CN108940304A - A kind of Mn/Ce/Cu base low-temperature plasma body catalyst and preparation and application - Google Patents

Abstract

The invention belongs to catalysis material technical field, a kind of Mn/Ce/Cu base low-temperature plasma body catalyst and preparation and application are disclosed.Manganese Metal salt, salt containing ce metal and copper-containing metal salt will be contained to be dissolved in DMF, addition organic ligand ultrasonic mixing is uniform, and gained mixed solution is reacted at a temperature of 80~120 DEG C, and solid product is soaked in DMF and is activated, and obtains activation crystal；Gained activation crystal is washed, dry, it is then roasted in 300~400 DEG C, obtains Mn/Ce/Cu base low-temperature plasma body catalyst.MOFs material at high temperature calcining is directly prepared the carbon-based catalysis material of nanoporous by the present invention, has many advantages, such as metal active constituent high degree of dispersion, stable structure, and it is possible to prevente effectively from metal active constituent reunion, catalytic activity and stability significantly improve.

Description

A Mn/Ce/Cu-based low-temperature plasma catalyst and its preparation and application

technical field

The invention belongs to the technical field of catalytic materials, and in particular relates to a Mn/Ce/Cu-based low-temperature plasma catalyst and its preparation and application.

Background technique

Volatile organic compounds (volatile organic compounds, VOCs) are various, including alkanes, olefins, halogenated hydrocarbons, esters, aldehydes, ketones and aromatic compounds, mainly from pharmaceutical, petrochemical, printing and other industries. Most VOCs are toxic and will react under light to form photochemical smog, which is one of the precursors of ozone pollution and PM2.5. Long-term stay in an environment containing volatile organic compounds will increase the possibility of diseases such as cancer. Therefore, it has extremely important application value to carry out industrial volatile organic compound pollution control.

In order to effectively control VOCs pollution in organic waste gas, the technologies widely used at home and abroad include catalytic combustion method, adsorption method, absorption method, etc. In recent years, the treatment technologies studied include biofilm method, photocatalytic oxidation method, plasma method, etc. Among many VOCs treatment technologies, low-temperature plasma can quickly degrade VOCs at room temperature and pressure, and has attracted much attention. However, pure low-temperature plasma technology has high energy consumption and low selectivity, and some VOCs will be produced into toxic by-products during the degradation process. In order to overcome these shortcomings, the low-temperature plasma is coupled with catalytic oxidation technology, that is, the catalyst is loaded in the discharge area of the plasma. Under the synergistic effect of the plasma and the catalyst, the catalytic oxidation efficiency and selectivity of VOCs organic pollutants are greatly improved. improve. Catalysts are the core of low-temperature plasma catalytic oxidation technology. The reported catalysts include transition metal catalysts and noble metal catalysts. For example, HTQuoc An et al [An HTQ, Huu TP, Van TL, et al. Application of atmospheric non thermal plasma-catalysis hybrid system for air pollution control: Toluene removal[J].Catalysis Today,2011,176(1):474-477 .] prepared a series of catalysts containing elements such as Ag, Au, Cu, Co, Mn, La and Nb, wherein 1% (mass fraction) Au/Al ₂ O ₃ and Nb ₂ O ₅ catalysts, the conversion rate of its toluene Reached 96%. Huang Haibao et al [Long Liping, Zhao Jianguo, Yang Lixian et al. MnO ₂ /Al ₂ O ₃ Catalyzed Ozone Oxidation of Toluene at Room Temperature[J]. Acta Catalytica Sinica, 2011,32(6):904-916.] TiO ₂ /γ-/Al ₂ O ₃ /foamed nickel combined with plasma to treat VOCs can improve the CO ₂ selectivity of the product, but the catalyst is easily deactivated by the accumulation of by-products. Wu Junliang et al[Wu Junliang, Xia Qibin, Liu Zhimeng, et al.Comparison of the activity of Mn, Fe and Cu oxides in low temperature plasma catalytic oxidation of toluene[J]. Functional Materials, 2012,43(10):1332-1335. ] Combining metal-organic framework material MIL-101 with plasma to treat toluene, the conversion rate of toluene reaches 100%, and the _CO2 selectivity reaches 70%, which can significantly reduce the reaction by-products. Due to the relatively poor stability (including thermal stability, chemical stability, etc.) of the MOFs framework itself, its industrial application is greatly limited.

