JP6879680B2 - Method for producing high silica chabazite type zeolite and high silica chabazite type zeolite - Google Patents

Description

The present invention relates to a method for producing a chabazite-type zeolite having a high Cavan ratio (hereinafter, also referred to as a high silica chabazite-type zeolite) and a chabazite-type zeolite having a high Cavan ratio.

Zeolites have a variety of compositions and structures. The structure of zeolite is classified by the structure code using three letters of the alphabet at the International Zeolite Society. The chabazite-type zeolite in the present invention has a structure classified as CHA by a structural code.

Chabazite-type zeolite is used for gas separation, reduction of nitrogen oxides contained in automobile exhaust gas, conversion of lower alcohols and other oxygen-containing hydrocarbons to liquid fuels, and catalysts for the production of dimethylamine. It can be used (Patent Document 1).

When chabazite-type zeolite is used as a catalyst for reducing nitrogen oxides contained in automobile exhaust gas, there is a problem (water heat resistance) that the crystal structure of chabazite-type zeolite is destroyed by the moisture contained in the exhaust gas. is there. In order to solve the above problems, _{chabazite-type zeolite having a high Cavan ratio (SiO 2} / Al ₂ O ₃ molar ratio) is required (Patent Document 2).

In addition, chabazite-type zeolite is generally synthesized using an organic structure-determining agent (Structure-directing agent: SDA). The synthetic method using an organic structure defining agent has a large environmental load and is high in cost. Therefore, a method for synthesizing chabazite-type zeolite without using an organic structure-regulating agent has been widely studied (Patent Document 2).

However, it has been difficult to obtain a chabazite-type zeolite having a high Cavan ratio by the method for synthesizing a chabazite-type zeolite without using an organic structure-regulating agent.

It is widely known that faujasite-type zeolite and the like have a high Cavan ratio when acid-treated (Patent Document 3). However, when the chabazite-type zeolite is acid-treated, there is a problem that the crystal structure is destroyed although the Cavan ratio is increased.

U.S. Pat. No. 6,709,644 JP 2015-101506 Japanese Unexamined Patent Publication No. 09-20601

A chabazite-type zeolite having a high Cavan ratio and high crystallinity can be synthesized without using an organic structure-regulating agent.

The above problems can be solved by acid-treating the chabazite-type zeolite having the following characteristics (a) and (b).
(A) Cavan ratio (SiO ₂ / Al ₂ O ₃ molar ratio) is 6.5 or more (b) Relative crystallinity is 100% or more

A chabazite-type zeolite having a high Cavan ratio and crystallinity (also referred to as relative crystallinity in the present invention) can be obtained without using an organic structure defining agent.

5 is an X-ray diffraction pattern in Example 1 and Comparative Example 1. It is an SEM image (magnification 30,000 times) in Example 1. It is an SEM image (magnification 30,000 times) in Comparative Example 1. It is a scatter diagram of the Cavan ratio (X-axis) and the relative crystallinity (Y-axis) of the high silica chabazite type zeolite in Examples and Comparative Examples.

The method for producing the high silica chabazite type zeolite of the present invention will be described below.

The method for producing a high silica chabazite type zeolite of the present invention (hereinafter, also referred to as the production method of the present invention) includes the following steps 1 and 2.
1. 1. Step of preparing chabazite type zeolite 2. A step of contacting a chabazite-type zeolite with an acid solution to obtain a high-silica chabazite-type zeolite (hereinafter, also referred to as an acid treatment step).

[Chavazite type zeolite]
The Cavan ratio of the chabazite-type zeolite used in the production method of the present invention is 6.5 or more. In the present invention, the Cavan ratio is calculated from the following formula.
Keiban ratio [-] = SiO ₂ [mоl] / Al ₂ O ₃ [mоl]
The Cavan ratio of the chabazite-type zeolite is preferably in the following range. If the Cavan ratio is too low, the crystallinity is lowered in the acid treatment, which is not preferable. Further, it is difficult to synthesize a chabazite-type zeolite having an excessively high Cavan ratio without using an organic structure-regulating agent, which is not preferable.
<Preferable Chabazite Zeolite Keiban Ratio>
Kayban ratio = 7-12

The relative crystallinity of the chabazite-type zeolite used in the production method of the present invention is 100% or more. The relative crystallinity of the present invention is the chabazite-type zeolite (R1) synthesized based on the Chabazite synthesis method described on the website of the International Zeolite Society (http://www.iza-online.org/synthesis/). It is obtained from the X-ray diffraction pattern of the chabazite-type zeolite used in the production method of the present invention. Specifically, in each X-ray diffraction pattern, the total value of the heights of the peaks attributed to the Miller indexes (100), (20-1), and (3-1-1) is used, and the following formula is used. The relative crystallinity is obtained.
Relative crystallinity [%] = H / H _R1 x 100
H: Total H height above the peak of chabazite-type zeolite for use in the production method of the present invention _R1: chabazite-type zeolite synthesized based on the method of synthesizing Chabazite described in HP of the International Zeolite Association of (R1) The sum of the heights of each of the above peaks

The relative crystallinity of the chabazite-type zeolite used in the production method of the present invention is preferably in the following range. If the relative crystallinity is too low, the relative crystallinity of the high silica chabazite type zeolite obtained in the acid treatment step is also low, which is not preferable. Chabazite-type zeolite having a relative crystallinity of more than 150% is difficult to synthesize.
<Preferable relative crystallinity of chabazite-type zeolite>
Relative crystallinity = 120-150 [%]

Further, the X-ray diffraction patterns are (100), (200), (20-1), (21-1), (211), (3-1-1), (310), (3-1-2). ), It can be judged that it is a chabazite type zeolite when it has all the peaks attributed to the Miller index.

