High-activity platinum-carbon catalyst, preparation method thereof and application of high-activity platinum-carbon catalyst in catalytic purification of formaldehyde

Abstract

The invention belongs to the technical field of catalysts, and relates to a high-activity platinum-carbon catalyst, a preparation method thereof and application of the high-activity platinum-carbon catalyst in catalytic purification of formaldehyde. The invention discloses a high-activity platinum-carbon catalyst which is of a core-shell structure and is characterized in that porous metal modified pore-expanded activated carbon M-AC is taken as a core, a TiO2 nano layer is deposited on the surface of the core, and Pt-coated TiO2 is loaded on the surface of the TiO2 nano layer; the metal M in the porous metal modified chambering activated carbon M-AC is one or two of alkali metals K and Na; the TiO2 nano layer on the surface of the porous metal modified chambering activated carbon M-AC is partially migrated to the surfaces of platinum nano particles to form Pt-coated TiO2. The invention further discloses the high-activity platinum-carbon catalyst which has a good formaldehyde catalytic purification effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and relates to a highly active platinum-carbon catalyst, a preparation method thereof, and an application thereof in catalytic purification of formaldehyde. Background Art

[0002] As one of the most typical and harmful pollutants indoors, formaldehyde seriously threatens human health and has thus attracted wide attention from the public. In the field of household air purification, traditional activated carbon adsorption materials have been used for a long time due to their porous characteristics, but their inherent defects are becoming increasingly prominent: the limited adsorption capacity leads to significant timeliness limitations in their purification effect.

[0003] In recent years, noble metal catalytic oxidation technology has attracted great attention from the academic community due to its breakthrough degradation efficiency, and the catalyst system supported on porous materials has become a research hotspot. However, this technical system still faces key scientific bottlenecks: there are essential defects in the noble metal dispersion mechanism. Active components represented by platinum (Pt) nanoparticles are prone to surface migration and aggregation during high-temperature activation, resulting in a continuous decline in the effective exposure rate of active sites. At the same time, the electronic interaction between the support and the metal interface is weak, and it is difficult to form a stable chemical bond, resulting in serious insufficient stability of the catalyst. At present, there is no effective synergistic mechanism between improving catalytic activity and maintaining long-term stability, and a systematic breakthrough needs to be achieved through carrier structure design, interface engineering regulation, and reaction mechanism innovation. Summary of the Invention

[0004] The object of the present invention is to address the above problems existing in the prior art and propose a highly active platinum-carbon catalyst with a core-shell structure, which takes porous metal-modified expanded activated carbon M-AC as the core, deposits a TiO 2 nanolayer on the surface of the core, and a platinum nanoparticle is further loaded on the surface of the TiO 2 nanolayer, and the surface of the platinum nanoparticle is coated with a TiO 2 nanolayer; the highly active platinum-carbon catalyst with this structure has a good catalytic purification effect on formaldehyde.

[0005] One object of the present invention is achieved through the following technical solutions: A highly active platinum-carbon catalyst has a core-shell structure, which takes porous metal-modified expanded activated carbon M-AC as the core, deposits a TiO 2 nanolayer on the surface of the core, and a platinum nanoparticle coated with a TiO 2 nanolayer is loaded on the surface of the TiO 2 nanolayer, Pt@TiO 2 ; The metal M in the porous metal-modified expanded activated carbon M-AC is one or two of alkali metals K and Na; The TiO on the surface of the porous metal-modified expanded activated carbon M-AC2 The nano-layer partially migrates to the surface of platinum nanoparticles to form a coating of TiO 2 The platinum nanoparticles of the nano-layer Pt@TiO 2 .

[0006] Preferably, the high-activity platinum-carbon catalyst uses porous metal-modified expanded activated carbon M-AC as the core, deposits a TiO 2 nano-layer containing trivalent titanium on the core surface, and then loads platinum nanoparticles on the surface of the TiO 2 nano-layer. Subsequently, part of the TiO 2 nano-layer migrates to the surface of the platinum nanoparticles to form platinum nanoparticles Pt@TiO 2 coated with the TiO 2 .

[0007] More preferably, the high-activity platinum-carbon catalyst uses porous metal-modified expanded activated carbon M-AC as the core, deposits a TiO 2 nano-layer containing trivalent titanium on the core surface through a hydrothermal reaction, and then loads platinum nanoparticles on the surface of the TiO 2 nano-layer through microwave treatment. Subsequently, it is calcined in an atmosphere to make part of the TiO 2 nano-layer migrate to the surface of the platinum nanoparticles to form platinum nanoparticles Pt@TiO 2 coated with the TiO 2 .

[0008] Preferably, the average particle size of the porous metal-modified expanded activated carbon M-AC is 1 μm to 10 mm.

[0009] Preferably, the average particle size of the porous metal-modified expanded activated carbon M-AC is 500 to 10 mesh.

[0010] More preferably, the average particle size of the porous metal-modified expanded activated carbon M-AC is 200 to 20 mesh.

[0011] Preferably, the thickness of the TiO 2 nano-layer wrapped on the surface of the porous metal-modified expanded activated carbon M-AC is 0.1 to 10 nm.

[0012] More preferably, the thickness of the TiO 2 nano-layer wrapped on the surface of the porous metal-modified expanded activated carbon M-AC is 0.1 to 5 nm.

[0013] Even more preferably, the thickness of the TiO 2 nano-layer wrapped on the surface of the porous metal-modified expanded activated carbon M-AC is 1 to 3 nm.

