Method for preparing catalyst material based on hydrothermal method

Abstract

The invention provides a method for preparing a catalyst material based on a hydrothermal method, and relates to the technical field of exhaust gas aftertreatment catalytic materials. The method comprises the following steps: dissolving cerium salt and transition metal salt in deionized water to form a precursor solution; taking hexadecyl trimethyl ammonium bromide as a template agent, and dissolving the template agent in the precursor solution; dropwise adding ammonia water into the precursor solution to adjust the pH value to alkalescence; putting the precursor solution into a reaction kettle for high-temperature hydrothermal treatment; filtering, drying and grinding the solution subjected to hydrothermal treatment, and then carrying out high-temperature roasting treatment; and performing segmented reduction on the roasted sample by using hydrogen to obtain the catalyst material. The preparation method has remarkable technical effects in the aspects of increase of active sites of the catalyst, increase of specific surface area, remarkable improvement of future application prospect and performance and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of exhaust gas post-treatment catalytic materials, and in particular to a method for preparing a catalyst material based on a hydrothermal method. Background Art

[0002] The urgency of global greenhouse gas emission reduction and air pollution control has promoted the rapid development of methane and VOCs catalytic purification technology. According to statistics from the International Energy Agency, methane emissions will reach 135 million tons (CO2 equivalent) in 2022, of which oil and gas extraction and coal combustion processes contribute more than 30%, and the concentration of benzene in VOCs emitted from landfills can reach 1200-2500 mg / m 3 The ozone produced by its photochemical reaction accounts for more than 70% of the pollution incidents in urban summer. Traditional thermal combustion needs to operate at 800-1000℃, and the energy consumption is as high as 4.2×10 3 kWh / ton of exhaust gas, and the amount of secondary NOx pollutants generated exceeds 180ppm; in contrast, catalytic combustion technology can reduce the temperature to below 500℃ and reduce energy consumption by 60%, but the existing catalyst system still cannot meet the demanding working conditions. Although precious metal catalysts (such as 0.5% Pt / Al2O3) can achieve methane T90 at 350℃, their cost accounts for more than 45% of the total equipment investment (about 3.2 million yuan / ton of catalyst), and in diesel vehicle exhaust aftertreatment (space velocity 50,000h -1 , containing 10% water vapor), the activity dropped by 52% after aging at 600℃ for 100 hours. The cost of non-precious metal catalysts is only 1 / 20 of that of commercial Mn-Ce oxide catalysts, but their performance is lacking: the methane T90 of commercial Mn-Ce oxide catalysts is generally 520-560℃, and the porosity is low (<50m 2 / g), the proportion of mesopores is less than 30%, and in actual tail gas treatment (containing 5% SO2, 200ppm Cl-), 50% activity decay occurs after 200 hours of operation.

[0003] Current research shows that improving the pore structure and active sites of the catalyst can effectively improve the activity of the catalyst. How to further achieve this goal has become the main direction of optimizing non-precious metal catalysts. Summary of the invention

[0004] In view of this, the present invention provides a method for preparing a catalyst material based on a hydrothermal method to solve the above problems.

[0005] In order to solve the above problems, the specific technical solutions adopted by the present invention are as follows:

[0006] A method for preparing a catalyst material based on a hydrothermal method comprises the following steps:

[0007] S10. Dissolve the cerium salt and the transition metal salt in deionized water to obtain a precursor solution;

[0008] Among them, the transition metal salt includes nickel salt or a mixture of nickel salt and zirconium salt;

[0009] S20. Dissolve cetyltrimethylammonium bromide as a template agent in the precursor solution;

[0010] S30. Dropwise add ammonia water to the precursor solution until the pH value of the precursor solution is 8 - 9;

[0011] S40. Transfer the precursor solution with a pH value of 8 - 9 to a reaction kettle for high-temperature hydrothermal treatment;

[0012] S50. After the mixture obtained after the hydrothermal treatment is filtered, dried, and ground, perform high-temperature calcination treatment to obtain a calcined sample;

[0013] S60. Reduce the calcined sample in segments with hydrogen to obtain a catalyst material.

