Adsorbent and method for manufacturing same

Abstract

Provided is an adsorbent having a core-shell structure, wherein: the core is configured from a zeolite; the shell meets the following requirements (A)-(C), i.e., (A) the shell is a silicate or is a silicate-based oxide configured from an aluminosilicate in which the molar ratio SiO2 / Al2O3 is 750 or higher, (B) the shell has a zeolite structure, and (C) all ratios (ISi-OH / ISi-O) of the peak intensity ISi-OH of Si-OH peaks ((3,788±50) cm–1) to the peak intensity ISi-O of Si-O peaks ((1,868±70) cm–1) are equal to or less than 3.0; and the structure of the zeolite constituting the core and the structure of the zeolite constituting the shell do not have a shared composite structural unit.

Description

Adsorbent and its manufacturing method

[0001] The present invention relates to an adsorbent and a method for producing the same. ２ The present invention relates to an adsorbent suitable for adsorbing , and a method for producing the adsorbent.

[0002] In the fields of exhaust gas purification and carbon neutrality, adsorbents that adsorb specific target substances are used.

[0003] For example, FAU-type zeolite is ２ However, FAU-type zeolite is known as an adsorbent material for CO when water is present in the atmosphere. ２ Competitive adsorption occurs between CO and water, ２ However, there is a problem in that the amount of adsorption decreases.

[0004] In order to solve this problem, attempts have been made to prepare composite particles by using a zeolite core having gas adsorption ability and coating the core with a shell having hydrophobic and gas diffusing properties.

[0005] For example, Non-Patent Document 1 describes composite particles in which a zeolite 13X core is coated with a silicalite shell, and Non-Patent Document 2 describes composite particles in which a Na-Y zeolite core is coated with a silicalite shell.

[0006] Mater. Chem. Phys. , 2012(133), pp1144-1151Ind. Eng. Chem. Res. , 2018(57), pp16358-16366

[0007] Core-shell zeolite materials are expected to be adsorbents that do not reduce the amount of adsorption of target substances even when water is present in the atmosphere. However, core-shell zeolite materials obtained by conventional methods have insufficient shell coverage and many Si-OH bonds on the shell surface, resulting in insufficient hydrophobicity.

[0008] In this regard, Non-Patent Document 1 describes that the hydrophobicity of composite particles can be improved by silylating the surfaces thereof. However, surface-silylated composite particles have low heat resistance, and their applications are limited.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an adsorbent that is highly heat-resistant and that suppresses a decrease in the amount of an adsorbed substance in the presence of water, and a method for producing the same.

[0010] The present invention is as follows.

[0011] <<Aspect 1>> An adsorbent having a core-shell structure, wherein the core is made of zeolite, and the shell satisfies the following requirements (A) to (C): (A) silicate or SiO ２ / Al ２ O ３ (B) a silicate-based oxide composed of an aluminosilicate having a molar ratio of 750 or more; (B) having a zeolite structure; and (C) a Si—O peak ((1,868±70) cm ) in FT-IR of the adsorbent. －１ ) peak intensity I Ｓｉ－Ｏ The Si-OH peak ((3,788±50) cm －１ ) peak intensity I Ｓｉ－ＯＨ The ratio (I Ｓｉ－ＯＨ / I Ｓｉ－Ｏ ) is 3.0 or less, and the structure of the zeolite constituting the core and the structure of the zeolite constituting the shell do not have a common composite structural unit. ２ / Al ２ O ３ The adsorbent according to Aspect 1, wherein the molar ratio is 20 or less. Aspect 3: The adsorbent according to Aspect 1 or 2, wherein the zeolite constituting the core has a framework structure selected from FAU, AEI, and CHA. Aspect 4: The substance to be adsorbed by the adsorbent is CO ２The adsorbent according to any one of Aspects 1 to 3, wherein the adsorbent is a zeolite-based core having an alkali metal or alkaline earth metal supported thereon. Aspect 5: The adsorbent according to any one of Aspects 1 to 4, wherein an alkali metal or alkaline earth metal is supported on the zeolite constituting the core. Aspect 6: The adsorbent according to any one of Aspects 1 to 5, wherein the silicate-based oxide constituting the shell has an MFI framework structure. Aspect 7: The adsorbent according to any one of Aspects 1 to 6, wherein the shell has a coverage of 75% or more. The adsorbent according to Aspect 8: A method for producing the adsorbent according to any one of Aspects 1 to 7, comprising: ２ / Al ２ O ３ a silicate-based oxide composed of an aluminosilicate having a molar ratio of 750 or more; depositing a seed shell composed of the silicate-based oxide on the surface of the core to synthesize an adsorbent precursor; and heating the adsorbent precursor in the presence of a silicate-based oxide source and an organic structure-directing agent to grow crystals of the shell. Aspect 9: The method for producing an adsorbent according to Aspect 8, wherein synthesizing the adsorbent precursor is carried out by spray-drying a mixture of the core and the silicate-based oxide. Aspect 10: The method for producing an adsorbent according to Aspect 8, wherein synthesizing the adsorbent precursor is carried out by heating a mixture of the core and the silicate-based oxide.

[0012] According to the present invention, there are provided an adsorbent that is highly heat-resistant and in which the decrease in the amount of adsorbed substances in the presence of water is suppressed, and a method for producing the same.

[0013] FIG. 1(a) is an FE-SEM image of Na-FAU (FAU core) used as a raw material in Example 1, and FIG. 1(b) is an FE-SEM image of the core-shell type FAU-MFI composite obtained in Example 1. FIG. 2 is an SEM image of the core-shell type FAU-MFI composite obtained in Example 1. FIG. 3 is an FE-SEM image of the core-shell type FAU-MFI composite precursor obtained in Comparative Example 1. FIG. 4 is an FT-IR chart measured for the FAU core and the sample of Example 1 60 seconds after the start of the flow of a water-containing nitrogen gas stream. FIG. 5 is a graph showing the change in water adsorption rate over time measured for each of the FAU-MFI composites obtained in Examples 1 and 3 and Comparative Examples 1 and 2.

[0014] The adsorbent of the present invention is an adsorbent having a core-shell structure, wherein the core is made of zeolite, and the shell satisfies the following requirements (A) to (C): (A) silicate or SiO ２ / Al ２ O ３ (B) a silicate-based oxide composed of an aluminosilicate having a molar ratio of 750 or more; (B) having a zeolite structure; and (C) a Si—O peak ((1,868±70) cm ) in FT-IR of the adsorbent. －１ ) peak intensity I Ｓｉ－Ｏ The Si-OH peak ((3,788±50) cm －１ ) peak intensity I Ｓｉ－ＯＨ The ratio (I Ｓｉ－ＯＨ / I Ｓｉ－Ｏ ) is 3.0 or less, and the structure of the zeolite constituting the core and the structure of the zeolite constituting the shell do not have a common composite structural unit.

[0015] The core of the adsorbent of the present invention is composed of zeolite. Zeolite is advantageous as an adsorbent core in that the aluminosilicate that constitutes it is generally suitable for gas adsorption, and the pore size that is optimal for adsorption of the target substance can be selected by selecting the framework structure.

[0016] The shell of the adsorbent of the present invention is made of silicate or SiO ２ / Al ２ O ３ The adsorbent is made of a silicate-based oxide composed of aluminosilicate with a molar ratio of 750 or more. That is, the shell of the adsorbent has an extremely low content of aluminum element or does not contain aluminum element at all. Such a shell is highly hydrophobic. The adsorbent of the present invention, which includes a highly hydrophobic shell, can adsorb a target substance to be adsorbed in a desired amount even in the coexistence of water. Here, "SiO ２ / Al ２ O ３ The "molar ratio" refers to the ratio of alumina (Al ２ O ３ ) to silica (SiO ２ ) molar ratio (SiO ２ / Al ２ O ３ ) means

[0017] The shell has a zeolite structure. The zeolite structure has pores. In the adsorbent of the present invention, which includes a shell having pores, the gas containing the substance to be adsorbed can easily permeate the shell, so the presence of the shell does not interfere with the adsorption of the substance to be adsorbed to a great extent.

