CN112044175A - A kind of composite catalytic filter material for degrading dioxin at low temperature and preparation method thereof - Google Patents

Abstract

The invention discloses a composite catalytic filter material for degrading dioxin at low temperature and a preparation method thereof, belonging to the technical field of waste incineration tail gas treatment_x‑MnCeO_xA composite catalytic filter material of a three-way catalyst. The invention has the advantages that: (1) has excellent low-temperature activity on the catalytic degradation of dioxinAnd selectivity; (2) an active component V with high activity and excellent chlorine poisoning resistance is added into the filter material, and the active component V is effectively oxidized by low-temperature plasma, so that the catalytic activity and the chlorine poisoning resistance are improved; (3) the catalyst is uniformly and firmly loaded on the surface of the filter material by an in-situ precipitation method, the preparation conditions are mild, the original performance and stability of the filter material are maintained, and the service life is long.

Description

A kind of composite catalytic filter material for degrading dioxin at low temperature and preparation method thereof

technical field

The invention belongs to the technical field of waste incineration tail gas treatment, and in particular relates to a composite catalytic filter material for degrading dioxin at low temperature and a preparation method thereof.

Background technique

In recent years, my country's domestic waste incineration industry has achieved great development, and the ratio of waste incineration disposal will continue to rise. The scale of waste incineration power plants under construction and planned continues to expand. The “avoidance effect” cannot be ignored, especially the trace dioxin pollutants emitted from incineration flue gas pose a serious threat to the environment and human health, which has attracted great attention from the country. In 2014, China stipulated that the dioxin emission standard was lowered to 0.1ngTEQ/ ^Nm3 (GB18485-2014).

At present, waste incineration plants mainly use the combination of activated carbon injection and bag dust removal to implement terminal control of dioxin emissions, and a small number of incineration plants will also use SCR systems to assist in the control of dioxin emissions. However, the activated carbon adsorption technology only realizes the transfer of dioxins from the gas phase flue gas to the solid phase fly ash, which increases the processing burden of the fly ash. Catalytic degradation technology can completely mineralize organic pollutants such as dioxins into inorganic small molecules such as CO ₂ , H ₂ O and HCl, without secondary pollution, and is considered to be a more potential dioxin terminal control technology. Due to the high content of acid gas components and strong bonding properties in the waste incineration flue gas, the catalytic reaction system tends to be arranged after the bag dust removal, such as the SCR system. However, the smoke temperature after bag dust removal is only about 150-170 °C, and research shows that the active temperature of vanadium-based catalysts with better activity for degrading dioxin is above 200 °C. If the reheater is added before the catalytic reaction system, it will greatly increase the equipment cost and operating cost. Therefore, developing a catalyst that can efficiently degrade dioxin under low temperature conditions and applying it to the filter material in the bag filter can greatly reduce costs while achieving environmental protection indicators.

Polyphenylene sulfide filter material, polytetrafluoroethylene filter material and polyimide filter material have the properties of high temperature resistance, acid and alkali resistance, hydrolysis resistance and high flame retardancy, and are the preferred filter bag materials for waste incineration plants. . Due to these properties, it is difficult for the filter media to effectively bind the catalyst particles, and the filter bags are often impacted by the airflow during the actual operation of the flue gas treatment system. Among the commonly used composite catalytic filter media preparation methods, the ultrasonic impregnation method only attaches the catalyst to the surface of the filter media through physical adsorption, the bonding strength is low, and the catalyst is easy to fall off; the membrane cracking method, coating method and other methods ensure the catalyst and filter media. High-strength binding, but there is a problem that the active sites of the catalyst are covered, resulting in a greatly reduced catalyst utilization efficiency.

Chinese patent CN103212245A discloses a dedusting filter material containing _MnO2 catalyst and its preparation method and application. The method is to make acidic potassium permanganate and pyrrole monomer undergo a redox reaction on the surface of the filter material, and potassium permanganate is reduced The _MnO2 -forming catalyst is dispersed in the polypyrrole molecule. The catalytic filter material is prepared by the in-situ oxidation method, which improves the bonding strength of the catalyst and the filter material, and has the function of removing PM2.5 and _NOx at the same time. The disadvantage is that the supported low-temperature Mn-based catalyst is prone to chlorine poisoning and deactivation, and the incineration flue gas contains a certain concentration of HCl acid gas and chlorinated organic pollutants. Therefore, a catalytic filter with excellent anti-chlorine poisoning performance is researched and developed. material is necessary.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a composite catalytic filter material for degrading dioxin at low temperature and a preparation method thereof. By loading the catalyst on the dust removal filter material to form an integrated filter material with catalysis and dust removal functions, the efficient control of dioxin emissions and the the purpose of reducing costs. The present invention obtains a composite catalytic filter material with excellent anti-poisoning ability by effectively oxidizing V active components by low-temperature plasma.

