analysis. The conversion rate of HMF and the yield of FDCA are shown in Table 1 below.

[0083] Table 1. Yield of FDCA and conversion of HMF

[0084] Example catalyst HMF conversion rate / % FDCA yield / % Example 8 Example 1 99.92% 81.05% Example 9 Example 2 99.76% 75.06% Example 10 Example 3 99.59% 85.77% Example 11 Example 4 100% 77.02% Example 12 Example 5 99.27% 81.62% Example 13 Example 6 99.30% 80.19% Example 14 Example 7 99.77% 74.84%

[0085] As shown in Table 1, different hydrothermal temperatures and NaOH dosages jointly regulate the structure and activity of the CuO catalyst, resulting in a non-monotonic wave-like variation in FDCA yield. With a fixed NaOH content of 2.4 g, CuO crystallization and structural rearrangement gradually improve at 100-140℃, increasing the content of active sites, and the yield initially decreases before rising to a peak (85.77%). Further heating to 160℃ leads to excessive grain growth and aggregation, reducing the available active sites and decreasing the yield. However, at 180℃, local structural reconstruction occurs, compensating for the activity loss to some extent, and the yield recovers slightly.

[0086] At 140℃, adjusting the alkali content revealed that 1.2g of NaOH resulted in insufficient precipitation and uneven crystallization, leading to a slight decrease in yield (80.19%). 4.8g of NaOH potentially exacerbated grain aggregation, causing a significant decrease in yield (74.84%). Only by controlling the alkali content within a specific range could optimal crystal facet exposure be achieved, effectively optimizing the distribution of surface active sites. Therefore, a hydrothermal temperature of 140℃ and 2.4g of NaOH represent the optimal preparation conditions for 111-faceted CuO. Deviations in temperature or alkali content disrupted the structure-activity balance, ultimately resulting in a yield variation characterized by an initial decrease followed by an increase, then a further decrease followed by an increase, and finally a gradual decrease.

[0087] Example 15 Effect of different volumes of tert-butyl hydroperoxide on FDCA yield

[0088] 20 mg of the catalyst prepared in Example 3, 12.6 mg of HMF, 2 mL of dimethyl sulfoxide, and 600 μL of tert-butyl hydroperoxide were packed into a batch reactor and reacted at 80 °C for 4 h. After the reaction was completed, samples were taken for analysis. The HMF conversion rate was 99.76%, and the FDCA yield was 81.32%.

[0089] Example 16 Effect of different reaction temperatures on FDCA yield

[0090] 20 mg of the catalyst prepared in Example 3, 12.6 mg of HMF, 2 mL of dimethyl sulfoxide, and 550 μL of tert-butyl hydroperoxide were packed into a batch reactor and reacted at 90 °C for 4 h. After the reaction was completed, samples were taken for analysis. The HMF conversion rate was 99.99%, and the FDCA yield was 43.46%.

[0091] Example 17 Effect of different reaction times on FDCA yield

[0092] 20 mg of the catalyst prepared in Example 3, 12.6 mg of HMF, 2 mL of dimethyl sulfoxide, and 550 μL of tert-butyl hydrogen peroxide were packed into a batch reactor and reacted at 80 °C for 3 h. After the reaction was completed, samples were taken for analysis. The HMF conversion rate was 99.91%, and the FDCA yield was 80.23%.

[0093] Example 18 Effect of different reaction times on FDCA yield

[0094] 20 mg of the catalyst prepared in Example 3, 12.6 mg of HMF, 2 mL of dimethyl sulfoxide, and 550 μL of tert-butyl hydroperoxide were packed into a batch reactor and reacted at 80 °C for 5 h. After the reaction was completed, samples were taken for analysis. The HMF conversion rate was 99.80%, and the FDCA yield was 74.22%.

[0095] Example 19 Catalyst Recovery

[0096] The catalyst after the reaction in Example 10 was filtered and recovered. It was washed three times with deionized water and ethanol, respectively, and then dried in a 60°C oven. It was then taken out and put into use.

[0097] Example 20 Catalyst Recycling

[0098] The catalyst recovered in Example 19 was reused five more times using the method described in Example 10. The results were as follows: Figure 3 As shown. Here, cycle number 1 refers to the first use of the prepared catalyst; cycle number 2 refers to the first reuse of the prepared catalyst; cycle number 3 refers to the second reuse of the prepared catalyst, and so on. Figure 3 It can be seen that the catalyst prepared by this invention still has good catalytic activity and selectivity after multiple recycling processes.

[0099] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a copper-based catalyst, characterized in that: Includes the following steps: (1) NaOH solution was slowly added dropwise to C4H6CuO4·H2O solution and stirred to obtain a blue mixed solution; (2) Transfer the blue mixed solution to a reaction vessel and heat it in an oven at 100-200℃ for 12-48h to obtain a solid-liquid mixture; (3) After centrifuging, washing and drying the solid-liquid mixture, the copper-based catalyst is obtained.

2. The preparation method according to claim 1, characterized in that: In step (1), the concentration of the C4H6CuO4·H2O solution is 0.1-5 mol / L; the concentration of the NaOH solution is 0.5-2 mol / L.

3. The preparation method according to claim 1, characterized in that: In step (1), the stirring time is 30-60 minutes.

4. The preparation method according to claim 1, characterized in that: In step (3), the black solid after centrifugation of the solid-liquid mixture is washed 2-4 times with deionized water and ethanol, and then dried at 50-100℃ for 12-48h.

5. A copper-based catalyst prepared by the preparation method according to any one of claims 1-4.

6. The copper-based catalyst according to claim 5, characterized in that: The copper-based catalyst has a specific surface area of ​​2 m². 2 / g-10m 2 / g, pore volume is 0.01mL / g-0.10mL / g, and average pore size is 20nm-50nm.

7. The use of a copper-based catalyst prepared by the method according to any one of claims 1-4 in the alkali-free oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid.

8. The application according to claim 7, characterized in that: The preparation process of the 2,5-furandicarboxylic acid is as follows: copper-based catalyst, 5-hydroxymethylfurfural, solvent, and tert-butyl hydroperoxide are added to a reactor and reacted at 60-100℃ for 1-8 hours. The 2,5-furandicarboxylic acid is obtained after the reaction is completed.

9. The application according to claim 8, characterized in that: The mass ratio of the copper-based catalyst to 5-hydroxymethylfurfural is 1-20:1-20, and the volume ratio of the solvent to tert-butyl hydroperoxide is 1-40:0.1-5.

10. The application according to claim 8 or 9, characterized in that: The solvent is one of dimethyl sulfoxide, acetonitrile, tert-butanol, or water.

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