Bifunctional catalyst for simultaneously removing CO and NOx as well as preparation method and application of bifunctional catalyst

Abstract

The invention belongs to the technical field of flue gas purification, and discloses a bifunctional catalyst which is simple in preparation process, excellent in low-temperature catalytic activity, N2 selectivity, sulfur resistance and water resistance and capable of removing CO and NOx at the same time, and a preparation method and application of the bifunctional catalyst. The bifunctional catalyst for simultaneously removing CO and NOx comprises microspheres formed by assembling nano-particles and a shell layer coated on the surfaces of the microspheres, the nanoparticles are mainly composed of Cu, V and O; and the shell layer is mainly made of TiO2. The preparation method of the bifunctional catalyst comprises the following steps: (1) taking basic cupric carbonate and V2O5 as raw materials, and synthesizing Cu3V2O7 (OH) 2.2 H2O microspheres through a hydrothermal method; and (2) synthesizing the bifunctional catalyst by using the Cu3V2O7 (OH) 2.2 H2O microspheres, tetrabutyl titanate and ammonia water as raw materials through a hydrothermal method.

Description

Technical Field

[0001] This invention relates to the technical field of flue gas purification, and more specifically, to a bifunctional catalyst for simultaneously removing CO and NOx, its preparation method, and its application. Background Technology

[0002] Nitrogen oxides (NO) X NO and carbon monoxide (CO) are two of the most common air pollutants, widely present in industrial and mobile pollution sources. They pose a significant threat to the environment and human health. Therefore, controlling NO is crucial. X CO and NOx emissions are crucial for both environmental protection and human health. Several technologies are available for removing these pollutants, including CO oxidation, NH3 selective catalytic reduction (NH3-SCR), and CO selective catalytic reduction (CO-SCR). CO-SCR is considered the best method for simultaneously eliminating CO and NOx. However, a major limitation of this technology is that in oxygen-rich environments, CO reacts more readily with oxygen to form carbon dioxide, rather than preferentially acting as a reducing agent with NOx. x reaction.

[0003] To achieve simultaneous control of CO and NO under oxygen-rich conditions, a technology coupling NH3-SCR denitrification and CO oxidation has been proposed. This technology leverages the heat of reaction released during CO oxidation to promote NOx reduction, thereby reducing energy consumption while achieving synergistic removal of both pollutants. Therefore, developing bifunctional catalysts capable of simultaneously catalyzing NH3-SCR and CO oxidation is of great significance. Currently, transition metal oxide catalysts (such as Cu and Co) are widely studied due to their low cost and certain catalytic activity. Among them, copper-based catalysts exhibit good NH3-SCR and CO oxidation activities in the medium- and low-temperature range. However, these catalysts typically have low N2 selectivity and poor resistance to sulfur and water, limiting their application under real-world environmental conditions. On the other hand, noble metal catalysts (such as Rh, Pd, and Pt) possess excellent NH3-SCR and CO oxidation activities at low temperatures, but their high cost and poor high-temperature stability also limit their large-scale application. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a bifunctional catalyst that simultaneously removes CO and NOx, which has a simple preparation process, excellent low-temperature catalytic activity, N2 selectivity, and sulfur and water resistance, as well as its preparation method and application. The technical solution is as follows:

[0005] This bifunctional catalyst simultaneously removes CO and NOx, comprising microspheres assembled from nanoparticles and a shell coating the surface of the microspheres; the nanoparticles are mainly composed of Cu, V, and O; and the shell is mainly TiO2.

[0006] As a further improvement to the above-mentioned bifunctional catalyst, the XRD pattern of the bifunctional catalyst, in addition to the characteristic peak of TiO2, also has the characteristic peak of one of Cu3(OH)2V2O7·2H2O, Cu3V2O8, and Cu2V2O7.

[0007] As a further improvement to the aforementioned bifunctional catalyst: the Cu 2p spectrum exhibits peaks for Cu 2P3 / 2 and Cu 2P1 / 2; the O 1s spectrum exhibits peaks for lattice oxygen and surface adsorbed oxygen; and the Ti 2p spectrum exhibits peaks for Ti 2p... 1 / 2 and Ti 2p 3 / 2 The peak; the V2p spectrum has V 5+ and V 4+ The peak.

