Pt / TiO 2 Preparation method of catalyst and its application in NH 3 -Application of SCO reaction

Abstract

The invention discloses a preparation method of a Pt / TiO2 catalyst and its application in NH3-SCO reaction. The preparation method comprises the following steps: providing nano titanium dioxide; mixing a platinum source, water and alcohol to prepare a platinum source solution; placing the nano titanium dioxide in the platinum source solution, turning on ultraviolet light for photodeposition reaction, and then filtering and drying the precipitate to obtain a Pt / TiO2 catalyst. The method can prepare a Pt / TiO2 catalyst with low noble metal loading, high and low temperature activity and high N2 selectivity.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of inorganic metal oxide supported platinum catalyst materials, and relates to the preparation of ammonia slip catalyst for motor vehicle exhaust treatment and its application in ammonia selective oxidation purification reaction (NH3-SCO). The preparation method is simple, safe and stable, and can improve the low-temperature activity of the catalyst. Background Art

[0002] Ammonia selective oxidation purification reaction (NH3-SCO) refers to the selective catalytic oxidation of harmful ammonia into nitrogen in an aerobic environment in the presence of a catalyst. However, NH3 can be oxidized not only into harmless N2 and H2O in an oxidizing atmosphere, but also into harmful nitrogen oxides such as NO, N2O, and NO2, as shown in Formulas 2, 3, and 4. Therefore, the core issue of this technical means is to select an efficient catalyst that can selectively oxidize NH3 into N2 and H2O, while producing as little or no NO as possible. x .

[0003] 4 NH3+3 O2→2 N2+6 H2O(1)

[0004] 4 NH3+5 O2→4 NO+6 H2O(2)

[0005] 2 NH3+2 O2→N2O +3 H2O(3)

[0006] 4 NH3+7 O2→4 NO2+6 H2O(4)

[0007] At present, the main ammonia emission reduction technologies include absorption, adsorption, biofiltration, catalytic combustion, catalytic oxidation and other methods. Among them, NH3-SCO can produce N2 and H2O, which is an ideal ammonia removal technology. The key to this technology is NH3-SCO catalyst. Such catalysts are mostly transition metals or precious metals loaded on materials such as metal oxides and molecular sieves to achieve better low-temperature activity or N2 selectivity.

[0008] Precious metals are widely used in the selective oxidation of ammonia due to their superior catalytic activity compared to other types of catalysts, especially excellent low-temperature activity. Precious metals mainly include elements such as Pt, Pd, and Ru. Generally, their metal salts are used as precursors and loaded on carriers through impregnation, ion exchange, and other methods to prepare precious metal catalysts.

[0009] NH3-SCO catalysts, such as Pt-loaded catalysts, have high prices for precious metals and high content of precious metals in the catalysts, which increases their application costs. In addition, such catalysts have low selectivity for N2, generally at T 90The N2 selectivity is 60% and there are side reactions, which easily generate byproducts such as NO, N2O, and NO2. These problems and challenges limit its wide application in the future National VII emission standards. In addition, the existing noble metal NH3-SCO catalyst has a noble metal loading of about 2wt%. 90 To reduce T 90 There is a need to further increase the loading of precious metals. Summary of the invention

[0010] The present invention provides a method for preparing a Pt / TiO2 catalyst by a photodeposition method, aiming to prepare a Pt / TiO2 catalyst with low noble metal loading, high low temperature activity and high N2 selectivity.

[0011] In order to achieve the above objectives, the present invention provides a method for preparing a Pt / TiO2 catalyst by a photodeposition method, comprising the following steps:

[0012] Provide nano titanium dioxide;

[0013] Mixing a platinum source, water, and alcohol to prepare a platinum source solution;

[0014] The nano-titanium dioxide is placed in a platinum source solution, ultraviolet light is turned on for photodeposition reaction, and then the precipitate is filtered and dried to obtain a Pt / TiO2 catalyst.

[0015] According to the first aspect of the present invention, in some embodiments, providing nano titanium dioxide comprises:

[0016] Titanium isopropoxide or butyl titanate is hydrolyzed in an isopropanol aqueous solution, and the hydrolyzate is dried and calcined to obtain nano titanium dioxide.

[0017] According to the first aspect of the present invention, in some embodiments, the nano-titanium dioxide provided is commercially available nano-titanium dioxide.

