Hydrogenation catalyst and preparation method and application thereof

Abstract

The present invention discloses a hydrogenation catalyst, a method for preparing the catalyst, and an application thereof. The method for preparing the hydrogenation catalyst comprises: dissolving an organic ligand in a first organic solution to obtain a ligand solution; dissolving a zinc salt in a second organic solution to obtain a zinc salt solution; adding the zinc salt solution to the ligand solution under stirring to carry out a coordination reaction to obtain a crude precursor; vacuum drying the crude precursor to obtain a precursor; and calcining the precursor to obtain the catalyst. The catalyst prepared by this method is particularly suitable for the preparation of cinnamyl alcohol by transfer catalytic hydrogenation of cinnamaldehyde, has a high cinnamyl alcohol hydrogenation conversion rate and cinnamyl alcohol selectivity, and has certain cyclic stability.

Description

Technical Field

[0001] The present invention relates to the field of chemistry, and in particular to a hydrogenation catalyst and a preparation method and application thereof, and more particularly to a method for preparing a hydrogenation catalyst, a hydrogenation catalyst, and a hydrogenation reaction. Background Art

[0002] Fundamental research in catalysis is rapidly advancing, and with it, increasing interest in regulating reaction selectivity, particularly in the selective hydrogenation of α,β-unsaturated aldehydes. The selective hydrogenation of cinnamaldehyde (CAL) is a prime example of this selective hydrogenation reaction. The C=O hydrogenation product, cinnamyl alcohol (COL), is not only a raw material for synthesizing flavors, fragrances, and fixatives, but is also an important pharmaceutical intermediate. However, due to the lower C=C bond energy than the C=O bond energy in the structure, C=C hydrogenation is thermodynamically more likely to produce phenylpropanal. Therefore, achieving highly selective C=O hydrogenation remains a challenge.

[0003] Hydrogenation reactions are usually carried out through two pathways. The first is to use hydrogen as a hydrogen donor. In this pathway, researchers usually control the adsorption mode of CAL by adjusting the electronic structure and steric hindrance, thereby achieving selective hydrogenation of C=O. However, this method usually has some disadvantages, such as the need for scarce precious metals, the complex synthesis of multi-metal catalysts, and the construction of steric hindrance will occupy some active sites, thereby reducing the conversion rate. In addition, using hydrogen as a hydrogen source usually requires a high-pressure environment and special facilities for storing, transporting and processing high-pressure hydrogen, which is highly dangerous and uneconomical. Another approach is catalytic transfer hydrogenation (CTH) using hydrogen-containing polyatomic molecules (such as formic acid and its salts, hydrazine, alcohols, etc.) as donors. This method has relatively mild reaction conditions and low equipment requirements. It also greatly reduces the risk of the reaction. In addition, its diversity of hydrogen sources also provides new ideas for improving the selectivity and conversion rate of the reaction. Therefore, the CTH reaction is a hydrogenation pathway with broad application prospects.

[0004] Currently, heterogeneous catalysts are widely used in catalysis due to their ease of separation. Precious metal catalysts such as Pt, Au, Ag, Ir, Ru, Rh, Os, and Pd have been extensively developed and applied for the CTH reaction of α,β-unsaturated aldehydes. However, the high cost and low selectivity of these precious metal catalysts make the development of cost-effective and efficient CTH catalysts for the selective hydrogenation of α,β-unsaturated aldehydes of great practical significance. Currently, catalysts based on 3d transition elements such as Fe, Co, Ni, Cu, and Mn have been explored for the CTH reaction due to their unique electronic structures. However, compared to precious metal catalysts, their catalytic performance requires further investigation and improvement. Compared to increasingly depleted elements such as Co and Ni, Zn is abundant on Earth and offers a more cost-effective catalyst. Therefore, the development of highly active and selective zinc-based catalysts is of great research value and application significance. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, one object of the present invention is to provide a method for preparing a hydrogenation catalyst, which has mild reaction conditions and does not require acidification treatment.

