A TiO2-supported MnO x -CeO x Methods for synergistic catalytic oxidation of VOCs and mercury using catalysts

Abstract

The application discloses a TiO2 loaded MnO x -CeO x Method for synergistically catalyzing oxidation of VOCs and mercury by catalyst. The catalyst of the application is composed of a {101} high-energy crystal face exposed TiO2 carrier, MnO x and CeO x , and is prepared by depositing MnO x and CeO x on the {101} high-energy crystal face exposed TiO2, wherein the {101} high-energy crystal face exposed TiO2 carrier is prepared by a hydrothermal method, the active components MnO x and CeO x are prepared by taking Mn(NO3)2, KMnO4 and Ce(NO3)3·6H2O as metal sources, the mass fraction of MnOx in the catalyst is 5% to 15%, the content of CeO x is 5% to 15%, and the balance is TiO2. The catalyst prepared by the application is an octahedron with a large specific surface area, provides more active sites for electron gain and loss, and can efficiently synergistically catalyze oxidation of VOCs and Hg 0 .

Description

Technical Field

[0001] This invention relates to the field of flue gas purification catalyst preparation, specifically to a TiO2-supported MnO... x -CeO x A method for the synergistic catalytic oxidation of VOCs and mercury using catalysts. Background Technology

[0002] VOCs, as important air pollutants, are carcinogenic, teratogenic, and biotoxic. They are also important precursors to other air pollutants such as ozone, photochemical smog, and secondary organic aerosols. (Hg) 0 It is environmentally persistent, bioaccumulative, and highly toxic, and is classified as a Group 1 carcinogen. In industries such as cement, the incomplete decomposition of raw materials releases large amounts of VOCs and Hg. 0 This results in the simultaneous presence of VOCs and Hg in the emitted exhaust gas. 0 Large amounts of VOCs and Hg 0 Not only do they cause serious harm to the ecosystem, but they also severely impact human health. Therefore, effective control of VOCs and Hg is crucial. 0 Emissions are imminent.

[0003] Currently, VOCs removal methods mainly include adsorption, absorption, catalytic oxidation, and combustion. Adsorption and absorption methods often require large amounts of adsorbent and further analysis and collection, making the process cumbersome and costly. Combustion directly ignites and burns VOCs in the exhaust gas to remove them; however, this method has certain safety hazards and is not favored in practical applications. Catalytic oxidation, due to its low energy consumption, simple process, and complete reaction, is considered the most promising technology. Catalytic oxidation can oxidize VOCs into smaller molecules such as CO2 and H2O. Simultaneously, catalytic oxidation can also remove Hg... 0 Converted into water-soluble Hg 2+ Easy to remove. Traditional noble metal catalysts such as Au, Ag, and Pt have excellent low-temperature activity, but their high price limits their widespread use. Mn-based catalysts have good medium- and low-temperature catalytic oxidation performance, and Ce-based catalysts have excellent oxygen storage and release capabilities. MnCe catalysts are often used in catalytic oxidation reactions, are widely available, inexpensive, and have good application prospects. Anatase TiO2, as a widely used catalyst support, has attracted widespread attention from researchers due to its stable physicochemical properties and good catalytic performance. Adjusting its exposed crystal facets can change the surface coordination environment, thereby enhancing the interaction between TiO2 and active components and improving catalyst activity. {101} High-energy crystal facet exposure can provide more electron gain and loss, thus providing more active sites, increasing the overall redox performance of the catalyst, thereby improving reactant adsorption activation, oxygen mobility, and electron transfer, and thus increasing VOCs and Hg.0 The catalytic performance of [the material / organism] is thus improved. Therefore, if a TiO2-supported MnO with an exposed {101} high-energy crystal plane can be prepared, [this process will improve the catalytic performance]. x -CeO x Catalysts may be able to reduce VOCs and Hg in low-temperature industrial flue gas. 0 Highly efficient and collaborative removal. Summary of the Invention

[0004] Targeting the catalytic oxidation of VOCs and Hg 0 To address the technical problems existing in catalysts, such as competitive adsorption, mismatched activity temperature windows, and catalyst deactivation due to carbon deposition, this invention provides a TiO2-supported MnO catalyst. x -CeO x A method for the synergistic catalytic oxidation of VOCs and mercury using catalysts. First, a TiO2-supported MnO crystal with a truncated octahedral {101} high-energy crystal facet is obtained to expose TiO2. x -CeO x Catalysts for the synergistic catalytic oxidation of VOCs and Hg 0 It has excellent performance.

