MnO2-loaded ultralow-quantity monatomic Cu catalyst as well as preparation method and application of MnO2-loaded ultralow-quantity monatomic Cu catalyst

Abstract

The invention discloses a MnO2 loaded ultralow-quantity monatomic Cu catalyst as well as a preparation method and application thereof, and belongs to the technical field of green chemical catalysis and new material preparation. The preparation method of the MnO2 loaded ultralow-quantity monatomic Cu catalyst comprises the following steps: uniformly mixing manganous nitrate, urea, citric acid and distilled water to obtain a mixed solution 1; adding a potassium permanganate solution into the mixed solution 1 for reaction to obtain a mixed solution 2; adjusting the pH value of the mixed solution 2, then adding a copper source, uniformly stirring, carrying out hydrothermal reaction, and then sequentially centrifuging, washing, drying and calcining to obtain the Cu / MnO2 catalyst, the Cu / MnO2 is subjected to pretreatment under the H2 atmosphere, and the MnO2 loaded ultra-low-quantity monatomic Cu catalyst is obtained; the catalyst prepared by the method disclosed by the invention can be used for CO low-temperature oxidation sulfur-resistant reaction, so that the reaction can work for a long time in a sulfur-containing atmosphere, and the performance of the reaction is kept for 35 hours and is not reduced, thereby providing reference for further research on the sulfur-resistant performance of an ultra-low-loading catalyst.

Description

Technical Field

[0001] The present invention belongs to the technical fields of green chemical catalysis and new material preparation, and particularly relates to a MnO2-supported ultra-low amount of single-atom Cu catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] CO is a colorless and odorless toxic gas that can stably exist in the environment for a long time and is extremely harmful to the environment and human health. Currently, the steel industry is one of the main sources of CO emissions, and its emission sources mainly come from the incomplete combustion of coke fuel in the steel sintering process. Due to the issuance of national environmental protection policies, it has become particularly important to control CO emissions in the steel industry.

[0003] According to statistics, the flue gas at the head of the sintering machine not only contains CO gas with a relatively high concentration (10000mg / m 3 ), but also contains a small amount of SO2 gas. Even after desulfurization treatment in the later stage, there is still 10 - 35mg / m 3 of SO2. Due to the electrophilicity of SO2 gas, it is easy to adsorb on active metal sites, resulting in a reduction of surface active sites and ultimately catalyst deactivation. The presence of SO2 poses a severe challenge to the sulfur tolerance of CO catalytic oxidation catalysts.

[0004] Currently, many patents on catalysts for low-temperature sulfur resistance of CO have been reported at home and abroad. For example, CN119281325A discloses a composite metal oxide catalyst with noble metal Pd as the active component for high sulfur resistance in low-temperature CO oxidation, but the use of the active component Pd is expensive and not convenient for widespread use, and the loading amount is high and the atomic utilization rate is low. CN117085678A discloses a monolithic catalyst for medium and low-temperature water and sulfur-resistant CO oxidation, but its preparation process is complex and the performance is greatly affected by toxic atmospheres. CN119114094A discloses a highly efficient sulfur and water-resistant Cu-OMS type catalyst for CO oxidation, but it has high energy consumption and poor stability.

[0005] Although certain achievements have been made in the research on sulfur resistance performance of existing catalysts, the reaction temperature is high, the stability is poor, and the achievements are not significant. Moreover, precious metals are mostly used in material selection and the loading amount is relatively high, which is not conducive to the widespread application of catalysts.