[0018] Furthermore, the adsorbent of the present invention has a Si—O peak ((1,868±70) cm ) in FT-IR. －１ ) peak intensity I Ｓｉ－Ｏ The Si-OH peak ((3,788±50) cm －１ ) peak intensity I Ｓｉ－ＯＨ The ratio (I Ｓｉ－ＯＨ / I Ｓｉ－Ｏ ) shows a small value of 3.0 or less. Ｓｉ－ＯＨ / I Ｓｉ－Ｏ A small value of the ratio (I) means that the concentration of Si—OH groups in the shell is low and the shell is highly hydrophobic. Ｓｉ－ＯＨ / I Ｓｉ－Ｏ ) is as small as 3.0 or less, the shell is highly hydrophobic. Therefore, the adsorbent of the present invention has the advantage that, even in the coexistence of water, competitive adsorption between the substance to be adsorbed and water is suppressed, and the degree of loss of the amount of the substance to be adsorbed is small.

[0019] The elements constituting the adsorbent of the present invention will be explained below in order.

[0020] <Core> The core in the adsorbent of the present invention has the function of adsorbing the target substance. The core is made of zeolite. Zeolite has excellent adsorption capacity and is therefore ideal as the core in the adsorbent of the present invention.

[0021] SiO of zeolite that constitutes the core ２ / Al ２ O ３ The molar ratio may be 0.5 or more, 1.0 or more, 1.5 or more, or 2.0 or more to increase durability, and may be 500 or less, 300 or less, 100 or less, 80 or less, 40 or less, 20 or less, 10 or less, or 5.0 or less to increase the amount of adsorption of the substance to be adsorbed.

[0022] The International Zeolite Association assigns a skeleton code consisting of three capital letters to the skeletal structure of a zeolite. In this specification, a zeolite having a certain skeleton structure may be referred to by the skeleton code indicating the skeleton structure. Furthermore, an ion-exchanged zeolite may be referred to by a notation in which the ion species and the skeleton code are combined with a hyphen. For example, a zeolite having a skeleton structure represented by the skeleton code FAU may be written as "FAU," and an FAU ion-exchanged with Na may be written as "Na-FAU."

[0023] In addition, the pore diameter of a zeolite may be referred to in the present specification. This pore diameter is the value listed as the "Maximum diameter of a sphere that can diffuse along" in the Database of Zeolite Structures (URL: https: / / asia.iza-structure.org / IZA-SC / ftc_table.php) published by the International Zeolite Society. If this value differs among the a-axis, b-axis, and c-axis directions, the largest pore diameter among these pore diameters is used. In this database, for example, the pore diameters of AFI are listed as a-axis: 2.22 Å, b-axis: 2.22 Å, and c-axis: 7.42 Å. In the present specification, the largest value among these, "7.42 Å," is considered to be the pore diameter of AFI.

[0024] The framework structure of the zeolite constituting the core of the adsorbent of the present invention may be appropriately selected depending on the substance to be adsorbed. ２ In this case, the zeolite of the core may be one or more selected from, for example, AFI, ATO, BEA, CHA, CON, FAU, GME, LTA, LTL, MOR, MTW, AFX, AEI, MFI, OFF, and the like.

[0025] The adsorption target substance is CO ２ In this case, the pore diameter of the core zeolite may be 3.5 Å or more, 4.0 Å or more, 5.0 Å or more, 6.0 Å or more, 7.0 Å or more, or 7.2 Å or more, and may be 10.0 Å or less, 9.0 Å or less, or 8.0 Å or less. ２ In this case, the zeolite of the core may be one or more selected from AFI, CHA, FAU, AEI, GME, LTA, LTL, MFI, MOR, OFF, etc., and in particular may be one or more selected from FAU, AEI, and CHA.

[0026] The adsorption target substance is CO ２In this case, the zeolite core may be supported with an alkali metal or alkaline earth metal. Zeolites supported with an alkali metal or alkaline earth metal have high basicity, and therefore, CO ２ This has the advantage of increasing the amount of adsorption.

[0027] The particle size of the zeolite constituting the core of the adsorbent of the present invention may be 1.0 μm or more, 1.2 μm or more, 1.5 μm or more, or 2.0 μm or more, and may be 5.0 μm or less, 4.0 μm or less, 3.5 μm or less, or 3.0 μm or less. This particle size is a number average particle size obtained by microscopic observation.

[0028] <Shell> The shell in the adsorbent of the present invention has the function of imparting hydrophobicity to the adsorbent and protecting the zeolite core from moisture while allowing the substance to be adsorbed to pass through to the core.

[0029] The shell satisfies all of the following requirements (A) to (C): (A) silicate or SiO ２ / Al ２ O ３ (B) a silicate-based oxide composed of an aluminosilicate having a molar ratio of 750 or more; (B) having a zeolite structure; and (C) a Si—O peak ((1,868±70) cm ) in FT-IR of the adsorbent. －１ ) peak intensity I Ｓｉ－Ｏ The Si-OH peak ((3,788±50) cm －１ ) peak intensity I Ｓｉ－ＯＨ The ratio (I Ｓｉ－ＯＨ / I Ｓｉ－Ｏ ) is 3.0 or less.

[0030] The requirements (A) to (C) that the adsorbent shell must satisfy will be explained below in order.

[0031] (A) Silicate or SiO ２ / Al ２ O ３ The adsorbent shell is a silicate-based oxide composed of aluminosilicate with a molar ratio of 750 or more. ２ / Al ２ O ３It is a silicate-based oxide composed of aluminosilicate with a molar ratio of 750 or more.

[0032] The shell of the adsorbent is composed of such a silicate-based oxide, which ensures high hydrophobicity and pores, as described above. The adsorbent of the present invention, which includes such a shell, has the advantage of being able to adsorb a desired amount of a target substance even in the presence of water.

[0033] In order to achieve the above purpose, when the silicate-based oxide is an aluminosilicate, its SiO ２ / Al ２ O ３ The molar ratio is 750 or greater, and may be 1,000 or greater, 1,500 or greater, 2,000 or greater, 2,500 or greater, 3,000 or greater, 4,000 or greater, or 5,000 or greater.

[0034] (B) Having a Zeolite Structure The shell of the adsorbent has a zeolite structure.

[0035] Zeolite has a porous structure that allows the target substance to pass through efficiently to the core. Furthermore, by selecting the pore size, it may be possible to deliver only a specific target substance to the core.

[0036] The pore diameter of the silicate-based oxide constituting the shell may be 3.0 Å or more, 3.5 Å or more, or 4.0 Å or more, and may be 8.0 Å or less, 7.0 Å or less, 6.0 Å or less, or 5.0 Å or less.

[0037] The zeolite structure of the silicate-based oxide constituting the shell may be, for example, AEL, EUO, FER, HEU, MEL, MFI, NES, TON, WEI, etc., and may have one or more framework structures selected from these.

[0038] The shell in the adsorbent of the present invention may in particular be a silicate-based oxide having an MFI-type framework structure.

