Composition for purifying waste gas and method for producing the same

Abstract

The present invention provides an exhaust gas purification composition containing a phosphorus-containing BEA type zeolite with further improved heat resistance and a method for manufacturing the same. An exhaust gas purification composition, which is an exhaust gas purification composition containing a phosphorus-containing BEA type zeolite, and the pore volume ratio (V2 / V1) of the micropore volume V2 in the range of 2 nm or less in pore diameter measured by the SF method to the mesopore volume V1 in the range of 2 nm or more and 100 nm or less in pore diameter measured by the BJH method of the phosphorus-containing BEA type zeolite is 2.0 or more.

Description

Technical Field

[0001] The present invention relates to a composition for purifying exhaust gas containing zeolite and a method for manufacturing the same. Background Art

[0002] Exhaust gas discharged from internal combustion engines such as gasoline engines and diesel engines of automobiles and motorcycles (also referred to as riding vehicles) contains harmful components such as hydrocarbons (HC) derived from unburned fuel, carbon monoxide (CO) derived from incomplete combustion, and nitrogen oxides (NO x ) etc. A composition for purifying exhaust gas for an exhaust gas purification catalyst is used to treat such exhaust gas from internal combustion engines. For example, hydrocarbons (HC) in the exhaust gas are oxidized and converted into water and carbon dioxide for purification. Carbon monoxide (CO) is oxidized and converted into carbon dioxide for purification. In addition, nitrogen oxides (NO x ) are reduced and converted into nitrogen for purification. The purification of hydrocarbons (HC) by a catalyst is greatly affected by the exhaust gas temperature, and generally requires a high temperature of 300°C or higher. When the exhaust gas temperature is low just after the internal combustion engine is started, although hydrocarbons (HC) are difficult to be purified by the catalyst, hydrocarbons (HC) are easily discharged just after the internal combustion engine is started. Therefore, a composition for purifying exhaust gas is needed which adsorbs hydrocarbons (HC) in advance just after the internal combustion engine is started and releases and purifies hydrocarbons (HC) when the exhaust gas temperature reaches 300°C or higher and the catalyst is activated.

[0003] For example, Patent Document 1 discloses a method for activating a zeolite catalyst containing an element of Group 11 of the periodic table and phosphorus. However, the technique described in Patent Document 1 is a technique for decomposing hexane at a temperature of 550°C, and there are problems in durability, for example, when used for exhaust gas purification at high temperatures in the range of 900°C or higher and 1100°C. Patent Document 2 discloses a composition for purifying exhaust gas containing phosphorus-containing BEA type zeolite which can maintain the structure of BEA type zeolite even in a severe thermal environment.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2012-239924

[0007] Patent Document 2: International Publication No. 2018 / 131195 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] Since BEA type zeolite has excellent adsorption ability for hydrocarbons (HC), further improvement in heat resistance in a severe thermal environment is required.

[0010] For this reason, an object of the present invention is to provide a composition for purifying exhaust gas and a method for producing the same, the composition for purifying exhaust gas containing a phosphorus-containing BEA zeolite that can be used even in a severe thermal environment and has further improved heat resistance.

[0011] Solutions for Solving the Problems

[0012] The present invention provides a composition for purifying exhaust gas, which is a composition for purifying exhaust gas containing a phosphorus-containing BEA zeolite, and the pore volume ratio (V2 / V1) of the micropore volume V2 in the range of 2 nm or less in pore diameter measured by the SF method to the mesopore volume V1 in the range of more than 2 nm and 100 nm or less in pore diameter measured by the BJH method of the phosphorus-containing BEA zeolite is 2.0 or more.

[0013] The present invention provides a method for producing a composition for purifying exhaust gas, which is a method for producing a composition for purifying exhaust gas containing a phosphorus-containing BEA zeolite, and includes the following steps:

[0014] A step of preparing a BEA zeolite, wherein the pore volume ratio (V2 / V1) of the micropore volume V2 in the range of 2 nm or less in pore diameter measured by the SF method to the mesopore volume V1 in the range of more than 2 nm and 100 nm or less in pore diameter measured by the BJH method of the BEA zeolite is 1.8 or more;

[0015] A step of bringing the BEA zeolite into contact with a phosphorus-containing compound so that the phosphorus-containing compound adheres to the BEA zeolite; and,

[0016] A step of heat-treating the BEA zeolite containing the phosphorus-containing compound to obtain a phosphorus-containing BEA zeolite.

[0017] Effects of the Invention

[0018] The present invention can provide a composition for purifying exhaust gas, which contains a phosphorus-containing BEA zeolite, has further improved heat resistance, and reduces mesopores that cause defects in the framework structure in a severe thermal environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A chart showing the pore size distribution and cumulative pore size distribution measured by the BJH method for the exhaust gas purification compositions of Example 1 and Comparative Example 3. DETAILED DESCRIPTION

[0020] Next, the present invention will be described based on examples of embodiments. However, the present invention is not limited to the embodiments described below.

[0021] An example of an embodiment of the present invention is a composition for purifying exhaust gas, which is a composition for purifying exhaust gas containing phosphorus-containing BEA zeolite. The micropore volume V2 in the range of 2 nm or less in pore diameter measured by the SF method (Saito-Foley method) of the phosphorus-containing BEA zeolite has a pore volume ratio (V2 / V1) of 2.0 or more with respect to the mesopore volume V1 in the range of 2 nm or more and 100 nm or less in pore diameter measured by the BJH method (Barrett-Joyner-Halenda method). Specifically, the micropore volume V2 is the micropore volume of the pore diameter in the range of 0 nm or more and 2 nm or less measured by the SF method described in detail later.

