A Pt(K)-Mn2O3 / SiO2 catalyst with strong Si-O-Mn and Mn-O-Pt bonds, and a preparation method and application thereof

Abstract

The application belongs to the technical field of catalysts, and particularly relates to a Pt(K)-Mn2O3 / SiO2 catalyst with strong Si-O-Mn bonds and Mn-O-Pt bonds, a preparation method and application thereof. The Pt(K)-Mn2O3 / SiO2 catalyst is prepared by the following method: (1) mixing mesoporous SiO2, a manganese salt solution and a citric acid solution, stirring, rotary evaporation, drying, and first calcination to obtain a Mn2O3 / SiO2 carrier; (2) loading Pt nanoparticles and K ions on the Mn2O3 / SiO2 carrier by an impregnation method; and (3) drying and second calcination to obtain the Pt(K)-Mn2O3 / SiO2 catalyst. By introducing citric acid, the application prevents the agglomeration of Mn2O3 in the calcination process, improves the strength of the Si-O-Mn bonds and Mn-O-Pt bonds, and thus enhances the activity and stability of the catalyst. The Pt(K)-Mn2O3 / SiO2 catalyst prepared by the application can be applied to the catalytic oxidation of acetone.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalysts, and particularly relates to a Pt(K)-Mn2O3 / SiO2 catalyst with strong Si-O-Mn bonds and Mn-O-Pt bonds, a preparation method thereof and application. BACKGROUND

[0002] With the rapid development of global industry, the environmental problems of modern industry tend to be complex. On the basis of the original industrial development, the environmental problems caused by emerging industries have deepened the current environmental pollution situation, and the atmospheric pollution problem has become increasingly serious worldwide. The massive emission of harmful gases not only poses a great threat to human health and the survival of organisms, but also poses a great threat to the ecological environment on which human beings depend. Volatile organic compounds (VOCs) are a major class of environmental pollutants and are considered the second major atmospheric pollutant after dust, mainly including non-methane hydrocarbons, oxygen-containing organic compounds (OVOCs), halogenated hydrocarbons, nitrogen-containing organic compounds and sulfur-containing organic compounds, etc., which are mainly derived from waste gas emissions of various industrial enterprises. VOCs have the characteristics of large emission, wide range, strong toxicity, easy volatilization, difficult prevention and control, etc. Among them, OVOCs have high reactivity and are easy to participate in atmospheric photochemical reactions, and have the characteristics of a large number of types, different properties, difficult collection and difficult treatment. The treatment of OVOCs and other VOCs is one of the frontiers of atmospheric pollution treatment. Acetone is one of the main OVOCs, which has high reactivity in the formation of ozone and secondary aerosols, and is harmful to human health and the atmosphere. In actual treatment of industrial enterprises, catalytic oxidation technology is usually used, mainly because this technology has the characteristics of simplicity, high efficiency, low temperature, and less by-products. The development of high-efficiency catalysts is one of the main tasks of catalytic oxidation technology, which is challenging.

[0003] Chinese patent application file CN108816272A discloses a preparation method of a microporous molecular sieve loaded iron-manganese two-component catalyst containing a vapor deposition method, and a method for catalytic oxidation and degradation of acetone using the microporous molecular sieve loaded iron-manganese two-component catalyst. The preparation method of the catalyst comprises the following steps: 1, solid-liquid mixture preparation; 2, ion exchange process; 3, material filling before vapor deposition; 4, first heat treatment; 5, second heat treatment; 6, third heat treatment. The catalyst has the advantages of safe operation, simple steps and low cost, but the active component of the catalyst prepared by the preparation method is not firmly loaded and is easy to be lost from the carrier during the reaction.

[0004] Chinese patent application file CN106669660A discloses a hierarchical structure MnO x / TiO2 nanofiber catalyst and preparation method thereof, the hierarchical structure MnO x / TiO2 nanofiber catalyst, comprising a primary structure and a secondary structure. The primary structure is a titanium dioxide nanofiber obtained by an electrospinning method, and the secondary structure is a manganese oxide nanoneedle obtained by crystal growth on the primary structure by a hydrothermal method. The MnO x Preparation method of / TiO2 nanofiber catalyst, using an electrospinning-hydrothermal synthesis method to prepare MnO x / TiO2 nanofiber, having a large specific surface area and high surface energy, can be applied to catalytic oxidation of VOCs, especially for acetone emitted in industrial tail gas. However, the required reaction temperature of the catalyst is high.