[0006] It should be noted that the present invention is completed based on the following work of the inventors:

[0007] In recent years, single-atom catalysts (SACs) have shown great potential in various reactions such as electrocatalysis, photocatalysis, and organic catalysis due to their unique electronic and geometric structures, well-dispersed active centers, and uniform structure. In addition, the nitrogen in the nitrogen-doped carbon support can not only act as an anchoring site to coordinate with the metal, but also act as a basic site to participate in the transfer hydrogenation reaction, thereby improving the catalytic activity. Based on the above research results, the inventors believe that atomically dispersed zinc-based single-atom catalysts can efficiently convert α,β-unsaturated aldehydes into α,β-unsaturated alcohols via the CTH pathway. In addition, to date, there have been no reports of successful cases of zinc-based single-atom catalysts catalyzing the synthesis of α,β-unsaturated alcohols from α,β-unsaturated aldehydes.

[0008] Therefore, according to one aspect of the present invention, the present invention provides a method for preparing a hydrogenation catalyst. According to an embodiment of the present invention, the method comprises: dissolving an organic ligand in a first organic solution to obtain a ligand solution; dissolving a zinc salt in a second organic solution to obtain a zinc salt solution; adding the zinc salt solution to the ligand solution under stirring conditions to carry out a coordination reaction to obtain a crude precursor; vacuum drying the crude precursor to obtain a precursor; and calcining the precursor to obtain the catalyst, wherein the catalyst is a Zn-N x The structure is the active site.

[0009] According to the method for preparing a hydrogenation catalyst according to an embodiment of the present invention, the characteristic of the low boiling point of zinc metal is utilized, and the evaporation of zinc during the high-temperature calcination process not only provides a pore structure, but also avoids the agglomeration of zinc atoms, and avoids the waste of resources in the acid treatment process. At the same time, there is no need to load other metals during the preparation process, and high catalytic transfer hydrogenation catalytic activity can be obtained without multiple treatments. This method has a simple preparation process, low cost, and is easy to mass produce. Moreover, the catalyst prepared by the method is particularly suitable for preparing cinnamyl alcohol by cinnamaldehyde transfer catalytic hydrogenation, has high cinnamyl alcohol hydrogenation conversion and product cinnamyl alcohol selectivity, and simultaneously converts the alcohol as a hydrogen source into corresponding ketone, and has certain cyclic stability.

[0010] In addition, the method for preparing a hydrogenation catalyst according to the above embodiment of the present invention may also have the following additional technical features:

[0011] According to an embodiment of the present invention, the organic ligand is 2-methylimidazole.

[0012] According to an embodiment of the present invention, the zinc salt is zinc nitrate hexahydrate.

[0013] According to an embodiment of the present invention, the reaction temperature of the coordination reaction is 25-40° C., and the reaction time is 3-5 hours.

[0014] According to an embodiment of the present invention, the vacuum drying process is carried out at 50-70° C. for 10-15 hours.

[0015] According to an embodiment of the present invention, the calcination treatment is carried out under oxygen-free conditions, gradually raising the temperature to 700-1000° C. and maintaining the temperature for 60-120 minutes.

[0016] According to an embodiment of the present invention, the temperature of the calcination treatment is 690-710° C., and the coordination numbers of the catalyst are 3.2±0.3 and 3.9±0.5.

[0017] According to an embodiment of the present invention, the temperature of the calcination treatment is 790-810° C., and the coordination number of the catalyst is 4.1±0.6.

[0018] According to an embodiment of the present invention, the temperature of the calcination treatment is 890-910° C., and the coordination number of the catalyst is 3.2±0.5.

[0019] According to an embodiment of the present invention, the temperature of the calcination treatment is 990-1010° C., and the coordination number of the catalyst is 2.9±0.5.

[0020] Furthermore, according to another aspect of the present invention, a hydrogenation catalyst is provided. According to an embodiment of the present invention, the hydrogenation catalyst is prepared using the aforementioned method. Thus, the catalyst is particularly suitable for the transfer catalytic hydrogenation of cinnamaldehyde to produce cinnamyl alcohol, exhibiting high cinnamylaldehyde hydrogenation conversion and selectivity for the product cinnamyl alcohol, while simultaneously converting the alcohol serving as a hydrogen source into the corresponding ketone, and exhibiting a certain degree of cyclic stability.

[0021] According to an embodiment of the present invention, the catalyst is Zn-N x is an active site, wherein N is pyridinic nitrogen, pyrrolic nitrogen, graphitic nitrogen, oxidized nitrogen or a nitrogen atom coordinated with metallic zinc. Preferably, the nitrogen atom coordinated with metallic zinc is pyridinic nitrogen.