[0022] Zeolite refers to a crystalline substance in which tetrahedral TO 4 units (T is a central atom) share oxygen (O) atoms and are three-dimensionally linked to form an extended regular micropore. Specifically, it includes silicates, germanates, and arsenates described in the structure committee dataset of the International Zeolite Association (hereinafter sometimes referred to as "IZA").

[0023] Here, silicates include, for example, aluminosilicates, gallium silicates, iron silicates, titanium silicates, borosilicates, etc. Germanates include, for example, aluminum germanates, etc. Arsenates include, for example, aluminum arsenates, etc. Aluminosilicates used as zeolites also include, for example, substances in which a part of Si or Al in the framework is replaced by divalent or trivalent cations such as Ti, Ga, Mg, Mn, Fe, Co, Zn, etc. Zeolites preferably use zeolites containing crystalline aluminosilicates.

[0024] The zeolite contained in the composition for purifying exhaust gas preferably contains BEA zeolite. The framework structure of the zeolite is databaseized by IZA. In BEA zeolite, it contains mesopores in the range of 2 nm or more and 100 nm or less in pore diameter measured by the BJH method and micropores in the range of 2 nm or less in pore diameter. Here, the pore diameter refers to the crystallographic free diameter of the channels defined by IZA. Regarding the pore diameter, it refers to the average diameter in the case where the shape of the pore (channel) is a perfect circle. In the case where the shape of the pore is elongated in one direction such as an ellipse, it refers to the minor axis.

[0025] The composition for waste gas purification contains phosphorus-containing BEA zeolite. Since the mesopores that cause defects in the framework structure are modified with phosphorus, the pore diameter of the mesopores becomes smaller and becomes micropores, and the pore volume of the mesopores contained in the BEA zeolite can be reduced. It is considered that the mesopores contained in the zeolite will cause defects in the framework structure when placed in a harsh thermal environment. The phosphorus-containing BEA zeolite contained in the composition for waste gas purification can maintain the framework structure and further improve the heat resistance even when placed in a harsh thermal environment because the mesopores that cause defects in the framework structure are reduced.

[0026] It is speculated that the phosphorus generated from the phosphorus source, for example, forms phosphate ions. In BEA zeolite with a pore volume ratio V2 / V1 of 1.8 or more, it is speculated that it is easier to bind to the Lewis acid center as a metal ion than to the Brønsted acid center. Therefore, in the phosphorus-containing BEA zeolite with a pore volume ratio of 2.0 or more, even when the mesopores are modified with phosphorus and the pore diameter becomes smaller and becomes micropores, the Brønsted acid centers on the surface are maintained. The phosphorus-containing BEA zeolite contained in the composition for waste gas purification has reduced mesopores that cause defects when heated. Even when placed in a harsh thermal environment, it can maintain the framework structure of the BEA zeolite and adsorb hydrocarbons (HC) in the framework structure. The Brønsted acid centers and Lewis acid centers present on the surface of the BEA zeolite can be used to speculate the presence of each acid center (hydroxyl group (OH)) by infrared absorption spectra using infrared spectroscopy (IR) with pyridine as a probe molecule. For example, when the infrared absorption spectrum of BEA zeolite is measured by infrared spectroscopy (IR) using pyridine as a probe molecule, the absorption bands of the probe molecule appear in different wavenumber regions according to the difference between the Brønsted acid center and the Lewis acid center, and further, the absorption bands of the acid center (hydroxyl group (OH group)) appear in a wavenumber region different from the absorption bands of each probe molecule. From the wavenumber regions of the absorption bands of the probe molecule and the absorption bands of the hydroxyl group (OH group), the Brønsted acid center and the Lewis acid center derived from defects of metal ions, etc. can be speculated.

[0027] The micropore volume V2 in the range of pore diameters below 2 nm of the phosphorus-containing BEA zeolite measured by the SF method is 2.0 or more relative to the mesopore volume V1 in the range of pore diameters of 2 nm or more and 100 nm or less measured by the BJH method. If the pore volume ratio (V2 / V1) of the phosphorus-containing BEA zeolite is 2.0 or more, the micropore volume V2 is larger than the mesopore volume V1, the mesopores causing the defect of the framework structure are reduced, and the framework structure can be maintained even when placed in a severe thermal environment, and the heat resistance is further improved. In addition, the phosphorus-containing BEA zeolite adsorbs hydrocarbons (HC) in the micropores, and can maintain the high purification performance of hydrocarbons (HC). The pore volume ratio (V2 / V1) of the phosphorus-containing BEA zeolite is preferably such that the micropore volume V2 is larger than the mesopore volume V1. The pore volume ratio (V2 / V1) is preferably 2.2 or more, more preferably 2.4 or more, and further preferably 2.5 or more. The upper limit value of the pore volume ratio (V2 / V1) is not particularly limited, and from the viewpoint of maintaining the strength of the BEA zeolite, the pore volume ratio (V2 / V1) can be 10 or less, can be 6.5 or less, or can be 4.0 or less.

[0028] The mesopore volume V1 is the total volume of pores with pore diameters of 2 nm or more and 100 nm or less calculated from the nitrogen adsorption isotherm by the BJH method (Barrett-Joyner-Halenda method) described in ISO 15901-2.

[0029] The micropore volume V2 is the total volume of pores with pore diameters of 0 nm or more and 2 nm or less calculated from the nitrogen adsorption isotherm by the SF method (Saito-Foley method) using the constants described in ISO 15901-3 (JIS Z8831-3). When measuring the mesopore volume V1 and the micropore volume V2, in order to remove adsorbed volatile substances such as pre-attached water or organic substances, the sample to be measured is pretreated by heating and vacuum evacuation under the conditions described in the following examples.

