CN111215049B

CN111215049B - Mn doped with Cr ions3O4Thermocatalytic material and preparation method and application thereof

Info

Publication number: CN111215049B
Application number: CN202010141692.7A
Authority: CN
Inventors: 范晓星; 杨媛; 成祥祥
Original assignee: Liaoning University
Current assignee: Liaoning University
Priority date: 2020-03-04
Filing date: 2020-03-04
Publication date: 2022-07-19
Anticipated expiration: 2040-03-04
Also published as: CN111215049A

Abstract

The invention discloses Cr ion doped Mn₃O₄A thermal catalytic material, a preparation method and application thereof. Adding chromium salt or chromium alkali into aqueous solution of manganese salt, adding the mixed solution into aqueous alkali, performing ultrasonic treatment, centrifuging, drying and cooling to obtain precursor, grinding the precursor, and performing high-temperature calcination treatment to obtain Cr-Mn₃O₄. The Cr ion prepared by the method of the invention is doped with Mn₃O₄Thermal catalytic material, improved Mn₃O₄Under the dark condition, the defect of low thermal response at low temperature is overcome, the movement of lattice oxygen in the lattice is improved, the initial temperature required by the reaction is reduced, the thermal degradation rate is improved, and the thermal catalytic activity can be effectively improved. It can be used to degrade organic pollutants by heating under dark conditions.

Description

Mn doped with Cr ions3O4Thermal catalytic material and preparation method and application thereof

Technical Field

The invention relates to a preparation method of a doped material and application of thermal catalytic performance in the technical field of degradation of volatile organic pollutants under dark conditions, in particular to Cr ion doped Mn₃O₄A thermal catalytic material, a preparation method and application thereof.

Background

With the development of human society, the burning of fossil fuels raises a serious environmental problem, and the acquisition and conversion of solar energy into usable energy has become a key problem in human society. In recent years, the photocatalytic degradation of organic pollutants has attracted more and more attention due to its advantages of no pollution, mild reaction conditions, and the like. However, due to the effect of the photocatalytic material on its own bandwidth, the larger the bandwidth, the smaller the photoresponse range, and the lower the photocatalytic efficiency. On the basis, the thermocatalysis material under different temperatures in a dark condition is provided, and the thermocatalysis technology is sustainable development and environment-friendly, and has the characteristics of no secondary pollution, cyclic regeneration and the like. The thermocatalytic mechanism is generally the oxidation of the contaminant by the crystal lattice in the catalyst, producing oxygen vacancies and a reactive oxygen catalyst. Subsequently, the oxygen vacancies and oxygen generate lattice oxygen. Doping is an effective and simple method for improving the thermocatalytic performance, because the doping can cause the change of the specific surface area, and the doping of doping ions can generate lattice defects, so that oxygen atoms in lattices are easier to migrate, the initial temperature of the reaction is reduced, and the thermocatalytic reaction efficiency is improved.

Disclosure of Invention

The invention aims to provide a Cr ion doped Mn₃O₄The method is easy to operate, simple, convenient, low in cost, mild in condition and favorable for large-scale production.

In order to realize the purpose, the invention adopts the technical scheme that: doping Mn with Cr ions₃O₄The preparation method of the thermocatalytic material comprises the following steps:

1) preparing an aqueous solution of manganese salt; preparing an alkali solution;

2) adding chromium salt or chromium alkali into the aqueous solution of manganese salt, and performing ultrasonic treatment to uniformly mix the chromium salt or the chromium alkali with the aqueous solution of manganese salt;

3) adding the mixed solution obtained in the step 2) into an alkali solution; ultrasonically mixing the mixture evenly; centrifuging to obtain a precipitate, drying and cooling to obtain a precursor;

4) and 3) carrying out high-temperature calcination treatment on the precursor obtained in the step 3) to obtain a target product.

Preferably, the Cr ions are doped with Mn₃O₄The thermal catalysis material is prepared by using manganese salt as a manganese acetate, manganese nitrate or manganese chloride in the step 1).

Preferably, the Cr ions mentioned above are doped with Mn₃O₄A thermal catalytic material, wherein in the step 1), the alkali solution is sodium hydroxide aqueous solutionAn aqueous potassium hydroxide solution or an aqueous ammonium hydroxide solution.

Preferably, the Cr ions mentioned above are doped with Mn₃O₄The thermal catalysis material is prepared by the step 2) that the chromium salt is chromium nitrate and the chromium base is chromium hydroxide.

Preferably, the Cr ions are doped with Mn₃O₄Thermocatalytic material, step 2), in molar ratio, Mn²⁺：Cr³⁺＝1：0.01-0.2。

Preferably, the Cr ions are doped with Mn₃O₄Thermocatalytic material, step 2), in molar ratio, Mn²⁺: OH in alkali^-＝1：2-4。

Preferably, the Cr ions mentioned above are doped with Mn₃O₄The thermal catalysis material, in the step 3), the drying temperature is 50-100 ℃.