[0022] According to an embodiment of the present invention, the Zn-N x Zn in the structure is a zinc atom, and x is 3 or 4.

[0023] According to an embodiment of the present invention, the hydrogenation catalyst exhibits different coordination conditions at different calcination temperatures. The catalyst obtained by calcining at 700°C has two coordination numbers of 3.2±0.3 and 3.9±0.5. The catalyst obtained by calcining at 800°C has a coordination number of 4.1±0.6, that is, Zn-N4 coordination. The catalysts obtained by calcining at 900°C and 1000°C have Zn-N3 coordination, and the coordination numbers are 3.2±0.5 and 2.9±0.5, respectively.

[0024] According to an embodiment of the present invention, the hydrogenation catalyst is a dodecahedron and is porous.

[0025] According to an embodiment of the present invention, the particle size of the hydrogenation catalyst is 400-600 nm.

[0026] Furthermore, according to another aspect of the present invention, the present invention provides a hydrogenation reaction. According to an embodiment of the present invention, the reaction is carried out under the catalysis of the aforementioned hydrogenation catalyst.

[0027] The hydrogenation reaction according to the embodiment of the present invention is catalyzed by the aforementioned catalyst, with high conversion rate and selectivity, and can obtain an additional product, ketone, with low catalytic cost, and is suitable for large-scale application.

[0028] According to an embodiment of the present invention, the hydrogenation reaction is a selective hydrogenation reaction of cinnamaldehyde and its derivatives.

[0029] According to an embodiment of the present invention, the selective hydrogenation is the carbonyl hydrogenation of the cinnamaldehyde and its derivatives.

[0030] According to an embodiment of the present invention, the solvent for the hydrogenation reaction is an alcohol containing β-H.

[0031] According to an embodiment of the present invention, the mass ratio of the catalyst to the cinnamaldehyde and its derivatives is 0.9-3.2:1.

[0032] According to an embodiment of the present invention, the conversion rate of cinnamaldehyde and its derivatives is not less than 90%, and the selectivity is not less than 80%.

[0033] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0035] Figure 1 Schematic diagrams showing electron microscopy results of ZIF-8 synthesized at different temperatures according to one embodiment of the present invention, (a) ZIF-8 synthesized at 25°C; (b) ZIF-8 synthesized at 30°C; (c) ZIF-8 synthesized at 40°C;

[0036] Figure 2 Schematic diagrams showing electron microscopy results of Zn / NC-T catalysts calcined at different temperatures according to one embodiment of the present invention, wherein: (a) Zn / NC-700 catalyst calcined at 700°C; (b) Zn / NC-800 catalyst calcined at 800°C; (c) Zn / NC-900 catalyst calcined at 900°C; (d) Zn / NC-1000 catalyst calcined at 1000°C;

[0037] Figure 3 shows a schematic diagram of X-ray diffraction results of Zn / NC according to one embodiment of the present invention;

[0038] Figure 4 A schematic diagram showing the results of spherical aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) of a Zn / NC single-atom catalyst according to one embodiment of the present invention is shown;

[0039] Figure 5 Schematic diagrams of Fourier transform-extended X-ray absorption fine structures of different catalysts according to one embodiment of the present invention are shown, including: (a) Zn / NC-700; (b) Zn / NC-800; (c) Zn / NC-900; and (d) Zn / NC-1000. DETAILED DESCRIPTION

[0040] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0041] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, features defined as "first" or "second" may explicitly or implicitly include one or more of such features. Furthermore, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0042] According to one aspect of the present invention, the present invention provides a method for preparing a hydrogenation catalyst. According to an embodiment of the present invention, the method comprises: dissolving an organic ligand in a first organic solution to obtain a ligand solution; dissolving a zinc salt in a second organic solution to obtain a zinc salt solution; adding the zinc salt solution to the ligand solution under stirring conditions to carry out a coordination reaction to obtain a crude precursor; vacuum drying the crude precursor to obtain a precursor; and calcining the precursor to obtain the catalyst, wherein the catalyst is a Zn-N x The structure is the active site.

