WO2021066432A1 - Economical method for producing zeolite catalyst having improved reaction activity and hydrothermal stability by controlling aluminum content and distribution - Google Patents

Abstract

The present invention relates to a method for producing a zeolite catalyst, and provides a zeolite preparation method wherein in the synthesis of zeolite, a filtration solid prepared by removing water from a synthetic stock solution using excessive water or an impregnation solid prepared by reducing the use amount of water from the start is subjected to a hydrothermal reaction, and thus zeolite having excellent crystallinity without impurities can be synthesized, and in such a case, the amounts of reactants are drastically reduced, leading to improvements in reactor efficiency and energy consumption and a reduction in amount of wastewater generated. Provided is also a method for producing a zeolite catalyst, wherein the zeolite synthesized by the present invention is changed in view of physicochemical properties including a Si/Al molar ratio, a particle size, and the like, and therefore, a catalyst produced using the zeolite can obtain the effects of improving reaction activity, hydrothermal stability, and the like.

Description

An economical zeolite catalyst manufacturing method with improved reaction activity and hydrothermal stability by controlling aluminum content and distribution

The present invention relates to a method for producing a zeolite catalyst, and more specifically, to a method for producing an economical zeolite catalyst in which reaction activity and hydrothermal stability are improved by controlling aluminum content and distribution.

Zeolite is a porous material having a unique shape or size of pores and regular channels, and is widely used as an adsorbent, separating agent, and detergent support. In addition, since the acidity can be widely controlled by controlling the ratio of silicon and aluminum atoms in the zeolite skeleton, it is used as a catalyst in various fields including the petrochemical industry.

Zeolite is synthesized through a hydrothermal synthesis method that heats a synthetic mother liquor prepared by dissolving silica and alumina raw materials, structure-inducing substances, and complexing substances, etc., which are skeleton components, in water.

In a general hydrothermal synthesis method, since a synthetic mother liquor is prepared using an excess of water, mixing is easy, and since it reacts in a uniform state, reproducibility is excellent.

Therefore, in terms of zeolite manufacturing cost and environmental aspects, research is needed to reduce the economic or environmental burden by reducing the use of water.

However, if the amount of water is reduced when preparing the synthetic mother liquor, it is difficult to uniformly mix the raw materials and the synthesis reproducibility is lowered. In addition, it is not easy to concentrate the synthetic mother liquor because the type of zeolite produced is limited depending on the amount of water.

Therefore, there is a need for a synthetic method in which properties such as crystallinity and purity of the generated zeolite are maintained while increasing the economic and environmental effects by reducing the use of water during hydrothermal synthesis.

The present invention was conceived to solve the above problems, and an object of the present invention is to improve reaction activity and hydrothermal stability by controlling the aluminum content and distribution of the zeolite catalyst, and to increase the zeolite production efficiency to obtain economical effects at the same time. It is to provide a method for producing a zeolite catalyst.

Specifically, the purpose of improving the zeolite synthesis method is to provide a method capable of controlling the Si/Al molar ratio, particle size, shape, etc. of the generated zeolite by controlling the aluminum content and distribution in the zeolite skeleton.

In addition, the present invention is to provide a method for producing a zeolite catalyst with improved reaction activity and hydrothermal stability that can secure economic and environmental effects at the same time by greatly reducing the amount of water used in the hydrothermal synthesis of zeolite.

In order to achieve the above object, the present invention comprises the steps of preparing a synthetic mother liquor by dissolving a zeolite precursor, a structure-inducing material, and a complexing material in water; Filtering the synthetic mother liquor to obtain a filtered solid from which water has been removed; It provides a zeolite synthesis method comprising a; step of synthesizing zeolite by hydrothermal reaction of the filtered solid.

In a preferred embodiment, the water content of the filtered solid is less than 50%, and 50 to 80% of water is removed from the synthetic mother liquor.

In a preferred embodiment, the hydrothermal reaction is carried out by placing the filtered solid in a sealed high-pressure cooker and rotating at a temperature of 50 to 200°C at 0 to 60 rpm, and the temperature and the number of rotations can be adjusted according to the type of zeolite to be synthesized.