[0014] Preferably, in the S10:

[0015] When the transition metal salt is nickel salt, the molar ratio of cerium salt to nickel salt is (75 - 90):(10 - 25);

[0016] When the transition metal salt is a mixture of nickel salt and zirconium salt, the molar ratio of cerium salt to nickel salt to zirconium salt is (75 - 90):(10 - 25):(1 - 5).

[0017] Preferably, the cerium salt includes at least one of cerium nitrate, cerium chloride, cerium acetate, and cerium oxalate; the nickel salt includes at least one of nickel nitrate, nickel chloride, and nickel acetate; the zirconium salt includes at least one of zirconium nitrate, zirconium chloride, and zirconium acetate.

[0018] Preferably, the S10 specifically includes:

[0019] Add the cerium salt and the transition metal salt to deionized water, and stir until completely dissolved to obtain a precursor solution;

[0020] The addition amount of the deionized water is 40 mL of deionized water added for every 0.01 mol of the total reactants;

[0021] The total reactants are a mixture of cerium salt and transition metal salt;

[0022] The stirring speed is 300 - 350 r / min.

[0023] Preferably, the cerium salt includes at least one of cerium nitrate, cerium chloride, cerium acetate, and cerium oxalate; the nickel salt includes at least one of nickel nitrate, nickel chloride, and nickel acetate; the zirconium salt includes at least one of zirconium nitrate, zirconium chloride, and zirconium acetate.

[0024] Preferably, the S20 specifically includes:

[0025] Add cetyltrimethylammonium bromide to the precursor solution and stir until completely dissolved;

[0026] Among them, the addition amount of cetyltrimethylammonium bromide is 0.1 g of cetyltrimethylammonium bromide added for every 0.01 mol of the total reactants;

[0027] The total reactants are a mixture of cerium salt and transition metal salt;

[0028] The conditions for the stirring are to stir at a speed of 300 - 350 r / min for 1 - 2 h.

[0029] Preferably, the S30 specifically includes:

[0030] S301. While stirring, add ammonia water dropwise to the precursor solution until a precipitate is formed;

[0031] S302. While stirring, continue to add ammonia water dropwise to the precursor solution until the precipitate is completely dissolved;

[0032] S303. While stirring, continue to add ammonia water dropwise to the precursor solution until the pH value of the precursor solution is 8 - 9;

[0033] The stirring speeds in S301, S302, and S303 are the same, all being 300 - 350 r / min.

[0034] Preferably, the S40 specifically includes:

[0035] After continuously stirring the precursor solution with a pH value of 8 - 9, transfer it to the polytetrafluoroethylene inner liner of the reaction kettle, then place the polytetrafluoroethylene inner liner into the stainless - steel outer shell and place it in an oven for high - temperature hydrothermal treatment;

[0036] Among them, the conditions for the continuous stirring are to stir at a speed of 300 - 350 r / min for 1 - 2 h; the loading amount of the precursor solution is 3 / 4 - 4 / 5 of the volume of the polytetrafluoroethylene inner liner; the temperature of the high - temperature hydrothermal treatment is 160 °C, and the time of the high - temperature hydrothermal treatment is 12 h.

[0037] Preferably, the S50 specifically includes:

[0038] S501. After the hydrothermal treatment of the high - temperature hydrothermal treatment is completed, naturally cool the reaction kettle to room temperature;

[0039] S502. Filter the mixture in the polytetrafluoroethylene inner liner of the reactor;

[0040] S503. After drying and grinding the obtained solid, conduct high-temperature calcination treatment. After the high-temperature calcination treatment is completed, naturally cool it to room temperature to obtain the calcined sample.

[0041] Preferably, the drying conditions are drying at 80 °C for 12 - 24 h; the calcination conditions are holding at 550 °C for 3 h with a heating rate of 3 °C / min.