[0005] Chinese patent application file CN114570432A discloses an acetone oxidation catalyst, comprising metal framework material MOFs and metal nanoparticles NMPs, the metal organic framework material MOFs wraps the metal nanoparticles NMPs, the metal organic framework material MOFs is a carrier, and the metal nanoparticles NMPs are catalytic oxidation active centers. Continuous oxidation treatment of acetone under low temperature conditions is achieved. However, the preparation process is seriously polluted, the metal organic framework is easily damaged, and the catalyst stability is poor.

[0006] Therefore, how to provide a VOCs catalyst with low reaction temperature, high efficiency and stability is a technical problem to be solved by those skilled in the art. SUMMARY

[0007] The primary purpose of the present application is to provide a Pt(K)-Mn2O3 / SiO2(Pt-Mn / KS-xCA) catalyst with strong Si-O-Mn and Mn-O-Pt bonds and a preparation method thereof, aiming at the shortcomings and deficiencies of existing catalysts.

[0008] Another purpose of the present application is to provide the application of the above-mentioned Pt(K)-Mn2O3 / SiO2 catalyst.

[0009] One purpose of the present application is achieved by the following technical solutions:

[0010] A preparation method of a Pt(K)-Mn2O3 / SiO2 catalyst with strong Si-O-Mn and Mn-O-Pt bonds, comprising the following steps:

[0011] (1) dispersing mesoporous SiO2 in water to obtain solution A;

[0012] (2) mixing a manganese salt solution with a citric acid (CA) solution, stirring and aging to obtain solution B;

[0013] (3) mixing the solution A with the solution B, stirring, then rotary evaporation, drying, and then first calcination to obtain the Mn2O3 / SiO2 carrier;

[0014] (4) dispersing the Mn2O3 / SiO2 carrier, Pt nanoparticles and potassium salt obtained in step (3) in water, stirring, then rotary evaporation, drying, and second calcination to obtain the Pt(K)-Mn2O3 / SiO2 catalyst.

[0015] As a preference, the manganese salt is one of manganese nitrate, manganese sulfate, manganese chloride, and any hydrate thereof, or a mixture of several thereof in any ratio.

[0016] As a preference, the potassium salt is one of potassium nitrate, potassium sulfate, potassium chloride, potassium silicate, and any hydrate thereof, or a mixture of several thereof in any ratio.

[0017] As a preference, the Pt(K)-Mn2O3 / SiO2 catalyst contains Mn2O3 nanoparticles with an average particle size of 1.5-8.0 nm, further preferably 1.5-6.0 nm.

[0018] As a preference, the molar ratio of the manganese salt to citric acid is 1:15-1:1; further preferably, the molar ratio of the manganese salt to citric acid is 1:9-1:3; further preferably, the molar ratio of the manganese salt to citric acid is 1:6.

[0019] As a preference, the stirring aging time in step (2) is 1-4 h, the stirring time in step (3) is 4-8 h, and the stirring time in step (4) is 1-5 h.

[0020] As a preference, the rotary evaporation temperature is set at 40-80°C; further preferably, the rotary evaporation temperature is set at 50-70°C.

[0021] As a preference, the drying temperature in step (3) is set at 60-100°C, and the drying time is 4-8 h. An example is drying in an oven.

[0022] As a preference, the drying temperature in step (4) is set at 40-100°C, and the drying time is 4-8 h. An example is vacuum drying.

[0023] As a preference, the loading of Pt is 0.1-0.8 wt.%, the loading of K is 0.05-0.6 wt.%, and the loading of Mn is 2-8 wt.%.

[0024] As a preference, the loading of Pt is 0.2-0.6 wt.%, the loading of K is 0.1-0.4 wt.%, and the loading of Mn is 3-6 wt.%.

[0025] Further preferably, the loading amount of Pt is 0.3-0.4 wt.%, the loading amount of K is 0.2-0.3 wt.%, and the loading amount of Mn is 4-5 wt.%.

[0026] The loading amount of Mn refers to the mass ratio of Mn atoms contained in the added manganese salt to the mass of mesoporous SiO2 in the A solution, and the loading amount of Pt or K refers to the mass ratio of K atoms contained in the added potassium salt or the mass of Pt nanoparticles to the mass of Mn2O3 / SiO2 carrier.

[0027] As preferred, the first calcination temperature is 200-500°C, and the time is 3-6h.

[0028] Further preferably, the first calcination temperature is 300-400°C, and the time is 4-6h.

[0029] As preferred, the second calcination temperature is 200-400°C, and the time is 1-3h.