[0008] As a further improvement to the above-mentioned bifunctional catalyst, the diameter of the bifunctional catalyst is 2500-2750 nm; the thickness of the shell is 16-25 nm.

[0009] The preparation method of the above-mentioned bifunctional catalyst includes the following steps:

[0010] (1) Cu3V2O7(OH)2·2H2O microspheres were synthesized by hydrothermal method using basic copper carbonate and V2O5 as raw materials;

[0011] (2) A bifunctional catalyst was synthesized by hydrothermal method using Cu3V2O7(OH)2·2H2O microspheres, tetrabutyl titanate and ammonia as raw materials.

[0012] As a further improvement to the above preparation method: Step (1) is as follows: After stirring and mixing the basic copper carbonate solution and V2O5 solution at room temperature, the mixture is then transferred to a polytetrafluoroethylene reactor for hydrothermal reaction. After the reaction is completed, the precipitate is collected, washed and dried to obtain Cu3V2O7(OH)2·2H2O microspheres.

[0013] As a further improvement to the above preparation method: the mass fraction of basic copper carbonate solution is 1.6-2.0%, and the mass fraction of V2O5 solution is 6-7%; the volume ratio of basic copper carbonate solution to V2O5 solution is 25:9; stirring is carried out at room temperature for 1 hour; the hydrothermal reaction temperature is 120℃, and the hydrothermal reaction time is 24 hours.

[0014] As a further improvement to the above preparation method: Step (2) is as follows: Cu3V2O7(OH)2·2H2O microspheres are dispersed in ethanol, tetrabutyl titanate is added under stirring, ammonia is added dropwise after stirring for a period of time and stirring is continued for a period of time, and then transferred to a polytetrafluoroethylene reactor for hydrothermal reaction. After the reaction is completed, the precipitate is collected, washed and dried, and finally calcined to obtain the bifunctional catalyst.

[0015] As a further improvement to the above preparation method: the solid-liquid ratio of Cu3V2O7(OH)2·2H2O microspheres to ethanol was 1g:40mL, and the volume ratio of tetrabutyl titanate to ethanol was 2.1:40. After stirring for 1 hour, ammonia water was added dropwise and stirring was continued for another hour; the hydrothermal reaction temperature was 150℃ and the reaction time was 12 hours; the calcination temperature was 300℃ and the calcination time was 1 hour; the mass fraction of ammonia water was 25-30%, and the volume of ammonia water accounted for 0.3% of the total volume.

[0016] The flue gas purification method uses the aforementioned bifunctional catalyst to convert CO and NOx in the flue gas into CO2 and N2.

[0017] As can be seen, the bifunctional catalyst prepared by the hydrothermal method in this invention has a core-shell structure, consisting of microspheres assembled from Cu / V / O nanoparticles and a TiO2 shell coating the surface of the microspheres. The TiO2 shell not only acts as a physical barrier to effectively inhibit the migration and volatilization of vanadium species in the core microspheres during calcination, but also improves the thermal and chemical stability of the active phase, avoiding the formation of the inactive V2O5 phase at high temperatures, thereby significantly improving the catalyst's resistance to NO. X Simultaneous removal of CO. Furthermore, the core-shell structure increases the catalyst's specific surface area, enhancing the proportion of adsorbed oxygen. The resulting Ti-O-Cu and Ti-OV dual interfaces alter the charge environment, promoting electron transfer and facilitating the effective adsorption and activation of reactants.

[0018] Verification has shown that the bifunctional catalyst of this invention can achieve NO reduction of over 90% at 212°C and 195°C, respectively. X It achieves high conversion rates for CO and N2, while also exhibiting excellent N2 selectivity. Compared to simple core microspheres, it significantly enhances the catalytic activity of the bifunctional catalyst and its resistance to sulfur and water in the reaction. It provides new insights and strategies for the simultaneous removal of CO and NOx from industrial flue gas and has good practicality.

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to aid in understanding the invention. The content provided in the drawings and their related descriptions can be used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0021] Figure 1 This is a schematic diagram of the catalytic performance testing device of the present invention.

[0022] Figure 2 The curves showing the CO conversion rate of CVO and CVO@TiO2-Y as a function of temperature.

[0023] Figure 3 The NO conversion rates of CVO and CVO@TiO2-Y as a function of temperature are shown in the figures.

