CN111215051A

CN111215051A - Inert carrier loaded Pt-based formaldehyde elimination catalyst at room temperature, and preparation and application thereof

Info

Publication number: CN111215051A
Application number: CN201811423907.3A
Authority: CN
Inventors: 王晓东; 孙秀成; 林坚
Original assignee: Dalian Institute of Chemical Physics of CAS
Current assignee: Dalian Institute of Chemical Physics of CAS
Priority date: 2018-11-27
Filing date: 2018-11-27
Publication date: 2020-06-02
Anticipated expiration: 2038-11-27
Also published as: CN111215051B

Abstract

The invention relates to a catalyst for eliminating formaldehyde in a closed room at room temperature, in particular to an inert carrier loaded Pt-based catalyst and preparation and application thereof. Pt is highly dispersed in a size of 0.5 to 1nm, and the support is alumina, silica, activated carbon, boron nitride, or the like. Pt is loaded on the carrier, and the content of the Pt is 0.001-0.01% of the total mass of the catalyst. The catalyst is suitable for completely eliminating formaldehyde with relatively wide concentration (5-100 ppm) at room temperature, and the product is CO₂And H₂And O, further purifying air and improving the living environment.

Description

Inert carrier loaded Pt-based formaldehyde elimination catalyst at room temperature, and preparation and application thereof

Technical Field

The invention relates to a catalyst for eliminating formaldehyde by room-temperature oxidation in a closed space, in particular to an inert carrier loaded Pt-based catalyst for eliminating trace formaldehyde for room-temperature air purification and a preparation method and application thereof.

Background

Formaldehyde is one of the main pollutants in a closed space, particularly in a newly decorated household room, and has poor volatility and a detention period of several years. The chronic exposure of micro-formaldehyde can cause pharyngolaryngitis, bronchitis, pneumonia and even lung cancer, thus eliminating formaldehyde pairsThe human health and the social development have very important meanings. The catalytic oxidation method can completely and chemically decompose formaldehyde into CO₂And H₂O, the method has low energy consumption and is environment-friendly, and the key is to select a proper catalyst to completely eliminate the formaldehyde at room temperature.

At present, the Pt-based catalyst is the optimal catalyst for eliminating formaldehyde at room temperature. In 2005, zhangzhan bin et al earlier conducted Pt-based catalyst research, in which a Pt precursor was supported on TiO by an impregnation method₂The catalyst formed can completely eliminate formaldehyde with 100ppm at room temperature [ Catal. Commun.,2005,6, 211-214-]. Subsequent treatment of Pt/TiO₂The catalyst is modified, the surface of the carrier is rich in hydroxyl by adding alkali metal (Li, Na and K), the reaction path is changed, and the decomposition of intermediate species formate is accelerated, so that the room-temperature catalytic activity of the catalyst is improved [ Angew]. Next, the development research of Pt-based catalyst mainly focuses on hydroxyl-rich carrier or increasing the hydroxyl on the surface of the carrier by adding auxiliary agent (Ni, Fe, etc.), such as Pt/AlOOH [ application. Catal. B2015, 163,306-],PtNi(OH)x/γ-Al₂O₃[Appl.Catal.B2017,200,543-551],Pt/NiFe-LDH[Catal.Sci.Technol.2017,7,1573-1580]，Pt/MnO_x-CeO₂[Appl.Catal.B,2008,81:115-121]And the like. Although the catalyst shows excellent room-temperature formaldehyde elimination performance, in order to keep higher catalytic activity, the Pt loading is often higher and reaches more than 1 wt%, so that the cost of the catalyst is high, and the practical application of the catalyst is restricted.

Recently, researchers have also begun to focus on lower loadings of Pt-based catalysts, Huang et al use sodium borohydride to reduce chloroplatinic acid, followed by TiO loading₂In the above, it was found that formaldehyde could be completely eliminated at room temperature only at a Pt content of 0.1 wt% [ J.Catal.2011,280,60-67 ]]. Wu et al used a vacuum drying followed by reduction to obtain a Pt/SiO loading of 0.2 wt%₂The catalyst is found that the treatment method can control the size of Pt particles to be 0.5-0.8 nm, and compared with Pt species with the size of 8nm, the formaldehyde conversion rate is improved by multiple times (J.Catal.2017, 355, 87-100)]. However, these catalysts show higher activity only in low concentration formaldehyde (-10 ppm) feed gas and withThe stability of the humidity is reduced due to the increase of the relative humidity, the humidity tolerance is to be further improved, and the popularization and the application of the humidity in the actual environment with large relative humidity change are limited. The subject group reported that Pt/TiO with a loading of 0.1% was synthesized in two steps by a colloidal precipitation method₂The catalyst was used for formaldehyde oxidation to achieve complete conversion of 160ppm formaldehyde catalyzed at room temperature (patent No. 201818003222.8). However, the key to the formaldehyde elimination catalyst is that the support must rely on a high specific surface area of TiO₂The problems of the amplification synthesis and the complicated preparation steps of the carrier bring difficulties to the practical application of the carrier. At present, no Pt-based catalyst which is loaded on a commercial inert carrier with a loading of ppm level and can eliminate formaldehyde with a wider concentration (5-100 ppm) at room temperature is reported.

