WO2018176779A1 - 一种介孔臭氧氧化催化剂及其制备和应用方法 - Google Patents

一种介孔臭氧氧化催化剂及其制备和应用方法 Download PDF

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WO2018176779A1
WO2018176779A1 PCT/CN2017/104494 CN2017104494W WO2018176779A1 WO 2018176779 A1 WO2018176779 A1 WO 2018176779A1 CN 2017104494 W CN2017104494 W CN 2017104494W WO 2018176779 A1 WO2018176779 A1 WO 2018176779A1
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mesoporous
titanium
ozone oxidation
catalyst
solution
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French (fr)
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潘丙才
单超
许友
杨志超
张炜铭
吕路
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Nanjing University
Nanjing Tech University
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Nanjing Tech University
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Definitions

  • the invention belongs to the technical field of water treatment, and more particularly to a mesoporous ozone oxidation catalyst and a preparation and application method thereof.
  • Ozone oxidation technology is now increasingly used at the end of wastewater treatment to deeply degrade organic pollutants in wastewater.
  • ozone oxidation generally has a low degree of mineralization of pollutants, which is not only detrimental to the compliance of chemical oxygen demand (COD), and intermediate products produced by incomplete degradation of some organic substances may have higher toxicity, resulting in toxicity of wastewater. Instead, it rises. Therefore, the complete mineralization of organic matter has become the most ideal target for ozone oxidation. It is of great significance to try to improve the mineralization degree of organic pollutants in the ozone oxidation process.
  • Ozone oxidation mainly has two mechanisms, one is direct oxidation mechanism, that is, ozone directly reacts with pollutants; the other is indirect oxidation mechanism, that is, ozone is first converted into reactive oxygen species such as hydroxyl radicals and then reacts with pollutants. Since direct oxidation has a high degree of selectivity, the degree of mineralization of degradation is low, and oxidation by hydroxyl radicals is non-selective, and the oxidation ability of hydroxyl radicals is stronger than that of ozone, so the degree of mineralization is high. In order to improve the efficiency of ozone conversion to hydroxyl radicals and increase the degree of mineralization of pollutant degradation, it is necessary to develop a highly efficient ozone oxidation catalyst. In order to avoid the introduction of secondary pollution, it is particularly important to develop highly efficient heterogeneous catalysts.
  • heterogeneous ozone oxidation catalysts have been widely reported in the scientific literature, which have high catalytic activity, but most of them are powder catalysts with particle sizes at the nanometer and micrometer scales. In practical applications, fluid resistance The force is large, and it is difficult to separate from the liquid after treatment, which is not conducive to the design of industrial grade reactor.
  • the widely used ceramsite and ceramic-based ozone oxidation catalyst can generally reach the millimeter-scale particle size, but the pore structure is relatively lacking, the specific surface And the pore volume is generally small; carbon-based catalysts such as activated carbon and high molecular polymer will gradually lose mass in a strong oxidizing environment, and the stability is insufficient; the molecular sieve-based catalyst contains elements such as silicon and aluminum, and the acid and alkali resistance is difficult to satisfy at the same time. It has poor stability and is easy to release toxic and harmful elements.
  • the present invention provides a mesoporous ozone oxidation catalyst and a preparation and application method thereof.
  • the mesoporous ozone oxidation catalyst of the invention has good catalytic activity, good long-lasting activity, hydrodynamic property, pore structure, acid-base resistance/ligand stability, oxidation resistance, mechanical strength and thermal stability;
  • the preparation process of the mesoporous ozone oxidation catalyst is flexible, and the physical structure of the mesoporous ozone oxidation catalyst can be regulated by the template method;
  • the application method of the mesoporous ozone oxidation catalyst of the invention is suitable for the fixed bed or fluidization with low running cost
  • the bed reactor has high efficiency of pollutant degradation and significantly increases the mineralization degree of pollutants in the wastewater.
  • the present invention adopts the following technical solutions:
  • a mesoporous ozone oxidation catalyst is a metal oxide, the catalyst is in the form of solid spherical particles, the spherical particles of the catalyst have a diameter of 0.7 to 1.2 mm, and the active component is a cerium-titanium-zirconium composite oxide in the transmission electron Parallel lattice fringes were observed under the microscope, and the stripe spacing was 0.332-0.339 nm, which was between the typical crystalline yttrium oxide interplanar spacing (0.312 nm) and the typical anatase crystalline titanium dioxide interplanar spacing (0.352 nm). between.
  • the catalyst contains cerium, titanium, zirconium and oxygen, and contains With or without calcium, the mass fraction of strontium is 10% to 15%, the mass fraction of titanium is 30% to 50%, the mass fraction of zirconium is 5% to 15%, and the mass fraction of oxygen is 30% to 50%.
  • the elemental mass fraction is less than 2%.
  • the spherical particles have pores, the pores have an average pore diameter of 4.0 to 7.0 nm, the spherical particles have a specific surface area of 160 to 200 m 2 /g, and the pore volume is 0.31 to 0.34 cm 3 /g.
  • the valence state of the cerium-containing element is composed of trivalent and tetravalent, wherein trivalent cerium accounts for 45% to 55% of the total proportion of cerium, and the surface of the spherical particle has a large amount of trivalent cerium/tetravalent. ⁇ Oxidation-reduction pair has excellent catalytic ability.
  • a method for preparing a mesoporous ozone oxidation catalyst the steps of which are:
  • titanium zirconium composite oxide ball The calcium alginate gel template ball prepared in the step (1) is washed with absolute ethanol to remove internal water, and then placed in a titanium zirconium alkoxide mixed solution for 12 to 24 hours. Then, it is transferred to an aqueous solution of isopropyl alcohol for 12 to 24 hours, taken out and dried at room temperature for 24 to 72 hours, then dried at 55 to 65 ° C for 4 to 8 hours, and then calcined at 350 to 600 ° C for 3 to 8 hours. After cooling to room temperature, washing with a nitric acid solution, washing with water, and drying to obtain a titanium zirconium composite oxide sphere;
  • Impregnation The titanium-zirconium composite oxide ball obtained in the step (2) is immersed in a solution of Ce(NO 3 ) 3 for 2-8 hours, and then filtered, and the filtered solid powder is dried at 105 ° C. 12 ⁇ 24h, a solid powder is obtained;
  • the titanium zirconium alkoxide mixed solution is A solution prepared from titanium isopropoxide and a n-propanol solution of zirconium n-propoxide having a mass fraction of 70% by volume ratio of 2:1 to 6:1.
  • the mass of the titanium zirconium alkoxide mixed solution is 2 to 8 times the mass of the calcium alginate gel template ball, and the aqueous solution of isopropanol is pure water and isopropanol. Volume ratio (0.5 to 2): 1 formulated solution.
  • the concentration of the Ce(NO 3 ) 3 solution in the step (3) is from 0.10 to 0.25 mol/L.
  • a method for applying a mesoporous ozone oxidation catalyst which is prepared by the above-mentioned preparation method of a mesoporous ozone oxidation catalyst, which is prepared into a fixed bed or fluidized bed reactor;
  • the wastewater is continuously or batch-fed into the above reactor;
  • the ozone-containing gas is continuously or intermittently introduced into the wastewater, and the pollutant is degraded by the mesoporous ozone oxidation catalyst, and the wastewater is continuously or intermittently discharged from the reactor, mesoporous
  • the ozone oxidation catalyst is separated from the wastewater by gravity and left in the reactor to complete the treatment of the wastewater.
  • the catalyst when the catalytic performance of the pollutants is accumulated on the catalyst, the catalyst is taken out of the reactor, washed with water and dried, and then calcined at a temperature of 200 to 500 ° C for 2 to 6 hours, and then placed in the reaction after cooling. Re-use in the device.
  • the mesoporous ozonation catalyst has a unique crystal phase structure and a novel substance is formed.
  • the crystal phase of the cerium oxide contained in the catalyst is different from that of the strontium oxide crystal obtained by direct calcination; the catalyst is not a cerium oxide and a titanium zirconium composite oxide.
