N-doped auxiliary agent modified TiO2 loaded Pt-based CO oxidation catalyst and preparation method thereof

Abstract

The invention discloses an N-doped auxiliary agent modified TiO2 loaded Pt-based CO oxidation catalyst and a preparation method thereof, and belongs to the field of environmental engineering. The catalyst comprises a carrier, an N-doped auxiliary agent and an active component, the carrier is TiO2, the N-doped auxiliary agent is N-doped MoO3 and / or WO3, and the active component is Pt. The preparation method comprises the following steps: (1) loading an auxiliary agent MoO3 and / or WO3 on a TiO2 carrier to obtain an auxiliary agent modified carrier; (2) placing the auxiliary agent modified carrier in a tubular furnace, and carrying out heat treatment in NH3 / N2 mixed gas to obtain an N-doped auxiliary agent modified carrier; and (3) loading Pt on the N-doped auxiliary agent modified carrier, so as to obtain the N-doped auxiliary agent modified TiO2 loaded Pt-based CO oxidation catalyst. The obtained catalyst has good low-temperature CO oxidation catalysis activity and sulfur poisoning resistance, and can be used for removing CO in tail gas of steel sintering, coking, boilers and the like.

Description

TECHNICAL FIELD

[0001] The application relates to an N-doping assistant modified TiO2 loaded Pt-based CO oxidation catalyst and a preparation method thereof, which can be used for removing CO in tail gas of steel sintering, coking, boiler and the like and recovering reaction heat at the same time, and belongs to the field of environmental engineering. BACKGROUND

[0002] Waste gas discharged in the production process of sintering, coking and the like of steel enterprises contains high-concentration CO gas and is an important CO emission source. With the continuous promotion of air pollution prevention and control work in various regions, CO, as one of the main air pollutants, has attracted more and more attention. CO is a toxic gas, and when its concentration in the air reaches 0.1%, it can cause fatal poisoning in a short time. At the same time, CO is an important energy material, and its combustion (oxidation) process will release a large amount of heat. The catalytic oxidation method for removing CO in industrial flue gas has the advantages of low operation temperature, high removal efficiency and recycling of CO oxidation heat. In addition, the CO oxidation unit can be arranged in the catalytic denitration device, so that no additional CO oxidation reactor is needed.

[0003] Since the temperature of industrial flue gas is often low (100-200 DEG C) and contains a large amount of H2O, and the flue gas after desulfurization treatment still contains a small amount of SO2, the developed CO oxidation catalyst needs to have high activity at a relatively low temperature and resistance to H2O and SO2. Platinum group noble metal catalysts have high catalytic activity for CO oxidation, and H2O can promote the oxidation of CO when TiO2 and the like are used as the carrier, so they are widely studied for eliminating CO in industrial flue gas. One of the current research focuses is to improve the utilization rate of noble metals to reduce their loadings, thereby reducing the cost of the catalyst; the other focus is to improve the resistance of the catalyst to SO2 and the like. SO2 is adsorbed and oxidized on the surface of the catalyst to form sulfate species, which causes the active metal and / or the carrier to be covered or sulfated, which is one of the main reasons for the poisoning and deactivation of the catalyst.

[0004] CN121130881A discloses a catalyst for CO removal from sulfur-containing sintering flue gas and its preparation method. This invention uses concentrated sulfuric acid impregnation combined with power gradient microwave treatment to treat a TiO2 support. Pt, La, and Ce active components are simultaneously loaded onto the treated support, resulting in a CO oxidation catalyst with certain activity and sulfur resistance. The CO conversion rate can reach 90% at 200 °C under sulfur- and water-containing conditions. CN117258820A discloses a method for preparing an acidified N-doped Pt / TiO2-N catalyst and the catalyst itself. This invention modifies the TiO2 support sequentially using dilute sulfuric acid impregnation, H2 reduction treatment, and NH3 treatment. This increases the acidity of the support while introducing N groups. During the impregnation process, the N anchoring effect on Pt improves the dispersion of Pt. The prepared catalysts can achieve high CO conversion rates at 160–180 °C when the reaction gas is free of sulfur and water, and can achieve stable operation at 200 °C when the reaction gas contains 50 ppm SO2 and 15% H2O. The preparation processes of the above CO oxidation catalysts are all relatively complex, and the stable operating temperature of the catalysts remains high under sulfur-containing conditions. Summary of the Invention

[0005] This invention proposes a Pt-based CO oxidation catalyst supported on TiO2 with N-doped additive and its preparation method. The CO oxidation catalyst exhibits high activity and sulfur resistance at relatively low temperatures and can be used to remove CO from tail gases from steel sintering, coking, and boiler processes. The catalyst preparation method employs a strategy of using N-doped additive to modify TiO2 to promote Pt dispersion and the synergistic effect of Pt and the additive. The preparation process is simple and suitable for large-scale production.

