A high-stability platinum-carbon catalyst for indoor formaldehyde catalytic purification at room temperature and a preparation method thereof

Abstract

The application belongs to the technical field of indoor air purification, and relates to a high-stability platinum-carbon catalyst for indoor formaldehyde normal-temperature catalytic purification and a preparation method thereof. + The preparation method comprises the following steps: adding nitrogenized activated carbon AC-N into a complex solution [Pt-Cit-K]; then, Pt-Cit-K / AC-N is obtained through temperature reduction under an inert atmosphere containing a reducing gas; Pt-Cit-K / AC-N is immersed in an ammonium dihydrogen phosphate aqueous solution, dried, and then subjected to potassium secondary fixation under an air atmosphere to obtain Pt-Cit-K / AC-N-APD; the Pt-Cit-K / AC-N-APD is dispersed into an ethanol / water solution containing cetyltrimethylammonium bromide to obtain a mixed solution, ethyl silicate is added, the pH is adjusted, and after stirring at room temperature, the high-stability platinum-carbon catalyst Pt-Cit-K@SiO2 / AC-N-APD for indoor formaldehyde normal-temperature catalytic purification is obtained. The catalyst has good formaldehyde conversion rate and stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of indoor air purification, and relates to a high-stability platinum-carbon catalyst for indoor formaldehyde normal-temperature catalytic purification and a preparation method thereof. BACKGROUND

[0002] Indoor formaldehyde is a common indoor air pollutant, which has serious harm to human health, and long-term exposure can cause respiratory diseases and even cancer. Therefore, it is of great significance to efficiently control indoor formaldehyde pollution. Platinum-carbon (Pt / C) catalyst has become a research hotspot in this field due to its excellent catalytic activity for formaldehyde at normal temperature. However, the traditional Pt / C catalyst still has obvious deficiencies in practical application, including easy sintering of Pt particles, physical poisoning in water vapor environment, and chemical poisoning of reaction intermediates, which seriously restricts its catalytic efficiency and service life and limits its large-scale application in indoor air purification.

[0003] In view of the above problems, various improvement strategies have been proposed in existing research. For example, the stability of the catalyst is improved by modifying the carrier, but the effect of a single modification method is limited; the sintering is inhibited by controlling the size of the noble metal particles, but it is still difficult to completely avoid particle growth in the conventional reaction process; the anti-poisoning performance is enhanced by surface modification, but it often comes at the cost of part of the activity. Therefore, it is an urgent need to develop a comprehensive modification strategy to synergistically improve the stability, anti-poisoning ability and catalytic activity of the Pt / C catalyst. SUMMARY

[0004] The purpose of the present application is to solve the above-mentioned problems existing in the prior art, and a preparation method of a high-stability platinum-carbon catalyst for indoor formaldehyde normal-temperature catalytic purification is proposed. The method modifies the activated carbon carrier, precisely controls the size of the metal particles, and constructs a hydrophobic coating layer on the surface, which synergistically inhibits the migration, diffusion and sintering of Pt particles at high temperature, thereby ensuring a small and uniform particle size of Pt nanoparticles; and significantly improves the stability and catalytic performance of the platinum-carbon catalyst.

[0005] One purpose of the present application is achieved by the following technical solutions:

[0006] A preparation method of a high-stability platinum-carbon catalyst for indoor formaldehyde normal-temperature catalytic purification, comprising:

[0007] (1) uniformly mix the pretreated activated carbon and a nitrogen source, place them in an inert atmosphere, and heat to 300-600℃ for nitriding to obtain nitrided activated carbon AC-N;

[0008] (2) complex the complexing agent, platinum precursor and water, add KOH to pH 7.0-9.0 to obtain a complex solution [Pt-Cit-K]+ ;

[0009] (3) adding the nitrided activated carbon AC-N of step (1) into the complex solution [Pt-Cit-K] of step (2), and performing ultrasonic treatment, aging, and drying; then reducing at 200-280°C for 0.1-6h under an inert atmosphere containing a reducing gas to obtain Pt-Cit-K / AC-N; +

[0010] (4) immersing the Pt-Cit-K / AC-N of step (3) in an aqueous solution of ammonium dihydrogen phosphate with a concentration of 0.1-5wt% for 0.1-24h, and drying; then performing potassium secondary fixation at 300-450°C for 0.1-6h under an air atmosphere to obtain Pt-Cit-K / AC-N-APD;

[0011] (5) dispersing the Pt-Cit-K / AC-N-APD of step (4) into an ethanol / water solution containing cetyltrimethylammonium bromide to obtain a mixed solution, adding tetraethyl orthosilicate TEOS into the mixed solution, adjusting the pH to 7.0-9.0, and stirring at room temperature for 1-48h to obtain a high-stability platinum carbon catalyst Pt-Cit-K@SiO2 / AC-N-APD for indoor formaldehyde catalytic purification at room temperature.

[0012] Preferably, the activated carbon after pretreatment in step (1) is an activated carbon after acid washing, and the acid washing process comprises: placing the activated carbon in an acid solution with a concentration of 0.1-10wt%, stirring at 10-80°C for 1-24h, then washing to neutral with water and drying.

[0013] Further preferably, the mass-volume ratio of the activated carbon to the acid solution is 1g:(30-100)mL.

[0014] Further preferably, the acid solution comprises one or more of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.

[0015] Preferably, the mass ratio of the activated carbon after pretreatment in step (1) to the nitrogen source is 1:(0.05-0.5).

[0016] Preferably, the mixing in step (1) comprises one or more of mechanical mixing, mixing after adding water and drying, and mortar grinding.

[0017] Preferably, the inert atmosphere in step (1) is nitrogen.

[0018] Preferably, the nitrogen source in step (1) comprises urea.

[0019] ​As preferred, the complexing agent in the step (2) comprises one or more of citric acid, tartaric acid, glycolic acid and gluconic acid; and the platinum precursor comprises one or more of platinum nitrate, potassium chloroplatinate and chloroplatinic acid.

[0020] As preferred, the mass of the complexing agent, the mass of the platinum precursor and the volume of water in the step (2) are in the ratio of (1-20) g: 1 g: (300-1000) ml.

