CN113731402A

CN113731402A - Catalyst and preparation method and application thereof

Info

Publication number: CN113731402A
Application number: CN202111046348.0A
Authority: CN
Inventors: 钟子宜; 谢汉杰
Original assignee: Guangdong Israel Institute Of Technology
Current assignee: Guangdong Israel Institute Of Technology
Priority date: 2021-09-07
Filing date: 2021-09-07
Publication date: 2021-12-03
Anticipated expiration: 2041-09-07
Also published as: CN113731402B

Abstract

The invention discloses a catalyst, a preparation method and application thereof, and relates to the technical field of preparation of formaldehyde oxidation catalysts. The invention provides a preparation method of a catalyst, which comprises the following steps: (1) sequentially adding an iron-containing compound, a manganese-containing compound and a chelating agent into deionized water, and stirring in a water bath to obtain a gel A; (2) drying the gel prepared in the step (1) to obtain a solid B, and calcining and grinding the solid B to obtain the catalyst; wherein the molar ratio of the iron ions in the iron-containing compound to the manganese ions in the manganese-containing compound is: iron ions: manganese ion 1-7: 1-7. The invention provides a preparation method of the catalyst, which is simple, convenient, green, pollution-free and low in cost and can be used for industrial preparation.

Description

Catalyst and preparation method and application thereof

Technical Field

The invention relates to the technical field of preparation of formaldehyde oxidation catalysts, in particular to a catalyst and a preparation method and application thereof.

Background

Formaldehyde gas is one of the most major indoor air pollutants. Newly decorated house decoration materials and the like can continuously release formaldehyde. Due to the extremely strong water solubility, volatility and irritation, formaldehyde can quickly permeate into the respiratory system and the digestive system of a human body and cause irreversible damage to white blood cells and red blood cells, thereby seriously threatening the physical health of people. Currently formaldehyde is classified by the world health organization as a carcinogenic and teratogenic substance. Prolonged exposure to formaldehyde gas at low concentrations may lead to nasopharyngeal carcinoma, colon cancer, genetic mutations, and the like. Formaldehyde, at air concentrations above 0.082ppm, can cause damage to the eye and nasal mucosa. According to the relevant regulations of the national standard of the people's republic of China, namely the indoor air quality standard, the highest allowable formaldehyde concentration of the indoor air is 0.082 ppm. With the acceleration of urbanization, people are indoors most of the day, so that the task of efficiently purifying indoor formaldehyde is urgent.

Currently, the main methods for purifying indoor formaldehyde gas are: physical adsorption, photocatalytic oxidation of formaldehyde, and thermal catalytic oxidation of formaldehyde. The physical adsorption method mainly uses an adsorbent with a large specific surface to remove formaldehyde in air through physical adsorption, but formaldehyde is not really removed, an inner core needs to be replaced periodically after an adsorption column is saturated in adsorption, the saturated inner core can also be placed in the air for heating and regeneration, and formaldehyde gas adsorbed by the method finally returns to the atmosphere. Meanwhile, the adsorption period is short, and the adsorption is required to be frequently replaced, so that the method is a method with non-permanent indexes. The photocatalytic oxidation of formaldehyde mainly utilizes photo-excited semiconductor nano materials (such as titanium dioxide, bismuth trioxide and zinc oxide) to generate photo-generated charges and form high-activity oxygen species on the surface, formaldehyde gas can be efficiently oxidized into carbon dioxide and water, long-time light irradiation is needed, the generated photo-generated charges are easy to compound, the catalytic activity needs to be improved, and other toxic and harmful secondary products can be generated to cause secondary pollution to indoor air. The thermal catalytic formaldehyde oxidation method promotes the catalyst to oxidize formaldehyde molecules into carbon dioxide and water by heating, but the high temperature is not suitable for the life of residents, so that the development of the room-temperature or even low-temperature oxidation catalyst is necessary, and the formaldehyde gas can be efficiently oxidized into the nontoxic and harmless carbon dioxide and water at the normal temperature or even the low temperature. At present, the normal temperature (low temperature) catalyst mainly focuses on the support (such as mesoporous molecular sieve SBA-15, alumina and the like) with a large specific surface on which noble metals (platinum, palladium, gold and the like) are supported, and the cost is high (CN 201810550473.7). Still a small part of the catalyst is transition metal oxide (cobalt oxide and manganese oxide), but 100% conversion is difficult to achieve at room temperature (cn201910982016. x). Meanwhile, most of the catalysts are easy to deactivate and difficult to regenerate for recycling, so that the development of a catalyst which is efficient and stable at low temperature and can be regenerated is particularly important.

