CN114602449B - ZnZrO (zinc ZrO-rich alloy) 2 Surface solid solution catalyst, preparation method and application thereof - Google Patents

Abstract

This application discloses a ZnZrO ₂ surface solid solution catalyst and its preparation method and application. The catalyst includes a ZrO ₂ bulk phase and a solid solution formed on the surface of the ZrO ₂ bulk phase; the solid solution is formed by Zn dissolving on the ZrO ₂ surface. The ZnZrO ₂ surface solid solution catalyst provided by this application not only has high methanol selectivity, but also has the characteristics of large specific surface area, good stability, and strong heat resistance. It can be used in the reaction of carbon dioxide hydrogenation to synthesize methanol, and can effectively improve the conversion of carbon dioxide. rate and methanol space-time yield.

Description

A ZnZrO2 surface solid solution catalyst and its preparation method and application

Technical field

The present application relates to a ZnZrO ₂ surface solid solution catalyst and its preparation method and application, belonging to the field of catalysts.

Background technique

A series of environmental problems such as the greenhouse effect and ocean acidification caused by CO ₂ have attracted widespread attention around the world. _CO2 emission reduction is urgent.

Using renewable energy to produce hydrogen and then using CO ₂ catalytic hydrogenation technology to synthesize chemicals and fuels can not only reduce CO ₂ emissions, but also use CO ₂ as a carbon resource and effectively utilize it. It can be said to kill two birds with one stone. Methanol can not only be used as fuel, but also one of the most important chemical raw materials, and can be further used to synthesize various organic chemicals. Utilizing _CO2 hydrogenation to synthesize methanol is the most effective strategy to achieve the above route.

The most studied catalysts for the hydrogenation of _CO2 to methanol are Cu-based catalysts. Most studies use co-precipitation method to synthesize CuZnAl catalysts and add additives to the catalyst for modification. Judging from the current research results, the best results are Zr or Ti-modified CuZnAl catalysts (Petrochemical Industry, 2009, 38(5), 482; Acta Fuel Chemistry, 2011, 39(12), 912). However, the methanol selectivity on Cu-based catalysts is generally not higher than 60%, which will reduce the utilization of raw materials. In addition, the hydrogenation of carbon dioxide to methanol is an exothermic reaction, and a large amount of heat is released during the reaction. The Cu-based catalyst has poor heat resistance and produces water. The presence of water will promote the sintering of Cu. There are also many studies using In ₂ O ₃ as an active component, but In ₂ O ₃ is easily reduced to metal In, and the melting point of metal In is very low. Therefore, the catalyst will undergo reduction and sintering under hydrogenation conditions, and the catalyst life cannot be guaranteed. , in addition, the selectivity of by-product methane is also relatively high. Chinese patent CN109420486A discloses a ZnZrO _x solid solution catalyst for the hydrogenation of CO ₂ to synthesize methanol. The ZnZrO _x solid solution catalyst is prepared by a precipitation method. The catalyst can effectively inhibit the reverse water gas shift reaction, thereby improving the selectivity of methanol, and It has the advantages of strong heat resistance, anti-sintering and good stability. However, the co-precipitation method requires multiple washings of the catalyst and generates a large amount of wastewater. At the same time, in order to maintain the structure of its solid solution, precise control of conditions is required for both the precipitation and roasting processes, and a higher roasting temperature is required, making the steps more cumbersome. In addition, the solid solution catalyst has a small specific surface area, which limits the conversion rate of the reaction and the space-time yield of methanol. There are also literature reports on supported ZnO/ZrO ₂ catalysts prepared by directly impregnating zinc nitrate on the ZrO ₂ carrier. However, since the crystal structure of ZrO ₂ has already been formed, Zn cannot be embedded into the ZrO ₂ crystal lattice to form a solid solution through impregnation and low-temperature roasting. The synergistic effect of Zn and Zr is greatly weakened, so the performance of supported ZnO/ _ZrO catalysts is usually poor.

Contents of the invention

According to one aspect of the present application, a _ZnZrO surface solid solution catalyst is provided, which has a large specific surface area, good stability, high carbon dioxide conversion rate and methanol space-time yield.

