JP7838245B2 - Hydrocarbon adsorbent and method for adsorbing hydrocarbons - Google Patents

Description

This disclosure relates to hydrocarbon adsorbents and methods for adsorbing hydrocarbons.

Exhaust gases emitted from internal combustion engines used in mobile vehicles such as automobiles and ships contain a large amount of hydrocarbons. These hydrocarbons are purified by a three-way catalytic converter. A temperature environment of 200°C or higher is required for the three-way catalytic converter to function. Therefore, in temperature ranges where the three-way catalytic converter does not function, such as during a cold start, hydrocarbons are adsorbed onto a hydrocarbon adsorbent. When the temperature range in which the three-way catalytic converter begins to function is reached, the hydrocarbons are released from the adsorbent, thus decomposing and purifying the hydrocarbons with the three-way catalytic converter. Compositions containing zeolite are commonly used as hydrocarbon adsorbents. The higher the hydrocarbon desorption initiation temperature of the composition, the more active the three-way catalytic converter can be in releasing the hydrocarbons. Therefore, compositions with a high hydrocarbon desorption initiation temperature are desired as they are advantageous for hydrocarbon purification.

Patent Document 1 proposes a composition containing a zeolite with at least one ion having an electronegativity of 1.40 or higher as a composition with a high hydrocarbon desorption initiation temperature. Although Patent Document 1 provides a composition with a high desorption initiation temperature, it requires the use of a precious metal as a catalyst, and the hydrocarbon adsorbent positioned before the three-way catalyst is exposed to even higher temperatures. Therefore, the composition in Patent Document 1 lacks the heat resistance necessary for practical use as a hydrocarbon adsorbent for purifying hydrocarbons emitted from internal combustion engines, and is also disadvantageous in terms of cost.

Patent Document 2 proposes a hydrocarbon adsorbent consisting of a zeolite containing an alkali metal.

Japanese Patent Application Publication No. 11-005020 Japanese Patent Publication No. 2001-293368

The hydrocarbon adsorbent described in Patent Document 2 had the problem that the desorption initiation temperature of hydrocarbons was not sufficiently high. This disclosure aims to provide a hydrocarbon adsorbent with a high desorption initiation temperature, and at least one of the following: a hydrocarbon adsorbent and a method for adsorbing hydrocarbons using the hydrocarbon adsorbent.

The inventors investigated the hydrocarbon adsorption properties of compositions containing zeolite. As a result, they found that hydrocarbon adsorbents containing zeolite with the following pore structure exhibit a high hydrocarbon desorption initiation temperature.

In other words, the present invention is as described in the claims, and the gist of this disclosure is as follows:
[1] A hydrocarbon adsorbent comprising a zeolite having three-dimensional pores consisting of two or more pores selected from the group of 10-membered ring pores, 12-membered ring pores, 14-membered ring pores, and 18-membered ring pores.
[2] The hydrocarbon adsorbent according to [1] above, wherein the three-dimensional pore is a three-dimensional pore consisting of two or more pores selected from the group of 10-membered ring pores, 12-membered ring pores, and 14-membered ring pores.
[3] The hydrocarbon adsorbent according to [1] above, wherein the three-dimensional pores consist of 10-membered ring pores and 12-membered ring pores.
[4] A hydrocarbon adsorbent according to any one of [1] to [3] above, containing a metal.
[5] The hydrocarbon adsorbent according to [4] above, wherein the metal is at least one of rubidium and cesium.
[6] The hydrocarbon adsorbent according to [4] or [5], wherein the main peak in the MAS NMR spectrum for the metal is located between -250 ppm and -130 ppm.
[7] The hydrocarbon adsorbent according to [4] to [6] above, wherein the main peak in the MAS NMR spectrum for the metal is located at -250 ppm or more and -150 ppm or less.
[8] A hydrocarbon adsorbent according to [4] to [7] above, wherein the main peak in the ¹³³ Cs MAS NMR spectrum is located between -300 ppm and -130 ppm.
[9] A hydrocarbon adsorbent according to [4] to [8] above, wherein the main peak in the ¹³³ Cs MAS NMR spectrum is located between -300 ppm and -130 ppm.
[10] The hydrocarbon adsorbent according to any one of [1] to [9] above, wherein the zeolite is a zeolite having a molar ratio of silica to alumina ( _SiO₂ / _{Al₂O₃ ratio} ) of 2 or more and 200 or less.
[11] The hydrocarbon adsorbent according to any one of [1] to [10] above, wherein the zeolite is a zeolite having at least one structure selected from an MSE structure and a CON structure.
[12] A method for adsorbing hydrocarbons, characterized by contacting a hydrocarbon-containing fluid with a hydrocarbon adsorbent according to any one of [1] to [11] above.

This disclosure aims to achieve at least one of the following objectives: to provide a hydrocarbon adsorbent with a high hydrocarbon desorption initiation temperature when the _SiO₂ / _{Al₂O₃ ratio} is similar; and to provide a method for adsorbing hydrocarbons using the hydrocarbon adsorbent.

This figure shows the ¹³³ Cs MAS NMR spectrum and waveform separation results for Example 1. This figure shows the ^133Cs MAS NMR spectrum and waveform separation results for Comparative Example 3.

The hydrocarbon adsorbent described herein will be explained below with reference to an example of an embodiment.

The hydrocarbon adsorbent of this embodiment is characterized by containing a zeolite having three-dimensional pores consisting of two or more pores selected from the group consisting of 10-membered ring pores, 12-membered ring pores, 14-membered ring pores, and 18-membered ring pores.

In this embodiment, the zeolite is a compound in which the skeletal atoms (hereinafter also referred to as "T atoms") have a regular structure mediated by oxygen (O), and the T atoms consist of at least one of metal atoms, metalloid atoms, and other atoms. Examples of metal atoms include one or more selected from the group consisting of iron (Fe), aluminum (Al), gallium (Ga), tin (Sn), and titanium (Ti), as well as other transition metal elements. Examples of metalloid atoms include one or more selected from the group consisting of boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), and tellurium (Te), and an example of other atoms is phosphorus (P). Examples of specific zeolites include metallosilicates, such as one or more selected from the group consisting of aluminosilicate, ferrosilicate, and gallosilicate, where the T atom is composed of a metal atom and silicon, and metal phosphates such as at least one of aluminophosphate (AlPO) and silicoaluminophosphate (SAPO). However, it is preferable that the zeolite contained in the hydrocarbon adsorbent of this embodiment does not contain phosphorus as the T atom.

The zeolite contained in the hydrocarbon adsorbent of this embodiment is preferably a metallosilicate, and more preferably a crystalline aluminosilicate. A crystalline aluminosilicate is a compound having a crystalline structure consisting of repeating networks of aluminum (Al) and silicon (Si) mediated by oxygen (O). A crystalline aluminosilicate may have a structure in which at least a portion of the T atoms of aluminum and silicon are substituted with at least one of the metallic atoms and metalloid atoms of aluminum and silicon.

The zeolite framework structure (used interchangeably with crystal structure, and hereinafter also referred to as "zeolite structure") is a framework structure specified by the structure code (hereinafter simply referred to as "structure code") defined by the Structure Commission of the International Zeolite Association. It can be identified by comparing the XRD patterns (hereinafter also referred to as "reference patterns") of each zeolite structure described in *Collection of Simulated XRD Powder Patterns for Zeolites, Fifth Revised Edition* (2007) with the XRD pattern of the target zeolite.

In this embodiment, the XRD pattern may be obtained from an XRD measurement under the following conditions.

