Titanium dioxide-based catalyst and preparation method thereof

Abstract

The invention relates to a titanium dioxide-based catalyst and a preparation method thereof, belongs to the technical field of catalyst resource utilization, and solves the problems of low resource utilization rate and high production cost caused by the fact that recycled titanium dioxide cannot be used as a raw material to prepare the titanium dioxide-based catalyst in the prior art. The preparation method comprises the following steps: a, preparing an ammonium metavanadate solution; b, adding the ammonium metavanadate solution into the titanium dioxide powder, stirring, drying, roasting and grinding to obtain V2O5-TiO2 particles; c, preparing an ammonium metatungstate aqueous solution; step d, adding an ammonium metatungstate aqueous solution into the V2O5-TiO2 particles, stirring, drying, roasting and grinding to obtain V2O5 / WO3-TiO2; in the step b, the titanium dioxide powder is recovered from the industrial inactivated denitration catalyst.

Description

Technical Field

[0001] This invention relates to the field of catalyst resource utilization technology, and in particular to a titanium dioxide-based catalyst and its preparation method. Background Technology

[0002] Titanium dioxide has a wide range of applications, covering fields such as batteries, electronic components, and catalysts. In the battery industry, its high ionic conductivity and chemical stability make it a candidate material for high-performance batteries. In the field of optics and electronic device development, due to its unique structure and optical properties, titanium dioxide is used to prepare optical devices and electronic components. In the field of catalysts, its high specific surface area and chemical stability make it a promising material for catalyst design and reaction control, and it can be used as a catalyst or catalyst support.

[0003] Existing processes for recovering titanium dioxide from industrial deactivated denitration catalysts yield titanium dioxide with low purity. Therefore, the recovered titanium dioxide cannot be used as a raw material to prepare titanium dioxide-based catalysts, and only virgin titanium dioxide can be used as a raw material, resulting in low resource utilization and high production costs. Summary of the Invention

[0004] In view of the above analysis, the present invention aims to provide a titanium dioxide-based catalyst and its preparation method. The titanium dioxide obtained by the existing process of recovering titanium dioxide from industrial deactivated denitration catalysts has low purity. Therefore, it is impossible to use the recovered titanium dioxide as a raw material to prepare titanium dioxide-based catalysts. Only new titanium dioxide can be used as a raw material, which leads to low resource utilization and high production costs.

[0005] The objective of this invention is mainly achieved through the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a titanium dioxide-based catalyst, comprising the following steps:

[0007] Step a: Recover titanium dioxide from industrial deactivated denitration catalyst;

[0008] Step b: Prepare ammonium metavanadate solution;

[0009] Step c: Add ammonium metavanadate solution to titanium dioxide, stir, dry, calcine, and grind to obtain V2O5-TiO2 particles;

[0010] Step d: Prepare an aqueous solution of ammonium metatungstate;

[0011] Step e: Add ammonium metatungstate aqueous solution to V2O5-TiO2 particles, stir, dry, calcine, and grind to obtain V2O5 / WO3-TiO2;

[0012] In step a, the recovery of titanium dioxide powder from the industrial deactivated denitration catalyst involves stepwise leaching of W and V from the industrial deactivated denitration catalyst using two alkaline solutions of different concentrations.

[0013] Optionally, the co-solvent includes one or more of oxalic acid solution, monoethanolamine solution, and diethanolamine solution.

[0014] Optionally, in step b, the concentration of the prepared ammonium metavanadate solution is 0.4-0.6 mol / L.

[0015] Optionally, in step c, the mass-to-volume ratio of titanium dioxide and ammonium metavanadate solution is (0.3-0.5):1.

[0016] Optionally, the particle size of titanium dioxide is 50-100 mesh.

[0017] Optionally, in step c, the roasting temperature is 250-350℃ and the roasting time is 2-4 hours.

[0018] Optionally, in step e, the calcination temperature is 500-600℃ and the calcination time is 2-4 hours.

[0019] Optionally, in step e, the mass-to-volume ratio of V2O5-TiO2 particles to ammonium metatungstate aqueous solution is (1.5-2.5):1.

[0020] Optionally, in step e, the particle size of the V2O5 / WO3-TiO2 particles is 60-80 mesh.

[0021] Optionally, in step c, the titanium dioxide powder has a small particle size, with a most probable particle size of 18.6-19.3 nm; a narrow particle size distribution, with a D(30) particle size below 30 nm, a D(50) particle size below 40 nm, and a D(90) particle size below 50 nm; and a total surface acidity of not less than 4.68 × 10⁻⁶. -4 mol / g; purity > 99.2%.

[0022] Step a includes the following steps:

[0023] Step 1: Mix the industrial deactivated denitration catalyst with the first alkaline solution, add a dispersant to the mixed solution to obtain the first suspension, transfer the first suspension into the reactor, react, remove the supernatant to obtain the solid;

[0024] Step 2: Mix the solid obtained in Step 1 with the second alkaline solution to obtain the second suspension. Transfer the second suspension into the reactor and react to obtain filter residue.

[0025] Step 3: Add acid solution to the filter residue obtained in Step 2 to obtain a solid-liquid mixture. Transfer the solid-liquid mixture into a reactor for nucleation and crystallization to obtain a third suspension. Separate the suspension to obtain high-purity TiO2.

