Hydrocarbon adsorbent and hydrocarbon adsorption method

Abstract

An object of the present invention is to provide a hydrocarbon adsorbent having a high hydrocarbon desorption start temperature, or to provide a hydrocarbon adsorption method using the hydrocarbon adsorbent. The hydrocarbon adsorbent comprises an alkali metal and a zeolite having a ring structure of 10 or more members, wherein the alkali metal content is 1 to 40% by mass relative to 100% by mass of the hydrocarbon adsorbent, and the zeolite having a ring structure of 10 or more members is 99 to 60% by mass relative to 100% by mass of the hydrocarbon adsorbent, and at least a portion of the alkali metal is in an ion-exchangeable state.

Description

Technical Field

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

[0002] Exhaust gas emitted from internal combustion engines used in mobile vehicles such as automobiles and ships contains a large amount of hydrocarbons. Hydrocarbons emitted from internal combustion engines are purified by a three-way catalyst. For the three-way catalyst to function, a temperature environment of 200°C or higher is required. Therefore, within the temperature range where the three-way catalyst does not function, such as during a cold start, hydrocarbons are adsorbed on a hydrocarbon adsorbent. Within the temperature range where the three-way catalyst begins to function, hydrocarbons are released from the adsorbent and decomposed and purified by the three-way catalyst. A composition containing zeolite is commonly used as a hydrocarbon adsorbent. As this composition increases, the higher the hydrocarbon desorption start temperature, the more hydrocarbons are released while the three-way catalyst is highly active, which is beneficial for hydrocarbon purification. Therefore, a composition with a high hydrocarbon desorption start temperature is required.

[0003] Patent Document 1 proposes a composition containing zeolite containing at least one ion of an element having an electronegativity of 1.40 or greater as a composition having a high hydrocarbon desorption starting temperature.

[0004] Patent Document 2 proposes a hydrocarbon adsorbent composed of zeolite containing an alkali metal.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 11-005020

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2001-293368 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] While Patent Document 1 achieves a composition with a high desorption start temperature, it requires the use of a precious metal as the catalyst material, and the hydrocarbon adsorbent in the preceding stage of the three-way catalyst is exposed to higher temperatures than the three-way catalyst. Consequently, the hydrocarbon adsorbent lacks the heat resistance required for practical use in purifying hydrocarbons exhausted from internal combustion engines, and is also cost-prohibitive. The hydrocarbon adsorbent of Patent Document 2 suffers from an insufficiently high hydrocarbon desorption start temperature. The present disclosure aims to provide a hydrocarbon adsorbent with a high hydrocarbon desorption start temperature, or a hydrocarbon adsorption method using the hydrocarbon adsorbent.

[0011] Solutions for solving problems

[0012] The present inventors have studied the adsorption characteristics of a composition containing zeolite and have found that a specific hydrocarbon adsorbent has a high hydrocarbon desorption starting temperature.

[0013] That is, the present invention is as described in the claims, and the gist of the present disclosure is as follows.

[0014] [1] A hydrocarbon adsorbent, characterized in that the hydrocarbon adsorbent contains 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% by mass relative to 100% by mass of the hydrocarbon adsorbent, and the content of the zeolite having a ring structure of 10 or more members is 99 to 60% by mass relative to 100% by mass of the hydrocarbon adsorbent, and at least a portion of the alkali metal is in an ion-exchangeable state.

[0015] [2] The hydrocarbon adsorbent according to [1] above, 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.

[0016] [3] The hydrocarbon adsorbent according to [1] or [2] above, 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.

[0017] [4] The hydrocarbon adsorbent according to any one of [1] to [3] above, wherein the alkali metal is one or more selected from the group consisting of sodium, potassium, rubidium, and cesium.

[0018] [5] The hydrocarbon adsorbent according to [4] above, wherein the alkali metal is rubidium and / or cesium.

[0019] [6] The hydrocarbon adsorbent according to [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.

[0020] [7] The hydrocarbon adsorbent according to [6] 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 20 or less.

[0021] [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 at least one structure selected from the group consisting of a BEA structure, an MFI structure, a MOR structure, and a FAU structure.

[0022] [9] A method for adsorbing hydrocarbons using the hydrocarbon adsorbent described in any one of [1] to [8] above.

[0023] Effects of the Invention

[0024] According to the present disclosure, at least one object of providing a hydrocarbon adsorbent having a high hydrocarbon desorption starting temperature and a hydrocarbon adsorption method using the hydrocarbon adsorbent is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a graph plotting the relationship between the hydrocarbon desorption starting temperature and the SiO2 / Al2O3 ratio of Examples and Comparative Examples. DETAILED DESCRIPTION

[0026] The following describes an example embodiment of the hydrocarbon adsorbent disclosed herein. It should be noted that the term "to" in this disclosure, when used to indicate a range, includes both upper and lower limits. For example, the term "1 to 40%" is synonymous with "1% or more and 40% or less." Furthermore, the term "A and / or B" is synonymous with "at least one of A and B." For example, the term "rubidium and / or cesium" is synonymous with "at least one of rubidium and cesium."