Contents of the invention

In view of the above shortcomings and deficiencies in the prior art, the primary purpose of the present invention is to provide a method for preparing a Mn/Ce/Cu-based low-temperature plasma catalyst.

Another object of the present invention is to provide a Mn/Ce/Cu-based low-temperature plasma catalyst prepared by the above method.

Another object of the present invention is to provide the application of the above-mentioned Mn/Ce/Cu-based low-temperature plasma catalyst in low-temperature plasma catalytic oxidation degradation of VOCs.

Another object of the present invention is to provide the above-mentioned application.

The object of the invention is achieved through the following technical solutions:

A kind of preparation method of Mn/Ce/Cu base low-temperature plasma catalyst, comprises following preparation steps:

(1) dissolving manganese-containing metal salts, cerium-containing metal salts and copper-containing metal salts in DMF, adding organic ligands and ultrasonically mixing to obtain a mixed solution;

(2) reacting the mixed solution obtained in step (1) at a temperature of 80-120° C., immersing the solid product in DMF for activation to obtain activated crystals;

(3) The activated crystal obtained in the step (2) is washed, dried, and then calcined at 300-400° C. to obtain a Mn/Ce/Cu-based low-temperature plasma catalyst.

Further, the manganese-containing metal salt in step (1) is selected from at least one of manganese nitrate, manganese sulfate, manganese carbonate, and manganese acetate; the cerium-containing metal salt is selected from cerium nitrate, cerium sulfate, cerium carbonate, At least one of cerium acetate; the copper-containing metal salt is selected from at least one of copper nitrate and copper sulfate.

Further, the amount of the manganese-containing metal salt, cerium-containing metal salt and copper-containing metal salt in step (1) is 1:2:(1-2) according to the molar ratio of manganese element, cerium element and copper element. More preferably 1:2:1, 1:2:1.5 or 1:2:2.

Further, the organic ligand in step (1) is selected from formic acid or acetic acid, more preferably formic acid.

Further, the molar ratio of the amount of the organic ligand in step (1) to the manganese element in the manganese-containing metal salt is 1: (5.8-9); more preferably 1:5.8, 1:7.2 or 1:9 .

Further, the reaction time in step (2) is 10-15 hours.

Further, the time for activating by immersing in DMF in step (2) is 12-24 hours.

Further, the calcination in step (3) is carried out under an air atmosphere, and the calcination time is 2-3 hours.

A Mn/Ce/Cu-based low-temperature plasma catalyst is prepared by the above method.

Application of the above-mentioned Mn/Ce/Cu-based low-temperature plasma catalyst in low-temperature plasma catalytic oxidation degradation of VOCs.

The principle of the invention is: directly calcining the MOFs material at a high temperature under a certain air atmosphere, carbonizing the organic ligands, and obtaining the nanoporous carbon-based catalytic material. The carbonized MOFs-based catalytic material prepared by this method has the advantages of highly dispersed metal active components and stable structure, and can effectively avoid the agglomeration of metal active components, and its catalytic activity and stability are significantly improved. /Ce/Cu-based MOF catalytic material, applied to a low-temperature plasma catalytic oxidation VOCs system, can achieve efficient removal of VOCs under normal temperature and pressure conditions.

The preparation method of the present invention and the resulting product have the following advantages and beneficial effects:

(1) Compared with traditional supported catalysts, the catalyst of the present invention has the characteristics of highly dispersed metal active components, high porosity and stable structure, which can effectively avoid the agglomeration of metal active components and make it highly catalytic to VOCs such as toluene Oxidation activity;

(2) The raw materials used in the preparation method of the present invention are cheap and easy to obtain, and the preparation method is simple, which is conducive to large-scale industrial application;

(3) Compared with the existing catalytic technology, the combination of the catalyst of the present invention and the plasma device can rapidly catalyze the oxidation of toluene at normal temperature and pressure, the conversion rate of toluene can reach 100%, and the _CO selectivity is as high as 88%.

