CN107486205A - Pt/Bi2O3Catalyst, preparation method, gaseous formaldehyde biodegrading process - Google Patents

Abstract

The invention provides a preparation method of a Pt/Bi ₂ O ₃ catalyst. The preparation method comprises the following steps: a. hydrolyzing Bi ³⁺ ions in a Bi salt solution in an alkaline environment to form a Bi ₂ O ₃ precipitate, and obtaining Bi ₂ O ₃ powder after centrifugal washing and drying; b. The ₂ O ₃ powder is dispersed in a solution system containing H ₂ PtCl ₆ and a sacrificial agent, and then stirred under light conditions to obtain a Pt/Bi ₂ O ₃ catalyst. The invention also provides a Pt/Bi ₂ O ₃ catalyst prepared by the preparation method and a gaseous formaldehyde degradation method.

Description

Pt/Bi2O3 catalyst, preparation method, gaseous formaldehyde degradation method

technical field

The invention belongs to the technical field _of formaldehyde catalytic degradation, and in particular relates to a Pt/ _Bi2O3 catalyst, a preparation method thereof, and a gaseous formaldehyde degradation method.

Background technique

With the development of social economy and the improvement of people's living needs, people's production rhythm is constantly accelerating, so that a large amount of harmful substances are discharged into the air and water, causing serious pollution and serious harm to people's health. For example, formaldehyde additives are widely used in the production of building materials, decorative materials and fabrics, causing formaldehyde to continuously volatilize indoors and become one of the main indoor air pollutants. For this reason, people have tried various methods to remove these organic pollutants.

Among them, thermocatalytic and photocatalytic methods have attracted more and more attention because of their high efficiency, safety and no secondary pollution. The effect of thermal catalysis is obviously better than that of photocatalysis. Therefore, in the research of removing gaseous formaldehyde, people more often use the method of noble metal thermal catalysis.

At present, the noble metal thermocatalysis method mainly carries out the oxidative decomposition of gaseous formaldehyde at room temperature by loading a small amount of noble metals, such as Pt, Au, and Pd, on a porous substrate carrier. Studies have shown that noble metal catalysts can exhibit good catalytic activity for formaldehyde degradation and oxidize formaldehyde to CO ₂ and H ₂ O if the substrate is selected properly.

However, in the study of thermocatalytic room temperature degradation of gaseous formaldehyde, the enhancement of noble metal catalysts is still the focus of research. However, at present, the enhancement of thermal catalysts is mainly achieved by adjusting the material of the substrate material and increasing the specific surface area of the substrate material. There are few studies on performance enhancement by other means, and it is necessary to explore new methods to achieve performance enhancement. In addition, the noble metal thermal catalyst itself has weak oxidation ability and cannot oxidize larger molecules. Therefore, in practical applications, it may be covered by some larger volatile organic molecules, resulting in catalyst deactivation.

Contents of the invention

The object of the present invention is to provide a Pt/Bi ₂ O ₃ catalyst, a preparation method, and a gaseous formaldehyde degradation method.

The technical scheme of the present invention is as follows: a preparation method of a Pt/Bi ₂ O ₃ catalyst comprises the following steps: a. In an alkaline environment, Bi ³⁺ ions in the Bi salt solution are hydrolyzed to generate Bi ₂ O ₃ precipitates, and centrifugal washing Obtain Bi ₂ O ₃ powder after drying; b. Disperse the Bi ₂ O ₃ powder in a solution system containing H ₂ PtCl ₆ and a sacrificial agent, and then stir under light conditions to obtain a Pt/Bi ₂ O ₃ catalyst.

Preferably, step a specifically includes the following steps: dissolving Bi(NO ₃ ) ₃ .5H ₂ O in distilled water to form a solution, and adding nitric acid to prevent hydrolysis to realize the configuration of Bi(NO ₃ ) ₃ solution; dissolving NaOH solution Add dropwise into the Bi(NO ₃ ) ₃ solution, stir for several hours to obtain a pale yellow Bi ₂ O ₃ precipitate; centrifuge, wash thoroughly with distilled water and absolute ethanol, and dry at 80°C to obtain a pale yellow Bi ₂ O 3 O ₃ powder.

Preferably, the Bi ₂ O ₃ precipitate obtained in step a is rod-shaped Bi ₂ O ₃ precipitate.

