CN116059955B - EVS-10-based manganese-loaded catalytic adsorbent for flue gas mercury removal and denitration, and preparation method and application thereof - Google Patents

Abstract

The disclosure relates to an EVS-10-based manganese-loaded catalytic adsorbent for flue gas mercury removal and denitration, and a preparation method and application thereof. The catalytic adsorbent comprises a carrier and an active component loaded on the carrier; wherein the carrier comprises an EVS-10 molecular sieve, and the active component comprises manganese oxide; the mass fraction of the carrier is 85-99 wt% and the mass fraction of the active component is 1-15 wt% based on the total weight of the catalytic adsorbent. The active components comprising manganese oxide are loaded on the EVS-10 molecular sieve, so that Hg ⁰ can be adsorbed and catalytically oxidized, NOx can be catalytically reduced, and the synergistic removal of Hg ⁰ and NOx is realized; the molecular sieve EVS-10 is not only a carrier, but also contains active component vanadium in the framework, and the active component manganese oxide has high dispersity on the carrier, so that the elemental mercury and nitrogen oxides in the coal-fired flue gas can be cooperatively removed.

Description

EVS-10-based manganese-loaded catalytic adsorbent for flue gas mercury removal and denitration, and preparation method and application thereof

Technical Field

The invention relates to the technical field of environmental protection and air pollution control, in particular to an EVS-10-based manganese-loaded catalytic adsorbent for flue gas mercury removal and denitration, and a preparation method and application thereof.

Background

With the development of industrial technology, coal-fired power plants are considered as the largest source of artificial mercury emissions worldwide. Mercury, a toxic heavy metal, can cause serious harm to human health and the ecological environment. Therefore, research on how to realize efficient removal of mercury in flue gas of coal-fired power plants has important significance for protecting ecological environment.

Hg ²⁺、Hg^p and Hg ⁰ are the three main forms of flue gas mercury. At present, relatively effective removal technology is provided for Hg ²⁺ and Hg ^p. For example, hg ²⁺ is dissolved in water and can be efficiently removed by a wet desulfurization device of a pollutant control device; hg ^p is readily available for incorporation into fly ash and removal by particulate control devices such as bag house dust collectors or electrostatic precipitators. However, hg ⁰ in the flue gas has the characteristics of being insoluble in water, volatile and quite stable at low temperature, so that the Hg is difficult to remove by the existing pollutant control equipment and can be directly discharged into the atmosphere. Therefore, how to control the discharge of Hg ⁰ becomes the key for removing mercury in the flue gas of the coal-fired power plant.

The mercury removal by the adsorbent method and the mercury removal by the catalytic oxidation method are two widely studied mercury removal methods at present. The mercury removal by the adsorbent method is to remove Hg ⁰ by physical or chemical adsorption on the surface of the adsorbent and then by a particulate matter control device; the catalyst is used for catalytic oxidation and demercuration, and Hg ⁰ is efficiently oxidized into Hg ²⁺ and then removed by a wet desulphurization device. The existing molecular sieve catalyst, such as molecular sieve EVS-10, has a certain capability of catalyzing and oxidizing elemental mercury, and the efficiency of catalyzing and oxidizing mercury is about 48%. The ability of molecular sieve catalysts to remove mercury is still low.

In addition to elemental mercury, nitrogen oxides are also a common air pollutant from fire coal, causing acid rain and the greenhouse effect. The proportion of NO in the nitrogen oxide (NO _x) accounts for more than 95%, so that the key for removing the nitrogen oxide is to remove the NO. The most effective and widely used technology for removing NO from coal-fired flue gas is NH ₃ Selective Catalytic Reduction (SCR) technology. The SCR catalyst studied at present is mainly prepared by loading metal oxides such as V₂O₅、CuO、Cr₂O₃、CeO₂、Fe₂O₃、MnOx、Co₂O₃ and the like on carriers such as Al ₂O₃、SiO₂、TiO₂、ZrO₂, carbon materials, molecular sieves and the like. The existing EVS-10 molecular sieve has certain mercury removal capability, but has poor catalytic denitration performance (only 14% of removal efficiency), and cannot achieve mercury removal and denitration effects at the same time.

