A copper-zinc-zirconium ternary catalyst for synthesizing methanol and a preparation method and application thereof

Abstract

The application provides a copper-zinc-zirconium ternary catalyst for synthesizing methanol and a preparation method and application thereof, adopts a double-nozzle flame spraying pyrolysis method, and comprises the following steps: (1) mixing precursor compound I with solvent I to obtain solution I, and pumping the solution I into nozzle I; (2) mixing precursor compound II and precursor compound III with solvent II to obtain solution II, and pumping the solution II into nozzle II; (3) the nozzle I and the nozzle II simultaneously perform the same operation: igniting combustion gas to form a flame, dispersing gas disperses the solution in the nozzle center injection needle opening into small droplets, and the solution is introduced into the flame for combustion; the oxides generated by the two nozzles are collected in a collection area to obtain the copper-zinc-zirconium ternary catalyst; the precursor compound I is selected from one of a copper precursor compound, a zinc precursor compound or a zirconium precursor compound, and the rest is the selection of the precursor compound II and the precursor compound III.

Description

TECHNICAL FIELD

[0001] The application relates to a copper-zinc-zirconium ternary catalyst for synthesizing methanol and a preparation method and application thereof, and belongs to the field of catalyst preparation. BACKGROUND

[0002] Carbon dioxide catalytic hydrogenation to synthesize methanol and carbon monoxide is a reasonable technical route for utilizing carbon dioxide. Methanol is an important chemical raw material, and the annual demand in the world is 50 million tons. The production of methanol from carbon dioxide not only plays a role in carbon sequestration, but also can be directly used as fuel to realize carbon cycle. It can also be converted into formaldehyde, dimethyl ether, olefins and other high-value chemicals. Using carbon dioxide as a carbon source and hydrogen produced by new energy, not only reduces the dependence on fossil fuels, but also makes the produced methanol one of the important industrial raw materials, so that the route of carbon dioxide hydrogenation to methanol has important research significance.

[0003] Studies have shown that among the many carbon dioxide hydrogenation to methanol catalysts, Cu, Zn and Zr three components all have important roles in the reaction process. For example, the particle size of copper directly affects the catalytic activity (Chinese patent 201410141351.4; Chinese patent 201510695863.X); the zinc component can promote the dispersion of copper particles and form a strong interaction with copper (Chinese patent 201910048079.8); tetragonal zirconia can stabilize the monovalent active copper species (Chinese patent 202110010231.0). At present, there are many studies on Cu-Zn-Zr ternary component catalysts (Chinese patent 201010590420.1; Chinese patent 202110641510.7; Chinese patent 202111545432.7), but they are all directly mixed with the three components to promote the interaction between the three components (Chinese patent 202011043607.X), and do not pay attention to the influence of the action of certain two components on the overall catalyst. Although the overall performance of the catalyst is improved, it is still not ideal. How to highlight the interaction between different components and unique active centers is an important technology for catalyst design, preparation and optimization. However, due to the limitations of the preparation methods themselves, such as traditional impregnation method, precipitation method, hydrothermal synthesis method, sol-gel method and citric acid complexation method, it is impossible to guarantee flexible regulation and control of the interaction between different components. In addition, the operation is complex, the preparation period is long, the equipment investment and production operation cost are high, and the multi-step high-temperature treatment program is also easy to cause particle agglomeration. The three components together may affect each other between the components, and cannot achieve the optimal catalytic effect. SUMMARY

[0004] To further regulate the interactions between different components in a ternary catalyst, the single-nozzle flame jet pyrolysis method can be developed into a dual-nozzle flame jet pyrolysis method. Different components are distributed into two nozzles and ejected simultaneously, preparing a ternary Cu-Zn-Zr catalyst in one step. Flame jet pyrolysis is a novel method for preparing multifunctional nanomaterials developed in recent years. The entire process is simple and rapid, involving only two steps: precursor mixing and flame combustion. It has a short preparation cycle, is easy to scale up, and eliminates subsequent heat treatment and washing / separation processes, saving investment and operating costs. Using the improved dual-nozzle method to prepare this ternary Cu-Zn-Zr catalyst not only ensures that the interaction between the two components is not affected by the third component but also avoids the reduction in activity caused by factors such as metal particle size and specific surface area due to multi-step preparation methods, thereby further optimizing catalyst performance.