Chinese patent application No. 2004110102837.3 discloses that noble metals (gold, silver, etc.) are supported on oxides (zirconia, alumina) by impregnation or precipitation for conversion of formaldehyde gas. However, the morphology is not controllable, and the small specific surface can not be used for commercialization. Chinese patent application No. 200610011663.9 discloses loading noble metals (gold, silver, etc.) on a manganese oxide-cerium oxide composite oxide by a precipitation-precipitation method. The disadvantage is still the increased cost due to the use of precious metals. The chinese invention patent of application No. 201810276968.5 discloses loading titanium dioxide on a ceria-manganese oxide carrier, treating 500ppb of formaldehyde at normal temperature, and reaching 60% in 3 hours. However, the treated air still can not meet the domestic indoor air quality standard. Chinese patent application No. 201910865957.5 discloses an oxide/titania catalyst for photocatalytic degradation of formaldehyde into carbon dioxide and water. But use copper which is more costly and has a degradation time of up to 2 hours. The Chinese patent application No. 201410012802.4 discloses a method for efficiently catalyzing formaldehyde pollutants by using air particle filtering materials and loading high-oxidation-activity sodium hydrohalite-type manganese oxides as reactive substances, but the treatment amount is small, and the degradation rate is reduced to 58% after 2500mg of formaldehyde is treated. Patent WO2018098450a1 discloses a reaction system integrating a catalyst and regeneration, wherein the catalyst comprises manganese oxide and noble metal supported on titanium dioxide, and the catalyst life is prolonged by exposing the catalyst to water or heating. European patent EP2239322A1 discloses that enzymes loaded on fabrics have a formaldehyde degradation rate of up to 75%, but are difficult to regenerate. Application No. CN201810813407.4 discloses a method for achieving 99% formaldehyde removal at room temperature after 10 hours by processing natural manganese-rich limonite ore. Application No. 201510371764.6 discloses a manganese-doped maghemite catalyst synthesized by a sodium hydroxide coprecipitation method, wherein the removal rate of high-concentration formaldehyde (1000ppm) at 300 ℃ can reach 90%. Application number 201910905664.5 discloses a hydrothermal method for preparing a ferro-manganese catalyst, then loading the ferro-manganese catalyst on silica gel liquid, finally coating the silica gel liquid loaded with the catalyst on a filter screen, wherein the removal rate of formaldehyde can reach more than 90% after 24 hours at room temperature. Application No. 201811403686.3 discloses a method for loading manganese oxide on an ozone modified activated carbon support by an impregnation method, with a formaldehyde removal rate of up to 88%. The invention patent CN105268452A discloses a mesoporous SiO₂The formaldehyde degradation catalyst loaded with the copper-manganese composite oxide completely degrades formaldehyde at 75-125 ℃, and the reaction temperature is high.

Disclosure of Invention

Based on the above, the invention aims to overcome the defects of the prior art and provide a catalyst which has low cost and good activity stability, can degrade formaldehyde at normal temperature and can be recycled and regenerated, and a preparation method thereof.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows: a preparation method of the catalyst comprises the following steps:

(1) sequentially adding an iron-containing compound, a manganese-containing compound and a chelating agent into deionized water, and stirring in a water bath to obtain a gel A;

(3) drying the gel prepared in the step (2) to obtain a solid B, and calcining and grinding the solid B to obtain the catalyst;

wherein the molar ratio of the iron ions in the iron-containing compound to the manganese ions in the manganese-containing compound is: iron ions: manganese ion 1-7: 1-7.

The inventor of the application finds in the practical experiment process that the iron-containing compound and the manganese-containing compound can generate high-activity Fe component when the molar ratio is in the range₃Mn₃O₈. When the molar ratio of the iron ion in the iron-containing compound to the manganese ion in the manganese-containing compound is out of the specific range provided by the present invention, Fe, which is a highly active ingredient, is hardly generated₃Mn₃O₈The formaldehyde removing effect is obviously reduced.

The invention provides a preparation method of a catalyst, which can adjust the valence distribution of manganese ions in an active component by utilizing variable-valence iron ions so as to adjust the concentration of oxygen vacancies, wherein the concentration of the oxygen vacancies is directly related to the oxidation capability of the oxygen vacancies and can generate active intermediates of superoxide ions, hydroxyl and peroxy with oxygen or water molecules in the air, and formaldehyde gas is gradually oxidized into formate or carbonate and is further completely oxidized into carbon dioxide and water.

Preferably, the molar ratio of the iron ions in the iron-containing compound to the manganese ions in the manganese-containing compound is: iron ions: manganese ion 1-3: 1-3. The inventor of the application finds that the high-activity component Fe is generated when the molar ratio of the iron ions in the iron-containing compound to the manganese ions in the manganese-containing compound is 1-3:1-3 in the practical test process₃Mn₃O₈The formaldehyde catalyzing effect is better when the molar ratio of the iron ions in the iron-containing compound and the manganese ions in the manganese-containing compound is far higher than that when the molar ratio is not in the specific molar ratio range.