[0024] Figure 4 The curves showing the N2 selectivity of CVO and CVO@TiO2-Y as a function of temperature.

[0025] Figure 5 The graph shows the sulfur and water resistance properties of CVO and CVO@TiO2-0.3.

[0026] Figure 6 Low-magnification and high-magnification SEM images of CVO.

[0027] Figure 7 SEM image of CVO@TiO2-Y.

[0028] Figure 8 Elemental surface scan of CVO@TiO2-0.3.

[0029] Figure 9 Line scan of elements in CVO@TiO2-0.3.

[0030] Figure 10 XRD pattern of CVO-Z.

[0031] Figure 11 XRD pattern of CVO@TiO2-Z.

[0032] Figure 12 XRD pattern of CVO@TiO2-Y.

[0033] Figure 13 N2 adsorption-desorption isotherms for CVO and CVO@TiO2-Y.

[0034] Figure 14 Pore ​​size distribution curves for CVO and CVO@TiO2-Y.

[0035] Figure 15H2-TPR, O2-TPD, NH3-TPD, and CO-TPD plots for CVO and CVO@TiO2-Y.

[0036] Figure 16 The Cu 2p, O 1s, Ti 2p, and V 2p spectra of CVO and CVO@TiO2-Y are shown. Detailed Implementation

[0037] The present invention will now be clearly and completely described in conjunction with the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Before describing the present invention in conjunction with the accompanying drawings, it should be particularly noted that:

[0038] The technical solutions and features provided in the various parts of this invention, including the following description, can be combined with each other without conflict.

[0039] Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0040] Regarding the terminology and units used in this invention: The terms "comprising," "having," and any variations thereof in the specification, claims, and related parts of this invention are intended to cover non-exclusive inclusion.

[0041] An embodiment of the preparation method of the bifunctional catalyst for simultaneous removal of CO and NOx of the present invention includes the following steps:

[0042] (1) Under vigorous stirring, 100 mL of basic copper carbonate solution (mass fraction 1.85%) was added to 36 mL of V2O5 solution (mass fraction 6.43%), and stirred at room temperature for 1 hour. The resulting solution was transferred to a polytetrafluoroethylene reactor and placed in an oven at 120 °C for 24 hours. After the reaction, the precipitate was collected, washed three times with ethanol and deionized water, and dried in an oven for 12 hours to obtain Cu3V2O7(OH)2·2H2O microspheres, denoted as CVO.

[0043] (2) Dissolve 1g of Cu3V2O7(OH)2·2H2O microspheres prepared in step (1) in 40mL of ethanol. Add 2.1mL of tetrabutyl titanate (TBOT) under vigorous stirring. After stirring for 1 hour, add 28% ammonia water dropwise and continue stirring for 1 hour. Transfer the resulting solution to a polytetrafluoroethylene reactor and place it in an oven at 150℃ for 12 hours. After the reaction, collect the precipitate, wash it three times with ethanol and deionized water, dry it in an oven for 12 hours, and finally calcine it for 1 hour to obtain the bifunctional catalyst, denoted as CVO@TiO2.

[0044] Based on the volume fraction Y of ammonia, the bifunctional catalyst is denoted as CVO@TiO2-Y, where Y = 0.2, 0.3, 0.4, or 0.5.

[0045] To investigate the mechanism, CVO was calcined. Based on the calcination temperature Z, the calcined product of CVO was denoted as CVO-Z, and the bifunctional catalyst was denoted as CVO@TiO2-Z, where Z = Uncalcined, 200℃, 300℃, 400℃, or 500℃.

[0046] The beneficial effects of the present invention will be illustrated below through performance testing and characterization.

[0047] Figure 1 This is a schematic diagram of the catalytic performance testing device of the present invention. Figure 1 As shown, the device is equipped with multiple independent gas pipelines, providing NO, CO, NH3, O2, and N2 respectively. Each pipeline is equipped with a mass flow meter for precise control and regulation of the flow rate of each gas. All gases first enter a mixer for uniform mixing. The mixed gas then passes through a fixed-bed reactor containing the catalyst to be tested, which is placed in a heating furnace. The heating furnace provides a precise and stable operating temperature for the catalytic reaction. The reacted gas first enters a flue gas analyzer to monitor and record the concentration changes of each component in real time, thereby directly calculating the catalyst conversion rate and selectivity. Then, it passes through a rotor flow meter to visually monitor the total gas flow rate. Finally, the tested exhaust gas enters an exhaust gas treatment unit for harmless treatment. In addition, a humidifier can inject a certain amount of water vapor into the simulated flue gas to examine the activity and stability of the catalyst under humid conditions.