[0043] According to the method for preparing a hydrogenation catalyst in accordance with an embodiment of the present invention, the low boiling point of zinc metal is utilized, and the evaporation of zinc during the high-temperature calcination process not only provides a pore structure, but also avoids the agglomeration of zinc atoms, thereby avoiding the waste of resources in the acid treatment process. At the same time, there is no need to load other metals during the preparation process, and high catalytic transfer hydrogenation catalytic activity can be obtained without multiple treatments. This method has a simple preparation process, low cost, and is easy to mass produce. Furthermore, the catalyst prepared by the method is particularly suitable for preparing cinnamyl alcohol by cinnamaldehyde transfer catalytic hydrogenation, and a variety of β-H-containing alcohols can be used as a hydrogen source, with high cinnamyl alcohol hydrogenation conversion and product cinnamyl alcohol selectivity, while the alcohol as a hydrogen source is converted into corresponding ketones, and has certain cyclic stability.

[0044] According to an embodiment of the present invention, the organic ligand is 2-methylimidazole. Thus, by utilizing the coordination of N and Zn of 2-methylimidazole, 2-methylimidazole can be deprotonated under the action of a solvent or heat to react with zinc ions to form ZIF-8 crystal nuclei. Furthermore, excess neutral 2-methylimidazole is adsorbed on the positively charged surface of ZIF-8 nanocrystals, thereby terminating the growth of ZIF-8 and obtaining crystal nuclei of appropriate size.

[0045] According to an embodiment of the present invention, the zinc salt is zinc nitrate hexahydrate. Therefore, zinc nitrate hexahydrate can easily ionize zinc ions to coordinate with the ligand without introducing other ions.

[0046] According to an embodiment of the present invention, the reaction temperature of the coordination reaction is 25-40° C., and the reaction time is 3-5 hours. Therefore, the reaction conditions do not require heating and the reaction time is short, simple and mild.

[0047] According to an embodiment of the present invention, the vacuum drying process is performed at 50-70°C for 10-15 hours. Specifically, the crude precursor is washed three times with methanol and then vacuum dried, which is conducive to removing the impurity solution residue on the surface of the crude precursor. The drying conditions are also conducive to fully drying the crude precursor.

[0048] According to an embodiment of the present invention, the calcination treatment is carried out under oxygen-free conditions, gradually raising the temperature to 700-1000°C and maintaining it for 60-120 minutes. Thus, the calcination temperature and time can increase the specific surface area of ​​the catalyst, which is beneficial for the transport of the substrate.

[0049] The inventors found that the hydrogenation catalyst exhibits different coordination conditions at different calcination temperatures. According to some embodiments of the present invention, the calcination treatment temperature is 690-710°C, preferably 700°C, and the coordination number of the catalyst is 3.2±0.3 and 3.9±0.5; according to some embodiments of the present invention, the calcination treatment temperature is 790-810°C, preferably 800°C, and the coordination number of the catalyst is 4.1±0.6; according to some embodiments of the present invention, the calcination treatment temperature is 890-910°C, preferably 900°C, and the coordination number of the catalyst is 3.2±0.5; according to some embodiments of the present invention, the calcination treatment temperature is 990-1010°C, preferably 1000°C, and the coordination number of the catalyst is 2.9±0.5. Among them, the tri-coordinate catalyst (coordination number 3) calcined at 900°C performed better than the tetra-coordinate catalyst (coordination number 4) calcined at 800°C. The reason may be that the substrates cinnamaldehyde and isopropanol are more easily adsorbed on the Zn / NC-900 catalyst than on the Zn / NC-800 catalyst, and the energy barrier of the reaction process is also lower.

[0050] According to some embodiments of the present invention, the calcination process is performed using a tube furnace.

[0051] According to some embodiments of the present invention, the calcination process is performed at a gradually increasing temperature of 5°C / min. This gradually increasing temperature facilitates the removal of volatile impurities such as chemically bound water, decomposition of unreacted inorganic and organic matter, increased specific surface area, and more robust coordination between the zinc metal and nitrogen.

[0052] Furthermore, according to another aspect of the present invention, a hydrogenation catalyst is provided. According to an embodiment of the present invention, the hydrogenation catalyst is prepared using the aforementioned method. Thus, the catalyst is particularly suitable for the transfer catalytic hydrogenation of cinnamaldehyde to produce cinnamyl alcohol, and can use a variety of β-H-containing alcohols as hydrogen sources. It has high cinnamylaldehyde hydrogenation conversion and cinnamyl alcohol selectivity, and has certain cyclic stability.