[0014] Preferably, the coated TiO 2Platinum nanoparticles Pt@TiO with a nanolayer 2 has an average particle size of 0.1 to 10 nm.

[0015] Further preferably, the TiO 2 nanolayer-coated platinum nanoparticles Pt@TiO 2 has an average particle size of 0.2 to 4 nm.

[0016] Preferably, the average thickness of the TiO 2 nanolayer coated on the surface of the platinum nanoparticles is 0.5 to 5 nm.

[0017] Further preferably, the average thickness of the TiO 2 nanolayer coated on the surface of the platinum nanoparticles is 1 to 2 nm.

[0018] Preferably, the method for preparing the TiO 2 nanolayer coated on the surface of the platinum nanoparticles includes: heating Pt / TiO 2 / M-AC in a reducing atmosphere to 300 - 700 °C and reacting for 1 - 6 h.

[0019] Further preferably, the Pt / TiO 2 / M-AC has a porous metal-modified expanded pore activated carbon M-AC as the core, deposits a TiO 2 nanolayer on the core surface, and platinum nanoparticles are also loaded on the surface of the TiO 2 nanolayer.

[0020] Further preferably, the reducing atmosphere is a 1 - 10 vol.% H 2 / N 2 mixed gas.

[0021] Further preferably, the reducing atmosphere can be replaced by an inert atmosphere, and the inert atmosphere includes one or two of nitrogen and helium.

[0022] Further preferably, the heating temperature is 450 - 540 °C, the time is 2 - 4 h, and the heating rate is 1 - 5 °C / min.

[0023] Preferably, the specific surface area of the porous metal-modified expanded pore activated carbon M-AC is 910 - 980 m 2 / g.

[0024] More preferably, the specific surface area of the porous metal-modified expanded pore activated carbon M-AC is 940 - 970 m 2 / g.

[0025] Preferably, the porous metal-modified expanded pore activated carbon M-AC is prepared by alkali leaching and calcining activated carbon AC.

[0026] Preferably, the preparation method of the porous metal-modified expanded activated carbon M-AC includes: impregnating activated carbon in an alkaline solution, ultrasonicating, standing, drying, and then roasting in nitrogen at 400-800 °C for 1-12 h to obtain it.

[0027] More preferably, the specific surface area of the activated carbon is 980-1100 m 2 / g.

[0028] More preferably, the alkaline solution is one or two of KOH solution and NaOH solution.

[0029] Preferably, the specific surface area of the porous metal-modified expanded activated carbon M-AC < the specific surface area of the activated carbon AC.

[0030] Preferably, the raw materials of the TiO 2 nano-layer deposited on the surface of the porous metal-modified expanded activated carbon M-AC include a titanium source, urea, a reducing agent, and an organic solvent.

[0031] Preferably, the 60-99% platinum nanoparticles are in the metallic state Pt.

[0032] Preferably, in the highly active platinum-carbon catalyst, the loading amount of platinum nanoparticles is 0.05-0.3 wt.%.

[0033] Preferably, based on AC, the Pt loading amount is 0.1-0.5 wt.%.

[0034] The second object of the present invention is achieved by the following technical solution: A preparation method of a highly active platinum-carbon catalyst, including: (1) Impregnating activated carbon in an alkaline solution, ultrasonicating, standing, drying, and then roasting in nitrogen to obtain metal-modified expanded activated carbon M-AC; (2) Dissolving a titanium source, urea, and a reducing agent in an organic solvent, adding the metal-modified expanded activated carbon M-AC in (1) and mixing evenly, and after hydrothermal reaction, vacuum drying to obtain TiO 2 / M-AC; (3) Dissolving a platinum source and an organic complexing agent in water, adding the TiO 2 / M-AC in (2) and mixing evenly, and performing microwave treatment at a power of 600-1000 W and a frequency of 1-3 GHz for 1-120 min to obtain Pt / TiO 2 / M-AC; (4) In a mixed gas of hydrogen / nitrogen or an inert atmosphere, heating and roasting Pt / TiO 2 / M-AC to obtain a highly active platinum-carbon catalyst Pt@TiO 2 / K-AC.

[0035] Preferably, the alkaline solution in (1) is one or more of KOH solution and NaOH solution.

[0036] Preferably, the molar ratio of the titanium source, urea, and reducing agent in (2) is 1:(1 - 5):(0.5 - 2).

[0037] Preferably, the mass - to - volume ratio of the titanium source and the organic solvent in (2) is (0.1 - 5) g:500 ml.

[0038] Preferably, the titanium source in (2) is one or more of titanium isopropoxide, titanium ethoxide, titanium methoxide, titanium octylate, tetrabutyl titanate, and tert - butyl titanate.

[0039] Preferably, the reducing agent in (2) is one or more of ascorbic acid, ethylene glycol, sodium sulfite, dimercaprol, and sodium thiosulfate.

[0040] Preferably, the organic solvent in (2) is one or more of ethylene glycol methyl ether, acetone, dichloromethane, ethanol, methanol, and tetrahydrofuran.

[0041] Preferably, the mass ratio of the titanium source and M - AC in (2) is (0.8 - 2):20.

[0042] Preferably, the hydrothermal reaction temperature in (2) is 130 - 280 °C and the time is 1 - 24 h.

[0043] Preferably, the TiO 2 / M - AC's TiO 2 nano - layer contains trivalent titanium.

