A strong metal-support interaction, sub-nanoscale dispersed silica supported copper composite material, and a preparation method and application thereof

Abstract

The application belongs to the field of material preparation, and discloses a preparation method of silica supported copper composite material with strong metal-support interaction and sub-nanometer dispersion and application thereof. First, the microporous pure silicon molecular sieve is subjected to alkali treatment, and appropriate mesoporous structure is introduced, which is beneficial to the dispersion of copper species, and the accessibility of the microporous channel left is improved, thereby being beneficial to the formation of sub-nanometer copper clusters in the microporous channel and the opening and participating in catalytic reaction. Second, the dissolved silica in the alkali treatment process and the surface-activated silica are reacted with the subsequently added copper ions to generate copper silicate, which further promotes the dispersion of copper species and the strong interaction between the metal and the carrier. Finally, hydrothermal crystallization can promote the generation of copper silicate on the surface of Silicalite-1, and improve the stability of the catalytic structure. The preparation method is simple, green, environmentally friendly, high in activity, good in stability, cheap and easy to obtain, and can efficiently catalyze the anaerobic dehydrogenation of 2,3-butanediol, and has a good industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of materials preparation, and specifically relates to a strong metal-carrier interaction, sub-nanometer dispersed silicon dioxide-supported copper material (Cu / SiO2), its preparation method, and its application in the selective dehydrogenation conversion of 2,3-butanediol. Background Technology

[0002] The maturity and widespread adoption of green processes for synthesizing 2,3-butanediol from biomass monosaccharides via microbial fermentation have made large-scale industrial production possible, while also accelerating the development of technologies for converting 2,3-butanediol into high-value-added products. Specifically, 2,3-butanediol can be selectively dehydrogenated without oxygen to produce 3-hydroxybutanone, an important chemical widely used in fragrances, food, and tobacco. Furthermore, this dehydrogenation process produces only the target product 3-hydroxybutanone and hydrogen, with no other byproducts, making it environmentally friendly and highly atom-economical.

[0003] Currently, there are few studies and reports on the selective dehydrogenation of 2,3-butanediol to produce 3-hydroxybutanone. Yuan et al. prepared silica-supported copper catalysts for the oxygen-free dehydrogenation of 2,3-butanediol using both ammonia stripping and a one-step method, and found that the catalytic activity originated from the Cu at the metal-support interface. 0 and Cu 2+ The synergistic effect of [the catalyst] (Journal of Catalysis 2020, 382, ​​256; ACS Sustainable Chemistry & Engineering 2020, 8, 15716). Recently, studies have found that although copper nanoparticles lack catalytic dehydrogenation properties, sub-nanometer dispersed copper clusters exhibit catalytic activity for the dehydrogenation of 2,3-butanediol (Sustainable Chemistry and Pharmacy 2024, 37, 101380). Kurniawan et al. added crown ether reagents to assist the synthesis of Cu / SiO2 catalysts via impregnation and used them for the dehydrogenation of 2,3-butanediol (Chemistry 2023, 5, 406). Compared to Cu / SiO2 catalysts, CuZnAl, Cu / Al2O3, and Cu / ZrO2 exhibit significantly lower catalytic activity for the dehydrogenation of 2,3-butanediol (Topics in Catalysis 2020, 63, 866; Industrial & Engineering Chemistry Research 2022, 61, 3530). Besides focusing on the dehydrogenation activity and selectivity of the catalysts, the stability of the catalytic structure also needs improvement. Therefore, the unique dehydrogenation mechanism of 2,3-butanediol requires the prepared Cu / SiO2 catalyst to possess strong metal-support interactions and sub-nanometer dispersion of the active components.

[0004] Silicalite-1 is a pure silica molecular sieve with a microporous structure (MFI) and high stability, characterized by regular micropores (approximately 0.55 nm in diameter). It is widely used for gas separation, adsorption, and as a catalyst support. However, the microporous structure of Silicalite-1 limits its application in reactions involving macromolecules. Therefore, alkaline treatment is often used to sacrifice some micropores and introduce a suitable amount of mesoporous structure. Although the well-developed mesoporous structure and high specific surface area are beneficial for the dispersion of copper species, the sub-nanometer copper clusters within and at the pore openings decrease with the reduction of the number of micropores. Furthermore, Cu / SiO2 catalysts prepared using traditional impregnation, precipitation, and ammonia stripping methods not only exhibit low copper dispersion but also weak catalytic structural stability. Summary of the Invention

[0005] To address the aforementioned issues, the present invention aims to provide a method for preparing a silicon dioxide-supported copper material (Cu / SiO2) with strong metal-support interaction and sub-nanometer dispersion, and its application in the oxygen-free dehydrogenation of 2,3-butanediol. This method can significantly improve the conversion rate of 2,3-butanediol, the selectivity of 3-hydroxybutanone, and the stability of the catalytic structure. The reaction is green and efficient, and the catalyst can be separated and recycled.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A copper-supported silica material with strong metal-carrier interaction and sub-nanometer dispersion is disclosed. The copper-supported silica material with strong metal-carrier interaction and sub-nanometer dispersion is Cu / SiO2, with a Cu loading of 5.0-25 wt.%. Copper exists in both metallic and ionic forms. The sub-nanometer copper clusters have a particle size of less than 0.55 nm.

[0008] Furthermore, the Cu loading of the strongly metal-carrier-interacting, sub-nanometer dispersed silica-supported copper material Cu / SiO2 is 5.0-23 wt.%.

[0009] Furthermore, the Cu loading of the strongly metal-carrier-interacting, sub-nanometer dispersed silica-supported copper material Cu / SiO2 is 10.0-22 wt.%.

[0010] Furthermore, the Cu loading of the strongly metal-carrier-interacting, sub-nanometer dispersed silica-supported copper material Cu / SiO2 is 15.0-22 wt.%.

[0011] Furthermore, the Cu loading of the strongly metal-carrier-interacting, sub-nanometer dispersed silica-supported copper material Cu / SiO2 is 19.0-21 wt.%.