Disclosure of Invention

The invention aims to provide an inert carrier loaded high-efficiency Pt-based formaldehyde room temperature elimination catalyst, and preparation and application thereof.

In order to achieve the purpose, the invention adopts the technical scheme that;

the catalyst for eliminating formaldehyde at room temperature consists of an inert carrier and Pt, wherein the content of Pt is ppm and accounts for 0.001-0.01% of the total mass of the catalyst. Inert supports include alumina, silica, activated carbon, boron nitride, and the like.

The catalyst is prepared by a sol-impregnation method, a Pt precursor sol is obtained by reducing with low-carbon alcohol, wherein the concentration of metal platinum ions is 10-50 ppm, the pH is controlled to be 12-13 by strong base, the catalyst is stirred for 1-3 h at room temperature and then transferred into an oil bath at 80-160 ℃ for reduction. And then adding an inert carrier for dipping, stirring for 2-6 h, standing and aging for 1-3 h, filtering, washing, drying, roasting and reducing to obtain the target catalyst.

The low-carbon alcohol is methanol, ethylene glycol, glycerol and 1, 4-butanediol, and the strong base is NaOH and KOH.

The catalyst needs a series of treatments, the conditions are drying for 8-24H, roasting at 200-500 ℃ for 3-6H, and subjecting to 10-100 vol.% H₂And reducing for 0.5-2 h by using the/He.

The catalyst can be used in a wide range of concentrations at room temperatureEliminating formaldehyde, namely passing feed gas which comprises 5-100 ppm of formaldehyde, the balance of air and a certain humidity through a fixed bed reactor filled with a catalyst, wherein the mass space velocity is 1x10⁴～1x10⁶mLg_cat ^-1h^-1And testing the concentration of the formaldehyde in the tail gas at normal pressure and room temperature.

Compared with the prior art, the invention has the substantial characteristics that:

1. the catalyst prepared by the method has extremely low noble metal loading capacity, the obtained Pt particles are relatively uniform in size, the activity of the catalyst is favorably improved, the used carrier is an inert carrier, and a commercial oxide is used, so that the catalyst has economy, and the room-temperature formaldehyde elimination effect is equivalent to the reported activity of the Pt-based catalyst loaded by an active carrier.

2. The method for preparing the catalyst has the advantages of simplified process, one-step synthesis and simple and convenient operation.

3. The conversion rate of formaldehyde reaches 100% in a wider formaldehyde concentration range, and the air purification is facilitated. The catalyst is suitable for completely eliminating formaldehyde with relatively wide concentration (5-100 ppm) at room temperature, and the product is CO₂And H₂And O, further purifying air and improving the living environment.

Drawings

FIG. 1 is a photograph of inert supported alumina supported Pt catalyst HAADF-STEM prepared in example 1 and comparative examples 1 and 2.

Fig. 2 is a graph showing formaldehyde elimination performance test of the inert carrier alumina-supported Pt catalysts prepared in examples 1,2 and 3.

FIG. 3 shows Pt/Al prepared in example 1 of the present invention and comparative example 1₂O₃And (3) comparing the formaldehyde elimination performance of the catalyst.

FIG. 4 is a graph showing Pt/Al prepared in example 1 of the present invention and comparative example 2₂O₃And (3) comparing the formaldehyde elimination performance of the catalyst.

Detailed Description

Example 1:

10mL of H with a concentration of 10ppm₂PtCl₆The glycerol solution is placed in a 100mL three-neck flask, and 10mL of 0.2mol L of glycerol solution is added^-1Stirring and mixing the solution at room temperature for 1h, transferring the solution into an oil bath kettle at the temperature of 130 ℃ for reduction for 1h, adding 1.0g of alumina into the solution, stirring the solution for 3h, standing the solution for 1h, filtering the solution while the solution is hot, and washing the solution. Drying the filter cake in a 100 ℃ oven for 10h, roasting in a muffle furnace at 500 ℃ for 4h, and reducing with pure hydrogen at 300 ℃ for 1h to obtain 0.01 wt.% of Pt/Al₂O₃-a Col catalyst.