[0026] Optionally, in step 1, the dispersant is acrylate, polyurethane, polyacrylamide, polyvinyl alcohol, or polyethylene glycol.

[0027] Optionally, the volume of the dispersant accounts for 1‰-5‰ of the volume of the first suspension.

[0028] Optionally, in steps 1, 2 and 3, the reactor is a microfilm reactor.

[0029] Optionally, the slit of the microfilm reactor is 0.1-0.5 mm.

[0030] Optionally, both the first alkaline solution and the second alkaline solution are mixtures of one or more of the following solutions: NaOH solution, KOH solution, sodium bicarbonate solution, and sodium carbonate solution.

[0031] Optionally, in step 3, the acid solution is an organic acid solution.

[0032] Optionally, the organic acid solution is one or more mixed acids selected from tartaric acid, citric acid, lauric acid, and oxalic acid.

[0033] Alternatively, the flocculant may include one or more of starch, cellulose, and chitosan.

[0034] Optionally, the flocculant accounts for 0.01%-0.05% of the slurry mass.

[0035] Optionally, the concentration of the organic acid solution is 0.5-2 mol / L.

[0036] Optionally, the crystallization temperature is 90-100℃ and the crystallization time is 2-5h.

[0037] Secondly, the present invention also provides a titanium dioxide-based catalyst, which is prepared by the above-described preparation method.

[0038] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0039] The method for preparing titanium dioxide-based catalysts in this invention does not use novel titanium dioxide as the raw material. Instead, it utilizes titanium dioxide recovered from industrial deactivated denitration catalysts, which not only improves resource utilization but also reduces production costs. Specifically, in the titanium dioxide recovery process, two alkaline solutions of different concentrations are used to leach W and V from the industrial deactivated denitration catalyst in steps, thereby improving the purity of the recovered titanium dioxide (>99.2%). This allows the recovered titanium dioxide to be used in the preparation of titanium dioxide-based catalysts.

[0040] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages will become apparent from the description or may be learned by practicing the invention. Attached Figure Description

[0041] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0042] Figure 1 The X-ray diffraction pattern of the sample obtained in Example 1 of this invention;

[0043] Figure 2(a) is a scanning electron microscope image of the sample obtained in Example 1 of the present invention;

[0044] Figure 2(b) is a scanning electron microscope image of the sample obtained in Comparative Example 5 of the present invention;

[0045] Figure 3(a) shows the particle size distribution of the sample in Figure 2(a);

[0046] Figure 3(b) shows the particle size distribution of the sample in Figure 2(b). Detailed Implementation

[0047] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0048] This invention uses industrial deactivated denitration catalysts as raw materials to prepare and synthesize high-purity titanium dioxide with small particle size and well-controlled microstructure, and uses this as a basis to prepare titanium dioxide-based industrial catalysts.

[0049] In a first aspect, the present invention provides a method for preparing a titanium dioxide-based catalyst, comprising the following steps:

[0050] Step a: Recover titanium dioxide from industrial deactivated denitration catalyst;

[0051] Step b: Prepare ammonium metavanadate solution;

[0052] Step c: Add ammonium metavanadate solution to titanium dioxide, stir, dry, calcine, and grind to obtain V2O5-TiO2 particles;

[0053] Step d: Prepare an aqueous solution of ammonium metatungstate;

[0054] Step e: Add ammonium metatungstate aqueous solution to V2O5-TiO2 particles, stir, dry, calcine, and grind to obtain V2O5 / WO3-TiO2;

[0055] In step a, the recovery of titanium dioxide powder from the industrial deactivated denitration catalyst involves stepwise leaching of W and V from the industrial deactivated denitration catalyst using two alkaline solutions of different concentrations.

[0056] Specifically, step b includes: dissolving ammonium metavanadate in a co-solvent to obtain an ammonium metavanadate solution.

[0057] Cosolvents include one or more of oxalic acid solutions, monoethanolamine solutions, and diethanolamine solutions.

[0058] In step b, the concentration of the prepared ammonium metavanadate solution is 0.4-0.6 mol / L.

[0059] In step c, the particle size of the titanium dioxide powder is 50-100 mesh. The mass-to-volume ratio of the titanium dioxide powder to the ammonium metavanadate solution is (0.3-0.5):1, where the mass of the titanium dioxide powder is in grams and the volume of the ammonium metavanadate solution is in mL.

[0060] In step c, the roasting temperature is 250-350℃, for example, 250℃, 280℃, 300℃, 330℃, 350℃. The roasting time is 2-4 hours, for example, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours.

[0061] In steps c and e, the stirring speed is 2000-4000 r / min and the stirring time is 10-20 minutes.

[0062] In steps c and e, the drying temperature is 90-130℃, for example, 90℃, 100℃, 110℃, 120℃, 130℃. The drying time is 10-20 hours, for example, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours.

[0063] Step d includes: dissolving ammonium metatungstate in water to obtain an aqueous solution of ammonium metatungstate. The concentration of the prepared aqueous solution of ammonium metatungstate is 0.2-0.3 g / mL.

[0064] In step e, the mass-to-volume ratio of V2O5-TiO2 particles to ammonium metatungstate aqueous solution is (1.5-2.5):1, wherein the mass of V2O5-TiO2 particles is in grams and the volume of ammonium metatungstate aqueous solution is in mL.