[0044] Preferably, the Pt / TiO 2 / M - AC has a porous metal - modified expanded - pore activated carbon M - AC as the core, deposits a TiO 2 nano - layer on the core surface, and then loads platinum nanoparticles on the surface of the TiO 2 nano - layer.

[0045] More preferably, 60 - 99% of the platinum nanoparticles are metallic platinum.

[0046] Preferably, the platinum source in (3) is one or more of platinum nitrate, tetraammineplatinum nitrate, and chloroplatinic acid.

[0047] Preferably, the mass ratio of the platinum source and the organic complexing agent in (3) is 1:(1 - 10).

[0048] Preferably, the organic complexing agent in (3) is one or more of citric acid, tartaric acid, and gluconic acid.

[0049] Preferably, the mass ratio of the platinum source to TiO 2 / M-AC is 1:(100 - 200).

[0050] Preferably, the hydrogen content in the hydrogen / nitrogen mixed gas in (4) is 1 - 20 vol.%.

[0051] More preferably, the hydrogen content in the hydrogen / nitrogen mixed gas in (4) is 2 - 8 vol.%.

[0052] Preferably, the temperature-raising calcination temperature in (4) is 300 - 800 °C, and the time is 1 - 12 h.

[0053] More preferably, the temperature-raising calcination temperature in (4) is 400 - 600 °C, and the time is 2 - 5 h.

[0054] The third object of the present invention is achieved by the following technical solutions: An application of a high-activity platinum-carbon catalyst in the catalytic purification of formaldehyde.

[0055] Preferably, the application includes: at room temperature, loading 10 - 100 mg of the high-activity platinum-carbon catalyst into a glass reaction tube; one end of the glass reaction tube is connected to a formaldehyde generating device, and the other end is connected to a gas concentration detector. Set the gas flow rate and volumetric space velocity of the formaldehyde generating device to make the generated formaldehyde gas concentration reach the set value of 100 - 300 ppm, and continuously introduce the formaldehyde gas into the glass reaction tube. At this time, as the starting time of the test, record the formaldehyde concentration and carbon dioxide concentration at stages within 48 h from the start of the test.

[0056] More preferably, the gas flow rate is 10 - 500 mL / min, and the volumetric space velocity is 100000 - 300000 h -1 . More preferably, the relative humidity in the glass reaction tube is 30 - 90%.

[0057] More preferably, the test time > 0 h, the formaldehyde removal rate > 98%, the carbon dioxide yield > 98%, and the carbon dioxide selectivity is 100%.

[0058] Even more preferably, within 0.5 - 24 h after the start of the test, the formaldehyde removal rate is 100%, the carbon dioxide yield is 100%, and the carbon dioxide selectivity is 100%.

[0059] More preferably, within 24 - 48 h after the start of the test, the formaldehyde removal rate is 93 - 100%.

[0060] Compared with the prior art, the present invention has the following beneficial effects: 1. The high-activity platinum-carbon catalyst of the present invention has a core-shell structure, which takes porous metal-modified expanded activated carbon M-AC as the core, deposits a TiO 2 nanolayer on the surface of the core, and also loads Pt@TiO 2 on the surface of the TiO 2 nanolayer; the TiO 2 nanolayer on the surface of the platinum nanoparticles in Pt@TiO 2 limits the agglomeration of platinum nanoparticles, improves the dispersion and stability of platinum nanoparticles. At the same time, the TiO 2 nanolayer in Pt@TiO 2 has an electronic modification effect on platinum nanoparticles, which is beneficial to the catalyst to activate oxygen and water and improve the activity of the catalyst; 2. The high-activity platinum-carbon catalyst of the present invention takes porous metal-modified expanded activated carbon M-AC as the core. The modification of alkali metals enhances hydrophilicity and metal loading sites; and the alkali metals, as catalytic aids, are beneficial to significantly improve the effect of the catalyst for oxidizing formaldehyde at room temperature; 3. In the preparation process of the TiO 2 / M-AC TiO 2 nanolayer of the present invention, organic solvents are selected to inhibit grain agglomeration, urea is used to regulate the hydrothermal environment to form a uniform TiO 2 nanolayer, and reducing agents promote the generation of Ti 3+ ; and the trivalent titanium contained in the TiO 2 nanolayer promotes the formation of a coating layer on the surface of platinum particles under a high-temperature atmosphere; 4. In the preparation method of the high-activity platinum-carbon catalyst of the present invention, after depositing a TiO 2 nanolayer on the surface of porous metal-modified expanded activated carbon M-AC, microwave treatment is carried out. The complexing agent chelates platinum ions, and small-sized platinum nanoparticles are rapidly generated on the surface of the TiO 2 nanolayer, and the platinum nanoparticles in the obtained Pt / TiO 2 / M-AC have high dispersion; at the same time, metallic platinum is obtained during the microwave process; 5. The present invention adopts temperature-programmed reduction (TPR) interface reconstruction to partially migrate the TiO 2 nanolayer to the surface of platinum nanoparticles and wrap it to form a Pt@TiO 2 core-shell structure; 6. The high-activity platinum-carbon catalyst of the present invention is used for catalytic purification of formaldehyde, with a high formaldehyde removal rate; and a high carbon dioxide selectivity and no secondary pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1TEM mapping of AC and its EDS spectrum adopted by the present invention.

[0062] Figure 2 TEM mapping of K-AC and its EDS spectrum in Example 1 of the present invention.

[0063] Figure 3 TEM mapping of TiO 2 / K-AC and its EDS spectrum.

[0064] Figure 4 TEM mapping of Pt@TiO 2 / K-AC and its EDS spectrum.