[0027] The hydrocarbon adsorbent disclosed herein is characterized in that the content of alkali metal is 1 to 40% by mass relative to 100% by mass of the hydrocarbon adsorbent, and the content of zeolite having a ring structure of 10 or more members (hereinafter also referred to as "large-pore zeolite") is 99 to 60% by mass relative to 100% by mass of the hydrocarbon adsorbent (hereinafter the content of alkali metal relative to 100% by mass of the hydrocarbon adsorbent will also be referred to as "alkali metal content", and the content of large-pore zeolite relative to 100% by mass of the hydrocarbon adsorbent will also be referred to as "zeolite content"). Specifically, the hydrocarbon adsorbent disclosed herein is characterized in that it contains 1 to 40% by mass of alkali metals and 99 to 60% by mass of large-pore zeolite relative to 100% by mass of the hydrocarbon adsorbent. Preferably, it contains 5 to 40% by mass of alkali metals and 95 to 60% by mass of large-pore zeolite relative to 100% by mass of the hydrocarbon adsorbent (5 to 40% by mass of alkali metal content and 95 to 60% by mass of zeolite relative to 100% by mass of the hydrocarbon adsorbent). More preferably, it contains 10 to 40% by mass of alkali metals and 90 to 60% by mass of large-pore zeolite relative to 100% by mass of the hydrocarbon adsorbent (10 to 40% by mass of alkali metal content and 90 to 60% by mass of zeolite relative to 100% by mass of the hydrocarbon adsorbent). Furthermore, the hydrocarbon adsorbent disclosed herein is characterized in that at least a portion of the alkali metal is in an ion-exchangeable state.

[0028] It should be noted that the alkali metal mentioned above refers to an alkali metal element, and its elemental state is not particularly limited, but is preferably in an ionic state.

[0029] Based on this technical feature, the hydrocarbon adsorbent disclosed herein has usable heat resistance and a high hydrocarbon desorption starting temperature.

[0030] 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 composed of a repeating network of aluminum (Al) and silicon (Si) via oxygen (O).

[0031] In the present disclosure, zeolite is a compound having a regular structure of framework atoms (hereinafter also referred to as "T atoms") connected by oxygen (O), and is a compound composed of at least one of metal atoms, semi-metal atoms, and other atoms. Examples of metal atoms include at least one selected from the group consisting of iron (Fe), aluminum (Al), gallium (Ga), tin (Sn), and titanium (Ti), boron (B), and other transition metal elements. Examples of semi-metal atoms include at least one selected from the group consisting of boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), and tellurium (Te). Examples of atoms other than metal atoms and semi-metal atoms include phosphorus (P). Examples of zeolites in the present disclosure include, in addition to aluminosilicates, metal silicates such as ferrosilicates and gallosilicates, and zeolite analogs such as SAPOs (silicoaluminophosphates) and AlPOs (aluminophosphates).

[0032] The framework structure of a zeolite (interchangeably used with the crystal structure, hereinafter also referred to as the "zeolite structure") is determined by the structure codes (hereinafter also referred to as the "structure codes") specified by the Structure Commission of the International Zeolite Association. This framework structure is identified by comparing the XRD patterns of each zeolite structure described in the Collection of simulated XRD powder patterns for zeolites, Fifth revised edition (2007) (hereinafter also referred to as the "reference pattern") with the XRD pattern of the zeolite being tested.

[0033] In the present disclosure, the XRD pattern may be obtained by XRD measurement under the following conditions.

[0034] Accelerating current and voltage: 40mA and 40kV

[0035] Radiation source: CuKα rays

[0036] Measurement mode: continuous scanning

[0037] Scanning conditions: 40° / min

[0038] Measurement range: 2θ = 3° to 43°

[0039] Divergence longitudinal limiting slit: 10mm

[0040] Divergence / entrance slit: 1°

[0041] Light receiving slit: open

[0042] Sunlight receiving slit: 5°

[0043] Detector: Semiconductor detector (D / teX Ultra)

[0044] Use Ni filter

[0045] In the present disclosure, a "ring structure" refers to a cyclic skeleton structure composed of T atoms and oxygen atoms, and a "ring structure of 10 or more members" refers to a skeleton structure composed of 10 or more T atoms and oxygen atoms, for example, a 10-membered ring, a 12-membered ring, a 14-membered ring, or an 18-membered ring structure.

[0046] In the present disclosure, examples of large-pore zeolites include zeolites having a BEA structure, MFI structure, FAU structure, FER structure, or MOR structure. Zeolites having a BEA structure, MFI structure, FAU structure, or MOR structure are preferred due to their high hydrocarbon desorption starting temperature. Zeolites having a BEA structure or MFI structure are more preferred, and zeolites having an MFI structure are even more preferred. Zeolites having a specific zeolite structure are also referred to as "-type zeolites." For example, zeolites having a BEA structure, preferably zeolites having only a BEA structure, are also referred to as BEA-type zeolites.

[0047] The hydrocarbon adsorbent disclosed herein contains an alkali metal. The alkali metal (type of alkali metal) disclosed herein is not particularly limited, and examples thereof include 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. It should be noted that two or more alkali metals may coexist.