[0018] According to the first aspect of the present invention, in some embodiments, the platinum source is one or more of chloroplatinic acid (H2PtCl6), platinum nitrate (Pt(NO3)2), platinum acetate (Pt(CH3COO)2), platinum chloride (PtCl2), tetraammineplatinum nitrate ((NH3)4·Pt(NO3)2); and / or the alcohol is one or more of methanol, ethanol, propanol, isopropanol, and glycerol.

[0019] According to the first aspect of the present invention, in some embodiments, the volume ratio of water to alcohol in the platinum source solution is 1-10:1.

[0020] According to the first aspect of the present invention, in some embodiments, the concentration of platinum element in the platinum source solution is 10-50 mg / mL, and the concentration of titanium dioxide is 10-50 g / L.

[0021] According to the first aspect of the present invention, in some embodiments, the wavelength range of the ultraviolet light is 100-380 nm; and / or the intensity of the ultraviolet light is 2-100 W / m 2 ; and / or, the photodeposition reaction time is 1 to 6 hours.

[0022] The second aspect of the present invention provides a Pt / TiO2 catalyst prepared by the above-mentioned method for preparing a Pt / TiO2 catalyst by photodeposition.

[0023] The third aspect of the present invention provides the application of the above-mentioned Pt / TiO2 catalyst in the field of selective oxidation purification of ammonia.

[0024] A fourth aspect of the present invention provides an ammonia slip catalyst (ASC) for installation after a selective catalytic reduction reactor (SCR), wherein the ammonia slip catalyst comprises the above-mentioned Pt / TiO2 catalyst.

[0025] A fifth aspect of the present invention provides a vehicle comprising the above-mentioned ammonia slip catalyst.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The preparation method provided by the present invention starts from simple and readily available raw materials, and does not require high temperature and high pressure reaction conditions and high temperature reduction in an active atmosphere, thereby reducing the synthesis time and cost. The preparation method has simple steps, is easy to operate, is economically and environmentally friendly, and has dual benefits.

[0028] 2. Compared with the existing noble metal NH3-SCO catalyst, the Pt / TiO2 catalyst prepared in the present invention has a low noble metal loading, high low-temperature activity and maintains a high N2 selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 : XRD pattern of hv-1%Pt-TiO2 (homemade)-glycerol.

[0031] Figure 2: SEM image of hv-1%Pt-TiO2 (homemade)-glycerol.

[0032] Figure 3 : XRD pattern of hv-1%Pt / TiO2 (commercially available)-glycerol.

[0033] Figure 4 : SEM image of hv-1%Pt / TiO2 (commercially available)-glycerol.

[0034] Figure 5 : XRD pattern of hv-0.5%Pt / TiO2 (homemade)-glycerol.

[0035] Figure 6 : SEM image of hv-0.5%Pt-TiO2 (homemade)-glycerol.

[0036] Figure 7 : XRD pattern of hv-0.5%Pt / TiO2 (commercially available)-glycerol.

[0037] Figure 8 : SEM image of hv-0.5%Pt / TiO2 (commercially available)-glycerol.

[0038] Fig. 9 : XRD pattern of hv-1%Pt-TiO2 (homemade)-methanol.

[0039] Fig.10 : SEM image of hv-1%Pt-TiO2 (homemade)-methanol.

[0040] Fig.11 : XRD pattern of hv-1%Pt / TiO2 (commercially available)-methanol.

[0041] Fig.12 : SEM image of hv-1%Pt / TiO2 (commercially available)-methanol.

[0042] Fig.13 : XRD pattern of hv-0.5%Pt / TiO2 (homemade)-methanol.

[0043] Fig.14 : SEM image of hv-0.5%Pt-TiO2 (homemade)-methanol.

[0044] Fig.15 : XRD pattern of hv-0.5%Pt / TiO2 (commercially available)-methanol.

[0045] Fig.16 : SEM image of hv-0.5%Pt / TiO2 (commercially available)-methanol.

[0046] Fig.17: XRD pattern of H2-1%Pt-TiO2 (commercially available).

[0047] Fig.18 : SEM image of H2-1%Pt-TiO2 (commercially available).

[0048] Fig.19 : XRD pattern of H2-1%Pt / TiO2 (homemade).

[0049] Fig. 20 : SEM image of H2-1%Pt-TiO2 (homemade).

[0050] Fig.21 : Transmission electron microscope images of the Pt / TiO2 catalysts prepared in Examples 1 to 6; wherein, Figure a is a hv-0.5%Pt-TiO2 (homemade) - glycerol catalyst, Figure b is a hv-1%Pt-TiO2 (commercially available) - glycerol catalyst, Figure c is a H2-1%Pt / TiO2 (commercially available) catalyst, and Figure d is a H2-1%Pt / TiO2 (homemade) catalyst; Figure e is a hv-1%Pt / TiO2 (homemade) - methanol catalyst, and Figure f is a hv-1%Pt / TiO2 (commercially available) - methanol.

