Hydrocarbon adsorbent and hydrocarbon adsorption method

Abstract

To provide a hydrocarbon adsorbent having a high hydrocarbon desorption start temperature, or to provide a hydrocarbon adsorption method that uses the hydrocarbon adsorbent.SOLUTION: Used is a hydrocarbon adsorbent containing an alkali metal and zeolite having a ring structure made up of 10 or more rings. The content of the alkali metal is 1 to 40 mass% with respect to 100 mass% of the hydrocarbon adsorbent, the content of the zeolite having the ring structure made up of 10 or more rings is 99 to 60 mass% with respect to 100 mass% of the hydrocarbon adsorbent, and at least a portion of the alkali metal is in an ion exchangeable state.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to hydrocarbon adsorbents and methods for adsorbing hydrocarbons. [Background technology]

[0002] 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 using a three-way catalyst. Because a three-way catalyst requires a temperature environment of 200°C or higher to function, hydrocarbons are adsorbed onto a hydrocarbon adsorbent at temperatures where the three-way catalyst does not function, such as during cold starts. The hydrocarbons are then released from the adsorbent at temperatures where the three-way catalyst begins to function, and are then decomposed and purified by the three-way catalyst. Zeolite-containing compositions are commonly used as hydrocarbon adsorbents, but the higher the hydrocarbon desorption initiation temperature, the more active the three-way catalyst will be in releasing hydrocarbons, which is advantageous for purifying hydrocarbons. Therefore, a composition with a high hydrocarbon desorption initiation temperature is desired.

[0003] Patent Document 1 proposes a composition containing zeolite containing at least one ion with an elemental electronegativity of 1.40 or more as a composition having a high hydrocarbon desorption initiation temperature.

[0004] Patent Document 2 proposes a hydrocarbon adsorbent made of zeolite containing an alkali metal. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-005020 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-293368 Summary of the Invention [Problem to be solved by the invention]

[0006] Although Patent Document 1 provides a composition with a high desorption initiation temperature, it requires the use of a precious metal as a catalytic material, and the hydrocarbon adsorbent located in the upstream stage of the three-way catalyst is exposed to higher temperatures, so it does not have heat resistance sufficient for practical use as a hydrocarbon adsorbent for purifying hydrocarbons emitted from internal combustion engines, and is also disadvantageous in terms of cost. The hydrocarbon adsorbent of Patent Document 2 has the problem that its hydrocarbon desorption initiation temperature is not sufficiently high. The present disclosure aims to provide a hydrocarbon adsorbent with a high hydrocarbon desorption initiation temperature, or to provide a hydrocarbon adsorption method using such a hydrocarbon adsorbent. [Means for solving the problem]

[0007] The present inventors have investigated the adsorption characteristics of compositions containing zeolites and have found that certain hydrocarbon adsorbents have a high hydrocarbon desorption initiation temperature.

[0008] That is, the present invention is as defined in the claims, and the gist of the present disclosure is as follows. [1] A hydrocarbon adsorbent containing an alkali metal and a zeolite having a ring structure of 10 or more members, characterized in that the content of the alkali metal is 1 to 40 mass% relative to 100 mass% of the hydrocarbon adsorbent, the content of the zeolite having a ring structure of 10 or more members is 99 to 60 mass% relative to 100 mass% of the hydrocarbon adsorbent, and at least a part of the alkali metal is in an ion-exchangeable state. [2] The hydrocarbon adsorbent according to [1] above, wherein the content of alkali metals in an ion-exchangeable state is 1% by mass or more and 40% by mass or less, relative to 100% by mass of the composition. [3] The hydrocarbon adsorbent according to [1] or [2] above, wherein the content of alkali metals in an ion-exchangeable state is 4% by mass or more and 40% by mass or less, relative to 100% by mass of the composition. [4] The hydrocarbon adsorbent according to any one of [1] to [3] above, wherein the alkali metal is at least one selected from the group consisting of sodium, potassium, rubidium, and cesium. [5] The hydrocarbon adsorbent according to the above [4], wherein the alkali metal is rubidium and / or cesium. [6] The hydrocarbon adsorbent according to any one of [1] to [5] above, wherein the molar ratio of silica to alumina (SiO2 / Al2O3 ratio) of the zeolite having a ring structure of 10 or more members is 5 or more and 35 or less. [7] The hydrocarbon adsorbent according to the above [6], wherein the molar ratio of silica to alumina (SiO2 / Al2O3 ratio) of the zeolite having a ring structure of 10 or more members is 5 or more and 20 or less. [8] The hydrocarbon adsorbent according to any one of [1] to [7] above, wherein the zeolite having a ring structure of 10 or more members is a zeolite having one or more structures selected from the group consisting of a BEA structure, an MFI structure, an MOR structure, and an FAU structure. [9] A method for adsorbing hydrocarbons using the hydrocarbon adsorbent according to any one of [1] to [8] above. [Effects of the Invention]

[0009] The present disclosure achieves at least one of the following objectives: to provide a hydrocarbon adsorbent having a high hydrocarbon desorption onset temperature; and to provide a hydrocarbon adsorption method using the hydrocarbon adsorbent. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a graph showing the relationship between hydrocarbon desorption starting temperature and SiO2 / Al2O3 ratio in Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0011] The hydrocarbon adsorbent of the present disclosure will be described below with reference to an example embodiment. In this disclosure, the use of "to" to indicate a range includes both the upper and lower limits, for example, 1 to 40% is equivalent to 1% or more and 40% or less. In this disclosure, the use of "A and / or B" is equivalent to "at least one of A and B," for example, the use of "rubidium and / or cesium" is equivalent to "at least one of rubidium and cesium."