Further preferably, the molar ratio of the iron ions in the iron-containing compound to the manganese ions in the manganese-containing compound is: iron ions: manganese ion 1: 1. The inventor of the application finds that in the practical experiment process, when the molar ratio of the iron ions in the iron-containing compound to the manganese ions in the manganese-containing compound is 1:1, pure-phase high-activity Fe is generated₃Mn₃O₈In this case, the degradation rate of formaldehyde is maximized, and the catalyst has a high activity for oxidizing formaldehyde.

Preferably, the iron-containing compound and the iron-containing compound are catalyst precursors, and the iron-containing compound comprises at least one of ferric chloride, ferric nitrate and ferric sulfate; the manganese-containing compound comprises at least one of manganese nitrate, manganese sulfate and manganese chloride; the chelating agent comprises at least one of citric acid, sodium citrate, sodium hexadecylbenzene sulfonate, hexadecyl trimethyl ammonium bromide and chitosan.

Preferably, in the step (1), the water bath stirring temperature is 40-90 ℃, and the water bath stirring time is 3-5 h; in the step (2), the drying temperature is 90-110 ℃, and the drying time is 10-15 h; the calcining temperature is 300-500 ℃, and the calcining time is 2-8 h.

In addition, the invention provides a catalyst prepared by the preparation method of the catalyst.

Preferably, the catalyst may be regenerated by heating; the temperature for heating and regenerating is 100-500 ℃. Meanwhile, the catalyst can achieve regeneration circulation through hydrogen peroxide solution treatment, illumination and other modes, wherein the hydrogen peroxide treatment time is 0.1-3 hours, and the hydrogen peroxide can be regenerated when the mass concentration is 0.1-10%; the illumination time is 1-15 hours, and the iron-containing compound are used as catalyst precursors; thereby improving the utilization of the catalyst.

Preferably, the catalyst further comprises a carrier, and the carrier comprises at least one of gamma-alumina, mesoporous molecular sieve and titanium dioxide oxide. Further preferably, the pore size of the mesoporous molecular sieve is in the range of 2-5 nm.

Further preferably, the support is a titania oxide, such as titania P25. In the process of practical tests, the inventor of the application finds that when the carrier is titanium dioxide P25, the activity and stability of the reaction are optimal when formaldehyde is degraded.

When the above catalyst comprises a support, the preparation method is as follows:

(1) dispersing a carrier into deionized water to obtain carrier dispersion liquid;

(2) sequentially adding an iron-containing compound, a manganese-containing compound and a chelating agent into the carrier dispersion liquid, and stirring in a water bath to obtain gel A;

(3) and (3) drying the gel prepared in the step (2) to obtain a solid B, and calcining and grinding the solid B to obtain the catalyst.

Further, the invention provides application of the catalyst in degrading formaldehyde products.

Compared with the prior art, the invention has the beneficial effects that: the invention can adjust the valence distribution of manganese ions in the active component by utilizing variable valence iron ions so as to adjust the concentration of oxygen vacancies, the concentration of the oxygen vacancies is directly related to the oxidation capability of the oxygen vacancies, and can generate active intermediates of superoxide ions, hydroxyl and peroxy with oxygen or water molecules in the air, so that formaldehyde gas is gradually oxidized into formate or carbonate, and further completely oxidized into carbon dioxide and water.

The invention is beneficial to increasing the number of active centers by loading the catalyst on a carrier with a larger specific surface, thereby improving the reaction activity and stability. Meanwhile, the catalyst can be regenerated after simple heat treatment (250 ℃) in the air, and adsorbates covered on the surface and the like can be decomposed and removed at higher temperature, so that the re-exposure of active sites is realized, and the activity is recovered.

The method is simple, convenient and quick, green and pollution-free, has low cost (the ferro-manganese compound and the carrier are cheap materials), and can be used for industrial preparation. Meanwhile, the catalyst has good thermal stability and formaldehyde purification stability, and the catalyst is simple to regenerate. The preparation method of the catalyst can be popularized to the preparation and the same application of other binary metal oxide catalysts.

The patent provides a supported catalyst which is obtained by loading a ferro-manganese catalyst on an alumina titanium oxide carrier through in-situ gelation by an impregnation method and has better stability and better effect (the formaldehyde removal rate can reach 99-100% at room temperature). Compared with the existing catalyst, the normal-temperature formaldehyde purification catalyst provided by the invention can reach 90% in 1 hour of formaldehyde degradation rate at 25 ℃ and high space velocity (300L/(g h)), and can reach 99% in 5 hours.

