A nickel-zinc intermetallic compound / ZnO catalyst, a preparation method and application thereof

Abstract

The application provides a nickel-zinc intermetallic compound / ZnO catalyst for CO2 hydrogenation to produce methanol under normal pressure, and a preparation method and application thereof. The prepared nickel-zinc intermetallic compound / ZnO catalyst has ZnO as a carrier, NiZn intermetallic compound as an active component, and a molar ratio of nickel to zinc in the catalyst is (0.01-2):1. The preparation method comprises the following steps: preparing a mixed compound precursor containing nickel and zinc, wherein the molar ratio of nickel to zinc in the precursor is (0.01-2):1; annealing the mixed compound precursor containing nickel and zinc under a first temperature in an air atmosphere; and reducing the annealed precursor under a second temperature to obtain the nickel-zinc intermetallic compound / ZnO catalyst. The nickel-zinc intermetallic compound / ZnO catalyst has low cost, simple preparation method, high catalytic activity and methanol selectivity, stable performance, can promote CO2 hydrogenation to produce methanol under normal pressure, effectively inhibit the occurrence of CO2 to CO and methanation side reactions, and greatly improve the methanol selectivity.

Description

Technical Field

[0001] This invention relates to the field of catalysis technology, and in particular to a method for preparing an in-situ synthesized nickel-zinc intermetallic compound / ZnO catalyst, the nickel-zinc intermetallic compound / ZnO catalyst prepared by the method, and the application of the nickel-zinc intermetallic compound / ZnO catalyst in the selective hydrogenation of CO2 to methanol at atmospheric pressure. Background Technology

[0002] In a time when pressing issues such as climate change and fossil fuel depletion are prominent, there is an urgent need to take measures to minimize greenhouse gas emissions and seek alternative carbon sources for energy and chemicals. Using H2 to directly convert the greenhouse gas CO2 into value-added chemicals offers a promising solution to address these two problems.

[0003] Green methanol, synthesized directly from CO2 and green H2, also known as liquid sunshine, is attracting increasing attention. Traditional industrial methanol production relies on syngas as a feedstock, requiring high temperature and pressure conditions (typically 200-300℃ and 3-10 MPa). This fossil fuel-based process demands substantial equipment investment and can lead to significant energy waste. In contrast, green methanol utilizes renewable green H2, allowing for smaller, inherently decentralized installations. Catalytic reaction units operating under low pressure and mild conditions are highly attractive for their compatibility with green H2 feedstock and for their cost reduction. Currently, catalysts for the hydrogenation of CO2 to methanol at atmospheric or near-ambient pressure mainly include rare or noble metals such as Pd, In, and Ga. The high price of these catalysts limits their large-scale application. Therefore, there is an urgent need to develop a highly active and inexpensive non-noble metal catalyst. Summary of the Invention

[0004] In view of the above problems, the present invention proposes a method for preparing an in-situ synthesized nickel-zinc intermetallic compound / ZnO catalyst that overcomes or at least partially solves the above problems, the nickel-zinc intermetallic compound / ZnO catalyst prepared by the method, and the application of the nickel-zinc intermetallic compound / ZnO catalyst in the selective hydrogenation of CO2 at atmospheric pressure to prepare methanol.

[0005] One object of the present invention is to provide a simple, reliable and low-cost method for preparing a nickel-zinc intermetallic compound / ZnO catalyst.

[0006] Another object of the present invention is to provide a nickel-zinc intermetallic compound / ZnO catalyst with high activity, high methanol selectivity and high stability prepared by this method.

[0007] One objective of this invention is to provide an application of the aforementioned nickel-zinc intermetallic compound / ZnO catalyst in the CO2 hydrogenation to methanol reaction under normal pressure, which effectively suppresses the CO2 to CO production and methanation side reactions, and significantly improves methanol selectivity.

[0008] According to one aspect of the present invention, a method for preparing an in-situ synthesized nickel-zinc intermetallic compound / ZnO catalyst is provided, comprising:

[0009] Step S1: Prepare a mixed compound precursor containing nickel and zinc, wherein the molar ratio of nickel to zinc in the precursor is (0.01-2):1;

[0010] Step S2: Anneal the mixed compound precursor in air at a first temperature; and

[0011] Step S3: The annealed precursor is reduced at a second temperature to obtain a nickel-zinc intermetallic compound / ZnO catalyst.