[0012] The hydrocarbon adsorbent of the present disclosure is characterized in that the content of alkali metals relative to 100 mass% of the hydrocarbon adsorbent is 1 to 40 mass% and the content of zeolite having a ring structure of 10 or more members (hereinafter also referred to as "large pore zeolite") relative to 100 mass% of the hydrocarbon adsorbent is 99 to 60 mass% (hereinafter also referred to as "large pore zeolite") (the content of alkali metals relative to 100 mass% of the hydrocarbon adsorbent is also referred to as "alkali metal content", and the content of large pore zeolite relative to 100 mass% of the hydrocarbon adsorbent is also referred to as "zeolite content"). That is, the hydrocarbon adsorbent of the present disclosure is characterized by containing 1 to 40 mass% of an alkali metal and 99 to 60 mass% of a large pore zeolite relative to 100 mass% of the hydrocarbon adsorbent, preferably 5 to 40 mass% of an alkali metal and 95 to 60 mass% of a large pore zeolite relative to 100 mass% of the hydrocarbon adsorbent (the alkali metal content is 5 to 40 mass% and the zeolite content is 95 to 60 mass%), and more preferably 10 to 40 mass% of an alkali metal and 90 to 60 mass% of a large pore zeolite relative to 100 mass% of the hydrocarbon adsorbent (the alkali metal content is 10 to 40 mass% and the zeolite content is 90 to 60 mass%). Furthermore, the hydrocarbon adsorbent of the present disclosure is characterized in that at least a portion of the alkali metal is in an ion-exchangeable state.

[0013] The alkali metal mentioned above refers to an alkali metal element, and although there are no particular limitations on the elemental state, it is preferably in an ionic state.

[0014] The hydrocarbon adsorbent of the present disclosure has usable heat resistance and a high hydrocarbon desorption initiation temperature based on its constituent requirements.

[0015] The zeolite (large pore zeolite) contained in the hydrocarbon adsorbent of the present disclosure is preferably a crystalline aluminosilicate. Crystalline aluminosilicate is a zeolite having a crystal structure consisting of a repeating network of aluminum (Al) and silicon (Si) atoms interposed by oxygen (O).

[0016] In the present disclosure, zeolite is a compound having a regular structure in which skeleton atoms (hereinafter also referred to as "T atoms") are connected by oxygen (O), and the T atoms are 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 boron (B) and 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 examples of other atoms include phosphorus (P). In addition to aluminosilicates, examples of zeolites in the present disclosure include metallosilicates such as ferrosilicate and gallosilicate, and zeolite-related substances such as SAPO (silicoaluminophosphate) and AlPO (aluminophosphate).

[0017] The skeletal structure of a zeolite (used interchangeably with the crystalline structure, and hereinafter also referred to as the "zeolite structure") is a skeletal structure specified by the structure code (hereinafter also referred to simply as the "structure code") established by the Structure Commission of the International Zeolite Association, and can be identified by comparing the XRD pattern of the target zeolite with the XRD pattern of each zeolite structure (hereinafter also referred to as the "reference pattern") described in Collection of simulated XRD powder patterns for zeolites, Fifth revised edition (2007).

[0018] In the present disclosure, the XRD patterns may be obtained by XRD measurement under the following conditions.

[0019] Acceleration current / voltage: 40mA / 40kV Radiation source: CuKα radiation (λ=1.5405Å) Measurement mode: Continuous scan Scan condition: 40° / min Measurement range: 2θ=3° to 43° Divergence vertical limit slit: 10mm Divergence / entrance slit: 1° Receiving slit: open Receiving solar slit: 5° Detector: Semiconductor detector (D / teX Ultra) Ni filter used In the present disclosure, a "ring structure" refers to a cyclic skeletal structure composed of T atoms and oxygen atoms, and a "10- or more-membered ring structure" refers to a skeletal structure composed of 10 or more T atoms and oxygen atoms, such as a 10-, 12-, 14-, or 18-membered ring structure.

[0020] In the present disclosure, examples of large pore zeolites include zeolites having a BEA structure, an MFI structure, an FAU structure, an FER structure, or an MOR structure. In terms of the high hydrocarbon desorption onset temperature, zeolites having a BEA structure, an MFI structure, an FAU structure, or an MOR structure are preferred, zeolites having a BEA structure or an MFI structure are more preferred, and zeolites having an MFI structure are even more preferred. In the present disclosure, zeolites having a specific zeolite structure are also referred to as "type zeolites," and for example, a zeolite having a BEA structure, preferably a zeolite having only a BEA structure, is also referred to as a BEA-type zeolite.

[0021] The hydrocarbon adsorbent of the present disclosure contains an alkali metal. The alkali metal (type of alkali metal) of the present disclosure is not particularly limited, but may be, for example, one or more selected from the group consisting of sodium, potassium, rubidium, and cesium. The alkali metal is preferably rubidium and / or cesium, and more preferably cesium. Note that two or more types of alkali metals may coexist.

[0022] The alkali metal contained in the hydrocarbon adsorbent of the present disclosure is not particularly limited, and may be the alkali metal contained in the large-pore zeolite contained in the hydrocarbon adsorbent. Examples of the alkali metal include those contained in the zeolite itself obtained during hydrothermal synthesis (after the crystallization step) described below (i.e., the alkali metal contained in the zeolite by crystallization), and alkali metals contained in the zeolite by post-treatment (e.g., those contained in the zeolite after impregnation with an alkali metal, or those contained in the zeolite after ion-exchange with hydrogen ions or ammonium ions and then impregnated with an alkali metal).

[0023] The hydrocarbon adsorbent of the present disclosure contains at least an alkali metal that is supported on the zeolite in a post-treatment and that is not desorbed by ion exchange. The presence of such an alkali metal is thought to be one of the reasons why the hydrocarbon adsorbent of the present disclosure is likely to exhibit a higher desorption onset temperature. The post-treatment and ion exchange in this case may be performed by any known method for introducing an alkali metal into a zeolite.

[0024] In the hydrocarbon adsorbent of the present disclosure, at least a portion of the alkali metal is in an ion-exchangeable state. This allows the hydrocarbon adsorbent to exhibit a higher hydrocarbon desorption onset temperature. In the present disclosure, "the alkali metal is in an ion-exchangeable state" means that some or all of the alkali metal contained in the zeolite is ion-exchangeable with another alkali metal (i.e., a different type of alkali metal). A hydrocarbon adsorbent having an alkali metal in such a state can be produced, for example, by the production method described below.

[0025] Whether an alkali metal is in an ion-exchangeable state can be determined by ion-exchanging the hydrocarbon adsorbent with an alkali metal not included in the hydrocarbon adsorbent of the present disclosure and examining whether the alkali metal originally contained in the hydrocarbon adsorbent is lost (ion-exchanged) through the ion exchange. For example, if 50% of the total amount of alkali metal originally contained is lost (exchanged) through the ion exchange, this means that 50% of the total amount of alkali metal is in an ion-exchangeable state. Also, if the total amount of alkali metal originally contained is lost (exchanged) through the ion exchange, this means that 100% of the total amount of alkali metal is ion-exchangeable.

