Catalyst, process for its preparation and use, and process for the synthesis of methanol

Abstract

The present application relates to the technical field of alcohol synthesis, in particular to a kind of catalyst and its preparation method and application and the method for synthesizing methanol.The catalyst of the present application includes: modified aluminum-based metal organic framework and active component copper oxide and zinc oxide supported on the modified aluminum-based metal organic framework, wherein the modified aluminum-based metal organic framework is the product obtained by etching aluminum-based metal organic framework.The preparation method of the catalyst of the present application includes: (1) etching aluminum-based metal organic framework with a solution to obtain product 1;(2) the product 1 is precipitated with copper-zinc solution to obtain product 2;(3) the product 2 is dried and calcined to obtain the catalyst.When the catalyst of the present application is applied to the reaction of preparing methanol from synthesis gas, it has high catalytic activity and thermal stability.

Description

Technical Field

[0001] This invention relates to the field of methanol synthesis technology, specifically to a catalyst, its preparation method and application, and a method for synthesizing methanol. Background Technology

[0002] Methanol is a fundamental product of C1 chemistry and a raw material for organic chemicals. It is also a clean liquid fuel, easy to store and transport, and an important energy carrier. The methanol synthesis catalyst is a key factor determining the effectiveness of the methanol synthesis reaction. Currently, the most widely used methanol synthesis catalyst in industry is the Cu-ZnO-Al2O3 catalyst. However, traditional methods for synthesizing Cu-ZnO-Al2O3 catalysts often employ co-precipitation. The difference in precipitation rates of different metals prevents them from precipitating simultaneously and uniformly, thus affecting the metal dispersion and particle size. In severe cases, this can lead to a decrease in catalytic activity and shorten the catalyst's lifespan.

[0003] Metal-organic frameworks (MOFs) are a novel type of crystalline porous material. The coordination interaction between metal ions and organic ligands endows MOFs with regular, rigid, and modifiable pore structures, possessing the inherent advantage of confining metal particles. However, the structures of most MOFs collapse rapidly in aqueous solutions; furthermore, most MOFs exhibit limited thermal stability, with metal-organic ligand bond breaking occurring at temperatures above 200°C, thus restricting their application in methanol synthesis catalysis. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of large particle size and low dispersion of active components in existing catalysts for methanol synthesis, as well as poor water and thermal stability of metal-organic framework supports, and to provide a catalyst, its preparation method and application, and a method for synthesizing methanol.

[0005] To achieve the above objectives, a first aspect of the present invention provides a catalyst comprising: a modified aluminum-based metal-organic framework and active components copper oxide and zinc oxide supported on the modified aluminum-based metal-organic framework;

[0006] The modified aluminum-based metal-organic framework is a product obtained by etching an aluminum-based metal-organic framework.

[0007] A second aspect of the present invention provides a method for preparing a catalyst, wherein the method comprises:

[0008] (1) The aluminum-based metal-organic framework was etched with a solution to obtain product 1;

[0009] (2) The product 1 is subjected to a precipitation reaction with copper-zinc solution to obtain product 2;

[0010] (3) The product 2 is dried and calcined to obtain the catalyst.

[0011] A third aspect of the present invention provides a catalyst prepared by the method described in the second aspect.

[0012] The fourth aspect of the present invention provides the application of the catalyst described in the first aspect or the catalyst described in the third aspect in methanol synthesis.

[0013] A fifth aspect of the present invention provides a method for synthesizing methanol, wherein the method comprises:

[0014] (1) The catalyst is reduced to obtain the reduced catalyst;

[0015] (2) In the presence of the reduced catalyst obtained in step (1), the syngas is reacted to obtain methanol;

[0016] The catalyst is either the catalyst described in the first aspect or the catalyst described in the third aspect.

[0017] Through the above technical solution, this invention introduces abundant and uniformly distributed alkaline sites into a rigid aluminum-based metal-organic framework structure with superior water and thermal stability by etching, preferably using an alkaline solution. The presence of these alkaline sites allows for in-situ copper-zinc neutralization reactions within the pores. Following calcination, an aluminum-based metal-organic framework composite material with confined copper-zinc active particles is obtained. X-ray diffraction testing and catalytic activity evaluation of the aluminum-based metal-organic framework composite material prepared by this invention show that it yields smaller-sized, more dispersed copper-zinc active particles adapted to the metal-organic framework pores. Furthermore, the confinement of the metal-organic framework pores slows down the thermal migration and aggregation of active particles, thereby improving catalyst activity and thermal stability. Detailed Implementation

[0018] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0019] The following detailed description of specific embodiments of the present invention, in conjunction with tables, is provided. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0020] The first aspect of the present invention provides a catalyst comprising: a modified aluminum-based metal-organic framework and active components copper oxide and zinc oxide supported on the modified aluminum-based metal-organic framework;

[0021] The modified aluminum-based metal-organic framework is a product obtained by etching an aluminum-based metal-organic framework.