In a preferred embodiment, the zeolite precursor may be a synthetic or natural zeolite of USY, FAU, or BEA type, and a solid form of kaolin or fly ash, but is not limited thereto, but is not limited to sodium silicate in a liquid state, It is possible to use a mixture of sodium aluminate, aluminum oxide or aluminum alkoxide with coroidal silica, fumed silica or tetraortho silicate.

In a preferred embodiment, the water filtered from the synthetic mother liquor is reused for the next preparation of the synthetic mother liquor to reduce the amount of alkaline wastewater generated.

In a preferred embodiment, the structure-inducing material uses an organic compound containing quaternary ammonium ions, and in some cases, an inorganic base or other types of organic compounds may be used.

In addition, the present invention comprises the steps of preparing a reaction solution by dissolving a structure-inducing substance and a complexing substance in water; Impregnating the reaction solution into a zeolite precursor to prepare an impregnated solid; It further provides a zeolite synthesis method comprising a; step of synthesizing zeolite by hydrothermal reaction of the impregnated solid.

In a preferred embodiment, the impregnation of the reaction solution is performed by incipient wetness impregnation.For example, when USY zeolite is used as a precursor, it is possible to synthesize if it is more than 11 g of water per 10 g of USY zeolite.

In a preferred embodiment, before the impregnated solid is subjected to hydrothermal reaction, ultrasonic treatment is performed at 40° C. for 1 to 2 hours for even dispersion of the reaction solution, followed by aging at room temperature for 0 to 12 hours.

In a preferred embodiment, the zeolite precursor is a synthetic or natural zeolite of USY, FAU or BEA type, or a solid form of kaolin or fly ash, etc. may be used.

In a preferred embodiment, zeolite seeds may be included in the impregnated solid. In this case, pure zeolite without impurities can be obtained and the time required for hydrothermal reaction can be shortened, which is more economical.

In addition, the present invention further provides a zeolite catalyst manufacturing method in which hydrogen or alkali metal, alkaline earth metal, transition metal, noble metal, etc. are ion-exchanged or impregnated with the zeolite synthesized by the above zeolite synthesis method.

In addition, zeolites such as CHA, AEI, AFX, ERI, LTA, MFI, BEA, FAU, MEL, and MOR can be synthesized through the present invention and can be prepared as a catalyst.

The present invention has the following excellent effects.

According to the present invention, when the zeolite is hydrothermally synthesized by preparing a filtered solid or an impregnated solid, it is possible to control the Si/Al molar ratio and particle size of the generated zeolite, thereby producing a zeolite catalyst with improved reaction activity and hydrothermal stability. have.

In addition, by significantly reducing water, which occupies most of the zeolite synthetic mother liquor, hydrothermal synthesis, economical and eco-friendly effects can be obtained at the same time.

1 is a flowchart of a zeolite synthesis method according to an embodiment of the present invention.

2 is a flowchart of a zeolite synthesis method according to another embodiment of the present invention.

3 is a graph showing the XRD pattern and nitrogen adsorption isotherms of CHA zeolites according to Examples 1, 2, and Comparative Example 1 of the present invention.

4 is an electron microscope photograph of CHA zeolite according to Examples 1, 2 and Comparative Example 1 of the present invention.

5 is an XRD pattern before and after hydrothermal treatment at 750° C. of Cu/CHA catalysts according to Examples 1, 2, and Comparative Example 1 of the present invention.

6 is a nitrogen adsorption isotherm before and after 750° C. hydrothermal treatment of Cu/CHA catalysts according to Examples 1, 2, and Comparative Example 1 of the present invention.

7 is a graph showing the SCR reaction activity before and after 750° C. hydrothermal treatment of Cu/CHA catalysts according to Examples 1, 2, and Comparative Example 1 of the present invention.

8 is an XRD pattern and a nitrogen adsorption isotherm after 900° C. hydrothermal treatment of Cu/CHA catalysts according to Example 1 and Comparative Example 1 of the present invention.

9 is a graph showing the XRD pattern and nitrogen adsorption isotherms of AEI zeolite according to Examples 3, 4 and Comparative Example 2 of the present invention.

10 is an electron microscope photograph of AEI zeolite according to Examples 3, 4 and Comparative Example 2 of the present invention.

11 is an XRD pattern of Cu/AEI catalysts according to Examples 3, 4, and 2 of the present invention before and after hydrothermal treatment at 750°C.