[0012] This invention also provides a method for preparing the above-mentioned strong metal-carrier interaction, sub-nanometer dispersion silica-supported copper material, the method comprising the following steps:

[0013] S1. Add microporous pure silicon molecular sieve Silicalite-1 powder to an alkaline aqueous solution and etch it by vigorous stirring at a certain temperature. The alkaline aqueous solution is an organic base aqueous solution or ammonia water.

[0014] S2. Add copper salt and, after it is completely dissolved, adjust the pH of the synthesis solution to alkaline.

[0015] S3. The synthesis solution is subjected to hydrothermal crystallization to obtain Cu / SiO2 precursor, which is then washed, dried, calcined, and reduced to obtain Cu / SiO2.

[0016] Furthermore, in step S1, the organic base is tetrapropylammonium hydroxide and / or tetraethylammonium hydroxide.

[0017] Furthermore, in step S1, when the alkaline aqueous solution is an organic base aqueous solution, the mass ratio of the organic base aqueous solution to Silicalite-1 is 15-30:1.

[0018] Furthermore, in step S1, when the alkaline aqueous solution is an ammonia solution, the mass ratio of the ammonia solution to Silicalite-1 is 6-30:1.

[0019] Furthermore, in step S1, the concentration of the organic base is 0.3-1.0 mol / L.

[0020] Furthermore, in step S1, the concentration of ammonia is 10-15.5 mol / L.

[0021] Furthermore, in step S1, the temperature at which the alkaline solution etches Silicalite-1 is 40-70°C.

[0022] Furthermore, in step S1, the etching time for Silicalite-1 with alkaline solution is 0.5-3 hours.

[0023] Furthermore, in step S2, the copper salt is copper nitrate or copper chloride.

[0024] Furthermore, in step S2, when the copper salt is copper nitrate, the mass ratio of the amount of copper salt added to Silicalite-1 is 0.2-0.85:1.

[0025] Furthermore, in step S2, when the copper salt is copper chloride, the mass ratio of the amount of copper salt added to Silicalite-1 is 0.2-0.6:1.

[0026] In this invention, step S2 controls the Cu loading in Cu / SiO2 to be between 5.0-25 wt.% by controlling the ratio of the amount of copper salt added to the mass of the microporous pure silicon molecular sieve.

[0027] Furthermore, in step S2, the pH of the synthesis solution is adjusted to 8-11.

[0028] Furthermore, in step S2, the pH of the synthesis solution is adjusted to 10.

[0029] Furthermore, in step S2, the pH of the synthesis solution is adjusted to 8.

[0030] Furthermore, in step S2, inorganic acid and / or ammonia are added to adjust the pH of the synthesis solution.

[0031] Furthermore, in step S2, the concentration of the inorganic acid is 1.0-3.0 mol / L.

[0032] Furthermore, in step S2, the concentration of the inorganic acid is 2.0 mol / L.

[0033] Furthermore, in step S3, the temperature for hydrothermal crystallization of the synthetic liquid is 110-170℃.

[0034] Furthermore, in step S3, the temperature for hydrothermal crystallization of the synthetic liquid is 130°C.

[0035] Furthermore, in step S3, the hydrothermal crystallization time of the synthetic liquid is 12-48 hours.

[0036] Furthermore, in step S3, the calcination includes calcining the Cu / SiO2 precursor at a temperature of 450-600°C in an air atmosphere.

[0037] Furthermore, in step S3, the calcination includes calcining the Cu / SiO2 precursor in an air atmosphere for 3-6 hours.

[0038] Furthermore, in step S3, the reduction includes Cu / SiO2 hydrogen reduction at a temperature of 250-400°C in a hydrogen atmosphere.

[0039] Furthermore, in step S3, the reduction includes Cu / SiO2 hydrogen reduction in a hydrogen atmosphere for 1-3 hours.

[0040] Furthermore, the method for etching Silicalite-1 with an organic base aqueous solution and preparing Cu / SiO2 includes the following steps:

[0041] S1. Weigh 1 part by weight of Silicalite-1 powder and add it to 15-30 parts by weight of an aqueous solution of an organic base with a concentration of 0.3-1.0 mol / L, wherein the organic base includes tetrapropylammonium hydroxide and / or tetraethylammonium hydroxide, and stir at 40-70°C for 0.5-3 hours.

[0042] S2. Add 0.2-0.85 parts by weight of copper salt. After dissolving, add an inorganic acid with a concentration of 1.0-3.0 mol / L to adjust the pH of the synthesis solution to 8-11.

[0043] S3. Place the synthesis solution at 110-170℃ for hydrothermal crystallization for 12-48 hours. The resulting solid is the Cu / SiO2 precursor. After washing, drying, calcining in air at 450-600℃ for 3-6 hours, and reducing in hydrogen at 250-400℃ for 1-3 hours, Cu / SiO2 is obtained.

[0044] Furthermore, the method for etching Silicalite-1 with an organic base aqueous solution and preparing Cu / SiO2 includes the following steps:

[0045] S1. Weigh 1 part by weight of Silicalite-1 powder and add it to 24 parts by weight of an aqueous solution of organic base (such as tetrapropylammonium hydroxide, tetraethylammonium hydroxide, etc.) with a concentration of 0.50 mol / L, and stir at 50°C for 1 hour.

[0046] S2. Add 0.75 parts by weight of copper nitrate, stir for 1 hour, then add 2.0 mol / L hydrochloric acid to adjust the pH of the synthesis solution to 10.

[0047] S3. The synthesis solution was hydrothermally crystallized at 130°C for 18 hours. The resulting solid was washed with water, dried at 110°C, calcined at 550°C in air for 5 hours, and reduced at 300°C in hydrogen for 1 hour to obtain Cu / SiO2.

[0048] Furthermore, the method for etching Silicalite-1 with ammonia solution and preparing Cu / SiO2 includes the following steps:

[0049] S1. Weigh 1 part by weight of Silicalite-1 powder and add it to 6-30 parts by weight of ammonia solution with a concentration of 10-15.5 mol / L, and stir at 40-70℃ for 0.5-3 hours.