Preferably, the Cr ions mentioned above are doped with Mn₃O₄The thermal catalysis material in the step 4), the high temperature calcination treatment is carried out at the temperature of 300-600 ℃ for 2-3 h.

The above-mentioned Cr ion-doped Mn₃O₄The application of the thermal catalytic material in catalytic degradation of gaseous pollutants under dark heating conditions.

Preferably, for the above-mentioned application, the gaseous contaminant is isopropanol.

The invention has the beneficial effects that:

1. the invention provides Cr ion doped Mn₃O₄The preparation method of the thermal catalytic material successfully constructs a doping structure, and the structure can more easily move lattice oxygen and can effectively improve the thermal catalytic activity.

2. The preparation method provided by the invention has the advantages of cheap and easily available raw materials, simple and convenient operation, greatly reduced cost, no toxicity, no pollution to the environment and realization of green chemistry.

3. The invention provides Cr ion doped Mn₃O₄The thermal catalytic material, chromium doped mangano-manganic oxide can generate lattice defects, so that oxygen atoms in the lattice are easier to migrate, the thermal catalytic activity can be promoted, and the thermal catalytic material is important for improving the thermal catalytic materialThe main function is that the Cr ions provided by the invention are doped with Mn₃O₄The degradation rate of the thermal catalytic material for degrading the isopropanol is far higher than that of Mn under the dark heating condition₃O₄。

Drawings

FIG. 1 shows pure Mn prepared in example 1₃O₄And Cr ion doped Mn₃O₄XRD contrast patterns of the thermocatalytic materials.

FIG. 2a shows Cr-Mn₃O₄(10%) EDS energy spectrum of the sample.

FIG. 2b shows Cr-Mn₃O₄(10%) topography of the sample.

FIG. 2c shows Cr-Mn₃O₄(10%) distribution pattern of O element on sample surface.

FIG. 2d shows Cr-Mn₃O₄(10%) distribution of Mn element on the surface of the sample.

FIG. 2e shows Cr-Mn₃O₄(10%) distribution of Cr element on the surface of the sample.

FIG. 3 is a graph comparing the degradation rate of the thermo-catalytic material prepared in example 1 to degrade isopropanol.

FIG. 4 is a graph of the thermal catalytic stability of the thermo-catalytic material prepared in example 1 for degrading isopropanol.

Detailed Description

Example 1

(I) doping of Cr ions with Mn₃O₄Thermo-catalytic material Cr-Mn₃O₄

The preparation method comprises the following steps:

1) adding 2.86g of 50% manganese nitrate into a beaker filled with 10ml of deionized water, and stirring for 15min to fully dissolve the manganese nitrate;

2) adding 0.64g of sodium hydroxide into a beaker containing 10ml of deionized water, and stirring for 15min to fully dissolve the sodium hydroxide;

3) 1.28g of chromium nitrate nonahydrate (the molar weight of Cr is 10 percent of the molar weight of Mn) is added into the manganese salt solution obtained in the step 1), and the mixture is subjected to ultrasonic treatment to be uniformly mixed;

4) dripping the mixed solution obtained in the step 3) into a sodium hydroxide solution, and carrying out ultrasonic treatment for 30 minutes until the solution is uniformly mixed;

5) putting the solution obtained in the step 4) into a centrifugal machine, and centrifuging to obtain a precipitate.

6) Putting the mixed solution obtained in the step 5) into an oven, drying at 60 ℃, and naturally cooling to obtain a precursor;

7) grinding the precursor obtained in the step 6), heating to 400 ℃ at the heating rate of 5 ℃/min, and calcining for 2h to obtain the Cr ion doped Mn₃O₄Thermo-catalytic material Cr-Mn₃O₄。

Comparative example (II) pure Mn₃O₄Thermal catalytic material

The preparation method comprises the following steps: pouring 2.86g of 50% manganese nitrate into a beaker containing 10ml of aqueous solution, adding 0.64g of sodium hydroxide into the beaker containing 10ml of deionized water, dropwise adding the manganese nitrate solution into the sodium hydroxide solution, and carrying out ultrasonic treatment for 30 minutes to fully dissolve the manganese nitrate solution; then placing the mixture in an oven to be dried at 60 ℃ to obtain a precursor; heating the obtained precursor to 450 ℃ at the heating rate of 5 ℃/min, and calcining for 2h to obtain pure Mn₃O₄A thermocatalytic material.

(III) detection

FIG. 1 shows the preparation of Cr ion doped Mn₃O₄Thermocatalytic material and pure Mn₃O₄XRD test pattern of the thermocatalytic material, as can be seen from FIG. 1, pure Mn₃O₄The diffraction peak of the photocatalytic material sample is completely consistent with the peak spectrum of the manganomanganic oxide standard card, which indicates that the prepared pure Mn₃O₄The thermo-catalytic material is indeed trimanganese tetroxide. Mn with 10% of Cr ion doping amount is prepared₃O₄The sample of the thermocatalytic material had Mn₃O₄Diffraction peaks whose peak spectra completely coincide. For Cr-Mn, because the doping amount is very small, XRD can not clearly scan a diffraction peak about Cr ions₃O₄(10%) the samples were subjected to elemental analysis, as shown in fig. 2 c-2 e, which showed that elements such as oxygen, manganese, chromium, etc. had significant strong signals and were uniformly distributed. As shown in FIG. 2a, no additional residual element was found in the EDS results, demonstrating that the Cr ion doped Mn prepared by the present invention₃O₄The thermal catalytic material is doped with Cr ions.