[0051] Fig. 22 : STEM-EDS image of hv-1%Pt / TiO2 (homemade)-glycerol sample.

[0052] Fig.23 : SCO activity of Pt / TiO2 catalyst.

[0053] Fig.24 : SCO activity of Pt / TiO2 catalyst.

[0054] Fig.25 : N2 selectivity of Pt / TiO2 catalyst.

[0055] Fig.26 : N2 selectivity of Pt / TiO2 catalyst.

[0056] Fig. 27 : NH3-SCO activity of Pt-based catalysts on different TiO2 supports. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0058] For simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form an unambiguous range; and any lower limit can be combined with other lower limits to form an unambiguous range. Similarly, any upper limit can be combined with any other upper limit to form an unambiguous range. In addition, although not explicitly stated, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unambiguous range.

[0059] It should be noted that, in the description of this article, unless otherwise specified, "above", "below" are inclusive numbers, and the meaning of "multiple" in "one or more" is two or more. Relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the process, method, article or equipment including the elements.

[0060] In the description of this specification, the description with reference to the terms "any embodiment / method", "one embodiment / method", "some embodiments / methods", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment / method or example are included in at least one embodiment / method or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment / method or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments / methods or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments / methods or examples described in this specification and the features of the different embodiments / methods or examples, unless they are contradictory.

[0061] The above summary of the invention of the present invention is not intended to describe each disclosed embodiment or each implementation in the present invention. The following description more specifically illustrates exemplary embodiments. These embodiments can be used in various combinations. In each example, the enumeration is only used as a representative group and should not be interpreted as exhaustive.

[0062] In the prior art, noble metals (Pt, Pd, Ru) are generally loaded on a carrier by impregnation or ion exchange to prepare a noble metal catalyst for catalysis of ammonia selective oxidation reaction. However, the loading amount of noble metals is generally high, resulting in high catalyst cost, and such catalysts have low selectivity for N2, and there are side reactions, which easily generate byproducts such as NO, N2O, and NO2. These problems and challenges limit the widespread application of such catalysts in the future National VII emission standards.

[0063] The noble metal NH3-SCO catalyst uses noble metal atoms as active components. Therefore, generally, after the noble metal precursor is loaded on the acidic carrier by impregnation or ion exchange, it is calcined in an oxygen atmosphere to oxidize the noble metal into metal oxides, fixed on the carrier, and then reduced in a reducing atmosphere, also known as activation, to obtain the noble metal NH3-SCO catalyst.

[0064] After in-depth research, the inventor found that the platinum source was dissolved in an alcohol-water mixture to make a platinum source solution. Under ultraviolet light, the platinum source solution would undergo a photodeposition reaction, and the platinum element would be deposited on the carrier surface in atomic form. The obtained Pt / TiO2 catalyst has high low-temperature activity and N2 selectivity: Common precious metal NH3-SCO catalyst T 90 The T of the Pt / TiO2 catalyst obtained by the present invention is 225°C. 90 The common noble metal NH3-SCO catalyst has a temperature of 170℃. 90 The N2 selectivity is 60% at T 90 The N2 selectivity is 80%. 90 Refers to the temperature at which the NH3 conversion rate reaches 90%.

[0065] Based on the above findings, the present invention provides a method for preparing a Pt / TiO2 catalyst and its application in the NH3-SCO reaction.

[0066] Preparation method

[0067] The method for preparing a Pt / TiO2 catalyst by a photodeposition method provided by the present invention comprises the following steps:

[0068] Provide nano titanium dioxide;

[0069] Mixing a platinum source, water, and alcohol to prepare a platinum source solution;

[0070] The nano-titanium dioxide is placed in a platinum source solution, ultraviolet light is turned on for photodeposition reaction, and then the precipitate is filtered and dried to obtain a Pt / TiO2 catalyst.

[0071] In the preparation method provided by the present invention, ultraviolet light irradiation and the presence of alcohol are indispensable, and the principle is as follows: ultraviolet light irradiation provides photogenerated electrons and holes, and alcohol, as a sacrificial reagent, provides additional electrons to promote the reduction of precious metal ions. The combination of the two enables the photodeposition method to efficiently load precious metals such as platinum on the surface of titanium dioxide. The core of this process is the generation and utilization of photogenerated electron-hole pairs, and the oxidation reaction of alcohol molecules, all of which are inseparable from ultraviolet light irradiation and the presence of alcohol.