[0022] According to the present invention, the aluminum-based metal-organic framework (Al-MOF) not only possesses a regular, rigid, and modifiable pore structure, but also, when used as a support in a catalyst, can confine the active component particles, affecting the particle size and dispersion of the active component copper-zinc oxide particles, thereby influencing the catalyst's activity and thermal stability. Secondly, by etching the support, the present invention introduces abundant and uniformly distributed active sites into the structure of the aluminum-based metal-organic framework, further improving the dispersion of the active component copper-zinc oxide particles and confining the active component particles, thus mitigating the tendency of active particles to migrate and aggregate under heat, thereby further enhancing the catalyst's activity and thermal stability. Furthermore, the aluminum-based metal-organic framework of the present invention exhibits superior water and thermal stability; its structure is not easily collapsed or destroyed in the aqueous phase and can maintain its structure even at temperatures above 200°C, expanding the application of metal-organic frameworks in the field of methanol synthesis catalysis.

[0023] According to the present invention, in order to enable the aluminum-based metal-organic framework to have superior water stability and thermal stability, making the catalyst suitable for application in aqueous solutions and high-temperature environments, improving catalyst activity and thermal stability, and broadening the application field of the catalyst, preferably, the aluminum-based metal-organic framework is prepared by a hydrothermal reaction of aluminum salt and ligand; specifically, the aluminum salt and ligand are dissolved in a solvent and a hydrothermal reaction is carried out at a certain temperature. The solvent used in the hydrothermal reaction is not particularly limited, as long as it can dissolve the aluminum salt and ligand. Preferably, the solvent is water. Preferably, after the hydrothermal reaction, the method further includes washing and drying the solid particles obtained from the hydrothermal reaction.

[0024] Preferably, the pyrolysis temperature of the aluminum-based metal-organic framework is 400-500℃, and more preferably 450-480℃.

[0025] Preferably, the hydrothermal reaction temperature is 100-200℃ and the time is 8-30h; more preferably, the hydrothermal reaction temperature is 120-170℃ and the time is 12-15h.

[0026] The present invention does not particularly limit the aluminum salt, as long as it can dissolve in the solvent used in the hydrothermal reaction. Preferably, the aluminum salt is selected from at least one of aluminum nitrate, aluminum carbonate, aluminum sulfate, aluminum chloride or aluminum isopropoxide.

[0027] Preferably, the ligand is selected from at least one of pyromellitic acid, terephthalic acid, and pyridinecarboxylic acid;

[0028] Preferably, the molar ratio of the aluminum salt to the ligand is 1-5, more preferably 1-3;

[0029] According to the present invention, in order to better load the active component copper-zinc oxide particles on the etched carrier surface, preferably, the etching is performed by treating the aluminum-based metal-organic framework with an alkali.

[0030] More preferably, the alkali is at least one selected from NaOH, Na2CO3, and NaHCO3.

[0031] According to the present invention, in order to increase the dispersion of copper and zinc particles of the catalyst active components and the accessibility of active sites, and to improve the activity and thermal stability of the catalyst, preferably, the average particle size of the copper oxide is 6-10 nm and the average particle size of the zinc oxide is 3-6 nm.

[0032] More preferably, the average particle size of the copper oxide is 7-8 nm, and the average particle size of the zinc oxide is 4-5 nm.

[0033] According to the present invention, the molar ratio of copper to zinc in the active component is 1-10:1, more preferably 1-5:1.

[0034] According to the present invention, in order to better load the active components of the catalyst onto the aluminum-based metal-organic framework, slow down the thermal migration and aggregation of active particles, and prevent the decrease in catalyst activity and thermal stability, preferably, the molar ratio of copper and zinc to aluminum in the aluminum-based metal-organic framework in the catalyst is 1:0.03-7.5, more preferably 1:0.05-5.

[0035] In this invention, the composition and structure of the catalyst can be determined by means of inductively coupled plasma spectroscopy (ICP), X-ray diffraction, etc., or can be calculated by the amount of feed in a specific implementation.

[0036] This invention does not particularly limit the preparation method of the composite resin, as long as a catalyst with the above-mentioned composition can be obtained. According to a preferred embodiment of the present invention, a second aspect of the present invention provides a method for preparing a catalyst, wherein the method includes:

[0037] (1) The aluminum-based metal-organic framework was etched with a solution to obtain product 1;

[0038] (2) The product 1 is reacted with copper-zinc liquid to obtain product 2;

[0039] (3) The product 2 is dried and calcined to obtain the catalyst.

[0040] According to the present invention, the preparation method utilizes an alkaline solution to etch an aluminum-based metal-organic framework (Al-MOF), introducing abundant and uniformly distributed alkaline active sites into the metal-organic framework structure. The presence of these alkaline active sites allows the in-situ reaction for preparing active components to occur within the pores of the metal-organic framework. After drying and calcination, an aluminum-based metal-organic framework composite material with confined copper-zinc active particles is obtained. Due to the confinement effect of the Al-MOF active sites on the copper-zinc active particles, the copper-zinc active particles in the composite material are adapted to the pores of the metal-organic framework. By controlling the acidity, alkalinity, concentration, and etching time of the etching solution during the preparation process, the density and distribution of the introduced active sites can be controlled, resulting in copper-zinc active particles with smaller size and higher dispersion, and the thermal migration and aggregation of active particles can be slowed down, thereby improving the activity and thermal stability of the catalyst.