[0048] The test conditions were: gas flow rate of 450 mL / min and space velocity of 15000 h⁻¹. -1 The mixed gas entering the catalyst bed uses nitrogen as a carrier and contains 1000 ppm CO, 500 ppm NH3, 500 ppm NO, 5 vol % O2, 5 vol% H2O (when in use), and 20 ppm SO2 (when in use).

[0049] NO conversion (%), CO conversion (%), and N2 selectivity (%) are calculated using the following formulas:

[0050]

[0051] Among them, [NO] in and [NO] out These represent the concentrations of NO in the gas streams entering and leaving the catalyst bed, respectively; [NH3] in and [NH3] out These represent the concentrations of NH3 in the gas streams entering and leaving the catalyst bed, respectively; [CO] in and [CO] out These represent the CO concentrations in the gas streams entering and leaving the catalyst bed, respectively.

[0052] Figure 2 The curves showing the CO conversion rate of CVO and CVO@TiO2-Y as a function of temperature. Figure 3 The NO conversion rates of CVO and CVO@TiO2-Y as a function of temperature are shown in the figures.

[0053] like Figure 2-3 As shown, CVO exhibits catalytic performance in the simultaneous removal of NO and CO, with NO and CO conversion rates reaching 80% at 240℃ and 304℃, respectively. The CO conversion rate of CVO@TiO2-Y obtained by coating CVO with TiO2 is higher than that of CVO throughout the entire temperature range, and the NO conversion rate increases from 88% to 100%, indicating that the TiO2 shell significantly improves the performance of CVO in the NH3-SCR coupled CO oxidation process.

[0054] Table 1 shows the catalytic performance data of CVO and CVO@TiO2-Y. As shown in Table 1, the NO conversion rate and CO conversion rate first increase and then decrease with the increase of coating thickness (the higher the amount of ammonia, the greater the coating thickness). CVO@TiO2-0.3 exhibits the highest catalytic activity, with its T... 90 (NO) and T 90 (CO) were 212℃ and 195℃ respectively. T 90 The temperature at which the conversion rate reaches 90%.

[0055] Figure 4 The curves showing the N2 selectivity of CVO and CVO@TiO2-Y as a function of temperature.

[0056] like Figure 4As shown, CVO produces byproducts at the beginning of the reaction, leading to a decrease in N2 selectivity, while CVO@TiO2-Y only begins to produce byproducts at 220℃, indicating that CVO@TiO2-Y has very high N2 selectivity.

[0057] Figure 5 The graph shows the sulfur and water resistance properties of CVO and CVO@TiO2-0.3.

[0058] like Figure 5 As shown, before the introduction of water vapor and SO2, CVO@TiO2-0.3 exhibited a 100% NO conversion rate and a 97% CO conversion rate at 220℃. When water vapor and SO2 were introduced, the NO conversion rate remained at 100%, while the CO conversion rate decreased to 91%. However, after the introduction of water vapor and SO2, the NO conversion rate of CVO plummeted from 65% to 0, while the CO conversion rate remained at 0. This demonstrates that CVO@TiO2-0.3 exhibits significantly enhanced resistance to water vapor and SO2, indicating that the TiO2 shell plays a crucial role in improving sulfur resistance.

[0059] Figure 6 Low-magnification and high-magnification SEM images of CVO.

[0060] like Figure 6 As shown, CVO is assembled from nanoparticles into uniformly sized spherical particles with a rough surface.

[0061] Figure 7 SEM image of CVO@TiO2-Y.

[0062] like Figure 7 As shown, CVO@TiO2-Y has a diameter of 2500-2750 nm, a smooth surface, and a shell thickness that gradually increases with the amount of ammonia used. The shell thickness of CVO@TiO2-Y was measured to be 16-25 nm using FIB-SEM images, with CVO@TiO2-0.3 having a shell thickness of 19.17 nm.

