High-activity and high-selectivity methanol cracking catalyst and preparation method thereof

Abstract

The invention belongs to the technical field of synthesis gas chemical industry and catalytic materials, and particularly relates to a copper-based catalyst for hydrogen production through methanol cracking and a preparation method thereof. The catalyst comprises a catalyst metal active component, an auxiliary agent and a catalyst carrier, wherein the metal active component is copper and can be one of copper nitrate, copper carbonate and copper sulfate, and the content of the metal active component is 70-88%. Compared with the prior art, the catalyst provided by the invention provides a strong Lewis acid site, can promote migration and deep dehydrogenation of methoxyl intermediates for methanol dehydrogenation on the surface of Cu metal, remarkably improves the selectivity of main products CO and H2, and reduces the selectivity of intermediate products dimethyl ether and methyl formate.

Description

Technical Field

[0001] This invention belongs to the field of syngas chemical engineering and catalytic materials technology, especially copper-based catalysts for methanol cracking to produce hydrogen and their preparation methods. Background Technology

[0002] Hydrogen energy is a highly efficient, renewable, and clean energy source with a high specific heat capacity; however, its storage and transportation pose serious safety risks. Currently, stable and easily transportable liquid fuel-based hydrogen production methods have been developed. Methanol is a promising liquid organic hydrogen carrier, safe, inexpensive, and with a high hydrogen-to-carbon ratio. Methanol can be produced by hydrogenating carbon dioxide, and the resulting methanol can be transferred to locations where hydrogen is needed. The carbon dioxide can then undergo further hydrogenation, enabling feasible transportation and utilization of hydrogen. In methanol-to-hydrogen production, copper-based catalysts possess advantages such as high catalytic activity, simple preparation processes, low cost, and ease of industrialization. However, currently commercially available Cu / ZnO / Al₂O₃ catalysts suffer from low activity, easy carbon deposition and sintering, and the high proportion of dimethyl ether and methyl formate as byproducts in methanol cracking easily clogs the reaction apparatus. Therefore, preparing highly active Cu-based catalysts with low byproducts remains a major challenge for Cu-based catalysts. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a catalyst that can significantly improve the catalytic performance of the catalyst, has good catalytic activity, H2 and CO selectivity, and low ether and ester selectivity, and can meet the requirements of large-scale methanol-to-hydrogen production.

[0004] A highly active and selective methanol cracking catalyst includes: a catalyst metal active component, an additive, and a catalyst support;

[0005] The active metal component is copper, which may be one of copper nitrate, copper carbonate, or copper sulfate, with a content of 70-88%.

[0006] The catalyst support is SiO2, and the Si source content is 1-5%.

[0007] The auxiliary agent is at least one of chromium, magnesium, and barium; its content is 1-25%.

[0008] Furthermore, the catalyst has a specific surface area of ​​69-97 m². 2 / g, pore volume 0.49-0.68cm 3 / g, pore size 13-26nm.

[0009] Furthermore, the Si source is one of sodium silicate, potassium silicate, silica sol, and diatomaceous earth, with a content of 1%-5%.

[0010] To achieve the above objectives, the present invention further provides a method for preparing a highly active and selective methanol cracking catalyst, wherein the method includes the following steps:

[0011] (1) Weigh out the corresponding mass of Cu 2+ Prepare salt solution a using a metal salt solution;

[0012] (2) Weigh the corresponding mass of Cr 3+ A metal salt solution is prepared to form salt solution b; the chromium metal salt is either chromium nitrate or chromium sulfate; the Cu / Cr mass ratio in salt solution a and salt solution b is 6.9 to 10.9. When the Cu / Cr mass ratio is controlled within the corresponding range, Cu at the Cu-Cr2O3 interface promotes the initial activation and decomposition of methanol, greatly improves the selectivity of H2 and CO, and inhibits the generation of byproducts such as methane and dimethyl ether.

[0013] (3) Dissolve the precipitant in water to prepare alkaline solution 1; the precipitant is one of sodium carbonate, sodium bicarbonate and sodium hydroxide;

[0014] (4) Dissolve the appropriate amount of silicon source and precipitant in water and perform ultrasonic treatment to obtain silicon-containing alkaline solution 2;

[0015] (5) Weigh out the appropriate mass of barium metal salt and dissolve it to obtain barium metal salt solution 3; the barium metal salt is one of barium nitrate / barium chloride / barium hydroxide / barium carbonate, and the content is less than 8%.