[0072] The preparation method provided by the present invention starts from simple and readily available raw materials, and does not require high temperature and high pressure reaction conditions and high temperature reduction in an active atmosphere, thereby reducing synthesis time and cost. The method has simple steps and is easy to operate, and has dual benefits of being economical and environmentally friendly.

[0073] In some embodiments of the present invention, the nano-titanium dioxide is in anatase phase or rutile phase, or a mixed crystal phase of the two, such as commercially available Degussa P25, which is a mixed crystal phase of anatase phase and rutile phase.

[0074] In some embodiments of the present invention, the method of providing nano titanium dioxide is: hydrolyzing titanium isopropoxide or butyl titanate in an isopropanol aqueous solution, drying and calcining the hydrolyzate to obtain nano titanium dioxide. The nano titanium dioxide obtained in this way is anatase phase. The drying temperature is 100-120°C; the calcination temperature is 600-700°C, preferably 640-660°C; the calcination atmosphere is an oxygen atmosphere, and the oxygen atmosphere is preferably air.

[0075] In some embodiments of the present invention, nano titanium dioxide is provided by providing commercially available nano titanium dioxide. The particle size of titanium dioxide is not intended to be limited. In some embodiments of the present invention, the particle size of commercially available titanium dioxide is 20-50 nm. In addition, the commercially available titanium dioxide is anatase phase titanium dioxide.

[0076] In some embodiments of the present invention, the platinum source used is one or more of chloroplatinic acid (H2PtCl6), platinum nitrate (Pt(NO3)2), platinum acetate (Pt(CH3COO)2), platinum chloride (PtCl2), tetraammine platinum nitrate ((NH3)4·Pt(NO3)2); and / or, the alcohol is one or more of methanol, ethanol, propanol, isopropanol, and glycerol. These platinum sources and alcohols are all soluble in water. Therefore, the platinum source, water, and alcohol can form a uniform platinum source solution, thereby preparing for the uniform deposition of Pt on titanium dioxide.

[0077] In some embodiments of the present invention, the volume ratio of water to alcohol in the platinum source solution is 1~10:1. This ratio can ensure that the platinum source, water and alcohol can form a uniform platinum source solution, and avoid poor reduction effect caused by too little alcohol content and metal agglomeration caused by too much alcohol content.

[0078] In some embodiments of the present invention, the concentration of platinum in the platinum source solution is 10-50 mg / mL, and the concentration of titanium dioxide is 10-50 g / L. The concentrations of platinum and titanium dioxide are controlled within the above ranges to effectively control the dispersion and anchoring of platinum on the surface of titanium dioxide.

[0079] In some embodiments of the present invention, the wavelength range of the ultraviolet light is 100-380 nm, and the photodeposition reaction can provide ultraviolet light of a single wavelength or ultraviolet light of mixed wavelengths.

[0080] In some embodiments of the present invention, the intensity of the ultraviolet light is 2 to 100 W / m 2 .

[0081] In some embodiments of the present invention, the photodeposition reaction time is 1 to 6 hours. Controlling the photodeposition reaction time within the above range can ensure that most of the platinum source is precipitated and avoid low preparation efficiency due to too long a time.

[0082] In some embodiments of the present invention, the atmosphere for turning on the ultraviolet light to perform the photo-deposition reaction may be an inert atmosphere or nitrogen.

[0083] Pt / TiO2 Catalyst

[0084] The Pt / TiO2 catalyst prepared by the above-mentioned method for preparing the Pt / TiO2 catalyst by the optical deposition method has a high degree of dispersion of Pt atoms and excellent low-temperature activity. 90 It can be as low as 170℃ and has high N2 selectivity. 90 The lower is greater than 70%.

[0085] The existing noble metal NH3-SCO catalyst has a noble metal loading of about 2 wt%. 90 The loading amount of precious metals needs to be further increased. The Pt / TiO2 catalyst prepared by the present invention has a Pt loading amount of 0.86wt% T 90 It can be as low as 170°C and when the Pt loading is as low as 0.4%, it still has high low-temperature activity.

[0086] In particular, when titanium dioxide is prepared by the following method, its low temperature activity is slightly better than that of commercially available anatase TiO2 and Pt / TiO2 catalyst obtained by commercially available Degussa P25: titanium isopropoxide is hydrolyzed in an isopropanol aqueous solution, and the hydrolyzate is dried and calcined to obtain titanium dioxide. This method obtains anatase phase nano-titanium dioxide.

