Cerium modified copper-manganese catalyst, preparation method thereof and application of cerium modified copper-manganese catalyst in CO catalytic oxidation

Abstract

The invention discloses a cerium-modified copper-manganese catalyst, a preparation method thereof and application of the cerium-modified copper-manganese catalyst in CO catalytic oxidation. Dissolving a copper salt, a manganese salt and a doping auxiliary agent in water to obtain a copper-manganese mixed solution; adding a precipitant into the copper-manganese mixed solution to carry out precipitation reaction I, and after the reaction is completed, carrying out aging and solid-liquid separation to obtain a composite precipitate I; drying and roasting the composite precipitate I to obtain a copper-manganese mixed oxide; mixing the copper-manganese mixed oxide with a cerium salt solution, adding a precipitant to carry out precipitation reaction II, and after the reaction is completed, carrying out aging and solid-liquid separation to obtain a composite precipitate II; the composite precipitate II is dried and roasted II, and the cerium modified copper-manganese catalyst is obtained and has high low-temperature activity and moisture stability, the conversion rate of catalytic flue gas CO is high, the industrial application value is excellent, the preparation technology is simple, the process is short, and industrial production is facilitated.

Description

Technical Field

[0001] The invention relates to a catalytic material, in particular to a cerium-modified copper-manganese catalyst, and also to a preparation method of the cerium-modified copper-manganese catalyst and application of the cerium-modified copper-manganese catalyst in catalytic oxidation of CO, belonging to the technical field of flue gas treatment. Background Art

[0002] Carbon monoxide, as a common component of industrial flue gas, causes serious harm to the ecological environment. In order to meet the requirements of green environmental protection policies, flue gas decarbonization treatment is urgently needed. At present, solid catalytic process is widely used in flue gas treatment in iron and steel metallurgy, thermal power generation and other industries due to its advantages such as high carbon monoxide removal efficiency, low raw material cost, simple operation and small footprint. Precious metals were often used as catalyst raw materials in the past, but they were costly and had low yields. In recent years, they have gradually been replaced by transition metals, such as copper-manganese catalysts. However, copper-manganese oxides have defects such as insufficient catalytic activity below 200°C and poor water resistance. At the same time, industrial waste gases such as sintering flue gas contain a large amount of water vapor, which seriously restricts its promotion and application in the industrial field.

[0003] In order to overcome the defects of transition metals in the application of humid and low-temperature flue gas, scientists have made many attempts to improve the traditional process in order to improve the activity and stability of metal oxides in low-temperature and humid environments. Among them, the heteroatom surface modification process has been proven to have development potential. At present, the research on the carbon monoxide catalytic mechanism on the surface of metal oxides is gradually deepening, and the number of projects using heteroatom surface modification to improve the surface efficiency by adjusting the carbon monoxide reaction mechanism is gradually increasing.

[0004] The properties of the catalyst prepared by the multi-metal co-precipitation method are limited by the uniformity of the mixing of multiple metal elements inside. During the high-temperature calcination process, segregation is more likely to occur and a secondary phase is formed, causing phase separation, which affects the overall uniformity and stability of the multi-metal catalyst. Multiple metal elements no longer form mixed oxides, but crystallize into phases independently. The dense, high-crystallinity phase has poor adsorption and activation capabilities for gas molecules.

[0005] US Patent (Publication No. US20140291250A1) discloses a one-step oxidation-reduction method for preparing Mn-Ce catalyst. 4+ The existence of Mn, after phase separation, exists in the form of Mn5O8, Mn2O3 and Mn3O4. xThe activity is relatively low and can only be applied to sewage treatment, VOCs catalytic combustion and other fields, but not to low-concentration CO catalytic combustion. The literature (“A robust ceria-based high entropy oxide catalyst for efficient propane oxidation”, Fuel, 2025, 380: 133252) discloses the use of a one-step co-precipitation method to prepare a multi-catalyst containing Cu, Mn and Ce. Characterization shows that as calcination proceeds, it is difficult to maintain a single fluorite structure inside the particles. Instead, manganese, nickel and copper oxide species segregate to form a secondary phase. Phase separation greatly inhibits the synergistic effect of different metal species on the promotion of CO catalytic oxidation. Summary of the invention

[0006] In view of the shortcomings of the prior art, the object of the present invention is to provide a cerium-modified copper-manganese catalyst having a uniform ternary metal mixed state, exhibiting low-temperature high catalytic activity for CO, as well as good thermal stability and water resistance.