12 is a nitrogen adsorption isotherm before and after 750° C. hydrothermal treatment of Cu/AEI catalysts according to Examples 3, 4 and Comparative Example 2 of the present invention.

13 is a graph showing the SCR reaction activity of Cu/AEI catalysts according to Examples 3, 4, and 2 of the present invention before and after hydrothermal treatment at 750°C.

14 is a graph showing the XRD pattern and nitrogen adsorption isotherms of AFX zeolites according to Examples 5, 6, and 3 of the present invention.

15 is an electron microscope photograph of AFX zeolite according to Examples 5, 6, and 3 of the present invention.

16 is an XRD pattern of Cu/AFX catalysts according to Examples 5, 6, and 3 of the present invention before and after hydrothermal treatment at 750°C.

17 is a nitrogen adsorption isotherm before and after 750° C. hydrothermal treatment of Cu/AFX catalysts according to Examples 5, 6, and 3 of the present invention.

18 is a graph showing the SCR reaction activity of Cu/AFX catalysts according to Examples 5, 6, and 3 of the present invention before and after hydrothermal treatment at 750°C.

As for terms used in the present invention, general terms that are currently widely used are selected, but in certain cases, some terms are arbitrarily selected by the applicant. In this case, the meanings described or used in the detailed description of the invention are considered rather than the names of simple terms. Therefore, the meaning should be grasped.

Hereinafter, with reference to the preferred embodiments shown in the accompanying drawings will be described in detail the technical configuration of the present invention.

However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. The same reference numerals denote the same elements throughout the specification.

1 is a flowchart of a zeolite synthesis method according to an embodiment of the present invention.

Referring to FIG. 1, in the zeolite synthesis method according to an embodiment of the present invention, first, a zeolite precursor, a composition inducing material, and a complexing material are dissolved in sufficient water to prepare a synthetic mother liquor (S1000).

In addition, the zeolite precursor is a raw material of silica and alumina, and synthetic or natural zeolite of USY, FAU or BEA type, and kaolin or fly ash in solid form may be used. Sodium silicate, coroidal silica, fumed silica, or tetraortho silicate may be mixed with sodium aluminate, aluminum oxide or aluminum alkoxide.

In addition, as the structure directing agent (SDA), an organic compound including quaternary ammonium ions may be mainly used depending on the type of zeolite, but inorganic bases or other types of organic compounds may be used in some cases. .

In addition, the complexing material may be an alkali hydroxide solution containing sodium hydroxide.

Next, the synthetic mother liquor is added to a filtering device to remove water, and then filtered solids are obtained (S1100).

In addition, 50 to 80% of water is removed from the synthetic mother liquor, and the water content of the filtered solid is less than 50%.

At this time, the filtered water can be reused to make a synthetic mother liquor, and in this case, the amount of alkaline wastewater generated can be reduced.

Next, the filtered solid is hydrothermally reacted to synthesize zeolite (S1200).

In addition, the hydrothermal reaction is carried out by placing the filtered solid in a sealed high-pressure cooker and rotating at a temperature of 50 to 200°C at 0 to 60 rpm, and the temperature and rotation speed can be adjusted according to the type of zeolite to be synthesized.

2 is a flowchart of a zeolite synthesis method according to another embodiment of the present invention.

Referring to FIG. 2, the zeolite synthesis method according to another embodiment of the present invention is different from the one embodiment of the present invention in synthesizing zeolite from impregnated solids rather than from filtration solids.

First, a reaction solution is prepared by dissolving the structure-inducing substance and the complexing substance in water (S2000).

Here, since the structure-inducing material and the complexing material are substantially the same as those of the structure-inducing material and the complexing material of the embodiment of the present invention, detailed descriptions will be omitted.

Next, the reaction solution is impregnated with the zeolite precursor to prepare an impregnated solid (S2100).

In addition, the impregnation is performed by incipient wetness impregnation, in which the amount of the solution is added to the extent that the zeolite precursor starts to get wet (incipient wetness).For example, when USY zeolite is used as a precursor, USY zeolite Synthesis is possible if it is more than 11g of water per 10g.

In addition, since the zeolite precursor is substantially the same as the zeolite precursor of one embodiment of the present invention, detailed descriptions will be omitted.

