KR20240030476A - method for manufacturing of metal ion-exchanged synthetic zeolite for adsorption of Ammonia gas from coal fly ash - Google Patents

Abstract

The present invention relates to a method of producing zeolite with excellent crystallinity and ammonia gas adsorption performance by ion-exchanging transition metals and an appropriate combination of coal fly ash (CFA) and alkali. ) and solid sodium hydroxide (NaOH) were melted at a weight ratio of 0.7 to 1.1 NaOH/CFA, then water was added, aged at 30°C for 5 hours and crystallized at 50 to 90°C for 1 to 5 hours to produce synthetic zeolite. It consists of manufacturing zeolite for ammonia gas adsorption (M-HDZ) by exchanging the prepared synthetic zeolite (HDZ) with a transition metal ion selected from Mn, Fe, Co, and Cu.
The present invention is environmentally friendly in that it develops an adsorption material using fly ash, which is a hazardous material and a waste, and the zeolite (M-HDZ) ion-exchanged with a transition metal of the present invention removes ammonia (a major precursor that causes secondary fine dust). It has an excellent effect in removing NH ₃ ).

Description

Method for manufacturing of metal ion-exchanged synthetic zeolite for adsorption of Ammonia gas from coal fly ash}

The present invention relates to a method for producing a synthetic zeolite for adsorbing ammonia gas in which metal ions are exchanged from coal fly ash, and specifically relates to a method for producing a synthetic zeolite for adsorbing ammonia gas in which transition metal ions are exchanged from coal fly ash.

Ammonia is a nitrogen-based odor substance that causes bad odor, and is discharged into the atmosphere through various routes such as environmental infrastructure and industrial facilities. In particular, it is very important to reduce or remove ammonia nitrogen because the release of ammonia nitrogen not only causes water pollution but also causes bad odors and is a source of air pollution. Ammonia itself has a significant impact on the air environment, but ammonia-related As the number of days with high concentrations of secondary fine dust increases, the need for ammonia removal is increasing.

Most studies on the application of zeolite for ammonia adsorption were limited to the removal of ammonia nitrogen present in aqueous solution. There are some cases of application ^to the adsorption of ammonia gas using ^zeolite Cases of applying zeolite as an adsorbent for gas removal are very rare.

Coal fly ash is generated in large quantities as a combustion by-product in thermal power plants using coal as a raw material, and because it is not regulated as hazardous waste, it is widely recycled in various industrial fields such as construction, environment, and agriculture. Coal fly ash is known to be a very suitable precursor material for zeolite synthesis because it contains high Si and Al components.

As a prior art related to the production of zeolite using coal fly ash, for example, in Patent Document 1, coal fly ash heat-treated at 700-900°C was reacted with a 1-5N alkali solution, and then separated into solid and liquid for fractionation. An amount of aluminum-containing material calculated by the reaction molar ratio of SiO ₂ /Al ₂ O ₃ is added to a supernatant, aged at 20-30°C for 6-24 hours, and subjected to hydrothermal treatment to separate solid zeolite from coal fly ash. In the method of producing type A zeolite, in the step of separating the solid zeolite by hydrothermal treatment, considering the remaining Si, Al, and alkali concentration in the dehydrated alkaline aqueous solution, an alkali agent, an aluminum-containing material, water, and a Na source are used. A method for producing type A zeolite from coal fly ash is disclosed, which is characterized by circular use by adding sodium chloride. In Patent Document 2, a primary treatment product heat-treated by mixing coal fly ash and an alkali material is dissolved in water, A method for mass synthesizing Na-A type zeolite with a tetragonal crystal structure is disclosed by mixing one or more of an aluminum source, a silica source, and a zeolite seed to form a secondary treatment product and then crystallizing it through aging and hydrothermal reaction.