[0048] The alkali metal contained in the hydrocarbon adsorbent of the present disclosure is not particularly limited and may be an alkali metal contained in the large-pore zeolite contained in the hydrocarbon adsorbent. Examples of such alkali metals include: alkali metals contained in the zeolite itself obtained during the hydrothermal synthesis (after the crystallization step) described below (i.e., alkali metals contained in the zeolite during crystallization); alkali metals contained in the zeolite during post-treatment (e.g., alkali metals contained in the zeolite by impregnation of the zeolite with an alkali metal, or alkali metals contained in the zeolite by impregnation of the zeolite with an alkali metal after ion exchange with hydrogen ions or ammonium ions).

[0049] The hydrocarbon adsorbent disclosed herein contains at least an alkali metal supported on the zeolite during post-treatment, which is not desorbed by ion exchange. The presence of such an alkali metal is believed to be one of the reasons why the hydrocarbon adsorbent disclosed herein tends to exhibit a higher desorption onset temperature. In this case, post-treatment and ion exchange can be known methods for introducing the alkali metal into the zeolite.

[0050] In the hydrocarbon adsorbent disclosed herein, the aforementioned alkali metal is characterized by at least a portion being in an ion-exchangeable state. Consequently, the hydrocarbon adsorbent exhibits a higher hydrocarbon desorption onset temperature. In the present disclosure, "alkali metal in an ion-exchangeable state" means that a portion or all of the alkali metal contained in the zeolite is in a state capable of ion-exchange with another alkali metal (i.e., another type of alkali metal). A hydrocarbon adsorbent containing alkali metal in such a state can be produced, for example, using the production method described below.

[0051] Whether the alkali metal is ion-exchangeable can be determined by subjecting the hydrocarbon adsorbent to ion exchange with an alkali metal of a type not included in the hydrocarbon adsorbent of the present disclosure, and examining whether the alkali metal originally contained in the hydrocarbon adsorbent is lost (exchanged) by the ion exchange. For example, if 50% of the total amount of alkali metal originally contained is lost (exchanged) by the ion exchange, then 50% of the total amount of alkali metal is ion-exchangeable. Alternatively, if the entire amount of alkali metal originally contained is lost (exchanged) by the ion exchange, then 100% of the total amount of alkali metal is ion-exchangeable.

[0052] In view of the high hydrocarbon desorption starting temperature, the proportion of alkali metals that can ion-exchange with other types of alkali metals in the total amount of alkali metals contained in the hydrocarbon adsorbent of the present disclosure (assuming 100 mol%), that is, 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%. That is, in the hydrocarbon adsorbent of the present disclosure, it is preferred that 30 to 100 mol% of the total amount of alkali metals be in an ion-exchangeable state, and more preferably 50 to 95 mol% of the total amount of alkali metals be in an ion-exchangeable state.

[0053] The alkali metal contained in the hydrocarbon adsorbent of the present disclosure 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.

[0054] 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. Preferably, 30 to 100 mol% of the total amount (100 mol%) of the rubidium and / or cesium is ion-exchangeable, and more preferably 50 to 95 mol%.

[0055] In other embodiments, the alkali metal contained in the hydrocarbon adsorbent of the present disclosure is preferably sodium and / or potassium.

[0056] In this case, it is preferred that the sodium and / or potassium contained in the hydrocarbon adsorbent of the present disclosure can be ion-exchanged with rubidium and / or cesium, and preferably 30 to 100 mol% of the total amount (100 mol%) of the sodium and / or potassium is in an ion-exchangeable state, and more preferably 50 to 95 mol% is in an ion-exchangeable state.

[0057] The amount of alkali metal in the present disclosure can be measured by inductively coupled plasma atomic emission spectrometry (ICP-AES), and the quantification of alkali metal in an ion-exchangeable state can be performed by the method described in the Examples.

[0058] Furthermore, the alkali metal in an ion-exchangeable state in a hydrocarbon adsorbent composed of a large-pore zeolite containing an alkali metal can be quantified using the following method. Specifically, an aqueous solution containing an alkali metal of a different type (e.g., sodium (Na)) is passed through a hydrocarbon adsorbent composed of a large-pore zeolite containing an alkali metal (e.g., cesium (Cs)). The aqueous solution is used in an amount such that the alkali metal (Na) is in significant excess relative to the aluminum content of the large-pore zeolite contained in the hydrocarbon adsorbent (e.g., the amount of Na in the solution is 5 times the molar equivalent of the aluminum content of the large-pore zeolite). After the solution is passed through, the hydrocarbon adsorbent is washed by passing a sufficient amount of warm water (50-70°C) (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 replaces the alkali metal (Cs) originally contained with the other type of alkali metal (Na).

[0059] The molar ratio of the alkali metal (Cs) to aluminum in the hydrocarbon adsorbent before the solution is passed and after drying is determined, and the ratio (molar ratio) of the alkali metal in an ion-exchangeable state can be determined from the following formula.