[0006] Based on the existence of the above problems, the present invention proposes a preparation method of a MnO2-supported ultra-low amount of single-atom Cu catalyst and its application in low-temperature CO oxidation and sulfur resistance. Summary of the Invention

[0007] In view of the above technical problems, the present invention proposes a MnO2-supported ultra-low amount of single-atom Cu catalyst, a preparation method thereof, and an application thereof.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] One of the technical solutions of the present invention:

[0010] A preparation method of an MnO₂-supported ultra-low amount of single-atom Cu catalyst, comprising the following steps:

[0011] Mix 50 wt.% manganese nitrate solution, urea, citric acid and distilled water evenly to obtain mixture 1;

[0012] Add potassium permanganate solution to the mixture 1 for reaction to obtain mixture 2;

[0013] Adjust the pH of the mixture 2, then add a copper source, stir evenly, carry out hydrothermal reaction, and then carry out centrifugation, washing, drying and calcination in sequence to obtain a Cu / MnO₂ catalyst;

[0014] Pretreat the Cu / MnO₂ in a H₂ atmosphere (in this atmosphere, hydrogen is 10 vol.% + helium is 90 vol.%, and the same applies to the following hydrogen pretreatment) to obtain an MnO₂-supported ultra-low amount of single-atom Cu catalyst.

[0015] Optionally, in the mixture 1, based on MnO₂, the molar ratio of manganese nitrate, urea, citric acid and distilled water in the 50% manganese nitrate solution is (1 - 10):5:5:2500.

[0016] Optionally, the mass concentration of the potassium permanganate solution is 40%; the potassium permanganate solution is obtained by dissolving potassium permanganate in UP water (ultrapure water).

[0017] Optionally, based on MnO₂, the molar ratio of potassium permanganate in the potassium permanganate solution to manganese nitrate in the mixture 1 is (0.8 - 1):1.

[0018] Optionally, the pH = 8 - 10, which is adjusted by 25 wt.% ammonia water.

[0019] Optionally, the copper source is copper nitrate trihydrate.

[0020] Further, based on Cu, the molar ratio of copper nitrate trihydrate to the sum of manganese nitrate and potassium permanganate in the mixture 1 is (0 - 0.001):1, where the dosage of copper nitrate trihydrate is not zero.

[0021] Optionally, the conditions in the hydrothermal reaction process are: reacting at 200 °C for 20 - 24 h; and / or,

[0022] The conditions during the calcination process are as follows: calcination is carried out at 380 °C for 4 h in flowing air at 20 ml / min.

[0023] Optionally, the pretreatment process is as follows: treatment is carried out for 60 min under the conditions of a hydrogen atmosphere and a temperature of 300 - 400 °C.

[0024] The second technical solution of the present invention:

[0025] A MnO₂-supported ultra-low amount of single-atom Cu catalyst is prepared by the above preparation method; the copper loading in the MnO₂-supported ultra-low amount of single-atom Cu catalyst is 0 - 0.1%, where the loading is not 0. That is, the amount of substance of copper in the catalyst is 0 - 0.1% of that of manganese.

[0026] The third technical solution of the present invention:

[0027] Application of the MnO₂-supported ultra-low amount of single-atom Cu catalyst in the fields of anti-sulfur CO low-temperature oxidation, water-gas shift reaction, and preferential oxidation of CO under hydrogen-rich conditions.

[0028] Optionally, in the field of anti-sulfur CO low-temperature oxidation, for each unit of the MnO₂-supported ultra-low amount of single-atom Cu catalyst, the SO₂ concentration in the feed can be 0 - 1000 ppm / g cat , and the reaction temperature is 60 - 200 °C.

[0029] Optionally, in the field of anti-sulfur CO low-temperature oxidation, the volume ratio of O₂ to CO in the anti-sulfur CO low-temperature oxidation is 1:1.

[0030] Compared with the prior art, the present invention has the following advantages and technical effects:

[0031] (1) The Cu / One-Mn catalyst prepared by the method of the present invention can greatly reduce the sensitivity to oxygen during the reaction process. Compared with ordinary syngas, the volume ratio of O₂ to CO in the present invention is only 1:1, thereby improving the reaction activity and solving the problem that the catalyst activity depends on the O₂ concentration.