[0065] In step e, the roasting temperature is 500-600℃, for example, 500℃, 520℃, 550℃, 580℃, 600℃. The roasting time is 2-4 hours, for example, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours.

[0066] In step e, V2O5 / WO3-TiO2 particles with a particle size of 60-80 mesh are obtained by sieving.

[0067] Specifically, in step a, titanium dioxide with high purity, small particle size, and well-controlled microstructure was prepared and synthesized using industrial deactivated denitrification catalyst as raw material.

[0068] This invention is applicable to catalysts deactivated after industrial denitration reactions. Exemplary examples show the main chemical components of deactivated denitration catalysts as illustrated in Table 1.

[0069] Table 1. Main chemical components of the deactivated denitrification catalyst

[0070]

[0071]

[0072] This invention utilizes microfluidic membrane technology to prepare high-purity titanium dioxide. The overall technical concept is as follows: In an alkaline solution, under the combined action of a microfluidic membrane reactor and a dispersant, the vanadium and tungsten components in the deactivated denitrification catalyst are separated from the titanium components. Through alkalinity adjustment (the concentration of the second alkaline solution is greater than that of the first alkaline solution), high-purity titanium slag is obtained. The obtained high-purity titanium slag is reacted with an organic acid. The reaction process is divided into two stages—nucleation and crystallization—using a microfluidic membrane reactor. With the assistance of a flocculant, the mixture is dried and calcined to obtain a high-purity titanium dioxide product with a narrow particle size distribution and weak surface acidity.

[0073] Specifically, the recycling method of the present invention includes the following steps:

[0074] Step 1 (High-efficiency leaching of W and V): The deactivated denitrification catalyst is pretreated and mixed with the first alkaline solution. A dispersant is added to the mixed solution to obtain the first suspension. The first suspension is transferred into a microfilm reactor, backmixed, centrifuged, and the supernatant is removed to obtain the solid.

[0075] Step 2 (conversion of titanium dioxide to titanate): The solid obtained in Step 1 is mixed with the second alkaline solution to obtain the second suspension. The second suspension is transferred to a microfilm reactor, backmixed, transferred to a reaction vessel for reaction, centrifuged, and the filter residue is obtained.

[0076] Step 3 (conversion of titanate to titanium dioxide): Add organic acid solution to the filter residue obtained in step 2 to obtain a solid-liquid mixture. Transfer the solid-liquid mixture into a micro-liquid membrane reactor to nucleate and obtain a slurry. Add flocculant to the slurry, crystallize, and obtain a third suspension. Centrifuge, wash, dry, and calcine to obtain high-purity TiO2.

[0077] In this invention, step 1 achieves efficient leaching of W and V from the deactivated denitration catalyst and converts some of the titanium dioxide in the deactivated denitration catalyst into titanate. Step 2 converts the titanium in the deactivated denitration catalyst that has not been converted into titanate into titanate. Step 3 converts titanate into titanium dioxide and removes other impurities such as Ca, Fe, and Al contained in the deactivated denitration catalyst.

[0078] Specifically, the liquid-to-solid ratio in the mixed solution of step 1 is (2-6):1, for example, 2:1, 3:1, 4:1, 5:1, 6:1.

[0079] The purpose of adding a dispersant in step 1 is to improve solid-liquid contact, thereby shortening the backmixing time (i.e., the time for the vanadium and tungsten components in the deactivated denitration catalyst to separate from the titanium components), and thus improving the recovery efficiency. The dispersant can be acrylate, polyurethane, polyacrylamide, polyvinyl alcohol, or polyethylene glycol. The volume of the dispersant is 1‰-5‰ of the volume of the first suspension, for example, 1‰, 2‰, 3‰, 4‰, or 5‰.

[0080] Specifically, in step 1, the backmixing time is 5-10 minutes, for example, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, or 10 minutes. The backmixing temperature is 50-100℃, for example, 50℃, 60℃, 70℃, 80℃, 90℃, or 100℃.

[0081] In step 1, the slit of the microfilm reactor during backmixing is 0.1-0.5 mm, for example, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, or 0.5 mm.

[0082] Specifically, the first alkaline solution is a NaOH solution, KOH solution, sodium bicarbonate solution, or sodium carbonate solution with a mass concentration of 5wt%-10wt%, for example, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, or 10wt%.

[0083] Specifically, in step 2, the liquid-to-solid ratio of the second suspension is (2-6):1, for example, 2:1, 3:1, 4:1, 5:1, 6:1.

[0084] In step 2, the second alkaline solution is a NaOH solution, KOH solution, sodium bicarbonate solution, or sodium carbonate solution, and its mass concentration is greater than that of the first alkaline solution. Specifically, the mass concentration of the second alkaline solution is 20-40 wt%, for example, 20 wt%, 22 wt%, 24 wt%, 25 wt%, 27 wt%, 28 wt%, 30 wt%, 35 wt%, or 40 wt%.

[0085] It should be noted that the purpose of adding alkaline solution in step 1 of this invention is twofold: firstly, to efficiently leach W and V from the deactivated denitration catalyst; and secondly, to convert some of the titanium dioxide in the deactivated denitration catalyst into titanate. The purpose of adding alkaline solution in step 2 is to convert the titanium in the deactivated denitration catalyst that has not been converted into titanate into titanate.