[0042] Preferably, the S60 specifically includes:

[0043] S601. Pour the calcined sample into a quartz crucible;

[0044] S602. Place the quartz crucible into a tube furnace;

[0045] S603. Introduce hydrogen and argon into the tube furnace;

[0046] S604. Use the tube furnace for segmented heating to reduce the catalyst material;

[0047] S605. After the reduction is completed, stop introducing hydrogen and continue to introduce argon until it naturally cools to room temperature to obtain the catalyst material;

[0048] Among them, in the S603, the total flow rate of hydrogen and argon introduced is 60000 mL / g·h, and the volume concentration of hydrogen accounts for 10% of the total amount of hydrogen and argon; cat -1 h -1 , and the volume concentration of hydrogen accounts for 10% of the total amount of hydrogen and argon;

[0049] In the S604, using the tube furnace for segmented heating includes first heating from room temperature to 300 °C and holding for 1 h for pre-reduction with a heating rate of 3 °C / min, and then continuing to heat to 450 °C at a heating rate of 3 °C / min and holding for 2 h.

[0050] The beneficial effects of the present invention are as follows:

[0051] The present invention uses cetyltrimethylammonium bromide as a template agent, synthesizes a cerium-based methane catalytic oxidation catalyst material by a hydrothermal method, introduces a pore structure, and reduces nickel elements with hydrogen after the hydrothermal process, significantly improving the specific surface area and active sites of the catalytic material, thereby improving the activity of the catalyst, solving the problems of low specific surface area and insufficient catalytic activity of non-noble metal methane catalytic oxidation catalysts, and showing significant technical effects in terms of increased active sites, improved specific surface area, future application prospects, and significant performance improvement. Description of the Drawings

[0052] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings. In the accompanying drawings:

[0053] Figure 1 is the process flow diagram of preparing the catalyst material based on the hydrothermal method in the present invention;

[0054] Figure 2 is the schematic diagram of an example of preparing the catalyst material based on the hydrothermal method according to Embodiment 1 of the present invention;

[0055] Figure 3 is the X-ray diffraction pattern of the catalyst material prepared in Embodiments 1-3 of the present invention;

[0056] Figure 4 is the schematic diagram showing the change of CH4 conversion rate of the catalyst material prepared in Embodiments 1-3 of the present invention with temperature. Specific implementation method

[0058] In order to enable those skilled in the art to better understand the technical solutions in this application, the following will clearly and completely describe the technical solutions in the embodiments of this application in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of this application.

[0059] According to an embodiment of the present invention, a method for preparing a catalyst material based on the hydrothermal method is provided.

[0060] Now, the present invention will be further described in conjunction with the accompanying drawings and specific implementation manners. As Figure 1-2 shown, the method for preparing a catalyst material based on the hydrothermal method according to an embodiment of the present invention includes the following steps:

[0061] S10. Dissolve a cerium salt and a transition metal salt in deionized water to obtain a precursor solution;

[0062] Specifically, it includes:

[0063] Add a cerium salt and a transition metal salt to deionized water, and stir until completely dissolved to obtain a precursor solution;

[0064] Among them, the transition metal salt includes a nickel salt or a mixture of a nickel salt and a zirconium salt;

[0065] When the transition metal salt is a nickel salt, the molar ratio of the cerium salt to the nickel salt is (75 - 90):(10 - 25);

[0066] When the transition metal salt is a mixture of a nickel salt and a zirconium salt, the molar ratio of the cerium salt to the nickel salt to the zirconium salt is (75 - 90):(10 - 25):(1 - 5);

[0067] The addition amount of the deionized water is 40 mL of deionized water added for every 0.01 mol of the total reactants;

[0068] The total reactants are a mixture of a cerium salt and a transition metal salt;

[0069] The cerium salt includes at least one of cerium nitrate, cerium chloride, cerium acetate, and cerium oxalate; the nickel salt includes at least one of nickel nitrate, nickel chloride, and nickel acetate; the zirconium salt includes at least one of zirconium nitrate, zirconium chloride, and zirconium acetate;

[0070] The stirring speed is 300 - 350 r / min;

[0071] S20. Use cetyltrimethylammonium bromide as a template agent and dissolve it in the precursor solution;

[0072] Specifically, it includes:

[0073] Add cetyltrimethylammonium bromide to the precursor solution and stir until it is completely dissolved;

[0074] Among them, the addition amount of cetyltrimethylammonium bromide is 0.1 g of cetyltrimethylammonium bromide added for every 0.01 mol of the total reactants;

[0075] The total reactants are a mixture of a cerium salt and a transition metal salt;