The content of K in the chabazite-type zeolite for use in the production method of the present invention is preferably in K ₂ O in terms in the following ranges. If the K content is not in the following range, the crystallinity may decrease in the acid treatment, which is not preferable. In the present invention, the K content is measured by the same method as in Examples described later.
<K content of preferable chabazite type zeolite>
K ₂ O = 9.7 to 15.27 [mass%]

The chabazite-type zeolite used in the production method of the present invention contains Si and Al. The contents of Si and Al of the chabazite-type zeolite used in the production method of the present invention are preferably in the following ranges in _{terms of oxides (Si is converted to SiO 2} and Al is converted to Al ₂ O _3).
SiO ₂ = 67.2-79.6 [mass%]
Al ₂ O ₃ = 10.1 to 17.5 [mass%]
The Si and Al contents of the chabazite-type zeolite used in the production method of the present invention are measured by the same method as the K content.

The chabazite-type zeolite used in the production method of the present invention preferably contains substantially no P in its crystal structure. Therefore, it is preferable that SAPO-34, which is one of the chabazite-type zeolites containing P in the crystal structure, is not contained in the chabazite-type zeolite used in the production method of the present invention. In addition, P contained in a synthetic raw material or the like may remain in the chabazite-type zeolite used in the production method of the present invention. In such a case, if the content is about 1000 ppm or less, it can be understood that the content is substantially not contained. The P content of the chabazite-type zeolite used in the production method of the present invention is measured by the same method as the K content.

The specific surface area of the chabazite-type zeolite used in the production method of the present invention is preferably in the following range. If the specific surface area is too low, the activity and the like will decrease when used as a catalyst and the like, which is not preferable. Chabazite-type zeolite having a specific surface area ^{of more than 600 m 2} / g is difficult to synthesize. The specific surface area is measured by the same method as in Examples described later.
<Specific surface area of preferable chabazite type zeolite>
Specific surface area = 350-600 [m ² / g]

The average particle size of the chabazite-type zeolite used in the production method of the present invention is preferably in the following range . Average particle size is measured by the same method as in Example to be described later.
<Preferable average particle size of chabazite zeolite>
Average particle size = 0.1 to 1.2 [μm]

The chabazite-type zeolite used in the production method of the present invention is preferably synthesized without using an organic structure-determining agent. When the organic structure defining agent is not used, the environmental load and cost can be reduced. As a synthetic method that does not use an organic structure defining agent, for example, a conventionally known method such as Patent Document 2 can be used. Even a chabazite-type zeolite synthesized using an organic structure-determining agent is considered to exert the effect of the present invention as long as it is a production method satisfying the constitution of the present invention.
Here, examples of the organic structure defining agent include quaternary ammonium salts such as TEAH (tetraethylammonium hydroxide) and organic amines.

[Acid treatment process]
The acid treatment step in the production method of the present invention is a step of bringing the chabazite-type zeolite into contact with the acid solution. When the chabazite-type zeolite precipitates or aggregates in the acid solution, it is preferable to maintain the state in which the chabazite-type zeolite is dispersed in the acid solution by performing stirring, sonication, or the like.

The acid solution used in the acid treatment step contains water and an acid. As the acid, an inorganic acid or an organic acid can be used, but it is preferable to use an inorganic acid. Further, sulfuric acid is preferable. The acid concentration is preferably in the following range. If the acid concentration is too low, Al is less likely to be desorbed in the acid treatment step, which is not preferable. Further, if the acid concentration is too high, the relative crystallinity of the high silica chabazite type zeolite obtained in the acid treatment step is lowered, which is not preferable.
<Preferable acid concentration>
Acid concentration = 1.0 to 4.0% by mass

The pH of the acid solution used in the acid treatment step is preferably in the following range. If the pH of the acid solution is too high, Al is difficult to be desorbed in the acid treatment step, which is not preferable.
<Preferable acid solution pH>
Acid solution pH = 1.5-3.0

The treatment temperature in the acid treatment step of the present invention is preferably in the following range. The treatment temperature in the acid treatment step of the present invention is the temperature of the acid solution. If the treatment temperature is too high, the relative crystallinity of the high silica chabazite type zeolite obtained in the acid treatment step decreases, which is not preferable.
<Preferable processing temperature>
Processing temperature = 20-98 ° C

The high silica chabazite type zeolite of the present invention will be described below.
The high silica chabazite type zeolite of the present invention can be produced by the above-mentioned production method of the present invention.

[High silica chabazite type zeolite]
The Cavan ratio of the high silica chabazite type zeolite of the present invention is 7.5 or more. The Cavan ratio of the high silica chabazite type zeolite of the present invention is preferably in the following range. If the Cavan ratio is too low, the water heat resistance deteriorates, which is not preferable. Conventionally, it has been difficult to synthesize a high silica chabazite type zeolite having a high Cavan ratio without using an organic structure defining agent (SDA), but the present inventor has stated that it can be produced by the above-mentioned production method of the present invention. Found.
<Cayban ratio of preferable high silica chabazite type zeolite>
Cavan ratio = 7.5-12

The relative crystallinity of the high silica chabazite type zeolite of the present invention is 105% or more. The relative crystallinity of the high silica chabazite type zeolite of the present invention is preferably in the following range. If the relative crystallinity is too low, the catalytic activity will be low when used as a catalyst, which is not preferable. Further, when Cu is supported on _{the high silica chabazite type zeolite of the present invention to synthesize the high silica chabazite type zeolite for the NH 3-} SCR reaction described later, the crystal structure is easily destroyed, which is not preferable.
<Preferable relative crystallinity of high silica chabazite type zeolite>
Relative crystallinity = 105-150 [%]

The content of K in the high-silica chabazite-type zeolite of the present invention may be from 7.0 to 11.6% by mass K ₂ O conversion. This is derived from the chabazite-type zeolite before the acid treatment, but may be removed by ion exchange or the like if necessary.