[0039] (C) Si—O peak ((1,868±70) cm ) in FT-IR of the adsorbent －１ ) peak intensity IＳｉ－Ｏ The Si-OH peak ((3,788±50) cm －１ ) peak intensity I Ｓｉ－ＯＨ The ratio (I Ｓｉ－ＯＨ / I Ｓｉ－Ｏ ) is 3.0 or less. The ratio of the adsorbent (I Ｓｉ－ＯＨ / I Ｓｉ－Ｏ ) of 3.0 or less means that the amount of Si—OH groups in the shell is small. This indicates that the shell is highly hydrophobic, and this enables the adsorbent of the present invention to exhibit high adsorption capacity even in the coexistence of water.

[0040] Ratio (I Ｓｉ－ＯＨ / I Ｓｉ－Ｏ ) may be 2.8 or less, 2.6 or less, 2.4 or less, 2.2 or less, 2.0 or less, or 1.8 or less. Ｓｉ－ＯＨ / I Ｓｉ－Ｏ ) may be zero (0), but in relation to the effects of the present invention, the ratio (I Ｓｉ－ＯＨ / I Ｓｉ－Ｏ ) is sufficient if it is 0.5 or more, 1.0 or more, or even 1.5 or more.

[0041] The FT-IR of the adsorbent may be measured by a transmission method in accordance with JIS K0117:2017 (General rules for infrared spectroscopic analysis).

[0042] In the adsorbent of the present invention, the shell coverage may be 75% or more. By having the shell coverage of 75% or more, the adsorbent has very high heat resistance while highly suppressing the decrease in the amount of the adsorbed substance in the presence of water. From this perspective, the shell coverage may be 78% or more, 80% or more, 82% or more, 85% or more, 90% or more, or 95% or more, or may be 100%.

[0043] The shell coverage of the adsorbent of the present invention is defined as the ratio of the area of ​​the adsorbent surface that is covered with the shell and where the core is not exposed. The shell coverage may be measured by a method known to those skilled in the art, such as XPS, FIB-SEM, or FT-IR. The method for measuring the shell coverage is based on the SiO ２ / Al ２ O ３It may be selected appropriately depending on the molar ratio.

[0044] For example, the SiO ２ / Al ２ O ３ When the molar ratio is 5 or less, the coverage of the shell is determined based on the results of XPS analysis of the adsorbent, and is determined based on the SiO of each of the core and shell. ２ / Al ２ O ３ It may be calculated by calculation taking into account the molar ratio. ２ / Al ２ O ３ When the molar ratio exceeds 5, the coverage of the shell may be measured by FIB-SEM, FT-IR, or the like.

[0045] The measurement of the shell coverage by FIB-SEM may be carried out, for example, by image analysis of an SEM image of a cross section of the adsorbent processed by FIB.

[0046] The shell coverage may be measured by FT-IR, for example, by FT-IR measurement of an adsorbent to which quinoline has been adsorbed. In this case, quinoline has a large molecular size and cannot be adsorbed into the pores of the core, but is adsorbed only to the shell. Therefore, the shell coverage can be calculated from the peak intensity of quinoline in FT-IR.

[0047] The shell proportion in the adsorbent of the present invention may be 15% by mass or more, 20% by mass or more, 25% by mass or more, or 30% by mass or more, and may be 50% by mass or less, 45% by mass or less, 40% by mass or less, or 35% by mass or less, based on the total mass of the adsorbent. If the shell proportion is within this range, the adsorbent will have very high heat resistance while being highly inhibited from reducing the amount of adsorption of the substance to be adsorbed in the presence of water.

[0048] The shell ratio in the adsorbent of the present invention is defined as the ratio of the mass of the shell to the total mass of the adsorbent.

[0049] The shell thickness of the adsorbent of the present invention may be 100 nm or more, 120 nm or more, 150 nm or more, 170 nm or more, 200 nm or more, or 220 nm or more, and may be 1,000 nm or less, 500 nm or less, 400 nm or less, 300 nm or less, or 250 nm or less. If the shell thickness is within this range, the adsorbent will have very high heat resistance while being highly inhibited from reducing the amount of adsorption of the substance to be adsorbed in the presence of water. If the shell thickness is too thick, it may be difficult for the substance to be adsorbed to pass through, which may be undesirable.

[0050] The shell thickness of the adsorbent of the present invention may be measured as a number average value by observation under an electron microscope.

[0051] <The structure of the zeolite constituting the core and the structure of the zeolite constituting the shell do not share a common composite structural unit> Furthermore, in the adsorbent of the present invention, it is required that the structure of the zeolite constituting the core and the structure of the zeolite constituting the shell do not share a common composite structural unit.

[0052] Zeolites are composed of a combination of basic structures called "Composite Building Units (CBUs)" which are formed by linking multiple TO4 units (several to several tens of units) together, each of which is a TO4 unit consisting of a tetracoordinated Si atom or Al atom and an O atom. One type of zeolite may contain one or more types of CBUs.

[0053] For example, zeolites with framework structures of FAU, AEI, CHA, BEA, and MFI are each composed of the following CBUs: FAU: d6r, sod (2 types) AEI: d6r (1 type) CHA: d6r, cha (2 types) BEA: mor, bea, mtw (3 types) MFI: mor, cas, mfi, mel (4 types)

[0054] For example, BEA and MFI have a composite structural unit called "mor" as a common composite structural unit. Therefore, for example, a core-shell adsorbent having a BEA-type core and an MFI-type shell does not fall under the category of the adsorbent of the present invention.

[0055] On the other hand, for example, FAU and MFI do not have a common composite structural unit, and therefore, for example, a core-shell adsorbent having an FAU-type core and an MFI-type shell falls under the adsorbent of the present invention if it satisfies other requirements.

[0056] As verified in the examples described later, the CO ２ Therefore, a core-shell type adsorbent having a high adsorption amount can be obtained.

[0057] Also, the core CO ２ High adsorption capacity and SiO ２ / Al ２ O ３ It is desirable to be able to increase the molar ratio to make the shell more hydrophobic.

[0058] From the above viewpoints, in the adsorbent of the present invention, the zeolite constituting the core may have a skeletal structure selected from FAU, AEI, and CHA, and the silicate-based oxide constituting the shell may have a skeletal structure of MFI.

[0059] <Core and shell SiO ２ / Al ２ O ３ Method for measuring the molar ratio> The SiO of the core and shell in the adsorbent of the present invention ２ / Al ２ O ３ The molar ratio may be measured, for example, by scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX) of a cross section of the adsorbent.

[0060] In SEM-EDX, first, SEM analysis of the cross section of the adsorbent is performed, and in the obtained SEM image, the core portion and shell portion of the adsorbent are defined based on the contrast of the image. Next, in this SEM image, one imaginary line is set so as to pass through both the core portion and the shell portion. Subsequently, EDX line analysis is performed along the set imaginary line, and the Si element concentration and Al element concentration (mass%) in each of the core portion and the shell portion are measured. Then, from the obtained measured values, the SiO ２ / Al ２ O ３ The molar ratio can be calculated.

[0061] <<Method for Producing Adsorbent>> The adsorbent of the present invention described above may be produced by any method as long as it satisfies the above-mentioned characteristics.

[0062] The adsorbent of the present invention may be produced, for example, by the following production method.

[0063] A core composed of zeolite and a silicate or SiO ２ / Al ２ O ３ a silicate-based oxide comprising an aluminosilicate having a molar ratio of 750 or greater (contact of a core with a silicate-based oxide); synthesizing an adsorbent precursor by depositing a seed shell comprising the silicate-based oxide on the surface of the core (synthesis of an adsorbent precursor); and heating the adsorbent precursor in the presence of a silicate-based oxide source and an organic structure-directing agent to grow shell crystals (shell crystal growth).

[0064] The resulting adsorbent may be calcined as necessary before use.