[0076] The stirring condition is to stir at a speed of 300 - 350 r / min for 1 - 2 h;

[0077] It should be noted that the addition amount of cetyltrimethylammonium bromide is 0.1 g of cetyltrimethylammonium bromide added for every 0.01 mol of the total reactants, and the total reactants are a mixture of a cerium salt and a transition metal salt; the stirring condition is to stir at a speed of 300 - 350 r / min for 1 - 2 h;

[0078] S30. Dropwise add ammonia water to the precursor solution until the pH value of the precursor solution is 8 - 9;

[0079] Specifically, at a stirring speed of 300 - 350 r / min, use a dropper to slowly add ammonia water to the precursor solution. After a period of time, a grayish-white precipitate is formed. Continue to add ammonia water, and the precipitate slowly dissolves, and the solution gradually turns milky blue. Subsequently, while measuring the pH of the solution with a pH meter, continue to fine-tune the pH with ammonia water until the pH of the precursor solution stabilizes at 8 - 9;

[0080] S40. Transfer the precursor solution with a pH value of 8 - 9 to a reaction kettle for high-temperature hydrothermal treatment;

[0081] Specifically include:

[0082] After continuously stirring the precursor solution with a pH value of 8 - 9 at a speed of 300 - 350 r / min for 1 - 2 h, transfer it to the PTFE inner liner of the reaction kettle, and the loading amount accounts for 3 / 4 - 4 / 5 of the volume of the PTFE inner liner. Then, place the PTFE inner liner into the stainless steel outer shell and put it in an oven for high-temperature hydrothermal treatment. The temperature of the high-temperature hydrothermal treatment is 160 °C, and the time of the high-temperature hydrothermal treatment is 12 h;

[0083] S50. After the mixture obtained after hydrothermal treatment is filtered, dried, and ground, perform high-temperature roasting treatment to obtain the roasted sample;

[0084] Specifically include:

[0085] S501. After the high-temperature hydrothermal treatment is completed, let the reaction kettle cool naturally to room temperature;

[0086] S502. Filter the mixture in the PTFE inner liner of the reaction kettle:

[0087] Lay the filter paper on the Buchner funnel and wet it with deionized water;

[0088] Press the Buchner funnel on the filter flask and connect the filter flask to a water-type vacuum pump;

[0089] Shake the PTFE inner liner well, then open the bottle cap and pour the mixture into the Buchner funnel for filtration;

[0090] Rinse the residue in the PTFE inner liner with deionized water, then pour it into the Buchner funnel and repeat twice;

[0091] S503. After drying and grinding the solid obtained by filtration, perform high-temperature roasting treatment. After the high-temperature roasting treatment is completed, cool it naturally to room temperature to obtain the roasted sample in the form of yellowish-black powder;

[0092] The conditions for drying are drying at 80 °C for 12 - 24 h; the conditions for roasting are maintaining at 550 °C for 3 h, and the heating rate is 3 °C / min;

[0093] S60. The calcined sample is reducted in stages with hydrogen to obtain a catalyst material;

[0094] Specifically, it includes the following steps:

[0095] S601. Pour the calcined sample into a quartz crucible;

[0096] S602. Place the quartz crucible into a tube furnace;

[0097] S603. Introduce hydrogen and argon into the tube furnace;

[0098] S604. Use the tube furnace to heat in stages to reduce the catalyst material;

[0099] S605. After the reduction is completed, stop introducing hydrogen and continue to introduce argon until it cools naturally to room temperature to obtain a black - gray catalyst material;

[0100] Among them, in the step S603, the total flow rate of hydrogen and argon introduced is 60000 mL / g cat -1 h -1 , and the volume concentration of hydrogen accounts for 10% of the total amount of hydrogen and argon;

[0101] In the step S604, using the tube furnace to heat in stages includes first heating from room temperature to 300 °C and holding for 1 h for pre - reduction, with a heating rate of 3 °C / min, and then continuing to heat to 450 °C at a heating rate of 3 °C / min and holding for 2 h.

