CN113731402B

CN113731402B - Catalyst and preparation method and application thereof

Info

Publication number: CN113731402B
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: 2024-05-28
Anticipated expiration: 2041-09-07
Also published as: CN113731402A

Abstract

The invention discloses a catalyst, a preparation method and application thereof, and relates to the technical field of formaldehyde oxidation catalyst preparation. 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 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 mole ratio of iron ions in the iron-containing compound to manganese ions in the manganese-containing compound is as follows: iron ions: manganese ions = 1-7:1-7. The invention provides a preparation method of the catalyst, which is simple, quick, green, pollution-free and low in cost and can be industrially prepared.

Description

Catalyst and preparation method and application thereof

Technical Field

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

Background

Formaldehyde gas is one of the most predominant indoor air pollutants. Formaldehyde is continuously released from new house decoration materials and the like. Due to its extremely strong water solubility, volatility and irritation, formaldehyde can quickly penetrate into the respiratory system and digestive system of human body and cause irreversible damage to white blood cells and red blood cells, severely threatening the physical health of people. Formaldehyde has been currently 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, etc. Formaldehyde can cause damage to the eye and nasal mucosa at air concentrations exceeding 0.082ppm. The highest allowable formaldehyde concentration of the indoor air is 0.082ppm according to the relevant regulations of national standard of the people's republic of China. With the acceleration of urban design, most of the time of the day people are indoors, so the task of efficiently purifying indoor formaldehyde is urgent.

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

Chinese patent application 2004110102837.3 discloses the use of noble metals (gold, silver, etc.) supported on oxides (zirconia, alumina) by impregnation or precipitation for the conversion of formaldehyde gas. However, the morphology is not controllable, and the smaller specific surface cannot realize commercial application. Chinese patent application No. 200610011663.9 discloses the loading of noble metals (gold, silver, etc.) on ceria composite oxides by precipitation-precipitation. The disadvantage is still the increased costs caused by the use of noble metals. The chinese patent application No. 201810276968.5 discloses that titania is supported on a ceria-manganese oxide carrier, and formaldehyde of 500ppb is treated at normal temperature for 3 hours up to 60%. However, the treated air still cannot meet the domestic indoor air quality standard. Chinese patent application number 201910865957.5 discloses an oxide/titania catalyst for photocatalytic degradation of formaldehyde to carbon dioxide and water. But with the use of costly copper and degradation times as long as 2 hours. The Chinese patent application number 201410012802.4 discloses a method for efficiently catalyzing formaldehyde pollutants by using air particulate matter filtering material and sodium silicate type manganese oxide with high oxidation activity as a reactive substance, wherein the treatment capacity is small, and the degradation rate is attenuated to 58% after 2500mg of formaldehyde is treated. Patent WO2018098450A1 discloses a reaction system integrating a catalyst and regeneration, the catalyst used comprising manganese oxide and noble metal supported on titania or the like, the life of the catalyst being prolonged by exposing the catalyst to water or heating. European patent EP2239322A1 discloses that enzymes supported on fabrics can degrade formaldehyde up to 75% but are difficult to regenerate. Patent application number CN201810813407.4 discloses a method for achieving a removal rate of 99% formaldehyde at room temperature after 10 hours by processing natural manganese-rich limonite ore. Application number 201510371764.6 discloses a manganese doped maghemite catalyst synthesized by a sodium hydroxide coprecipitation method, and the removal rate of high concentration formaldehyde (1000 ppm) can reach 90% at 300 ℃. Application number 201910905664.5 discloses a hydrothermal method for preparing a ferro-manganese catalyst, then loading the ferro-manganese catalyst on a silicon dioxide glue solution, and finally coating the silicon dioxide glue solution loaded with the catalyst on a filter screen, wherein the formaldehyde removal rate can reach more than 90% after 24 hours at room temperature. Application number 201811403686.3 discloses a method for loading manganese oxide on an ozone modified active carbon carrier by an impregnation method, wherein the removal rate of formaldehyde can reach 88% at most. The invention patent CN105268452A discloses a formaldehyde degradation catalyst of copper-manganese composite oxide loaded on mesoporous SiO ₂, the catalyst can completely degrade formaldehyde at 75-125 ℃, and the reaction temperature is higher.

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, good activity stability, can degrade formaldehyde at normal temperature and can be recycled and a preparation method thereof.