[0050] S2. Add 0.2-0.85 parts by weight of copper nitrate. After dissolving, adjust the pH of the synthesis solution to 8-11 by removing ammonia.

[0051] S3. Place the synthesis solution at 110-170℃ for hydrothermal crystallization for 12-48 hours. The resulting solid is the Cu / SiO2 precursor. After washing, drying, calcining in air at 450-600℃ for 3-6 hours, and reducing in hydrogen at 250-400℃ for 1-3 hours, Cu / SiO2 is obtained.

[0052] Furthermore, the method for etching Silicalite-1 with ammonia solution and preparing Cu / SiO2 includes the following steps:

[0053] S1. Weigh 1 part by weight of Silicalite-1 powder and add it to 11 parts by weight of ammonia solution with a concentration of 15.5 mol / L. Stir vigorously at 70°C for 4 hours.

[0054] S2. Add 0.75 parts by weight of copper nitrate, stir for 2 hours to dissolve, and then evaporate ammonia until the solution pH is 8.0.

[0055] S3. The synthesis solution was placed at 160℃ for hydrothermal crystallization for 48 hours. The resulting solid was washed with water, dried at 110℃, calcined at 550℃ in air for 5 hours, and reduced at 300℃ in hydrogen for 1 hour to obtain Cu / SiO2.

[0056] This invention also provides a silicon dioxide-supported copper material with strong metal-carrier interaction and sub-nanometer dispersion prepared by the above method.

[0057] Furthermore, the microporous specific surface area of ​​the silicon dioxide-supported copper material with strong metal-carrier interaction and sub-nanometer dispersion is 0-130 m². 2 / g.

[0058] Furthermore, the microporous specific surface area of ​​the silicon dioxide-supported copper material with strong metal-carrier interaction and sub-nanometer dispersion is 60-120 m². 2 / g.

[0059] Furthermore, the outer surface specific surface area of ​​the silicon dioxide-supported copper material with strong metal-carrier interaction and sub-nanometer dispersion is 130-220 m². 2 / g.

[0060] Furthermore, the external surface area of ​​the silicon dioxide-loaded copper material with strong metal-carrier interaction and sub-nanometer dispersion is 170-220 m² / g.

[0061] Furthermore, the micropore volume of the silicon dioxide-supported copper material with strong metal-carrier interaction and sub-nanometer dispersion is 0-0.05 cm³. 3 / g.

[0062] Furthermore, the total pore volume of the silicon dioxide-supported copper material with strong metal-carrier interaction and sub-nanometer dispersion is 0.3-0.6 cm³. 3 / g.

[0063] This invention also provides the application of the copper-supported silica material with strong metal-support interaction and sub-nanometer dispersion prepared by the above method in the selective dehydrogenation reaction of 2,3-butanediol.

[0064] Furthermore, the space time for the dehydrogenation of 2,3-butanediol is 0.016-0.10 hours, and the reaction temperature is 220-280℃.

[0065] Furthermore, in the catalytic selective dehydrogenation reaction of 2,3-butanediol, the conversion rate of 2,3-butanediol is 5-90%.

[0066] Beneficial effects

[0067] (1) In this invention, an alkaline solution is first used to etch microporous pure silicon molecular sieve Silicalite-1 to introduce an appropriate amount of mesoporous structure, which increases the external specific surface area and is conducive to the dispersion of copper elements. At the same time, the accessibility of the remaining micropores is improved, which is conducive to the formation of sub-nanometer copper clusters in the micropores and at the openings and their participation in the catalytic reaction. Secondly, the dissolved silica and surface-activated silica during the alkaline treatment react with the subsequently added copper ions to generate copper silicate, which further promotes the dispersion of copper species and the strong metal-support interaction. In the second step of hydrothermal crystallization, the organic base also acts as a micropore template agent, which can coat some copper species into the micropores, restrict their growth, and is conducive to the formation of sub-nanometer copper clusters. Finally, hydrothermal crystallization can promote the formation of copper silicate on the surface of Silicalite-1 and improve the stability of the catalytic structure.

[0068] (2) The Cu / SiO2 material described in this invention is used to catalyze the dehydrogenation reaction of 2,3-butanediol. The strong metal-support interaction and sub-nanometer copper clusters can significantly improve the dehydrogenation conversion rate of 2,3-butanediol. At the same time, the catalytic structure after hydrothermal crystallization is more stable and the catalytic life is longer. The catalytic reaction is green and efficient, and the catalyst can be separated and recycled.

[0069] (3) The Cu / SiO2 material preparation method of the present invention is simple, has low synthesis cost, and simple process, and has good prospects for industrial application. Attached Figure Description

[0070] Figure 1 TEM images of the Cu / SiO2-Tp-0.5-10 material prepared in Example 1 of this invention at different magnifications;

[0071] Figure 2The image shows the XRD pattern of the Cu / SiO2-Tp-0.5-10 material prepared in Example 1 of this invention.

[0072] Figure 3 The image shows the Cu 2p XPS spectrum of the Cu / SiO2-Tp-0.5-10 material prepared in Example 1 of this invention.

[0073] Figure 4 The FTIR spectrum of the Cu / SiO2-Tp-0.5-10 material prepared in Example 1 of this invention;

[0074] Figure 5 The XRD patterns are of the Cu / SiO2-Tp-0.3-10 and Cu / SiO2-Tp-1.0-10 materials prepared in Example 2 of this invention.

[0075] Figure 6 The XRD patterns are of the Cu / SiO2-Tp-0.5-9 and Cu / SiO2-Tp-0.5-11 materials prepared in Example 3 of this invention;

[0076] Figure 7 These are TEM images of the Cu / SiO2-NH3-10 material prepared in Example 4 of this invention at different magnifications;

[0077] Figure 8 The image shows the XRD pattern of the Cu / SiO2-NH3-10 material prepared in Example 4 of this invention.

