Titanium-modified composite catalyst, preparation method and application thereof

Abstract

The invention provides a titanium-modified composite catalyst, a preparation method and application thereof, the titanium-modified composite catalyst comprises (a) Pd-(b) Pt / CexTiyO2, a and b respectively represent the loading capacities of Pd and Pt, a and b are respectively 0.25-0.5% (w / w), the molar ratio of x to y is 1: 0.3-3, introduction of Ti in the composite catalyst promotes transfer of electrons between carriers in active components, and the specific surface area of the composite catalyst is increased. When the catalyst is used, a large number of oxygen vacancy defects and Ce < 3 + > can be generated, adsorption and activation of reactant molecules are promoted, and the catalyst has good activity, poisoning resistance and CO oxidation capacity. Compared with a Pd-Pt / CeO2 series catalyst, the activity of the Pd-Pt / CeTiO2 series catalyst added with the auxiliary agent Ti is obviously enhanced.

Description

Technical Field

[0001] This application relates to the fields of carbon monoxide catalytic oxidation materials and air pollution control technology, and in particular to a titanium-modified composite catalyst, its preparation method and its uses. Background Technology

[0002] In recent years, the characteristics of air pollution have shifted from localized and singular air pollution to regional and complex air pollution, drawing increasing public attention. Emissions of unconventional pollutants such as carbon monoxide (CO) are attracting growing attention, primarily originating from industrial flue gas and vehicle exhaust from the incomplete combustion of fossil fuels. Relevant regulations now require online CO monitoring of sintering flue gas and adherence to a CO concentration of 5000 mg / m³. 3 The emission standards. Among CO purification technologies, catalytic oxidation is clearly the most efficient, energy-saving, and pollution-free purification method. Moreover, the chemical heat released by the complete oxidation of CO can supplement the selective catalytic reduction (SCR) denitrification process. The key element of catalytic oxidation is the catalyst.

[0003] Currently, although researchers both domestically and internationally have conducted numerous studies on low-temperature CO oxidation catalysts from aspects such as compositional regulation and preparation condition optimization, fundamental problems such as low CO removal activity, poor resistance to poisoning, and susceptibility to side reactions at low temperatures remain unresolved. Firstly, the temperature of sintering flue gas in steelmaking is typically between 150-200 °C, and no catalytic system with good CO removal performance has yet been found in this temperature range. Although many reported catalytic systems exhibit good CO oxidation efficiency between 150-200 °C, most sintering flue gas in steelmaking also contains PM, SO2, and water vapor, requiring further improvement in the catalyst's resistance to poisoning. Secondly, side reactions such as SO2 oxidation easily occur on the catalyst; therefore, designing novel and highly efficient CO catalytic oxidation catalysts requires balancing redox properties and comprehensively regulating the catalyst's acid-base properties. Summary of the Invention

[0004] To address the technical problems existing in the prior art, this application provides a titanium-modified composite catalyst, its preparation method, and its uses. The composite catalyst described in this application has good CO oxidation ability.

[0005] The specific technical solution of this application is as follows: 1. A titanium-modified composite catalyst having the composition (a)Pd-(b)Pt / Ce x Ti y O2, where a and b represent the loading of Pd and Pt respectively, a and b are 0.25-0.5% (w / w) respectively, and the molar ratio of x and y is 1:0.3-3.

[0006] 2. The composite catalyst according to item 1, wherein the molar ratio of x to y is 1:0.5-2.

[0007] 3. The composite catalyst according to item 1 or 2, wherein the composite catalyst has a characteristic peak at 2θ of 25.3 ± 0.5° in X-ray diffraction.

[0008] 4. The composite catalyst according to item 3, wherein the composite catalyst has characteristic peaks at 2θ of 28.5±0.5°, 33.1±0.5°, 47.9±0.5°, and 57.1±0.5° in X-ray diffraction.

[0009] 5. A method for preparing the composite catalyst according to any one of items 1-4, comprising: Ammonia water was added to a solution containing cerium salts, and the solution was filtered and dried, followed by calcination to obtain CeO2 oxide. A solution containing tetrabutyl titanate was added to the CeO2 oxide, water was added and the mixture was stirred until dry, followed by drying and calcination to obtain Ce. x Ti y O2 composite oxides; To Ce x Ti y A solution containing a palladium salt and a solution containing a platinum salt were added to an O2 composite oxide, and the mixture was stirred until dry. The resulting product was then dried and calcined to obtain (a) Pd-(b) Pt / Ce. x Ti y O2 composite catalyst.