[0005] According to one aspect of this application, a method for preparing a copper-zinc-zirconium ternary catalyst for methanol synthesis is provided, which employs a dual-nozzle flame jet pyrolysis method;

[0006] Includes the following steps:

[0007] (1) Mix precursor compound I with solvent I to obtain solution I, and pump solution I into nozzle I;

[0008] (2) Precursor compound II and precursor compound III are mixed with solvent II to obtain solution II, and solution II is pumped into nozzle II;

[0009] (4) The nozzle I and the nozzle II perform the same operation simultaneously: ignite the combustion gas to form a flame, and disperse the solution at the injection needle in the center of the nozzle into small droplets and introduce them into the flame for combustion;

[0010] The oxides produced by the two nozzles converge in the collection area to obtain a copper-zinc-zirconium ternary catalyst.

[0011] The precursor compound I is selected from one of the precursor compounds of copper, zinc, or zirconium, and the remainder is a selection of the precursor compounds II and III.

[0012] The copper precursor compound is selected from at least one of copper acetylacetonate, copper nitrate, copper acetate, or copper diethylhexanoate.

[0013] The zinc precursor compound is selected from at least one of zinc acetylacetonate, zinc acetate, or zinc nitrate.

[0014] The zirconium precursor compound is selected from at least one of zirconium n-butoxide, zirconium acetate, zirconium acetylacetone, zirconium nitrate, or zirconium citrate.

[0015] The solvent I is selected from at least one of alcohol, liquid hydrocarbon or organic acid;

[0016] The solvent II is selected from at least one of alcohol, liquid hydrocarbon or organic acid;

[0017] The alcohol is selected from at least one of methanol, ethanol or sec-butanol;

[0018] The liquid hydrocarbon is selected from at least one of octane, cyclohexane or xylene;

[0019] The organic acid is selected from at least one of oxalic acid, citric acid, diethylhexanoic acid or benzoic acid.

[0020] The molar concentration of copper ions in the solution I or solution II is 0.1-2 mol / L;

[0021] The concentration of zinc ions is 0.01-2 mol / L;

[0022] The concentration of zirconium ions is 0.01-2 mol / L;

[0023] Optionally, the concentration of zinc ions in the solution I or solution II is 0.1-0.5 mol / L;

[0024] The concentration of zirconium ions is 0.1-0.5 mol / L;

[0025] Optionally, the concentration ratio of zinc ions to zirconium ions in the solution I or solution II is 0.05-10;

[0026] The molar amount of copper ions is calculated based on the molar amount of copper element in the precursor compound of copper;

[0027] The molar amount of zinc ions is calculated based on the molar amount of zinc element in the precursor compound of zinc;

[0028] The molar amount of zirconium ions is calculated based on the molar amount of zirconium element in the precursor compound of zirconium.

[0029] The speed of pumping the solution I into the nozzle I is 1-10 mL / min;

[0030] The speed of pumping the solution II into the nozzle II is 1-10 mL / min;

[0031] The combustion gas comprises methane and oxygen;

[0032] The flow rate of methane in the combustion gas is 0.1-5 L / min;

[0033] The flow rate of oxygen in the combustion gas is 0.1-5 L / min;

[0034] The dispersing gas is an oxygen-containing gas;

[0035] The flow rate of the oxygen-containing gas is 1-10 L / min.

[0036] The convergence area is determined by the center distance of the nozzles I and II and the angle formed by the flames:

[0037] The center distance of the nozzles I and II is 1-30 cm;

[0038] Optionally, the center distance of the nozzles I and II is 5-15 cm;

[0039] The angle formed by the flames of the nozzles I and II is 10-120 degrees;

[0040] Optionally, the angle formed by the flames of the nozzles I and II is 30-90 degrees.

[0041] Both of the nozzles have the same structure, which includes an injection needle, combustion gas and dispersing gas;

[0042] According to another aspect of the present application, a copper-zinc-zirconium ternary catalyst is provided, which is obtained by the above-mentioned preparation method.

[0043] In the copper-zinc-zirconium ternary catalyst, the mass content of copper oxide is 5-50%;

[0044] Optionally, in the copper-zinc-zirconium ternary catalyst, the mass content of copper oxide is 10-30%.

[0045] In the copper-zinc-zirconium ternary catalyst, the mass content of zinc oxide is 5-50%;

[0046] Optionally, in the copper-zinc-zirconium ternary catalyst, the mass content of zinc oxide is 10-30%.