[0065] Figure 5 TEM mapping of Pt@TiO 2 / K-AC STEM image.

[0066] Figure 6 STEM image of Pt / TiO 2 / K-AC (left), STEM image of Pt@TiO 2 / K-AC (right).

[0067] Figure 7 EPR spectrum of TiO 2 / K-AC. Detailed implementation manners

[0068] The technical solution of the present invention will be further described and illustrated through specific examples below. It should be understood that the specific examples described here are only used to help understand the present invention and are not used to specifically limit the present invention.

[0069] Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commonly used raw materials in the art, and the methods used in the embodiments are all conventional methods in the art.

[0070] In this article, the preparation method of the highly active platinum-carbon catalyst includes: (1) Immerse activated carbon in an alkaline solution with a concentration of 1-20 wt.%, ultrasonic for 1-60 min, then stand for 6-48 h, dry, and then calcine at 400-800 °C for 1-12 h under nitrogen protection to obtain metal-modified and pore-expanded activated carbon M-AC; The M is one or both of K and Na; (2) Dissolve a titanium source, urea, and a reducing agent with a mass ratio of 1:(1 - 5):(2 - 10) in an organic solvent, add the metal-modified mesoporous activated carbon M-AC in (1), mix well, and conduct a hydrothermal reaction at 130 - 280 °C for 1 - 24 h, followed by vacuum drying to obtain TiO 2 / M-AC; (3) Dissolve a platinum source and an organic complexing agent with a mass ratio of 1:(1 - 10) in water, add the TiO 2 / M-AC in (2), mix well, and conduct microwave treatment at a power of 600 - 1000 W and a frequency of 1 - 3 GHz for 1 - 120 min to obtain Pt / TiO 2 / M-AC; (4) In a mixed gas of 1 - 20 vol.% hydrogen / nitrogen or an inert atmosphere, place the Pt / TiO 2 / M-AC in a furnace and heat it from room temperature to 300 - 800 °C at a heating rate of 1 - 10 °C / min, and then calcine it at 300 - 800 °C for 1 - 12 h to obtain the Pt@TiO 2 / K-AC catalyst.

[0071] In this article, the high-activity platinum-carbon catalyst has a core-shell structure, with mesoporous metal-modified mesoporous activated carbon M-AC with an average particle size of 1 μm - 10 mm as the core, and a TiO 2 nanolayer with an average thickness of 0.1 - 10 nm is deposited on the core surface. On the surface of this TiO 2 nanolayer, platinum nanoparticles Pt@TiO 2 coated with a TiO 2 nanolayer are loaded; The platinum nanoparticles Pt@TiO 2 coated with a TiO 2 nanolayer have an average particle size of 0.1 - 10 nm, and the average thickness of the TiO 2 nanolayer coated on its surface is 0.5 - 5 nm; The metal M in the mesoporous metal-modified mesoporous activated carbon M-AC is one or two of alkali metals K and Na.

[0072] Example 1

[0073] The structure of the Pt@TiO 2 / K-AC catalyst in this example is a core-shell structure, with mesoporous metal-modified mesoporous activated carbon K-AC with an average particle size of 50 mesh as the core, and a TiO 2 nanolayer is deposited on the core surface. On the surface of the TiO 2 nanolayer, platinum nanoparticles with an average particle size of 3 nm and coated with an average thickness of 1 nm of a TiO 2 nanolayer are also loaded.

[0074] (1) Take 20 g of activated carbon AC (specific surface area ~980 m2 / g), it was immersed in 400 ml of 8 wt.% KOH solution, ultrasonicated for 30 min, then left standing for 12 h, filtered, dried at 100 °C for 6 h, and then calcined at 600 °C for 3 h under nitrogen protection to obtain potassium-modified mesoporous activated carbon K-AC; According to the BET test, the specific surface area of K-AC is 950 m 2 / g; Figure 1 , 2 Figure 3-10 are the TEM mapping and EDS spectra of activated carbon AC and potassium-modified mesoporous activated carbon K-AC, indicating that K is uniformly distributed in the activated carbon.

[0075] (2) 5 mmol of titanium isopropoxide, 10 mmol of urea, and 5 mmol of ascorbic acid were dissolved in 500 ml of ethylene glycol monomethyl ether, 20 g of K-AC was added, and the mixture was stirred at room temperature for 2 h; then it was transferred to a reaction kettle and hydrothermally reacted at 180 °C for 10 h, cooled and dried in vacuo to obtain TiO 2 / K-AC; The electron micrograph and EDS spectrum of TiO 2 / K-AC are shown in Figure 3 , indicating that the positions of Ti and C elements are similar and both are uniformly distributed, suggesting that the surface of K-AC is covered with a TiO 2 nanolayer with an average thickness of 1.5 nm.

[0076] The EPR spectrum of TiO 2 / K-AC is shown in Figure 7 , indicating that there are trivalent titanium ions in TiO 2 / K-AC.

[0077] (3) 0.1 g of platinum nitrate and 0.3 g of citric acid were dissolved in 50 ml of water, 15 g of TiO 2 / K-AC was added, ultrasonically dispersed for 30 min, then placed in a microwave reactor, microwave-treated at a power of 800 W and a frequency of 2.45 GHz for 10 min, taken out, washed with water and dried to obtain Pt / TiO 2 / M-AC, on the surface of which Pt nanoparticles with an average particle size of 2 nm are uniformly dispersed; (4) In a 5 vol.% hydrogen / nitrogen mixed gas, Pt / TiO 2 / M-AC was heated to 500 °C and kept at this temperature for 3 h to obtain a core-shell structured Pt@TiO 2 / K-AC catalyst.