[0087] application

[0088] The application of the above Pt / TiO2 catalyst in the field of selective oxidation purification of ammonia can reduce the cost of the catalyst. 90 The reduction can reduce the energy consumption of the ammonia selective oxidation purification reaction, thereby further reducing the cost of ammonia treatment. In addition, the above-mentioned Pt / TiO2 catalyst has a high nitrogen selectivity, reduces the production of by-products such as NO, N2O, and NO2, and reduces NO x pollute.

[0089] Ammonia slip catalyst

[0090] To reduce NO in vehicle exhaust x In this field, urea tanks and selective catalytic reduction reactors are installed on vehicles to reduce NO in exhaust gas using ammonia provided by urea. x However, ammonia will inevitably escape with the tail gas. In order to avoid ammonia leakage, an ammonia escape catalyst (ASC) can be installed after the selective catalytic reduction reactor (SCR) to treat the ammonia that escapes during the selective catalytic reduction reaction, oxidize it into harmless nitrogen, and then discharge it. Therefore, the Pt / TiO2 catalyst of the present invention can be used in the ammonia escape catalyst (ASC), and more than 90% of ammonia can be oxidized at a relatively low temperature, and the content of byproducts such as NO, N2O, and NO2 in the treated gas is relatively low. In addition, the ammonia escape catalyst using the Pt / TiO2 catalyst of the present invention has a low cost.

[0091] vehicle

[0092] The present invention provides a vehicle, which includes the above-mentioned ammonia slip catalyst, and can oxidize more than 90% of ammonia at a relatively low temperature, and the byproducts such as NO, N2O, and NO2 in the treated gas are relatively low. In addition, the cost of the vehicle using the ammonia slip catalyst of the present invention is relatively low.

[0093] Example

[0094] The technical scheme of the present invention is described in detail below through examples. If the manufacturer's brand or preparation method is not specified, the raw materials, equipment or solvents used are all common raw materials, equipment or solvents on the market. Unless otherwise specified, the raw materials of the same name used in the following examples and comparative examples are the same raw materials. In the following examples, the wavelength of the ultraviolet lamp is 365nm; the commercially available titanium dioxide is anatase phase, and the particle size range is 20~50nm.

[0095] Example 1: hv-1% Pt / TiO2 (homemade)-glycerol

[0096] This embodiment provides a method for preparing a Pt / TiO2 catalyst, and the specific steps are as follows:

[0097] (1) Add 20 mL of isopropanol and 5 mL of titanium isopropoxide to 20 mL of water and stir at room temperature for 0.5 h to allow it to fully hydrolyze. Filter the solid product by centrifugation and dry it in an oven at 110 °C overnight to obtain a sample powder.

[0098] (2) The sample powder obtained in step (1) is calcined at 650°C in an air atmosphere for 2 hours to obtain a TiO2 carrier.

[0099] (3) Weigh 1 g of TiO2 carrier into a quartz photocatalytic reactor, add 35 mL of water, 5 mL of glycerol, and 500 uL of chloroplatinic acid solution (containing Pt: 20 mg / mL); introduce argon into the reactor for 0.5 h, seal the reactor, and irradiate with ultraviolet light for 6 h at room temperature. Centrifuge and filter out the solid product, dry it overnight at room temperature, and obtain a Pt / TiO2 catalyst, recorded as hv-1%Pt / TiO2 (homemade)-glycerol.

[0100] Example 2: hv-1%Pt / TiO2 (commercially available)-glycerol

[0101] This embodiment provides a method for preparing a Pt / TiO2 catalyst, and the specific steps are as follows:

[0102] Weigh 1 g of commercially available anatase TiO2 in a quartz photocatalytic reactor, add 35 mL of water, 5 mL of glycerol, and 500 uL of chloroplatinic acid solution (containing Pt: 20 mg / mL); introduce argon into the reactor for 0.5 h, seal the reactor, and irradiate with ultraviolet light for 6 h at room temperature. Centrifuge and filter out the solid product, dry it overnight at room temperature, and obtain a Pt / TiO2 catalyst, recorded as hv-1% Pt / TiO2 (commercially available)-glycerol.