[0102] Example 1:

[0103] S10. Add 0.015 mol of cerium nitrate hexahydrate (Ce(NO3)3·6H2O), 0.004 mol of nickel nitrate hexahydrate (Ni(NO3)2·6H2O), and 0.001 mol of zirconium nitrate pentahydrate (Zr(NO3)4·5H2O) into 80 mL of deionized water, and stir at a stirring speed of 350 r / min until completely dissolved to obtain a precursor solution;

[0104] S20. Add 0.2 g of cetyltrimethylammonium bromide into the precursor solution and stir for 2 h at a stirring speed of 350 r / min to fully dissolve the cetyltrimethylammonium bromide;

[0105] S30. Dropwise add ammonia water to the precursor solution until the pH value of the precursor solution is 9;

[0106] S301. Under a stirring speed of 350 r / min, dropwise add ammonia water to the precursor solution until a gray - white precipitate is formed in the solution;

[0107] S302. At a stirring speed of 350 r / min, continue to dropwise add ammonia water until the precipitate completely dissolves, obtaining a blue solution;

[0108] S303. At a stirring speed of 350 r / min, while continuing to dropwise add ammonia water, use a pH meter to measure the pH value of the solution. When the pH of the precursor solution stabilizes at 9, stop dropping ammonia water;

[0109] S40. After continuously stirring the precursor solution with a pH of 9 at a speed of 350 r / min for 1 h, transfer it to the polytetrafluoroethylene inner liner of a 100 mL reaction kettle. The loading amount of the precursor solution accounts for 4 / 5 of the volume of the polytetrafluoroethylene inner liner. Then, place the polytetrafluoroethylene inner liner into the stainless-steel outer shell and place it in an oven for high-temperature hydrothermal treatment. The temperature of the high-temperature hydrothermal treatment is 160 °C, and the time of the high-temperature hydrothermal treatment is 12 h;

[0110] S50. After filtering, drying, and grinding the mixture obtained after the hydrothermal treatment, perform high-temperature roasting treatment to obtain a roasted sample;

[0111] S501. After the high-temperature hydrothermal treatment is completed, naturally cool the reaction kettle to room temperature;

[0112] S502. Filter the mixture in the polytetrafluoroethylene inner liner of the reaction kettle;

[0113] Place a Buchner funnel with an inner diameter of 10 cm on a 500 mL filter flask. Connect the filter flask to a water-type vacuum pump using a rubber tube. Subsequently, place a filter paper with a diameter of 10 cm on the Buchner funnel and wet it with deionized water to make it fit tightly with the Buchner funnel;

[0114] Shake the polytetrafluoroethylene inner liner cooled to room temperature, pour it into the Buchner funnel with a glass rod for drainage, and turn on the water-type vacuum pump for suction filtration;

[0115] Rinse the residue in the polytetrafluoroethylene inner liner with deionized water, stir it with a glass cup, and pour it into the Buchner funnel. Repeat twice;

[0116] After suction filtration is completed, turn off the water-type vacuum pump. Put the filter paper together with the solid matter on the filter paper into a 200 mL beaker, and then place the beaker in an oven for drying. The drying temperature is 80 °C, and the drying time is 12 hours. Subsequently, naturally cool it to room temperature;

[0117] Pour the dried sample into an agate mortar for grinding. After sufficient grinding, pour it into a quartz crucible. Place the quartz crucible in a muffle furnace for roasting. Set the heating rate to 3 °C / min. Heat the sample from room temperature to 550 °C, and then naturally cool it to room temperature to obtain a roasted sample in the form of a yellowish-black powder;

[0118] S60. The calcined sample is reduced stepwise with hydrogen to obtain a catalyst material;

[0119] Put the calcined sample into a tubular furnace. After sealing, continuously introduce hydrogen and argon. The total flow rate of hydrogen and argon is 60000 mL / g cat -1 h -1 , the volume concentration of hydrogen accounts for 10% of the total amount of hydrogen and argon. After ventilating for 5 minutes to completely exhaust the air in the furnace, then open the tubular furnace for heating. The heating rate is 3 °C / min. After heating from room temperature to 300 °C, keep the temperature for 1 h for pre-reduction. Subsequently, continue to heat at a heating rate of 3 °C / min to 450 °C and keep the temperature for 2 h. After the insulation ends, stop introducing hydrogen and keep the argon flow rate unchanged, and let the sample cool naturally to room temperature to obtain a black-gray catalyst material;

[0120] This catalyst material is a high-performance porous methane catalytic oxidation catalyst material.