[0010] 6. The method according to claim 7, wherein the cerium-containing salt is cerium nitrate, cerium ammonium nitrate, cerium sulfate, cerium acetate, or cerium citrate; and / or The palladium-containing salt is palladium nitrate; and / or The platinum-containing salt is platinum nitrate.

[0011] 7. The method according to item 5 or 6, wherein the molar ratio of the CeO2 oxide and tetrabutyl titanate is 1:0.3-3, preferably 1:0.5-2.

[0012] 8. The method according to any one of items 5-7, wherein the drying temperature is 80-120°C and the drying time is 12-24 h; and / or The roasting temperature is 450-650℃, and the roasting time is 1-3 hours.

[0013] 9. The use of the composite catalyst described in any one of items 1-4 or the composite catalyst prepared by any one of items 5-8 in the oxidation of CO; Optionally, the composite catalyst is used to oxidize CO emitted from sintering flue gas of steel plants, coal-fired power plants, coking plants, biomass boilers, gas-fired power plants, cement kilns, or mobile sources of diesel vehicles.

[0014] 10. A method for oxidizing CO, comprising: CO reaction gas is passed into a reactor containing a composite catalyst as described in any one of items 1-4 or a composite catalyst prepared by any one of items 5-8 to produce CO2.

[0015] Beneficial effects The composite catalyst described in this application can leverage the synergistic catalytic effect between the titanium-modified CeO2 composite support and the noble metals Pd and Pt, thereby improving the catalyst activity to a certain extent. The introduction of Ti promotes electron transfer between the supports and the active components, generating a large number of oxygen vacancy defects and CeO2. 3+ This promotes the adsorption and activation of reactant molecules, giving it good activity and anti-poisoning properties, as well as excellent CO oxidation capacity. Compared with the Pd-Pt / CeO2 series catalysts, the activity of the Pd-Pt / CeTiO2 series catalysts is significantly enhanced after the addition of the auxiliary agent (the temperature point for complete CO reaction is reduced by 20-40 ℃). This can provide theoretical and technical support for the purification and removal of CO from sintering flue gas in iron and steel, and can also be extended to the CO removal problems in industries such as coking, biomass boilers, gas-fired power plants, and cement kilns. Attached Figure Description

[0016] Figure 1 The images show a comparison of the XRD patterns of the composite catalysts prepared in Examples 1-3 and Comparative Examples 1-3.

[0017] Figure 2 The graph shows a comparison of the catalytic CO oxidation performance of the composite catalysts prepared in Examples 1-3 and Comparative Examples 1-3.

[0018] Figure 3 This is a schematic diagram of the catalytic CO oxidation performance of the composite catalysts prepared in Examples 1 and 4-5.

[0019] Figure 4 This is a graph showing the catalytic CO oxidation performance of the composite catalyst prepared in Comparative Example 4.

[0020] Figure 5 This is a graph showing the catalytic CO oxidation performance of the composite catalyst prepared in Comparative Example 5.

[0021] Figure 6 The diagram shows the continuous operation stability of the composite catalyst prepared in Example 1.

[0022] Figure 7The graph shows the stability of the catalyst prepared in Example 1 under continuous operation at 280°C against 10 ppm toluene. Detailed Implementation

[0023] The present application will now be described in detail with reference to the described embodiments. Although specific embodiments of the present application are shown, it should be understood that the present application can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this application will be thorough and complete, and will fully convey the scope of the present application to those skilled in the art.

[0024] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions in the specification are preferred embodiments for carrying out this application; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of this application. The scope of protection of this application shall be determined by the appended claims.

[0025] This application provides a titanium-modified composite catalyst with the following composition: (a) Pd-(b) Pt / Ce x Ti y O2, where a and b represent the loading amounts of Pd and Pt, respectively, and a and b are 0.25-0.5% (w / w), and the molar ratio of x to y is 1:0.3-3, preferably 1:0.5-2.

[0026] For example, a and b can be 0.25% (w / w), 0.26% (w / w), 0.27% (w / w), 0.28% (w / w), 0.29% (w / w), 0.30% (w / w) respectively. ), 0.31%(w / w), 0.32%(w / w), 0.33%(w / w), 0.34%(w / w), 0.35%(w / w), 0.36%(w / w), 0.37%( w / w), 0.38%(w / w), 0.39%(w / w), 0.40%(w / w), 0.41%(w / w), 0.42%(w / w), 0.43%(w / w), 0.4 4%(w / w), 0.45%(w / w), 0.46%(w / w), 0.47%(w / w), 0.48%(w / w), 0.49%(w / w), 0.50%(w / w), etc.