[0103] Example 3: hv-0.5%Pt / TiO2 (homemade)-glycerol

[0104] This embodiment provides a method for preparing a Pt / TiO2 catalyst, and the specific steps are as follows:

[0105] (1) Add 20 mL of isopropanol and 5 mL of titanium isopropoxide to 20 mL of water and stir at room temperature for 0.5 h to allow it to fully hydrolyze. Filter the solid product by centrifugation and dry it in an oven at 110 °C overnight to obtain a sample powder.

[0106] (2) The sample powder obtained in step (1) is calcined at 650°C in an air atmosphere for 2 hours to obtain a TiO2 carrier.

[0107] (3) Weigh 1 g of TiO2 carrier into a quartz photocatalytic reactor, add 35 mL of water, 5 mL of glycerol, and 250 uL of chloroplatinic acid solution (Pt content: 20 mg / mL); introduce argon into the reactor for 0.5 h, seal the reactor, and irradiate with ultraviolet light for 6 h at room temperature. Centrifuge and filter out the solid product, dry it overnight at room temperature, and obtain a Pt / TiO2 catalyst, recorded as hv-0.5%Pt / TiO2 (homemade)-glycerol.

[0108] Example 4: hv-0.5% Pt / TiO2 (commercially available)-glycerol

[0109] This embodiment provides a method for preparing a Pt / TiO2 catalyst, and the specific steps are as follows:

[0110] Weigh 1 g of commercially available anatase TiO2 in a quartz photocatalytic reactor, add 35 mL of water, 5 mL of glycerol, and 250 uL of chloroplatinic acid solution (containing Pt: 20 mg / mL); introduce argon into the reactor for 0.5 h, seal the reactor, and irradiate with ultraviolet light for 6 h at room temperature. Centrifuge and filter out the solid product, dry it overnight at room temperature, and obtain a Pt / TiO2 catalyst, recorded as hv-0.5%Pt / TiO2 (commercially available)-glycerol.

[0111] Example 5: hv-1%Pt / TiO2 (homemade)-methanol

[0112] This embodiment provides a method for preparing a Pt / TiO2 catalyst, and the specific steps are as follows:

[0113] (1) Add 20 mL of isopropanol and 5 mL of titanium isopropoxide to 20 mL of water and stir at room temperature for 0.5 h to allow it to fully hydrolyze. Filter the solid product by centrifugation and dry it in an oven at 110 °C overnight to obtain a sample powder.

[0114] (2) The sample powder obtained in step (1) is calcined at 650°C in an air atmosphere for 2 hours to obtain a TiO2 carrier.

[0115] (3) Weigh 0.25 g of TiO2 carrier into a quartz photocatalytic reactor, add 45 mL of water, 5 mL of methanol, and 125 uL of chloroplatinic acid solution (containing Pt: 20 mg / mL); introduce argon into the reactor for 0.5 h, seal the reactor, and irradiate with UV light for 6 h at room temperature. Centrifuge and filter out the solid product, dry it overnight at room temperature, and obtain Pt / TiO2 catalyst, recorded as hv-1%Pt / TiO2 (homemade)-methanol.

[0116] Example 6: hv-1% Pt / TiO2 (commercially available)-methanol

[0117] Weigh 0.25 g of commercially available anatase TiO2 in a quartz photocatalytic reactor, add 45 mL of water, 5 mL of methanol, and 125 uL of chloroplatinic acid solution (containing Pt: 20 mg / mL); introduce argon into the reactor for 0.5 h, seal the reactor, and irradiate with ultraviolet light for 6 h at room temperature. Centrifuge and filter out the solid product, dry it overnight at room temperature, and obtain a Pt / TiO2 catalyst, recorded as hv-1% Pt / TiO2 (commercially available)-methanol.

[0118] Example 7: hv-0.5%Pt / TiO2 (homemade)-methanol

[0119] This embodiment provides a method for preparing a Pt / TiO2 catalyst, and the specific steps are as follows:

[0120] (1) Add 20 mL of isopropanol and 5 mL of titanium isopropoxide to 20 mL of water and stir at room temperature for 0.5 h to allow it to fully hydrolyze. Filter the solid product by centrifugation and dry it in an oven at 110 °C overnight to obtain a sample powder.

[0121] (2) The sample powder obtained in step (1) is calcined at 650°C in an air atmosphere for 2 hours to obtain a TiO2 carrier.

[0122] (3) Weigh 0.25 g of TiO2 carrier into a quartz photocatalytic reactor, add 45 mL of water, 5 mL of methanol, and 62.5 uL of chloroplatinic acid solution (containing Pt: 20 mg / mL); introduce argon into the reactor for 0.5 h, seal the reactor, and irradiate with UV light for 6 h at room temperature. Centrifuge and filter out the solid product, dry it overnight at room temperature, and obtain Pt / TiO2 catalyst, recorded as hv-0.5%Pt / TiO2 (homemade)-methanol.