The catalyst includes a ZrO ₂ bulk phase and a solid solution formed on the surface of the ZrO ₂ bulk phase;

A solid solution is formed by Zn dissolving on the _ZrO surface.

Optionally, in the catalyst, the Zn content in the solid solution is 0.1% to 30%;

Among them, Zn is measured by the mass of ZnO.

Specifically, the lower limit of the mass fraction of ZnO in the catalyst can be independently selected from 0.1%, 1%, 5.2%, 9.1%, and 10%; the upper limit of the mass fraction of ZnO in the catalyst can be independently selected from 13%, 15%, 20%, and 26 %, 30%.

According to another aspect of the present application, a method for preparing the above-mentioned ZnZrO ₂ surface solid solution catalyst is provided, and the preparation method includes any one of method one, method two, and method three:

Method 1: Use the impregnation method to synthesize the ZnZrO ₂ surface solid solution catalyst

1-1) Obtain suspension I containing Zn precursor and ZrO ₂ precursor;

1-2) Remove the solvent in the suspension I described in step 1-1) and roast the remaining solid phase to obtain the ZnZrO ₂ surface solid solution catalyst;

Method 2: Synthesis of ZnZrO ₂ surface solid solution catalyst using deposition precipitation method

2-1) Obtain suspension II containing Zn precursor and ZrO ₂ precursor;

2-2) Obtain solution III containing precipitant;

2-3) Mix the suspension II in step 2-1) and the solution III in step 2-2) and filter to obtain a precipitate;

2-4) Calculate the precipitation to obtain the ZnZrO ₂ surface solid solution catalyst;

Method three:

3-1) Pour the gas phase Zn precursor into the dry material containing the ZrO ₂ precursor, and operate to deposit Zn in the Zn precursor on the surface of the ZrO ₂ precursor to obtain an intermediate;

3-2) Calculate the intermediate to obtain the ZnZrO ₂ surface solid solution catalyst.

Optionally, the Zn precursor is measured by the mass of ZnO, the ZrO ₂ precursor is measured by the mass of ZrO ₂ , and the mass ratio of the Zn precursor to the ZrO ₂ precursor is 1:999 to 3:7;

Preferably, the Zn precursor is at least one of zinc nitrate, zinc acetate, zinc halide, diethylzinc, and zinclocene;

Preferably, the _ZrO2 precursor is at least one of zirconium carbonate, zirconium hydroxide, basic zirconium carbonate and oxygen-deficient zirconium oxide _ZrO2 .

Specifically, the lower limit of the mass ratio of Zn precursor to ZrO ₂ precursor can be independently selected from 1:999, 1:99, 5:95, 1:9, 12:88; the mass ratio of Zn precursor to ZrO ₂ precursor The lower and upper limits can be independently selected from 15:85, 17:83, 2:8, 25:75, and 3:7.

Optionally, the calcination temperature is 300 to 800°C.

Preferably, the calcination is performed under a protective atmosphere, and further preferably, the protective atmosphere is at least one of nitrogen and argon.

Preferably, the roasting time is 3 to 5 hours.

Optionally, the reaction product is dried before roasting, and the drying temperature is 100-150°C.

Specifically, the lower limit of the calcination temperature can be independently selected from 300°C, 350°C, 400°C, 450°C, and 500°C; the upper limit of the calcination temperature can be independently selected from 550°C, 600°C, 650°C, 700°C, and 800°C.

Optionally, in method one, the content of Zn precursor in suspension I is 0.01-10 mol/L.

Specifically, the lower limit of the Zn precursor content can be independently selected from 0.01mol/L, 0.5mol/L, 1 mol/L, 3.2mol/L, 5mol/L; the upper limit of the Zn precursor content can be independently selected from 6mol/L , 7mol/L, 8mol/L, 9mol/L, 10mol/L.

In the impregnation method (ie method 1), preferably, the Zn precursor is at least one of zinc nitrate, zinc acetate, zinc halide, and diethyl zinc.