In addition, according to the prior art related to zeolite ion-exchanged with a transition metal in Patent Document 3, raw materials of silica, raw materials of alumina, basic substances, distilled water, and structure-inducing materials containing a benzyl group are stirred to form a synthetic mother liquor in the form of a hydrogel, and silica (SiO ₂ ) Preparing a synthetic mother solution containing 0.2 to 0.4 M of a structure-directing material containing a benzyl group per 1.0 M; A first step of producing Na-form zeolite (as-made) by separating, washing, and drying the solid obtained by hydrothermal treatment while rotating the synthetic mother liquor; A second step of producing H-SSZ-13 by exchanging hydrogen ions to remove Na ions remaining in the Na-form zeolite (as-made); And a third step of producing M-SSZ-13, where M is a transition metal, by exchanging transition metal ions with H-SSZ-13. Preparation of zeolite in which transition metal ions are exchanged with improved hydrothermal stability. The method is disclosed.

The inventor of the present invention confirmed that synthetic zeolite exchanged with transition metal ions prepared from coal fly ash had excellent ammonia gas adsorption performance and completed the present invention.

Patent Document 1; Republic of Korea Patent Publication Registration No. 10-0274118 Patent Document 2; Republic of Korea Patent Publication Registration No. 10-2060505 Patent Document 3; Republic of Korea Patent Publication Registration No. 10-1902694

The problem to be solved by the present invention relates to a method for producing synthetic zeolite in which metal ions for ammonia gas adsorption are exchanged from coal fly ash (CFA), and more specifically, to the method of producing a synthetic zeolite in which metal ions for ammonia gas adsorption are exchanged from coal fly ash (CFA). For the purpose of providing a method for producing zeolite with excellent crystallinity and ammonia gas adsorption performance by an appropriate combination and exchange with transition metal ions, and a zeolite for ammonia gas adsorption (M-HDZ) in which transition metal ions are exchanged manufactured thereby. It is done.

In the following, the present invention is abbreviated as 'CFA' for coal fly ash (CFA), 'HDZ' for synthetic zeolite, and 'M-HDZ' for zeolite exchanged with transition metal ions (M-HDZ). Also, in 'M-HDZ', 'M' represents a transition metal selected from Mn, Fe, Co, and Cu.

In the present invention, as a means of solving the problem, a method of manufacturing a synthetic zeolite for adsorbing ammonia gas in which metal ions are exchanged from coal fly ash is melted at a high temperature of 550 ° C. and then pulverized. The first process of obtaining pulverized material, the second process of producing synthetic zeolite (HDZ) by adding water to the pulverized material of the first process, maturation and crystallization, and the process of converting the synthetic zeolite (HDZ) of the second process into transition gold ions. It consists of a third process of producing zeolite for ammonia gas adsorption (M-HDZ) by exchanging it.

One embodiment of the method for producing a synthetic zeolite for adsorbing ammonia gas in which metal ions are exchanged from coal fly ash according to the present invention is a). Si/Al is fixed at a weight ratio of 1.2, coal fly ash (CFA) and solid sodium hydroxide (NaOH) are melted at a high temperature of 550°C for 2 hours with a weight ratio of NaOH/CFA of 0.7 to 1.1, and then ground. The first process of obtaining pulverized material, b). A second process in which synthetic zeolite (HDZ) is produced by adding water to the pulverized product of the first process at a weight ratio of 1:5, maturing at 30°C for 1 to 5 hours, and crystallizing at 50 to 90°C for 1 to 5 hours. process and c). The third process consists of manufacturing zeolite for ammonia gas adsorption (M-HDZ) by exchanging the synthetic zeolite (HDZ) of the second process with a transition metal ion selected from Mn, Fe, Co, and Cu.

The first and second processes according to the present invention are processes for producing zeolite by melt/hydrothermal synthesis, and the melt/hydrothermal synthesis method produces Na ₂ from quartz, mullite, etc. contained in fly ash (CFA), which can be easily used as a zeolite source. By changing it to amorphous and water-soluble forms such as SiO ₃ and NaAlSiO ₄ , it is highly soluble in water or aqueous alkaline solutions, and more components of SiO ₂ and Al ₂ SO ₃ required for zeolite synthesis can be obtained than through hydrothermal synthesis.

The NaOH/CFA ratio of coal fly ash (CFA) and solid sodium hydroxide (NaOH) in the first process according to the present invention is 0.9% by weight.

In the second process according to the present invention, synthetic zeolite (HDZ) is produced by crystallization at 90°C for 5 hours.