[0026] Of the total amount of alkali metals contained in the hydrocarbon adsorbent of the present disclosure (defined as 100 mol %), the proportion of alkali metals that can be ion-exchanged with another type of alkali metal, i.e., the proportion of alkali metals in an ion-exchangeable state in the hydrocarbon adsorbent of the present disclosure, is preferably in the range of 30 to 100 mol %, and more preferably in the range of 50 to 95 mol %, in order to achieve a high hydrocarbon desorption initiation temperature. That is, in the hydrocarbon adsorbent of the present disclosure, preferably 30 to 100 mol % of the total amount of alkali metals is in an ion-exchangeable state, and more preferably 50 to 95 mol % of the total amount of alkali metals is in an ion-exchangeable state.

[0027] The alkali metal contained in the hydrocarbon adsorbent of the present disclosure can be, for example, one or more selected from the group consisting of sodium, potassium, rubidium, and cesium. The alkali metal is preferably rubidium and / or cesium.

[0028] In this case, the rubidium and / or cesium contained in the hydrocarbon adsorbent of the present disclosure is preferably ion-exchangeable with sodium and / or potassium. Of the total amount (100 mol%) of the rubidium and / or cesium, 30 to 100 mol% is preferably in an ion-exchangeable state, and 50 to 95 mol% is more preferably in an ion-exchangeable state.

[0029] In another embodiment, the alkali metal contained in the hydrocarbon adsorbent of the present disclosure is preferably sodium and / or potassium.

[0030] In this case, the sodium and / or potassium contained in the hydrocarbon adsorbent of the present disclosure is preferably ion-exchangeable with rubidium and / or cesium, and of the total amount (100 mol %) of the sodium and / or potassium, it is preferable that 30 to 100 mol % is in an ion-exchangeable state, and more preferably 50 to 95 mol % is in an ion-exchangeable state.

[0031] Here, the amount of alkali metal in the present disclosure can be measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES), and the amount of alkali metal in an ion-exchangeable state can be quantified by the method described in the Examples.

[0032] Furthermore, the amount of alkali metal in an ion-exchangeable state in a hydrocarbon adsorbent made of large-pore zeolite containing an alkali metal can be quantified by the following method. Specifically, an aqueous solution containing a different type of alkali metal (e.g., sodium (Na)) from the alkali metal (e.g., cesium (Cs)) is passed through a hydrocarbon adsorbent made of large-pore zeolite containing the alkali metal. The amount of the aqueous solution used should be such that the alkali metal (Na) is in large excess relative to the amount of aluminum in the large-pore zeolite contained in the hydrocarbon adsorbent (e.g., an amount of Na that is 5 times the molar equivalent of the amount of aluminum in the large-pore zeolite). After passing the solution through the hydrocarbon adsorbent, the adsorbent is washed by passing a sufficient amount of hot water (50-70°C) through the adsorbent (e.g., 8-12 times the mass of the hydrocarbon adsorbent). The washed hydrocarbon adsorbent is then dried at 110°C in the air. This exchanges the alkali metal (Cs) originally contained in the adsorbent with a different type of alkali metal (Na).

[0033] The molar ratio of alkali metal (Cs) to aluminum in the hydrocarbon adsorbent before and after the liquid is passed through can be determined, and the proportion (molar ratio) of alkali metal in an ion-exchangeable state can be calculated using the following formula.

[0034] R = [{Me / Al(before)-Me / Al(after)} ÷ Me / Al(before)]×100 In the above formula, R is the proportion (mol%) of ion-exchangeable alkali metal, Me / Al(before) is the molar ratio of alkali metal to aluminum in the hydrocarbon adsorbent before passing a liquid, and Me / Al(after) is the molar ratio of alkali metal to aluminum in the hydrocarbon adsorbent after drying. The alkali metals (Me) in Me / Al(before) and Me / Al(after) are both the same type of alkali metal as the alkali metal contained in the hydrocarbon adsorbent before passing a liquid.

[0035] The content of the ion-exchangeable alkali metal contained in the hydrocarbon adsorbent of the present disclosure is preferably 0.01% by mass or more and 40% by mass or less, more preferably 1% by mass or more and 40% by mass or less, and even more preferably 4% by mass or more and 40% by mass or less, relative to 100% by mass of the hydrocarbon adsorbent.

[0036] The content (mass %) of alkali metals in an ion-exchangeable state can be determined by multiplying the alkali metal content (mass %) of the large pore zeolite contained in the hydrocarbon adsorbent of the present disclosure by the proportion (%) of alkali metals in an ion-exchangeable state among the alkali metals contained therein.

[0037] The molar ratio of silica to alumina (hereinafter also referred to as the "SiO2 / Al2O3 ratio") in the large pore zeolite contained in the hydrocarbon adsorbent of the present disclosure is not particularly limited, but in terms of a high hydrocarbon desorption initiation temperature, it may be 5 or more and 40 or less, or even 5 or more and 35 or less, more preferably 5 or more and 30 or less, even more preferably 5 or more and 20 or less, even more preferably 5 or more and 18 or less, still more preferably 5 or more and 15 or less, and particularly preferably 5 or more and 10 or less.

[0038] Large pore zeolites have a high hydrocarbon desorption temperature and a BET specific surface area of ​​200m 2 / g or more 800m 2 / g or less, and 2 / g or more 700m 2 It is more preferable that the saturation coefficient is 1 / g or less.

[0039] The hydrocarbon adsorbent of the present disclosure may contain components other than those described above, as necessary. Examples of the components other than those described above include, but are not limited to, a binder.

[0040] In the present disclosure, a preferred hydrocarbon adsorbent is a hydrocarbon adsorbent containing an alkali metal selected from the group consisting of sodium, potassium, rubidium, and cesium, and one or more zeolites selected from the group consisting of BEA-type zeolite, FAU-type zeolite, MOR-type zeolite, and MFI-type zeolite, each having an SiO2 / Al2O3 ratio of 5 to 40, wherein the content of the alkali metal is 1% by mass to 30% by mass, relative to 100% by mass of the hydrocarbon adsorbent, the content of the zeolite is 70% by mass to 99% by mass, and 20% by mass to 98% by mass of the alkali metal is in an ion-exchangeable state.

