CN107774244A - ZrO2Base catalyst and preparation method thereof and the application in thermal degradation formaldehyde - Google Patents

Abstract

The invention discloses a ZrO2 _- based catalyst and its preparation method and its application in thermally degrading formaldehyde. The preparation method is carried out according to the following steps: Step ₁ , at room temperature, ZrOCl2 _· 8H2O and metal chloride salt into high-purity water, stirred for at least 30min; wherein M=Mn, Ni or Pd; step 2, in the solution prepared in step 1, drop excess ammonia, H ₃ BO ₃ or thiourea to generate Precipitate; the precipitate is left to stand for at least 0.5 hours, and the impurity ions in the solution are removed after standing; step 3, the precipitate obtained in step 2 is heated at 100-120°C for 12-14h, ground for at least 5min, at 600- Calcined at 700°C for 2.5 to 3 hours, and cooled naturally to room temperature. The ZrO2 _- based catalyst of the present invention has high efficiency for the thermocatalytic degradation of formaldehyde organic pollutants. The method for thermocatalytic degradation of formaldehyde is simple, requires low implementation conditions, and is easy to operate; And thermal catalytic effect is better.

Description

ZrO2-Based Catalyst and Its Preparation Method and Application in Thermal Degradation of Formaldehyde

technical field

The invention belongs to the scientific and technical field of environmental pollution control, and specifically relates to a ZrO2 _- based catalyst, a preparation method thereof, and an application in thermally degrading formaldehyde.

Background technique

As an important chemical raw material, formaldehyde (HCHO) is widely used in building materials and decorative materials. Studies have shown that human beings stay indoors with formaldehyde content ≥30mg/ ^m3 for a long time, which will cause various diseases, such as skin diseases and cancer. Formaldehyde has been identified as a carcinogenic and teratogenic substance by the World Health Organization. Therefore, formaldehyde pollution has become a big problem to be solved urgently. At present, the most commonly used methods for controlling formaldehyde pollution are physical adsorption technology, plant purification method, plasma technology and catalytic oxidation method, etc. Among them, both physical adsorption technology and plant purification method have the problem of incomplete removal; plasma technology consumes a lot of power and is It is easy to produce secondary pollution; the catalytic oxidation method mainly includes photocatalytic oxidation method and thermal catalytic oxidation method. Photocatalytic oxidation method needs to use ultraviolet light as light source, which has high cost and short life. Oxidation method is to convert formaldehyde into non-polluting carbon dioxide and water by using oxygen in the air as an oxide at low temperature without light source. Because of its low cost, high efficiency and thorough removal, it has become the most effective way to remove indoor formaldehyde pollution. A treatment method of foreground has gradually become a research hotspot in the field of catalysis. However, most of the current thermal catalysts use oxides as carriers and are prepared by noble metal doping or compounding methods, and the cost is relatively high.

Contents of the invention

Aiming at the deficiencies in the prior art, the object of the present invention is to provide a kind of ZrO ₂ base catalyst and its preparation method and the application in thermal degradation formaldehyde.

The present invention is achieved through the following technical solutions.

A kind of ZrO _The preparation method of base catalyst, carry out according to the following steps:

Step 1, put ZrOCl ₂ ·8H ₂ O and metal chloride salt into high-purity water according to the chemical formula ZrO ₂ -M x%, 0≤x≤30, and stir for at least 30 minutes at room temperature 20-25°C; , said M=Mn, Ni or Pd, said x is the ratio of the amount of metal ion M to the sum of metal ion M and Zr ion materials;

Step 2, add excess ammonia water, H ₃ BO ₃ or thiourea dropwise to the solution prepared in step 1 to generate a precipitate; leave the precipitate for at least 0.5 hours, and remove impurity ions in the solution after standing ;

Step 3: heat the precipitate obtained in step 2 at 100-120°C for 12-14h, grind for at least 5min, calcinate at 600-700°C for 2.5-3h, and cool naturally to room temperature at 20-25°C to obtain ZrO2 _- based catalyst powder.

In the above technical solution, in the step 1, the stirring is magnetic stirring.

In the above technical solution, the metal chloride salt is MnCl ₂ ·4H ₂ O, NiCl ₂ ·6H ₂ O or PdCl ₂ .

A ZrO2 _- based catalyst prepared by the above preparation method.

In the above technical scheme, the metal ion M enters the lattice of ZrO ₂ to replace the Zr ion and occupy the position of the Zr ion.