  • the simple combination is not a supported catalyst formed by supporting cerium oxide nanoparticles in nanopores of titanium-zirconium composite oxide spheres, but a new cerium-titanium-zirconium composite oxide is formed.
  • the catalytic effect of the catalyst is not a simple superposition of the effect of the titanium-zirconium composite oxide sphere and the cerium oxide, and the degree of mineralization is high, which can significantly increase the degree of mineralization of ozone oxidation.
  • the catalyst has a wide range of applications and can more efficiently catalyze ozone oxidation of contaminants under the condition of coexistence of sulfate.
  • a mesoporous ozonation catalyst according to the present invention which has a millimeter-scale spherical particle shape, has small water flow and gas flow resistance, and has good hydrodynamic characteristics; and has parallel lattice fringes in a spherical particle cross section, indicating that a kind of lattice fringe is formed.
  • the new metal composite oxide which has high catalytic activity for ozone oxidation reaction, can improve the efficiency of ozone conversion to hydroxyl radicals, and significantly promote the mineralization degree of refractory pollutants, compared with the non-catalytic effect.
  • the mesoporous ozonation catalyst of the present invention has a reaction efficiency of 9 to 10 times;
  • a mesoporous ozonation catalyst of the invention having a rich pore structure, an average pore diameter of 4.0 to 7.0 nm, belonging to a mesoporous structure, a specific surface area of 160 to 200 m 2 /g, and a pore volume of 0.31 to 0.34 cm 3 / g, is conducive to the adsorption of pollutants and intragranular diffusion mass transfer;
  • a mesoporous ozonation catalyst according to the present invention the composition of which is a metal oxide, has a compressive strength of more than 6.5 N, and has high mechanical strength, and is favorable for not to be broken under the load-bearing or collision conditions in the reactor;
  • a mesoporous ozonation catalyst according to the present invention which comprises a cerium-titanium-zirconium composite oxide, which has high acid/base/ligand stability, and is oxalic acid in a wide pH range (2 to 12) and in water.
  • the ligand does not dissolve under the coexistence condition, the self-active component does not dissolve, does not release toxic and harmful elements, and does not cause secondary pollution to the treated sewage;
  • a mesoporous ozonation catalyst of the present invention wherein the active component is yttrium titanium zirconium composite oxidation , with long-lasting activity, the catalytic performance is basically stable during long-term or repeated use;
  • the main component of the cerium-titanium-zirconium composite oxide is an inorganic oxide, which has high oxidation resistance, and does not significantly change its structure and properties in a strong oxidizing environment of hydroxyl radicals and ozone. ;
  • the main component of the cerium-titanium-zirconium composite oxide is an inorganic oxide, and is itself prepared by high-temperature calcination, has high thermal stability, and is heated to 500 in an air atmosphere. °C does not change significantly, which is beneficial to the thermal regeneration of the catalyst;
  • the preparation method of a mesoporous ozone oxidation catalyst of the invention is flexible in process, and can change ozone by changing parameters such as ratio of titanium zirconium alkoxide mixed solution, calcination temperature, concentration of Ce(NO 3 ) 3 immersion liquid in a limited range.
  • the pore structure, active component content and compressive strength of the oxidation catalyst are regulated;
  • the application method of a mesoporous ozone oxidation catalyst of the invention is suitable for a fixed bed or a fluidized bed reactor with low operation cost, high pollutant degradation efficiency, remarkablely improving mineralization degree of pollutants in waste water, and catalyst Thermal regeneration can be performed when the performance of refractory organic matter is reduced.
  • Example 1 is a lattice fringe of a mesoporous ozone oxidation catalyst prepared in Example 1 of the present invention under a transmission electron microscope;
  • Example 2 is an X-ray diffraction (XRD) pattern of a mesoporous ozonation catalyst prepared in Example 1 of the present invention and a control material thereof after grinding;
  • XRD X-ray diffraction
  • Figure 3 is a graph showing the relationship between the concentration of oxalic acid and the reaction time in Example 4 of the present invention.
  • Figure 4 is a graph showing the relationship between the concentration of oxalic acid and the reaction time in Example 5 of the present invention.
  • Figure 5 is a graph showing the relationship between the concentration of oxalic acid and the reaction time in Example 6 of the present invention.
  • the intermediate pore ozone oxidation catalyst is repeatedly used to catalyze ozone oxidation
  • Figure 7 is a graph showing the relationship between the concentration of oxalic acid and the reaction time in Example 8 of the present invention.
  • Figure 8 is an electron paramagnetic resonance (EPR) pattern of Example 8 of the present invention.
  • titanium zirconium composite oxide sphere The calcium alginate gel template sphere prepared in the step (1) is washed with absolute ethanol, and then infiltrated in a titanium zirconium alkoxide mixed solution for 24 hours, and then transferred to Soaked in isopropyl alcohol aqueous solution for 12h, taken out and dried at room temperature for 48h, dried at 60 °C for 6h, then calcined at 500 °C for 5h, cooled to room temperature, washed with 0.1mol / L nitric acid, washed with water, dried at 60 ° C for 12h, Titanium zirconium composite oxide ball, the titanium zirconium alkoxide mixed solution is prepared from titanium (IV) isopropoxide and n-propanol solution of zirconium (IV) n-propoxide having a mass fraction of 5:1 by volume ratio of 5:1.
  • the solution, the titanium zirconium alkoxide mixed solution has a mass of 5 times the mass of the calcium alginate gel pellet, and the aqueous solution of isopropanol is a solution prepared by mixing pure water and isopropyl alcohol in a volume ratio of 1:1;
  • the titanium-zirconium composite oxide sphere prepared in the step (2) is immersed in a 0.14 mol/L solution of Ce(NO 3 ) 3 for 5 hours, and then dried at 105 ° C for 12 hours after filtration;
  • the prepared ozone oxidation catalyst is a spherical particle with a diameter distribution of 0.8-1.0 mm and characterized by N 2 adsorption desorption.
  • the specific surface area is 179.9 m 2 /g
  • the pore volume is 0.323 cm 3 /g
  • the average pore diameter is 5.04.
  • Nm using a particle strength tester to randomly select 10 particles to test the average value, the compressive strength is 7.6N.
  • the polished catalyst samples were observed by scanning electron microscopy and the energy spectrum test was carried out. The results showed that the elements of cerium, titanium, zirconium, oxygen and calcium contained 12.1%, 37.9%, 9.3%, 39.7%, and 1.0%, respectively.
  • a small amount of calcium is caused by a small amount of calcium in the calcium alginate template in the clear process of nitric acid; the spherical particles of the prepared catalyst are cut open, the cross section is observed under a scanning electron microscope, and the energy spectrum is performed along the diameter. Scanning, four elements of yttrium, titanium, zirconium and oxygen are evenly distributed throughout the section. Characterized by X-ray photoelectron spectroscopy (XPS, the same below), the valence of lanthanum is composed of trivalent and tetravalent, and the proportion of trivalent is 49%. Observed under a transmission electron microscope, as shown in Fig. 1, there are parallel lattice fringes, and the stripe pitch is 0.336 nm, indicating that a new substance having a unique crystal phase structure is formed in the obtained ozone oxidation catalyst.
  • XPS X-ray photoelectron spectroscopy
  • the ozone oxidation catalyst prepared above was ground and subjected to powder X-ray diffraction (XRD, the same hereinafter). As a result, as shown in Fig. 2(B), there was no significant diffraction peak.
  • the XRD pattern of the cerium oxide powder obtained by calcining Ce(NO 3 ) 3 for 3 hours at a temperature of 450 ° C is as shown in Fig. 2(A), and shows a distinct cerium oxide crystal form, which is consistent with JC PDF card 34-0394.
  • the XRD pattern of the powder obtained by mixing the above cerium oxide powder with the titanium-zirconium composite oxide ball obtained by the ball-milled composite oxide obtained in the step (2) according to the mass fraction of cerium in the above ozone oxidation catalyst is as shown in Fig. 2(C). It is shown that the above crystal form of cerium oxide is still exhibited. It can be seen that the crystal phase of cerium oxide in the ozone oxidation catalyst is different from that of the cerium oxide crystal obtained by direct calcination, indicating that the ozone oxidation catalyst prepared by impregnating the mesoporous structure of the titanium zirconium composite oxide sphere is not cerium oxide and titanium zirconium. A simple combination of composite oxides results in the formation of a new niobium-titanium-zirconium composite oxide.