[0041] An example of a hydrocarbon adsorbent that exhibits a higher desorption initiation temperature is a hydrocarbon adsorbent containing cesium and one or more zeolites selected from the group consisting of BEA-type zeolite, FAU-type zeolite, MOR-type zeolite, and MFI-type zeolite, each having an SiO2 / Al2O3 ratio of 5 to 30, wherein the cesium content is 8 to 30 mass% relative to 100 mass% of the hydrocarbon adsorbent, the zeolite content is 70 to 92 mass%, and 40 to 98 mass% of the alkali metal is in an ion-exchangeable state.

[0042] An example of a hydrocarbon adsorbent that exhibits an even higher desorption onset temperature is a hydrocarbon adsorbent that contains cesium and one or more zeolites selected from the group consisting of BEA-type zeolite, FAU-type zeolite, MOR-type zeolite, and MFI-type zeolite, each having an SiO2 / Al2O3 ratio of 5 to 20, in which the cesium content is 10 to 30 mass% relative to 100 mass% of the hydrocarbon adsorbent, the zeolite content is 70 to 90 mass%, and 20 to 96 mass% of the alkali metal is in an ion-exchangeable state.

[0043] An example of a hydrocarbon adsorbent that exhibits a particularly high desorption onset temperature is a hydrocarbon adsorbent that contains cesium and one or more zeolites selected from the group consisting of FAU zeolite, MOR zeolite, and MFI zeolite, each having an SiO2 / Al2O3 ratio of 5 to 17, wherein the cesium content is 10 to 30 mass% relative to 100 mass% of the hydrocarbon adsorbent, the zeolite content is 70 to 90 mass%, and 20 to 95 mass% of the alkali metal is in an ion-exchangeable state.

[0044] Next, a method for producing the hydrocarbon adsorbent of the present disclosure will be described.

[0045] The hydrocarbon adsorbent of the present disclosure can be produced by any method, including an alkali metal-incorporating step of incorporating an alkali metal into a large pore zeolite, or a crystallization step of hydrothermally treating a composition containing a silica source, an alumina source, an alkali source, and water (hereinafter also referred to as the "raw material composition") to obtain a crystallized product, and an alkali metal-incorporating step of incorporating an alkali metal. This production method also corresponds to a method for producing the large pore zeolite contained in the hydrocarbon adsorbent of the present disclosure. In the crystallization step, a structure-directing agent (hereinafter also referred to as "SDA") can be additionally used, if necessary, by hydrothermally treating the raw material composition containing SDA. While it is preferable not to use SDA in order to simplify the production process, it is preferable to use SDA in order to broaden the scope of production control.

[0046] The silica source is at least one of silica and its precursor, such as at least one selected from the group consisting of colloidal silica, amorphous silica, sodium silicate, tetraethyl orthosilicate, and aluminosilicate gel. Of these, at least one of colloidal silica and amorphous silica is preferred, with colloidal silica or amorphous silica being more preferred.

[0047] The alumina source is at least one of alumina and its precursor, such as at least one selected from the group consisting of aluminum nitrate, aluminum sulfate, sodium aluminate, aluminum hydroxide, aluminum chloride, aluminosilicate gel, and metallic aluminum. Among these, at least one of aluminum hydroxide and aluminum sulfate is preferred, with aluminum hydroxide or aluminum sulfate being more preferred.

[0048] The alkalinity source may be at least one selected from the group consisting of various salts such as hydroxides, halides, and carbonates of lithium, sodium, potassium, rubidium, cesium, francium, magnesium, calcium, strontium, and ammonium. Among these, one or more hydroxides selected from the group consisting of sodium, potassium, and ammonium are preferred, and hydroxides of sodium, potassium, or ammonium are more preferred.

[0049] The raw material composition may contain SDA as needed. Examples of the structure-directing agent include tetraethylammonium hydroxide (hereinafter also referred to as "TEAOH"), tetraethylammonium bromide, tetrapropylammonium hydroxide, tetrapropylammonium bromide, and dimethyldipropylammonium salt (hereinafter also referred to as "MePrN"). + The dimethyldipropylammonium salt is not particularly limited, but examples thereof include dimethyldipropylammonium hydroxide, dimethyldipropylammonium chloride, and dimethyldipropylammonium bromide.

[0050] In the method for producing a zeolite according to the present disclosure, it is desirable that the raw material composition contain zeolite seed crystals (hereinafter simply referred to as "seed crystals"). The use of seed crystals increases the crystallization rate of the zeolite, shortens the time required for producing the zeolite, and improves the yield.

[0051] The seed crystal is preferably an aluminosilicate having an LTL structure, an LTA structure, an MOR structure, an MFI structure, a BEA structure, an FAU structure, a CHA structure, or a YFI structure.

[0052] The SiO2 / Al2O3 molar ratio of the seed crystals is preferably 2-100, and more preferably 3-60.

[0053] The amount of seed crystals added (i.e., the content of seed crystals in the raw material composition) is preferably small. On the other hand, in consideration of the reaction rate and the effect of suppressing impurities, the content of seed crystals is preferably 0.1 to 60 mass % and more preferably 0.5 to 40 mass % of the silica component contained in the raw material composition.

[0054] The content of seed crystals in the raw material composition (hereinafter also referred to as "seed crystal content") is calculated from the mass of silicon (Si) contained in the raw material composition converted into SiO2 using the following formula.

[0055] Seed crystal content (mass%) = (SiO mass of seed crystal) / (SiO mass of raw material composition) × 100 As a preferred composition of the raw material composition, the following composition (molar composition) can be exemplified.

[0056] SiO2 / Al2O3 ratio = 3 or more and 40 or less SDA / SiO2 ratio = 0 or more and 0.50 or less Me / SiO2 ratio = 0 or more and 0.50 or less H2O / SiO2 ratio = 3 or more and 100 or less In the above formula, "Me" represents an alkali metal element.

[0057] In the crystallization step, the raw material composition can be crystallized by hydrothermal treatment. The conditions for the hydrothermal treatment are not particularly limited as long as the conditions are such that the large pore zeolite is crystallized. For example, the following conditions can be mentioned:

[0058] Crystallization temperature: 80℃ or higher and 200℃ or lower Crystallization time: 1 hour to 10 days Crystallization pressure: Autogenous pressure The large-pore zeolite is obtained by the above crystallization process. After the crystallization process, the obtained large-pore zeolite may be subjected to recovery, washing, drying, and calcination processes by any method, and may further be subjected to dealumination treatment to adjust the SiO2 / Al2O3 ratio to any value.