[0030] Further preferably, the second calcination temperature is 200-300°C, and the time is 2-3h.

[0031] As preferred, the calcination temperature increasing rate is 1-5°C / min.

[0032] The preparation method of mesoporous SiO2 is not particularly limited, and any preparation method of mesoporous SiO2 is within the protection scope of the present application. As listed, the preparation method of mesoporous SiO2 comprises the following steps:

[0033] (1) Dissolve cetyltrimethylammonium bromide in water, add concentrated ammonia, and stir;

[0034] (2) Add a mixed solution of n-hexane and tetraethyl orthosilicate drop by drop;

[0035] (3) Continue to stir to form a white and uniform emulsion solution;

[0036] (4) Collect the white solid by filtration, wash with water and anhydrous ethanol, and dry;

[0037] (5) Calcine the powder obtained in step (4) for 1-5h to obtain mesoporous SiO2.

[0038] In the above preparation method of mesoporous SiO2, as preferred, the mass percentage of the concentrated ammonia is 25-28 wt.%.

[0039] As preferred, the stirring time in the above method for preparing mesoporous SiO2 is 15-40 min. As preferred, the stirring temperature in step (3) is 30-40℃ and the stirring time is 10-14 h. As preferred, the drying temperature in step (4) is 50-80℃ and the drying time is 8-14 h, and further preferably, the drying temperature in step (4) is 60-70℃ and the drying time is 10-12 h. As preferred, the calcination temperature in step (5) is 400-700℃ and the calcination time is 3-6 h, and further preferably, the calcination temperature in step (5) is 500-600℃ and the calcination time is 4-5 h. As preferred, the heating rate in step (5) is 1℃ / min.

[0040] The method for preparing the Pt nanoparticles is not particularly limited, and any method for preparing Pt nanoparticles is within the protection scope of the present application. As an enumeration, the method for preparing the Pt nanoparticles comprises the following steps:

[0041] (1) dissolving sodium hydroxide in ethylene glycol solution, adding chloroplatinic acid hexahydrate, continuously stirring to form a yellow-brown solution;

[0042] (2) transferring the mixed solution into a three-neck flask, heating under the protection of nitrogen gas to obtain a black and uniform colloidal solution;

[0043] (3) cooling, adding dilute hydrochloric acid solution into the colloidal solution to adjust the pH value;

[0044] (4) adding ethanol with a mass ratio of 1:(0.5-2), and then collecting the Pt nanoparticles, and re-dispersing the collected Pt nanoparticles in ethanol containing polyvinylpyrrolidone (K30).

[0045] As preferred, the stirring in step (1) of the above method for preparing Pt nanoparticles is carried out at room temperature and the stirring time is 0.5-2 h. As preferred, the heating temperature in step (2) is 80-100℃ and the heating time is 1-4 h. As preferred, the pH value is 3-4.

[0046] The stirring rate in the present application is preferably 100-1000 rpm.

[0047] Another object of the present application is achieved by the following technical scheme:

[0048] The above Pt(K)-Mn2O3 / SiO2 catalyst is applied to the catalytic oxidation of acetone, and the reaction temperature (T 90 ) for achieving 90% conversion rate of acetone under normal pressure is only 180-193℃.

[0049] Compared with the prior art, the present application has the following beneficial effects:

[0050] 1, the introduction of citric acid, citric acid rich hydroxyl group can be complexation with Mn ions, thereby effectively isolated Mn ions, prevent the agglomeration of Mn2O3 in the calcination process; while the MnO2 in Pt-Mn / KS into Mn2O3 in Pt-Mn / KS-xCA.

[0051] 2, enhance the dispersibility of Mn2O3, reduce the average particle size of the loaded Mn2O3 nanoparticles, improve the catalytic activity.

[0052] 3, the appropriate amount of citric acid can be through the metal-support electronic interaction, improve the strength of Si-O-Mn bond and Mn-O-Pt bond, thereby improving the activity and stability of Pt(K)-Mn2O3 / SiO2 catalyst.