[0078] According to Figures 4 - 6 It can be seen that in the Pt@TiO 2 / K-AC catalyst, TiO 2Partial migration and coating of Pt nanoparticles to form Pt@TiO 2 core-shell structure, TiO 2 The average thickness of the coating layer is 1 nm.

[0079] Example 2

[0080] The Pt@TiO of this example 2 / K-AC catalyst structure is a core-shell structure. Using porous metal with an average particle size of 500 mesh to modify the expanded pore activated carbon K-AC as the core, TiO 2 nanolayer is deposited on the core surface. On the TiO 2 nanolayer surface, there is also loaded with platinum nanoparticles with an average particle size of 2.7 nm and coated with an average thickness of 1.2 nm of TiO 2 nanolayer.

[0081] (1) Immerse 20 g of activated carbon AC (specific surface area ~980 m 2 / g) in 300 ml of a KOH solution with a concentration of 7 wt.%, ultrasonic for 30 min, then let it stand for 12 h, filter and dry at 100 °C for 6 h, and then calcine at 500 °C for 4 h under nitrogen protection to obtain potassium-modified expanded pore activated carbon K-AC; (2) Dissolve 5 mmol of tetrabutyl titanate, 10 mmol of urea, and 5 mmol of ethylene glycol in 500 ml of acetone, add 20 g of K-AC, and stir at room temperature for 2 h; then transfer to a reaction kettle and hydrothermal react at 180 °C for 10 h, cool and dry in vacuum to obtain TiO 2 / K-AC; (3) Dissolve 0.1 g of tetraammineplatinum nitrate and 0.3 g of citric acid in 50 ml of water, add 20 g of TiO 2 / K-AC, ultrasonic disperse for 30 min, then place it in a microwave reactor, microwave treat at a power of 800 W and a frequency of 2.45 GHz for 10 min, take it out, wash with water and dry to obtain Pt / TiO 2 / K-AC, on its surface are uniformly dispersed Pt nanoparticles with an average particle size of 1.5 nm; (4) In a mixed gas of 6 vol.% hydrogen / nitrogen, heat Pt / TiO 2 / K-AC to 550 °C and keep it warm for 3 h to obtain the core-shell structure Pt@TiO 2 / K-AC catalyst.

[0082] Example 3

[0083] The Pt@TiO of this example 2The structure of the Pt@TiO₂ / Na-AC catalyst is a core-shell structure. The core is porous metal-modified and expanded pore activated carbon Na-AC with an average particle size of 10 mesh. A TiO₂ nano-layer is deposited on the surface of the core. 2 On the surface of the TiO₂ 2 nano-layer, platinum nanoparticles with an average particle size of 4 nm and coated with a TiO₂ nano-layer with an average thickness of 1.5 nm are also loaded. 2

[0084] (1) 20 g of activated carbon AC (specific surface area ~980 m² / g) was impregnated in 500 ml of an 8 wt.% NaOH solution. After ultrasonic treatment for 30 min, it was left standing for 12 h. After filtration, it was dried at 100 °C for 6 h, and then calcined at 600 °C for 3 h under nitrogen protection to obtain sodium-modified and expanded pore activated carbon Na-AC. 2 (2) 5 mmol of tetrabutyl titanate, 10 mmol of urea, and 5 mmol of ascorbic acid were dissolved in 500 ml of ethylene glycol monomethyl ether. 20 g of Na-AC was added, and the mixture was stirred at room temperature for 2 h. Then it was transferred to a reaction kettle and hydrothermally reacted at 180 °C for 10 h. After cooling, it was dried under vacuum to obtain TiO₂ / Na-AC. 2 (3) 0.12 g of chloroplatinic acid and 0.3 g of tartaric acid were dissolved in 50 ml of water. 15 g of TiO₂ / Na-AC was added, and it was ultrasonically dispersed for 30 min. Then it was placed in a microwave reactor and microwave-treated at a power of 800 W and a frequency of 2.45 GHz for 10 min. After taking it out, it was washed with water and dried to obtain Pt / TiO₂ / Na-AC. 2 2 (4) In a mixed gas of 10 vol.% hydrogen / nitrogen, Pt / TiO₂ / M-AC was heated to 550 °C and held for 3 h to obtain the core-shell structured Pt@TiO₂ / Na-AC catalyst. 2 2

[0085] Example 4

[0086] The structure of the Pt@TiO₂ / Na-AC catalyst in this example is a core-shell structure. The core is porous metal-modified and expanded pore activated carbon Na-AC with an average particle size of 70 mesh. A TiO₂ nano-layer is deposited on the surface of the core. 2 2 On the surface of the TiO₂ 2 nano-layer, platinum nanoparticles with an average particle size of 3 nm and coated with a TiO₂ nano-layer with an average thickness of 1.5 nm are also loaded. 2