[0059] It is preferable to subject the large pore zeolite obtained after the crystallization step to a calcination step, in order to increase the hydrocarbon desorption initiation temperature.

[0060] The calcination step is a step for removing SDA from the large pore zeolite. The calcination conditions are arbitrary, but examples of the calcination conditions include an oxidizing atmosphere, a calcination temperature of 400°C to 800°C, and a calcination time of 0.5 to 12 hours.

[0061] The manufacturing method of the present disclosure includes an alkali metal-incorporating step. The alkali metal-incorporating step is a step in which an alkali metal is brought into contact with a large pore zeolite to incorporate the alkali metal into the zeolite. As a result, the alkali metal is incorporated, and at least a portion of the alkali metal is rendered ion-exchangeable. In the alkali metal-incorporating step, the alkali metal is incorporated so as to intentionally create a state in which the alkali metal is not coordinated to some of the ion exchange sites (alkali metal coordination sites) in the framework (zeolite structure) of the large pore zeolite. This is thought to result in at least a portion of the alkali metal contained in the resulting large pore zeolite and hydrocarbon adsorbent being rendered ion-exchangeable, thereby increasing the hydrocarbon desorption initiation temperature.

[0062] The alkali metal to be contained is not particularly limited, and may be one or more selected from the group consisting of sodium, potassium, rubidium, and cesium. The alkali metal is preferably rubidium and / or cesium, and more preferably cesium. Two or more types of alkali metals may be contained simultaneously, continuously, or intermittently.

[0063] When sodium, potassium, rubidium, or cesium is contained in the large pore zeolite of the present disclosure, it is preferable to use a compound of sodium, potassium, rubidium, or cesium, and it is more preferable to use at least one of the group consisting of an inorganic acid salt containing sodium, potassium, rubidium, or cesium, and further, a sulfate, nitrate, acetate, hydroxide, and chloride containing sodium, potassium, rubidium, or cesium.

[0064] The alkali metal-incorporating step may be any method that incorporates an alkali metal into at least one of the ion exchange sites and pores of the large-pore zeolite. Specific examples of the alkali metal-incorporating step include at least one method selected from the group consisting of an ion exchange method, an evaporation-to-dryness method, and an impregnation method. The impregnation method and a method of mixing an aqueous solution containing an alkali metal compound with the zeolite are preferred.

[0065] In the alkali metal-containing step, the alkali metal is contained so as to intentionally create a state in which the alkali metal is not coordinated to some of the ion exchange sites (alkali metal coordination sites) of the large-pore zeolite framework. That is, in the alkali metal-containing step, at least a portion of the alkali metal contained in the hydrocarbon adsorbent is made ion-exchangeable. The method is not particularly limited, but an example thereof is the method described in the Examples of the present disclosure (a method in which the zeolite is used as a fixed bed and an alkali metal solution is passed through the fixed bed to support the alkali metal). A specific example of the alkali metal-containing step is a method in which a zeolite deposit obtained by filtering a zeolite-containing slurry is used as a fixed bed and an alkali metal solution is passed continuously or intermittently from above the fixed bed. The moisture content of the zeolite deposit can be, for example, 35% by mass to 75% by mass, 40% by mass to 75% by mass, 40% by mass to 70% by mass, or 50% by mass to 70% by mass. The density of the zeolite deposit is 0.25 g / cm. 3 More than 0.9g / cm 3 or less, or 0.3 g / cm 3 More than 0.7g / cm 3 The following points can be mentioned.

[0066] The manufacturing method of the present disclosure may include at least one of a washing step, a drying step, and an activation step after the alkali metal-containing step.

[0067] The washing step after the alkali metal-containing step is a step for removing impurities from the zeolite, and may be carried out by any washing method, such as washing the large pore zeolite with a sufficient amount of pure water.

[0068] The drying step after the alkali metal-containing step is a step for removing moisture from the zeolite, and can be performed by treating (drying) the zeolite in the atmosphere at a temperature of 100° C. to 200° C., preferably 110° C. to 190° C. The treatment time is optional, but can be, for example, 1 hour to 2 hours.

[0069] The activation step after the alkali metal-containing step is a step aimed at removing organic matter from the zeolite, and can be performed by treating (activating) the zeolite in the air at a temperature above 200° C. and not higher than 600° C., preferably above 300° C. and not higher than 600° C. The treatment time is optional, but can be, for example, from 1 hour to 2 hours.

[0070] The hydrocarbon adsorbent of the present disclosure is a hydrocarbon adsorbent containing the large pore zeolite obtained as described above, and may be a hydrocarbon adsorbent made of a large pore zeolite containing an alkali metal.

[0071] The hydrocarbon adsorbent of the present disclosure may have any shape depending on the application, and is preferably at least one of a powder and a molded body. Specific molded body shapes include at least one selected from the group consisting of spherical, approximately spherical, ellipsoidal, disk-like, cylindrical, polyhedral, irregular, and petal-like shapes.

[0072] When the hydrocarbon adsorbent is used as a powder, the hydrocarbon adsorbent can be mixed with a solvent such as water or alcohol to form a slurry, and the slurry can be coated on a substrate to form an adsorption member.

[0073] When the hydrocarbon adsorbent of the present disclosure is formed into a molded product, the hydrocarbon adsorbent may be mixed with a binder as needed and molded by any method. The binder may preferably be at least one selected from the group consisting of silica, alumina, kaolin, attapulgite, montmorillonite, bentonite, aloene, and sepiolite. The molding method may, for example, be at least one selected from the group consisting of rolling granulation molding, press molding, extrusion molding, injection molding, slip casting, and sheet molding.

[0074] The hydrocarbon adsorbent of the present disclosure is preferably a hydrocarbon adsorbent for adsorbing hydrocarbons at 160° C. or less, more preferably a hydrocarbon adsorbent for adsorbing hydrocarbons at 160° C. or less and desorbing the adsorbed hydrocarbons at a temperature higher than 160° C. Furthermore, it is more preferably a hydrocarbon adsorbent for adsorbing hydrocarbons at 170° C. or less and desorbing the adsorbed hydrocarbons at a temperature higher than 170° C., or a hydrocarbon adsorbent for adsorbing hydrocarbons at 180° C. or less and desorbing the adsorbed hydrocarbons at a temperature higher than 180° C. The hydrocarbon adsorbent of the present disclosure can be used in a hydrocarbon adsorption method.