Optionally, in method two, the content of Zn precursor in the suspension II is 0.01 to 7 mol/L;

In the solution III, the content of the precipitating agent is 0.01~14mol/L;

Preferably, the precipitating agent is at least one of ammonia, ammonium carbonate, ammonium bicarbonate, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide and potassium hydroxide.

Preferably, a precipitant is added to adjust the pH of the reaction system to 6.0-8.0;

Preferably, in solution I, solution II, and solution III, the solvent is water, methanol, ethanol, etc.;

In the deposition method (ie, method 2), preferably, the Zn precursor is at least one of zinc nitrate, zinc acetate, zinc halide, and diethyl zinc.

Specifically, the lower limit of the concentration of the Zn precursor solution can be independently selected from 0.01mol/L, 0.5mol/L, 1mol/L, 3.2mol/L, 5mol/L; the upper limit of the concentration of the Zn precursor solution can be independently selected from 6mol/L. L, 7mol/L, 8mol/L, 9mol/L, 7mol/L.

Specifically, the lower limit of the precipitant content can be independently selected from 0.01mol/L, 0.1mol/L, 1mol/L, 3mol/L, 5mol/L; the upper limit of the precipitant content can be independently selected from 7mol/L, 9mol/L , 10mol/L, 12mol/L, 14mol/L.

Optionally, step 3-1) is: heating the ZrO ₂ precursor in a reaction furnace at 25-300°C, introducing the gas phase Zn precursor, and operating to deposit Zn in the Zn precursor on the surface of the ZrO ₂ precursor to obtain intermediate.

Preferably, the heating temperature is 25-300°C;

Specifically, the lower limit of the heating temperature can be independently selected from 25°C, 50°C, 75°C, 100°C, and 125°C; the upper limit of the heating temperature can be independently selected from 150°C, 175°C, 200°C, 250°C, and 300°C.

Optionally, in step 3-1), the operation is: decompose or react the gas phase Zn precursor by controlling the temperature or introducing substances that can react with the gas phase Zn precursor, so that Zn is deposited on the surface of the ZrO ₂ precursor.

Optionally, the decomposition control temperature is 50 to 500°C;

Preferably, the reaction conditions are: the reaction temperature is 100-200°C.

Preferably, the substance capable of reacting with the gas phase Zn precursor is at least one of O ₂ , H ₂ O, and O ₃ .

Specifically, the lower limit of the decomposition control temperature can be independently selected from 50°C, 100°C, 150°C, 200°C, and 250°C; the upper limit of the decomposition control temperature can be independently selected from 300°C, 350°C, 400°C, 450°C, and 500°C. .

Specifically, the lower limit of the reaction temperature can be independently selected from 100°C, 110°C, 120°C, 130°C, and 150°C; the upper limit of the reaction temperature can be independently selected from 160°C, 170°C, 180°C, 190°C, and 200°C.

A specific implementation mode of the present application is to add ZrO ₂ precursor to the reaction furnace and heat it to 25~300°C, introduce the gasified Zn precursor through inert gas, control the reaction temperature to 50~500°C, and react for 0.1min~30min , causing the Zn precursor to decompose and obtain the product.

In order for the gas phase Zn precursor to decompose and deposit on the _ZrO precursor surface, the reaction temperature should be higher than the vaporization temperature of the Zn precursor. The specific reaction temperature varies according to the vaporization temperature of different types of Zn precursors.

Another specific implementation mode of this application is to add ZrO ₂ precursor to the reaction furnace and heat it to 25-300°C, introduce the vaporized Zn precursor through inert gas, and after vacuuming, introduce the gas phase Zn precursor containing The inert gas of the reacted substance controls the reaction temperature to 50 to 500°C, and the reaction is 0.1 to 30 minutes. Through the reaction between the gas phase Zn precursor and the oxidizing substance, Zn is deposited on the surface of the ZrO ₂ precursor to obtain the product.

In order to completely react the gas phase Zn precursor, an excessive amount of substances capable of reacting with the gas phase Zn precursor should be introduced. Those skilled in the art can select the amount of substances that can react with the gas phase Zn precursor according to the specific amount of the gas phase Zn precursor.