Example 2:

1mL of H with a concentration of 50ppm₂PtCl₆The glycerol solution was placed in a 100mL three-necked flask, and 10mL of 0.11mol L was added thereto^-1Stirring and mixing the solution at room temperature for 1h, transferring the solution into an oil bath kettle at the temperature of 130 ℃ for reduction for 1h, adding 1.0g of alumina into the solution, stirring the solution for 3h, standing the solution for 1h, filtering the solution while the solution is hot, and washing the solution. Drying the filter cake in a 100 ℃ oven for 10h, roasting in a muffle furnace at 500 ℃ for 4h, and reducing with pure hydrogen at 300 ℃ for 1h to obtain 0.005 wt.% of Pt/Al₂O₃-a Col catalyst.

Example 3:

0.2mL of H with a concentration of 50ppm₂PtCl₆The glycerol solution was placed in a 100mL three-necked flask, and 10mL of 0.11mol L was added thereto^-1Stirring and mixing the solution at room temperature for 1h, transferring the solution into an oil bath kettle at the temperature of 130 ℃ for reduction for 1h, adding 1.0g of alumina into the solution, stirring the solution for 3h, standing the solution for 1h, filtering the solution while the solution is hot, and washing the solution. Drying the filter cake in a 100 ℃ oven for 10h, roasting in a muffle furnace at 500 ℃ for 4h, and reducing with pure hydrogen at 300 ℃ for 1h to obtain 0.001 wt.% of Pt/Al₂O₃-a Col catalyst.

Comparative example 1

Preparation of Pt/Al by deposition precipitation method₂O₃A catalyst. Dispersing 1.0g of alumina in 100mL of ultrapure water to form a suspension, and stirring at 80 ℃ for 15 min; adding 10mL of 10ppm chloroplatinic acid aqueous solution into 100mL ultrapure water, stirring for dilution, stirring at 80 ℃ for 15min, and passing through a constant flow pump for 3mL min^-1Dropwise adding into the carrier suspension under vigorous stirring, adjusting pH to 9.2, stirring at 80 deg.C for 3 hr, aging for 1 hr, filtering while hot, washing, and drying in oven at 100 deg.C for 10 hr. Roasting in a muffle furnace at 500 ℃ for 4h, and reducing pure hydrogen at 300 ℃ for 1h to obtain 0.01 wt.% of Pt/Al₂O₃-a DP catalyst.

Comparative example 2

Pt/Al is prepared by adopting an isometric impregnation method₂O₃A catalyst. Dripping 1mL of chloroplatinic acid solution with the concentration of 100ppm into 1.0g of alumina, uniformly stirring by using a glass rod, drying in a drying oven at 100 ℃ for 10 hours, roasting in a muffle furnace at 500 ℃ for 4 hours, and reducing with pure hydrogen at 300 ℃ for 1 hour to obtain 0.01 wt.% of Pt/Al₂O₃-an IMP catalyst.

In order to evaluate the catalytic performance of the prepared catalyst, a formaldehyde elimination performance test is carried out on the catalyst by a micro-reverse evaluation device. Adopting a fixed bed reactor, filling 50mg of catalyst into a U-shaped reaction tube, and introducing the catalyst into the reaction tube at a flow rate of 100mL min^-1With a composition of 30ppm HCHO +20 vol.% O₂+ He, relative humidity adjusted to 50%, mass space velocity of 1.2X 10⁵mLg_cat ^-1h^-1And carrying out temperature programming activity test on the catalyst. The testing temperature interval is 20-80 ℃, samples are taken once every 20min, samples are taken three times at each temperature point, and CO in the outlet of the chromatographic detection reactor is recorded₂The concentration of (c). Due to CO in the experimental process₂In ppm order, so that a nickel converter is arranged in a FID detector of a chromatograph to capture CO₂Concentration of CO produced₂At H₂Hydrogenation in atmosphere for total conversion to CH₄From CH₄To quantify the product CO₂The concentration of (c).

The HCHO conversion was calculated as follows:

HCHO Conversion(％)＝[CO₂]/[CO₂]_A×100％

wherein: [ CO ]₂]_AFor complete conversion of formaldehyde into CO₂Time corresponding CH₄Chromatographic peak area

[CO₂]For CO formed under different reaction temperature conditions₂Corresponding CH₄Chromatographic peak area.

