阅读说明：本技术 一种催化剂及其制备方法、应用 (Catalyst, and preparation method and application thereof ) 是由 商庆浩 王宁 李宗强 于 2021-06-30 设计创作，主要内容包括：一种催化剂及其制备方法、应用。本发明提供一种催化剂,该催化剂包括二氧化钛和负载在二氧化钛上的铑,铑的粒径小于1nm。由于催化剂中铑的粒径小于1nm,所以铑在催化剂中具有很好的分散度,可以提高催化剂的催化转化效率。(A catalyst, a preparation method and application thereof. The invention provides a catalyst, which comprises titanium dioxide and rhodium loaded on the titanium dioxide, wherein the particle size of the rhodium is less than 1 nm. The particle size of rhodium in the catalyst is less than 1nm, so that the rhodium has good dispersity in the catalyst, and the catalytic conversion efficiency of the catalyst can be improved.)

1. A catalyst, characterized in that the catalyst comprises titanium dioxide and rhodium supported on the titanium dioxide;

the particle size of the rhodium is less than 1 nm.

2. The catalyst according to claim 1, wherein the titanium dioxide is contained in an amount of 97.5 to 99.5% by mass and the rhodium is contained in an amount of 0.5 to 2.5% by mass, based on the total mass of the catalyst.

3. A method for preparing the catalyst of claim 1 or 2, comprising the steps of:

1) dripping a rhodium chloride aqueous solution into a titanium dioxide aqueous solution at the speed of 0.5-1.5mL/min to obtain a first mixed solution;

2) adjusting the pH value of the first mixed solution to 9-10 to obtain a second mixed solution;

3) carrying out post-treatment on the second mixed solution to obtain an intermediate catalyst; the post-treatment at least comprises filtering treatment and drying treatment in sequence;

4) and roasting the intermediate catalyst at the temperature of 280-320 ℃ to obtain the catalyst.

4. The method for preparing a catalyst according to claim 3, wherein the concentration of the aqueous rhodium chloride solution is 0.8 to 1.2mg_Rh/mL。

5. The method for preparing a catalyst according to claim 3 or 4, wherein the temperature in step 1) is 65 to 75 ℃.

6. The method for producing a catalyst according to any one of claims 3 to 5, wherein in step 1), the aqueous titanium dioxide solution is a stirred aqueous titanium dioxide solution;

the stirring speed is 700-1000 r/min.

7. The method for preparing a catalyst according to any one of claims 3 to 6, wherein the temperature of the drying treatment is 80 to 110 ℃ and the time of the drying treatment is 8 to 12 hours.

8. The method for producing a catalyst according to any one of claims 3 to 7, wherein the post-treatment further comprises a stirring treatment and a standing treatment;

the post-treatment comprises the step of sequentially carrying out the stirring treatment, the standing treatment, the filtering treatment and the drying treatment on the second mixed solution.

9. The method for preparing the catalyst according to claim 8, wherein the temperature of the stirring treatment is 75-85 ℃, the time of the stirring treatment is 5.5-6.5h, and the rotation speed of the stirring treatment is 700-; and/or the presence of a gas in the gas,

the temperature of the standing treatment is 75-85 ℃, and the time of the standing treatment is 2.5-3.5 h.

10. An air conditioner is characterized by comprising a formaldehyde removal module; the formaldehyde removal module comprises the catalyst of claim 1 or 2; and/or the presence of a gas in the gas,

the formaldehyde removal module comprises a catalyst prepared by the method for preparing the catalyst according to any one of claims 3 to 9.

Technical Field

The invention relates to a catalyst, a preparation method and application thereof, and belongs to the technical field of air purification.

Background

Formaldehyde is one of the main pollutants of indoor environment, and formaldehyde is a carcinogen and seriously harms human health. At present, after the new house decoration is finished, most of formaldehyde removing methods adopted by users are ventilation and air exchange, but the formaldehyde removing method is long in treatment time and poor in treatment effect. The air conditioner is used as an indoor air conditioner, not only has the temperature and humidity control function, but also can be provided with a formaldehyde removal module to remove indoor formaldehyde. At present, most of formaldehyde removing air conditioners adopt an adsorption principle to remove formaldehyde, and the problem that secondary pollution is easily caused after an adsorption material is saturated exists.

The catalytic formaldehyde removal is a novel formaldehyde removal technology, formaldehyde is converted into carbon dioxide and water at room temperature through a catalyst, and the method has the advantages of simplicity, convenience and high efficiency. However, the existing catalyst for removing formaldehyde not only has complex preparation method and higher preparation cost, but also has the defect of low catalytic conversion efficiency.

Disclosure of Invention

The invention provides a catalyst which has high catalytic conversion efficiency.

The invention provides a preparation method of a catalyst, which can prepare the catalyst with high catalytic conversion efficiency, and has simple preparation process and low preparation cost.