Application of one of the aforementioned ZrO2 _- based catalysts in the thermal degradation of formaldehyde.

In the above technical solution, the ZrO2 _- based catalyst is placed in a formaldehyde environment for at least 25 hours at 25-70° C. without special light conditions.

In the above technical solution, the ZrO ₂ -based catalyst is placed in a closed formaldehyde environment for at least 25 hours at 50-65° C. without special light.

In the above technical solution, when M=Mn, 15<x≤20, preferably x=20.

In the above technical solution, when M=Ni, 0<x≤9, preferably x=1.

In the above technical solution, when M=Pd, 0<x≤25, preferably x=20.

Compared with the prior art, the ZrO2 _- based catalyst of the present invention has higher efficiency for the thermocatalytic degradation of formaldehyde organic pollutants, the method of thermocatalytic degradation of formaldehyde is simple, the implementation condition requirements are low, and it is easy to operate; and the thermocatalytic effect is relatively it is good.

Description of drawings

Fig. 1 is pure ZrO ₂ and the X-ray diffraction spectrum (XRD) of the ZrO ₂ -Mnx% sample that embodiment 2 prepares;

Figure 2 is a partially enlarged view of Figure 1;

Fig. 3 is the high-resolution TEM spectrogram of pure ZrO ₂ and ZrO ₂ -Mnx% sample, (a) pure ZrO ₂ , (b) ZrO ₂ -Mnx% (x=5), (c) ZrO ₂ -Mnx% ( x=20);

Fig. 4 is the concentration-time curve of pure ZrO ₂ and ZrO ₂ -Mnx% samples thermocatalytic degradation product CO ₂ of HCHO;

Fig. 5 is pure ZrO ₂ and the X-ray diffraction spectrum of the ZrO ₂ -Nix% sample that embodiment 3 prepares;

Figure 6 is a partially enlarged view of Figure 5;

Fig. 7 is the HR-TEM figure of pure ZrO ₂ (A) and ZrO ₂ -Ni9% (B);

Fig. 8 is the concentration-time curve of pure ZrO ₂ and ZrO ₂ -Nix% samples thermocatalytically degrading HCHO to generate CO ₂ ;

Fig. 9 is pure ZrO ₂ and the X-ray diffraction spectrum of the ZrO ₂ -Pdx% sample that embodiment 4 prepares;

Figure 10 is a high-resolution TEM of pure ZrO ₂ (A), ZrO ₂ -Pd5% (B) and ZrO ₂ -Pd20% (C, D);

Fig. 11 is the concentration-time curves of pure ZrO ₂ and ZrO ₂ -Pdx% samples thermocatalytically degrading HCHO to generate CO ₂ .

Detailed ways

In a specific embodiment of the present invention, the drug purchase situation is as follows:

The crystal form and crystal structure of the sample were determined by X-ray powder diffractometer (model and parameters: Rigaku D/max-2500, Cu target, Kα line, Japan). The transmission electron microscope model is Tecnai G2F20 (Philips). The gas chromatograph model is GC7890F (Shanghai Tianmei Scientific Instrument Co., Ltd.).

According to references (Zhang C, He H, Tanaka K.Catalytic performance and mechanism of a Pt/TiO ₂ catalyst for the oxidation of formaldehyde at room temperature[J].Applied Catalysis B:Environmental,2006,65(1):37-43 ) shows that in the process of thermal catalytic degradation of formaldehyde, it is first oxidized to formic acid, and then the formic acid is dehydrated to produce intermediate product carbon monoxide, and finally the intermediate product carbon monoxide is oxidized by oxygen to generate carbon dioxide. According to the conservation of carbon elements before and after the reaction, by determining the concentration to determine the amount of formaldehyde degraded by thermocatalysis.

In order to conveniently test the effect of ZrO ₂ -based catalyst on the degradation of formaldehyde, a simulated environment was established, and the test proved that the accuracy of the simulated environment and the actual environment to test the effect of ZrO ₂ -based catalyst on the degradation of formaldehyde was almost the same. For this reason, in the specific embodiment of the present invention, all adopt this simulated environment to test the ZrO2 _- based catalyst degradation effect of formaldehyde. Adopt simulated environment to test ZrO _The method for degrading formaldehyde of base catalyst is as follows:

In a tubular closed glass reactor (400mL), ultrasonically disperse an appropriate amount (5-10g) of the catalyst into the ethanol solution to obtain a mixed solution, and apply the mixed solution on a glass slide by the scraping method, and the fixed scraping area is 7cm ×2.1cm, then put two glass slides with catalyst attached into the reactor, seal it, inject 10uL formaldehyde solution into the tube-type closed glass reactor with a micro-injector, and place the tube-type closed glass reactor at 338K In a constant temperature box, without special light (that is, dark conditions), after a certain period of time (at least 1 hour) formaldehyde is completely volatilized and adsorbed on the surface of the catalyst to balance, and 0.4 mL of reaction gas is sampled every 4 hours.