In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: a method for preparing a catalyst comprising the steps of:

(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 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 mole ratio of iron ions in the iron-containing compound to manganese ions in the manganese-containing compound is as follows: iron ions: manganese ions = 1-7:1-7.

The inventors of the present application found during practical experiments that iron-containing compounds and manganese-containing compounds can produce Fe ₃Mn₃O₈ as a high active ingredient when the above molar ratio is within the above range. When the molar ratio of the iron ions in the iron-containing compound to the manganese ions in the manganese-containing compound is out of the specific range provided by the present application, the high active ingredient Fe ₃Mn₃O₈ is hardly produced, and the formaldehyde removing effect is remarkably reduced.

The invention provides a preparation method of a catalyst, which can adjust the valence distribution of manganese ions in an active ingredient 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 the oxygen vacancies can generate super-oxygen ions, hydroxyl and peroxy active intermediates of 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.

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 ions = 1-3:1-3. The inventors of the present application found in practical experiments that when the molar ratio of iron ions in the iron-containing compound to manganese ions in the manganese-containing compound is 1-3:1-3, the resulting high active ingredient Fe ₃Mn₃O₈ is much higher than when the molar ratio of iron ions in the iron-containing compound to manganese ions in the manganese-containing compound is not within the above-mentioned specific molar ratio range, and that the effect of catalyzing formaldehyde is also better.

Further preferably, the molar ratio of iron ions in the iron-containing compound to manganese ions in the manganese-containing compound is: iron ions: manganese ions=1:1. In the practical test process, the inventor discovers that when the molar ratio of iron ions in the iron-containing compound to manganese ions in the manganese-containing compound is 1:1, pure-phase high-activity component Fe ₃Mn₃O₈ is generated, and at the moment, the degradation rate of formaldehyde reaches the highest, and the high activity of the catalyst on formaldehyde oxidation is related to the high activity of the catalyst.

Preferably, the iron-containing compound and the iron-containing compound are catalyst precursors, wherein 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 hexadecyl benzene sulfonate, cetyltrimethyl ammonium bromide and chitosan.

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

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 of the heating regeneration is 100-500 ℃. Meanwhile, the catalyst can reach regeneration circulation through the modes of hydrogen peroxide solution treatment, illumination and the like, wherein the hydrogen peroxide treatment time is 0.1-3 hours, and the hydrogen peroxide mass concentration is 0.1-10% and can be regenerated; the illumination time is 1-15 hours, and the iron-containing compound is a catalyst precursor; thereby improving the utilization rate 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 mesoporous molecular sieve has a pore size ranging from 2 to 5nm.

Further preferably, the support is a titania oxide, such as titania P25. The inventor discovers that when the carrier is titanium dioxide P25 in the actual test process, the activity and stability of the reaction are optimal when formaldehyde is degraded.

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

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

(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 active ingredients by utilizing variable valence iron ions, thereby adjusting the concentration of oxygen vacancies, wherein the concentration of the oxygen vacancies is directly related to the oxidation capability of the oxygen vacancies, and the oxygen vacancies can generate super-oxygen ions, hydroxyl and peroxy active intermediates of 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 catalyst is loaded on the carrier with a larger specific surface, so that the number of active centers is increased, and the reactivity and stability are improved. Meanwhile, the catalyst can be regenerated after simple heat treatment (250 ℃) in the air, and adsorbates and the like covered on the surface can be decomposed and removed at a higher temperature, so that the re-exposure of active sites is realized, and the activity is recovered.

The method is simple, convenient and quick, is green and pollution-free, has low cost (the ferro-manganese compound and the carrier are both low-cost materials), and can be industrially prepared. Meanwhile, the catalyst has good thermal stability and formaldehyde purification stability, and the catalyst is easy 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 prepared by carrying an iron-manganese catalyst on an alumina titanium oxide carrier through in-situ gelation by an impregnation method, 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 purifying catalyst provided by the invention has the advantages that the degradation rate of formaldehyde can reach 90% in 1 hour at the high space velocity (300L/(g h)) at 25 ℃ and the time 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 XRD patterns 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 various temperatures for example 10;

fig. 6 is an XRD pattern after regeneration treatment of the catalyst Fe/mn=1:1 prepared in example 10 and hydrogen peroxide;

FIG. 7 is a graph showing the number of heating regeneration cycles of the catalyst prepared in example 10, fe/Mn=1:1;

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

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

Detailed Description

For a better description of the objects, technical solutions 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 are conventional methods unless otherwise specified, and the materials, reagents, etc. used, unless otherwise specified, are commercially available.