Next, in order to evenly disperse the reaction solution in the impregnated solid, it is subjected to ultrasonic treatment at 40° C. for 1 to 2 hours, and then aged at room temperature for 0 to 12 hours.

In addition, in some cases, zeolite seeds can be added to the impregnated solid, and in this case, pure zeolite without impurities can be obtained and the time required for hydrothermal reaction can be shortened, which is more economical.

Next, the impregnated solid is subjected to a hydrothermal reaction to synthesize zeolite (S2200).

In addition, through the embodiments of the present invention, zeolites such as CHA, AEI, AFX, ERI, LTA, MFI, BEA, FAU, MEL, MOR, etc. can be synthesized, and hydrogen or alkali metal, alkaline earth metal, transition A zeolite catalyst can be prepared by ion-exchanging or impregnating metals, precious metals, and the like.

Hereinafter, preferred examples and comparative examples are presented to aid in understanding of the present invention. However, the following examples are only intended to aid understanding of the present invention, and the present invention is not limited to the following examples.

[Example 1: CHA Zeolite Synthesis-Filtrated Solid]

In 90 g of excess water, 10 g of USY zeolite (Si/Al=15), a raw material for silica and alumina, 9.3 g of benzyltrimethylammonium chloride, and 2.1 g of NaOH, a complexing material, are mixed with a composition of 1.0 SiO ₂ : 0.3 SDA: A synthetic mother liquor containing 0.3 NaOH: 30 H _{2 O was prepared.}

The synthetic mother liquor was aged at room temperature for 6 hours and then separated into 18 g of filtered solid and 93 g of filtrate using a vacuum filter to remove 84% of the liquid reactant.

The separated filtered solid was subjected to hydrothermal reaction for 4 days while rotating at 140° C. at 40 rpm to synthesize 7.4 g of CHA zeolite.

For comparison, in Comparative Example 1, CHA zeolite was synthesized by hydrothermal reaction in the original state of the synthetic mother liquor having a _{composition of 1.0 SiO 2} : 0.3 SDA: 0.3 NaOH: 23 H _{2 O without removing water.}

The synthesized CHA zeolite was fired for 6 hours while flowing air in a kiln heated to 550°C, and ^{Na +} ions were removed _{through NH 4} ⁺ ion exchange. NH ₄ -form CHA was further ion-exchanged for Cu to prepare a Cu/CHA catalyst, and catalytic activity was investigated through SCR reaction. In addition, in order to test the hydrothermal stability of the prepared catalyst, it was subjected to hydrothermal treatment for 12 hours while flowing air containing 10% water in a Cu/CHA catalyst layer heated to 750° C. at 100 ml/min.

[Example 2: CHA zeolite synthesis-impregnated solids]

After dissolving 3.5 g of benzyltrimethylammonium hydroxide and 0.8 g of NaOH in 16 g of water, 10 g of USY zeolite (Si/Al=15) was impregnated. At this time, the composition of the reactant was 1.0 SiO ₂ : 0.13 SDA: 0.13 NaOH: 5.3 H ₂ O. For homogeneous mixing of the reactants, ultrasonic treatment was performed at 40° C. for 1 hour and then aged at room temperature for 12 hours, and then hydrothermal reaction was performed for 4 days while rotating at 140° C. at 40 rpm. After washing and drying, 7.2 g of CHA zeolite was recovered. In the case of impregnated solids, the amount of water used can be reduced to 11 g, and CHA zeolite having a uniform particle size was reproducibly produced without aging after sonication.

The catalyst in which Cu was ion-exchanged was prepared in the same manner as in Example 1, and hydrothermal treatment at 750°C was also performed in the same manner.

Table 1 summarizes the amount of reactants, the amount of the product, and the properties of the generated zeolite when synthesizing CHA zeolite through filtered solids and impregnated solids.