[0053] According to an embodiment of the present invention, the N of the catalyst is pyridinic nitrogen, pyrrolic nitrogen, graphitic nitrogen, oxidized nitrogen or a nitrogen atom coordinated with metallic zinc. Preferably, the nitrogen atom coordinated with metallic zinc is pyridinic nitrogen. According to an embodiment of the present invention, the Zn-N x Zn is a zinc atom, and x is 3 or 4. Thus, zinc is supported on nitrogen-doped carbon in the form of a single atom, resulting in a unique microporous structure that exposes more active sites per unit mass, reduces substrate mass transfer and diffusion resistance, and can be used in catalytic hydrogenation reactions, especially the transfer catalytic hydrogenation of cinnamaldehyde to produce cinnamyl alcohol. It exhibits high cinnamylaldehyde hydrogenation conversion and cinnamyl alcohol selectivity, as well as certain cyclic stability.

[0054] According to an embodiment of the present invention, the Zn-N x The coordination number of the structure is 3.2 ± 0.3, 3.9 ± 0.5, 4.1 ± 0.6, 3.2 ± 0.5 or 2.9 ± 0.5. Specifically, the hydrogenation catalyst presents different coordination situations at different calcination temperatures. The catalyst obtained by calcining at 700 ° C has two coordination numbers of 3.2 ± 0.3 and 3.9 ± 0.5. The coordination number of the catalyst obtained by calcining at 800 ° C is 4.1 ± 0.6, i.e., Zn-N4 coordination, and the catalyst obtained by calcining at 900 ° C and 1000 ° C is Zn-N3 coordination, with coordination numbers of 3.2 ± 0.5 and 2.9 ± 0.5, respectively. According to an embodiment of the present invention, the hydrogenation catalyst is dodecahedral and porous. Thus, the structure of the catalyst shows that it is a heterogeneous catalyst, which is more conducive to the separation and purification of products than homogeneous catalysts, and is porous, has a large specific surface area, and has a high catalytic efficiency.

[0055] According to an embodiment of the present invention, the particle size of the hydrogenation catalyst is 400-600 nm. Therefore, this particle size has a large specific surface area, and the preparation conditions are mild, and there is no need for an excessive ratio of zinc to ligand, resulting in low preparation cost.

[0056] Furthermore, according to another aspect of the present invention, the present invention provides a hydrogenation reaction. According to an embodiment of the present invention, the reaction is carried out under the catalysis of the aforementioned hydrogenation catalyst.

[0057] The hydrogenation reaction according to the embodiment of the present invention is catalyzed by the aforementioned catalyst, has high conversion rate and selectivity, low catalytic cost, and is suitable for large-scale application.

[0058] According to an embodiment of the present invention, the hydrogenation reaction is a selective hydrogenation reaction of cinnamaldehyde and its derivatives. The selectivity of the catalytic reaction is high.

[0059] According to an embodiment of the present invention, the selective hydrogenation is the carbonyl hydrogenation of the cinnamaldehyde and its derivatives, that is, the transfer catalytic hydrogenation of cinnamaldehyde to prepare cinnamyl alcohol.

[0060] According to an embodiment of the present invention, the mass ratio of the catalyst to the cinnamaldehyde and its derivatives is 0.9-3.2:1. Thus, the catalytic efficiency is high.

[0061] According to an embodiment of the present invention, the conversion rate of cinnamaldehyde and its derivatives is not less than 90%, and the selectivity is not less than 80%.

[0062] According to an embodiment of the present invention, the solvent for the hydrogenation reaction is an alcohol containing β-H. Thus, the alcohol β-H serves as a hydrogen donor for the hydrogenation reaction, and after dehydrogenation, an additional product ketone is obtained, further improving the economic benefits of the reaction.

[0063] According to an embodiment of the present invention, the derivatives of cinnamaldehyde include 3-methylcrotonaldehyde, α-methylcinnamaldehyde, furfural, 5-hydroxymethylfurfural, α-amylcinnamaldehyde, 4-nitrocinnamaldehyde, and 4-methoxycinnamaldehyde.

[0064] The present invention will be described below with reference to specific examples. It should be noted that these examples are merely illustrative and are not to be construed as limiting the present invention.