[0065] The method for producing an adsorbent of the present invention has the advantage that a core-shell structure can be formed without considering the commonality of structure between the zeolite constituting the shell and the zeolite constituting the core.

[0066] The elements constituting the above-mentioned method for producing an adsorbent will be explained below in order.

[0067] <Contacting the Core with a Silica-Based Oxide> First, the core is brought into contact with a silicate-based oxide. (Core) The core may be appropriately selected depending on the desired core in the adsorbent of the present invention. When the substance to be adsorbed is CO ２ When the alkali cation is CO 2 , a zeolite substituted with an alkali cation may be used. The alkali cation may be, for example, an alkali metal cation, an alkaline earth metal cation, an ammonium cation, etc. In such a zeolite, the alkali cation is CO 2 . ２ Therefore, compared with other cation-substituted materials (e.g., H-zeolite) that have only physical adsorption sites, ２ The advantage of this is that the amount of alkali cations adsorbed is increased. ＋ It may be.

[0068] The core for producing the adsorbent of the present invention can be, for example, SiO ２ / Al ２ O ３ The polyisocyanate may be one or more selected from AFI, ATO, BEA, CHA, CON, FAU, GME, LTA, LTL, MOR, MTW, AFX, AEI, MFI, OFF, and the like, having a molar ratio of 0.5 to 10 and a particle size of 1.0 μm to 5.0 μm.

[0069] The core may be surface-modified with a polycation upon contact with the silicate-based compound, such as an ammonium polycation, a quaternary ammonium cation, or the like.

[0070] The polycationic surface modification of the core may be carried out, for example, by contacting the core with a polycationizing agent, which may be selected from, for example, poly(diallyldimethylammonium chloride), alkylmethylamine, etc.

[0071] The amount of the polycationizing agent used may be 0.5 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the core. The core and the polycationizing agent may be contacted, for example, in water. The contact temperature may be appropriately selected from the range of 0°C or more and 100°C or less, but room temperature is sufficient.

[0072] (Silicate-based oxide) The silicate-based oxide is a component that is deposited on the surface of the core by contact with the core, forming a "seed shell." Therefore, this silicate-based oxide may have the same framework structure as the desired shell in the adsorbent of the present invention. This silicate-based oxide may be, for example, an MFI-type silicate. The SiO of this silicate ２ / Al ２ O ３ The molar ratio is arbitrary. ２ / Al ２ O ３ The molar ratio is adjusted to the desired SiO ２ / Al ２ O ３ Even if the molar ratio is different, the SiO of the silicate-based oxide source used for the crystal growth of the shell may be ２ / Al ２ O ３ By changing the molar ratio, the SiO ２ / Al ２ O ３ The molar ratio can be controlled to a desired value.

[0073] The particle size of the silicate-based oxide may be, for example, 30 nm or more and 120 nm or less.

[0074] The silicate-based oxide may be synthesized by heating a suitable silicate-based oxide source in the presence of water. The silicate-based oxide may be synthesized in the presence of an organic structure directing agent (OSDA).

[0075] The silicate-based oxide source used here may be selected from any silicon source, such as orthosilicic acid, alkoxides of silicic acid, alkali metal salts of silicic acid, fumed silica, colloidal silica, etc., and one or more selected from these may be used. Specifically, the alkoxides of silicic acid may be, for example, tetraethyl orthosilicate, and the alkali metal salts of silicic acid may be, for example, sodium silicate.

[0076] When the shell of the desired adsorbent contains Al, the silicate oxide source may contain Al, or a mixture of the silicate oxide source and the Al source may be used. Examples of the silicate oxide source containing Al include aluminosilicate, alkoxides of aluminosilicate, and alkali metal salts of aluminosilicate. Examples of the Al source include aluminates, Al(OiPr) ３ The aluminate may be, for example, sodium aluminate.

[0077] When synthesizing a silicate-based oxide, an organic structure directing agent (OSDA) may be optionally present. For example, an OSDA capable of forming an MFI structure may be selected. Specific examples of the OSDA include alkylammonium hydroxides and 1,2,3-triethylimidazolium. Examples of the alkylammonium hydroxide include tetramethylammonium hydroxide, tetraethylammonium hydroxide, benzyltrimethylammonium hydroxide, N,N,N-trimethyladamantanammonium hydroxide, N,N-diethyl-2,6-dimethylpiperidinium hydroxide, and 1,4-bis(1-azabicyclo[2.2.2]octane)butyl hydroxide.

[0078] The amount of OSDA used may be 0.3 parts by mass or more, 15 parts by mass or more, or 30 parts by mass or more, and may be 680 parts by mass or less, 340 parts by mass or less, or 240 parts by mass or less, per 100 parts by mass of the silica-equivalent mass of the silicate-based oxide source.

[0079] When the amount of OSDA used is expressed as a molar ratio, the ratio of the number of moles of OSDA to 1 mole of silicon atoms in the silicate-based oxide source (OSDA / Si) can be, for example, in the range of 0.1 to 0.7.

[0080] The silicate-based oxide may be synthesized by heating the silicate-based oxide source as described above in the presence of water, optionally in the presence of an OSDA. The synthesis of the silicate-based oxide may typically be carried out in water.

[0081] The heating temperature when synthesizing the silicate-based oxide may be, for example, 50° C. or more and 175° C. or less, and the heating time may be, for example, 10 hours or more and 300 hours or less.

[0082] (Conditions for Contacting Cores with a Silica-Based Oxide) The contacting of the cores with a silicate-based oxide is carried out in the presence of water. Typically, the contacting of the cores with a silicate-based oxide may be carried out in water. In this case, the contacting of the cores with a silicate-based oxide is carried out in the form of a mixture containing the cores and the silicate-based oxide in water. When the two are contacted in this manner, the resulting mixture can be conveniently used as is in the next step, "synthesis of an adsorbent precursor (deposition of a seed shell)."

[0083] The amount of silicate-based oxide used may be, for example, 70 parts by mass or more, 100 parts by mass or more, or 200 parts by mass or more, expressed as the silica-equivalent mass of silicate-based oxide per 100 parts by mass of the core, and may be, for example, 10,000 parts by mass or less, 3,400 parts by mass or less, or 2,000 parts by mass or less.

[0084] <Synthesis of Adsorbent Precursor (Deposition of Seed Shell)> Next, a seed shell made of a silicate-based oxide is deposited on the core to synthesize the adsorbent precursor.

[0085] Deposition of the seed shell onto the core may be carried out, for example, by spray drying a mixture of the core and the silicate-based oxide, by heating a mixture of the core and the silicate-based oxide, or the like.

[0086] The mixture of the core and the silicate-based oxide may contain water. The mixture of the core and the silicate-based oxide containing water may be prepared by adding the core and the silicate-based oxide to water, or the mixture obtained when the core and the silicate-based oxide are contacted in water may be used as is.

[0087] The mixture of the core and silicate-based oxide may be spray-dried using a commercially available spray-drying device at a predetermined flow rate and at a temperature of, for example, 100 to 300°C.

[0088] The mixture of the core and silicate-based oxide may be heated, for example, at a temperature of 50° C. or more and 120° C. or less for a time of 12 hours or more and 150 hours or less.

[0089] <Shell Crystal Growth> The adsorbent precursor obtained above is then heated in the presence of a silicate-based oxide source and an organic structure-directing agent to grow shell crystals.

[0090] (Silicate-Based Oxide Source) The silicate-based oxide source used for growing the shell crystals may be appropriately selected from the silicate-based oxide sources exemplified above as silicate-based oxide sources for synthesizing the silicate-based oxide that will become the "seed shell".