[0053] 4, the Pt(K)-Mn2O3 / SiO2 catalyst prepared by the present application has strong Si-O-Mn bond and Mn-O-Pt bond, and the stronger the strength of Si-O-Mn bond and Mn-O-Pt bond, the lower the T 90 , the stronger the catalytic performance of acetone. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 XDR spectra of examples 1-3 and comparative example 1;

[0055] Figure 2 TEM images of examples 1-3 and comparative example 1;

[0056] Figure 3 H2-TPR graphs of examples 1-3 and comparative example 1;

[0057] Figure 4 Infrared spectra of examples 1-3 and comparative example 1;

[0058] Figure 5 Raman spectra of examples 1-3 and comparative example 1;

[0059] Figure 6 UV-Vis absorption spectra of examples 1-3 and comparative example 1;

[0060] Figure 7 XPS graphs of Mn 2p, O 1s, Pt 2p of examples 1-3 and comparative example 1;

[0061] Figure 8 CA / Mn ratio (molar ratio of citric acid to Mn) and Pt 0 / Pt 2+ ratio and Mn 3+ / Mn 4+The relationship between the ratio and the absorbance / infrared wave number;

[0062] Figure 9 A schematic diagram of the effect of citric acid on the physical and chemical properties of the catalyst;

[0063] Figure 10 A comparison chart of the catalytic performance of the Pt-Mn / KS and Pt-Mn / KS-xCA catalysts of Examples 1-3 and Comparative Example 1 on the oxidation of acetone;

[0064] Figure 11 A comparison chart of the catalytic performance of the Pt-Mn / KS and Pt-Mn / KS-xCA catalysts of Examples 1-3 and Comparative Example 1 on the oxidation of acetone; 90 A chart of the relationship between the Si-O-Mn / Mn-O-Pt bond strength;

[0065] Figure 12 A chart of the long-term running stability test of the Pt-Mn / KS-6CA and Pt-Mn / KS catalysts of Example 2 and Comparative Example 1 on the catalytic oxidation of acetone. DETAILED DESCRIPTION

[0066] Hereinafter, the technical solutions of the present application will be further described and illustrated by specific examples and drawings. However, these examples are exemplary, and the disclosure of the present application is not limited thereto. The drawings used herein are merely for better illustration of the disclosed content of the present application, and do not have limiting effect on the scope of protection. If not specifically stated, the raw materials used in the following specific examples of the present application are all commonly used raw materials in the art, and the methods used in the examples are all conventional methods in the art.

[0067] In the following examples and comparative examples, the mesoporous SiO2 was prepared by the following method:

[0068] (1) 2.0 g of hexadecyltrimethylammonium bromide was dissolved in 300 mL of deionized water, 15.0 mL of concentrated ammonia water (28 wt.%) was added, and stirred for 20 min;

[0069] (2) A mixed solution of n-hexane (40 mL) and tetraethyl orthosilicate (10 mL) was added dropwise;

[0070] (3) Stirring was continued in a water bath at 35°C for 12 h to form a white uniform emulsion;

[0071] (4) The white solid was collected by filtration, washed with deionized water and anhydrous ethanol three times each, and dried in a vacuum drying oven at 60°C overnight;

[0072] (5) The powder obtained in (4) was calcined in a muffle furnace at 550°C for 4 h (heating rate 1°C / min) to obtain mesoporous SiO2.

[0073] The Pt nanoparticles were prepared by the following method:

[0074] (1) Dissolve 0.55 g of sodium hydroxide in 100 mL of ethylene glycol solution, add 0.5 g of chloroplatinic acid hexahydrate, continuously stir at room temperature for 1 h, and form a yellow-brown solution;

[0075] (2) Transfer the mixed solution into a three-necked flask, heat at 90°C for 2 h under nitrogen gas flow protection, and obtain a black uniform colloidal solution;

[0076] (3) Cool to room temperature, add an appropriate amount of dilute hydrochloric acid solution to the colloidal solution, and adjust the pH value to 3.5;

[0077] (4) Add ethanol in a mass ratio of 1:1, then centrifugally collect the Pt nanoparticles, and redispersed the collected Pt nanoparticles in ethanol containing 150 mg of polyvinylpyrrolidone (K30).

[0078] Example 1

[0079] The Pt(K)-Mn2O3 / SiO2 catalyst provided in this example has strong Si-O-Mn and Mn-O-Pt bonds, and is prepared by the following steps:

[0080] (1) Ultrasonically disperse 0.25 g of mesoporous SiO2 in 100 mL of deionized water to obtain an A solution;

[0081] (2) Mix 10 mL of a manganese nitrate solution (2.27×10 -2 mol / L) with 10 mL of a citric acid solution (6.81×10 - 2 mol / L), ultrasonically treat for 30 min, and stir and age for 2 h to obtain a B solution;

[0082] (3) Mix the A solution with the B solution, ultrasonically treat for 30 min, and then stir for 6 h, and then rotary evaporate at 60°C to remove excess water;

[0083] (4) Dry the sample obtained in (3) above in an oven at 80°C for 6 h;