[0063] Figure 8 Elemental surface scan of CVO@TiO2-0.3.

[0064] like Figure 8 As shown, the CVO@TiO2-0.3 surface contains Cu, V, O, and Ti elements, and the elements are uniformly distributed on the surface.

[0065] Figure 9 Line scan of elements in CVO@TiO2-0.3.

[0066] like Figure 9 As shown, when scanning towards the edge, the Ti content increases significantly compared to Cu, V, and O.

[0067] Figure 10 XRD pattern of CVO-Z.

[0068] like Figure 10 As shown, each sample is composed of multiple crystalline phases. Diffraction peaks at ~15.4° (200), ~20.3° (001), ~26.2° (110), ~31.0° (400), and ~47.3° (002) match those of V2O5 (JCPDS No. 41-1426). When the calcination temperature is less than 400℃, a series of diffraction peaks at ~11.7° (020), ~23.9° (040), ~29.8° (-131), ~34.3° (002), and ~49.2° (202) are characteristic peaks of Cu3(OH)2V2O7·2H2O (JCPDS No. 46-1443) of vanadinite are observed. When the calcination temperature rises to 400℃, diffraction peaks begin to appear at ~23.8°(-112), ~26.8°(021), ~28.9°(310), ~32.8°(002) and ~47.8°(022), which are consistent with Cu2V2O7 (JCPDS No. 26-0569).

[0069] Figure 11 XRD pattern of CVO@TiO2-Z.

[0070] like Figure 11 As shown, all samples exhibited diffraction peaks at ~25.3°(101), ~37.8°(004), ~48.0°(200), ~53.9°(105), and ~55.1°(211), matching anatase TiO2 (JCPDS No. 21-1272), indicating successful TiO2 shell synthesis. The uncalcined and calcined samples at 200℃ showed the copper vanadate phase, the calcined sample at 300℃ showed the Cu3V2O8 phase (JCPDS No. 49-0689), and the calcined samples at 400℃ and 500℃ showed the Cu2V2O7 phase. This demonstrates that samples calcined at different temperatures correspond to different copper vanadate crystal phases. None of the samples showed the presence of the V2O5 phase, indicating that the shell protects CVO and prevents the active components of copper vanadate from partially decomposing into V2O5.

[0071] Figure 12 XRD pattern of CVO@TiO2-Y.

[0072] like Figure 12As shown, after CVO is coated with TiO2 and calcined at 300℃, characteristic peaks of TiO2 and Cu3V2O8 can be observed. With increasing TiO2 shell thickness, the peak intensity increases, indicating an increase in TiO2 content and the formation of anatase structure with higher crystallinity and larger grain size. Furthermore, with increasing TiO2 shell thickness, its protective effect on the core component is stronger, resulting in better crystallinity of Cu3V2O8 grains, thus continuously increasing the intensity of its diffraction peaks.

[0073] Figure 13 N2 adsorption-desorption isotherms for CVO and CVO@TiO2-Y. Figure 14 The pore size distribution curves for CVO and CVO@TiO2-Y are shown in Table 1. Table 1 also displays the specific surface area, pore volume, and average pore size of CVO and CVO@TiO2-Y.

[0074] like Figure 13 As shown, the isotherm shapes of all samples are consistent with typical type IV isotherms, exhibiting an H3-type hysteresis loop, indicating that all samples possess a mesoporous structure. Figure 14 As shown in Table 1, CVO@TiO2-0.3 exhibits the highest specific surface area (46.96 m²) due to the optimal TiO2 coating thickness and the interaction between Cu, V, and Ti at the core-shell interface. 2 / g), pore volume (5.49cm³) 3 The small average pore size (4.96 nm) and the small average pore size ( / g) indicate that it can expose more surface active sites and accommodate more reactant molecules, providing a basis for reactant contact.

[0075] Table 1

[0076]

[0077] Figure 15 H2-TPR, O2-TPD, NH3-TPD, and CO-TPD plots for CVO and CVO@TiO2-Y.