[0027] The molar ratio of x and y (n)x :n y The ratios can be 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.0, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2.0, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3.0, etc.

[0028] In this application, no restrictions are placed on the method for determining the loading of Pd and Pt. Those skilled in the art can make conventional choices based on actual needs. For example, inductively coupled plasma spectroscopy (ICP) can be used to determine the loading of Pd and Pt.

[0029] In some embodiments, the composite catalyst exhibits a characteristic peak at 2θ of 25.3 ± 0.5° in X-ray diffraction. In some embodiments, the composite catalyst exhibits characteristic peaks at 2θ of 28.5 ± 0.5°, 33.1 ± 0.5°, 47.9 ± 0.5°, and 57.1 ± 0.5° in X-ray diffraction.

[0030] The composite catalyst described in this application has Ti placed in the CeO2 lattice, which significantly enhances the activity of the composite catalyst.

[0031] This application provides a method for preparing the composite catalyst described in any one of the above claims, comprising: Ammonia water was added to a solution containing cerium salts, and the solution was filtered and dried, followed by calcination to obtain CeO2 oxide. A solution containing tetrabutyl titanate was added to the CeO2 oxide, water was added and the mixture was stirred until dry, followed by drying and calcination to obtain Ce. x Ti y O2 composite oxides; To Ce x Ti y A solution containing a palladium salt and a solution containing a platinum salt were added to an O2 composite oxide, and the mixture was stirred until dry. The resulting product was then dried and calcined to obtain (a) Pd-(b) Pt / Ce. x Ti y O2 composite catalyst.

[0032] This application obtains CeO2 oxide by first preparing CeO2 oxide, then adding a solution containing tetrabutyl titanate, adding water, stirring until dry, and then drying and calcining. x Ti y In O2 composite oxides, Ti is incorporated into CeO2 oxides, which can improve the catalytic activity of the composite catalyst.

[0033] In this application, adding ammonia to a solution containing cerium-containing salts means maintaining the pH of the solution within an alkaline range, preferably within the range of 8-10, and more preferably within the range of 8-9.

[0034] In this application, the vacuum filtration drying is performed using methods conventional in the art.

[0035] In this application, the term "solution containing tetrabutyl titanate" refers to a solution obtained by dissolving tetrabutyl titanate in some organic solvents. This application does not impose any restrictions on the organic solvents used, and those skilled in the art can make conventional selections based on actual needs, as long as they meet the requirements of this application. For example, the organic solvents can be ethanol, methanol, isopropanol, etc.

[0036] In some embodiments, the cerium-containing salt is cerium nitrate, cerium ammonium nitrate, cerium sulfate, cerium acetate, cerium citrate; and / or The palladium-containing salt is palladium nitrate; and / or The platinum-containing salt is platinum nitrate.

[0037] In some embodiments, the molar ratio of CeO2 oxide to tetrabutyl titanate is 1:0.3-3, preferably 1:0.5-2.

[0038] For example, the molar ratio of CeO2 oxide to tetrabutyl titanate (n CeO2氧化物 :n 钛酸四丁酯 The ratios can be 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.0, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2.0, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3.0, etc.

[0039] In some embodiments, the drying temperature is 80-120°C, and the drying time is 12-24 hours; and / or The roasting temperature is 450-650℃, and the roasting time is 1-3 hours.

[0040] In some embodiments, the drying temperature may be, for example, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, etc. The drying time can be 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, etc.

[0041] The roasting temperature can be 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 570℃, 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, 640℃, 650℃, etc.

[0042] The roasting time can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, etc.

[0043] This application provides the use of the composite catalyst described in any one of the above claims or the composite catalyst prepared by the method described in any one of the above claims in the oxidation of CO.

[0044] The addition of Ti to the composite catalyst described in this application can significantly enhance its catalytic activity, which can provide theoretical and technical support for the purification and removal of CO from sintering flue gas in iron and steel.

[0045] Example This application provides a general and / or specific description of the materials and test methods used in the experiments. In the following examples, unless otherwise specified, % represents wt%, i.e., weight percentage. Reagents or instruments used, unless otherwise specified, are all commercially available conventional reagent products.