The high silica chabazite type zeolite of the present invention contains Si and Al. The Si and Al contents of the high silica chabazite type zeolite of the present invention are preferably in the following range in _{terms of oxides (Si is converted to SiO 2} and Al is converted to Al ₂ O _3).
SiO ₂ = 71.1-81.9 [mass%]
Al ₂ O ₃ = 10.9 to 17.0 [mass%]
The Si and Al contents of the high silica chabazite type zeolite of the present invention are measured by the same method as the above-mentioned K content.

It is preferable that the high silica chabazite type zeolite of the present invention contains substantially no P in its crystal structure. Therefore, it is preferable that SAPO-34, which is one of the chabazite-type zeolites containing P in the crystal structure, is not contained in the high-silica chabazite-type zeolite of the present invention. In addition, P contained in the synthetic raw material or the like may remain in the high silica chabazite type zeolite of the present invention. In such a case, if the content is about 1000 ppm or less, it can be understood that the content is substantially not contained. The P content of the high silica chabazite type zeolite of the present invention is measured by the same method as the above-mentioned K content.

The specific surface area of the high silica chabazite type zeolite of the present invention is preferably in the following range. If the specific surface area is too low, the catalytic activity will be low, which is not preferable. High silica chabazite type zeolite having a specific surface area of more ^{than 600 m 2} / g is difficult to synthesize.
<Specific surface area of preferable high silica chabazite type zeolite>
Specific surface area = 350-600 [m ² / g]

The high silica chabazite type zeolite of the present invention has a relative crystallinity of 100% or more after being treated at 700 ° C. for 3 hours while adding _{H 2 O at a rate of 1 ml / min in an air atmosphere.} This indicates that the high silica chabazite type zeolite of the present invention can maintain its crystal structure even in a high temperature and high humidity environment. The high silica chabazite type zeolite of the present invention preferably has a relative crystallinity in the following range after being treated at 700 ° C. for 3 hours while adding _{H 2 O at a rate of 1 ml / min in an air atmosphere.} .. If this is lower than 100%, it is not preferable to use the high silica chabazite type zeolite of the present invention under high temperature and high humidity because the crystal structure of the zeolite cannot be effectively used. Further, the high silica chabazite type zeolite of the present invention in which this exceeds 150% is difficult to synthesize.
<Preferable relative crystallinity of high silica chabazite type zeolite (after treatment at 700 ° C. for 3 hours while adding _{H 2 O at a rate of 1 ml / min in an air atmosphere)>}
100-150 [%]

[High silica chabazite type zeolite for _{NH 3-SCR reaction]}
The high silica chabazite type zeolite of the present invention exhibits catalytic activity in the _{NH 3-SCR reaction when supporting Cu.} Hereinafter, _{the high silica chabazite type zeolite for NH 3-} SCR reaction will be described in detail.

The high silica chabazite type zeolite for _{NH 3-} SCR reaction of the present invention contains Cu. The amount of Cu supported is preferably in the following range with respect to the high silica chabazite type zeolite of the present invention as a base. If the amount of Cu supported is too small, the NH _3- SCR activity is lowered, which is not preferable. Further, if the amount of Cu supported is too large, the durability is lowered, which is not preferable. In particular, when used in a water vapor atmosphere at a high temperature, the crystal structure is liable to be destroyed.
<Preferable Cu loading amount>
Cu loading amount = 2 to 10% by mass

The composition of the high-silica chabazite-type zeolite for NH ₃ -SCR reaction of the present invention preferably contains 0 to 0.2% by weight of K in K ₂ O conversion. The high-silica chabazite-type zeolite for _{NH 3-} SCR reaction having a composition in the following range _{has more excellent NH 3-} SCR activity and better water heat resistance when used as a catalyst. If the content of K is too large, it becomes difficult for Cu to exchange ions with the high silica chabazite type zeolite, which is not preferable.
<Composition of high silica chabazite type zeolite for preferable NH _{3-SCR reaction>}
K ₂ O = 0 to 0.099 [mass%]

The Cavan ratio of the high silica chabazite type zeolite for _{the NH 3-} SCR reaction of the present invention is 7.5 or more. The Cavan ratio of the high silica chabazite type zeolite for _{the NH 3-} SCR reaction of the present invention is preferably in the following range. NH ₃ high-silica chabazite-type zeolite for -SCR reaction silica-alumina ratio is in the range below, together with the NH ₃ -SCR reaction increases, hydrothermal resistance is increased.
<Cayban ratio of high silica chabazite type zeolite for preferable NH _{3-SCR reaction>}
Kayban ratio = 8 to 9.9

The high silica chabazite type zeolite for _{NH 3-} SCR reaction of the present invention contains Si and Al. The Si and Al contents of the high silica chabazite type zeolite for _{the NH 3-} SCR reaction of the present invention _{are in the following range in terms of oxides (Si is converted to SiO 2} and Al is converted to Al ₂ O ₃ ). Is preferable.
SiO ₂ = 73.3 to 86.9% by mass
Al ₂ O ₃ = 10.1 to 18.1% by mass
The Si and Al contents of the high silica chabazite type zeolite for _{the NH 3-} SCR reaction of the present invention are measured by the same method as the above-mentioned K content.