The invention provides an air conditioner which can efficiently and conveniently remove formaldehyde.

The present invention provides a catalyst, wherein the catalyst comprises titanium dioxide and rhodium supported on the titanium dioxide;

the particle size of the rhodium is less than 1 nm.

The catalyst as described above, wherein the titanium dioxide is contained in an amount of 97.5 to 99.5% by mass and the rhodium is contained in an amount of 0.5 to 2.5% by mass, based on the total mass of the catalyst.

The invention provides a preparation method of a catalyst, which comprises the following steps:

1) dripping a rhodium chloride aqueous solution into a titanium dioxide aqueous solution at the speed of 0.5-1.5mL/min to obtain a first mixed solution;

2) adjusting the pH value of the first mixed solution to 9-10 to obtain a second mixed solution;

3) carrying out post-treatment on the second mixed solution to obtain an intermediate catalyst; the post-treatment at least comprises filtering treatment and drying treatment in sequence;

4) and roasting the intermediate catalyst at the temperature of 280-320 ℃ to obtain the catalyst.

The process for producing a catalyst as described above, wherein the concentration of the aqueous rhodium chloride solution is 0.8 to 1.2mg_Rh/mL。

The method for preparing the catalyst as described above, wherein the temperature in the step 1) is 65 to 75 ℃.

The method for producing a catalyst as described above, wherein in the step 1), the aqueous titanium dioxide solution is a titanium dioxide aqueous solution under stirring;

the stirring speed is 700-1000 r/min.

The preparation method of the catalyst is characterized in that the temperature of the drying treatment is 80-110 ℃, and the time of the drying treatment is 8-12 h.

The preparation method of the catalytic additive, wherein the post-treatment further comprises stirring treatment and standing treatment;

the post-treatment comprises the step of sequentially carrying out the stirring treatment, the standing treatment, the filtering treatment and the drying treatment on the second mixed solution.

The preparation method of the catalyst comprises the steps of stirring at 75-85 deg.C for 5.5-6.5h at a rotation speed of 700-1000 r/min; and/or the presence of a gas in the gas,

the temperature of the standing treatment is 75-85 ℃, and the time of the standing treatment is 2.5-3.5 h.

The invention provides an air conditioner, which comprises a formaldehyde removal module; the formaldehyde removal module comprises the catalyst; and/or the presence of a gas in the gas,

the formaldehyde removal module comprises the catalyst prepared by the preparation method of the catalyst.

The invention provides a catalyst, which comprises titanium dioxide and rhodium loaded on the titanium dioxide, wherein the particle size of the rhodium is less than 1 nm. The particle size of rhodium in the catalyst is less than 1nm, so that the rhodium has good dispersity in the catalyst, and the catalytic conversion efficiency of the catalyst can be improved.

The invention provides a preparation method of a catalyst, which can prepare a catalyst comprising titanium dioxide and rhodium loaded on the titanium dioxide, wherein the particle size of the rhodium is less than 1 nm. The prepared catalyst has high rhodium dispersion degree, so the catalyst has high catalytic conversion efficiency, and the preparation method has simple operation and low preparation cost.

The invention provides an air conditioner, wherein a formaldehyde removing unit of the air conditioner comprises the catalyst and/or the catalyst prepared by the preparation method, so that the air conditioner can efficiently and conveniently remove formaldehyde, and the formaldehyde removing cost is low.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the related art, the drawings used in the description of the embodiments of the present invention or the related art are briefly introduced below. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.

FIG. 1 is a Transmission Electron Microscope (TEM) image of a catalyst in some embodiments of the invention;

FIG. 2 is a TEM image of a catalyst in further embodiments of the present invention;

FIG. 3 is a graph showing the catalytic conversion efficiency of formaldehyde by the catalyst of example 1 of the present invention;

FIG. 4 is XRD spectra of titanium dioxide, a catalyst loaded with 0.5 wt% rhodium, and a catalyst loaded with 2.5 wt% rhodium in accordance with the present invention;

FIG. 5 is a hydrogen-temperature programmed reduction (H) of titania and a catalyst supporting 2.5 wt% rhodium in accordance with the present invention₂TPR) spectrum.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

FIG. 1 is a Transmission Electron Microscope (TEM) image of a catalyst in some embodiments of the invention; FIG. 2 is a TEM image of a catalyst in further embodiments of the invention.

As shown in fig. 1 or fig. 2, a first aspect of the present invention provides a catalyst comprising titania and rhodium supported on the titania;

the grain size of rhodium is less than 1 nm.

In the present invention, the particle size of rhodium is less than 1nm, which means that the maximum particle size of rhodium is less than 1 nm. Rhodium smaller than 1nm is referred to herein as sub-nanoparticles.