[0046] Example 1: Preparation of 0.5Pd-0.5Pt / Ce1Ti1O2 composite catalyst (a) 0.2 mol of cerium nitrate was dissolved in 100 mL of deionized water and stirred at room temperature for 30 min to obtain a clear solution. Then, excess ammonia was added dropwise to the clear solution to make the pH value of the solution 8. The resulting mixed solution was filtered, washed, dried at 120 °C for 12 h, and then placed in a muffle furnace and calcined at 500 °C for 1 h to obtain CeO2 oxide.

[0047] (b) Weigh 6.8064 g of tetrabutyl titanate (0.02 mol) and disperse it in 10 mL of ethanol. Mix it with 3.4423 g of the solid obtained in step (a) (0.02 mol) and stir. Then add excess deionized water dropwise and stir in a water bath at 80 °C. Dry the solid at 120 °C for 12 h, grind it for 30 min, and then place it in a muffle furnace and calcine it at 500 °C for 1 h to obtain Ce1Ti1O2 oxide. (c) Weigh 2 g of the solid obtained in step (b) and place it in a crucible. Then add 1 mL of platinum nitrate solution (0.01 g / mL) and 1 mL of palladium nitrate solution (0.01 g / mL) and stir to dry in a water bath at 80 °C. Dry at 120 °C for 12 h, then place it in a muffle furnace and calcine at 500 °C for 1 h. Finally, place it in a tube furnace and pretreat at 300 °C for 1 h in a 5% H2 atmosphere to obtain the 0.5Pd-0.5Pt / Ce1Ti1O2 composite catalyst.

[0048] Example 2 0.5Pd-0.5Pt / Ce1Ti 0.5 Preparation of O2 composite catalyst (a) Weigh 0.1 mol of cerium nitrate and dissolve it in 100 mL of deionized water. Stir at room temperature for 30 min. Then, add excess ammonia dropwise to the clear solution to make the pH value of the solution 9. After filtering and washing the resulting mixed solution, dry it at 120 °C for 24 h. Then, place it in a muffle furnace and calcine it at 500 °C for 2 h to obtain CeO2 oxide.

[0049] (b) Weigh 3.4032 g of tetrabutyl titanate (0.01 mol) and disperse it in 10 mL of ethanol. Mix it with 3.4423 g of the solid obtained in step (a) (0.02 mol) and stir. Then add excess deionized water dropwise and stir to dry in a water bath at 80 °C. Dry the resulting solid at 120 °C for 12 h, grind it for 40 min, and then calcine it in a muffle furnace at 500 °C for 1 h to obtain Ce1Ti. 0.5 O2 oxides; (c) Weigh 2 g of the solid obtained in step (b) into a crucible, then add 1 mL of platinum nitrate solution (0.01 g / mL) and 1 mL of palladium nitrate solution (0.01 g / mL), and stir to dry in a water bath at 80 °C; dry at 120 °C for 12 h, then place in a muffle furnace and calcine at 500 °C for 2 h, and finally place in a tube furnace and pretreat at 300 °C for 1 h in a 5% H2 atmosphere to obtain 0.5Pd-0.5Pt / Ce1Ti. 0.5 O2 composite catalyst.

[0050] Example 3 0.5Pd-0.5Pt / Ce1Ti 1.5 Preparation of O2 composite catalyst (a) Weigh 0.3 mol of cerium nitrate and dissolve it in 100 mL of deionized water. Stir at room temperature for 30 min. Then, add excess ammonia dropwise to the clear solution to make the pH value of the solution 8. After filtering and washing the resulting mixed solution, dry it at 120 °C for 12 h. Then, place it in a muffle furnace and calcine it at 500 °C for 1 h to obtain CeO2 oxide.

[0051] (b) Weigh 10.2096 g of tetrabutyl titanate (0.03 mol) and disperse it in 20 mL of ethanol. Mix it with 3.4423 g of the solid obtained in step (a) (0.02 mol) and stir. Then add excess deionized water dropwise. Stir the mixture in a water bath at 80 °C until dry. Dry the resulting solid at 120 °C for 12 h, grind it for 30 min, and then calcine it in a muffle furnace at 500 °C for 1 h to obtain Ce1Ti. 1.5 O2 oxides; (c) Weigh 2 g of the solid obtained in step (b) into a crucible, then add 1 mL of platinum nitrate solution (0.01 g / mL) and 1 mL of palladium nitrate solution (0.01 g / mL), and stir to dry in a water bath at 80 °C; dry at 120 °C for 12 h, then place in a muffle furnace and calcine at 500 °C for 2 h, and finally place in a tube furnace and pretreat at 300 °C for 1 h in a 5% H2 atmosphere to obtain 0.5Pd-0.5Pt / Ce1Ti. 1.5 O2 composite catalyst.

