Titanium-rich vacancy titania supported catalyst, its preparation method and application

Abstract

This invention provides a titanium dioxide supported catalyst with titanium vacancies, its preparation method, and its application. The preparation method includes the following steps: (1) mixing titanium dioxide raw material with a fluorine-containing etchant and performing etching treatment; separating the resulting mixture into solid and liquid components; and heat-treating the resulting solid to obtain a titanium dioxide support rich in titanium vacancies; (2) mixing an active metal precursor solution with the titanium dioxide support to load the active component; and activating the solid obtained after solid-liquid separation to obtain a titanium dioxide supported catalyst. This invention provides a simple, low-cost, and easily scalable HF etching method for preparing anatase supports rich in titanium vacancies, thereby obtaining a Pd-based catalyst that possesses ultra-high room temperature formaldehyde oxidation activity requiring only room temperature treatment.

Description

Technical Field

[0001] This invention relates to the field of formaldehyde purification technology, and in particular to a titanium dioxide supported catalyst with titanium vacancy-rich sites, its preparation method, and its application. Background Technology

[0002] Indoor formaldehyde pollution seriously endangers human health and has become one of the most concerning hidden killers in modern residential environments. Formaldehyde, a common indoor volatile organic compound, is mainly released slowly from engineered wood products, adhesives, paints, and various decoration materials, with a release period of 3 to 15 years. The World Health Organization has classified it as a Group 1 carcinogen. Long-term exposure to low concentrations of formaldehyde can continuously irritate the respiratory, immune, and nervous systems, causing discomfort in the eyes, nose, and throat, chronic respiratory diseases, weakened immunity, and even increasing the risk of leukemia and nasopharyngeal carcinoma. The cumulative toxic effects of formaldehyde are particularly pronounced for sensitive groups such as children, the elderly, and pregnant women. With the increasing airtightness of modern buildings and the widespread adoption of new decoration styles, indoor formaldehyde pollution is becoming increasingly prominent.

[0003] Developing efficient and low-energy-consumption room-temperature catalytic purification technologies is a current research hotspot and challenge. While catalytic systems based on noble metals (such as Pt and Pd) supported on titanium dioxide (TiO2) show promise, the surface of unmodified commercial TiO2 supports is relatively inert, resulting in weak interactions with noble metals and low catalyst activity. To improve performance, existing technologies mainly rely on creating defects (such as oxygen vacancies) on the support to activate TiO2. The mainstream methods include wet chemical etching, high-temperature reducing gas treatment, and hydrothermal / solvothermal methods. However, these methods all have significant limitations: wet chemical etching is difficult to control precisely, easily causing support structural collapse and potentially introducing impurity ions that poison active sites; high-temperature reducing treatment is complex, energy-intensive, and involves flammable and explosive gases, posing significant safety risks; hydrothermal / solvothermal methods are complex, time-consuming, and costly. Furthermore, these methods have inherent defects in terms of process, safety, or cost, and the types of defects they generate have limited impact on performance improvement. More importantly, even if a defective TiO2 support is prepared using the above method, the supported noble metal catalyst usually still needs to undergo high-temperature reduction treatment above 300°C to obtain considerable room-temperature formaldehyde catalytic activity, which further increases the energy consumption and process complexity of the overall process.

[0004] Addressing the key pain points of existing technologies, such as complex processes, high energy consumption and costs, and reliance on high-temperature post-treatment, it is of great significance to provide a simple, low-cost, and easily scalable process for the catalytic purification of formaldehyde using catalysts. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention provides an HF etching method that is simple, low-cost and easy to scale up, thereby obtaining a Pd-based catalyst that has ultra-high room temperature formaldehyde oxidation activity with only room temperature reduction treatment.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing a titanium dioxide-supported catalyst rich in titanium vacancies, the method comprising the following steps:

[0008] (1) Mix titanium dioxide raw material with fluorine-containing etchant and perform etching treatment. Separate the resulting mixture into solid and liquid components and heat treat the resulting solid to obtain titanium dioxide carrier rich in titanium vacancies.

[0009] (2) The active component is loaded onto the mixed active metal precursor solution and the titanium dioxide support. The solid obtained after solid-liquid separation is activated to obtain the titanium dioxide supported catalyst.