[0030] The micropore volume V2 of the phosphorus-containing BEA zeolite is preferably in the range of 0.1 cm 3 / g or more and 0.3 cm 3 / g or less, more preferably in the range of 0.12 cm 3 / g or more and 0.29 cm 3 / g or less, further preferably in the range of 0.15 cm 3 / g or more and 0.28 cm 3 / g or less, particularly preferably in the range of 0.16 cm 3 / g or more and 0.28 cm 3 / g or less. If the micropore volume V2 of the phosphorus-containing BEA zeolite is within 0.1 cm3 0.1 cm³ / g or more and 0.3 cm³ / g or less 3 When within the range of 0.1 cm³ / g or more and 0.3 cm³ / g or less, the pore volume ratio (V2 / V1) of the micropore volume to the mesopore volume becomes 2.0 or more, and the micropore volume can be sufficiently increased relative to the mesopore volume. If the micropore volume V2 of the phosphorus-containing BEA zeolite is within the range of 0.1 cm³ / g or more and 0.3 cm³ / g or less 3 0.1 cm³ / g or more and 0.3 cm³ / g or less 3 / g, then hydrocarbons (HC) can be efficiently adsorbed in the micropores, and the hydrocarbons (HC) can be oxidized to purify the hydrocarbons (HC).

[0031] The mesopore volume V1 of the phosphorus-containing BEA zeolite is preferably within the range of 0.001 cm³ / g or more and 0.08 cm³ / g or less, more preferably 0.075 cm³ / g or less, further preferably 0.070 cm³ / g or less, and particularly preferably 0.065 cm³ / g or less. The smaller the mesopore volume V1 of the phosphorus-containing BEA zeolite, the more preferable it is. However, it is difficult to form a BEA zeolite without mesopores, and mesopores with a volume of 0.001 cm³ / g or more will be included. For the phosphorus-containing BEA zeolite with a pore volume ratio V2 / V1 of 2.0 or more according to the present embodiment, since the mesopores are modified with phosphorus, the mesopore volume can be reduced to 0.08 cm³ / g or less. 3 0.001 cm³ / g or more and 0.08 cm³ / g or less 3 0.075 cm³ / g or less 3 0.070 cm³ / g or less 3 0.065 cm³ / g or less 3 / g or less. The smaller the mesopore volume V1 of the phosphorus-containing BEA zeolite, the more preferable it is. However, it is difficult to form a BEA zeolite without mesopores, and mesopores with a volume of 0.001 cm³ / g or more will be included. For the phosphorus-containing BEA zeolite with a pore volume ratio V2 / V1 of 2.0 or more according to the present embodiment, since the mesopores are modified with phosphorus, the mesopore volume can be reduced to 0.08 cm³ / g or less. 3 0.08 cm³ / g or less 3 / g or less.

[0032] The molar ratio of phosphorus to aluminum in the phosphorus-containing BEA zeolite, i.e., the P / Al molar ratio, is preferably within the range of 0.7 or more and 1.0 or less. If phosphorus (P) relative to TO which forms the framework structure of the BEA zeolite 4When the molar ratio of Al of the T atom (central atom) of the unit, i.e., the P / Al molar ratio, is in the range of 0.7 or more and 1.0 or less, the phosphorus contained in the BEA-type zeolite is modified on the Lewis acid center formed by Al, and the Bronsted acid center that can maintain the active site for the oxidation of adsorbed hydrocarbons (HC) can be maintained. Therefore, the mesopores that cause defects in the framework structure can be reduced while maintaining the purification performance, and the framework structure can be maintained even in a severe thermal environment, and the heat resistance can be further improved. When the P / Al molar ratio in the phosphorus-containing BEA-type zeolite increases and exceeds 1, the content of phosphorus increases, and the Bronsted acid center that is the active site for the oxidation reaction of hydrocarbons may be modified by phosphorus, resulting in a reduction in the active site and sometimes it is difficult to maintain the purification performance. The amounts of aluminum (Al) and phosphorus (P) in the phosphorus-containing BEA-type zeolite can be measured using a fluorescent X-ray analyzer (for example, manufactured by Rigaku Corporation) as a composition analyzer for the method described in the following examples, and the amounts of aluminum (Al) and phosphorus (P) in the phosphorus-containing BEA-type zeolite are calculated from the obtained measurement values.

[0033] The SiO 2 / Al 2 O 3 molar ratio of the phosphorus-containing BEA-type zeolite is preferably in the range of 10 or more and 100 or less, more preferably in the range of 20 or more and 90 or less, and further preferably in the range of 25 or more and 80 or less. If the SiO 2 / Al 2 O 3 molar ratio of the phosphorus-containing BEA-type zeolite is in the range of 10 or more and 100 or less, the maintenance of the framework structure of the BEA-type zeolite and the high adsorption capacity of hydrocarbons (HC) can be highly balanced in a severe thermal environment. In addition, if the SiO 2 / Al 2 O 3 molar ratio of the phosphorus-containing BEA-type zeolite is in the range of 10 or more and 100 or less, it has sufficient Bronsted acid centers that are the active sites for the oxidation reaction when purifying the adsorbed hydrocarbons (HC). The SiO 2 / Al 2 O 3 molar ratio can be measured using a fluorescent X-ray analyzer (for example, manufactured by Rigaku Corporation) as a composition analyzer for the method described in the following examples, and the amounts of aluminum (Al) and silicon (Si) in the phosphorus-containing BEA-type zeolite are measured, and the SiO 2 / Al 2 O 3 molar ratio is calculated from the obtained measurement values.

[0034] Next, an example of a method for manufacturing a composition for purifying exhaust gas will be described. The method for manufacturing a composition for purifying exhaust gas is not limited to the example described below.