[0021] Further preferred, the mass ratio of the complexing agent and the platinum precursor is (10-15): 1.

[0022] As preferred, in the step (2), KOH is added to a pH of 7.1-8.6.

[0023] As preferred, in the step (3), the nitrogenated activated carbon AC-N and the complex solution [Pt-Cit-K] are mixed in the ratio of (1-10): 1. +

[0024] Further preferred, in the step (3), the nitrogenated activated carbon AC-N and the complex solution [Pt-Cit-K] are mixed in the ratio of (1-3): 1. +

[0025] As preferred, in the step (3), the reducing gas is H2, and the inert atmosphere is argon and / or nitrogen.

[0026] Further preferred, the inert atmosphere containing the reducing gas is 1-10 vol% H2 / Ar.

[0027] As preferred, in the step (3), the average particle size of Pt-Cit-K / AC-N is 1-3 nm.

[0028] As preferred, in the step (5), the mass of Pt-Cit-K / AC-N-APD, the mass of cetyltrimethylammonium bromide, the volume of the ethanol / water solution, and the volume of ethyl silicate TEOS are in the ratio of 1 g: (0.1-0.5) g: (50-200) ml: (1-10) ml.

[0029] Further preferred, the volume ratio of ethanol and water in the ethanol / water solution is (0.1-10): 1.

[0030] As preferred, in the step (5), the pH is adjusted to 7.0-9.5.

[0031] Further preferred, in the step (5), the pH is adjusted to 7.1-9.1.

[0032] ​​The second object of the present application is achieved by the following technical solutions:

[0033] A high-stability platinum carbon catalyst for indoor formaldehyde normal-temperature catalytic purification is prepared by the preparation method; the high-stability platinum carbon catalyst for indoor formaldehyde normal-temperature catalytic purification is a core-shell structure, wherein the inner core is Pt-Cit-K / AC-N-APD, and the shell layer is a SiO2 layer.

[0034] Preferably, the average particle size of the high-stability platinum carbon catalyst for indoor formaldehyde normal-temperature catalytic purification is 1-6 nm.

[0035] Preferably, the average thickness of the shell layer is 0.1-2 nm, and the average particle size of the inner core is 1-3 nm.

[0036] Further preferably, the average thickness of the shell layer is 0.5-2 nm, and the average particle size of the inner core is 1-2.5 nm.

[0037] The third object of the present application is achieved by the following technical solutions:

[0038] An application of a high-stability platinum carbon catalyst for indoor formaldehyde normal-temperature catalytic purification comprises:

[0039] The high-stability platinum carbon catalyst for indoor formaldehyde normal-temperature catalytic purification is loaded in a reaction device, formaldehyde / air mixed gas with a formaldehyde concentration of 100 ppm is introduced, and the space velocity is set to 95,000 h-1. -1 At room temperature, the initial formaldehyde conversion rate is >95%, and the formaldehyde conversion rate is >90% after 24 h of reaction.

[0040] Preferably, the retention rate of the formaldehyde conversion rate of the high-stability platinum carbon catalyst for indoor formaldehyde normal-temperature catalytic purification after 24 h of reaction is >94%.

[0041] Compared with the prior art, the present application has the following beneficial effects:

[0042] 1. The present application solves the problems of easy migration and agglomeration of Pt particles due to hydrogen bonds and chemical adsorption of reaction intermediates in the reaction process of traditional platinum carbon catalysts from the source, significantly improves the comprehensive performance and service life of the high-stability platinum carbon catalyst for indoor formaldehyde normal-temperature catalytic purification, and the like.

[0043] 2. The present application introduces nitrogen elements on the surface of the pretreated activated carbon by nitrogenization treatment, not only adjusts the electronic structure of the carrier, but also improves the surface chemical properties, thereby providing anchoring sites for high-dispersion loading of Pt and significantly enhancing the anti-falling stability of Pt on the surface of the carrier.

[0044] 3、The present application promotes the formation of stable [Pt-Cit-K] complex by precisely regulating the pH value of the impregnation system and combining with the ultrasonic-assisted impregnation technology, ensuring the uniform distribution of Pt elements on the surface of the carrier at the sub-nanometer level; at the same time, as an electron-donating additive, the introduced K element can regulate the electron density of the outer layer of Pt elements and promote its ability to activate water and oxygen; +

[0045] 4、The present application adopts a mild gas reduction method to precisely control the size of Pt nanoparticles, avoiding the decline of catalytic activity caused by excessively large particles; compared with the reduction method with a reducing agent solution, the gas reduction method has the advantages of milder operating conditions, avoidance of impurities introduced by liquid phase, more uniform and easy-to-control particle size, etc.

[0046] 5、The present application further enhances the stability and anti-poisoning ability of the catalyst through potassium secondary fixation and porous hydrophobic silica coating; potassium secondary fixation strengthens the chemical bonding between K, Pt and the surface of the carrier, effectively inhibiting the migration, diffusion and agglomeration of Pt particles; the porous hydrophobic silica coating layer has both porous structure and hydrophobic properties, which not only ensures the rapid diffusion of formaldehyde molecules to the Pt active sites, but also effectively prevents the diffusion and agglomeration of active sites on the surface of AC, further prolonging the service life of the catalyst. BRIEF DESCRIPTION OF DRAWINGS

[0047] Fig. 1 Figure 1 is the Pt-Cit-K / AC-N particle size distribution chart and EDS mapping chart in Example 1 of the present application.

[0048] Fig. 2 Figure 2 is the Pt-Cit-K / AC-N-APD particle size distribution chart and EDS mapping chart in Example 1 of the present application.

[0049] Fig. 3 Figure 3 is the Pt-Cit-K@SiO2 / AC-N-APD particle size distribution chart and EDS mapping chart in Example 1 of the present application. DETAILED DESCRIPTION

[0050] The technical solutions of the present application will be further described and explained by specific examples, and it should be understood that the specific examples described herein are only used to help understand the present application, and are not used to limit the specific application of the present application.

[0051] If not specifically stated, the raw materials used in the 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.