Drawings

FIG. 1 is a graph showing the catalytic oxidation performance of formaldehyde at room temperature for examples 1-6;

FIG. 2 is an XRD spectrum of examples 1-6;

FIG. 3 is a graph showing the catalytic oxidation performance of formaldehyde at room temperature for examples 7-11;

FIG. 4 is a graph showing the catalytic oxidation performance of formaldehyde at room temperature for examples 11-15;

FIG. 5 is a graph of the catalytic oxidation performance of formaldehyde at different temperatures for example 10;

FIG. 6 is an XRD pattern of the catalyst Fe/Mn ═ 1:1 prepared in example 10 and after regeneration treatment with hydrogen peroxide;

FIG. 7 is a graph of the number of heat regeneration cycles for the catalyst Fe/Mn 1:1 prepared in example 10;

FIG. 8 is a graph showing the number of regeneration cycles of example 10 after treatment with a hydrogen peroxide solution;

FIG. 9 is a graph showing the number of light regeneration cycles in example 16.

Detailed Description

To better illustrate the objects, aspects and advantages of the present invention, the present invention will be further described with reference to the accompanying drawings and specific embodiments. In the examples, the experimental methods used were all conventional methods unless otherwise specified, and the materials, reagents and the like used were commercially available without otherwise specified.

Examples 1 to 6

The invention discloses an embodiment 1-6, which researches the influence of a carrier on the activity and stability of a reaction when formaldehyde is degraded, and comprises the following specific embodiments:

example 1

Firstly, 0.500g of carrier mesoporous molecular sieve SBA-15 is dispersed into 20ml of deionized water, 0.0580g of citric acid is dissolved in the dispersion liquid and stirred for half an hour at a temperature, 0.120g of manganese nitrate solution with the mass fraction of 50% and 0.100g of ferric nitrate are sequentially dissolved in the dispersion liquid, the mixture is stirred in a water bath at a temperature of 80 ℃ for 4 hours, gelation is carried out, and then the mixture is dried in an oven at a temperature of 100 ℃ for 12 hours. Calcining the solid in air at 500 ℃ for 4 hours, and grinding to obtain the catalyst Fe-Mn/SBA-15.

Example 2

Firstly, preparing an APTES modified SBA-15 carrier; adding 1.00g of carrier mesoporous molecular sieve SBA-15 into 0.100M ethanol solution of APTES, heating for 3 hours at 80 ℃, centrifugally cleaning for three times by using ethanol after the reaction is finished, and drying in a vacuum oven at 100 ℃ to prepare APTES modified SBA-15;

then, 0.500g of APTES-SBA-15 is dispersed into 20ml of deionized water, 0.120g of a 50% manganese nitrate solution and 0.100g of ferric nitrate are sequentially added and dissolved into the dispersion, and the mixture is stirred in a water bath at a temperature of 80 ℃ for 4 hours to gelatinize, and then is dried in an oven at a temperature of 100 ℃ for 12 hours. Calcining the solid in air at 500 ℃ for 4 hours, and grinding to obtain the catalyst Fe-Mn/APTES-SBA-15.

Example 3

Firstly, 0.500g of acid alumina is dispersed into 20ml of deionized water, 0.0580g of citric acid is dissolved in the dispersion liquid and stirred for half an hour at a temperature, 0.120g of manganese nitrate solution with the mass fraction of 50% and 0.100g of ferric nitrate are sequentially added and dissolved in the dispersion liquid, the mixture is stirred in a water bath with the temperature of 80 ℃ for 4 hours, gelation is carried out, and then the mixture is dried in an oven with the temperature of 100 ℃ for 12 hours. Calcining the solid in air at 500 ℃ for 4 hours, and grinding to obtain the catalyst Fe-Mn/A-Al₂O₃。

Example 4

Firstly, 0.500g of neutral alumina is dispersed into 20ml of deionized water, 0.0580g of citric acid is dissolved in the dispersion liquid and stirred for half an hour at a temperature, 0.120g of manganese nitrate solution with the mass fraction of 50% and 0.100g of ferric nitrate are sequentially added and dissolved in the dispersion liquid, the mixture is stirred in a water bath at 80 ℃ for 4 hours, gelation is carried out, and then the mixture is dried in an oven at 100 ℃ for 12 hours. Calcining the solid in air at 500 ℃ for 4 hours, and grinding to obtain the catalyst Fe-Mn/N-Al₂O₃。