[0091] The amount of the silicate-based oxide source used, expressed as the silica-equivalent mass of the silicate-based oxide source relative to 100 parts by mass of the adsorbent precursor, may be more than 0 parts by mass, 0.1 parts by mass or more, 1 part by mass or more, or 5 parts by mass or more, or may be 100 parts by mass or less, 50 parts by mass or less, or 25 parts by mass or less, and may be selected appropriately depending on the desired shell ratio.

[0092] <Organic Structure Directing Agent> The organic structure directing agent (OSDA) used for growing the shell crystals may be appropriately selected from the OSDAs exemplified above as OSDAs for synthesizing the silicate-based oxide that becomes the "seed shell."

[0093] The amount of OSDA used may be 3 parts by mass or more, 20 parts by mass or more, or 30 parts by mass or more, and may be 240 parts by mass or less, 120 parts by mass or less, 100 parts by mass or less, or 85 parts by mass or less, per 100 parts by mass of the adsorbent precursor.

[0094] (Conditions for Shell Crystal Growth) Shell crystal growth may be carried out in the presence of water, or in the coexistence of an alcohol. Typically, a mixture containing an adsorbent precursor, a silicate-based oxide source, an organic structure directing agent, and an alcohol is heated in water.

[0095] The alcohol has the function of making the silicate-based oxide source more soluble in the solvent. Examples of alcohol that can be used include ethanol and methanol, and ethanol is preferred. The amount of alcohol used may be more than 0 parts by mass, 10 parts by mass or more, 75 parts by mass or more, or 150 parts by mass or more, and may be 15,000 parts by mass or less, 7,500 parts by mass or less, 4,000 parts by mass or less, or 3,000 parts by mass or less, per 100 parts by mass of the adsorbent precursor.

[0096] The heating temperature for growing the shell crystals may be, for example, 80° C. or more, 100° C. or more, 120° C. or more, 150° C. or more, or 180° C. or more, and 300° C. or less, 250° C. or less, 200° C. or less, 180° C. or less, or 150° C. or less. The heating time for growing the shell crystals may be, for example, 10 minutes or more, 20 minutes or more, 30 minutes or more, 1 hour or more, 2 hours or more, 4 hours or more, 6 hours or more, 8 hours or more, 12 hours or more, or 24 hours or more, and 72 hours or less, 48 ​​hours or less, 36 hours or less, 24 hours or less, 12 hours or less, 8 hours or less, 6 hours or less, 4 hours or less, or 2 hours or less.

[0097] Here, when the heating temperature is relatively high, the heating time may be relatively short, and when the heating time is relatively long, the heating temperature may be relatively low. For example, when the heating temperature is 80°C or higher and 150°C or lower, the heating time may be 6 hours or higher and 72 hours or lower. For example, when the heating temperature is 180°C or higher and 300°C or lower, the heating time may be 10 minutes or higher and 2 hours or lower.

[0098] <Washing and Calcination> The adsorbent of the present invention can be obtained as described above. The obtained adsorbent may be washed and calcined as necessary before use.

[0099] The washing may be carried out with, for example, one or more solvents selected from water and organic solvents. Washing with a water-soluble organic solvent or a mixed solvent containing water and a water-soluble organic solvent is particularly preferred. The water-soluble organic solvent may be selected from, for example, methanol, ethanol, acetone, n-propanol, i-propanol, etc. This washing removes residual organic matter derived from the silicate-based oxide source, OSDA, etc.

[0100] The firing may be performed, for example, at a temperature of 400° C. to 800° C. for a time of 1 hour to 12 hours. Air is sufficient as the ambient atmosphere during firing. This firing not only burns off any remaining organic matter that could not be removed by washing, but also has the advantage of fixing the shell to the surface of the core.

[0101] I. Effect of Manufacturing Method of Core-Shell Composite In Examples 1 to 6 and Comparative Examples 1 to 4, the CO absorption of core-shell FAU-MFI composites (adsorbents) manufactured by various methods was investigated. ２ The adsorption amount was investigated. FAU has two types of composite structural units (CBUs): d6r and sod, and MFI has four types of CBUs: mor, cas, mfi, and mel. Example 1 In Example 1, MFI was deposited on the surface of FAU by spray drying.

[0102] 1. Synthesis of core-shell type FAU-MFI complex (1) Pretreatment of FAU core surface (synthesis of PDADMAC-modified Na-FAU) Na-FAU (SiO ２ / Al ２ O ３ 100 g of a solution (molar ratio = 2.2, Na / Al = 0.65 (molar ratio), particle size 2-3 μm) was added, and ultrasonic waves were applied for 2 hours. 5.6 g of a PDADMAC (poly(diallyldimethylammonium chloride)) aqueous solution (35% by mass, manufactured by Sigma-Aldrich) was added and stirred to modify the FAU surface with PDADMAC. The solid content was then collected by centrifugation to obtain PDADMAC-modified Na-FAU.

[0103] (2) Synthesis of nano-MFI shell: In 100 g of water, a TEOS (tetraethyl orthosilicate) aqueous solution (SiO ２ 180 g of a 28% by mass equivalent aqueous solution of tetrapropylammonium hydroxide (TPAOH) (manufactured by Tokyo Chemical Industry Co., Ltd.) and 100 g of an aqueous solution of tetrapropylammonium hydroxide (TPAOH) (40% by mass, manufactured by Seichem Japan Co., Ltd.) as an organic structure directing agent (OSDA) were added and mixed, and the mixture was maintained at 80°C for 96 hours with stirring to carry out hydrothermal synthesis, thereby obtaining a dispersion containing a seed shell (MFI-type silicate).

[0104] (3) Deposition of MFI on the FAU surface (synthesis of core-shell type FAU-MFI composite precursor) The PDADMAC-modified Na-FAU obtained in "(1) Pretreatment of the FAU core surface" was added to a dispersion containing the nano-MFI shell obtained in "(2) Synthesis of nano-MFI shell" to obtain a mixture. While stirring this mixture, spray drying was carried out using a laboratory spray dryer (manufactured by Okawara Manufacturing Co., Ltd.) at a flow rate of 18 mL / min and a temperature of 200°C to deposit a seed shell on the surface of the core. The obtained powder was collected to obtain a core-shell type FAU-MFI composite precursor. Here, the mass of FAU in the mixture and the SiO ２ The ratio of the converted mass of TEOS to the mass of TEOS was set to 2.08.

[0105] (4) Crystal Growth of MFI Shell (Synthesis of Core-Shell FAU-MFI Composite) 8 g of a TEOS aqueous solution, 1.3 g of a TPAOH aqueous solution, and 33 g of ethanol were added to 143 g of water and stirred thoroughly to obtain an MFI shell precursor solution. 10 g of the core-shell FAU-MFI composite precursor obtained in "(3) Deposition of MFI on the FAU Surface" was added to this solution, and the container was sealed. This container was then placed in an autoclave and rotated at 20 rpm while maintaining the temperature at 135°C for 24 hours to perform hydrothermal synthesis and grow shell crystals.

[0106] Next, the solid content in the reaction mixture was recovered by centrifugation at a rotation speed of 300 rpm, and washed with water and then with acetone. These washings were carried out by adding water or acetone in an amount twice the mass of the solid content, stirring for 15 minutes, and then centrifuging for 30 minutes. Next, the solid content after washing was recovered, dried at 100°C for 10 hours, and then calcined at 550°C for 5 hours to obtain a core-shell type FAU-MFI composite (adsorbent). The shell of the obtained core-shell type FAU-MFI composite did not contain Al atoms, and therefore the SiO ２ / Al ２ O ３ The molar ratio is ∞ (infinity).