[0035] The method for manufacturing a composition for purifying exhaust gas containing a phosphorus-containing BEA zeolite includes the following steps: a step of preparing a BEA zeolite, wherein the ratio (V2 / V1) of the micropore volume V2 in the range of pore diameter of 2 nm or less to the mesopore volume V1 in the range of pore diameter of 2 nm or more and 100 nm or less measured by the BJH method of the BEA zeolite is 1.8 or more; a step of bringing the BEA zeolite into contact with a phosphorus-containing compound to attach the phosphorus-containing compound to the BEA zeolite; and a step of heat-treating the BEA zeolite containing the phosphorus-containing compound to obtain a phosphorus-containing BEA zeolite.

[0036] Step of preparing BEA zeolite

[0037] As the BEA zeolite, a BEA zeolite is prepared in which the pore volume ratio (V2 / V1) of the micropore volume V2 in the range of pore diameter of 2 nm or less to the mesopore volume V1 in the range of pore diameter of 2 nm or more and 100 nm or less measured by the BJH method is 1.8 or more. The pore volume ratio (V2 / V1) of the prepared BEA zeolite is preferably 2.0 or more, more preferably 2.2 or more, further preferably 2.4 or more, and particularly preferably 2.5 or more. The pore volume ratio (V2 / V1) of the prepared BEA zeolite can be 8.0 or less, and can also be 7.0 or less. As the phosphorus-containing BEA zeolite, if the pore volume ratio (V2 / V1) is 1.8 or more, phosphorus can modify the mesopores, reduce the pore diameter of the mesopores to form micropores, reduce the mesopores that cause defects in the framework structure, and further improve the heat resistance. The BEA zeolite can be used after being dried before contacting with the phosphorus-containing compound. In the case of drying the BEA zeolite, the drying temperature can be set to 80°C or more and 200°C or less, and the drying time can be set to 0.5 hour or more and 5 hours or less. In addition, the pressure during drying is not particularly limited, and can be atmospheric pressure (0.1 MPa), or under reduced pressure of 0.1 MPa or less.

[0038] Step of attaching a phosphorus-containing compound

[0039] As methods for bringing a BEA-type zeolite into contact with a phosphorus-containing compound and attaching the phosphorus-containing compound to the BEA-type zeolite, there may be mentioned a vapor deposition method, an impregnation method, a precipitation method, an ion exchange method, etc. As the vapor deposition method, there may be mentioned a method of placing the BEA-type zeolite and the phosphorus-containing compound in a container, and evaporating the phosphorus-containing compound at normal temperature or by heating to attach it to the BEA-type zeolite. As the impregnation method, there may be mentioned a method of impregnating the BEA-type zeolite in a liquid obtained by mixing the phosphorus-containing compound and a solvent, and heating and drying the mixed solution under normal pressure or reduced pressure to attach the phosphorus-containing compound to the BEA-type zeolite. Here, the phosphorus-containing compound attached to the BEA-type zeolite may be phosphorus or a phosphorus-containing ion. As the impregnation method, there may be mentioned an incipient wetness method, an evaporation to dryness method, a pore-filling method, a spraying method, an equilibrium adsorption method, etc. As the precipitation method, there may be mentioned a kneading method, a deposition method, etc.

[0040] In the case of attaching phosphorus to the BEA-type zeolite by the vapor deposition method, as the phosphorus-containing compound, there may be mentioned trimethyl phosphate, triethyl phosphate, trimethyl phosphite, triethyl phosphite, etc. From the viewpoint of low boiling point, trimethyl phosphate is preferred. In the case of attaching phosphorus to the BEA-type zeolite by the impregnation method, the phosphorus-containing compound is preferably water-soluble, and there may be mentioned, for example, trimethyl phosphate, triethyl phosphate, trimethyl phosphite, triethyl phosphite, phosphoric acid, dihydrogen phosphates such as ammonium dihydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, hydrogen phosphates such as diammonium hydrogen phosphate, dipotassium hydrogen phosphate, etc. As phosphoric acid, there may be mentioned orthophosphoric acid (H 3 PO 4 ), pyrophosphoric acid (H 4 P 2 O 7 ), triphosphoric acid (H 5 P 3 O 10 ), polyphosphoric acid, metaphosphoric acid (HPO 3) Phosphoric acid, metaphosphoric acid, etc. From the viewpoint of easy drying, phosphoric acids such as orthophosphoric acid, trimethyl phosphate, ammonium dihydrogen phosphate or diammonium hydrogen phosphate are preferred. Examples of the solvent mixed with the phosphorus-containing compound include polar organic solvents such as deionized water, ethanol, isopropyl alcohol, and acetone. From the viewpoints of easy operation and easy drying, deionized water and ethanol are preferably used. With respect to the total amount of the mixed solution of 100% by mass, the phosphorus-containing compound may be in the range of 1% by mass or more and 25% by mass or less, may be in the range of 2% by mass or more and 20% by mass or less, or may be in the range of 5% by mass or more and 15% by mass or less. When attaching the phosphorus-containing compound to the BEA type zeolite by an impregnation method, the time for impregnating the BEA type zeolite in the mixed solution may be set to 0.5 hours or more and 2 hours or less. After impregnation, the BEA type zeolite containing the phosphorus-containing compound may be dried, the drying temperature may be set to 80°C or more and 200°C or less, and the drying time may be set to 0.5 hours or more and 5 hours or less. In addition, the pressure during drying is not particularly limited and may be atmospheric pressure (0.1 MPa) or under reduced pressure of 0.1 MPa or less.

[0041] Heat treatment step

[0042] After attaching the phosphorus-containing compound to the BEA type zeolite by a vapor deposition method or an impregnation method, heat treatment is performed to obtain a phosphorus-containing BEA type zeolite. In order to maintain the framework structure of the BEA type zeolite and modify the mesopores with phosphorus, the heat treatment temperature is preferably in the range of 200°C or more and 800°C or less, more preferably in the range of 400°C or more and 700°C or less. The atmosphere for heat treatment may be an air atmosphere or an inert gas atmosphere such as nitrogen.