[0012] Optionally, the molar ratio of nickel to zinc in the precursor is (0.1-1):1.

[0013] Optionally, the first temperature is in the range of 300℃-900℃, and step S1 specifically includes:

[0014] The mixed compound precursor was heated from room temperature to a first temperature in air at a heating rate of 1-20℃ / min, and then annealed at the first temperature for 2-12 hours.

[0015] Optionally, the first temperature is in the range of 400℃-800℃.

[0016] Optionally, the second temperature is in the range of 400℃-600℃, and step S2 specifically includes:

[0017] The annealed precursor is heated from room temperature to a second temperature at a heating rate of 0.5-10℃ / min in a reducing atmosphere, and then subjected to reduction treatment at the second temperature for 1-10 hours. The reducing atmosphere is formed by hydrogen or a mixture containing hydrogen.

[0018] Optionally, the precursor containing the mixed compound of nickel and zinc is a mixture of nickel oxide and zinc oxide powder, zinc oxide powder impregnated with nickel salt, nickel oxide powder impregnated with zinc salt, or hydroxide powder co-precipitated from a mixed solution of nickel salt and zinc salt.

[0019] According to another aspect of the present invention, a nickel-zinc intermetallic compound / ZnO catalyst prepared according to the aforementioned preparation method is also provided.

[0020] According to another aspect of the present invention, the application of the aforementioned nickel-zinc intermetallic compound / ZnO catalyst in the selective hydrogenation of CO2 at atmospheric pressure to prepare methanol is also provided.

[0021] Optionally, the application method specifically includes:

[0022] In a gas-solid fixed-bed reactor, a mixture of CO2 and H2 with an H2 / CO2 molar ratio of 1-9 undergoes selective hydrogenation at 150-400°C under the catalysis of a nickel-zinc intermetallic compound / ZnO catalyst.

[0023] The method for preparing nickel-zinc intermetallic compound / ZnO catalyst provided by the present invention involves in-situ synthesis of nickel-zinc intermetallic compound / ZnO catalyst by high-temperature annealing and high-temperature reduction treatment of a mixed compound precursor containing nickel and zinc. The method is simple and reliable, easy to operate, low in cost, and suitable for large-scale production.

[0024] Furthermore, in the preparation method of the nickel-zinc intermetallic compound / ZnO catalyst provided by the present invention, only oxide powder, nickel salt, zinc salt, alkaline solution, deionized water and other reagents are needed, without any organic reagents. The raw materials are green and environmentally friendly, reducing environmental pollution.

[0025] The nickel-zinc intermetallic compound / ZnO catalyst provided by this invention uses excess ZnO as a support, and the NiZn intermetallic compound phase can suppress the occurrence of CO2 methanation and reverse water gas side reactions. This catalyst exhibits high activity and high methanol selectivity, with methanol selectivity reaching 100% among organic products. The catalyst also possesses excellent stability. Therefore, this catalyst can promote the CO2 hydrogenation to methanol reaction under normal pressure, effectively suppress the CO2 to CO production and methanation side reactions, and significantly improve methanol selectivity.

[0026] The nickel-zinc intermetallic compound / ZnO catalyst of this invention, when applied to the CO2 hydrogenation to methanol reaction under normal pressure, can stably promote the CO2 hydrogenation to methanol reaction under normal pressure, effectively suppress the occurrence of CO2 to CO and methanation side reactions, and significantly improve methanol selectivity.

[0027] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below.

[0028] The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0029] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0030] Figure 1 This is a schematic flowchart of a method for preparing an in-situ synthesized nickel-zinc intermetallic compound / ZnO catalyst according to an embodiment of the present invention.

[0031] Figure 2 XRD patterns of nickel-zinc intermetallic compound / ZnO catalysts with different nickel / zinc ratios prepared in Examples 1 to 7;

[0032] Figures 3a to 3c Comparison of catalytic performance of nickel-zinc intermetallic compound / ZnO catalysts with different nickel / zinc ratios prepared in Examples 1 to 7;

[0033] Figure 4a and Figure 4b Comparison of catalytic performance of nickel-zinc intermetallic compound / ZnO catalysts with a nickel / zinc ratio of 1:2 prepared at different air annealing temperatures in Examples 8 to 11;

[0034] Figure 5a and Figure 5b The graph shows a comparison of the catalytic performance of nickel-zinc intermetallic compound / ZnO catalysts prepared at different reduction temperatures in Examples 12 to 16 with a nickel / zinc ratio of 1:2.