In this application, "ZnZrO ₂ " is only a representation of the material and does not represent the actual chemical ratio;

"Gaseous Zn precursor" refers to a gaseous Zn precursor formed by heating and vaporizing a Zn precursor.

According to yet another aspect of the present application, the application of the _ZnZrO2 surface solid solution catalyst for the hydrogenation of carbon dioxide to synthesize methanol is provided.

A method of hydrogenating carbon dioxide to synthesize methanol, using carbon dioxide and hydrogen as raw materials, reacting in the presence of a catalyst to obtain methanol;

The catalyst is any of the above catalysts, or at least one of the catalysts prepared by any of the above methods.

Optionally, the reaction temperature is 280-400°C, the reaction pressure is 1-10MPa, the space velocity is 3000-80000mL/(g·h), and the molar ratio of n(H ₂ ):n(CO ₂ )=1-8.

Preferably, the reaction temperature is 290 to 360°C.

Specifically, the lower limit of the reaction temperature can be independently selected from 280°C, 300°C, 320°C, 340°C, and 345°C; the upper limit of the reaction temperature can be independently selected from 350°C, 360°C, 370°C, 380°C, and 400°C.

Specifically, the lower limit of the reaction pressure can be independently selected from 1MPa, 2MPa, 3MPa, 4MPa, and 5 MPa; the upper limit of the reaction pressure can be independently selected from 6MPa, 7MPa, 8MPa, 9MPa, and 10MPa.

Specifically, the lower limit of the reaction space velocity can be independently selected from 3000mL/(g·h), 5000mL/(g·h), 10000mL/(g·h), 24000mL/(g·h), 40000mL/(g·h) ; The upper limit of the reaction pressure can be independently selected from 50000mL/(g·h), 57000mL/(g·h), 65000mL/(g·h), 70000mL/(g·h), and 80000mL/(g·h).

Specifically, the lower limit of the n(H ₂ ):n(CO ₂ ) molar ratio can be independently selected from 1, 1.5, 2, 3, 3.5; the lower limit of the n(H ₂ ):n(CO ₂ ) molar ratio can be independently selected from 4 ,5,6,7,8.

The beneficial effects this application can produce include:

1) The ZnZrO ₂ surface solid solution catalyst provided by this application not only has high methanol selectivity, but also has the characteristics of large specific surface area, good stability, and strong heat resistance. It can be used in the reaction of carbon dioxide hydrogenation to synthesize methanol and can achieve high conversion. Continuously convert carbon dioxide and obtain methanol with high efficiency and high selectivity, effectively improving the carbon dioxide conversion rate and methanol space-time yield.

2) The preparation method of the ZnZrO ₂ surface solid solution catalyst provided in this application is simple, requires little wastewater discharge during the preparation process, and can synthesize high-performance ZnZrO ₂ surface solid solution catalyst in a green and environmentally friendly manner.

3) The preparation method of _ZnZrO2 surface solid solution catalyst provided by this application uses highly active zirconium oxide precursors such as zirconium carbonate, zirconium hydroxide, basic zirconium carbonate and oxygen-deficient zirconium oxide. Such zirconium oxide precursors The defective sites and structural changes that exist and are generated during the thermal decomposition process can help the migration of Zn on its surface, thereby forming a surface solid solution, which greatly enhances the synergistic effect between Zn and Zr.

Description of the drawings

Figure 1 is the X-ray diffraction spectrum of the catalyst obtained in Example 5 and Comparative Example 3 of the present application;

Figure 2 is the electron paramagnetic resonance spectrum of the catalyst obtained in Example 6 of the present application;

Figure 3 is a stability test diagram of the catalyst obtained in Example 4 of the present application participating in the reaction.

Detailed ways

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

Unless otherwise specified, the raw materials in the examples of this application were all purchased through commercial channels. The oxygen-deficient zirconium oxide ZrO _x corresponds to the white color of zirconium oxide (ZrO ₂ ), which is usually brown. (Obtained by calcining zirconium hydroxide, zirconium carbonate, and basic zirconium carbonate in nitrogen or argon gas).

The analysis methods in the examples of this application are as follows:

The specific surface area and pore size distribution analyzer (model Quantachrome NOVA) was used to analyze the specific surface area of the catalyst.