[0041] According to the method provided by the present invention, the type and preparation of aluminum-based metal-organic frameworks (Al-MOFs) can be the same as described in the first aspect of the present invention, and will not be repeated here.

[0042] According to the preparation method of the present invention, in order to effectively etch the aluminum-based metal-organic framework Al-MOF, the introduced active sites can enable the copper-zinc salt to react in situ within the pores of the metal-organic framework. Preferably, in step (1), the solution is an alkaline solution, and more preferably a NaOH, Na2CO3 or NaHCO3 solution.

[0043] According to the preparation method of the present invention, in order to control the density and distribution of active sites introduced by etching in the structural channels of the metal-organic framework, so that the prepared copper-zinc active particles have a smaller size and higher dispersibility, preferably, in step (1), the concentration of the alkaline solution is 1-10 mol / L, more preferably 1-5 mol / L.

[0044] Preferably, in step (1), the etching temperature is 20-200℃ and the time is 12-60h. More preferably, the etching temperature is 25-150℃ and the time is 12-48h.

[0045] According to the preparation method of the present invention, in order to enable the copper-zinc liquid and the precipitant to better react in situ in the structural pores of the metal-organic framework, so that the obtained copper-zinc active particles have a smaller size and higher dispersion, thereby improving the activity and thermal stability of the catalyst, preferably, in step (2), the copper-zinc liquid contains a copper compound and a zinc compound; more preferably, the copper compound is selected from at least one of copper nitrate, copper chloride, and copper sulfate, and the zinc compound is selected from at least one of zinc nitrate, zinc chloride, and zinc sulfate.

[0046] According to the preparation method of the present invention, in order to make the obtained catalyst have high activity in methanol synthesis, preferably, in step (2), the molar ratio of copper compound to zinc compound in the copper-zinc liquid is 1-10:1, and more preferably, the molar ratio of copper compound to zinc compound is 1-5:1.

[0047] According to the preparation method of the present invention, in order to promote the in-situ reaction in the pores of the metal-organic framework structure, preferably, in step (2), the reaction temperature is 20-80℃, the time is 10-80min, and the pH of the reaction system is 4-10. More preferably, the reaction temperature is 25-60℃, the time is 15-60min, and the pH of the reaction system is 5-9.

[0048] According to the preparation method of the present invention, in order to better load the active components of the catalyst onto the aluminum-based metal-organic framework Al-MOF, slow down the thermal migration and agglomeration of active particles, and prevent the decrease in catalyst activity and thermal stability, preferably, in step (2), the molar ratio of copper and zinc in the copper-zinc oxide particles to aluminum in the aluminum-based metal-organic framework Al-MOF is 1:0.03-7.5, and more preferably 1:0.05-5.

[0049] According to the preparation method of the present invention, in order to make the prepared catalyst have high catalytic activity and thermal stability, preferably, in step (3), the drying temperature is 60-150℃ and the time is 5-24h; more preferably, the drying temperature is 80-120℃ and the time is 6-12h.

[0050] Preferably, the roasting temperature is 200-600℃ and the time is 20-100 min; more preferably, the roasting temperature is 300-400℃ and the time is 30-60 min.

[0051] According to the technical solution of the present invention, by adjusting the acidity, alkalinity, concentration and etching time of the etching solution during the preparation process, the density and distribution of the introduced active sites can be controlled, so that the prepared copper-zinc active particles can have adjustable size and dispersion to adapt to different reaction conditions in the methanol synthesis process, expand the application field of the metal-organic framework supported copper-zinc catalyst prepared by the present invention, and save costs.

[0052] A third aspect of the present invention provides a catalyst prepared by the method described in the second aspect.

[0053] The fourth aspect of the present invention provides the application of the catalyst described in the first aspect or the catalyst described in the third aspect in methanol synthesis.

[0054] A fifth aspect of the present invention provides a method for synthesizing methanol, wherein the method comprises:

[0055] (1) The catalyst is reduced to obtain the reduced catalyst;

[0056] (2) In the presence of the reduced catalyst obtained in step (1), the syngas is reacted to obtain methanol;

[0057] The catalyst is either the catalyst described in the first aspect or the catalyst described in the third aspect.

[0058] According to the method for synthesizing methanol of the present invention, preferably, in step (1), the reduction process is as follows: under normal pressure in a mixed atmosphere containing hydrogen and nitrogen, at 5-20℃·h -1 The temperature is increased to 200-300℃ at a rate and maintained for 5-10 hours.

[0059] More preferably, in the mixed atmosphere, the volume ratio of hydrogen to nitrogen is 5-10:90-95.

[0060] According to the method for synthesizing methanol of the present invention, preferably, in step (2), based on the total volume of the synthesis gas, the content of CO in the synthesis gas is 13-15% by volume, the content of CO2 is 3-5% by volume, the content of hydrogen is 55-65% by volume, and the content of nitrogen is 15-29% by volume.

[0061] Preferably, the reaction temperature is 200-300℃, the pressure is 3-8MPa, and the time is 5-15h.

[0062] The present invention will be described in detail below through embodiments.