[0060] R=[{Me / Al(before)-Me / Al(after)}÷Me / Al(before)]×100

[0061] In the above formula, R is the ratio of ion-exchangeable alkali metal (mol %), Me / Al(before) is the molar ratio of alkali metal to aluminum in the hydrocarbon adsorbent before passing the solution, and Me / Al(after) is the molar ratio of alkali metal to aluminum in the hydrocarbon adsorbent after drying. The alkali metal (Me) in Me / Al(before) and Me / Al(after) is the same type of alkali metal as that contained in the hydrocarbon adsorbent before passing the solution.

[0062] 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 further preferably 4% by mass or more and 40% by mass or less, relative to 100% by mass of the hydrocarbon adsorbent.

[0063] 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 ratio (%) of alkali metals in an ion-exchangeable state in the contained alkali metals.

[0064] The molar ratio of silica to alumina (hereinafter also referred to as "SiO2 / Al2O3 ratio") of the large-pore zeolite contained in the hydrocarbon adsorbent disclosed herein is not particularly limited. However, from the perspective of a high desorption starting temperature of hydrocarbons, a molar ratio of 5 to 40 can be cited, further a molar ratio of 5 to 35 can be cited, more preferably 5 to 30 or less, further preferably 5 to 20 or less, further more preferably 5 to 18 or less, still further preferably 5 to 15 or less, and particularly preferably 5 to 10 or less.

[0065] The BET specific surface area of the large-pore zeolite is preferably 200 m2 due to the high desorption starting temperature of hydrocarbons. 2 / g and above and 800m 2 / g or less, more preferably 300m 2 / g and above 700m 2 / g or less.

[0066] The hydrocarbon adsorbent of the present disclosure may contain components other than the above-mentioned components as needed. Components other than the above-mentioned components are not particularly limited, and examples thereof include a binder and the like.

[0067] In the present disclosure, preferred hydrocarbon adsorbents include those 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 zeolite, FAU zeolite, MOR zeolite, and MFI zeolite, having a SiO2 / Al2O3 ratio of 5 or more and 40 or less, wherein the content of the alkali metal is 1% by mass or more and 30% by mass or less relative to 100% by mass of the hydrocarbon adsorbent, the content of the zeolite is 70% by mass or more and 99% by mass or less relative to 100% by mass of the hydrocarbon adsorbent, and 20% by mass or more and 98% by mass or less of the alkali metal is in an ion-exchangeable state.

[0068] Examples of hydrocarbon adsorbents exhibiting a higher desorption start temperature include hydrocarbon adsorbents 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 having a SiO2 / Al2O3 ratio of 5 or more and 30 or less, wherein the cesium content is 8% by mass or more and 30% by mass or less relative to 100% by mass of the hydrocarbon adsorbent, the zeolite content is 70% by mass or more and 92% by mass or less relative to 100% by mass of the hydrocarbon adsorbent, and 40% by mass or more and 98% by mass or less of the alkali metal is in an ion-exchangeable state.

[0069] Examples of hydrocarbon adsorbents exhibiting a further high desorption start temperature include hydrocarbon adsorbents 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 having a SiO2 / Al2O3 ratio of 5 or more and 20 or less, wherein the cesium content is 10% by mass or more and 30% by mass or less relative to 100% by mass of the hydrocarbon adsorbent, the zeolite content is 70% by mass or more and 90% by mass or less relative to 100% by mass of the hydrocarbon adsorbent, and 20% by mass or more and 96% by mass or less of the alkali metal is in an ion-exchangeable state.

[0070] Examples of hydrocarbon adsorbents exhibiting a particularly high desorption start temperature include hydrocarbon adsorbents containing: cesium; and one or more zeolites selected from the group consisting of FAU-type zeolites, MOR-type zeolites, and MFI-type zeolites having a SiO2 / Al2O3 ratio of 5 or more and 17 or less, wherein the cesium content is 10% by mass or more and 30% by mass or less relative to 100% by mass of the hydrocarbon adsorbent, the zeolite content is 70% by mass or more and 90% by mass or less relative to 100% by mass of the hydrocarbon adsorbent, and 20% by mass or more and 95% by mass or less of the alkali metal is in an ion-exchangeable state.

[0071] Next, the method for producing the hydrocarbon adsorbent of the present disclosure will be described.

[0072] The hydrocarbon adsorbent production method disclosed herein can be any method, but the hydrocarbon adsorbent disclosed herein can be obtained by a production method comprising an alkali metal inclusion step in which alkali metals are included in the large-pore zeolite; or by a production method comprising a crystallization step in which a composition comprising a silica source, an alumina source, an alkali source, and water (hereinafter referred to as the "raw material composition") is hydrothermally treated to obtain a crystallized product, and an alkali metal inclusion step in which the crystallized product contains alkali metals. This production method also corresponds to the production method of the large-pore zeolite contained in the hydrocarbon adsorbent disclosed herein. It should be noted that a structure directing agent (hereinafter referred to as "SDA") can be additionally used in the aforementioned crystallization step, if necessary, by hydrothermally treating the raw material composition containing SDA. While it is preferable not to use SDA to simplify the production process, it is preferable to use SDA to expand the scope of production management.

[0073] The silica source is at least one of silica and its precursor, and examples thereof include at least one selected from the group consisting of colloidal silica, amorphous silica, sodium silicate, tetraethyl orthosilicate, and aluminosilicate gel. Among these, at least one of colloidal silica and amorphous silica is preferred, and colloidal silica or amorphous silica is more preferred.