[0052] In this paper, the preparation method of a high-stability platinum-carbon catalyst for indoor formaldehyde catalytic purification at room temperature comprises: ​

[0053] (1) 1-20 g activated carbon is placed in 500 ml acid solution with a concentration of 0.1-10 wt%, stirred at 10-80 °C for 1-24 h, then washed with water to neutral, and dried at 80-150 °C;

[0054] The acid-washed activated carbon with a mass ratio of 1: (0.05-0.5) is mixed with a nitrogen source, placed in a nitrogen atmosphere, and nitrided at a rate of 1-20 °C / min to 300-600 °C for 1-6 h to obtain nitrided activated carbon AC-N;

[0055] (2) The complexing agent, platinum precursor, and water are stirred to complex with a mass-volume ratio of (5-20) g: 1 g: (300-1000) ml, and KOH is added to obtain a complex solution [Pt-Cit-K] + ;

[0056] (3) The nitrided activated carbon AC-N of step (1) is added to the complex solution [Pt-Cit-K] + of step (2), and the mass ratio of the amount of nitrided activated carbon AC-N to the complexing agent in the complex solution [Pt-Cit-K] + is (1-10): 1; it is ultrasonically treated at 10-80 kHz and 100-500 W for 1-60 min, then aged for 1-6 h, then dried and transferred to an inert atmosphere containing a reducing gas, heated to 200-280 °C at a rate of 1-20 °C / min, and reduced for 0.1-6 h to obtain Pt-Cit-K / AC-N;

[0057] The particle size of the Pt-Cit-K / AC-N is 1-3 nm;

[0058] (4) The Pt-Cit-K / AC-N of step (3) is immersed in an aqueous ammonium dihydrogen phosphate solution with a concentration of 0.1-5 wt% for 0.1-24 h, taken out and dried, then transferred to an air atmosphere, heated to 300-450 °C at a rate of 1-20 °C / min, and kept for 0.1-6 h for potassium secondary fixation to obtain Pt-Cit-K / AC-N-APD;

[0059] (5) 1-5 g of the Pt-Cit-K / AC-N-APD of step (4) is dispersed in 100-1000 ml of an ethanol / water solution containing 0.1-1 g of cetyltrimethylammonium bromide to obtain a mixed solution, 1-10 ml of ethyl silicate TEOS is added to the mixed solution, the pH is adjusted to 7.0-9.5, and it is stirred at room temperature for 1-48 h, then washed and dried to obtain a high-stability platinum carbon catalyst Pt-Cit-K@SiO2 / AC-N-APD for indoor formaldehyde catalytic purification at room temperature;

[0060] The high-stability platinum carbon catalyst Pt-Cit-K@SiO2 / AC-N-APD for indoor formaldehyde catalytic purification at room temperature is a core-shell structure, which comprises an inner core Pt-Cit-K / AC-N-APD with an average particle size of 1-3 nm and a SiO2 shell layer with an average thickness of 0.1-2 nm.

[0061] In this paper, the particle size of the Pt-Cit-K / AC-N obtained by the acid washing, nitriding and impregnation steps is 1-3 nm.

[0062] In this paper, the formaldehyde adsorption test of the high-stability platinum carbon catalyst for indoor formaldehyde catalytic purification at room temperature includes:

[0063] 1. Reaction device: fixed bed reactor, wherein the high-stability platinum carbon catalyst for indoor formaldehyde catalytic purification at room temperature is loaded in the catalyst bed, and the gas is continuously introduced from the inlet and discharged from the outlet;

[0064] 2. Reaction gas: formaldehyde concentration is 100 ppm, air is the balance gas, and the relative humidity is 50%; before the reaction starts, the impurity gas in the reaction device is removed by purging with the balance gas, and the formaldehyde / air mixed gas is switched in;

[0065] 3. Reaction temperature: room temperature (25°C);

[0066] 4. Space velocity: 95000 h -1 (unit time gas volume passing through the catalyst bed is 95000 times the volume of the catalyst);

[0067] 5. Formaldehyde conversion rate: the reaction is run until the formaldehyde concentration at the outlet is stable, and the initial formaldehyde conversion rate is calculated; continue to run for 24 h, and calculate the formaldehyde conversion rate after 24 h of reaction.

[0068] Example 1

[0069] The preparation method of the high-stability platinum carbon catalyst for indoor formaldehyde catalytic purification at room temperature in this example includes:

[0070] (1) 10 g of activated carbon (200 mesh) was placed in 500 ml of 5 wt% nitric acid solution, stirred at 70°C for 3 h, then washed with water several times until neutral, and dried at 120°C to obtain the acid-washed activated carbon. 5 g of the acid-washed activated carbon, 0.5 g of nitrogen source (urea) and 50 g of water were mixed and stirred for 2 h, dried at 60°C, then transferred to a tube furnace, and heated to 400°C at a rate of 5°C / min under nitrogen atmosphere for 2 h to obtain the nitrided activated carbon AC-N.

[0071] (2) Weigh 3g of citric acid and dissolve it in 100mL of deionized water. Add 5mL of 0.1mol / L platinum nitrate solution and stir to complex for 30min. Then add 1mol / L KOH solution to adjust and fix the pH to 8.0 to obtain the complex solution [Pt-Cit-K]. + .

[0072] (3) Weigh 5g of the nitrided activated carbon AC-N from step (1) and add it to the complex solution [Pt-Cit-K] from step (2). + In the process, the sample was ultrasonically treated with a 40kHz probe at 300W for 30 minutes, followed by static aging for 2 hours. Then, it was dried by rotary evaporation. The dried sample was then transferred to a tube furnace and reduced to 220℃ for 1.5 hours at a rate of 3℃ / min under an atmosphere containing 5 vol% H2 / Ar to obtain Pt-Cit-K / AC-N.

[0073] (4) The Pt-Cit-K / AC-N from step (3) was immersed in an aqueous solution of 0.5 wt% ammonium dihydrogen phosphate for 6 h in equal volume. After being removed, it was dried at 80 °C and then transferred to a tube furnace. Under an air atmosphere, the temperature was increased to 320 °C at a rate of 2 °C / min and held for 1 h to perform secondary potassium fixation, thus obtaining Pt-Cit-K / AC-N-APD.