[0010] This invention employs a fluorine-containing etchant for a simple, controllable, and reproducible etching process on titanium dioxide raw materials. Utilizing the selective attack of fluoride ions on titanium sites in the titanium dioxide lattice, stable and water-soluble fluorine-titanium complexes are formed. This allows for a one-step in-situ construction of a TiO2 support rich in highly active titanium vacancies without disrupting the overall crystal structure of the matrix. Compared to oxygen vacancies introduced by traditional high-temperature reduction and atmosphere treatment methods, the titanium vacancies constructed in this invention offer significant advantages: they can more precisely and efficiently control the band structure and electron distribution of TiO2, inducing the formation of local electric fields and charge polarization centers, thus providing an excellent interfacial microenvironment for the anchoring, dispersion, and activation of noble metal active components. Based on this, supported noble metal catalysts are prepared using this TiO2 support. Because titanium vacancies significantly enhance the adsorption strength and capacity of reactant molecules, optimize the adsorption configuration of reactants, effectively promote interfacial electron transfer and the transformation of intermediate species in the catalytic reaction, ultimately achieving a significant improvement in catalyst performance.

[0011] As a preferred embodiment of the present invention, the fluorine-containing etching agent comprises an aqueous solution of hydrofluoric acid.

[0012] Preferably, the mass concentration of the hydrofluoric acid aqueous solution is 4.8%-9.7%, for example, it can be 4.8%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5% or 9.7%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0013] This invention controls the mass concentration of the hydrofluoric acid aqueous solution within the aforementioned range, enabling the controllable introduction of titanium vacancies. By precisely controlling the concentration, titanium atoms can be selectively removed without damaging the overall framework, leaving abundant cation vacancies. If the concentration is too high, fluoride ions rapidly attack and dissolve a large amount of titanium dioxide, causing severe damage to the material structure or even complete dissolution, resulting in a significant loss of precursors and a substantial reduction in process economy and raw material utilization. If the concentration is too low, the fluoride ion concentration is insufficient to effectively destroy the stable passivation film on the titanium dioxide surface, resulting in a weak etching reaction that essentially remains at the surface cleaning stage, failing to effectively introduce titanium vacancies.

[0014] Preferably, the titanium dioxide raw material includes any one or a combination of at least two of anatase phase titanium dioxide, rutile phase titanium dioxide, or brookite phase titanium dioxide.

[0015] Preferably, the solid-liquid ratio of the titanium dioxide raw material to the fluorine-containing etchant is 1:(12-20) g / mL, for example, it can be 1:12 g / mL, 1:13 g / mL, 1:14 g / mL, 1:15 g / mL, 1:16 g / mL, 1:17 g / mL, 1:18 g / mL, 1:19 g / mL or 1:20 g / mL, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0016] As a preferred technical solution of the present invention, the etching process includes: mixing titanium dioxide raw material with fluorine-containing etching agent and stirring, and after stirring, allowing it to stand, centrifuging, washing and drying in sequence.

[0017] Preferably, the stirring time is 25-35 min, for example, it can be 25 min, 26 min, 27 min, 28 min, 29 min, 30 min, 31 min, 32 min, 33 min, 34 min or 35 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] This invention controls the stirring time during the etching process within the aforementioned range, allowing sufficient time for fluoride ions to diffuse and dissolve the lattice layer by layer. While maintaining the framework, it selectively removes titanium atoms, forming cation vacancies of the target concentration. If the etching time is too short, the etchant fails to reach the subsurface lattice, and a large number of titanium atoms are not removed, resulting in too few titanium dioxide vacancies. If the time is too long, it can easily lead to the collapse of the material structure, loss of the significance of vacancies, and excessive reaction causing fluoride ions to indiscriminately dissolve a large amount of titanium dioxide, resulting in the collapse of the nanostructure, excessive fragmentation of particles, or even complete dissolution.

[0019] Preferably, the stirring temperature is 20-30℃, for example, it can be 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃ or 30℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] Preferably, the settling time is 5-15 minutes, for example, it can be 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes or 15 minutes, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] As a preferred technical solution of the present invention, the Ti / O ratio of the titanium dioxide support rich in titanium vacancies is (0.33-0.41):1, for example, it can be 0.33:1, 0.34:1, 0.35:1, 0.36:1, 0.37:1, 0.38:1, 0.39:1, 0.40:1 or 0.41:1, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] Preferably, the specific surface area of ​​the titanium dioxide support rich in titanium vacancies is 47-60 m². 2 / g, for example, could be 47 m 2 / g、48 m 2 / g、49 m 2 / g、50 m 2 / g、51 m 2 / g、52 m 2 / g、53 m 2 / g、54 m 2 / g、55 m 2 / g、56 m 2 / g、57 m 2 / g、58 m 2 / g、59 m 2 / g or 60 m 2 / g, etc., but not limited to the listed values, other unlisted values ​​within the range also apply.