[0123] Example 8: hv-0.5%Pt / TiO2 (commercially available)-methanol

[0124] This embodiment provides a method for preparing a Pt / TiO2 catalyst, and the specific steps are as follows:

[0125] Weigh 0.25 g of commercially available anatase TiO2 in a quartz photocatalytic reactor, add 45 mL of water, 5 mL of methanol, and 62.5 uL of chloroplatinic acid solution (containing Pt: 20 mg / mL); introduce argon into the reactor for 0.5 h, seal the reactor, and irradiate with ultraviolet light for 6 h at room temperature. Centrifuge and filter out the solid product, dry it overnight at room temperature, and obtain a Pt / TiO2 catalyst, recorded as hv-0.5%Pt / TiO2 (commercially available)-methanol.

[0126] Comparative Example 1: H2-1%Pt / TiO2 (commercially available)

[0127] This comparative example provides a method for preparing a Pt / TiO2 catalyst, and the specific steps are as follows:

[0128] Weigh 1 g of commercially available anatase TiO2 into a mortar, add 500 uL of chloroplatinic acid solution (Pt content: 20 mg / mL), and grind evenly.

[0129] The solid product was calcined at 550°C in a hydrogen atmosphere for 2 hours to obtain a Pt / TiO2 catalyst, recorded as H2-1%Pt / TiO2 (commercially available).

[0130] Comparative Example 2: H2-1%Pt / TiO2 (homemade)

[0131] This comparative example provides a method for preparing a Pt / TiO2 catalyst, and the specific steps are as follows:

[0132] (1) Add 20 mL of isopropanol and 5 mL of titanium isopropoxide to 20 mL of water and stir at room temperature for 0.5 h to allow it to fully hydrolyze. Filter the solid product by centrifugation and dry it in an oven at 110 °C overnight to obtain a sample powder.

[0133] (2) The sample powder obtained in step (1) was calcined at 650°C in an air atmosphere for 2 hours to obtain a TiO2 carrier.

[0134] (3) Weigh 1 g of TiO2 carrier into a mortar, add 500 μL of chloroplatinic acid solution (Pt content: 20 mg / mL), and grind evenly.

[0135] (4) The solid product was calcined at 550°C in a hydrogen atmosphere for 2 hours to obtain a Pt / TiO2 catalyst, denoted as H2-1%Pt / TiO2 (homemade).

[0136] Comparative Example 3: hv-1%Pt / P25-glycerol

[0137] This comparative example provides a method for preparing a Pt / TiO2 catalyst, and the specific steps are as follows:

[0138] Weigh 1 g of commercially available Degussa P25 in a quartz photocatalytic reactor, add 35 mL of water, 5 mL of glycerol, and 500 uL of chloroplatinic acid solution (containing Pt: 20 mg / mL); introduce argon into the reactor for 0.5 h, seal the reactor, and irradiate with ultraviolet light for 6 h at room temperature. Centrifuge and filter out the solid product, dry it overnight at room temperature, and obtain a Pt / TiO2 catalyst, recorded as hv-1%Pt / P25-glycerol.

[0139] Fig.21The transmission electron microscope images of the Pt / TiO2 catalysts prepared in Examples 1 to 6 are shown in the figure. As shown in the figure, the Pt / TiO2 catalysts have a particle stacking morphology, and it can be seen that the Pt particles of each Pt / TiO2 catalyst are evenly dispersed.

[0140] Scanning transmission electron microscopy-energy dispersive X-ray spectrometer (STEM-EDS) was used to detect the Ti, O, and Pt elements in the hv-1%Pt / TiO2 (homemade)-glycerol sample. Fig. 22 As shown, the Ti, O, and Pt elements of the hv-1%Pt / TiO2 (homemade)-glycerol sample are evenly distributed, and highly dispersed and evenly loaded Pt clusters can be seen on the sample surface.

[0141] Sample test: NH3-SCO activity test was carried out in a fixed bed quartz reactor with an inner diameter of 6 mm. 0.1 g of catalyst with a particle size of 40-60 mesh was placed in the tubular reactor. The test conditions were: 400 ppm NH3, 10 vol.% O2 and balance gas N2. The total flow rate was 500 mL / min and the mass space velocity (WHSV) was about 300,000 mL g -1 h -1 .