It is preferable that the high silica chabazite type zeolite for _{the NH 3-} SCR reaction of the present invention contains substantially no P in its crystal structure. Therefore, it is preferable that SAPO-34, which is one of the chabazite-type zeolites containing P in the crystal structure, is not contained in the high-silica chabazite-type zeolite for the _{NH 3-SCR reaction of the present invention.} In addition, P contained in the synthetic raw material or the like may remain in the high silica chabazite type zeolite for the _{NH 3-SCR reaction of the present invention.} In such a case, if the content is about 1000 ppm or less, it can be understood that the content is substantially not contained. _{The P content of the high silica chabazite type zeolite for the NH 3-} SCR reaction of the present invention is measured by the same method as the above-mentioned K content.

The relative crystallinity of the high silica chabazite type zeolite for _{the NH 3-} SCR reaction of the present invention is 100% or more. The relative crystallinity of the high silica chabazite type zeolite for _{the NH 3-} SCR reaction of the present invention is preferably in the following range. If the relative crystallinity is high, the NH _3- SCR activity increases, but it is difficult to synthesize the high silica chabazite type zeolite for the _{NH 3-} SCR reaction of the present invention in which the relative crystallinity is larger than the following range.
<Relative crystallinity of high silica chabazite type zeolite for preferable NH _{3-SCR reaction>}
Relative crystallinity = 140-180%

The specific surface area of the high silica chabazite type zeolite for _{the NH 3-} SCR reaction of the present invention is preferably in the following range. If the specific surface area is too low, the NH _3- SCR activity will be low, which is not preferable. The high silica chabazite type zeolite for the _{NH 3-} SCR reaction of the present invention having a specific surface area ^{larger than 600 m 2 / g is difficult to synthesize.}
<Preferable specific surface area of high silica chabazite type zeolite for _{NH 3-SCR reaction of the present invention>}
Specific surface area = 350-600 [m ² / g]

The outer surface area of the high silica chabazite type zeolite for _{the NH 3-} SCR reaction of the present invention ^{is preferably 22 m 2} / g or more. _{The high silica chabazite type zeolite for the NH 3-} SCR reaction of the present invention having a large outer surface area is preferable because the access between the pores and the interface of the zeolite is increased, so that the NH _3- SCR activity is high. Further, when carrying Cu, it is preferable because it is easily diffused into the pores of the zeolite. _{The high silica chabazite type zeolite for the NH 3-} SCR reaction of the present invention is more preferably in the following range. It is difficult to synthesize a high silica chabazite type zeolite for the _{NH 3-} SCR reaction of the present invention having an outer surface area ^{larger than 40 m 2 / g.}
<Outer surface area of high silica chabazite type zeolite for more preferable NH _{3-SCR reaction>}
External surface area = 22-40 m ² / g

The ratio of the specific surface area to the outer surface area (specific surface area / outer surface area) of the high silica chabazite type zeolite for _{the NH 3-} SCR reaction of the present invention is preferably in the following range. The high-silica chabazite-type zeolite for the _{NH 3-} SCR reaction of the present invention in which the ratio of the specific surface area to the outer surface area is in the following range has a _{high NH 3-} SCR reaction activity.
(Specific surface area / outer surface area) = 10 to 18.5

The average particle size of the high silica chabazite type zeolite for _{the NH 3-} SCR reaction of the present invention is preferably in the following range. If the average particle size is too small, the relative crystallinity tends to be low, which is not preferable. On the other hand, if the average particle size is too large, the above-mentioned outer surface area tends to decrease, which is not preferable.
<Preferable average particle size of chabazite zeolite>
Average particle size = 0.5-5 [μm]

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[Synthesis of chabazite-type zeolite (1)]

0.168 kg of sodium aluminate aqueous solution containing 22% by mass of Al as an Al ₂ O ₃ equivalent concentration and 17% by mass of Na as a Na ₂ O equivalent concentration was reduced to 1.35 kg of a sodium hydroxide aqueous solution having a NaOH concentration of 21.65% by mass. It was added with stirring to dissolve, and cooled to 30 ° C. While stirring this solution, it was added to 1.361 kg of a sodium silicate aqueous solution containing _{24% by mass of Si as a SiO 2} equivalent concentration and 7.7% by mass of Na as a Na _{2 O equivalent concentration.} The composition of the solution at this time is the oxide molar ratio.
Na ₂ O / Al ₂ O ₃ = 16
SiO ₂ / Al ₂ O ₃ = 15
H ₂ O / Al ₂ O ₃ = 330
Met. Then, this solution was allowed to stand at 30 ° C. for 15 hours to prepare an aluminosilicate solution.

A silica sol containing 5.66 kg of water and 30% by mass of _{SiO 2 in} 22.78 kg of an aqueous sodium silicate solution containing 24% by mass of Si as a SiO ₂ concentration and 7.7% by mass of Na as a Na _{2 O equivalent.} Chemicals: Catalyst SI-30: average particle size 10 nm) 18.97 kg and 2.88 kg of the aluminosilicate solution were added and mixed by stirring. To this, 10.03 kg of an aqueous sodium aluminate solution containing 22% by mass of Al as an Al ₂ O ₃ equivalent concentration and 17% by mass of Na as a Na ₂ O equivalent concentration was added, and the mixture was aged with stirring at room temperature for 3 hours to obtain a mixed hydrogel slurry. Was prepared. The composition of the mixed hydrogel slurry at this time is the oxide molar ratio.
Na ₂ O / Al ₂ O ₃ = 2.80
SiO ₂ / Al ₂ O ₃ = 8.70
H ₂ O / Al ₂ O ₃ = 108
Met.