[0007] The second object of the present invention is to provide a method for preparing a cerium-modified copper-manganese catalyst. The preparation method synthesizes the cerium-modified copper-manganese catalyst by a two-step method, which can solve the problem of uneven mixing of multi-component metals in the one-step synthesis of the cerium-modified copper-manganese catalyst, and the adverse effects of metal element crystallization segregation and phase separation. The preparation method is simple, the conditions are mild, and it meets the requirements of mass production.

[0008] The third object of the present invention is to provide a cerium-modified copper-manganese catalyst for use in catalyzing the oxidation of carbon monoxide, which can achieve efficient oxidation and removal of carbon monoxide at a temperature not higher than 200°C and exhibit high water resistance.

[0009] In order to achieve the above technical objectives, the present invention provides a method for preparing a cerium-modified copper-manganese catalyst, which comprises the following steps:

[0010] 1) dissolving a copper salt, a manganese salt and a doping aid in water to obtain a copper-manganese mixed solution; adding a precipitant to the copper-manganese mixed solution to perform a precipitation reaction I, and after the reaction is completed, performing aging and solid-liquid separation to obtain a composite precipitate I; and drying and calcining the composite precipitate I to obtain a copper-manganese mixed oxide;

[0011] 2) After the copper-manganese mixed oxide and the cerium salt solution are mixed, a precipitant is added to carry out a precipitation reaction II. After the reaction is completed, aging and solid-liquid separation are carried out to obtain a composite precipitate II; the composite precipitate II is dried and calcined II to obtain a cerium-modified copper-manganese catalyst; the amount of the cerium salt solution is measured at 5-10wt% of the mass of cerium ions to the mass of the copper-manganese mixed oxide.