[0063] Example 1

[0064] (1) Preparation of aluminum-based metal-organic framework: 3.75 g of aluminum nitrate nonahydrate and 2.10 g of trimesic acid were dissolved in 160 mL of water and reacted at 150 °C for 24 h. The mixture was washed with deionized water and dried at 100 °C to obtain solid particles of aluminum-based metal-organic framework Al-MOF-I.

[0065] Etching of aluminum-based metal-organic frameworks: 1.00 g of aluminum-based metal-organic framework Al-MOF-I was immersed in 20 mL of 1 M NaOH solution and etched at 25 °C for 12 h. After washing with deionized water, product 1 was obtained.

[0066] (2) At 25°C, copper-zinc solution and NaOH prepared by copper nitrate and zinc nitrate were added concurrently to the suspension of product 1 to carry out neutralization and precipitation reaction. The molar ratio of copper, zinc and aluminum (based on the aluminum content in aluminum-based metal-organic framework) was 10:10:1. After aging for 30 min, the precipitation endpoint was reached when the pH reached 5. The product was washed with deionized water to obtain product 2.

[0067] (3) The product 2 was dried at 80°C for 6 hours and then calcined in air at 300°C for 30 minutes to obtain catalyst 1.

[0068] Thermogravimetric analysis was performed on the aluminum-based metal-organic framework Al-MOF-I obtained in step (1), and the pyrolysis temperature of the aluminum-based metal-organic framework Al-MOF-I was found to be 500℃.

[0069] Example 2

[0070] (1) Preparation of aluminum-based metal-organic framework: 2.04 g of aluminum isopropoxide and 2.10 g of trimesic acid were dissolved in 160 mL of water and reacted at 150 °C for 24 h. The mixture was washed with deionized water and dried at 100 °C to obtain solid particulate aluminum-based metal-organic framework Al-MOF-II.

[0071] Etching of aluminum-based metal-organic frameworks: 1.00 g of aluminum-based metal-organic framework Al-MOF-II was immersed in 20 mL of 1 M NaOH solution and etched at 25 °C for 12 h. After washing with deionized water, product 1 was obtained.

[0072] (2) At 25°C, copper-zinc solution and NaOH prepared by copper nitrate and zinc nitrate were added concurrently to the suspension of product 1 to carry out neutralization and precipitation reaction. The molar ratio of copper, zinc and aluminum (based on the aluminum content in aluminum-based metal-organic framework) was 10:10:1. After aging for 30 min, the precipitation endpoint was reached when the pH reached 5. The product was washed with deionized water to obtain product 2.

[0073] (3) The product 2 was dried at 80°C for 6 hours and then calcined in air at 300°C for 30 minutes to obtain catalyst 2.

[0074] Thermogravimetric analysis was performed on the aluminum-based metal-organic framework Al-MOF-II obtained in step (1), and the pyrolysis temperature of the aluminum-based metal-organic framework Al-MOF-II was found to be 450℃.

[0075] Example 3

[0076] (1) Preparation of aluminum-based metal-organic framework: 3.75 g of aluminum nitrate nonahydrate and 6.30 g of trimesic acid were dissolved in 160 mL of water and reacted at 150 °C for 24 h. The mixture was washed with deionized water and dried at 100 °C to obtain solid particulate aluminum-based metal-organic framework Al-MOF-III.

[0077] Etching of aluminum-based metal-organic frameworks: 1.00 g of aluminum-based metal-organic framework Al-MOF-III was immersed in 20 mL of 1 M NaOH solution and etched at 25 °C for 12 h. After washing with deionized water, product 1 was obtained.

[0078] (2) At 25°C, copper-zinc solution and NaOH prepared by copper nitrate and zinc nitrate were added concurrently to the suspension of product 1 to carry out neutralization and precipitation reaction. The molar ratio of copper, zinc and aluminum (based on the aluminum content in aluminum-based metal-organic framework) was 10:10:1. After aging for 30 min, the precipitation endpoint was reached when the pH reached 5. The product was washed with deionized water to obtain product 2.

[0079] (3) The product 2 was dried at 80°C for 6 hours and then calcined in air at 300°C for 30 minutes to obtain catalyst 3.

[0080] Thermogravimetric analysis was performed on the aluminum-based metal-organic framework Al-MOF-III obtained in step (1), and the pyrolysis temperature of the aluminum-based metal-organic framework Al-MOF-III was found to be 400℃.

[0081] Example 4

[0082] (1) Preparation of aluminum-based metal-organic framework: 3.75 g of aluminum nitrate nonahydrate and 2.10 g of trimesic acid were dissolved in 160 mL of water and reacted at 150 °C for 24 h. The mixture was washed with deionized water and dried at 100 °C to obtain solid particulate aluminum-based metal-organic framework Al-MOF-I.

[0083] Etching of aluminum-based metal-organic frameworks: 1.00 g of aluminum-based metal-organic framework Al-MOF-I was immersed in 20 mL of 1 M NaHCO3 solution and etched at 25 °C for 12 h. After washing with deionized water, product 1 was obtained.

[0084] (2) At 25°C, copper-zinc solution and NaHCO3 prepared by copper nitrate and zinc nitrate were added concurrently to the suspension of product 1 to carry out neutralization and precipitation reaction. The molar ratio of copper, zinc and aluminum (based on the aluminum content in aluminum-based metal-organic framework) was 10:10:1. After aging for 30 min, the precipitation endpoint was reached when the pH reached 5. The product was washed with deionized water to obtain product 2.