  • the prepared catalyst samples were observed under a scanning transmission microscope (STEM), and five sample regions with a size of about 20 nm square were randomly selected for energy spectrum scanning to map the element distribution with a resolution of 0.6-0.7 nm. The results showed that five regions were obtained. They all contain antimony, titanium, zirconium and oxygen, and the four elements are evenly distributed in each region. From the ⁇ element distribution map, no outline of any ruthenium-containing nanoparticles was observed. Correlation analysis was carried out on the relative content data of the four element distribution maps in each region, and the number of points was not less than 900. The results showed that all four elements were significantly correlated at the 0.01 level.
  • STEM scanning transmission microscope
  • the prepared mesoporous ozonation catalyst is not a supported catalyst formed by supporting cerium oxide nanoparticles in nanopores of titanium-zirconium composite oxide spheres, but a new cerium-titanium-zirconium composite oxide is formed.
  • the ozone oxidation catalyst provided by the invention has good hydrodynamic characteristics, pore structure, mechanical strength and thermal stability, and a new substance is formed in the obtained ozone oxidation catalyst, which has a unique crystal phase structure and is not oxidized.
  • the simple combination of cerium and titanium-zirconium composite oxide is not a supported catalyst formed by supporting cerium oxide nanoparticles in nanopores of titanium-zirconium composite oxide spheres, but a new cerium-titanium-zirconium composite oxide is formed.
  • titanium zirconium composite oxide sphere The calcium alginate gel template sphere prepared in the step (1) is washed with absolute ethanol, then placed in a titanium zirconium alkoxide mixture solution for 12 hours, and then transferred to Soaked in isopropyl alcohol aqueous solution for 24h, taken out and dried at room temperature for 24h, dried at 65 °C for 4h, then at 350 Calcination at °C for 8h, cooling to room temperature, washing with 0.1mol/L nitric acid, washing with water, drying at 60 °C for 12h, to obtain titanium zirconium composite oxide ball, the titanium zirconium alkoxide mixed solution is made of titanium isopropoxide (IV) And a solution of 70% n-propanol zirconium (IV) n-propanol solution prepared in a volume ratio of 6:1, the mass of the titanium zirconium alkoxide mixed solution is the mass of the calcium alginate gel pellet 2 a solution of pure water and is
  • the titanium zirconium composite oxide sphere prepared in the step (2) is immersed in a 0.25 mol/L Ce(NO 3 ) 3 solution for 2 hours, and filtered and dried at 105 ° C for 24 hours;
  • the obtained ozone oxidation catalyst was spherical particles having a diameter of 0.7 to 0.9 mm.
  • the same test method as in Example 1 was carried out to measure a specific surface area of 195.0 m 2 /g, a pore volume of 0.310 cm 3 /g, and an average pore diameter. It was 4.09 nm and the compressive strength was 6.5 N. Containing lanthanum, titanium, zirconium, oxygen and calcium, the mass fraction of the five elements is 15.0%, 48.7%, 5.2%, 30.6%, 0.5%; the valence of lanthanum is composed of trivalent and tetravalent, among which trivalent The proportion is 45%. Parallel lattice fringes were observed under a transmission electron microscope with a stripe pitch of 0.332 nm.
  • titanium zirconium composite oxide sphere calcium alginate gel prepared in the step (1)
  • the template sphere was washed with absolute ethanol, and then immersed in a titanium zirconium alkoxide mixture solution for 18 hours, then transferred to an isopropanol aqueous solution for 18 hours, taken out and dried at room temperature for 72 hours, dried at 55 ° C for 8 hours, and then at 600 ° C.
  • Calcined for 3 h cooled to room temperature, washed with 0.1 mol/L nitric acid, washed with water, and dried at 60 ° C for 24 h to obtain a titanium zirconium composite oxide ball.
  • the titanium zirconium alkoxide mixed solution is composed of titanium (IV) isopropoxide and mass. a solution of 70% n-propanol zirconium (IV) n-propanol solution prepared in a volume ratio of 2:1, the mass of the titanium zirconium alkoxide mixed solution is 8 times the mass of the calcium alginate gel pellet.
  • the aqueous solution of isopropanol is a solution prepared by mixing pure water and isopropyl alcohol in a volume ratio of 2:1;
  • the titanium-zirconium composite oxide sphere prepared in the step (2) is immersed in a 0.10 mol/L Ce(NO 3 ) 3 solution for 8 hours, and filtered and dried at 105 ° C for 16 hours;
  • the solid powder obtained in the step (3) is calcined at a temperature of 500 ° C for 2 hours to obtain a spherical mesoporous cerium titanium zirconium composite oxide ozone oxidation catalyst.
  • the obtained ozone oxidation catalyst was spherical particles having a diameter of 0.9 to 1.2 mm.
  • the same test method as in Example 1 was carried out to measure a specific surface area of 163.1 m 2 /g, a pore volume of 0.338 cm 3 /g, and an average pore diameter. It is 6.84 nm and the compressive strength is 10.2 N. Containing lanthanum, titanium, zirconium and oxygen, the mass fractions of the four elements are 10.2%, 31.1%, 14.7%, and 44.0%, respectively; the valence of lanthanum is composed of trivalent and tetravalent, and the ratio of trivalent is 53. %. Parallel lattice fringes were observed under a transmission electron microscope with a stripe pitch of 0.339 nm.
  • a mesoporous ozonation catalyst of the present embodiment has the same composition as in Example 1, and 2.5 g of the ozone oxidation catalyst prepared in Example 1 or the titanium-zirconium composite oxide obtained in the step (2) is taken.
  • the ball was placed in a 10 cm inner diameter bubble column reactor.
  • the bottom of the reactor was equipped with a microporous sand core air disk, and the outer layer was provided with a constant temperature circulating water bath interlayer, and a constant temperature circulating water of 25 ° C was introduced into the interlayer.
  • the oxalic acid solution with an initial oxalic acid concentration of 100 mg/L was prepared by using anhydrous oxalic acid and ultrapure water, and the pH of the solution was determined to be 3.0, the volume of the solution was 500 mL, the temperature was 25 ° C, and the above-mentioned bubble column reactor was added, and then the ozone was gas-phased.
  • the ozone/oxygen mixed gas with a concentration of 15 mg/L was dispersed into a small bubble into the solution at the flow rate of 0.2 L/min from the bottom of the reactor.
  • the sample was taken at a series of time points and passed through high performance liquid chromatography.
  • the change of oxalic acid concentration in water was measured with time, and the above ozone/oxygen gas was replaced by oxygen to test the adsorption effect of the material on oxalic acid.
  • ⁇ shows the case of ozone oxidation alone in Example 4
  • ⁇ shows the case of adsorption of the titanium zirconium composite oxide ball in Example 4
  • ⁇ shows the adsorption of the mesoporous ozone oxidation catalyst of Example 4
  • ⁇ indicates the implementation.
  • ⁇ indicates the case where the intervening ozone oxidation catalyst of Example 4 catalyzed ozone oxidation.
  • Fig. 3 show that the degradation rate of oxalic acid by mesoporous ozonation catalyst is more than 85% at 120 minutes, and the degradation rate of simple oxidation treatment is only 8%.
  • the degradation of titanium-zirconium composite oxide spheres is added.
  • the rate is also only 30%, so the mesoporous ozonation catalyst of this embodiment has a significantly higher degradation efficiency of oxalic acid than that of ozone alone or by using titanium-zirconium composite oxide spheres.
  • the adsorption effect of the mesoporous ozone oxidation catalyst and the titanium zirconium composite oxide sphere on oxalic acid was 30%, so that the removal of oxalic acid by the mesoporous ozonation catalyst of the present embodiment mainly relied on catalytic oxidation rather than adsorption.