[0086] This invention employs a two-step process of adding an alkaline solution. By controlling the mass concentration of the second alkaline solution to be greater than that of the first alkaline solution, the aforementioned objective is achieved, resulting in a more complete reaction. This facilitates the removal of metals such as V and W, thereby improving the purity of titanium dioxide. Furthermore, by selecting a mass concentration of 5-10 wt% for the first alkaline solution and 20-40 wt% for the second alkaline solution, the degree of reaction is further enhanced, thereby increasing the purity of titanium dioxide. Specifically, the purity of the titanium dioxide recovered by this invention is >99.2%.

[0087] Specifically, the backmixing time in step 2 is 1-10 minutes, for example, 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, and 10 minutes. The backmixing temperature is 50-100℃, for example, 50℃, 60℃, 70℃, 80℃, 90℃, and 100℃.

[0088] In step 2, the slit of the microfilm reactor during backmixing is 0.1-0.5 mm, for example, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, or 0.5 mm.

[0089] In step 2, the reaction temperature in the reactor is 120-150℃, for example, 120℃, 130℃, 140℃, 150℃.

[0090] The reaction pressure is 0.3-2 MPa, for example, 0.3 MPa, 0.5 MPa, 0.8 MPa, 1 MPa, 1.3 MPa, 1.5 MPa, 0.7 MPa, 1.8 MPa, 2 MPa.

[0091] The reaction time is 2-5 hours, for example, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, and 5 hours.

[0092] Specifically, in step 3, the addition of organic acid solution serves to regulate the particle size distribution of the finally recovered titanium dioxide, more precisely, to make the particle size distribution of titanium dioxide narrower. This invention achieves a very narrow particle size distribution of the recovered titanium dioxide by adding organic acid solution and controlling the amount of organic acid solution added. Specifically, the recovered titanium dioxide has a D(30) particle size of less than 30 nm, a D(50) particle size of less than 40 nm, and a D(90) particle size of less than 50 nm. Exemplarily, the concentration of the organic acid solution is 0.5-2 mol / L, for example, 0.5 mol / L, 0.7 mol / L, 0.5 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, and 2 mol / L.

[0093] In step 3, the mass-volume concentration of the solid-liquid mixture is 0.1-0.5 g / mL, for example, 0.1 g / mL, 0.2 g / mL, 0.3 g / mL, 0.4 g / mL, or 0.5 g / mL.

[0094] The organic acid is one or more mixed acids selected from tartaric acid, citric acid, lauric acid, and oxalic acid. The flocculant is one or more selected from starch, cellulose, and chitosan.

[0095] In step 3, the slit width of the microfilm reactor is 0.1-0.5 mm, for example, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, or 0.5 mm. The nucleation temperature is 50-100℃, for example, 50℃, 60℃, 70℃, 80℃, 90℃, or 100℃. The nucleation time is 1-10 min, for example, 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, or 10 min.

[0096] The role of adding flocculant in step 3 is to precipitate small particles in the solid-liquid mixture, causing the fine titanium dioxide particles to crystallize and grow, making them separable from the reaction system and thus improving the recovery rate of titanium dioxide. The flocculant used is one or more of starch, cellulose, and chitosan.

[0097] The added flocculant accounts for 0.01%-0.05% of the slurry mass, for example, 0.01%, 0.02%, 0.03%, 0.04%, or 0.05%. The crystallization temperature is 90-100℃, for example, 90℃, 95℃, 100℃, 105℃, 110℃, or 120℃. The crystallization time is 2-5 hours, for example, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, or 5 hours.

[0098] In step 3, the volume of the added organic acid solution is 2-6 times the mass of the industrial deactivated denitration catalyst. The mass of the industrial deactivated denitration catalyst is expressed in grams (g), and the volume of the organic acid solution is expressed in milliliters (mL).

[0099] In step 3, the drying temperature is 50-100℃, for example, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃. The drying time is 4-6 hours, for example, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours.

[0100] In step 3, the calcination is carried out in a muffle furnace, with the temperature increased to 500-900℃ at a heating rate of 2-10℃ / min, for example, 500℃, 600℃, 700℃, 800℃, and 900℃. The calcination time is 4-6 hours, for example, 4 hours, 4.5 hours, 5 hours, 5.5 hours, and 6 hours.

[0101] Additionally, in steps 1 to 3, the centrifugation speed is 3000-5000 r / min, for example, 3000 r / min, 4000 r / min, and 5000 r / min. Washing is performed with deionized water.

[0102] Compared with the prior art, the present invention has the following technical effects:

[0103] (1) This invention employs a two-step addition of alkaline solution. By controlling the mass concentration of the second alkaline solution to be greater than that of the first alkaline solution, efficient leaching of W and V from the deactivated denitrification catalyst can be achieved in step 1, and some of the titanium dioxide in the deactivated denitrification catalyst can be converted into titanate. In step 2, the titanium in the deactivated denitrification catalyst that has not been converted into titanate is converted into titanate. Overall, the reaction is more complete, which is beneficial for removing metals such as V and W, thereby improving the purity of titanium dioxide. Furthermore, by selecting the mass concentration of the first alkaline solution to be 3wt%-10wt% and the mass concentration of the second alkaline solution to be 20wt%-40wt%, the degree of reaction is further improved, thereby improving the purity of titanium dioxide. Specifically, the purity of the titanium dioxide recovered by this invention is >99.2%.

