Supported Pt-coated M / TiO2 core-shell structure catalyst as well as preparation method and application thereof

Abstract

The invention provides a supported Pt (at) M / TiO2 core-shell structure catalyst as well as a preparation method and application thereof. The supported Pt (at) M / TiO2 core-shell structure catalyst is prepared by the following steps: (1) mixing nano titanium dioxide, a dispersing agent, a complexing agent, a Pt precursor and an M precursor in water to obtain dispersion liquid; (2) carrying out photo-reduction reaction on the dispersion liquid under illumination, and carrying out ultrasonic treatment at the same time, so as to obtain Pt (at) M / TiO2 mixed liquid; and (3) impregnating a carrier in the Pt-coated M / TiO2 mixed solution, aging, drying and roasting to obtain the supported Pt-coated M / TiO2 core-shell structure catalyst. The supported Pt (at) M / TiO2 core-shell structure catalyst has good catalytic activity and poison resistance, and the preparation method is simple, green and environmentally friendly.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst preparation, and specifically relates to a supported Pt@M / TiO 2 Core-shell structure catalyst and its preparation method and application. Background Art

[0002] VOCs (volatile organic compounds) contain many carcinogens that can harm the liver, kidneys, brain and nervous system, and are also responsible for the generation of PM2.5 and O 3 As the main pollutant that has increased in recent years, the attention and investment in VOCs treatment have gradually increased. VOCs emitted during industrial production are of many types, complex components, and have great differences in properties. Among the many VOCs treatment technologies, catalytic oxidation technology is one of the most promising and efficient chemical treatment technologies, with the advantages of low-temperature catalytic activity, no secondary pollution, high treatment efficiency, and a wide range of applications. The quality of the catalyst performance has a decisive influence on the catalytic efficiency and operating costs.

[0003] At present, the VOCs catalysts used in industry are mainly supported precious metal catalysts, which are widely used in the catalytic combustion of VOCs due to their excellent catalytic performance and high stability. The usual preparation process is to prepare precious metal dispersion and carrier dispersion separately, and then load the carrier dispersion and precious metal dispersion on the honeycomb frame carrier in turn to obtain the final supported precious metal catalyst.

[0004] Among the precious metals, platinum is a commonly used ideal catalyst, but its limited resources and easy to be poisoned limit its application in VOCs catalysts. Although single precious metals have good catalytic performance, the two metals in the dual precious metal catalyst will produce a synergistic effect, which has better catalytic activity than single precious metal catalysts. By preparing Pt@M dual precious core-shell structure, the catalytic activity of VOCs catalysts can be effectively improved. At present, the main methods for preparing Pt@M core-shell structure are replacement method and step-by-step reduction method.

[0005] CN108236952A discloses a method for preparing a precious metal formaldehyde eliminator radiator coating, wherein the method adopts fluoride ion control, controls the Pt coverage on the Pd surface in the core-shell structure through the substitution reaction between Pd and Pt, utilizes the selective adsorption of fluoride ions, and performs reduction under heating conditions to achieve the purpose of controlling the deposition state of Pt atoms on the Pd surface. The Pd@Pt core-shell structure synthesized by the invention, in which the Pt as the shell layer has poor anti-pollution properties as a catalyst and is easily oxidized by SO 2 , H 2 S, NO 2The catalyst loses its activity due to pollution, which in turn affects the catalytic activity of the core layer Pd, resulting in a decrease in the overall catalyst performance. Therefore, this catalyst is only suitable for SO 2、 H 2 S, NO 2 In the field of indoor air purification with low content of such substances.

[0006] CN108745350A discloses a preparation method and application of a bimetallic core-shell catalyst. The specific preparation method is to firstly prepare AgNO 3 , a protective agent and a reducing agent are added to the solvent and stirred to obtain a first product; a Pd source is then added to the first product and stirred to obtain a second product; the second product is extracted with an organic solvent, and the organic phase is collected to obtain a third product; finally, a carrier is added to the third product, and the product is allowed to stand for adsorption and then filtered, and the precipitate is collected and dried to obtain a bimetallic core-shell Ag@Pd / TiO 2 Catalyst products. This patent adds a reducing agent and adopts a step-by-step reduction method to prepare a bimetallic core-shell catalyst. The prepared catalyst has Ag as the core layer and Pd as the shell layer. Ag has a poor adsorption capacity for oxygen. As the core layer, it further reduces the coverage of oxygen on its surface, limiting the catalytic activity. In order to ensure the complete reduction of the bimetal, an excess of reducing agent needs to be added. At the same time, an organic solvent needs to be used to extract and collect the bimetallic with a core-shell structure. The preparation process is long, more reagents are used, and the environmental pollution is greater, which increases the difficulty of three waste treatments and the cost of catalyst preparation.