[0047] The rest is zirconium oxide.

[0048] According to another aspect of the present application, a method for thermocatalytic hydrogenation of carbon dioxide is provided, in which a mixed gas atmosphere containing hydrogen and carbon dioxide is contacted with a catalyst to occur hydrogenation reaction, thereby obtaining methanol.

[0049] The catalyst is selected from the above-mentioned copper-zinc-zirconium ternary catalyst.

[0050] The catalyst is reduced before use.

[0051] The temperature of the reduction is 200-500℃.

[0052] Optionally, the temperature of the reduction is 240-400℃.

[0053] The time for the reduction is 0.5-4h

[0054] The temperature for the hydrogenation reaction is 150-300℃;

[0055] Optionally, the temperature for the hydrogenation reaction is 180-250℃;

[0056] The pressure for the hydrogenation reaction is 0.1-10.0MPa;

[0057] Optionally, the pressure for the hydrogenation reaction is 1.0-5.0MPa;

[0058] The molar ratio of the hydrogen to the carbon dioxide is 1-10;

[0059] Optionally, the molar ratio of the hydrogen to the carbon dioxide is 2-5;

[0060] Optionally, the gas space velocity of the mixed atmosphere is 2040-24000mL / (h·g cat ).

[0061] The advantages of the present application are:

[0062] (1) The three components in the ternary catalyst can be divided into two groups, two components are divided in the same group, and strong interaction is generated between the two components without the interference of the third component;

[0063] (2) The third component can be loaded in one step, avoiding the influence of particle sintering caused by secondary combustion in the step-by-step process;

[0064] (3) Both groups are subjected to high-temperature quenching process by flame spraying method, and both have the characteristics of active lattice oxygen, high dispersion and large specific surface area;

[0065] (4) The two-step preparation is simplified to one step, the preparation process is simple and fast, no subsequent high-temperature calcination treatment is needed, and energy saving and emission reduction are achieved. BRIEF DESCRIPTION OF DRAWINGS

[0066] Figure 1 The X-ray diffraction patterns of the catalysts of Examples 1-3 and Comparative Example 1.

[0067] Figure 2 The scanning transmission electron image and the copper, zinc and zirconium element distribution scanning map of Example 1.

[0068] Figure 3 The scanning transmission electron image and the copper, zinc and zirconium element distribution scanning map of Example 2.

[0069] Figure 4 The scanning transmission electron image and the copper, zinc and zirconium element distribution scanning map of Example 3. DETAILED DESCRIPTION

[0070] The application will be described in detail below with reference to examples, but the application is not limited to these examples.

[0071] Example 1

[0072] Cu(OAc)2.2H2O (2.64 g) was dissolved in 20 ml of methanol and 80 ml of 2- ethylhexanoic acid to give a 100 ml solution, which was labeled as solution 1. Zn(OAc)2.2H2O (1.43 g) and Zr(OEt)4 (45.5 g, 6 wt% Zr) were dissolved in 25 ml of methanol and 25 ml of 2-ethylhexanoic acid to give a 100 ml solution, which was labeled as solution 2, with a Zr molar concentration of 0.3 M. Both solutions were placed in an ultrasonic stirrer and stirred at room temperature until a clear solution was obtained. Solution 1 and solution 2 were pumped into two nozzles at a rate of 5 ml / min each using two syringes. The flame combustion gas was a mixture of methane (0.75 L / min) and oxygen (1.6 L / min), and the dispersion gas was oxygen (5 L / min, pressure drop 3 bar). Both nozzles were identical. The center distance of the two nozzles was adjusted to 10 cm, and the two flame angles were 60 degrees. The nanoparticles produced by the two nozzles were collected above the flame, and the resulting catalyst particles were collected on the top of a collection bucket using a glass fiber filter paper with the help of a vacuum pump. This process separated the Cu component from the Zn-Zr component, and the resulting catalyst was labeled as Cat-1, with a Cu:Zn:Zr molar ratio of 20:8:72.