[0104] (2) This invention improves solid-liquid contact by adding a dispersant, thereby shortening the backmixing time (i.e., the time for the vanadium and tungsten components in the deactivated denitration catalyst to separate from the titanium components), and thus improving the recovery efficiency. Specifically, the backmixing time of this invention does not exceed 10 minutes, while the separation time of the prior art is 10-30 minutes. Furthermore, by using a two-step method of adding high and low concentration alkaline solutions, the alkaline washing time of the high-concentration alkali is greatly shortened (the alkaline washing time of the high-concentration alkali in this invention is only 2-5 hours, while the alkaline washing time of the prior art is 8 hours), further improving the recovery efficiency.

[0105] (3) This invention, by adding an organic acid solution during the conversion of titanate to titanium dioxide, controls the particle size distribution of the final recovered titanium dioxide, resulting in a narrower particle size distribution. Furthermore, by controlling the amount of organic acid solution added, the particle size distribution of the recovered titanium dioxide becomes extremely narrow. Specifically, the recovered titanium dioxide has a D(30) particle size below 30 nm, a D(50) particle size below 40 nm, and a D(90) particle size below 50 nm. On the other hand, using organic acid helps control the total surface acidity of the product, ensuring that the total surface acidity of the recovered titanium dioxide is not less than 4.68 × 10⁻⁶. -4 The total acid content of titanium dioxide is mol / g, which meets the requirements for total acid content in photocatalysts and denitration catalysts. Furthermore, compared to existing technologies that use strong inorganic acids, this invention utilizes a weak organic acid, which significantly reduces pollution and energy consumption.

[0106] (4) In this invention, a flocculant is added during the nucleation process to precipitate small particles in the solid-liquid mixture, allowing the fine titanium dioxide particles to crystallize and grow, thus enabling them to be separated from the reaction system and improving the recovery rate of titanium dioxide. Specifically, the recovery rate of titanium dioxide in the deactivated denitrification catalyst of this invention is greater than 98%.

[0107] (5) This invention proposes a high-purity titanium dioxide product and an efficient preparation method using a deactivated denitrification catalyst as raw material. The obtained titanium dioxide particles have small particle sizes, with the most probable particle size being only 18.6-19.3 nm. Furthermore, the particle size distribution is narrow, with D(30) particle size below 30 nm, D(50) particle size below 40 nm, and D(90) particle size below 50 nm, and the total surface acidity is not less than 4.68 × 10⁻⁶. -4 The titanium dioxide concentration is mol / g (meeting the requirements for total acidity of titanium dioxide in photocatalysts and denitration catalysts), and the titanium dioxide purity is >99.2%. After applying this technology, the titanium dioxide recovery rate from the deactivated denitration catalyst is >98%, the component separation time in alkaline solution is no more than 10 min, and the nucleation time in acid solution is no more than 10 min. The titanium dioxide recovered from the deactivated catalyst can be used in the preparation of photocatalysts, electrocatalysts, and denitration catalysts, and can achieve efficient decomposition of rhodamine and nitrogen oxides under mild conditions.

[0108] Secondly, the present invention also provides a high-purity titanium dioxide, which is recovered using the above-mentioned recycling process. It has a small particle size, with a most probable particle size of 18.6-19.3 nm; a narrow particle size distribution, with D(30) particle size below 30 nm, D(50) particle size below 40 nm, and D(90) particle size below 50 nm; and a total surface acid content of not less than 4.68 × 10⁻⁶. -4 mol / g (meets the requirements for total acidity of titanium dioxide for photocatalysts and denitration catalysts); titanium dioxide purity > 99.2%.

[0109] Thirdly, this invention also provides an application of high-purity titanium dioxide recovered using the above-mentioned recycling process in the preparation of photocatalysts, electrocatalysts, and denitration catalysts, enabling efficient decomposition of rhodamine and nitrogen oxides under mild conditions. Specifically, the high-purity titanium dioxide recovered from the deactivated denitration catalyst using the above-mentioned recycling process can be directly used as a photocatalyst for the degradation of rhodamine, achieving a degradation efficiency exceeding 90%. This marks the first time that functionalized regenerated titanium dioxide from deactivated denitration catalysts has been used in photocatalysis. Alternatively, the high-purity titanium dioxide recovered from the deactivated denitration catalyst using the above-mentioned recycling process can be used as a support to prepare a denitration catalyst, achieving a denitration efficiency of 90%, thus realizing the closed-loop utilization of the deactivated denitration catalyst.

[0110] The content and technical solutions of the present invention will be described in detail and completely below with reference to specific embodiments. However, it is obvious that the specific embodiments described in the further description are only a part of the content of the present invention, that is, they are not limited to the embodiments described herein.

[0111] Unless otherwise specified, all raw materials used in this invention can be obtained from commercially available sources.

[0112] Example 1

[0113] Step 1: Weigh 50g of industrial deactivated denitration catalyst powder sieved to 50-100μm and mix it with 100mL of 10wt% NaOH solution. Add a dispersant (acrylate) to the mixture, with the volume of the dispersant accounting for 1‰ of the suspension. Pour the mixed suspension into a microfilm reactor, adjust the slit of the microfilm reactor to 0.1mm, set the temperature to 50℃, and backmix the suspension in the microfilm reactor for 10min. Centrifuge (3000r / min) and remove the supernatant.