[0032] (2) The 0.1Cu / One-Mn catalyst prepared in Example 1 of the present invention solves the problem that sulfur species deposit on the catalyst surface during the CO low-temperature oxidation process, resulting in catalyst deactivation; for example, the 0.1Cu / IM-Mn catalyst obtained by the ordinary method (impregnation method) in Comparative Example 1 has a low conversion rate (the conversion rate of the 0.1Cu / IM-Mn catalyst at 120 °C is only 42%), and the reaction stability is very unsatisfactory (the stability is less than 25 h under the same reaction conditions), while the catalyst 0.1Cu / One-Mn prepared in Example 1 of the present invention not only has an optimal single-pass conversion rate greater than 60% at 120 °C, but also the catalytic stability time can reach 35 h, having excellent stability.

[0033] (3) The synthesis process of the 0.1Cu / One-Mn catalyst prepared by the method of the present invention is simple; meanwhile, the addition of a small amount of Cu in the catalyst prepared by the present invention promotes the reduction of Mn-O at low temperatures.

[0034] (4) The 0.1Cu / One-Mn catalyst prepared by the method of the present invention has more defects on the surface of the carrier ( Figure 2 ), which enables single-atom Cu to be well fixed on the defects of the carrier when introduced, improving the dispersion of the metal. Compared with the traditional 0.1Cu / IM-Mn catalyst (Comparative Example 1), the active sites of the 0.1Cu / One-Mn catalyst synthesized by the method of the present invention are not easily agglomerated and are more stable.

[0035] (5) Compared with the synthesis by the traditional impregnation method, the steps of synthesizing the catalyst by the method of the present invention are simple and the number of synthesis steps is small, which can be mass-produced. At the same time, the catalyst regeneration is simple, only requiring calcination in hydrogen at 400 °C for 5 h (as Figure 4 shown), and it is suitable for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0037] Figure 1 is a graph showing the results of the stability test of the 0.1Cu / One-Mn catalyst prepared in Example 1 of the present invention and the 0.1Cu / IM-Mn prepared in Comparative Example 1 in a mixed gas environment containing 50 ppm sulfur dioxide;

[0038] Figure 2 is the O2-TPD spectrum of the 0.1Cu / One-Mn catalyst prepared in Example 1 of the present invention and the catalysts prepared in Comparative Example 1 and Comparative Example 2;

[0039] Figure 3 is the H2-TPD spectrum of the 0.1Cu / One-Mn catalyst prepared in Example 1 of the present invention and the catalyst prepared in Comparative Example 1;

[0040] Figure 4 is the regeneration experiment of the 0.1Cu / One-Mn catalyst prepared in Example 1 of the present invention;

[0041] Figure 5 is the application of the 0.1Cu / One-Mn catalyst prepared in Example 1 of the present invention to the reverse water-gas shift reaction;

[0042] Figure 6The 0.1Cu / One-Mn catalyst prepared in Example 1 of the present invention was applied to the preferential oxidation reaction of CO under hydrogen-rich conditions. Detailed implementation manners

[0043] The various exemplary implementation manners of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0044] It should be understood that the terms used in the present invention are only for describing specific implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0045] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0046] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific implementation manners of the present invention specification, which are obvious to those skilled in the art. Other implementation manners obtained from the present invention specification are obvious to those skilled in the art. The present invention specification and examples are only exemplary.

[0047] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0048] In order to overcome the problems of low sulfur resistance and easy deactivation of commercial catalysts in the process of low-temperature oxidation of CO, the present invention discloses a MnO2-supported ultra-low amount of single-atom Cu catalyst, its preparation method, and its application in low-temperature oxidation and sulfur resistance. This catalyst can enable the reaction to work for a long time at a high SO2 concentration (50 ppm), and the deactivation rate of CO is less than 10%, and the stability is greater than 35 h. Specifically:

[0049] A preparation method of a MnO2-supported ultra-low amount of single-atom Cu catalyst, comprising the following steps:

[0050] (1) Dissolve 50% manganese nitrate solution, urea, and citric acid in distilled water respectively and then mix them one by one. After sufficient ultrasonic treatment, a mixed solution is obtained;

[0051] (2) Let the mixed solution stand, and then add potassium permanganate solution thereto, and carry out a stirring reaction;

[0052] (3) Adjust the pH of the reacted solution, then add copper nitrate trihydrate thereto, transfer the mixed solution into a reaction kettle lined with polytetrafluoroethylene for reaction, and carry out centrifugal separation to obtain a solid product. Wash and dry the solid product and then calcine it to obtain a Cu / MnO2 catalyst;

[0053] (4) Pretreat the Cu / MnO2 catalyst with hydrogen to obtain a non-noble metal single-atom Cu-loaded Mn-based catalyst Cu / One-Mn with an ultra-low loading amount.