[0023] Preferably, the electron paramagnetic resonance spectrum of the titanium dioxide support rich in titanium vacancies has a characteristic peak in the range of g value 2.015-2.016.

[0024] As a preferred technical solution of the present invention, the temperature of the heat treatment is 420-480℃, for example, it can be 420℃, 430℃, 440℃, 450℃, 460℃, 470℃ or 480℃, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0025] Preferably, the heat treatment time is 40-80 min, for example, it can be 40 min, 45 min, 50 min, 55 min, 60 min, 65 min, 70 min, 75 min or 80 min, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] As a preferred embodiment of the present invention, the active metal in the active metal precursor solution includes palladium.

[0027] Preferably, the active metal precursor includes any one or a combination of at least two of palladium nitrate, palladium acetate, or palladium chloride.

[0028] Preferably, the concentration of the active metal in the active metal precursor solution is 0.36-0.44 g / L, for example, it can be 0.36 g / L, 0.37 g / L, 0.38 g / L, 0.39 g / L, 0.40 g / L, 0.41 g / L, 0.42 g / L, 0.43 g / L or 0.44 g / L, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] Preferably, the solid-liquid ratio of the titanium dioxide carrier to the active metal precursor solution is 1:(25-35) g / L, for example, it can be 1:25 g / L, 1:26 g / L, 1:27 g / L, 1:28 g / L, 1:29 g / L, 1:30 g / L, 1:31 g / L, 1:32 g / L, 1:33 g / L, 1:34 g / L or 1:35 g / L, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] As a preferred embodiment of the present invention, the active metal precursor solution is mixed with the titanium dioxide support and then stirred.

[0031] Preferably, the stirring temperature is 20-30℃, such as 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃, or 30℃, but not limited to the listed values; other unlisted values ​​within the range are also applicable. Preferably, the stirring speed is 450-550 r / min, such as 450 r / min, 460 r / min, 470 r / min, 480 r / min, 490 r / min, 500 r / min, 510 r / min, 520 r / min, 530 r / min, 540 r / min, or 550 r / min, but not limited to the listed values; other unlisted values ​​within the range are also applicable.

[0032] Preferably, the stirring time is 0.5-1.5 h, for example, it can be 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1.0 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h or 1.5 h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] As a preferred embodiment of the present invention, the gas atmosphere for the activation treatment includes hydrogen and nitrogen.

[0034] Preferably, the volume ratio of hydrogen to nitrogen is 1:(3-5), for example, it can be 1:3, 1:3.5, 1:4, 1:4.5 or 1:5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the gas flow rate for the activation treatment is 90-110 mL / min, for example, it can be 90 mL / min, 94 mL / min, 98 mL / min, 102 mL / min, 106 mL / min or 110 mL / min, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0036] In a second aspect, the present invention provides a titanium-rich vacancy titanium dioxide supported catalyst, which is prepared by the preparation method described in the first aspect.

[0037] Preferably, the specific surface area of ​​the titanium dioxide-supported catalyst with titanium vacancy sites is 45.5-53 m². 2 / g, for example, could be 45.5 m 2 / g、46 m 2 / g、47 m 2 / g、48 m 2 / g、49 m2 / g、50 m 2 / g、51 m 2 / g、52 m 2 / g or 53 m 2 / g, etc., but not limited to the listed values, other unlisted values ​​within the range also apply.

[0038] Preferably, the particle size of the active metal in the titanium dioxide supported catalyst with titanium vacancy is 3.6-6.8 nm, for example, it can be 3.6 nm, 4.6 nm, 5.6 nm, 6.6 nm or 6.8 nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] Thirdly, the present invention provides an application of the titanium-rich vacancy titanium dioxide supported catalyst as described in the second aspect, wherein the titanium-rich vacancy titanium dioxide supported catalyst is used to purify formaldehyde.