[0052] Example 4: Preparation of 0.5Pd-0.5Pt / Ce1Ti2O2 composite catalyst The difference between Example 4 and Example 1 is that 13.6128 g of tetrabutyl titanate (0.04 mol) was used to prepare the composite catalyst.

[0053] Example 5 0.5Pd-0.5Pt / Ce1Ti 0.3 Preparation of O2 composite catalyst The difference between Example 5 and Example 1 is that 2.04192 g of tetrabutyl titanate (0.006 mol) was used to prepare the composite catalyst.

[0054] Comparative Example 1: Preparation of 0.5Pd-0.5Pt / CeO2 composite catalyst (a) Weigh 0.3 mol of cerium nitrate and dissolve it in 100 mL of deionized water. Stir at room temperature for 30 min. Then, add excess ammonia dropwise to the clear solution to make the pH value of the solution 8. After filtering and washing the resulting mixed solution, dry it at 120 °C for 12 h. Then, place it in a muffle furnace and calcine it at 500 °C for 1 h to obtain CeO2 oxide.

[0055] (b) Weigh 2 g of the solid obtained in step (a) and place it in a crucible. Then add 1 mL of platinum nitrate solution (0.01 g / mL) and 1 mL of palladium nitrate solution (0.01 g / mL) and stir to dry in a water bath at 80 °C. Dry at 120 °C for 12 h, then place it in a muffle furnace and calcine at 500 °C for 2 h. Finally, place it in a tube furnace and pretreat at 300 °C for 1 h in a 5% H2 atmosphere to obtain the 0.5Pd-0.5Pt / CeO2 composite catalyst.

[0056] Comparative Example 2: Preparation of 0.5Pd-0.25Pt / CeO2 composite catalyst (a) Weigh 0.2 mol of cerium nitrate and dissolve it in 100 mL of deionized water. Stir at room temperature for 30 min. Then, add excess ammonia dropwise to the clear solution to make the pH value of the solution 8. After filtering and washing the resulting mixed solution, dry it at 120 °C for 12 h, and then place it in a muffle furnace and calcine it at 500 °C for 1 h to obtain CeO2 oxide. (b) Weigh 2 g of the solid obtained in step (a) and place it in a crucible. Then add 0.1 mL of platinum nitrate solution (0.01 g / mL) and 1 mL of palladium nitrate solution (0.01 g / mL) and stir to dry in a water bath at 80 °C. Dry at 120 °C for 12 h, then place it in a muffle furnace and calcine at 500 °C for 2 h. Finally, place it in a tube furnace and pretreat at 300 °C for 1 h in a 5% H2 atmosphere to obtain the 0.5Pd-0.25Pt / CeO2 composite catalyst.

[0057] Preparation of Comparative Example 3: 0.5Pd / CeO2 Composite Catalyst a) Weigh 0.2 mol of cerium nitrate and dissolve it in 100 mL of deionized water, stirring at room temperature for 30 min; then add excess ammonia dropwise to the clear solution to make the pH value of the solution 8. After filtering and washing the resulting mixed solution, dry it at 120 ℃ for 12 h, and then place it in a muffle furnace and calcine it at 500 ℃ for 1 h to obtain CeO2 oxide; c) Weigh 2 g of the solid obtained in step (a) and place it in a crucible. Then add 1 mL of palladium nitrate solution (0.01 g / mL) and stir dry in a water bath at 80 °C. Dry at 120 °C for 12 h, then place it in a muffle furnace and calcine at 500 °C for 2 h. Finally, place it in a tube furnace and pretreat at 300 °C for 1 h in a 5% H2 atmosphere to obtain the 0.5Pd / CeO2 composite catalyst.

[0058] Comparative Example 4: Preparation of 0.5Pd-0.5Pt / CeTiO2-(S) composite catalyst (a) 0.2 mol of cerium nitrate was dissolved in 100 mL of deionized water and stirred at room temperature for 30 min to obtain a clear solution. Then, excess ammonia was added dropwise to the clear solution to make the pH value of the solution 8. The resulting mixed solution was filtered, washed, dried at 120 °C for 12 h, and then placed in a muffle furnace and calcined at 500 °C for 1 h to obtain CeO2 oxide.