	Reactant (g)		Product (g)		Surface area (m 2 /g)	Pore volume (cm 3 /g)	Si/Al
	Silica	Total amount	Based on 10g silica	Based on 10 g of reactant
Comparative Example 1	10	89	7.9	0.9	579	0.29	12.1
Example 1	10	18	7.4	4.1	601	0.33	10.9
Example 2	10	30	7.2	2.4	602	0.31	11.6

3 shows the XRD pattern and nitrogen adsorption isotherms of the CHA zeolite synthesized through Examples 1 and 2, and Comparative Example 1. Both Comparative Example 1 using an excess of water or Example 1 and Example 2 in which the amount of water was significantly reduced showed the X-ray diffraction pattern of CHA as reported in the literature. In addition, CHA zeolite having a very large surface area and pore volume was synthesized due to the well-developed micropores.

4 shows an electron microscope (SEM) picture of the CHA zeolite. Regardless of the synthesis method in which the water content is different, cubic-shaped particles having a uniform size were obtained, and the size was also very similar to 0.5 μm. However, the Si/Al molar ratio of CHA generated according to the synthesis method was slightly different. Comparative Example 1 produced CHA having a high silica content with a Si/Al molar ratio of 12.1, but Example 1 and Example 2 produced CHA having a higher Al content of 10.9 and 11.6, respectively.

5 shows the XRD patterns before and after 750° C. hydrothermal treatment of the Cu/CHA catalyst. Regardless of the catalyst preparation method, there is almost no change in the X-ray diffraction pattern before and after the hydrothermal treatment, showing that the hydrothermal stability of the Cu/CHA catalyst is very excellent.

6 shows nitrogen adsorption isotherms before and after 750° C. hydrothermal treatment of the Cu/CHA catalyst. Like the XRD results, no change in micropore due to hydrothermal treatment was observed.

Table 2 summarizes the characteristics of the Cu/CHA catalyst before and after 750°C hydrothermal treatment.

	Si/Al	Cu content (wt%)	Surface area (m 2 /g)		Pore volume (cm 3 /g)
			Before hydrothermal treatment	After hydrothermal treatment	Before hydrothermal treatment	After hydrothermal treatment
Comparative Example 1	13.5	2.1	584	584	0.29	0.31
Example 1	10.9	2.7	537	545	0.27	0.29
Example 2	11.6	2.5	548	576	0.30	0.32

7 shows the results of investigation of the SCR reaction activity before and after 750° C. hydrothermal treatment of the Cu/CHA catalyst. The catalysts prepared from Examples 1 and 2 have better low-temperature activity at 150°C than in Comparative Example 1, but are somewhat less active at high temperatures of 450°C or higher. However, after hydrothermal treatment at 750°C, Example 1 exhibited excellent activity in the entire temperature range because the high-temperature activity was rather improved.

FIG. 8 shows the XRD pattern and nitrogen adsorption isotherms of the Cu/CHA catalysts prepared from Example 1 and Comparative Example 1 of the present invention after hydrothermal treatment at 900°C. It can be seen that the Cu/CHA prepared from Example 1 maintains the CHA crystal structure and micropores well even after hydrothermal treatment at 900°C.

According to Example 1 of the present invention, even though more than 80% of water was removed during the zeolite synthesis process, CHA zeolite having excellent crystallinity was produced, and the hydrothermal stability was also very excellent. Therefore, the method of synthesizing zeolite by preparing a filtered solid is not only an economical synthesis method capable of increasing reactor efficiency, but also an effective method of preparing a zeolite catalyst capable of improving catalyst performance and hydrothermal stability.

[Example 3: Synthesis of AEI Zeolite-Filtrated Solids]

The composition is 1.0 by mixing 45 g of excess water with 10 g of USY zeolite (Si/Al=15), a raw material for silica and alumina, 5.3 g of N , N -dimethyl-3,5-dimethylpiperidium hydroxide, and 1.7 g of NaOH, which are structural inducing materials. A _{synthetic mother liquor containing SiO 2} : 0.2 SDA: 0.25 NaOH: 15 H ₂ O was prepared. The synthetic mother liquor was aged at room temperature for 12 hours and then separated into 22 g of solid and 40 g of filtrate using a vacuum filtration device to reduce the amount of reactant to 1/3. The separated filtered solid was rotated at 160° C. at 40 rpm and subjected to hydrothermal reaction for 4 days. After the synthesis was completed, the generated zeolite was washed and dried at 90° C. for 12 hours or more, and the final weight of the zeolite was 4.4 g. For comparison, in Comparative Example 2, AEI zeolite was synthesized by hydrothermal reaction in the original state without removing water from the prepared synthetic mother liquor.