[0121] In view of the challenges from the material body and the preparation process, when using the hydrothermal method to synthesize the CeO2 catalyst (also known as the cerium-based catalyst) in the present invention, cetyltrimethylammonium bromide is used as a porous templating agent, and Ni and Zr elements are uniformly doped in the cerium-based catalyst, thereby preparing a porous catalyst with the synergistic effect of multiple elements. The catalyst material prepared by this method has excellent performance, high activity, and high porosity.

[0122] The morphology and structure of the catalyst affect the specific surface area, the dispersion of active components, and the density of active sites. The macropores in the material can efficiently transfer mass, while the mesopores can increase the specific surface area to improve the utilization efficiency of the catalyst.

[0123] In the Ce-Ni-Zr ternary catalyst system for catalytic methane oxidation, cerium (Ce), nickel (Ni), and zirconium (Zr) jointly optimize the catalytic performance through the complementary element characteristics and synergistic effect. Ce provides dynamic oxygen storage capacity in the form of CeO2, and its Ce 3+ / Ce 4+ redox cycle can store lattice oxygen under oxygen-rich conditions and release active oxygen species when oxygen is lacking, directly participating in the cleavage of the C-H bond of methane; Ni, as the core active site, weakens the C-H bond by interacting with methane molecules through d electron orbitals, and at the same time mediates the oxygen transfer process, transferring the lattice oxygen provided by CeO2 to the reaction interface to promote the deep oxidation of the intermediate product CO to CeO2; Zr constructs a high thermal stability framework in the form of ZrO2, and significantly increases the oxygen vacancy concentration by forming a Ce-Zr solid solution with CeO2 and inhibits high-temperature sintering. The synergistic effect of the three is reflected in three aspects: First, the Ce-Zr solid solution optimizes the electronic structure, Zr 4+Doping causes lattice distortion of CeO2, enhances the formation energy of oxygen vacancies, and at the same time makes the Ni species in a rich electron state by capturing electrons with oxygen vacancies, thus improving the methane adsorption capacity. Second, the mesopores of ZrO2 and the micropores of CeO2 construct a hierarchical pore structure, greatly increasing the methane diffusion rate and effectively alleviating the internal diffusion limitation. Third, the high dispersion of Ni nanoparticles on the Ce-Zr support and the strong metal-support interaction (SMSI) inhibit the sintering of the active components. In addition, the acidic sites on the surface of ZrO2 preferentially adsorb SO2, protecting the Ni active centers from poisoning. This dual structural-electronic synergistic design breaks through the contradiction of "high activity - low stability" in traditional catalysts, providing a reliable solution for the efficient purification of methane in industrial waste gases and mobile source tail gases.

[0124] Example 2:

[0125] Without doping with Zr element, a Ce-Ni catalyst with a Ce:Ni (molar ratio) of 90:10 was prepared, and the synthesis steps were the same as those in Example 1.

[0126] Example 3:

[0127] Without doping with Zr element, a Ce-Ni catalyst with a Ce:Ni (molar ratio) of 80:20 was prepared, and the synthesis steps were the same as those in Example 1.

[0128] Test Example:

[0129] The catalyst materials prepared in Examples 1-3 were tested, specifically as follows:

[0130] (1) Using a fully automatic specific surface area analyzer (model: ASAP2020HD88), the morphology of the catalyst materials prepared in Examples 1-3 was measured, and the measurement results are shown in Table 1.

[0131] Table 1

[0132] Test sample <![CDATA[Specific surface area (m 2 / g)]]> Average pore size (nm) Example 1 105.23 7.68 Example 2 96.95 9.57 Example 3 73.81 11.14

[0133] As can be seen from Table 1, the catalyst materials prepared by the present invention have the characteristics of large specific surface area and small average pore size. Their pore sizes conform to the typical characteristics of mesoporous materials. As methane catalytic oxidation catalyst materials, they have good mass transfer ability and accessibility of catalytic active sites, and high catalytic activity.