[0078] Figure 9 The Cu 2p XPS spectrum of the Cu / SiO2-NH3-10 material prepared in Example 4 of this invention;

[0079] Figure 10 The image shows the FTIR spectrum of the Cu / SiO2-NH3-10 material prepared in Example 4 of this invention.

[0080] Figure 11 This is a TEM image of the Cu / SiO2-Im material prepared in Comparative Example 1 of this invention;

[0081] Figure 12 This is a TEM image of the Cu / SiO2-Pr material prepared in Comparative Example 2 of this invention;

[0082] Figure 13 This is a TEM image of the Cu / SiO2-Ae material prepared in Comparative Example 3 of this invention;

[0083] Figure 14 The curves showing the conversion rate of 2,3-butanediol dehydrogenation catalyzed by Cu / SiO2-Tp-xy materials prepared in Examples 1-3 of this invention as a function of reaction time are shown.

[0084] Figure 15 The conversion rate of 2,3-butanediol dehydrogenation catalyzed by Cu / SiO2-NH3-z materials prepared in Examples 4 and 5 of this invention as a function of reaction time is shown.

[0085] Figure 16 Stability test of Cu / SiO2-Tp-0.5-10 material prepared in Example 1 of this invention for catalyzing the dehydrogenation of 2,3-butanediol;

[0086] Figure 17 The stability of the Cu / SiO2-NH3-10 material prepared in Example 4 of this invention for catalyzing the dehydrogenation of 2,3-butanediol was tested. Detailed Implementation

[0087] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0088] When the catalyst described in this invention is used in the dehydrogenation reaction of 2,3-butanediol, it can achieve excellent catalytic performance, including high 2,3-butanediol conversion, 3-hydroxybutanone selectivity, and structural stability.

[0089] The preparation method of Cu / SiO2, a silicon dioxide-supported copper material with strong metal-carrier interaction and sub-nanometer dispersion, includes the following specific steps for alkali treatment using an organic base aqueous solution or an ammonia aqueous solution:

[0090] The first method involves etching Silicalite-1 with an organic base aqueous solution to prepare Cu / SiO2, and the method includes the following steps:

[0091] S1. Weigh 1 part by weight of Silicalite-1 powder and add it to 15-30 parts by weight of an aqueous solution of an organic base with a concentration of 0.3-1.0 mol / L, wherein the organic base includes tetrapropylammonium hydroxide and / or tetraethylammonium hydroxide, and stir at 40-70°C for 0.5-3 hours.

[0092] S2. Add 0.2-0.85 parts by weight of copper salt. After dissolving, add an inorganic acid with a concentration of 1.0-3.0 mol / L to adjust the pH of the synthesis solution to 8-11.

[0093] S3. Place the synthesis solution at 110-170℃ for hydrothermal crystallization for 12-48 hours. The resulting solid is the Cu / SiO2 precursor. After washing, drying, calcining in air at 450-600℃ for 3-6 hours, and reducing in hydrogen at 250-400℃ for 1-3 hours, Cu / SiO2 is obtained.

[0094] The second method involves etching Silicalite-1 with an ammonia solution to prepare Cu / SiO2, and the method includes the following steps:

[0095] S1. Weigh 1 part by weight of Silicalite-1 powder and add it to 6-30 parts by weight of ammonia solution with a concentration of 10-15.5 mol / L, and stir at 40-70℃ for 0.5-3 hours.

[0096] S2. Add 0.2-0.85 parts by weight of copper salt. After dissolving, adjust the pH of the synthesis solution to 8-11 by removing ammonia.

[0097] S3. Place the synthesis solution at 110-170℃ for hydrothermal crystallization for 12-48 hours. The resulting solid is the Cu / SiO2 precursor. After washing, drying, calcining in air at 450-600℃ for 3-6 hours, and reducing in hydrogen at 250-400℃ for 1-3 hours, Cu / SiO2 is obtained.

[0098] Furthermore, in this invention, the Cu loading of the Cu / SiO2 material is 5.0-25 wt.%.

[0099] Furthermore, the Cu loading is preferably 20 wt.%.

[0100] To verify the catalytic performance of the prepared Cu / SiO2, this embodiment of the invention uses it in the dehydrogenation reaction of 2,3-butanediol. Preferably, the dehydrogenation reaction temperature of the 2,3-butanediol is 240-260℃ and the mass space time is 0.025-0.050 hours.

[0101] Example 1

[0102] S1. Weigh 2.0g of Silicalite-1 powder and add it to 47mL (48g) of 0.50mol / L tetrapropylammonium hydroxide aqueous solution, and stir vigorously at 50℃ for 1 hour;

[0103] S2. Add 1.5g of copper nitrate, stir vigorously for 1 hour, then add 2.0mol / L hydrochloric acid to adjust the pH of the synthesis solution to 10.

[0104] S3. The synthesis solution was hydrothermally crystallized at 130℃ for 18 hours. The resulting solid was washed with water, dried at 110℃, calcined at 550℃ in air for 5 hours, and reduced at 300℃ in hydrogen for 1 hour. The Cu / SiO2 material obtained was denoted as Cu / SiO2-Tp-0.5-10.

[0105] Example 2

[0106] Example 1 was repeated, except that the concentration of the tetrapropylammonium hydroxide aqueous solution was changed to 0.30 mol / L, and the resulting Cu / SiO2 materials were denoted as Cu / SiO2-Tp-0.3-10.

[0107] Example 3

[0108] Example 1 was repeated, except that the concentration of the tetrapropylammonium hydroxide aqueous solution was changed to 1.0 mol / L, and the resulting Cu / SiO2 materials were denoted as Cu / SiO2-Tp-1.0-10.

[0109] The elemental analysis results of the Cu / SiO2-Tp materials prepared in Examples 1-3 are shown in Table 1. The Cu loading in the Cu / SiO2-Tp materials prepared in Examples 1-3 is as high as 19.3-20.5 wt.%, especially the Cu / SiO2-Tp-0.5-10 material prepared in Example 1, which has a Cu loading as high as 20.5 wt.%.