[0073] Example 2

[0074] A solution of 2.64 g of copper acetate monohydrate and 45.5 g of zirconium 2- ethylhexanoate (6% Zr) in 25 ml of methanol and 25 ml of 2-ethylhexanoic acid was prepared to give a 100 ml solution, noted as solution 1, with a molar concentration of Zr of 0.3 M. A solution of 1.43 g of zinc acetate dihydrate in 20 ml of methanol and 80 ml of 2-ethylhexanoic acid was prepared to give a 100 ml solution, noted as solution 2. Both solutions were placed in an ultrasonic stirrer and stirred at room temperature until a clear solution was obtained. Both solutions were pumped into the nozzles at a rate of 5 ml / min using two syringes. The flame combustion gas was a mixture of methane (0.75 L / min) and oxygen (1.6 L / min) and the dispersion gas was oxygen (5 L / min, pressure drop 3 bar). The two nozzles were identical. The center-to-center distance of the two nozzles was adjusted to 10 cm and the two flame angles were set to 60 degrees. The nanoparticles produced by the two nozzles were collected above the flame and the resulting catalyst particles were collected on the top of a collection bucket using a glass fiber filter paper with the help of a vacuum pump. This process isolated the Zn component from the Cu-Zr component and the resulting catalyst was noted as Cat-2 with a molar ratio of Cu, Zn and Zr of 20:8:72.

[0075] Example 3

[0076] A solution of 2.64 g of copper acetate monohydrate and 1.43 g of zinc acetate dihydrate in 20 ml of methanol and 80 ml of 2-ethylhexanoic acid was prepared to give a 100 ml solution, noted as solution 1. A solution of 45.5 g of zirconium 2- ethylhexanoate (6% Zr) in 25 ml of methanol and 25 ml of 2-ethylhexanoic acid was prepared to give a 100 ml solution, noted as solution 2, with a molar concentration of Zr of 0.3 M. Both solutions were placed in an ultrasonic stirrer and stirred at room temperature until a clear solution was obtained. Both solutions were pumped into the nozzles at a rate of 5 ml / min using two syringes. The flame combustion gas was a mixture of methane (0.75 L / min) and oxygen (1.6 L / min) and the dispersion gas was oxygen (5 L / min, pressure drop 3 bar). The two nozzles were identical. The center-to-center distance of the two nozzles was adjusted to 10 cm and the two flame angles were set to 60 degrees. The nanoparticles produced by the two nozzles were collected above the flame and the resulting catalyst particles were collected on the top of a collection bucket using a glass fiber filter paper with the help of a vacuum pump. This process isolated the Zr component from the Cu-Zn component and the resulting catalyst was noted as Cat-3 with a molar ratio of Cu, Zn and Zr of 20:8:72.

[0077] Example 4

[0078] A solution of 2.64 g of copper acetate monohydrate in 20 ml of methanol and 80 ml of 2-ethylhexanoic acid was prepared to give a 100 ml solution, noted as solution 1. A solution of 5.72 g of zinc acetate dihydrate and 30.3 g of zirconium 2-ethylhexanoate (6% Zr) in 35 ml of methanol and 35 ml of 2-ethylhexanoic acid was prepared to give a 100 ml solution, noted as solution 2, with a molar concentration of Zr of 0.3 M. Both solutions were placed in an ultrasonic stirrer and stirred at room temperature until a clear solution was obtained. Both solutions were pumped into the nozzles at a rate of 5 ml / min using two syringes. The flame combustion gas was a mixture of methane (0.75 L / min) and oxygen (1.6 L / min) and the dispersion gas was oxygen (5 L / min, pressure drop 3 bar). The two nozzles were identical. The center distance of the two nozzles was adjusted to 10 cm and the two flame angles were 60 degrees. The nanoparticles produced by the two nozzles were collected above the flame and the resulting catalyst particles were collected on the top of a collection bucket using a glass fiber filter paper with the help of a vacuum pump. This process isolated the Cu component from the Zn-Zr component and adjusted the Zn to Zr component ratio. The catalyst prepared was noted as Cat-5 with a Cu, Zn and Zr molar ratio of 20:32:48.