[0084] (5) Calcine in a muffle furnace at 350°C for 4 h (temperature rising rate 2°C / min) to obtain a Mn / S-3CA material (molar ratio of citric acid / Mn is 3:1);

[0085] (6) Disperse 0.25 g of the Mn / S-3CA obtained in (5) in 8.75×10 -4 g of Pt nanoparticles and 1 mL of potassium nitrate (3.21×10 -2 mol / L) in 100 mL of deionized water, and ultrasonically treat for 30 min;

[0086] (7) stirring at room temperature for 3 h, rotary evaporation at 60 °C to remove excess water;

[0087] (8) drying the solid product obtained in (8) at 60 °C under vacuum for 6 h, calcination in a muffle furnace at 250 °C for 2 h (heating rate 2 °C / min) to obtain the Pt-Mn / KS-3CA material.

[0088] Example 2

[0089] The Pt(K)-Mn2O3 / SiO2catalyst provided in this example having strong Si-O-Mn and Mn-O-Pt bonds is prepared by the following steps:

[0090] (1) 0.25 g of mesoporous SiO2is ultrasonically dispersed in 100 mL of deionized water to obtain solution A;

[0091] (2) 10 mL of manganese nitrate solution (2.27 x 10 -2 mol / L) and 10 mL of citric acid solution (13.62 x 10 - 2 mol / L) are mixed, ultrasonically treated for 30 min, and stirred for aging for 2 h to obtain solution B;

[0092] (3) solution A is mixed with solution B, ultrasonically treated for 30 min, and stirred for 6 h, followed by rotary evaporation at 60 °C to remove excess water;

[0093] (4) the sample obtained in (3) above is dried in an oven at 80 °C for 6 h;

[0094] (5) calcination in a muffle furnace at 350 °C for 4 h (heating rate 2 °C / min) to obtain the Mn / S-6CA material (molar ratio of citric acid / Mn is 6:1);

[0095] (6) 0.25 g of Mn / S-6CA obtained in (5) is dispersed in 100 mL of deionized water with 8.75 x 10 -4 g of Pt nanoparticles and 1 mL of potassium nitrate (3.21 x 10 -2 mol / L), and ultrasonically treated for 30 min;

[0096] (7) stirring at room temperature for 3 h, rotary evaporation at 60 °C to remove excess water;

[0097] (8) drying the solid product obtained in (8) at 60 °C under vacuum for 6 h, calcination in a muffle furnace at 250 °C for 2 h (heating rate 2 °C / min) to obtain the Pt-Mn / KS-6CA material.

[0098] Example 3

[0099] The Pt(K)-Mn2O3 / SiO2 catalyst provided by the embodiment has strong Si-O-Mn bonds and Mn-O-Pt bonds and is prepared by the following steps:

[0100] (1) 0.25 g of mesoporous SiO2 was ultrasonically dispersed in 100 mL of deionized water to obtain an A solution;

[0101] (2) 10 mL of a manganese nitrate solution (2.27 x 10 -2 mol / L) and 10 mL of a citric acid solution (20.43 x 10 - 2 mol / L) were mixed, ultrasonically treated for 30 min, and stirred and aged for 2 h to obtain a B solution;

[0102] (3) The A solution and the B solution were mixed, ultrasonically treated for 30 min, and stirred for 6 h, followed by rotary evaporation at 60°C to remove excess water;

[0103] (4) The sample obtained in (3) was dried in an oven at 80°C for 6 h;

[0104] (5) Calcination was performed in a muffle furnace at 350°C for 4 h (the temperature was raised at a rate of 2°C / min) to obtain a Mn / S-3CA material (the molar ratio of citric acid to Mn was 9:1);

[0105] (6) 0.25 g of the Mn / S-9CA obtained in (5) was dispersed in 100 mL of deionized water together with 8.75 x 10 -4 g of Pt nanoparticles and 1 mL of potassium nitrate (3.21 x 10 -2 mol / L), and ultrasonically treated for 30 min;

[0106] (7) Stirring was performed at room temperature for 3 h, and rotary evaporation was performed at 60°C to remove excess water;

[0107] (8) The solid product obtained in (8) was vacuum dried at 60°C for 6 h, and calcination was performed in a muffle furnace at 250°C for 2 h (the temperature was raised at a rate of 2°C / min) to obtain a Pt-Mn / KS-9CA material.