[0012] The preparation method of the cerium-modified copper-manganese catalyst provided by the present invention is achieved by a two-step method, first preparing a copper-manganese oxide matrix, and then doping the cerium element on its surface. Compared with the cerium-modified copper-manganese catalyst prepared by direct coprecipitation in the one-step method, the cerium-modified copper-manganese catalyst prepared by the two-step method has a uniform multi-component metal mixture in the outer surface area of ​​gas-solid contact, which greatly avoids the adverse effects of metal element crystal segregation and phase separation. More specifically, the present invention first constructs the main copper-manganese mixed oxide matrix with copper and manganese species by coprecipitation, and then distributes the cerium element on the surface of the copper-manganese mixed oxide matrix by impregnation. The cerium species is embedded in the lattice of the copper-manganese mixed oxide, destroying the large particles with high crystallization on the surface and eliminating the spinel structure, and using the atomic property difference between the cerium species and the copper-manganese species to cause lattice distortion, generating oxygen vacancy sites to capture oxygen molecules in the air, thereby anchoring the active oxygen groups on the surface of the modified catalyst to maintain stability. At the same time, the cerium ions doped on the surface of the cerium-modified copper-manganese catalyst have a higher ionic radius and lower electronegativity than copper ions and manganese ions. Their outer orbits are in a full electron state and have an orbital shielding effect. Therefore, the low-valent cerium ions have insufficient bonding strength to oxygen atoms, making it difficult to stably bind oxygen species alone. They are easy to alternate with manganese ions on the surface and form a common composite oxygen vacancy structure. Compared with the single manganese oxide phase, the oxygen elements on the surface are tightly bound by manganese species. The interaction between the cerium-manganese bimetallic weakens the bonding of the composite oxygen vacancies on the surface of the modified catalyst to the active oxygen therein. This increases the tendency of the surface lattice oxygen to detach from the metal site and participate in the carbon monoxide oxidation reaction. When carbon monoxide is adsorbed and contacts the active oxygen, the energy barrier to be overcome is reduced. This greatly increases the proportion of surface lattice oxygen participating in the carbon monoxide oxidation reaction. In addition, the carbonate product formed by the hydration reaction forms a bridge-like bond between the catalyst surface and the two metal sites. At the active sites formed by low-valent manganese ions, the carbonate surface is complexed into a symmetrical bridge structure. This structure has high stability and is difficult to thermally decompose at low temperatures. Therefore, the thermal activation regeneration temperature of the catalyst increases, making it difficult to adapt to the low-temperature flue gas environment. At the composite site formed by cerium embedding and manganese species, the two ends of the carbonate are respectively combined with manganese ions and cerium ions. Due to the large difference in the radius of the two metal ions, the carbonate formed is also an asymmetric bridge structure, and its stability is much lower than that of the symmetrical carbonate bridge. Macroscopically, it is manifested as a great decrease in the adsorption intensity of carbonate species on the surface of the heteroatom cerium modified catalyst, which can be reversibly decomposed at the corresponding temperature of the sintering flue gas. This not only improves the low-temperature activity of the catalyst, but also greatly slows down the accumulation rate of carbonate on the surface. The poisoning effect of water vapor on it is reduced, thereby improving the water resistance of the catalyst.

[0013] As a preferred solution, the ratio of the copper salt to the manganese salt is measured at a molar ratio of Mn / Cu of 2.5:1 to 4:1. As a further preferred solution, the copper base is copper nitrate and the manganese salt is manganese nitrate. The selection of nitrate can avoid the introduction of other elements such as halogens and sulfur, thereby effectively preventing the generation of impurities such as halides and sulfonic acid substitutions. The molar ratio of manganese and copper will affect its catalytic activity. + Acting as CO adsorption site and forming Cu-CO carbonyl structure while Mn 3+ / Mn 4+ It can act as a circulation site to adsorb / release active oxygen. If the Cu content relative to Mn is too low, the surface CO adsorption is insufficient and the oxidation efficiency is poor. If the Cu content is too high, the excess Cu species cannot form the spinel structure of CuMn2O4, and then form a copper oxide phase alone, causing waste. The most suitable Mn / Cu molar ratio is 2.5:1~4:1.

[0014] As a preferred solution, the doping aid is nitric acid, and the amount of the doping aid added to the copper-manganese mixed solution is to maintain the nitrate concentration at 3-7 mol / L. Nitric acid promotes dissolution and creates an acidic environment to prevent copper salts and manganese salts from reversibly precipitating or agglomerating to form large particle colloids, which helps the metal species to be fully dispersed in the liquid environment in the form of ions, and is conducive to uniform mixing of phases.

[0015] As a preferred solution, in 1) and 2), the precipitant includes ammonia water and / or urea; the amount of the precipitant is used to control the pH value of the solution system to 4 to 5. The precipitant is preferably urea or ammonia water that is easy to decompose and volatilize, which can avoid the introduction of other elements such as carbonate, thereby effectively preventing the generation of heat-stable impurities such as carbonates.

[0016] As a preferred solution, in 1) and 2), the aging condition is: standing at a temperature of 60-100°C for more than 0.5h. Aging under appropriate conditions can further increase the precipitation yield and make the crystals grow, which is better for subsequent solid-liquid separation.

[0017] As a preferred solution, the conditions of the precipitation reaction I are: temperature of 30-80° C. and time of 0.5-1 h.