[0040] The titanium dioxide supported catalyst with titanium vacancy prepared in this invention can achieve complete catalytic oxidation of formaldehyde at room temperature by only reducing it at room temperature (25°C). This effectively fills the technical gap in the existing technology where it is difficult to achieve efficient catalytic purification of formaldehyde under mild room temperature reduction conditions, and provides a brand-new catalytic system and technical route for efficient removal of formaldehyde at room temperature.

[0041] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0042] (1) The preparation method of titanium dioxide supported catalyst with titanium vacancy provided by the present invention is simple and has significant cost advantages. Compared with the hydrothermal method, it eliminates the need for high pressure reactor and long-term high temperature process. The prepared catalyst does not require any high temperature reduction pretreatment, which greatly simplifies the process, shortens the cycle, and reduces equipment and energy costs, and has excellent prospects for large-scale production.

[0043] (2) The titanium dioxide supported catalyst with titanium vacancy provided by the present invention can more effectively modulate the band structure and electronic state of titanium dioxide than the oxygen vacancy generated by traditional methods, forming a stronger local electric field, thereby providing a better microenvironment for anchoring and activating noble metals. The formaldehyde conversion rate of 100% at room temperature can be achieved by reduction and activation at 25°C. Detailed Implementation

[0044] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0045] It should be clarified that any use of the process provided in the embodiments of the present invention or any substitution or change of conventional data falls within the protection and disclosure scope of the present invention.

[0046] Example 1

[0047] This embodiment provides a method for preparing a titanium dioxide-supported catalyst rich in titanium vacancies, the preparation method comprising the following steps:

[0048] (1) 10 mL of 48% hydrofluoric acid aqueous solution was added to 40 mL of deionized water to prepare a 9.6% hydrofluoric acid aqueous solution. The anatase phase titanium dioxide raw material was mixed with the 9.6% hydrofluoric acid aqueous solution, and the solid-liquid ratio of the titanium dioxide raw material to the hydrofluoric acid aqueous solution was 1:17 g / mL. The mixture was etched under stirring for 30 min at 25°C. After stirring, it was allowed to stand for 10 min, then centrifuged three times at 8000 r / min for 10 min each time, washed, and dried. The resulting solid was calcined at 450°C for 60 min to obtain a titanium dioxide support rich in titanium vacancies (specific surface area of ​​51.5 m²). 2 / g, Ti / O ratio is 0.33);

[0049] (2) A palladium nitrate aqueous solution and the titanium dioxide support were mixed at a solid-liquid ratio of 1:30 g / L. The concentration of palladium nitrate in the aqueous solution was 0.41 g / L. After mixing, the mixture was stirred at 25°C, 500 r / min, and for 1 h. The resulting mixture was then subjected to vacuum rotary evaporation for 30 min and activation treatment. The activation treatment was performed in a hydrogen and nitrogen atmosphere with a hydrogen to nitrogen volume ratio of 1:4 and a gas flow rate of 100 mL / min, resulting in a titanium dioxide supported catalyst (specific surface area of ​​46.9 m²). 2 / g, the active metal particle size is 6.8 nm), the catalyst is designated as Pd / TiO2-10%.

[0050] The formaldehyde removal rate of the catalyst Pd / TiO2-10% provided in this embodiment is shown in Table 1. The reaction conditions were: 25℃, HCHO concentration 120 ppm, relative humidity 35%, O2 volume fraction 20%, He as balance gas, and WHSV 300,000 mL (g) cat ·h) -1 .

[0051] Example 2

[0052] This embodiment provides a method for preparing a titanium dioxide-supported catalyst rich in titanium vacancies, the preparation method comprising the following steps:

[0053] (1) 7.5 mL of 48% hydrofluoric acid aqueous solution was added to 42.5 mL of deionized water to prepare a 7.2% hydrofluoric acid aqueous solution. The titanium dioxide raw material of the brookite phase was mixed with the 7.2% hydrofluoric acid aqueous solution, with a solid-liquid ratio of 1:20 g / mL. Etching was performed under stirring for 25 min at 30°C. After stirring, the mixture was allowed to stand for 20 min, then centrifuged three times at 8000 r / min for 10 min each time. The mixture was then washed and dried. The resulting solid was calcined at 480°C for 40 min to obtain a titanium dioxide support rich in titanium vacancies (specific surface area of ​​49.3 m²). 2 / g, Ti / O ratio is 0.41).