[0016] (6) Salt solution a and alkali solution 2 are emulsified and mixed under a high-speed shear machine at a shearing speed of 10000-15000 r / min. After the addition of alkali solution 2, alkali solution 1 is used to continue to control the pH. The precipitation conditions are controlled at pH = 5-8 and precipitation temperature at 70-90℃ to obtain precipitate A.

[0017] (7) At the same time, salt solution b and alkali solution 2 are emulsified and mixed under a high-speed shear machine with a shearing speed of 10000-15000 r / min. After the addition of alkali solution 2, alkali solution 1 is used to continue to control the pH = 6-10 and the precipitation temperature 65-85℃ to obtain precipitate B.

[0018] (8) The slurries of precipitate A and precipitate B obtained above are fed into the reactor to obtain precipitate C. Alkali solution 1 is added dropwise to adjust the pH to 6-9, the precipitation temperature is 60-90℃, the stirring speed is 200-300r / min, the stirring speed is reduced after the feeding is completed, and the stirring is stopped after stabilizing for 5-60min. The standing aging time is 4-8h.

[0019] (9) Drying: Dry the washed sample at 60-90℃ for 12 hours;

[0020] (10) Impregnation: Add barium metal salt solution 3 to the dried powdered catalyst, mix well, seal and age for 2-6 hours, and dry at 90℃ for 8 hours;

[0021] (11) Calcination: Place in a high-temperature furnace and program the temperature to rise from room temperature to 250-550℃. Calcinate at a constant temperature for 4-8 hours. When the temperature drops to room temperature, the calcined product is obtained. The calcined product is mixed evenly with graphite to obtain a mixture. The mixture is then pressed into tablets to obtain a catalyst.

[0022] 1. Compared with the prior art, the present invention has the following advantages: The preparation method of the present invention adds the silicon source support to an alkaline solution instead of a nitrate solution, thus preparing a catalyst with higher activity and better stability. The silicon source dissociates into smaller and more stable silicate ions (such as SiO3) when dissolved in the alkaline solution. 2- Or more complex oligomers), uniformly dispersed to form an "active carrier" solution, the tiny crystal nuclei formed by precipitation are promptly surrounded and stabilized by silicate species, effectively preventing their further growth and aggregation, forming smaller, more dispersed Cu nanoparticles. Furthermore, using the technical solution described in this invention, SiO2 serves as the structural framework, uniformly forming during the precipitation process, constructing a well-developed mesoporous structure with a large specific surface area. This exposes most of the copper active sites on the pore surface, further enhancing catalytic activity.

[0023] 2. Existing commercial catalysts, due to the fact that ZnO primarily disperses and stabilizes Cu particles, lack efficient dehydrogenation centers. Their surface properties tend to hydrogenate oxygen-containing intermediates rather than deeply dehydrogenate, resulting in high selectivity for byproducts (dimethyl ether, methyl formate). The catalyst described in this invention, however, provides strong Lewis acid sites, which can promote the migration and deep dehydrogenation of methoxy intermediates in methanol dehydrogenation on the Cu metal surface, significantly improving the selectivity of the main products CO and H2, while reducing the selectivity of the intermediates dimethyl ether and methyl formate.

[0024] 3. In this invention, the alkaline metal salt that acts as a catalyst promoter can selectively cover or neutralize the acidic sites on the catalyst surface, effectively cutting off the pathway of methanol dehydration to dimethyl ether, which is more conducive to the methanol molecule dehydrogenation cracking pathway (CH3OH→CO+2H2), and further reducing the selectivity of dimethyl ether and methyl formate. Attached Figure Description

[0025] Figure 1 Comparison of XRD patterns of catalysts in Example 2 and Comparative Example 3;

[0026] Figure 2 Comparison of TPR-H2 spectra of catalysts in Example 2 and Comparative Example 3. Detailed Implementation

[0027] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0028] All reagents used were commercially available.