[0005] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0006] A TiO2-supported MnO x -CeO x A method for the synergistic catalytic oxidation of VOCs and mercury using catalysts, wherein the catalyst consists of TiO2 and MnO exposed by {101} high-energy crystal planes. x and CeO x Composition, denoted as MnO x -CeO x / TiO2-{101} is used for the synergistic catalytic oxidation of VOCs and mercury. The catalytic oxidation efficiency of VOCs can reach 100% at 230℃~310℃, and the conversion rate of mercury can also reach 100% at 100℃~310℃.

[0007] Furthermore, the catalyst consists of the following components by mass percentage:

[0008] MnOx 5%–15%, CeO x 5% to 15%, with the balance being TiO2, and the sum of the mass percentages of all components being 100%.

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

[0010] S1. TiCl4 was added dropwise to dilute hydrochloric acid solution under ice-water bath conditions with stirring to obtain TiCl4 aqueous solution. Then, the pH value of TiCl4 aqueous solution was adjusted to 7-8 by adding dilute ammonia water dropwise to obtain a white precipitate. After centrifugation and washing with ultrapure water, fresh Ti(OH)4 precursor was obtained. The Ti(OH)4 precursor was dispersed in a mixture of NH4Cl, isopropanol and water. After stirring and sonication, it was placed in a high-pressure reactor for reaction and the precipitate was collected. After washing with ultrapure water and anhydrous ethanol, the product was collected by centrifugation, dried, sieved and calcined to obtain {101} high-energy crystal facet exposed TiO2-{101}.

[0011] S2. Add TiO2-{101} to manganese nitrate solution and stir until completely dispersed. Then, add potassium permanganate solution dropwise and sonicate until completely dispersed. After standing, collect the precipitate, dry it, and obtain {101} high-energy crystal facet exposed TiO2-loaded MnO. x powder;

[0012] S3. The powder obtained in S2 is impregnated in a cerium nitrate solution, and then dried and calcined to obtain a composite material.

[0013] Furthermore, in S1, the temperature of the ice-water bath is -5 to 0℃, the concentration of dilute hydrochloric acid is 0.3 to 0.5 mol / L, the volume ratio of TiCl4 solution to dilute hydrochloric acid solution is 5 to 8:40 to 60, and the mass fraction of ammonia solution is 4.0 to 6.0%.

[0014] Further, in S1, Ti(OH)4 is dispersed in a mixture of NH4Cl, isopropanol, and water, with the following amounts: Ti(OH)4, NH4Cl, isopropanol, and water: 2.0–4.0 g : 0.2–0.8 g : 15–30 mL : 15–30 mL. The reaction temperature in the high-pressure reactor is 160–200 °C for 18–30 h. The drying temperature is 60–80 °C for 20–30 h. The sieve used is a 160–200 mesh sieve. The calcination temperature is 500–700 °C for 2–4 h.

[0015] Further, in S2, the ratio of TiO2-{101} to manganese nitrate solution is 1.0-3.0 g: 10-30 mL, and the concentration of manganese nitrate solution is 0.17-0.18 mol / L; the stirring temperature is 15℃-45℃, and the time is 12-36 h; the ratio of potassium permanganate solution to TiO2-{101} is 10-30 mL: 1.0-3.0 g, and the concentration of potassium permanganate solution is 0.05-0.06 mol / L; the standing time is 6-10 h; and the drying temperature is 80-120℃, and the time is 12-36 h.

[0016] Furthermore, in S3, the concentration of cerium nitrate solution is 0.25–0.35 mol / L, and the immersion time is 6–10 h.

[0017] Furthermore, the drying process is divided into two stages: the first stage drying temperature is 30–70℃ and the drying time is 24–36 h; the second stage drying temperature is 80–120℃ and the drying time is 24–36 h. Calcination is carried out in a muffle furnace with a programmed heating rate of 5–10℃ / min, a calcination temperature of 200–500℃, and a calcination time of 2–6 h.