[0018] As a preferred solution, the conditions of the calcination I are: temperature of 400-600°C and time of 1-2h;

[0019] As a preferred solution, the conditions of the precipitation reaction II are: temperature of 30-80° C. and time of 0.5-1 h.

[0020] As a preferred solution, the conditions of the calcination II are: temperature of 100-400°C and time of 1-2 hours. If the calcination temperature is too high or too low, the catalytic performance of the oxidation of CO will be reduced.

[0021] In the technical solution of the present invention, an appropriate amount of cerium doping can construct surface oxygen vacancies to increase the oxygen saturation adsorption capacity and improve its water resistance. However, too low a cerium doping amount cannot achieve the purpose of modifying the catalytic activity of the copper-manganese catalyst, and excessive cerium doping will instead reduce the catalytic activity of the copper-manganese catalyst.

[0022] The drying process involved in the present invention has a temperature of 90-110°C.

[0023] The invention also provides a cerium-modified copper-manganese catalyst, which is obtained by the preparation method.

[0024] As a preferred embodiment, the specific surface area of ​​the cerium-modified copper-manganese catalyst is 200-250 m 2 / g, bulk density is 0.60~0.70g / cm 3 The specific surface area and bulk density of the cerium-modified copper-manganese catalyst are controlled within an optimal range, and carbon monoxide can be better removed from low-temperature humid flue gas.

[0025] The present invention provides an application of a cerium-modified copper-manganese catalyst for catalyzing the oxidation of carbon monoxide. The cerium-modified copper-manganese catalyst of the present invention is particularly suitable for oxidative removal of carbon monoxide in flue gas. For example, the cerium-modified copper-manganese catalyst is filled in a reactor, and the filling amount of the cerium-modified copper-manganese catalyst is proportional to the flow rate of the flue gas. The optimal mass space velocity of the flue gas is 25-35 m / s. 3 / (h·kg). The carbon monoxide concentration in the flue gas is 8000~10000ppm. The flue gas is a by-product discharged at the end of sintering production and other links in a steel plant. After catalytic oxidation by a cerium-modified copper-manganese catalyst, the concentration of carbon monoxide in the flue gas can be reduced to below 1000ppm, and the removal efficiency of carbon monoxide is higher than 90%, and can reach 99% at 200℃.

[0026] The present invention compares the chemical reaction pathway changes of the copper-manganese mixed oxide without cerium doping modification and the copper-manganese catalyst modified with cerium in removing carbon monoxide from low-temperature humid flue gas. Figure 2 As shown, from Figure 2It can be seen that if the copper-manganese mixed oxide is not doped with cerium, the adsorbed oxygen species are limited by the number of oxygen vacancies, and the lattice oxygen species are not active enough to migrate and react on the surface. In addition, they are easy to form a stable carbonate structure on the surface when in contact with water, and accumulate to form a covering layer at low temperatures, causing irreversible deactivation. The carbon monoxide conversion rate of flue gas is low and the service life of the catalyst is short. After the cerium-modified copper-manganese catalyst is used, the newly constructed surface oxygen vacancies increase the oxygen saturation adsorption capacity, the lattice distortion intensifies the lattice oxygen surface migration and oxidation reaction, and the carbonate products formed in the humid flue gas can be decomposed at the corresponding temperature of the sintering flue gas, so that the influence caused by the hydration reaction becomes reversible deactivation.