Preferably, after the Bi ₂ O ₃ powder is dispersed in the solution system containing H ₂ PtCl ₆ and a sacrificial agent in step b, the suspension is treated with a light source with a wavelength >400nm under constant stirring. Irradiation was carried out until the suspension turned gray-black.

Preferably, ethanol is used as a sacrificial agent for H ₂ PtCl ₆ in step b.

A Pt/Bi ₂ O ₃ catalyst, the Pt/Bi ₂ O ₃ catalyst is prepared by any of the above-mentioned preparation methods, and the Pt/Bi ₂ O ₃ catalyst is suitable for photothermal co-catalytic degradation at room temperature Gaseous formaldehyde under conditions.

A method for degrading gaseous formaldehyde, using the above-mentioned Pt/Bi ₂ O ₃ catalyst to degrade gaseous formaldehyde under the common conditions of room temperature and lighting.

Preferably, at room temperature, the Pt/Bi ₂ O ₃ catalyst is irradiated with a daily LED lamp.

The beneficial effects of the present invention are: the preparation method provides a simple method for preparing a Pt/Bi ₂ O ₃ catalyst with obvious formaldehyde catalytic degradation performance, the method is prepared at room temperature and in a strong alkaline environment, and does not After calcination treatment, the operation is simple and easy to control;

Also, since there is no need

Moreover, the prepared Pt/Bi ₂ O ₃ catalyst can greatly improve the degradation effect of gaseous formaldehyde under the common conditions of room temperature and light irradiation.

Description of drawings

The accompanying drawings described here are used to provide a further understanding of the present invention, and constitute a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention, and do not constitute improper limitations to the present invention. In the attached picture:

_Fig . ₁ is the XRD spectrogram of _Bi2O3 and Pt/ _Bi2O3 catalyst that the embodiment of the present invention provides;

Fig. 2 is Bi ₂ O ₃ and Pt/Bi ₂ O ₃ SEM images of catalysts provided by the embodiments of the present invention;

_Fig . ₃ is the ultraviolet-visible diffuse reflectance spectrogram of _Bi2O3 and Pt/ _Bi2O3 provided by the embodiment of the present invention;

Figure 4 is a schematic diagram of (a) the relative concentration of formaldehyde and (b) the change of _CO2 concentration in the gaseous formaldehyde degradation experiment.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

Unless the context clearly states otherwise, although the steps in the present invention are arranged with labels, they are not used to limit the order of the steps, unless the order of the steps is clearly stated or the execution of a certain step requires other steps as a basis, otherwise The relative order of the steps can be adjusted. It can be understood that the term "and/or" used herein refers to and covers any and all possible combinations of one or more of the associated listed items.

The preparation method _of the Pt/ _Bi2O3 catalyst provided by the embodiments of the present invention comprises the following steps:

1. Hydrolyze the Bi ³⁺ ions in the Bi salt solution in an alkaline environment to form a Bi ₂ O ₃ precipitate, and obtain Bi ₂ O ₃ powder after centrifugal washing and drying.

Specifically, step 1 specifically includes the following steps:

Dissolve Bi(NO ₃ ) ₃ ·5H ₂ O in distilled water to make a solution, and add nitric acid to prevent hydrolysis, so as to realize the configuration of Bi(NO ₃ ) ₃ solution;

NaOH solution was added dropwise to the Bi(NO ₃ ) ₃ solution, and stirred for several hours to obtain a pale yellow Bi ₂ O ₃ precipitate;

After centrifugation, washing with distilled water and absolute ethanol, and drying at 80°C, pale yellow _{Bi2O3 powder} was obtained.

Moreover, the Bi ₂ O ₃ precipitate obtained in step one is a rod-shaped Bi ₂ O ₃ precipitate.

2. Disperse the Bi ₂ O ₃ powder in a solution system containing H ₂ PtCl ₆ and a sacrificial agent, and then stir under light conditions to obtain a Pt/Bi2O3 catalyst.

Specifically, after dispersing the Bi ₂ O ₃ powder in the solution system containing H ₂ PtCl ₆ and the sacrificial agent in step 2, under constant stirring conditions, use a light source with a wavelength > 400nm to lighten the suspension Irradiation was carried out until the suspension turned gray-black. Preferably, ethanol is used as the sacrificial agent of H ₂ PtCl ₆ in the second step. That is to say, Pt particles are deposited on the surface of Bi ₂ O ₃ by visible light photoreduction to obtain Pt/Bi ₂ O ₃ composites.