It will be appreciated that in the catalyst of the invention, in which titania is the support and rhodium is supported as the catalytically active material on the titania support, all of the rhodium of the invention has a particle size of less than 1 nm.

In the invention, rhodium is sub-nano particles, so that rhodium has good dispersity in the catalyst, and when the catalyst is used for catalytic reaction, more rhodium can participate in the catalytic reaction, thereby improving the catalytic conversion efficiency of the catalyst. The catalyst has good catalytic conversion efficiency on formaldehyde, and the catalytic conversion efficiency of the catalyst on formaldehyde can reach 100%.

In some embodiments of the invention, the titanium dioxide is present in an amount of 97.5 to 99.5 mass% and the rhodium is present in an amount of 0.5 to 2.5 mass%, based on the total mass of the catalyst.

In the invention, when the mass percentage of rhodium is too high based on the total mass of the catalyst, the catalytic conversion efficiency of the catalyst can be improved, but the rhodium with too high mass percentage can increase the production cost of the catalyst. In the invention, when the mass percentage of rhodium is 0.5-2.5%, the catalyst has higher catalytic conversion efficiency and the production cost is not excessively increased.

A second aspect of the present invention provides a method for preparing a catalyst, comprising the steps of:

1) dripping a rhodium chloride aqueous solution into a titanium dioxide aqueous solution at the speed of 0.5-1.5mL/min to obtain a first mixed solution;

2) adjusting the pH value of the first mixed solution to 9-10 to obtain a second mixed solution;

3) carrying out post-treatment on the second mixed solution to obtain an intermediate catalyst; the post-treatment at least comprises filtering treatment and drying treatment in sequence;

4) the intermediate catalyst is roasted at the temperature of 280-320 ℃ to obtain the catalyst.

Specifically, a rhodium chloride aqueous solution is dripped into a titanium dioxide aqueous solution at the speed of 0.5-1.5mL/min to obtain a first mixed solution containing rhodium and titanium dioxide; then adjusting the pH value of the first mixed solution until the pH value is 9-10 to obtain a second mixed solution, wherein the second mixed solution contains titanium dioxide loaded with rhodium; then, filtering the second mixed solution to filter out titanium dioxide loaded with rhodium in the second mixed solution, drying the filtered titanium dioxide loaded with rhodium to remove moisture in the titanium dioxide loaded with rhodium to obtain dried titanium dioxide loaded with rhodium, namely the intermediate catalyst; finally, the intermediate catalyst is placed in the atmosphere of 280-320 ℃ for roasting, so that the rhodium and the titanium dioxide are better combined, and the catalyst is obtained.

In the step 2), the pH value of the first mixed solution may be adjusted by using an alkaline solution, and the alkaline solution is not particularly limited in the present invention and may be an alkali commonly used in the artThe alkaline solution may be, for example, an aqueous NaOH solution. In a specific embodiment, the concentration of the aqueous NaOH solution is 0.5mol L^-1。

According to the catalyst preparation method, the dripping speed of the rhodium chloride aqueous solution in the step 1) is too high, so that the catalyst with the rhodium particle size smaller than 1nm is difficult to obtain, and if the dripping speed of the rhodium chloride aqueous solution is too low, the first mixed solution can be obtained within too long time, so that the preparation time is increased, and the production efficiency is reduced. Therefore, in order to obtain a catalyst with rhodium of which the particle diameter is less than 1nm more quickly, the dropping speed of the rhodium chloride aqueous solution in the step 1) is 0.5-1.5 mL/min.

According to the preparation method of the catalyst, the catalyst with the rhodium particle size smaller than 1nm can be obtained under the condition of saving production time only if the dripping speed of the rhodium chloride aqueous solution, the pH value of the second mixed solution and the roasting treatment temperature are required to be within the specific ranges, so that the dispersion degree of the rhodium in the catalyst is improved, and the catalyst has high catalytic conversion efficiency. The preparation method of the catalyst also has the advantages of simple operation and low preparation cost.

In some embodiments of the invention, the concentration of the aqueous rhodium chloride solution is 0.8 to 1.2mg_RhIn mL, the concentration of the aqueous rhodium chloride solution refers to the mass of rhodium contained per mL of water.

In the invention, if the concentration of the rhodium chloride aqueous solution is too low, a large amount of rhodium chloride aqueous solution is needed to prepare the catalyst of the invention, and the large amount of rhodium chloride aqueous solution brings inconvenience to the subsequent preparation process, so that the preparation process is complicated to operate; if the concentration of the aqueous rhodium chloride solution is too high, the production cost of the catalyst becomes too high. Therefore, in order to save the production cost of the catalyst and simplify the preparation process, the concentration of the rhodium chloride aqueous solution is 0.8-1.2mg_Rh/mL。

In the invention, in order to better load rhodium on titanium dioxide, the preparation time of the catalyst is reduced, and the preparation efficiency of the catalyst is improved. In some embodiments of the invention, the temperature in step 1) is from 65 to 75 ℃. Namely, in the step 1), a rhodium chloride aqueous solution with the temperature of 65-75 ℃ is dripped into a titanium dioxide aqueous solution with the temperature of 65-75 ℃ at the speed of 0.5-1.5mL/min to obtain a first mixed solution.

