CN105013322A - Use of manganite catalyst in catalytic oxidation of formaldehyde - Google Patents

Abstract

The invention provides a use of a manganese oxide catalyst for catalyzing the oxidation of formaldehyde, and the manganese oxide is manganese dioxide in gamma or/and delta crystal form. The present invention has the manganese dioxide that adopts δ crystal form as catalyst catalytic oxidation formaldehyde and has following advantage: (1) the light-off temperature of catalytic oxidation formaldehyde is low, at high formaldehyde concentration high space velocity (concentration 170ppm, space velocity 100,000mL/(g· h)), the conversion rate at 50°C has reached 37%, and it is completely converted at 80°C, and its activity is in the forefront among non-precious metal catalysts; (2) excellent stability, on the one hand, its crystal form remains stable before and after the catalytic reaction, and on the other hand On the one hand the catalytic conversion remains unchanged in the long-term activity test.

Description

Application of a manganese oxide catalyst for catalytic oxidation of formaldehyde

technical field

The invention belongs to the technical field of formaldehyde catalysis, and in particular relates to the use of a manganese oxide catalyst for catalytic oxidation of formaldehyde.

Background technique

As a binder, formaldehyde has the functions of strengthening the hardness of artificial floors, preventing insects, and preventing corrosion, so it is widely used in furniture and decoration materials. On the other hand, formaldehyde is also gradually released from the adhesive into the surrounding environment, which leads to serious pollution of the indoor air. The test results of the Indoor Environment Testing Committee of China Interior Decoration Association also show that formaldehyde has become the main pollutant in newly decorated rooms in China. Exposure to a certain amount of formaldehyde gas for a long time can irritate the eyes, nose, throat and other organs in mild cases, and cause fatigue and allergic reactions in severe cases, and even cause tumors, endangering human health. Therefore, it is urgent to explore and research on efficient removal methods of formaldehyde.

At present, the methods for removing indoor formaldehyde mainly include photocatalytic method, plasma decomposition method, adsorption method and catalytic oxidation method. Among them, the catalytic oxidation method can completely oxidize formaldehyde into carbon dioxide and water at low temperature or even room temperature, without the need for light or plasma to excite the catalyst, and without the limitation of saturated adsorption of the adsorbent, thus breaking through many limitations of the first three methods. At present, the catalysts for removing formaldehyde are mainly supported noble metal catalysts and transition metal oxide catalysts. Noble metal catalysts can completely remove formaldehyde at room temperature, but they are expensive, which leads to the gradual attention to the research of transition metal oxides.

CN 103691461A discloses a method for applying a loaded gold hydroxyapatite catalyst, using calcium nitrate and diamine hydrogen phosphate as precursors, and obtaining carrier hydroxyapatite by liquid phase deposition; using chloroauric acid as a precursor, and Hydroxyapatite is used as carrier, and urea homogeneous precipitation method is adopted to prepare the supported gold hydroxyapatite catalyst. The catalyst can catalyze the removal of formaldehyde at room temperature, but its disadvantage is that the active material is gold, and its price will hinder the commercial application of the improved catalyst.

CN 103962163A discloses a preparation method of transition metal-doped hydroxyapatite and its catalytic oxidation to formaldehyde. The method has simple steps and a short period, but its catalytic activity is not high compared with noble metal catalysts. Therefore, the study of highly active non-noble metal catalysts for catalytic oxidation of formaldehyde will have far-reaching practical significance.

Existing technologies (Tian Hua, He Junhui, Research Progress in Catalyzed Oxidation of Formaldehyde by Manganese Oxide, Chemical Bulletin, Volume 76, No. 2, 2013, Pages 100-106) only disclose the use of manganese dioxide in α and β crystal forms for formaldehyde purify. They require high temperature for complete removal of formaldehyde under high load, that is, high space velocity and high formaldehyde concentration (100000mL/(g h) and 170ppm), which cannot meet the practical application.

Contents of the invention

Based on this, the object of the present invention is to provide a method for catalytically oxidizing formaldehyde, which uses manganese oxides of different crystal forms as catalysts to achieve efficient oxidation of formaldehyde.

In order to achieve the above object, the present invention adopts following technical scheme:

A use of a manganese oxide catalyst for catalyzing the oxidation of formaldehyde, the manganese oxide being manganese dioxide in gamma or/and delta crystal form.

Preferably, in the present invention, the manganese oxide is manganese dioxide in δ crystal form. The present invention uses the manganese dioxide of δ crystal form to catalyze the oxidation of formaldehyde, which has the advantages of high conversion rate and low catalytic temperature. (100000mL/(g·h)) test conditions still show a high catalytic conversion rate, and can still achieve complete (100%) conversion of formaldehyde at 80°C.