[0043] After attaching the phosphorus-containing compound to the BEA type zeolite, by performing heat treatment, the mesopores are modified with phosphorus, the pore diameter of the mesopores becomes smaller and becomes micropores, the mesopores that cause defects in the framework structure can be reduced, and the heat resistance can be further improved.

[0044] The pore volume ratio (V2 / V1) of the micropore volume V2 in the range of 2 nm or less in pore diameter measured by the SF method to the mesopore volume V1 in the range of 2 nm or more and 100 nm or less in pore diameter measured by the BJH method of the phosphorus-containing BEA type zeolite obtained in the above manner is 2.0 or more. The micropore volume V2 is larger than the mesopore volume V1, the mesopores that cause defects in the framework structure are reduced, and the framework structure can be maintained even when placed in a severe thermal environment, and the heat resistance can be further improved.

[0045] The exhaust gas purification composition containing phosphorus-containing BEA zeolite obtained in the above manner can maintain the framework structure of BEA zeolite and exhibit a stable hydrocarbon (HC) adsorption capacity even when exposed to a high temperature in the range of 900 °C or higher and 1100 °C or lower, for example, in the range of 900 °C or higher and 1000 °C or lower, because the mesopores causing the defect of the framework structure are reduced. Further, the phosphorus-containing BEA zeolite contained in the exhaust gas purification composition can maintain the Bronsted acid sites that are the active sites for the oxidation reaction of the adsorbed hydrocarbon (HC) even when modified with phosphorus. Therefore, even when exposed to a high temperature in the range of 900 °C or higher and 1100 °C or lower, it exhibits stable high purification performance. Such an exhaust gas purification composition can exhibit stable high exhaust gas purification performance as an exhaust gas purification catalyst for internal combustion engines powered by fossil fuels such as gasoline engines and diesel engines. In particular, the exhaust gas purification composition of the present embodiment can be suitably used for purifying the exhaust gas discharged from internal combustion engines of automobiles, motorcycles, etc. due to its high heat resistance. The exhaust gas purification composition of the present embodiment can be effectively used for purifying hydrocarbons (HC) in particular in exhaust gas. The exhaust gas purification composition of the present embodiment can be suitably used for purifying hydrocarbons (HC) contained in the exhaust gas flowing through the exhaust passage of an internal combustion engine, and can also provide an exhaust gas purification method.

[0046] The exhaust gas purification composition may be an exhaust gas purification composition composed of a phosphorus-containing BEA zeolite having a pore volume ratio (V2 / V1) of 2.0 or more, or may contain other components in addition to the phosphorus-containing BEA zeolite. As other components, for example, conventionally known catalyst materials other than the phosphorus-containing BEA zeolite contained in the exhaust gas purification composition of the present embodiment can be cited.

[0047] The exhaust gas purification composition can be in any form such as powder, paste, granular, etc. For example, the exhaust gas purification composition of the present embodiment can be used as a catalyst layer formed on a catalyst support. As the catalyst support, for example, a support made of a ceramic or metal material can be used. As the ceramic used as the catalyst support, alumina (Al 2 O 3 ), mullite (3Al 2 O 3 -2SiO 2 ), cordierite (2MgO - 2Al 2 O 3 -5SiO 2 ), aluminum titanate (Al 2 TiO 5) Examples include silicon carbide (SiC), etc. As the metal material used as the catalyst support, for example, stainless steel, etc. can be cited. The shape of the catalyst support is not particularly limited, but for example, honeycomb shape, plate shape, pellet shape, etc. can be cited.

[0048] The catalyst structure formed by using the exhaust gas purification composition of the present embodiment for the catalyst layer may contain a catalyst layer composed of a conventionally known catalyst material other than the exhaust gas purification composition of the present embodiment. In addition, the catalyst structure used for the catalyst layer formed on the catalyst support can be used in a DPF (Diesel Particulate Filter) or GPF (Gasoline Particulate Filter) in the form of a catalyst structure having a catalyst layer formed on the catalyst support using the exhaust gas purification composition of the present embodiment.

[0049] Hereinafter, the present invention will be described in more detail using Examples and Comparative Examples. However, the present invention is not limited to these Examples.

[0050] Example 1

[0051] Proton-type BEA zeolite a dried in an air atmosphere at 0.1 MPa and 150 °C for 8 hours was prepared. The SiO 2 / Al 2 O 3 molar ratio of proton-type BEA zeolite a measured by the method described later was 37.5, and the pore volume ratio V2 / V1 was 2.9. A phosphorus-containing compound was attached to the prepared proton-type BEA zeolite a by vapor deposition. Specifically, 3.00 g (dry weight) of the dried proton-type BEA zeolite and 0.31 g of 99 mass% trimethyl phosphate were placed in a sealed container, and after reducing the pressure to 0.1 MPa, it was left standing at 80 °C for 8 hours to obtain BEA zeolite vapor-deposited with the phosphorus-containing compound. The powder of the obtained BEA zeolite containing the phosphorus-containing compound was dried in an air atmosphere at 0.1 MPa and 120 °C for 2 hours. The dried powder of the BEA zeolite containing the phosphorus-containing compound was heat-treated in an air atmosphere at 0.1 MPa and 600 °C for 3 hours to produce a powder of phosphorus-containing BEA zeolite, and an exhaust gas purification composition composed of phosphorus-containing BEA zeolite was obtained.

[0052] Example 2

[0053] Except that the amount of trimethyl phosphate used was changed to 0.37 g, in the same manner as in Example 1, a powder of phosphorus-containing BEA zeolite was produced, and an exhaust gas purification composition composed of phosphorus-containing BEA zeolite was obtained.

