A highly active platinum-carbon catalyst, its preparation method and its application in catalytic purification of formaldehyde

Abstract

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. The present invention discloses a highly active platinum-carbon catalyst, which has a core-shell structure. It uses porous metal-modified and pore-expanded activated carbon M-AC as the core, deposits a TiO₂ nano-layer on the surface of the core, and loads Pt@TiO₂ on the surface of the TiO₂ nano-layer; the metal M in the porous metal-modified and pore-expanded activated carbon M-AC is one or two of alkali metals K and Na; part of the TiO₂ nano-layer on the surface of the porous metal-modified and pore-expanded activated carbon M-AC migrates to the surface of platinum nanoparticles to form Pt@TiO₂. The present invention also discloses that the highly active platinum-carbon catalyst has a good catalytic purification effect on formaldehyde.

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 thus has been widely focused on by 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. Among them, 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. The 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 electron 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, no effective synergistic mechanism has been established 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 TiO2 nanolayer on the core surface, and also loads platinum nanoparticles on the surface of the TiO2 nanolayer, and the surface of the platinum nanoparticles is coated with a TiO2 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:

[0006] 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 TiO2 nanolayer on the core surface, and loads platinum nanoparticles Pt@TiO2 coated with a TiO2 nanolayer on the surface of the TiO2 nanolayer;

[0007] In the porous metal-modified expanded activated carbon M-AC, the metal M is one or two of alkali metals K and Na;

[0008] Part of the TiO2 nanolayer on the surface of the porous metal-modified expanded activated carbon M-AC migrates to the surface of the platinum nanoparticles to form platinum nanoparticles Pt@TiO2 coated with a TiO2 nanolayer.

[0009] Preferably, 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 core surface, platinum nanoparticles are 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 Pt@TiO2 coated with the TiO2 nanolayer.

[0010] More preferably, 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 core surface by hydrothermal reaction, platinum nanoparticles are loaded on the surface of the TiO2 nanolayer by microwave treatment, and then calcination in an atmosphere is carried out to make part of the TiO2 nanolayer migrate to the surface of the platinum nanoparticles to form platinum nanoparticles Pt@TiO2 coated with the TiO2 nanolayer.

[0011] Preferably, the average particle size of the porous metal-modified expanded pore activated carbon M-AC is 1 μm to 10 mm.

[0012] Preferably, the average particle size of the porous metal-modified expanded pore activated carbon M-AC is 500 to 10 mesh.

[0013] More preferably, the average particle size of the porous metal-modified expanded pore activated carbon M-AC is 200 to 20 mesh.

[0014] Preferably, the thickness of the TiO2 nanolayer coated on the surface of the porous metal-modified expanded pore activated carbon M-AC is 0.1 to 10 nm.

[0015] More preferably, the thickness of the TiO2 nanolayer coated on the surface of the porous metal-modified expanded pore activated carbon M-AC is 0.1 to 5 nm.

[0016] Even more preferably, the thickness of the TiO2 nanolayer coated on the surface of the porous metal-modified expanded pore activated carbon M-AC is 1 to 3 nm.

[0017] Preferably, the average particle size of the platinum nanoparticles Pt@TiO2 coated with the TiO2 nanolayer is 0.1 to 10 nm.

[0018] More preferably, the average particle size of the platinum nanoparticles Pt@TiO2 coated with the TiO2 nanolayer is 0.2 to 4 nm.

[0019] Preferably, the average thickness of the TiO2 nanolayer coated on the surface of the platinum nanoparticles is 0.5 to 5 nm.

[0020] More preferably, the average thickness of the TiO2 nanolayer coated on the surface of the platinum nanoparticles is 1 to 2 nm.

[0021] Preferably, the method for preparing the TiO2 nanolayer coated on the surface of the platinum nanoparticles comprises: heating Pt / TiO2 / M-AC in a reducing atmosphere to 300-700 °C for reaction for 1-6 h.

[0022] More preferably, the Pt / TiO2 / M-AC has a 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 are further loaded on the surface of the TiO2 nanolayer.

[0023] More preferably, the reducing atmosphere is a 1-10 vol.% H2 / N2 mixed gas.

[0024] More preferably, the reducing atmosphere can be replaced by an inert atmosphere, and the inert atmosphere includes one or two of nitrogen and helium.

[0025] More preferably, the heating temperature is 450-540 °C, the time is 2-4 h, and the heating rate is 1-5 °C / min.