60.3 kg of the mixed hydrogel slurry was hydrothermally treated in a crystallization tank at 95 ° C. for 35 hours. Then, it cooled to 70 degreeC and filtered to obtain 29.5 kg of Na-Y type zeolite cake. The obtained Na-Y-type zeolite cake was further washed, filtered, and dried to prepare Na-Y-type zeolite.

An aqueous solution containing 500 g of Na-Y-type zeolite and 280 g of ammonium sulfate was heated to 80 ° C. and ion-exchanged for 2 hours with stirring, filtered, washed, dried and fired at 550 ° C. for 5 hours. Furthermore, the operations of ion exchange, filtration, washing, and drying were performed twice under the above conditions, _{and 0.95 (NH 4} ) ₂ O · 0.05 Na ₂ O · Al ₂ O ₃ · _{with an NH 4} ion exchange rate of 95%. A 5SiO ₂ zeolite ( _{also referred to as NH 4 (95)} Y-type zeolite) was prepared.

Then, _{water was added to NH 4 (95)} Y-type zeolite to adjust the water content so as to contain 50% by mass of water. A container was filled with a moisture-adjusted NH _{4 (95)} Y-type zeolite, the temperature was raised to 600 ° C., and steam treatment was performed for 2 hours to prepare a hyperstable faujasite-type zeolite.

To 500 g of this hyperstable faujasite-type zeolite, 495 g of sulfuric acid having a concentration of 25% by mass was added dropwise over 0.5 hours to perform a dealumination treatment to prepare a faujasite-type zeolite having a Cavan ratio of 9.0.

A faujasite-type zeolite slurry having a concentration of 20% by mass of the faujasite-type zeolite was prepared and subjected to a miniaturization treatment with a bead mill (manufactured by Ashizawa Finetech Co., Ltd .: LMZ015). The miniaturization conditions at this time were 0.5 mm for zirconia beads, a peripheral speed of 10 m / s, and the bead filling amount was 85% in terms of volume. 95 g of the finely divided faujasite type zeolite type slurry and 60 g of water were mixed, and then 5.5 g of KOH having a KOH concentration of 95.5% by mass was mixed to prepare a synthetic slurry. The synthetic slurry was hydrothermally treated at 150 ° C. for 48 hours. Then, the synthetic slurry subjected to hydrothermal treatment was taken out, filtered, washed, and dried to prepare a chabazite type zeolite (1).

[Measurement method of Cavan ratio]
The contents of Si, Al, and K of the chabazite-type zeolite (1) obtained by the above method were measured under the following conditions. Each composition was calculated as mass% in terms of oxide. Further, the calculated _{composition of SiO 2} and Al ₂ O ₃ was converted into a molar ratio to calculate the Cavan ratio (SiO ₂ / Al ₂ O ₃ ). The results are shown in the columns of Examples 1 to 4 in Table 1.
<Measurement of Si, Al, K content>
Measurement method: ICP emission spectrometer: ICP730-ES (manufactured by VARIAN Co., Ltd.)
Sample dissolution: Acid dissolution

[Measurement method of relative crystallinity]
The synthesis was carried out based on the Chabazite synthesis method described on the website of the International Zeolite Society (http://www.iza-online.org/synthesis/). Specifically, 25.0 g of HY-type zeolite having a Cavan ratio of 5.2 was added to a solution obtained by mixing 26.8 ml of 198.2 ml of ion-exchanged water and 45% by mass of KOH solution, and the mixture was stirred for 30 seconds. This slurry was crystallized at 95 ° C. for 96 hours. The obtained slurry was washed twice with 500 ml of water and then dried to obtain a chabazite-type zeolite (R1).

The chabazite-type zeolite (1) and the chabazite-type zeolite (R1) obtained by the above method were subjected to X-ray diffraction measurement under the following conditions.
<X-ray diffraction measurement conditions>
Equipment: MiniFlex (manufactured by Rigaku Co., Ltd.)
Operation axis: 2θ / θ
Source: CuKα
Measurement method: Continuous voltage: 40 kV
Current: 15mA
Start angle: 2θ = 5 °
End angle: 2θ = 50 °
Sampling width: 0.020 °
Scan speed: 10.000 ° / min

From the X-ray diffraction pattern obtained by the above X-ray diffraction measurement, the total value of the heights of the peaks belonging to the Miller indexes (100), (20-1), and (3-1-1) was obtained. The relative crystallinity was calculated by the following formula. The results are shown in the columns of Examples 1 to 4 in Table 1.
Relative crystallinity [%] = H / H _R1 x 100
H: The above total height of each peak of chabazite-type zeolite (1) H _R1: The above sum of the peak heights of the chabazite-type zeolite (R1)

[Method of measuring specific surface area]
An aqueous solution containing 10 g of chabazite-type zeolite (1) and 5 g of ammonium sulfate was heated to 60 ° C., ion-exchanged for 1 hour with stirring, and then filtered and washed. This operation was performed twice. The specific surface area of the chabazite-type zeolite obtained by the above method was measured under the following conditions. The results are shown in the columns of Examples 1 to 4 in Table 1.
<Specific surface area measurement conditions>
Equipment BELSORP-miniII (manufactured by Microtrack Bell Co., Ltd.)
Method BET multi-point method Pretreatment 300 ° C-60min After firing in an electric furnace, 300 ° C-2hr vacuum firing Sample mass approx. 0.05 g
Specifically, a sample is taken in a measurement cell, the above pretreatment is performed, and an adsorption isotherm _{with N 2 gas is obtained using a pore distribution measuring device.} From the adsorption isotherm, the amount of monolayer adsorption is determined from the intercept and slope when connecting points that become more straight in the range of relative pressure of 0.05 to 0.35 by the BET analysis method. The specific surface area is calculated from the adsorbed amount by the BET formula.