[0079] Example 5

[0080] A solution of 2.64 g of copper acetate monohydrate in 20 ml of methanol and 80 ml of 2-ethylhexanoic acid was prepared to give a 100 ml solution, noted as solution 1. A solution of 5.72 g of zinc acetate dihydrate and 30.3 g of zirconium 2-ethylhexanoate (6% Zr) in 35 ml of methanol and 35 ml of 2-ethylhexanoic acid was prepared to give a 100 ml solution, noted as solution 2, with a molar concentration of Zr of 0.3 M. Both solutions were placed in an ultrasonic stirrer and stirred at room temperature until a clear solution was obtained. Both solutions were pumped into the nozzles at a rate of 5 ml / min using two syringes. The flame combustion gas was a mixture of methane (0.75 L / min) and oxygen (1.6 L / min) and the dispersion gas was oxygen (5 L / min, pressure drop 3 bar). The two nozzles were identical. The center distance of the two nozzles was adjusted to 10 cm and the two flame angles were 60 degrees. The nanoparticles produced by the two nozzles were collected above the flame and the resulting catalyst particles were collected on the top of a collection bucket using a glass fiber filter paper with the help of a vacuum pump. This process isolated the Cu component from the Zn-Zr component and adjusted the Zn to Zr component ratio. The catalyst prepared was noted as Cat-5 with a Cu, Zn and Zr molar ratio of 20:32:48.

[0081] Example 6

[0082] Two solutions were prepared as in Example 1. The center-to-center distance of the two nozzles was adjusted to 5 cm, and the two flame horn angles were adjusted to 60 degrees. The nanoparticles produced by the two nozzles were collected above the flame, and the resulting catalyst particles were collected on the top of a collection bucket using a glass fiber filter paper with the help of a vacuum pump. This process adjusted the mixing region of the Cu component and the Zn-Zr component to be closer to the direction of the flame, and the resulting catalyst was labeled Cat-6.

[0083] Example 7

[0084] Two solutions were prepared as in Example 1. The center-to-center distance of the two nozzles was adjusted to 15 cm, and the two flame horn angles were adjusted to 60 degrees. The nanoparticles produced by the two nozzles were collected above the flame, and the resulting catalyst particles were collected on the top of a collection bucket using a glass fiber filter paper with the help of a vacuum pump. This process adjusted the mixing region of the Cu component and the Zn-Zr component to be farther from the direction of the flame, and the resulting catalyst was labeled Cat-7.

[0085] Example 8

[0086] Two solutions were prepared as in Example 1. The center-to-center distance of the two nozzles was adjusted to 10 cm, and the two flame horn angles were adjusted to 45 degrees. The nanoparticles produced by the two nozzles were collected above the flame, and the resulting catalyst particles were collected on the top of a collection bucket using a glass fiber filter paper with the help of a vacuum pump. This process adjusted the mixing region of the Cu component and the Zn-Zr component to be farther from the direction of the flame, and the resulting catalyst was labeled Cat-8.

[0087] Example 9

[0088] Two solutions were prepared as in Example 1. The center-to-center distance of the two nozzles was adjusted to 10 cm, and the two flame horn angles were adjusted to 90 degrees. The nanoparticles produced by the two nozzles were collected above the flame, and the resulting catalyst particles were collected on the top of a collection bucket using a glass fiber filter paper with the help of a vacuum pump. This process adjusted the mixing region of the Cu component and the Zn-Zr component to be closer to the direction of the flame, and the resulting catalyst was labeled Cat-9.

[0089] Comparative Example 1

[0090] Cu(OAc)2.2H2O (2.64 g), Zn(OAc)2.2H2O (1.43 g) and Zr(O2EtC)4 (45.5 g, 6% Zr) were dissolved in a mixture of 25 ml methanol and 25 ml 2-ethylhexanoic acid to give 100 ml solution, which was then placed in an ultrasonic stirrer and stirred at room temperature until a clear solution was obtained. The prepared solution was pumped into the nozzle at a rate of 5 ml / min using a syringe. The flame combustion gas was a mixture of methane (0.75 L / min) and oxygen (1.6 L / min), and the dispersion gas was oxygen (5 L / min, pressure drop 3 bar). The nozzle was located directly below the centre of the collection bucket, with the flame pointing vertically upwards, and the resulting catalyst particles were collected on a glass fibre filter paper at the top of the collection bucket with the aid of a vacuum pump. The Cu-Zn-Zr three-component mixture was prepared in this way, and the catalyst produced was designated Cat-10.

[0091] The results of the examples show that:

[0092] Table 1. Reaction performance of carbon dioxide hydrogenation to methanol on catalysts of Examples 1, 2, 3 and Comparative Example 1.

[0093] Table 2. Reaction performance of carbon dioxide hydrogenation to methanol on catalysts of Examples 1, 4 and 5.

[0094] Table 3. Reaction performance of carbon dioxide hydrogenation to methanol on catalysts of Examples 1, 6, 7, 8 and 9.

[0095] Table 4. Effect of space velocity on the reaction performance of carbon dioxide hydrogenation to methanol on the catalyst of Example 1.