[0029] Examples 1-4

[0030] Example 1

[0031] (1) Weigh 323.15g of copper nitrate trihydrate and dissolve it in 1000mL of deionized water to prepare salt solution a;

[0032] (2) Weigh 76.95g of chromium nitrate nonahydrate and dissolve it in 1000mL of deionized water to prepare salt solution b;

[0033] (3) Dissolve 316g Na2CO3 in 3000mL of deionized water to form alkaline solution 1;

[0034] (4) Dissolve 10.72g of silica sol and 106g of Na2CO3 in 2000mL of deionized water and sonicate to form alkaline solution 2.

[0035] (5) Dissolve 4.76g of barium nitrate in 100mL of deionized water to form a barium metal salt solution 3;

[0036] (6) Salt solution a and 1000 mL of alkaline solution 2 were emulsified and mixed under a high-speed shear machine. After the alkaline solution 2 was added dropwise, the pH was controlled by alkaline solution 1. The rotation speed was 10000-12000 r / min. The precipitation conditions were controlled at pH=7 and precipitation temperature at 70℃ to obtain precipitate A.

[0037] (7) At the same time, salt solution b and 1000 mL of alkaline solution 2 are emulsified and mixed under a high-speed shear machine. After the alkaline solution 2 is added dropwise, the pH is controlled by alkaline solution 1. The rotation speed is 10000~12000r / min, and the precipitation conditions are controlled at pH=8 and precipitation temperature at 85℃ to obtain precipitate B.

[0038] (8) The slurries of precipitates A and B obtained above are fed into the reactor in parallel to obtain precipitate C. Alkali solution 1 is added dropwise to adjust the pH to 7, the precipitation temperature is 70℃, the stirring speed is 260r / min, the stirring speed is reduced after the feeding is completed, the rotation speed is controlled at 100r / min, the stabilization time is 10min, then the stirring is stopped, and the standing aging time is 4-8h.

[0039] (9) Drying: Dry the washed sample at 60-90℃ for 12 hours;

[0040] (10) Add barium metal salt solution 3 to the dried powder and mix well. Seal and age for 6 hours, then dry at 90°C for 8 hours.

[0041] (11) Calcination: Placed in a high-temperature furnace, the temperature is increased from room temperature to 300°C at a rate of 1°C / min, and calcined at a constant temperature for 4 hours. When the temperature drops to room temperature, the calcined product is obtained. The calcined product is mixed with graphite to obtain a mixture. The mixture is then pressed into tablets to obtain a catalyst.

[0042] Example 2

[0043] Based on the preparation method in Example 1, in step (1), 330.76g of copper nitrate trihydrate was weighed and dissolved in 1000mL of deionized water to prepare salt solution a; in step (2), 61.56g of chromium nitrate nonahydrate was weighed and dissolved in 1000mL of deionized water to prepare salt solution b; in step (4), 4.28g of silica sol and 106g of Na2CO3 were weighed and dissolved in 2000mL of deionized water, and ultrasonically treated to form alkaline solution 2; other steps remained unchanged.

[0044] Example 3

[0045] Based on the preparation method in Example 1, in step (1), 315.56g of copper nitrate trihydrate was weighed and dissolved in 1000mL of deionized water to prepare salt solution a; in step (2), 92.34g of chromium nitrate nonahydrate was weighed and dissolved in 1000mL of deionized water to prepare salt solution b; in step (4), 21.38g of silica sol and 106g of Na2CO3 were weighed and dissolved in 2000mL of deionized water, and ultrasonically treated to form alkaline solution 2; other steps remained unchanged.

[0046] Example 4

[0047] Based on the preparation method of Example 1, in step (1), 304.15g of copper nitrate trihydrate was weighed and dissolved in 1000mL of deionized water to prepare salt solution a; in step (2), 115.43g of chromium nitrate nonahydrate was weighed and dissolved in 1000mL of deionized water to prepare salt solution b; in step (4), 12.84g of silica sol and 106g of Na2CO3 were weighed and dissolved in 2000mL of deionized water, and ultrasonically treated to form alkaline solution 2; other steps remained unchanged.

[0048] Comparative Examples 1-2

[0049] Comparative Example 1:

[0050] Commercially available copper-zinc-aluminum catalysts were used.