[0026] Preferably, the specific surface area of the porous metal-modified expanded pore activated carbon M-AC is 910-980 m 2 / g.

[0027] Even more preferably, the specific surface area of the porous metal-modified expanded pore activated carbon M-AC is 940-970 m 2 / g.

[0028] Preferably, the porous metal-modified expanded pore activated carbon M-AC is obtained by subjecting activated carbon AC to alkali leaching and calcination.

[0029] Preferably, the method for preparing the porous metal-modified expanded pore activated carbon M-AC comprises: impregnating activated carbon in an alkaline solution, ultrasonicating, standing, drying, and then calcining in nitrogen at 400-800 °C for 1-12 h to obtain.

[0030] More preferably, the specific surface area of the activated carbon is 980-1100 m 2 / g.

[0031] More preferably, the alkaline solution is one or two of a KOH solution and an NaOH solution.

[0032] Preferably, the specific surface area of the porous metal-modified expanded pore activated carbon M-AC < the specific surface area of the activated carbon AC.

[0033] Preferably, the raw materials for the TiO2 nanolayer deposited on the surface of the porous metal-modified expanded pore activated carbon M-AC include a titanium source, urea, a reducing agent, and an organic solvent.

[0034] Preferably, the 60-99% platinum nanoparticles are metallic Pt.

[0035] Preferably, in the highly active platinum-carbon catalyst, the loading amount of platinum nanoparticles is 0.05-0.3 wt.%.

[0036] Preferably, based on AC, the Pt loading amount is 0.1-0.5 wt.%.

[0037] The second object of the present invention is achieved by the following technical solutions:

[0038] A preparation method of a highly active platinum-carbon catalyst, comprising:

[0039] (1) Immerse activated carbon in an alkaline solution, ultrasonicate, stand still, dry, and then calcine in nitrogen to obtain metal-modified and pore-expanded activated carbon M-AC;

[0040] (2) Dissolve a titanium source, urea, and a reducing agent in an organic solvent, add the metal-modified and pore-expanded activated carbon M-AC in (1), mix well, carry out a hydrothermal reaction, and then vacuum dry to obtain TiO2 / M-AC;

[0041] (3) Dissolve a platinum source and an organic complexing agent in water, add the TiO2 / M-AC in (2), mix well, and carry out 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;

[0042] (4) In a mixed gas of hydrogen / nitrogen or an inert atmosphere, heat up and calcine Pt / TiO2 / M-AC to obtain a highly active platinum-carbon catalyst Pt@TiO2 / K-AC.

[0043] Preferably, the alkaline solution in (1) is one or more of a KOH solution and an NaOH solution.

[0044] Preferably, the molar ratio of the titanium source, urea, and the reducing agent in (2) is 1:(1-5):(0.5-2).

[0045] Preferably, the mass-volume ratio of the titanium source and the organic solvent in (2) is (0.1-5) g:500 ml.

[0046] Preferably, the titanium source in (2) is one or more of titanium isopropoxide, tetraethyl titanate, methyl titanate, octyl titanate, tetrabutyl titanate, and tert-butyl titanate.

[0047] Preferably, the reducing agent in (2) is one or more of ascorbic acid, ethylene glycol, sodium sulfite, dimercaprol, and sodium thiosulfate.

[0048] Preferably, the organic solvent in (2) is one or more of ethylene glycol methyl ether, acetone, dichloromethane, ethanol, methanol, and tetrahydrofuran.

[0049] Preferably, the mass ratio of the titanium source to M-AC in (2) is (0.8~2):20.

[0050] Preferably, the hydrothermal reaction temperature in (2) is 130~280 °C, and the time is 1~24 h.

[0051] Preferably, the TiO2 nano-layer of TiO2 / M-AC in (2) contains trivalent titanium.

[0052] Preferably, in (3), Pt / TiO2 / M-AC uses porous metal-modified expanded pore activated carbon M-AC as the core, deposits a TiO2 nano-layer on the core surface, and then loads platinum nanoparticles on the surface of the TiO2 nano-layer.

[0053] More preferably, 60~99% of the platinum nanoparticles are metallic platinum.

[0054] Preferably, the platinum source in (3) is one or more of platinum nitrate, tetraammineplatinum nitrate, and chloroplatinic acid.

[0055] Preferably, the mass ratio of the platinum source to the organic complexing agent in (3) is 1:(1~10).

[0056] Preferably, the organic complexing agent in (3) is one or more of citric acid, tartaric acid, and gluconic acid.