[0007] CN108579758A discloses a controllable bimetallic core-shell nanostructure, catalyst, preparation method and application thereof, wherein the preparation method is to subject a first uniform mixed reaction system comprising a noble metal salt, a stabilizer, a reducing agent and a solvent to an oxidation-reduction reaction in a protective atmosphere, and to age the system to obtain a noble metal nanoparticle sol; and to subject a second uniform mixed reaction system comprising a noble metal nanoparticle sol, a transition metal salt, a stabilizer, an alkaline substance, a reducing agent and a solvent to an oxidation-reduction reaction, and to age the system to obtain a bimetallic core-shell nanostructure comprising a noble metal core and a shell layer covering the core. The present invention adopts a seed-mediated method to prepare a catalyst having a noble metal nanoparticle as a core and a transition metal nanoparticle as a shell in a stepwise oxidation-reduction manner.

[0008] At present, although the core-shell structured noble metal catalysts have shown high research value in the field of heterogeneous catalysis due to their unique structural characteristics, the existing technology has disadvantages such as complicated reaction conditions, high preparation cost, and reagent residues in the preparation process. Therefore, the design is simple and feasible, and the use of surfactants, reducing agents and other reagents is reduced to prepare the supported Pt@M dual noble core-shell structure catalyst, which needs to be further developed in the application research of VOCs catalysts. Summary of the invention

[0009] In order to solve the above problems, the present invention aims to provide a supported Pt@M / TiO 2 Core-shell structure catalyst and its preparation method and application. 2 The core-shell structure catalyst has good catalytic activity and anti-poisoning performance, and the preparation method is simple.

[0010] In order to achieve the above object, the present invention provides a supported Pt@M / TiO 2 The preparation method of the core-shell structure catalyst comprises the following steps:

[0011] (1) mixing nano titanium dioxide, a dispersant, a complexing agent, a Pt precursor, and an M precursor in water to obtain a dispersion;

[0012] (2) The dispersion was subjected to photoreduction reaction under light and ultrasonic treatment to obtain Pt@M / TiO 2 Mixed liquid;

[0013] (3) Pt@M / TiO 2 The mixed solution is impregnated into the carrier, and after aging, drying and calcination, the supported Pt@M / TiO 2 A core-shell structure catalyst; wherein M comprises one or a combination of two or more of Pd, Rh, and Ag, and the complexing agent contains both amino and carboxyl structures.

[0014] According to a specific embodiment of the present invention, preferably, in step (1), the complexing agent includes aminoacetic acid.

[0015] According to a specific embodiment of the present invention, preferably, in step (1), the concentration of the dispersant in the dispersion is 10-40 g / L.

[0016] According to a specific embodiment of the present invention, preferably, in step (1), the dispersant includes one or a combination of two or more of PVP K5, PVP K15, PVP K30, and PVP K90.

[0017] According to a specific embodiment of the present invention, preferably, in step (1), the concentration of the complexing agent in the dispersion is 1-20 g / L.

[0018] According to a specific embodiment of the present invention, preferably, in step (1), the Pt precursor is selected from platinum salts, and the M precursor is selected from palladium salts, rhodium salts, silver salts, or a combination of two or more thereof.

[0019] According to a specific embodiment of the present invention, preferably, in step (1), the mass ratio of Pt to M is 1:(1-10).

[0020] According to a specific embodiment of the present invention, preferably, in step (1), the total mass of Pt and M is 0.1-3.0% of the mass of the carrier.

[0021] According to a specific embodiment of the present invention, preferably, in step (1), the mass of the nano titanium dioxide is 8-20% of the mass of the carrier.

[0022] According to a specific embodiment of the present invention, preferably, in step (2), the illumination conditions are visible light illumination for 36-120 h or ultraviolet light illumination for 12-36 h.

[0023] According to a specific embodiment of the present invention, preferably, the power of the ultraviolet light is 200-500W.

[0024] According to a specific embodiment of the present invention, preferably, in step (3), equal volume impregnation is adopted.