[0035] Figure 6 The results show the long-term stability evaluation of a nickel-zinc intermetallic compound / ZnO catalyst with a nickel / zinc ratio of 1:2 according to an embodiment of the present invention at 250°C. Detailed Implementation

[0036] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0037] This invention provides a method for preparing an in-situ synthesized nickel-zinc intermetallic compound / ZnO catalyst.

[0038] Figure 1 This is a schematic flow chart illustrating a method for preparing an in-situ synthesized nickel-zinc intermetallic compound / ZnO catalyst according to an embodiment of the present invention. See also... Figure 1 As shown, the preparation method includes the following steps:

[0039] Step S1: Prepare a mixed compound precursor containing nickel and zinc, wherein the molar ratio of nickel to zinc in the precursor is (0.01-2):1;

[0040] Step S2: Anneal the mixed compound precursor in air at a first temperature; and

[0041] Step S3: The annealed precursor is reduced at a second temperature to obtain a nickel-zinc intermetallic compound / ZnO catalyst.

[0042] The method for preparing nickel-zinc intermetallic compound / ZnO catalyst provided in this invention involves in-situ synthesis of the nickel-zinc intermetallic compound / ZnO catalyst through high-temperature annealing and high-temperature reduction treatment of a mixed compound precursor containing nickel and zinc. The method is simple, reliable, easy to operate, low in cost, and suitable for large-scale production.

[0043] In some optional embodiments, the precursor containing the mixed compound of nickel and zinc in step S1 may be a mixture of nickel oxide and zinc oxide powders, zinc oxide powder impregnated with nickel salts, nickel oxide powder impregnated with zinc salts, or hydroxide powder co-precipitated from a mixed solution of nickel and zinc salts.

[0044] Accordingly, step S1 may specifically include: mixing nickel oxide powder and zinc oxide powder to obtain a nickel-zinc mixed compound precursor with a nickel-zinc molar ratio of (0.01-2):1. The mixing can be achieved by conventional mixing methods.

[0045] Alternatively, step S1 may specifically include: impregnating zinc oxide powder with nickel salts to obtain a precursor of a mixed compound containing nickel and zinc with a nickel to zinc molar ratio of (0.01-2):1. Nickel salt impregnation can be achieved using conventional impregnation methods. The nickel salt can be any commonly used nickel salt, such as nickel nitrate, nickel chloride, nickel sulfate, etc.

[0046] Alternatively, step S1 may specifically include: impregnating nickel oxide powder with zinc salt to obtain a precursor of a mixed compound containing nickel and zinc with a nickel to zinc molar ratio of (0.01-2):1. Zinc salt impregnation can be achieved by conventional impregnation methods. The zinc salt can be any commonly used zinc salt, such as zinc nitrate, zinc chloride, zinc sulfate, etc.

[0047] Alternatively, step S1 may specifically include: preparing a mixed solution of nickel and zinc salts, adding an alkaline solution to the mixed solution for co-precipitation, and obtaining a mixed solution of nickel and zinc salts. The nickel salt can be any commonly used nickel salt, such as nickel nitrate, nickel chloride, nickel sulfate, etc. The zinc salt can be any commonly used zinc salt, such as zinc nitrate, zinc chloride, zinc sulfate, etc. The alkaline solution can be any commonly used alkaline solution, such as sodium hydroxide and sodium carbonate solutions, etc.

[0048] In the preparation method of nickel-zinc intermetallic compound / ZnO catalyst provided in the embodiments of the present invention, only oxide powder, nickel salt, zinc salt, alkaline solution, deionized water and other reagents are needed, without any organic reagents. The raw materials are green and environmentally friendly, reducing environmental pollution.

[0049] In step S1, the molar ratio of nickel to zinc in the mixed compound precursor is (0.01-2):1. Preferably, the molar ratio of nickel to zinc in the mixed compound precursor is (0.1-1):1. More preferably, the molar ratio of nickel to zinc in the mixed compound precursor is (0.3-1):1. Even more preferably, the molar ratio of nickel to zinc in the mixed compound precursor is (0.5-1):1. Most preferably, the molar ratio of nickel to zinc in the mixed compound precursor is 0.5:1.