Disclosure of Invention

The invention aims to provide an EVS-10-based manganese-loaded catalytic adsorbent for flue gas mercury removal and denitration, a preparation method and application thereof, and the catalytic adsorbent can realize the synergistic removal of mercury and nitrogen oxides.

In order to achieve the above object, a first aspect of the present disclosure provides an EVS-10-based manganese-loaded catalytic adsorbent for flue gas mercury removal and denitration, the catalytic adsorbent comprising a carrier and an active component supported on the carrier; wherein the carrier comprises an EVS-10 molecular sieve, and the active component comprises manganese oxide; the mass fraction of the carrier is 85-99 wt% and the mass fraction of the active component is 1-15 wt% based on the total weight of the catalytic adsorbent.

A second aspect of the present disclosure provides a method of preparing the catalytic adsorbent for mercury removal and denitration according to the first aspect of the present disclosure, comprising the steps of:

(1) Mixing an EVS-10 molecular sieve, a manganese source and water to obtain a raw material mixture;

(2) And (3) contacting the raw material mixture, the alkali solution and the hydrogen peroxide for oxidation reaction.

Optionally, in the step (1), the weight ratio of the EVS-10 molecular sieve to the manganese source to the water is (0.2-0.3): (0.0125-0.08): 1.

Optionally, the manganese source is a soluble manganese salt selected from one or more of manganese acetate, manganese chloride and manganese nitrate.

Optionally, the raw material mixture further comprises a dispersing aid; the dispersing aid is selected from one or more of polymethacrylic acid, polyacrylic acid and hydrolyzed polymaleic anhydride, and is preferably polymethacrylic acid;

The weight ratio of the dispersing auxiliary to the manganese source is (0.5-3): (2-6);

optionally, step (1) includes: mixing the manganese source, water and optionally the dispersing aid, performing ultrasonic treatment and adding the EVS-10 molecular sieve to obtain the raw material mixture.

Optionally, in step (2), the alkaline solution comprises sodium hydroxide solution; the mass ratio of the hydrogen peroxide in the hydrogen peroxide to the manganese source in the step (1) is (0.7-2.5): (0.9-1.5).

Optionally, the volume ratio of the sodium hydroxide solution to the water in the step (1) is 0.3-0.7: 1.

Optionally, the oxidizing reaction conditions in step (2) include: the reaction temperature is 40-80 ℃ and the reaction time is 0.5-2 h.

Optionally, step (2) further comprises: adding the alkali solution into the raw material mixture, performing ultrasonic treatment for 5-30 minutes, and then adding the hydrogen peroxide to perform the oxidation reaction; and

Filtering, washing and drying the oxidation reaction product, then screening, and taking the undersize product to obtain the catalytic adsorbent; wherein the drying temperature is 70-110 ℃.

A third aspect of the disclosure provides an application of the catalytic adsorbent according to the first aspect of the disclosure in the field of flue gas mercury removal and denitration; optionally, the flue gas is flue gas of a coal-fired power plant.

Through the technical scheme, the EVS-10-based manganese-loaded catalytic adsorbent for flue gas mercury removal and denitration and the preparation method and application thereof are provided, and active components comprising manganese oxide are loaded on the EVS-10 molecular sieve, so that Hg ⁰ can be adsorbed and catalytically oxidized, NOx can be catalytically reduced, and the synergistic removal of Hg ⁰ and NOx is realized; the molecular sieve EVS-10 is a carrier and is loaded with a manganese oxide active component, and the skeleton contains an active component vanadium, so that the catalytic adsorbent has excellent mercury removal efficiency and higher denitration efficiency, and can cooperatively remove elemental mercury and nitrogen oxides in coal-fired flue gas; compared with the existing method for simultaneously installing mercury removal equipment and denitration equipment, the catalytic adsorbent provided by the invention can reduce equipment installation and use cost; the catalytic adsorbent is relatively simple to synthesize, can be recycled, effectively reduces the comprehensive cost, and is suitable for industrial production.

Additional features and advantages of the present disclosure will be set forth in the detailed description which follows.