[0025] According to a specific embodiment of the present invention, preferably, in step (3), aging is performed at 20-40°C for 8-24h (e.g. 12h), drying is performed at 100-120°C for 8-24h, and calcination is performed at 500-600°C for 4-6h.

[0026] According to a specific embodiment of the present invention, preferably, in step (3), the carrier is a pretreated framework carrier.

[0027] According to a specific embodiment of the present invention, preferably, the pretreatment process comprises the following steps: soaking the cordierite honeycomb carrier with a mesh size of 80-480 in nitric acid or hydrochloric acid with a volume concentration of 5-10% for 6-12 hours for acid treatment.

[0028] According to a specific embodiment of the present invention, the above preparation method comprises the following specific steps:

[0029] (1) Pretreatment of the frame carrier: The cordierite honeycomb carrier with a mesh size of 80-480 is placed in nitric acid or hydrochloric acid with a volume concentration of 5-10% for 6-12 hours for acid treatment, and the volume of deionized water when the cordierite honeycomb carrier after acid treatment is immersed in equal volume needs to be tested;

[0030] (2) preparing a carrier dispersion: weighing a certain mass of nano-titanium dioxide, and dispersing it in a certain amount of deionized water by stirring or ultrasonication to form a titanium dioxide carrier dispersion, which is recorded as solution A; wherein the mass of the nano-titanium dioxide weighed is 8-20% of the mass of the desired loaded framework carrier, and the volume of the deionized water is equal to the volume of the deionized water obtained in step (1);

[0031] (3) Mixing the carrier and the noble metal active component: adding a dispersant to solution A, stirring evenly, and then adding aminoacetic acid to obtain a mixed solution B; then adding a mixed precursor of platinum and M in a certain proportion to the mixed solution B, mixing evenly, so that the total mass of the noble metal is 0.1-3.0% of the mass of the desired loading framework carrier, to obtain a mixed solution C;

[0032] Wherein, the dispersant is one of PVP K5, PVP K15, PVP K30, and PVP K90, and the mass concentration of the dispersant in the mixed solution B is 10-40 g / L; the mass concentration of the aminoacetic acid in the mixed solution B is 1-20 g / L; the platinum precursor is any one of the platinum salts; the M is one of the precious metals Pd, Rh, and Ag, and the M precursor is any one of the palladium salt, rhodium salt, and silver salt; the mass ratio of Pt to M is 1:(1-10);

[0033] (4) Preparation of Pt@M / TiO 2 :The mixed solution C is subjected to photoreduction reaction under visible light or ultraviolet light, and ultrasound is used at the same time. The platinum precursor is first reduced to a single substance of platinum as a core. Under the joint action of single substance platinum and titanium dioxide, the noble metal M precursor takes platinum as the core and forms a shell layer on its epitaxial growth to form a Pt@M core-shell nanostructure, which is loaded on nano-titanium dioxide to obtain Pt@M / TiO 2 The mixed solution is recorded as mixed solution D;

[0034] The visible light reduction time is 36-120h; the ultraviolet light power is 200-500w, and the illumination time is 12-36h;

[0035] (5) Preparation of loaded Pt@M / TiO 2 Core-shell structure catalyst: The prepared mixed solution D was impregnated in equal volumes on the pretreated framework support, then aged at 20-40°C for 12 h, dried at 100-120°C for 8 h, and calcined at 500-600°C for 4 h-6 h to finally obtain the supported Pt@M / TiO 2 Core-shell structure catalyst.

[0036] The present invention also provides a supported Pt@M / TiO prepared by the above preparation method. 2 Core-shell structure catalyst.

[0037] The present invention also provides the above-mentioned supported Pt@M / TiO 2 Application of core-shell structure catalysts in VOCs treatment.

[0038] The present invention combines photocatalytic technology with conventional impregnation technology to provide a supported Pt@M / TiO 2 Core-shell structure catalyst, Pt@M / TiO2 The active component Pt@M is a core-shell nanostructure, where Pt is the core, M represents a noble metal, and TiO 2 As a carrier.