[0108] Example 4

[0109] The Pt(K)-Mn2O3 / SiO2 catalyst provided by the embodiment has strong Si-O-Mn bonds and Mn-O-Pt bonds and is prepared by the following steps:

[0110] (1) 0.25 g of mesoporous SiO2 was ultrasonically dispersed in 100 mL of deionized water to obtain an A solution;

[0111] (2) 10 mL of a manganese nitrate solution (2.27 x 10 -2mol / L) and 10 mL of a citric acid solution (9.08 x 10 - 2 mol / L) was mixed, ultrasonicated for 30 min, and aged for 3 h with stirring to obtain solution B;

[0112] (3) Solution A was mixed with solution B, ultrasonicated for 30 min, and aged for 5 h with stirring, followed by rotary evaporation at 50°C to remove excess water;

[0113] (4) The sample obtained in (3) above was dried in an oven at 100°C for 4 h;

[0114] (5) Calcination in a muffle furnace at 300°C for 6 h (heating rate 2°C / min) to obtain the Mn / S-4CA material (molar ratio of citric acid / Mn was 4:1);

[0115] (6) 0.25 g of the Mn / S-4CA obtained in (5) was mixed with 8.75 x 10 -4 g of Pt nanoparticles and 1 mL of potassium nitrate (3.21 x 10 -2 mol / L) dispersed in 100 mL of deionized water, and ultrasonicated for 30 min;

[0116] (7) Stirring at room temperature for 3 h, and rotary evaporation at 60°C to remove excess water;

[0117] (8) The solid product obtained in (8) was dried at 50°C under vacuum for 8 h, and calcined in a muffle furnace at 200°C for 3 h (heating rate 2°C / min) to obtain the Pt-Mn / KS-4CA material.

[0118] Comparative Example 1

[0119] Comparative Example 1 differs from Example 1 only in that no citric acid was added in Comparative Example 1, and Comparative Example 1 obtained a Pt-Mn / KS material.

[0120] Characterization

[0121] The XRD patterns of Examples 1-3 and Comparative Example 1 are shown in Figure 1 .

[0122] As can be seen from Figure 1 , the diffraction peak at 2θ = 23.1° is attributed to mesoporous SiO2. The (211) crystal plane of MnO2was found in the XRD pattern of Pt-Mn / KS, while the other Pt-Mn / KS-xCA catalysts had no MnO2peak, indicating that the addition of citric acid enhanced the dispersibility of MnO x 2. The low content and high dispersion of Mn and Pt resulted in no corresponding diffraction peaks in the XRD patterns of the Pt-Mn / KS-xCA catalysts.

[0123] The TEM images of Examples 1-3 and Comparative Example 1 are shown inFigure 2 As shown.

[0124] from Figure 2 It can be seen that as the amount of citric acid added increases, MnO x The average particle size of the nanoparticles gradually decreases, with the size order being Pt-Mn / KS (9.0±2.1 nm) > Pt-Mn / KS-3CA (5.4±1.6 nm) > Pt-Mn / KS-6CA (4.1±0.2 nm) > Pt-Mn / KS-9CA (2.9±0.7 nm). This is because the citric acid added in this invention contains abundant hydroxyl groups, which can effectively isolate Mn ions through the complexation of hydroxyl groups with Mn, preventing MnO from escaping during calcination. x The reunion.

[0125] The H2-TPR diagrams of Examples 1-3 and Comparative Example 1 are shown below. Figure 3 As shown.

[0126] from Figure 3 It can be seen that Pt-Mn / KS-3CA (0.51 mmol·g) cal -1 Pt-Mn / KS-6CA (0.49 mmol·g) cal -1 ) and Pt-Mn / KS-9CA (0.48 mmol·g cal -1 The H2 consumption of Pt-Mn / KS is much lower than that of Pt-Mn / KS (1.30 mmol·g). cal -1 The main reduction peak of Pt-Mn / KS is attributed to the reduction process of MnO2→Mn2O3→Mn3O4→MnO. The main reduction peak of the Pt-Mn / KS-xCA catalyst is also attributed to the reduction process of Mn2O3→Mn3O4→MnO. H2-TPR results indicate that after the introduction of citric acid, MnO2 in Pt-Mn / KS is converted to Mn2O3 in Pt-Mn / KS-xCA.

[0127] The infrared spectra of Examples 1-3 and Comparative Example 1 are as follows: Figure 4 As shown.

[0128] from Figure 4 It can be seen that the SiO2 support at 458 cm⁻¹ -1 and 965cm -1 The peaks at these locations belong to the stretching vibrations of the Si-O bond and the Si-OH group, respectively. (Introduction of MnO...) x Subsequently, these two peaks were replaced by the Mn-O bond peak and the Si-O-Mn bond peak, respectively. Furthermore, with the increase of citric acid content, the Si-O-Mn bond peak first shifted red and then blue, indicating that the Si-O-Mn bond strength first increased and then decreased.