The catalyst in which Cu was ion-exchanged was prepared in the same manner as in Example 1, and hydrothermal treatment at 750°C was also performed in the same manner.

[Example 4: AEI zeolite synthesis-impregnated solids]

After dissolving 5.3 g of N , N -dimethyl-3,5-dimethylpiperidium hydroxide and 1.7 g of NaOH in 19 g of water, it was impregnated with 10 g of USY zeolite (Si/Al=15). For homogeneous mixing of the reactants, the reaction mixture was subjected to ultrasonic treatment at 40° C. for 1 hour and then aged at room temperature for 12 hours, and then rotated at 160° C. at 40 rpm for 4 days hydrothermal reaction. The zeolite weight obtained after washing and drying was 6.7 g. In the case of preparing the impregnated solid, the amount of water used could be reduced to 11 g, and since AEI having a uniform particle size is reproducibly generated without aging after sonication, the synthesis time can be shortened.

The catalyst in which Cu was ion-exchanged was prepared in the same manner as in Example 1, and hydrothermal treatment at 750°C was also performed in the same manner.

Table 3 summarizes the amount of reactant and product, and properties of the generated zeolite when synthesizing AEI zeolite through filtered solids and impregnated solids.

	Reactant (g)		Product (g)		Surface area (m 2 /g)	Pore volume (cm 3 /g)	Si/Al
	Silica	Total amount	Based on 10g silica	Based on 10 g of reactant
Comparative Example 2	10	62	5.2	0.8	584	0.28	10.6
Example 3	10	22	4.4	2.0	567	0.28	7.0
Example 4	10	36	6.7	1.9	601	0.30	11.5

9 shows the XRD pattern and nitrogen adsorption isotherms of AEI zeolite synthesized through Example 3, Example 4, and Comparative Example 2. Both Comparative Example 2 using an excess of water and Example 3 and Example 4, in which the amount of water was significantly reduced, showed an X-ray diffraction pattern of AEI as reported in the literature. In addition, AEI zeolite having a very large surface area and pore volume was synthesized due to the well-developed micropores.

10 shows an electron microscope (SEM) photograph of the AEI zeolite. All uniform cubic-shaped particles were obtained, but the size showed a large difference depending on the synthesis method. Comparative Example 2 in which a synthetic mother liquor was prepared using an excess of water and Example 3 in which the liquid phase was removed by filtration showed a particle size of about 1 to 1.5 μm, but Example 4 through an impregnated solid using a small amount of water was 0.2 to The particle size was greatly reduced to 0.5 μm. As a result of elemental analysis by EDX attached to the SEM, the Si/Al molar ratio was different depending on the synthesis method. In the case of Example 3 using the filtered solid material, the Si/Al molar ratio was 7.0, and the Al content was the highest, and in Example 4, the Si/Al molar ratio was 11.5, which was much higher in the silica content.

11 shows the XRD patterns before and after 750° C. hydrothermal treatment of the Cu/AEI catalyst synthesized through the present invention. Regardless of the catalyst preparation method, all Cu/AEI catalysts did not show a significant difference in the XRD diffraction pattern before and after 750°C hydrothermal treatment, indicating that structural collapse due to hydrothermal treatment did not proceed.

12 shows nitrogen adsorption isotherms before and after 750° C. hydrothermal treatment of the Cu/AEI catalyst. Unlike Comparative Example 2, in which the surface area slightly decreased due to a decrease in micropore after 750°C hydrothermal treatment, in the case of Examples 3 and 4, the surface area was rather increased, indicating that the hydrothermal stability of the catalyst prepared according to the present invention was improved.

Table 4 summarizes the properties before and after hydrothermal treatment of the Cu/AEI catalyst.

	Si/Al	Cu content (wt%)	Surface area (m 2 /g)		Pore volume (cm 3 /g)
			Before hydrothermal treatment	After hydrothermal treatment	Before hydrothermal treatment	After hydrothermal treatment
Comparative Example 2	10.6	1.8	601	535	0.30	0.28
Example 3	7.0	3.1	481	501	0.25	0.25
Example 4	11.5	2.7	556	571	0.29	0.30

13 shows the results of investigation of the SCR reaction activity before and after 750° C. hydrothermal treatment of the Cu/AEI catalyst. Even after hydrothermal treatment at 750°C, the catalytic activity was well maintained.In particular, the catalyst of Example 4 prepared from zeolite synthesized through impregnated solids, unlike other catalysts, showed 60% activity at a low temperature of 150°C even after hydrothermal treatment at 750°C. Hydrothermal stability was excellent enough to appear close.