[0057] Preferably, the mass ratio of the platinum source to TiO2 / M-AC in (3) is 1:(100~200).

[0058] Preferably, the hydrogen content in the hydrogen / nitrogen mixed gas in (4) is 1~20 vol.%.

[0059] More preferably, the hydrogen content in the hydrogen / nitrogen mixed gas in (4) is 2~8 vol.%.

[0060] Preferably, the temperature-raising calcination temperature in (4) is 300~800 °C, and the time is 1~12 h.

[0061] More preferably, the temperature-raising calcination temperature in (4) is 400~600 °C, and the time is 2~5 h.

[0062] The third object of the present invention is achieved by the following technical solutions:

[0063] An application of a highly active platinum-carbon catalyst in the catalytic purification of formaldehyde.

[0064] Preferably, the application includes: at room temperature, loading 10-100 mg of highly active platinum-carbon catalyst into a glass reaction tube; one end of the 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 and volumetric space velocity of the formaldehyde generation device to make the generated concentration of formaldehyde gas 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 within 48 h from the start of the test.

[0065] More preferably, the gas flow rate is 10-500 mL / min, and the volumetric space velocity is 100,000-300,000 h -1 . More preferably, the relative humidity in the glass reaction tube is 30-90%.

[0066] More preferably, the test time > 0 h, the formaldehyde removal rate > 98%, the carbon dioxide production rate > 98%, and the carbon dioxide selectivity is 100%.

[0067] Even more preferably, within 0.5-24 h after the start of the test, the formaldehyde removal rate is 100%, the carbon dioxide production rate is 100%, and the carbon dioxide selectivity is 100%.

[0068] More preferably, within 24-48 h after the start of the test, the formaldehyde removal rate is 93-100%.

[0069] Compared with the prior art, the present invention has the following beneficial effects:

[0070] 1. The highly active platinum-carbon catalyst of the present invention has a core-shell structure, which uses porous metal-modified expanded pore activated carbon M-AC as the core, deposits a TiO2 nanolayer on the core surface, and also loads Pt@TiO2 on the surface of the TiO2 nanolayer; the TiO2 nanolayer on the surface of the platinum nanoparticles in Pt@TiO2 restricts the aggregation of platinum nanoparticles, improves the dispersion and stability of platinum nanoparticles. At the same time, the TiO2 nanolayer in Pt@TiO2 has an electronic modification effect on platinum nanoparticles, which is beneficial to the activation of oxygen and water by the catalyst and improves the activity of the catalyst;

[0071] 2. The highly active platinum-carbon catalyst of the present invention uses porous metal-modified expanded pore activated carbon M-AC as the core, and the modification of alkali metals enhances hydrophilicity and metal loading sites; and alkali metals as catalytic aids are beneficial to significantly improving the effect of the catalyst for oxidizing formaldehyde at room temperature;

[0072] 3. In the preparation process of the TiO2 nanolayer of TiO2 / M-AC of the present invention, organic solvents are selected to inhibit grain aggregation, urea is used to regulate the hydrothermal environment to form a uniform TiO2 nanolayer, and reducing agents promote Ti 3+Generated; and the trivalent titanium contained in the TiO2 nanolayer promotes the formation of a coating layer on the surface of platinum particles in a high-temperature atmosphere;

[0073] 4. In the preparation method of the highly active platinum-carbon catalyst of the present invention, after depositing a TiO2 nanolayer on the surface of porous metal-modified and pore-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 TiO2 nanolayer, and the platinum nanoparticles in the obtained Pt / TiO2 / M-AC have a high dispersion degree; at the same time, metallic platinum is obtained during the microwave process;

[0074] 5. The present invention adopts temperature-programmed reduction (TPR) interface reconstruction to partially migrate the TiO2 nanolayer to the surface of platinum nanoparticles and wrap it to form a Pt@TiO2 core-shell structure;

[0075] 6. The highly active platinum-carbon catalyst of the present invention is used for catalytic purification of formaldehyde, and has a high formaldehyde removal rate; and has a high carbon dioxide selectivity and no secondary pollution. Brief Description of the Drawings

[0076] Figure 1 It is the TEM mapping and EDS spectrum of the AC adopted by the present invention.

[0077] Figure 2 It is the TEM mapping and EDS spectrum of K-AC in Example 1 of the present invention.

[0078] Figure 3 It is the TEM mapping and EDS spectrum of TiO2 / K-AC in Example 1 of the present invention.

[0079] Figure 4 It is the TEM mapping and EDS spectrum of Pt@TiO2 / K-AC in Example 1 of the present invention.