Acceleration current and voltage: 40mA/40kV
Radiation source: CuKα radiation (λ=1.5405Å)
Measurement mode: Continuous scan
Scanning conditions: 40°/min
Measurement range: 2θ = 3° to 43°
Detector: Semiconductor detector In this embodiment, a zeolite having a zeolite structure indicated by a specific structural code is also referred to as "~-type zeolite". For example, CON structure (or CON type) means a zeolite structure specified by the structural code "CON", and CON-type zeolite is a zeolite having a zeolite structure specified by the structural code "CON".

The pores in zeolites are formed by a cyclic structure consisting of T atoms and oxygen atoms bonded to them (hereinafter also referred to as "skeletal oxygen"). The pore diameter of a zeolite is determined by the number of skeletal oxygen atoms bonded to the T atoms forming the pore. In this embodiment, a ring surrounded by six skeletal oxygen atoms is called a six-membered oxygen ring, a ring surrounded by eight skeletal oxygen atoms is called an eight-membered oxygen ring, a ring surrounded by ten skeletal oxygen atoms is called a ten-membered oxygen ring, a ring surrounded by twelve skeletal oxygen atoms is called a twelve-membered oxygen ring, a ring surrounded by fourteen skeletal oxygen atoms is called a fourteen-membered oxygen ring, a ring surrounded by eighteen skeletal oxygen atoms is called an eighteen-membered oxygen ring, and so on. A ring surrounded by n skeletal oxygen atoms is called an "n-membered oxygen ring" or simply an "n-membered ring," and the pores formed by these n-membered oxygen rings are called "n-membered ring pores" (where n is an integer of 3 or more). The pore diameter tends to increase as the number of skeletal oxygen atoms in an n-membered ring pore increases.

The pore dimensions of zeolites are generally known to be one-dimensional pores (more specifically, tunnel-type one-dimensional pores or cage-type one-dimensional pores), two-dimensional pores, and three-dimensional pores. In this embodiment, the pore dimensions can be classified in the same way as the dimensions classified by Channel dimension (Sortion) as defined by IZA, where dimension 1 corresponds to one-dimensional pores, dimension 2 to two-dimensional pores, and dimension 3 to three-dimensional pores. The pore dimensions can be checked, for example, on the IZA homepage (https://asia.iza-structure.org/IZA-SC/search_cs.html). Specifically, the zeolite having one-dimensional pores in this embodiment is a zeolite in which pores are formed only in one-dimensional directions, and these pores do not have a structure in which they intersect with other pores. The zeolite having one-dimensional pores is characterized in that the pore spaces formed by the above-mentioned pores are connected in a straight line. Examples of such zeolite structures include one or more selected from the group consisting of MOR structure, LTL structure, DON structure, CFI structure, and AFI structure. Two-dimensional pores refer to a pore structure in which one-dimensional pores are connected to each other in different directions, such as lateral holes, and are characterized in that the pore spaces are connected in a planar manner. Examples of zeolite structures having two-dimensional pores include one or more selected from the group consisting of NES structure, MWW structure, and FER structure. Three-dimensional pores refer to a pore structure in which two-dimensional pores are further connected by other holes (for example, pores located in different directions from the two pores forming the two-dimensional pores, such as vertical holes), and are characterized by having a structure in which the pore space is connected in three dimensions: up, down, left, right, front, and back. Examples of zeolite structures having three-dimensional pores include one or more selected from the group consisting of FAU structure, *BEA structure, MFI structure, CON structure, MSE structure, IWR structure, BEC structure, BOG structure, BSV structure, DFO structure, EMT structure, IMF structure, IRR structure, ISV structure, ITG structure, ITT structure, IWS structure, JSR structure, JST structure, MEL structure, POS structure, SAO structure, SOV structure, UWY structure, *-ITN structure, and *SFV structure. In other words, zeolites with one-dimensional pores are zeolites with linear pores, zeolites with two-dimensional pores are zeolites with planar pores, and zeolites with three-dimensional pores are zeolites with three-dimensional pores.

Note that IZA also uses a classification of pore dimensions based on pores with more than 6-membered rings (Open Pore > 6 rings) (Channel dimension (topological)). The pore dimensions in this embodiment may differ from the topological classification of pore dimensions.

Examples of zeolites having three-dimensional pores (hereinafter also referred to as "three-dimensional pore zeolites") include one or more selected from the group consisting of FAU-type zeolite, *BEA-type zeolite, MSE-type zeolite, and CON-type zeolite. The zeolite contained in the hydrocarbon adsorbent of this embodiment is characterized by being a zeolite having three-dimensional pores consisting of two or more pores selected from the group consisting of 10-membered ring pores, 12-membered ring pores, 14-membered ring pores, and 18-membered ring pores. That is, the zeolite in the hydrocarbon adsorbent of this embodiment does not include zeolites having three-dimensional pores consisting only of 10-membered rings, three-dimensional pore zeolites consisting only of 12-membered rings, or zeolites having three-dimensional pores consisting only of 10-membered ring pores, 12-membered ring pores, 14-membered ring pores, or 18-membered ring pores. For example, the FAU structure, *BEA structure, or EMT structure are zeolite structures having a three-dimensional pore consisting of three 12-membered rings (12-12-12-membered rings), and are different from the zeolite structure of the zeolite contained in the hydrocarbon adsorbent of this embodiment. On the other hand, for example, a zeolite structure having a three-dimensional pore consisting of one 12-membered ring and two 10-membered rings (12-10-10-membered rings) (CON structure), or a zeolite structure having a three-dimensional pore formed by one 12-membered ring and two 10-membered rings (12-10-10-membered rings) (IWR structure) are examples of the zeolite structures of the zeolite contained in the hydrocarbon adsorbent of this embodiment. Thus, the zeolite in the hydrocarbon adsorbent of this embodiment is a three-dimensional pore zeolite having two or more pores with different numbers of member rings, selected from the group of 10-membered ring pores, 12-membered ring pores, 14-membered ring pores, and 18-membered ring pores. Such zeolites are not particularly limited, but examples include one or more selected from the group consisting of MSE-type zeolite, CON-type zeolite, IWR-type zeolite, *SFV-type zeolite, BOG-type zeolite, IRR-type zeolite, ITG-type zeolite, ITT-type zeolite, POS-type zeolite, UWY-type zeolite, and *-ITN-type zeolite, and it is preferable that at least one of MSE-type zeolite and CON-type zeolite is used. In another embodiment, the zeolite contained in the hydrocarbon adsorbent of this embodiment may be any zeolite containing one or more zeolite structures selected from the group consisting of MSE structure, CON structure, IWR structure, *SFV structure, BOG structure, IRR structure, ITG structure, ITT structure, POS structure, UWY structure, and *-ITN structure, and may also be a zeolite containing these zeolite structures and other zeolite structures, a so-called intercrystalline material. Examples of intercrystalline zeolites include those having a structure in which a zeolite structure with at least one-dimensional and two-dimensional pores is stacked with a zeolite structure with three-dimensional pores. It is believed that having such complex pore shapes allows water and hydrocarbons to move through different diffusion paths, enabling only small water molecules to desorb even from narrow diffusion paths. This results in a more favorable competitive adsorption between hydrocarbons and water, ultimately leading to a higher desorption initiation temperature for hydrocarbons.

Furthermore, the zeolite contained in the hydrocarbon adsorbent of this embodiment is preferably a zeolite having three-dimensional pores consisting of two or more pores selected from the group of 10-membered ring pores, 12-membered ring pores, and 14-membered ring pores, and more preferably a zeolite having three-dimensional pores consisting of 10-membered ring pores and 12-membered ring pores, in terms of excellent hydrocarbon adsorption performance.