[0085] (3) The product 2 was dried at 80°C for 6 hours and then calcined in air at 300°C for 30 minutes to obtain catalyst 4.

[0086] Example 5

[0087] (1) Preparation of aluminum-based metal-organic framework: 3.75 g of aluminum nitrate nonahydrate and 2.10 g of trimesic acid were dissolved in 160 mL of water and reacted at 150 °C for 24 h. The mixture was washed with deionized water and dried at 100 °C to obtain solid particulate aluminum-based metal-organic framework Al-MOF-I.

[0088] Etching of aluminum-based metal-organic frameworks: 1.00 g of aluminum-based metal-organic framework Al-MOF-I was immersed in 20 mL of 5 M NaOH solution and etched at 150 °C for 48 h. After washing with deionized water, product 1 was obtained.

[0089] (2) At 25°C, copper-zinc solution and NaOH prepared by copper nitrate and zinc nitrate were added concurrently to the suspension of product 1 to carry out neutralization and precipitation reaction. The molar ratio of copper, zinc and aluminum (based on the aluminum content in aluminum-based metal-organic framework) was 10:10:1. After aging for 30 min, the precipitation endpoint was reached when the pH reached 5. The product was washed with deionized water to obtain product 2.

[0090] (3) The product 2 was dried at 80°C for 6 hours and then calcined in air at 300°C for 30 minutes to obtain catalyst 5.

[0091] Example 6

[0092] (1) Preparation of aluminum-based metal-organic framework: 3.75 g of aluminum nitrate nonahydrate and 2.10 g of trimesic acid were dissolved in 160 mL of water and reacted at 150 °C for 24 h. The mixture was washed with deionized water and dried at 100 °C to obtain solid particulate aluminum-based metal-organic framework Al-MOF-I.

[0093] Etching of aluminum-based metal-organic frameworks: 1.00 g of aluminum-based metal-organic framework Al-MOF-I was immersed in 20 mL of 1 M NaOH solution and etched at 25 °C for 12 h. After washing with deionized water, product 1 was obtained.

[0094] (2) At 25°C, copper-zinc solution and NaOH prepared by copper nitrate and zinc nitrate were added concurrently to the suspension of product 1 to carry out neutralization and precipitation reaction. The molar ratio of copper, zinc and aluminum (based on the aluminum content in aluminum-based metal-organic framework) was 1:1:10. After aging for 30 min, the precipitation endpoint was reached when the pH reached 5. The product was washed with deionized water to obtain product 2.

[0095] (3) The product 2 was dried at 80°C for 6 hours and then calcined in air at 300°C for 30 minutes to obtain catalyst 6.

[0096] Example 7

[0097] (1) Preparation of aluminum-based metal-organic framework: 3.75 g of aluminum nitrate nonahydrate and 2.10 g of trimesic acid were dissolved in 160 mL of water and reacted at 150 °C for 24 h. The mixture was washed with deionized water and dried at 100 °C to obtain solid particulate aluminum-based metal-organic framework Al-MOF-I.

[0098] Etching of aluminum-based metal-organic frameworks: 1.00 g of aluminum-based metal-organic framework Al-MOF-I was immersed in 20 mL of 1 M NaOH solution and etched at 25 °C for 12 h. After washing with deionized water, product 1 was obtained.

[0099] (2) At 60°C, copper-zinc solution and NaOH prepared by copper nitrate and zinc nitrate were added concurrently to the suspension of product 1 to carry out neutralization and precipitation reaction. The molar ratio of copper, zinc and aluminum (based on the aluminum content in aluminum-based metal-organic framework) was 10:10:1. After aging for 30 min, the precipitation endpoint was reached when the pH reached 9. The product was washed with deionized water to obtain product 2.

[0100] (3) The product 2 was dried at 80°C for 6 hours and then calcined in air at 300°C for 30 minutes to obtain catalyst 7.

[0101] Example 8

[0102] (1) Preparation of aluminum-based metal-organic framework: 3.75 g of aluminum nitrate nonahydrate and 2.10 g of trimesic acid were dissolved in 160 mL of water and reacted at 150 °C for 24 h. The mixture was washed with deionized water and dried at 100 °C to obtain solid particulate aluminum-based metal-organic framework Al-MOF-I.

[0103] Etching of aluminum-based metal-organic frameworks: 1.00 g of aluminum-based metal-organic framework Al-MOF-I was immersed in 20 mL of 1 M NaOH solution and etched at 25 °C for 12 h. After washing with deionized water, product 1 was obtained.

[0104] (2) At 25°C, copper-zinc solution and NaOH prepared by copper nitrate and zinc nitrate were added concurrently to the suspension of product 1 to carry out neutralization and precipitation reaction. The molar ratio of copper, zinc and aluminum (based on the aluminum content in aluminum-based metal-organic framework) was 10:10:1. After aging for 30 min, the precipitation endpoint was reached when the pH reached 5. The product was washed with deionized water to obtain product 2.