[0065] Below in conjunction with embodiment, scheme of the present invention will be explained.It will be appreciated by those skilled in the art that the following examples are merely for illustration of the present invention and should not be considered as limiting the scope of the present invention.Unindicated specific technology or condition in the embodiment, according to the technology or condition described in the document in this area or according to product specification sheet, carry out.Reagents used therein or instrument do not indicate manufacturer, are all conventional products that can be obtained by commercial means, for example, can be purchased from Sigma company.

[0066] Preparation Example 1

[0067] The hydrogenation catalyst was prepared using the method of the embodiment of the present invention. The specific method is as follows:

[0068] (1) Preparation of ZIF-8 Precursor: 1.314 g of 2-methylimidazole was dissolved in 25 mL of methanol to form solution A. 1.190 g of zinc nitrate hexahydrate was dissolved in 20 mL of methanol to form solution B. Solution B was rapidly added to solution A with stirring, and the mixture was stirred at 25-40°C for 4 h. After the reaction, the mixture was centrifuged, washed three times with methanol, and dried under vacuum at 60°C for 12 h to obtain a white ZIF-8 solid.

[0069] (2) Preparation of Zn / NC-T: Grind the dried sample from the previous step into a powder and place it in a porcelain boat. Transfer the boat to a tube furnace and remove the air by passing nitrogen through it for 30 minutes. Then, begin heating at a rate of 5°C / min and maintain the temperature at 700-1000°C for 1 hour. Allow the sample to cool naturally to room temperature before removing the porcelain boat. Label this as Zn / NC-T, where T is the calcination temperature.

[0070] (3) Transmission electron microscopy characterization:

[0071] Figure 1 and Figure 2 Transmission electron microscopy (TEM) photographs of ZIF-8 prepared in Example 1 and Zn / NC prepared in Example 2 are shown. It can be observed that the morphology of ZIF-8 and Zn / NC are both dodecahedral, the surface of ZIF-8 is smooth, and the surface of Zn / NC is rough. The prepared Zn / NC electron microscopy samples were observed from multiple angles, and no nanoparticles were observed on the surface.

[0072] (4) Spherical aberration electron microscopy characterization:

[0073] The Zn / NC prepared in Example 1 was characterized by spherical aberration electron microscopy. Figure 3 As shown in the figure, Zn exists as independent and obvious bright spots in the spherical aberration electron microscope, proving that metallic Zn is dispersed in the NC support in the form of single atoms.

[0074] (5) X-ray diffraction characterization:

[0075] The X-ray diffraction pattern of Zn / NC prepared in this example is as follows Figure 4 As shown in Figure 5, Zn / NC exhibits the (002) and (101) crystal planes of graphitic carbon, and no peaks corresponding to zinc oxide and zinc nanoparticles appear.

[0076] (6) Synchrotron radiation characterization:

[0077] The Fourier transform-extended X-ray absorption fine structure spectrum of Zn / NC-T prepared in this example is as follows Figure 5The fitting parameters are shown in Table 1, indicating that the metal Zn in the catalysts obtained at different calcination temperatures exists in the form of single atoms and is coordinated with the nitrogen in the nitrogen-doped carbon support. Different calcination temperatures exhibit different coordination states. The sample calcined at 700°C has two coordination numbers of 3.2±0.3 and 3.9±0.5. The sample calcined at 800°C has a coordination number of 4.1±0.6, that is, Zn-N4 coordination. The samples calcined at 900°C and 1000°C have Zn-N3 coordination, with coordination numbers of 3.2±0.5 and 2.9±0.5, respectively.

[0078] Table 1

[0079]

[0080] Comparative Example 1

[0081] Preparation of NC: Other conditions and steps of this comparative example are the same as those for the preparation of Zn / NC in Example 1, except that the ZIF-8 powder is replaced by chitosan.

[0082] Comparative Example 2

[0083] Preparation of ZnO: The other conditions and steps of this comparative example are the same as those for the preparation of Zn / NC in Example 1, except that it is first calcined in an air atmosphere at 400°C for 1 h, and then transferred to a nitrogen atmosphere for calcination at 900°C for 1 h.

[0084] Comparative Example 3

[0085] Preparation of Zn / NC-acid: Other conditions and steps of this comparative example were the same as those for the preparation of Zn / NC in Example 1, except that after obtaining Zn / NC, 100 mg of Zn / NC was weighed and treated with 0.5 mol / L hydrochloric acid at 80°C for 5 h.