Example 5

Firstly, 0.500g of alkaline alumina is dispersed into 20ml of deionized water, 0.0580g of citric acid is dissolved in the dispersion liquid and stirred at the temperature for half an hour, 0.120g of manganese nitrate solution with the mass fraction of 50% and 0.100g of ferric nitrate are sequentially added and dissolved in the dispersion liquid, the mixture is stirred in a water bath at the temperature of 80 ℃ for 4 hours, gelation is carried out, and then the mixture is dried in an oven at the temperature of 100 ℃ for 12 hours. Calcining the solid in air at 500 ℃ for 4 hours, and grinding to obtain the catalystFe-Mn/B-Al₂O₃。

Example 6

Firstly, 0.500g of titanium dioxide P25 is dispersed into 20ml of deionized water, 0.0580g of citric acid is dissolved in the dispersion liquid and stirred for half an hour at a temperature, 0.120g of manganese nitrate solution with the mass fraction of 50% and 0.100g of ferric nitrate are sequentially added and dissolved in the dispersion liquid, the mixture is stirred in a water bath at 80 ℃ for 4 hours, gelation is carried out, and then the mixture is dried in an oven at 100 ℃ for 12 hours. Calcining the solid in air at 500 ℃ for 4 hours, and grinding to obtain the catalyst Fe-Mn/P25.

Examples 7 to 11

Examples 7 to 11 of the present invention investigate the influence of the molar ratio of iron ions in iron-containing compounds and manganese ions in manganese-containing compounds on the degradation degree of formaldehyde when formaldehyde is degraded; in examples 7 to 11 of the present invention, in order to examine the influence of the molar ratio on the degradation degree of formaldehyde, the active ingredient catalyst was not combined with the carrier, and only the influence of the molar ratio of iron ions in the iron-containing compound and manganese ions in the manganese-containing compound on the degradation degree of formaldehyde was examined.

Example 7

16.2g of ferric nitrate solid and 9.22g of citric acid are sequentially added into 20ml of deionized water, stirred in a water bath at 80 ℃ for 4 hours, gelatinized, and dried in an oven at 100 ℃ for 12 hours. Calcining the solid in air at 500 ℃ for 4 hours, and grinding to obtain the catalyst Fe₂O₃。

Example 8

12.1g of ferric nitrate solid, 3.58g of a 50% manganese nitrate solution and 9.22g of citric acid are sequentially added into 20ml of deionized water, stirred in a water bath at a temperature of 80 ℃ for 4 hours, gelatinized, and dried in an oven at a temperature of 100 ℃ for 12 hours. Calcining the solid in air at 500 ℃ for 4 hours, and grinding to obtain the catalyst Fe/Mn which is 3:1 in a molar ratio.

Example 9

4.04g of ferric nitrate solid, 10.7g of a manganese nitrate solution with the mass fraction of 50% and 9.22g of citric acid are sequentially added into 20ml of deionized water, stirred in a water bath at 80 ℃ for 4 hours, gelatinized and dried in an oven at 100 ℃ for 12 hours. Calcining the solid in air at 500 ℃ for 4 hours, and grinding to obtain the catalyst Fe/Mn which is 1:3 in a molar ratio.

Example 10

8.08g of ferric nitrate solid, 7.16g of a manganese nitrate solution with the mass fraction of 50% and 9.22g of citric acid are sequentially added into 20ml of deionized water, stirred in a water bath at 80 ℃ for 4 hours, gelatinized and dried in an oven at 100 ℃ for 12 hours. Calcining the solid in air at 500 ℃ for 4 hours, and grinding to obtain the catalyst Fe/Mn which is 1:1 in a molar ratio.

Example 11

14.3g of a 50% manganese nitrate solution and 9.22g of citric acid are sequentially added into 20ml of deionized water, stirred in a water bath at 80 ℃ for 4 hours, gelatinized and dried in a 100-DEG oven for 12 hours. Calcining the solid in air at 500 ℃ for 4 hours, and grinding to obtain the catalyst Mn₃O₄。

Examples 12 to 15

Examples 12-15 of the present invention explore that when degrading formaldehyde, specific active ingredients of the present invention are not employed: an iron-containing compound, a manganese-containing compound, and a chelating agent. Examples 12-15 catalyst preparations were carried out using an aluminum-containing compound, a manganese-containing compound, and a chelating agent, and examples 12-15 were specifically prepared as follows:

example 12

15.0g of aluminum nitrate solid and 9.22g of citric acid are sequentially added into 20ml of deionized water, stirred for 4 hours in a water bath at a temperature of 80 ℃, gelatinized, and dried for 12 hours in an oven at a temperature of 100 ℃. Calcining the solid in air at 500 ℃ for 4 hours, and grinding to obtain catalyst Al₂O₃。

Example 13

11.3g of aluminum nitrate solid, 3.58g of a 50% manganese nitrate solution and 9.22g of citric acid are sequentially added into 20ml of deionized water, stirred in a water bath at a temperature of 80 ℃ for 4 hours, gelatinized, and dried in an oven at a temperature of 100 ℃ for 12 hours. Calcining the solid in air at 500 ℃ for 4 hours, and grinding to obtain the catalyst Al/Mn which is 3:1 in a molar ratio.