[0075] The hydrocarbon adsorbents of the present disclosure are capable of adsorbing hydrocarbons by a method comprising contacting a hydrocarbon-containing fluid with the hydrocarbon adsorbent of the present disclosure.

[0076] The hydrocarbon-containing fluid may include, for example, a hydrocarbon-containing gas or a hydrocarbon-containing liquid.

[0077] The hydrocarbon-containing gas is a gas containing at least one type of hydrocarbon, preferably a gas containing two or more types of hydrocarbons. Examples of hydrocarbons contained in the hydrocarbon-containing gas include at least one selected from the group consisting of paraffins, olefins, and aromatic hydrocarbons. The hydrocarbons may have one or more carbon atoms, preferably from one to fifteen. Preferably, the hydrocarbons contained in the hydrocarbon-containing gas are at least two selected from the group consisting of methane, ethane, ethylene, propylene, butane, linear paraffins having five or more carbon atoms, linear olefins having five or more carbon atoms, benzene, toluene, and xylene. Preferably, the hydrocarbons contained in the hydrocarbon-containing gas are at least two selected from the group consisting of methane, ethane, ethylene, propylene, butane, benzene, toluene, and xylene. More preferably, the hydrocarbons are at least one selected from the group consisting of methane, ethane, ethylene, and propylene, and at least one selected from the group consisting of benzene, toluene, and xylene. The hydrocarbon-containing gas may contain at least one selected from the group consisting of 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 gas from an internal combustion engine.

[0078] Preferably, the contact temperature in this step is from room temperature to 200°C. [Example]

[0079] The hydrocarbon adsorbent of the present disclosure will be described in more detail below in examples, but the present disclosure is not limited to these examples.

[0080] (Identification of crystal structure) XRD measurements of the samples were performed using a standard X-ray diffractometer (Ultima IV Protectus, manufactured by Rigaku Corporation). CuKα radiation (λ = 1.5405 Å) was used as the radiation source, and measurements were performed in the 2θ range of 3° to 43°. The obtained XRD pattern was compared with a reference pattern to identify the crystal structure. Detailed measurement conditions are shown below.

[0081] Acceleration current / voltage: 40mA / 40kV Radiation source: CuKα radiation (λ=1.5405Å) Measurement mode: Continuous scan (2θ / θ scan) Scan condition: 40° / min Measurement range: 2θ=3° to 43° Divergence vertical limit slit: 10mm Divergence / entrance slit: 1° Receiving slit: open Receiving solar slit: 5° Detector: D / teX Ultra Ni filter used (composition analysis) The sample solution for measurement was prepared by dissolving the sample in a mixed aqueous solution of hydrofluoric acid and nitric acid, and the sample solution was measured by inductively coupled plasma atomic emission spectrometry (ICP-AES) using a general ICP device (device name: OPTIMA5300DV, manufactured by PerkinElmer). From the obtained measured values ​​of Si, Al, and alkali metals (Cs, Na, etc.), the composition of the sample, such as the SiO2 / Al2O3 ratio and the content (mass%) of alkali metals, was determined.

[0082] More specifically, the measurement sample solution was prepared as follows. 48% hydrofluoric acid, 60% nitric acid, and water were mixed in a volume ratio of 1:1:50 to obtain a mixed acid aqueous solution. Approximately 0.01 g of sample was dissolved in 10 ml of the obtained mixed acid aqueous solution so that the concentration of each measurement element was within the calibration curve concentration range, thereby preparing the measurement solution. The calibration curve concentrations and measurement wavelengths for each measurement element are shown in Table 1.

[0083] [Table 1]

[0084] Example 1 (Synthesis of large pore zeolite (BEA type zeolite)) A 35 mass% TEAOH aqueous solution, a 48 mass% potassium hydroxide aqueous solution, pure water, and amorphous aluminosilicate (SiO2 / Al2O3 ratio = 18.2) were mixed, and then 1.5 mass% of zeolite β (product name: HSZ930NHA, manufactured by Tosoh Corporation) was added as seed crystals to obtain a raw material composition having the following molar composition.

[0085] SiO2 / Al2O3 ratio =18.2 TEAOH / SiO2 ratio =0.12 K / SiO2 ratio =0.12 H2O / SiO2 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 a crystallized product. The resulting crystallized product was subjected to solid-liquid separation, washed with pure water, and then dried at 110°C in air for 24 hours to recover the product. The resulting crystallized product was calcined at 600°C in air for 2 hours to obtain a calcined product. This calcined product was mixed with a 20% aqueous ammonium chloride solution containing 30 molar equivalents of NH4, a large excess relative to the Al content of the calcined product. The mixed aqueous solution was stirred at 80°C for 24 hours and then filtered. This process was repeated twice to perform a stirring and mixing process, followed by drying overnight at 110°C in air. This resulted in a large-pore zeolite (BEA-type zeolite) with a SiO2 / Al2O3 ratio of 18 and an NH4 cation type. The Na and K concentrations of the resulting BEA-type zeolite were below the detection limit.

[0086] (Impregnation of alkali metal (Cs)) A 2% by mass aqueous solution of cesium chloride was prepared using cesium chloride (special grade, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.). The amount of cesium chloride aqueous solution was used to impregnate (impregnate) the alkali metal, in an amount that would result in 4 molar equivalents of alkali metal (Cs) relative to the amount of Al in the BEA-type zeolite (large pore zeolite) obtained above.

[0087] The obtained BEA-type zeolite was mixed with water and then subjected to solid-liquid separation by filtration to produce a cake of the obtained zeolite. After the above-mentioned cesium chloride aqueous solution was passed through the cake, hot water (60°C) in an amount 10 times the mass of the zeolite (cake) was passed through to wash the cake. After washing, the cake was impregnated with an alkali metal (Cs) by drying at 110°C in the air for 24 hours to obtain a Cs-containing BEA-type zeolite, which was used as the hydrocarbon adsorbent of this example. ICP analysis was performed on the obtained hydrocarbon adsorbent to determine the alkali metal (Cs in this example) content (mass%) in the hydrocarbon adsorbent and the "Cs / Al molar ratio (before treatment)."