[0074] The alumina source is at least one of alumina and its precursor, and examples thereof include 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, and aluminum hydroxide or aluminum sulfate is more preferred.

[0075] Examples of the alkali source include 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.

[0076] The raw material composition may further contain SDA as needed. As the structure directing agent, for example, tetraethylammonium hydroxide (hereinafter also referred to as "TEAOH"), tetraethylammonium bromide, tetrapropylammonium hydroxide, tetrapropylammonium bromide and dimethyldipropylammonium salt (hereinafter also referred to as "Me2Pr2N + "). The dimethyldipropylammonium salt is not particularly limited, and examples thereof include dimethyldipropylammonium hydroxide, dimethyldipropylammonium chloride, and dimethyldipropylammonium bromide.

[0077] In the zeolite production method disclosed herein, it is desirable that the raw material composition contain zeolite seed crystals (hereinafter also referred to as "seed crystals"). By using seed crystals, the zeolite crystallization rate is accelerated, the time required for zeolite production can be shortened, and the yield can be further improved.

[0078] The seed crystal is desirably an aluminosilicate having an LTL structure, an LTA structure, a MOR structure, an MFI structure, a BEA structure, a FAU structure, a CHA structure, or a YFI structure.

[0079] The SiO2 / Al2O3 molar ratio of the seed crystal is preferably 2 to 100, more preferably 3 to 60.

[0080] The amount of seed crystals added (i.e., the seed crystal content in the raw material composition) is preferably relatively low. On the other hand, considering the reaction rate, the effect of suppressing impurities, etc., the seed crystal content is preferably 0.1 to 60% by mass, more preferably 0.5 to 40% by mass, relative to the silica component in the raw material composition.

[0081] The content of seed crystals in the raw material composition (hereinafter also referred to as "seed crystal content") can be calculated according to the following formula from the mass of silicon (Si) contained in the raw material composition converted into SiO2.

[0082] Seed crystal content (mass %) = (mass of SiO2 in seed crystal) / (mass of SiO2 in raw material composition) × 100

[0083] As preferred compositions of the raw material composition, the following compositions (molar compositions) can be exemplified.

[0084] SiO2 / Al2O3 ratio = 3 or more and 40 or less

[0085] SDA / SiO2 ratio = 0 or more and 0.50 or less

[0086] Me / SiO2 ratio = 0 or more and 0.50 or less

[0087] H2O / SiO2 ratio = 3 or more and 100 or less

[0088] In the above formula, "Me" represents an alkali metal element.

[0089] 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 they allow the large pore zeolite to be crystallized, and examples thereof include the following conditions.

[0090] Crystallization temperature: above 80℃ and below 200℃

[0091] Crystallization time: 1 hour to 10 days

[0092] Crystallization pressure: autogenous pressure

[0093] The large-pore zeolite can be obtained by the above crystallization step. After the crystallization step, the large-pore zeolite obtained can be subjected to the steps of recovery, washing, drying and calcination by any method, and can further be subjected to dealumination treatment to set the SiO2 / Al2O3 ratio to any value.

[0094] From the viewpoint of increasing the desorption start temperature of hydrocarbons, it is preferred that the large-pore zeolite obtained after the crystallization step be subjected to a calcination step.

[0095] The calcination step is a step for removing SDA from the large-pore zeolite. Calcination conditions are arbitrary, but examples thereof include a calcination temperature of 400° C. to 800° C. and a calcination time of 0.5 to 12 hours in an oxidizing atmosphere.

[0096] The manufacturing method disclosed herein includes an alkali metal inclusion step. The purpose of the alkali metal inclusion step is to bring the alkali metal into contact with the large-pore zeolite so that the zeolite contains the alkali metal. Thus, while the alkali metal is contained, at least a portion of it is in an ion-exchangeable state. In the alkali metal inclusion step, the alkali metal is intentionally included in a state where the alkali metal is not coordinated to a portion of the ion exchange sites (alkali metal coordination sites) in the large-pore zeolite framework (zeolite structure). As a result, at least a portion of the alkali metal contained in the resulting large-pore zeolite and hydrocarbon adsorbent is in an ion-exchangeable state, which is believed to increase the hydrocarbon desorption start temperature.

[0097] The alkali metal 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. It should be noted that two or more alkali metals may be contained simultaneously, continuously, or intermittently.

[0098] When the large pore zeolite of the present disclosure contains sodium, potassium, rubidium, or cesium, it is preferred to use a compound of sodium, potassium, rubidium, or cesium, more preferably to use an inorganic acid salt containing sodium, potassium, rubidium, or cesium, and even more preferably to use at least one member selected from the group consisting of sulfates, nitrates, acetates, hydroxides, and chlorides containing sodium, potassium, rubidium, or cesium.

[0099] The alkali metal inclusion step may be a method for incorporating an alkali metal into at least one of the ion exchange sites and pores of the large-pore zeolite. Specific methods include at least one selected from the group consisting of ion exchange, evaporation to dryness, and impregnation. The impregnation method is preferred, and a method in which an aqueous solution containing an alkali metal compound is mixed with the zeolite is more preferred.