Description of drawings

FIG. 1 is an XRD pattern of Mn/Ce/Cu-based low-temperature plasma catalysts obtained in Examples 1-3 of the present invention.

Fig. 2 is a diagram of toluene conversion rates of Mn/Ce/Cu-based low-temperature plasma catalysts obtained in Examples 1-3 of the present invention under different plasma energy densities.

Fig. 3 is a CO ₂ selectivity diagram of Mn/Ce/Cu-based low-temperature plasma catalysts obtained in Examples 1-3 of the present invention under different plasma energy densities.

Detailed ways

The present invention will be further described in detail below in conjunction with the embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

Example 1

(1) Add 520 μL of 50% Mn(NO ₃ ) ₂ aqueous solution, 1.94 g of Ce(NO ₃ ) ₃ 6H ₂ O and 0.54 g of Cu(NO ₃ ) ₂ 3H ₂ O into 80 mL of DMF, and add 1000 μL Formic acid, ultrasonically mixed for 10 minutes to obtain a mixed solution;

(2) Place the mixed solution in an oven at 80°C for 10 hours. After the solution is cooled, remove the supernatant, add fresh DMF, soak and activate at room temperature for 12 hours, and obtain an activated crystal material (Mn/Ce/Cu-MOF);

(3) The activated crystal material is washed with DMF, filtered, and the filtered material is dried in a vacuum oven at 50°C; the dried crystal material is put into a muffle furnace and roasted at 300°C for 2h to obtain Mn/ Ce/Cu based low temperature plasma catalyst.

Example 2

(1) Add 520 μL of 50% Mn(NO ₃ ) ₂ aqueous solution, 1.94 g of Ce(NO ₃ ) ₃ ·6H ₂ O and 0.81 g of Cu(NO ₃ ) ₂ ·3H ₂ O into 80 mL of DMF, and add 1200 μL Formic acid, ultrasonically mixed for 10 minutes to obtain a mixed solution;

(2) Place the mixed solution in an oven at 100°C for 12 hours. After the solution is cooled, remove the supernatant, add fresh DMF, soak and activate at room temperature for 18 hours, and obtain an activated crystal material (Mn/Ce/Cu-MOF);

(3) The activated crystal material is washed with DMF, filtered, and the filtered material is dried in a vacuum oven at 50°C; the dried crystal material is baked in a muffle furnace at 350°C for 2.5h to obtain Mn /Ce/Cu based low temperature plasma catalyst.

Example 3

(1) Add 520 μL of 50% Mn(NO ₃ ) ₂ aqueous solution, 1.94 g of Ce(NO ₃ ) ₃ ·6H ₂ O and 1.08 g of Cu(NO ₃ ) ₂ ·3H ₂ O into 80 mL of DMF, and add 1500 μL Formic acid, ultrasonically mixed for 10 minutes to obtain a mixed solution;

(2) Place the mixed solution in an oven at 120°C for 15 hours. After the solution is cooled, remove the supernatant, add fresh DMF, soak and activate at room temperature for 24 hours, and obtain an activated crystal material (Mn/Ce/Cu-MOF);

(3) The activated crystal material is washed with DMF, filtered, and the filtered material is dried in a vacuum oven at 50° C.; the dried crystal material is put into a muffle furnace and roasted at 400° C. for 3 hours to obtain Mn/ Ce/Cu based low temperature plasma catalyst.

The characterization and performance measurement of above embodiment gained catalyst sample:

(1) X-ray diffraction analysis

A D8-ADVANCE X-ray diffractometer from German Bruker Company was adopted, and the operating conditions were copper target, 40KV, 40mA, step size 0.02 degrees, and scanning speed 17.7 seconds/step. The Mn/Ce/Cu-based low-temperature plasma catalysts prepared in Examples 1-3 were respectively characterized.