[0074] (5) Disperse 2g of Pt-Cit-K / AC-N-APD from step (4) into 200ml of ethanol / water solution containing 0.5g of cetyltrimethylammonium bromide (volume ratio of ethanol to water is 1:1) to obtain a mixed solution. Add 4mL of tetraethyl orthosilicate (TEOS) to the mixed solution, adjust the pH to 9.0 with ammonia, stir at room temperature for 18h, wash with ethanol 3 times, and dry at 80℃ to obtain a highly stable platinum-carbon catalyst Pt-Cit-K@SiO2 / AC-N-APD for indoor formaldehyde room temperature catalytic purification.

[0075] according to Figs. 1-3 It can be seen that in this embodiment, the average particle size of Pt-Cit-K / AC-N is 1.8 nm; the average particle size of Pt-Cit-K / AC-N-APD is 2.8 nm; and the average particle size of Pt-Cit-K@SiO2 / AC-N-APD is 3.5 nm.

[0076] In this embodiment, the formaldehyde conversion rates of Pt-Cit-K / AC-N and Pt-Cit-K@SiO2 / AC-N-APD were tested. The initial formaldehyde conversion rate of Pt-Cit-K / AC-N was 95%, and the formaldehyde conversion rate after 24 hours of reaction was 90%. The initial formaldehyde conversion rate of Pt-Cit-K@SiO2 / AC-N-APD was 98.5%, and the formaldehyde conversion rate after 24 hours of reaction was 95.2%.

[0077] Example 2

[0078] The preparation method of the high-stability platinum carbon catalyst for indoor formaldehyde catalytic purification at room temperature in this embodiment comprises:

[0079] (1) 10 g of activated carbon (200 mesh) was placed in 500 ml of 5 wt% sulfuric acid solution, stirred at 60°C for 4 h, then washed with water several times until neutral, and dried at 110°C to obtain acid-washed activated carbon. 5 g of acid-washed activated carbon, 0.5 g of nitrogen source (urea), and 50 g of water were mixed and stirred for 2 h, dried at 60°C, then transferred to a tube furnace, and heated to 400°C at a rate of 5°C / min under nitrogen atmosphere for 2 h to obtain nitrided activated carbon AC-N.

[0080] (2) 2 g of citric acid was dissolved in 100 mL of deionized water, 5 mL of 0.1 mol / L platinum nitrate solution was added, stirred for 30 min, then 1 mol / L KOH solution was added to adjust and fix the pH to 7.6, to obtain the complex solution [Pt-Cit-K] + .

[0081] (3) 5 g of nitrided activated carbon AC-N of step (1) was added to the complex solution [Pt-Cit-K] + of step (2), and 40 kHz probe ultrasonic was used to treat for 30 min under ice bath conditions at 250 W, then aged for 2 h; then dried, and then the dried sample was transferred to a tube furnace, heated to 200°C at a rate of 3°C / min under 5 vol% H2 / Ar atmosphere for 1.5 h to reduce, to obtain Pt-Cit-K / AC-N.

[0082] (4) Pt-Cit-K / AC-N of step (3) was placed in 0.5 wt% ammonium dihydrogen phosphate aqueous solution for equal volume impregnation for 5 h, then taken out and dried at 80°C, then transferred to a tube furnace, heated to 300°C at a rate of 2°C / min under air atmosphere and kept for 1 h for potassium secondary fixation, to obtain Pt-Cit-K / AC-N-APD;

[0083] (5) 2 g of the Pt-Cit-K / AC-N-APD of step (4) was dispersed into a 200 ml ethanol / water solution (volume ratio of ethanol to water was 2:1) containing 0.5 g of cetyltrimethylammonium bromide, 4 mL of ethyl silicate (TEOS) was added into the solution, the pH was adjusted to 8.5 by adding ammonia, and the mixture was stirred at room temperature for 18 h. After ethanol washing for 3 times, the product was dried at 80°C to obtain the high-stability platinum carbon catalyst Pt-Cit-K@SiO2 / AC-N-APD for indoor formaldehyde catalytic purification at room temperature. In this example, the average particle size of Pt-Cit-K / AC-N and Pt-Cit-K@SiO2 / AC-N-APD was shown in Table 1; the formaldehyde conversion rate and the formaldehyde conversion rate after 24 h of reaction of the high-stability platinum carbon catalyst Pt-Cit-K@SiO2 / AC-N-APD for indoor formaldehyde catalytic purification at room temperature was shown in Table 1.

[0084] Example 3

[0085] In this example, the preparation method of the high-stability platinum carbon catalyst for indoor formaldehyde catalytic purification at room temperature included:

[0086] (1) 10 g of activated carbon (50 mesh) was placed in a 500 ml 5 wt% nitric acid solution, stirred at 70°C for 3 h, then washed with water to neutralize multiple times, and dried at 120°C to obtain the acid-washed activated carbon. 5 g of the acid-washed activated carbon, 0.5 g of a nitrogen source (urea), and 50 g of water were mixed and stirred for 2 h, and then transferred to a tube furnace and heated to 400°C at a rate of 5°C / min under a nitrogen atmosphere for 2 h to obtain the nitrided activated carbon AC-N.

[0087] (2) The same as step (2) of Example 1.

[0088] (3) The same as step (3) of Example 1.

[0089] (4) The same as step (4) of Example 1.

[0090] (5) The same as step (5) of Example 1.

[0091] In this example, the average particle size of Pt-Cit-K / AC-N and Pt-Cit-K@SiO2 / AC-N-APD was shown in Table 1; the formaldehyde conversion rate and the formaldehyde conversion rate after 24 h of reaction of the high-stability platinum carbon catalyst Pt-Cit-K@SiO2 / AC-N-APD for indoor formaldehyde catalytic purification at room temperature was shown in Table 1.

[0092] Example 4

[0093] In this example, the preparation method of the platinum carbon catalyst for indoor formaldehyde catalytic purification at room temperature included:

[0094] (1) The same as step (1) of Example 1.