[0100] It should be noted that, in the alkali metal containing process, the alkali metal is contained in a state in which the alkali metal is intentionally not coordinated to a part of the ion exchange sites (alkali metal coordination sites) of the large-pore zeolite framework. That is, in the alkali metal containing process, at least a part of the alkali metal contained in the hydrocarbon adsorbent is made into an ion-exchangeable state. This method is not particularly limited, and for example, the method described in the embodiment of the present disclosure (a method of loading the alkali metal by making the zeolite as a fixed bed and making the alkali metal solution flow on the fixed bed) can be exemplified. As a specific method of the alkali metal containing process, a method can be listed as follows: a zeolite precipitate obtained by filtering a slurry containing zeolite is used as a fixed bed, and an alkali metal solution is continuously or intermittently passed from above the fixed bed. The moisture content of the zeolite precipitate can be exemplified as 35% by mass and less than 75% by mass, 40% by mass and less than 75% by mass, or 50% by mass and less than 70% by mass. The density of the zeolite precipitate can be 0.25 g / cm 3 Above and 0.9g / cm 3 Below or 0.3g / cm 3 Above and 0.7g / cm 3 the following.

[0101] It should be noted that the production method of the present disclosure may further include at least one of a washing step, a drying step, and an activation step after the alkali metal inclusion step.

[0102] The washing step after the alkali metal addition step is to remove impurities and the like from the zeolite, and any washing method may be used. For example, the large-pore zeolite may be washed with a sufficient amount of pure water.

[0103] The purpose of the drying step after the alkali metal addition step is to remove moisture from the zeolite. For example, the zeolite is treated (dried) in the air at 100°C to 200°C, preferably 110°C to 190°C. The treatment time is optional, but can be 1 to 2 hours.

[0104] The purpose of the activation step after the alkali metal addition step is to remove organic matter from the zeolite. For example, treatment (activation) can be performed in the atmosphere at a temperature exceeding 200°C and not exceeding 600°C, preferably exceeding 300°C and not exceeding 600°C. The treatment time is optional, but can be exemplified by a temperature of 1 to 2 hours.

[0105] The hydrocarbon adsorbent of the present disclosure is a hydrocarbon adsorbent comprising the large-pore zeolite obtained as described above, and may be a hydrocarbon adsorbent composed of a large-pore zeolite containing an alkali metal.

[0106] The hydrocarbon adsorbent disclosed herein may be in any shape depending on the intended use, preferably in the form of at least one of a powder and a molded body. Specific shapes of the molded body include at least one selected from the group consisting of a sphere, a substantially spherical shape, an ellipse, a disc, a cylinder, a polyhedron, an irregular shape, and a petal shape.

[0107] When the hydrocarbon adsorbent is used in the form of a powder, the hydrocarbon adsorbent may be mixed with a solvent such as water or alcohol to prepare a slurry, and the slurry may be coated on a substrate to prepare an adsorption member.

[0108] When the hydrocarbon adsorbent disclosed herein is formed into a molded article, it can be mixed with a binder as needed and molded by any method. Preferred binders include, for example, at least one member selected from the group consisting of silica, alumina, kaolin, attapulgite, montmorillonite, bentonite, allophane, and sepiolite. Molding methods include, for example, at least one member selected from the group consisting of tumbling granulation, press molding, extrusion molding, injection molding, casting molding, and sheet molding.

[0109] The hydrocarbon adsorbent disclosed herein is preferably a hydrocarbon adsorbent for adsorbing hydrocarbons at a temperature of 160°C or lower, more preferably a hydrocarbon adsorbent for adsorbing hydrocarbons at a temperature of 160°C or lower and desorbing the adsorbed hydrocarbons at a temperature exceeding 160°C. Even more preferably, it is a hydrocarbon adsorbent for adsorbing hydrocarbons at a temperature of 170°C or lower and desorbing the adsorbed hydrocarbons at a temperature exceeding 170°C, or a hydrocarbon adsorbent for adsorbing hydrocarbons at a temperature of 180°C or lower and desorbing the adsorbed hydrocarbons at a temperature exceeding 180°C. The hydrocarbon adsorbent disclosed herein can be used in a hydrocarbon adsorption method.

[0110] The hydrocarbon adsorbent of the present disclosure can adsorb hydrocarbons by a method comprising a step of bringing a hydrocarbon-containing fluid into contact with the hydrocarbon adsorbent of the present disclosure.

[0111] Examples of the hydrocarbon-containing fluid include hydrocarbon-containing gas and hydrocarbon-containing liquid.

[0112] A hydrocarbon-containing gas is a gas containing at least one hydrocarbon, preferably a gas containing two or more hydrocarbons. The hydrocarbon contained in the hydrocarbon-containing gas can include at least one of the group consisting of alkanes, alkenes, and aromatic hydrocarbons. The number of carbon atoms in the hydrocarbon can be 1 or more, preferably 1 or more and 15 or less. Preferably, the hydrocarbons contained in the hydrocarbon-containing gas are at least two of the group consisting of methane, ethane, ethylene, propylene, butane, linear alkanes with a carbon number of 5 or more, linear alkenes with a carbon number of 5 or more, benzene, toluene, and xylene. Preferably, at least two of the group consisting of methane, ethane, ethylene, propylene, butane, benzene, toluene, and xylene are contained in the hydrocarbon-containing gas. More preferably, at least one of the group consisting of methane, ethane, ethylene, and propylene and at least one of the group consisting of benzene, toluene, and xylene are contained in the hydrocarbon-containing gas. The hydrocarbon-containing gas may also include at least one of 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 internal combustion engines.