[0080] Figure 5 It is the STEM image of Pt@TiO2 / K-AC in Example 1 of the present invention.

[0081] Figure 6 It is the STEM image of Pt / TiO2 / K-AC (left) and the STEM image of Pt@TiO2 / K-AC (right) in Example 1 of the present invention.

[0082] Figure 7 It is the EPR spectrum of TiO2 / K-AC in Example 1 of the present invention. Detailed Embodiments

[0083] The technical solutions of the present invention will be further described and illustrated below through specific embodiments. It should be understood that the specific embodiments described here are only used to help understand the present invention and are not used to specifically limit the present invention.

[0084] Unless otherwise specified, the raw materials used in the embodiments of the present invention are all common raw materials in the art, and the methods used in the embodiments are all conventional methods in the art.

[0085] In this article, the preparation method of the highly active platinum-carbon catalyst includes:

[0086] (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;

[0087] The M is one or both of K and Na;

[0088] (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 and pore-expanded activated carbon M-AC in (1), mix well, and carry out a hydrothermal reaction at 130-280 °C for 1-24 h, and then vacuum dry to obtain TiO2 / M-AC;

[0089] (3) Dissolve a platinum source and an organic complexing agent with a mass ratio of 1:(1-10) in water, add the TiO2 / M-AC in (2), mix well, and carry out 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;

[0090] (4) In a mixed gas of 1-20 vol.% hydrogen / nitrogen or an inert atmosphere, place Pt / TiO2 / M-AC in a temperature range of 300-800 °C and heat it for 1-12 h to obtain a Pt@TiO2 / K-AC catalyst.

[0091] In this article, the highly active platinum-carbon catalyst has a core-shell structure, which uses porous metal-modified and pore-expanded activated carbon M-AC with an average particle size of 1 μm-10 mm as the core, deposits a TiO2 nanolayer with an average thickness of 0.1-10 nm on the core surface, and platinum nanoparticles Pt@TiO2 coated with the TiO2 nanolayer are loaded on the surface of the TiO2 nanolayer;

[0092] The average particle size of the platinum nanoparticles Pt@TiO2 coated with the TiO2 nanolayer is 0.1-10 nm, and the average thickness of the TiO2 nanolayer coated on its surface is 0.5-5 nm;

[0093] The metal M in the porous metal-modified and pore-expanded activated carbon M-AC is one or both of the alkali metals K and Na.

[0094] Example 1

[0095] The Pt@TiO2 / K-AC catalyst of this embodiment has a core-shell structure, with porous metal-modified and pore-expanded activated carbon K-AC with an average particle size of 50 mesh as the core. A TiO2 nanolayer is deposited on the surface of the core, and platinum nanoparticles with an average particle size of 3 nm and coated with a TiO2 nanolayer with an average thickness of 1 nm are also loaded on the surface of the TiO2 nanolayer.

[0096] (1) Immerse 20 g of activated carbon AC (specific surface area ~980 m 2 / g) in 400 ml of a KOH solution with a concentration of 8 wt.%, ultrasonicate for 30 min, then let it stand for 12 h. After filtration, dry it at 100 °C for 6 h, and then calcine it at 600 °C for 3 h under nitrogen protection to obtain potassium-modified and pore-expanded activated carbon K-AC;

[0097] According to the BET test, the specific surface area of K-AC is 950 m 2 / g;

[0098] Figure 1 , 2 are the TEM mapping and EDS spectra of activated carbon AC and potassium-modified and pore-expanded activated carbon K-AC. It can be seen that K is evenly distributed in the activated carbon.

[0099] (2) Dissolve 5 mmol of titanium isopropoxide, 10 mmol of urea, and 5 mmol of ascorbic acid in 500 ml of ethylene glycol monomethyl ether, add 20 g of K-AC, and stir at room temperature for 2 h; then transfer it to a reaction kettle and carry out a hydrothermal reaction at 180 °C for 10 h. After cooling, dry it under vacuum to obtain TiO2 / K-AC;

[0100] The electron microscopy image and EDS spectrum of TiO2 / K-AC are shown in Figure 3 . It can be seen that the positions of Ti elements and C elements are similar and both are evenly distributed, indicating that the surface of K-AC is covered with a TiO2 nanolayer with an average thickness of 1.5 nm.

[0101] The EPR image of TiO2 / K-AC is shown in Figure 7 . It can be seen that trivalent titanium ions exist in TiO2 / K-AC.