[0018] This invention employs a hydrothermal method to synthesize TiO2-{101} with exposed {101} crystal planes, and then uses TiO2-{101} as a support to synthesize MnO via a deposition method. x -CeO x / TiO2-{101} catalyst, then used for the synergistic catalytic oxidation of VOCs and Hg. 0 Exposing the {101} surface of the TiO2 support allows MnO to... x CeO x Uniform dispersion on the support surface avoids aggregation of active components, thereby exposing more active sites. Simultaneously, TiO2-{101} and MnO... x CeO x This results in stronger interactions between the support and the active component, increasing the overall redox properties of the catalyst. Increasing the number of active sites can enhance the activity of reactant molecules (VOCs, Hg). 0 It can adsorb and activate (O2), lowering the reaction activation energy, and its excellent redox properties can effectively control VOCs and Hg. 0 Deep oxidation is crucial. MnO x -CeO x / TiO2-{101} catalyst in VOCs and Hg 0 It also exhibits good performance in catalytic oxidation reactions, thereby improving the efficiency of VOCs and Hg reduction. 0 This provides an effective approach to enhance synergistic oxidation performance.

[0019] The technical advantages of this invention are as follows:

[0020] The catalyst prepared in this invention is TiO2-supported MnO x -CeO x The catalyst exhibits excellent and efficient synergistic catalytic oxidation performance of VOCs and mercury. The catalytic oxidation efficiency of VOCs can reach 100% at 230℃~310℃, and the conversion rate of mercury can also reach 100% at 100℃~310℃. The exposure of the {101} high-energy crystal facet can provide more active sites by gaining and losing more electrons, effectively improving the redox performance of the catalyst. Attached Figure Description

[0021] Figure 1 MnO prepared in Example 2 x -CeO x Scanning electron microscope image of the / TiO2-{101} catalyst.

[0022] Figure 2 MnO prepared in Example 2 x -CeO x The curves of adsorption-desorption tests on the / TiO2-{101} catalyst.

[0023] Figure 3 MnO prepared in Example 2 x -CeO x Figure showing the pore size distribution test results of the / TiO2-{101} catalyst.

[0024] Figure 4 MnO prepared in Example 2 x -CeO x XRD pattern of the / TiO2-{101} catalyst. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited thereto.

[0026] Example 1

[0027] The preparation method of TiO2-{101} support with exposed {101} crystal planes includes the following steps:

[0028] (1) Place 50 mL (0.4 mol / L) hydrochloric acid solution in an ice-water bath and add 6.0 mL TiCl4 solution dropwise while stirring to obtain a clear TiCl4 solution;

[0029] (2) While stirring, add the TiCl4 solution obtained in step (1) dropwise to 80 mL (5.0 wt%) ammonia water to obtain a white suspension. After the addition is complete, adjust the pH of the solution to 7-8. Then stir the mixed solution at room temperature for 1 h, centrifuge, and wash with ultrapure water 2-3 times. Finally, centrifuge and collect the white product as Ti(OH)4 precursor.

[0030] (3) Take 2.0g of the fresh Ti(OH)4 precursor obtained in step (2) and disperse it in a mixture of 0.2g NH4Cl, 15ml water and 15ml isopropanol. After stirring and sonication, a suspension is obtained. Then, place it in a 100mL high-pressure reactor and react at 180℃ for 24 hours.

[0031] (4) Collect the precipitate after the reaction in step (3), wash with 500 mL of ultrapure water, wash with 200 mL of anhydrous ethanol, wash with 500 mL of ultrapure water 2-3 times, collect by centrifugation (6000 r / min, 5 min), and dry at 60 °C for 30 h. Pass through a 200 mesh sieve, and finally calcine at 600 °C for 2 h in a muffle furnace. After cooling to room temperature, TiO2-{101} is obtained.