[0078] like Figure 15 As shown, the H2-TPR plot reveals three reduction peaks for CVO at 387°C, 423°C, and 447°C, corresponding to Cu, respectively. 2+ →Cu + Cu + →Cu0、V 5+ →V 4+Compared to CVO, the reduction peaks of Cu and V in CVO@TiO2-Y shift to lower temperatures. This is due to the interaction between TiO2 and CVO; TiO2 donates electrons to CVO, making it easier for CVO to lose oxygen atoms and be reduced, forming an interface structure favorable for reduction. Among them, CVO@TiO2-0.3 has the lowest reduction temperature and the highest redox activity, which is consistent with its highest NH3-SCR and CO oxidation activities.

[0079] In the O2-TPD diagram, peaks in the 300-450℃ range correspond to surface chemisorbed oxygen, while peaks above 600℃ correspond to bulk lattice oxygen. The desorption peaks of CVO all originate from bulk lattice oxygen (O²⁻). -) After coating with a TiO2 shell, the oxygen species in CVO@TiO2-Y changed significantly, with its desorption peak mainly originating from surface-active oxygen. As the coating thickness increased, the peak intensity first increased and then decreased, with the peak area of ​​CVO@TiO2-0.3 reaching its maximum, consistent with the trend of Oβ proportion changes in XPS. Furthermore, the peaks of lattice oxygen shifted towards lower temperatures, indicating that the TiO2 shell promoted the activation and migration of oxygen species, accelerating CO oxidation.

[0080] In the NH3-TPD diagram, CVO shows the smallest NH3 desorption peak, indicating that its surface acidity is weaker. Compared with CVO, CVO@TiO2-Y has a larger desorption peak area at medium and low temperatures, and more acid sites on its surface promote the adsorption of alkaline NH3, thereby improving the NO conversion rate. Therefore, the denitrification efficiency of CVO@TiO2-Y at medium and low temperatures is significantly higher than that of CVO.

[0081] In the CO-TPD diagram, the CO adsorption peaks of CVO, CVO@TiO2-0.2, and CVO@TiO2-0.5 at 200-500℃ are very weak, indicating that the absence of a TiO2 shell, or an excessively thin or thick TiO2 shell, will weaken the adsorption capacity for CO, resulting in their extremely weak oxidation capacity for CO.

[0082] Figure 16 The Cu 2p, O 1s, Ti 2p, and V 2p spectra of CVO and CVO@TiO2-Y are shown in Table 2. The surface chemical composition of CVO and CVO@TiO2-Y is also shown in Table 2.

[0083] like Figure 16 As shown, the Cu 2p spectrum exhibits two main peaks: Cu 2P3 / 2 and Cu 2P1 / 2. The Cu 2p3 / 2 spin-orbit peak, after fitting deconvolution, shows two characteristic peaks, corresponding to Cu 2P3 / 2 and Cu 2P1 / 2, respectively. + (932.7 eV) and Cu 2+ (934.2 eV). Compared to CVO, Cu in CVO@TiO2-Y 2+ and Cu+ The binding energy of Cu decreases. As shown in Table 2, Cu + / (Cu + +Cu 2+ The proportion increased from 15.36% to 19.68%, a change that can be attributed to the altered charge environment resulting from the interaction between Ti and Cu species. The degree of binding energy shift in CVO@TiO2-Y and Cu... + / (Cu + +Cu 2+ The binding energy of CVO@TiO2-0.3 first increases and then decreases with increasing TiO2 coating thickness, while that of Cu decreases the most. + / (Cu + +Cu 2+ The maximum value is consistent with its highest CO catalytic activity.

[0084] The O 1s spectra of each sample can be divided into two distinct peaks. The peak with binding energies of 530.09–530.25 eV is attributed to lattice oxygen (Oα), while the peak with binding energies of 531.80–532.03 eV is related to surface-adsorbed oxygen (O). β (Related to) CVO@TiO2-Y. β The proportion of O2 is higher than that of CVO, indicating that the TiO2 shell contributes additional O2. β This improves the oxygen mobility and reactivity in the catalyst, which is beneficial for CO oxidation and NH3-SCR reactions. CVO@TiO2-Y's O β / (O α +O β The ratio first increases and then decreases with the increase of TiO2 shell thickness, consistent with the catalyst activity test performance.

[0085] Peaks at 458.8 eV and 464.6 eV were observed in the Ti 2p spectra of all samples, corresponding to Ti 2p peaks, respectively. 1 / 2 and Ti 2p 3 / 2 Belongs to Ti 4+ Species.