[0105] (3) The product 2 was dried at 120°C for 12 hours and then calcined in air at 400°C for 30 minutes to obtain catalyst 8.

[0106] Comparative Example 1

[0107] (1) Dissolve 241.6 g of copper nitrate trihydrate, 297.5 g of zinc nitrate hexahydrate and 37.5 g of aluminum nitrate nonahydrate in 1 L of water. Add the mixed solution and 4300 mL of 1 M NaOH aqueous solution to a continuous neutralization reactor simultaneously using a metering pump. React at 25 °C and pH = 5.0 for 30 min. Wash with deionized water to obtain the intermediate product.

[0108] (2) The intermediate product was dried in an oven at 80°C for 6 hours, and then calcined in air at 300°C for 30 minutes to obtain catalyst 9.

[0109] X-ray diffraction tests were performed on the catalysts prepared in the examples and comparative examples, and the average particle size of the catalysts is shown in Table 1.

[0110] Table 1

[0111] Index Average particle diameter of copper oxide (nm) Average particle diameter of zinc oxide (nm) Example 1 8.1 5.2 Example 2 7.6 4.3 Example 3 7.5 5.0 Example 4 7.0 4.2 Example 5 7.4 4.9 Example 6 7.1 4.8 Example 7 7.2 5.0 Example 8 7.9 5.1 Comparative Example 1 11.2 8.8

[0112] As can be seen from Table 1, under the same synthesis conditions, compared with Comparative Example 1, the catalyst prepared in the Example has a smaller average particle size of active ions. Smaller grain size means that the copper-zinc component has higher dispersion and more accessible active sites in the structure, thereby improving the catalyst's activity and thermal stability. In addition, by adjusting the acidity, alkalinity, concentration, and etching time of the etching solution during the preparation process, this invention controls the density and distribution of the introduced active sites, enabling the prepared copper-zinc active particles to have adjustable size and dispersion to adapt to different reaction conditions in the methanol synthesis process. This expands the application field of the metal-organic framework supported copper-zinc catalyst prepared by this invention and saves costs.

[0113] Test case

[0114] The catalysts prepared in the examples and comparative examples were applied to the methanol synthesis process. Using syngas as feedstock, the catalyst activity was evaluated in a micro-fixed-bed continuous flow reactor. The syngas composition, based on the total volume, was: CO 13-15 vol%, CO2 3-5 vol%, H2 55-65 vol%, with the balance being N2. Before the reaction, the catalyst was placed in an H2 / N2 mixture containing 5% H2 at atmospheric pressure and at 20°C·h. -1 The temperature was rapidly increased to 250°C for reduction treatment, with a catalyst loading of 4 mL; subsequently, the syngas space velocity was 10000 h⁻¹. -1 The catalytic reaction for methanol synthesis was carried out under the conditions of a reaction pressure of 5.0 MPa and a reaction temperature of 250 °C, and the initial methanol yield was measured to evaluate the initial activity of the catalysts prepared in the examples and comparative examples. The test results are shown in Table 2.

[0115] The catalyst was heat-treated for 5 hours under a syngas atmosphere, atmospheric pressure, and 400°C. The activity test conditions were then repeated, and the methanol yield was measured to evaluate the catalyst's activity after heat treatment. The test results are shown in Table 2. (Initial methanol yield - methanol yield after heat treatment) / initial methanol yield * 100% is the activity degradation ratio after heat treatment. The calculation results of the activity degradation ratio of the catalysts prepared in the examples and comparative examples are shown in Table 2.

[0116] Table 2

[0117]

[0118] As shown in Table 2, under the same synthesis conditions, compared with Comparative Example 1, the initial yield of methanol was higher when using the catalyst prepared in the examples for methanol synthesis; the yield of methanol was still higher when using the heat-treated catalyst for methanol synthesis; and compared with Comparative Example 1, the activity decline rate of the catalyst prepared in the examples after heat treatment was smaller, indicating that the aluminum-based metal-organic framework support in the catalyst prepared in the examples has high thermal stability and can have a certain confinement effect on the active component particles of the catalyst, which can inhibit the migration and aggregation of catalytic active particles during heat treatment, thereby improving the activity and thermal stability of the catalyst.

[0119] Comparing Example 1 and Example 3, under the same conditions for catalyst preparation, the ratio of raw materials for preparing aluminum-based metal-organic framework supports was changed. It was found that Example 3 increased the feed ratio of the ligand trimesic acid in the raw materials, and the catalyst obtained had higher initial activity. However, after heat treatment, the activity of the catalyst was lower than that in Example 1, and the activity degradation rate after heat treatment was also greater than that of the latter. This indicates that the reduction of aluminum content in the catalyst support is not conducive to the improvement of catalyst thermal stability.

[0120] Comparing Example 1 and Example 4, under the same catalyst preparation conditions, the alkalinity of the solution used to etch the aluminum-based metal-organic framework was changed. It was found that the initial activity of the catalyst obtained by etching the support with a weaker alkaline NaHCO3 solution was higher than that of the catalyst obtained by etching the support with a stronger alkaline NaOH solution. However, after heat treatment, the activity of the former was lower than that of the latter, and the activity degradation rate of the former after heat treatment was greater than that of the latter. This indicates that after etching the support with a weaker alkaline solution, the confinement effect of the support on the catalytic active particles is smaller, and the thermal stability of the obtained catalyst is poor.