To achieve the above object, the present invention provides the following technical solutions:

Using high temperature resistant filter material as catalyst carrier, through the steps of filter material activation, in-situ precipitation, impregnation of V active components and low temperature plasma oxidation, a composite catalytic filter material loaded with VOx- _MnCeOx ternary catalyst _is prepared.

Preferably, the high temperature resistant filter material is one of polyphenylene sulfide needle felt filter material, polytetrafluoroethylene needle felt filter material and polyimide needle felt filter material.

Preferably, the high temperature resistant filter material is prepared by opening, compounding, carding, laying, needle punching, heat setting and singeing calendering of the short fibers of the filter material.

Preferably, the specific steps are as follows:

(1) Filter material activation: The high temperature resistant filter material is completely immersed in 0.001-0.004mol/L sodium dodecyl sulfate solution, and ultrasonically activated for 1-2h;

(2) In-situ precipitation: a). Impregnation Ce active component: add cerium chloride heptahydrate to the sodium dodecyl sulfate solution in step (1), and stir at room temperature for 12-16h;

b). KMnO ₄ oxidation: add 0.08-0.17mol/L potassium permanganate solution dropwise to the solution obtained in step a), stir in a water bath at 80°C for 4-6 hours, take out the filter material after the reaction, and use deionized water and anhydrous ethanol, and then dried at 105 °C for 12 h to obtain a catalytic filter material loaded with MnCeO _x catalyst;

(3) Impregnation V active component: prepare a mixed solution of ammonium metavanadate and oxalic acid dihydrate in a molar ratio of 1:2, immerse the catalytic filter material obtained in step b) in the mixed solution at room temperature, stand for 10-12 hours, and then Place in an oven at 105°C for 12h;

(4) Low-temperature plasma oxidation: the filter material obtained in step (3) is placed in a dielectric barrier discharge plasma reactor, the reaction atmosphere is introduced, the power is turned on, the effective voltage is set at 9-15kV, and the discharge frequency reaches 7-12kHz , the continuous discharge time is _30-60min , and the composite catalytic filter material loaded with the VOx- _MnCeOx three-way catalyst is prepared.

Preferably, in the step (4), the reaction atmosphere is a mixed gas of O ₂ and N ₂ , or a mixed gas of O ₂ and Ar.

Preferably, in the reaction atmosphere, the volume fraction of O ₂ is 10%-30%.

A composite catalytic filter material prepared by a method for preparing a composite catalytic filter material for degrading dioxin at low temperature, wherein in the composite catalytic filter material, the molar ratio of VOx- _MnCeOx three-way catalyst components _is Mn:Ce:V =1:0.1～0.5:0.06～0.2.

Preferably, the VO _x -MnCeO _x three-way catalyst loading of the composite catalytic filter material is 80-160 g/m ² .

Compared with the prior art, the beneficial effects of the present invention are:

(1) It has excellent low-temperature activity and selectivity for the catalytic degradation of dioxins.

(2) The active component V with high activity and excellent anti-chlorine poisoning ability is added to the filter material, and the active component V is effectively oxidized by low-temperature plasma to improve the catalytic activity and anti-chlorine poisoning ability.

(3) The catalyst is uniformly and firmly loaded on the surface of the filter material by the in-situ precipitation method, the preparation conditions are mild, the original performance and stability of the filter material are maintained, and the service life is long.

Description of drawings

Fig. 1 is the flow chart of the preparation method of the present invention.

FIG. 2 is an SEM image of the composite catalytic filter material prepared in Example 2. FIG.

3 is an XPS diagram of the composite catalytic filter material prepared in Example 2.

FIG. 4 is a diagram of a catalytic degradation experimental device in the present invention.