[0086] Application Example 1

[0087] The catalyst prepared in Example 1 was used for the hydrogenation reaction of cinnamaldehyde. The specific process was as follows:

[0088] Add 60 mg of catalyst, 49 mg of cinnamaldehyde, and 35 mL of isopropanol to a 50 mL round-bottom flask in sequence. After installing the condenser, use a double-row tube to ventilate the device so that it is filled with nitrogen. Finally, put a balloon filled with nitrogen on the top of the condenser and seal all interfaces with sealing film. Set the heating stirrer temperature to 100°C and the speed to 600 rpm. Start the timer after reaching the temperature and react for 5 hours.

[0089] After the reaction is completed, about 50 mg of the internal standard biphenyl is added to the round-bottom flask. After the biphenyl is completely dissolved, about 2.0 mL of the reacted solution is taken out with a syringe, and impurities such as catalyst powder are filtered out with a filter membrane. Then, the solution is diluted a certain multiple (to ensure that the concentration of the reactant is less than 100 ppm), and the diluted solution is injected through a microinjector, and the product content is analyzed by gas chromatography.

[0090] Comparative Application Example 1

[0091] The catalyst prepared in Comparative Example 1 was used for the hydrogenation reaction of cinnamaldehyde. The other conditions and steps of this application example were the same as those in Application Example 1, except that the amount of NC catalyst used was 52.8 mg.

[0092] Application Comparative Example 2

[0093] The catalyst prepared in Comparative Example 2 was used for the hydrogenation reaction of cinnamaldehyde, and the remaining methods were the same as those in Application Example 1.

[0094] Application Comparative Example 3

[0095] The catalyst prepared in Comparative Example 3 was used for the hydrogenation reaction of cinnamaldehyde, and the remaining methods were the same as those in Application Example 1.

[0096] Comparative Application Example 4

[0097] The precursor ZIF-8 was used for the hydrogenation reaction of cinnamaldehyde, and the remaining methods were the same as those in Application Example 1.

[0098] Application Comparative Example 5

[0099] Zn(NO3)2 was used for the hydrogenation reaction of cinnamaldehyde in an amount of 13 mg. The rest of the method was the same as that in Application Example 1.

[0100] Application Comparative Example 6

[0101] NC+Zn(NO3)2 was used for the hydrogenation reaction of cinnamaldehyde. The catalyst dosage was NC (52.8 mg) and Zn(NO3)2 (13 mg). The rest of the method was the same as that in Application Example 1.

[0102] Application Comparative Example 7

[0103] ZnPc was used for the hydrogenation reaction of cinnamaldehyde in an amount of 25.4 mg. The remaining procedures were the same as those in Application Example 1.

[0104] The conversion rate is calculated as follows:

[0105] Conversion rate % = cinnamaldehyde consumption in the reaction / cinnamaldehyde feed amount × 100%;

[0106] The selectivity is calculated as follows:

[0107] Selectivity % = molar amount of cinnamyl alcohol produced / molar amount of cinnamaldehyde consumed in the reaction × 100%

[0108] The conversion and selectivity results of Application Example 1 and Comparative Application Examples 1-7 are shown in Table 2, indicating that the prepared Zn / NC catalyst exhibits the best catalytic performance. Under the reaction conditions of 80°C and 5h, a cinnamaldehyde conversion rate of 95.4% and a cinnamyl alcohol selectivity of 95.5% can be achieved, while the conversion rate and selectivity of the catalysts used in the comparative application examples are poor.

[0109] Table 2

[0110]

[0111] Application Example 2

[0112] The other conditions and steps in this application example were identical to those in Application Example 1, except that cinnamaldehyde was replaced with 31 mg of 3-methylcrotonaldehyde, the catalyst was increased to 100 mg, and the reaction time was extended to 11 hours. A 97% conversion of 3-methylcrotonaldehyde and a 90% selectivity for 3-methylcrotonol were achieved.

[0113] Application Example 3

[0114] The other conditions and steps in this application example were identical to those in Application Example 1, except that cinnamaldehyde was replaced with 56 mg of α-methylcinnamaldehyde and the reaction time was extended to 12 h. A 94% conversion of α-methylcinnamaldehyde and a 97% selectivity for α-methylcinnamyl alcohol were achieved.