In some embodiments of the invention, in step 1), the aqueous titanium dioxide solution is a stirred aqueous titanium dioxide solution;

the stirring speed is 700-1000 r/min.

It can be understood that, in the step 1), the rhodium chloride aqueous solution is dripped into the titanium dioxide aqueous solution with the stirring speed of 700-1000r/min at the speed of 0.5-1.5mL/min to obtain the first mixed solution.

In the invention, the rhodium chloride aqueous solution is dripped into the titanium dioxide aqueous solution in stirring to obtain the first solution, so that rhodium can be better loaded on the titanium dioxide, and the yield of the catalyst is improved. However, if the stirring speed is too high, the titanium dioxide aqueous solution may splash and excessive energy consumption may occur; the stirring speed is too slow, and it is difficult to sufficiently exert the stirring effect. Therefore, in the invention, the stirring speed is 700-.

In some embodiments of the present invention, the temperature of the drying treatment is 80 to 110 ℃ and the time of the drying treatment is 8 to 12 hours.

In the present invention, when the temperature of the drying treatment is too high, it is difficult to form a catalyst in which the particle size of rhodium is less than 1 nm; if the temperature of the drying treatment is too low, it takes too long to completely remove the moisture from the rhodium-loaded titanium dioxide. The temperature of the drying treatment is therefore 80-110 c in order to remove the moisture of the rhodium-loaded titania sufficiently in a short period of time and without affecting the performance of the finally formed catalyst.

In the present invention, if the time for the several drying treatments is too short, it is difficult to sufficiently remove the moisture in the titanium dioxide loaded with rhodium; if the drying treatment is carried out for too long, the performance of the finally obtained catalyst is affected. Therefore, the drying treatment time is 8 to 12 hours in order to remove the moisture in the rhodium-loaded titanium dioxide more sufficiently without affecting the performance of the finally obtained catalyst.

In some embodiments of the invention, the post-treatment further comprises a stirring treatment and a standing treatment;

the post-treatment comprises the steps of stirring, standing, filtering and drying the second mixed solution in sequence.

It can be understood that the second mixed solution is stirred, so that rhodium in the second mixed solution is more fully contacted with the titanium dioxide, and more rhodium is loaded on the titanium dioxide; then standing the stirred second mixed solution to enable the titanium dioxide loaded with rhodium in the second mixed solution to be more precipitated; then filtering the precipitated second mixed solution, and filtering titanium dioxide loaded with rhodium in the second mixed solution; and finally, drying the filtered titanium dioxide loaded with rhodium to remove moisture of the titanium dioxide loaded with rhodium so as to obtain the intermediate catalyst.

In the invention, the post-treatment also comprises stirring treatment and standing treatment, so that rhodium in the second mixed solution can be more fully contacted with titanium dioxide, and the yield of the catalyst is further improved.

In some embodiments of the invention, in order to further increase the yield of the catalyst, the temperature of the stirring treatment is 65-75 ℃, the time of the stirring treatment is 5.5-6.5h, and the rotating speed of the stirring treatment is 700-; and/or the presence of a gas in the gas,

the temperature of the standing treatment is 65-75 ℃, and the time of the standing treatment is 2.5-3.5 h.

A third aspect of the present invention provides an air conditioner, comprising a formaldehyde removal module; the formaldehyde removal module comprises the catalyst; and/or the presence of a gas in the gas,

the formaldehyde removal module comprises the catalyst prepared by the preparation method of the catalyst.

According to the air conditioner, the catalyst in the formaldehyde removing module is titanium dioxide loaded rhodium catalyst, the particle size of rhodium in the catalyst is less than 1nm, and the dispersion degree of rhodium in the catalyst is high, so that the air conditioner has high formaldehyde catalytic conversion rate, the catalytic conversion rate of formaldehyde can reach 100%, and the formaldehyde can be removed efficiently and conveniently.

Hereinafter, the technical solution of the present invention will be described in detail with reference to specific examples.

Example 1

The catalyst of this example was prepared by a process comprising the steps of:

1) solution preparation

1.0g of TiO₂Adding into a beaker filled with 100mL of ultrapure water, placing the beaker in a 70 ℃ water bath, stirring for 20min to form uniform TiO₂An aqueous solution;

the mass concentration of the preparation is 1mg_RhRhCl/mL₃.3H₂And (4) O aqueous solution.