[0121] Comparing Example 1 and Example 5, under the same catalyst preparation conditions, the concentration of the solution used to etch the aluminum-based metal-organic framework and the etching time were changed. It was found that Example 5 used a high-concentration NaOH (5M) solution to etch the support at a relatively high temperature (150°C) for a prolonged period (48 hours), resulting in a catalyst with higher activity. However, after heat treatment, the catalyst activity was lower than that in Example 1, and the activity degradation rate after heat treatment was also greater. This indicates that using a high-concentration strong alkaline solution to etch the aluminum-based metal-organic framework for a long time at a high temperature will destroy the original regular and rigid pore structure of the metal-organic framework, reduce the confinement effect of the support on the catalytically active particles, and thus affect the thermal stability of the catalyst.

[0122] Comparing Example 1 and Example 6, under the same conditions for catalyst preparation, the ratio of the support to the copper-zinc liquid was changed. It was found that the molar ratio of copper, zinc and aluminum in the catalyst prepared in Example 6 was small, so the catalytic activity was low when applied to methanol synthesis. However, the activity decay rate of the heat-treated catalyst was small, indicating that when the support ratio is large, the confinement effect on the catalytic active particles is stronger, which is beneficial to improving the thermal stability of the catalyst.

[0123] Comparing Example 1 and Example 7, under the same conditions for catalyst preparation, the temperature of the neutralization reaction between copper-zinc solution and alkali was changed. It was found that the neutralization reaction temperature in Example 7 was higher, and the initial catalytic activity of the catalyst was higher. However, after heat treatment, the activity of the catalyst was lower than that in Example 1, and the proportion of activity degradation after heat treatment was also greater than that of the latter. This indicates that a higher temperature for the neutralization reaction is not conducive to improving the thermal stability of the catalyst.

[0124] Comparing Example 1 and Example 8, under the same conditions for catalyst preparation, the drying and calcination temperatures of the product after neutralization reaction were changed. It was found that the catalyst obtained by increasing the drying and calcination temperature in Example 8 had higher initial catalytic activity. However, after heat treatment, the catalyst activity was lower than that in Example 1, and the activity degradation rate after heat treatment was also greater than that of the latter. This indicates that excessively high drying and calcination temperatures cause active particles to migrate too quickly, which is not conducive to improving the thermal stability of the catalyst.

[0125] As can be seen from the above examples and comparative examples, the catalyst support of the present invention has superior water stability and thermal stability, and also has a confinement effect on catalytic active particles, which can slow down the migration and aggregation of catalytic active particles when heated, thereby improving the thermal stability of the catalyst. In addition, by using the preparation method of the present invention, abundant and uniformly distributed alkaline sites are introduced into the aluminum-based metal-organic framework structure of the catalyst support through etching. The presence of these alkaline sites allows the in-situ neutralization reaction of copper and zinc to occur within the pores. After calcination, smaller-sized and more dispersed copper-zinc active particles adapted to the pores of the metal-organic framework can be obtained, thereby improving the activity of the catalyst.

[0126] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A catalyst, characterized in that, The catalyst comprises: a modified aluminum-based metal-organic framework and active components copper oxide and zinc oxide supported on the modified aluminum-based metal-organic framework; The modified aluminum-based metal-organic framework is a product obtained by etching an aluminum-based metal-organic framework. The method for preparing the catalyst includes the following steps: (1) The aluminum-based metal-organic framework was etched with a solution to obtain product 1; (2) The product 1 is subjected to a precipitation reaction with copper-zinc solution to obtain product 2; (3) The product 2 is dried and calcined to obtain the catalyst; The etching temperature is 25-150℃, and the etching time is 12-48h; In step (1), the solution is an alkaline solution, wherein the alkaline solution is a NaOH, Na2CO3 or NaHCO3 solution.

2. The catalyst according to claim 1, wherein, The aluminum-based metal-organic framework is prepared by a hydrothermal reaction of aluminum salt and ligand.

3. The catalyst according to claim 2, wherein, The pyrolysis temperature of the aluminum-based metal-organic framework is 400-500℃.

4. The catalyst according to claim 2, wherein, The hydrothermal reaction is carried out at a temperature of 100-200℃ for 8-30 hours.

5. The catalyst according to claim 2, wherein, The aluminum salt is selected from at least one of aluminum nitrate, aluminum carbonate, aluminum sulfate, aluminum chloride, or aluminum isopropoxide.

6. The catalyst according to claim 2, wherein, The ligand is selected from at least one of pyromellitic acid, terephthalic acid, and pyridinecarboxylic acid.

7. The catalyst according to claim 2, wherein, The molar ratio of the aluminum salt to the ligand is 1-5.

8. The catalyst according to claim 7, wherein, The molar ratio of the aluminum salt to the ligand is 1-3.

9. The catalyst according to any one of claims 1-8, wherein, The copper oxide has an average particle size of 6-10 nm, and / or the zinc oxide has an average particle size of 3-6 nm.

10. The catalyst according to claim 9, wherein, The copper oxide has an average particle size of 7-8 nm, and / or the zinc oxide has an average particle size of 4-5 nm.