[0086] In the V 2p spectra of each sample, the two peaks with binding energies of 517.28–517.40 eV and 516.60–516.70 eV are attributed to V 2p, respectively. 5+ and V 4+ As the thickness of the TiO2 shell increases, V 5+ / (V 4+ +V 5+ The percentage increased from 36.66% to 43.34%, but decreased as the TiO2 shell thickness further increased.

[0087] Table 2

[0088]

[0089] The foregoing has described the relevant content of the present invention. Those skilled in the art will be able to implement the present invention based on these descriptions. All other embodiments obtained by those skilled in the art based on the above description of the present invention without inventive effort should fall within the scope of protection of the present invention.

Claims

1. A bifunctional catalyst for simultaneously removing CO and NOx, characterized in that: It has microspheres assembled from nanoparticles and a shell covering the surface of the microspheres; the nanoparticles are mainly composed of Cu, V and O; the shell is mainly TiO2.

2. The bifunctional catalyst as described in claim 1, characterized in that: In addition to the characteristic peaks of TiO2, the XRD pattern of the bifunctional catalyst also has characteristic peaks of one of Cu3(OH)2V2O7·2H2O, Cu3V2O8, and Cu2V2O7.

3. The bifunctional catalyst as described in claim 1, characterized in that: The Cu 2p spectrum shows peaks for Cu 2P3 / 2 and Cu 2P1 / 2; the O 1s spectrum shows peaks for lattice oxygen and surface adsorbed oxygen; the Ti 2p spectrum shows peaks for Ti 2p. 1 / 2 and Ti 2p 3 / 2 The peak; the V 2p spectrum has V 5+ and V 4+ The peak.

4. The bifunctional catalyst as described in claim 1, characterized in that: The bifunctional catalyst has a diameter of 2500-2750 nm and a shell thickness of 16-25 nm.

5. The method for preparing the bifunctional catalyst according to any one of claims 1-4, characterized in that: Includes the following steps: (1) Cu3V2O7(OH)2·2H2O microspheres were synthesized by hydrothermal method using basic copper carbonate and V2O5 as raw materials; (2) A bifunctional catalyst was synthesized by hydrothermal method using Cu3V2O7(OH)2·2H2O microspheres, tetrabutyl titanate and ammonia as raw materials.

6. The preparation method according to claim 5, characterized in that: Step (1) is as follows: After stirring and mixing the basic copper carbonate solution and V2O5 solution at room temperature, the mixture is transferred to a polytetrafluoroethylene reactor for hydrothermal reaction. After the reaction is completed, the precipitate is collected, washed and dried to obtain Cu3V2O7(OH)2·2H2O microspheres.

7. The preparation method according to claim 6, characterized in that: The mass fraction of the basic copper carbonate solution is 1.6-2.0%, and the mass fraction of the V2O5 solution is 6-7%; the volume ratio of the basic copper carbonate solution to the V2O5 solution is 25:9; the mixture is stirred at room temperature for 1 hour; the hydrothermal reaction temperature is 120℃, and the hydrothermal reaction time is 24 hours.

8. The preparation method according to claim 5, characterized in that: Step (2) is as follows: Cu3V2O7(OH)2·2H2O microspheres are dispersed in ethanol, tetrabutyl titanate is added under stirring, ammonia is added dropwise after stirring for a period of time and stirring is continued for a period of time, and then transferred to a polytetrafluoroethylene reactor for hydrothermal reaction. After the reaction is completed, the precipitate is collected, washed and dried, and finally calcined to obtain the bifunctional catalyst.

9. The preparation method according to claim 8, characterized in that: The solid-liquid ratio of Cu3V2O7(OH)2·2H2O microspheres to ethanol was 1g:40mL, and the volume ratio of tetrabutyl titanate to ethanol was 2.1:

40. After stirring for 1 hour, ammonia water was added dropwise and stirring was continued for another hour. The hydrothermal reaction temperature was 150℃ and the reaction time was 12 hours. The calcination temperature was 300℃ and the calcination time was 1 hour. The mass fraction of ammonia water was 25-30%, and the volume of ammonia water accounted for 0.3% of the total volume.

10. A method for purifying flue gas, characterized in that: The bifunctional catalyst described in any one of claims 1-4 is used to convert CO and NOx in flue gas into CO2 and N2.

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