[0054] In some alternative embodiments, based on MnO2, the molar ratio of the 50% manganese nitrate solution, urea, citric acid, and distilled water is (1 - 10):5:5:2500.

[0055] In some alternative embodiments, based on MnO2, the addition amount of potassium permanganate in the potassium permanganate solution is 80 - 100% of the amount of Mn in the mixed solution in step (1), preferably 90%.

[0056] In some alternative embodiments, in step (3), 25% ammonia water is added to adjust the pH to 8 - 10.

[0057] In some alternative embodiments, based on Cu, the dosage of copper nitrate trihydrate is 0 - 0.1% of the amount of Mn (the total amount of Mn in manganese nitrate and potassium permanganate), and the dosage of copper nitrate trihydrate is not 0. The purpose is to insert single-site Cu into the unsaturated Mn-O sites to further regulate the local microenvironment of the Mn-O sites.

[0058] In some alternative embodiments, the mixed solution is carried out under static conditions and autogenous pressure in a stainless steel autoclave lined with polytetrafluoroethylene. The crystallization temperature is 200°C and the time is 20 - 24 h.

[0059] In some alternative embodiments, the washing process is carried out using distilled water and absolute ethanol, and absolute ethanol is washed at least 5 times.

[0060] In some alternative embodiments, the drying process is as follows: in flowing air at 20 mL / min, the drying temperature is 100°C and overnight.

[0061] In some alternative embodiments, the calcination process is as follows: in flowing air at 20 mL / min, the calcination temperature is 380°C and the time is 4 h.

[0062] In some alternative embodiments, the specific pre-treatment operation is as follows: treatment is carried out using H2, the temperature does not exceed 400 °C, the time is 60 min, preferably 400 °C.

[0063] In some alternative embodiments, the method for preparing a non-noble metal single-atom Cu-loaded Mn-based catalyst with an ultra-low loading amount of the present invention includes the following steps:

[0064] Using 50 wt.% manganese nitrate solution (Mn(NO3)2), urea (CH4N2O), citric acid (C6H8O7) and distilled water as starting materials, taking the 50% manganese nitrate solution based on MnO2, the above raw materials are dissolved in appropriate amounts of distilled water according to a molar ratio of (1-10):5:5:2500, and a clear precursor solution is obtained after mixing. Subsequently, ultrasonic treatment is carried out at room temperature for 1 h to obtain a uniformly mixed solution denoted as mixed solution 1. Then, a potassium permanganate solution is added dropwise to the above mixed solution 1 at room temperature, and after sufficient stirring, a mixed solution 2 is obtained;

[0065] The pH of the above mixed solution 2 is adjusted to 8-10 with 25% aqueous ammonia solution to obtain a mixed solution 3, and stirring is carried out for 12 h; subsequently, copper nitrate trihydrate (Cu(NO3)2·3H2O) is added to obtain a mixed solution 4 (the addition amount of copper nitrate trihydrate is 0.1% of the molar amount of Mn), and stirring is carried out for 2 h; then, it is placed in a stainless steel autoclave with a polytetrafluoroethylene lining and crystallized at 200 °C for 22 h. The solid product obtained by centrifugal separation is washed several times with distilled water and then washed 5 times with absolute ethanol, dried overnight at 100 °C, and calcined at 380 °C in flowing air for 4 h to obtain a 0.1Cu / MnO2 catalyst.

[0066] The 0.1Cu / MnO2 catalyst is pre-treated in an H2 atmosphere at a temperature not exceeding 400 °C for 60 min to obtain the ultra-low loading amount of non-noble metal single-atom Cu-loaded Mn-based catalyst 0.1Cu / One-Mn.