[0006] This invention is achieved through the following technical solution:

[0007] One objective of this invention is to provide a Pt-based CO oxidation catalyst supported on TiO2 and modified with an N-doped auxiliary agent. The catalyst comprises a support, an N-doped auxiliary agent, and an active component, wherein the support is TiO2, the N-doped auxiliary agent is N-doped MoO3 and / or WO3, and the active component is Pt.

[0008] Furthermore, in the CO oxidation catalyst, the N-doped auxiliary agent is loaded on the original support to obtain an N-doped auxiliary agent modified support, while the active component is loaded on the N-doped auxiliary agent modified support.

[0009] Furthermore, the content of the active component Pt in the CO oxidation catalyst is 0.1~1.0 wt.%, and the content of the auxiliary agent MoO3 and / or WO3 is 0.5~5.0 wt.%.

[0010] Another object of the present invention is to provide a method for preparing a TiO2-supported Pt-based CO oxidation catalyst modified with N-doped promoter, the preparation method comprising the following steps:

[0011] (1) Disperse the TiO2 support in deionized water and dissolve the precursor of the additive in deionized water. Then mix the two solutions (suspension) evenly and place the resulting mixture in an ultrasonic water bath at 50~80 ℃. Stir for 1~5 h and then place it in an oven to dry at 100~120 ℃. Grind the dried material into powder and place it in a muffle furnace to calcine in an air atmosphere at 300~500 ℃ for 2~4 h. After cooling, the additive-modified support is obtained.

[0012] (2) Place the carrier modified by the additive obtained in step (1) in a tube furnace, introduce NH3 / N2 mixed gas, heat to 300~500 ℃ at a heating rate of 3~5℃ / min, treat for 3~5 h and then cool to room temperature to obtain the carrier modified by N doped additive.

[0013] (3) Disperse the N-doped auxiliary modified support obtained in step (2) in deionized water, and dissolve the Pt precursor in deionized water. Then mix the two solutions (suspension) evenly and place the resulting mixture in an ultrasonic water bath at 50~80 ℃. After stirring for 1~5 h, place it in an oven and dry it at 100~120 ℃. Grind the dried material into powder and place it in a muffle furnace. Calcine it in an air atmosphere at 400~600 ℃ for 2~4 h. After cooling, obtain the Pt-based CO oxidation catalyst supported on TiO2 modified by N-doped auxiliary.

[0014] Further, the precursor of the auxiliary agent in step (1) includes a precursor of MoO3 and / or WO3, wherein the precursor of MoO3 is a molybdate substance, such as ammonium molybdate, ammonium phosphomolybdate, etc., or one or more of them; the precursor of WO3 is a tungstate substance, such as ammonium metatungstate, ammonium paratungstate, etc., or one or more of them.

[0015] Further, the concentration of NH3 in the NH3 / N2 mixed gas in step (2) is 1~5 vol.%.

[0016] Furthermore, the precursor of Pt in step (3) is any one or more of chloroplatinic acid hexahydrate, platinum nitrate, and tetraammineplatinum chloride.

[0017] The present invention provides a TiO2-supported Pt-based CO oxidation catalyst modified with N-doped additive and its preparation method, which has at least the following beneficial effects:

[0018] 1. The prepared catalyst has good low-temperature catalytic CO oxidation activity and sulfur poisoning resistance. It can achieve complete CO conversion at around 100 ℃ under water (10% H2O) conditions, and achieve efficient and stable CO conversion at above 180 ℃ under sulfur and water (50 ppm SO2, 10% H2O) conditions.

[0019] 2. The catalyst preparation process is simple and the conditions are controllable. The amount of precious metals used is low, which greatly reduces the cost of catalyst raw materials and production, and makes it easy to scale up production and promote market application. Attached Figure Description

[0020] Figure 1 This is a schematic flowchart of a method for preparing a Pt-based CO oxidation catalyst supported on TiO2 with N-doped additives, according to an embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram of the catalytic CO oxidation activity of the catalysts obtained in Example 1 and Comparative Example 1 of the present invention.