[0134] (2) Using a polycrystalline X-ray diffractometer (TTR III type), the crystal structures of the catalyst materials prepared in Examples 1-3 were observed, and the measured X-ray diffraction patterns are as Figure 3 shown. According to Figure 3It can be seen that only the cubic fluorite phase of CeO2 exists in Ce90Ni10, indicating that all Ni elements have entered the CeO2 lattice and formed a solid solution with it; Ni elemental phases also exist in Ce80Ni20 and Ce75Ni20Zr5, indicating that CeO2 has reached the solid solubility limit for Ni, and the excess Ni elements form metallic nickel after hydrogen reduction and serve as additional active sites for methane oxidation; in addition, the cubic fluorite phase of CeO2 in Ce75Ni20Zr5 shifts towards a higher angle, indicating that the successful entry of Zr into the CeO2 lattice leads to lattice distortion, which also generates more oxygen vacancies to promote the oxidation reaction.

[0135] (3) Using a fixed-bed reactor, the activities of the catalyst materials prepared in Examples 1-3 were observed and measured, and the measurement results are as Figure 4 shown. According to Figure 4 it can be seen that the catalytic activities of the catalyst materials prepared in this invention have all reached the advanced level of non-noble metal oxide catalysts. The activity of the catalyst increases with the doping amount of Ni. In addition, the small amount of doping of Zr provides a large number of oxygen vacancies, which also makes the catalytic activity of Ce75Ni20Zr5 the highest, and T90 reaches 425 °C, with remarkable effects.

[0136] In summary, by means of the above technical solutions of this invention, this invention uses the synergistic effect of multiple elements and cetyltrimethylammonium bromide as a porous template agent, synthesizes a cerium-based methane catalytic oxidation catalyst material by hydrothermal method, and reduces the possible nickel oxide generated during the hydrothermal process with hydrogen and the calcination process, significantly improving the specific surface area and active sites of the catalytic material, thereby improving the activity of the catalyst, solving the problems of low specific surface area and insufficient catalytic activity of the methane catalytic oxidation catalyst material, and showing remarkable technical effects in terms of increasing active sites, enhancing adsorption effect, future application prospects and significant performance improvement.

[0137] Among them, the increase in active sites: compared with the prior art, the specific surface area of this invention is significantly improved, increasing the active sites on the catalyst surface, thereby improving the catalytic activity of the catalyst;

[0138] Enhanced adsorption effect: The three elements produce a synergistic effect, greatly improving the adsorption capacity of the catalyst surface;

[0139] Future application prospects: This invention has broad application prospects and is a significant improvement in the performance of non-noble metal catalysts. Especially in the field of exhaust gas post-treatment, it greatly improves the efficiency of methane catalytic oxidation and plays an important role in reducing the greenhouse effect.

[0140] The specific embodiments described above further elaborate on the object, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only for the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a catalyst material by hydrothermal method, characterized in that, It includes the following steps: S10. Dissolve a cerium salt and a transition metal salt in deionized water to obtain a precursor solution; Among them, the transition metal salt includes a nickel salt or a mixture of a nickel salt and a zirconium salt; S20. Dissolve cetyltrimethylammonium bromide as a template agent in the precursor solution; S30. Dropwise add ammonia water to the precursor solution until the pH value of the precursor solution is 8 - 9; S40. Transfer the precursor solution with a pH value of 8 - 9 to a reaction kettle for high-temperature hydrothermal treatment; S50. After the hydrothermal treatment is completed, the obtained mixture is filtered, dried, ground, and then subjected to high-temperature calcination treatment to obtain a calcined sample; S60. Segmentally reduce the calcined sample with hydrogen to obtain a catalyst material.

2. The method for preparing a catalyst material based on the hydrothermal method according to claim 1, characterized in that, In the above S10: When the transition metal salt is a nickel salt, the molar ratio of the cerium salt to the nickel salt is (75 - 90):(10 - 25); When the transition metal salt is a mixture of a nickel salt and a zirconium salt, the molar ratio of the cerium salt to the nickel salt to the zirconium salt is (75 - 90):(10 - 25):(1 - 5).