The zeolite (M-HDZ) exchanged with one transition metal ion selected from Mn, Fe, Co, and Cu in the third process according to the present invention has a transition metal content of 3 to 5% by weight.

It is a zeolite (M-HDZ) exchanged with one transition metal ion selected from Mn, Fe, Co, and Cu, prepared by the production method according to the present invention.

The present invention is environmentally friendly in that it develops an adsorption material by utilizing fly ash, which is a waste and a hazardous material that is the primary fine dust generator in the atmosphere, and the zeolite (M-HDZ) exchanged with the transition metal ion of the present invention is a secondary Not only is it highly effective in removing ammonia (NH ₃ ) gas, a major precursor that causes fine dust, but it is also very technologically and commercially advantageous, as cases of applying zeolite as an adsorbent for ammonia gas removal are very rare.

Figure 1 shows XRD patterns for synthetic zeolite (HDZ) and Mn-HDZ, Fe-HDZ, Co-HDZ, and Cu-HDZ.
Figure 2 is a diagram of NH ₃ -TPD of HDZ and Mn-HDZ, Fe-HDZ, Co-HDZ and Cu-HDZ
Figure 3 is a chart of acidity for HDZ and Mn-HDZ, Fe-HDZ, Co-HDZ and Cu-HDZ.
NH ₃ gas adsorption breakthrough curve in Figure 4
Figure 5 is an adsorption capacity chart of HDZ, Mn-HDZ, Fe-HDZ, Co-HDZ, and Cu-HDZ.

Hereinafter, the present invention will be described in more detail through <Examples> and <Test Examples>, etc., but the present invention is not limited by the description below.

The method for producing a synthetic zeolite for adsorbing ammonia gas in which metal ions are exchanged from coal fly ash according to the present invention is a). Si/Al is fixed at 1.2, coal fly ash and solid sodium hydroxide (NaOH) are melted at a high temperature of 550°C for 2 hours with a weight ratio of NaOH/CFA of 0.7 to 1.1, and then pulverized to produce the pulverized product. The first process of obtaining, b). A second process of producing synthetic zeolite (HDZ) by adding water to the pulverized product of the first process at a weight ratio of 1:5, maturing at 30°C for 5 hours and crystallizing at 50 to 90°C for 1 to 5 hours, and c). The third process involves ion-exchanging the synthetic zeolite (HDZ) from the second process with a transition metal selected from Mn, Fe, Co, and Cu to produce zeolite ion-exchanged with the transition metal (M-HDZ).

The first and second processes according to the present invention consist of manufacturing zeolite by melt/hydrothermal synthesis, and the melt/hydrothermal synthesis method produces more components of SiO ₂ and Al ₂ SO ₃ necessary for zeolite synthesis than the hydrothermal synthesis method. You can get a lot.

In the first process of the present invention, Si/Al is fixed at a weight ratio of 1.2, coal fly ash (CFA) and solid sodium hydroxide (NaOH) are mixed so that the NaOH/CFA ratio is 0.7 to 1.1, and 2 times at a high temperature of 550°C. After melting for a period of time, the melt is pulverized to obtain pulverized material in order to elute the components of SiO ₂ and Al ₂ SO ₃ in the form of ions.

Since the representative zeolite A theoretically has Si/Al of 1, the Al source does not need to be in excess of the Si source, and the coal fly ash has a Si/Al of 1.2, so it is fixed as is. If the Al component in the coal fly ash is relatively insufficient, the Al source is used. Supplement as needed.

The coal fly ash (CFA) selected above is fly ash discharged from coal-fired power plants and is classified as industrial waste. The basic components of fly ash include various components such as silica, alumina, iron oxide, and calcium oxide, and SiO ₂ + If the content of Al ₂ SO ₃ is more than 70%, it is desirable for synthesizing adsorption materials.

In addition, a small amount of reagent grade zeolite (WAKO)-A seed is added to promote the reaction and at the same time suppress the formation of unwanted adsorption materials such as Na-P.

If the content of SiO ₂ + Al ₂ SO ₃ in coal fly ash (CFA) is less than 50%, almost no crystallization occurs when an adsorbent material is synthesized. Even if crystallization occurs, a large amount of Al source or Si source deficiency must be supplemented, and coal Among the fly ash components, CaO interferes with the synthesis of adsorption materials, so coal fly ash with a content of 10% or less is preferable for the synthesis of adsorption materials.