[0022] Figure 3 This is a schematic diagram of the catalytic CO oxidation activity of the catalysts obtained in Example 2 and Comparative Example 2 of the present invention.

[0023] Figure 4 This is a schematic diagram of the sulfur resistance performance of the catalysts obtained in Example 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0024] The present invention will be further described below with reference to the embodiments, but the present invention is not limited to the following embodiments.

[0025] Example 1

[0026] Figure 1 The flowchart of the preparation method of Pt-based CO oxidation catalyst supported on TiO2 modified with N-doped auxiliary agent provided in Example 1 is shown in the following figure.

[0027] (1) Weigh 24.33 g of TiO2 support and disperse it in deionized water. Separately weigh 0.30 g of ammonium molybdate tetrahydrate ((NH4)6Mo7O 24 MoO3-modified TiO2 (MoO3 / TiO2) was obtained by dissolving the two solutions (suspension) in deionized water, mixing them evenly, and placing the mixture in an ultrasonic water bath at 75 °C for 5 h. After stirring, the mixture was placed in an oven and dried at 110 °C. The dried material was then ground into powder and placed in a muffle furnace and calcined in air at 400 °C for 2 h. After cooling, the MoO3-modified TiO2 (MoO3 / TiO2) support was obtained.

[0028] (2) The MoO3-modified TiO2 (MoO3 / TiO2) support obtained in step (1) is placed in a tube furnace, and 1 vol.% NH3 / N2 mixed gas is introduced. The temperature is heated to 400 ℃ at a heating rate of 3 ℃ / min. After treatment for 3 h, it is cooled to room temperature to obtain N-doped MoO3-modified TiO2 (N-MoO3 / TiO2) support.

[0029] (3) Disperse the N-doped MoO3 modified TiO2 (N-MoO3 / TiO2) support obtained in step (2) in deionized water. Separately weigh 0.20 g of platinum nitrate (Pt(NO3)2) and dissolve it in deionized water. Mix the two solutions (suspension) evenly and place the resulting mixture in an ultrasonic water bath at 75 ℃. After stirring for 5 h, place it in an oven and dry it at 110 ℃. Grind the dried material into powder and place it in a muffle furnace. Calcine it in air at 500 ℃ for 3 h. After cooling, obtain the N-doped MoO3 modified TiO2 supported Pt-based (Pt / N-MoO3 / TiO2) CO oxidation catalyst.

[0030] Example 2

[0031] The catalyst preparation method is the same as in Example 1, but the auxiliary precursor used in step (1) is ammonium paratungstate ((NH4)). 10 H2(W2O7)6), with an amount of 0.27 g, was used to finally prepare a Pt-based (Pt / N-WO3 / TiO2) CO oxidation catalyst supported on TiO2 and doped with WO3.

[0032] Comparative Example 1

[0033] Following the catalyst preparation method in Example 1, but omitting step (2), a MoO3-modified TiO2-supported Pt-based (Pt / MoO3 / TiO2) CO oxidation catalyst was finally prepared.

[0034] Comparative Example 2

[0035] Following the catalyst preparation method in Example 2, but without step (2), a WO3-modified TiO2-supported Pt-based (Pt / WO3 / TiO2) CO oxidation catalyst was finally prepared.

[0036] Test Example 1

[0037] The catalytic activity of the catalysts obtained in Examples 1, 2, Comparative Example 1, and Comparative Example 2 for CO oxidation was tested under simulated flue gas composition of 8000 ppm CO, 16% O2, 10% H2O, and N2 equilibrium, with a space velocity of 45000 mL / (g·h). The results are as follows: Figure 2 and 3As shown, the catalysts obtained in Examples 1 and 2 achieved complete CO conversion at minimum temperatures of 100 and 110 °C, respectively, while the catalysts obtained in Comparative Examples 1 and 2 required a higher temperature (120 °C) to achieve complete CO conversion. Clearly, N-doping modification of the promoters (MoO3 and WO3) supported on TiO2 significantly improved the activity of the subsequently supported Pt catalyst in catalyzing CO oxidation.