[0027] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0028] 1) In view of the one-step co-precipitation redox-related process commonly used in the preparation process of multi-metal oxides in the prior art, there are defects such as crystal segregation causing phase separation during high temperature, inhibiting the synergistic effect of different metal species to form a coupling effect, and the appearance of secondary phases reduces the practicality of multi-metal catalysts. The cerium-modified copper-manganese catalyst provided by the present invention is prepared by a two-step method, which can make the main body of the copper-manganese mixed oxide more evenly mixed, effectively avoiding the formation of secondary phases due to crystal maturation and agglomeration during high-temperature calcination, and the cerium element is concentrated on the outer surface of the particles, which makes the utilization rate of the cerium species higher and presents a uniform ternary metal mixed state at the gas-solid contact surface. A small amount of cerium is embedded in the copper-manganese lattice and highly dispersed to form microcrystals or adsorbed on the inner side of the pore wall. These changes greatly improve the efficiency and durability of the carbon monoxide oxidation reaction, and the cerium-modified copper-manganese catalyst can be used for the oxidation and removal of carbon monoxide components in the flue gas of the steel industry. Compared with the use of copper-manganese mixed oxides for flue gas terminal treatment, cerium-modified copper-manganese catalyst can reduce the energy consumption of flue gas treatment, improve the efficiency of carbon monoxide removal, and extend the service life of the catalyst and removal tower, reduce the cost of flue gas treatment, and achieve clean production.

[0029] 2) The present invention adopts a two-step method to synthesize the cerium-modified copper-manganese catalyst, which has a simple preparation process, low equipment requirements, and a much higher mixing uniformity of the metal components at the gas-solid contact surface than the catalysts obtained by other preparation methods. The operating temperature is low, which has a great cost advantage and has expected industrial application value.

[0030] 3) The copper-manganese-cerium ternary solid catalyst of the present invention obtains higher catalytic activity in a relatively low temperature range, and the carbon monoxide conversion rate reaches more than 99% at 200°C. The low-temperature activity and water resistance are much higher than those of other Ce-containing multi-metal oxide catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a scanning electron microscope image of the cerium-modified copper-manganese catalyst prepared in Example 1.

[0032] Figure 2 The changes in the reaction pathways of carbon monoxide oxidation and water deactivation on the surface of copper-manganese catalysts and cerium-modified copper-manganese catalysts during the treatment of carbon monoxide in flue gas.

[0033] Figure 3 The surface imaging comparison of the cerium-modified copper-manganese catalyst (M200) prepared by the two-step method in Example 1 and the cerium-modified copper-manganese catalyst prepared by the one-step molding method in Comparative Example 1 is shown; it can be seen from the figure that the cerium-modified copper-manganese catalyst prepared by the one-step molding method has surface defects, not only the structural strength is uneven and large void defects are formed, but more importantly, the metal elements are unevenly distributed on the surface: the distribution areas of the three elements Cu / Mn / Ce are not highly overlapped but deviated, which proves that species segregation occurs on the particle surface; while the surface of the cerium-modified copper-manganese catalyst prepared by the two-step method not only has a more uniform structure and strength, but also the three elements Cu / Mn / Ce are fully and evenly covered, fully mixed with each other to form a unified physical phase system, and the more uniform distribution of surface elements not only improves the contact boundary between different elements to exert a coupling effect, but also forms a more uniform strength of the formed material, reducing the probability of adverse phenomena such as local breakage. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0035] Example 1

[0036] A steel plant filled the carbon monoxide catalytic combustion tower with a cerium-modified copper-manganese catalyst prepared by a two-step method. The filling amount was about 250g, and the flue gas space velocity was 25m 3 / (h·kg), used for flue gas carbon monoxide terminal treatment. The copper-manganese catalyst is prepared by a two-step method, and the specific preparation method is as follows:

[0037] In the first step, industrial-grade manganese nitrate tetrahydrate and copper nitrate pentahydrate with a purity of >98% are prepared into solutions respectively and mixed, wherein the concentration of the manganese nitrate solution is 0.5 mol / L, and the concentration of the copper nitrate solution is 0.5 mol / L. The two salt solutions are evenly mixed, and nitric acid is added as a promoter. The nitrate ion concentration in the mixed solution is adjusted to 5 mol / L, and the molar ratio of Mn(NO3)2:Cu(NO3)2 is maintained at 3:1. After stirring for 1 hour, about 1 L of industrial ammonia water containing 25% ammonia is introduced as a precipitant to precipitate at 30°C for 0.5 hour. After the mixed solution is aged at 60°C for 0.5 hour, the mixed precipitate is obtained by filtration. After the mixed precipitate is dried at 110°C air conditions for 12 hours, it is calcined in an air environment at 550°C for 2 hours to obtain copper manganese oxide.