[0088] (Quantitative determination of alkali metals in ion-exchangeable state) The amount of alkali metal in an ion-exchangeable state was determined as follows.

[0089] The Cs-containing BEA-type zeolite (the hydrocarbon adsorbent of this example) was additionally impregnated with Na. Sodium chloride (manufactured by Manac Corporation) was used to prepare a 2 mass% aqueous sodium chloride solution. The sodium chloride aqueous solution was used in an amount that would provide 5 molar equivalents of alkali metal (Na) relative to the amount of Al in the hydrocarbon adsorbent (zeolite) obtained by impregnation with Cs, i.e., for ion exchange of Cs with Na.

[0090] The obtained Cs-containing BEA-type zeolite was mixed with water and filtered through a separatory funnel to produce a zeolite cake. After the sodium chloride aqueous solution was passed through the cake, hot water (60°C) in an amount 10 times the mass of the obtained zeolite was passed through to wash it. After washing, it was dried at 110°C in the air to obtain an additional Na-impregnated product. ICP analysis was performed on the obtained additional impregnated product to determine the "Cs / Al molar ratio (after treatment)," and the amount of ion-exchangeable cesium, i.e., the amount of cesium in an ion-exchangeable state (%), of the total amount of cesium in the hydrocarbon adsorbent was calculated using the following formula.

[0091] [ka]

[0092] Furthermore, the alkali metal content (mass%) in an ion-exchangeable state contained in the BEA zeolite contained in the hydrocarbon adsorbent of this example was calculated by multiplying the alkali metal content (mass%) determined above by the alkali metal content (mass%) in an ion-exchangeable state. The results are shown in Table 2.

[0093] Example 2 The hydrocarbon adsorbent of this example was obtained in the same manner as in Example 1, except that FAU-type zeolite (product name: HSZ-320NAA, manufactured by Tosoh Corporation, SiO / AlO=6) was used instead of BEA-type zeolite, and the alkali metal (Cs in this example) content (mass%) and ion-exchangeable cesium were quantified.

[0094] Example 3 The hydrocarbon adsorbent of this example was obtained in the same manner as in Example 1, except that FAU-type zeolite (product name: HSZ-341NHA, manufactured by Tosoh Corporation, SiO / AlO=7) was used instead of BEA-type zeolite, and the alkali metal (Cs in this example) content (mass%) was quantified.

[0095] Example 4 The hydrocarbon adsorbent of this example was obtained in the same manner as in Example 1, except that MOR-type zeolite (product name: HSZ-610HOA, manufactured by Tosoh Corporation, SiO / AlO=11) was used instead of BEA-type zeolite, and the alkali metal (Cs in this example) content (mass%) was quantified.

[0096] Example 5 The hydrocarbon adsorbent of this example was obtained in the same manner as in Example 1, except that MFI zeolite (product name: HSZ-820NHA, manufactured by Tosoh Corporation, SiO / AlO=23) was used instead of BEA zeolite, and the alkali metal (Cs in this example) content (mass%) and ion-exchangeable cesium were quantified.

[0097] Example 6 The hydrocarbon adsorbent of this example was obtained in the same manner as in Example 1, except that BEA-type zeolite (product name: HSZ-931HOA, manufactured by Tosoh Corporation, SiO / AlO=28) was used instead of the BEA-type zeolite used in Example 1, and the alkali metal (Cs in this example) content (mass%) was quantified.

[0098] Example 7 The hydrocarbon adsorbent of this example was obtained in the same manner as in Example 1, except that MFI zeolite (product name: HSZ-830NHA, manufactured by Tosoh Corporation, SiO / AlO=28) was used instead of BEA zeolite, and the alkali metal (Cs in this example) content (mass%) was quantified.

[0099] Example 8 The hydrocarbon adsorbent of this example was obtained in the same manner as in Example 5, except that impregnation with an alkali metal was carried out in the following manner. Specifically, a 5% by mass aqueous solution of cesium chloride, equivalent to 2 molar equivalents of Cs relative to the Al content of the zeolite, was used to mix the cesium chloride aqueous solution with the zeolite, and the mixed aqueous solution was stirred at 80°C for 24 hours and then filtered. This procedure was repeated twice. The resulting zeolite was washed with 60°C water in an amount 10 times the mass of the zeolite. After washing, the zeolite was dried in the air at 110°C to be impregnated with an alkali metal (Cs).

[0100] Example 9 The hydrocarbon adsorbent of this example was obtained in the same manner as in Example 8, except that MFI zeolite (product name: HSZ-840NHA, manufactured by Tosoh Corporation, SiO / AlO=39) was used instead of the MFI zeolite used in Example 8.

[0101] Example 10 The hydrocarbon adsorbent of this example was obtained in the same manner as in Example 1, except that MFI type zeolite (product name: HSZ-840NHA, manufactured by Tosoh Corporation, SiO2 / Al2O3=39) was used instead of BEA type zeolite.

[0102] Example 11 The hydrocarbon adsorbent of this example was obtained in the same manner as in Example 10, except that a 10 mass % aqueous solution of sodium chloride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used instead of the cesium chloride aqueous solution, and that the alkali metal impregnation (Na impregnation) treatment was carried out with a liquid amount such that the amount of Na was 50 molar equivalents relative to the amount of Al in the zeolite.

[0103] Example 12 The hydrocarbon adsorbent of this example was obtained in the same manner as in Example 10, except that a 2 mass % aqueous solution of potassium chloride (manufactured by Kanto Chemical Co., Inc.) was used instead of the cesium chloride aqueous solution, and that the alkali metal impregnation (K impregnation) treatment was carried out in an amount of liquid such that the amount of K was 10 molar equivalents relative to the amount of Al in the zeolite.

[0104] Example 13 The hydrocarbon adsorbent of this example was obtained in the same manner as in Example 10, except that a 2 mass% aqueous solution of rubidium chloride (manufactured by Kanto Chemical) was used instead of the cesium chloride aqueous solution, and that the alkali metal impregnation (Rb impregnation) treatment was performed in an amount of liquid such that the amount of Rb was 2 molar equivalents relative to the amount of Al in the zeolite.