2) Mixing

6.3mL of 1mg_RhRhCl/mL₃.3H₂Adding the O aqueous solution into a beaker of 100mL of ultrapure water, placing the beaker in a 70 ℃ water bath, stirring for 40min until the mixture is uniform, and obtaining diluted RhCl₃.3H₂An aqueous solution of O;

the diluted RhCl was added at a rate of 1mL/min₃.3H₂Dropwise adding O aqueous solution at constant speed to TiO under vigorous stirring₂Obtaining a first mixed solution in the water solution;

wherein the stirring speed is 800r/min, and the temperature is 70 ℃.

3) Adjusting pH

And (3) adjusting the pH value of the first mixed solution to about 9.5 by using 0.5mol/L NaOH aqueous solution to obtain a second mixed solution.

4) Post-treatment

Placing the beaker filled with the second mixed solution in a water bath at 80 ℃ for stirring treatment and standing treatment in sequence, and filtering and drying the second mixed solution after standing treatment to obtain an intermediate catalyst;

wherein the stirring treatment time is 6h, the stirring treatment rotating speed is 800r/min, the standing treatment time is 3h, the drying treatment temperature is 100 ℃, and the drying treatment time is 10 h.

5) Roasting

Grinding the intermediate catalyst, and then placing the ground intermediate catalyst in a muffle furnace at 300 ℃ for roasting treatment to obtain a catalyst;

wherein the roasting treatment time is 6 hours.

The surface of the catalyst obtained in example 1 was observed using TEM, and as shown in fig. 1, the particle size of rhodium in the catalyst obtained in example 1 was less than 1 nm.

The loading of rhodium in the catalyst obtained in inventive example 1 was 0.5 wt%.

Example 2

The catalyst of this example was prepared by a process comprising the steps of:

1) solution preparation

1.0g of TiO₂Adding into a beaker filled with 100mL of ultrapure water, placing the beaker in a 70 ℃ water bath, stirring for 20min to form uniform TiO₂An aqueous solution;

the mass concentration of the preparation is 1mg_RhRhCl/mL₃.3H₂And (4) O aqueous solution.

2) Mixing

6.3mL of 1mg_RhRhCl/mL₃.3H₂Adding the O aqueous solution into a beaker of 100mL of ultrapure water, placing the beaker in a 70 ℃ water bath, stirring for 40min until the mixture is uniform, and obtaining diluted RhCl₃.3H₂An aqueous solution of O;

the diluted RhCl was added at a rate of 1mL/min₃.3H₂Dropwise adding O aqueous solution at constant speed to TiO under vigorous stirring₂Obtaining a first mixed solution in the water solution;

wherein the stirring speed is 800r/min, and the temperature is 70 ℃.

3) Adjusting pH

And (3) adjusting the pH value of the first mixed solution to about 9.5 by using 0.5mol/L NaOH aqueous solution to obtain a second mixed solution.

4) Post-treatment

Filtering and drying the second mixed solution to obtain an intermediate catalyst;

wherein the drying temperature is 100 ℃, and the drying time is 10 h.

5) Roasting

Grinding the intermediate catalyst, and then placing the ground intermediate catalyst in a muffle furnace at 300 ℃ for roasting treatment to obtain a catalyst;

wherein the roasting treatment time is 6 hours.

The surface of the catalyst obtained in example 2 was observed using TEM, and the particle size of rhodium in the catalyst obtained in example 2 was less than 1 nm.

The loading of rhodium in the catalyst obtained in example 2 of the present invention was 0.3 wt%.

Example 3

The catalyst of this example was prepared by a process comprising the steps of:

1) solution preparation

1.0g of TiO₂Adding into a beaker filled with 100mL of ultrapure water, placing the beaker in a 70 ℃ water bath, stirring for 20min to form uniform TiO₂An aqueous solution;

the mass concentration of the preparation is 0.5mg_RhRhCl/mL₃.3H₂And (4) O aqueous solution.

2) Mixing

12.6mL of 0.7mg_RhRhCl/mL₃.3H₂Adding the O aqueous solution into a beaker of 100mL of ultrapure water, placing the beaker in a 70 ℃ water bath, stirring for 40min until the mixture is uniform, and obtaining diluted RhCl₃.3H₂An aqueous solution of O;

the diluted RhCl was added at a rate of 1mL/min₃.3H₂Dropwise adding O aqueous solution at constant speed to TiO under vigorous stirring₂Obtaining a first mixed solution in the water solution;

wherein the stirring speed is 800r/min, and the temperature is 70 ℃.

3) Adjusting pH

And (3) adjusting the pH value of the first mixed solution to about 9.5 by using 0.5mol/L NaOH aqueous solution to obtain a second mixed solution.