[0050] In some embodiments, step S2 may specifically include: subjecting a mixed compound precursor containing nickel and zinc to high-temperature annealing in an air atmosphere.

[0051] In some further embodiments, the mixed compound precursor is first heated from room temperature to a first temperature in an air atmosphere at a heating rate of 1-20 °C / min, and then annealed at the first temperature for 2-12 h. The air flow rate can be 2-100 mL / min.

[0052] After annealing, the annealed precursor can be cooled to room temperature before subsequent reduction treatment.

[0053] In some alternative embodiments, the first temperature is in the range of 300°C to 900°C, for example, 400°C, 500°C, 600°C, 700°C or 800°C.

[0054] In some preferred embodiments, the first temperature is in the range of 400°C to 800°C.

[0055] In some embodiments, step S3 may specifically include: subjecting the annealed precursor to high-temperature reduction treatment in a reducing atmosphere. The reducing atmosphere is formed by a reducing gas. The reduction treatment is carried out at atmospheric pressure.

[0056] In some embodiments, the reducing gas may be pure hydrogen with a purity greater than 99.9%.

[0057] In other embodiments, the reducing gas can be a hydrogen-containing mixture, with a hydrogen volume content of 5%-100%. Other gases besides hydrogen can be inert gases, such as nitrogen or argon.

[0058] In some further embodiments, the annealed precursor is first heated from room temperature to a second temperature in a reducing atmosphere at a heating rate of 0.5-10 °C / min, and then reduced at the second temperature for 1-10 h. The flow rate of the reducing gas can be 2-100 mL / min. Heating is performed by programmed temperature rise.

[0059] After reduction treatment, the prepared product can be cooled to room temperature.

[0060] In some alternative embodiments, the second temperature is in the range of 400°C to 600°C, for example, 400°C, 450°C, 500°C, 550°C or 600°C.

[0061] The present invention also provides a nickel-zinc intermetallic compound / ZnO catalyst prepared by the aforementioned preparation method. In this catalyst, the molar ratio of nickel to zinc is (0.01-2):1, the catalyst support is ZnO, and the active component is a NiZn intermetallic compound.

[0062] In the nickel-zinc intermetallic compound / ZnO catalyst provided in this invention, excess ZnO serves as a support, and the NiZn intermetallic compound phase can suppress the occurrence of CO2 methanation and reverse water-gas side reactions. This catalyst exhibits high activity and high methanol selectivity, with methanol selectivity reaching 100% among organic products. The catalyst also possesses excellent stability. Therefore, this catalyst can promote the CO2 hydrogenation to methanol reaction under normal pressure, effectively suppress the CO2 to CO production and methanation side reactions, and significantly improve methanol selectivity.

[0063] This invention also provides the application of the aforementioned nickel-zinc intermetallic compound / ZnO catalyst in the selective hydrogenation of CO2 at atmospheric pressure to prepare methanol.

[0064] The nickel-zinc intermetallic compound / ZnO catalyst of this invention, when applied to the CO2 hydrogenation to methanol reaction under normal pressure, can stably promote the CO2 hydrogenation to methanol reaction under normal pressure, effectively suppress the occurrence of CO2 to CO and methanation side reactions, and significantly improve methanol selectivity.

[0065] In some embodiments, the method of applying the aforementioned nickel-zinc intermetallic compound / ZnO catalyst in the selective hydrogenation of CO2 to methanol at ambient pressure specifically includes:

[0066] In a gas-solid fixed-bed reactor, a mixture of CO2 and H2 with an H2 / CO2 molar ratio of 1-9 undergoes selective hydrogenation at 150-300°C under the catalysis of a nickel-zinc intermetallic compound / ZnO catalyst.

[0067] Selective hydrogenation reactions are carried out at or near atmospheric pressure, and the mass hourly space velocity can be controlled between 2400 and 36000 mL / (g·h).

[0068] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0069] It should be noted that the NxZy catalyst referred to in the following examples is a nickel-zinc intermetallic compound / ZnO catalyst, where x:y represents the molar ratio (i.e., molar ratio) of the Ni and Zn metal elements fed. Experimental methods not specifically described in the examples are generally performed under conventional conditions, as described in the manual, or as recommended by the manufacturer. Unless otherwise specified, the general equipment, materials, and reagents used are commercially available. All raw materials used in the following examples and comparative examples are commercially available.