[0095] (2) 3 g of citric acid was weighed and dissolved in 100 mL of deionized water, 5 mL of 0.1 mol / L platinum nitrate solution was added, and the complexation was stirred for 30 min, then 1 mol / L KOH solution was added to adjust and fix the pH to 7.1, to obtain a complex solution [Pt-Cit-K]. + .

[0096] (3) The same as step (3) of Example 1.

[0097] (4) The same as step (4) of Example 1.

[0098] (5) The same as step (5) of Example 1.

[0099] The average particle size of Pt-Cit-K / AC-N, Pt-Cit-K@SiO2 / AC-N-APD in this example is shown in Table 1; the formaldehyde conversion rate of platinum carbon catalyst Pt-Cit-K@SiO2 / AC-N-APD for indoor formaldehyde catalytic purification at room temperature and the formaldehyde conversion rate after 24 h of reaction are shown in Table 1.

[0100] Comparative Example 1

[0101] The preparation method of platinum carbon catalyst for indoor formaldehyde catalytic purification at room temperature in this comparative example comprises:

[0102] (1) 10 g of activated carbon (200 mesh) was placed in 500 ml of 5 wt% nitric acid solution, stirred at 70°C for 3 h, then washed with water several times until neutral, and dried at 120°C to obtain the acid-washed activated carbon.

[0103] (2) The same as step (2) of Example 1.

[0104] (3) The same as step (3) of Example 1.

[0105] (4) The same as step (4) of Example 1.

[0106] (5) The same as step (5) of Example 1.

[0107] The average particle size of Pt-Cit-K / AC, Pt-Cit-K@SiO2 / AC-APD in this comparative example is shown in Table 1; the formaldehyde conversion rate of platinum carbon catalyst Pt-Cit-K@SiO2 / AC-APD for indoor formaldehyde catalytic purification at room temperature and the formaldehyde conversion rate after 24 h of reaction are shown in Table 1.

[0108] Comparative Example 2

[0109] The preparation method of platinum carbon catalyst for indoor formaldehyde catalytic purification at room temperature in this comparative example comprises:

[0110] (1) The same as step (1) of Example 1.

[0111] (2) The same as step (2) of Example 1.

[0112] (3) The same as step (3) of Example 1.

[0113] (4) The same as step (5) of Example 1.

[0114] The average particle size of Pt-Cit-K / AC-N and Pt-Cit-K / AC-N-APD in the present comparative example is shown in Table 1; the formaldehyde conversion rate of platinum carbon catalyst Pt-Cit-K / AC-N-APD for indoor formaldehyde catalytic purification at room temperature and the formaldehyde conversion rate after 24 hours of reaction are shown in Table 1.

[0115] Comparative Example 3

[0116] The preparation method of platinum carbon catalyst for indoor formaldehyde catalytic purification at room temperature in the present comparative example comprises:

[0117] (1) The same as step (1) of Example 1.

[0118] (2) The same as step (2) of Example 1.

[0119] (3) The same as step (3) of Example 1.

[0120] (4) The same as step (4) of Example 1.

[0121] The average particle size of Pt-Cit-K / AC-N and Pt-Cit-K / AC-N-APD in the present comparative example is shown in Table 1; the formaldehyde conversion rate of platinum carbon catalyst Pt-Cit-K / AC-N-APD for indoor formaldehyde catalytic purification at room temperature and the formaldehyde conversion rate after 24 hours of reaction are shown in Table 1.

[0122] Comparative Example 4

[0123] The preparation method of platinum carbon catalyst for indoor formaldehyde catalytic purification at room temperature in the present comparative example comprises:

[0124] (1) The same as step (1) of Example 1.

[0125] (2) The same as step (2) of Example 1.

[0126] (3) 5g of the nitrided activated carbon AC-N of step (1) is added to the complex solution [Pt-Cit-K] of step (2). +In the present case, the PtO-K / AC was obtained by ultrasonic treatment at 40 kHz, 300 W for 30 min under ice-bath condition, followed by aging for 2 h, and then dried by rotary evaporation.

[0127] (4) The same as step (4) of Example 1.

[0128] (5) The same as step (5) of Example 1.

[0129] The average particle sizes of PtO-K / AC-N and PtO-K@SiO2 / AC-N in the present comparative example are shown in Table 1; the formaldehyde conversion rate of the platinum carbon catalyst PtO-K@SiO2 / AC-N for indoor formaldehyde catalytic purification at room temperature and the formaldehyde conversion rate after 24 h of reaction are shown in Table 1.

[0130] Comparative Example 5

[0131] The preparation method of the platinum carbon catalyst for indoor formaldehyde catalytic purification in the present comparative example comprises:

[0132] (1) The same as step (1) of Example 1.

[0133] (2) 3 g of citric acid was dissolved in 100 mL of deionized water, 5 mL of platinum nitrate solution with a concentration of 0.1 mol / L was added, and the mixture was stirred for complexation for 30 min. Then, 1 mol / L of KOH solution was added to adjust and fix the pH to 6.0, to obtain a complex solution [Pt-Cit-K] + .

[0134] (3) The same as step (3) of Example 1.

[0135] (4) The same as step (4) of Example 1.

[0136] (5) The same as step (5) of Example 1.

[0137] The average particle sizes of Pt-Cit-K / AC-N and Pt-Cit-K@SiO2 / AC-N-APD in the present comparative example are shown in Table 1; the formaldehyde conversion rate of the platinum carbon catalyst Pt-Cit-K@SiO2 / AC-N-APD for indoor formaldehyde catalytic purification at room temperature and the formaldehyde conversion rate after 24 h of reaction are shown in Table 1.

[0138] Comparative Example 6

[0139] The preparation method of the platinum carbon catalyst for indoor formaldehyde catalytic purification in the present comparative example comprises:

[0140] (1) The same as step (1) of Example 1.

[0141] (2) Take 3 g of citric acid and dissolve it in 100 mL of deionized water, add 5 mL of platinum nitrate solution with a concentration of 0.1 mol / L, stir and complex for 30 min, then add 1 mol / L KOH solution to adjust and fix the pH to 10.0 to obtain the complex solution [Pt-Cit-K] + .