[0054] (2) A palladium chloride aqueous solution and the titanium dioxide support were mixed at a solid-liquid ratio of 1:35 g / L. The concentration of palladium nitrate in the palladium nitrate aqueous solution was 0.44 g / L. After mixing, the mixture was stirred at a temperature of 20°C, a rotation speed of 550 r / min, and a time of 1.5 h. The resulting mixture was then subjected to vacuum rotary evaporation for 30 min and activation treatment. The activation treatment was performed in a hydrogen and nitrogen atmosphere with a hydrogen to nitrogen volume ratio of 1:5 and a gas flow rate of 110 mL / min, resulting in a titanium dioxide supported catalyst (specific surface area of ​​48.2 m²). 2 / g, the particle size of the active metal is 3.9 nm), the catalyst is designated as Pd / TiO2-7.5%-brookite.

[0055] The formaldehyde removal rate of the Pd / TiO2-7.5% catalyst provided in this embodiment is shown in Table 1. The reaction conditions were: 25℃, HCHO concentration 120 ppm, relative humidity 35%, O2 volume fraction 20%, He as balance gas, and WHSV 300,000 mL (g) cat ·h) -1 .

[0056] Example 3

[0057] This embodiment provides a method for preparing a titanium dioxide-supported catalyst rich in titanium vacancies, the preparation method comprising the following steps:

[0058] (1) Add 5 mL of 48% hydrofluoric acid aqueous solution to 45 mL of deionized water to prepare a 4.8% hydrofluoric acid aqueous solution. Mix the rutile phase titanium dioxide raw material with the 4.8% hydrofluoric acid aqueous solution. The solid-liquid ratio of the titanium dioxide raw material to the hydrofluoric acid aqueous solution is 1:12 g / mL. Etch the mixture under stirring for 35 min at 20°C. After stirring, let it stand for 15 min, then centrifuge three times at 8000 r / min for 10 min each time. Wash and dry the solid. Calcinate the resulting solid at 420°C for 80 min to obtain a titanium dioxide support rich in titanium vacancies (specific surface area of ​​47.7 m²). 2 / g, Ti / O ratio is 0.37);

[0059] (2) A palladium acetate aqueous solution and the titanium dioxide support were mixed at a solid-liquid ratio of 1:25 g / L. The concentration of palladium nitrate in the palladium nitrate aqueous solution was 0.36 g / L. After mixing, the mixture was stirred at a temperature of 30°C, a rotation speed of 450 r / min, and a time of 0.5 h. The resulting mixture was then subjected to vacuum rotary evaporation for 30 min and activation treatment. The activation treatment was performed in a hydrogen and nitrogen atmosphere with a hydrogen to nitrogen volume ratio of 1:3 and a gas flow rate of 90 mL / min, resulting in a titanium dioxide supported catalyst (specific surface area of ​​45.5 m²). 2 / g, the active metal particle size is 4.2 nm), the catalyst is designated as Pd / TiO2-5%-rutile.

[0060] The formaldehyde removal rate of the Pd / TiO2-5% catalyst provided in this embodiment is shown in Table 1. The reaction conditions were: 25℃, HCHO concentration 120 ppm, relative humidity 35%, O2 volume fraction 20%, He as balance gas, and WHSV 300,000 mL (g) cat ·h) -1 .

[0061] Example 4

[0062] This embodiment provides a method for preparing a titanium dioxide supported catalyst with titanium vacancy. The only difference between this method and Example 1 is that 2 mL of a 48% hydrofluoric acid aqueous solution is added to 48 mL of deionized water to prepare a 4.8% hydrofluoric acid aqueous solution. Then, the titanium dioxide raw material is etched using the 4.8% hydrofluoric acid aqueous solution. All other steps are the same as in Example 1.

[0063] Example 5

[0064] This embodiment provides a method for preparing a titanium dioxide supported catalyst with titanium vacancy. The only difference between this method and Example 1 is that 15 mL of a 48% hydrofluoric acid aqueous solution is added to 35 mL of deionized water to prepare a 14% hydrofluoric acid aqueous solution. Then, the titanium dioxide raw material is etched using the 14% hydrofluoric acid aqueous solution. All other aspects are the same as in Example 1.