[0070] In Examples 1 to 7 below, NxZy catalysts with different nickel contents were prepared respectively.

[0071] Example 1

[0072] Weigh 1.939 g of Ni(NO3)3·6H2O and 3.967 g of Zn(NO3)2·6H2O, and add 20 mL of H2O to a beaker to mix and dissolve, obtaining a metal precursor solution. Separately, prepare a 4M NaOH aqueous solution using 40 mL of H2O and 6.4 g of NaOH for titration. Add the 4M NaOH aqueous solution and the metal precursor solution simultaneously to a 0.5M Na2CO3 aqueous solution, stirring vigorously until the pH of the suspension reaches 12. After the suspension has precipitated for 12 hours, centrifuge the resulting suspension to obtain the precipitate. Then, wash the precipitate with deionized water and distilled water to remove unreacted NaOH and Na2CO3. Repeat this washing step 4-5 times until the pH of the supernatant reaches 7. The obtained product was freeze-dried overnight, then placed in a tube furnace and calcined at 800°C for 3 hours in air at a heating rate of 10°C / min. The atmosphere was then changed to pure H2, and the product was reduced at 500°C for 2 hours at a heating rate of 1°C / min to obtain N1Z2.

[0073] Example 2

[0074] In this embodiment, except that the amount of Ni(NO3)3·6H2O is 2.908g and the amount of Zn(NO3)2·6H2O is 2.975g, the rest of the preparation steps are exactly the same as in Example 1, and N1Z1 is obtained.

[0075] Example 3

[0076] In this embodiment, except that the amount of Ni(NO3)3·6H2O is 1.454g and the amount of Zn(NO3)2·6H2O is 4.461g, the rest of the preparation steps are exactly the same as in Example 1, and N1Z3 is obtained.

[0077] Example 4

[0078] In this embodiment, except that the amount of Ni(NO3)3·6H2O is 1.163g and the amount of Zn(NO3)2·6H2O is 4.758g, the rest of the preparation steps are exactly the same as in Example 1, and N1Z4 is obtained.

[0079] Example 5

[0080] In this embodiment, except that the amount of Ni(NO3)3·6H2O is 0.582g and the amount of Zn(NO3)2·6H2O is 5.353g, the rest of the preparation steps are exactly the same as in Example 1, and N1Z9 is obtained.

[0081] Example 6

[0082] In this embodiment, except that the amount of Ni(NO3)3·6H2O is 3.839g and the amount of Zn(NO3)2·6H2O is 1.963g, the rest of the preparation steps are exactly the same as in Example 1, and N2Z1 is obtained.

[0083] Example 7

[0084] In this embodiment, except that the amount of Ni(NO3)3·6H2O is 44.362g and the amount of Zn(NO3)2·6H2O is 1.487g, the rest of the preparation steps are exactly the same as in Example 1, and N3Z1 is obtained.

[0085] In Examples 8 to 11 below, N1Z2 catalysts were prepared at different air annealing temperatures.

[0086] Example 8

[0087] Weigh 1.939 g of Ni(NO3)3·6H2O and 3.967 g of Zn(NO3)2·6H2O, and add 20 mL of H2O to a beaker to mix and dissolve, obtaining a metal precursor solution. Separately, prepare a 4M NaOH aqueous solution using 40 mL of H2O and 6.4 g of NaOH for titration. Add the 4M NaOH aqueous solution and the metal precursor solution simultaneously to a 0.5M Na2CO3 aqueous solution, stirring vigorously until the pH of the suspension reaches 12. After stirring and allowing the suspension to precipitate for 12 hours, separate the precipitate from the resulting suspension. Wash the precipitate with deionized water and distilled water to remove unreacted NaOH and Na2CO3. Repeat this washing step 4-5 times until the pH of the supernatant reaches 7. The obtained product was freeze-dried overnight, then placed in a tube furnace and calcined at 800°C for 3 hours in air at a heating rate of 10°C / min. The atmosphere was then changed to pure H2 and reduced at 500°C for 2 hours at a heating rate of 1°C / min to obtain 800-N1Z2 (where 800 indicates the air annealing temperature of 800°C).