Example 14

7.50g of aluminum nitrate solid, 8.08g of a 50% manganese nitrate solution and 9.22g of citric acid are sequentially added into 20ml of deionized water, stirred in a water bath at a temperature of 80 ℃ for 4 hours, gelatinized, and dried in an oven at a temperature of 100 ℃ for 12 hours. Calcining the solid in air at 500 ℃ for 4 hours, and grinding to obtain the catalyst Al/Mn which is 1:1 in a molar ratio.

Example 15

3.00g of aluminum nitrate solid, 10.7g of a 50% manganese nitrate solution and 9.22g of citric acid are sequentially added into 20ml of deionized water, stirred in a water bath at a temperature of 80 ℃ for 4 hours, gelatinized, and dried in an oven at a temperature of 100 ℃ for 12 hours. Calcining the solid in air at 500 ℃ for 4 hours, and grinding to obtain the catalyst Al/Mn which is 1:3 in a molar ratio.

Example 16

50.0mg of the catalyst Fe-Mn/B-gamma-alumina prepared in example 5 and 50.0mg of titanium dioxide P25 were mixed by grinding and filled in a stainless steel reaction tube to perform catalytic oxidation reaction on formaldehyde with a concentration of 115ppm at a space velocity of 500 ml/min. After the catalyst is inactivated, the catalytic oxidation reaction of formaldehyde with the same concentration is carried out after the catalyst is irradiated for 12 hours under simulated sunlight, and the activity of the catalyst is recovered.

Examples 17 to 21

In the embodiments 17-21 of the present invention, different chelating agents are used for the preparation of the catalyst, and the specific preparation method of the catalyst in the embodiments 17-21 is as follows:

example 17

8.08g of ferric nitrate solid, 7.16g of a 50% manganese nitrate solution by mass and 8.74g of cetyltrimethylammonium bromide are sequentially added into 20ml of deionized water, stirred in a water bath at 80 ℃ for 4 hours, gelatinized, and dried in an oven at 100 ℃ for 12 hours. Calcining the solid in air at 500 ℃ for 4 hours, and grinding to obtain the catalyst.

Example 18

8.08g of ferric nitrate solid, 7.16g of a 50 mass percent manganese nitrate solution and 17.5g of cetyltrimethylammonium bromide are sequentially added into 20ml of deionized water, stirred in a water bath at a temperature of 80 ℃ for 4 hours, gelatinized, and dried in an oven at a temperature of 100 ℃ for 12 hours. Calcining the solid in air at 500 ℃ for 4 hours, and grinding to obtain the catalyst.

Example 19

8.08g of ferric nitrate solid, 7.16g of a 50 mass percent manganese nitrate solution and 26.2g of cetyltrimethylammonium bromide are sequentially added into 20ml of deionized water, stirred in a water bath at a temperature of 80 ℃ for 4 hours, gelatinized, and dried in an oven at a temperature of 100 ℃ for 12 hours. Calcining the solid in air at 500 ℃ for 4 hours, and grinding to obtain the catalyst.

Example 20

8.08g of ferric nitrate solid, 7.16g of a manganese nitrate solution with the mass fraction of 50% and 12.3g of sodium citrate are sequentially added into 20ml of deionized water, stirred in a water bath at 80 ℃ for 4 hours, gelatinized, and dried in an oven at 100 ℃ for 12 hours. Calcining the solid in air at 500 ℃ for 4 hours, and grinding to obtain the catalyst.

Example 21

8.08g of ferric nitrate solid and 7.16g of a manganese nitrate solution with the mass fraction of 50% are sequentially added into 20ml of deionized water, stirred for 4 hours in a water bath at 80 ℃, and then dried for 12 hours in an oven at 100 ℃. Calcining the solid in air at 500 ℃ for 4 hours, and grinding to obtain the catalyst.

Test example 1 Effect verification

The test process comprises the following steps:

the catalyst prepared in the embodiment is filled in a fixed bed stainless steel reaction tube, 500ml/min of air is introduced into formaldehyde with a certain concentration, the formaldehyde concentration is stabilized without introducing the catalyst for 4 hours, after stabilization, a formaldehyde detector is used for determining the initial stable concentration, then a switch valve is opened to introduce the formaldehyde, the formaldehyde detector is used for detecting the formaldehyde concentration of tail gas, and data is recorded once in 10 minutes. And subtracting the tail gas formaldehyde concentration from the initial formaldehyde concentration, and dividing the result by the initial formaldehyde concentration to obtain the formaldehyde degradation rate.