[0065] Example 6

[0066] This embodiment provides a method for preparing a titanium dioxide supported catalyst with titanium vacancies. The only difference between this method and Example 1 is that the etching and stirring time is changed to 20 min, while the rest is the same as in Example 1.

[0067] Example 7

[0068] This embodiment provides a method for preparing a titanium dioxide supported catalyst with titanium vacancy. The only difference between this method and Example 1 is that the etching and stirring time is changed to 40 min, while the rest is the same as in Example 1.

[0069] Comparative Example 1

[0070] This comparative example provides a method for preparing a titanium dioxide supported catalyst with titanium vacancies. The only difference between this method and Example 1 is that the titanium dioxide raw material is not subjected to hydrofluoric acid etching treatment and is directly used as a support to prepare the catalyst. The resulting catalyst is denoted as Pd / TiO2-0%-anatase. All other aspects are the same as in Example 1.

[0071] The formaldehyde removal rates of the Pd / TiO2-0% catalyst provided in this comparative example are shown in Table 1. The reaction conditions were: 25℃, HCHO concentration 120 ppm, relative humidity 35%, O2 volume fraction 20%, He as the equilibrium gas, and WHSV 300,000 mL (g) cat ·h) -1 .

[0072] Comparative Example 2

[0073] This comparative example provides a method for preparing an oxygen-vacancy-enriched titanium dioxide supported catalyst. The only difference between this method and Example 1 is that the titanium dioxide raw material is not subjected to hydrofluoric acid etching treatment, but is instead reduced with hydrogen at 600°C to introduce oxygen vacancies on the support surface. Then, palladium is supported on this material, and the resulting catalyst is denoted as Pd / TiO2-600H2. All other aspects are the same as in Example 1.

[0074] The formaldehyde removal rates of the Pd / TiO2-0% catalyst provided in this comparative example are shown in Table 1. The reaction conditions were: 25℃, HCHO concentration 120 ppm, relative humidity 35%, O2 volume fraction 20%, He as the equilibrium gas, and WHSV 300,000 mL (g) cat ·h) -1 .

[0075] Performance testing

[0076] The formaldehyde adsorption performance of the catalysts provided in the examples and comparative examples was tested under the following conditions: 25°C, HCHO concentration 120 ppm, relative humidity 35%, O2 volume fraction 20%, He as equilibrium gas, and WHSV 300,000 mL (g) cat ·h) -1 The results are shown in Table 1.

[0077] The formula for calculating the HCHO conversion rate is:

[0078]

[0079] Wherein, [HCHO]in and [HCHO]out represent the HCHO concentrations (ppm) at the inlet and outlet, respectively.

[0080]

[0081] As shown in Table 1, the titanium dioxide supported catalyst with titanium vacancy provided by this invention does not require any high-temperature reduction pretreatment. After loading, the Pd precursor can be converted into highly dispersed, electron-rich, and highly active Pd species through mild chemical reduction at room temperature, exhibiting excellent room-temperature catalytic performance. The final catalyst shows a preferred conversion rate of 99.9% for formaldehyde at room temperature (25 °C), solving the industry problems of "low activity" and "requiring high-temperature activation" in room-temperature catalysis.

[0082] A comprehensive comparison of Examples 1 and 4-7 shows that the etchant concentration mainly determines the driving force and selectivity of the etching reaction. If the etchant concentration is too high, fluoride ions will violently attack and dissolve a large amount of titanium dioxide, causing severe collapse of the support framework and a large loss of precursors. At the same time, Ti vacancies cannot be effectively formed because Ti and O are indiscriminately etched. If the etchant concentration is too low, the surface passivation film cannot be destroyed due to insufficient fluoride ions, and the etching reaction is weak and only stays at the surface cleaning stage, failing to introduce Ti vacancies. The etching time mainly affects the etching depth and structural integrity. If the etching time is too long, the etching will penetrate into the bulk phase and cause framework collapse. Similarly, due to excessive etching, it is difficult to selectively generate Ti vacancies. If the etching time is too short, the etching only acts on the surface layer and the reaction is insufficient, which also fails to effectively construct Ti vacancies in the lattice. Both of these parameters deviating from the optimal range are not conducive to the effective construction of active sites of Pd / TiO2 catalyst and the improvement of formaldehyde oxidation performance. Principle: The introduction of Ti vacancies significantly enhances the anchoring effect on the supported metal, primarily due to the hybridization between the d orbitals of the supported metal and the 2p orbitals of the O atom at the Ti vacancy, which is a relatively strong effect. In contrast, the anchoring of the supported metal by oxygen vacancies is mainly through the hybridization between the d orbitals of the Ti atom at the oxygen vacancy and the d orbitals of the supported metal, which is relatively weak. Therefore, compared to catalysts with or without oxygen vacancies, Pd / Ti catalysts with Ti vacancies exhibit excellent formaldehyde oxidation activity even at 25°C.