[0088] Example 9

[0089] In this embodiment, except that the air annealing temperature is 300°C, the other preparation steps are exactly the same as in Example 8, resulting in 300-N1Z2 (where 300 indicates that the air annealing temperature is 300°C).

[0090] Example 10

[0091] In this embodiment, except that the air annealing temperature is 400°C, the other preparation steps are exactly the same as in Example 8, resulting in 400-N1Z2 (where 400 indicates that the air annealing temperature is 400°C).

[0092] Example 11

[0093] In this embodiment, except that the air annealing temperature is 600°C, the other preparation steps are exactly the same as in Example 8, resulting in 600-N1Z2 (where 600 indicates that the air annealing temperature is 600°C).

[0094] In Examples 12 to 16 below, N1Z2 catalysts were prepared at different reduction temperatures.

[0095] Example 12

[0096] Weigh 1.939 g of Ni(NO3)3·6H2O and 3.967 g of Zn(NO3)2·6H2O, and add 20 mL of H2O to a beaker to mix and dissolve, obtaining a metal precursor solution. Separately, prepare a 4M NaOH aqueous solution using 40 mL of H2O and 6.4 g of NaOH for titration. Add the 4M NaOH aqueous solution and the metal precursor solution simultaneously to a 0.5M Na2CO3 aqueous solution, stirring vigorously until the pH of the suspension reaches 12. After stirring and allowing the suspension to precipitate for 12 hours, separate the precipitate from the resulting suspension. Wash the precipitate with deionized water and distilled water to remove unreacted NaOH and Na2CO3. Repeat this washing step 4-5 times until the pH of the supernatant reaches 7. The obtained product was freeze-dried overnight, then placed in a tube furnace and calcined at 800°C for 3 hours in air at a heating rate of 10°C / min. The atmosphere was then changed to pure H2 and reduced at 500°C for 2 hours at a heating rate of 1°C / min to obtain 500r-N1Z2 (where 500r indicates the reduction temperature of 500°C).

[0097] Example 13

[0098] In this embodiment, except for the reduction temperature of 300℃, the other preparation steps are exactly the same as in Example 12, resulting in 300r-N1Z2 (where 300r indicates the reduction temperature of 300℃).

[0099] Example 14

[0100] In this embodiment, except for the reduction temperature of 400℃, the other preparation steps are exactly the same as in Example 12, resulting in 400r-N1Z2 (where 400r indicates the reduction temperature of 400℃).

[0101] Example 15

[0102] In this embodiment, except for the reduction temperature of 600℃, the other preparation steps are exactly the same as in Example 12, resulting in 600r-N1Z2 (where 600r indicates the reduction temperature of 600℃).

[0103] Example 16

[0104] In this embodiment, except that the reduction temperature is 200℃, the other preparation steps are exactly the same as in Example 12, and 200r-N1Z2 is obtained (where 200r indicates the reduction temperature is 200℃).

[0105] Example 17

[0106] In Example 17, except that the amount of Ni(NO3)3·6H2O was 0.058g and the amount of Zn(NO3)2·6H2O was 5.890g, the other preparation steps were exactly the same as in Example 1, and N1Z99 was obtained.

[0107] The catalysts obtained in Examples 1-7 were subjected to XRD pattern analysis, and the results are as follows: Figure 2 As shown in the image. (Comparison) Figure 2 The XRD patterns of the catalysts show that for samples where Ni accounts for more than 50% of the Ni+Zn content (such as N3Z1 and N2Z1), the structure is similar to that of metallic Ni. The introduction of Zn leads to lattice expansion, resulting in a leftward shift of the XRD peak position (44.7° → 43.9°), indicating the formation of a Ni-Zn alloy. When the Zn content exceeds 33%, a diffraction peak at 46.84° appears, indicating the formation of the NiZn intermetallic compound. Further increasing the Zn content to 50% causes the Ni-Zn alloy structure, which retains the metallic Ni structure, to disappear, and the NiZn intermetallic compound content reaches its peak. Subsequent increases in Zn content do not lead to a change in the relative Ni / Zn content of the Ni-Zn alloy phase; the peak position remains fixed at 43.6° of the NiZn structure, but its peak intensity decreases with increasing Zn content, while the diffraction peak intensity corresponding to the ZnO structure gradually increases. This indicates that after the Ni / Zn ratio reaches 1, the proportion of the NiZn phase in the overall phase composition begins to decrease.