In the figure: 1- Dioxin generation source system, 2- Catalytic degradation reaction system, 3- Exhaust gas collection system.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

In the invention, the high temperature resistant filter material is used as the catalyst carrier, and the composite catalytic filter material loaded with the VOx- _MnCeOx ternary catalyst _is prepared through the steps of filter material activation, in-situ precipitation, impregnation of V active components and low temperature plasma oxidation.

The high-temperature resistant filter material in the present invention is one of the polyphenylene sulfide needle-punched felt filter material, the polytetrafluoroethylene needle-punched felt filter material and the polyimide needle-punched felt filter material. Prepared by opening, compounding, carding, laying, needling, heat setting and singeing calendering. The high-temperature resistant filter materials in the following examples all use polyphenylene sulfide needle-punched felt filter materials.

Example 1

As shown in Figure 1, the preparation method of the present invention is as follows:

(1) Activation of filter material: First, cut a polyphenylene sulfide needle-punched felt filter material disc with a diameter of 20mm, wash it three times with deionized water, dry it in an oven at 105 ° C for 6 hours, and weigh; weigh 0.0577g Sodium dodecyl sulfate powder was prepared into 200mL 0.001mol/L sodium dodecyl sulfate solution with deionized water as solvent, and the dried polyphenylene sulfide disc was immersed in the solution and activated by ultrasonic for 1h.

(2) In-situ precipitation: a). Impregnation of Ce active component: Weigh 0.3251 g of cerium chloride heptahydrate into the solution obtained in step (1), and stir at room temperature for 12 hours.

b). KMnO ₄ oxidation: Weigh 1.3790g potassium permanganate powder, dissolve it in 100mL deionized water, prepare a 0.08mol/L potassium permanganate solution, add 100mL 0.08mol/L potassium permanganate solution one by one It was added dropwise to the solution obtained in step a), stirred in a water bath for 4 hours, and the filter material was taken out, washed three times with deionized water and absolute ethanol, and dried in an oven at 105 ° C for 12 hours to obtain a catalyst loaded with MnCeO _x catalyst. filter media.

(3) Impregnation V active component: Weigh 0.0612g of ammonium metavanadate and 0.1320g of oxalic acid dihydrate, dissolve in 10mL of deionized water, put into the catalytic filtration filter material obtained in step b), stand for immersion for 10h, 105°C Dry for 12h.

(4) Low-temperature plasma oxidation: the filter material obtained in step (3) is placed in a dielectric barrier discharge plasma reactor, and a mixture of O ₂ and N ₂ with an oxygen volume fraction of 10%, or an oxygen volume fraction of A mixture of 10% _O2 and Ar, turn on the plasma power supply, set the effective voltage to 9kV, the discharge frequency to 7KHz, and the continuous discharge time to 30min. A composite catalytic filter material loaded with a VOx- _MnCeOx ternary catalyst _is prepared, wherein the molar ratio of the VOx- _MnCeOx ternary catalyst components _is Mn:Ce:V=1:0.1:0.06. The VO _x -MnCeO _x ternary catalyst loading amount of the composite catalytic filter material was calculated by weighing to be 80 g/m ² .

Example 2

(1) Activation of filter material: First, cut a polyphenylene sulfide needle-punched felt filter material disc with a diameter of 20mm, wash it three times with deionized water, dry it in an oven at 105 ° C for 6 hours, and weigh; weigh 0.2307g Sodium dodecyl sulfate powder was prepared into 200mL 0.004mol/L sodium dodecyl sulfate solution with deionized water as solvent, and the dried polyphenylene sulfide disc was immersed in the solution and activated by ultrasonic for 2h.

(2) In-situ precipitation: a): Impregnation Ce active component: weigh 0.6502 g of cerium chloride heptahydrate, add it to the solution obtained in step (1), and stir at room temperature for 16 hours.

b): KMnO4 oxidation: Weigh _2.7580g potassium permanganate powder, dissolve it in 100mL deionized water, prepare a 0.17mol/L potassium permanganate solution, drop 100mL 0.17mol/L potassium permanganate solution The solution was added to the solution obtained in step a), and the reaction was stirred in a water bath for 6 hours. The filter material was taken out, washed three times with deionized water and anhydrous ethanol, and dried in an oven at 105 ° C for 12 hours to obtain a catalyst loaded with MnCeO _x catalyst. filter media.