Detailed Description

The following describes specific embodiments of the present disclosure in detail. It should be understood that the detailed description and specific examples, while indicating and illustrating the disclosure, are not intended to limit the disclosure.

The first aspect of the present disclosure provides an EVS-10-based manganese-loaded catalytic adsorbent for flue gas mercury removal and denitration, the catalytic adsorbent comprising a carrier and an active component loaded on the carrier; wherein the carrier comprises an EVS-10 molecular sieve, and the active component comprises manganese oxide; the mass fraction of the carrier is 85-99 wt% and the mass fraction of the active component is 1-15 wt% based on the total weight of the catalytic adsorbent.

The active components comprising manganese oxide are loaded on the EVS-10 molecular sieve, so that Hg ⁰ can be adsorbed and catalytically oxidized, NOx can be catalytically reduced, and the synergistic removal of Hg ⁰ and NOx is realized; the molecular sieve EVS-10 is a carrier and is loaded with a manganese oxide active component with high dispersity, and the framework contains an active component vanadium, so that the catalytic adsorbent has excellent mercury removal efficiency and higher denitration efficiency, and can cooperatively remove elemental mercury and nitrogen oxides in coal-fired flue gas, and compared with the existing flue gas treatment process requiring simultaneous installation of mercury removal equipment and denitration equipment, the catalytic adsorbent provided by the invention can reduce equipment installation and use cost; the catalytic adsorbent is relatively simple to synthesize, can be recycled, effectively reduces the comprehensive cost, and is suitable for industrial production.

In the present disclosure, EVS-10 molecular sieve refers to vanadium silicate molecular sieve, which is a kind of molecular sieve in which vanadium completely replaces titanium in titanosilicate molecular sieve ETS-10. According to the method, the EVS-10 molecular sieve is used as a carrier, the molecular sieve framework contains vanadium (V) active components, and the EVS-10 molecular sieve is loaded with active components comprising manganese oxide, so that the manganese oxide and vanadium atoms in the framework exert synergistic catalytic oxidation, and the catalytic adsorbent can achieve Hg ⁰ removal efficiency of more than 92% and nitrogen oxide removal efficiency of more than 90%.

In one embodiment, the support is an EVS-10 molecular sieve; in terms of element mole, si in the EVS-10 molecular sieve: na: k: the molar ratio of V is 3.92:1.39:0.48:1. in the present disclosure, XRF spectroscopy is used to determine the chemical composition of the EVS-10 molecular sieve.

A second aspect of the present disclosure provides a method of preparing the catalytic adsorbent for mercury removal and denitration according to the first aspect of the present disclosure, comprising the steps of:

(1) Mixing an EVS-10 molecular sieve, a manganese source and water to obtain a raw material mixture;

(2) And (3) contacting the raw material mixture, the alkali solution and the hydrogen peroxide for oxidation reaction.

In experiments, the inventor discovers a method for loading manganese oxide, which is different from the traditional dipping and roasting process, firstly, a manganese source and an EVS-10 molecular sieve are dispersed in water, then the raw material mixture is subjected to oxidation reaction under alkaline conditions and under the oxidation action of hydrogen peroxide, and the manganese source is oxidized into a high-dispersion manganese oxide active component on the surface of the molecular sieve, so that the catalyst adsorbent for mercury removal and denitration is obtained. The synthesis method provided by the disclosure is stable and reliable, the comprehensive use cost of the catalytic adsorbent is low, and the method has good industrial application prospect. The EVS-10 molecular sieves employed in the present disclosure may be prepared according to existing methods, for example, as disclosed in literature Zijian Zhou,Tiantian Cao,et al."Vanadium silicate(EVS)-supported silver nanoparticles:A novel catalytic sorbent for elemental mercury removal from flue gas".Journal of Hazardous Materials,375(2019)1-8.

In a specific embodiment, the EVS-10 molecular sieve adopted in the present disclosure can be prepared by a hydrothermal method, and specifically comprises: dissolving sodium silicate in deionized water; then NaOH, KCl, naF and NaCl were added to the solution to give solution A. Then VOSO ₄ was dissolved in deionized water to give solution B. Solution a and solution B were mixed and stirred and aged at room temperature. The aged mixture was transferred to an autoclave for continued aging. And washing the synthesized product with deionized water and drying to obtain the EVS-10 molecular sieve. The amount of each reactant and the reaction conditions in the preparation process can be adjusted according to actual requirements.