Preferably, in the present invention, in the process of catalytic oxidation of formaldehyde, the initial concentration of formaldehyde is 0-170ppm and does not include 0, such as 10ppm, 30ppm, 50ppm, 70ppm, 90ppm, 110ppm, 130ppm, 150ppm or 170ppm. By adopting the manganese dioxide in the δ crystal form of the present invention, 100% conversion of formaldehyde at 80° C. can be realized at a high concentration (up to 170 ppm).

Preferably, in the present invention, during the catalytic oxidation of formaldehyde, the space velocity is 0-100000mL/(g·h) and excluding 0, the space velocity is, for example, 100000mL/(g·h). By adopting the δ crystal form manganese dioxide of the present invention, 100% conversion of formaldehyde at 80° C. can be realized at high space velocity (100,000 mL/(g·h)).

In the present invention, in the process of catalytic oxidation of formaldehyde, the amount of manganese oxide is any amount.

Preferably, the manganese dioxide in the δ crystal form is synthesized by a hydrothermal method using manganese sulfate as a reducing agent, potassium permanganate or ammonium persulfate as an oxidizing agent, as follows:

Add the required oxidizing agent, reducing agent and deionized water into the hydrothermal reaction kettle, dissolve the oxidizing agent and reducing agent thoroughly by stirring, and then place it in a constant temperature box at 200-240°C for reaction, and filter the contents of the reaction kettle after the reaction , washed and dried, then roasted in air.

The present invention prepares manganese dioxide in the δ crystal form by adopting a specific hydrothermal reaction temperature of 200 to 240°C (such as 205°C, 210°C, 215°C, 220°C, 225°C, 230°C or 235°C), so that the obtained δ The crystalline form of manganese dioxide has excellent formaldehyde catalytic activity, and it still shows high catalytic activity under the test conditions of high concentration (170ppm) and high space velocity (100000mL/(g h)), and it can still be used at 80°C. Complete (100%) conversion of formaldehyde can be achieved.

Preferably, the reaction is carried out in a thermostat at 200-240°C for 18-30 hours, such as 19h, 20h, 21h, 22h, 23h, 24h, 25h, 26h, 27h, 28h or 29h, preferably 24h. When the time is lower than 18h, the catalyst cannot form sufficient δ crystal form, and if the time is higher than 30h, heat will be wasted.

Preferably, the drying time is 12-24 hours, such as 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours or 23 hours.

Preferably, the calcination temperature is 300-450°C, such as 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, 410°C, 420°C , 430°C or 440°C. If the calcination temperature is lower than 300°C, the catalyst cannot be in a sufficiently stable state, and if the calcination temperature is higher than 450°C, it will easily cause Ag sintering. The calcination time is 3-6 hours, such as 3.3h, 3.6h, 3.9h, 4.2h, 4.5h, 4.8h, 5.1h, 5.4h or 5.7h. If it is lower than 3h, the catalyst cannot be calcined, and if it is higher than 6h, it will Easy to sinter and increase production cost.

Preferably, the surface of the manganese oxide is loaded with elemental silver as an active component. Supporting the active component silver can significantly improve the catalytic activity of the catalyst.

Preferably, the active component elemental silver accounts for 2-10% by mass of the sum of the mass of silver and manganese oxide, such as 2%, 3%, 4%, 5%, 6%, 7%, 8%. , 9% or 10%, preferably 8%.

The present invention also provides a method for catalytically oxidizing formaldehyde, which uses manganese dioxide in δ crystal form as a catalyst. Preferably, the catalytic oxidation of formaldehyde is carried out under the conditions of high concentration (formaldehyde concentration 170ppm) and high space velocity (100000mL/(g·h)). Under the conditions of this concentration and space velocity, complete (100%) conversion of formaldehyde can be achieved at 80°C. That is, when the formaldehyde concentration is 170ppm, the space velocity is 100000mL/(g·h), and the temperature is 80°C, 100% formaldehyde is completely converted. Further preferably, the manganese dioxide in the δ crystal form uses manganese sulfate as a reducing agent, potassium permanganate or ammonium persulfate as an oxidizing agent, and is synthesized by a hydrothermal method, as follows: add the required oxidizing agent to a hydrothermal reaction kettle , reducing agent and deionized water, the oxidizing agent and reducing agent are completely dissolved by stirring, and then placed in a constant temperature box at 200-240°C for reaction. After the reaction, the contents of the reactor are filtered, washed and dried, and then roasted in the air . Further preferably, the reaction is carried out in a thermostat at 200-240°C for 18-30 hours, such as 19h, 20h, 21h, 22h, 23h, 24h, 25h, 26h, 27h, 28h or 29h, preferably 24h. When the time is lower than 18h, the catalyst cannot form sufficient δ crystal form, and if the time is higher than 30h, heat will be wasted. Further preferably, the calcination temperature is 300-450°C, such as 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, 410°C, 420°C °C, 430°C or 440°C. If the calcination temperature is lower than 300°C, the catalyst cannot be in a sufficiently stable state, and if the calcination temperature is higher than 450°C, it will easily cause Ag sintering. The calcination time is 3-6 hours, such as 3.3h, 3.6h, 3.9h, 4.2h, 4.5h, 4.8h, 5.1h, 5.4h or 5.7h. If it is lower than 3h, the catalyst cannot be calcined, and if it is higher than 6h, it will Easy to sinter and increase production cost. Further preferably, the surface of the manganese oxide is loaded with elemental silver as an active component. Supporting the active component silver can significantly improve the catalytic activity of the catalyst. Preferably, the active component elemental silver accounts for 2-10% by mass of the sum of the mass of silver and manganese oxide, such as 2%, 3%, 4%, 5%, 6%, 7%, 8%. , 9% or 10%, preferably 8%.

