Formaldehyde degradation catalyst as well as preparation method and application thereof

Abstract

The invention relates to a formaldehyde degradation catalyst as well as a preparation method and application thereof. The formaldehyde degradation catalyst comprises a carrier and an active component Pd loaded on the carrier, the carrier is CeO < 1-x > Cl, and 0 lt; xlt; 1; the catalyst has rich oxygen vacancies and electron-rich Pd sites, the Pd sites can generate more high-activity free radicals, and the catalytic performance of the catalyst for degrading formaldehyde at room temperature is remarkably improved by fully utilizing the synergistic enhancement effect between the oxygen vacancies and the active sites, so that the catalyst can be widely applied to degradation of formaldehyde.

Description

Technical Field

[0001] The invention relates to the technical field of formaldehyde catalysis, and in particular to a formaldehyde degradation catalyst and a preparation method and application thereof. Background Art

[0002] Formaldehyde is a typical pollutant that is widely present in the surrounding water environment and indoor environment. Long-term exposure to HCHO, even at low concentrations, can cause serious harm to human health, such as allergic dermatitis, eye irritation, pneumonia, and even cancer. Therefore, the development of effective methods to remove HCHO is of great significance to improving the surrounding environment.

[0003] Researchers have studied many strategies for removing HCHO pollutants, mainly physical adsorption, biological treatment, catalytic oxidation, etc. Physical adsorption has disadvantages such as easy adsorption saturation and difficult desorption. Biological treatment has disadvantages such as high cost and low efficiency. Compared with the above methods, catalytic oxidation is green, efficient, low cost, low energy consumption, and has broad application prospects. Among them, photocatalytic oxidation and room temperature catalytic oxidation have been reported more. Room temperature catalytic oxidation is a very promising HCHO degradation technology. It can make full use of ambient temperature as an energy supply to degrade HCHO into non-toxic and harmless H2O and CO2, but this technology faces the bottleneck of low catalytic performance in practical applications.

[0004] In order to achieve the best catalytic activity in the HCHO degradation process, the researchers focused on the optimization of the catalyst structure design, mainly involving the following two aspects, specifically, improving the catalyst's ability to capture HCHO in the early stage of HCHO catalytic degradation and the HCHO catalytic degradation stage. Whether the catalyst can produce a large number of highly active free radicals is the key to affecting the efficiency of HCHO degradation. The researchers focused on the development and loading of precious metals (Pd, Pt and Au) as room temperature catalytic oxidation catalysts to obtain good activity to produce active substances.

[0005] CeO2 can be used in Ce 4+ and Ce 3+ Switching between two oxidation states, it is often used as a catalyst substrate. The disadvantage is that hydroxyl groups and carbonates and / or carboxylic acids are easily formed on its surface, making it difficult to effectively disperse the precious metal particles.

[0006] Based on the above technical problems, how to develop a formaldehyde catalyst with uniformly dispersed active substances and higher catalyst efficiency and provide a catalyst preparation method with a simple preparation method and large-scale production has become a problem to be solved urgently. Summary of the invention

[0007] In order to solve the above technical problems, the present invention aims to provide a formaldehyde degradation catalyst and its preparation method and use. The catalyst of the present invention has abundant oxygen vacancies and electron-rich Pd sites, and the Pd sites can generate more highly active free radicals. By making full use of the synergistic enhancement effect between oxygen vacancies and active sites, the catalytic performance of the room temperature formaldehyde degradation catalyst is significantly improved, so that the catalyst can be widely used in the degradation of formaldehyde.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a formaldehyde degradation catalyst, the formaldehyde degradation catalyst comprising a carrier and an active component Pd supported on the carrier; the carrier is CeO 1-x Cl, where 0 <x<1。

[0010] The present invention constructs an oxygen-rich vacancy system CeO 1-x Cl / Pd, oxygen vacancies and Pd sites play important roles in the initial stage and mineralization stage of HCHO degradation, respectively. Studies have shown that the presence of chloride ions is conducive to the dispersion of noble metal active sites, and the substitution of chloride ions for lattice oxygen on CeO2 will convert CeO2 into CeOCl. The role of oxygen vacancies is mainly to enrich HCHO in the surrounding environment, and the electron-rich Pd sites interact with O2 to generate highly active ·O2 - , thereby further oxidizing the HCHO pollutant. The formaldehyde catalyst of the present invention fully utilizes the synergistic enhancement effect between oxygen vacancies and Pd sites to improve the efficiency of the catalyst in degrading formaldehyde at room temperature.