Results

Pt/Al prepared from inventive example 1 shown in FIG. 1₂O₃HAADF-STEM picture of-Col catalyst shows that Pt is in nanoclusters (0.8-1) in the catalyst prepared in example 1.2nm) in a uniform and highly dispersed form in an inert carrier Al₂O₃Surface, and comparative example 1 Pt/Al prepared by deposition precipitation₂O₃DP catalyst and Pt/Al prepared by the isovolumetric impregnation method in comparative example 2₂O₃The particle size of Pt in the IMP catalyst is not uniform, and large particles with nanometer sizes are distributed on the carrier.

As shown in FIG. 2, the formaldehyde elimination performance test chart of the catalyst prepared in the inventive examples 1,2 and 3 shows that only the carrier Al₂O₃When the catalyst is used, the catalyst has almost no activity, the formaldehyde elimination performance is improved after a very small amount (0.001 wt%) of Pt is loaded, and 30ppm of formaldehyde can be completely eliminated at 60 ℃. The elimination performance of the catalyst is continuously improved along with the increase of the loading amount, and when the Pt loading amount is increased to 0.01 wt%, formaldehyde can be completely eliminated at room temperature. The results show that the catalyst exhibits excellent low temperature formaldehyde elimination performance at Pt loading levels of only ppm and on an inert support.

Pt/Al prepared from inventive example 1 and comparative example 1 shown in FIG. 3₂O₃Comparison of formaldehyde elimination performance of catalyst, Pt/Al prepared by deposition precipitation method₂O₃The conversion of formaldehyde was only 70% at room temperature and 100% at 60 ℃ when the loading of the-DP catalyst was the same as 0.01 wt%, whereas the Pt/Al synthesized in example 1 by sol-impregnation method was used₂O₃The Col catalyst can completely eliminate formaldehyde at room temperature, which shows that the performance of eliminating formaldehyde at room temperature of the catalyst is related to the preparation method of the catalyst, and the catalyst prepared by adopting the sol-impregnation method has more excellent catalytic activity.

Pt/Al prepared from inventive example 1 and comparative example 2 shown in FIG. 4₂O₃Comparison of formaldehyde elimination performance of catalyst, Pt/Al prepared by traditional isometric impregnation method₂O₃IMP catalyst, with a conversion rate of only 57% at room temperature and complete conversion of formaldehyde at 80 ℃, and Pt/Al prepared by sol-impregnation₂O₃The conversion rate of formaldehyde of the Col catalyst at room temperature is 100 percent, which shows that the performance of the catalyst for eliminating formaldehyde at room temperature and the preparation method of the catalyst haveAnd the catalyst prepared by adopting the sol-impregnation method has more excellent catalytic activity.

Claims

1. An inert carrier loaded Pt-based formaldehyde elimination catalyst at room temperature is characterized in that: the catalyst comprises an active component Pt and an inert carrier, wherein the mass content of the active component Pt is 0.001-0.01 wt% of the total mass of the catalyst, and the inert carrier is one or more of alumina, silicon oxide, active carbon and boron nitride.

2. The catalyst of claim 1, wherein: the mass content of the active component Pt is preferably 0.005-0.01 wt% of the total mass of the catalyst.

3. A method for preparing the catalyst of claim 1 or 2, wherein: prepared by a sol-dip method; firstly, reducing by using low-carbon alcohol to obtain Pt precursor sol, wherein the concentration of metal platinum ions is 10-50 ppm, controlling the pH value to be 12-13 by using NaOH and KOH, stirring at room temperature, and then transferring into an oil bath at 80-160 ℃ for reduction; and then adding an inert carrier for impregnation, stirring for 2-6 h, standing and aging for 1-3 h, filtering, washing, drying, roasting and reducing to obtain a final product.

4. The method of claim 3, wherein: the lower alcohol is one or more of methanol, ethylene glycol, glycerol and 1, 4-butanediol.

5. The method of claim 3, wherein: and (3) putting a soluble Pt compound serving as a precursor into low-carbon alcohol to form sol.

6. The method of claim 3, wherein: and adjusting the pH of the system to be 12-13 by adding one or more of NaOH, KOH, NaOH low-carbon alcohol solution and KOH low-carbon alcohol solution.

7. The method of claim 3, wherein: roasting at 500 deg.c for 4 hr and reducing with pure hydrogen at 300 deg.c for 1 hr.

8. Use of a catalyst according to claim 1 or 2, wherein: the catalyst can be used for eliminating formaldehyde in room-temperature gas.

9. The use of claim 8, wherein: the concentration of formaldehyde in the gas is 5-100 ppm, and the balance is air, CO and CO₂、H₂O or nitrogen.