[0087] (1) 20 g of activated carbon AC (specific surface area ~980 m² / g) was impregnated in 500 ml of an 8 wt.% NaOH solution. 2 / g) was impregnated in 500 ml of 8 wt.% NaOH solution, sonicated for 30 min, then left standing for 12 h, filtered, dried at 100 °C for 6 h, and then calcined at 600 °C for 3 h under nitrogen protection to obtain sodium-modified mesoporous activated carbon Na-AC; (2) 5 mmol of tetrabutyl titanate, 10 mmol of urea, and 5 mmol of ascorbic acid were dissolved in 500 ml of ethylene glycol monomethyl ether, 20 g of Na-AC was added, and the mixture was stirred at room temperature for 2 h; then it was transferred to a reaction kettle and hydrothermally reacted at 180 °C for 10 h, cooled and dried in vacuo to obtain TiO 2 / Na-AC; (3) 0.12 g of chloroplatinic acid and 0.3 g of tartaric acid were dissolved in 50 ml of water, 15 g of TiO 2 / Na-AC was added, sonicated for 30 min, then placed in a microwave reactor, microwave-treated at a power of 800 W and a frequency of 2.45 GHz for 10 min, taken out, washed with water and dried to obtain Pt / TiO 2 / Na-AC; (4) In nitrogen, Pt / TiO 2 / M-AC was heated to 600 °C and held for 3 h to obtain a core-shell structured Pt@TiO 2 / Na-AC catalyst, the average particle size of Pt was 1.5 nm, and the average thickness of the TiO 2 coating layer was 1.5 nm.

[0088] Comparative Example 1 The structure of the Pt@TiO 2 -AC' catalyst prepared in this comparative example was: using activated carbon AC with an average particle size of 50 mesh as the core, depositing a TiO 2 nanolayer on the core surface, and a platinum nanoparticle with an average particle size of 3.5 nm and a TiO 2 nanolayer with an average coating thickness of 1.5 nm was also loaded on the surface of the TiO 2 nanolayer.

[0089] (1) 10 g of activated carbon AC (specific surface area ~980 m 2 / g) was calcined at 600 °C for 3 h under nitrogen protection to obtain activated carbon AC'; (2 - 4) were carried out according to steps (2 - 4) of Example 1.

[0090] Comparative Example 2 The structure of the Pt@TiO 2 / K-AC catalyst prepared in this comparative example was: using porous metal-modified mesoporous activated carbon K-AC with an average particle size of 50 mesh as the core, depositing a TiO 2 nanolayer on the core surface, and on the TiO 2The surface of the nano-layer is also loaded with platinum nanoparticles with an average particle size of 2.2 nm, and the surface is coated with TiO with an average thickness of 0.2 nm. 2 nano-layer of the platinum nanoparticles.

[0091] (1) Conduct according to step (1) of Example 1; (2) Dissolve 5 mmol of titanium isopropoxide and 10 mmol of urea in 500 ml of ethylene glycol methyl ether, add 20 g of K-AC, and stir at room temperature for 2 h; then transfer to a reaction kettle, carry out hydrothermal reaction at 180 °C for 10 h, and dry in vacuum after cooling to obtain TiO 2 / K-AC; (3 - 4) Conduct according to steps (3 - 4) of Example 1.

[0092] Comparative Example 3 The Pt@TiO 2 / K-AC catalyst structure prepared in this comparative example is: using porous metal with an average particle size of 50 mesh to modify the expanded pore activated carbon K-AC as the core, depositing TiO 2 nano-layer on the core surface, and on the surface of the TiO 2 nano-layer is also loaded with platinum nanoparticles with an average particle size of 3 nm, and there is no obvious TiO 2 nano-layer on the surface of the platinum nanoparticles.

[0093] (1) Conduct according to step (1) of Example 1.

[0094] (2) Dissolve 5 mmol of titanium isopropoxide in 400 ml of ethylene glycol methyl ether, add 20 g of K-AC, stir at room temperature for 2 h, dropwise add 100 ml of water, continue to stir at room temperature for 12 h, and then dry in vacuum at 60 °C for 12 h to obtain TiO 2 / K-AC; (3 - 4) Conduct according to steps (3 - 4) of Example 1.

[0095] Comparative Example 4 The Pt@TiO 2 / K-AC catalyst structure prepared in this comparative example is: using porous metal with an average particle size of 50 mesh to modify the expanded pore activated carbon K-AC as the core, depositing TiO 2 nano-layer on the core surface, and on the surface of the TiO 2 nano-layer is also loaded with platinum nanoparticles with an average particle size of 3.2 nm, and the surface is coated with TiO with an average thickness of 1.5 nm 2 nano-layer of the platinum nanoparticles.

[0096] (1 - 2) Conduct according to steps (1 - 2) of Example 1.

[0097] (3) Dissolve 0.1 g of tetraammineplatinum nitrate in 50 ml of water, add 20 g of TiO2 / K-AC, ultrasonically disperse for 30 min, then place it in a microwave reactor and microwave-treat it at a power of 800 W and a frequency of 2.45 GHz for 10 min. After taking it out, wash it with water and dry it to obtain Pt / TiO 2 / M-AC; (4)Carry out according to step (4) of Example 1.

[0098] Comparative Example 5 The Pt@TiO prepared in this comparative example 2 / K-AC catalyst structure is: using porous metal-modified expanded pore activated carbon K-AC with an average particle size of 50 mesh as the core, depositing a TiO 2 nano-layer on the core surface, and on the TiO 2 nano-layer surface, there is also a platinum nanoparticle with an average particle size of 4 nm and a TiO with an average coating thickness of 1.5 nm coated on its surface 2 nano-layer.

[0099] (1~2)Carry out according to steps (1~2) of Example 1.

[0100] (3)Dissolve 0.1 g of tetraammineplatinum nitrate and 0.3 g of citric acid in 50 ml of water, add 20 g of TiO 2 / K-AC, ultrasonically disperse for 30 min to obtain Pt / TiO 2 / M-AC; (4)Carry out according to step (4) of Example 1.