[0108] The catalysts obtained in Examples 1-17 were used in the hydrogenation of carbon dioxide to methanol, and their catalytic activities were quantitatively compared.

[0109] The method for using the aforementioned catalyst to catalyze the hydrogenation of carbon dioxide to methanol specifically includes the following steps:

[0110] Step 1: Loading the catalyst.

[0111] The catalyst was sieved, and 100 mg of 20-40 mesh catalyst was loaded into a fixed-bed quartz tube reactor.

[0112] Step 2: Reduce and activate the catalyst.

[0113] The reducing gas was pure hydrogen, with a flow rate of 20 mL / min. The temperature was increased from 25 °C to 400 °C at a rate of 10 °C / min, and the reduction time was 60 min.

[0114] Step 3: Catalyst performance testing. The reactants were a mixture of CO2 and H2, with an H2:CO2 molar ratio of 5, a mass hourly space velocity (HHSV) of 14.4 L / (g·h), an incident light intensity of 0.3-0.6 sun, a corresponding reaction temperature of 230-270℃, and a pressure of atmospheric or near-atmospheric pressure. The reaction conditions for catalyst stability testing were: an incident light intensity of 0.45 sun, a reaction temperature of 250℃, a HHSV of 14.4 L / (g·h), and a reaction time of 170 h.

[0115] The composition of the tail gas and feed gas after the reaction was analyzed using a GC7920 chromatograph system. The detectors used were a TCD (Thermal Conductivity Detector) and a FID (Flame Ionization Detector). The TCD was used for the analysis of CO2, CO, and H2; FID1 was used for the quantitative analysis of methanol and methane; and FID2 was used for the quantitative analysis of carbon monoxide and methane.

[0116] For NxZy catalysts with different nickel contents, the activity of seven groups of samples (N3Z1, N2Z1, N1Z1, N1Z2, N1Z3, N1Z4, and N1Z9) prepared in Examples 1-7 was tested, and the results are as follows: Figures 3a to 3c As shown. It should be noted that, Figures 3a to 3c In the diagram, the horizontal axis represents the test temperature for catalytic performance. The performance test results of N3Z1, N2Z1, N1Z1, N1Z2, N1Z3, N1Z4, and N1Z9 at each test temperature are displayed sequentially from left to right.

[0117] Depend on Figures 3a to 3c It is evident that catalysts N3Z1, N2Z1, N1Z1, N1Z2, N1Z3, N1Z4, and N1Z9 do not exhibit CH4 production performance. Moreover, catalysts with Ni content in the range of 25-66% show superior CO2-to-methanol conversion capabilities, with catalyst N1Z2 exhibiting the best methanol production activity and the highest CO2 conversion rate.

[0118] The performance of N1Z2 catalysts prepared in Examples 8-11 at different air annealing temperatures on CO2 conversion and methanol production was compared, and the results are as follows: Figure 4a and Figure 4b As shown, where, Figure 4a and Figure 4b The horizontal axis represents the test temperature for catalytic performance. (From...) Figure 4a and Figure 4b It is evident that the catalyst exhibits the optimal CO2 conversion rate and methanol production at an annealing temperature of 800℃.

[0119] The performance of the N1Z2 catalysts prepared in Examples 12-16 at different reduction temperatures on CO2 conversion and methanol production was compared, and the results are as follows: Figure 5a and Figure 5b As shown, where, Figure 5a and Figure 5b The horizontal axis represents the test temperature for catalytic performance.

[0120] Depend on Figure 5a and Figure 5bIt is evident that CO2 conversion and methanol production first increase and then decrease with increasing reduction temperature. No methanol production was detected at reduction temperatures below 400℃, indicating that the formation of NiZn intermetallic compounds with methanol-generating activity requires a reduction temperature above 400℃. At 400℃, methanol production and carbon dioxide conversion reach their extreme values; further increases in temperature lead to a decrease in both methanol production and CO2 conversion rates.

[0121] The long-term stability of the N1Z2 catalyst was tested and evaluated under the following reaction conditions: incident light intensity of 0.45 sun, reaction temperature of 250℃, mass hourly space velocity of 14.4 L / (g·h), and reaction time of 170 h. The results are as follows: Figure 6 As shown.