As an example of the zeolite included in the hydrocarbon adsorbent of this embodiment, at least one of MSE-type zeolite and CON-type zeolite can be mentioned. MES-type zeolite and CON-type zeolite are zeolites having a zeolite structure with three-dimensional pores consisting of 12-membered ring pores and 10-membered ring pores, respectively.

The hydrocarbon adsorbent of this embodiment may contain a metal (hereinafter referred to as the "target metal"). The target metal is a metal included as an atom other than the T atom. While the target metal is not particularly limited, examples include one or more selected from the group consisting of alkali metals, alkaline earth metals, and transition metals. At least one of alkali metals and alkaline earth metals, and more preferably alkali metals, are preferred. These may be included individually or in combination.

Furthermore, the term "target metal" refers to a metallic element, and its elemental state is not particularly limited; at least one of ions or oxides can be exemplified. However, it is preferable that the target metal be included at least as an ion. Additionally, a target metal in an ion-exchangeable state is considered to be at least in an ionic state.

The alkali metals mentioned above are not particularly limited, but examples include one or more selected from the group consisting of sodium, potassium, rubidium, and cesium. At least one of rubidium and cesium is preferred, and cesium is more preferred, due to their high hydrocarbon desorption initiation temperatures. Two or more alkali metals may be present in the same state.

The aforementioned alkaline earth metals are not particularly limited, but examples include one or more selected from the group consisting of beryllium, magnesium, calcium, strontium, and barium. At least one of magnesium and calcium is preferred due to their high hydrocarbon desorption initiation temperatures. Two or more of these alkaline earth metals may be present in the same state.

The transition metals mentioned above are not particularly limited, but examples include one or more selected from the group consisting of manganese, iron, cobalt, nickel, copper, molybdenum, silver, and zinc, preferably at least one of iron and copper, and more preferably copper. Two or more of these transition metals may be present in the same state.

The target metal may be in a state where at least two or more alkali metals, alkaline earth metals, and transition metals coexist.

The content of the target metal in the hydrocarbon adsorbent of this embodiment is not particularly limited, but in terms of a high hydrocarbon desorption initiation temperature, examples include a target metal mass percentage of 1% or more, 3% or more, 5% or more, or 10% or more when the hydrocarbon adsorbent of this embodiment is considered as 100% by mass, and also 40% or less, 30% or less, 20% or less, or 15% or less by mass. Furthermore, if the hydrocarbon adsorbent of this embodiment contains a binder or the like described later, the target metal mass percentage when the hydrocarbon adsorbent of this embodiment is considered as 100% by mass may be 60% or less or 50% or less by mass.

Furthermore, regarding the content of the target metal in the hydrocarbon adsorbent of this embodiment, in terms of the high desorption initiation temperature of hydrocarbons, it is preferable that the ratio of target metal [mol] / Al [mol] is 0.01 or more and 10 or less, based on the amount of Al in the zeolite contained in the hydrocarbon adsorbent of this embodiment, more preferably 0.02 or more and 8 or less, and even more preferably 0.05 or more and 5 or less.

The metals contained in the zeolite can be those contained in the zeolite itself obtained during hydrothermal synthesis (after the crystallization process) as described later, those contained in zeolites that have been further treated with metal support, or those contained in zeolites that have been ion-exchanged with hydrogen ions or ammonium ions before being treated with metal support. The state of the target metal in this embodiment is not particularly limited, but it is preferable that the metal be in an ion-exchangeable state, that is, it is preferable that the target metal be an ion in an ion-exchangeable state. An example of an ion-exchangeable metal ion is that it exists as a countercation of an anion such as ^the aluminum anion ( _AlO₄- ) which is the T atom.

In this embodiment, an ion-exchangeable state means a state in which at least a portion of the target metal can be exchanged for another metal. This state can be confirmed by the fact that at least a portion of the target metal contained in the hydrocarbon adsorbent of this embodiment is exchanged for another metal. Examples of metal ions that are not in an ion-exchangeable state include, for example, metal ions present at ion-exchange sites such as inside closed pores, which are substantially unable to exchange ions.

The amount of the target metal in an ion-exchangeable state can be determined from the following formula. This can be quantified by ion-exchange treatment of the hydrocarbon adsorbent with a different metal (hereinafter also referred to as the "exchange metal") and measuring the difference in the target metal content of the hydrocarbon adsorbent before and after ion exchange.

This quantitative analysis can be performed using analytical instruments such as ICP.

The ion exchange treatment method described above can be any general ion exchange method using an exchange metal, and may involve exchanging the target metal contained in the hydrocarbon adsorbent of this embodiment with a metal that can be exchanged for ions (for example, Na if the target metal is Cs). Conditions for the ion exchange treatment include flowing the exchange metal in excess of the amount of anions such as aluminum anions ( _AlO₄- ), which are the T atoms of the zeolite contained in the hydrocarbon adsorbent of this embodiment (for example, 5 to 10 equivalent amounts) at room temperature (20 to ³⁵ °C). It is preferable that the exchange metal is flowed in an aqueous solution containing the exchange metal. The exchange time is preferably 1 minute or more and 1 day or less.

Of the total target metal contained in the hydrocarbon adsorbent of this embodiment, the proportion of the target metal that can be ion-exchanged with an exchange metal is preferably 30 mol% to 100 mol%, and more preferably 50 mol% to 95 mol%, at a point where the hydrocarbon desorption initiation temperature is high.

The hydrocarbon adsorbent of this embodiment containing the target metal preferably has a main peak in the MAS NMR spectrum for the target metal located at -130 ppm or below, and more preferably at -150 ppm or below, due to its high hydrocarbon desorption initiation temperature. Furthermore, the main peak may be located at -250 ppm or above, or -200 ppm or above. The main peak in the MAS NMR spectrum refers to the peak with the highest intensity among the detected peaks. The peak position refers to the chemical shift position [ppm] of the peak top for each peak.

When the main peak is located below -130 ppm, the interaction between the target metal and the zeolite is small, and the target metal acts strongly with the hydrocarbon, which tends to increase the desorption initiation temperature of the hydrocarbon. Furthermore, in the zeolite having three-dimensional pores consisting of two or more pores selected from the group of 10-membered ring pores, 12-membered ring pores, 14-membered ring pores, and 18-membered ring pores in this embodiment, it is thought that the hydrocarbon adsorbed in the complex-shaped pores is retained by the action of the target metal, which tends to increase the desorption initiation temperature of the hydrocarbon in particular. For example, when cesium is included as the target metal, it is preferable that the main peak in the ¹³³ Cs MAS NMR spectrum is located below -130 ppm, and more preferably below -150 ppm. Also, it can be exemplified that it is located above -250 ppm or above, or above -200 ppm. The ¹³³ Cs MAS NMR spectrum can be measured under the following conditions.
• Pre-treatment and sampling of measurement samples:
The sample to be measured is obtained by pretreatment by heating and dehydration, followed by sampling in a nitrogen glove box. Heating and dehydration is performed by raising the temperature to 400°C at a rate of 0.25°C/min under vacuum, holding for 5 hours, and then cooling to room temperature.
・Measurement device Device name: Varian NMR System 400 (manufactured by Varian)
Probe: 4 mmφ solid probe; Analysis software (NMR measurement): VnmrJ version 4.2
・NMR measurement conditions Resonance frequency: 52.4MHz (133Cs)
Pulse width: 3.8 μs (π/2)
Rotation frequency: 15 kHz
Repeat time: 2 seconds
Import time: 10ms
Cumulative number of measurements: 2048 Observation center: -150 ppm
Observation range: 120 kHz
Reference (0 ppm): 1.0 M CsCl aqueous solution, Fourier transform conditions. Points: 4096 points
Window function: Exponential function (LB: 25 kHz) Furthermore, in the hydrocarbon adsorbent of this embodiment containing the target metal, it is preferable that the peak located on the highest magnetic field side (i.e., having the smallest chemical shift) after waveform separation in the MAS NMR spectrum for the target metal is located at -171 ppm or lower, given the high desorption start temperature of hydrocarbons. It is also possible that the peak is located at -300 ppm or higher, or -250 ppm or higher. For example, when cesium is included as the target metal, it is preferable that the peak located on the highest magnetic field side after waveform separation in the ¹³³ Cs MAS NMR spectrum is located at -171 ppm or lower. It is also possible that the peak is located at -300 ppm or higher, or -250 ppm or higher. The ¹³³ Cs MAS NMR spectrum can be waveform separated under the following conditions.
• Waveform separation conditions Waveform separation software: GRAMS/AI version 8.0 (manufactured by Thermo Fisher Scientific)
Separation method: Fitting with a Gaussian function The zeolite contained in the hydrocarbon adsorbent of this embodiment has a molar ratio of silica to alumina (hereinafter also referred to as the " _SiO₂ / _{Al₂O₃ ratio} ") of 2 to 200, and more preferably 2 to 100. In addition, it is particularly preferable that the ratio is 5 to 100, 5 to 75, 5 to 50, or 5 to 25, which are the points at which the desorption initiation temperature of hydrocarbons is high. Furthermore, the _SiO₂ / _{Al₂O₃ ratio} is 5 or more, 10 or more, or 15 or more, and also 65 or less, 55 or less, or 30 or less.