[0032] Example 2

[0033] Synergistic catalytic oxidation of VOCs and Hg 0 The method for preparing the MnCe / TiO2-{101} catalyst includes the following steps:

[0034] (1) Immerse 2.0g of TiO2 powder in 20mL (0.18mol / L) of manganese nitrate solution and stir at 25℃ for 20h;

[0035] (2) Add 20 mL (0.06 mol / L) potassium permanganate solution dropwise to the solution obtained in step (1) under ultrasonic conditions. The ultrasonic conditions are 40 kHz for 20 min. The resulting precipitate is left to stand at room temperature for 10 h.

[0036] (3) The precipitate obtained in step (2) is separated by filtration, and the precipitate is dried at 105°C for 20 hours to obtain solid powder;

[0037] (4) Immerse the solid powder obtained in step (3) in 15 mL (0.35 mol / L) of cerium nitrate solution for 12 h, then keep it at 50 °C for 30 h, dry it at 105 °C for 30 h, and finally calcine it in a muffle furnace at 300 °C for 3 h with a heating rate of 5-10 °C / min to obtain MnO. x -CeO x / TiO2-{101} catalyst.

[0038] Example 3

[0039] Catalyst synergistic oxidation of VOCs and Hg 0 Performance evaluation

[0040] The MnCe / TiO2-{101} catalyst of this invention synergistically catalyzes the oxidation of VOCs and Hg. 0 Performance tests were conducted in a fixed-bed reactor. The catalyst from Example 2 was loaded into the catalytic reactor, and the simulated flue gas of the gas distribution system consisted of 10 vol.% O2 and 100 μg / m³. 3 Hg 0 The system consists of 100 ppm VOCs and a balance gas N2, with the total gas flow rate maintained at 200 mL / min and the volumetric hourly space velocity (GHSV) at 40,000 h⁻¹. -1The reaction temperature was controlled within the range of 100–310℃ to test the synergistic catalytic oxidation of VOCs and Hg by the catalyst. 0 Conversion efficiency.

[0041] The results showed that the T90 of VOCs was 225℃, and within the temperature range of 100–310℃, Hg 0 The removal rate can reach 100%.

[0042] Example 4

[0043] BET and SEM tests of the catalyst

[0044] The specific surface area and pore structure of the catalyst were analyzed using an automated gas adsorption system (Quantachrom NOVA-2200e, USA) for N2 physical adsorption experiments. The specific surface area, total pore volume, and pore size distribution of the catalyst were determined. A 0.1 g sample was degassed at 180 °C for 5 h, and then N2 was used as the adsorbate at 77 K for measurements. Specific surface area, total pore volume, and average pore size were obtained according to the Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) methods. Furthermore, scanning electron microscopy (SEM) analysis was performed using a Hitachi JEOL JSM-6360LV scanning electron microscope. The test results are as follows: Figure 1 , Figure 2 , Figure 3 As shown.

[0045] The results showed that the prepared MnO x -CeO x The / TiO2-{101} catalyst has a large specific surface area of ​​(102.5 m²). 2 / g), which is beneficial to the catalytic reaction. SEM images show that the catalyst of this invention has a truncated octahedral structure, indicating that it is supported on MnO. x and CeO x The morphology and structure of the TiO2-{101} support remained unchanged, and the MnO x and CeO x Uniform dispersion on the carrier surface helps expose more active sites.

[0046] Example 5

[0047] XRD testing of catalyst

[0048] The phase structure of the catalyst was analyzed and characterized using a Rigaku rotaflex D / MAX-2500 / pc X-ray diffractometer from Hitachi, Japan. The test conditions were Cu target Ka-ray (λ = 1.5406 Å), scanning 2θ range of 10–80°, and scanning speed of 10° / min. The test results are shown below. Figure 4 As shown in the figure. The results show that only the diffraction peaks of anatase TiO2 were detected, indicating that the MnO loaded by this method... x and CeO x The TiO2 crystal phase remained unchanged. No MnO was detected. x and CeO x The characteristic diffraction peaks indicate that MnO x and CeO x Highly dispersed amorphous MnO on the TiO2 surface. x and CeO x To synergistically catalyze the oxidation of VOCs and Hg 0 It provides more reactive sites, promotes the adsorption and activation of reactant molecules, accelerates catalytic oxidation reactions, and enhances the synergistic catalytic oxidation of VOCs and Hg. 0 active.