[0083] A comprehensive comparison of Example 1 and Comparative Examples 1-2 shows that constructing oxygen vacancies and Ti vacancies on the TiO2 support can effectively improve the formaldehyde oxidation catalytic performance of the Pd / TiO2 catalyst, with the introduction of Ti vacancies having a more significant effect on improving catalytic activity.

[0084] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for producing a titanium-rich vacancy titania supported catalyst, characterized by, The preparation method includes the following steps: (1) Mix titanium dioxide raw material with fluorine-containing etchant and perform etching treatment. Separate the resulting mixture into solid and liquid components and heat treat the resulting solid to obtain titanium dioxide carrier rich in titanium vacancies. (2) The active component is loaded onto the mixed active metal precursor solution and the titanium dioxide support. The solid obtained after solid-liquid separation is activated to obtain the titanium dioxide supported catalyst.

2. The production method according to claim 1, characterized by, The fluorine-containing etching agent includes an aqueous solution of hydrofluoric acid; Preferably, the mass concentration of the hydrofluoric acid aqueous solution is 4.8%-9.7%; Preferably, the titanium dioxide raw material includes any one or a combination of at least two of anatase phase titanium dioxide, rutile phase titanium dioxide, or brookite phase titanium dioxide; Preferably, the solid-liquid ratio of the titanium dioxide raw material to the fluorine-containing etchant is 1:(12-20)g / mL.

3. The production method according to claim 1 or 2, characterized by, The etching process includes: mixing titanium dioxide raw material with a fluorine-containing etching agent and stirring, and then allowing it to stand, washing and drying in sequence after stirring. Preferably, the stirring time is 25-35 min; Preferably, the stirring temperature is 20-30℃; Preferably, the settling time is 5-15 minutes.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The Ti / O ratio of the titanium dioxide support rich in titanium vacancies is (0.33-0.41):1; Preferably, the specific surface area of the titanium dioxide support enriched in titanium vacancies is between 47 and 60 m 2 / g; Preferably, the electron paramagnetic resonance spectrum of the titanium dioxide support rich in titanium vacancies has a characteristic peak in the range of g value 2.015-2.

016.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The heat treatment temperature is 420-480℃; Preferably, the heat treatment time is 40-80 min.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The active metal in the active metal precursor solution includes palladium; Preferably, the active metal precursor includes any one or a combination of at least two of palladium nitrate, palladium acetate, or palladium chloride; Preferably, the concentration of the active metal in the active metal precursor solution is 0.36-0.44 g / L; Preferably, the solid-liquid ratio of the titanium dioxide carrier to the active metal precursor solution is 1:(25-35)g / L.

7. The preparation method according to any one of claims 1 to 6, characterized in that, The active metal precursor solution is mixed with the titanium dioxide support and then stirred. Preferably, the stirring temperature is 20-30℃; Preferably, the stirring speed is 450-550 r / min; Preferably, the stirring time is 0.5-1.5 h.

8. The preparation method according to any one of claims 1 to 7, characterized in that, The gas atmosphere for the activation treatment includes hydrogen and nitrogen; Preferably, the volume ratio of hydrogen to nitrogen is 1:(3-5); Preferably, the gas flow rate for the activation treatment is 90-110 mL / min.

9. A titanium dioxide-supported catalyst rich in titanium vacancies, characterized in that, The titanium-rich vacancy titanium dioxide supported catalyst was prepared using the preparation method described in any one of claims 1 to 8; Preferably, the specific surface area of the titanium-rich vacancy titania supported catalyst is 45.5-53 m 2 / g; Preferably, the particle size of the active metal in the titanium dioxide supported catalyst with titanium vacancies is 3.6-6.8 nm.

10. The application of the titanium-vacancy-rich titanium dioxide supported catalyst as described in claim 9, characterized in that, The application includes formaldehyde purification.

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