[0110] The pore structure parameters of Cu / SiO2-Tp-0.5-10 obtained by nitrogen adsorption-desorption testing are shown in Table 1. On the one hand, compared with Silicalite-1, the external specific surface area of ​​Cu / SiO2-Tp materials prepared in Examples 1-3 is significantly increased, and the micropore volume is significantly decreased, indicating that the alkaline treatment with tetrapropylammonium hydroxide solution in Examples 1-3 effectively introduced a mesoporous structure. On the other hand, with the increase of tetrapropylammonium hydroxide concentration, the micropore specific surface area and pore volume gradually decrease, while the external surface area and total pore volume significantly increase.

[0111] Figure 1 Images a and 1b are TEM images of the Cu / SiO2-Tp-0.5-10 material prepared in Example 1. The Silicalite-1 surface is wrinkled and has numerous mesopores. Cu nanoparticles are uniformly dispersed on the Silicalite-1 surface, with an average particle size of approximately 5.0 nm. Figure 1 In the high-resolution TEM image c, sub-nanometer Cu clusters are dispersed within or at the openings of Silicalite-1 micropores with an average pore size of approximately 0.55 nm, indicating that the Cu cluster particle size is less than 0.55 nm.

[0112] Figure 2 The XRD pattern of the Cu / SiO2-Tp-0.5-10 material prepared in Example 1 shows that, in addition to the characteristic diffraction peak of Silicalite-1, the weak diffraction peak of metallic copper indicates that the copper particles are highly dispersed. The presence of characteristic diffraction peaks of CuO and Cu2O indicates that some copper interacts strongly with the support silica, resulting in it not being reduced.

[0113] Figure 5The images show the XRD patterns of the Cu / SiO2-Tp-0.3-10 materials prepared in Example 2 and the Cu / SiO2-Tp-1.0-10 materials prepared in Example 3. Figure 2 , 5 As can be seen, the diffraction peaks of Silicalite-1 decrease significantly with increasing tetrapropylammonium hydroxide concentration, indicating that the Silicalite-1 crystal structure gradually dissolves and collapses. Simultaneously, the dissolved or surface-activated silica reacts with copper ions to form copper silicate, promoting the dispersion of copper species and thus reducing the intensity of the metallic copper diffraction peaks. The presence of characteristic diffraction peaks of CuO and Cu2O indicates a strong interaction between some copper and the supporting silica, resulting in some copper remaining unreduced and existing as ions in Cu / SiO2-Tp-0.3-10 and Cu / SiO2-Tp-1.0-10.

[0114] Figure 3 The Cu 2p XPS spectrum of the Cu / SiO2-Tp-0.5-10 material prepared in Example 1 can determine the Cu content. 0 and Cu 2+ coexist.

[0115] Figure 4 The FTIR spectrum of the Cu / SiO2-Tp-0.5-10 material prepared in Example 1 is located at 948 cm⁻¹. -1 The infrared characteristic absorption band is attributed to the Si-O bond vibration in the -Cu-O-Si- structure. The stable -Cu-O-Si- structure is not easily reduced, thus allowing some copper species to exist in Cu / SiO2-Tp-0.5-10 in ionic form.

[0116] Table 1. Cu loading and pore structure parameters of Cu / SiO2 materials prepared in Examples 1-4 of this invention.

[0117]

[0118]

[0119] Based on the structures of Examples 1, 2 and 3, the present invention selects a tetrapropylammonium hydroxide NaOH aqueous solution concentration of 0.50 mol / L to further investigate the effect of the pH of the synthesis solution on the reaction and products in step S2, as detailed in Examples 4 and 5.

[0120] Example 4

[0121] Example 1 was repeated, except that the pH of the synthesis solution was adjusted to 9, and the resulting Cu / SiO2 material was denoted as Cu / SiO2-Tp-0.5-9.

[0122] Example 5

[0123] Example 1 was repeated, except that the pH of the synthesis solution was adjusted to 11, and the resulting Cu / SiO2 material was denoted as Cu / SiO2-Tp-0.5-11.

[0124] The elemental analysis results of the Cu / SiO2-Tp materials prepared in Examples 4 and 5 are shown in Table 1. The Cu loading in the prepared Cu / SiO2-Tp-0.5-9 and Cu / SiO2-Tp-0.5-11 materials were 20.7 wt.% and 19.9 wt.%, respectively.

[0125] The pore structure parameters of Cu / SiO2-Tp-0.5-9 and Cu / SiO2-Tp-0.5-11 obtained by nitrogen adsorption-desorption test are shown in Table 1. According to the data of Examples 1, 4 and 5, it can be seen that as the pH value increases, the micropore specific surface area and pore volume do not change significantly, but the external surface area and total pore volume increase significantly. This indicates that the higher the pH of the synthesis solution is adjusted, the more favorable it is for the formation of the pore structure of Cu / SiO2-Tp material.

[0126] Figure 6 The XRD patterns of Cu / SiO2-Tp-0.5-9 and Cu / SiO2-Tp-0.5-11 materials prepared in Example 4 and Example 5 respectively are shown. As can be seen from the figures, the intensity of the Silicalite-1 diffraction peak does not change significantly with increasing pH, while the diffraction peak of metallic copper gradually strengthens, indicating an increase in Cu loading. The presence of characteristic diffraction peaks of CuO and Cu2O indicates a strong interaction between some copper and the supporting silica, resulting in some copper remaining unreduced and existing as ions in Cu / SiO2-Tp-0.5-9 and Cu / SiO2-Tp-0.5-11.

[0127] Example 6

[0128] S1. Weigh 2.0g of Silicalite-1 powder and add it to 10 times its mass of a 15.5mol / L ammonia solution (about 20mL). Stir vigorously at 70℃ for 4 hours.