[Example 5: AFX Zeolite Synthesis-Filtrated Solids]

In 45 g of excess water, 10 g of USY zeolite (Si/Al=15), a raw material for silica and alumina, 1,1′-(hexane-1,6-diyl)bis(1-methyl-pyrrolidin-1), a structure-inducing material -ium) hydroxide 9.6g and NaOH 1.7g were mixed to prepare a synthetic mother liquor having _{a composition of 1.0 SiO 2} : 0.2 SDA: 0.25 NaOH: 15 H _{2 O.} The synthetic mother liquor was aged at room temperature for 12 hours and then separated into 26 g of solid and 40 g of filtrate using a vacuum filtration device to reduce the amount of reactant to 1/3. The separated filtered solid was recovered, rotated at 170° C. at 60 rpm, and subjected to hydrothermal reaction for 4 days. The zeolite weight obtained after washing and drying was 3.1 g. For comparison, in Comparative Example 3, in 50 g of water, 10 g of USY zeolite (Si/Al=15) as a raw material for silica and alumina, and 1,1′-(hexane-1,6-diyl)bis(1-methyl) as a structural inducing material -pyrrolidin-1-ium) bromide 20.7g and NaOH 4.0g were mixed to _{synthesize a synthetic mother liquor having a composition of 1.0 SiO 2} : 0.3 SDA: 0.6 NaOH: 16.7 H ₂ O by hydrothermal reaction to synthesize AFX zeolite.

The catalyst in which Cu was ion-exchanged was prepared in the same manner as in Example 1, and hydrothermal treatment at 750°C was also performed in the same manner.

[Example 6: AFX zeolite synthesis-impregnated solids]

After dissolving 7.8 g of 1,1′-(pentane-1,5-diyl)bis(1-methyl-pyrrolidin-1-ium) hydroxide and 1.7 g of NaOH in 22 g of water, USY zeolite (Si/Al=15) Impregnated in 10 g. At this time, the composition of the reactant was 1.0 SiO ₂ : 0.17 SDA: 0.26 NaOH: 7.5 H ₂ O. For homogeneous mixing of the reactants, ultrasonic treatment was performed at 40° C. for 1 hour and then aged at room temperature for 12 hours, followed by hydrothermal reaction for 4 days while rotating at 170° C. at 60 rpm. After washing and drying, 4.5 g of AFX zeolite was recovered. In the case of impregnated solids, the amount of water used can be reduced to 11 g, and AFX having a uniform particle size was reproducibly generated without aging after sonication.

The catalyst in which Cu was ion-exchanged was prepared in the same manner as in Example 1, and hydrothermal treatment at 750°C was also performed in the same manner.

Table 5 summarizes the amount of reactants, the amount of the product, and the properties of the generated zeolite when synthesizing AFX zeolite through filtered solids and impregnated solids.

	Reactant (g)		Product (g)		Surface area (m 2 /g)	Pore volume (cm 3 /g)	Si/Al
	Silica	Total amount	Based on 10g silica	Based on 10 g of reactant
Comparative Example 3	10	85	2.9	0.3	598	0.29	4.8
Example 5	10	26	3.1	1.2	600	0.30	6.5
Example 6	10	42	4.5	1.1	599	0.31	7.8

14 shows the XRD patterns and nitrogen adsorption isotherms of the AFX zeolite synthesized through Examples 5 and 6 and Comparative Example 3. Regardless of the synthesis method, all showed the same X-ray diffraction pattern of AFX as reported in the literature. In addition, fine pores were well developed, resulting in AFX zeolite having a very large surface area and pore volume.