[0129] The Raman spectra of Example 1-3 and Comparative Example 1 are shown in Figure 5 .

[0130] It can be seen from Figure 5 that the small peak near 970 cm -1 belongs to Si-O-Mn bond. The peak intensity increases from Pt-Mn / KS to Pt-Mn / KS-6CA and decreases from Pt-Mn / KS-6CA to Pt-Mn / KS-9CA, which is consistent with the result of infrared spectrum. The peak at about 495 cm -1 is assigned to the bending vibration of O-Mn-O, and the Mn-O lattice stretching vibration of [MnO6] octahedron is located at about 605 cm -1 .

[0131] The UV-visible absorption spectra of Example 1-3 and Comparative Example 1 are shown in Figure 6 .

[0132] It can be seen from Figure 6 that the weak peak at about 520 nm belongs to Mn-O-Pt bond, and the greater the absorbance, the stronger the Mn-O-Pt bond. With the increase of the amount of citric acid, the Mn-O-Pt bond is first strong and then weak. Among them, Pt-Mn / KS-6CA has the strongest Mn-O-Pt bond.

[0133] The XPS graphs of Mn 2p, O 1s and Pt 2p of Example 1-3 and Comparative Example 1 are shown in Figure 7 .

[0134] It can be seen from Figure 7 that the Mn 3+ / Mn 4+ , O latt / O ads and Pt 0 / Pt 2+ ratios of the catalysts are in the order of Pt-Mn / KS-6CA < Pt-Mn / KS-9CA < Pt-Mn / KS-3CA < Pt-Mn / KS. With the increase of CA / Mn ratio, the ratios of the above three are first increased and then decreased.

[0135] The relationship between CA / Mn ratio and Pt 0 / Pt 2+ ratio and Mn 3+ / Mn 4+ ratio and absorbance / infrared wave number of Example 1-3 and Comparative Example 1 is shown in Figure 8 .

[0136] The higher the absorbance of UV-Vis spectrum, the stronger the Mn-O-Pt bond, and the greater the infrared wave number, the stronger the Si-O-Mn bond. From Figure 8 It can be seen that when the CA / Mn ratio is 0-6, the strength of Si-O-Mn bond and Mn-O-Pt bond gradually increases, and when the CA / Mn ratio is 6-9, the strength of Si-O-Mn bond and Mn-O-Pt bond decreases.

[0137] The effect of citric acid on the physical and chemical properties of the catalyst is shown in Figure 9 .

[0138] From Figure 9 It can be seen that compared with Pt-Mn / KS, the complexation of citric acid hydroxyl with Mn effectively prevents the agglomeration of Mn2O3, so that the dispersion of Mn2O3 on the surface of Pt-Mn / KS-6CA catalyst is better and the particle size is smaller. Therefore, appropriate amount of citric acid can improve the strength of Si-O-Mn bond and Mn-O-Pt bond through metal-support electronic interaction.

[0139] Catalytic performance

[0140] The catalytic performance of Pt-Mn / KS and Pt-Mn / KS-xCA catalysts obtained in Examples 1-3 and Comparative Example 1 for acetone oxidation is shown in Figure 10 .

[0141] T 90 represents the temperature at which the conversion rate of acetone is 90%. According to the T 90 value, it can be seen from Figure 10 that the catalytic activity of Pt-Mn / KS and Pt-Mn / KS-xCA is: Pt-Mn / KS-6CA (T 90 = 180℃) > Pt-Mn / KS-9CA (T 90 = 183℃) > Pt-Mn / KS-3CA (T 90 = 191℃) > Pt-Mn / KS (T 90 = 195℃), which is significantly affected by the amount of citric acid. Pt-Mn / KS-6CA shows the best catalytic activity for acetone oxidation.

[0142] The relationship between T 90 of Examples 1-3 and Comparative Example 1 and the strength of Si-O-Mn / Mn-O-Pt bond is shown in Figure 11 .

[0143] From Figure 11 it can be seen that T 90The Si-O-Mn bond and the Mn-O-Pt bond are negatively correlated with the strength. The Pt-Mn / KS-6CA has the strongest Si-O-Mn bond and the Mn-O-Pt bond, and thus exhibits the best catalytic performance.