[0129] S2. Add 1.5g of copper nitrate, stir for 2 hours, then evaporate ammonia until the solution pH is 8.0;

[0130] S3. The synthesis solution was hydrothermally crystallized at 160℃ for 48 hours. The resulting solid was washed with water, dried at 110℃, calcined at 550℃ in air for 5 hours, and reduced at 300℃ in hydrogen for 1 hour. The Cu / SiO2 material obtained was denoted as Cu / SiO2-NH3-10.

[0131] The elemental analysis results are shown in Table 1. The Cu loading in the prepared Cu / SiO2-NH3-10 material is 19.5 wt.%.

[0132] The pore structure parameters of Cu / SiO2-NH3-10 obtained by nitrogen adsorption-desorption test are shown in Table 1. Compared with Silicalite-1, the external specific surface area and micropore volume of Cu / SiO2-Tp material prepared in Example 6 are significantly increased, indicating that the mesoporous structure can be effectively introduced by the alkaline treatment with ammonia solution.

[0133] Figure 7 Images a and 7b are TEM images of the prepared Cu / SiO2-NH3-10 material. The Silicalite-1 surface is wrinkled and contains numerous mesopores. Cu nanoparticles are uniformly dispersed on the Silicalite-1 surface, with an average particle size of approximately 4.5 nm. Figure 7 In the high-resolution TEM image c, sub-nanometer Cu clusters exist within or at the openings of Silicalite-1 micropores with an average pore size of approximately 0.55 nm, indicating that the Cu cluster particle size is less than 0.55 nm.

[0134] Figure 8 The XRD pattern of the prepared Cu / SiO2-NH3-10 material shows that, in addition to the characteristic diffraction peak of Silicalite-1, the weak diffraction peak of metallic copper indicates that the copper particles are highly dispersed. The presence of characteristic diffraction peaks of CuO and Cu2O indicates that some copper interacts strongly with the support silica, resulting in it not being reduced.

[0135] Figure 9 The Cu 2p XPS spectrum of the prepared Cu / SiO2-NH3-10 material can be used to determine Cu 0 and Cu 2+ coexist.

[0136] Figure 10 The FTIR spectrum of the prepared Cu / SiO2-NH3-10 material is shown at 948 cm⁻¹. -1 The infrared characteristic absorption band is attributed to the Si-O bond vibration in the -Cu-O-Si- structure. The stable -Cu-O-Si- structure is not easily reduced, thus allowing some copper species to exist in Cu / SiO2-NH3-10 in ionic form.

[0137] Example 7

[0138] Example 6 was repeated, except that the mass ratio of ammonia solution to Silicalite-1 was 6:1, and the resulting Cu / SiO2 material was denoted as Cu / SiO2-NH3-6.

[0139] Example 8

[0140] Example 6 was repeated, except that the mass ratio of ammonia solution to Silicalite-1 was 30:1, and the resulting Cu / SiO2 material was denoted as Cu / SiO2-NH3-30.

[0141] The pore structure parameters of Cu / SiO2-NH3-6 and Cu / SiO2-NH3-30 obtained by nitrogen adsorption-desorption tests are shown in Table 1. On the one hand, compared with Silicalite-1, the external specific surface area of ​​Cu / SiO2-NH3 materials prepared in Examples 7 and 8 is significantly increased, and the micropore volume is significantly decreased, indicating that the ammonia treatment in Examples 7 and 8 effectively introduced a mesoporous structure. On the other hand, with the increase of ammonia dosage, the micropore specific surface area and pore volume gradually decrease, while the external surface area and total pore volume significantly increase.

[0142] Comparative Example 1

[0143] Copper was loaded using an impregnation method, and the detailed preparation steps are as follows.

[0144] 1.1 g of copper nitrate was dissolved in 5.0 mL of water. The copper nitrate solution was then added dropwise to 1.5 g of Silicalite-1 powder. After stirring at room temperature for 2 hours, the mixture was dried at 110 °C, calcined at 550 °C in air for 5 hours, and reduced at 300 °C in hydrogen for 1 hour. The resulting Cu / SiO2 material was denoted as Cu / SiO2-Im.

[0145] The elemental analysis results of the Cu / SiO2-Im material prepared in Comparative Example 1 are shown in Table 1, indicating that the Cu loading in the prepared Cu / SiO2-Im material is 20.2 wt.%.

[0146] The pore structure parameters of Cu / SiO2-Im obtained by nitrogen adsorption-desorption test are shown in Table 1. They are similar to the pore structure of Silicalite-1. The pore structure of Cu / SiO2-Im prepared in this comparative example is mainly micropores.

[0147] Figure 11 The image shows a TEM image of the Cu / SiO2-Im material prepared in Comparative Example 1. As can be seen from the image, Cu is dispersed as large nanoparticles on the surface of Silicalite-1, with an average particle size of about 16 nm.

[0148] Comparative Example 2

[0149] Copper was loaded using a precipitation method, and the detailed preparation steps are as follows.

[0150] 1.5 g of Silicalite-1 powder was weighed and added to 35 mL of 0.50 mol / L NaOH aqueous solution, and stirred vigorously at 40 °C for 0.5 hours. Subsequently, 5 mL of 1.2 mol / L copper nitrate aqueous solution was added dropwise. The resulting solid was dried at 110 °C, calcined at 550 °C in air for 5 hours, and reduced at 300 °C in hydrogen atmosphere for 1 hour. The Cu / SiO2 material obtained was denoted as Cu / SiO2-Pr.

[0151] The elemental analysis results of the Cu / SiO2-Im material prepared in Comparative Example 2 are shown in Table 1, indicating that the Cu loading in the prepared Cu / SiO2-Pr material is 19.0 wt.%.

[0152] The pore structure parameters of Cu / SiO2-Pr obtained by nitrogen adsorption-desorption test are shown in Table 1. They are similar to the pore structure of Silicalite-1. The pore structure of Cu / SiO2-Im prepared in this comparative example is mainly micropores.