[0011] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0012] Preferably, the loading amount of the active component Pd on the carrier is 4.0wt%-6.0wt%, for example, it can be 4.0wt%, 4.5wt%, 5.0wt%, 5.5wt% or 6.0wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0013] The present invention controls the loading amount of the active component Pd on the carrier to be 4.0wt%-6.0wt%, which can ensure that the carrier is CeO 1-xCl, and the catalytic efficiency of the obtained catalyst is better. However, if the loading amount is lower than 4.0wt%, CeO2 is not completely reacted to form CeOCl, resulting in lower catalytic efficiency. If the loading amount is higher than 6.0wt%, it will cause agglomeration between the precious metal particles, thereby reducing their dispersion and reducing the number of active sites on the catalyst surface, thereby reducing the catalytic efficiency.

[0014] In a second aspect, the present invention provides a method for preparing the formaldehyde degradation catalyst as described in the first aspect, the preparation method comprising the following steps:

[0015] The chlorine-containing palladium salt is mixed with an inorganic acid to obtain a chlorine-containing palladium salt solution; the chlorine-containing palladium salt solution is mixed with CeO2, and a catalyst precursor is obtained through drying and grinding; and the catalyst precursor is calcined under a reducing atmosphere to obtain the formaldehyde degradation catalyst.

[0016] The present invention uses an inorganic acid to promote the dissolution of a chlorine-containing palladium salt, then impregnates CeO2 and a chlorine-containing palladium salt solution according to a certain ratio, and then reduces them under an argon-hydrogen atmosphere. This method is suitable for preparing a noble metal catalyst and a catalyst with a low content of active components. Different from the conventional preparation method using a surfactant, since there is a metal-support interaction between the carrier and the active component, even if a surfactant is not used, the active component can be evenly distributed on the carrier to avoid agglomeration. In addition, there is no need to introduce an additional solvent during the preparation process, which not only avoids the introduction of impurities, saves preparation raw materials and costs, but also simplifies the preparation process, making it more suitable for large-scale production.

[0017] Preferably, the chlorine-containing palladium salt comprises palladium chloride or ammonium chloropalladate, preferably palladium chloride.

[0018] Preferably, the inorganic acid comprises any one of hydrochloric acid, acetic acid, nitric acid or carbonic acid, or a combination of at least two thereof, wherein typical but non-limiting combinations include a combination of hydrochloric acid and acetic acid, a combination of acetic acid and nitric acid, a combination of nitric acid and carbonic acid, a combination of hydrochloric acid, acetic acid and nitric acid, a combination of acetic acid, nitric acid and carbonic acid, and a combination of hydrochloric acid, acetic acid, nitric acid and carbonic acid, preferably hydrochloric acid.

[0019] The function of the inorganic acid used in the present invention is to accelerate the dissolution rate of the chlorine-containing palladium salt in water to form a uniform chlorine-containing palladium salt solution.

[0020] Preferably, the concentration of palladium ions in the chlorine-containing palladium salt solution is 0.01-0.1 mol / L, for example, it can be 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L or 0.1 mol / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are equally applicable.

[0021] In the present invention, the concentration of palladium ions in the chlorine-containing palladium salt solution is further controlled to be 0.01-0.1 mol / L to ensure that the palladium ions can be completely loaded on the catalyst support and evenly distributed. If the concentration is too high, it is not conducive to the uniform dispersion of the active components, affecting the distribution of the catalyst active sites and the catalytic effect; if the concentration is too low, the volume of the solution is large when the chlorine-containing palladium salt solution is mixed with CeO2, the drying reaction time is too long, and the sample preparation efficiency is low.

[0022] Preferably, the method for preparing CeO2 comprises: calcining and grinding cerium salt in air to obtain CeO2.