The zeolite contained in the hydrocarbon adsorbent of this embodiment preferably has a BET specific surface area of 200 ^m² /g or more and 800 ^m² /g or less, and more preferably 300 ^m² /g or more and 700 ^m² /g or less, in that it has a high hydrocarbon desorption initiation temperature.

The zeolite contained in the hydrocarbon adsorbent of this embodiment may, for example, have a crystal particle size of 0.01 μm or more, or 0.1 μm or more, or 50 μm or less, or 20 μm or less.

Furthermore, the hydrocarbon adsorbent of this embodiment may contain other components besides the zeolite and target metal described above, such as binders, and is not particularly limited. Examples include one or more components selected from the group consisting of silica, alumina, kaolin, attapulgite, montmorillonite, bentonite, alloene, and sepiolite.

The desorption initiation temperature of the hydrocarbon adsorbent in this embodiment can be measured by the method described below.

<Measurement Sample>
Shape: Hydrocarbon adsorbent with aggregate diameter of 20-30 mesh and irregularly formed shape. Manufacturing method: Pressure molding and pulverization. <Pretreatment>
Atmosphere: Nitrogen flow atmosphere Temperature: 500℃
Time: 1 hour <Hydrogen adsorption and desorption conditions>
The sample to be measured is packed into a fixed-bed flow-through reaction tube at atmospheric pressure, and a hydrocarbon-containing gas is flowed through it under the following conditions.

Hydrocarbon-containing gas: Toluene 3000 ppm C (methane equivalent concentration)
Water 3% by volume
Nitrogen remaining gas flow rate: 200 mL/min Measurement temperature: 50-600°C
Heating rate: 10°C/min <Measurement of desorption initiation temperature>
The hydrocarbon concentration (methane equivalent; hereinafter also referred to as "inlet concentration") of the hydrocarbon-containing gas at the inlet side of the atmospheric pressure fixed-bed flow reaction tube, and the hydrocarbon concentration (methane equivalent; hereinafter also referred to as "outlet concentration") of the hydrocarbon-containing gas at the outlet side of the atmospheric pressure fixed-bed flow reaction tube are measured using a hydrogen ionization detector (FID).

The integral value of the inlet concentration is used to determine the amount of hydrocarbon that passed through the hydrocarbon adsorbent. Subtracting the integral value of the outlet concentration (methane equivalent concentration) from this amount of hydrocarbon is calculated, and the amount of hydrocarbon adsorbed in the sample is defined as the hydrocarbon desorption amount per unit mass of hydrocarbon adsorbent (μmolC/g). The temperature at which the hydrocarbon desorption amount first reaches 0 μmolC/g as the measurement temperature increases is defined as the desorption start temperature.

Next, the method for producing the hydrocarbon adsorbent of this embodiment will be described.

The hydrocarbon adsorbent of this embodiment may consist solely of a zeolite having three-dimensional pores consisting of two or more pores selected from the group of 10-membered ring pores, 12-membered ring pores, 14-membered ring pores, and 18-membered ring pores, or it may be manufactured by mixing the zeolite with the other components mentioned above.

The zeolite having three-dimensional pores consisting of two or more pores selected from the group of 10-membered ring pores, 12-membered ring pores, 14-membered ring pores, and 18-membered ring pores, contained in the hydrocarbon adsorbent of this embodiment, can be manufactured by a manufacturing method that includes a crystallization step in which a composition containing a silica source, an alumina source, an alkali source, and water (hereinafter also referred to as the "raw material composition") is hydrothermally treated to obtain a crystallized product. This manufacturing method may also include a metal-containing step after the crystallization step in which a metal is added.

The aforementioned silica source is at least one of silica and its precursors, and examples include one or more selected from the group consisting of colloidal silica, amorphous silica, sodium silicate, tetraethyl orthosilicate, and aluminosilicate gel.

The alumina source mentioned above is at least one of alumina and its precursors, and includes, for example, one or more selected from the group consisting of aluminum sulfate, sodium aluminate, aluminum hydroxide, aluminum chloride, aluminosilicate gel, and metallic aluminum.

Examples of the alkali source include one or more selected from the group of various salts such as sodium, potassium, ammonium hydroxides, halides, and carbonates.

The above raw material composition may optionally contain a structure-directing agent (hereinafter also referred to as "SDA"). Examples of structure-directing agents include N,N,N-trimethyl-(+)-cis-miltanylammonium, hexamethonium, 1,1-dialkyl-4-alkylcyclohexylpiperazine-1-ium, 1,1-dialkyl-4-cyclohexylpiperazine-1-ium, 1,1'-((3as,6as)-octahydropentalene-2,5-diyl)bis(1-methylpiperidine-1-ium), and 1,1'-(butane-1,4-di (Il)bis(1-methylpiperidine-1-ium), 1,1'-(pentan-1,5-diyl)bis(1-methylpiperidine-1-ium), 1,1'-(hexane-1,6-diyl)bis(1-methylpiperidine-1-ium), 3-hydroxy-1-(4-(1-methylpiperidine-1-ium-1-yl)butyl)quinucidin-1-ium, 3-hydroxy-1-(5-(1-methylpiperidine-1-ium-1-yl )Pentyl)Quinucidine-1-ium, N,N,N,N-tetraethylbicyclo[2.2.2]-octo-7-en-dipyrrolidinium, N,N-dimethyl-N'-cyclohexylpiperidineium, dimethyldipropylammonium, tetraethylammonium, 1,6-bis(N-cyclohexylpyrrolidinium)hexanedication, 1,4-bis(N-cyclohexylpiperidineium)butanedication, 1,4-bis One or more of the following can be selected from the group consisting of (N-cyclohexylpyrrolidinium)butanedication, 1,4-bis(N-cyclopentylpiperidinium)butanedication, 1,5-bis(N,N-dimethylcyclohexylammonium)pentanedication, N,N,N-trimethyltricyclo[5.2.1.0]-decaneammonium, and (6R,10S)-6,10-dimethyl-5-azoniaspiro[4.5]decanecation. Since SDA is often a cation, it is sufficient for it to be included in the raw material composition as a salt paired with one or more anions selected from the group consisting of fluoride, chloride, bromide, iodide, and hydroxide (hereinafter, salts of SDA are also referred to as "SDAX").