[0102] (3) Dissolve 0.1 g of platinum nitrate and 0.3 g of citric acid in 50 ml of water, add 15 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 / TiO2 / M-AC, on the surface of which Pt nanoparticles with an average particle size of 2 nm are evenly dispersed;

[0103] (4) In a mixed gas of 5 vol.% hydrogen / nitrogen, heat Pt / TiO2 / M-AC to 500 °C and hold for 3 h to obtain the core-shell structured Pt@TiO2 / K-AC catalyst.

[0104] According to Figures 4 - 6 It can be seen that in the Pt@TiO2 / K-AC catalyst, part of TiO2 migrates and coats the Pt nanoparticles to form a Pt@TiO2 core-shell structure, and the average thickness of the TiO2 coating layer is 1 nm.

[0105] Example 2

[0106] The structure of the Pt@TiO2 / K-AC catalyst in this example is a core-shell structure. The core is porous metal-modified expanded pore activated carbon K-AC with an average particle size of 500 mesh. A TiO2 nanolayer is deposited on the surface of the core, and platinum nanoparticles with an average particle size of 2.7 nm and coated with a TiO2 nanolayer with an average thickness of 1.2 nm are also loaded on the surface of the TiO2 nanolayer.

[0107] (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.%, ultrasonically treat 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;

[0108] (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 hydrothermally react at 180 °C for 10 h, cool and dry in vacuum to obtain TiO2 / K-AC;

[0109] (3) Dissolve 0.1 g of tetraammineplatinum nitrate and 0.3 g of citric acid 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 at a power of 800 W and a frequency of 2.45 GHz for 10 min. After taking it out, wash with water and dry to obtain Pt / TiO2 / K-AC, on the surface of which Pt nanoparticles with an average particle size of 1.5 nm are uniformly dispersed;

[0110] (4) In a mixed gas of 6 vol.% hydrogen / nitrogen, heat Pt / TiO2 / K-AC to 550 °C and hold for 3 h to obtain the core-shell structured Pt@TiO2 / K-AC catalyst.

[0111] Example 3

[0112] The Pt@TiO2 / Na-AC catalyst structure in this example is a core-shell structure. The core is porous metal-modified expanded activated carbon Na-AC with an average particle size of 10 mesh. A TiO2 nano-layer is deposited on the surface of the core, and 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 on the surface of the TiO2 nano-layer.

[0113] (1) Immerse 20 g of activated carbon AC (specific surface area ~980 m 2 / g) in 500 ml of an 8 wt.% NaOH solution, ultrasonicate for 30 min, then let it stand for 12 h. After filtration, dry it at 100 °C for 6 h, and then calcine it at 600 °C for 3 h under nitrogen protection to obtain sodium-modified expanded activated carbon Na-AC;

[0114] (2) Dissolve 5 mmol of tetrabutyl titanate, 10 mmol of urea, and 5 mmol of ascorbic acid in 500 ml of ethylene glycol methyl ether, add 20 g of Na-AC, and stir at room temperature for 2 h; then transfer it to a reaction kettle and hydrothermally react at 180 °C for 10 h. After cooling, dry it under vacuum to obtain TiO2 / Na-AC;

[0115] (3) Dissolve 0.12 g of chloroplatinic acid and 0.3 g of tartaric acid in 50 ml of water, add 15 g of TiO2 / Na-AC, ultrasonic 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 / TiO2 / Na-AC;

[0116] (4) In a mixed gas of 10 vol.% hydrogen / nitrogen, heat Pt / TiO2 / M-AC to 550 °C and keep it warm for 3 h to obtain the core-shell structured Pt@TiO2 / Na-AC catalyst.

[0117] Example 4

[0118] The Pt@TiO2 / Na-AC catalyst structure in this example is a core-shell structure. The core is porous metal-modified expanded activated carbon Na-AC with an average particle size of 70 mesh. A TiO2 nano-layer is deposited on the surface of the core, and 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 on the surface of the TiO2 nano-layer.