Examples 1 to 6

In the invention of examples 1-6, the influence of the carrier on the activity and stability of the reaction when degrading formaldehyde is explored, and the specific examples are set as follows:

example 1

Firstly, dispersing 0.500g of carrier mesoporous molecular sieve SBA-15 into 20ml of deionized water, dissolving 0.0580g of citric acid in the dispersion liquid, stirring for half an hour at room temperature, dissolving 0.120g of 50% manganese nitrate solution and 0.100g of ferric nitrate in the dispersion liquid in sequence, stirring for 4 hours in water bath for gelation, and drying in an oven at 100 ℃ for 12 hours. The solid is put into air to be calcined for 4 hours at 500 ℃, and then is ground 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 with ethanol for three times after the reaction is finished, and drying in a vacuum oven at 100 ℃ to obtain APTES modified SBA-15;

Then, 0.500g of APTES-SBA-15 was dispersed in 20ml of deionized water, 0.120g of a 50% by mass fraction manganese nitrate solution and 0.100g of ferric nitrate were sequentially added to the above dispersion, and the mixture was stirred in an 80-DEG water bath for 4 hours to gel and then dried in an oven at 100 DEG for 12 hours. The solid is put into air to be calcined for 4 hours at 500 ℃, and then is ground 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 room temperature, 0.120g of 50% manganese nitrate solution and 0.100g of ferric nitrate are sequentially added and sequentially dissolved in the dispersion liquid, and the mixture is stirred in an 80-DEG water bath for 4 hours for gelation, and then dried in an oven for 12 hours at 100 ℃. The solid is put into air to be calcined for 4 hours at 500 ℃, and then is ground to obtain the catalyst Fe-Mn/A-Al ₂O₃.

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 room temperature, 0.120g of 50% manganese nitrate solution and 0.100g of ferric nitrate are sequentially added and sequentially dissolved in the dispersion liquid, the mixture is stirred in a water bath at 80 ℃ for 4 hours to gel, and then the mixture is dried in an oven at 100 ℃ for 12 hours. The solid is put into air to be calcined for 4 hours at 500 ℃, and then is ground to obtain the catalyst Fe-Mn/N-Al ₂O₃.

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 for half an hour at room temperature, 0.120g of 50% manganese nitrate solution and 0.100g of ferric nitrate are sequentially added and sequentially dissolved in the dispersion liquid, the mixture is stirred in a water bath at 80 ℃ for 4 hours to gel, 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/B-Al ₂O₃.

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 room temperature, 0.120g of 50% manganese nitrate solution and 0.100g of ferric nitrate are sequentially added and sequentially dissolved in the dispersion liquid, the mixture is stirred in a water bath at 80 ℃ for 4 hours to gel, and then the mixture is dried in an oven at 100 ℃ for 12 hours. The solid was calcined in air at 500℃for 4 hours and then ground to obtain a catalyst Fe-Mn/P25.

Examples 7 to 11

In the invention, the influence of the molar ratio of iron ions in the iron-containing compound to manganese ions in the manganese-containing compound on the degradation degree of formaldehyde is explored in the embodiments 7-11; in examples 7 to 11 of the present invention, the effect of the molar ratio on the degradation degree of formaldehyde was examined, and the effect 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 only without combining the active ingredient catalyst with the carrier.

Example 7

16.2G ferric nitrate solid and 9.22g citric acid were added sequentially to 20ml deionized water, stirred in a water bath at 80℃for 4 hours to gel, and dried in an oven at 100℃for 12 hours. The solid was calcined in air at 500 degrees for 4 hours and then ground to obtain catalyst Fe ₂O₃.

Example 8

12.1G of ferric nitrate solid, 3.58g of 50% manganese nitrate solution and 9.22g of citric acid are added into 20ml of deionized water in sequence, stirred in a water bath at 80 ℃ for 4 hours, gelled and dried in an oven at 100 ℃ for 12 hours. The solid was calcined in air at 500 degrees for 4 hours and then ground to give a catalyst Fe/mn=3:1 in a molar ratio.