[0023] Preferably, the cerium salt comprises any one of cerium nitrate, cerium carbonate, cerium sulfate or cerium acetate, or a combination of at least two thereof, wherein typical but non-limiting combinations include a combination of cerium nitrate and cerium carbonate, a combination of cerium carbonate and cerium sulfate, a combination of cerium sulfate and cerium acetate, a combination of cerium nitrate, cerium carbonate and cerium sulfate, a combination of cerium carbonate, cerium sulfate and cerium acetate, preferably cerium nitrate.

[0024] Preferably, the calcination temperature is 400°C-500°C, for example, it can be 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C or 500°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] Preferably, the heating rate of the calcination is 5°C / min-10°C / min, for example, it can be 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min or 10°C / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] Preferably, the calcination time is 2 h-10 h, for example, 2 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h or 10 h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] Preferably, the mass ratio of CeO2 to the chlorine-containing palladium salt is 1:(0.04-0.06), for example, it can be 1:0.04, 1:0.045, 1:0.05, 1:0.055 or 1:0.06, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] In the present invention, the mass ratio of CeO2 to the chlorine-containing palladium salt is further controlled to be 1:(0.04-0.06) to regulate the content of the active component palladium in the carrier and ensure that the palladium ions can be completely loaded on the catalyst carrier and evenly distributed.

[0029] Preferably, the drying temperature is 70°C-90°C, for example, 70°C, 75°C, 80°C, 85°C or 90°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] Preferably, the drying time is 12 h-72 h, for example, 12 h, 24 h, 36 h, 48 h, 50 h, 60 h, 70 h or 72 h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] The purpose of drying in the present invention is to completely remove the solvent, and the drying time can be adjusted according to the actual sample state.

[0032] Preferably, the reducing atmosphere comprises an argon-hydrogen mixture, in which the hydrogen content is 5 vol%-10 vol%, for example, it can be 5 vol%, 6 vol%, 7 vol%, 8 vol%, 9 vol% or 10 vol%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] Preferably, the calcination temperature is 350°C-550°C, for example, 350°C, 400°C, 450°C, 500°C or 550°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] The present invention further regulates the calcination temperature to be 350°C-550°C. If the calcination temperature is too low, the sample cannot be fully reduced, or the calcination time needs to be extended, increasing the overall energy consumption. If the calcination temperature is too high, the structure of the sample will be destroyed, affecting the purity and performance of the material.

[0035] Preferably, the heating rate of the calcination is 5°C / min-10°C / min, for example, it can be 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min or 10°C / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] Preferably, the calcination time is 0.5h-4h, for example, 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h or 4h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] As a preferred technical solution of the preparation method of the present invention, the preparation method comprises the following steps:

[0038] The method comprises mixing palladium chloride and hydrochloric acid to obtain a palladium chloride solution with a palladium ion concentration of 0.01-0.1 mol / L; calcining cerium nitrate at 400-500° C. in air for 2 h-10 h, and grinding to obtain CeO2; mixing the palladium chloride solution and CeO2 according to a mass ratio of CeO2 to palladium chloride of 1:(0.04-0.06), drying at 70-90° C. for 12 h-72 h, and grinding to obtain a catalyst precursor; calcining the catalyst precursor at 350-550° C. for 0.5 h-4 h in a reducing atmosphere of argon-hydrogen mixed gas, wherein the hydrogen content is 5 vol%-10 vol%, to obtain the formaldehyde degradation catalyst.

[0039] In a third aspect, the present invention provides a use of the formaldehyde degradation catalyst as described in the first aspect, wherein the formaldehyde degradation catalyst is used to degrade formaldehyde.

[0040] The catalyst provided by the present invention improves the efficiency of the catalyst in degrading formaldehyde at room temperature by making full use of the synergistic enhancement effect between oxygen vacancies and Pd sites. Compared with the traditional catalyst using cerium dioxide as a carrier, the formaldehyde degradation catalyst provided by the present invention can achieve a catalytic efficiency of more than 75% at room temperature, and the degradation rate of HCHO is significantly improved in acidic and alkaline environments.