The reaction gas is injected into the gas chromatograph to detect formaldehyde and the product CO ₂ after formaldehyde degradation. The gas chromatograph uses a TDX-01 (1m×φ3mm) chromatographic column, uses high-purity N ₂ as the carrier gas, and a hydrogen flame detector (FID). A conversion furnace is installed between the detector and the chromatographic column, which can realize the hydrogenation reaction of CO ₂ (CO ₂ +4H ₂ →CH ₄ +2H ₂ O), and then detect the concentration changes of formaldehyde and CO ₂ .

Below in conjunction with accompanying drawing and embodiment _ZrO base catalyst of the present invention and its preparation method and the application in thermal degradation formaldehyde are described in detail,

Example 1

Pure ZrO2 is prepared by direct hydrolysis precipitation method _:

Step 1: Put ZrOCl ₂ ·8H ₂ O into 16 mL of high-purity water at a room temperature of 20-25° C., and stir for 30 min.

Step 2, the solution prepared in step 1 was left to stand for 40min to generate a precipitate, and the Cl ions in the solution were removed;

Step 3: Heat the precipitate obtained in step 2 at 100°C for 12h, grind for 5min, calcinate at 600°C for 2.5h, and cool naturally to room temperature 20-25°C to obtain ZrO ₂ powder.

The following pure ZrO ₂ is the ZrO ₂ powder prepared in Example 1.

Example 2

Step 1. Put ZrOCl ₂ ·8H ₂ O and MnCl ₂ ·4H ₂ O into 16 mL of high-purity water according to the chemical formula ZrO ₂ -Mnx%, 0<x≤30, and stir for 30 minutes at room temperature 20-25°C; x is the ratio of the amount of the metal ion Mn to the sum of the amount of metal ions Mn and Zr ions.

Step 2, adding excess ammonia water dropwise to the solution prepared in step 1 to produce a brown precipitate; leave the precipitate for 40 minutes, and remove the Cl ions in the solution after standing;

Step 3: Heat the precipitate obtained in step 2 at 100°C for 12h, grind for 5min, calcinate at 600°C for 2.5h, and cool naturally to room temperature 20-25°C to obtain ZrO ₂ -based catalyst powder.

Fig. 1 is the X-ray diffraction spectrum (XRD) of the pure ZrO ₂ that embodiment 1 prepares and the ZrO ₂ -Mnx% sample that embodiment 2 prepares, and Fig. 2 is the local enlargement figure of Fig. 1, and wherein, curve 1 is pure ZrO2 catalyst, curve ₂ is the ZrO2 _- Mnx% catalyst of x=1, curve 3 is the ZrO2-Mnx% catalyst of x=5, curve 4 is the ZrO2 _{- Mnx} % catalyst of x=9, curve 5 is For ZrO ₂ -Mnx% catalyst with x=15, curve 6 is for ZrO ₂ -Mnx% catalyst with x=20, and curve 7 is for ZrO ₂ -Mnx% catalyst with x=30.