(3) Impregnation V active component: Weigh 0.1225g of ammonium metavanadate and 0.2640g of oxalic acid dihydrate, dissolve in 10mL of deionized water, put into the catalytic filtration filter material obtained in step b), stand for immersion for 12h, 105°C Dry for 12h.

(4) Low-temperature plasma oxidation: the filter material obtained in step (3) is placed in a dielectric barrier discharge plasma reactor, and a mixture of O ₂ and N ₂ with an oxygen volume fraction of 30% or an oxygen volume fraction is introduced For a mixture of 30% O ₂ and Ar, turn on the plasma power supply, set the effective voltage at 15kV, the discharge frequency to 12kHz, and the continuous discharge time to be 60min. A composite catalytic filter material loaded with a VOx- _MnCeOx ternary catalyst _is prepared, wherein the molar ratio of the VOx- _MnCeOx ternary catalyst components _is Mn:Ce:V=1:0.5:0.2. The VO _x -MnCeO _x ternary catalyst loading amount of the composite catalytic filter material was calculated by weighing to be 160 g/m ² .

Figure 2 shows the SEM image of the composite catalytic filter material prepared in Example 2. It can be seen from the figure that the filter material is loaded with white particles; Catalyst powder, XPS test, energy spectrum analysis of V 2p ^3/2 . As shown in Figure 3, V usually exists in two valence states on the catalyst surface: V ⁵⁺ and V ⁴⁺ , of which V ⁵⁺ has the highest content, accounting for 68%, indicating that the oxidation of part of low-valent vanadium into low-valent vanadium by low-temperature plasma treatment high-value vanadium.

The catalytic degradation performance of composite catalytic filter media was evaluated in a self-made catalytic degradation experimental device. As shown in Figure 4, the catalytic degradation experimental device mainly includes a dioxin generation source system 1, a catalytic degradation reaction system 2 and an exhaust gas collection system 3. The dioxin generation source system consists of a micro syringe pump CMA400 (CMA Microdialysis AB, USA), a micro syringe (0.5 mL), a nebulizer (Meinhard USA), an air preheating section and a mass flow meter. During the experiment, the dioxin solution (also known as dioxin stock solution) in the micro-syringe was injected into the nebulizer at a constant speed (1 μL/min) via the micro-injection pump, and the carrier gas (N ₂ :O ₂ ≈9:1) The stock solution is fully atomized by the atomizer, and the carrier gas flow rate is 1L/min, and then enters the preheating section to fully volatilize and remove the solvent, and finally a stable dioxin gas flow is continuously generated at the outlet of the preheating section. The preheating section of the quartz tube of the dioxin generating source device has a certain adsorption effect on dioxins. Therefore, before the catalytic degradation experiment starts, the generating source device must be transported by air for a period of time (4 to 12 hours), so that the quartz tube wall reaches the level of dioxins. Dynamic equilibrium of British adsorption. The dioxins in the exhaust gas were collected by XAD-2 resin and toluene washing bottle, and then the two were mixed and pretreated by the US EPA 1613 method, and 13C was added during the pretreatment process for internal standard. The dioxin samples adsorbed on the catalytic filter media were individually pretreated using the US EPA 1613 method in order to calculate the degradation efficiency. After a series of pretreatment processes such as sooting, acid washing, column passing, and nitrogen blowing, the samples were concentrated into sample vials, and finally detected by JMS-800D high-resolution chromatography and high-resolution mass spectrometry (HRGC/HRMS) from JEOL, Japan. Dioxin content in the sample.

The composite catalytic filter material prepared in Example 2 was tested in a self-made catalytic degradation experimental device. The reaction temperature was set to 140°C, 160°C, 180°C, and 200°C, respectively, the gas flow rate was 500 mL/min, the volume fraction of O ₂ was 11%, N ₂ was used as the equilibrium gas, and the concentration of dioxin was 5.5 ng/Nm ³ . The test results are shown in Table 1.

Performance index: Removal efficiency:

Degradation efficiency:

where C _in is the concentration of dioxin at the inlet, C _out is the concentration of dioxin at the outlet, and C _catalyst is the dioxin adsorbed on the catalytic filter material per unit time.