[0101] Comparative Example 6 The Pt@TiO prepared in this comparative example 2 / K-AC catalyst structure is: using porous metal-modified expanded pore activated carbon K-AC with an average particle size of 50 mesh as the core, depositing a TiO 2 nano-layer on the core surface, and on the TiO 2 nano-layer surface, there is also a platinum nanoparticle with an average particle size of 3 nm, and there is no obvious TiO 2 nano-layer on the surface of the platinum nanoparticle.

[0102] (1~3)Carry out according to steps (1~3) of Example 1 to obtain Pt / TiO 2 / M-AC.

[0103] (4)In a mixed gas of 5 vol.% hydrogen / nitrogen, heat Pt / TiO 2 / M-AC to 200 °C and keep it warm for 3 h to obtain the catalyst Pt / TiO 2 / M-AC.

[0104] Comparative Example 7 The Pt@TiO prepared in this comparative example2 The structure of the / K-AC catalyst is as follows: porous metal with an average particle size of 50 mesh is used to modify the pore-expanded activated carbon K-AC as the core, and a TiO 2 nano-layer is deposited on the surface of the core. On the surface of the TiO 2 nano-layer, platinum oxide nanoparticles with an average particle size of 3 nm are also loaded, and there is no obvious TiO 2 nano-layer on the surface of the platinum oxide nanoparticles.

[0105] (1 - 3) are carried out according to the steps (1 - 3) of Example 1 to obtain Pt / TiO 2 / M-AC.

[0106] (4) In a mixed gas of 20 vol.% oxygen / nitrogen in air, heat Pt / TiO 2 / M-AC to 500 °C and keep it for 3 h to obtain the catalyst PtO / TiO 2 / M-AC.

[0107] Application Example 1 At room temperature of 25 °C, load 60 mg of the highly active platinum-carbon catalyst of Example 1 into a quartz glass reaction tube with an inner diameter of 4 mm, and keep the relative humidity of the quartz glass reaction tube at 60%; use an inert gas to remove air and maintain a constant pressure in the reaction tube. One end of the quartz glass reaction tube is connected to a formaldehyde generation device, and the other end is connected to a gas concentration detector. Set the gas flow rate of the formaldehyde generation device to 100 mL / min and the volumetric space velocity to 100,000 h -1 . After the formaldehyde gas generation concentration reaches the set value of 150 ppm stably, continuously introduce the formaldehyde gas into the quartz glass reaction tube. At this time, it is used as the starting time of the test. Record the formaldehyde concentration and carbon dioxide concentration at 0.5 h, 1 h, 3 h, 12 h, 24 h, and 48 h after the start of the test, as shown in Table 1.

[0108] Table 1. Data table of the catalytic performance of the highly active platinum-carbon catalyst in Example 1

[0109] Formaldehyde removal rate = [(initial formaldehyde concentration - remaining formaldehyde concentration) / initial formaldehyde concentration] × 100%.

[0110] CO 2 Yield = [generated carbon dioxide concentration / initial formaldehyde concentration] × 100%.

[0111] It can be seen that from 0.5 h to 24 h after the start of the test, the formaldehyde removal rate is 100% and the carbon dioxide selectivity is 100%. After 48 h of the start of the test, the formaldehyde removal rate drops to 95%.

[0112] Application Examples 2 - 4 According to the steps of Application Example 1, the catalysts in Examples 2 to 4 were used for formaldehyde purification, and the results are shown in Table 2.

[0113] Application Comparative Examples 1 to 7 According to the steps of Application Example 1, the catalysts in Comparative Examples 1 to 7 were used for formaldehyde purification, and the results are shown in Table 2.

[0114] Application Comparative Example 8 According to the steps of Application Example 1, Pt / TiO in Example 1(3) 2 / M-AC was used for formaldehyde purification, and the results are shown in Table 2.

[0115] Application Comparative Examples 9 to 10 According to the steps of Application Example 1, K-AC and AC in Example 1(1) were used for formaldehyde purification, and the results are shown in Table 2.

[0116] Table 2. Performance Results of Platinum Carbon Catalysts for Formaldehyde Purification

[0117] In summary, the high-activity platinum carbon catalyst of the present invention has a core-shell structure, with porous metal-modified expanded pore activated carbon M-AC as the core. The modification of alkali metal elements enhances hydrophilicity and metal loading sites, and at the same time acts as a catalyst promoter, which is beneficial to significantly improving the effect of the catalyst for room-temperature oxidation of formaldehyde; a TiO containing trivalent titanium is deposited on the surface of the M-AC core 2 nanolayer; platinum nanoparticles are also loaded on the surface of the TiO 2 nanolayer. During the high-temperature treatment process, under the action of trivalent titanium, the TiO deposited on the surface of the M-AC core 2 nanolayer migrates to the surface of the platinum particles to form a coating layer, so that the surface of the platinum nanoparticles is loaded with a coated TiO 2 nanolayer; the TiO on the surface of the platinum nanoparticles 2 nanolayer restricts the aggregation of platinum nanoparticles, improves the dispersion and stability of platinum nanoparticles, and at the same time the coating layer TiO 2 has an electronic modification effect on the platinum particles, which is beneficial to the catalyst to activate oxygen and water and improve the activity of the catalyst.