The coal fly ash (CFA) comes in the form of hard glassy spherical particles, mainly hollow particles, and porous amorphous particles, but hollow particles have the lowest surface area compared to volume, so they are preferable for synthesizing adsorption materials, and have a size of 20 to 30. It is about ㎛.

In the second process of the present invention, the components of SiO ₂ and Al ₂ SO ₃ are eluted from the pulverized material in the form of ions, then the eluted aqueous solution is aged at 30°C for 5 hours and then aged at 50 to 90°C for 0.5 to 5 hours. This is a crystallization process, and consists of washing and filtering the crystallized solid several times and then drying the solid at 100°C for 2 hours to produce synthetic zeolite (HDZ).

The third process of the present invention is to produce zeolite (M-HDZ) exchanged with transition metal ions by reacting with a transition metal precursor to increase the ammonia gas adsorption capacity of the synthetic zeolite (HDZ) prepared in the second process. It comes true.

In the M-HDZ, M represents a transition metal selected from Mn, Fe, Co, and Cu, and ion exchange is performed by reacting with a solution of 1 to 5% by weight of the transition metal precursor at 30° C. for 24 hours, and the transition metal precursor is The substance consists of one selected from hydrochloride, nitrate and sulfate.

After completion of the ion exchange reaction, it is filtered and washed with distilled water, and then dried at 105°C for 2 hours. The zeolite exchanged with the dried transition metal ion is calcined at 550°C for 2 hours to remove the remaining Cl ^- , It consists in removing N0 ₃ ^- or SO ₄ ^2- ions.

Hereinafter, the method for producing zeolite ion-exchanged from coal fly ash to a transition metal for gaseous ammonia adsorption according to the present invention will be described in more detail through <Examples> and <Test Examples>.

<Example 1>

In a 300 ml stainless steel reactor coated with Teflon where stirring and temperature are controlled, the Si/Al ratio was fixed to 1.2 as synthesis conditions, and coal fly ash (CFA) and solid sodium hydroxide (NaOH) were added so that the NaOH/CFA weight ratio was 0.9. ) is added and fired at 550°C for 1 hour, then pulverized at room temperature to obtain pulverized product (first process).

The pulverized material and water obtained above were added to the synthesis reactor at a weight ratio of 1:5, then aged at 30°C for 5 hours while stirring, and then crystallized at 90°C for 5 hours to prepare synthetic zeolite (HDZ). (2nd process).

In a reaction vessel, a 5% by weight aqueous solution of Mn hydrochloride, a transition metal, was added to the raw material of the synthetic zeolite (HDZ) prepared above, and reacted with stirring at 30°C for 24 hours. The reactants were repeated three times. After filtering and washing, it was dried at 105°C for 2 hours.

The dried Mn ion-exchanged zeolite (Mn-HDZ) was calcined at 550°C for 2 hours to remove remaining chlorine ions and produce Mn-ion exchanged zeolite (Mn-HDZ) with a content of 5% by weight. (3rd process).

The remaining portion of the synthetic zeolite (HDZ) obtained in the second step was equally divided, an aqueous solution of 5% by weight of hydrochloride of each of the transition metals Fe, Co, and Cu was added, and the zeolite (Mn-HDZ) exchanged with the Mn ion was added. ) were reacted under the same conditions to produce Fe-HDZ, Co-HDZ, and Cu-HDZ in which 5% by weight of transition metals were ion-exchanged (third process).

The XRD patterns for the synthetic zeolite (HDZ) prepared above, Mn-HDZ, Fe-HDZ, Co-HDZ, and Cu-HDZ are shown in [Figure 1].

<Test Example 1> Ammonia desorption experiment at elevated temperature (NH ₃ -TPD)

In order to analyze the scattering intensity characteristics of the synthetic zeolite (HDZ) prepared in <Example 1> and each of Mn-HDZ, Fe-HDZ, Co-HDZ, and Cu-HDZ, an ammonia elevated temperature desorption experiment (NH ₃ -TPD) was performed. carried out.