[Measurement method of average particle size]
The average particle size was measured from scanning electron micrographs (SEMs) of chabazite zeolite. Specifically, the largest diameter was measured for one chabazite-type zeolite particle in the image. Ten particles were measured by this method, and the average value was taken as the average particle diameter. The results are shown in Table 1.

[Synthesis of chabazite-type zeolite (2)]
0.168 kg of sodium aluminate aqueous solution containing 22% by mass of Al in _{terms of Al 2} O _{3 and 17% by mass of Na in terms of Na 2} O, and 1.35 kg of sodium hydroxide aqueous solution containing 21.65% by mass of NaOH. Was added with stirring to dissolve, and cooled to 30 ° C. While stirring this solution, 1.361 kg of a sodium silicate aqueous solution containing 24% by mass of _{Si in terms of SiO 2 and 7.7% by mass of Na in terms of Na 2 O was added.} The composition of the solution at this time is the oxide molar ratio.
Na ₂ O / Al ₂ O ₃ = 16
SiO ₂ / Al ₂ O ₃ = 15
H ₂ O / Al ₂ O ₃ = 330
Met. Then, this solution was allowed to stand at 30 ° C. for 15 hours to prepare an aluminosilicate solution.

A sodium silicate aqueous solution containing 24% by mass of Si as a SiO ₂ equivalent concentration and 7.7% by mass of Na as a Na ₂ O equivalent concentration, 5.66 kg of water and _{30% by mass of SiO 2} concentration silica sol (JGC Catalysts and Chemicals). Manufacture: Catalyst SI-30: average particle size 10 nm) 18.97 kg and 2.88 kg of the aluminosilicate solution were added and mixed by stirring. To this, 10.03 kg of an aqueous sodium aluminate solution containing 22% by mass of Al as an Al ₂ O ₃ equivalent concentration and 17% by mass of Na as a Na ₂ O equivalent concentration was added, and the mixture was aged with stirring at room temperature for 3 hours to obtain a mixed hydrogel slurry. Was prepared. At this time, the composition of the mixed hydrogel slurry is based on the oxide molar ratio.
Na ₂ O / Al ₂ O ₃ = 2.80
SiO ₂ / Al ₂ O ₃ = 8.70
H ₂ O / Al ₂ O ₃ = 108
Met.

60.3 kg of the mixed hydrogel slurry was hydrothermally treated in a crystallization tank at 95 ° C. for 35 hours. Then, it cooled to 70 degreeC and filtered to obtain 29.5 kg of Na-Y type zeolite cake. The obtained Na-Y-type zeolite cake was further washed, filtered, and dried to prepare Na-Y-type zeolite.

An aqueous solution containing 500 g of Na-Y-type zeolite and 280 g of ammonium sulfate was heated to 80 ° C. and ion-exchanged for 2 hours with stirring, filtered, washed, dried and fired at 550 ° C. for 5 hours. Furthermore, the operations of ion exchange, filtration, washing, and drying were performed twice under the above conditions, _{and 0.95 (NH 4} ) ₂ O · 0.05 Na ₂ O · Al ₂ O ₃ · _{with an NH 4} ion exchange rate of 95%. A 5SiO ₂ zeolite was prepared. Then, it was calcined at 550 ° C. for 5 hours to prepare a faujasite type zeolite.

20 g of this faujasite-type zeolite was dispersed in 80 g of water, and then 6.5 g of KOH having a KOH concentration of 95.5% by mass was mixed to prepare a synthetic slurry. The synthetic slurry was hydrothermally treated at 95 ° C. for 48 hours. Then, the synthetic slurry was taken out, filtered, washed, and dried to prepare a chabazite type zeolite (2). For this chabazite-type zeolite (2), the Cavan ratio, relative crystallinity, specific surface area, and average particle size were measured by the same method as for the chabazite-type zeolite (1). The results are shown in the columns of Comparative Examples 1 to 6 in Table 1.

[Example 1]
10 g of chabazite-type zeolite (1) was brought into contact with an acid solution having a sulfuric acid concentration of 1.45% by mass, and the mixture was kept stirred at 95 ° C. for 1 hour. After the retention was completed, it was filtered, washed and dried to obtain a high silica chabazite type zeolite.

For the obtained high silica chabazite type zeolite, the Cavan ratio, relative crystallinity (%), composition, and specific surface area were measured by using the above-mentioned method. The results are shown in Table 1. The X-ray diffraction pattern is shown in FIG. Further, an SEM image is shown in FIG.

The obtained high silica chabazite type zeolite was evaluated for water heat resistance using the following method.

[Evaluation method of water and heat resistance]
The obtained high silica chabazite type zeolite was steam-treated at a high temperature under the following conditions. The results are shown in Table 2.
<Steam treatment conditions>
Equipment: Ring furnace Temperature: 700 ℃
Time: 3 hours Gas: _{Add H 2} O to the annular furnace at a rate of 1 ml / min in an air atmosphere. For the high silica chabazite type zeolite after steam treatment, measure the relative crystallinity (%) by the method described above. did.