Examples 1-6 test conditions: the catalyst is 0.10g, the room temperature is normal pressure, 115ppm of formaldehyde, the air flow rate is 500ml/min, and the humidity is 22%;

examples 7-11 test conditions: the catalyst is 0.10g, the room temperature is normal pressure, 115ppm of formaldehyde, the air flow rate is 500ml/min, and the humidity is 22%;

example 10 test conditions: the catalyst is 0.050g, the temperature is different under normal pressure, 115ppm of formaldehyde, the air flow rate is 500ml/min, and the humidity is 22%;

examples 11-15 test conditions: the catalyst is 0.10g, the room temperature is normal pressure, 115ppm of formaldehyde, the air flow rate is 500ml/min, and the humidity is 22%;

the experimental results are as follows:

in the invention, the examples 1 to 6 explore the influence of the carrier on the activity and stability of the reaction when degrading formaldehyde, and fig. 1 is a formaldehyde catalytic oxidation performance diagram of the examples 1 to 6, and as can be seen from fig. 1, the experiment shows that the formaldehyde concentration is stable in 0 to 1 hour before the formaldehyde is introduced into the catalyst, and the formaldehyde is introduced into the fixed bed reactor for reaction after the formaldehyde concentration is stable. Fe-Mn/P25 and Fe-Mn/APTES-SBA-15 still worked at room temperature for 12 and 7 hours.

FIG. 2 is the XRD patterns of examples 1-6, from which it can be seen that substantially no ferromanganese oxide active species are observed in the XRD patterns of SBA-15 and APTES-SBA-15, probably due to the growth and high dispersion of ferromanganese oxide in the channels, and the ferromanganese oxide in the active sites is dispersed in the channels, and formaldehyde molecules enter the channels to undergo catalytic oxidation reaction with the active sites to be converted into intermediates and further into carbon dioxide and water.

FIG. 3 is a graph showing the catalytic oxidation performance of formaldehyde at room temperature in examples 7 to 11, wherein the graph shows that the test of stable formaldehyde concentration is carried out 0 to 1 hour before the formaldehyde is introduced into the catalyst, and the formaldehyde is introduced into the fixed bed reactor for reaction after the formaldehyde concentration is stable; the catalyst comprising the active ingredient provided by the invention has good formaldehyde degradation effect, wherein the catalytic activity of Fe/Mn is 1:1 to be optimal, probably because the high-activity ingredient Fe is generated when the molar ratio of iron ions in the iron-containing compound to manganese ions in the manganese-containing compound is 1:1₃Mn₃O₈At this time, the degradation rate of formaldehyde reaches the highest.

FIG. 4 is a graph showing the catalytic oxidation performance of formaldehyde at room temperature in examples 11 to 15, wherein the test shows that the concentration of formaldehyde is stable in 0 to 1 hour before the formaldehyde is introduced into the catalyst, and the formaldehyde is introduced into the fixed bed reactor for reaction after the concentration of formaldehyde is stable. The formation of mixed oxides from aluminum manganese does not improve reactivity.

FIG. 5 is a graph showing the catalytic oxidation performance of formaldehyde at different temperatures in example 10, wherein the amount of the catalyst is reduced to 50 mg, the air flow rate is unchanged, after formaldehyde is introduced into the catalyst for reaction, a point is measured every 15 minutes, the average value is measured three times, and then the reaction furnace is heated to the corresponding temperature. The airspeed is increased, the degradation rate of the iron-manganese oxide to formaldehyde can reach 70% at room temperature, and the time can also reach 99%.

FIG. 6 is an XRD pattern of the catalyst Fe/Mn ═ 1:1 prepared in example 10, comparing Fe with that of Fe-Mn ratio 1:1₃Mn₃O₈The product was judged to be a highly active iron-manganese oxide Fe (Standard card No. ICSD) (#28665)₃Mn₃O₈The excellent catalytic oxidation activity of the catalyst on formaldehyde is concerned. Meanwhile, after the catalyst is treated by hydrogen peroxide (3%) for 10 minutes, the crystal phase of the catalyst is still high-activity iron-manganese oxide Fe₃Mn₃O₈It is demonstrated that the hydrogen peroxide treatment of the catalyst does not cause structural phase change, and is a green and simple treatment method.

Test example 2 regeneration cycle test

Regeneration cycle test procedure:

the catalyst prepared in the embodiment is filled in a fixed bed stainless steel reaction tube, 500ml/min of air is introduced into formaldehyde with a certain concentration, after the formaldehyde concentration is stable, a formaldehyde detector is used for determining the initial stable concentration, then a switch valve is opened to introduce the formaldehyde, the formaldehyde detector is used for detecting the formaldehyde concentration of tail gas, and data is recorded for 10 minutes.