An electron paramagnetic resonance spectrometer (model Bruker A200) was used to analyze the oxygen defects of the catalyst.

The structure of the catalyst was analyzed using an X-ray diffractometer (model: Rigaku D/Max 2500/PC).

In one embodiment of the present application, the ZnZrO ₂ surface solid solution catalyst is prepared by an impregnation method. It includes the following steps: prepare a Zn precursor solution with a concentration of 0.01 to 10 mol/L, and add ZrO ₂ precursor; volatilize the solvent by heating or ultrasonic treatment; and then calcining at 300 to 800°C to obtain a ZnZrO ₂ surface solid solution catalyst. The Zn precursor used is one or more of zinc nitrate, zinc acetate, zinc halide, and diethyl zinc; the ZrO ₂ precursor used is zirconium carbonate, zirconium hydroxide, basic zirconium carbonate and oxygen-containing defects. One or more than two kinds of zirconia.

In one embodiment of the present application, the ZnZrO ₂ surface solid solution catalyst is prepared by a deposition precipitation method. It includes the following steps: prepare a Zn precursor solution with a concentration of 0.01~7mol/L, and add _ZrO2 precursor; prepare a precipitant solution with a concentration of 0.01~7mol/L; add the precipitant solution to the Zn precursor solution; filter The precipitate obtained is washed, dried at 60-130°C, and calcined at 300-800°C to obtain a ZnZrO ₂ surface solid solution catalyst. The Zn precursor used is one or more of zinc nitrate, zinc acetate, zinc halide, and diethyl zinc; the ZrO ₂ precursor used is zirconium carbonate, zirconium hydroxide, basic zirconium carbonate and oxygen-containing defects. One or more than two kinds of zirconia. The precipitant used is one or more of ammonia, ammonium carbonate, ammonium bicarbonate, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide and potassium hydroxide.

In one embodiment of the present application, the ZnZrO ₂ surface solid solution catalyst is prepared using a vapor deposition method. It includes the following steps: putting the ZrO ₂ precursor into the reaction furnace and controlling the temperature to 25-300°C; introducing the gas phase Zn precursor into the reaction furnace; controlling the temperature or introducing substances that can react with the gas phase Zn precursor. The gas phase Zn precursor decomposes or reacts to deposit Zn on the surface of the ZrO ₂ precursor; it is then calcined at 300 to 800°C to obtain a ZnZrO ₂ surface solid solution catalyst. The gas-phase Zn precursor used is one or more of zinc chloride, diethyl zinc, and zincocene; the substances used to react with the gas-phase Zn precursor are O ₂ , H ₂ O, and O ₃ One or more than two types. The beneficial effect is the green and simple synthesis of high-performance _ZnZrO2 surface solid solution catalyst.

In this application, the activity evaluation of the catalyst for the hydrogenation of carbon dioxide to methanol was carried out on a pressurized fixed-bed continuous flow reactor-GC combination system. Before the reaction, use pure hydrogen or nitrogen, argon or hydrogen diluted with nitrogen or argon to activate at 280~400°C for 0.5~12h. The conditions for hydrogenating carbon dioxide to synthesize methanol are: reaction pressure 1 to 10 MPa, reaction temperature 280 to 400°C, space velocity 3000 to 80000h ^–1 , n(H ₂ ): n(CO ₂ ) molar ratio = 1 to 8. The reaction tail gas is discharged to normal pressure through the back pressure valve, and is sampled through the ten-way valve of the gas chromatograph while maintaining temperature at 150°C. The thermal conductivity detector (TCD) and hydrogen flame detector (FID) of the Agilent GC-7890B gas chromatograph are combined. Online analysis. The former chromatographic column is a combination of 5A molecular sieve and Propark Q (Agilent), with a column length of 3m, using H ₂ as carrier gas, working at 85°C, and used to separate and detect CO ₂ , Ar, and CO; the latter chromatographic column is TG- BOND Q capillary column (Thermo Fisher), with specifications of 30m×0.32mm×10μm, using _N2 as carrier gas, is used for separation and detection of low carbon hydrocarbons and alcohols. The _CO2 conversion rate and the C-group selectivity and space-time yield of carbon-containing products such as CO, alcohols, and hydrocarbons are calculated by the C-group normalization method.