Table 1: The catalytic performance of the composite catalytic filter material prepared in Example 2 on dioxins.

temperature(℃) Removal efficiency (%) Degradation efficiency (%) 140 90.50 26.50 160 94.77 59.47 180 94.04 67.47 200 94.70 78.01

It can be seen from the test results that the composite catalytic filter material supporting the VOx- _{MnCeOx ternary} catalyst prepared in Example 2 has a dioxin removal efficiency of more than 90% at 140-200 °C, and has excellent dioxin removal efficiency. British low temperature catalytic activity.

It will be apparent to those skilled in the art that the present invention is not limited to the details of the above-described exemplary embodiments, but that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments are to be regarded in all respects as illustrative and not restrictive, and the scope of the invention is to be defined by the appended claims rather than the foregoing description, which are therefore intended to fall within the scope of the claims. All changes within the meaning and range of the equivalents of , are included in the present invention. Any reference signs in the claims shall not be construed as limiting the involved claim.

Claims (8)

1. a kind of preparation method of the composite catalytic filter material of low temperature degradation dioxin, it is characterized in that: take high temperature resistant filter material as catalyst carrier, through filter material activation, in-situ precipitation, impregnation V active component and low temperature plasma oxidation step to prepare a composite catalytic filter material supporting a _VOx - _MnCeOx three-way catalyst. 2. the preparation method of the composite catalytic filter material of a kind of low temperature degradation dioxin according to claim 1, is characterized in that: described high temperature resistant filter material is polyphenylene sulfide needle felt filter material, polytetrafluoroethylene One of the needle felt filter material and the polyimide needle felt filter material. 3. the preparation method of the composite catalytic filter material of a kind of low temperature degradation dioxin according to claim 1, it is characterized in that: described high temperature resistant filter material is by filter material short fiber through opening, compound mixing, carding , Laying, needle punching, heat setting and singeing calendering. 4. the preparation method of the composite catalytic filter material of a kind of low temperature degradation dioxin according to claim 1, is characterized in that, concrete steps are as follows: (1) Filter material activation: The high temperature resistant filter material is completely immersed in 0.001-0.004mol/L sodium dodecyl sulfate solution, and ultrasonically activated for 1-2h; (2) In-situ precipitation: a). Impregnation Ce active component: add cerium chloride heptahydrate to the sodium dodecyl sulfate solution in step (1), and stir at room temperature for 12-16h; b). KMnO ₄ oxidation: add 0.08-0.17mol/L potassium permanganate solution dropwise to the solution obtained in step a), stir in a water bath at 80°C for 4-6 hours, take out the filter material after the reaction, and use deionized water and anhydrous ethanol, and then dried at 105 °C for 12 h to obtain a catalytic filter material loaded with MnCeO _x catalyst; (3) Impregnation V active component: prepare a mixed solution of ammonium metavanadate and oxalic acid dihydrate according to a molar ratio of 1:2, immerse the catalytic filtration filter material obtained in step b) in the mixed solution at room temperature, and let stand for 10-12h, Then dry at 105°C for 12h; (4) Low-temperature plasma oxidation: the filter material obtained in step (3) is placed in a dielectric barrier discharge plasma reactor, the reaction atmosphere is introduced, the power is turned on, the effective voltage is set at 9-15kV, and the discharge frequency reaches 7-12kHz , the continuous discharge time is _30-60min , and the composite catalytic filter material loaded with the VOx- _MnCeOx three-way catalyst is prepared. 5. the preparation method of the composite catalytic filter material of a kind of low-temperature degradation dioxin according to claim 4, is characterized in that: in described step (4), reaction atmosphere is O ₂ and N ₂ mixed gas or or A mixture of O ₂ and Ar. 6 . The method for preparing a composite catalytic filter material for degrading dioxins at low temperature according to claim 5 , wherein in the reaction atmosphere, the volume fraction of O ₂ is 10%-30%. 7 . 7. a composite catalytic filter material made based on the preparation method of the composite catalytic filter material of a kind of low-temperature degradation dioxin described in any one of claims 1-6, it is characterized in that: in the described composite catalytic filter material, The molar ratio of the VO _x -MnCeO _x three-way catalyst components is Mn:Ce:V=1:0.1-0.5:0.06-0.2. 8. the composite catalytic filter material of a kind of low-temperature degradation dioxin according to claim 7, is characterized in that: the VO _x -MnCeO _x ternary catalyst load of described composite catalytic filter material is ^80-160g /m .

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