Fig. 1 is the XRD spectrum of the Mn/Ce/Cu-based low-temperature plasma catalyst prepared in Examples 1-3 of the present invention. It can be seen from Figure 1 that the three catalysts all have the same XRD spectrum, the characteristic peak positions are the same, and the peak width is wider, indicating that the target catalysts were synthesized in Examples 1-3.

(2) Catalytic oxidation performance test

The Mn/Ce/Cu-based low-temperature plasma catalysts obtained in Examples 1-3 were respectively taken, pressed on the surface, passed through a 40-60 mesh sieve, and loaded into a scanning plasma device. The activity test conditions are as follows: the reaction temperature is 35° C., the reaction pressure is normal pressure, the total gas flow rate is 100 mL/min, the toluene concentration is 30 ppm, and the carrier gas is dry air. Toluene concentration and _CO2 concentration were detected by gas chromatography.

Fig. 2 is a diagram of toluene conversion rates of the catalysts obtained in Examples 1-3 of the present invention under different plasma energy densities. The catalyst in Example 2 has the best ability to degrade toluene, and the degradation rate reaches 100% when the energy density is 294J/L.

Fig. 3 is a _CO2 selectivity diagram of the catalysts obtained in Examples 1-3 of the present invention under different plasma energy densities. It can be seen from the figure that as the energy density increases, the _CO2 selectivity increases. When the energy density is 294J/L, the catalyst in Example 2 has the best _CO2 selectivity, and its _CO2 selectivity Reached 88%.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (10)

1. a preparation method of Mn/Ce/Cu base low-temperature plasma catalyst, is characterized in that comprising following preparation steps: (1) dissolving manganese-containing metal salts, cerium-containing metal salts and copper-containing metal salts in DMF, adding organic ligands and ultrasonically mixing to obtain a mixed solution; (2) reacting the mixed solution obtained in step (1) at a temperature of 80-120° C., immersing the solid product in DMF for activation to obtain activated crystals; (3) The activated crystal obtained in the step (2) is washed, dried, and then calcined at 300-400° C. to obtain a Mn/Ce/Cu-based low-temperature plasma catalyst. 2. the preparation method of a kind of Mn/Ce/Cu base low-temperature plasma catalyst according to claim 1 is characterized in that: the manganese-containing metal salt described in step (1) is selected from manganese nitrate, manganese sulfate, manganese carbonate , at least one of manganese acetate; the cerium-containing metal salt is selected from at least one of cerium nitrate, cerium sulfate, cerium carbonate, and cerium acetate; the copper-containing metal salt is selected from at least one of copper nitrate and copper sulfate A sort of. 3. the preparation method of a kind of Mn/Ce/Cu base low-temperature plasma catalyst according to claim 1 is characterized in that: the manganese-containing metal salt, the cerium-containing metal salt and the copper-containing metal salt described in the step (1) The dosage is 1:2:(1-2) according to the molar ratio of manganese element, cerium element and copper element. 4. The preparation method of a Mn/Ce/Cu-based low-temperature plasma catalyst according to claim 1, characterized in that: the organic ligand in step (1) is selected from formic acid or acetic acid. 5. the preparation method of a kind of Mn/Ce/Cu base low-temperature plasma catalyst according to claim 1 is characterized in that: the consumption of organic ligand described in step (1) and the manganese element in the manganese metal salt The molar ratio is 1:(5.8～9). 6. The method for preparing a Mn/Ce/Cu-based low-temperature plasma catalyst according to claim 1, characterized in that: the reaction time in step (2) is 10-15 hours. 7. The method for preparing a Mn/Ce/Cu-based low-temperature plasma catalyst according to claim 1, characterized in that: in step (2), the time for immersing in DMF for activation is 12 to 24 hours. 8. the preparation method of a kind of Mn/Ce/Cu base low-temperature plasma catalyst according to claim 1 is characterized in that: the roasting described in step (3) is roasting under air atmosphere, and roasting time is 2～ 3h. 9. A Mn/Ce/Cu-based low-temperature plasma catalyst, characterized in that it is prepared by the method according to any one of claims 1-8. 10. The application of the Mn/Ce/Cu-based low-temperature plasma catalyst according to claim 9 in the low-temperature plasma catalytic oxidation degradation of VOCs.