Preferably, the raw material composition has the following molar composition. In the following composition, SDAX is a salt of SDA, and X is an anion other than fluorine.

SiO ₂ /Al ₂ O ₃ ratio = 2 or more and 500 or less SDAX/SiO ₂ ratio = 0.00 or more and 0.80 or less
Na/SiO2 _ratio = 0.00 or more and 0.80 or less
K/SiO2 _ratio = 0.00 or more and 0.80 or less
X/SiO2 ratio = 0.00 or more and 2.0 or less
HF/SiO2 ratio = 0.00 or more and 1.0 or less
_H₂O / _SiO₂ ratio = 2 or more and 100 or less By adjusting the above conditions in various ways within the scope of common sense of the art, it is possible to selectively produce zeolites having three-dimensional pores consisting of two or more pores selected from the group of 10-membered ring pores, 12-membered ring pores, 14-membered ring pores, and 18-membered ring pores. More specific examples are not limited, but one example is shown below.

For example, a method for producing MSE-type zeolite involves crystallizing a raw material composition having the following molar composition. In the following composition, SDA is dimethyldipropylammonium cation, 1,1-dialkyl-4-alkylcyclohexylpiperazine-1-ium cation, 1,1-dialkyl-4-cyclohexylpiperazine-1-ium cation, 1,1'-((3as,6as)-octahydropentalene-2,5-diyl)bis(1-methylpiperidine-1-ium) cation, 1,1'-(butane-1,4-diyl)bis(1-methylpiperidine-1-ium) cation, 1,1' It is one or more selected from the group consisting of -(pentan-1,5-diyl)bis(1-methylpiperidine-1-ium) cation, 3-hydroxy-1-(4-(1-methylpiperidine-1-ium-1-yl)butyl)quinuquixidine-1-ium cation, 3-hydroxy-1-(5-(1-methylpiperidine-1-ium-1-yl)pentyl)quinuquixidine-1-ium cation, N,N,N,N-tetraethylbicyclo[2.2.2]-octo _- 7-en-dipyrrolidinium cation, N,N-dimethyl-N'-cyclohexylpiperazinium cation, and tetraethylammonium cation, and is preferably a dimethyldipropylammonium cation (hereinafter also referred to as " _Me2Pr2N ⁺ ").

_SiO₂ / _{Al₂O₃ ratio} = 2 or more, 15 or more, or 20 or more,
500 or less, 100 or less, or 50 or less SDA/SiO2 _ratio = 0.00 or more, 0.05 or more, or 0.10 or more, and
0.40 or less, 0.30 or less, or 0.20 or less
Na/SiO2 _ratio = 0.00 or higher or 0.10 or higher,
0.80 or less, 0.40 or less, or 0.20 or less
K/SiO2 _ratio = 0.00 or higher or 0.10 or higher,
0.80 or less, 0.40 or less, or 0.20 or less _H₂O /SiO₂ _ratio = 2 or more or 3 or more,
100 or less, 50 or less, or 15 or less For example, a method for producing CON-type zeolite is to crystallize a raw material composition having the following molar composition. In the following composition, SDAX is one or more selected from the group consisting of trimethyl-(-)-cismiltanylammonium hydroxide (hereinafter also referred to as "TMMAOH"), trimethyl-(-)-cismiltanylammonium iodide, and trimethyl-(-)-cismiltanylammonium hydroxydobromide, and is preferably TMMAOH.

_SiO₂ / _{Al₂O₃ ratio} = 2 or more, 15 or more, or 20 or more,
500 or less, 100 or less, or 60 or less SDAX/SiO2 _ratio = 0.00 or more, 0.05 or more, or 0.10 or more,
1.00 or less, 0.80 or less, or 0.60 or less
HF/SiO2 ratio = 0.00 or higher or 0.10 or higher,
1.0 or less or 0.6 or less _H₂O /SiO₂ _ratio = 2 or more or 3 or more,
100 or less, 50 or less, or 15 or less. The raw material composition may contain seed crystals, and it is preferable that the seed crystals are zeolites having a ring structure of 8 or more oxygen rings. The seed crystal content in the raw material composition (hereinafter also referred to as "seed crystal content") is preferably 0% by mass or more and 30% by mass or less, and more preferably 1% by mass or more and 10% by mass or less, as a ratio of the mass of silicon (Si) contained in the seed crystals, converted to _SiO2 , to the _mass of silicon (Si) contained in the raw material composition (raw material composition excluding seed crystals), converted to SiO2.

In the crystallization process, the raw material composition can be crystallized, for example, by hydrothermal treatment. While there are no particular limitations on the conditions for hydrothermal treatment, the following conditions are examples:

Crystallization temperature: 120°C to 200°C Crystallization time: 1 hour to 20 days Crystallization pressure: Self-generating pressure By the above crystallization process, a zeolite having three-dimensional pores consisting of two or more pores selected from the group of 10-membered ring pores, 12-membered ring pores, 14-membered ring pores, and 18-membered ring pores is obtained. After the crystallization process, the obtained zeolite may be subjected to recovery, washing, drying, and calcination by any method, and further, it may be dealuminized to set the _SiO₂ / _Al₂O₃ ratio to _any value.

It is preferable to subject the material to a calcination process after the crystallization process, as this allows for a higher desorption initiation temperature for hydrocarbons.

The calcination process involves removing SDA from zeolite having three-dimensional pores consisting of two or more pores selected from the group of 10-membered ring pores, 12-membered ring pores, 14-membered ring pores, and 18-membered ring pores. While the calcination conditions are arbitrary, possible conditions include a calcination atmosphere, a calcination temperature of 400°C to 800°C, and a calcination time of 0.5 hours to 12 hours.

The aforementioned metal-containing step involves contacting the aforementioned metal with a zeolite having three-dimensional pores consisting of two or more pores selected from the group of 10-membered ring pores, 12-membered ring pores, 14-membered ring pores, and 18-membered ring pores, with the objective of containing the metal in the zeolite. In this embodiment, it is believed that the metal-containing step makes at least a portion of the metal contained in the ion exchange sites of the zeolite skeleton having three-dimensional pores consisting of two or more pores selected from the group of 10-membered ring pores, 12-membered ring pores, 14-membered ring pores, and 18-membered ring pores, capable of ion exchange, thereby raising the desorption initiation temperature of hydrocarbons.

The metals to be included are as described above.

The metal source to be included is not particularly limited, but for example, when a zeolite having three-dimensional pores consisting of two or more pores selected from the group of 10-membered ring pores, 12-membered ring pores, 14-membered ring pores, and 18-membered ring pores in this embodiment is to contain one or more selected from the group of sodium, potassium, rubidium, and cesium, it is preferable to use a compound containing one or more selected from the group of sodium, potassium, rubidium, and cesium. It is even more preferable to use an inorganic salt containing one or more selected from the group of sodium, potassium, rubidium, and cesium, and further, one or more selected from the group of sulfates, nitrates, acetates, hydroxides, and chlorides containing one or more selected from the group of sodium, potassium, rubidium, and cesium.

The metal-containing process can be any method by which the metal is contained in the ion-exchange sites of a zeolite having three-dimensional pores consisting of two or more pores selected from the group of 10-membered ring pores, 12-membered ring pores, 14-membered ring pores, and 18-membered ring pores. Specific methods include one or more selected from the group of ion-exchange methods, evaporation to dryness methods, and impregnation-supported methods. The impregnation-supported method, and more preferably a method of mixing an aqueous solution containing a metal compound with the zeolite, are preferred. This results in the metal being supported in the ion-exchange sites.