[0096] Table 5. Component content and copper particle size on catalysts of Examples 1, 2 and 3.

[0097] Figure 1 X-ray diffraction patterns of catalysts of Examples 1 to 3 and Comparative Example 1.

[0098] Figure 2 Scanning transmission electron image and copper, zinc and zirconium element distribution scanning diagram of Example 1.

[0099] Figure 3 Scanning transmission electron image and copper, zinc and zirconium element distribution scanning diagram of Example 2.

[0100] Figure 4 Scanning transmission electron image and copper, zinc and zirconium element distribution scanning diagram of Example 3.

[0101] 1. Comparison of catalysts prepared using double nozzle and single nozzle (Table 1): reduction using pure H2 (25 ml / min), reduction temperature 300°C, reduction time 1 h. Reaction conditions: molar ratio H2 / CO2 = 3, temperature 220-260°C, space velocity 6000 ml / (h.gcat ), pressure 3.0 MPa. The effect of reaction temperature on the catalyst performance was investigated, and the catalysts of Example 1-3 (Cat-1, Cat-2, Cat-3) and Comparative Example 1 (Cat-10) were tested, and the test results are shown in Table 1. The component contents of the four catalysts are the same, the CO2 conversion rates are relatively close, but the methanol selectivity from large to small is Cat-1 > Cat-3 > Cat-2 > Cat-10, indicating that the preparation method of separating different components by using double nozzles is beneficial to improve the selectivity of methanol, and the performance of separating Cu component and Zn-Zr component is the best.

[0102] 2, Effect of zinc-zirconium ratio on catalyst performance (Table 2): reduced by pure H2 (25 ml / min), reduction temperature 300°C, reduction time 1h. Reaction conditions: molar ratio H2 / CO2 = 3, temperature 220-260°C, space velocity 6000 ml / (h.g cat ), pressure 3.0 MPa. The effect of reaction temperature on the catalyst performance was investigated, and the catalysts of Example 1 and Example 4-5 were tested, and the test results are shown in Table 2. The preparation methods of the three catalysts are the same, but the ratios of Zn and Zr components are different, and the CO2 conversion rate and the methanol selectivity increase first and then decrease with the increase of Zn content, indicating that there is a strong interaction between the Zn-Zr two components and an active phase is generated, and the number of active phases increases with the increase of Zn content, but excessive Zn may cause the structure of the active phase to be destroyed.

[0103] 3, Effect of distance and angle between double nozzles on catalyst performance (Table 3): reduced by pure H2 (25 ml / min), reduction temperature 300°C, reduction time 1h. Reaction conditions: molar ratio H2 / CO2 = 3, temperature 220-260°C, space velocity 6000 ml / (h.g cat ), pressure 3.0 MPa. The effect of reaction temperature on the catalyst performance was investigated, and the catalysts of Example 1 and Example 6-9 were tested, and the test results are shown in Table 3. The preparation methods of the five catalysts are similar, only the distance and angle between the two nozzles are adjusted, the closer the distance between the two nozzles or the larger the angle, the stronger the interaction between the components in the two nozzles, and the closer to the effect of single nozzle. On the contrary, the farther the distance between the two nozzles or the smaller the angle, the weaker the interaction between the components in the two nozzles, and the larger the oxide particles formed by each component when mixed. However, too far distance or too small angle may also cause the components of the two nozzles to not mix well.

[0104] 4, Effect of reaction space velocity on catalyst performance (Table 4): reduced by pure H2 (25 ml / min), reduction temperature 300°C, reduction time 1h. Reaction conditions: molar ratio H2 / CO2 = 3, temperature 240°C, space velocity 6000-24000 ml / (h.gcat ), the pressure was 3.0 MPa, and the effect of different space velocities on the reaction performance of Cat-1 at the same temperature was investigated. The test results are shown in Table 4. With the increase of space velocity, the conversion rate decreased, but the selectivity increased. A high space velocity would bring a higher yield.

[0105] 5. The dispersion of Cu particles was determined by N2O oxidation method, the content of each component was determined by inductively coupled plasma emission spectrometer (ICP), and the specific surface area of the catalyst was determined by physical adsorption method. The results are shown in Table 5. The results show that the catalyst prepared by the single-nozzle flame spraying method (Cat-10) has smaller copper particles, higher copper dispersion, and larger exposed surface area than the catalyst prepared by the double-nozzle flame spraying method (Cat-1, Cat-2, and Cat-3). However, the catalytic performance of Cat-10 is the lowest. This indicates that the CO2 conversion rate and methanol selectivity are not completely related to the size of copper particles. In addition, the components and contents of different catalysts are basically the same, which excludes the influence of component content.