[0051] Comparative Example 2:

[0052] CuZnAl catalyst was prepared using a dual-current co-precipitation method. The specific steps are as follows:

[0053] (1) Dissolve 0.04 mol Zn(NO3)2 and 0.04 mol Al(NO3)3 in 500 mL of deionized water and sonicate to form salt solution a;

[0054] (2) Dissolve 0.44 mol Cu(NO3)2, 0.09 mol Zn(NO3)2 and 0.06 mol Al(NO3)3 in 500 mL of deionized water and sonicate to form salt solution b;

[0055] (3) Dissolve 1 mol Na2CO3 in 1000 mL of deionized water and sonicate to form an alkaline solution c;

[0056] (4) Salt solution a and alkaline solution c are emulsified and mixed under a high-speed shear machine at a shear rate of 10,000 to 15,000 r / min. The precipitation conditions are controlled at pH 6 to 6.5 and precipitation temperature 80 to 85℃ to obtain precipitate A.

[0057] (5) At the same time, salt solution b and alkaline solution c are emulsified and mixed under another high-speed shear machine, and the precipitation conditions are controlled at pH=8 and precipitation temperature at 80℃ to obtain precipitate B;

[0058] (6) The slurries of precipitates A and B obtained above are fed into the sedimentation reactor C in parallel. Precipitant c is added dropwise to adjust the pH to 8. The sedimentation temperature is 80℃ and the stirring speed is 260r / min. After the feeding is completed, the stirring speed is reduced and stabilized for 10min. Then the stirring is stopped and the standing aging time is 4-8h.

[0059] (7) Drying: Dry the washed sample at 60-90℃ for 12 hours;

[0060] (8) Calcination: Placed in a high-temperature furnace, the temperature is increased from room temperature to 300°C at a rate of 1°C / min, and calcined at a constant temperature for 4 hours. When the temperature drops to room temperature, the calcined product is obtained. The calcined product is mixed with 3% graphite to obtain a mixture. The mixture is then pressed into tablets to obtain the catalyst.

[0061] Comparative Example 3:

[0062] Based on the preparation method of Comparative Example 2, in step (1), 0.015 mol of Ba(NO3)2 was added and dissolved by ultrasonication with other metal salts to form salt solution a, while other conditions remained unchanged.

[0063] Table 1. Specific surface area, pore volume, and pore size test values ​​for Examples 1-4 and Comparative Examples 1-3

[0064]

[0065] Table 2 Performance test results of Examples 1-4 and Comparative Examples 1-3

[0066]

[0067]

[0068] Performance testing

[0069] The copper-zinc-aluminum methanol cracking catalysts of Examples 1-10 and Comparative Examples 1-3 were subjected to the following performance tests, and the test results are shown in Tables 1 and 2.

[0070] 1. Specific surface area, pore volume, and pore size

[0071] Measured on a COULTERSA 3100 analyzer

[0072] 2. Methanol conversion rate, H2 selectivity, CO selectivity, dimethyl ether selectivity, and methyl formate selectivity

[0073] The methanol cracking catalyst was used in a 20 mL fixed-bed reaction to test its catalytic performance. The reaction liquid was methanol, the liquid hourly space velocity was 0.3 h⁻¹, the reaction pressure was 0.5 MPa, and the catalyst performance test was conducted at 240 °C.

[0074] CH3OH conversion rate = (mass of methanol entering per unit time - mass of methanol exiting per unit time) / mass of methanol entering per unit time × 100%.

[0075] H2 selectivity = Amount of hydrogen produced per unit time / 2 * Amount of methanol converted per unit time × 100%.

[0076] CO selectivity = CO content in gas phase composition / (CO content in gas phase composition + CO2 content in gas phase composition + CH4 content in gas phase composition) × 100%.

[0077] Dimethyl ether selectivity = mass of dimethyl ether per unit time / (mass of gas and liquid removed per unit time - mass of methanol removed per unit time) × 100%.

[0078] Methyl formate selectivity = mass of methyl formate per unit time / (mass of gas and liquid removed per unit time - mass of methanol removed per unit time) × 100%.

[0079] Referring to Tables 1 and 2, a comparison of Examples 1-4 shows that the methanol conversion rate, CO selectivity, H2 selectivity, dimethyl ether selectivity, methyl formate selectivity, and specific surface area of ​​Example 1 are all higher than those of Examples 2-4, indicating that when the copper-chromium ratio is controlled within a certain range, the catalyst has high activity and selectivity.