In a preferred embodiment, in the step (1), the weight ratio of the EVS-10 molecular sieve, the manganese source and the water is (0.2 to 0.3): (0.0125-0.08): 1.

In one embodiment, in step (1), the manganese source is a soluble manganese salt selected from one or more of manganese acetate, manganese chloride and manganese nitrate.

The inventors of the present disclosure have surprisingly found in the study that, in the process of preparing the catalytic adsorbent, a manganese source and a dispersing aid are simultaneously introduced, and Mn ions and the dispersing aid form a complex (chelate), so that an alkaline solution (such as sodium hydroxide) is added later, and the complex of Mn ions which is uniformly dispersed is obtained and can exist in the system stably, thereby further avoiding the agglomeration phenomenon; after the oxidant (such as hydrogen peroxide) is added, manganese ions in the system are oxidized into a monodisperse or small-particle-size (nano-size) manganese oxide active component on the surface of the EVS-10 molecular sieve, and the dispersity of the manganese oxide active component on the molecular sieve is improved.

In a preferred embodiment, the raw material mixture further comprises a dispersing aid; the dispersing aid is selected from one or more of polymethacrylic acid, polyacrylic acid and hydrolyzed polymaleic anhydride, preferably polymethacrylic acid. The dispersity of the active component can be further improved by adopting the polymethacrylic acid as a dispersing auxiliary. The molecular weight of the dispersing aid in the present disclosure may vary over a wide range, and may be selected according to actual requirements.

In a further preferred embodiment, the weight ratio of the dispersing aid to the manganese source is (0.5 to 3): (2-6).

In a specific embodiment, step (1) further comprises: mixing the manganese source, water and optionally the dispersing aid, performing ultrasonic treatment and adding the EVS-10 molecular sieve to obtain the raw material mixture.

In one embodiment, in step (2), the alkaline solution is sodium hydroxide solution; preferably, the volume ratio of the sodium hydroxide solution to the water in the step (1) is 0.3-0.7: 1, a step of;

The mass ratio of the hydrogen peroxide in the hydrogen peroxide to the manganese source in the step (1) is (0.7-2.5): (0.9-1.5).

In one embodiment, the oxidizing reaction conditions in step (2) include: the reaction temperature is 40-80 ℃ and the reaction time is 0.5-2 h.

In an alternative embodiment, step (2) further comprises: adding the alkali solution into the raw material mixture, performing ultrasonic treatment for 5-30 minutes, and then adding the hydrogen peroxide to perform the oxidation reaction; filtering, washing and drying the oxidation reaction product, and then screening, and taking undersize products to obtain the catalytic adsorbent; wherein the drying temperature is 70-110 ℃. Specifically, after drying and cooling to room temperature, sieving is carried out by adopting a 100-mesh sieve, and the undersize is taken as the final catalytic adsorbent.

A third aspect of the disclosure provides an application of the catalytic adsorbent according to the first aspect of the disclosure in the field of flue gas mercury removal and denitration; optionally, the flue gas is flue gas of a coal-fired power plant.

The invention is further illustrated below in connection with specific embodiments, but the scope of the invention as claimed is not limited to the examples described.

The chemicals used in each example were commercially available from public sources.

The EVS-10 molecular sieves used in the examples and comparative examples below were prepared according to the methods disclosed in document Zijian Zhou,Tiantian Cao,et al."Vanadium silicate(EVS)-supported silver nanoparticles:A novel catalytic sorbent for elemental mercury removal from flue gas".Journal of Hazardous Materials,375(2019)1-8.

In the following examples, 30 wt% hydrogen peroxide means that the mass fraction of H ₂O₂ in the solution in the aqueous solution is 30%.

Ultrasonic treatment refers to treatment with a conventional ultrasonic instrument for uniform mixing and dispersion.