Specifically, the preparation method may include the following examples:

Example 1

Dissolve 1g Bi(NO ₃ ) ₃ 5H ₂ O in 40mL distilled water to form a solution, add a small amount of nitric acid to prevent hydrolysis, then add 80ml NaOH solution (0.05g/mL) dropwise into the Bi(NO ₃ ) ₃ solution, stir After 3 hours, a pale yellow precipitate was obtained, which was centrifuged, washed thoroughly with distilled water and absolute ethanol, and dried at 80°C to obtain a pale yellow Bi ₂ O ₃ powder;

Disperse 0.2g of dried Bi ₂ O ₃ in 40mL aqueous solution dissolved with 0.01mmol H ₂ PtCl ₆ and a small amount of ethanol, under constant stirring, irradiate with a 30W LED lamp (wavelength>400nm) for 1h, and the suspension The solution turned gray-black, washed thoroughly with distilled water and absolute ethanol, centrifuged, and then dried to obtain Pt/Bi ₂ O ₃ .

Example 2

Dissolve 1g Bi(NO ₃ ) ₃ 5H ₂ O in 40mL distilled water to form a solution, add a small amount of nitric acid to prevent hydrolysis, then add 80ml NaOH solution (0.05g/mL) dropwise into the Bi(NO ₃ ) ₃ solution, stir After 3 hours, a pale yellow precipitate was obtained, which was separated by centrifugation, washed thoroughly with distilled water and absolute ethanol, and dried at 80°C to obtain a pale yellow Bi ₂ O ₃ powder; take 0.2 g of dried Bi ₂ O ₃ and disperse it in a solution containing 0.005 mmol H ₂ In the 40mL aqueous solution of PtCl ₆ and a small amount of ethanol, under constant stirring, irradiate with a 30W LED lamp (wavelength>400nm) for 1h. It is then dried to obtain Pt/Bi ₂ O ₃ .

Example 3

Dissolve 1g Bi(NO ₃ ) ₃ 5H ₂ O in 40mL distilled water to form a solution, add a small amount of nitric acid to prevent hydrolysis, then add 80ml NaOH solution (0.05g/mL) dropwise into the Bi(NO ₃ ) ₃ solution, stir After 3 hours, a pale yellow precipitate was obtained, which was separated by centrifugation, washed thoroughly with distilled water and absolute ethanol, and dried at 80°C to obtain a pale yellow Bi ₂ O ₃ powder; take 0.2 g of dried Bi ₂ O ₃ and disperse it in a solution containing 0.02 mmol H ₂ In 40mL aqueous solution of PtCl ₆ and a small amount of ethanol, under constant stirring, irradiate with a 30W LED lamp (wavelength>400nm) for 1h, at this time the suspension turns grayish black, fully wash with distilled water and absolute ethanol, centrifuge, It is then dried to obtain Pt/Bi ₂ O ₃ .

Example 4

Dissolve 1g Bi(NO ₃ ) ₃ ·5H ₂ O in 40mL distilled water to form a solution, add a small amount of nitric acid to prevent hydrolysis, then add 80ml NaOH solution (0.02g/mL) dropwise to the Bi(NO ₃ ) ₃ solution, stir After ₃ hours, a pale yellow precipitate was obtained, which was separated by centrifugation, washed thoroughly with distilled water and absolute ethanol, and dried at 80°C to obtain a pale yellow Bi ₂ O ₃ powder _{; 2} In 40mL aqueous solution of PtCl ₆ and a small amount of ethanol, under constant stirring, irradiate with a 30W LED lamp (wavelength>400nm) for 1h, at this time the suspension turns grayish black, fully wash with distilled water and absolute ethanol, centrifuge, It is then dried to obtain Pt/Bi ₂ O ₃ .

Example 5

Dissolve 1g Bi(NO ₃ ) ₃ ·5H ₂ O in 40mL distilled water to form a solution, add a small amount of nitric acid to prevent hydrolysis, then add 80ml NaOH solution (0.1g/mL) dropwise into the Bi(NO ₃ ) ₃ solution, stir After ₃ hours, a pale yellow precipitate was obtained, which was separated by centrifugation, washed thoroughly with distilled water and absolute ethanol, and dried at 80°C to obtain a pale yellow Bi ₂ O ₃ powder _{; 2} In 40mL aqueous solution of PtCl ₆ and a small amount of ethanol, under constant stirring, irradiate with a 30W LED lamp (wavelength>400nm) for 1h, at this time the suspension turns grayish black, fully wash with distilled water and absolute ethanol, centrifuge, It is then dried to obtain Pt/Bi ₂ O ₃ .