[0041] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0042] Compared with the prior art, the present invention has at least the following beneficial effects:

[0043] (1) The present invention constructs an oxygen-rich vacancy system CeO 1-x Cl / Pd, oxygen vacancies and Pd sites play important roles in the initial stage and mineralization stage of HCHO degradation, respectively. Studies have shown that the presence of chloride ions is conducive to the dispersion of noble metal active sites, and the substitution of chloride ions for lattice oxygen on CeO2 will convert CeO2 into CeOCl. The role of oxygen vacancies is mainly to enrich HCHO in the surrounding environment, and the electron-rich Pd sites interact with O2 to generate highly active ·O2 - , thereby further oxidizing the HCHO pollutant. The present invention improves the efficiency of the catalyst in degrading formaldehyde at room temperature by making full use of the synergistic enhancement effect between oxygen vacancies and Pd sites.

[0044] (2) The present invention uses an inorganic acid to promote the dissolution of the chlorine-containing palladium salt, and no additional solvent is required during the preparation process, which not only avoids the introduction of impurities, saves preparation raw materials and costs, but also simplifies the preparation process and is more suitable for large-scale production.

[0045] (3) The catalyst provided by the present invention improves the efficiency of formaldehyde degradation at room temperature by fully utilizing the synergistic enhancement effect between oxygen vacancies and Pd sites. Compared with the traditional catalyst using cerium dioxide as the carrier, the formaldehyde degradation catalyst provided by the present invention can achieve a catalytic efficiency of more than 75% at room temperature, and the degradation rate of HCHO is significantly increased in acidic and alkaline environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is the XRD pattern of the formaldehyde degradation catalyst provided in Example 1 of the present invention;

[0047] Figure 2 is the scanning electron microscope image of the formaldehyde degradation catalyst provided in Example 1 of the present invention at a scale of 1 μm;

[0048] Figure 3 is the high-resolution transmission electron microscope image of the formaldehyde degradation catalyst provided in Example 1 of the present invention at a scale of 10 nm;

[0049] Figure 4 is the free radical quenching curve of the formaldehyde degradation catalyst provided in Example 1 of the present invention for catalytic degradation of formaldehyde solution at room temperature;

[0050] Figure 5 is the EPR spectrum of the formaldehyde degradation catalyst provided in Example 1 of the present invention;

[0051] Figure 6 is the DMPO-·O2 of the formaldehyde degradation catalyst provided in Example 1 of the present invention - spin-trapping ESR spectrum. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0052] The technical solution of the present invention will be further described below with reference to the drawings and through specific embodiments. However, the following examples are only simple examples of the present invention and do not represent or limit the scope of the protection of the rights of the present invention. The scope of protection of the present invention is subject to the claims.

[0053] In the following examples, unless otherwise specified, all reagents and consumables are purchased from conventional reagent manufacturers in the art; unless otherwise specified, the experimental methods and technical means used are conventional methods and means in the art.

[0054] Example 1

[0055] This example provides a formaldehyde degradation catalyst, and the formaldehyde degradation catalyst includes a carrier and an active component Pd supported on the carrier; the carrier is CeO 1-x Cl, where 0 < x < 1, and the loading amount of the active component Pd on the carrier is 6 wt%;

[0056] The preparation method of the formaldehyde degradation catalyst provided in this embodiment comprises the following steps:

[0057] The method comprises the following steps: dissolving palladium chloride in hydrochloric acid, adding an appropriate amount of deionized water to obtain a palladium chloride solution with a palladium ion concentration of 0.01 mol / L; calcining CeN3O9·6H2O in air at 450° C. for 4 hours, and grinding the mixture after cooling to obtain CeO2; mixing the palladium chloride solution with CeO2 at a mass ratio of CeO2 to palladium chloride of 1:0.06, drying the mixture at 80° C. for 36 hours, and grinding the mixture to obtain a catalyst precursor; and calcining the catalyst precursor in an argon-hydrogen mixed gas with a hydrogen content of 5 vol% at 400° C. for 1 hour to obtain the formaldehyde degradation catalyst.

[0058] The XRD pattern of the prepared formaldehyde degradation catalyst is as follows: Figure 1 As shown in the figure, the diffraction peaks at 12.9°, 25.4°, 31.0°, 34.2°, 40.9°, 44.4°, 51.8°, 57.2° and 58.5° correspond to the (001), (101), (110), (102), (112), (200), (211), (212) and (104) planes of CeOCl (PDF#81-0791), that is, the obtained catalyst support is CeO 1-x Cl.