[0142] (3) The same as step (3) of Example 1.

[0143] (4) The same as step (4) of Example 1.

[0144] (5) The same as step (5) of Example 1.

[0145] The average particle size of Pt-Cit-K / AC-N, Pt-Cit-K@SiO2 / AC-N-APD in the present comparative example is shown in Table 1; the formaldehyde conversion rate of the platinum carbon catalyst Pt-Cit-K@SiO2 / AC-N-APD for indoor formaldehyde catalytic purification at room temperature and the formaldehyde conversion rate after 24 h of reaction are shown in Table 1.

[0146] Comparative Example 7

[0147] The preparation method of the platinum carbon catalyst for indoor formaldehyde catalytic purification at room temperature in the present comparative example comprises:

[0148] (1) The same as step (1) of Example 1.

[0149] (2) Take 3 g of citric acid and dissolve it in 100 mL of deionized water, add 5 mL of platinum nitrate solution with a concentration of 0.1 mol / L, stir and complex for 30 min, then add ammonia water to adjust and fix the pH to 8.0 to obtain the complex solution [Pt-Cit] + .

[0150] (3) The same as step (3) of Example 1.

[0151] (4) The same as step (4) of Example 1.

[0152] (5) The same as step (5) of Example 1.

[0153] The average particle size of Pt / AC-N, Pt@SiO2 / AC-N-APD in the present comparative example is shown in Table 1; the formaldehyde conversion rate of the platinum carbon catalyst Pt@SiO2 / AC-N-APD for indoor formaldehyde catalytic purification at room temperature and the formaldehyde conversion rate after 24 h of reaction are shown in Table 1.

[0154] Comparative Example 8

[0155] The preparation method of the platinum carbon catalyst for indoor formaldehyde catalytic purification at room temperature in the present comparative example comprises:

[0156] (1) The same as step (1) of Example 1.

[0157] (2) 3 g of citric acid was weighed and dissolved in 100 mL of deionized water, 5 mL of platinum nitrate solution with a concentration of 0.1 mol / L was added, and the complex was stirred for 30 min to obtain a complex solution [Pt-Cit-Na]. + .

[0158] (3) The same as step (3) of Example 1.

[0159] (4) The same as step (4) of Example 1.

[0160] (5) The same as step (5) of Example 1.

[0161] The average particle size of Pt-Cit-Na / AC-N, Pt-Cit-Na@SiO2 / AC-N-APD in the present comparative example is shown in Table 1; the formaldehyde conversion rate of the platinum carbon catalyst Pt-Cit-Na@SiO2 / AC-N-APD for indoor formaldehyde catalytic purification at room temperature and the formaldehyde conversion rate after 24 h of reaction are shown in Table 1.

[0162] Comparative Example 9

[0163] The preparation method of the platinum carbon catalyst for indoor formaldehyde catalytic purification at room temperature in the present comparative example comprises:

[0164] (1) The same as step (1) of Example 1.

[0165] (2) 3 g of citric acid was weighed and dissolved in 100 mL of deionized water, 5 mL of platinum nitrate solution with a concentration of 0.1 mol / L was added, and the complex was stirred for 30 min to obtain a complex solution [Pt-Cit]. + .

[0166] (3) The same as step (3) of Example 1.

[0167] (4) The same as step (4) of Example 1.

[0168] (5) The same as step (5) of Example 1.

[0169] The average particle size of Pt / AC-N, Pt@SiO2 / AC-N-APD in the present comparative example is shown in Table 1; the formaldehyde conversion rate of the platinum carbon catalyst Pt@SiO2 / AC-N-APD for indoor formaldehyde catalytic purification at room temperature and the formaldehyde conversion rate after 24 h of reaction are shown in Table 1.

[0170] Comparative Example 10

[0171] The preparation method of the platinum-carbon catalyst for indoor formaldehyde catalytic purification at room temperature in the present comparative example comprises:

[0172] (1) The same as step (1) of Example 1.

[0173] (2) 3 g of citric acid was weighed and dissolved in 100 mL of deionized water, 5 mL of platinum nitrate solution with a concentration of 0.1 mol / L was added, and the complex was complexed for 30 min by stirring to obtain a complex solution [Pt-Cit]. + .

[0174] (3) The same as step (3) of Example 1.

[0175] (4) The same as step (5) of Example 1.

[0176] The average particle size of Pt / AC and Pt@SiO2 / AC in the present comparative example is shown in Table 1; the formaldehyde conversion rate of the platinum-carbon catalyst Pt@SiO2 / AC for indoor formaldehyde catalytic purification at room temperature and the formaldehyde conversion rate after 24 h of reaction are shown in Table 1.

[0177] Comparative Example 11

[0178] The preparation method of the platinum-carbon catalyst for indoor formaldehyde catalytic purification at room temperature in the present comparative example comprises:

[0179] (1) 10 g of activated carbon (200 mesh) was placed in 500 ml of 5 wt% nitric acid solution, stirred at 70°C for 3 h, then washed with water to neutralize multiple times, and dried at 120°C to obtain the acid-washed activated carbon. 5 g of the acid-washed activated carbon was mixed with 5 g of nitrogen source (urea) by ball milling, and then nitrided at 400°C for 2 h under a nitrogen atmosphere at a rate of 5°C / min to obtain the nitrided activated carbon AC-N.

[0180] (2) The same as step (2) of Example 1.

[0181] (3) The same as step (3) of Example 1.

[0182] (4) The same as step (4) of Example 1.

[0183] (5) The same as step (5) of Example 1.

[0184] The average particle size of Pt-Cit-K / AC-N and Pt-Cit-K@SiO2 / AC-N-APD in the present comparative example is shown in Table 1; the formaldehyde conversion rate of the platinum-carbon catalyst Pt-Cit-K@SiO2 / AC-N-APD for indoor formaldehyde catalytic purification at room temperature and the formaldehyde conversion rate after 24 h of reaction are shown in Table 1.