[0067] The embodiment of the present invention discloses an ultra-low loading amount of non-noble metal single-atom Cu-loaded Mn-based catalyst (0.1Cu / One-Mn) prepared by the above preparation method. The 0.1Cu / One-Mn catalyst can achieve efficient sulfur resistance at a low temperature of only 120 °C.

[0068] In addition, the present invention also discloses the application of the above 0.1Cu / One-Mn catalyst in the sulfur resistance of low-temperature catalytic CO oxidation. And the above 0.1Cu / One-Mn catalyst can also be applied to catalytic water-gas shift reaction (as Figure 5 shown) and preferential oxidation reaction of CO under hydrogen-rich conditions (as Figure 6 shown).

[0069] In summary, the 0.1Cu / One-Mn catalyst prepared in this invention is not only applicable to the sulfur dioxide-resistant reaction of CO oxidation at low temperatures, but can also be applied to the CO preferential oxidation reaction and the water-gas shift reaction under hydrogen-rich conditions. Specifically, the present invention further improves the catalyst's CO oxidation performance by constructing a defect-rich support with oxygen vacancies. Secondly, the 0.1Cu / One-Mn catalyst synthesized via a one-step method increases the metal-support interaction, thereby suppressing carbon and sulfur accumulation on the catalyst during the reaction, thereby improving the single-pass conversion rate and stability of the reaction.

[0070] Unless otherwise specified, the "room temperature" in the present invention refers to 20-30°C.

[0071] All raw materials used in this invention were commercially available. The CO+O₂ mixture used in the examples was purchased from Dalian Date Gas Co., Ltd. with a purity greater than 99%. High-purity helium was purchased from Kunming Guangruida Gas Co., Ltd. with a purity greater than 99.999%. Copper nitrate trihydrate, urea, and other raw materials were purchased from Shanghai Macklin Co., Ltd. The CO conversion rate in the examples was measured using gas chromatography at a column temperature of 100°C and a TCD detector with an injection volume of 0.5 μL.

[0072] The technical solution of the present invention is further illustrated by the following examples.

[0073] Example 1

[0074] A method for preparing a MnO2-loaded ultra-low-amount single-atom Cu catalyst comprises the following steps:

[0075] (1) Using a 50% manganese nitrate solution, urea, citric acid, and distilled water as starting materials, the 50% manganese nitrate solution is calculated as MnO2, and the molar ratio of the above raw materials is 8:5:5:2500, which are dissolved in distilled water and then mixed to obtain a clear precursor solution, and then ultrasonicated at room temperature for 1 hour to obtain a uniform mixed solution 1;

[0076] (2) adding potassium permanganate solution (potassium permanganate solution is prepared by dissolving potassium permanganate in UP water, wherein the amount of potassium permanganate added is the same as the amount of Mn in the mixed solution 1) dropwise to the mixed solution 1 at room temperature, and stirring vigorously to obtain a mixed solution 2;

[0077] (3) 25% aqueous ammonia solution was added to the mixed solution 2 to adjust the pH of the mixed solution to 8, obtaining mixed solution 3, and the mixed solution 3 was stirred for 12 h; subsequently, copper nitrate trihydrate was added to the mixed solution 3, and the addition amount of copper nitrate trihydrate was 0.1% of the amount of substance of Mn (manganese nitrate + potassium permanganate), obtaining mixed solution 4, and it was stirred for 2 h; then the mixed solution 4 was placed in a stainless-steel autoclave with a polytetrafluoroethylene lining and crystallized at 200 °C under static conditions and autogenous pressure for 22 h. The solid product obtained by centrifugal separation was washed several times with distilled water and then washed 5 times with absolute ethanol, dried overnight at 100 °C, and calcined at 380 °C in flowing air for 4 h to obtain 0.1Cu / Mn catalyst;

[0078] (4) The 0.1Cu / Mn prepared above was taken and loaded into a fixed bed, and pretreated at 400 °C for 60 min in an H2 atmosphere (in this atmosphere, hydrogen 10 vol.% + helium 90 vol.%) to obtain 0.1Cu / One-Mn catalyst.