4) Post-treatment

Placing the beaker filled with the second mixed solution in a water bath at 80 ℃ for stirring treatment and standing treatment in sequence, and filtering and drying the second mixed solution after standing treatment to obtain an intermediate catalyst;

wherein the stirring treatment time is 6h, the stirring treatment rotating speed is 800r/min, the standing treatment time is 3h, the drying treatment temperature is 100 ℃, and the drying treatment time is 10 h.

5) Roasting

Grinding the intermediate catalyst, and then placing the ground intermediate catalyst in a muffle furnace at 300 ℃ for roasting treatment to obtain a catalyst;

wherein the roasting treatment time is 6 hours.

The surface of the catalyst obtained in example 3 was observed using TEM, and the particle size of rhodium in the catalyst obtained in example 3 was less than 1 nm.

The loading of rhodium in the catalyst obtained in example 3 of the present invention was 0.4 wt%.

Example 4

The catalyst of this example was prepared by a process comprising the steps of:

1) solution preparation

1.0g of TiO₂Adding into a beaker filled with 100mL of ultrapure water, placing the beaker in a 90 ℃ water bath, and stirring for 20min to form uniform TiO₂An aqueous solution;

the mass concentration of the preparation is 1mg_RhRhCl/mL₃.3H₂And (4) O aqueous solution.

2) Mixing

6.3mL of 1mg_RhRhCl/mL₃.3H₂Adding the O aqueous solution into a beaker of 100mL of ultrapure water, placing the beaker in a 70 ℃ water bath, stirring for 40min until the mixture is uniform, and obtaining diluted RhCl₃.3H₂An aqueous solution of O;

the diluted RhCl was added at a rate of 1mL/min₃.3H₂Dropwise adding O aqueous solution at constant speed to TiO under vigorous stirring₂Obtaining a first mixed solution in the water solution;

wherein the stirring speed is 800r/min, and the temperature is 70 ℃.

3) Adjusting pH

And (3) adjusting the pH value of the first mixed solution to about 9.5 by using 0.5mol/L NaOH aqueous solution to obtain a second mixed solution.

4) Post-treatment

Placing the beaker filled with the second mixed solution in a water bath at 80 ℃ for stirring treatment and standing treatment in sequence, and filtering and drying the second mixed solution after standing treatment to obtain an intermediate catalyst;

wherein the stirring treatment time is 6h, the stirring treatment rotating speed is 800r/min, the standing treatment time is 3h, the drying treatment temperature is 100 ℃, and the drying treatment time is 10 h.

5) Roasting

Grinding the intermediate catalyst, and then placing the ground intermediate catalyst in a muffle furnace at 300 ℃ for roasting treatment to obtain a catalyst;

wherein the roasting treatment time is 6 hours.

The surface of the catalyst obtained in example 4 was observed using TEM, and the particle size of rhodium in the catalyst obtained in example 4 was less than 1 nm.

The loading of rhodium in the catalyst obtained in inventive example 4 was 0.4 wt%.

Example 5

The catalyst of this example was prepared by a process comprising the steps of:

1) solution preparation

1.0g of TiO₂Adding into a beaker filled with 100mL of ultrapure water, placing the beaker in a 70 ℃ water bath, stirring for 20min to form uniform TiO₂An aqueous solution;

the mass concentration of the preparation is 1mg_RhRhCl/mL₃.3H₂And (4) O aqueous solution.

2) Mixing

6.3mL of 1mg_RhRhCl/mL₃.3H₂Adding the O aqueous solution into a beaker of 100mL of ultrapure water, placing the beaker in a 70 ℃ water bath, stirring for 40min until the mixture is uniform, and obtaining diluted RhCl₃.3H₂An aqueous solution of O;

the diluted RhCl was added at a rate of 1mL/min₃.3H₂Dropwise adding O aqueous solution to standing TiO at constant speed₂Obtaining a first mixed solution in the water solution;

wherein the temperature is 70 ℃.

3) Adjusting pH

And (3) adjusting the pH value of the first mixed solution to about 9.5 by using 0.5mol/L NaOH aqueous solution to obtain a second mixed solution.

4) Post-treatment

Placing the beaker filled with the second mixed solution in a water bath at 80 ℃ for stirring treatment and standing treatment in sequence, and filtering and drying the second mixed solution after standing treatment to obtain an intermediate catalyst;

wherein the stirring treatment time is 6h, the stirring treatment rotating speed is 800r/min, the standing treatment time is 3h, the drying treatment temperature is 100 ℃, and the drying treatment time is 10 h.

5) Roasting

Grinding the intermediate catalyst, and then placing the ground intermediate catalyst in a muffle furnace at 300 ℃ for roasting treatment to obtain a catalyst;

wherein the roasting treatment time is 6 hours.

The surface of the catalyst obtained in example 5 was observed using TEM, and as shown in fig. 5, the particle size of rhodium in the catalyst obtained in example 5 was less than 1 nm.