[0119] (1) Immerse 20 g of activated carbon AC (specific surface area ~980 m 2 / g) in 500 ml of an 8 wt.% NaOH solution, ultrasonicate for 30 min, then let it stand for 12 h. After filtration, dry it at 100 °C for 6 h, and then calcine it at 600 °C for 3 h under nitrogen protection to obtain sodium-modified expanded activated carbon Na-AC;

[0120] (2) Dissolve 5 mmol of tetrabutyl titanate, 10 mmol of urea, and 5 mmol of ascorbic acid in 500 ml of ethylene glycol methyl ether, add 20 g of Na-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, cool and then dry under vacuum to obtain TiO2 / Na-AC;

[0121] (3) Dissolve 0.12 g of chloroplatinic acid and 0.3 g of tartaric acid in 50 ml of water, add 15 g of TiO2 / Na-AC, disperse ultrasonically for 30 min, then place in a microwave reactor, and carry out microwave treatment at a power of 800 W and a frequency of 2.45 GHz for 10 min. After taking out, wash with water and dry to obtain Pt / TiO2 / Na-AC;

[0122] (4) Under nitrogen, heat Pt / TiO2 / M-AC to 600 °C and keep it warm for 3 h to obtain the core-shell structured Pt@TiO2 / Na-AC catalyst. The average particle size of Pt is 1.5 nm, and the average thickness of the TiO2 coating layer is 1.5 nm.

[0123] Comparative Example 1

[0124] The structure of the Pt@TiO2-AC’ catalyst prepared in this comparative example is as follows: using activated carbon AC with an average particle size of 50 mesh as the core, depositing a TiO2 nanolayer on the core surface, and also loading platinum nanoparticles with an average particle size of 3.5 nm and a TiO2 nanolayer with an average coating thickness of 1.5 nm on the surface of the TiO2 nanolayer.

[0125] (1) Calcinate 10 g of activated carbon AC (specific surface area ~980 m 2 / g) at 600 °C for 3 h under nitrogen protection to obtain activated carbon AC’;

[0126] (2 - 4) Follow the steps (2 - 4) of Example 1.

[0127] Comparative Example 2

[0128] The structure of the Pt@TiO2 / K-AC catalyst prepared in this comparative example is as follows: using porous metal-modified and pore-expanded activated carbon K-AC with an average particle size of 50 mesh as the core, depositing a TiO2 nanolayer on the core surface, and also loading platinum nanoparticles with an average particle size of 2.2 nm and a TiO2 nanolayer with an average coating thickness of 0.2 nm on the surface of the TiO2 nanolayer.

[0129] (1) Follow the step (1) of Example 1.

[0130] (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, cool and then dry under vacuum to obtain TiO2 / K-AC;

[0131] (3 - 4) Carry out according to steps (3 - 4) of Example 1.

[0132] Comparative Example 3

[0133] The structure of the Pt@TiO2 / K-AC catalyst prepared in this comparative example is as follows: using porous metal-modified expanded pore activated carbon K-AC with an average particle size of 50 mesh as the core, depositing a TiO2 nano-layer on the core surface, and also loading platinum nanoparticles with an average particle size of 3 nm on the TiO2 nano-layer surface, and there is no obvious TiO2 nano-layer on the surface of the platinum nanoparticles.

[0134] (1) Carry out according to step (1) of Example 1.

[0135] (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, add 100 ml of water dropwise, continue to stir at room temperature for 12 h, and then dry under vacuum at 60 °C for 12 h to obtain TiO2 / K-AC;

[0136] (3 - 4) Carry out according to steps (3 - 4) of Example 1.

[0137] Comparative Example 4

[0138] The structure of the Pt@TiO2 / K-AC catalyst prepared in this comparative example is as follows: using porous metal-modified expanded pore activated carbon K-AC with an average particle size of 50 mesh as the core, depositing a TiO2 nano-layer on the core surface, and also loading platinum nanoparticles with an average particle size of 3.2 nm on the TiO2 nano-layer surface, and the platinum nanoparticles are coated with a TiO2 nano-layer with an average thickness of 1.5 nm.

[0139] (1 - 2) Carry out according to steps (1 - 2) of Example 1.

[0140] (3) Dissolve 0.1 g of tetraammineplatinum nitrate in 50 ml of water, add 20 g of TiO2 / K-AC, disperse ultrasonically for 30 min, then place it in a microwave reactor, carry out microwave treatment 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 / TiO2 / M-AC;

[0141] (4) Carry out according to step (4) of Example 1.

[0142] Comparative Example 5

[0143] The structure of the Pt@TiO2 / K-AC catalyst prepared in this comparative example is as follows: The core is the porous metal-modified and pore-expanded activated carbon K-AC with an average particle size of 50 mesh. A TiO2 nanolayer is deposited on the surface of the core, and platinum nanoparticles with an average particle size of 4 nm and coated with a TiO2 nanolayer with an average thickness of 1.5 nm are also loaded on the surface of the TiO2 nanolayer.