Claims

1. A TiO2-supported MnO x -CeO x A method for the synergistic catalytic oxidation of VOCs and mercury using catalysts, characterized in that, The catalyst consists of TiO2 and MnO exposed by {101} high-energy crystal planes. x and CeO x Composition, denoted as MnO x -CeO x / TiO2-{101}, the catalyst is used for the synergistic catalytic oxidation of VOCs and mercury; the catalyst is composed of the following components by mass percentage: MnOx 5%~15%, CeO x 5%~15%, with the balance being TiO2, and the sum of the mass percentages of all components being 100%; The preparation method of the catalyst includes the following steps: S1. TiCl4 was added dropwise to dilute hydrochloric acid solution under ice-water bath conditions with stirring to obtain an aqueous solution of TiCl4. Then, the pH of the TiCl4 aqueous solution was adjusted to 7-8 by adding dilute ammonia water dropwise to obtain a white precipitate. After centrifugation and washing with ultrapure water, fresh Ti(OH)4 precursor was obtained. The Ti(OH)4 precursor was dispersed in a mixture of NH4Cl, isopropanol and water. After stirring and sonication, it was placed in a high-pressure reactor for reaction and the precipitate was collected. After washing with ultrapure water and anhydrous ethanol, the product was collected by centrifugation, dried, sieved and calcined to obtain {101} high-energy crystal facet exposed TiO2-{101}. S2. Add TiO2-{101} to manganese nitrate solution and stir until completely dispersed. Then, add potassium permanganate solution dropwise and sonicate until completely dispersed. After standing, collect the precipitate, dry it, and obtain {101} high-energy crystal facet exposed TiO2-loaded MnO. x powder; S3. The powder obtained in S2 is impregnated in a cerium nitrate solution, and then dried and calcined to obtain a composite material.

2. The method according to claim 1, characterized in that, The temperature range for catalytic oxidation is 100℃~310℃.

3. The method according to claim 1, characterized in that, The temperature for catalytic oxidation is 230℃~310℃.

4. The method according to claim 1, characterized in that, In S1, the temperature of the ice-water bath is -5~0℃, the concentration of dilute hydrochloric acid is 0.3~0.5mol / L, the volume ratio of TiCl4 solution to dilute hydrochloric acid solution is 5~8:40~60, and the mass fraction of ammonia solution is 4.0~6.0%.

5. The method according to claim 1, characterized in that, In S1, Ti(OH)4 is dispersed in a mixture of NH4Cl, isopropanol, and water. The amounts of Ti(OH)4, NH4Cl, isopropanol, and water are 2.0~4.0g: 0.2-0.8g: 15~30mL: 15~30mL. The reaction temperature in the high-pressure reactor is 160~200℃, and the time is 18~30h. The drying temperature is 60~80℃, and the time is 20~30h. The sieve is a 160~200 mesh sieve. The calcination temperature is 500~700℃, and the time is 2~4h.

6. The method according to claim 1, characterized in that, In S2, the ratio of TiO2-{101} to manganese nitrate solution is 1.0-3.0 g: 10-30 mL, and the concentration of manganese nitrate solution is 0.17-0.18 mol / L; the stirring temperature is 15℃-45℃, and the stirring time is 12-36 h; the ratio of potassium permanganate solution to TiO2-{101} is 10-30 mL: 1.0-3.0 g, and the concentration of potassium permanganate solution is 0.05-0.06 mol / L; the standing time is 6-10 h; the drying temperature is 80-120℃, and the drying time is 12-36 h.

7. The method according to claim 1, characterized in that, In S3, the concentration of cerium nitrate solution is 0.25~0.35mol / L, and the immersion time is 6~10h.

8. The method according to claim 1, characterized in that, In S3, drying is divided into two stages. The first stage drying temperature is 30~70℃ and the drying time is 24~36h. The second stage drying temperature is 80~120℃ and the drying time is 24~36h. Calcination is carried out in a muffle furnace with a programmed heating rate of 5~10℃ / min, a calcination temperature of 200~500℃, and a calcination time of 2~6h.

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