It can be seen from the figure that the characteristic peaks of tetragonal phase appear at 30.1°, 34.5°, 35.1°, 50.1°, 50.5°, 59.2°, 59.9°, 62.6° of pure ZrO ₂ and ZrO ₂ -Mnx% samples, and at 28.1° and 31.2° The characteristic peak of the monoclinic phase appears at the ° position, showing a mixed phase structure of monoclinic and tetragonal. The peaks at 28.1° and 31.4° of the remaining ZrO ₂ -Mnx% samples disappeared, showing a single tetragonal structure, and with the increase of Mn ion doping content, the characteristic peaks all shifted to larger angles. According to common knowledge, metal ions can enter the oxide lattice in two ways, one is interstitial doping, only when the radius of the metal ion is much smaller than the metal ion in the oxide, the dopant ions can enter the oxide In the lattice gap; the other is substitutional doping, when the radius of the dopant ion is close to the radius of the metal ion in the oxide, substitutional doping often occurs. In Example 2 of the present invention, the ionic radius of the doping ion Mn ²⁺ is 66pm, and the Zr ⁴⁺ ion radius in ZrO ₂ is 72pm. If Mn ²⁺ enters the crystal lattice of ZrO ₂ in an interstitial manner, the lattice The larger the parameters, the larger the volume. According to the Bragg diffraction formula, the XRD diffraction peaks will shift in small angles. However, in Figure 1 and Figure 2, the XRD results show that the diffraction peaks are shifted towards large angles. Therefore, it is impossible for Mn ²⁺ to enter the lattice of ZrO ₂ in an interstitial manner. On the contrary, if Mn ²⁺ enters the lattice to replace the position of Zr ⁴⁺ , since Mn ²⁺ is smaller than the radius of Zr ⁴⁺ , the unit cell parameters and unit cell volume of ZrO ₂ will decrease, and the X-ray diffraction peak will be towards The large-angle movement is consistent with the test results, so Mn ²⁺ is likely to enter the lattice of ZrO ₂ through substitutional doping.

Fig. 3 is the high-resolution TEM spectrogram of ZrO ₂ , ZrO ₂ -Mnx% (x=5) and ZrO ₂ -Mnx% (x=20) samples, in Fig. 3 (a), the interplanetary spacing of mark 0.297nm corresponds to The (101) plane of the pure ZrO ₂ sample, in Fig. 3(b), the interplanar spacing of the (101) plane of the ZrO ₂ -Mnx% (x=5) sample is 0.294nm, and this interplanar spacing is in the ZrO ₂ -Mnx% (x=20) is 0.292nm in the sample (as shown in Figure 3c). The results show that the interplanar spacing of the ZrO ₂ -Mnx% sample decreases after doping, which is consistent with the XRD results. Therefore, Mn ions are doped by substitution Doping into the ZrO ₂ lattice.

According to the above method, the ZrO2 _- based catalyst was used to test the thermal catalytic degradation of formaldehyde in a simulated environment, and the thermal catalytic activity of the catalyst was evaluated according to the concentration of _CO2 generated. The test results are shown in Figure 4.

The blank in Figure 4 is a blank experiment without any catalyst. After 22 hours of thermal decomposition of formaldehyde in the blank experiment, only a small amount of _CO2 was generated in the reactor, indicating that HCHO would not be decomposed under thermal catalytic conditions. It can be seen from the figure that the thermal catalytic degradation of formaldehyde by pure ZrO ₂ has very low activity to generate CO ₂ , and the concentration of CO ₂ generated after 22 hours of reaction is only 37.6374×10 ^-6 mol·L ^-1 . For the doped sample, the thermocatalytic activity of ZrO ₂ -Mn20% is the highest, which is about 2.8 times that of pure ZrO ₂ , and the concentration of CO ₂ produced after 22 hours of reaction is 103.8891×10 ^-6 mol·L ^-1 .

Example 3

Step 1: Put ZrOCl ₂ ·8H ₂ O and NiCl ₂ ·6H ₂ O into 16 mL of high-purity water according to the ratio of chemical formula ZrO ₂ -Nix% at room temperature 20-25°C, and stir for at least 30 minutes; x is the metal ion Ni The ratio of the amount of species to the sum of the species of metal ions Ni and Zr ions.

Step 2, drip excessive ammoniacal liquor in the solution that step 1 makes, to generate precipitate (in the solution that step 1 makes, drip ammoniacal liquor, after stopping to generate precipitate in the solution, stop dripping ammoniacal liquor.); The precipitate was left to stand for 40 minutes, and the Cl ions in the solution were removed after standing;

Step 3: Heat the precipitate obtained in step 2 at 100°C for 12h, grind for 5min, calcinate at 600°C for 2.5h, and cool naturally to room temperature 20-25°C to obtain ZrO ₂ -based catalyst powder.

Use X-ray diffraction spectrum to obtain the crystal structure information of the sample, the results are shown in Figure 5 and Figure 6, wherein, curve 1 is pure ZrO ₂ , curve 2 is ZrO ₂ -Nix% catalyst with x=0.5, and curve 3 is x =1 for ZrO2 _- Nix% catalyst, curve 4 for ZrO2-Nix% catalyst for x=5, curve ₅ for ZrO2 _- Nix% catalyst for x=9.