3. The method for preparing a catalyst material based on the hydrothermal method according to claim 2, characterized in that, The cerium salt includes at least one of cerium nitrate, cerium chloride, cerium acetate, and cerium oxalate; the nickel salt includes at least one of nickel nitrate, nickel chloride, and nickel acetate; the zirconium salt includes at least one of zirconium nitrate, zirconium chloride, and zirconium acetate.

4. A method for preparing a catalyst material based on the hydrothermal method according to claim 1, characterized in that, The above S10 specifically includes: Add the cerium salt and the transition metal salt to deionized water, and stir until completely dissolved to obtain a precursor solution; Among them, the addition amount of the deionized water is 40 mL of deionized water added for every 0.01 mol of the total reactants; The total reactants are a mixture of a cerium salt and a transition metal salt; The stirring speed is 300 - 350 r / min.

5. A method for preparing a catalyst material based on the hydrothermal method according to claim 1, characterized in that, The above S20 specifically includes: Add cetyltrimethylammonium bromide to the precursor solution and stir until completely dissolved; Among them, the addition amount of the cetyltrimethylammonium bromide is 0.1 g of cetyltrimethylammonium bromide added for every 0.01 mol of the total reactants; The total reactants are a mixture of a cerium salt and a transition metal salt; The stirring condition is to stir at a speed of 300 - 350 r / min for 1 - 2 h.

6. A method for preparing a catalyst material based on the hydrothermal method according to claim 1, characterized in that, The above S30 specifically includes: S301. Under stirring, dropwise add ammonia water to the precursor solution until a precipitate is formed; S302. Under stirring, continue to dropwise add ammonia water to the precursor solution until the precipitate is completely dissolved; S303. Under stirring, continue to dropwise add ammonia water to the precursor solution until the pH value of the precursor solution is 8 - 9; The stirring speeds in S301, S302, and S303 are the same, all being 300 - 350 r / min.

7. A method for preparing a catalyst material based on the hydrothermal method according to claim 1, characterized in that, The above S40 specifically includes: After continuously stirring the precursor solution with a pH value of 8 - 9, transfer it to the polytetrafluoroethylene inner liner of the reaction kettle, then place the polytetrafluoroethylene inner liner into the stainless steel outer shell, and place it in an oven for high-temperature hydrothermal treatment; Among them, the conditions for continuous stirring are stirring at a speed of 300 - 350 r / min for 1 - 2 h; the loading amount of the precursor solution is 3 / 4 - 4 / 5 of the volume of the polytetrafluoroethylene inner liner; the temperature of the hydrothermal treatment is 160 °C, and the time of the hydrothermal treatment is 12 h.

8. A method for preparing a catalyst material based on the hydrothermal method according to claim 1, characterized in that, The said S50 specifically includes: S501. After the hydrothermal treatment is completed, naturally cool the reaction kettle to room temperature. S502. Filter the mixture in the polytetrafluoroethylene inner liner of the reaction kettle. S503. After drying and grinding the obtained solid, conduct high-temperature calcination treatment. After the high-temperature calcination treatment is completed, naturally cool to room temperature to obtain the calcined sample.

9. A method for preparing a catalyst material based on the hydrothermal method according to claim 8, characterized in that, The conditions for drying are drying at 80 °C for 12 - 24 h; the conditions for calcination are holding at 550 °C for 3 h, and the heating rate is 3 °C / min.

10. A method for preparing a catalyst material based on the hydrothermal method according to claim 1, characterized in that, The said S60 specifically includes: S601. Pour the calcined sample into a quartz crucible. S602. Place the quartz crucible into a tube furnace. S603. Introduce hydrogen and argon into the tube furnace. S604. Use the tube furnace for segmented heating to reduce the catalyst material. S605. After the reduction is completed, stop introducing hydrogen and continue to introduce argon until it naturally cools to room temperature to obtain the catalyst material. Among them, in the step S603, the total flow rate of hydrogen and argon introduced is 60000 mL / g cat -1 h -1 , and the volume concentration of hydrogen accounts for 10% of the total amount of hydrogen and argon; In the said S604, using the tube furnace for segmented heating includes first heating from room temperature to 300 °C and holding for 1 h for pre-reduction, with a heating rate of 3 °C / min, and then continuing to heat at a heating rate of 3 °C / min to 450 °C and holding for 2 h.

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