[0122] Depend on Figure 6 It can be seen that the yield of methanol and its selectivity in the total organic products remain unchanged within a reaction time of 170 h, which indicates that the N1Z2 catalyst has excellent stability and good methanol selectivity.

[0123] The N1Z99 catalyst prepared in Example 17 was used to catalyze the hydrogenation of carbon dioxide to methanol under the aforementioned steps and reaction conditions. The product did not contain CH4 and contained approximately 1 μmol g of MeOH STY. -1 h -1 It is evident that, with a nickel-zinc intermetallic compound / ZnO catalyst having a molar ratio of approximately 0.01:1, the resulting catalyst still exhibits methanol production activity and good methanol selectivity.

[0124] Test data show that the NxZy catalyst of this invention not only possesses high activity and high methanol selectivity, but more importantly, it also exhibits high stability. Long-term stability evaluation results of the N1Z2 catalyst of this invention at a reaction temperature of 250°C show that the methanol yield remains at 100 μmol / (g·h) within a reaction time of 160 h, and the methanol selectivity among the organic products remains at 100%. This indicates that the NxZy catalyst possesses excellent stability and good methanol selectivity.

[0125] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0126] Therefore, those skilled in the art should recognize that although numerous exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Thus, the scope of the present invention should be understood and construed as covering all such other variations or modifications.

Claims

1. The application of a nickel-zinc intermetallic compound / ZnO catalyst in the selective hydrogenation of CO2 to methanol at ambient pressure, wherein the catalytic reaction is carried out under light and heating conditions, wherein... The nickel-zinc intermetallic compound / ZnO catalyst, using ZnO as a support, was synthesized in situ using the following preparation method: Step S1: Prepare a mixed compound precursor containing nickel and zinc, wherein the molar ratio of nickel to zinc in the precursor is (0.01-2):1; Step S2: Anneal the mixed compound precursor in air at a first temperature; as well as Step S3: The annealed precursor is reduced at a second temperature to obtain a nickel-zinc intermetallic compound / ZnO catalyst, wherein the second temperature is in the range of 400-500℃.

2. The application of the nickel-zinc intermetallic compound / ZnO catalyst according to claim 1 in the selective hydrogenation of CO2 to methanol at ambient pressure, characterized in that, The molar ratio of nickel to zinc in the precursor is (0.1-1):

1.

3. The application of the nickel-zinc intermetallic compound / ZnO catalyst according to claim 1 in the selective hydrogenation of CO2 to methanol at ambient pressure, characterized in that, The first temperature is in the range of 300℃-900℃, and step S2 specifically includes: The mixed compound precursor is heated from room temperature to the first temperature in air at a heating rate of 1-20 °C / min, and then annealed at the first temperature for 2-12 h.

4. The application of the nickel-zinc intermetallic compound / ZnO catalyst according to claim 1 in the selective hydrogenation of CO2 to methanol at ambient pressure, characterized in that, Step S3 specifically includes: The annealed precursor is heated from room temperature to the second temperature at a heating rate of 0.5-10℃ / min in a reducing atmosphere, and then subjected to reduction treatment at the second temperature for 1-10 h, wherein the reducing atmosphere is formed by hydrogen or a hydrogen-containing mixture.

5. The application of the nickel-zinc intermetallic compound / ZnO catalyst according to claim 1 in the selective hydrogenation of CO2 to methanol at ambient pressure, characterized in that, The precursor of the mixed compound containing nickel and zinc is a mixture of nickel oxide and zinc oxide powder, zinc oxide powder impregnated with nickel salt, nickel oxide powder impregnated with zinc salt, or hydroxide powder co-precipitated from a mixed solution of nickel salt and zinc salt.

6. The application of the nickel-zinc intermetallic compound / ZnO catalyst according to claim 1 in the selective hydrogenation of CO2 to methanol at ambient pressure, characterized in that, The specific methods of the application include: In a gas-solid fixed-bed reactor, a mixture of CO2 and H2 with an H2 / CO2 molar ratio of 1-9 undergoes selective hydrogenation at 150-300°C under the catalysis of the nickel-zinc intermetallic compound / ZnO catalyst, with an incident light intensity of 0.3-0.6 sun.

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