[0079] Comparative Example 1

[0080] The 0.1Cu / IM-Mn catalyst synthesized by the impregnation method instead of the above one-step method was used. The specific steps were as follows:

[0081] Steps (1) and (2) were the same as those in Example 1;

[0082] (3) 25% aqueous ammonia solution was added to the mixed solution 2 to adjust the pH of the mixed solution to 8, obtaining mixed solution 3, and the mixed solution 3 was stirred for 12 h; then the mixed solution was placed in a stainless-steel autoclave with a polytetrafluoroethylene lining and crystallized at 200 °C under static conditions and autogenous pressure for 22 h. The solid product obtained by centrifugal separation was washed several times with distilled water and then washed 5 times with absolute ethanol, dried overnight at 100 °C, and calcined at 380 °C in flowing air for 4 h to obtain manganese dioxide support;

[0083] (4) According to the content of Cu in the one-step method in Example 1, the relative content of Cu in the impregnation method was determined to be 0.1%. That is, 0.004 g of Cu(NO3)2·3H2O was taken in a 100 mL crucible and 1.5 mL of deionized water was added and fully dissolved. Then 1 g of MnO2 support was added to the crucible and stirred for 20 min; after standing overnight, it was dried at 100 °C for 24 h, and then calcined at 380 °C for 4 h;

[0084] (5) The same as step (4) of Example 1, and finally the catalyst 0.1Cu / IM-Mn was prepared and used in the CO low-temperature oxidation anti-sulfur dioxide reaction.

[0085] Comparative Example 2

[0086] The difference from Example 1 is that copper nitrate trihydrate is not added in step (3), and the other preparation processes and conditions are the same as those in Example 1, obtaining the MnO2 support.

[0087] Comparative Example 3

[0088] Commercial MnO2 was used to synthesize 0.1Cu / C-Mn catalyst;

[0089] The specific preparation process is as follows:

[0090] Taking the directly purchased commercial catalyst MnO2 as the support, 0.1Cu / C-Mn catalyst was prepared by the impregnation method, and the steps were the same as steps (4) and (5) in Comparative Example 1.

[0091] Comparative Example 4

[0092] The difference from Example 1 is that

[0093] The calcination temperature in step (3) was 550 °C, and calcined for 4 hours to obtain 0.1Cu / Mn-550 catalyst;

[0094] In step (4), take the 0.1Cu / Mn-550 prepared above, load it into a fixed bed, and pretreat it with H2 at 400 °C for 60 min to obtain 0.1Cu / One-Mn-550 catalyst.

[0095] Effect verification

[0096] Effect Example 1

[0097] The 0.1Cu / One-Mn catalyst prepared in Example 1 and the catalysts prepared in Comparative Examples 1-4 (the addition amount of the catalyst was 50 mg) were used in the low-temperature oxidation of CO against sulfur dioxide reaction, the O2 content was 1 vol%, the CO content was 1 vol%, the feed space velocity of CO was 36000 mL g cat -1 h -1 , and the sulfur dioxide content was 50 ppm.

[0098] The catalytic activity test was sampled after maintaining for 40 min at the set temperature, the sampling interval was 20 °C, and the heating rate was 5 °C / min. Among them, the calculation formula for the conversion rate of carbon monoxide is:

[0099]

[0100] In the formula, [CO] in is the amount of CO entering the system, [CO] out is the amount of CO leaving the system. Table 1 shows the CO conversion rates of different catalysts at different initial temperatures.