  • the total organic carbon in the solution was measured as a function of time. The results showed that the total organic carbon concentration was proportional to the oxalic acid concentration, indicating that the oxalic acid was mineralized.
  • oxalic acid is a substance which can hardly be degraded by oxidation with ozone alone under acidic conditions and belongs to one of the common end products of ozone oxidation
  • the results of the present examples show that the ozone oxidation catalyst provided by the present invention has high catalytic activity and degree of mineralization. High, can significantly increase the degree of mineralization of ozone oxidation.
  • ⁇ indicates the adsorption of cerium oxide powder
  • ⁇ indicates the adsorption of the mixture
  • ⁇ indicates the adsorption of the mesoporous ozone oxidation catalyst of the present embodiment
  • ⁇ indicates the case where the cerium oxide powder catalyzed the oxidation of ozone
  • ⁇ indicates the case where the mesoporous ozone oxidation catalyst of this embodiment catalyzes the oxidation of ozone.
  • the zirconium composite oxide/cerium oxide mixture at this time, the adsorption of oxalic acid to all of the three states reached a saturated state, so that the removal of the mesoporous ozonation catalyst of the present embodiment mainly relies on catalytic oxidation rather than adsorption.
  • This example shows that the catalytic effect of the mesoporous ozonation catalyst of the present invention is not a simple superposition of the effect of the titanium-zirconium composite oxide sphere and the cerium oxide, and the degree of mineralization is high, which can significantly improve the degree of mineralization of ozone oxidation.
  • a mesoporous ozonation catalyst having the same composition as in Example 1 was added with 500 mg/L of sulfate in the oxalic acid solution component of Example 1, and the other conditions were the same as in Example 4, for example,
  • ⁇ indicates the adsorption of the mesoporous ozone oxidation catalyst under the condition of no sulfate
  • ⁇ indicates the adsorption of the mesoporous ozonation catalyst under the condition of coexistence of sulfate
  • ⁇ indicates the mesoporous ozonation catalyst without sulfate.
  • ⁇ indicates that the mesoporous ozone oxidation catalyst catalyzes the oxidation of ozone under the condition of coexistence of sulfate.
  • the degradation rate of oxalic acid by mesoporous ozonation catalyst was 90% under the condition of no sulfate, and the degradation rate of oxalic acid by mesoporous ozonation catalyst was 95% under the condition of coexistence of sulfate.
  • the mesoporous ozonation catalyst provided by the invention not only does not inhibit the oxidation effect, but is more efficient.
  • Electron paramagnetic resonance (EPR) characterization indicates that the process produces sulfate radicals, which further enhances its catalytic activity.
  • the mesoporous ozonation catalyst provided by the present invention has a wide range of application and can more efficiently catalyze ozone oxidation of contaminants under the condition of coexistence of sulfate.
  • Example 4 After the catalyst in Example 4 was recovered and subjected to thermal regeneration treatment at 200 ° C, the experiment of Example 4 was repeated, and the experiment was repeated for 8 rounds.
  • FIG. 6 it can be seen that the mesoporous ozone oxidation catalyst provided by the present invention was repeated. It has maintained high catalytic activity during reuse. The concentration of strontium in each round of water was determined during the reuse process. The concentrations in the first three rounds were 0.044, 0.012, and 0.008 mg/L, respectively, and the remaining effluents were not detected.
  • the catalyst for the recovery experiment will be recovered and then characterized by XPS. The valence of the lanthanum element remains. However, it consists of trivalent and tetravalent, and the proportion of trivalent is 50%, which is almost the same as the newly prepared catalyst.
  • a mesoporous ozonation catalyst of the present embodiment has the same composition as that of the first embodiment, and different concentrations of t-butanol are added as the hydroxyl radical trapping agent in the oxalic acid solution component of the embodiment 1, and the other conditions are the same.
  • ⁇ indicates the case of ozone oxidation alone
  • ⁇ indicates the adsorption of the mesoporous ozone oxidation catalyst
  • ⁇ indicates the oxidation of the mesoporous ozone oxidation catalyst under the condition of adding 40 mg/L of t-butanol.
  • ⁇ indicates the case of catalytic ozonation by a mesoporous ozonation catalyst under the condition of adding 5 mg/L of t-butanol
  • ⁇ indicates the case of catalytic ozonation by mesoporous ozonation catalyst without adding t-butanol.
  • the degradation rate of oxalic acid by mesoporous ozonation catalyst was 40% under the condition of adding 40 mg/L t-butanol; the degradation rate of oxalic acid by mesoporous ozone oxidation catalyst under the condition of adding 5 mg/L t-butanol was 60. %; the degradation rate of oxalic acid to mesoporous ozonation catalyst without adding tert-butanol was 90%; experiments showed that the efficiency of catalytic ozonation of oxalic acid gradually decreased with the increase of tert-butanol concentration, indicating mesoporous ozonation provided by the present invention.
  • the catalyst catalyzes the mechanism of ozone oxidation of oxalic acid by converting ozone into hydroxyl radicals with stronger oxidizing ability, and then mineralizing it by acting on oxalic acid.
  • the EPR spectrum of the ozonation oxidation of the mesoporous ozonation catalyst prepared in Example 1 using 5,5-dimethyl-1-oxo-pyrroline (DMPO) as a spin-trapping agent is shown in Fig. 8. It can be seen that the ozone oxidation alone does not produce a distinct signal peak, and the catalytic oxidation of the ozone by the mesoporous ozone oxidation catalyst provided by the present invention produces a distinct hydroxyl radical signal peak.
  • DMPO 5,5-dimethyl-1-oxo-pyrroline
  • the mesoporous ozonation catalyst provided by the present invention catalyzes the mechanism of ozone oxidation by converting ozone into a hydroxyl radical having a stronger oxidizing ability to act on a contaminant.