[0144] (1-2) Follow the steps (1-2) of Example 1.

[0145] Dissolve 0.1 g of tetraammineplatinum nitrate and 0.3 g of citric acid in 50 ml of water, add 20 g of TiO2 / K-AC, and ultrasonically disperse for 30 min to obtain Pt / TiO2 / M-AC.

[0146] (4) Follow the step (4) of Example 1.

[0147] Comparative Example 6

[0148] The structure of the Pt@TiO2 / K-AC catalyst prepared in this comparative example is as follows: The core is the porous metal-modified and pore-expanded activated carbon K-AC with an average particle size of 50 mesh. A TiO2 nanolayer is deposited on the surface of the core, and platinum nanoparticles with an average particle size of 3 nm are also loaded on the surface of the TiO2 nanolayer, and there is no obvious TiO2 nanolayer on the surface of the platinum nanoparticles.

[0149] (1-3) Follow the steps (1-3) of Example 1 to obtain Pt / TiO2 / M-AC.

[0150] In a mixed gas of 5 vol.% hydrogen / nitrogen, heat Pt / TiO2 / M-AC to 200 °C and keep it warm for 3 h to obtain the catalyst Pt / TiO2 / M-AC.

[0151] Comparative Example 7

[0152] The structure of the Pt@TiO2 / K-AC catalyst prepared in this comparative example is as follows: The core is the porous metal-modified and pore-expanded activated carbon K-AC with an average particle size of 50 mesh. A TiO2 nanolayer is deposited on the surface of the core, and platinum oxide nanoparticles with an average particle size of 3 nm are also loaded on the surface of the TiO2 nanolayer, and there is no obvious TiO2 nanolayer on the surface of the platinum oxide nanoparticles.

[0153] (1-3) Follow the steps (1-3) of Example 1 to obtain Pt / TiO2 / M-AC.

[0154] In a mixed gas of 20 vol.% oxygen / nitrogen in air, heat Pt / TiO2 / M-AC to 500 °C and keep it warm for 3 h to obtain the catalyst PtO / TiO2 / M-AC.

[0155] Application Example 1

[0156] At room temperature of 25 °C, 60 mg of the highly active platinum-carbon catalyst of Example 1 was loaded into a quartz glass reaction tube with an inner diameter of 4 mm, and the relative humidity of the quartz glass reaction tube was maintained at 60%; the air was removed with an inert gas and the pressure in the reaction tube was kept constant. One end of the quartz glass reaction tube was connected to a formaldehyde generation device, and a gas concentration detector was connected to the other end. The gas flow rate of the formaldehyde generation device was set at 100 mL / min, and the volume space velocity was 100,000 h -1 . After the formaldehyde gas generation concentration reached the set value of 150 ppm stably, the formaldehyde gas was continuously introduced into the quartz glass reaction tube. At this time, it was used as the starting time of the test. After 0.5 h, 1 h, 3 h, 12 h, 24 h, and 48 h from the start of the test, the formaldehyde concentration and carbon dioxide concentration were recorded respectively, as shown in Table 1.

[0157] Table 1. Data table of the catalytic performance of the highly active platinum-carbon catalyst in Example 1

[0158]

[0159] Formaldehyde removal rate = [(initial formaldehyde concentration - remaining formaldehyde concentration) / initial formaldehyde concentration] × 100%.

[0160] CO2 yield = [generated carbon dioxide concentration / initial formaldehyde concentration] × 100%.

[0161] It can be seen that from 0.5 h to 24 h from the start of the test, the formaldehyde removal rate was 100% and the carbon dioxide selectivity was 100%. After 48 h from the start of the test, the formaldehyde removal rate decreased to 95%.

[0162] Application Examples 2-4

[0163] According to the steps of Application Example 1, the catalysts in Examples 2-4 were used for formaldehyde purification, and the results are shown in Table 2.

[0164] Application Comparative Examples 1-7

[0165] According to the steps of Application Example 1, the catalysts in Comparative Examples 1-7 were used for formaldehyde purification, and the results are shown in Table 2.

[0166] Application Comparative Example 8

[0167] According to the steps of Application Example 1, Pt / TiO2 / M-AC in Example 1(3) was used for formaldehyde purification, and the results are shown in Table 2.

[0168] Application Comparative Examples 9-10

[0169] 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.