[0039] The present invention has the following beneficial effects:

[0040] 1. Under the action of aminoacetic acid, the strong electron-donating group "amino" combines with platinum in the system with the best electron-capturing ability, while the weak electron-donating group "carboxyl" combines with the noble metal M, and the two noble metals are complexed together before light reduction; under light conditions, the platinum in the complexed double noble metals, with its lowest Fermi level, is preferentially reduced to nano-scale single platinum. In this stage, ultrasound is used to ensure the uniform dispersion of platinum, prevent platinum particles from agglomerating to ensure its nanoparticle size, and achieve uniform photoreduction of platinum; and the defoaming effect of ultrasound is used to accelerate the overflow of generated gas, avoid the introduction of additional sacrificial agents, and prevent the generated reducing gas from causing premature reduction of other noble metals in the system. Since the noble metal M is still in a complex state, it will not be reduced at this stage; when the platinum in the system is completely reduced, it can be used as a photocatalyst to reduce M, and with platinum as the core, it forms a shell layer on its epitaxial growth to obtain a Pt@M core-shell nanostructure, and ultrasound is used to prevent the agglomeration of the nanostructure. Titanium dioxide with semiconductor properties in the system can excite electrons and accelerate the photoreduction process of precious metals. In the preparation method of the present invention, the core-shell structure of precious metals is reduced and generated in one step. The process steps are simple and easy to implement. 2 The catalyst can be prepared by coating it on a honeycomb frame carrier, for example;

[0041] 2. Compared with the use of platinum as a catalyst alone, the Pt@M core-shell nanostructure formed by the present invention has the characteristic of relatively abundant resources. At the same time, the platinum wrapped in the shell layer can effectively prevent the platinum from being easily poisoned when used as a catalyst, thereby improving the stability of the catalyst. Platinum has the best ability to capture electrons, and can quickly transfer the electrons generated when the shell metal is used as a catalyst to the core layer, and quickly restore the catalytic activity of the shell metal. Due to the mutual synergy and nano effect of the precious metals between the core-shell structure, the utilization rate of the active sites during the catalytic reaction is improved, thereby greatly improving the catalytic performance of the Pt@M core-shell nanostructure catalyst in treating VOCs, effectively improving the catalyst reaction activity and catalyst stability;

[0042] 3. In the preparation process of the catalyst of the present invention, no additional surfactants, templates, reducing agents and other agents are used, the reaction conditions are mild, equal volume impregnation is used in the impregnation process, no additional wastewater is generated, the preparation process is green, and the pollution to the environment is small; the process route is short, the preparation method is simple and controllable, the catalyst cost can be effectively reduced, the production steps are simple, and it is suitable for industrial promotion and application. DETAILED DESCRIPTION

[0043] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

[0044] Catalyst precious metal loading = total precious metal mass / framework carrier mass, unit: %;

[0045] Toluene conversion rate = (1-(outlet concentration / inlet concentration)) × 100%;

[0046] Toluene concentration detection method: Agilent 8860 gas chromatograph (FID detector);

[0047] Catalyst evaluation method: Toluene is used as the target, and toluene is gasified and mixed with air to form a toluene content of 1000 mg / m 3 The mixed gas is heated at 16000h under programmed temperature. -1 The fixed space velocity of the toluene enters the fixed bed catalytic reactor, and the catalyst activity is measured by comparing the reaction temperature (T90) when the toluene conversion rate is 90%. The lower the T90, the higher the catalyst activity.

[0048] Catalyst anti-toxicity evaluation method: Toluene is used as the object, and toluene is gasified and mixed with sulfur dioxide and air to form a toluene content of 1000 mg / m 3 、Sulfur dioxide content 30mg / m 3 The mixed gas is heated at 16000h under programmed temperature. -1 The catalyst is put into a fixed bed catalytic reactor at a fixed space velocity and runs for 48 hours. The catalyst's anti-toxicity is measured by comparing the increase in reaction temperature (T90) when the toluene conversion rate is 90%. The less the T90 increases, the better the catalyst's anti-toxicity.

[0049] Example 1

[0050] This embodiment provides a supported Pt@M / TiO 2 The core-shell structure catalyst is prepared by the following steps:

[0051] (1) Weigh 100 g of a 240-mesh cordierite honeycomb substrate and soak it in 5% by volume nitric acid for 6 h to obtain a pretreated frame substrate. The test showed that the volume of deionized water required for equal volume immersion was 60 mL;

[0052] (2) 10 g of nano-titanium dioxide was weighed and dispersed in 60 mL of deionized water by ultrasound, which was recorded as solution A; 2.4 g of PVP K30 was dissolved in solution A, stirred evenly, and then 0.6 g of aminoacetic acid was added to obtain a mixed solution B; 0.54 g of platinum nitrate and 1.43 g of palladium nitrate were weighed respectively, wherein the mass ratio of Pt:Pd was 1:2, and mixed evenly with the mixed solution B, and then irradiated with 200 W ultraviolet light for 12 h, and combined with ultrasound, finally obtaining Pt@Pd / TiO with a total mass of 1 g of precious metals. 2 ;

[0053] (3) Prepared Pt@Pd / TiO 2 After being impregnated with an equal volume of the acidified framework support, the supported Pt@Pd / TiO was obtained by aging at 30 °C for 12 h, drying at 100 °C for 8 h, and calcining at 550 °C for 6 h. 2 Core-shell structure catalyst, wherein the catalyst loading is 1%.