Furthermore, in the metal-containing process, it is preferable to intentionally create a state in which the metal does not coordinate to some of the ion exchange sites (metal coordination sites) in the zeolite skeleton having three-dimensional pores consisting of two or more pores selected from the group of 10-membered ring pores, 12-membered ring pores, 14-membered ring pores, and 18-membered ring pores. In other words, it is preferable to make at least a portion of the metal contained in the hydrocarbon adsorbent ion-exchangeable. While not particularly limited, one example of this method is to use zeolite as a fixed bed and support the metal by circulating a metal solution through the fixed bed.

Furthermore, the manufacturing method of this embodiment may include one or more steps after the metal-containing step, such as a washing step, a drying step, and an activation step.

The cleaning process after the metal-containing process aims to remove impurities, and any cleaning method can be used. For example, this could involve washing the zeolite after the metal-supporting treatment with a sufficient amount of pure water.

The drying process after the metal-containing process aims to remove any remaining moisture from the surface and pores of the zeolite. An example of this process is to treat the zeolite in air at a temperature of 100°C to 200°C, preferably 110°C to 190°C.

The activation process aims to remove organic matter from the zeolite. This process can be exemplified by treatment in air at a temperature exceeding 200°C but not exceeding 600°C, and preferably at a temperature exceeding 300°C but not exceeding 600°C.

The hydrocarbon adsorbent of this embodiment can be used in any shape depending on the application, and is not particularly limited; for example, it can be used in the form of a powder, molded body, or adsorbent member. Specific molded body shapes include one or more selected from the group consisting of spherical, substantially spherical, elliptical, disc-shaped, cylindrical, polyhedral, irregularly shaped, and petal-shaped.

When the hydrocarbon adsorbent of this embodiment is made into a molded body, it is possible to mold a hydrocarbon adsorbent made of the zeolite described above, but it is preferable to mold a hydrocarbon adsorbent containing further additives to the zeolite, in terms of superior operability and durability. Examples of molding methods include one or more selected from the group consisting of rolling granulation, press molding, extrusion molding, injection molding, casting, and sheet molding.

When the hydrocarbon adsorbent of this embodiment is used as an adsorbent, the adsorbent can be manufactured by mixing the hydrocarbon adsorbent with additives such as binders as needed, in a solvent such as water or alcohol to produce a slurry, and then coating the substrate with this slurry.

The hydrocarbon adsorbent of this embodiment can be used in hydrocarbon adsorption methods.

The hydrocarbon adsorbent of this embodiment can adsorb hydrocarbons by a method comprising the step of contacting a hydrocarbon-containing fluid with the hydrocarbon adsorbent of this embodiment.

Examples of hydrocarbon-containing fluids include at least one of a hydrocarbon-containing gas and a hydrocarbon-containing liquid.

The hydrocarbon-containing gas is a gas containing at least one hydrocarbon, and preferably contains two or more hydrocarbons. The hydrocarbons contained in the hydrocarbon-containing gas include at least one of the groups paraffin, olefin, and aromatic hydrocarbons. The number of carbon atoms in the hydrocarbon may be one or more, and preferably between 1 and 15. Preferably, the hydrocarbons contained in the hydrocarbon-containing gas are at least one or two of the groups methane, ethane, ethylene, propylene, butane, linear paraffin with 5 or more carbon atoms, linear olefin with 5 or more carbon atoms, benzene, toluene, and xylene; more preferably at least one of the groups methane, ethane, ethylene, propylene, butane, benzene, toluene, and xylene, and more preferably at least one of the groups methane, ethane, ethylene, and propylene, and at least one of the groups benzene, toluene, and xylene. The hydrocarbon-containing gas may also contain at least one of the groups carbon monoxide, carbon dioxide, hydrogen, oxygen, nitrogen, nitrogen oxides, sulfur oxides, and water. Specific examples of hydrocarbon-containing gases include combustion gases such as exhaust gases from internal combustion engines.

In the hydrocarbon adsorption method, the hydrocarbon-containing gas preferably contains one or more hydrocarbons selected from the group consisting of meta-xylene, ortho-xylene, and branched paraffins.

Preferably, the contact temperature during this process is room temperature to 200°C.

The hydrocarbon adsorbent of this embodiment exhibits the effect of a higher hydrocarbon desorption initiation temperature compared to hydrocarbon adsorbents other than those of this embodiment. It is generally known that the hydrocarbon desorption initiation temperature correlates with the SAR ratio, but the hydrocarbon adsorbent of this embodiment shows an unprecedentedly high hydrocarbon desorption initiation temperature under the same SAR conditions.
In other words, the hydrocarbon adsorbent of this embodiment exhibits the effect of showing a high hydrocarbon desorption initiation temperature under high SAR conditions. Furthermore, since a higher SAR increases the hydrophobicity of the zeolite, durability is improved, and therefore, a higher SAR is preferable for hydrocarbon adsorbents.

The hydrocarbon adsorbents of this disclosure will be described in more detail below in the examples. However, this disclosure is not limited to these examples.

(Identification of crystal structure)
XRD measurements of the sample were performed using a standard X-ray diffractometer (device name: Ultima IV Protectus, manufactured by Rigaku Corporation). The measurement conditions were as follows:

Acceleration current and voltage: 40mA/40kV
Radiation source: CuKα radiation (λ=1.5405Å)
Measurement mode: Continuous scan
Scanning conditions: 40°/min
Measurement range: 2θ = 3° to 43°
Divergence vertical limiting slit: 10 mm
Divergence/Induction Slit: 1°
Light-receiving slit: open
Detector: D/teX Ultra
The obtained XRD pattern was compared with a reference pattern using a Ni filter to identify the crystal structure of the sample.

(composition analysis)
A sample solution was prepared by dissolving the sample in a mixed aqueous solution of hydrofluoric acid and nitric acid. The sample solution was measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES) using a general ICP instrument (instrument name: OPTIMA5300DV, PerkinElmer). From the obtained measurements of Si, Al, and alkali metals (Cs and Na, etc.), the _SiO₂ / _{Al₂O₃ molar} ratio and the mass percentage of alkali metals in the sample were determined.

(Measurement of MAS NMR spectrum)
A hydrocarbon adsorbent containing cesium as the target metal was pretreated by heating and dehydrating, and then sampled in a nitrogen glove box to prepare the measurement sample. Heating and dehydration was performed under vacuum, raising the temperature to 400°C at 0.25°C/min, holding for 5 hours, and then cooling to room temperature. The ^133Cs MAS NMR spectrum of the obtained measurement sample was measured under the following conditions. The peak showing the highest intensity among the measured peaks was designated as the main peak. Furthermore, waveform separation was performed on the measured peaks. The measurement results and waveform separation results of the ^133Cs MAS NMR spectrum of Example 1 and Comparative Example 3 are shown in Figures 1 and 2, respectively. In Figure 1, the solid line represents the raw data, the dashed line represents the fitting curve, and the dotted, dashed, double-dotted, and long dashed lines represent the separated peaks after waveform separation. In Figure 4, the solid line represents the raw data, the dashed line represents the fitting curve, and the dotted and dashed lines represent the separated peaks after waveform separation. <Conditions>
Equipment name: Varian NMR System 400 (manufactured by Varian)
Probe: 4 mmφ solid probe; Analysis software (NMR measurement): VnmrJ version 4.2
・NMR measurement conditions Resonance frequency: 52.4MHz (133Cs)
Pulse width: 3.8 μs (π/2)
Rotation frequency: 15 kHz
Repeat time: 2 seconds
Import time: 10ms
Cumulative number of measurements: 2048 Observation center: -150 ppm
Observation range: 120 kHz
Reference (0 ppm): 1.0 M CsCl aqueous solution, Fourier transform conditions. Points: 4096 points
Window function: Exponential function (LB: 25 kHz)
• Waveform separation conditions Waveform separation software: GRAMS/AI version 8.0 (manufactured by Thermo Fisher Scientific)
Separation method: Fitting with a Gaussian function. In Example 1, Comparative Example 1, and Comparative Example 2, the spinning sideband (hereinafter also referred to as "SSB") was fitted with one waveform, and the main peak was fitted with four waveforms. In Example 2 and Comparative Example 5, the SSB was fitted with one waveform, and the main peak was fitted with three waveforms. In Comparative Example 3, the main peak was fitted with two waveforms.