[0114] Step 2: Mix the solid obtained in Step 1 with 100 mL of 30 wt% concentrated NaOH solution. Pour the mixed suspension into a microfilm reactor, adjust the slit of the microfilm reactor to 0.1 mm, set the temperature to 50 °C, and backmix the suspension in the microfilm reactor for 10 min. Then transfer it to a reaction vessel and react at 120 °C and 0.3 MPa for 4 h. After centrifugation, obtain the filter residue.

[0115] Step 3: Add 100 mL of organic acid (tartaric acid) solution to the filter residue obtained in Step 2, pour it into a microfilm reactor with a slit width of 0.1 mm and a temperature of 50 °C, and nucleate for 10 min to obtain a slurry. Add flocculant (starch) at a mass of 0.01% of the total mass, and crystallize at 90 °C for 5 h. After centrifugation and washing, the resulting suspension is dried in an oven at 50 °C for 6 h, then placed in a muffle furnace and heated to 500 °C at a heating rate of 2 °C / min for 6 h. High-purity TiO2 product is obtained.

[0116] Step 4: Preparation of titanium dioxide-based catalyst:

[0117] Step a: Dissolve 0.13 g of ammonium metavanadate in 22 mL of oxalic acid solution to obtain ammonium metavanadate solution;

[0118] Step b: Add ammonium metavanadate solution to 8.9 g of titanium dioxide powder obtained in step 3, stir (3000 r / min, 15 min), dry (110 ℃, 12 h), calcine (300 ℃, 3 h), and grind to obtain V2O5-TiO2 particles;

[0119] Step c: Dissolve 1.04 g of ammonium metatungstate in 5 mL of water to obtain an aqueous solution of ammonium metatungstate;

[0120] Step d: Add ammonium metatungstate aqueous solution to 9 g of V2O5-TiO2 particles, stir, dry (110℃, 12h), calcine (550℃, 3h), cool, grind and sieve to obtain V2O5 / WO3-TiO2.

[0121] Example 2

[0122] Step 1: Weigh 50g of industrial deactivated denitration catalyst powder sieved to 50-100μm and mix it with 300mL of 5wt% NaOH solution. Add a dispersant (polyurethane) to the mixture, with the volume of the dispersant accounting for 5‰ of the suspension. Pour the mixed suspension into a microfilm reactor, adjust the slit of the microfilm reactor to 0.5mm, set the temperature to 100℃, and backmix the suspension in the microfilm reactor for 5min. Centrifuge (5000r / min) to remove the supernatant.

[0123] Step 2: Mix the solid obtained in Step 1 with 300 mL of 20 wt% concentrated NaOH solution. Pour the mixed suspension into a microfilm reactor, adjust the slit of the microfilm reactor to 0.5 mm, set the temperature to 100 °C, and backmix the suspension in the microfilm reactor for 1 min. Then transfer it to a reaction vessel and react at 150 °C and 2 MPa for 2 h. After centrifugation (5000 r / min), obtain the filter residue.

[0124] Step 3: Add 200 mL of organic acid (citric acid) solution to the filter residue obtained in Step 2, pour it into a microfilm reactor with a slit width of 0.5 mm and a temperature of 100℃ for 1 min to nucleate and obtain a slurry. Add flocculant (cellulose) at a mass of 0.05% of the total mass, and crystallize at 120℃ for 2 h. The resulting suspension is centrifuged (5000 r / min), washed with deionized water, dried in an oven at 100℃ for 4 h, and then placed in a muffle furnace and heated to 900℃ at a heating rate of 10℃ / min for 4 h. High-purity TiO2 product is obtained.

[0125] Step 4: Preparation of titanium dioxide-based catalyst:

[0126] Step a: Dissolve 0.13 g of ammonium metavanadate in 22 mL of oxalic acid solution to obtain ammonium metavanadate solution;

[0127] Step b: Add ammonium metavanadate solution to 8.9 g of titanium dioxide powder obtained in step 3, stir (3000 r / min, 15 min), dry (110 ℃, 12 h), calcine (300 ℃, 3 h), and grind to obtain V2O5-TiO2 particles;

[0128] Step c: Dissolve 1.04 g of ammonium metatungstate in 5 mL of water to obtain an aqueous solution of ammonium metatungstate;

[0129] Step d: Add ammonium metatungstate aqueous solution to 9 g of V2O5-TiO2 particles, stir, dry (110℃, 12h), calcine (550℃, 3h), cool, grind and sieve to obtain V2O5 / WO3-TiO2.

[0130] Example 3

[0131] Step 1: Weigh 50g of industrial deactivated denitration catalyst powder sieved to 50-100μm and mix it with 200mL of 8wt% NaOH solution. Add a dispersant (polyethylene glycol) to the mixture, with the volume of the dispersant accounting for 3‰ of the suspension. Pour the mixed suspension into a microfilm reactor, adjust the slit of the microfilm reactor to 0.2mm, set the temperature to 80℃, and backmix the suspension in the microfilm reactor for 8min. Centrifuge (4000r / min) and remove the supernatant.