[0059] (b) Weigh 6.8064 g of titanium sulfate and disperse it in 10 mL of ethanol. Mix it with 3.4423 g of the solid obtained in step (a) and stir. Then add excess deionized water dropwise. Stir dry in a water bath at 80 °C. Dry the resulting solid at 120 °C for 12 h. Grind it for 30 min. Then place it in a muffle furnace and calcine it at 500 °C for 1 h to obtain CeTiO2-(S) oxide. (c) Weigh 2 g of the solid obtained in step (b) and place it in a crucible. Then add 1 mL of platinum nitrate solution (0.01 g / mL) and 1 mL of palladium nitrate solution (0.01 g / mL) and stir to dry in a water bath at 80 °C. Dry at 120 °C for 12 h, then place it in a muffle furnace and calcine at 500 °C for 1 h. Finally, place it in a tube furnace and pretreat at 300 °C for 1 h in a 5% H2 atmosphere to obtain the 0.5Pd-0.5Pt / CeTiO2-(S) composite catalyst.

[0060] Preparation of Comparative Example 5: 0.5Pd-0.5Pt / CeO2-TiO2 Composite Catalyst (a) 6.8064 g of tetrabutyl titanate (0.02 mol) was weighed and dispersed in 20 mL of ethanol, and mixed with 0.02 mol of cerium nitrate. The mixture was stirred in a water bath at 80 °C and dried. The resulting solid was dried at 120 °C for 12 h, ground for 30 min, and then placed in a muffle furnace and calcined at 500 °C for 1 h to obtain CeO2-TiO2 composite catalyst oxide. (c) Weigh 2 g of the solid obtained in step (b) and place it in a crucible. Then add 1 mL of platinum nitrate solution (0.01 g / mL) and 1 mL of palladium nitrate solution (0.01 g / mL) and stir to dry in a water bath at 80 °C. Dry at 120 °C for 12 h, then place it in a muffle furnace and calcine at 500 °C for 1 h. Finally, place it in a tube furnace and pretreat at 300 °C for 1 h in a 5% H2 atmosphere to obtain the 0.5Pd-0.5Pt / CeO2-TiO2 composite catalyst.

[0061] Experimental Example 1. XRD test The crystal forms of the composite catalysts in Examples 1-3 and Comparative Examples 1-3 were tested using X-ray diffraction, and the results are as follows: Figure 1 As shown. All samples exhibited characteristic diffraction peaks of the fluorite phase CeO2 (PDF#04-0593), with diffraction peaks at 2θ = 28.5°, 33.1°, 47.9°, 57.1°, 59.1°, 69.4°, 76.7°, and 79.1° corresponding to the (111), (200), (220), (311), (222), (400), (331), and (420) crystal planes of CeO2, respectively. In contrast to the composite catalysts of Comparative Examples 1-3, the catalysts of Examples 1-3 showed characteristic diffraction peaks of the anatase (101) crystal plane at 2θ = 25.3° (PDF#83-2243). Subsequently, it was found that with the introduction of Ti, the intensity of the characteristic diffraction peaks of CeO2 weakened, while the intensity of the characteristic diffraction peaks of TiO2 strengthened. Furthermore, no diffraction peaks of any Pd and Pt species were observed in the XRD pattern, and the Pt and Pd loaded samples did not show any phase difference with CeO2 and TiO2, indicating that no new species were generated. This suggests that Pt and Pd are highly dispersed on the catalyst surface in the form of extremely small nanoparticles or clusters, which may also be attributed to the low loading.

[0062] 2. CO oxidation performance experiment 100 mg of the composite catalysts from Examples 1-5 and Comparative Examples 1-5 (40-60 mesh) were mixed with 100 mg of quartz sand or SiC and loaded into reaction tubes for experiments. A reaction gas containing a certain concentration of CO (1% CO, 1% O2, with the remainder being N2 as a balance gas, total flow rate 100 mL / min) was prepared and introduced into the catalytic bed for the catalytic reaction. The gas hourly space velocity (GHSV) was 60,000 mL / g. cat •h. The CO oxidation performance of the catalyst was tested at different temperatures, and the results are as follows: Figure 2-5 As shown. The composite catalyst of Example 1 operated stably for 50 hours at a reaction temperature of 70 °C, and the results are as follows. Figure 6 As shown. Subsequently, 10 ppm of toluene was added during the reaction, and the temperature was raised to 280 °C. The composite catalyst of Example 1 was continuously operated for 50 hours, and the results are as follows. Figure 7 As shown.