(Preparation and pretreatment of hydrocarbon adsorbent samples)
The desorption start temperature of hydrocarbons was measured for the hydrocarbon adsorbents obtained in the examples and comparative examples described later. The obtained hydrocarbon adsorbents were each pressure-molded and pulverized to form amorphous molded bodies with an aggregation diameter of 20 to 30 mesh, and the resulting molded bodies were used as measurement samples. 0.1 g of each measurement sample was packed into a fixed-bed flow reaction tube at atmospheric pressure, treated at 500°C for 1 hour under nitrogen flow, and then cooled to 50°C as a pretreatment.

(Hydroxide adsorption by hydrocarbon adsorbents)
The hydrocarbon-containing gas was passed through each hydrocarbon adsorbent that had undergone the above pretreatment, and the amount of adsorbed hydrocarbons was measured between 50°C and 200°C to determine the amount of adsorbed hydrocarbons. The composition of the hydrocarbon-containing gas and the measurement conditions are shown below.

Hydrocarbon-containing gas: Toluene 3000 ppm C (methane equivalent concentration)
Water 3% by volume
Nitrogen remaining gas flow rate: 200 mL/min Measurement temperature: 50-600°C
Heating rate: 10°C/min (Measurement of the desorption start temperature of hydrocarbons in hydrocarbon adsorbent)
A hydrogen ionization detector (FID) was used to continuously quantitatively analyze hydrocarbons in the gas after it had passed through a hydrocarbon adsorbent. The hydrocarbon concentration (methane equivalent; hereinafter referred to as "inlet concentration") of the hydrocarbon-containing gas at the inlet side of the atmospheric pressure fixed-bed flow reaction tube and the hydrocarbon concentration (methane equivalent; hereinafter referred to as "outlet concentration") of the hydrocarbon-containing gas at the outlet side of the atmospheric pressure fixed-bed flow reaction tube were measured.

The amount of hydrocarbons that passed through the hydrocarbon adsorbent was determined by using the integral value of the inlet concentration. The amount of hydrocarbons adsorbed by each adsorbent was then calculated by subtracting the integral value of the outlet concentration (methane equivalent concentration) from this amount, and this was expressed as the hydrocarbon desorption amount per unit weight of the hydrocarbon adsorbent (μmolC/g). The temperature at which the hydrocarbon desorption amount reached 0 μmolC/g as the temperature of the sample increased was defined as the desorption start temperature.

Example 1 (Synthesis of MSE-type zeolite having three-dimensional pores consisting of 12-membered ring pores and 10-membered ring pores)
Nipsil LP (manufactured by Tosoh Silica Co., Ltd.), Y-type zeolite (product name: HSZ-350HUA, manufactured by Tosoh Corporation), aqueous sodium silicate solution ( _SiO₂ : 28.9 wt%, _Na₂O : 9.3 wt%), _{Me₂Pr₂NOH ,} KOH, and _H₂O were mixed to obtain a raw material composition having the following molar composition.

_SiO₂ / _Al₂O₃ / _{Me₂Pr₂ NOH} /NaOH/KOH/ _H₂O = 1/0.0278/0.17/0.15/0.15/5.0 ₍ molar ratio)
_SiO₂ / _{Al₂O 3} molar ratio = 36
_Me₂Pr₂N +/SiO₂ _molar ratio ₌ 0.17
Na/SiO ₂ molar ratio = 0.15
K/SiO _molar ratio = 0.15
_H₂O /SiO₂ _molar ratio = 5.0
5% by mass of seed crystals was added to the _SiO2 of the raw material composition. The resulting raw material composition was packed into an autoclave and crystallized under rotational conditions at 160°C for 3 days under autosynthesis pressure. After crystallization, it was calcined in air at 550°C. Next, the treatment with a 10% ammonium chloride aqueous solution at 80°C for 20 hours was repeated three times, and it was dried overnight in air at 110°C. This yielded an MSE-type zeolite with an _SiO2 / _{Al2O3 ratio} of 18 and a cation type of _NH4 .

(Bearing responsibility for Cs)
A 2% by mass aqueous solution of cesium chloride (manufactured by Fujifilm Wako Pure Chemical Industries (special grade)) was prepared. The amount of cesium chloride aqueous solution used was such that the amount of Cs (moles) was 2 equivalents to the amount of Al (moles) of the zeolite obtained above. Loading was performed on the zeolite on a cake obtained by mixing MSE zeolite with water and filtering it. That is, the above cesium chloride aqueous solution was poured onto the cake. Next, water at 60°C in an amount 10 times the volume of the MSE type zeolite was poured in to wash it. After washing, Cs was loaded by drying at 110°C in the air, and a hydrocarbon adsorbent of this example with a Cs content of 15.8% by mass was obtained.

Example 2 (Synthesis of CON-type zeolite having three-dimensional pores consisting of 12-membered rings and 10-membered rings)
A 15.9% aqueous solution of trimethyl-cis-mirtanylammonium hydroxide (TMMAOH), aluminum isopropoxide (Kishida Chemical), and tetraethoxysilane (TEOS, Kishida Chemical) were mixed and heated at 90°C for 20 hours to evaporate the water. TMMAOH was obtained by methylating (-)-cis-mirtanylamine (Aldrich) with iodomethane (Kishida Chemical), followed by ion exchange with ion exchange resin SA10AOH (Mitsubishi Chemical). The resulting solid was pulverized in a mortar, and then mixed with 48% hydrofluoric acid (Hirota Chemical Industry) and 5% by mass of CIT-1 as seed crystals to obtain the raw material composition. The molar composition of the obtained raw material composition is shown.

SiO ₂ /Al ₂ O ₃ /TMMAOH/HF/H ₂ O=1/0.02/0.5/0.5/5.0 (molar ratio)
_SiO₂ / _{Al₂O₃ ratio} = 50.0
TMMAOH/ _SiO2 ratio = 0.5
HF/ _SiO2 ratio = 0.5
_H2O / _SiO2 ratio = 5.0
The obtained composition was sealed in an autoclave with a Teflon® inner cylinder, and the autoclave was heated at 170°C under autocatalytic pressure for 7 days while standing to obtain the product. The product was filtered, washed, and dried overnight in air at 110°C. Then, organic matter incorporated into the framework was removed by heating at 450°C for 1 hour under nitrogen, followed by heating at 600°C for 2 hours under air. This yielded a CON-type zeolite with an _SiO₂ / _{Al₂O₃ ratio} of 53 and an H-type cation. The hydrocarbon adsorbent of this example, with a Cs content of 4.6% by mass, was obtained by the same method as in Example 1, except that the obtained CON-type zeolite was used.

Comparative Example 1
(*Synthesis of BEA-type zeolite)
A 35 wt% TEAOH aqueous solution, a 48 wt% potassium hydroxide aqueous solution, pure water, and amorphous aluminosilicate ( _{SiO₂ / Al₂O₃} = 18.2) were mixed, and then 1.5 wt% zeolite β (product name: HSZ930NHA, manufactured by Tosoh Corporation) was added as a seed crystal to obtain a raw material composition having the following molar composition.