[0118] All aspects, embodiments, and features of the present invention should be considered illustrative in all respects and do not limit the present invention. The scope of the present invention is only defined by the claims. Without departing from the spirit and scope of the claimed invention, those skilled in the art will appreciate other embodiments, modifications, and uses.

[0119] In the preparation method of the present invention, the order of each step is not limited to the listed order. For those of ordinary skill in the art, without creative efforts, the changes in the sequence of each step are also within the protection scope of the present invention. In addition, two or more steps or actions can be carried out simultaneously.

[0120] Finally, it should be noted that the specific embodiments described herein are merely illustrative of the present invention and do not limit the implementation manners of the present invention. Those skilled in the technical field to which the present invention pertains can make various modifications or supplements to the described specific embodiments or use similar ways for substitution. It is not necessary and impossible to list all implementation manners here. And these obvious changes or variations derived from the essential spirit of the present invention still fall within the protection scope of the present invention. Interpreting them as any additional restrictions is contrary to the spirit of the present invention.

Claims

1. A highly active platinum-carbon catalyst, characterized in that: The high-activity platinum carbon catalyst is a core-shell structure, which uses porous metal modified expanded pore activated carbon M-AC as the core, a TiO2 nanolayer is deposited on the surface of the core, and platinum nanoparticles Pt@TiO2 coated with the TiO2 nanolayer are loaded on the surface of the TiO2 nanolayer; The metal M in the porous metal modified expanded pore activated carbon M-AC is one or two of alkali metals K and Na; The TiO2 nanolayer on the surface of the porous metal modified expanded pore activated carbon M-AC partially migrates to the surface of the platinum nanoparticles to form platinum nanoparticles Pt@TiO2 coated with the TiO2 nanolayer.

2. The highly active platinum-carbon catalyst according to claim 1, characterized in that The average particle size of the porous metal modified expanded pore activated carbon M-AC is 1 μm to 10 mm.

3. The highly active platinum-carbon catalyst according to claim 1, characterized in that The thickness of the TiO2 nanolayer coated on the surface of the porous metal modified expanded pore activated carbon M-AC is 0.1-10 nm; the average particle size of the platinum nanoparticles Pt@TiO2 coated with the TiO2 nanolayer is 0.1-10 nm.

4. The highly active platinum-carbon catalyst according to claim 1, characterized in that The specific surface area of ​​the porous metal modified expanded pore activated carbon M-AC is less than the specific surface area of ​​the activated carbon AC.

5. The highly active platinum-carbon catalyst according to claim 1, characterized in that The high-activity platinum-carbon catalyst has a porous metal-modified expanded pore activated carbon M-AC as the core, a TiO2 nanolayer containing trivalent titanium is deposited on the surface of the core, platinum nanoparticles are then loaded on the surface of the TiO2 nanolayer, and then part of the TiO2 nanolayer migrates to the surface of the platinum nanoparticles to form platinum nanoparticles coated with the TiO2 nanolayer.

6. A method for preparing the highly active platinum-carbon catalyst according to claim 1, the method comprising: (1) The activated carbon is immersed in an alkaline solution, allowed to stand and dried after ultrasonic treatment, and then calcined in nitrogen to obtain metal-modified expanded pore activated carbon M-AC; (2) dissolving the titanium source, urea and reducing agent in an organic solvent, adding the metal-modified expanded pore activated carbon M-AC prepared in (1) and mixing, performing a hydrothermal reaction, and vacuum drying to obtain TiO2 / M-AC; (3) dissolving the platinum source and the organic complexing agent in water, adding the TiO2 / M-AC prepared in (2) and mixing, and subjecting the mixture to microwave treatment at a power of 600-1000 W and a frequency of 1-3 GHz for 1-120 min to obtain Pt / TiO2 / M-AC; (4) In a hydrogen / nitrogen mixed gas or inert atmosphere, Pt / TiO2 / M-AC is calcined at a high temperature to obtain a highly active platinum-carbon catalyst Pt@TiO2 / K-AC.

7. The method for preparing a highly active platinum-carbon catalyst according to claim 6, characterized in that: The mass ratio of the platinum source to the organic complexing agent in (3) is 1:(1-10); the organic complexing agent is one or more of citric acid, tartaric acid, and gluconic acid.

8. The method for preparing a highly active platinum-carbon catalyst according to claim 6, characterized in that: The content of hydrogen in the hydrogen / nitrogen mixed gas of (4) is 1-20 vol.%; the calcination temperature of (4) is 300-800°C, and the calcination time is 1-12 hours.

9. Application of a highly active platinum-carbon catalyst in catalytic purification of formaldehyde, characterized in that: The application includes: at room temperature, 10 to 100 mg of the high-activity platinum carbon catalyst as described in any one of claims 1 to 5 or the high-activity platinum carbon catalyst prepared by the preparation method of the high-activity platinum carbon catalyst as described in any one of claims 6 to 8 is loaded into a glass reaction tube; one end of the glass reaction tube is connected to a formaldehyde generator, and the other end is connected to a gas concentration detector, the gas flow rate and volume space velocity of the formaldehyde generator are set so that the formaldehyde gas concentration reaches a set value of 100 to 300 ppm, and the formaldehyde gas is continuously introduced into the glass reaction tube. This time is taken as the test start time, and the formaldehyde concentration and carbon dioxide concentration are recorded within 48 hours from the start of the test.

10. Use of the high-activity platinum-carbon catalyst according to claim 9 in catalytic purification of formaldehyde, characterized in that: The test time is >0h, the formaldehyde removal rate is >98%, and the carbon dioxide selectivity is 100%.

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