[0054] Evaluation results: Toluene T90 = 175°C;

[0055] Catalyst anti-toxicity evaluation results: After 48 hours of operation, toluene T90 = 200°C, with a temperature increase of 25°C.

[0056] Example 2

[0057] This embodiment provides a supported Pt@M / TiO 2 The core-shell structure catalyst is prepared by the following steps:

[0058] (1) Weigh 50 g of a 80-mesh cordierite honeycomb substrate and soak it in 10% by volume nitric acid for 12 h to obtain a pretreated frame substrate. The test showed that the volume of deionized water required for equal volume immersion was 34 mL;

[0059] (2) 10 g of nano-titanium dioxide was weighed and dispersed in 34 mL of deionized water by ultrasound, which was recorded as solution A; 0.68 g of PVP K90 was dissolved in solution A, stirred evenly, and then 0.68 g of aminoacetic acid was added to obtain a mixed solution B; 0.49 g of platinum nitrate and 1.89 g of silver nitrate were weighed respectively, wherein the mass ratio of Pt:Ag was 1:4, and mixed evenly with the mixed solution B, and then irradiated with 500 W ultraviolet light for 18 h, and combined with ultrasound, finally obtaining Pt@Ag / TiO with a total mass of 1.5 g of precious metals. 2 ;

[0060] (3) Prepared Pt@Ag / TiO 2 After being impregnated with an equal volume of the acidified framework support, the supported Pt@Ag / TiO was obtained by aging at 40°C for 8 h, drying at 120°C for 20 h, and calcining at 600°C for 4 h.2 Core-shell structure catalyst, wherein the catalyst loading is 3%.

[0061] Evaluation results: Toluene T90 = 170°C;

[0062] Catalyst anti-toxicity evaluation results: After 48 hours of operation, toluene T90 = 193°C, with a temperature increase of 23°C.

[0063] Example 3

[0064] This embodiment provides a supported Pt@M / TiO 2 The core-shell structure catalyst is prepared by the following steps:

[0065] (1) Weigh 50 g of a 120-mesh cordierite honeycomb substrate and soak it in 8% by volume nitric acid for 12 h to obtain a pretreated frame substrate. The test showed that the volume of deionized water required for equal volume immersion was 39 mL;

[0066] (2) 4 g of nano-titanium dioxide was weighed and dispersed in 39 mL of deionized water by ultrasound, which was recorded as solution A; 1.17 g of PVP K15 was dissolved in solution A, stirred evenly, and then 0.039 g of aminoacetic acid was added to obtain a mixed solution B; 0.82 g of platinum nitrate and 1.40 g of rhodium nitrate were weighed respectively, wherein the mass ratio of Pt:Rh was 1:1, and mixed evenly with the mixed solution B, and then irradiated with 400 W ultraviolet light for 24 h, and combined with ultrasound, finally obtaining a Pt@Rh / TiO with a total mass of 1 g of precious metal. 2 ;

[0067] (3) Prepared Pt@Rh / TiO 2 After being impregnated with an equal volume of the acidified framework support, the supported Pt@Rh / TiO was obtained by aging at 20 °C for 16 h, drying at 110 °C for 16 h, and calcining at 500 °C for 6 h. 2 Core-shell structure catalyst, wherein the catalyst loading is 2%.

[0068] Evaluation results: Toluene T90 = 168°C;

[0069] Catalyst anti-toxicity evaluation results: After 48 hours of operation, toluene T90 = 190°C, with a temperature increase of 22°C.