[0080] Comparing Example 1 and Comparative Example 1, it can be seen that the catalytic activity of the copper-chromium-silicon system is significantly higher than that of the copper-zinc-aluminum system. The copper-chromium-silicon catalyst prepared by dual-co-current has a larger specific surface area and pore volume, exposes more active sites, and has higher catalytic activity.

[0081] Furthermore, comparing Example 2 and Comparative Example 3, both catalysts were prepared using a dual-co-current precipitation method and had comparable specific surface areas, but their catalytic activities differed significantly, especially in the selectivity of the byproduct methyl formate. The methyl formate selectivity of the copper-chromium-silicon system was only 0.01 times that of the copper-zinc-aluminum system. This is because Cr2O3 plays a better role in dispersing and stabilizing the active component Cu. Figure 1 XRD clearly shows that the CuO diffraction peaks of the metal active component in Example 2 are broader, with smaller peak areas, and the grain size is relatively smaller. Figure 2 TPR was also verified, and it was clearly seen that, compared with Comparative Example 3, the copper oxide reduction peak in Example 2 shifted towards a lower temperature. CuO could be distributed in a finer and more uniform state in the CrSi oxide matrix, and hydrogen (H2) could diffuse more easily into the internal CuO active sites, improving catalytic activity. Moreover, as a basic oxide, Cr2O3 can promote the migration and deep dehydrogenation of methanol dehydrogenation intermediates on the Cu metal surface, reducing the formation of the intermediate product methyl formate.

[0082] Examples 5-7

[0083] Example 5

[0084] Based on the preparation method of Example 1, steps (5) and (10) are omitted, while other steps remain unchanged.

[0085] Example 6

[0086] Based on the preparation method of Example 1, in step (5), 3.81g of barium nitrate was weighed and dissolved in 100mL of deionized water to form barium metal salt solution 3; other steps remained unchanged.

[0087] Example 7

[0088] Based on the preparation method of Example 1, in step (5), 15.22g of barium nitrate was weighed and dissolved in 100mL of deionized water to form barium metal salt solution 3; other steps remained unchanged.

[0089] Examples 8-10

[0090] Example 8

[0091] Based on the preparation method of Example 1, in step (4), 10.90g of sodium silicate and 106g of Na2CO3 are dissolved in 2000mL of deionized water and ultrasonically treated to form alkaline solution 2. Other steps remain unchanged.

[0092] Example 9

[0093] Based on the preparation method of Example 1, in step (4), 6.72g of diatomaceous earth and 106g of Na2CO3 are dissolved in 2000mL of deionized water and ultrasonically treated to form alkaline solution 2. Other steps remain unchanged.

[0094] Example 10

[0095] Based on the preparation method of Example 1, in step (4), 13.78g of potassium silicate and 106g of Na2CO3 are dissolved in 2000mL of deionized water and ultrasonically treated to form alkaline solution 2. Other steps remain unchanged.

[0096] Table 3. Specific surface area, pore volume, and pore size test values ​​for Examples 5-10

[0097]

[0098] Table 4 Performance Test Table for Examples 5-10

[0099]

[0100] Referring to Tables 3 and 4, and comparing Examples 1 and 5-7, it can be seen that the introduction of barium salt in this application significantly increases the specific surface area and pore volume of the catalyst, exposes more active sites, and significantly improves the methanol conversion rate, H2 selectivity, and CO selectivity, while significantly reducing the selectivity of dimethyl ether and methyl formate. Furthermore, when the amount of barium salt introduced is 2.5% (Example 1), it is more conducive to adjusting the acidity and alkalinity of the catalyst surface, promoting deep methanol cracking, improving catalyst activity, and reducing by-product selectivity.

[0101] Comparing Examples 1 and 8-10, it can be seen that in step (4), both silicon oxides and silicates can be used in this application, mainly because they can both play a role in stabilizing the structure in the catalyst. Furthermore, silicon oxides (especially silica sol) are selected as the silicon source, which has a large specific surface area, which is conducive to the dispersion of copper particles and improves the activity and thermal stability of the catalyst.