[0185] Comparative Example 12

[0186] The preparation method of the platinum carbon catalyst for indoor formaldehyde room temperature catalytic purification in the present comparative example comprises:

[0187] (1) The same as step (1) of Example 1.

[0188] (2) The same as step (2) of Example 1.

[0189] (3) The same as step (3) of Example 1.

[0190] (4) The same as step (4) of Example 1.

[0191] (5) 1g of Pt-Cit-K / AC-N-APD of step (4) is dispersed into 200ml of an ethanol / water solution (the volume ratio of ethanol to water is 1:1) containing 0.5g of cetyltrimethylammonium bromide to obtain a first mixed solution, 4mL of ethyl silicate TEOS is added to the first mixed solution, ammonia water is added to adjust the pH to 9.0, and after stirring at room temperature for 18h, ethanol washing is performed 3 times, and drying is performed at 80℃ to obtain a high-stability platinum carbon catalyst Pt-K@SiO2 / AC for indoor formaldehyde room temperature catalytic purification.

[0192] The average particle size of Pt-Cit-K / AC-N and Pt-Cit-K@SiO2 / AC-N-APD in the present comparative example is shown in Table 1; the formaldehyde conversion rate of the platinum carbon catalyst Pt-Cit-K@SiO2 / AC-N-APD for indoor formaldehyde room temperature catalytic purification and the formaldehyde conversion rate after 24h of reaction are shown in Table 1.

[0193] Comparative Example 13

[0194] The preparation method of the platinum carbon catalyst for indoor formaldehyde room temperature catalytic purification in the present comparative example comprises:

[0195] (1) The same as step (1) of Example 1.

[0196] (2) The same as step (2) of Example 1.

[0197] (3) 5g of the nitrogenated activated carbon AC-N of step (1) is added to the complex solution [Pt-Cit-K] of step (2), 40kHz probe ultrasonic is used, ultrasonic treatment is performed under ice bath conditions at 300W for 30min, and then aging is performed for 2h; then rotary evaporation drying is performed, and then the freeze-dried sample is transferred to a tube furnace, reduction is performed at 500℃ under an atmosphere containing 5vol% H2 / Ar at a rate of 3℃ / min for 1.5h to obtain Pt-Cit-K / AC-N. +

[0198] (4) The same as step (4) of Example 1.

[0199] ​(5) The same as step (5) of Example 1.

[0200] The average particle sizes of Pt-Cit-K / AC-N and Pt-Cit-K@SiO2 / AC-N-APD in the present comparative example are shown in Table 1; the formaldehyde conversion rate of the platinum carbon catalyst Pt-Cit-K@SiO2 / AC-N-APD for indoor formaldehyde catalytic purification at room temperature and the formaldehyde conversion rate after 24 hours of reaction are shown in Table 1.

[0201] Comparative Example 14

[0202] The preparation method of the platinum carbon catalyst for indoor formaldehyde catalytic purification at room temperature in the present comparative example comprises:

[0203] (1) The same as step (1) of Example 1.

[0204] (2) 5 mL of a platinum nitrate solution with a concentration of 0.1 mol / L was added to 100 mL of deionized water, and the mixture was stirred for complexation for 30 min, and then 1 mol / L of a KOH solution was added to adjust and fix the pH to 8.0, to obtain an alkaline mixed solution containing a platinum hydroxyl complex.

[0205] (3) The same as step (3) of Example 1.

[0206] (4) The same as step (4) of Example 1.

[0207] (5) The same as step (5) of Example 1.

[0208] The average particle sizes of Pt-K / AC-N and Pt-K@SiO2 / AC-N-APD in the present comparative example are shown in Table 1; the formaldehyde conversion rate of the platinum carbon catalyst Pt-K@SiO2 / AC-N-APD for indoor formaldehyde catalytic purification at room temperature and the formaldehyde conversion rate after 24 hours of reaction are shown in Table 1.

[0209] Table 1, performance data table of the platinum carbon catalyst for indoor formaldehyde catalytic purification at room temperature

[0210]

[0211] According to the above table, the high-stability platinum carbon catalyst for indoor formaldehyde catalytic purification at room temperature of the present application has a good formaldehyde conversion rate, and maintains a high formaldehyde conversion rate for a certain period of time, achieving high stability.

[0212] In the present application, if the activated carbon is not subjected to nitrogenization treatment, the surface thereof lacks hydrophilic nitrogen-containing functional groups, which is not conducive to the entry of the impregnation solution into the pores, and affects the uniformity of Pt dispersion; if the nitrogenization is excessive, most of the pores of the activated carbon will be blocked, which is not conducive to the subsequent loading of Pt and K.

[0213] The complex solution in the application effectively complexes Pt and K, avoids the size growth of Pt, and thus maintains the catalyst activity. 2+ The complex solution in the application effectively complexes Pt and K, avoids the size growth of Pt, and thus maintains the catalyst activity. + The complex solution in the application effectively complexes Pt and K, avoids the size growth of Pt, and thus maintains the catalyst activity. 2+ The complex solution in the application effectively complexes Pt and K, avoids the size growth of Pt, and thus maintains the catalyst activity. - The complex solution in the application effectively complexes Pt and K, avoids the size growth of Pt, and thus maintains the catalyst activity. 2+ The complex solution in the application effectively complexes Pt and K, avoids the size growth of Pt, and thus maintains the catalyst activity.

[0214] The PtO obtained after the active carbon treated by nitridation is reacted with the complex solution is in an oxidation state and does not have the activity of catalyzing and purifying formaldehyde, and thus needs to be reduced.

[0215] The SiO2 coating layer of the platinum carbon catalyst can make the formaldehyde molecules quickly diffuse to the Pt active sites and effectively inhibit the migration and agglomeration of the active sites (Pt particles) on the surface of the active carbon.