[0142] The performance of the Pt / TiO2 catalysts prepared in Examples 1 to 8 and Comparative Examples 1 and 2 was tested. Fig.23 , Fig.24 As shown. N2 selectivity is Fig.25 , Fig.26 shown. Fig.23 The glycerol aqueous solution system was used to prepare the photodeposition catalyst, in which the T of hv-1%Pt / TiO2(homemade)-glycerol and hv-1%Pt / TiO2(commercially available)-glycerol 90 The temperature at which the NH3 conversion rate reaches 90% is about 170℃ and 180℃, and the T of other Pt / TiO2 catalysts 90 Approximately 210℃ to 230℃. Fig.24 The methanol-water system was used to prepare the photodeposition catalyst. The T of hv-1%Pt / TiO2 (homemade)-methanol and hv-1%Pt-TiO2 (commercially available)-methanol 90 (The temperature at which NH3 conversion reaches 90%) is about 175℃ and 180℃. The T 90 It is about 210℃ to 230℃. This shows that at the same Pt ​​loading, the catalyst prepared by the photodeposition method has a significant effect on improving its low-temperature activity. In addition, the Pt / TiO2 catalyst samples prepared in Examples 1 to 8 and Comparative Examples 1 and 2 all have good N2 selectivity. 90The temperature reached above 65%. Among them, hv-1%Pt-TiO2 (commercially available)-methanol and hv-1%Pt-TiO2 (homemade)-methanol showed extremely excellent low-temperature activity and nitrogen selectivity.

[0143] Fig. 27 The NH3-SCO activity of Pt-TiO2 catalysts with different supports is shown. It can be clearly seen that the low-temperature activity of the Pt / TiO2 catalysts obtained by homemade TiO2 in the glycerol aqueous solution system and the methanol aqueous solution system is slightly better than that of the Pt / TiO2 catalysts obtained by commercial anatase TiO2 and commercial Degussa P25.

[0144] The mass percentage (wt%) of the Pt element in the Pt / TiO2 catalyst was determined by inductively coupled plasma optical emission spectroscopy (ICP-OES), and the relevant properties are shown in Table 1. When the loading amount was 1wt%, the Pt element content was measured to be between 0.86wt% and 1.01wt%, and when the loading amount was 0.5wt%, the Pt element content was measured to be 0.42wt% and 0.43wt%, so the method of loading Pt on the prepared Pt / TiO2 catalyst is feasible. The content of the Pt / TiO2 catalyst prepared by the deposition method is slightly lower, which may be due to the loss of some Pt ​​in the sample prepared by optical deposition.

[0145] Table 1 Physical and chemical properties of each Pt / TiO2 catalyst sample

[0146]

[0147] The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. Application of a Pt / TiO2 catalyst prepared by a photodeposition method in the field of selective oxidation and purification of ammonia into nitrogen. The method for preparing the Pt / TiO2 catalyst by a photodeposition method comprises the following steps: Providing anatase phase nano titanium dioxide; Mixing a platinum source, water and alcohol to prepare a platinum source solution; the volume ratio of water to alcohol in the platinum source solution is 1-10:1; the concentration of platinum element in the platinum source solution is 10-50 mg / mL, and the concentration of titanium dioxide is 10-50 g / L; The nano-titanium dioxide is placed in a platinum source solution, ultraviolet light is turned on for photodeposition reaction, and then the precipitate is filtered and dried to obtain a Pt / TiO2 catalyst.

2. The use according to claim 1, characterized in that: The method of providing anatase phase nano titanium dioxide comprises: hydrolyzing titanium isopropoxide or butyl titanate in an isopropanol aqueous solution, drying and calcining the hydrolysis product to obtain anatase phase nano titanium dioxide.

3. The use according to claim 1, characterized in that: The platinum source is one or more of chloroplatinic acid, platinum nitrate, platinum acetate, platinum chloride, and tetraammine platinum nitrate; and / or, The alcohol is one or more of methanol, ethanol, propanol, isopropanol and glycerol.

4. The use according to claim 1, characterized in that: The wavelength of ultraviolet light is in the range of 100-380 nm; and / or, The intensity of UV light is 2~100 W / m 2 and / or, The photodeposition reaction time is 0.1~10 hours.

5. An ammonia slip catalyst, characterized in that: It is used to be installed after a selective catalytic reduction reactor, and the ammonia slip catalyst comprises the Pt / TiO2 catalyst described in the application according to any one of claims 1 to 4.

6. A vehicle, characterized in that: Comprising the ammonia slip catalyst as claimed in claim 5.

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