[0153] Figure 12 The image shows a TEM image of the Cu / SiO2-Pr material prepared in Comparative Example 2. As can be seen from the image, Cu is dispersed as large nanoparticles on the surface of Silicalite-1, with an average particle size of about 14 nm.

[0154] Comparative Example 3

[0155] Copper was loaded using the ammonia stripping method, and the detailed preparation steps are as follows.

[0156] Weigh 1.5g of Silicalite-1 powder and add it to 10 times the mass concentration of 15.5mol / L ammonia solution (about 15mL). Stir vigorously at 70℃ for 4 hours. Then, add 1.1g of copper nitrate and stir until the water is completely evaporated. The resulting solid is dried at 110℃, calcined at 550℃ in air for 5 hours, and reduced at 300℃ in hydrogen atmosphere for 1 hour. The Cu / SiO2 material obtained is denoted as Cu / SiO2-Ae.

[0157] The elemental analysis results of the Cu / SiO2-Im material prepared in Comparative Example 1 are shown in Table 1, indicating that the Cu loading in the prepared Cu / SiO2-Ae material is 19.5 wt.%.

[0158] The pore structure parameters of Cu / SiO2-Ae obtained by nitrogen adsorption-desorption test are shown in Table 1. They are similar to the pore structure of Silicalite-1. The Cu / SiO2-Im prepared in this comparative example has a large number of mesoporous structures.

[0159] Figure 13The image shows a TEM image of the Cu / SiO2-Ae material prepared in Comparative Example 3. As can be seen from the image, the surface of Silicalite-1 is wrinkled and has a large number of mesopores. Cu nanoparticles are uniformly dispersed on the surface of Silicalite-1 with an average particle size of about 8.0 nm.

[0160] Catalytic effect experiment

[0161] The copper / silica-supported materials Cu / SiO2 with strong metal-support interaction and sub-nanometer dispersion, prepared in Examples 1-8 and Comparative Examples 1-3, were used to catalyze the dehydrogenation reaction of 2,3-butanediol. A fixed-bed reactor was used at atmospheric pressure, with a carrier gas N2 flow rate of 40 mL / min, a mass space-time of 0.017 h, and a reaction temperature of 280 °C.

[0162] The experimental results are shown in Figure 14 The curves showing the conversion rate of 2,3-butanediol dehydrogenation catalyzed by Cu / SiO2-Tp-xy material as a function of reaction time and 15 show the conversion rate of 2,3-butanediol dehydrogenation catalyzed by Cu / SiO2-NH3-z material as a function of reaction time.

[0163] from Figure 14 It can be seen that the conversion rate of 2,3-butanediol on Cu / SiO2-Tp-xy exhibits a trend of first increasing and then decreasing with the concentration of tetrapropylammonium hydroxide and the pH value of the synthesis solution. The optimal concentration of tetrapropylammonium hydroxide is 0.3-0.7 mol / L, with catalytic activity reaching 5-55%, especially at a concentration of 0.5 mol / L, where the catalytic activity reaches 55%. The optimal pH value of the synthesis solution is 9-10.5, with catalytic activity reaching 15-55%, especially at pH=10, where the catalytic activity reaches 55%. Therefore, considering the two influencing factors of tetrapropylammonium hydroxide concentration and synthesis solution pH, Cu / SiO2-Tp-0.5-10 exhibits the highest catalytic activity. In addition, inorganic bases such as sodium hydroxide can leave a small amount of Na metal ions in the catalyst during use, which can be toxic to the catalyst. Furthermore, in addition to sub-nano clusters being beneficial to catalytic reactions, other factors can also have an impact. Therefore, it is not possible to limit the use to a single factor. At least compared to inorganic bases, the use of organic bases can form micropores to restrict the growth of Cu clusters, which is conducive to the formation of sub-nano copper clusters.

[0164] from Figure 15 It can be seen that the catalytic activity of Cu / SiO2-NH3-z reaches 70-83% with the increase of ammonia water dosage, and it first increases and then decreases. It reaches the maximum of 83% when the mass ratio of ammonia water dosage to Silicalite-1 is 10.

[0165] On the other hand, Table 2 shows the selectivity of the target product 3-hydroxybutanone on Cu / SiO2-Tp-xy and Cu / SiO2-NH3-z, and it can be seen that the selectivity of the target product is always maintained above 90%.

[0166] The copper / silica-supported materials Cu / SiO2 with strong metal-support interaction and sub-nanometer dispersion prepared in Examples 1 and 6 above were used for the dehydrogenation stability test of 2,3-butanediol. A fixed-bed reactor was used, and the test was conducted at atmospheric pressure with a carrier gas N2 flow rate of 40 mL / min, a mass space time of 0.025 h, and a reaction temperature of 260 °C.

[0167] The experimental results are shown in Figure 16 and 17 The catalytic activity of Cu / SiO2-Tp-0.5-10 and Cu / SiO2-NH3-10 decreased significantly with increasing reaction time, then gradually slowed down, demonstrating superior catalytic structural stability. Furthermore, Cu / SiO2-NH3-10 exhibited better activity and stability than Cu / SiO2-Tp-0.5-10.

[0168] The Cu / SiO2-Im, Cu / SiO2-Pr, and Cu / SiO2-Ae materials prepared in Comparative Examples 1-3 were used to catalyze the dehydrogenation reaction of 2,3-butanediol. A fixed-bed reactor was used, and the reaction was carried out at atmospheric pressure with a carrier gas N2 flow rate of 40 mL / min, a mass space time of 0.017 h, and a reaction temperature of 280 °C.

[0169] The experimental results are shown in Table 2. It can be seen that Cu / SiO2-Im has no catalytic activity, and the conversion rate of 2,3-butanediol on Cu / SiO2-Pr is only 5.2%. Although the conversion rate of 2,3-butanediol on Cu / SiO2-Ae is 51%, it drops to 4.4% after 8 hours of reaction, indicating poor stability of the catalytic structure.

[0170] Table 2. Catalytic performance of Pd / SiO2 materials prepared in Examples 1-8 and Comparative Examples 1-3 of this invention for the dehydrogenation of 2,3-butanediol.