[0070] Example 4

[0071] This embodiment provides a supported Pt@M / TiO 2 The core-shell structure catalyst is prepared by the following steps:

[0072] (1) Weigh 60 g of a 200-mesh cordierite honeycomb substrate and soak it in 5% by volume hydrochloric acid for 12 h to obtain a pretreated frame substrate. The test showed that the volume of deionized water required for equal volume immersion was 52 mL;

[0073] (2) 9 g of nano-titanium dioxide was weighed and dispersed in 52 mL of deionized water by ultrasound, which was recorded as solution A; 1.56 g of PVP K30 was dissolved in solution A, stirred evenly, and then 0.052 g of aminoacetic acid was added to obtain a mixed solution B; 1.73 g of platinum chloride and 0.42 g of palladium chloride were weighed respectively, wherein the mass ratio of Pt:Pd was 1:5, and mixed evenly with the mixed solution B, and then irradiated with visible light for 120 h, and ultrasonicated at the same time, finally obtaining Pt@Pd / TiO with a total mass of 0.3 g of precious metal. 2 ;

[0074] (3) Prepared Pt@Pd / TiO 2 After being impregnated with an equal volume of the acidified framework support, the supported Pt@Pd / TiO was obtained by aging at 25°C for 24 h, drying at 100°C for 12 h, and calcining at 500°C for 5 h. 2 Core-shell structure catalyst, wherein the catalyst loading is 0.5%.

[0075] Evaluation results: Toluene T90 = 184°C;

[0076] Catalyst anti-toxicity evaluation results: After 48 hours of operation, toluene T90 = 204°C, with a temperature increase of 20°C.

[0077] Example 5

[0078] This embodiment provides a supported Pt@M / TiO 2 The core-shell structure catalyst is prepared by the following steps:

[0079] (1) Weigh 40 g of a 480-mesh cordierite honeycomb substrate and soak it in 10% by volume hydrochloric acid for 10 h to obtain a pretreated frame substrate. The test showed that the volume of deionized water required for equal volume immersion was 34 mL;

[0080] (2) 3.4 g of nano-titanium dioxide was weighed and dispersed in 34 mL of deionized water by ultrasound, which was recorded as solution A; 1.36 g of PVP K90 was dissolved in solution A, stirred evenly, and then 0.51 g of aminoacetic acid was added to obtain a mixed solution B; 0.02 g of chloroplatinic acid and 0.22 g of palladium chloride were weighed respectively, wherein the mass ratio of Pt:Pd was 1:7, and mixed evenly with the mixed solution B, and then irradiated with visible light for 36 h, and ultrasonicated at the same time, finally obtaining Pt@Pd / TiO with a total mass of 0.08 g of precious metal. 2 ;

[0081] (3) Prepared Pt@Pd / TiO 2 After being impregnated with an equal volume of the acidified framework support, the supported Pt@Pd / TiO was obtained by aging at 35°C for 20 h, drying at 110°C for 24 h, and calcining at 550°C for 4 h. 2 Core-shell structure catalyst, wherein the catalyst loading is 0.2%.

[0082] Evaluation results: Toluene T90 = 193°C;

[0083] Catalyst anti-toxicity evaluation results: After 48 hours of operation, toluene T90 = 214°C, with a temperature increase of 21°C.

[0084] Comparative Example 1

[0085] This comparative example provides a supported core-shell structure catalyst, which is prepared by the following steps:

[0086] (1) Weigh 50 g of a 120-mesh cordierite honeycomb substrate and soak it in 8% by volume nitric acid for 12 h to obtain a pretreated frame substrate. The test showed that the volume of deionized water required for equal volume immersion was 39 mL;

[0087] (2) Weigh 4 g of nano-titanium dioxide and disperse it in 29 mL of deionized water by ultrasonication, which is referred to as solution A.

[0088] (3) 1.17g PVP K15 and 10mL methanol were added to a three-necked flask. After complete dissolution, 0.82g platinum nitrate was added thereto, and the mixture was refluxed at 120r / min and 70°C for 30min. Then 1.40g rhodium nitrate was added to the three-necked flask, and the mixture was refluxed at 120r / min and 70°C for 1.5h to obtain a Pt@Rh core-shell structure with a mass ratio of Pt:Rh of 1:1. After being evenly mixed with solution A, a Pt@Rh / TiO with a total mass of 1g of precious metal was obtained. 2 ;

[0089] (4) Prepared Pt@Rh / TiO 2 After being impregnated with an equal volume of the acidified framework support, the supported Pt@Rh / TiO was obtained by aging at 20 °C for 16 h, drying at 110 °C for 16 h, and calcining at 500 °C for 6 h. 2 Core-shell structure catalyst, wherein the catalyst loading is 2%.