It can be seen from the figure that the characteristic peaks of the tetragonal phase appear at 30.1°, 34.5°, 35.1°, 50.1°, 50.5°, 59.2°, 59.9°, and 62.6° for pure ZrO ₂ and ZrO ₂ -Ni0.5% samples, and at 28.1° The characteristic peak of monoclinic phase appears at the position of 31.2° and 31.2°, which is a mixed phase structure of monoclinic and tetragonal crystal forms. The samples of ZrO ₂ -Ni1%, ZrO ₂ -Ni5% and ZrO ₂ -Ni9% showed complete tetragonal crystal structure. Figure 6 shows the diffraction peaks after the characteristic peak of the tetragonal phase is amplified at 30.1°. It is obvious that the diffraction peaks of ZrO ₂ -Nix% samples after doping move to the direction of large angle, and with the increase of Ni doping amount, the shift The angle increases. During the doping process, when the ion radius of the doped metal ion is close to the metal ion radius in the oxide lattice, the doped metal ion will enter the oxide lattice to replace the metal ion and occupy its position, forming a substitutional doping . When the radius of the doped metal ions is much smaller than that of the metal ions in the oxide lattice, the doped metal ions will enter into the unit cells of the oxide to form interstitial doping. The ionic radius of doped Ni ²⁺ is 69pm, and the Zr ⁴⁺ ion radius in the ZrO ₂ lattice is 72pm. The ionic radii of the two are very close. Ni ions cannot enter the lattice gap of ZrO ₂ , and it is very likely to be doped by substitution. Impurities enter the lattice of ZrO2 and occupy the sites of Zr _ions . If Ni ions replace Zr ion positions, due to the smaller radius of Ni ions, the interplanar spacing (d hkl), unit cell parameters (a, b, c), unit cell volume, etc. of ZrO2 will decrease, according to the Bragg diffraction _formula d _hkl sinθ=kλ, it can be seen that the X-ray diffraction angle will move to a larger angle, which is consistent with the XRD test results.

Figure 7 (A) is the HR-TEM image of pure ZrO ₂ , the fringe spacing of 0.297nm corresponds to the (101) plane of the ZrO ₂ crystal, and Figure 7 (B) is the HR-TEM image of ZrO ₂ -Ni9%, the fringe The spacing is 0.294nm, and the fringe spacing in the HR-TEM image corresponds to the interplanar spacing of the crystal, indicating that the interplanar spacing of the ZrO ₂ -Ni9% sample is smaller than that of ZrO ₂ , that is, the crystal interplanar spacing of the sample after doping Ni ²⁺ ions The interplanar spacing decreases, which is consistent with the XRD results.

In summary, Ni ²⁺ ions enter the ZrO ₂ lattice by substitutional doping and occupy the positions of Zr ions.

According to the above method, the simulated environment is used to test the ZrO2 _- based catalyst for thermal catalytic degradation of formaldehyde, and the thermal catalytic activity of the catalyst is evaluated according to the concentration of generated _CO2 . The test results are shown in Figure 8. Figure 8 is the concentration change curve of CO ₂ produced by degrading HCHO under the thermocatalytic conditions of ZrO ₂ and ZrO ₂ -Nix% samples. It can be seen from the figure that when the Ni doping amount is 1%, the amount of CO ₂ generated is the largest and has the best thermal catalytic activity. Among them, only a small amount of _CO2 was generated in the thermal decomposition of formaldehyde experiment (that is, the blank curve without catalyst), indicating that HCHO would not be decomposed basically under thermal catalytic conditions. Pure ZrO ₂ has weak thermal catalytic activity, and the concentration of CO ₂ produced after 22 hours of reaction is 37.6374×10-6mol·L ^-1 , the thermal catalytic activity of ZrO ₂ -Ni0.5%, ZrO ₂ -Ni5% and ZrO ₂ -Ni9% Weaker, the thermocatalytic activity of ZrO ₂ -Ni1% is obviously higher than that of pure ZrO ₂ , and its CO ₂ concentration is 54.9596×10-6mol·L ^-1 , about 1.5 times that of pure ZrO ₂ .

Example 4

Step 1, put ZrOCl ₂ 8H ₂ O and PdCl ₂ into 16mL high-purity water at room temperature 20-25°C according to the ratio of chemical formula ZrO ₂ -Pdx%, and stir for 30 minutes; x is the amount of metal ion Pd and The ratio of the amount and species of metal ions Pd and Zr ions.