[0102] Examples 1-10 systematically demonstrate the influence of catalyst composition (Cu / Cr ratio, Si source type and amount, Ba promoter amount) and preparation process on catalyst performance. Examples 1-4 show that when the Cu / Cr mass ratio varies within the range of 6.9-10.9, both catalyst activity and selectivity remain at excellent levels, and the changes are continuous, proving the rationality of this ratio range. Examples 5-7 show that continuous changes in Ba promoter content from 0% to a certain level (such as in Example 7) can lead to performance improvement, proving the effectiveness of the promoter content range. Examples 1 and 8-10 show that high-activity catalysts can be obtained with different Si sources and amounts (1-5%), proving the feasibility of the support content range. The specific surface area of ​​the catalysts obtained in each example is (69.15-97.46 m²). 2 / g), pore volume (0.49-0.68cm³) 3 The physical parameters, such as g / g and pore size (13.29-26.43 nm), are all within or very close to the range defined in claim 2, and their changes are consistent with the performance change trend. Those skilled in the art can, based on the continuous variation pattern revealed in the above embodiments, implement the present invention within the entire parameter range defined in the claims through conventional adjustments and obtain the expected excellent results. The significant disadvantages of comparative examples 1-3 further demonstrate the necessity of the technical solution of the present invention.

[0103] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A highly active and selective methanol cracking catalyst, characterized in that, include: Catalyst metal active component, promoter and catalyst support; The active metal component is copper, which may be one of copper nitrate, copper carbonate, or copper sulfate, with a content of 70-88%. The catalyst support is SiO2, and the Si source content is 1-5%. The auxiliary agent is at least one of chromium, magnesium, and barium; its content is 1-25%.

2. The catalyst according to claim 1, characterized in that, Catalyst specific surface area 69-97m² 2 / g, pore volume 0.49-0.68cm 3 / g, pore size 13-26nm.

3. The catalyst according to claim 1, characterized in that, The Si source is one of sodium silicate, potassium silicate, silica sol, and diatomaceous earth, with a content of 1%-5%.

4. A method for preparing the catalyst according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Weigh out the corresponding mass of Cu 2+ Prepare salt solution a using a metal salt solution; (2) Weigh the corresponding mass of Cr 3+ A metal salt solution is prepared to form salt solution b; the chromium metal salt is either chromium nitrate or chromium sulfate. (3) Dissolve the precipitant in water to prepare alkaline solution 1; the precipitant is one of sodium carbonate, sodium bicarbonate and sodium hydroxide; (4) Dissolve the appropriate amount of silicon source and precipitant in water and sonicate them to obtain a silicon-containing alkaline solution 2. (5) Weigh out the corresponding mass of barium metal salt and dissolve it to obtain barium metal salt solution 3; (6) Salt solution a and alkali solution 2 are emulsified and mixed under a high-speed shear machine at a shearing speed of 10000-15000 r / min. After the addition of alkali solution 2, alkali solution 1 is used to continue to control the pH. The precipitation conditions are controlled at pH = 5-8 and precipitation temperature at 70-90℃ to obtain precipitate A. (7) At the same time, salt solution b and alkali solution 2 are emulsified and mixed under a high-speed shear machine with a shearing speed of 10000-15000 r / min. After the addition of alkali solution 2, alkali solution 1 is used to continue to control the pH. The precipitation conditions are controlled at pH = 6-10 and precipitation temperature at 65-85℃ to obtain precipitate B. (8) The slurries of precipitates A and B obtained above are fed into the reactor to obtain precipitate C. Alkali solution 1 is added dropwise to adjust the pH value to 6-9, the precipitation temperature is 60-90℃, the stirring speed is 200-300r / min, and the standing aging time is 4-8h. (9) Drying: Dry the washed sample at 60-90℃ for 12 hours; (10) Impregnation: Add barium metal salt solution 3 to the dried powdered catalyst and mix well. Seal and age for 2-6 hours, then dry at 90°C for 8 hours. (11) Calcination: Place in a high-temperature furnace and program the temperature to rise from room temperature to 250-550℃. Calcinate at a constant temperature for 4-8 hours. When the temperature drops to room temperature, the calcined product is obtained. The calcined product is mixed evenly with graphite to obtain a mixture. The mixture is then pressed into tablets to obtain a catalyst.

5. The method according to claim 4, characterized in that, The barium metal salt is one of barium nitrate / barium chloride / barium hydroxide / barium carbonate, and its content is less than 8%.

6. The method according to claim 4, characterized in that, The Cu / Cr mass ratio in salt solution a and salt solution b is 6.9 to 10.9.

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