[0090] Evaluation results: Toluene T90 = 175°C. The catalysts prepared in this comparative example and Example 3 have the same precious metal content, but the T90 of toluene is higher than the temperature of T90 in Example 3 by 168°C, indicating that the precious metal catalyst prepared by the present invention has higher catalytic activity.

[0091] The results of the catalyst anti-toxicity evaluation were as follows: after 48 h of operation, the toluene T90 was 220°C, with a temperature rise of 45°C, which was 22°C higher than the temperature rise in Example 3.

[0092] Comparative Example 2

[0093] This comparative example provides a supported core-shell structure catalyst, which is prepared by the following steps:

[0094] (1) Weigh 50 g of a 120-mesh cordierite honeycomb substrate and soak it in 8% by volume nitric acid for 12 h to obtain a pretreated frame substrate. The test showed that the volume of deionized water required for equal volume immersion was 39 mL;

[0095] (2) Weigh 4 g of nano-titanium dioxide and disperse it in 29 mL of deionized water by ultrasonication, which is referred to as solution A;

[0096] (3) 1.17g PVP K15 and 10mL methanol were added to a three-necked flask. After the solution was completely dissolved, 1.40g rhodium nitrate was added and refluxed at 120r / min and 70°C for 30min. Then 0.82g platinum nitrate was added to the three-necked flask and refluxed at 120r / min and 70°C for 1.5h to obtain a Rh@Pt core-shell structure with a mass ratio of Rh:Pt of 1:1. After being evenly mixed with solution A, a Rh@Pt / TiO with a total mass of 1g of precious metals was obtained. 2 ;

[0097] (4) Prepared Rh@Pt / TiO 2 After being impregnated with an equal volume of the acidified framework support, the supported Rh@Pt / TiO was obtained by aging at 20 °C for 16 h, drying at 110 °C for 16 h, and calcining at 500 °C for 6 h. 2 Core-shell structure catalyst, wherein the catalyst loading is 2%.

[0098] Evaluation results: Toluene T90 = 181°C.

[0099] Catalyst anti-toxicity evaluation results: After 48 hours of operation, toluene T90 = 250°C, and the temperature rise is 69°C, which is higher than the temperature rise of 45°C in Comparative Example 1. Since Pt has poor anti-pollution properties, it means that the catalyst with Pt as the core has better anti-toxicity.

[0100] Comparative Example 3

[0101] This comparative example provides a supported core-shell structure catalyst, which is prepared by the following steps:

[0102] (1) Weigh 40 g of 480 mesh cordierite honeycomb ceramics and soak them in 10% by volume hydrochloric acid for 10 h to obtain a pretreated frame carrier. The test shows that the volume of deionized water required for equal volume immersion is 34 mL;

[0103] (2) Weigh 3.4 g of nano-titanium dioxide and disperse it in 23 mL of deionized water by ultrasonication, which is referred to as solution A;

[0104] (3) 1.36g PVP K90 and 11mL methanol were added to a three-necked flask. After complete dissolution, 0.02g chloroplatinic acid was added and refluxed at 120r / min and 70°C for 30min. Then 0.22g palladium chloride was added to the three-necked flask and refluxed at 120r / min and 70°C for 1h to obtain a Pt@Pd core-shell structure with a mass ratio of Pt:Pd of 1:7. After being evenly mixed with solution A, a Pt@Pd / TiO with a total mass of 0.08g of precious metal was obtained. 2 ;

[0105] (4) Prepared Pt@Pd / TiO 2 After impregnation of equal volume into the acidified framework support, the supported Pt@Pd / TiO was obtained by aging at 35°C for 12 h, drying at 110°C for 8 h, and calcining at 550°C for 4 h. 2 Core-shell structure catalyst, wherein the catalyst loading is 0.2%.

[0106] Evaluation result: Toluene T90 = 207° C. The catalysts prepared in this comparative example and Example 5 have the same noble metal content, but the T90 of toluene is 193° C. higher than the T90 temperature in Example 5, indicating that the noble metal catalyst prepared by the present invention has higher catalytic activity.

[0107] The results of the catalyst anti-toxicity evaluation showed that after 48 hours of operation, the toluene T90 was 249°C, with a temperature rise of 42°C, which was 22°C higher than that in the embodiment.