[0054] Example 3

[0055] Proton-type BEA zeolite a prepared by drying in an air atmosphere at 0.1 MPa and room temperature for 8 hours. A phosphorus-containing compound was attached to the prepared proton-type BEA zeolite a by the incipient wetness impregnation method. Specifically, 3.00 g (dry weight) of the prepared proton-type BEA zeolite was impregnated in a mixed solution prepared by dissolving 0.26 g of trimethyl phosphate in 2.7 mL of deionized water as a solvent, and dried at 120 °C for 2 hours in an air atmosphere at 0.1 MPa. The solid of the dried BEA zeolite with the attached phosphorus-containing compound was heat-treated at 600 °C for 1 hour in an air atmosphere at 0.1 MPa to obtain a solid of phosphorus-containing BEA zeolite. The obtained solid was pulverized to produce a powder of phosphorus-containing BEA zeolite, and an exhaust gas purification composition composed of the powder of phosphorus-containing BEA zeolite was obtained.

[0056] Example 4

[0057] Except for using a mixed solution prepared by dissolving 0.24 g of diammonium hydrogen phosphate in 2.7 mL of deionized water, in the same manner as in Example 3, a phosphorus-containing compound was attached to BEA zeolite by the incipient wetness impregnation method to produce a powder of phosphorus-containing BEA zeolite, and an exhaust gas purification composition composed of the powder of phosphorus-containing BEA zeolite was obtained.

[0058] Example 5

[0059] Except for attaching the phosphorus-containing compound to the proton-type BEA zeolite by the evaporation method, the operation was carried out in the same manner as in Example 4. Specifically, 3.00 g (dry weight) of the prepared proton-type BEA zeolite was impregnated and added to a mixed solution prepared by dissolving 0.24 g of diammonium hydrogen phosphate in 2.7 mL of deionized water to obtain a slurry containing BEA zeolite. Except for heating and drying the obtained slurry in a beaker under stirring in an air atmosphere at 0.1 MPa, in the same manner as in Example 4, a powder of phosphorus-containing BEA zeolite was obtained. The powder of phosphorus-containing BEA zeolite was used as an exhaust gas purification composition.

[0060] Example 6

[0061] Proton-type BEA zeolite a prepared by drying in an air atmosphere at 0.1 MPa and 150 °C for 8 hours. Except for using a mixed solution prepared by dissolving 0.24 g of 85% orthophosphoric acid in 2.7 mL of deionized water, in the same manner as in Example 3, a phosphorus-containing compound was attached to BEA zeolite by the incipient wetness impregnation method to produce a powder of phosphorus-containing BEA zeolite, and an exhaust gas purification composition composed of the powder of phosphorus-containing BEA zeolite was obtained.

[0062] Example 7

[0063] Proton-type BEA zeolite b prepared by drying at 150 °C for 8 hours in an atmospheric atmosphere of 0.1 MPa. The SiO of proton-type BEA zeolite b measured by the method described below 2 / Al 2 O 3 The molar ratio is 37.4, and the pore volume ratio V2 / V1 is 6.9. Except for using proton-type BEA zeolite b, in the same manner as in Example 3, a phosphorus-containing compound was attached to BEA zeolite by the incipient wetness impregnation method to produce a powder of phosphorus-containing BEA zeolite, and an exhaust gas purification composition composed of the powder of phosphorus-containing BEA zeolite was obtained.

[0064] Comparative Example 1

[0065] Proton-type BEA zeolite c prepared by drying at 150 °C for 8 hours in an atmospheric atmosphere of 0.1 MPa. The SiO of proton-type BEA zeolite c measured by the method described below 2 / Al 2 O 3 The molar ratio is 32.0, and the pore volume ratio V2 / V1 is 1.6. It should be noted that as the proton-type BEA zeolite c, the same zeolite as the proton-type BEA zeolite used in Example 1 of International Publication No. 2018 / 131195 was used. Except for using proton-type BEA zeolite c, in the same manner as in Example 1, a phosphorus-containing compound was attached to BEA zeolite by the evaporation coating method to produce a powder of phosphorus-containing BEA zeolite, and an exhaust gas purification composition composed of the powder of phosphorus-containing BEA zeolite was obtained.

[0066] Comparative Example 2

[0067] Except that the amount of trimethyl phosphate used was changed to 0.73 g, in the same manner as in Comparative Example 1, a powder of phosphorus-containing BEA zeolite was produced, and an exhaust gas purification composition composed of the powder of phosphorus-containing BEA zeolite was obtained.

[0068] Comparative Example 3

[0069] The powder of proton-type BEA zeolite a prepared in Example 1 without phosphorus was used as the exhaust gas purification composition.

[0070] Comparative Example 4

[0071] The powder of proton-type BEA zeolite b prepared in Example 7 without phosphorus was used as the exhaust gas purification composition.

[0072] Comparative Example 5

[0073] The powder of proton-type BEA zeolite c prepared in Comparative Example 1 without phosphorus was used as the exhaust gas purification composition.

[0074] For the proton-type BEA zeolite prepared in each of the examples and comparative examples, and the exhaust gas purification composition of each of the examples and comparative examples, the following evaluations were carried out. The results are shown in Table 1. In Table 1, the vapor deposition method is denoted as "VD", the incipient wetness impregnation method is denoted as "IW", and the evaporation to dryness method is denoted as "DU".

[0075] SiO 2 / Al 2 O 3 Molar ratio

[0076] Using a scanning fluorescence X-ray analyzer (model: ZSX PrimusII, manufactured by Rigaku Corporation), the Si content and Al content in the BEA zeolite and the exhaust gas purification composition were measured, and the SiO 2 / Al 2 O 3 molar ratio was calculated from the obtained Si content and Al content. The method for preparing the measurement sample was carried out as follows.