Example 6

Dissolve 1g Bi(NO ₃ ) ₃ 5H ₂ O in 40mL distilled water to form a solution, add a small amount of nitric acid to prevent hydrolysis, then add 80ml NaOH solution (0.05g/mL) dropwise into the Bi(NO ₃ ) ₃ solution, stir After ₃ hours, a pale yellow precipitate was obtained, which was separated by centrifugation, washed thoroughly with distilled water and absolute ethanol, and dried at 80°C to obtain a pale yellow Bi ₂ O ₃ powder _{; 2} In 40mL aqueous solution of PtCl ₆ and a small amount of ethanol, under constant stirring, irradiate with a 30W LED lamp (wavelength>400nm) for 3h, at this time the suspension turns grayish black, fully wash with distilled water and absolute ethanol, centrifuge, It is then dried to obtain Pt/Bi ₂ O ₃ .

As shown in Figure 1 and Figure 2, a catalyst prepared by the above-mentioned preparation method is suitable for photothermal co-catalytic degradation of gaseous formaldehyde at room temperature. It should be noted that the catalyst is a Pt/Bi ₂ O ₃ catalyst. It should be understood that in this embodiment, the catalyst support in the Pt/Bi2O3 catalyst is rod-shaped Bi ₂ O ₃ , so that the Pt loading of the catalyst can be increased by increasing the specific surface area of the catalyst support.

A gaseous formaldehyde degradation method, the method uses the catalyst shown in Figure 1 and Figure 2 to carry out the degradation of gaseous formaldehyde under the common conditions of room temperature and lighting. Preferably, the Pt/Bi ₂ O ₃ catalyst is irradiated with a daily LED lamp.

Specifically, the operation steps of the method are as follows:

The formaldehyde degradation test was carried out in a self-made sealed gas phase reactor, and a multi-component gas analyzer (INNOVAair Tech Instruments Model 1412) was used for online monitoring. During the experiment, 100 mg of the prepared Pt/Bi ₂ O ₃ sample was weighed and dispersed in a petri dish with a diameter of 7 cm, moved into the reactor, covered with a frosted glass cover, and closed the reactor operation port. Inject 10 μL of 15% formaldehyde solution from the injection port, use the built-in fan to blow off the formaldehyde completely, and mix it with the air in the reactor evenly. The concentration of formaldehyde can be controlled at 130ppm. When the test shows that the concentration of formaldehyde is basically unchanged, the ground glass cover is pulled up by the traction wire to start the formaldehyde oxidation experiment, and the petri dish is irradiated with a 30W LED lamp to monitor the change of formaldehyde concentration. As a control, Bi ₂ O ₃ and Pt/Bi ₂ O ₃ were used to carry out the degradation experiment of gaseous formaldehyde under the condition of no light.

As shown in Figure 3 and Figure 4, the Pt/Bi ₂ O ₃ catalyst provided in this example can greatly improve the degradation effect of gaseous formaldehyde under the common conditions of room temperature and lighting.

Specifically, during the degradation reaction of gaseous formaldehyde, formaldehyde is oxidized to CO ₂ and water; under light conditions, the catalytic degradation effect of Pt/Bi ₂ O ₃ catalyst is significantly better than that without light. Under light conditions, both formaldehyde removal rate and CO ₂ generation rate increased significantly, and the formaldehyde removal rate in 1 h increased from 17% to 43% under no light condition.

The principle that the Pt/Bi ₂ O ₃ catalyst can greatly promote gaseous formaldehyde under the common conditions of room temperature and lighting is as follows:

The noble metal Pt was combined with a suitable visible light active catalyst Bi ₂ O ₃ to degrade gaseous formaldehyde by photothermal cocatalysis. Among them, the catalysis of the catalyst under the condition of no light is called thermal catalysis, and the catalysis of the catalyst under the condition of light is called photocatalysis.

Under the common conditions of room temperature and light irradiation, the Pt/ _Bi2O3 catalyst can simultaneously exert the thermal catalysis _of Pt and the photocatalysis of _Bi2O3 . _In the reaction process, Pt not only acts as a thermal catalyst for formaldehyde, It also acts as an electron trapping agent in the photocatalytic process, which promotes the photogenerated electron migration _of Bi ₂ O ₃ and the photogenerated holes to participate in the oxidation of formaldehyde, thereby _enhancing the performance of the photocatalyst. Good base material, which acts as a co-catalyst for thermocatalytic reactions. Due to the strong oxidation ability of the photocatalyst Bi ₂ O ₃ , it can decompose larger organic molecules, which is beneficial to prevent the deactivation of the catalyst Bi ₂ O ₃ caused by being covered by these organic molecules.