[0038] Test Example 2

[0039] The stability of the catalysts obtained in Example 1 and Comparative Example 1 for CO oxidation was tested under the following conditions: simulated flue gas composition of 8000 ppm CO, 16% O2, 10% H2O, 50 ppm SO2, and N2 equilibrium; space velocity of 90000 mL / (g·h); and inlet temperature of 185 ℃. The results are as follows: Figure 4 As shown, the catalyst obtained in Example 1 maintained a CO conversion rate of over 99% throughout the 12-hour test, while the catalyst obtained in Comparative Example 1 only achieved complete CO conversion in the first 1.5 hours, after which the CO conversion rate gradually decreased with time, dropping to around 26% at the end of the test. Clearly, the N-doping modification of the promoter (MoO3) supported on TiO2 significantly improved the sulfur resistance of the subsequently supported Pt catalyst.

[0040] The above test results show that the CO oxidation catalyst prepared by the method described in this invention has good low-temperature activity and sulfur poisoning resistance, and can be used to remove CO from tail gas in steel sintering, coking, boilers, etc., while recovering the heat of reaction.

[0041] Finally, it should be emphasized that the foregoing embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A Pt-based CO oxidation catalyst supported on TiO2 and modified with N-doped additive, characterized in that, The catalyst comprises a support, an N-doped auxiliary agent, and an active component, wherein the support is TiO2, the N-doped auxiliary agent is N-doped MoO3 and / or WO3, and the active component is Pt.

2. The Pt-based CO oxidation catalyst supported on TiO2 and modified with N-doped additive according to claim 1, characterized in that, In the CO oxidation catalyst, the N-doped promoter is loaded on the original support, while the active component is loaded on the support modified by the N-doped promoter.

3. A Pt-based CO oxidation catalyst supported on TiO2 and modified with an N-doped auxiliary agent according to any one of claims 1 and 2, characterized in that, The CO oxidation catalyst contains 0.1-1.0 wt.% of the active component Pt and 0.5-5.0 wt.% of the additives MoO3 and / or WO3.

4. A method for preparing a Pt-based CO oxidation catalyst supported on TiO2 with N-doped auxiliary agent as described in any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Disperse the TiO2 support in deionized water and dissolve the precursor of the additive in deionized water. Then mix the two solutions / suspensions evenly and place the resulting mixture in an ultrasonic water bath at 50~80 ℃. Stir for 1~5 h and then place it in an oven to dry at 100~120 ℃. Grind the dried material into powder and place it in a muffle furnace to calcine in an air atmosphere at 300~500 ℃ for 2~4 h. After cooling, the additive-modified support is obtained. (2) Place the carrier modified by the additive obtained in step (1) in a tube furnace, introduce NH3 / N2 mixed gas, heat to 300~500 ℃ at a heating rate of 3~5 ℃ / min, treat for 3~5 h and then cool to room temperature to obtain the carrier modified by N doped additive. (3) Disperse the N-doped auxiliary modified support obtained in step (2) in deionized water, and dissolve the Pt precursor in deionized water. Then mix the two solutions / suspensions evenly and place the resulting mixture in an ultrasonic water bath at 50~80 ℃. Stir for 1~5 h and then place it in an oven to dry at 100~120 ℃. Grind the dried material into powder and place it in a muffle furnace to calcine in an air atmosphere at 400~600 ℃ for 2~4 h. After cooling, obtain the Pt-based CO oxidation catalyst supported on TiO2 modified by N-doped auxiliary.

5. The preparation method according to claim 4, characterized in that, The precursor of the additive in step (1) includes a precursor of MoO3 and / or WO3, wherein the precursor of MoO3 is a molybdate substance, such as one or more of ammonium molybdate, ammonium phosphomolybdate, etc.; the precursor of WO3 is a tungstate substance, such as one or more of ammonium metatungstate, ammonium paratungstate, etc.

6. The preparation method according to claim 4, characterized in that, In step (2), the concentration of NH3 in the NH3 / N2 mixed gas is 1~5 vol.%.

7. The preparation method according to claim 4, characterized in that, The precursor of Pt in step (3) is any one or more of chloroplatinic acid hexahydrate, platinum nitrate, and tetraammineplatinum chloride.

8. An application of a Pt-based CO oxidation catalyst supported on TiO2 and modified with N-doped additives, prepared according to any one of claims 1 to 3 or according to any one of claims 4 to 7, for removing CO from tail gas from steel sintering, coking, boilers, etc.

9. According to the application described in claim 8, CO can be completely converted at around 100 °C under conditions containing water (10% H2O), and CO can be efficiently and stably converted at above 180 °C under conditions containing sulfur and water (50 ppm SO2, 10% H2O), including maintaining a CO conversion rate of over 99% for 12 hours.

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