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Abstract

一种介孔臭氧氧化催化剂及其制备和应用方法。该介孔臭氧氧化催化剂含铈、钛、锆、氧，为毫米级介孔球形颗粒，具有独特的晶相结构，同时具有持久稳定的催化活性、优良的流体力学特性、孔结构、抗压强度、耐酸碱/配体稳定性、耐氧化性和热稳定性，可显著提高臭氧氧化的矿化程度，反复回用后活性成分价态组成不变。其制备方法为，通过海藻酸钙模板法制备毫米级介孔钛锆复合物小球，再通过浸渍法将铈元素与钛锆复合物复合而制得。该催化剂可应用于固定床或流化床反应器处理废水，污染物积累时可进行热再生。

Description

一种介孔臭氧氧化催化剂及其制备和应用方法 技术领域
本发明属于水处理技术领域，更具体地说，涉及一种介孔臭氧氧化催化剂及其制备和应用方法。
背景技术
随着当今水污染问题引起日益关注，水污染控制愈发受到重视，废水在排放前必须进行深度处理以达到排放标准。臭氧氧化技术现在日渐普遍用于废水处理的末端，用于深度降解废水中的有机污染物。但是，臭氧氧化普遍存在污染物矿化程度低的问题，不仅不利于化学需氧量(COD)的达标，且部分有机物的不完全降解产生的中间产物可能具有更高的毒性，造成废水的毒性反而升高。因此，有机物的彻底矿化成为臭氧氧化的最理想目标，设法提高臭氧氧化过程的有机污染物矿化程度具有重要的意义。
臭氧氧化主要有两种机理，一种为直接氧化机理，即臭氧直接与污染物反应；另一种为间接氧化机理，即臭氧先转化为羟基自由基等活性氧物种再与污染物反应。由于直接氧化具有高度的选择性，故降解的矿化程度低，而通过羟基自由基氧化具有非选择性，且羟基自由基的氧化能力较臭氧更强，所以矿化程度高。为了提高臭氧转化为羟基自由基的效率，提高污染物降解的矿化程度，有必要开发高效的臭氧氧化催化剂。为避免引入二次污染，开发高效的非均相催化剂尤为重要。
科技文献中广泛报道了多种非均相臭氧氧化催化剂，具有较高的催化活性，但大多数为粉体催化剂，粒径在纳米和微米级别，在实际应用中流体阻 力大，处理后与液体分离难度大，不利于工业级反应器的设计；目前使用比较广泛的陶粒、陶瓷基臭氧氧化催化剂一般可达到毫米级别粒径，但其孔结构较为缺乏，比表面和孔容积一般较小；活性炭、高分子聚合物等碳基催化剂在强氧化环境中会逐渐发生质量损失，稳定性不足；分子筛基催化剂由于含有硅、铝等元素，耐酸耐碱特性难以同时满足，自身稳定性较差，且容易释放有毒有害元素。
发明内容
针对现有废水处理中臭氧氧化催化剂的流体力学性能差、催化效率低的问题，本发明提供了一种介孔臭氧氧化催化剂及其制备和应用方法。本发明的一种介孔臭氧氧化催化剂具有较好的催化活性、持久活性好、流体力学特性、孔结构、耐酸碱/配体稳定性、耐氧化性、机械强度和热稳定性；本发明的介孔臭氧氧化催化剂的制备工艺灵活，通过模板法可以对介孔臭氧氧化催化剂的物理结构进行调控；本发明的介孔臭氧氧化催化剂的应用方法，适用于运行成本低廉的固定床或流化床反应器，污染物降解效率高，显著提高废水中污染物的矿化程度。
为解决上述问题，本发明采用如下的技术方案：
一种介孔臭氧氧化催化剂，催化剂为金属氧化物，所述催化剂呈固体球形颗粒状，所述催化剂的球形颗粒的直径为0.7～1.2mm，活性成分为铈钛锆复合氧化物，在透射电子显微镜下观察有平行的晶格条纹，条纹间距为0.332～0.339nm,该间距介于典型晶态氧化铈晶面间距(0.312nm)和典型锐钛矿晶态二氧化钛晶面间距(0.352nm)之间。
作为本发明的进一步改进，所述催化剂中含有铈、钛、锆和氧，含有 或不含有钙，铈元素质量分数为10％～15％，钛元素质量分数为30％～50％，锆元素质量分数为5％～15％，氧元素质量分数为30％～50％，钙元素质量分数小于2％。
作为本发明的进一步改进，球形颗粒上具有孔，孔的平均孔径为4.0～7.0nm，球形颗粒的比表面积为160～200m2/g，孔容积为0.31～0.34cm3/g。
作为本发明的进一步改进，所含铈元素的价态由三价和四价组成，其中三价铈占铈元素总比例的45％～55％，球形颗粒表面具有大量的三价铈/四价铈氧化还原电对，具有优秀的催化能力。
一种介孔臭氧氧化催化剂的制备方法，其步骤为：
(1)制备海藻酸钙凝胶模板球：在室温下，向搅拌状态下的CaCl2水溶液中逐滴加入海藻酸钠水溶液，形成一定量凝胶球后停止滴加海藻酸钠溶液，继续搅拌12～24h使模板球内部海藻酸钠溶液完全转化为海藻酸钙凝胶，水洗得到海藻酸钙凝胶模板球；
(2)制备钛锆复合氧化物球：将步骤(1)中制得的海藻酸钙凝胶模板球用无水乙醇洗涤除去内部水分后，置于钛锆醇盐混合溶液中浸润12～24h，然后转移至异丙醇水溶液中浸泡12～24h，取出后在室温下干燥24～72h，再在55～65℃温度下干燥4～8h，然后在350～600℃温度下煅烧3～8h，冷却至室温后用硝酸溶液清洗，水洗，干燥，得到钛锆复合氧化物球；
(3)浸渍：将步骤(2)中制得的钛锆复合氧化物球放入Ce(NO3)3溶液中浸泡2～8h，然后进行过滤，将过滤后的固体粉末在105℃下干燥12～24h，得到固体状粉末；
(4)煅烧：将步骤(3)中得到的固体状粉末置于400～500℃温度下煅烧2～6h，完成上述的一种介孔臭氧氧化催化剂的制备。
作为本发明的进一步改进，步骤(2)中，所述钛锆醇盐混合溶液是 由异丙醇钛和质量分数为70％的正丙醇锆的正丙醇溶液按体积比2:1～6:1配制而成的溶液。
作为本发明的进一步改进，步骤(2)中，钛锆醇盐混合溶液的质量是海藻酸钙凝胶模板球质量的2～8倍，所述异丙醇水溶液为纯水和异丙醇按体积比(0.5～2):1配制的溶液。
作为本发明的进一步改进，步骤(3)中所述Ce(NO3)3溶液浓度为0.10～0.25mol/L。
一种介孔臭氧氧化催化剂的应用方法，通过上述的一种介孔臭氧氧化催化剂的制备方法，制备上述的一种介孔臭氧氧化催化剂，将其放入固定床或流化床反应器中；将废水连续或批量通入上述反应器；将含有臭氧的气体连续或间歇通入废水中，在介孔臭氧氧化催化剂的作用下，使污染物降解，将废水连续或间歇排出反应器，介孔臭氧氧化催化剂依靠重力作用与废水分离而留在反应器内，完成对废水的处理。
作为本发明的进一步改进，当催化剂上积累了污染物催化性能下降时，将催化剂取出反应器，经水洗和干燥后，置于200～500℃温度下焙烧2～6h，冷却后再放入反应器中重新使用。
通过透射电子显微镜(TEM)、扫描透射电子显微镜(STEM)、粉末X射线衍射(XRD)、N2吸附脱附、X射线光电子能谱(XPS)测试等多种方式进行表征，本技术方案提供的介孔臭氧氧化催化剂中有独特晶相结构的新物质生成，本催化剂所含的氧化铈的晶相与直接煅烧制得的氧化铈晶相不同；本催化剂不是氧化铈与钛锆复合氧化物的简单组合，亦不是将氧化铈纳米颗粒负载于钛锆复合氧化物球纳米孔内形成的负载型催化剂，而是生成了新的铈钛锆复合氧化物。本催化剂的催化效果不是钛锆复合氧化物球与氧化铈的效果的简单叠加， 并且其矿化程度高，可显著提高臭氧氧化的矿化程度。本催化剂具有宽广的适用范围，可在硫酸根共存条件下更高效的催化臭氧氧化污染物。本催化剂具有持久高效的催化活性，且具有较高的稳定性，即使在pH＝3的酸性条件下反复使用也不会释放活性成分或有毒有害元素，且经反复回用后活性成分价态组成不变。