[0132] Step 2: Mix the solid obtained in Step 1 with 200 mL of 25 wt% concentrated NaOH solution. Pour the mixed suspension into a microfilm reactor. Adjust the slit of the microfilm reactor to 0.1-0.5 mm and the temperature to 80 °C. Backmix the suspension in the microfilm reactor for 5 min, then transfer it to a reaction vessel. React at 125 °C and 1 MPa for 3.5 h. After centrifugation (4000 r / min), obtain the filter residue.

[0133] Step 3: Add 150 mL of organic acid (citric acid and lauric acid) solution to the filter residue obtained in Step 2, pour it into a microfilm reactor with a slit width of 0.2 mm and a temperature of 80℃ for 5 min to nucleate, and add flocculants (cellulose and chitosan) at a mass ratio of 0.03% of the total volume. Crystallize at 105℃ for 3.5 h. The resulting suspension is centrifuged (4000 r / min), washed with deionized water, dried in a 70℃ oven for 5 h, and then placed in a muffle furnace and calcined at a heating rate of 6℃ / min to 700℃ for 5 h. High-purity TiO2 product is obtained.

[0134] Step 4: Preparation of titanium dioxide-based catalyst:

[0135] Step a: Dissolve 0.13 g of ammonium metavanadate in 22 mL of oxalic acid solution to obtain ammonium metavanadate solution;

[0136] Step b: Add ammonium metavanadate solution to 8.9 g of titanium dioxide powder obtained in step 3, stir (3000 r / min, 15 min), dry (110 ℃, 12 h), calcine (300 ℃, 3 h), and grind to obtain V2O5-TiO2 particles;

[0137] Step c: Dissolve 1.04 g of ammonium metatungstate in 5 mL of water to obtain an aqueous solution of ammonium metatungstate;

[0138] Step d: Add ammonium metatungstate aqueous solution to 9 g of V2O5-TiO2 particles, stir, dry (110℃, 12h), calcine (550℃, 3h), cool, grind and sieve to obtain V2O5 / WO3-TiO2.

[0139] Comparative Example 1

[0140] The comparative example is basically the same as Example 3, except that the alkaline solution is not added in two steps, but is added in the first step and not added in the second step, and the concentration of the alkaline solution is 25 wt%.

[0141] Comparative Example 2

[0142] The comparative example is basically the same as Example 3, except that the concentration of the first alkaline solution is 25 wt% and the concentration of the second alkaline solution is 8 wt%, that is, the concentration of the first alkaline solution is greater than the concentration of the second alkaline solution.

[0143] Comparative Example 3

[0144] The comparative example is basically the same as Example 3, except that hydrochloric acid is added in the third step instead of an organic acid.

[0145] Comparative Example 4

[0146] The comparative example is basically the same as Example 3, except that the mass concentration of the first alkaline solution is 15 wt% (not in the range of 5 wt%-10 wt%) and the mass concentration of the second alkaline solution is 45 wt% (not in the range of 20 wt%-40 wt%).

[0147] Comparative Example 5

[0148] This comparative example is basically the same as Comparative Example 1, except that: instead of using a microfilm reactor, it is backmixed in a flask and then transferred to a reaction vessel for 8 hours.

[0149] The properties of titanium dioxide obtained in Examples 1-3 and Comparative Examples 1-3 were tested under the same test conditions, and the results are shown in Table 2.

[0150] Table 2. Some properties of titanium dioxide

[0151]

[0152] As shown in Table 2, the most probable particle size of titanium dioxide obtained in Examples 1-3 of this invention is 18.6-19.3 nm, thus proving that the titanium dioxide prepared by the method of this invention has a small particle size. The particle size distribution data in Table 2 show that the titanium dioxide prepared by the method of this invention has a narrow particle size distribution, with D(30) particles below 30 nm, D(50) particles below 40 nm, and D(90) particles below 50 nm. Furthermore, the total surface acid content is not less than 4.68 × 10⁻⁶. -4 The titanium dioxide content is mol / g (meeting the requirements for total acidity of titanium dioxide in photocatalysts and denitration catalysts), and the titanium dioxide purity is 99.2%-99.6%, all greater than 99.2%. After applying the technology of this invention, the recovery rate of titanium dioxide in the deactivated denitration catalyst is 98.7%-99.3%, all greater than 98%.

[0153] Table 2 also shows that when the alkaline solution was not added in two steps (Comparative Example 1), the purity of titanium dioxide was only 94.5%, significantly lower than the greater than 99.2% of the present invention. Furthermore, when the concentration of the first alkaline solution was greater than the concentration of the second alkaline solution (Comparative Example 2), the purity of titanium dioxide was only 95%, also significantly lower than the greater than 99.2% of the present invention. When hydrochloric acid was added in the third step instead of an organic acid (Comparative Example 3), the total surface acidity of titanium dioxide was 6.72 × 10⁻⁶. -4 mol / g, significantly higher than the 4.68 × 10⁻⁶ of the present invention. -4 The mol / g indicates that the titanium dioxide recovered using hydrochloric acid is more acidic than that recovered using organic acids. Furthermore, when a microfilm reactor is not used and the alkaline solution is not added in two steps, a longer reaction time (8 hours of alkaline washing, much longer than the 2-5 hours of the present invention) (Comparative Example 5) yields titanium dioxide with a most probable particle size of 24.2 nm, significantly higher than the 18.6-19.3 nm of the present invention, and a particle size distribution of 0-80 nm, which is significantly wider than the particle size distribution of the present invention. That is, even without a microfilm reactor and with a longer reaction time, the performance of the titanium dioxide obtained is far inferior to that of the present invention, even without a two-step addition of the alkaline solution.