[0038] In the second step, the copper manganese oxide was immersed in a 0.5 mol / L cerium nitrate solution, in which the amount of cerium nitrate was measured as 5wt% of the mass of cerium ions to the mass of copper manganese oxide. After stirring for 1 hour, about 1L of industrial ammonia water containing 25% ammonia was introduced as a precipitant for precipitation at 30°C for 0.5 hour. After the mixed solution was aged at 60°C for 0.5 hour, the mixed precipitate was filtered to obtain the mixed precipitate. After the mixed precipitate was dried at 110°C air conditions for 12 hours (divided into 6 groups of experimental controls), it was heated in an air environment at 50°C, 100°C, 200°C, 300°C, 400°C and 500°C for 1.5 hours, and the corresponding products were expressed as M50, M100, M200, M300, M400 and M500, respectively. The results of microscopic characterization and activity detection showed that the activity of the products under different calcination conditions was compared by measuring the temperature corresponding to the CO conversion rate of 50%. M100, M200, M300 and M400 showed good catalytic performance, and the corresponding temperatures for 50% CO conversion were 116°C, 88°C, 101°C and 123°C, respectively. However, M50 and Mn500 had lower catalytic activity, and their corresponding temperatures for 50% CO conversion were higher than 150°C. Among all the samples, M200 showed the best catalytic performance for CO oxidation, so the heating temperature was finally locked at 200°C.

[0039] The modified copper-manganese catalyst (M200) has a high content of oxygen vacancies on the surface, and the particle surface presents a densely arranged honeycomb structure, so it exhibits strong catalytic oxidation activity on a macro scale, such as Figure 1 As shown. This structure greatly expands the specific surface area of ​​the catalyst and increases the effective contact area between its surface and the flue gas. Moreover, the inner side of the mesoporous pore wall constructed on the surface is conducive to gas diffusion and adsorption, thereby effectively increasing the surface saturated adsorption capacity. The cerium element is embedded in the surface of the copper-manganese mixture particles, destroying the spinel structure of large particles, reducing the crystallinity and forming a slit-like mesoporous structure. The average particle diameter is about 1.5 mm, the surface pore size is concentrated in 10~35 nm, and the specific surface area is about 220 m 2 / g, bulk density is about 0.70g / cm3 During the catalytic oxidation process, the cerium modified catalyst (M200) is filled into the carbon monoxide catalytic combustion tower, and then 120°C wet flue gas is introduced for treatment. All steps are carried out under atmospheric pressure. The initial concentration of carbon monoxide is about 10,000 ppm, and the carbon monoxide removal rate exceeds 90% after the modified catalyst acts.

[0040] Example 2

[0041] A steel plant uses cerium-modified copper-manganese oxide to catalyze the removal of carbon monoxide from tail gas. The catalyst filling amount inside the reactor is about 500g, and the flue gas flow rate is controlled at 15m 3 / h, that is, mass airspeed 30m 3 / (h·kg).

[0042] In the first step, tetrahydrate manganese nitrate and pentahydrate copper nitrate are prepared into salt solutions respectively and mixed, and diluted nitric acid is added as a promoter, wherein the concentration of manganese copper nitrate is 2 mol / L, and the concentration of manganese nitrate solution is 1 mol / L. The nitric acid is used to adjust the nitrate ion concentration in the mixed solution to 3 mol / L. The two salt solutions are evenly mixed, and the mixing ratio keeps the mass ratio of Mn(NO3)2:Cu(NO3)2 at about 4:1. After stirring for 1 hour, about 1 L of industrial ammonia water containing 25% ammonia is introduced as a precipitant to carry out precipitation reaction at 40°C for 1 hour. After the mixed solution is aged at 60°C for 0.5 hour, the mixed precipitate is obtained by filtration, and the mixed precipitate is dried at 110°C air conditions for 12 hours, and then calcined at 600°C for 1 hour to obtain copper-manganese mixed oxide.