[0106] 6. The crystal phase structures of the catalysts of Examples 1-3 and Comparative Example 1 were investigated by X-ray diffractometer (XRD), as shown in Figure 1 . It is found that the crystal phase structures of the three components are not affected by the preparation method and preparation conditions. Because the zinc oxide content in the catalyst is low, it is difficult to distinguish in the XRD pattern.

[0107] 7. The morphologies of the catalysts of Examples 1-3 were investigated by high-angle annular dark-field image-scanning transmission electron image (HADDF) and copper, zinc, and zirconium element scanning distribution maps, as shown in Figures 2-4 . It is found that the morphologies of the three catalysts are not affected by the preparation method and preparation conditions.

[0108] It can be seen that the catalytic performance of the copper-zinc-zirconium ternary catalyst in the reaction of carbon dioxide hydrogenation to methanol is more affected by other factors, and the decisive factor needs to be prepared by the double-nozzle flame spraying method, and the effect is related to the distribution of different components in the double nozzle. Among them, the effect of separating the zinc-zirconium component from copper is the best. The preparation method using double nozzle can simultaneously strengthen the interaction of some components (zinc-zirconium) and weaken the interaction of some components (copper-zinc or copper-zirconium), leading to the change of the catalytic reaction path and causing the difference in performance. The advantage of this method is that the specific surface area of the prepared catalyst is similar, the size of copper particles is similar, and the component content is stable, and is not affected by the preparation method and preparation conditions. Under the condition of ensuring that other influencing factors are basically unchanged, the interaction between different components is adjusted and investigated alone, the catalytic mechanism is deeply understood, and guidance is provided for the optimization design of the catalyst.

[0109] Table 1 Reaction performance of carbon dioxide hydrogenation to methanol on the catalysts of Examples 1, 2, 3, and Comparative Example 1

[0110]

[0111]

[0112] Table 2 Reaction performance of carbon dioxide hydrogenation to methanol over catalysts of Examples 1, 4, 5

[0113]

[0114] Table 3 Reaction performance of carbon dioxide hydrogenation to methanol over catalysts of Examples 1, 6, 7, 8, 9

[0115]

[0116]

[0117] Table 4 Effect of space velocity on reaction performance of carbon dioxide hydrogenation to methanol over catalyst of Example 1

[0118]

[0119] Table 5 Content of each component and particle size of copper over catalysts of Examples 1, 2, 3

[0120]

[0121] The above is only several embodiments of the present application, and does not limit the present application in any form. Although the present application is disclosed with preferred embodiments, it is not intended to limit the present application. Any skilled person in the art can make some changes or modifications to the above disclosed technical contents without departing from the scope of the present application, and the equivalent embodiments are equivalent to the embodiments, and all belong to the scope of the technical solution.