[0059] The SEM image of the prepared formaldehyde degradation catalyst at 1 μm scale is shown in Figure 2 As shown in the figure, the catalyst presents a relatively rough surface, which is extremely beneficial for the capture of formaldehyde molecules in the early stage of formaldehyde catalytic degradation, and also provides more space for the loading of Pd.

[0060] The TEM image of the prepared formaldehyde degradation catalyst at 10 nm scale is as follows: Figure 3 As shown. The surface structure of the catalyst described in Example 1 was further observed by HRTEM, and continuous and uniform lattice fringes were clearly observed, indicating that the sample had good crystallinity. The calculated lattice spacing was 0.698 nm, corresponding to the (001) crystal plane of CeOCl.

[0061] The free radical quenching curve of the prepared formaldehyde degradation catalyst for catalytic degradation of formaldehyde solution at room temperature is shown in Figure 4 Benzoquinone (BQ) and isopropyl alcohol (IPA) were used as scavengers to capture O2 - Compared with the case without adding scavenger, the degradation rate of HCHO was only 36.6% after adding BQ to the catalytic system, indicating that ·O2 - It is the main active substance for HCHO degradation. However, IPA has a weak effect on the catalytic degradation of HCHO, indicating that ·OH plays a relatively small role in HCHO degradation.

[0062] The EPR spectrum of the prepared formaldehyde degradation catalyst is as Figure 5 shown. The EPR spectrum detected an obvious oxygen vacancy signal peak in the CeO 1-x Cl / Pd-6 catalyst, which can prove that the prepared sample has a rich oxygen vacancy structure.

[0063] The DMPO-·O2 - spin-trapping ESR spectrum of the prepared formaldehyde degradation catalyst is as Figure 6 shown. The ESR technique was used to determine the active species involved in the formaldehyde degradation process at room temperature. Figure 6 The signal peak of DMPO-·O2 - could be clearly observed, indicating that ·O2 - 确实存在。这可能与CeO 1-x Cl / Pd-6的结构容易产生·O2 - 有关,即O2很容易从样品表面富电子的Pd位点获得e - 生成·O2 - .

[0064] Example 2

[0065] This example provides a formaldehyde degradation catalyst, which includes a carrier and an active component Pd supported on the carrier; the carrier is CeO 1-x Cl, where 0 < x < 1, and the loading amount of the active component Pd on the carrier is 4 wt%;

[0066] The preparation method of the formaldehyde degradation catalyst provided in this example includes the following steps:

[0067] Dissolve palladium chloride in hydrochloric acid, add an appropriate amount of deionized water to obtain a palladium chloride solution with a palladium ion concentration of 0.01 mol / L; calcine CeN3O9·6H2O in air at 400 °C for 6 h, cool and then grind to obtain CeO2; mix the palladium chloride solution and CeO2 according to the mass ratio of CeO2 to palladium chloride of 1:0.04, dry at 70 °C for 72 h, and grind to obtain a catalyst precursor; calcine the catalyst precursor in an argon-hydrogen mixture with a hydrogen content of 5 vol% at 350 °C for 2 h to obtain the formaldehyde degradation catalyst.

[0068] Example 3

[0069] This example provides a formaldehyde degradation catalyst, which includes a carrier and an active component Pd supported on the carrier; the carrier is CeO 1-x Cl, where 0 < x < 1, and the loading amount of the active component Pd on the carrier is 5 wt%;

[0070] The preparation method of the formaldehyde degradation catalyst provided in this embodiment comprises the following steps:

[0071] The method comprises the following steps: dissolving palladium chloride in hydrochloric acid, adding an appropriate amount of deionized water to obtain a palladium chloride solution with a palladium ion concentration of 0.01 mol / L; calcining CeN3O9·6H2O in air at 500°C for 2h, grinding the mixture after cooling to obtain CeO2; mixing the palladium chloride solution with CeO2 at a mass ratio of CeO2 to palladium chloride of 1:0.05, drying the mixture at 90°C for 36h, and grinding the mixture to obtain a catalyst precursor; calcining the catalyst precursor in an argon-hydrogen mixed gas with a hydrogen content of 5 vol% at 500°C for 0.5h to obtain the formaldehyde degradation catalyst.