[0154] In addition, the titanium dioxide obtained in Examples 1-3 was also tested and characterized in this invention, and the results are shown in […]. Figure 1 And Figure 2. The specific test and characterization conditions are as follows:

[0155] The crystal structure of the catalyst material was characterized using a Shimadzu XRD-600 X-ray powder diffractometer (λ = 0.15406 nm). The instrument was equipped with a Cu target and used Kα rays. An appropriate amount of powdered catalyst was placed in the recess of a rectangular glass slide used for testing. The catalyst surface was flattened using a pressing plate and placed on the instrument's test stage. The scanning range was 2θ = 10–80 °C, the scanning speed was 1 deg / min, and the instrument error range was ±0.04 °C. X-ray diffraction was performed on the sample under these conditions, and the X-ray diffraction pattern (XRD) was obtained. See [link to XRD pattern]. Figure 1 .

[0156] The morphology of the molded catalyst was characterized using a scanning electron microscope (SEM, Zeiss Supra 55). The catalyst was dispersed in ethanol, sonicated for 15 min, and then dropped onto a silicon wafer for scanning. The particle size was then statistically analyzed using Nanomeasurer software.

[0157] Depend on Figure 1 It can be seen that only the diffraction peak of anatase TiO2 was observed in the final sample XRD pattern, indicating that the sample has high purity. That is, TiO2 was well extracted and separated under high concentration of alkaline solution and organic acid with weaker acidity than inorganic acid.

[0158] As can be seen from Figure 2(a), the sample particles in the embodiment of the present invention have an approximately elliptical morphology, a smooth and flat surface, and a relatively concentrated particle distribution (see Figure 3(a)).

[0159] As shown in Figure 2(b), although most of the particles in Comparative Example 5 are also elliptical, they contain obvious plate-like structures. These plate-like structures indicate the presence of insufficiently washed Na ions, resulting in low TiO2 purity and incomplete conversion of metatitanic acid, which is detrimental to subsequent catalyst synthesis. Furthermore, with the alkaline washing time halved (4 hours in Example 1 and 8 hours in Comparative Example 5), the particle size and particle size distribution of the samples in this invention are significantly lower than those in the comparative example (see Figure 3(b)), which is beneficial for the subsequent synthesis of titanium dioxide-based catalysts.

[0160] In addition, under the same process conditions, the catalysts prepared in Examples 1-3 were applied to the selective catalytic reduction denitrification process, and the denitrification efficiency is shown in Table 3.

[0161] Table 3 Denitrification efficiency

[0162]

[0163] As can be seen from Table 3, the purity of titanium dioxide obtained under different recycling process conditions is different, which in turn leads to different denitrification efficiencies of the prepared catalysts.

[0164] It should be noted that by replacing the dispersant, organic acid solution, and flocculant with other substances listed above except for Examples 1-3, or by replacing the amount of substances or process conditions with those listed above except for Examples 1-3, the properties of the obtained titanium dioxide are similar to those in Examples 1-3, and will not be listed here again.

[0165] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a titanium dioxide-based catalyst, characterized in that, Includes the following steps: Step a: Recover titanium dioxide from industrial deactivated denitration catalyst; Step b: Prepare ammonium metavanadate solution; Step c: Add ammonium metavanadate solution to titanium dioxide, stir, dry, calcine, and grind to obtain V2O5-TiO2 particles; Step d: Prepare an aqueous solution of ammonium metatungstate; Step e: Add ammonium metatungstate aqueous solution to V2O5-TiO2 particles, stir, dry, calcine, and grind to obtain V2O5 / WO3-TiO2; In step a, the recovery of titanium dioxide powder from the industrial deactivated denitration catalyst involves stepwise leaching of W and V from the industrial deactivated denitration catalyst using two alkaline solutions of different concentrations.

2. The preparation method according to claim 1, characterized in that, Cosolvents include one or more of oxalic acid solutions, monoethanolamine solutions, and diethanolamine solutions.

3. The preparation method according to claim 1, characterized in that, In step b, the concentration of the prepared ammonium metavanadate solution is 0.4-0.6 mol / L.

4. The preparation method according to claim 1, characterized in that, In step c, the mass-to-volume ratio of titanium dioxide powder to ammonium metavanadate solution is (0.3-0.5):

1.

5. The preparation method according to claim 4, characterized in that, The particle size of titanium dioxide is 50-100 mesh.

6. The preparation method according to claim 1, characterized in that, In step c, the roasting temperature is 250-350℃ and the roasting time is 2-4 hours.

7. The preparation method according to claim 1, characterized in that, In step e, the roasting temperature is 500-600℃ and the roasting time is 2-4 hours.

8. The preparation method according to claim 1, characterized in that, In step e, the mass-volume ratio of V2O5-TiO2 particles to ammonium metatungstate aqueous solution is (1.5-2.5):

1.

9. The preparation method according to claim 1, characterized in that, In step e, the particle size of the V2O5 / WO3-TiO2 particles is 60-80 mesh.

10. A titanium dioxide-based catalyst, characterized in that, It is prepared by the preparation method according to any one of claims 1-9.

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