Example 9

4.04G of ferric nitrate solid, 10.7g of 50% manganese nitrate solution and 9.22g of citric acid are added into 20ml of deionized water in sequence, stirred in a water bath at 80 ℃ for 4 hours, gelled and dried in an oven at 100 ℃ for 12 hours. The solid was calcined in air at 500 degrees for 4 hours and then ground to give a catalyst Fe/mn=1:3 in a molar ratio.

Example 10

8.08G of ferric nitrate solid, 7.16g of 50% manganese nitrate solution and 9.22g of citric acid are added into 20ml of deionized water in sequence, stirred in a water bath at 80 ℃ for 4 hours, gelled and dried in an oven at 100 ℃ for 12 hours. The solid was calcined in air at 500 degrees for 4 hours and then ground to give a catalyst Fe/mn=1:1 in a molar ratio.

Example 11

14.3G of 50% by mass manganese nitrate solution and 9.22g of citric acid were added sequentially to 20ml of deionized water, stirred in a water bath at 80℃for 4 hours to gel, and dried in a 100℃oven for 12 hours. The above solid was calcined in air at 500 degrees for 4 hours and then ground to obtain catalyst Mn ₃O₄.

Examples 12 to 15

In the embodiments 12-15 of the present invention, no specific active ingredients of the present invention were used when the degradation of formaldehyde was explored: an iron-containing compound, a manganese-containing compound, and a chelating agent. Examples 12-15 the preparation of catalysts using aluminum-containing compounds, manganese-containing compounds and chelating agents, examples 12-15 were prepared specifically as follows:

Example 12

15.0G of aluminum nitrate solid and 9.22g of citric acid were added to 20ml of deionized water in this order, and the mixture was stirred in a water bath at 80℃for 4 hours to gel and then dried in an oven at 100℃for 12 hours. The solid was calcined in air at 500 degrees for 4 hours and then ground to obtain catalyst Al ₂O₃.

Example 13

11.3G of aluminum nitrate solid, 3.58g of 50% manganese nitrate solution and 9.22g of citric acid are added into 20ml of deionized water in turn, stirred in a water bath at 80 ℃ for 4 hours, gelled and dried in an oven at 100 ℃ for 12 hours. The solid was calcined in air at 500 degrees for 4 hours and then ground to give a catalyst Al/mn=3:1 in a molar ratio.

Example 14

7.50G of aluminum nitrate solid, 8.08g of 50% manganese nitrate solution and 9.22g of citric acid are added into 20ml of deionized water in turn, stirred in a water bath at 80 ℃ for 4 hours, gelled and dried in an oven at 100 ℃ for 12 hours. The solid was calcined in air at 500 degrees for 4 hours and then ground to give a catalyst Al/mn=1:1 in a molar ratio.

Example 15

3.00G of aluminum nitrate solid, 10.7g of 50% manganese nitrate solution and 9.22g of citric acid are added into 20ml of deionized water in turn, stirred in a water bath at 80 ℃ for 4 hours, gelled and dried in an oven at 100 ℃ for 12 hours. The solid was calcined in air at 500 degrees for 4 hours and then ground to give a catalyst Al/mn=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 are ground and mixed, and the mixture is filled into a stainless steel reaction tube to perform catalytic oxidation reaction on formaldehyde with the concentration of 115ppm, and the airspeed is 500ml/min. After the catalyst is deactivated, the catalyst is irradiated for 12 hours under simulated sunlight, and then catalytic oxidation reaction of formaldehyde with the same concentration is carried out, so that the activity of the catalyst is recovered.

Examples 17 to 21

The catalysts of examples 17-21 of the present invention were prepared using different chelating agents, and the specific preparation methods of the catalysts of examples 17-21 were as follows:

example 17

8.08G of ferric nitrate solid, 7.16g of 50% manganese nitrate solution and 8.74g of cetyltrimethylammonium bromide are added into 20ml of deionized water in sequence, stirred in a water bath at 80 ℃ for 4 hours, gelled and dried in an oven at 100 ℃ for 12 hours. The solid was calcined in air at 500 degrees for 4 hours and then ground to obtain a catalyst.

Example 18

8.08G of ferric nitrate solid, 7.16g of manganese nitrate solution with the mass fraction of 50% and 17.5g of cetyltrimethylammonium bromide are added into 20ml of deionized water in sequence, stirred in a water bath at 80 ℃ for 4 hours, gelled and dried in an oven at 100 ℃ for 12 hours. The solid was calcined in air at 500 degrees for 4 hours and then ground to obtain a catalyst.