The loading of rhodium in the catalyst obtained in inventive example 5 was 0.2 wt%.

Example 6

The catalyst of this example was prepared by a process comprising the steps of:

1) solution preparation

1.0g of TiO₂Adding into a beaker filled with 100mL of ultrapure water, placing the beaker in a 70 ℃ water bath, stirring for 20min to form uniform TiO₂An aqueous solution;

the mass concentration of the preparation is 1mg_RhRhCl/mL₃.3H₂And (4) O aqueous solution.

2) Mixing

6.3mL of 1mg_RhRhCl/mL₃.3H₂Adding the O aqueous solution into a beaker of 100mL of ultrapure water, placing the beaker in a 70 ℃ water bath, stirring for 40min until the mixture is uniform, and obtaining diluted RhCl₃.3H₂An aqueous solution of O;

the diluted RhCl was added at a rate of 1mL/min₃.3H₂Dropwise adding O aqueous solution at constant speed to TiO under vigorous stirring₂Obtaining a first mixed solution in the water solution;

wherein the stirring speed is 800r/min, and the temperature is 70 ℃.

3) Adjusting pH

And (3) adjusting the pH value of the first mixed solution to about 9.5 by using 0.5mol/L NaOH aqueous solution to obtain a second mixed solution.

4) Post-treatment

Placing the beaker filled with the second mixed solution in a water bath at 80 ℃ for stirring treatment and standing treatment in sequence, and filtering and drying the second mixed solution after standing treatment to obtain an intermediate catalyst;

wherein the stirring treatment time is 6h, the stirring treatment rotating speed is 800r/min, the standing treatment time is 3h, the drying treatment temperature is 120 ℃, and the drying treatment time is 14 h.

5) Roasting

Grinding the intermediate catalyst, and then placing the ground intermediate catalyst in a muffle furnace at 300 ℃ for roasting treatment to obtain a catalyst;

wherein the roasting treatment time is 6 hours.

The surface of the catalyst obtained in example 6 was observed using TEM, and the particle size of rhodium in the catalyst obtained in example 6 was less than 1 nm.

The loading of rhodium in the catalyst obtained in inventive example 6 was 0.4 wt%.

Example 7

The catalyst of this example was prepared by a process comprising the steps of:

1) solution preparation

1.0g of TiO₂Adding into a beaker filled with 100mL of ultrapure water, placing the beaker in a 70 ℃ water bath, stirring for 20min to form uniform TiO₂An aqueous solution;

the mass concentration of the preparation is 1mg_RhRhCl/mL₃.3H₂And (4) O aqueous solution.

2) Mixing

6.3mL of 1mg_RhRhCl/mL₃.3H₂Adding the O aqueous solution into a beaker of 100mL of ultrapure water, placing the beaker in a 70 ℃ water bath, stirring for 40min until the mixture is uniform, and obtaining diluted RhCl₃.3H₂An aqueous solution of O;

the diluted RhCl was added at a rate of 1mL/min₃.3H₂Dropwise adding O aqueous solution at constant speed to TiO under vigorous stirring₂Obtaining a first mixed solution in the water solution;

wherein the stirring speed is 800r/min, and the temperature is 70 ℃.

3) Adjusting pH

And (3) adjusting the pH value of the first mixed solution to about 9.5 by using 0.5mol/L NaOH aqueous solution to obtain a second mixed solution.

4) Post-treatment

Placing the beaker containing the second mixed solution in a water bath at 90 ℃ for stirring treatment and standing treatment in sequence, and filtering and drying the second mixed solution after standing treatment to obtain an intermediate catalyst;

wherein the stirring treatment time is 7h, the stirring treatment rotating speed is 800r/min, the standing treatment time is 4h, the drying treatment temperature is 100 ℃, and the drying treatment time is 10 h.

5) Roasting

Grinding the intermediate catalyst, and then placing the ground intermediate catalyst in a muffle furnace at 300 ℃ for roasting treatment to obtain a catalyst;

wherein the roasting treatment time is 6 hours.

The surface of the catalyst obtained in example 7 was observed by TEM, and the particle diameters of rhodium in the catalyst obtained in example 7 were each less than 1 nm.

The loading of rhodium in the catalyst obtained in inventive example 7 was 0.4 wt%.

Example 8

The catalyst of this example was prepared by a process comprising the steps of:

1) solution preparation

1.0g of TiO₂Adding into a beaker filled with 100mL of ultrapure water, placing the beaker in a 70 ℃ water bath, stirring for 20min to form uniform TiO₂An aqueous solution;

the mass concentration of the preparation is 1mg_RhRhCl/mL₃.3H₂And (4) O aqueous solution.