[0115] Application Example 4

[0116] The other conditions and steps of this application example were the same as those of Application Example 3, except that cinnamaldehyde was replaced with 37 mg of furfural and the reaction time was 11 h. A furfural conversion rate of 99% and a furfuryl alcohol selectivity of 89% were achieved.

[0117] Application Example 5

[0118] This application example used the same conditions and steps as Example 3, except that cinnamaldehyde was replaced with 45 mg of 5-hydroxymethylfurfural and the reaction time was 11 hours. A 5-hydroxymethylfurfural conversion of >99% and a 2,5-dihydroxymethylfuran selectivity of 96% were achieved.

[0119] Application Example 6

[0120] The other conditions and steps in this application example were the same as those in Application Example 3, except that cinnamaldehyde was replaced with 33 mg of α-amylcinnamaldehyde and the reaction time was 11 hours. A 93% conversion rate of α-amylcinnamaldehyde and a 98% selectivity for α-amylcinnamyl alcohol were achieved.

[0121] Application Example 7

[0122] The other conditions and steps in this application example were identical to those in Application Example 3, except that cinnamaldehyde was replaced with 66 mg of 4-nitrocinnamaldehyde and the reaction time was 11 hours. A 4-nitrocinnamaldehyde conversion of >99% and a selectivity for 4-nitrocinnamyl alcohol of >99% were achieved.

[0123] Application Example 8

[0124] The other conditions and steps in this application example were identical to those in Application Example 3, except that cinnamaldehyde was replaced with 60 mg of 4-methoxycinnamaldehyde and the reaction time was 11 h. A 90% conversion of 4-methoxycinnamaldehyde and an 83% selectivity for 4-methoxycinnamyl alcohol were achieved.

[0125] The experimental results of Application Examples 2-8 are shown in Table 3, indicating that the prepared Zn / NC catalyst can achieve catalytic transfer hydrogenation of various substrates with high selectivity.

[0126] Table 3

[0127]

[0128] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0129] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A hydrogenation reaction, characterized in that The hydrogenation reaction is carried out under the catalysis of a hydrogenation catalyst, and the hydrogenation reaction is a selective hydrogenation reaction of cinnamaldehyde and its derivatives. Wherein, the method for preparing the hydrogenation catalyst comprises: dissolving an organic ligand in a first organic solution to obtain a ligand solution, wherein the organic ligand is 2-methylimidazole; dissolving a zinc salt in a second organic solution to obtain a zinc salt solution, wherein the zinc salt is zinc nitrate hexahydrate; Under stirring conditions, adding the zinc salt solution to the ligand solution to carry out a coordination reaction to obtain a crude precursor, wherein the reaction temperature of the coordination reaction is 25-40° C. and the reaction time is 3-5 hours; The crude precursor is subjected to vacuum drying to obtain a precursor, wherein the vacuum drying is performed at 50-70° C. for 10-15 hours; The precursor is calcined to obtain the catalyst. The calcination temperature is 900°C. The catalyst is composed of Zn-N x The structure is the active site, the Zn-N x Zn in the structure is a zinc atom, and the coordination number x is 3; Wherein, the selective hydrogenation is the carbonyl hydrogenation of the cinnamaldehyde and its derivatives, The solvent for the hydrogenation reaction is an alcohol containing β-H, and the alcohol containing β-H serves as a hydrogen source for hydrogenation.

2. The hydrogenation reaction according to claim 1, characterized in that The mass ratio of the catalyst to the cinnamaldehyde and its derivatives is 0.9-3.2:

1.

3. The hydrogenation reaction according to claim 1, characterized in that The conversion rate of cinnamaldehyde and its derivatives is not less than 90%, and the selectivity is not less than 80%.

4. The hydrogenation reaction according to claim 1, characterized in that The calcination treatment is carried out under inert conditions, gradually raising the temperature to 900° C. and maintaining the temperature for 60-120 minutes.

5. The hydrogenation reaction according to claim 1, characterized in that The nitrogen in the catalyst is pyridinic nitrogen, pyrrolic nitrogen, graphitic nitrogen or oxidized nitrogen.

6. The hydrogenation reaction according to claim 1, characterized in that The hydrogenation catalyst is dodecahedral and porous.

7. The hydrogenation reaction according to claim 1, characterized in that The particle size of the hydrogenation catalyst is 400-600 nm.

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