BETCAT-M (Belcat Inc., Japan) equipment equipped with NH ₃ -TPD and TCD (Thermal Conductivity Detector) was used, the amount of sample was 100 mg, and the pretreatment conditions are shown in [Table 1] below.

Step Time(min) Temperature(℃) Gas Flow rate(ml/min) One 5 30 He 50 2 52 550 He 50 3 60 550 He 50 4 One 30 He 50 5 10 30 He 50 6 30 30 5% _NH3 /He 50 7 15 30 He 50 8 52 550 He 30 9 30 550 He 30

After pretreatment, 5 mol/mol% NH ₃ /He gas (50 mL/min) was adsorbed at 30°C, and the ammonia desorbed was measured using TCD while raising the temperature at 10°C/min to 550°C, and NH ₃ - The TPD results are shown in [Figure 2].

As shown in [Figure 2], as a result of the ammonia desorption experiment, it can be seen that most ammonia desorption peaks appear at low temperature (LT) and high temperature (HT). In the case of M-HDZ ion exchanged at 5 wt% in [Figure 2] (b to e in Figure 2), the first LT desorption peak appeared around 100°C. In particular, when comparing HDZ and Mn-HDZ, compared to HDZ, The desorption temperature of ion-exchanged Mn-HDZ shifted to a slightly higher temperature, and the area of the desorption peak also increased. In addition, most secondary HT desorption peaks appeared around 300°C, but as shown in Cu-HDZ, when exchanged with Cu ions, the desorption peak decreased above 400°C. This shows that when desorbing ammonia gas adsorbed on zeolite exchanged with Cu ions, a higher temperature is required than on zeolite exchanged with other metal ions.

<Test Example 2> Measuring acidity

The acidity of synthetic zeolite (HDZ), Mn-HDZ, Fe-HDZ, Co-HDZ, and Cu-HDZ was measured using the NH ₃ -TPD area value in [Figure 2], and the results were measured in [Figure 2]. 3].

As shown in [Figure 3], the acid strength appeared in the order of Mn-HDZ > Cu-HDZ ≒ Co-HDZ > Fe-HDZ > HDZ, and Mn-HDZ has a higher acid strength than other cation-exchanged zeolites. You can see that It was judged that compared to HDZ, the acid sites of Mn-HDZ were evenly distributed on the pores and surface of zeolite through ion exchange, resulting in increased ammonia adsorption performance. In addition, in the case of ion-exchanged zeolite, Cu ²⁺ , Co ²⁺ , Fe ³⁺ or Mn ²⁺ ions within the HDZ are distributed uniformly in the synthesized zeolite during the ion exchange process, increasing the acid point number of the alumina site forming the structure. It appears that the adsorption performance for ammonia gas is improved depending on the method. This is believed to affect the size of the Brønsted acid site for NH ₃ gas adsorption by converting only the ions located on the HDZ surface to the desired amount.

<Test Example 3> NH ₃ gas adsorption breakthrough curve

An NH ₃ gas adsorption breakthrough experiment was performed on the synthetic zeolite (HDZ) prepared in <Example 1>, Mn-HDZ, Fe-HDZ, Co-HDZ, and Cu-HDZ, and as a result, NH of [FIG. 4] ₃ Gas adsorption breakthrough curve is shown.

As shown in [Figure 4], the ammonia adsorption breakthrough curve appeared in the order of Mn-HDZ > Co-HDZ > Cu-HDZ > Fe-HDZ > HDZ. In the case of HDZ, ammonia concentration was detected at 35 min, but ion exchange In the case of the zeolites, the ammonia concentration appeared at more than 47 min. In particular, in the case of Mn-HDZ, the ammonia peak was detected at 65 min, and the ammonia adsorption ability was improved by about 1.8 times more than before ion exchange. This showed that in the case of ion-exchanged Fe-HDZ, Cu-HDZ, Co-HDZ, and Mn-HDZ, 100% ion exchange was performed with Na ⁺ ions composed of HDZ. This is believed to have been replaced by Na ⁺ ions located inside the HDZ because the ion sizes of Fe ³⁺ , Co ³⁺ , Cu ²⁺ and Mn ²⁺ are much smaller than the size of Na ⁺ ions.