Example 1

Take 0.2ml of 3.2mol/L Zn(NO ₃ ) ₄ ·6H ₂ O aqueous solution in a 20mL beaker, add 2ml of water to dilute, then add 1g of zirconium carbonate, evaporate to dryness by ultrasonic, and dry in a 110°C oven at 400°C. Calculate in air for 4 hours to obtain the catalyst, which is recorded as 5.2% ZnZrO ₂ -1.

Example 2

Take 0.35ml of 3.2mol/L Zn(NO ₃ ) ₄ ·6H ₂ O aqueous solution in a 20mL beaker, add 2ml of water to dilute, then add 1g of oxygen-deficient zirconia, evaporate to dryness by ultrasonic, and bake in an oven at 110°C. Dry and calcined in nitrogen at 400°C for 4 hours to obtain a catalyst, recorded as 9.1% ZnZrO ₂ -2.

Example 3

Take 1ml of 3.2mol/L Zn(NO ₃ ) ₄ ·6H ₂ O aqueous solution in a 20mL beaker, add 2ml of water to dilute, then add 1g of basic zirconium carbonate, evaporate to dryness by ultrasonic, and dry in an oven at 110°C, 400 The catalyst was calcined in nitrogen at ℃ for 4 hours, which was recorded as 26% ZnZrO ₂ -3.

Example 4

Take 0.38ml of 3.2mol/L Zn(NO ₃ ) ₄ ·6H ₂ O aqueous solution in a 20mL beaker, add 2ml of water to dilute, then add 1g of zirconium hydroxide, evaporate to dryness by ultrasonic, and dry in an oven at 110°C, 500 Calculate in air at ℃ for 4 hours to obtain the catalyst, which is recorded as 10% ZnZrO ₂ -4.

Example 5

Take 0.38ml of 3.2mol/L Zn(NO ₃ ) ₄ ·6H ₂ O aqueous solution in a 20mL beaker, add 100ml of water to dilute, then add 1g of zirconium hydroxide, and while stirring, gradually drop in 0.1mol/L ammonia solution to reach pH is 7.0, filter the obtained precipitate, wash it with water, dry it in an oven at 110°C, and bake it in air at 500°C for 4 hours to obtain a catalyst, which is recorded as 10% ZnZrO ₂ -5.

Example 6

Take 1g of oxygen-deficient zirconia and put it into the reaction furnace, heat it to 200°C, pass in nitrogen containing diethyl zinc, vacuum and then pass in nitrogen containing water to react, the reaction temperature is 150°C, the reaction time for 5 minutes, put it into an oven at 110°C to dry, and calcined in air at 500°C for 4 hours to obtain a catalyst, which was recorded as ALD-5% ZnZrO ₂ -6.

Comparative Example 1 Preparation of ZnZrO _x solid solution catalyst

_{ZnZrO _ _ _ _ _ _ _ _} CO ₃ was prepared into 100 mL aqueous solution. Add the prepared ammonium carbonate solution dropwise into the mixed aqueous solution of zinc nitrate and zirconium nitrate at 70°C. The dropping speed is about 3mL/min and the stirring speed is 600r/min. After the (NH ₄ ) ₂ CO ₃ solution is consumed, the precipitated mother liquor is obtained and Aged at 70°C for 2 hours, cooled, naturally filtered, washed three times with deionized water, and filtered with suction. The resulting filter cake was dried at 60°C and roasted in air at 500°C for 3 hours to obtain a catalyst, recorded as 13% ZnZrO _x .

Comparative example 2

Commercial copper-zinc-aluminum catalyst is designated CuZnAl.

Comparative example 3

Take 0.38ml of 3.2mol/L Zn(NO ₃ ) ₄ ·6H ₂ O aqueous solution in a 20mL beaker, add 2ml of water to dilute, then add 1g of zirconia, evaporate to dryness by ultrasonic, and dry in an oven at 110°C, 500°C Calcined in air for 4 hours to obtain the catalyst, recorded as 10% ZnO/ZrO ₂ .