[0043] In the second step, the copper manganese oxide is immersed in a 2 mol / L cerium nitrate solution, wherein the amount of cerium nitrate (divided into five groups of experiments as a control) is measured at 0wt%, 2.5wt%, 5wt%, 7.5wt% and 10wt% of the mass of cerium ions to the mass of the copper manganese oxide, respectively. After stirring for 1 hour, about 1L of industrial ammonia water containing 25% ammonia is introduced as a precipitant to precipitate at 40°C for 0.5h. After the mixed solution is aged at 60°C for 0.5h, the mixed precipitate is filtered to obtain a mixed precipitate. After the mixed precipitate is dried at 110°C air conditions for 12h, the mixed precipitate is heated in an air environment at 300°C for 1.5h to obtain the final product of cerium-modified copper manganese oxide.

[0044] Comparing the effect of the surface loading of cerium species on the CO catalytic efficiency, the initial concentration of carbon monoxide was about 1 vol%. It was finally found that the product with a Ce content of 7.5 wt% showed the best reaction activity, and a CO conversion rate of 97% could be achieved at 110°C. When the Ce dosage was increased to 10 wt%, the CO conversion rate at 110°C dropped to 89%. This shows that excessive Ce has an adverse effect on the performance of the catalyst.

[0045] Example 3

[0046] The carbon monoxide removal in a steel plant relies on a continuous fluidized bed device composed of a catalyst filled in a reactor. 3 / h flue gas flow rate corresponds to 1kg catalyst unit dosage.

[0047] Copper-manganese co-oxide was prepared by co-precipitation method. The specific preparation method is shown in Example 1.

[0048] The copper manganese oxide obtained in the first step is immersed in a 0.5 mol / L cerium nitrate solution to complete the second step, wherein the amount of cerium nitrate is measured as 10 wt% of the mass of cerium ions to the mass of copper manganese oxide. After stirring for 1 hour, about 1L of industrial ammonia water containing 25% ammonia is introduced as a precipitant to precipitate at 30°C for 0.5 hours. After the mixed solution is aged at 60°C for 0.5 hours, the mixed precipitate is filtered to obtain a mixed precipitate. After the mixed precipitate is dried at 110°C air conditions for 12 hours, the mixed precipitate is heated in an air environment at 300°C for 1.5 hours to obtain cerium-modified copper manganese oxide. The average diameter of the product particles is 5mm, and the specific surface area of ​​the catalyst particles is about 200m 2 / g. At the same time, the original copper-manganese mixed oxide was filled into the fluidized bed under the same conditions, and the carbon monoxide removal efficiency and catalyst service life before and after cerium modification were compared. The initial CO conversion rate of the original copper-manganese catalyst bed at 120°C was about 65%. After 24 hours of action of 10vol% water vapor, the CO conversion rate dropped to 42% and showed a trend of further decline. The initial CO conversion rate of the cerium-modified catalyst exceeded 90%, and after 24 hours of action of water vapor, the conversion rate dropped to 83% and remained stable. The water poisoning phenomenon on the catalyst surface changed from an irreversible process to a reversible process, greatly extending its working life in humid flue gas.