Claims

1. A method for preparing a copper-zinc-zirconium ternary catalyst for synthesizing methanol, characterized in that, a double-nozzle flame spray pyrolysis method is adopted; and the method comprises the following steps: (1) mixing a precursor compound I with a solvent I to obtain a solution I, and pumping the solution I into a nozzle I; (2) mixing a precursor compound II and a precursor compound III with a solvent II to obtain a solution II, and pumping the solution II into a nozzle II; (3) the nozzle I and the nozzle II are simultaneously operated in the same way: igniting combustion gas to form a flame, dispersing gas disperses the solution in the nozzle center injection needle mouth into small droplets, and introducing the small droplets into the flame for combustion; and oxides generated by the two nozzles are collected in a collection area to obtain a copper-zinc-zirconium ternary catalyst; the precursor compound I, the precursor compound II or the precursor compound III is selected from one of a copper precursor compound, a zinc precursor compound or a zirconium precursor compound, wherein the selection of any two of the precursor compound I, the precursor compound II or the precursor compound III is not repeated. 2.The method according to claim 1, characterized in that, the copper precursor compound is selected from at least one of copper acetylacetonate, copper nitrate, copper acetate or copper diethylhexanoate; the zinc precursor compound is selected from at least one of zinc acetylacetonate, zinc acetate or zinc nitrate; the zirconium precursor compound is selected from at least one of zirconium n-butylate, zirconium acetate, zirconium acetylacetonate, zirconium nitrate or zirconium citrate; the solvent I is selected from at least one of an alcohol, a liquid hydrocarbon or an organic acid; and the solvent II is selected from at least one of an alcohol, a liquid hydrocarbon or an organic acid. 3.The method according to claim 2, characterized in that, the alcohol is selected from at least one of methanol, ethanol or sec-butanol. 4.The method according to claim 2, characterized in that, the liquid hydrocarbon is selected from at least one of octane, cyclohexane or xylene. 5.The method according to claim 2, characterized in that, the organic acid is selected from at least one of oxalic acid, citric acid, diethylhexanoic acid or benzoic acid. 6.The method according to claim 1, characterized in that, in the solution I or the solution II, the molar concentration of copper ions is 0.1-2 mol / L; the concentration of zinc ions is 0.01-2 mol / L; and the concentration of zirconium ions is 0.01-2 mol / L; the concentration ratio of the zinc ions and the zirconium ions in the solution I or the solution II is 0.05-10; the molar amount of the copper ions is based on the molar amount of copper element in the copper precursor compound; the molar amount of the zinc ions is based on the molar amount of zinc element in the zinc precursor compound; and the molar amount of the zirconium ions is based on the molar amount of zirconium element in the zirconium precursor compound. 7.The method according to claim 6, characterized in that, the concentration of the zinc ions is 0.1-0.5 mol / L. 8.The method according to claim 6, characterized in that, the concentration of the zirconium ions is 0.1-0.5 mol / L. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 9. The preparation method according to claim 1, wherein the speed of pumping the solution I into the nozzle I is 1-10 mL / min; the speed of pumping the solution II into the nozzle II is 1-10 mL / min; the combustion gas comprises methane and oxygen; the flow rate of the methane in the combustion gas is 0.1-5 L / min; the flow rate of the oxygen in the combustion gas is 0.1-5 L / min; the dispersion gas is an oxygen-containing gas; and the flow rate of the oxygen-containing gas is 1-10 L / min.

10. The preparation method according to claim 1, wherein the convergence area is determined by the center distance between the nozzles I and II and the angle formed by the flames; the center distance between the nozzles I and II is 1-30 cm; and the angle formed by the flames of the nozzles I and II is 10-120 degrees.

11. The preparation method according to claim 10, wherein the center distance between the nozzles I and II is 5-15 cm.

12. The preparation method according to claim 10, wherein the angle formed by the flames of the nozzles I and II is 30-90 degrees.

13. A copper-zinc-zirconium ternary catalyst, wherein the catalyst is obtained by the preparation method according to any one of claims 1-12.

14. The copper-zinc-zirconium ternary catalyst according to claim 13, wherein the mass content of copper oxide in the catalyst is 5-50%; the mass content of zinc oxide is 5-50%; and the rest is zirconium oxide.

15. The copper-zinc-zirconium ternary catalyst according to claim 14, wherein the mass content of copper oxide is 10-30%.

16. The copper-zinc-zirconium ternary catalyst according to claim 14, wherein the mass content of zinc oxide is 10-30%.

17. A method for the thermal catalytic hydrogenation of carbon dioxide, wherein a mixed gas atmosphere containing hydrogen and carbon dioxide is contacted with a catalyst to produce methanol by hydrogenation reaction; and the catalyst is selected from the copper-zinc-zirconium ternary catalysts according to claims 13-16.

18. The method according to claim 8, wherein the catalyst is reduced before use; the reduction temperature is 200-500 ℃; and the reduction time is 0.5-4 h.

19. The method according to claim 18, wherein the reduction temperature is 240-400 ℃.

20. The method according to claim 17, wherein the hydrogenation reaction temperature is 150-300 ℃; the hydrogenation reaction pressure is 0.1-10.0 MPa; the molar ratio of hydrogen to carbon dioxide is 1-10; and the gas hourly space velocity of the mixed gas atmosphere is 2040-24000 mL / (h·gcat).

21. The method according to claim 20, wherein the hydrogenation reaction temperature is 180-250 ℃.

22. The method according to claim 20, wherein ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The pressure of the hydrogenation reaction is 1.0-5.0 MPa.

23. The method of claim 20, wherein, The molar ratio of the hydrogen to the carbon dioxide is 2-5.

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