_SiO₂ / _{Al₂O₃ ratio} = 18.2
TEAOH/ _SiO2 ratio =0.12
K/ _SiO2 ratio =0.12
H ₂ O/SiO ₂ ratio = 12.0
Seed crystal = 1.5% by mass
The raw material composition was filled into a sealed container, and the container was rotated at 55 rpm while the raw material composition was reacted at 150°C for 48 hours to obtain crystals. The obtained crystals were separated into solid and liquid components, washed with pure water, and then dried in the air at 110°C to recover. The obtained crystals were calcined in the air at 600°C for 2 hours and treated with a 20% ammonium chloride aqueous solution, and then dried overnight in the air at 110°C. This yielded a BEA-type zeolite (zeolite β) having a three-dimensional pore structure consisting only of 12-membered ring pores, with an _SiO₂ / _Al₂O₃ ratio of 18 and _{a cation} type of _NH₄ .

The hydrocarbon adsorbent for this comparative example was obtained using the same method as in Example 1, except that the *BEA-type zeolite obtained above was used instead of the MSE-type zeolite.

Comparative Example 2 (Synthesis of YFI-type zeolite)
Colloidal silica AS-40 (manufactured by GRACE), zeolite Y (product name: HSZ-350HUA, manufactured by Tosoh Corporation), _{Me₂Pr₂NOH} , NaOH, KOH, and _H₂O were mixed to obtain _a raw material composition having the following molar composition.

SiO ₂ : 0.025 Al ₂ O ₃ : 0.17 Me ₂ Pr ₂ NOH: 0.15 NaOH: 0.17 KOH: 7 H ₂ O
_SiO₂ / _Al₂O₃ ratio = ₄₀
Me ₂ Pr ₂ NOH/SiO ₂ ratio = 0.17
Na+K/ _SiO2 ratio =0.32
H ₂ O/SiO ₂ ratio = 7.0
The obtained raw material composition was packed into an autoclave and crystallized at 160°C for 6 days under standing conditions. After crystallization, it was calcined at 550°C in air and treated with a 20% ammonium chloride aqueous solution, and dried overnight at 110°C in air. This yielded a YFI-type zeolite having a three-dimensional pore structure consisting only of 12-membered ring pores, with an _SiO₂ / _{Al₂O₃ ratio} of 18 and a cation type of _NH₄ .

The hydrocarbon adsorbent for this comparative example was obtained using the same method as in Example 1, except that the YFI-type zeolite obtained above was used instead of MSE zeolite.

Comparative Example 3
The hydrocarbon adsorbent for this comparative example was obtained in the same manner as in Example 1, except that a MOR-type zeolite with a one-dimensional pore structure (product name: HSZ-640HOA, manufactured by Tosoh Corporation, _SiO₂ / _Al₂O₃ = ₁₉ ) was used instead of an MSE-type zeolite.

Comparative Example 4
The hydrocarbon adsorbent for this comparative example was obtained in the same manner as in Example ₁ , except that instead of MSE zeolite, an MFI-type zeolite (product name: HSZ-870NHA, manufactured by Tosoh Corporation; _SiO₂ / _Al₂O₃ = 70) was calcined at 570°C for 2 hours in an air atmosphere to obtain an MFI-type zeolite having a three-dimensional pore structure consisting only of 10-membered ring pores with a cation type of H.

Comparative Example 5
The hydrocarbon adsorbent of this comparative example was obtained by the same method as in Example ₁ , except that an MFI-type zeolite (product name: HSZ-850NHA, manufactured by Tosoh Corporation; _SiO₂ / _Al₂O₃ = 51) was calcined at 570°C for 2 hours in an air atmosphere to obtain an MFI-type zeolite with a three-dimensional pore structure consisting only of 10-membered ring pores, resulting in an H-type cation, instead of an MSE-type zeolite.

Comparative Example 6
The hydrocarbon adsorbent for this comparative example was obtained in _the same manner as in Example 1, except that an MFI-type zeolite (product name: HSZ-840NHA, manufactured by Tosoh Corporation; _SiO₂ / _Al₂O₃ = 39) having a three-dimensional pore structure consisting only of 10-membered ring pores was used instead of an MSE-type zeolite.

The results for Example 1 and Comparative Examples 1 to 3 are shown in the table below.

From the table above, it can be seen that, for zeolites with _{similar SiO₂} / _Al₂O₃ ratios and target metal content, zeolites with three-dimensional pores exhibit a higher desorption initiation temperature than zeolites with one-dimensional pores. Furthermore, from a comparison of Example 1 and Comparative Example 1, it can be seen that zeolites with three-dimensional pores consisting of 10-membered rings and 12-membered rings are hydrocarbon adsorbents that exhibit a higher desorption initiation temperature than zeolites with three-dimensional pores consisting only of 12-membered rings.

Next, the results for Example 2 and Comparative Examples 4 to 6 are shown in the table below.

In the table above, "-" indicates that the value has not been measured. Examples 2 and Comparative Examples 4 to 6 are all zeolites having three-dimensional pores. From Comparative Examples 4 to 6, it can be confirmed that the desorption initiation temperature tends to decrease with decreasing _SiO₂ / _Al₂O₃ ratio, and that as the _SiO₂ / _Al₂O₃ ratio decreases from ₇₀ to ₃₉ , the desorption initiation temperature increases by about 20°C, from 143°C to 165°C. On the other hand, although Example 2 has an _SiO₂ / _Al₂O₃ ratio of ₅₃ , which is about the same as Comparative Example 5, it can be confirmed that the desorption initiation temperature is about the same as that of Comparative Example 6 _, which has an _SiO₂ / _Al₂O₃ ratio that is 10 or more lower than that of Comparative Example 5. From this, it can be confirmed that the hydrocarbon adsorbent of this embodiment exhibits a high desorption initiation temperature at a high _SiO₂ / _{Al₂O₃ ratio} , which was previously only achievable with conventional hydrocarbon adsorbents in the low _SiO₂ / _{Al₂O₃ ratio} range.

Claims (9)

A hydrocarbon adsorbent comprising a zeolite having an MSE structure , and containing at least one of the metals rubidium and cesium in an amount of 1% by mass or more and 20% by mass or less. The hydrocarbon adsorbent according to claim 1, wherein the amount of the metal is 3% by mass or more and 15% by mass or less. A hydrocarbon adsorbent according to claim 1 or 2, wherein the ratio of at least one of rubidium and cesium metal [mol] / Al [mol] is 0.01 or more and 10 or less. The hydrocarbon adsorbent according to any one of claims 1 to 3, wherein the metal is cesium. The hydrocarbon adsorbent according to claim 4 , wherein the main peak in the ¹³³ Cs MAS NMR spectrum is located between -300 ppm and -130 ppm. The hydrocarbon adsorbent according to claim 5 , wherein the main peak in the ¹³³ Cs MAS NMR spectrum is located between -250 ppm and -150 ppm. The hydrocarbon adsorbent according to any one of claims 1 to 6 , wherein the zeolite is a zeolite having a molar ratio of silica to alumina ( _SiO₂ / _{Al₂O₃ ratio} ) of 2 or more and 200 or less. The hydrocarbon adsorbent according to any one of claims 1 to 7 , wherein the zeolite is a zeolite having a molar ratio of silica to alumina ( _SiO₂ / _{Al₂O₃ ratio} ) of 2 or more and 100 or less. A method for adsorbing hydrocarbons, characterized by contacting a hydrocarbon-containing fluid with a hydrocarbon adsorbent according to any one of claims 1 to 8 .