2) Mixing

31.5mL of 1mg_RhRhCl/mL₃.3H₂Adding the O aqueous solution into a beaker of 100mL of ultrapure water, placing the beaker in a 70 ℃ water bath, stirring for 40min until the mixture is uniform, and obtaining diluted RhCl₃.3H₂An aqueous solution of O;

the diluted RhCl was added at a rate of 1mL/min₃.3H₂Dropwise adding O aqueous solution at constant speed to TiO under vigorous stirring₂Obtaining a first mixed solution in the water solution;

wherein the stirring speed is 800r/min, and the temperature is 70 ℃.

3) Adjusting pH

And (3) adjusting the pH value of the first mixed solution to about 9.5 by using 0.5mol/L NaOH aqueous solution to obtain a second mixed solution.

4) Post-treatment

Placing the beaker filled with the second mixed solution in a water bath at 80 ℃ for stirring treatment and standing treatment in sequence, and filtering and drying the second mixed solution after standing treatment to obtain an intermediate catalyst;

wherein the stirring treatment time is 6h, the stirring treatment rotating speed is 800r/min, the standing treatment time is 3h, the drying treatment temperature is 100 ℃, and the drying treatment time is 10 h.

5) Roasting

Grinding the intermediate catalyst, and then placing the ground intermediate catalyst in a muffle furnace at 300 ℃ for roasting treatment to obtain a catalyst;

wherein the roasting treatment time is 6 hours.

The surface of the catalyst obtained in example 8 was observed using TEM, and as shown in fig. 2, the particle size of rhodium in the catalyst obtained in example 8 was less than 1 nm.

The loading of rhodium in the catalyst obtained in inventive example 8 was 2.5 wt%.

Test examples

1. The formaldehyde oxidation performance of the catalyst in example 1 was evaluated by using an atmospheric fixed bed microreflection evaluation device, and the evaluation method included the following:

a certain amount (1-100 mg) of the catalyst in example 1 was weighed and placed in a U-shaped reaction tube, and the reaction temperature was controlled by a temperature controller. The paraformaldehyde is purged by helium to generate gaseous formaldehyde, and the concentration of the formaldehyde is controlled by the peripheral heating temperature and the flow rate of carrier gas He. The water in the reaction gas is carried by helium bubbles to carry water vapor at room temperature, and the relative humidity of the reaction gas is adjusted through the gas flow.

The reaction gas has a composition of 140-180 ppm HCHO and 20 vol.% O₂He is balance gas, relative humidity is 0-75%, total gas flow is 50-100 mL/min (STP), and mass space velocity is 30000mL g_cat ^-1h^-1. 20 vol.% H was required in advance before the catalyst testing₂Reduction treatment was carried out under a/He atmosphere, and then the catalyst was cooled to room temperature by purging with helium gas. The test temperature was 25 ℃ and the conversion of formaldehyde (HCHO) was determined by chromatography of CO in the outlet of the reactor₂The concentration is obtained. To detect trace CO₂Concentration, wherein a nickel converter is arranged in a chromatogram, and before gas enters a hydrogen Flame Ionization Detector (FID), hydrogenation reaction is carried out to generate CH under the action of the nickel converter₄By detecting CH₄To obtain product CO₂The concentration of (c).

FIG. 3 is a graph showing the catalytic conversion efficiency of formaldehyde by the catalyst of example 1 of the present invention. As can be seen from fig. 3, the catalytic conversion efficiency of the catalyst obtained in example 1 of the present invention to formaldehyde can reach one hundred%, and the catalyst has a good catalytic conversion efficiency.

2. Titanium dioxide, the 0.5 wt% rhodium-loaded catalyst obtained in example 1 (0.5 wt% Rh/TiO), respectively, were tested using XRD₂) And the 2.5 wt% rhodium-loaded catalyst obtained in example 8 (2.5 wt% Rh/TiO)₂)。

FIG. 4 is XRD spectra of titanium dioxide, a catalyst supporting 0.5 wt% rhodium, and a catalyst supporting 2.5 wt% rhodium in the present invention. As shown in fig. 4, the characteristic curves of the catalyst loaded with 0.5 wt% of rhodium and the catalyst loaded with 2.5 wt% of rhodium did not show a new characteristic peak, particularly, no Rh characteristic peak, compared to the characteristic peak curve of titanium dioxide, because the particle size of rhodium in the catalyst obtained by the present invention was less than 1nm, which could not be detected by XRD.

3. The titania and the 2.5 wt% rhodium-loaded catalyst obtained in example 8 were each tested using a temperature-programmed reduction method.

FIG. 5 is a hydrogen-temperature programmed reduction (H) of titania and a catalyst supporting 2.5 wt% rhodium in accordance with the present invention₂TPR) spectrum. As can be seen from FIG. 5, the catalyst of the present invention, which supports 2.5 wt% rhodium, has a sharp characteristic peak at 50 ℃ demonstrating high dispersion of rhodium in the catalyst of the present invention.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.