[0107] (5) Analysis (5-1) Measurement of Shell Ratio The raw material Na-FAU and the core-shell type FAU-MFI composite obtained above were observed using a field emission scanning electron microscope (FE-SEM). An FE-SEM image of Na-FAU is shown in Figure 1(a), and an FE-SEM image of the core-shell type FAU-MFI composite is shown in Figure 1(b). An SEM image of the cross section of the core-shell type FAU-MFI composite obtained above is shown in Figure 2. This SEM image was taken after a cross section of the sample was extracted from the core-shell type FAU-MFI composite powder by focused ion beam (FIB) processing. The FIB processing conditions were as follows: Pretreatment: After applying carbon paste to an aluminum sample stage, a core-shell type FAU-MFI composite powder was sprinkled on the carbon paste, and then osmium (Os) was evaporated for 5 seconds. Protective film: C deposition. Rough processing conditions: Acceleration voltage 30 kV, irradiation current 1.2 nA. Cleaning processing conditions: Acceleration voltage 30 kV (constant), irradiation current 0.75 nA → 0.26 nA → 41 pA (stepwise decrease).

[0108] Furthermore, the raw material FAU and the core-shell type FAU-MFI composite were subjected to X-ray fluorescence (XRF) analysis and X-ray photoelectron spectroscopy (XPS) analysis, respectively, to measure the shell ratio and shell coverage in the composite, taking advantage of the fact that the shell does not contain Al atoms. Furthermore, the core-shell type FAU-MFI composite was subjected to FT-IR analysis.

[0109] The shell ratio of the core-shell type FAU-MFI composite was calculated by the following formula: Shell ratio (mass%) = SiO ２ (FAU-MFI) - [{Al ２ O ３ (FAU-MFI) / 101.96}×SAR(FAU)×60.08]

[0110] The abbreviations in the above formula have the following meanings: SiO ２ (FAU-MFI): Silica content (mass%) in the core-shell type FAU-MFI composite determined by XRF quantitative analysis Al ２ O ３(FAU-MFI): alumina content (mass%) in the core-shell type FAU-MFI composite determined by XRF quantitative analysis. SAR(FAU): SiO of the raw material FAU core. ２ / Al ２ O ３ The molar ratios of 101.96 and 60.08 are Al ２ O ３ and SiO ２ is the formula weight.

[0111] (5-2) Measurement of Shell Coverage The shell coverage was determined by XPS analysis as follows. First, XPS analysis was performed on the raw material FAU and the obtained core-shell type FAU-MFI composite, and the amount of Al exposed on the surface of each sample was measured as the area of ​​the Al2p peak (Al peak area) (λ = 74 eV). Next, the shell coverage was calculated from each obtained Al peak area using the following formula: Coverage (%) = {(Al peak area of ​​raw material FAU - Al peak area of ​​FAU-MFI composite) / Al peak area of ​​raw material FAU} × 100

[0112] In the FT-IR of the core-shell type FAU-MFI composite, the Si-O peak of the MFI skeleton (1,868 ± 70 cm －１ ) peak intensity I Ｓｉ－Ｏ The Si—OH peak (3,788 ± 50 cm －１ ) peak intensity I Ｓｉ－ＯＨ / ratio (I Ｓｉ－ＯＨ / I Ｓｉ－Ｏ ) was calculated. Ｓｉ－ＯＨ / I Ｓｉ－Ｏ ) is smaller, the proportion of Si—OH is smaller, and therefore the number of defects in the shell is smaller.

[0113] FT-IR measurements were performed in accordance with JIS K0117:2017 (General Rules for Infrared Spectroscopic Analysis) using the following procedure. The zeolite samples obtained in each Example or Comparative Example were pulverized in a mortar. 10 mg of the pulverized material was compression molded under a pressure of 10 MPa to prepare a disk sample with a diameter of 10 mm. FT-IR measurements of the obtained disk sample were performed under the following conditions. Measurement device: Fourier transform infrared spectrophotometer "FT / IR-6600" manufactured by JASCO Corporation Measurement method: Transmission method Measurement wavelength range: 4,000 to 1,000 cm －１ Resolution: 4cm －１ Detector: Mid-band mercury cadmium telluride (MCT) detector Number of measurements: 64 Measurement temperature: 500°C Measurement atmosphere: 20% by volume O ２ / N ２ Under distribution

[0114] The spectrum of zeolite was measured by the following method. The same disk sample as above was loaded into the sample chamber of the measurement device, and 20% by volume O ２ / N ２ The measurement was carried out under the same conditions as above, except that the temperature was raised from room temperature to 500°C at a rate of 20°C / min under flow and the temperature was maintained at 500°C for 30 minutes before the measurement.

[0115] (5-3) Core and shell SiO ２ / Al ２ O ３ Measurement of the molar ratio of the core and shell SiO of the core-shell type FAU-MFI composite ２ / Al ２ O ３ The molar ratio was measured by SEM-EDX. The following measuring device was used for the SEM-EDX measurement. Measuring device: Dual beam scanning electron microscope, model name "Helios G4UX (FIB-SEM)" manufactured by Thermo Fisher. SEM: 5 kV / 0.1 nA, WD 4 mm, Dwell time 200 ns, resolution 1536 × 1024 pixels. EDS: 10 kV, 0.8 nA, Dwell time 150 μs, accumulation 40 times, resolution 512 pixels (Map analysis).

[0116] Specifically, the measurement was carried out as follows. First, SEM analysis was carried out on the core-shell type FAU-MFI composite powder whose cross section was exposed in the same manner as in "(5-1) Measurement of shell ratio" to obtain an SEM image. In the obtained SEM image, the core portion and shell portion of the adsorbent were defined based on the contrast of the image. A virtual line passing through both the core portion and the shell portion was set. Next, EDX line analysis was carried out along the set virtual line to measure the Si element concentration and Al element concentration (mass%) in each of the core portion and the shell portion. Then, from the obtained measured values, the SiO ２ / Al ２ O ３ The molar ratio was calculated.

[0117] (6) CO ２ Evaluation of adsorption amount Approximately 0.1 g of the core-shell type FAU-MFI composite was precisely weighed and placed in a sample tube of a catalyst analyzer "BELCAT II" (normal pressure flow type) manufactured by Microtrac BEL Co., Ltd., and CO2 was measured in the presence of the sample and in the blank state. ２ From the difference in the area of ​​the adsorption breakthrough curve, CO ２ The adsorption amount was calculated. The measurement was performed according to the following procedure. Heating: In a He stream at a flow rate of 30 mL / min, the temperature was increased from room temperature to 400°C at a rate of 10°C / min. Isothermal treatment: In a He stream at a flow rate of 30 mL / min, the temperature was maintained at 400°C for 30 minutes. Cooling: In a He stream at a flow rate of 30 mL / min, the temperature was decreased from 400°C to 50°C at a rate of 20°C / min. Measurement of adsorption breakthrough curve: While maintaining the temperature at 50°C, CO was added at a flow rate of 5 mL / min. ２ A model gas containing CO was flowed. ２ The adsorption breakthrough curve was measured.

[0118] CO ２ The composition of the model gas is as follows: CO ２ : 16% by volume H ２ O: 3% by volume He: balance

[0119] CO ２ The adsorption amount is calculated as CO ２ CO for 15 minutes after starting to flow the model gas ２The difference between the cumulative area of ​​the adsorption breakthrough curve in the presence of the sample and the blank was calculated, and this difference was assigned to the mass of the FAU core in the sample, which was calculated by multiplying the mass of the sample (g) by (100 - shell ratio (%)).

[0120] The results are shown in Table 1. In Table 1, the SiO ２ / Al ２ O ３ The molar ratios are shown both as theoretical values ​​based on the charge and as values ​​actually measured by the above-mentioned method. ２ / Al ２ O ３ The theoretical value of the molar ratio was ∞ (infinity).