[0063] Depend on Figure 2It can be seen that, compared with the composite catalysts of Comparative Examples 1-2, the composite catalysts of Examples 1-3 showed significantly improved activity after the addition of the promoter Ti (the temperature point for complete CO reaction decreased by 20-40 °C). Furthermore, as the molar fraction of Ti increased, the catalyst performance first increased and then decreased, reaching its optimal activity for CO at a Ce:Ti molar ratio of 1:1. Secondly, compared with Comparative Example 3, it was found that when a bimetallic catalyst was used, the overall CO activity of the bimetallic catalyst was superior to that of the monometallic catalyst. This is due to the synergistic effect and electronic effect between the bimetallic catalysts, which improved the catalytic activity.

[0064] from Figure 3 It can be seen that Examples 4-5 also have certain catalytic performance.

[0065] from Figure 3-5 It can be seen that the presence of sulfur in the composite catalyst greatly reduces its catalytic activity.

[0066] Depend on Figure 6 , Figure 7 It can be seen that the CO conversion rate of the composite catalyst is consistently maintained above 90% during long-term continuous catalytic oxidation of CO, indicating that the introduction of toluene does not affect the CO conversion rate, thus demonstrating that the composite catalyst exhibits excellent VOCs resistance performance.

[0067] The above description is merely a preferred embodiment of this application and is not intended to limit the application in any other way. Any person skilled in the art may make changes or modifications to the disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the protection scope of this application.

Claims

1. A titanium-modified composite catalyst having the following composition: (a) Pd-(b) Pt / Ce x Ti y O2, where, a and b represent the loading amounts of Pd and Pt, respectively, with a and b being 0.25-0.5% (w / w), and the molar ratio of x to y is 1:0.3-3.

2. The composite catalyst according to claim 1, wherein the molar ratio of x to y is 1:0.5-2.

3. The composite catalyst according to claim 1 or 2, wherein the composite catalyst has a characteristic peak at 2θ of 25.3 ± 0.5° under X-ray diffraction.

4. The composite catalyst according to claim 3, wherein the composite catalyst has characteristic peaks at 2θ of 28.5±0.5°, 33.1±0.5°, 47.9±0.5°, and 57.1±0.5° in X-ray diffraction.

5. A method for preparing the composite catalyst according to any one of claims 1-4, comprising: Ammonia water was added to a solution containing cerium salts, and the solution was filtered and dried, followed by calcination to obtain CeO2 oxide. A solution containing tetrabutyl titanate was added to the CeO2 oxide, water was added and the mixture was stirred until dry, followed by drying and calcination to obtain Ce. x Ti y O2 composite oxides; To Ce x Ti y A solution containing a palladium salt and a solution containing a platinum salt were added to an O2 composite oxide, and the mixture was stirred until dry. The resulting product was then dried and calcined to obtain (a) Pd-(b) Pt / Ce. x Ti y O2 composite catalyst.

6. The method of claim 7, wherein the cerium-containing salt is cerium nitrate, cerium ammonium nitrate, cerium sulfate, cerium acetate, or cerium citrate; and / or The palladium-containing salt is palladium nitrate; and / or The platinum-containing salt is platinum nitrate.

7. The method according to claim 5 or 6, wherein the molar ratio of CeO2 oxide to tetrabutyl titanate is 1:0.3-3, preferably 1:0.5-2.

8. The method according to any one of claims 5-7, wherein the drying temperature is 80-120°C and the drying time is 12-24 h; and / or The roasting temperature is 450-650℃, and the roasting time is 1-3 hours.

9. Use of the composite catalyst according to any one of claims 1-4 or the composite catalyst prepared by the method according to any one of claims 5-8 in the oxidation of CO; Optionally, the composite catalyst is used to oxidize CO emitted from sintering flue gas of steel plants, coal-fired power plants, coking plants, biomass boilers, gas-fired power plants, cement kilns, or mobile sources of diesel vehicles.

10. A method for oxidizing CO, comprising: CO reaction gas is passed into a reactor containing the composite catalyst of any one of claims 1-4 or the composite catalyst prepared by any one of claims 5-8 to produce CO2.

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