[0113] The contact temperature in this step is preferably room temperature to 200°C.

[0114] Example

[0115] The hydrocarbon adsorbent of the present disclosure is further described in detail in the following examples, but the present disclosure is not limited to these examples.

[0116] (Identification of crystal structure)

[0117] The XRD measurement of the sample was performed using a conventional X-ray diffractometer (Ultima IV Protectus, manufactured by Rigaku Corporation). The radiation source used was CuKα radiation. The measurement range is 3° to 43° 2θ, and the crystal structure is identified by comparing the obtained XRD pattern with a reference pattern. The detailed measurement conditions are shown below.

[0118] Accelerating current and voltage: 40mA and 40kV

[0119] Radiation source: CuKα rays

[0120] Measurement mode: continuous scanning (2θ / θ scanning)

[0121] Scanning conditions: 40° / min

[0122] Measurement range: 2θ = 3° to 43°

[0123] Divergence longitudinal limiting slit: 10mm

[0124] Divergence / entrance slit: 1°

[0125] Light receiving slit: open

[0126] Sunlight receiving slit: 5°

[0127] Detector: D / teX Ultra

[0128] Use Ni filter

[0129] (Composition Analysis)

[0130] The sample is dissolved in a mixed aqueous solution of hydrofluoric acid and nitric acid to prepare a sample solution for measurement. This sample solution is then analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES) using a conventional ICP apparatus (OPTIMA 5300DV, manufactured by PerkinElmer). The obtained measured values for Si, Al, and alkali metals (such as Cs and Na) are used to determine the sample's composition, including the SiO2 / Al2O3 ratio and the alkali metal content (mass %).

[0131] In more detail, the sample solution for measurement was prepared as follows. Specifically, 48% hydrofluoric acid, 60% nitric acid, and water were mixed at a volume ratio of 1:1:50 to prepare a mixed acid aqueous solution. Approximately 0.01 g of sample was dissolved in 10 ml of the resulting mixed acid aqueous solution, and the measurement solution was prepared so that the concentration of each element to be measured fell within the calibration curve concentration range. Table 1 shows the calibration curve concentration and measurement wavelength for each element to be measured.

[0132] [Table 1]

[0133] Determination of elements Calibration curve concentration (ppm) Measurement wavelength (nm) Na 10 589.6 K 10 766.5 Cs 50,100 455.5 Al 10 396.2 Si 202.1 251.6

[0134] Example 1

[0135] (Synthesis of Large-Pore Zeolite (BEA-Type Zeolite))

[0136] After mixing a 35% by mass aqueous solution of TEAOH, a 48% by mass aqueous solution of potassium hydroxide, pure water and amorphous aluminosilicate (SiO2 / Al2O3 ratio = 18.2), 1.5% by mass of 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.

[0137] SiO2 / Al2O3 ratio = 18.2

[0138] TEAOH / SiO2 ratio = 0.12

[0139] K / SiO2 ratio = 0.12

[0140] H2O / SiO2 ratio = 12.0

[0141] Seed crystal = 1.5 mass%

[0142] The raw material composition was placed in a sealed container and reacted at 150°C for 48 hours while rotating the container at 55 rpm to obtain crystals. The resulting crystals were separated into solid and liquid, washed with pure water, and then dried in air at 110°C for 24 hours and recovered. The resulting crystals were calcined in air at 600°C for 2 hours to obtain a calcined product. This product was then mixed with a 20% aqueous ammonium chloride solution containing a significant excess of NH4 relative to the Al content of the calcined product (i.e., 30 molar equivalents). The mixed aqueous solution was stirred at 80°C for 24 hours and then filtered. This stirring and mixing process was repeated twice, and the mixture was then dried in air at 110°C overnight. This yielded a large-pore zeolite (BEA-type zeolite) with a SiO2 / Al2O3 ratio of 18 and an NH4-type cation. The Na and K concentrations of the resulting BEA-type zeolite were below the detection limit.

[0143] (Impermeation of Alkali Metal (Cs))

[0144] A 2% by mass cesium chloride aqueous solution was prepared using cesium chloride (Fujifilm Wako Pure Chemical Industries, Ltd., special grade). This aqueous solution was used for alkali metal impregnation (impregnation) using an amount of cesium chloride sufficient to correspond to 4 molar equivalents of alkali metal (Cs) relative to the Al content of the BEA-type zeolite (large-pore zeolite) obtained above.