[0144] The long-time running stability test results of the Pt-Mn / KS-6CA and the Pt-Mn / KS catalysts of Example 2 and Comparative Example 1 in the catalytic oxidation of acetone are shown in Table 2. Figure 12

[0145] 150 mg of the catalyst material was loaded into a fixed-bed catalytic reaction device, and acetone waste gas was mixed and heated in a furnace, with an acetone waste gas concentration of 1000 ppm, a total flow rate of 100 ml / min (a ratio of nitrogen and oxygen of 4:1), an airspeed of 40000 mL / (g.h), and a reaction furnace temperature controlled at 200 DEG C. The conversion rate of the catalyst to acetone was continuously measured, and the results are shown in Table 2. Figure 12 Figure 12 It can be seen from Table 2 that the catalytic effect of the Pt-Mn / KS-6CA catalyst on acetone can be maintained at a conversion rate close to 100% throughout the continuous experiment of about 250 h, while the initial conversion rate of the Pt-Mn / KS catalyst is low, and the conversion rate of acetone gradually decreases with the increase of the experimental time. This indicates that the Pt-Mn / KS-6CA catalyst has the characteristics of long service life and stable performance in the catalytic oxidation of acetone.

[0146] In summary, the present application introduces citric acid on the basis of the Pt-Mn / KS, effectively prevents the agglomeration of MnO x in the calcination process, converts MnO2 into Mn2O3, and effectively enhances the dispersibility thereof; at the same time, with the increase of the amount of citric acid introduced, the strength of the Si-O-Mn bond and the Mn-O-Pt bond first increases and then decreases, and the Pt-Mn / KS-6CA obtained when the molar ratio of the manganese salt to citric acid is 1:6 has the strongest Si-O-Mn bond and the Mn-O-Pt bond, and exhibits the strongest catalytic activity when applied to the catalytic oxidation of acetone.

[0147] The specific embodiments described herein are merely illustrative of the spirit of the present application. Those skilled in the art to which the present application belongs can make various modifications or supplements to the described specific embodiments or replace them with similar ways without departing from the spirit of the present application or exceeding the scope defined by the appended claims.​​

Claims

1. A method for preparing a Pt(K)-Mn2O3 / SiO2 catalyst having strong Si-O-Mn bonds and Mn-O-Pt bonds, characterized by, The method comprises the following steps: (1) dispersing mesoporous SiO2 in water to obtain solution A; (2) mixing a manganese salt solution with a citric acid solution, stirring and aging to obtain solution B; (3) mixing solution A with solution B, stirring, rotary evaporation, drying, and then first calcination to obtain a Mn2O3 / SiO2 carrier; (4) dispersing the Mn2O3 / SiO2 carrier obtained in step (3), Pt nanoparticles and a potassium salt in water, stirring, then rotary evaporation, drying, and second calcination to obtain a Pt(K)-Mn2O3 / SiO2 catalyst. The molar ratio of the manganese salt to citric acid is 1:9-1:

1.

2. The method for preparing a Pt(K)-Mn203 / Si02 catalyst according to claim 1, characterized by, The manganese salt is one of manganese nitrate, manganese sulfate, manganese chloride, and any hydrate thereof, or a mixture of several thereof in any ratio.

3. The method for preparing a Pt(K)-Mn203 / Si02 catalyst according to claim 1, characterized by, The potassium salt is one of potassium nitrate, potassium sulfate, potassium chloride, potassium silicate, and any hydrate thereof, or a mixture of several thereof in any ratio.

4. The method for preparing a Pt(K)-Mn203 / Si02 catalyst according to claim 1, characterized by, The Pt(K)-Mn2O3 / SiO2 catalyst contains Mn2O3 nanoparticles with an average particle size of 1.5-8.0 nm.

5. The method for preparing a Pt(K)-Mn203 / Si02 catalyst according to claim 1, characterized by, The loading of Pt is 0.1-0.8 wt.%, the loading of K is 0.05-0.6 wt.%, and the loading of Mn is 2-8 wt.%.

6. The method for preparing a Pt(K)-Mn203 / Si02 catalyst according to claim 1, characterized by, The first calcination temperature is 200-500 ℃, and the time is 3-6 h.

7. The method for preparing a Pt(K)-Mn203 / Si02 catalyst according to claim 1, characterized by, The second calcination temperature is 200-400 ℃, and the time is 1-3 h.

8. A Pt(K)-Mn2O3 / SiO2 catalyst prepared by the method of any one of claims 1-7.

9. Use of the Pt(K)-Mn2O3 / SiO2 catalyst of claim 8 in the catalytic oxidation of acetone.

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