Step 2, dropwise excessive ammoniacal liquor in the solution that step 1 makes, to generate precipitate (the concentration of adding ammoniacal liquor is 10%); Said precipitate is left standstill 40min, after standing, remove the Cl ion in the solution: The solution is filtered, and after filtration, the precipitate is washed with deionized water to remove Cl ions;

Step 3: Heat the precipitate obtained in step 2 at 100°C for 12h, grind for 5min, calcinate at 600°C for 2.5h, and cool naturally to room temperature 20-25°C to obtain ZrO ₂ -based catalyst powder.

Fig. 9 is the XRD spectrogram of ZrO2 and ZrO2 _- Pdx% series sample, curve ₁ is the pure ZrO2 that embodiment 1 makes, curve ₂ is the ZrO2 _- Pdx% catalyst of x=1, curve 3 is x= 5 for ZrO ₂ -Pdx% catalyst, curve 4 for ZrO 2 -Pdx% catalyst for x=9, curve 5 for ZrO ₂ -Pdx% catalyst for x=15, curve 6 for ZrO ₂ -Pdx% catalyst for x= ₂₀ , Curve 7 is the ZrO ₂ -Pdx% catalyst with x=25.

It can be seen from Figure 9 that pure ZrO ₂ has diffraction peaks of tetragonal phase at 30.1°, 34.5°, 35.1°, 50.1°, 50.5°, 59.2°, 59.9°, and 62.6°, and monoclinic phase at 28.1° and 31.2° Therefore, pure ZrO ₂ is a mixed phase of monoclinic and tetragonal structures, and the diffraction peaks of ZrO ₂ -Pd1% and ZrO ₂ -Pd5% are similar to pure ZrO ₂ , and are also mixed phases of monoclinic and tetragonal structures, with higher concentrations The diffraction peaks at 28.1° and 31.2° of the ZrO ₂ -Pdx% sample disappeared, showing a complete tetragonal crystal structure, and PdO was detected in the ZrO ₂ -Pd15%, ZrO ₂ -Pd20% and ZrO ₂ -Pd25% samples Diffraction peaks.

Compared with pure ZrO ₂ , the diffraction peaks of Pd-doped ZrO ₂ sample shifted to the left at a small angle when the concentration of Pd was doped, and began to shift to a large angle as the Pd concentration increased to 9%.

There are usually two ways for metal ions to enter oxide crystals, interstitial doping and substitutional doping. Interstitial doping means that when the radius of the metal ion is much smaller than the metal ion in the oxide, the dopant ion will be in the lattice gap of the crystal; and when the radius of the metal ion is close to the metal ion radius of the oxide species, substitution often occurs formula doping. The ion radius of Pd ²⁺ is 84pm, which is slightly larger than that of Zr ⁴⁺ (72pm). Therefore, when the doping concentration is low, it is impossible for Pd ²⁺ to enter the lattice of ZrO ₂ in an interstitial manner, and it can only replace Zr ⁴⁺ The form of Pd 2+ enters the lattice of ZrO ₂ . Due to the large radius of Pd ²⁺ ions, the parameters of the unit cell and the volume of the unit cell become larger after entering the lattice of ZrO ₂ , so that the diffraction peak shifts to a small angle. When the concentration increased to 9%, PdO was gradually precipitated, and the diffraction peaks gradually shifted to large angles. This was because the valence state of Pd ions changed during the sintering process and became Pd ⁴⁺ with an ionic radius of 62pm. The ⁴⁺ ion radius is smaller than that of Zr ⁴⁺ , replacing the Zr ⁴⁺ position in ZrO ₂ will lead to a corresponding decrease in the unit cell parameters and volume of the sample, and a large angle shift of the diffraction peak, which is consistent with the result.