[0072] Example 4

[0073] This embodiment provides a formaldehyde degradation catalyst, which is different from Embodiment 1 only in that, when preparing the formaldehyde degradation catalyst, the mass ratio of CeO2 to palladium chloride is 1:0.01.

[0074] Example 5

[0075] This embodiment provides a formaldehyde degradation catalyst, which is different from Embodiment 1 only in that the calcination temperature is 300° C. when preparing the formaldehyde degradation catalyst.

[0076] Comparative Example 1

[0077] This comparative example provides a CeO2 catalyst, which is different from Example 1 only in that no palladium chloride solution is added when preparing the formaldehyde degradation catalyst, that is, no palladium is loaded.

[0078] Comparative Example 2

[0079] This comparative example provides a CeO2 / Pd catalyst, which is different from Example 1 only in that, when preparing the formaldehyde degradation catalyst, the mass ratio of CeO2 to palladium chloride is 1:0.002.

[0080] Test method:

[0081] Catalyst described in the foregoing description and comparative example is carried out the performance test of room temperature catalytic degradation formaldehyde solution, and testing procedure is as follows: in quartz reaction tube, add 50mL formaldehyde solution (10mg / L), then add 50mg catalyst in the above-mentioned solution.In formaldehyde degradation process, respectively at 0,5,10,20,30,60,90,120,150min, absorb suspension 2ml, remove the catalyst in the suspension with 0.22 micron Millipore filter.By UV-Vis spectrophotometer, record the absorbance at maximum absorption wavelength (411nm), and by formaldehyde standard curve, convert it to HCHO concentration, and calculate its degradation rate, the result is as shown in table 1.

[0082] Table 1

[0083]

[0084]

[0085] The test results show that:

[0086] (1) It can be seen from Examples 1-3 that the present invention constructs an oxygen-rich vacancy system CeO 1-x Cl / Pd, oxygen vacancies and Pd sites play important roles in the initial stage and mineralization stage of HCHO degradation, respectively. Studies have shown that the presence of chloride ions is conducive to the dispersion of noble metal active sites, and the substitution of chloride ions for lattice oxygen on CeO2 will convert CeO2 into CeOCl. The role of oxygen vacancies is mainly to enrich HCHO in the surrounding environment, and the electron-rich Pd sites interact with O2 to generate highly active ·O2 - , thereby further oxidizing the HCHO pollutant. The present invention improves the efficiency of the catalyst in degrading formaldehyde at room temperature by making full use of the synergistic enhancement effect between oxygen vacancies and Pd sites.

[0087] (2) By comparing Example 1 with Example 4, it can be seen that the present invention further controls the mass ratio of CeO2 to the chlorine-containing palladium salt to 1:(0.04-0.06) to regulate the content of the active component palladium in the carrier and ensure that the palladium ions can be completely loaded on the catalyst carrier and evenly distributed.

[0088] (3) By comparing Example 1 with Example 5, it can be seen that the present invention further adjusts the calcination temperature to 350°C-550°C. If the calcination temperature is too low, the sample cannot be fully reduced, or the calcination time needs to be extended, increasing the overall energy consumption. If the calcination temperature is too high, the structure of the sample will be destroyed, affecting the purity and performance of the material.

[0089] (4) It can be seen from Example 1 and Comparative Example 1 that when no palladium is loaded, only a small amount of oxygen vacancies can be generated after CeO2 is simply calcined in an argon-hydrogen atmosphere, and the efficiency of formaldehyde degradation at room temperature is significantly reduced. The present invention utilizes the synergistic enhancement effect between oxygen vacancies and active sites to improve the efficiency of formaldehyde degradation.

[0090] (5) It can be seen from Example 1 and Comparative Example 2 that when the conventional method is used to prepare the CeO2 / Pd catalyst, the oxygen vacancy content in the catalyst is less than that of the CeO2 / Pd catalyst of the present invention. 1-x Cl / Pd, its catalytic efficiency is significantly reduced.