[0101] Table 1 CO conversion rates of different catalysts at different initial temperatures

[0102]

[0103] As can be seen from Table 1, for the 0.1Cu / One-Mn catalyst prepared in Example 1, the initial CO conversion rate at a low temperature of 60 °C is 11%, and when the temperature reaches 120 °C, the conversion rate is greater than 60%. And at this temperature, the reaction stability can remain inactive within 35 h; when the temperature reaches 140 °C, the conversion rate is about 85%. At this reaction temperature, the reaction stability of the catalyst does not show inactivation within 35 h; for the catalyst prepared in Comparative Example 1, the CO conversion rate is only about 42% at the initial temperature of 120 °C. After continuous operation for 35 h, the CO conversion rate has completely inactivated; at the initial temperature of 140 °C, the CO conversion rate is about 71%. After continuous operation for 35 h, the CO conversion rate has completely inactivated; at 180 °C, there is no conversion rate; for the catalyst prepared in Comparative Example 2, the CO conversion rate is only about 41% at the initial temperature of 120 °C. After continuous operation for 35 h, the CO conversion rate has completely inactivated; at the initial temperature of 140 °C, the CO conversion rate is about 70%. After continuous operation for 35 h, the CO conversion rate has completely inactivated; at 180 °C, there is almost no conversion rate; the 0.1Cu / C-Mn catalyst prepared in Comparative Example 3 cannot catalyze the carbon monoxide reaction at low temperatures; for the catalyst prepared in Comparative Example 4, the initial CO conversion rate at 60 °C is only 2%, and even when the temperature reaches 180 °C, the conversion rate is still only about 10%.

[0104] Figure 1 This is the graph of the stability test results of the 0.1Cu / One-Mn catalyst prepared in Example 1 of the present invention and the 0.1Cu / IM-Mn prepared in Comparative Example 1 in a mixed gas environment containing 50 ppm of sulfur dioxide; as can be seen from the graph, under the reaction conditions of 1% CO + 1% O2 + 50 ppm SO2, the balance gas is He, the flow rate is 60 mL / min, and at 120 °C, the conversion rate of the 0.1Cu / One-Mn catalyst prepared in Example 1 still remains at about 60% after continuous operation for 35 h, while for the 0.1Cu / IM-Mn prepared in Comparative Example 1, under these conditions, the CO conversion rate gradually decreases until inactivation. That is, the 0.1Cu / One-Mn catalyst prepared in Example 1 of the present invention has excellent stability and a lower oxidation temperature.

[0105] Figure 2O2-TPD spectra of the 0.1Cu / One-Mn catalyst prepared in Example 1, Comparative Examples 1, and 2. The 0.1Cu / One-Mn catalyst exhibits a higher lattice oxygen content at medium temperatures, indicating that the difference in activity between the materials is due to lattice oxygen. The low-temperature peak is attributed to surface oxygen adsorbed by oxygen vacancies. The 0.1Cu / One-Mn catalyst clearly contains more oxygen vacancies, which can act as defective metal atoms.

[0106] Figure 3 The H2-TPD spectra of the 0.1Cu / One-Mn catalyst prepared in Example 1 of the present invention and the catalyst prepared in Comparative Example 1 are shown; by comparison, it is found that the catalyst 0.1Cu / IM-MnO2 prepared by the impregnation method has poor interaction force at low temperatures compared with the 0.1Cu / One-Mn catalyst.

[0107] Effect Example 2 (Regeneration Test)

[0108] A regeneration test was conducted. The 0.1Cu / One-Mn catalyst after catalytic reaction was calcined at 400℃ for 5h in H2 atmosphere for regeneration. The catalytic reaction conditions were: 1% CO + 1% O2 + 50ppm SO2, with He as the balance gas, a flow rate of 60mL / min, and a CO feed space velocity of 36000mL g cat -1 h -1 , the temperature during the reaction for 50 hours was 120°C.

[0109] Figure 4 This is a regeneration experiment of the 0.1Cu / One-Mn catalyst prepared in Example 1 of the present invention. After the introduction of SO2 for 50 hours, slight deactivation occurred. At this time, the catalyst was treated under H2 atmosphere and the activity of the catalyst was restored.