Fig. 10 is a high-resolution TEM of pure ZrO ₂ (A), ZrO ₂ -Pd5% (B) and ZrO ₂ -Pd20% (C, D). Figure A is the HR-TEM image of pure ZrO ₂ , the fringe spacing of 0.297nm corresponds to the (101) plane of the ZrO ₂ crystal, and Figure B is the HR-TEM image of ZrO ₂ -Pd5%, and the fringe spacing is 0.299nm. C and D are HR-TEM images of ZrO ₂ -Pd20%, corresponding to a fringe spacing of 0.292nm. Compared with pure ZrO ₂ , the ZrO ₂ -Pd5% sample has a slightly increased fringe spacing, which is due to the larger ionic radius of Pd ^{2 +} replaces Zr ⁴⁺ into the lattice of ZrO ₂ , resulting in an increase in its unit cell parameters and interplanar spacing. However, the fringe spacing of the ZrO ₂ -Pd20% sample decreases because Pd ²⁺ transforms into Pd ⁴⁺ with a larger ionic radius during sintering. This result is consistent with XRD analysis. In addition, a fringe spacing of 0.263nm was found in the ZrO ₂ -Pd20% sample, which corresponds to the (101) crystal plane of PdO after analysis, indicating that PdO appeared in the high concentration sample, which is consistent with the XRD results.

According to the above method, the ZrO2 _- based catalyst was tested for thermocatalytic degradation of formaldehyde in a simulated environment, and the thermocatalytic activity of the catalyst was evaluated according to the concentration of generated _CO2 . The test results are shown in Figure 11.

Figure 11 shows that after the introduction of Pd ions into the ZrO ₂ system, the corresponding thermocatalytic activity is improved, and the thermocatalytic activity is the strongest in the ZrO ₂ -Pd20% sample, and the CO ₂ concentration is 301.8378×10 ^-6 mol·L ^-1 , about 8.0 times that of pure ZrO ₂ . The catalytic activity of the ZrO ₂ -Pdx% sample increases with the increase of the doping amount. When the doping amount reaches a certain level, the catalytic activity no longer increases, and even begins to decline, indicating that the effect of Pd ion doping on the activity of the catalyst presents a Optimizing the relationship, the optimal doping amount is 20%, that is, the catalytic activity of ZrO ₂ -Pd20% is the highest.

The thermocatalytic degradation of formaldehyde can be achieved by adjusting the process parameters according to the content recorded in the content of the present invention, and the properties are basically consistent with the above-mentioned examples after testing.

The present invention has been described as an example above, and it should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacements that can be made by those skilled in the art without creative labor all fall within the scope of this invention. protection scope of the invention.

Claims (10)

1. A kind of 1. ZrO₂The preparation method of base catalyst, it is characterised in that carry out as steps described below：

   Step 1, in 20~25 DEG C of room temperature, according to chemical formula ZrO₂- Mx%, the proportioning of 0≤x≤30, by ZrOCl₂·8H₂O and gold Category chlorate is put into high purity water, stirs at least 30min；Wherein, described M=Mn, Ni or Pd, the x are the thing of metal ions M The amount of the amount of matter and metal ions M and Zr ionic species and ratio；

   Step 2, excess of ammonia water, H are added dropwise in solution made from step 1₃BO₃Or thiocarbamide, to generate sediment；Will be described heavy Starch stands at least 0.5 hour, and the foreign ion in solution is removed after standing；

   Step 3, step 2 gained sediment is heated into 12~14h at 100~120 DEG C, at least 5min is ground, at 600~700 DEG C 2.5~3h is calcined, 20~25 degrees Celsius of room temperature is naturally cooled to, that is, obtains ZrO₂Base catalyst fines.
2. 2. ZrO according to claim 1₂The preparation method of base catalyst, it is characterised in that in the step 1, stirring For magnetic agitation.
3. 3. ZrO according to claim 2₂The preparation method of base catalyst, it is characterised in that the metal chlorination salt is MnCl₂·4H₂O、NiCl₂·6H₂O or PdCl₂。
4. A kind of 4. ZrO made from preparation method with described in claims 1 to 3 any one₂Base catalyst.
5. 5. ZrO according to claim 4₂Base catalyst, it is characterised in that metal ions M enters ZrO₂Lattice in substitute Zr ions and the position for occupying the Zr ions.
6. A kind of 6. ZrO made from preparation method with described in claims 1 to 3 any one₂Base catalyst is in thermal degradation formaldehyde Application.
7. 7. application according to claim 6, it is characterised in that at 25~70 DEG C, under without special illumination condition, by institute State ZrO₂Base catalyst is placed in formaldehyde environment at least 25 hours, preferably 50~65 DEG C.
8. 8. application according to claim 7, it is characterised in that as M=Mn, 15 ＜ x≤20, preferably x=20.
9. 9. application according to claim 7, it is characterised in that as M=Ni, 0 ＜ x≤9, preferably x=1.
10. 10. application according to claim 7, it is characterised in that as M=Pd, 0 ＜ x≤25, preferably x=20.