The present invention prepares manganese dioxide in the δ crystal form by adopting a specific hydrothermal reaction temperature of 200 to 240°C (such as 205°C, 210°C, 215°C, 220°C, 225°C, 230°C or 235°C), so that the obtained δ The crystalline form of manganese dioxide has excellent formaldehyde catalytic activity, and it still shows high catalytic activity under the test conditions of high concentration (170ppm) and high space velocity (100000mL/(g h)), and it can still be used at 80°C. Complete (100%) conversion of formaldehyde can be achieved.

Compared with the prior art, the present invention has the following advantages of using manganese dioxide in δ crystal form as a catalyst to catalyze the oxidation of formaldehyde:

(1) The light-off temperature of catalytic oxidation of formaldehyde is low, and the conversion rate at 50°C has reached 37% at high formaldehyde concentration and high space velocity (concentration 170ppm, space velocity 100,000mL/(g h)), and it is completely converted at 80°C , its activity is in the forefront among non-precious metal catalysts;

(2) Excellent stability. On the one hand, its crystal form remains stable before and after the catalytic reaction. On the other hand, the catalytic conversion rate remains unchanged in the long-term (50h) activity test, at a concentration of 170ppm and a space velocity of 100,000mL/(g h ), at a temperature of 80°C, a conversion rate of 100% is always maintained, and at a concentration of 170ppm, a maximum space velocity of 150,000mL/(g h), and a temperature of 75°C, a conversion rate of 60% is always maintained;

(3) The use of non-toxic components reduces the harm to human health and the ecological environment, the preparation process is simple and easy, the cost is low, and industrialization is easy to realize.

Detailed ways

The technical solutions of the present invention will be further described below through specific embodiments.

Example 1

Prepare α, β, γ and δ crystal forms of manganese dioxide in the following manner:

Manganese sulfate is used as reducing agent, potassium permanganate or ammonium persulfate is used as oxidizing agent, and manganese dioxide catalysts of α, β, γ and δ crystal forms are prepared by hydrothermal synthesis, as follows:

Add the required precursor (i.e. oxidant and reductant) (X) and 80mL deionized water into a 100mL hydrothermal reaction kettle, dissolve the precursor completely by stirring, and then place it in a thermostat at a certain reaction temperature (Y) React for a certain period of time (Z), then filter, wash, and dry the contents of the reactor overnight, and then roast in air at 300°C. The following table lists specific values for X, Y, Z.

x Y Z α-MnO ₂ MnSO ₄ ·H ₂ O+KMnO ₄ 160°C 24h β-MnO ₂ MnSO ₄ ·H ₂ O+(NH ₄ ) ₂ S ₂ O ₈ 140°C 12 hours γ-MnO ₂ MnSO ₄ ·H ₂ O+(NH ₄ ) ₂ S ₂ O ₈ 90°C 24h δ-MnO ₂ MnSO ₄ ·H ₂ O+KMnO ₄ 200-240℃ 24h

Among the four kinds of manganese dioxide, the activity of δ crystal form manganese dioxide to catalyze the complete oxidation of formaldehyde is much higher than that of other crystal forms, showing its huge crystal form advantages. The relevant parameters of the catalytic formaldehyde activity of the four crystal forms of manganese dioxide are listed in the table below, arranged from high to low in activity. Test conditions: concentration 170ppm, space velocity 100,000mL/(g·h).

Example 2

Manganese dioxide in α, β, γ and δ crystal forms was prepared in the same manner as in Example 1.

At a concentration of 170ppm, a space velocity of 150,000mL/(g h), and a temperature of 75°C, the δ crystal form of manganese dioxide can maintain a conversion rate of 60% within 50 hours, and α, β, and γ are under the same conditions Under the next test, its activity gradually decreased after 5h.

Example 3

Manganese dioxide in α, β, γ and δ crystal forms was prepared by the same method as in Example 1.