[0121] Example 2 In Example 2, a core-shell type FAU-MFI complex was synthesized in the same manner as in Example 1, except that in "(4) Crystal growth of MFI shell", the conditions for growing the shell crystal were changed to 200°C and 30 minutes, and various evaluations were performed.

[0122] Example 3 In Example 3, MFI was deposited on the surface of FAU by hydrothermal synthesis.

[0123] In "(3) Deposition of MFI on the FAU surface," MFI was deposited on the FAU surface by hydrothermal synthesis according to the following procedure instead of spray drying. A core-shell type FAU-MFI composite was synthesized in the same manner as in Example 1, and various evaluations were performed.

[0124] Deposition of MFI on the FAU surface by hydrothermal synthesis was carried out by the following procedure.

[0125] The PDADMAC-modified Na-FAU obtained in "(1) Pretreatment of the FAU core surface" was added to the dispersion containing the nano-MFI shell obtained in "(2) Synthesis of the nano-MFI shell" to obtain a mixture. This mixture was sealed in a container, placed in an autoclave, and left to stand at 80°C for 24 hours to perform hydrothermal synthesis. Here, the mass of FAU in the mixture and the SiO ２ The ratio of the converted mass of TEOS to the mass of TEOS was set to 2.08.

[0126] The solids in the reaction mixture were collected by centrifugation at 300 rpm and washed with water and acetone, in that order. These washes were carried out by adding water or acetone in an amount twice the mass of the solids, stirring for 15 minutes, and then centrifuging for 30 minutes. The washed solids were then dried at 100°C for 12 hours to obtain a core-shell FAU-MFI composite precursor.

[0127] Example 4 In Example 4, a core-shell type FAU-MFI complex was synthesized in the same manner as in Example 3, except that in "(4) Crystal growth of MFI shell", the conditions for growing the shell crystal were changed to 200°C and 30 minutes, and various evaluations were performed.

[0128] Example 5 In Example 5, MFI was deposited on the surface of FAU by repeating spray drying twice.

[0129] An intermediate of a core-shell type FAU-MFI complex precursor was obtained by performing "(1) pretreatment of the FAU core surface," "(2) synthesis of a nano-MFI shell," and "(3) deposition of MFI on the FAU surface" in the same manner as in Example 1. Next, a core-shell type FAU-MFI complex precursor was obtained by performing "(1) pretreatment of the FAU core surface," "(2) synthesis of a nano-MFI shell," and "(3) deposition of MFI on the FAU surface" again by the same procedure, except that the obtained intermediate of the core-shell type FAU-MFI complex precursor was used instead of Na-FAU.

[0130] Using the product obtained above as the core-shell type FAU-MFI complex precursor, a core-shell type FAU-MFI complex was synthesized by carrying out "(4) Crystal growth of MFI shell" in the same manner as in Example 1, and various evaluations were carried out.

[0131] Example 6 In Example 4, MFI was deposited on the FAU surface by repeating the hydrothermal synthesis twice.

[0132] An intermediate for the core-shell type FAU-MFI complex precursor was obtained by carrying out "(1) Pretreatment of the FAU core surface," "(2) Synthesis of nano-MFI shell," and "(3) Deposition of MFI on the FAU surface" in the same manner as in Example 3. Here, the supernatant obtained by centrifugation, which was performed to recover the solid content from the reaction mixture obtained in "(3) Deposition of MFI on the FAU surface," was stored.

[0133] The resulting core-shell type FAU-MFI composite precursor intermediate was dried at 100° C. for 12 hours.

[0134] Next, "(1) Pretreatment of the FAU core surface" was carried out again by the same procedure, except that the dried intermediate of the core-shell type FAU-MFI complex precursor obtained above was used instead of Na-FAU.

[0135] A core-shell FAU-MFI complex precursor was obtained by performing "(3) Deposition of MFI on the FAU surface" again in the same manner as in Example 1, except that the pretreated intermediate obtained above was used instead of PDADMAC-modified Na-FAU and the centrifuged supernatant stored above was used instead of the MFI shell precursor solution. A core-shell FAU-MFI complex was synthesized by performing "(4) Crystal growth of MFI shell" in the same manner as in Example 1, except that the obtained core-shell FAU-MFI complex precursor was used, and various evaluations were performed.

[0136] Comparative Example 1 In Comparative Example 1, the core-shell type FAU-MFI composite precursor obtained by spray drying in the same manner as in Example 1 was subjected to various evaluations without carrying out "(4) Crystal growth of MFI shell."

[0137] An FE-SEM image of the core-shell type FAU-MFI composite precursor obtained in Comparative Example 1 is shown in FIG.

[0138] Comparative Example 2 In Comparative Example 2, similarly to Example 2, the core-shell type FAU-MFI composite precursor obtained by hydrothermal synthesis was subjected to various evaluations without carrying out "(4) Crystal growth of MFI shell."

[0139] Comparative Example 3 Comparative Example 3 was carried out in the same manner as Comparative Example 2, except that the hydrothermal synthesis temperature was changed. That is, except that the autoclave temperature in the hydrothermal synthesis in "(3) Deposition of MFI on the FAU surface" was set to 135°C, synthesis of a core-shell type FAU-MFI composite precursor was attempted in the same manner as Example 2, and the obtained product was subjected to various evaluations without being subjected to "(4) Crystal growth of MFI shell".

[0140] The product obtained in Comparative Example 3 did not have a core-shell structure, and therefore, "(6) CO ２ The "evaluation of the amount of adsorption" was not performed. It is presumed that the product obtained in Comparative Example 3 did not have a core-shell structure because there were areas where the shell silicate particles aggregated and the shell silicate grew into crystals of several μm in size.

[0141] Also, "ratio (I Ｓｉ－ＯＨ / I Ｓｉ－Ｏ The value "7.3" is listed in the "(Saturation)" column, but this is presumably due to the detection of Si-OH in the core in the FT-IR analysis.

[0142] In Comparative Example 4, the core-shell type FAU-MFI composite precursor obtained by repeating spray drying four times was subjected to various evaluations as it was, without carrying out "(4) Crystal growth of MFI shell." Specifically, a sample was prepared by the following procedure.

[0143] Similar to Example 1, "(1) Pretreatment of the FAU core surface," "(2) Synthesis of a nano-MFI shell," and "(3) Deposition of MFI on the FAU surface" were performed to obtain intermediate (1) of a core-shell type FAU-MFI complex precursor. Next, the same procedures as those of Example 1 were repeated, except that intermediate (1) of the core-shell type FAU-MFI complex precursor was used instead of Na-FAU, to obtain intermediate (2) of a core-shell type FAU-MFI complex precursor. Furthermore, the same cycle was repeated, and spray drying was performed a total of four times to obtain a core-shell type FAU-MFI complex precursor.

[0144] The obtained core-shell type FAU-MFI composite precursor was subjected to various evaluations as it was, without carrying out "(4) Crystal growth of MFI shell".

[0145] All the results are shown in Table 1.

[0146]

[0147] As can be seen from Table 1, the comparative adsorbent in which no shell crystal growth was performed exhibited a high CO ２ In contrast, the adsorbent of the example in which the shell crystal growth was properly performed and a predetermined core-shell structure was formed was able to adsorb a sufficiently large amount of CO ２ The adsorption amount is shown.