[0091] In summary, the present invention constructs an oxygen-rich vacancy system CeO 1-xCl / Pd, oxygen vacancies and Pd sites play important roles in the initial stage and mineralization stage of HCHO degradation, respectively. Studies have shown that the presence of chloride ions is conducive to the dispersion of noble metal active sites, and the substitution of chloride ions for lattice oxygen on CeO2 will convert CeO2 into CeOCl. The role of oxygen vacancies is mainly to enrich HCHO in the surrounding environment, and the electron-rich Pd sites interact with O2 to generate highly active ·O2 - , thereby further oxidizing the HCHO pollutant. The present invention improves the efficiency of the catalyst in degrading formaldehyde at room temperature by making full use of the synergistic enhancement effect between oxygen vacancies and Pd sites.

[0092] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A formaldehyde degradation catalyst, characterized in that: The formaldehyde degradation catalyst comprises a carrier and an active component Pd loaded on the carrier; the carrier is CeO 1-x Cl, where 0 <x<1。 2. The formaldehyde degradation catalyst according to claim 1, characterized in that The loading amount of the active component Pd on the carrier is 4.0 wt%-6.0 wt%.

3. A method for preparing a formaldehyde degradation catalyst as claimed in claim 1 or 2, characterized in that: The preparation method comprises the following steps: The chlorine-containing palladium salt is mixed with an inorganic acid to obtain a chlorine-containing palladium salt solution; the chlorine-containing palladium salt solution is mixed with CeO2, and a catalyst precursor is obtained through drying and grinding; and the catalyst precursor is calcined under a reducing atmosphere to obtain the formaldehyde degradation catalyst.

4. The preparation method according to claim 3, characterized in that: The chlorine-containing palladium salt includes palladium chloride or ammonium chloropalladate, preferably palladium chloride; Preferably, the inorganic acid comprises any one or a combination of at least two of hydrochloric acid, acetic acid, nitric acid or carbonic acid, preferably hydrochloric acid; Preferably, the concentration of palladium ions in the chlorine-containing palladium salt solution is 0.01-0.1 mol / L.

5. The preparation method according to claim 3 or 4, characterized in that: The preparation method of CeO2 comprises: roasting and grinding cerium salt in air to obtain CeO2; Preferably, the cerium salt comprises any one of cerium nitrate, cerium carbonate, cerium sulfate or cerium acetate, or a combination of at least two thereof, preferably cerium nitrate; Preferably, the calcination temperature is 400°C-500°C; Preferably, the heating rate of the calcination is 5°C / min-10°C / min; Preferably, the calcination time is 2h-10h.

6. The preparation method according to any one of claims 3 to 5, characterized in that: The mass ratio of CeO2 to chlorine-containing palladium salt is 1:(0.04-0.06); Preferably, the drying temperature is 70°C-90°C; Preferably, the drying time is 12h-72h.

7. The preparation method according to any one of claims 3 to 6, characterized in that: The reducing atmosphere comprises an argon-hydrogen mixed gas, wherein the content of hydrogen is 5 vol%-10 vol%.

8. The preparation method according to any one of claims 3 to 7, characterized in that: The calcination temperature is 350°C-550°C; Preferably, the heating rate of the calcination is 5°C / min-10°C / min; Preferably, the calcination time is 0.5h-4h.

9. The preparation method according to any one of claims 3 to 8, characterized in that: The preparation method comprises the following steps: The method comprises mixing palladium chloride and hydrochloric acid to obtain a palladium chloride solution with a palladium ion concentration of 0.01-0.1 mol / L; calcining cerium nitrate at 400-500° C. in air for 2 h-10 h, and grinding to obtain CeO2; mixing the palladium chloride solution and CeO2 according to a mass ratio of CeO2 to palladium chloride of 1:(0.04-0.06), drying at 70-90° C. for 12 h-72 h, and grinding to obtain a catalyst precursor; calcining the catalyst precursor at 350-550° C. for 0.5 h-4 h in a reducing atmosphere of argon-hydrogen mixed gas, wherein the hydrogen content is 5 vol%-10 vol%, to obtain the formaldehyde degradation catalyst.

10. A use of the formaldehyde degradation catalyst as claimed in claim 1 or 2, characterized in that: The formaldehyde degradation catalyst is used for degrading formaldehyde.

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