This is believed to be because ions located inside and on the surface of the HDZ are ion exchanged with transition metal cations, causing Brønsted acid sites to be evenly distributed in the zeolite, thereby increasing ammonia adsorption performance.

<Test Example 4> NH ₃ adsorption amount evaluation

The adsorption capacity of the adsorbent (mg adsorbate/g adsorbent), which represents the amount of adsorbate adsorbed up to the test time from the breakthrough curve obtained in the fixed bed adsorption experiment, can theoretically be obtained using [Calculation 1] below (Kim et al., 2010; Kim and Lee, 2012).

[Calculation Formula 1]

In the above calculation formula, q represents the adsorption capacity, C _A0 and C _A are the concentration of the adsorbent at the inlet and outlet of the reactor, Q is the mixed gas flow rate, w is the amount of adsorbent, M _w is the molecular weight of the adsorbent, and t is the reactor operating time. , In this test example, a fixed bed adsorption experiment was performed under the conditions of w = 0.1g, T = 20°C, Q = 100 mL/min, and C _A0 = 1,000ppm.

C _NH3 and t were obtained through regression analysis of the NH ₃ adsorption breakthrough curve in [Figure 4] using statistical analysis (Sigma plot 14.5), and the adsorption capacity was calculated using the above [Calculation 1], which is shown in [Figure 5].

As shown in [Figure 5], the adsorption capacity of NH ₃ is Mn-HDZ (56.0 mg/g) > Co-HDZ (45.0 mg/g) > Cu-HDZ (43.3 mg/g) > Fe-HDZ (36.0 mg) /g) > HDZ (27.4 mg/g), and previous research showed that as the strong acid site and acid strength increase, the catalytic activity increases and the affinity with the acidic gas SO ₂ increases, thereby reducing the amount of adsorption (Kim and Lee, 2012), and in the present invention, when transition metal ions (Cu ²⁺ , Co ²⁺ , Fe ³⁺ or Mn ²⁺ ) are ion exchanged in the pores of HDZ synthesized from fly ash, they are present in the HDZ pores. It is believed that the amount of adsorption of NH ₃ , an alkaline gas, increases as the acid point increases.

Claims (5)

a). The Si/Al ratio was fixed at 1.2, and coal fly ash (CFA) and solid sodium hydroxide (NaOH) were melted at a high temperature of 550°C for 2 hours with a weight ratio of NaOH/CFA of 0.7 to 1.1, and then ground. The first process of obtaining pulverized material,
b). A second process of producing synthetic zeolite (HDZ) by adding water to the pulverized product of the first process at a weight ratio of 1:5, maturing at 30°C for 5 hours and crystallizing at 50 to 90°C for 1 to 5 hours, and
c). Characterized by a third process of producing ammonia gas adsorption zeolite (M-HDZ) by exchanging the synthetic zeolite (HDZ) of the second process with a transition metal ion selected from Mn, Fe, Co, and Cu. Method for producing synthetic zeolite for adsorption of ammonia gas in which metal ions are exchanged from coal fly ash. In claim 1,
A synthetic zeolite for adsorbing ammonia gas in which metal ions are exchanged from coal fly ash, characterized in that the NaOH / CFA ratio of the coal fly ash (CFA) and solid sodium hydroxide (NaOH) in the first process is 0.9% by weight. Manufacturing method. In claim 2,
A method for producing synthetic zeolite for ammonia gas adsorption in which metal ions are exchanged from coal fly ash, characterized in that the crystallization in the second process is crystallized at 90° C. for 5 hours to produce synthetic zeolite (HDZ). In claim 3,
The zeolite (M-HDZ) exchanged with one transition metal ion selected from Mn, Fe, Co, and Cu in the third process is a metal ion extracted from coal fly ash, characterized in that the transition metal content is 3 to 5% by weight. Method for producing synthetic zeolite for adsorption of exchanged ammonia gas. A zeolite for ammonia adsorption characterized by a zeolite (M-HDZ) exchanged with one transition metal ion selected from Mn, Fe, Co, and Cu prepared by the production method according to any one of claims 1 to 4.