Catalyst evaluation

1. Use a specific surface area measuring instrument to detect the specific surface area of the catalyst prepared in the embodiment of the present application. It is found that each catalyst sample prepared by the method of the present application has a large specific surface area. Comparing the specific surface areas of the catalysts obtained in this application and the catalyst samples obtained in Comparative Examples, typically, the samples obtained in Examples 1, 2, 4 and Comparative Example 1 are used for illustration. The results are shown in Table 1:

Table 1 Catalyst specific surface results of Examples and Comparative Examples

catalyst Specific surface (m ² /g) Example 1 5.2%ZnZrO ₂ -1 46.2 Example 2 9.1%ZnZrO ₂ -2 98.7 Example 4 10%ZnZrO ₂ -4 68.6 Comparative example 1 13% _ZnZrOx 29.7

It can be seen that compared with the ZnZrO _x solid solution catalyst prepared by co-precipitation, the specific surface area of the catalyst of the present application is significantly increased.

2. Use an X-ray diffractometer to test the catalyst samples obtained in Examples 1-6, and find that a solid solution structure is formed on the surface of the catalyst. Typically, taking the sample obtained in Example 4 as an example, compare it with the catalyst sample in Comparative Example 3, as shown in Figure 1. Compared with the ordinary supported catalyst (10% ZnO/ZrO ₂ ), it can be found that 10% ZnZrO ₂ - The zirconium oxide diffraction peak of 4 slightly moves to a high angle, and the diffraction peak of zinc oxide does not appear when the ZnO content is 10%. This shows that it is likely to form a solid solution structure on the catalyst surface, which enhances the interaction between zinc oxide and zirconium oxide.

3. An electron paramagnetic resonance test was performed on the oxygen-deficient zirconia used in Example 6. The results are shown in Figure 2. Compared with ordinary zirconia, the oxygen defects cause a large number of unpaired electrons in the zirconia, showing strong The electron paramagnetic resonance signal, this oxygen defect contributes to the migration of Zn in _ZrO during the preparation process, thereby forming a solid solution.

4. Catalytic activity measurement

The catalyst sample was pressed into tablets, crushed, and screened into 40 to 80 mesh for evaluation.

Activity evaluation method: Weigh 0.1g of the screened catalyst sample and put it into a reaction tube with an inner diameter of 6 mm, reduce it at 320°C for 2 hours in pure H ₂ under normal pressure, with a flow rate of 30 mL/min, and then introduce the raw material gas n(H ₂ ) :n(CO ₂ )=3 for reaction.

In the evaluation method, the copper-zinc-aluminum catalyst in Comparative Example 2 was reduced at 250°C for 2 hours under normal pressure and in pure H _2. Other evaluation steps were the same as the above method.

The evaluation results are shown in Table 2.

Table 2 Examples and Comparative Examples Catalyst Evaluation Results

5. Catalyst stability measurement

According to the above evaluation method, the 10% ZnZrO ₂ -4 catalyst sample was subjected to a long-term stability test. The results are shown in Figure 3. During the 200-hour stability test, the methanol yield remained unchanged at 405 mg/gh. The temperature was raised to 400°C during the reaction to explore the high-temperature stability of the catalyst. After lowering the reaction temperature from 400°C back to 320°C, the methanol yield returned to 405 mg/gh. This shows that the catalyst not only has long-term stability but also has excellent high-temperature sintering resistance.

The above are only a few embodiments of the present application, and are not intended to limit the present application in any way. Although the present application is disclosed as above with preferred embodiments, they are not intended to limit the present application. Any skilled person familiar with this field, Without departing from the scope of the technical solution of this application, slight changes or modifications made using the technical content disclosed above are equivalent to equivalent implementation examples and fall within the scope of the technical solution.