[0077] Method for preparing the measurement sample

[0078] The BEA zeolite or the exhaust gas purification composition was put into a vinyl chloride tube with a diameter of 30 mm and compression molded to prepare a measurement sample.

[0079] P / Al molar ratio

[0080] Using a scanning fluorescence X-ray analyzer (model: ZSX PrimusII, manufactured by Rigaku Corporation), the P content and Al content in the BEA zeolite and the exhaust gas purification composition were measured, and the P / Al molar ratio was calculated from the obtained P content and Al content. The method for preparing the measurement sample was carried out as follows.

[0081] Method for preparing the measurement sample

[0082] The BEA zeolite or the exhaust gas purification composition was put into a vinyl chloride tube with a diameter of 30 mm and compression molded to prepare a measurement sample.

[0083] Mesopore volume V1 and micropore volume V2

[0084] Nitrogen adsorption isotherm measurement

[0085] The mesopore volume V1 and the micropore volume V2 were calculated from the nitrogen adsorption isotherm.

[0086] The nitrogen adsorption isotherm of BEA zeolite or the composition for waste gas purification was measured by a high-precision gas / vapor adsorption measurement device (model: BELSORP-maxII, manufactured by Microtrac Bell Co., Ltd.). High-purity nitrogen was adsorbed on the sample at 77K, and the measurement was carried out by the volumetric method. The measured sample was weighed at 0.1 g to 0.2 g in terms of dry weight into the sample tube. The measurement pretreatment was carried out by vacuum evacuation (1×10 -5 kPa) at 510 °C for 8 hours or more. The nitrogen adsorption isotherm was measured at a relative pressure (P / P 0 ) of 10.5 or less.

[0087] Method for measuring mesopore volume V1

[0088] The mesopore volume V1 was calculated from the nitrogen adsorption isotherm determined by using the method for determining the mesopore distribution of Barrett, Joyner, and Halenda (BJH method) described in ISO 15901-2. The desorption curve was used in the calculation, and the adsorption cross-sectional area of nitrogen molecules was set to 0.1620 nm 2 for calculation. The pore volume in the range of pore diameters of 2 nm or more and 100 nm or less was taken as the mesopore volume V1. It should be noted that the graphs of the pore size distribution and cumulative pore size distribution obtained by measuring the composition for waste gas purification in Example 1 and Comparative Example 3 are as Figure 1 shown. In the graph, the left vertical axis represents the pore area distribution, and the right vertical axis represents the cumulative pore volume of pores of 2 nm or more.

[0089] Method for measuring micropore volume V2

[0090] The micropore volume V2 was calculated from the measured nitrogen adsorption isotherm to obtain the micropore distribution and volume according to the SF method (Saito-Foley method) (A. Saito, H. C. Foley, Microporous Materials, 3 (1995) 531). The physical constants, parameters of the adsorbent material and adsorbate gas used for calculating the micropore volume were the constants described in Physical Parameters for MicroporoSize Calculation (ISO 15901-3, JIS Z8831-3). The adsorption cross-sectional area of nitrogen molecules was set to 0.1620 nm 2 for calculation. The pore volume in the range of pore diameters of 0 nm or more and 2 nm or less was taken as the micropore volume V2.

[0091] BET specific surface area

[0092] The specific surface area is calculated by the BET method using the nitrogen adsorption isotherm measured in accordance with ISO 9277 (JIS Z8330: 2013).

[0093] Thermal durability test

[0094] The exhaust gas purification compositions of the respective examples and comparative examples were subjected to a thermal durability test under the following cycle in an atmosphere of 10% by volume of H 2 O at 1000 °C for 25 hours.

[0095] Cycle: A model gas having the following composition was alternately circulated at a flow rate of 3 L / min for 80 seconds, and air was circulated at a flow rate of 3 L / min for 20 seconds.

[0096] Model gas composition: C 3 H 6 was 70 mL / min, O 2 was 70 mL / min, and N 2 was the balance.

[0097] Vaporized water vapor was mixed into the model gas and air from a water injection tank so as to be 10% by volume of H 2 O. The saturated water vapor pressure was adjusted by temperature to provide the above volume percentage of water vapor.

[0098] Specific surface area retention rate

[0099] The BET specific surface area of the exhaust gas purification composition before and after the thermal durability test was measured, and the ratio of the BET specific surface area after the thermal durability test to the BET specific surface area before the thermal durability test was calculated as the BET specific surface area retention rate. Specifically, the BET specific surface area retention rate was calculated by the following formula (1).

[0100] (1) Specific surface area retention rate (%) = (BET specific surface area after thermal durability test / BET specific surface area before thermal durability test) × 100

[0101] XRD retention rate

[0102] The X-ray diffraction spectrum of the exhaust gas purification composition before and after the thermal durability test was measured using an X-ray diffractometer (model: MiniFlex600, manufactured by Rigaku Corporation). The peak intensity of the strongest peak at a diffraction angle 2θ of around 22.4° in the X-ray diffraction spectra of the exhaust gas purification composition before and after the thermal durability test was taken as the XRD crystallinity, and the XRD retention rate was calculated by the following formula (2).

[0103] (2) XRD retention rate = (XRD crystallinity after thermal durability test / XRD crystallinity before thermal durability test) × 100

[0104] Toluene Adsorption Performance

[0105] 200 mg of the exhaust gas purification composition before and after the heat durability test was respectively filled into a flow reaction device, and at 50 °C of the evaluation gas with the composition shown below, it was circulated at a flow rate of 30 L / min for 30 minutes to adsorb toluene. Toluene was desorbed by the temperature-programmed desorption method, and the toluene desorption amount was measured by a mass spectrometer. In Table 1, the toluene adsorption amount of the exhaust gas purification composition after the heat durability test of Comparative Example 3 is set as 1.0 in arbitrary unit amounts. It should be noted that the measurement of toluene temperature-programmed desorption was carried out using a catalyst evaluation device (BELCAT and BELMass) manufactured by Microtrac Bell Corporation, and the measurement of the amount of desorbed toluene (i.e., the toluene adsorption amount of the exhaust gas purification composition) was carried out using ChemMaster manufactured by Microtrac Bell Corporation. It should be noted that the measurement of toluene adsorption performance was only carried out on the exhaust gas purification compositions of Examples 1, 4, 7 and Comparative Examples 1-4.