[Example 2]
A high silica chabazite type zeolite was obtained in the same manner as in Example 1 except that the sulfuric acid concentration was 1.65% by mass. The results of measuring the high silica chabazite type zeolite by the same method as in Example 1 are shown in Tables 1 and 2, respectively.

[Example 3]
A high silica chabazite type zeolite was obtained in the same manner as in Example 1 except that the sulfuric acid concentration was 2.59% by mass. The results of measuring the high silica chabazite type zeolite by the same method as in Example 1 are shown in Tables 1 and 2, respectively.

[Example 4]
A high silica chabazite type zeolite was obtained in the same manner as in Example 1 except that the sulfuric acid concentration was 2.93% by mass. The results of measuring the high silica chabazite type zeolite by the same method as in Example 1 are shown in Tables 1 and 2, respectively.

[Comparative Example 1]
10 g of chabazite-type zeolite (2) was brought into contact with an acid solution having a sulfuric acid concentration of 1.74% by mass, and the mixture was kept stirred at 95 ° C. for 1 hour. After the retention was completed, it was filtered, washed and dried to obtain a high silica chabazite type zeolite. The results of measuring the high silica chabazite type zeolite by the same method as in Example 1 are shown in Tables 1 and 2, respectively. The X-ray diffraction pattern is shown in FIG. Further, an SEM image is shown in FIG.

[Comparative Example 2]
A high silica chabazite type zeolite was obtained in the same manner as in Comparative Example 1 except that the sulfuric acid concentration was 2.58% by mass. The results of measuring the high silica chabazite type zeolite by the same method as in Example 1 are shown in Tables 1 and 2, respectively.

[Comparative Example 3]
A high silica chabazite type zeolite was obtained in the same manner as in Comparative Example 1 except that the sulfuric acid concentration was 3.15% by mass. The results of measuring the high silica chabazite type zeolite by the same method as in Example 1 are shown in Tables 1 and 2, respectively.

[Comparative Example 4]
A high silica chabazite type zeolite was obtained in the same manner as in Comparative Example 1 except that the sulfuric acid concentration was 3.55% by mass. The results of measuring the high silica chabazite type zeolite by the same method as in Example 1 are shown in Tables 1 and 2, respectively.

[Comparative Example 5]
A high silica chabazite type zeolite was obtained in the same manner as in Comparative Example 1 except that the sulfuric acid concentration was 3.86% by mass. The results of measuring the high silica chabazite type zeolite by the same method as in Example 1 are shown in Tables 1 and 2, respectively.

[Comparative Example 6]
A high silica chabazite type zeolite was obtained in the same manner as in Comparative Example 1 except that the sulfuric acid concentration was 4.10% by mass. The results of measuring the high silica chabazite type zeolite by the same method as in Example 1 are shown in Tables 1 and 2, respectively.

For Examples 1 to 4 and Comparative Examples 1 to 6, scatter plots were prepared with the Cavan ratio of the high silica chabazite type zeolite as the X-axis and the relative crystallinity as the Y-axis (FIG. 4). It was found that when a chabazite-type zeolite having a high Cavan ratio was used, the relative crystallinity was maintained even if the Cavan ratio was increased by the acid treatment step.

[Synthesis of chabazite-type zeolite (3)]
0.168 kg of sodium aluminate aqueous solution containing 22% by mass of Al in _{terms of Al 2} O _{3 and 17% by mass of Na in terms of Na 2} O, and 1.35 kg of sodium hydroxide aqueous solution containing 21.65% by mass of NaOH. Was added with stirring to dissolve, and cooled to 30 ° C. While stirring this solution, 1.361 kg of a sodium silicate aqueous solution containing 24% by mass of _{Si in terms of SiO 2 and 7.7% by mass of Na in terms of Na 2 O was added.} The composition of the solution at this time is the oxide molar ratio.
Na ₂ O / Al ₂ O ₃ = 16
SiO ₂ / Al ₂ O ₃ = 15
H ₂ O / Al ₂ O ₃ = 330
Met. Then, this solution was allowed to stand at 30 ° C. for 15 hours to prepare an aluminosilicate solution.

A sodium silicate aqueous solution containing 24% by mass of Si as a SiO ₂ equivalent concentration and 7.7% by mass of Na as a Na ₂ O equivalent concentration, 5.66 kg of water and _{30% by mass of SiO 2} concentration silica sol (JGC Catalysts and Chemicals). Manufacture: Catalyst SI-30: average particle size 10 nm) 18.97 kg and 2.88 kg of the aluminosilicate solution were added and mixed by stirring. To this, 10.03 kg of an aqueous sodium aluminate solution containing 22% by mass of Al as an Al ₂ O ₃ equivalent concentration and 17% by mass of Na as a Na ₂ O equivalent concentration was added, and the mixture was aged with stirring at room temperature for 3 hours to obtain a mixed hydrogel slurry. Was prepared. At this time, the composition of the mixed hydrogel slurry is based on the oxide molar ratio.
Na ₂ O / Al ₂ O ₃ = 2.80
SiO ₂ / Al ₂ O ₃ = 8.70
H ₂ O / Al ₂ O ₃ = 108
Met.

60.3 kg of the mixed hydrogel slurry was hydrothermally treated in a crystallization tank at 95 ° C. for 35 hours. Then, it cooled to 70 degreeC and filtered to obtain 29.5 kg of Na-Y type zeolite cake. The obtained Na-Y-type zeolite cake was further washed, filtered, and dried to prepare Na-Y-type zeolite.