EXAMPLE 2 use

(one) influence of different catalytic materials on catalytic degradation rate of isopropanol at different temperatures

The test process is as follows: 0.1g of pure Mn from example 1 were each taken₃O₄And Cr-Mn prepared by 10% of Cr doping amount₃O₄The thermocatalyst was separately loaded into a quartz flow reactor, which was then placed in a thermostat and then connected to flowing isopropanol, and the flow rate was adjusted to 1.37 ml/s. The isopropanol was subjected to thermocatalytic degradation under dark conditions at different temperatures and the peak areas of the degraded isopropanol and the initial isopropanol were recorded. The amount of degraded isopropyl alcohol, and the amount of initial isopropyl alcohol were calculated, as shown in FIG. 3, the Cr ion-doped Cr-Mn of the present invention₃O₄Mn with higher thermo-catalytic degradation rate than pure Mn in composite thermo-catalytic material₃O₄The effect is good. Comparative pure Mn at 120 deg.C₃O₄，Cr-Mn₃O₄The degradation rate of the composite material is improved by 60 percent.

(II) influence of different time on catalytic degradation rate of isopropanol

The test process is as follows: Cr-Mn prepared with a 10% Cr doping amount of 0.1g prepared in example 1₃O₄The thermocatalytic material was loaded into a quartz flow reactor, which was then placed in a thermostat and then connected to flowing isopropanol, and the flow rate was adjusted to 1.37 ml/s. The isopropanol was subjected to thermocatalytic degradation under dark conditions at 200 ℃ and the peak areas of degraded isopropanol and initial isopropanol at different reaction times were recorded. The amount of degraded isopropanol and the amount of initial isopropanol were calculated. As shown in FIG. 4, the degradation rate of isopropyl alcohol at 200 ℃ varied with the reaction time within the allowable range of error, and it can be seen that Cr-Mn produced by the present invention₃O₄The composite thermocatalytic material is very stable. The degradation rate reaches about 97.4 percent at 200 ℃.

Claims

Doping of Cr ions with Mn₃O₄The application of the thermal catalytic material in the catalytic degradation of isopropanol under the dark heating condition is characterized in that Cr ions are doped with Mn₃O₄Preparation of thermocatalytic materialsThe preparation method comprises the following steps:

1) preparing an aqueous solution of manganese salt; preparing an alkali solution;

2) adding chromium salt or chromium alkali into the aqueous solution of manganese salt, and performing ultrasonic treatment to uniformly mix the chromium salt or the chromium alkali with the aqueous solution of manganese salt;

3) adding the mixed solution obtained in the step 2) into an alkali solution, performing ultrasonic treatment to uniformly mix the mixed solution, centrifuging the mixed solution to obtain a precipitate, and drying and cooling the precipitate to obtain a precursor;

4) grinding the precursor obtained in the step 3), and then carrying out high-temperature calcination treatment to obtain a target product.
2. The Cr ion doped Mn of claim 1₃O₄The application of the thermal catalytic material in catalytic degradation of isopropanol under dark heating conditions is characterized in that in the step 1), the manganese salt is manganese acetate, manganese nitrate or manganese chloride.
3. Cr ion doped Mn as claimed in claim 1₃O₄The application of the thermal catalytic material in catalytic degradation of isopropanol under dark heating conditions is characterized in that in the step 1), the alkali solution is a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution or an ammonium hydroxide aqueous solution.
4. The Cr ion doped Mn of claim 1₃O₄The application of the thermal catalysis material in catalytic degradation of isopropanol under dark heating conditions is characterized in that in the step 2), the chromium salt is chromium nitrate, and the chromium base is chromium hydroxide.
5. The Cr ion doped Mn of claim 1₃O₄The application of the thermal catalytic material in catalytic degradation of isopropanol under dark heating condition is characterized in that in the step 2), Mn is added according to molar ratio^2＋：Cr^3＋=1：0.01 -0.2。
6. The Cr ion doped Mn of claim 1₃O₄Heating strip for thermal catalytic material in darkThe application of the catalytic degradation of isopropanol under the condition is characterized in that in the step 3), the molar ratio of Mn is used^2＋: OH in alkali^-=1：2-4。
7. The Cr ion doped Mn of claim 1₃O₄The application of the thermal catalysis material in catalyzing and degrading the isopropanol under the dark heating condition is characterized in that in the step 3), the drying temperature is 50-100 ℃.
8. The Cr ion doped Mn of claim 1₃O₄The application of the thermal catalytic material in catalytic degradation of isopropanol under dark heating conditions is characterized in that in the step 4), the high-temperature calcination treatment is carried out at the temperature of 300-600 ℃ for 2-3 h.