[0049] Comparative Example 1

[0050] A steel plant uses a one-step method to directly prepare Ce-modified copper-manganese oxide catalysts and uses them for flue gas treatment at the sintering head of the steel plant. Copper nitrate and manganese nitrate are used as metal precursors (Mn:Cu is in a ratio of 2.5:1), and nitric acid is added as a doping aid to make the nitrate concentration 3 mol / L to promote the full dispersion of copper and manganese salts. And during the stirring process, cerium nitrate solution is directly and slowly added so that Ce ions account for 10wt% of the total mass of copper-manganese mixed oxides. The resulting mixed solution is stirred while adding excess solid urea to precipitate it (the molar ratio of urea to the total amount of metal ions is 6:1). The obtained precipitate is directly filtered and dried under atmospheric pressure at 250°C for 10 hours. The specific surface area of ​​the product particles produced is about 80m 2 / g, which is far less than the specific surface area of ​​the product particles obtained by the two-step method in Example 1. In addition, the catalytic material can treat 10m3 containing 1vol% CO per 1kg 3The flue gas of the catalyst prepared by the one-step method can be treated with flue gas at a temperature of 220°C, and the conversion rate of CO in the flue gas environment after passing through the GGH heat exchanger is about 70% to 80%. It can be seen that the flue gas treatment efficiency and the conversion rate of CO at low temperature of the catalyst prepared by the one-step method are far inferior to those of the above three embodiments.

[0051] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. For those skilled in the art, improvements and changes obtained without departing from the technical concept of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a cerium-modified copper-manganese catalyst, characterized in that: The following steps are involved: 1) dissolving a copper salt, a manganese salt and a doping aid in water to obtain a copper-manganese mixed solution; adding a precipitant to the copper-manganese mixed solution to perform a precipitation reaction I, and after the reaction is completed, performing aging and solid-liquid separation to obtain a composite precipitate I; and drying and calcining the composite precipitate I to obtain a copper-manganese mixed oxide; 2) After the copper-manganese mixed oxide and the cerium salt solution are mixed, a precipitant is added to carry out a precipitation reaction II. After the reaction is completed, aging and solid-liquid separation are carried out to obtain a composite precipitate II; the composite precipitate II is dried and calcined II to obtain a cerium-modified copper-manganese catalyst; the amount of the cerium salt solution is measured at 5-10wt% of the mass of cerium ions to the mass of the copper-manganese mixed oxide.

2. The method for preparing a cerium-modified copper-manganese catalyst according to claim 1, characterized in that: The ratio of the copper salt to the manganese salt is measured at a molar ratio of Mn / Cu of 2.5:1 to 4:

1.

3. The method for preparing a cerium-modified copper-manganese catalyst according to claim 1, characterized in that: The doping aid is nitric acid; the amount of the doping aid in the copper-manganese mixed solution is to maintain a nitrate concentration of 3-7 mol / L.

4. The method for preparing a cerium-modified copper-manganese catalyst according to claim 1, characterized in that: In 1) and 2), the precipitant includes ammonia water and / or urea; the amount of the precipitant is used to control the pH value of the solution system to 4-5.

5. The method for preparing a cerium-modified copper-manganese catalyst according to claim 1, characterized in that: In 1) and 2), the aging conditions are: standing at a temperature of 60-100°C for more than 0.5h.

6. The method for preparing a cerium-modified copper-manganese catalyst according to claim 1, characterized in that: The conditions of the precipitation reaction I are: temperature of 30-80°C and time of 0.5-1h; The calcination conditions of I are: in an oxygen-containing atmosphere, the temperature is 400-600° C., and the time is 1-2 h; The conditions of the precipitation reaction II are: temperature of 30-80°C and time of 0.5-1h; The conditions of the calcination II are: in an oxygen-containing atmosphere, the temperature is 100-400° C., and the time is 1-2 hours.

7. A cerium-modified copper-manganese catalyst, characterized in that: Obtained by the preparation method according to any one of claims 1 to 6.

8. A cerium-modified copper-manganese catalyst according to claim 7, characterized in that: The specific surface area of ​​the cerium-modified copper-manganese catalyst is 200-250 m 2 / g, bulk density is 0.60~0.70g / cm 3 .

9. The use of a cerium-modified copper-manganese catalyst according to claim 7 or 8, characterized in that: Used to catalyze the oxidation of carbon monoxide.

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