Example 1

(1) 2.8G Mn (CH ₃COO)₂·4H₂ O and 6.0g PMAA are dissolved in 40mL deionized water, and 9.0g EVS-10 molecular sieve is added while ultrasonic treatment is carried out;

(2) Slowly adding 25mL of sodium hydroxide solution with the concentration of 2mol/L, carrying out ultrasonic treatment for 15 minutes, then adding 5mL of hydrogen peroxide with the concentration of 30 wt% and reacting for 1 hour at 60 ℃, filtering out a solid sample, repeatedly washing with ethanol and deionized water to wash out residual substances on the surface of a product obtained after the reaction, drying the sample at 80 ℃, screening the dried sample, sieving the dried sample with a 100-mesh sieve, taking out sieve grains, and obtaining the EVS-10 molecular sieve loaded with manganese oxide, and marking as sample 1.

Comparative example 1

A catalytic adsorbent was prepared by a procedure similar to example 1, except that in example 1: the EVS-10 molecular sieve was replaced with a commercially available ETS-10 molecular sieve. The other preparation steps were the same as in example 1, to obtain a manganese oxide-supported catalyst adsorbent, which was designated as sample D-1.

Example 2

(1) 0.72G of MnCl ₂ and 2.0g of PMAA are dissolved in 40mL of deionized water, and 9.5g of EVS-10 molecular sieve is added while ultrasonic treatment is carried out;

(2) Slowly adding 12mL of sodium hydroxide solution with the concentration of 2mol/L, carrying out ultrasonic treatment for 15 minutes, then adding 3mL of hydrogen peroxide with the concentration of 30 wt%, reacting for 1 hour at 60 ℃, filtering out a solid sample, repeatedly washing with ethanol and deionized water to wash out residual substances on the surface of a product obtained after the reaction, drying the sample at 80 ℃, and finally sieving the dried sample with a 100-mesh sieve, and taking out sieve grains. The manganese oxide-loaded EVS-10 molecular sieve was obtained and was designated as sample 2.

Example 3

A preparation similar to example 1 was used, with the difference that example 1: in the step (1), the dispersing auxiliary polymethacrylic acid was not added, and the other preparation processes and reaction parameters were the same as in example 1. The manganese oxide-loaded EVS-10 molecular sieve was obtained and was designated as sample 3.

Comparative example 2

4.3G of AgNO ₃ is weighed and dissolved in 100ml of deionized water, then 10g of EVS-10 molecular sieve is added, magnetic stirring is carried out for 6 hours in a light-proof environment, suction filtration is carried out, and the solution is repeatedly washed by the deionized water, dried at 80 ℃, and then placed in a tubular furnace for roasting for 1 hour under the nitrogen atmosphere at 250 ℃. The catalyst adsorbent carrying only silver nanoparticles was obtained and was designated as sample D-2.

The mass fractions of the carrier molecular sieve and the active component in the samples obtained in the above examples and comparative examples are shown in Table 1.

TABLE 1

Wherein the mass fraction of manganese oxide is calculated as MnO ₂.

Simulated smoke test case

The samples synthesized in the examples and the comparative examples are placed on an experimental system for simulating flue gas to perform mercury removal and denitration performance test. The simulated flue gas conditions were as follows: the concentration of 5% O ₂,12％CO₂,400ppm NO,400ppm NH₃,600ppm SO₂,30ppm HCl,Hg⁰ is 110 mug/m ³, the balance gas is N ₂, the total flow of the simulated flue gas is 500mL/min, and the test temperature is 250 ℃. Wherein the experimental system simulating the flue gas adopts an experimental system conventionally selected in the field. The results of the mercury removal and denitration test are shown in table 2 below.

TABLE 2

Sample of	Hg 0 removal efficiency (%)	NO x removal efficiency (%)
			1	94	94
D-1	75	65
			2	92	90
3	78	66
			D-2	100	21

As can be seen from table 2 above, the catalyst prepared using the EVS-10 molecular sieve in example 1 of the present disclosure has better Hg ⁰ removal efficiency and NO _x removal efficiency than the commercial ETS-10 molecular sieve in comparative example 1.