15 shows an electron microscope (SEM) picture of the AFX zeolite. There was a big difference in particle shape and size according to the synthesis method. In Comparative Example 3, hexagonal particles having a size of about 1.4 μm were obtained, Example 5 synthesized through filtered solids had an elliptical particle of 0.6 × 0.8 μm, and Example 6 synthesized through impregnated solids had an elliptical shape of 0.3 × 0.4 μm However, very small particles were produced. It is difficult to synthesize AFX zeolite having a high silica content with a Si/Al molar ratio of 5.0 or more by a general hydrothermal synthesis method, but in Example 5 of the present invention, the Si/Al molar ratio is 6.5, and in Example 6, the Si/Al molar ratio is 7.8. AFX with high content was synthesized.

16 shows the XRD patterns before and after the 750° C. hydrothermal treatment of the Cu/AFX catalyst. The catalyst prepared from Comparative Example 3 slightly decreased the intensity of the X-ray diffraction pattern after hydrothermal treatment, showing that part of the crystal structure was collapsed due to hydrothermal treatment. In contrast, the catalysts prepared from Examples 5 and 6 through the present invention did not show a significant difference in the XRD diffraction pattern even after hydrothermal treatment, so it can be seen that the crystal structure is well maintained.

Fig. 17 shows nitrogen adsorption isotherms before and after 750°C hydrothermal treatment of the Cu/AFX catalyst. In the case of the catalysts prepared from Examples 5 and 6, the surface area was rather increased after hydrothermal treatment at 750°C, whereas the catalyst of Comparative Example 3 prepared by the conventional hydrothermal synthesis method decreased the surface area by about 20%, and thus prepared according to the present invention. It shows that the hydrothermal stability of the catalyst is better.

Table 6 summarizes the properties before and after the hydrothermal treatment of the Cu/AFX catalyst.

	Si/Al	Cu content (wt%)	Surface area (m 2 /g)		Pore volume (cm 3 /g)
			Before hydrothermal treatment	After hydrothermal treatment	Before hydrothermal treatment	After hydrothermal treatment
Comparative Example 3	4.8	2.7	562	455	0.30	0.25
Example 5	6.5	3.9	520	535	0.29	0.29
Example 6	7.8	4.0	492	509	0.31	0.33

18 shows the results of investigation of the SCR reaction activity before and after 750° C. hydrothermal treatment of the Cu/AFX catalyst. Unlike Comparative Example 3, the catalysts prepared from Examples 5 and 6 showed a high NOx removal rate of 80% or more in a temperature range of 200 to 500°C both before and after hydrothermal treatment, showing that both reaction activity and hydrothermal stability were improved.

As described above, the present invention has been illustrated and described with reference to preferred embodiments, but is not limited to the above-described embodiments, and within the scope of the spirit of the present invention, those of ordinary skill in the art to which the present invention pertains. Various changes and modifications will be possible.

The present invention can be used industrially to prepare a zeolite catalyst.

Claims (7)

1. Dissolving a zeolite precursor, a structure-inducing material, and a complexing material in water to prepare a synthetic mother liquor;

   Filtering the synthetic mother liquor to obtain a filtered solid from which water has been removed; And

   A method for synthesizing zeolite comprising: synthesizing zeolite by hydrothermal reaction of the filtered solid material.
2. The method of claim 1,

   Zeolite synthesis method, characterized in that the water content of the filtered solid is less than 50%.
3. The method of claim 1,

   The hydrothermal reaction is carried out by placing the filtered solid in a sealed high-pressure cooker and rotating at a temperature of 50 to 200°C at 0 to 60 rpm.
4. The method of claim 1,

   The zeolite precursor is a synthetic or natural zeolite of USY, FAU or BEA type, kaolin or fly ash in solid form, sodium silicate in liquid state, coroidal silica, fumed silica or tetraortho silicate Zeolite synthesis method, characterized in that produced by mixing sodium aluminate, aluminum oxide or aluminum alkoxide.
5. The method of claim 1,

   The zeolite synthesis method, characterized in that the water filtered from the synthetic mother liquor is reused for the next preparation of the synthetic mother liquor.
6. The method of claim 1

   The structure-inducing material is a zeolite synthesis method, characterized in that the organic compound containing quaternary ammonium ions.
7. A zeolite catalyst manufacturing method for preparing a zeolite catalyst by ion-exchanging or impregnating hydrogen, alkali metal, alkaline earth metal, transition metal, and noble metal in the zeolite synthesized by the method of any one of claims 1 to 6.

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