相比于现有技术，本发明的有益效果为：
1.本发明的一种介孔臭氧氧化催化剂，呈毫米级球形颗粒状，水流和气流阻力小，具有良好的流体力学特性；在球形颗粒的剖面有平行的晶格条纹，表明生成了一种新的金属复合氧化物，该物质对臭氧氧化反应具有较高的催化活性，可提高臭氧转化为羟基自由基的效率，显著促进难降解污染物的矿化程度，与无催化效果相比，在本发明的介孔臭氧氧化催化剂的作用下，反应效率提高了9～10倍；
2.本发明的一种介孔臭氧氧化催化剂，具有丰富的孔结构，平均孔径4.0～7.0nm，属于介孔结构，比表面积达到160～200m2/g，孔容积达到0.31～0.34cm3/g，有利于污染物的吸附和粒内扩散传质；
3.本发明的一种介孔臭氧氧化催化剂，组成成分为金属氧化物，抗压强度大于6.5N，具有较高的机械强度，有利于在反应器内堆积承重或碰撞条件下不发生破碎；
4.本发明的一种介孔臭氧氧化催化剂，成分为铈钛锆复合氧化物，具有高度的耐酸/碱/配体的稳定性，在广泛的pH范围(2～12)内以及水中草酸等配体共存条件下不溶解，自身活性成分不溶出，不释放有毒有害元素，不会对处理后的污水造成二次污染；
5.本发明的一种介孔臭氧氧化催化剂，活性组分为铈钛锆复合氧化 物，具有持久活性，在长期或反复使用过程中催化性能基本保持稳定；
6.本发明的一种介孔臭氧氧化催化剂，主要成分铈钛锆复合氧化物属于无机氧化物，具有高度耐氧化性，在羟基自由基和臭氧强氧化环境中自身结构和性能不发生明显改变；
7.本发明的一种介孔臭氧氧化催化剂，主要成分铈钛锆复合氧化物属于无机氧化物，且本身经过高温煅烧制备而成，具有较高的热稳定性，在空气氛围中加热到500℃不发生明显改变，有利于催化剂热再生；
8.本发明的一种介孔臭氧氧化催化剂的制备方法，工艺灵活，通过在限定范围内改变钛锆醇盐混合溶液比例、煅烧温度、Ce(NO3)3浸渍液浓度等参数可对臭氧氧化催化剂的孔结构、活性组分含量和抗压强度等特性进行调控；
9.本发明的一种介孔臭氧氧化催化剂的应用方法，适用于运行成本低廉的固定床或流化床反应器，污染物降解效率高，显著提高废水中污染物的矿化程度，且催化剂积累难降解有机物性能下降时可进行热再生。
附图说明
图1为本发明实施例1中制备的介孔臭氧氧化催化剂在透射电子显微镜下的晶格条纹；
图2为本发明实施例1中制备的介孔臭氧氧化催化剂及其对照材料研磨后的X射线衍射(XRD)图谱；
图3为本发明实施例4中草酸浓度与反应时间的关系曲线图；
图4为本发明实施例5中草酸浓度与反应时间的关系曲线图；
图5为本发明实施例6中草酸浓度与反应时间的关系曲线图；
图6为本发明实施例7中介孔臭氧氧化催化剂反复回用催化臭氧氧化 草酸的8轮过程中草酸浓度与反应时间的关系曲线图；
图7为本发明实施例8中草酸浓度与反应时间的关系曲线图；
图8为本发明实施例8中电子顺磁共振(EPR)图谱。
具体实施方式
下面结合附图对本发明进行详细描述。
实施例1
介孔臭氧氧化催化剂的制备和表征
(1)海藻酸钙凝胶模板球的制备：在室温下，使用针头内径为0.41mm的注射器向0.27mol/L的CaCl2水溶液中逐滴加入质量分数为1.0％的海藻酸钠水溶液，使用注射泵将注射流量控制在4.5mL/h，形成凝胶球后继续搅拌24h，水洗得到海藻酸钙凝胶模板球；
(2)钛锆复合氧化物球的制备：将步骤(1)中制得的海藻酸钙凝胶模板球用无水乙醇洗涤后，置于钛锆醇盐混合溶液中浸润24h，然后转移至异丙醇水溶液中浸泡12h，取出后在室温下干燥48h，60℃干燥6h，然后在500℃温度下煅烧5h，冷却至室温用0.1mol/L硝酸清洗，水洗，60℃干燥12h，得到到钛锆复合氧化物球，所述钛锆醇盐混合溶液是由异丙醇钛(IV)和质量分数为70％的正丙醇锆(IV)的正丙醇溶液按体积比5:1配制而成的溶液，钛锆醇盐混合溶液的质量是海藻酸钙凝胶小球质量的5倍，所述异丙醇水溶液为纯水和异丙醇按体积比1:1配制的溶液；
(3)浸渍：将步骤(2)中制得的钛锆复合氧化物球在0.14mol/L的Ce(NO3)3溶液中浸泡5h，过滤后105℃干燥12h；
(4)将步骤(3)中得到的固体状粉末置于450℃温度下煅烧3h，得到球形介孔铈钛锆复合氧化物臭氧氧化催化剂。
制得的臭氧氧化催化剂为球形颗粒，直径分布在0.8～1.0mm之间，通过N2吸附脱附表征，测得比表面积179.9m2/g，孔容积0.323cm3/g，平均孔径为5.04nm，使用颗粒强度测试仪随机选取10个颗粒测试取平均值，抗压强度为7.6N。通过扫描电子显微镜观察研磨的催化剂样品，进行能谱测试，结果表明含有铈、钛、锆、氧、钙元素，五种元素质量分数分别为12.1％，37.9％，9.3％，39.7％，1.0％，其中含有少量的钙为海藻酸钙模板中的钙在硝酸清晰过程中的少量残留所致；将制得的催化剂的球形颗粒剖开，在扫描电子显微镜下观察剖面，通过沿直径进行能谱扫描，铈、钛、锆、氧四种元素都均匀分布于整个剖面。通过X射线光电子能谱(XPS，下同)表征，铈元素的价态由三价和四价组成，其中三价所占比例为49％。在透射电子显微镜下观察，如图1所示，有平行的晶格条纹，条纹间距为0.336nm，说明制得的臭氧氧化催化剂中有独特晶相结构的新物质生成。
将上述制得的臭氧氧化催化剂研磨进行粉末X射线衍射(XRD，下同)检测，结果如图2(B)所示，并无明显的衍射峰。在450℃温度下将Ce(NO3)3煅烧3h制得的氧化铈粉末的XRD图谱如图2(A)所示，表现出明显的二氧化铈晶型，与JCPDF卡片34-0394相符。将上述氧化铈粉末与步骤(2)中制得的钛锆复合氧化物球研磨所得粉末两者按照在上述臭氧氧化催化剂中的铈质量分数混合而成的粉末XRD图谱如图2(C)所示，仍然显示出上述二氧化铈的晶型。可见，臭氧氧化催化剂中的氧化铈的晶相与直接煅烧制得的氧化铈晶相不同，说明在上述钛锆复合氧化物球介孔结构中浸渍制得的臭氧氧化催化剂不是氧化铈与钛锆复合氧化物的简单组合，而是生成了新的铈钛锆复合氧化物。
在扫描透射显微镜(STEM)下观察制得的催化剂样品，随机选取5块尺寸约20nm见方的样品区域进行能谱扫描进行分辨率为0.6～0.7nm的元素分布图的绘制，结果表明5块区域均含铈、钛、锆、氧元素，且四种元素在每个区域均匀分布。从铈元素分布图上看，未见任何含铈的纳米颗粒的轮廓。将每个区域内的四种元素分布图导出的元素相对含量数据进行相关分析，点数不少于900个，结果显示四种元素均在0.01水平上两两显著相关。上述结果表明，制得的介孔臭氧氧化催化剂不是将氧化铈纳米颗粒负载于钛锆复合氧化物球纳米孔内形成的负载型催化剂，而是生成了新的铈钛锆复合氧化物。
以上结果显示出本发明提供的臭氧氧化催化剂具有良好的流体力学特性、孔结构、机械强度和热稳定性，且制得的臭氧氧化催化剂中有新物质生成，具有独特的晶相结构，不是氧化铈与钛锆复合氧化物的简单组合，亦不是将氧化铈纳米颗粒负载于钛锆复合氧化物球纳米孔内形成的负载型催化剂，而是生成了新的铈钛锆复合氧化物。
实施例2
介孔臭氧氧化催化剂的制备和表征