[0110] Effect Example 3

[0111] Water gas shift reaction conditions: in a 10% CO2 atmosphere, a volume ratio of hydrogen to carbon dioxide of 3:1, the balance gas being He, and a space velocity of 36000 mL·g cat -1 ·h -1 The reaction was carried out under the following conditions, wherein the amount of 0.1Cu / One-Mn catalyst prepared in Example 1 was 100 mg. The chemical reaction formula involved in the process is:

[0112] CO2+H2→CO+H2O;

[0113] Figure 5The 0.1Cu / One-Mn catalyst prepared in Example 1 of the present invention was applied to the reverse water gas reaction, and the conversion rate reached 25% at 500 °C, showing good activity among non-precious metal catalysts.

[0114] Effect Example 4

[0115] The reaction conditions for the preferential oxidation of CO under hydrogen-rich conditions: 1% CO + 1% O2 + 50% H2, with He as the balance gas, and the space velocity was maintained at 36000 mL·g cat -1 ·h -1 under the condition of. Among them, the addition amount of the 0.1Cu / One-Mn catalyst prepared in Example 1 was 100 mg.

[0116] The chemical reaction formula involved in the process is:

[0117] 2CO + O2 = 2CO2;

[0118] Figure 6 The 0.1Cu / One-Mn catalyst prepared in Example 1 of the present invention was applied to the preferential oxidation of CO under hydrogen-rich conditions. It can be seen from the figure that the 0.1Cu / One-Mn catalyst prepared in Example 1 has good catalytic performance during the preferential reaction of carbon monoxide.

[0119] The above is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A preparation method of an ultra-low loading single-atom Cu catalyst supported on MnO2, characterized in that, It includes the following steps: Mix manganese nitrate, urea, citric acid and water evenly to obtain mixture 1; Add a potassium permanganate solution to the mixture 1 for reaction to obtain mixture 2; Adjust the pH of the mixture 2 to be alkaline, then add a copper source, stir evenly, carry out a hydrothermal reaction, and then carry out centrifugation, washing, drying and calcination in sequence to obtain a Cu / MnO2 catalyst; Pretreat the Cu / MnO2 catalyst under a H2 atmosphere to obtain a MnO2-supported ultra-low loading single-atom Cu catalyst.

2. The preparation method of a MnO2-supported ultra-low loading single-atom Cu catalyst according to claim 1, wherein, In the mixture 1, the molar ratio of manganese nitrate, urea, citric acid and distilled water is (1-10):5:5:2500.

3. The preparation method of a MnO2-supported ultra-low-loading single-atom Cu catalyst according to claim 1, wherein, The molar ratio of potassium permanganate in the potassium permanganate solution to manganese nitrate in the mixture 1 is (0.8-1):

1.

4. The preparation method of a MnO2-supported ultra-low amount of single-atom Cu catalyst according to claim 1, characterized in that, The pH = 8-10.

5. The preparation method of a MnO2-supported ultra-low loading single-atom Cu catalyst according to claim 1, characterized in that, The copper source is copper nitrate trihydrate.

6. The preparation method of a MnO2-supported ultra-low-loading single-atom Cu catalyst according to claim 5, characterized in that, The molar ratio of the copper nitrate trihydrate to the sum of manganese nitrate and potassium permanganate in the mixture 1 is (0-0.001):1; among them, the dosage of the copper nitrate trihydrate is not 0.

7. The preparation method of a MnO2-supported ultra-low loading single-atom Cu catalyst according to claim 1, characterized in that, The conditions in the hydrothermal reaction process are: reacting at 200 °C for 20-24 h in flowing air at 20 ml / min; and / or, The conditions in the calcination process are: calcining at 380 °C for 4 h in flowing air at 20 ml / min.

8. The preparation method of a MnO2-supported ultra-low-loading single-atom Cu catalyst according to claim 1, characterized in that, The pretreatment process is: treating for 60 min under a hydrogen atmosphere at a temperature of 300-400 °C.

9. A MnO₂-supported ultra-low loading single-atom Cu catalyst, characterized in that, Prepared by the preparation method according to any one of claims 1-8.

10. Application of the MnO2-supported ultra-low loading single-atom Cu catalyst according to claim 9 in the fields of CO low-temperature oxidation anti-sulfur, water gas shift reaction and CO preferential oxidation reaction under hydrogen-rich conditions.

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