An aqueous solution containing 500 g of Na-Y-type zeolite and 280 g of ammonium sulfate was heated to 80 ° C. and ion-exchanged for 2 hours with stirring, filtered, washed, dried and fired at 550 ° C. for 5 hours. Furthermore, the operations of ion exchange, filtration, washing, and drying were performed twice under the above conditions, _{and 0.95 (NH 4} ) ₂ O · 0.05 Na ₂ O · Al ₂ O ₃ · _{with an NH 4} ion exchange rate of 95%. A 5SiO ₂ zeolite was prepared.

Then, _{water was added to NH 4 (95)} Y-type zeolite to adjust the water content so as to contain 50% by mass of water. A container was filled with a moisture-adjusted NH _{4 (95)} Y-type zeolite, the temperature was raised to 600 ° C., and steam treatment was performed for 2 hours to prepare a hyperstable faujasite-type zeolite.

330 g of sulfuric acid having a concentration of 25% by mass was added dropwise to 500 g of this hyperstable faujasite-type zeolite for 0.5 hours to perform a dealumination treatment to prepare a faujasite-type zeolite having a Cavan ratio of 7.0.

20 g of this faujasite-type zeolite was dispersed in 80 g of water, and then 7.0 g of KOH having a KOH concentration of 95.5% by mass was mixed to prepare a synthetic slurry. The synthetic slurry was hydrothermally treated at 95 ° C. for 48 hours. Then, the synthetic slurry was taken out, filtered, washed, and dried to prepare a chabazite type zeolite (3). For this chabazite-type zeolite (3), the Cavan ratio, relative crystallinity, specific surface area, and average particle size were measured by the same method as for the chabazite-type zeolite (1). The results are shown in the column of Example 5 in Table 1.

[Example 5]
10 g of chabazite-type zeolite (3) was brought into contact with an acid solution having a sulfuric acid concentration of 1.45% by mass, and the mixture was kept stirred at 95 ° C. for 1 hour. After the retention was completed, it was filtered, washed and dried to obtain a high silica chabazite type zeolite. The results of measuring the high silica chabazite type zeolite by the same method as in Example 1 are shown in Tables 1 and 2, respectively.

[High silica chabazite type zeolite for _{NH 3-SCR reaction]}
With ammonium sulfate, Examples 1-5, the high-silica chabazite-type zeolite obtained in Comparative Example 1-6, the concentration of K was ion exchanged until 0.1 wt% or less K ₂ O conversion. Next, it was immersed in a copper nitrate aqueous solution so that the amount of Cu supported was about 4% by mass in terms of Cu, to obtain a high silica chabazite type zeolite for _{NH 3-SCR reaction.} Specifically, 10 g of each of the above-mentioned high-silica chabazite-type zeolites was suspended in 100 g of a 1 mol / L copper nitrate trihydrate solution, heated to 80 ° C., ion-exchanged for 1 hour with stirring, and then filtered. Washed. This operation was repeated until the target Cu loading amount was reached.

The _{contents of Si, Al, K, and Cu of the obtained high silica chabazite type zeolite for NH 3-} SCR reaction were measured by the same method as in Example 1. Moreover, the specific surface area and the relative crystallinity were measured by the same method as in Example 1. The results are shown in Table 3.

The outer surface area of the obtained high silica chabazite type zeolite for _{NH 3-SCR reaction was measured by the following method.} The results are shown in Table 3.
[External surface area measurement method]
Measuring method Nitrogen adsorption method Measuring device BEL SORP-miniII (manufactured by Nippon Bell Co., Ltd.)
Sample amount about 0.05g
Pretreatment 300 ° C, 2 hours (under vacuum)
Relative pressure range 0-1.0
Calculation method External surface area: t-plot method

The obtained _{high silica chabazite type zeolite for NH 3-} SCR reaction was molded into granules, and then the NH _3- SCR activity was measured by the following method. The results are shown in Table 3.
<NH _3- SCR reaction evaluation conditions>
Reaction device Normal pressure fixed bed flow type reaction tube catalyst molded product 10cc
Reaction gas NO: 500 ppm, NH ₃ : 500 ppm, O ₂ : 10%, N ₂ : Balanced reaction gas flow rate 6000 cc / min
Reaction temperature 150 ° C, 200 ° C, 300 ° C
<NOx removal rate calculation method>
At each reaction temperature, the NOx concentration at the inlet of the reaction tube at the time of steady state is set to Cin,
The NOx concentration at the outlet of the reaction tube was taken as Cout, and the concentration was calculated from the following formula.
NOx removal rate [%] = {(Cin-Cout) / Cin} x 100

Claims (4)

High silica chabazite type for acid treatment of chabazite type zeolite having the following characteristics (a), (b) and (c) using an acid solution having a sulfuric acid concentration of 1.0 to 2.93% by mass. Zeolite production method.
(A) Cavan ratio (SiO ₂ / Al ₂ O ₃ molar ratio) is 6.5 or more (b) Relative crystallinity is 100% or more
(C) Average particle size is 0.1 to 1.2 μm K The use of the chabazite-type zeolite containing from 9.7 to 15.27 mass% in K ₂ O in terms of method of manufacturing a high-silica chabazite-type zeolite according to claim 1. The method for producing a high silica chabazite type zeolite according to claim 1 or 2, wherein the acid treatment is performed with an acid treatment solution containing 1 to 4% by mass of sulfuric acid. The method for producing a high-silica chabazite-type zeolite according to any one of claims 1 to 3, wherein the chabazite-type zeolite synthesized without using an organic structure-defining agent is used.

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