Moreover, it should be noted that in the Pt/Bi ₂ O ₃ catalyst provided in the examples of the present invention, Bi ₂ O ₃ has not been calcined, so that there are more hydroxyl groups on the surface of Bi ₂ O ₃ , and more hydroxyl groups are further beneficial to The thermal catalytic effect of Pt, and then improve the degradation effect of Pt/Bi ₂ O ₃ catalyst on gaseous formaldehyde under the common conditions of room temperature and light.

It will be apparent to those skilled in the art that the invention is not limited to the details of the above-described exemplary embodiments, but that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Accordingly, the embodiments should be regarded in all points of view as exemplary and not restrictive, the scope of the invention being defined by the appended claims rather than the foregoing description, and it is therefore intended that the scope of the invention be defined by the appended claims rather than by the foregoing description. All changes within the meaning and range of equivalents of the elements are embraced in the present invention. Any reference sign in a claim should not be construed as limiting the claim concerned.

In addition, it should be understood that although this specification is described according to implementation modes, not each implementation mode only includes an independent technical solution, and this description in the specification is only for clarity, and those skilled in the art should take the specification as a whole , the technical solutions in the various embodiments can also be properly combined to form other implementations that can be understood by those skilled in the art.

Claims (8)

1. A kind of 1. Pt/Bi₂O₃The preparation method of catalyst, it is characterised in that：Comprise the following steps：

   A, the Bi in Bi salting liquids is made in alkaline environment³⁺Ion hydrolysis generation Bi₂O₃Precipitation, centrifuge washing obtain after drying Bi₂O₃Powder；

   B, by the Bi₂O₃Powder is scattered in containing H₂PtCl₆In the solution system of sacrifice agent, then stir and obtain under illumination condition Obtain Pt/Bi₂O₃Catalyst.
2. 2. Pt/Bi according to claim 1₂O₃The preparation method of catalyst, it is characterised in that：Specifically included in step a Following steps：

   By Bi (NO₃)₃·5H₂O is dissolved in distilled water wiring solution-forming, and adds nitric acid and prevent from hydrolyzing, to realize configuration Bi (NO₃)₃It is molten Liquid；

   NaOH solution is added drop-wise to the Bi (NO₃)₃In solution, the stirring some time obtains flaxen Bi₂O₃Precipitation；

   It is centrifuged, and is fully washed with distilled water and absolute ethyl alcohol, 80 DEG C of dryings, obtains flaxen Bi₂O₃Powder.
3. 3. Pt/Bi according to claim 1₂O₃The preparation method of catalyst, it is characterised in that：Step a obtains the Bi₂O₃ Precipitation is bar-like Bi₂O₃Precipitation.
4. 4. Pt/Bi according to claim 1₂O₃The preparation method of catalyst, it is characterised in that：In stepb by described in Bi₂O₃Powder is scattered in containing H₂PtCl₆After in the solution system of sacrifice agent, under constant agitation, wavelength is used> 400nm lamp source is irradiated to suspension until the suspension is changed into grey black.
5. 5. Pt/Bi according to claim 1₂O₃The preparation method of catalyst, it is characterised in that：Ethanol is used in stepb As H₂PtCl₆Sacrifice agent.
6. A kind of 6. Pt/Bi₂O₃Catalyst, it is characterised in that：The Pt/Bi₂O₃Catalyst is used as described in claim 1-5 is any Pt/Bi₂O₃The preparation method of catalyst is prepared, and the Pt/Bi₂O₃Catalyst is applied to photo-thermal catalytic degradation room altogether Gaseous formaldehyde under the conditions of temperature.
7. 7. a kind of gaseous formaldehyde biodegrading process, it is characterised in that use Pt/Bi as claimed in claim 6₂O₃Catalyst is in room The degraded of gaseous formaldehyde is carried out under the common conditions that gentle lamp shines.
8. 8. gaseous formaldehyde biodegrading process according to claim 7, it is characterised in that：At ambient temperature, using daily LED Pt/Bi described in light irradiation₂O₃Catalyst.