[0170] Table 2. Performance Results of Platinum-Carbon Catalyst for Formaldehyde Purification

[0171]

[0172] In summary, the highly active platinum-carbon catalyst of the present invention has a core-shell structure, with porous metal-modified and pore-expanded activated carbon M-AC as the core. The modification of alkali metal elements enhances hydrophilicity and metal loading sites, and at the same time serves as a catalyst promoter, which is conducive to significantly improving the effect of the catalyst for oxidizing formaldehyde at room temperature; a TiO2 nanolayer containing trivalent titanium is deposited on the surface of the M-AC core; platinum nanoparticles are also loaded on the surface of the TiO2 nanolayer. During the high-temperature treatment process, under the action of trivalent titanium, the TiO2 nanolayer deposited on the surface of the M-AC core 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 TiO2 nanolayer; the TiO2 nanolayer on the surface of the platinum nanoparticles restricts the aggregation of platinum nanoparticles, improves the dispersion and stability of platinum nanoparticles, and at the same time the coating layer TiO2 has an electronic modification effect on the platinum particles, which is conducive to the catalyst to activate oxygen and water and improve the activity of the catalyst.

[0173] 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 understand other embodiments, modifications, and uses.

[0174] 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 prior and subsequent changes 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.

[0175] Finally, it should be noted that the specific embodiments described herein are only illustrative of the present invention and do not limit the implementation manners of the present invention. Those skilled in the art of the present invention can make various modifications or supplements to the described specific embodiments or use similar methods to replace them. It is not necessary and impossible to list all the implementation manners here. And these obvious changes or variations derived from the essence of the present invention still belong to the protection scope of the present invention. Interpreting them as any additional limitation 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 has a core-shell structure, with metal-modified and pore-expanded activated carbon M-AC as the core. A TiO2 nanolayer containing trivalent titanium is deposited on the surface of the core, and then platinum nanoparticles are loaded on the surface of the TiO2 nanolayer. Part of the TiO2 nanolayer on the surface of the metal-modified and pore-expanded activated carbon M-AC migrates to the surface of the platinum nanoparticles, forming platinum nanoparticles Pt@TiO2 coated with the TiO2 nanolayer; The metal M in the metal-modified and pore-expanded activated carbon M-AC is one or two of alkali metals K and Na.

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

3. The highly active platinum-carbon catalyst according to claim 1, wherein The thickness of the TiO2 nanolayer coated on the surface of the metal-modified and pore-expanded activated carbon M-AC is 0.1 to 10 nm.

4. The highly active platinum-carbon catalyst according to claim 1, wherein The average particle size of the platinum nanoparticles Pt@TiO2 coated with the TiO2 nanolayer is 0.1 to 10 nm.

5. The highly active platinum-carbon catalyst according to claim 1, wherein The specific surface area of the metal-modified and pore-expanded activated carbon M-AC < the specific surface area of the activated carbon AC.

6. A preparation method of the highly active platinum-carbon catalyst as described in claim 1, the preparation method comprising: (1) Immerse the activated carbon in an alkaline solution, ultrasonicate, stand still, dry, and then calcine in nitrogen to obtain the metal-modified and pore-expanded activated carbon M-AC; the metal M in the metal-modified and pore-expanded activated carbon M-AC is one or two of alkali metals K and Na; (2) Dissolve the titanium source, urea, and reducing agent in an organic solvent, add the metal-modified and pore-expanded activated carbon M-AC in (1), mix well, and after hydrothermal reaction, vacuum dry to obtain TiO2 / M-AC; (3) Dissolve the platinum source and the organic complexing agent in water, add the TiO2 / M-AC in (2), mix well, and perform microwave treatment at a power of 600 to 1000 W and a frequency of 1 to 3 GHz for 1 to 120 min to obtain Pt / TiO2 / M-AC; (4) In a mixed gas of hydrogen / nitrogen or an inert atmosphere, heat up and calcine Pt / TiO2 / M-AC to obtain the high-activity platinum-carbon catalyst Pt@TiO2 / K-AC.

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

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

9. Application of a highly active platinum-carbon catalyst in catalytic purification of formaldehyde, characterized in that, The application includes: at room temperature, load 10 to 100 mg of the high-activity platinum-carbon catalyst 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 described in any one of claims 6 to 8 into a glass reaction tube; one end of the 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 and volumetric space velocity of the formaldehyde generation device to make the formaldehyde gas generation concentration reach the set value of 100 to 300 ppm, and continuously introduce the formaldehyde gas into the glass reaction tube. At this time, take it as the test start time, and record the formaldehyde concentration and carbon dioxide concentration in the 48 h stage at the start of the test.

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

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