[0148] Evaluation of Hydrophobicity The change in water adsorption rate over time was examined for each of the Na-FAU (FAU core) used as the core in the above Examples and Comparative Examples, and the FAU-MFI composites obtained in Examples 1 and 3, and Comparative Examples 1 and 2, under the following conditions: Pretreatment: Under a nitrogen stream, the temperature was raised to 400°C at a heating rate of 20°C / min. After reaching 400°C, the temperature was maintained for 60 minutes, and then allowed to cool and decrease to 200°C. Measurement: FT-IR measurements were taken every 5 seconds while a hydrous nitrogen stream was passed through at 200°C. Composition of the hydrous nitrogen stream: 1.5% by volume of water (water vapor), nitrogen balance. Flow rate of the hydrous nitrogen stream: 200 mL / min.

[0149] 1,655 cm originating from the OH morphological vibration －１ The peak area around the peak was used as an index of the amount of water adsorption, and the ratio of the peak area at each measurement time to the peak area at saturated adsorption was calculated, and this was taken as the water adsorption rate. The peak area at saturated adsorption was the value at which the peak area no longer changed even after continued measurement under a stream of hydrated nitrogen.

[0150] Figure 4 shows FT-IR charts measured for the FAU core and the sample of Example 1 60 seconds after the start of the flow of the hydrated nitrogen gas. Figure 5 shows the change in water adsorption rate of each sample over time. In Figure 5, the samples with lines to the right have a slower water adsorption rate and therefore higher hydrophobicity.

[0151] Referring to Table 1, the following can be seen:

[0152] The shell ratio and the covering rate are in a nearly proportional relationship except for Comparative Example 3.

[0153] The coverage is 75% or more, and the ratio (I Ｓｉ－ＯＨ / I Ｓｉ－Ｏ ) is 3.0 or less, CO ２ It was confirmed that the amount of adsorption was large.

[0154] On the other hand, in the sample of Comparative Example 4, even though the coverage was 97%, CO ２ The amount of adsorption was insufficient. This is because the ratio (I Ｓｉ－ＯＨ / I Ｓｉ－Ｏ ) is higher than 3.0. Ｓｉ－ＯＨ / I Ｓｉ－Ｏ ) is high, it is thought that there are many defects in the shell. Therefore, the shell tends to aggregate, and CO ２ It is presumed that this is because the particles were prevented from passing through the shell and reaching the FAU core.

[0155] 5, the lines showing the change in water adsorption rate over time for the samples of Examples 1 and 3 are to the right of the lines for the samples of Comparative Examples 1 and 2. This shows that the samples of Examples 1 and 3 are more hydrophobic than the samples of Comparative Examples 1 and 2.

[0156] Comparing the results of FIG. 5 with those of Table 1, the CO ２ It is understood that the amount of adsorption correlates with the hydrophobicity. That is, the FAU-MFI complexes of Comparative Examples 1 and 2 have low hydrophobicity and are highly adsorbed by CO ２ The adsorption site is poisoned by water and CO ２ In contrast, the FAU-MFI complexes of Examples 1 and 3 are highly hydrophobic and have a high ability to adsorb CO ２ High CO ２ It is thought to indicate the amount of adsorption.

[0157] However, the present invention is not bound by any particular theory.

[0158] II. Effect of common composite structural unit The CO2 absorption of the core-shell composite (adsorbent) obtained in Example 1 and the adsorbents of Comparative Examples 5 and 6 below was investigated. ２ The adsorption amounts were compared to investigate the influence of the common composite unit (CBU) between the zeolites constituting the core and shell, respectively.

[0159] Comparative Example 5: Commercially available Na-BEA (SiO ２ / Al ２ O ３ The adsorbent (Na / Al molar ratio=50, Na / Al=0.65 (molar ratio), particle size 2-3 μm) was used as it was as the adsorbent of Comparative Example 5, and CO ２ The amount of adsorption was measured.

[0160] BEA has three composite structural units (CBUs): mor, d4r, and mtw.

[0161] Comparative Example 6 A core-shell type BEA-MFI composite (adsorbent) was obtained in the same manner as in Example 1, except that in "1. Synthesis of core-shell type FAU-MFI composite", the same Na-BEA as used in Comparative Example 5 was used instead of the FAU core. The shell proportion of the obtained BEA-MFI composite was measured using the same method as in Example 1 and was found to be 30 mass%.

[0162] There are four types of MFI CBUs: mor, cas, mfi, and mel.

[0163] The CO ２ The adsorption amounts are shown in Table 2.

[0164]

[0165] In the core-shell type BEA-MFI composite of Comparative Example 6, the BEA constituting the core and the MFI constituting the shell have "mor" as a common CBU. The adsorbent of Comparative Example 6 has a higher CO ２ The adsorption capacity was only slightly improved.

[0166] In contrast, in the core-shell type FAU-MFI composite of Example 1, the FAU constituting the core and the MFI constituting the shell do not have a common CBU.２ The adsorption capacity is extremely large.

[0167] From the above, in the adsorbent of the present invention, the structure of the zeolite constituting the core and the structure of the zeolite constituting the shell do not have a common composite structural unit, and therefore, CO ２ It was verified that the adsorption amount was significantly improved.

Claims

1. An adsorbent having a core-shell structure, the core is made of zeolite; The shell satisfies the following requirements (A) to (C): (A) Silicate or SiO ２ / Al ２ O ３ a silicate-based oxide composed of an aluminosilicate having a molar ratio of 750 or more; (B) having a zeolite structure, and (C) The Si—O peak ((1,868±70) cm ) in the FT-IR of the adsorbent. －１ ) peak intensity I Ｓｉ－Ｏ The Si-OH peak ((3,788±50) cm －１ ) peak intensity I Ｓｉ－ＯＨ The ratio (I Ｓｉ－ＯＨ / I Ｓｉ－Ｏ ) is 3.0 or less All of the above are satisfied, and the structure of the zeolite constituting the core and the structure of the zeolite constituting the shell do not have a common composite structural unit; Adsorbent material.

2. SiO of the zeolite that constitutes the core ２ / Al ２ O ３ 2. The adsorbent of claim 1, wherein the molar ratio is 20 or less.

3. 2. The adsorbent according to claim 1, wherein the zeolite constituting the core has a framework structure selected from FAU, AEI, and CHA.

4. The substance to be adsorbed by the adsorbent is CO ２ The adsorbent according to claim 1, wherein 5. The adsorbent according to claim 3, wherein the substance to be adsorbed by the adsorbent is CO 2 .

6. 2. The adsorbent according to claim 1, wherein an alkali metal or alkaline earth metal is supported on the zeolite constituting the core.

7. An adsorbent material as described in claim 3, wherein an alkali metal or alkaline earth metal is supported on the zeolite that constitutes the core.

8. 2. The adsorbent according to claim 1, wherein the silicate-based oxide constituting the shell has a framework structure of MFI.

9. An adsorbent material as described in claim 3, wherein the silicate-based oxide constituting the shell has a skeletal structure of MFI.

10. The adsorbent according to any one of claims 1 to 9, wherein the shell has a coverage of 75% or more.

11. A method for producing the adsorbent according to any one of claims 1 to 9, a core composed of zeolite; Silicate or SiO ２ / Al ２ O ３ a silicate-based oxide composed of an aluminosilicate having a molar ratio of 750 or more; contacting the depositing a seed shell composed of the silicate-based oxide on the surface of the core to synthesize an adsorbent precursor; and heating the adsorbent precursor in the presence of a silicate-based oxide source and an organic structure-directing agent to grow a shell crystal; Including, Method for manufacturing adsorbent.

12. synthesizing the adsorbent precursor, by spray drying a mixture of the core and the silicate-based oxide; A method for producing the adsorbent according to claim 11.

13. synthesizing the adsorbent precursor, by heating a mixture of the core and the silicate-based oxide; A method for producing the adsorbent according to claim 11.