[0216] In summary, the application realizes the atomic dispersion of Pt by the modification of the active carbon by nitridation, the regulation of the particle size, the combination of the precise regulation of the pH of the impregnation system and the formation of the stable [Pt-Cit-K] complex by ultrasonic assistance, the control of the size of the Pt nanoparticles by mild gas reduction, and the coating of the porous hydrophobic silicon dioxide by the secondary fixation of potassium. + The application solves the problems of the easy migration and agglomeration of the Pt particles of the traditional platinum carbon catalyst and the chemical adsorption of the intermediate products from the source, significantly improves the anti-poisoning ability and service life of the platinum carbon catalyst for the catalytic purification of indoor formaldehyde at room temperature, and has the advantages of mild operation, no introduction of liquid phase impurities, uniform and controllable Pt dispersion.

[0217] Aspects, embodiments, features of the present invention are to be considered illustrative only and not restrictive in all respects. The scope of the present invention is defined solely by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art, and the embodiments are not to be considered limited to the specific embodiments set forth herein, but rather are to be given the full scope of the claims.

[0218] In the preparation method of the present invention, the order of the steps is not limited to the listed order, and for those skilled in the art, the order of the steps can be changed without creative effort, and such changes are within the protection scope of the present invention. In addition, two or more steps or actions can be performed simultaneously.

[0219] Finally, it should be noted that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the scope of the embodiments of the present invention. Those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, and it is not necessary or possible to fully describe all embodiments here. Any obvious changes or variations derived from the spirit of the present invention are still within the protection scope of the present invention, and any additional limitations are contrary to the spirit of the present invention.

Claims

1. A method for preparing a high-stability platinum-carbon catalyst for indoor formaldehyde catalytic purification at room temperature, characterized in that, The preparation method comprises: (1) mixing the pretreated activated carbon with a nitrogen source, placing in an inert atmosphere, heating to 300-600 DEG C for nitriding, to obtain nitrided activated carbon AC-N; (2) The complexing agent, platinum precursor and water are stirred to complex, KOH is added to pH 7.0-9.0, and a complex solution [Pt-Cit-K] is obtained. + ; (3) Add the nitrided activated carbon AC-N from step (1) to the complex solution [Pt-Cit-K] from step (2). + The Pt-Cit-K / AC-N was subjected to ultrasonication, aging, and drying; then, under an inert atmosphere containing reducing gas, it was heated to 200-280℃ for 0.1-6 hours to obtain Pt-Cit-K / AC-N. (4) the Pt-Cit-K / AC-N of step (3) is immersed in an ammonium dihydrogen phosphate aqueous solution with a concentration of 0.1-5wt% for 0.1-24h, dried, and then heated to 300-450 DEG C under air atmosphere for 0.1-6h for potassium secondary fixation, to obtain Pt-Cit-K / AC-N-APD; (5) the Pt-Cit-K / AC-N-APD of step (4) is dispersed into an ethanol / water solution containing cetyltrimethylammonium bromide to obtain a mixed solution, tetraethyl orthosilicate TEOS is added to the mixed solution, the pH is adjusted to 7.0-9.0, and after stirring at room temperature for 1-48h, a high-stability platinum carbon catalyst Pt-Cit-K@SiO2 / AC-N-APD for indoor formaldehyde catalytic purification at room temperature is obtained.

2. The preparation method of high-stability platinum carbon catalyst for indoor formaldehyde room temperature catalytic purification according to claim 1, characterized in that, The pretreated activated carbon in step (1) is acid-washed activated carbon, and the acid washing process comprises: placing the activated carbon in an acid solution with a concentration of 0.1-10wt%, stirring at 10-80 DEG C for 1-24h, then washing to neutral and drying.

3. The method for preparing high-stability platinum carbon catalyst for indoor formaldehyde purification at room temperature according to claim 1, characterized in that, The mass ratio of the pretreated activated carbon in step (1) to the nitrogen source is 1: (0.05-0.5).

4. The method for preparing high-stability platinum carbon catalyst for indoor formaldehyde purification at room temperature according to claim 1, characterized in that, In step (2), the mass of the complexing agent, the mass of the platinum precursor, and the volume of water are in a ratio of (1-20) g: 1 g: (300-1000) ml.

5. The method for preparing high-stability platinum carbon catalyst for indoor formaldehyde purification at room temperature according to claim 1, characterized in that, In step (3), the reducing gas is H2, and the inert atmosphere is argon and / or nitrogen.

6. The method for preparing high-stability platinum carbon catalyst for indoor formaldehyde purification at room temperature according to claim 1, characterized in that, In step (5), the mass of Pt-Cit-K / AC-N-APD, the mass of cetyltrimethylammonium bromide, the volume of the ethanol / water solution, and the volume of tetraethyl orthosilicate TEOS are in a ratio of 1 g: (0.1-0.5) g: (50-200) ml: (1-10) ml.

7. A high-stability platinum-carbon catalyst for indoor formaldehyde catalytic purification at room temperature, characterized in that, It is prepared by the preparation method of the high-stability platinum carbon catalyst for indoor formaldehyde catalytic purification at room temperature according to any one of claims 1-6; the high-stability platinum carbon catalyst for indoor formaldehyde catalytic purification at room temperature has a core-shell structure, wherein the inner core is Pt-Cit-K / AC-N-APD, and the shell layer is a SiO2 layer. 8.The high-stability platinum-carbon catalyst for indoor formaldehyde purification at room temperature according to claim 7, characterized in that, The average particle size of the high-stability platinum carbon catalyst for indoor formaldehyde catalytic purification at room temperature is 1-6nm. 9.The high-stability platinum-carbon catalyst for indoor formaldehyde purification at room temperature according to claim 7, characterized in that, The average thickness of the shell layer is 0.1-2nm, and the average particle size of the inner core is 1-3nm.

10. The use of a high-stability platinum-carbon catalyst for indoor formaldehyde catalytic purification at room temperature, characterized in that, The application comprises: loading the high-stability platinum-carbon catalyst for indoor formaldehyde catalytic purification at room temperature as claimed in any one of claims 7-9 into a reaction device, passing in formaldehyde and air mixed gas with a formaldehyde concentration of 100 ppm, setting the space velocity to 95000 h -1 ; at room temperature, the initial formaldehyde conversion rate is >95%; after 24 h of reaction, the formaldehyde conversion rate is >90%.

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