Compared with comparative example 2, the nitrogen oxide removal efficiency of the D-2 adsorbent prepared in comparative example 2 by the prior art is extremely low and is only 21 percent. The catalytic adsorbent samples prepared by the method provided by the disclosure in examples 1-3 have high elemental mercury removal efficiency and nitrogen oxide removal efficiency, and realize synergistic removal of Hg ⁰ and NO _x.

Further comparing examples 1 to 3, it is evident that the catalyst adsorbent obtained in examples 1 to 2 has higher Hg ⁰ removal efficiency and NO _x removal efficiency when the dispersing aid is added.

The preferred embodiments of the present disclosure have been described in detail above, but the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solutions of the present disclosure within the scope of the technical concept of the present disclosure, and all the simple modifications belong to the protection scope of the present disclosure.

In addition, the specific features described in the above embodiments may be combined in any suitable manner without contradiction. The various possible combinations are not described further in this disclosure in order to avoid unnecessary repetition.

Moreover, any combination between the various embodiments of the present disclosure is possible as long as it does not depart from the spirit of the present disclosure, which should also be construed as the disclosure of the present disclosure.

Claims (10)

1. The EVS-10-based manganese-loaded catalytic adsorbent for flue gas mercury removal and denitration is characterized by comprising a carrier and an active component loaded on the carrier; the carrier comprises EVS-10 molecular sieve, and the active component comprises manganese oxide; based on the total weight of the catalytic adsorbent, the mass fraction of the carrier is 85-99 wt%, and the mass fraction of the active component is 1-15 wt%; the catalytic adsorbent is prepared by a method comprising the following steps:

(1) Mixing an EVS-10 molecular sieve, a manganese source and water to obtain a raw material mixture; the raw material mixture also comprises a dispersing auxiliary; the dispersing aid is selected from one or more of polymethacrylic acid, polyacrylic acid and hydrolyzed polymaleic anhydride;

(2) And (3) contacting the raw material mixture, the alkali solution and the hydrogen peroxide for oxidation reaction.

2. The EVS-10 based manganese-loaded catalytic adsorbent according to claim 1, wherein in the step (1), the weight ratio of the EVS-10 molecular sieve, the manganese source and water is (0.2 to 0.3): (0.0125-0.08): 1.

3. The EVS-10 based manganese-loaded catalytic adsorbent according to claim 1 or 2, wherein the manganese source is a soluble manganese salt selected from one or more of manganese acetate, manganese chloride and manganese nitrate.

4. The EVS-10 based manganese-loaded catalytic adsorbent according to claim 1, wherein the dispersion aid is polymethacrylic acid;

The weight ratio of the dispersing aid to the manganese source is (0.5-3): (2-6);

The step (1) comprises: and mixing the manganese source, water and the dispersing aid, performing ultrasonic treatment, and adding the EVS-10 molecular sieve to obtain the raw material mixture.

5. The EVS-10 based manganese-loaded catalytic adsorbent according to claim 1, wherein in step (2), the alkali solution comprises sodium hydroxide solution;

The mass ratio of the hydrogen peroxide in the hydrogen peroxide to the manganese source in the step (1) is (0.7-2.5): (0.9 to 1.5).

6. The EVS-10 based manganese-loaded catalytic adsorbent according to claim 5, wherein the volume ratio of the sodium hydroxide solution to the water in the step (1) is 0.3 to 0.7:1.

7. The EVS-10 based manganese-loaded catalytic adsorbent according to claim 1, wherein the conditions of the oxidation reaction in step (2) include: the reaction temperature is 40-80 ℃ and the reaction time is 0.5-2 h.

8. The EVS-10 based manganese-loaded catalytic adsorbent according to claim 5, wherein step (2) further comprises: adding the alkali solution into the raw material mixture, performing ultrasonic treatment for 5-30 minutes, and then adding the hydrogen peroxide to perform the oxidation reaction; and

Filtering, washing and drying the oxidation reaction product, then screening, and taking the undersize product to obtain the catalytic adsorbent; wherein the drying temperature is 70-110 ℃.

9. The use of the catalytic adsorbent according to any one of claims 1-8 in the field of flue gas mercury removal and denitration.

10. The use according to claim 9, wherein the flue gas is coal fired power plant flue gas.