Example 19

8.08G of ferric nitrate solid, 7.16g of 50% manganese nitrate solution and 26.2g of cetyltrimethylammonium bromide are added into 20ml of deionized water in sequence, stirred in a water bath at 80 ℃ for 4 hours, gelled and dried in an oven at 100 ℃ for 12 hours. The solid was calcined in air at 500 degrees for 4 hours and then ground to obtain a catalyst.

Example 20

8.08G of ferric nitrate solid, 7.16g of 50% manganese nitrate solution and 12.3g of sodium citrate are added into 20ml of deionized water in sequence, stirred in a water bath at 80 ℃ for 4 hours, gelled and dried in an oven at 100 ℃ for 12 hours. The solid was calcined in air at 500 degrees for 4 hours and then ground to obtain a catalyst.

Example 21

8.08G of ferric nitrate solid and 7.16g of 50% manganese nitrate solution are added into 20ml of deionized water in sequence, stirred for 4 hours in a water bath at 80 ℃, and dried in an oven at 100 ℃ for 12 hours. The solid was calcined in air at 500 degrees for 4 hours and then ground to obtain a 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 being introduced by the catalyst for 4 hours, the initial stabilized concentration is determined by a formaldehyde detector after stabilization, then a switch valve is opened to introduce formaldehyde, the formaldehyde concentration of tail gas is detected by the formaldehyde detector, and data is recorded once in 10 minutes. And subtracting the tail gas formaldehyde concentration from the initial formaldehyde concentration, and dividing the tail gas formaldehyde concentration by the initial formaldehyde concentration to obtain the degradation rate of formaldehyde.

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

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

experimental results:

In examples 1-6 of the present invention, the influence of the carrier on the activity and stability of the reaction was investigated, and FIG. 1 is a graph showing the catalytic oxidation performance of formaldehyde in examples 1-6, and as can be seen from FIG. 1, 0-1 hours is a formaldehyde concentration stabilization experiment before formaldehyde is introduced into the catalyst, and after the formaldehyde concentration is stabilized, the formaldehyde is introduced into the fixed bed reactor for reaction. Fe-Mn/P25 and Fe-Mn/APTES-SBA-15 can still operate for 12 and 7 hours at room temperature.

FIG. 2 is a graph showing XRD patterns of examples 1-6, wherein it can be seen that the active species of the ferro-manganese oxide are not basically observed in the XRD patterns of SBA-15 and APTES-SBA-15, probably due to the growth and high dispersion of the ferro-manganese oxide in the pore channels, the ferro-manganese oxide in the active center is dispersed in the pore channels, and formaldehyde molecules enter the pore channels to be converted into intermediates and then into carbon dioxide and water through catalytic oxidation reaction with the active center.

FIG. 3 is a graph showing the catalytic oxidation performance of formaldehyde at room temperature in examples 7-11, wherein the graph shows that 0-1 hour is a formaldehyde concentration stabilization experiment before formaldehyde is introduced into a catalyst, and the formaldehyde is introduced into a fixed bed reactor for reaction after the formaldehyde concentration is stabilized; the catalyst comprising the active ingredient provided by the invention has a good formaldehyde degradation effect, wherein the catalytic activity of Fe/Mn=1:1 is optimal, and probably because when the molar ratio of iron ions in the iron-containing compound to manganese ions in the manganese-containing compound is 1:1, high active ingredient Fe ₃Mn₃O₈ is generated, and the formaldehyde degradation rate is highest at the moment.

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

FIG. 5 is a graph showing the catalytic oxidation performance of formaldehyde at various temperatures in example 10, wherein the catalyst was reduced to 50 mg, the air flow rate was unchanged, the formaldehyde was introduced into the catalyst to react, a point was measured every 15 minutes, the average value was obtained three times, and the reaction furnace was heated to the corresponding temperature. The airspeed is improved, the degradation rate of the ferromanganese oxide to formaldehyde can reach 70% at room temperature, and the time can reach 99% after the time is prolonged.