[0106] Composition of the evaluation gas: 0.1 vol% toluene, 99.9 vol% helium

[0107] [Table 1]

[0108]

[0109] As shown in Table 1, the specific surface area retention rate of the exhaust gas purification compositions of Examples 1-7 was 65% or more, and the XRD retention rate was also 70% or more. From this result, it was confirmed that even after the heat durability test, the framework structure of the phosphorus-containing BEA type zeolite could be maintained, and the generation of framework structure defects was suppressed. In fact, the toluene adsorption amounts of the exhaust gas purification compositions of Examples 1, 4, 7 were more than that of Comparative Example 1 but less than that of Comparative Example 3 before the heat durability test, but after the heat durability test, the toluene adsorption performance was superior to that of Comparative Examples 1 and 3.

[0110] In Examples 1-6, the mesopore volume V1 after phosphorus modification decreased compared with that before phosphorus modification. In Example 7, the mesopore volume of the BEA type zeolite before phosphorus incorporation was small, so it was speculated that after attaching a phosphorus-containing compound to the BEA type zeolite and then performing heat treatment, the framework structure was slightly damaged and the mesopore volume increased. However, the pore volume ratio (V2 / V1) of Example 7 was 2.0 or more, so the generation of framework structure defects after the heat durability test was suppressed.

[0111] The pore volume ratio (V2 / V1) of the phosphorus-containing BEA zeolite of Comparative Examples 1 and 2 is less than 2.0, and the mesopores that cause defects in the framework structure cannot be sufficiently reduced. Therefore, the specific surface area retention rate and the XRD retention rate after the thermal durability test are low, and the framework structure is defective. Even when the pore volume ratio (V2 / V1) of the BEA zeolite of Comparative Examples 3 to 5 is 2.0 or more, since it does not contain phosphorus, the specific surface area retention rate and the XRD retention rate after the thermal durability test are very low, and the framework structure is defective.

[0112] Industrial Applicability

[0113] The exhaust gas purification composition according to the present invention can maintain the purification performance of hydrocarbons (HC) even when placed in a harsh thermal environment, and further improve the heat resistance. Therefore, the exhaust gas purification composition according to the present invention can be suitably used for purifying the exhaust gas discharged from internal combustion engines of automobiles, motorcycles, etc.

Claims

1. A composition for waste gas purification, which is a composition for waste gas purification containing phosphorus-containing BEA zeolite, In the BEA zeolite, it contains mesopores in the range of 2 nm or more and 100 nm or less in pore diameter measured by the BJH method and micropores in the range of 2 nm or less in pore diameter measured by the SF method, The pore volume ratio (V2 / V1) of the micropore volume V2 in the range of 2 nm or less in pore diameter measured by the SF method of the phosphorus-containing BEA zeolite to the mesopore volume V1 in the range of 2 nm or more and 100 nm or less in pore diameter measured by the BJH method is 2.0 or more, In the framework of the phosphorus-containing BEA zeolite, Si or Al is not replaced by divalent cations of Zn, and the SiO 2 / Al 2 O 3 molar ratio is 37.4 or more and 100 or less.

2. The composition for waste gas purification according to claim 1, wherein, The micropore volume V2 of the phosphorus-containing BEA zeolite is 0.1 cm 3 / g or more and within the range of 0.3 cm 3 / g or less.

3. The composition for waste gas purification according to claim 1 or 2, wherein, The mesopore volume V1 of the phosphorus-containing BEA zeolite is 0.001 cm 3 / g or more and within the range of 0.08 cm 3 / g or less.

4. The composition for waste gas purification according to claim 1 or 2, wherein, The P / Al molar ratio of the phosphorus-containing BEA zeolite is in the range of 0.7 or more and 1.0 or less.

5. A method for manufacturing a composition for waste gas purification, which is a method for manufacturing a composition for waste gas purification containing phosphorus-containing BEA zeolite, including the following steps: A step of preparing BEA zeolite, in the BEA zeolite, it contains mesopores in the range of 2 nm or more and 100 nm or less in pore diameter measured by the BJH method and micropores in the range of 2 nm or less in pore diameter measured by the SF method, The pore volume ratio (V2 / V1) of the micropore volume V2 in the range of 2 nm or less in pore diameter measured by the SF method of the BEA zeolite to the mesopore volume V1 in the range of 2 nm or more and 100 nm or less in pore diameter measured by the BJH method is 1.8 or more; A step of bringing the BEA zeolite into contact with a phosphorus-containing compound to attach the phosphorus-containing compound to the BEA zeolite; and, A step of heat-treating the BEA zeolite containing the phosphorus-containing compound to obtain a phosphorus-containing BEA zeolite, In the framework of the phosphorus-containing BEA zeolite, Si or Al is not replaced by divalent cations of Zn, and the SiO 2 / Al 2 O 3 molar ratio is 37.4 or more and 100 or less.

6. The method for manufacturing a composition for waste gas purification according to claim 5, wherein, The phosphorus-containing compound is at least one selected from the group consisting of phosphoric acid, trimethyl phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.

7. The method for manufacturing a composition for waste gas purification according to claim 5 or 6, wherein, The temperature for performing the heat treatment is in the range of 200 °C or more and 800 °C or less.

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