11. The catalyst according to any one of claims 1-8, wherein, In the active component, the molar ratio of copper to zinc is 1-10:

1.

12. The catalyst according to claim 11, wherein, In the active component, the molar ratio of copper to zinc is 1-5:

1.

13. The catalyst according to any one of claims 1-8, wherein, In the catalyst, the molar ratio of copper, zinc and aluminum in the aluminum-based metal-organic framework is 1:0.03-7.

5.

14. The catalyst according to claim 13, wherein, In the catalyst, the molar ratio of copper, zinc and aluminum in the aluminum-based metal-organic framework is 1:0.05-5.

15. A method for preparing the catalyst according to any one of claims 1-14, characterized in that, The method includes: (1) The aluminum-based metal-organic framework was etched with a solution to obtain product 1; (2) The product 1 is subjected to a precipitation reaction with copper-zinc solution to obtain product 2; (3) The product 2 is dried and calcined to obtain the catalyst; The etching temperature is 25-150℃, and the etching time is 12-48h; In step (1), the solution is an alkaline solution, wherein the alkaline solution is a NaOH, Na2CO3 or NaHCO3 solution.

16. The method according to claim 15, wherein, In step (1), the concentration of the alkaline solution is 1-10 mol / L.

17. The method according to claim 16, wherein, In step (1), the concentration of the alkaline solution is 1-5 mol / L.

18. The method according to claim 15, wherein, In step (1), the aluminum-based metal-organic framework is prepared by hydrothermal reaction of aluminum salt and ligand.

19. The method according to claim 18, wherein, In step (1), the pyrolysis temperature of the aluminum-based metal-organic framework is 400-500℃.

20. The method according to claim 18, wherein, The hydrothermal reaction is carried out at a temperature of 100-200℃ for 8-30 hours.

21. The method according to claim 18, wherein, The aluminum salt is selected from at least one of aluminum nitrate, aluminum carbonate, aluminum sulfate, aluminum chloride, or aluminum isopropoxide.

22. The method according to claim 18, wherein, The ligand is selected from at least one of pyromellitic acid, terephthalic acid, and pyridinecarboxylic acid.

23. The method according to claim 18, wherein, The molar ratio of the aluminum salt to the ligand is 1-5.

24. The method according to claim 23, wherein, The molar ratio of the aluminum salt to the ligand is 1-3.

25. The method according to any one of claims 15-24, wherein, In step (2), the copper-zinc liquid contains copper compounds and zinc compounds.

26. The method of claim 25, wherein, The copper compound is selected from at least one of copper nitrate, copper chloride, and copper sulfate, and the zinc compound is selected from at least one of zinc nitrate, zinc chloride, and zinc sulfate.

27. The method according to claim 26, wherein, The molar ratio of the copper compound to the zinc compound is 1-10:

1.

28. The method according to claim 27, wherein, The molar ratio of the copper compound to the zinc compound is 1-5:

1.

29. The method according to claim 15, wherein, In step (2), the temperature of the precipitation reaction is 20-80℃, the time is 10-80min, and the pH of the reaction system is 4-10.

30. The method according to claim 29, wherein, In step (2), the precipitation reaction is carried out at a temperature of 25-60℃ for 15-60 min, and the pH of the reaction system is 5-9.

31. The method according to any one of claims 15-24, wherein, In step (2), the molar ratio of copper, zinc and aluminum in the precipitation reaction is 1:0.03-7.

5.

32. The method according to claim 31, wherein, In the precipitation reaction, the molar ratio of copper, zinc and aluminum is 1:0.05-5.

33. The method according to claim 15, wherein, In step (3), the drying temperature is 60-150℃ and the time is 5-24h.

34. The method according to claim 33, wherein, The drying temperature is 80-120℃, and the time is 6-12 hours.

35. The method according to claim 15, wherein, In step (3), the roasting temperature is 200-400℃ and the time is 20-100min.

36. The method according to claim 35, wherein, The roasting temperature is 300-400℃ and the time is 30-60 minutes.

37. The use of the catalyst according to any one of claims 1-14 in methanol synthesis.

38. A method for synthesizing methanol, characterized in that, The method includes: (1) The catalyst is reduced to obtain the reduced catalyst; (2) In the presence of the reduced catalyst obtained in step (1), the syngas is reacted to obtain methanol; The catalyst is any one of the catalysts described in claims 1-14.

39. The method according to claim 38, wherein, In step (1), the reduction process is as follows: in a mixed atmosphere containing hydrogen and nitrogen, under normal pressure, at 5-20℃·h -1 The temperature is increased to 200-300℃ at a rate and maintained for 5-10 hours.

40. The method according to claim 39, wherein, In the mixed atmosphere, the volume ratio of hydrogen to nitrogen is 5-10:90-95.

41. The method according to claim 38, wherein, In step (2), based on the total volume of the syngas, the syngas contains 13-15% CO by volume, 3-5% CO2 by volume, 55-65% hydrogen by volume, and 15-29% nitrogen by volume. And / or, the reaction is carried out at a temperature of 200-300°C, a pressure of 3-8 MPa, and a time of 5-15 h.

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