Claims (16)

1. ZnZrO (zinc ZrO-rich alloy) ₂ The preparation method of the surface solid solution catalyst is characterized by comprising any one of a first method, a second method and a third method:

the method comprises the following steps: the ZnZrO is synthesized by adopting an impregnation method ₂ Surface solid solution catalyst

1-1) obtaining a precursor containing Zn and ZrO ₂ A precursor suspension I;

1-2) removing the solvent in the suspension I in the step 1-1), and roasting the rest solid phase to obtain the ZnZrO ₂ A surface solid solution catalyst;

the second method is as follows: znZrO synthesis by deposition precipitation method ₂ Surface solid solution catalyst

2-1) obtaining a precursor containing Zn and ZrO ₂ A precursor suspension II;

2-2) obtaining a solution III containing a precipitant;

2-3) mixing the suspension II in the step 2-1) with the solution III in the step 2-2), and filtering to obtain a precipitate;

2-4) roasting the precipitate to obtain the ZnZrO ₂ A surface solid solution catalyst;

and a third method:

3-1) to ZrO-containing ₂ Introducing a gas-phase Zn precursor into the dry material of the precursor, and operating to deposit Zn in the Zn precursor in ZrO ₂ The surface of the precursor is provided with an intermediate;

3-2) roasting the intermediate to obtain the ZnZrO ₂ A surface solid solution catalyst;

the ZrO ₂ The precursor is at least one of zirconium carbonate, zirconium hydroxide, zirconium basic carbonate and zirconium oxide with oxygen defect.

2. The method of claim 1, wherein the Zn precursor is in ZnMass, zrO ₂ The precursor is calculated by the mass of Zr, and the Zn precursor and ZrO ₂ The mass ratio of the precursors is 1:999-3:7.

3. The method of claim 1, wherein the Zn precursor is at least one of zinc nitrate, zinc acetate, zinc halide, diethyl zinc, zinc half-oxide.

4. The method of claim 1, wherein the firing temperature is 300 to 800 ℃.

5. The method according to claim 1, wherein in the first method, the content of the Zn precursor in the suspension liquid i is 0.01 to 10mol/L.

6. The method according to claim 1, wherein in the second method, the content of the Zn precursor in the suspension liquid ii is 0.01 to 7mol/L;

in the solution III, the content of the precipitant is 0.01-14 mol/L.

7. The method of claim 6, wherein the precipitant is at least one of ammonia, ammonium carbonate, ammonium bicarbonate, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide, and potassium hydroxide.

8. The method according to claim 1, wherein step 3-1) is: zrO (ZrO) ₂ Heating the precursor in a reaction furnace at 25-300 ℃, introducing a gas-phase Zn precursor, and operating to deposit Zn in the Zn precursor in ZrO ₂ The surface of the precursor is provided with an intermediate.

9. The method according to claim 1, wherein in step 3-1), the operations are: decomposing or reacting the vapor Zn precursor by controlling the temperature or introducing a substance capable of reacting with the vapor Zn precursor to deposit Zn on ZrO ₂ Precursor bodyA surface.

10. The method of claim 9, wherein the decomposition control temperature is 50-500 ℃.

11. The method of claim 9, wherein the reaction conditions are: the reaction temperature is 100-200 ℃.

12. The method according to claim 9, wherein the substance capable of reacting with the vapor phase Zn precursor is O ₂ 、H ₂ O、O ₃ At least one of them.

13. A catalyst prepared by the process of any one of claims 1 to 12, wherein the catalyst comprises ZrO ₂ Bulk phase and the ZrO ₂ Solid solutions formed on the bulk surfaces;

the solid solution is dissolved in ZrO by Zn ₂ And forming a surface.

14. The catalyst according to claim 13, wherein the Zn content in solid solution in the catalyst is 0.1% to 30%;

wherein Zn is calculated by mass of ZnO.

15. A method for synthesizing methanol by hydrogenation of carbon dioxide is characterized in that carbon dioxide and hydrogen are used as raw materials to react in the presence of a catalyst to obtain methanol;

the catalyst is at least one of the catalyst prepared by the method of any one of claims 1 to 12 or the catalyst of claim 13 or 14.

16. The process according to claim 15, wherein the reaction temperature is 280 to 400 ℃, the reaction pressure is 1 to 10MPa, the space velocity is 3000 to 80000 mL/(g.h), n (H) ₂ ):n(CO ₂ ) Molar ratio=1 to 8.