FIG. 6 shows XRD patterns of the catalyst prepared in example 10, wherein Fe/Mn=1:1, and when the ratio of Fe to Mn is 1:1, the product is judged to be high-activity iron manganese oxide Fe ₃Mn₃O₈ by comparing with the standard card number ICSD of Fe ₃Mn₃O₈: (# 28665), and the excellent catalytic oxidation activity of the catalyst to formaldehyde is related to the high-activity iron manganese oxide Fe ₃Mn₃O₈. Meanwhile, after the catalyst is treated by hydrogen peroxide (3%) for 10 minutes, the crystalline phase of the catalyst is still high-activity Fe ₃Mn₃O₈, which shows that the hydrogen peroxide treatment of the catalyst does not cause structural phase change, and the catalyst 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, an initial stable concentration is determined by a formaldehyde detector, then a switch valve is opened, formaldehyde is introduced, the formaldehyde concentration of tail gas is detected by the formaldehyde detector, and data is recorded once in 10 minutes.

After the catalyst is deactivated, the cyclic regeneration treatment is carried out:

The deactivated catalyst of example 10 was heated to 250℃with air for 2 hours, and the formaldehyde catalytic oxidation experiment was repeated three times. The deactivated catalyst of example 10 was treated with 10ml of 1% hydrogen peroxide solution for 10 minutes, dried and subjected to catalytic oxidation test to deactivate the catalyst of example 10. The deactivated catalyst of example 5 was irradiated for 12 hours under simulated sunlight and then subjected to catalytic oxidation of formaldehyde at the same concentration, i.e. example 16 of the present invention.

Example 10 conditions for air heating regeneration cycle test: the catalyst is 0.10g, the room temperature is normal pressure, the formaldehyde of 115ppm, the air flow rate is 500ml/min, and the humidity is 22%; regeneration conditions: heat treating with 250 deg.c air for 2 hr;

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

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

FIG. 7 is a graph showing the number of heat regeneration cycles of example 10, from which it can be seen that the activity of the catalyst was recovered after 250 degrees of air heat treatment, and the catalytic oxidation cycle was performed three times at room temperature. FIG. 8 is a graph showing the number of regeneration cycles for the hydrogen peroxide solution treatment of example 10, wherein the activity was substantially recovered after the treatment with 1% hydrogen peroxide solution at the room temperature of the catalyst, and the catalytic oxidation cycle was performed three times at room temperature. Fig. 9 is a graph of the number of regeneration cycles of the irradiation of the example 16, which shows that the catalyst activity is recovered by the irradiation of the sun-simulated light at the temperature of the catalyst chamber, and illustrates that the inert intermediate covered on the surface of the active site is decomposed or desorbed by the irradiation of the simulated sunlight.

FIGS. 7-9 collectively illustrate that after a large amount of formaldehyde gas is deactivated, the room temperature high activity iron manganese oxide (Fe ₃Mn₃O₈) can be used for recovering the activity in the application by oxidizing the catalyst at 250 ℃ for 2 hours, or the catalyst can be used for recovering the activity by treating the catalyst with commercial hydrogen peroxide for 10 minutes, or the Fe-Mn/B-gamma-alumina and titanium dioxide can be regenerated by light treatment after being mixed, which is very beneficial to the treatment of the deactivated catalyst in daily life, the service life of the catalyst is prolonged and the cost is reduced. The development of such supported catalysts can effectively purify indoor air.

Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the scope of the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention may be modified or substituted equally without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. The application of the pure-phase high-activity component Fe ₃Mn₃O₈ catalyst in degrading formaldehyde products is characterized in that the preparation method of the pure-phase high-activity component Fe ₃Mn₃O₈ 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 gel A; the temperature of water bath stirring is 40-90 ℃, and the time of water bath stirring is 3-5h; the chelating agent is citric acid;

(2) Drying the gel prepared in the step (1) to obtain a solid B, and calcining and grinding the solid B to obtain the pure-phase high-activity component Fe ₃Mn₃O₈ catalyst; the drying temperature is 90-110 ℃, and the drying time is 10-15h; the calcination temperature is 500 ℃, and the calcination time is 2-8h;

Wherein, the mole ratio of iron ions in the iron-containing compound to manganese ions in the manganese-containing compound is as follows: iron ions: manganese ions=1:1.

2. The use 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.

3. The use of claim 1, wherein the pure phase high activity component Fe ₃Mn₃O₈ catalyst further comprises a support comprising at least one of gamma alumina, mesoporous molecular sieve, titania oxide.

4. The use according to claim 3, wherein the support is a titania oxide.