[0105] Comparative Example 1 The hydrocarbon adsorbent of this comparative example was obtained in the same manner as in Example 1, except that MFI zeolite (product name: HSZ-840NHA, manufactured by Tosoh Corporation, SiO / AlO=39) was used instead of BEA zeolite, and that no alkali metal was impregnated.

[0106] Measurement example 1 (Preparation and pretreatment of measurement samples) The hydrocarbon desorption initiation temperatures of the hydrocarbon adsorbents obtained in the Examples and Comparative Examples were measured. The hydrocarbon adsorbents according to the Examples and Comparative Examples were each pressure-molded and pulverized to form irregularly shaped bodies with an aggregate size of 20 to 30 mesh, and the resulting bodies were used as measurement samples for the respective Examples and Comparative Examples. 1 g of each measurement sample was packed into an atmospheric pressure fixed-bed flow-type reactor and treated at 500°C for 1 hour under a nitrogen flow, followed by cooling to 50°C as a pretreatment.

[0107] (hydrocarbon adsorption) A hydrocarbon-containing gas was passed through each of the hydrocarbon adsorbents that had been pretreated as described above, and the amount of hydrocarbon adsorbed was measured between 50°C and 600°C, and this was taken as the amount of hydrocarbon adsorption. The composition of the hydrocarbon-containing gas and the measurement conditions are shown below.

[0108] Hydrocarbon-containing gas: Toluene 3000 ppmC by volume (methane equivalent concentration) Water 3% by volume Nitrogen Remainder Gas flow rate: 200 mL / min Measurement temperature: 50~600℃ Heating rate: 10°C / min (Measurement of hydrocarbon desorption onset temperature) Using a hydrogen ionization detector (FID), the hydrocarbons in the gas after passing through the hydrocarbon adsorbent were continuously quantitatively analyzed. The hydrocarbon concentration of the hydrocarbon-containing gas at the inlet side of the atmospheric pressure fixed-bed flow-type reactor (methane equivalent concentration; hereinafter referred to as "inlet concentration") and the hydrocarbon concentration of the hydrocarbon-containing gas at the outlet side of the atmospheric pressure fixed-bed flow-type reactor (methane equivalent concentration; hereinafter referred to as "outlet concentration") were measured.

[0109] The amount of hydrocarbons passing through the hydrocarbon adsorbent was determined by subtracting the integral of the outlet concentration (methane equivalent concentration) from the amount of hydrocarbons, and the amount of hydrocarbons adsorbed by each adsorbent was calculated as the amount of hydrocarbons desorbed per mass of hydrocarbon adsorbent (μmolC / g).The temperature at which the amount of hydrocarbons desorbed most quickly reached 0 μmolC / g as the temperature of the measurement sample increased was determined as the desorption start temperature.

[0110] The table below shows the hydrocarbon desorption start temperatures in Measurement Example 1. Figure 1 shows the relationship between the SiO2 / Al2O3 ratio and the desorption start temperature.

[0111] [Table 2]

[0112] In Table 2, "Me" represents an alkali metal, "total Me content" represents the total amount of alkali metals contained in the hydrocarbon adsorbent, "ion-exchangeable Me ratio" represents the ratio of alkali metals contained in the zeolite that are in an ion-exchangeable state, and "ion-exchangeable Me content" represents the content (mass%) of alkali metals contained in the zeolite that are in an ion-exchangeable state.

[0113] As shown in Table 2, the hydrocarbon adsorbents of the Examples have higher hydrocarbon desorption initiation temperatures and retain hydrocarbons up to higher temperatures than the hydrocarbon adsorbent of Comparative Example 1. In each Example, the hydrocarbon desorption initiation temperature tends to increase as the content of alkali metal in an ion-exchangeable state increases.

[0114] Furthermore, the hydrocarbon adsorbents of Examples 11 to 13, which contain Na, K, or Rb as an alkali metal, also have a higher hydrocarbon desorption start temperature than the hydrocarbon adsorbent of Comparative Example 1, similar to the hydrocarbon adsorbents of Examples 1 to 10.

[0115] Furthermore, Figure 1 shows that the hydrocarbon desorption onset temperature is proportional to the SiO2 / Al2O3 ratio, and regardless of the zeolite structure, the lower the SiO2 / Al2O3 ratio, the higher the hydrocarbon desorption onset temperature tends to be.

[0116] The entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2020-064909, filed on March 31, 2020, are hereby incorporated by reference as the disclosure of the specification of the present disclosure.

Claims

1. A hydrocarbon adsorbent containing an alkali metal and a zeolite having a ring structure of 10 or more members, wherein the content of the alkali metal is 1 to 40 mass % relative to 100 mass % of the hydrocarbon adsorbent, the content of the zeolite having a ring structure of 10 or more members is 99 to 60 mass % relative to 100 mass % of the hydrocarbon adsorbent, at least a part of the alkali metal is in an ion-exchangeable state, and the molar ratio of silica to alumina in the zeolite (SiO ２ / Al ２ O ３ Ratio) is 5 or more and 20 or less, the alkali metal is cesium, The zeolite having a ring structure of 10 or more members has a BEA structure, a FAU structure, or a MOR structure. A hydrocarbon adsorbent characterized by:

2. 2. The adsorbent for hydrocarbons according to claim 1, wherein the content of the alkali metal in an ion-exchangeable state is 1% by mass or more and 40% by mass or less, relative to 100% by mass of the composition.

3. 3. The hydrocarbon adsorbent according to claim 2, wherein the content of the alkali metal in an ion-exchangeable state is 4% by mass or more and 40% by mass or less, relative to 100% by mass of the composition.

4. A hydrocarbon adsorbent described in any one of claims 1 to 3, wherein the zeolite having a ring structure of 10 or more members has a BEA structure.

5. The molar ratio of silica to alumina in the zeolite (SiO ２ / Al ２ O ３ 5. The adsorbent for hydrocarbons according to claim 1, wherein the ratio (R) is 5 or more and 18 or less.

6. 6. The hydrocarbon adsorbent according to claim 1, which adsorbs hydrocarbons at a temperature of 160°C or less and desorbs the adsorbed hydrocarbons at a temperature exceeding 160°C.

7. A method for adsorbing hydrocarbons, which uses the hydrocarbon adsorbent according to any one of claims 1 to 6.

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