(1)海藻酸钙凝胶模板球的制备：在室温下，使用针头内径为0.25mm的注射器向0.27mol/L的CaCl2水溶液中逐滴加入质量分数为1.0％的海藻酸钠水溶液，使用注射泵将注射流量控制在4.5mL/h，形成凝胶球后继续搅拌12h，水洗得到海藻酸钙凝胶模板球；
(2)钛锆复合氧化物球的制备：将步骤(1)中制得的海藻酸钙凝胶模板球用无水乙醇洗涤后，置于钛锆醇盐混合溶液中浸润12h，然后转移至异丙醇水溶液中浸泡24h，取出后在室温下干燥24h，65℃干燥4h，然后在350 ℃温度下煅烧8h，冷却至室温用0.1mol/L硝酸清洗，水洗，60℃干燥12h，得到到钛锆复合氧化物球，所述钛锆醇盐混合溶液是由异丙醇钛(IV)和质量分数为70％的正丙醇锆(IV)的正丙醇溶液按体积比6:1配制而成的溶液，钛锆醇盐混合溶液的质量是海藻酸钙凝胶小球质量的2倍，所述异丙醇水溶液为纯水和异丙醇按体积比0.5:1配制的溶液；
(3)浸渍：将步骤(2)中制得的钛锆复合氧化物球在0.25mol/L的Ce(NO3)3溶液中浸泡2h，过滤后105℃干燥24h；
(4)将步骤(3)中得到的固体状粉末置于400℃温度下煅烧6h，得到球形介孔铈钛锆复合氧化物臭氧氧化催化剂。
制得的臭氧氧化催化剂为球形颗粒，直径分布在0.7～0.9mm之间，采用和实施例1相同的测试方法，测得比表面积195.0m2/g，孔容积0.310cm3/g，平均孔径为4.09nm，抗压强度为6.5N。含有铈、钛、锆、氧、钙元素，五种元素质量分数分别为15.0％，48.7％，5.2％，30.6％，0.5％；铈元素的价态由三价和四价组成，其中三价所占比例为45％。在透射电子显微镜下观察有平行的晶格条纹，条纹间距为0.332nm。
实施例3
介孔臭氧氧化催化剂的制备和表征
(1)海藻酸钙凝胶模板球的制备：在室温下，使用针头内径为0.69mm的注射器向0.27mol/L的CaCl2水溶液中逐滴加入质量分数为1.0％的海藻酸钠水溶液，使用注射泵将注射流量控制在4.5mL/h，形成凝胶球后继续搅拌18h，水洗得到海藻酸钙凝胶模板球；
(2)钛锆复合氧化物球的制备：将步骤(1)中制得的海藻酸钙凝胶 模板球用无水乙醇洗涤后，置于钛锆醇盐混合溶液中浸润18h，然后转移至异丙醇水溶液中浸泡18h，取出后在室温下干燥72h，55℃干燥8h，然后在600℃温度下煅烧3h，冷却至室温用0.1mol/L硝酸清洗，水洗，60℃干燥24h，得到到钛锆复合氧化物球，所述钛锆醇盐混合溶液是由异丙醇钛(IV)和质量分数为70％的正丙醇锆(IV)的正丙醇溶液按体积比2:1配制而成的溶液，钛锆醇盐混合溶液的质量是海藻酸钙凝胶小球质量的8倍，所述异丙醇水溶液为纯水和异丙醇按体积比2:1配制的溶液；
(3)浸渍：将步骤(2)中制得的钛锆复合氧化物球在0.10mol/L的Ce(NO3)3溶液中浸泡8h，过滤后105℃干燥16h；
(4)将步骤(3)中得到的固体状粉末置于500℃温度下煅烧2h，得到球形介孔铈钛锆复合氧化物臭氧氧化催化剂。
在500℃温度下煅烧2h，得到球形介孔铈钛锆复合氧化物臭氧氧化催化剂。
制得的臭氧氧化催化剂为球形颗粒，直径分布在0.9～1.2mm之间，采用和实施例1相同的测试方法，测得比表面积163.1m2/g，孔容积0.338cm3/g，平均孔径为6.84nm，抗压强度为10.2N。含有铈、钛、锆、氧元素，四种元素质量分数分别为10.2％，31.1％，14.7％，44.0％；铈元素的价态由三价和四价组成，其中三价所占比例为53％。在透射电子显微镜下观察有平行的晶格条纹，条纹间距为0.339nm。
实施例4
本实施例中的一种介孔臭氧氧化催化剂，组成成分与实施例1相同，取2.5g实施例1中制得的臭氧氧化催化剂或步骤(2)中所得的钛锆复合氧化物 球，置于内径10cm气泡柱反应器中，反应器底部装有微孔砂芯布气盘，且外层带有恒温循环水浴夹层，在夹层中通入25℃恒温循环水。用无水草酸和超纯水配制成初始草酸浓度为100mg/L的草酸溶液，测得溶液pH为3.0，溶液体积为500mL，温度为25℃，加入上述气泡柱反应器中，然后将臭氧气相浓度为15mg/L的臭氧/氧气混合气体以0.2L/min的流速由反应器底部为空砂芯布气盘分散成细小气泡通入溶液中，在一系列时间点取样，通过高效液相色谱测定水中草酸浓度随时间的变化，将上述臭氧/氧气气体替换为氧气进行实验，用来表明材料对草酸的吸附效果。
结果如图3，▲表示实施例4中单独臭氧氧化的情况，○表示实施例4中钛锆复合氧化物球吸附的情况，□表示实施例4中介孔臭氧氧化催化剂吸附的情况，●表示实施例4中钛锆复合氧化物球催化臭氧化的情况，■表示实施例4中介孔臭氧氧化催化剂催化臭氧氧化的情况。
图3结果表明，在实验120分钟时，添加介孔臭氧氧化催化剂对草酸的降解率达到了85％以上，而此时单纯氧化处理的降解率只有8％，添加钛锆复合氧化物球的降解率也只有30％，所以本实施例的介孔臭氧氧化催化剂，草酸的降解效率明显高于单独臭氧氧化或使用钛锆复合氧化物球进行催化。此时，介孔臭氧氧化催化剂和钛锆复合氧化物球对草酸的吸附效果为30％，所以表明本实施例的介孔臭氧氧化催化剂对草酸的去除主要依靠催化氧化而非吸附。测定溶液总有机碳随时间的变化，结果表明总有机碳浓度与草酸浓度成比例，说明草酸被矿化。因在酸性条件下草酸是使用单独臭氧氧化几乎不能降解的物质，属于常见的臭氧氧化终端产物之一，故本实施例结果表明本发明提供的臭氧氧化催化剂具有较高的催化活性，矿化程度高，可显著提高臭氧氧化的矿化程度。
实施例5
介孔臭氧氧化催化剂与钛锆复合氧化物球/氧化铈混合物催化性能对比
在多孔气体洗瓶中加入2.5g实施例1中制得介孔臭氧氧化催化剂，或相同质量的实施例1中制得的氧化铈粉末，或实施例1中制得的钛锆复合氧化物球/氧化铈粉末混合物，两者按其在介孔臭氧氧化催化剂中的质量分数进行配比。取500mL实施例4中配制的草酸溶液装入气体洗瓶中，然后将臭氧气相浓度为15mg/L的臭氧/氧气混合气体以0.2L/min的流速由气体洗瓶布气管分散成细小气泡通入溶液中，在一系列时间点取样，通过高效液相色谱测定水中草酸浓度随时间的变化，将上述臭氧/氧气气体替换为氧气进行实验，用来表明材料对草酸的吸附效果。
结果如图4，△表示氧化铈粉末吸附的情况，○表示混合物吸附的情况，□表示实本实施例的介孔臭氧氧化催化剂吸附的情况，▲表示氧化铈粉末催化臭氧氧化的情况，●表示混合物催化臭氧氧化的情况，■表示本实施例介孔臭氧氧化催化剂催化臭氧氧化的情况。图4结果表明，在实验10分钟时，氧化铈粉末对草酸的吸附就达到饱和，完成对草酸的吸附，这是由于氧化铈粒径细小，其对草酸的吸附较快，氧化铈粉末或钛锆复合氧化物/氧化铈混合物在前期(实验70分钟前)表现为催化效果较好，但使用本实施例提供的催化剂进行催化臭氧氧化，120min时草酸的降解效率即明显超过氧化铈粉末或钛锆复合氧化物/氧化铈混合物，而此时，三者对草酸的吸附均达到饱和状态，所以表明本实施例的介孔臭氧氧化催化剂草酸的去除主要依靠催化氧化而非吸附。本实施例表明，本发明的介孔臭氧氧化催化剂的催化效果不是钛锆复合氧化物球与氧化铈的效果的简单叠加，并且其矿化程度高，可显著提高臭氧氧化的矿化程度。