[0171]

[0172] In summary, this invention provides a copper-supported silica material Cu / SiO2 with strong metal-support interaction and sub-nanometer dispersion, which simultaneously achieves strong interaction between copper species and the support silica and sub-nanometer dispersion, thereby efficiently catalyzing the dehydrogenation conversion of 2,3-butanediol. Furthermore, the material preparation method described in this invention is simple, environmentally friendly, and highly active, showing good prospects for industrial application.

[0173] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A silica-supported copper composite material with strong metal-carrier interaction and sub-nanometer dispersion, characterized in that, The copper-supported silica material with strong metal-carrier interaction and sub-nanometer dispersion is Cu / SiO2, with a Cu loading of 5.0-25 wt.%; copper exists in both metallic and ionic forms; and the sub-nanometer copper clusters have a particle size of less than 0.55 nm. The preparation method of the aforementioned strong metal-carrier interaction, sub-nanometer dispersed silica-supported copper composite material includes the following steps: S1. Microporous pure silica molecular sieve Silicalite-1 powder is added to an alkaline aqueous solution and etched by vigorous stirring at a certain temperature. The alkaline aqueous solution is an organic base aqueous solution, and the organic base is tetrapropylammonium hydroxide and / or tetraethylammonium hydroxide. S2. Add copper salt, and after it dissolves, add inorganic acid to adjust the pH of the synthesis solution to 8-11. The inorganic acid is nitric acid and / or hydrochloric acid. S3. The synthesis solution is subjected to hydrothermal crystallization to obtain Cu / SiO2 precursor, which is then washed, dried, calcined, and reduced to obtain Cu / SiO2.

2. The silica-supported copper composite material with strong metal-carrier interaction and sub-nanometer dispersion according to claim 1, characterized in that, In step S1, the mass ratio of the organic base aqueous solution to Silicalite-1 is 15-30:

1.

3. The silica-supported copper composite material with strong metal-carrier interaction and sub-nanometer dispersion according to claim 1, characterized in that, In step S1, the concentration of the organic base is 0.3-1.0 mol / L.

4. The silica-supported copper composite material with strong metal-carrier interaction and sub-nanometer dispersion according to claim 3, characterized in that, In step S1, the concentration of the organic base is 0.3-0.7 mol / L.

5. The silica-supported copper composite material with strong metal-carrier interaction and sub-nanometer dispersion according to claim 4, characterized in that, In step S1, the concentration of the organic base is 0.5 mol / L.

6. The silica-supported copper composite material with strong metal-carrier interaction and sub-nanometer dispersion according to claim 1, characterized in that, In step S1, the etching temperature is 40-70 °C.

7. The silica-supported copper composite material with strong metal-carrier interaction and sub-nanometer dispersion according to claim 1, characterized in that, In step S1, the etching time is 0.5-3 hours.

8. The silica-supported copper composite material with strong metal-carrier interaction and sub-nanometer dispersion according to claim 1, characterized in that, In step S2, the copper salt is copper nitrate or copper chloride; When the copper salt is copper nitrate, the mass ratio of the amount of copper salt added to the mass of the microporous pure silica molecular sieve is 0.2-0.

85. When the copper salt is copper chloride, the mass ratio of the amount of copper salt added to the microporous pure silicon molecular sieve is 0.2-0.

6.

9. The silica-supported copper composite material with strong metal-carrier interaction and sub-nanometer dispersion according to claim 1, characterized in that, In step S2, the pH of the synthesis solution is adjusted to 9-10.

5.

10. The silica-supported copper composite material with strong metal-carrier interaction and sub-nanometer dispersion according to claim 9, characterized in that, In step S2, the pH of the synthesis solution is adjusted to 10.

11. The silica-supported copper composite material with strong metal-carrier interaction and sub-nanometer dispersion according to claim 1, characterized in that, In step S2, the concentration of the inorganic acid is 1.0-3.0 mol / L.

12. The silica-supported copper composite material with strong metal-carrier interaction and sub-nanometer dispersion according to claim 1, characterized in that, In step S3, the temperature for hydrothermal crystallization of the synthesis solution is 110-170 °C, and the crystallization time is 12-48 hours. The calcination includes calcining the Cu / SiO2 precursor in an air atmosphere at a temperature of 450-600 °C for 3-6 hours. The reduction process involves reducing the Cu / SiO2 precursor in a hydrogen atmosphere at a temperature of 250-400 °C for 1-3 hours.

13. The silica-supported copper composite material with strong metal-carrier interaction and sub-nanometer dispersion according to claim 1, characterized in that, The Cu loading of the strongly metal-carrier-interacting, sub-nanometer dispersed silica-supported copper material Cu / SiO2 is 5.0-23 wt.%.

14. The silica-supported copper composite material with strong metal-carrier interaction and sub-nanometer dispersion according to claim 1, characterized in that, The Cu loading of the strongly metal-carrier-interacting, sub-nanometer dispersed silica-supported copper material Cu / SiO2 is 10.0-22 wt.%.

15. The silica-supported copper composite material with strong metal-carrier interaction and sub-nanometer dispersion according to claim 1, characterized in that, The Cu loading of the strongly metal-carrier-interacting, sub-nanometer dispersed silica-supported copper material Cu / SiO2 is 15.0-22 wt.%.

16. The silica-supported copper composite material with strong metal-carrier interaction and sub-nanometer dispersion according to claim 1, characterized in that, The Cu loading of the strongly metal-carrier-interacting, sub-nanometer dispersed silica-supported copper material Cu / SiO2 is 19.0-21 wt.%.

17. The application of the strong metal-support, sub-nanometer dispersed silica-supported copper composite material according to any one of claims 1-16 in the catalytic dehydrogenation reaction of 2,3-butanediol.

18. The application as described in claim 17, characterized in that, The space time for the dehydrogenation of 2,3-butanediol is 0.016-0.10 hours, and the reaction temperature is 220-280 °C.

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