[0108] Comparative Example 4

[0109] This comparative example provides a supported core-shell structure catalyst, which is prepared by the following steps:

[0110] (1) Weigh 40 g of 480 mesh cordierite honeycomb ceramics and soak them in 10% by volume hydrochloric acid for 10 h to obtain a pretreated frame carrier. The test shows that the volume of deionized water required for equal volume immersion is 34 mL;

[0111] (2) Weigh 3.4 g of nano-titanium dioxide and disperse it in 23 mL of deionized water by ultrasonication, which is referred to as solution A;

[0112] (3) 1.36g PVP K90 and 11mL methanol were added to a three-necked flask. After complete dissolution, 0.22g palladium chloride was added thereto. The mixture was refluxed at 120r / min and 70°C for 30min. Then 0.02g chloroplatinic acid was added to the three-necked flask. The mixture was refluxed at 120r / min and 70°C for 1h to obtain a Pd@Pt core-shell structure with a mass ratio of Pd:Pt of 1:7. After being evenly mixed with solution A, a Pd@Pt / TiO with a total mass of 0.08g of precious metal was obtained. 2 ;

[0113] (4) Prepared Pd@Pt / TiO 2 After being impregnated with an equal volume of the acidified framework support, the supported Pd@Pt / TiO was obtained by aging at 35°C for 12 h, drying at 110°C for 8 h, and calcining at 550°C for 4 h. 2 Core-shell structure catalyst, wherein the catalyst loading is 0.2%.

[0114] Evaluation results: Toluene T90 = 201°C;

[0115] Catalyst anti-toxicity evaluation results: After 48 hours of operation, toluene T90 = 257°C, with a temperature rise of 56°C, which is higher than the temperature rise of 42°C in Comparative Example 3. Since Pt has poor anti-pollution properties, the catalyst with Pt as the core has better anti-toxicity.

Claims

1. Preparation method of a supported Pt@M / TiO 2 core-shell structured catalyst, which The following steps are involved: (1) mixing nano titanium dioxide, a dispersant, a complexing agent, a Pt precursor, and an M precursor in water to obtain a dispersion; (2) The dispersion was subjected to photoreduction reaction under light and ultrasonic treatment to obtain Pt@M / TiO 2 Mixed liquid; (3) Pt@M / TiO 2 The mixed solution is impregnated into the carrier, and after aging, drying and calcination, the supported Pt@M / TiO 2 Core-shell catalysts; Wherein, M includes one or a combination of two or more of Pd, Rh, and Ag, and the complexing agent contains both amino and carboxyl structures; Preferably, the complexing agent comprises glycine.

2. The preparation method according to claim 1, in, In step (1), the concentration of the dispersant in the dispersion is 10-40 g / L; Preferably, in step (1), the dispersant includes one or a combination of two or more of PVP K5, PVP K15, PVP K30, and PVP K90.

3. The preparation method according to claim 1, in, In step (1), the concentration of the complexing agent in the dispersion is 1-20 g / L.

4. The preparation method according to claim 1, in, In step (1), the Pt precursor is selected from platinum salt, and the M precursor is selected from palladium salt, rhodium salt, silver salt, or a combination of two or more thereof; Preferably, in step (1), the mass ratio of Pt to M is 1:(1-10); Preferably, in step (1), the total mass of Pt and M is 0.1-3.0% of the mass of the carrier.

5. The preparation method according to claim 1, in, In step (1), the mass of the nano titanium dioxide is 8-20% of the mass of the carrier.

6. The preparation method according to claim 1, in, In step (2), the illumination condition is visible light illumination for 36-120 hours or ultraviolet light illumination for 12-36 hours; Preferably, the power of the ultraviolet light is 200-500W.

7. The preparation method according to claim 1, in, In step (3), equal volume impregnation is adopted; Preferably, in step (3), the aging is carried out at 20-40°C for 8-24h, the drying is carried out at 100-120°C for 8-24h, and the calcination is carried out at 500-600°C for 4-6h.

8. The preparation method according to claim 1, in, In step (3), the carrier is a pre-treated framework carrier; Preferably, the pretreatment process comprises the following steps: soaking the cordierite honeycomb carrier with a mesh size of 80-480 in nitric acid or hydrochloric acid with a volume concentration of 5-10% for 6-12 hours for acid treatment.

9. The supported Pt@M / TiO prepared by the preparation method according to any one of claims 1 to 8 2 Core-shell structure catalyst.

10. Use of the supported Pt@M / TiO core-shell structured catalyst as claimed in claim 9 in the treatment of VOCs. 2 ​