实施例6
本实施例中的一种介孔臭氧氧化催化剂，组成成分与实施例1相同，在实施例1中的草酸溶液成分中增加500mg/L的硫酸根，其余条件与实施例4相同进行实验，如图5所示，□表示无硫酸根的条件下介孔臭氧氧化催化剂吸附的情况，△表示硫酸根共存条件下介孔臭氧氧化催化剂吸附的情况，■表示无硫酸根条件下介孔臭氧氧化催化剂催化臭氧氧化的情况，▲表示硫酸根共存的条件下介孔臭氧氧化催化剂催化臭氧氧化的情况。
120分钟时，在无硫酸根条件下添加介孔臭氧氧化催化剂对草酸的降解率为90％，硫酸根共存的条件下添加介孔臭氧氧化催化剂对草酸的降解率为95％，所以实验表明，在硫酸根共存条件下，使用本发明提供的介孔臭氧氧化催化剂，催化臭氧氧化效果不仅不受抑制，反而效率更高。采用电子顺磁共振(EPR)表征表明该过程产生硫酸根自由基，故进一步提高其催化活性。
本实施例说明本发明提供的介孔臭氧氧化催化剂具有宽广的适用范围，可在硫酸根共存条件下更高效的催化臭氧氧化污染物。
实施例7
介孔臭氧氧化催化剂再生反复回用催化臭氧氧化草酸及稳定性
将实施例4中的催化剂回收后经过200℃热再生处理，重复实施例4的实验，进行回用实验，共进行8轮，结果如图6，可见本发明提供的介孔臭氧氧化催化剂在反复回用中一直保持较高的催化活性。回用过程中测定每轮出水的铈浓度，前三轮浓度分别为0.044，0.012，0.008mg/L，其余每轮出水中均未检出。将进行完回用实验的催化剂回收，再进行XPS表征，铈元素的价态仍 然由三价和四价组成，其中三价所占比例为50％，与新制备催化剂几乎相同。
本实施例说明本发明提供的介孔臭氧氧化催化剂具有持久高效的催化活性，且具有较高的稳定性，即使在pH＝3的酸性条件下反复使用也不会释放活性成分或有毒有害元素，且经反复回用后活性成分价态组成不变。
实施例8
本实施例中的一种介孔臭氧氧化催化剂，组成成分与施例1相同，在实施例1中的草酸溶液组分中添加不同浓度的叔丁醇作为羟基自由基捕获剂，其余条件相同进行实验，结果如图7所示，■表示单独臭氧氧化的情况，○表示介孔臭氧氧化催化剂吸附的情况，▼表示添加40mg/L叔丁醇条件下介孔臭氧氧化催化剂催化臭氧氧化的情况，◆表示添加5mg/L叔丁醇条件下介孔臭氧氧化催化剂催化臭氧氧化的情况，▲表示不添加叔丁醇条件下介孔臭氧氧化催化剂催化臭氧氧化的情况。
可见，120分钟时，添加40mg/L叔丁醇条件下介孔臭氧氧化催化剂对草酸的降解率为30％；添加5mg/L叔丁醇条件下介孔臭氧氧化催化剂对草酸的降解率为60％；不添加叔丁醇条件下介孔臭氧氧化催化剂对草酸的降解率为90％；实验表明随叔丁醇浓度增加，催化臭氧氧化草酸的效率逐渐降低，表明本发明提供的介孔臭氧氧化催化剂催化臭氧氧化草酸的机理为将臭氧转化为氧化能力更强的羟基自由基，进而作用于草酸将其矿化。
采用5,5-二甲基-1-氧化吡咯啉(DMPO)作为自旋捕获剂，单独臭氧氧化和实施例1中制得的介孔臭氧氧化催化剂催化臭氧氧化的EPR谱如图8所示，可见，单独臭氧氧化未产生明显的信号峰，而采用本发明提供的介孔臭氧氧化催化剂催化臭氧氧化则产生了明显的羟基自由基信号峰。
本实施例证明了本发明提供的介孔臭氧氧化催化剂催化臭氧氧化的机理为将臭氧转化为氧化能力更强的羟基自由基作用于污染物。
以上示意性的对本实用新型及其实施方式进行了描述，该描述没有限制性，附图中所示的也只是本发明的实施方式之一，实际的结构并不局限于此。所以，如果本领域的普通技术人员受其启示，在不脱离本发明创造宗旨的情况下，不经创造性的设计出与该技术方案相似的结构方式及实施例，均应属于本发明的保护范围。

Claims (10)

  1. 一种介孔臭氧氧化催化剂，其特征在于：所述催化剂呈固体球形颗粒状，所述催化剂的球形颗粒的直径为0.7～1.2mm，活性成分为铈钛锆复合氧化物，在透射电子显微镜下观察有平行的晶格条纹，条纹间距为0.332～0.339nm。
  2. 根据权利要求1所述的一种介孔臭氧氧化催化剂，其特征在于：所述催化剂中含有铈、钛、锆和氧，铈元素质量分数为10％～15％，钛元素质量分数为30％～50％，锆元素质量分数为5％～15％，氧元素质量分数为30％～50％，钙元素质量分数小于2％。
  3. 根据权利要求2所述的一种介孔臭氧氧化催化剂，其特征在于：球形颗粒上具有孔，孔的平均孔径为4.0～7.0nm，球形颗粒的比表面积为160～200m2/g，孔容积为0.31～0.34cm3/g。
  4. 根据权利要求3所述的一种介孔臭氧氧化催化剂，其特征在于：所含铈元素的价态由三价和四价组成，其中三价铈占铈元素总比例的45％～55％。
  5. 一种介孔臭氧氧化催化剂的制备方法，其特征在于：
    (1)在室温下，向搅拌状态下的CaCl2水溶液中逐滴加入海藻酸钠水溶液，形成一定量凝胶球后停止滴加海藻酸钠溶液，继续搅拌12～24h使模板球内部海藻酸钠溶液完全转化为海藻酸钙凝胶，水洗得到海藻酸钙凝胶模板球；
    (2)将步骤(1)中制得的海藻酸钙凝胶模板球用无水乙醇洗涤除去内部水分后，置于钛锆醇盐混合溶液中浸润12～24h，然后转移至异丙醇水溶液中浸泡12～24h，取出后在室温下干燥24～72h，再在55～65℃温度下干燥4～8h，然后在350～600℃温度下煅烧3～8h，冷却至室温后用硝酸溶液清洗，水洗，干燥，得到钛锆复合氧化物球；
    (3)将步骤(2)中制得的钛锆复合氧化物球放入Ce(NO3)3溶液中浸泡2～8h，然后进行过滤，将过滤后的固体粉末在105℃下干燥12～24h，得到固 体状粉末；
    (4)将步骤(3)中得到的固体状粉末置于400～500℃温度下煅烧2～6h，完成介孔臭氧氧化催化剂的制备。
  6. 根据权利要求5所述的一种介孔臭氧氧化催化剂的制备方法，其特征在于：步骤(2)中，所述钛锆醇盐混合溶液是由异丙醇钛和质量分数为70％的正丙醇锆的正丙醇溶液按体积比2:1～6:1配制而成的溶液。
  7. 根据权利要求5所述的一种介孔臭氧氧化催化剂的制备方法，其特征在于：步骤(2)中，钛锆醇盐混合溶液的质量是海藻酸钙凝胶模板球质量的2～8倍，所述异丙醇水溶液为纯水和异丙醇按体积比(0.5～2):1配制的溶液。
  8. 根据权利要求5所述的一种介孔臭氧氧化催化剂的制备方法，其特征在于：步骤(3)中所述Ce(NO3)3溶液浓度为0.10～0.25mol/L。
  9. 一种介孔臭氧氧化催化剂的应用方法，其特征在于：将权利要求1-4任一项所述的一种介孔臭氧氧化催化剂放入固定床或流化床反应器中；将废水连续或批量通入上述反应器；将含有臭氧的气体连续或间歇通入废水中，在介孔臭氧氧化催化剂的作用下，使污染物降解，将废水连续或间歇排出反应器，介孔臭氧氧化催化剂依靠重力作用与废水分离而留在反应器内，完成对废水的处理。
  10. 根据权利要求9所述的一种介孔臭氧氧化催化剂的应用方法，其特征在于：当催化剂上积累了污染物催化性能下降时，将催化剂取出反应器，经水洗和干燥后，置于200～500℃温度下焙烧2～6h，冷却后再放入反应器中重新使用。
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