And (3) carrying out cyclic regeneration treatment after the catalyst is deactivated:

the deactivated catalyst of example 10 was heated to 250 ℃ for 2 hours by introducing air, and then the formaldehyde catalytic oxidation experiment was performed, and the experiment was repeated three times. The deactivated catalyst of example 10 was treated with 10 ml of 1% hydrogen peroxide solution for 10 minutes, dried and subjected to catalytic oxidation experiment to obtain the deactivated catalyst of example 10. The deactivated catalyst of the embodiment 5 is irradiated for 12 hours under simulated sunlight, and then the catalytic oxidation reaction of formaldehyde with the same concentration is carried out, namely the embodiment 16 of the invention.

Example 10 air heating regeneration cycle test conditions: the catalyst is 0.10g, the room temperature is normal pressure, 115ppm of formaldehyde, the air flow rate is 500ml/min, and the humidity is 22%; regeneration conditions are as follows: carrying out air heat treatment at 250 ℃ for 2 h;

example 10 hydrogen peroxide treatment regeneration cycle test conditions: catalyst 0.15g, normal pressure and room temperature, 200ppm formaldehyde, air flow rate 500ml/min, humidity 22%, regeneration conditions: treating with 1% hydrogen peroxide solution for 10 min;

example 16 regeneration cycle test conditions: catalyst 0.10g, normal pressure and room temperature, 115ppm formaldehyde, air flow rate of 100ml/min, humidity of 22%, regeneration conditions: introducing air to simulate sunlight for 12 hours;

FIG. 7 is a graph of the number of heating regeneration cycles of example 10, from which it can be seen that the activity of the catalyst was recovered after the 250 degree air heat treatment, and the catalytic oxidation was cycled three times at room temperature. FIG. 8 is a graph of the number of regeneration cycles of example 10 after treatment with a hydrogen peroxide solution, from which it can be seen that the activity of the catalyst was substantially restored after treatment with a 1% hydrogen peroxide solution at room temperature, and that the catalytic oxidation was performed three times at room temperature. FIG. 9 is a graph of the number of cycles of regeneration with light in example 16, from which it can be seen that the activity of the catalyst is restored by the simulated solar light at room temperature, indicating that the inert intermediate covered with the active site surface is decomposed or desorbed by the simulated solar light.

FIGS. 7-9 collectively illustrate the room temperature high activity of iron manganese oxides (Fe)₃Mn₃O₈) After the inactivation of a large amount of formaldehyde gas is treated, the activity can be recovered by oxidation treatment for 2 hours at 250 ℃ in application, or the activity can be recovered by treating the catalyst with commercially available hydrogen peroxide for 10 minutes, or the catalyst can be regenerated by light treatment after mixing Fe-Mn/B-gamma-alumina and titanium dioxide, which is very beneficial to treating the inactivated catalyst in daily life, prolonging the service life of the catalyst and reducing the cost. The development of such a supported catalyst can effectively purify indoor air.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A preparation method of a catalyst is characterized by comprising the following steps:

(2) drying the gel prepared in the step (1) to obtain a solid B, and calcining and grinding the solid B to obtain the catalyst;

2. The method of claim 1, wherein the molar ratio of iron ions in the iron-containing compound to manganese ions in the manganese-containing compound is: iron ions: manganese ion 1-3: 1-3.

3. The method of claim 2, wherein the molar ratio of the iron ions in the iron-containing compound to the manganese ions in the manganese-containing compound is: iron ions: manganese ion 1: 1.

4. The method of claim 1, wherein the iron-containing compound comprises at least one of ferric chloride, ferric nitrate, ferric sulfate; the manganese-containing compound comprises at least one of manganese nitrate, manganese sulfate and manganese chloride; the chelating agent comprises at least one of citric acid, sodium citrate, sodium hexadecylbenzene sulfonate, hexadecyl trimethyl ammonium bromide and chitosan.

5. The method for preparing the catalyst according to claim 1, wherein in the step (1), the temperature of water bath stirring is 40-90 ℃, and the time of water bath stirring is 3-5 h; in the step (2), the drying temperature is 90-110 ℃, and the drying time is 10-15 h; the calcining temperature is 300-500 ℃, and the calcining time is 2-8 h.

6. A catalyst prepared by the method of preparing a catalyst according to any one of claims 1 to 5.

7. The catalyst of claim 6, further comprising a support comprising at least one of gamma alumina, a mesoporous molecular sieve, and a titania oxide.

8. The catalyst of claim 7 wherein the support is a titania oxide.

9. Use of a catalyst according to any one of claims 6 to 8 for the degradation of formaldehyde products.