The relevant parameters of the catalytic formaldehyde activity of the four crystal forms of manganese dioxide are listed in the table below, arranged from high to low in activity. Test conditions: concentration 5ppm, space velocity 5000mL/(g·h).

Comparative example 1

Manganese dioxide in δ crystal form was prepared in the same manner as in Example 1, except that the hydrothermal reaction temperature was 180°C.

Comparative example 2

Manganese dioxide in δ crystal form was prepared in the same manner as in Example 1, except that the hydrothermal reaction temperature was 260°C.

Under high formaldehyde concentration and high space velocity (concentration 170ppm, space velocity 100,000mL/(g h)), test the catalytic activity of the catalyst of comparative example 1 and comparative example 2, the result shows:

The catalyst of Comparative Example 1 achieved 50% conversion of formaldehyde at 75°C and 100% conversion of formaldehyde at 110°C, and the catalyst of Comparative Example 2 achieved 50% conversion of formaldehyde at 80°C and 100% conversion of formaldehyde at 125°C.

Example 4

The manganese dioxide of α, β, γ and δ crystal forms was prepared by the same method as in Example 1, and the active component silver was loaded on the manganese dioxide, and the mass fraction of silver was 8 wt%.

Under high formaldehyde concentration and high space velocity (concentration 170ppm, space velocity 100,000mL/(g·h)), the catalytic activity of the catalyst of Example 4 was tested. The relevant parameters of the catalytic formaldehyde activity of the four crystal forms of manganese dioxide are listed in the table below. Test conditions: concentration 170ppm, space velocity 100,000mL/(g·h).

Example 5

All the other are the same as Example 4 except that the mass fraction of silver is 2wt%.

Under high formaldehyde concentration and high space velocity (concentration 170ppm, space velocity 100,000mL/(g·h)), the catalytic activity of the catalyst of Example 5 was tested. The relevant parameters of the catalytic formaldehyde activity of the four crystal forms of manganese dioxide are listed in the table below. Test conditions: concentration 170ppm, space velocity 100,000mL/(g·h).

Example 6

All the other are the same as Example 4 except that the mass fraction of silver is 10wt%.

Under high formaldehyde concentration and high space velocity (concentration 170ppm, space velocity 100,000mL/(g·h)), the catalytic activity of the catalyst of Example 6 was tested. The relevant parameters of the catalytic formaldehyde activity of the four crystal forms of manganese dioxide are listed in the table below. Test conditions: concentration 170ppm, space velocity 100,000mL/(g·h).

The applicant declares that the present invention illustrates the detailed methods of the present invention through the above-mentioned examples, but the present invention is not limited to the above-mentioned detailed methods, that is, it does not mean that the present invention must rely on the above-mentioned detailed methods to be implemented. Those skilled in the art should understand that any improvement of the present invention, the equivalent replacement of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the scope of protection and disclosure of the present invention.

Claims (10)

1. manganese oxide catalyst is used for a purposes for catalyze oxidation of formaldehyde, and described Mn oxide is that γ is or/and the manganese dioxide of δ crystal formation.

2. purposes as claimed in claim 1, it is characterized in that, described Mn oxide is the manganese dioxide of δ crystal formation.

3. purposes as claimed in claim 1 or 2, it is characterized in that, in catalyze oxidation of formaldehyde process, the initial concentration of formaldehyde is 0-170ppm and does not comprise 0.

4. the purposes as described in one of claim 1-3, is characterized in that, in catalyze oxidation of formaldehyde process, air speed is 0-100000mL/ (gh) and does not comprise 0.

5. the purposes as described in one of claim 1-4, is characterized in that, the manganese dioxide of described δ crystal formation take manganese sulfate as reducing agent, and potassium permanganate or ammonium persulfate are oxidant, adopts water heat transfer, specific as follows:

Requisite oxygen agent, reducing agent and deionized water is added in hydrothermal reaction kettle, by stirring, Oxidizing and Reducing Agents is thoroughly dissolved, and be placed in the insulating box of 200 ~ 240 DEG C and react, after reaction terminates, material in reactor to be filtered, washing and dry, roasting in atmosphere afterwards.

6. purposes as claimed in claim 5, is characterized in that, is placed in insulating box reaction 18 ~ 30h, the preferred 24h of 200 ~ 240 DEG C.

7. the purposes as described in claim 5 or 6, is characterized in that, described drying time is 12 ~ 24h.

8. the purposes as described in one of claim 5-7, is characterized in that, the temperature of described roasting is 300 ~ 450 DEG C, and roasting time is 3 ~ 6h.

9. the purposes as described in one of claim 1-8, is characterized in that, described Mn oxide area load has active component elemental silver.

10. purposes as claimed in claim 9, is characterized in that, the mass percent that described active component elemental silver accounts for the quality sum of silver and Mn oxide is 2-10%, preferably 8%.