[0145] The resulting BEA-type zeolite was mixed with water and filtered to separate the solid and liquid, resulting in a filter cake of the zeolite. The cesium chloride aqueous solution was passed through the filter cake, followed by a passage of hot water (60°C) 10 times the mass of the zeolite (filter cake) to wash the filter cake. After washing, the filter cake was dried at 110°C in air for 24 hours to impregnate it with alkali metal (Cs), yielding a Cs-containing BEA-type zeolite, which served as the hydrocarbon adsorbent of this example. The resulting hydrocarbon adsorbent was subjected to ICP analysis to determine the alkali metal (Cs in this example) content (mass %) and the "Cs / Al molar ratio (before treatment)" in the hydrocarbon adsorbent.

[0146] (Quantitative Amount of Alkali Metal in Ion-Exchangeable State)

[0147] The amount of the alkali metal in an ion-exchangeable state was determined as follows.

[0148] The Cs-containing BEA-type zeolite (the hydrocarbon adsorbent of this example) was additionally impregnated with Na. A 2% by mass sodium chloride aqueous solution was prepared using sodium chloride (manufactured by Manac Inc.). This sodium chloride aqueous solution was impregnated in an amount corresponding to 5 molar equivalents of alkali metal (Na) relative to the Al content of the hydrocarbon adsorbent (zeolite) obtained by impregnation with Cs, i.e., to ion-exchange the Cs with Na.

[0149] The resulting Cs-containing BEA zeolite was mixed with water and filtered using a funnel to produce a zeolite filter cake. The filter cake was then washed with hot water (60°C) 10 times the mass of the resulting zeolite after passing the aforementioned sodium chloride aqueous solution through it. After washing, it was dried at 110°C in air to obtain a Na-additionally impregnated product. The resulting additionally impregnated product was subjected to ICP analysis to determine the "Cs / Al molar ratio (after treatment)." The ion-exchangeable cesium (i.e., the amount of cesium in an ion-exchangeable state) in the total cesium content of the hydrocarbon adsorbent was calculated using the following formula.

[0150]

[0151] Furthermore, the alkali metal content (mass %) in an ion-exchangeable state contained in the BEA-type 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 (%) in an ion-exchangeable state. The results are shown in Table 2.

[0152] Example 2

[0153] The hydrocarbon adsorbent of this example was obtained in the same manner as in Example 1 except that FAU zeolite (product name: HSZ-320NAA, manufactured by TOSOH CORPORATION, SiO2 / Al2O3=6) was used instead of BEA zeolite, and the alkali metal (Cs in this example) content (mass %) and ion-exchangeable cesium were quantified.

[0154] Example 3

[0155] The hydrocarbon adsorbent of this example was obtained in the same manner as in Example 1 except that FAU zeolite (product name: HSZ-341NHA, manufactured by TOSOH CORPORATION, SiO2 / Al2O3=7) was used instead of BEA zeolite, and the alkali metal (Cs in this example) content (mass %) and ion-exchangeable cesium were quantified.

[0156] Example 4

[0157] The hydrocarbon adsorbent of this example was obtained in the same manner as in Example 1 except that MOR zeolite (product name: HSZ-610HOA, manufactured by TOSOH CORPORATION, SiO2 / Al2O3=11) was used instead of BEA zeolite, and the alkali metal (Cs in this example) content (mass %) was quantified.

[0158] Example 5

[0159] 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, SiO2 / Al2O3=23) was used instead of BEA zeolite, and the alkali metal (Cs in this example) content (mass %) and ion-exchangeable cesium were quantified.

[0160] Example 6

[0161] The hydrocarbon adsorbent of this example was obtained in the same manner as in Example 1 except that BEA zeolite (product name: HSZ-931HOA, manufactured by TOSOH CORPORATION, SiO2 / Al2O3=28) was used instead of the BEA zeolite used in Example 1, and the alkali metal (Cs in this example) content (mass %) was quantified.

[0162] Example 7

[0163] 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, SiO2 / Al2O3 = 28) was used instead of BEA zeolite, and the alkali metal (Cs in this example) content (mass %) was quantified.

[0164] Example 8

[0165] The hydrocarbon adsorbent of this example was obtained by the same method as in Example 5, except that the alkali metal impregnation was performed using the following method. Specifically, a 5% by mass cesium chloride aqueous solution was used, with the amount of Cs being 2 molar equivalents relative to the amount of Al in the zeolite. The cesium chloride aqueous solution and the zeolite were mixed, stirred at 80°C for 24 hours, and then filtered. This process was repeated twice. Ten times the mass of the resulting zeolite was then washed with 60°C water. After washing, the zeolite was dried at 110°C in air, thereby impregnating it with the alkali metal (Cs).

[0166] Example 9

[0167] 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 2 / Al 2 O 3 = 39) was used instead of the MFI zeolite used in Example 8.

[0168] Example 10

[0169] The hydrocarbon adsorbent of this example was obtained in the same manner as in Example 1 except that MFI zeolite (product name: HSZ-840NHA, manufactured by TOSOH CORPORATION, SiO 2 / Al 2 O 3 = 39) was used instead of BEA zeolite.

[0170] Example 11

[0171] The hydrocarbon adsorbent of this example was obtained in the same manner as in Example 10, except that a 10 mass % aqueous sodium chloride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) aqueous solution was used instead of the cesium chloride aqueous solution, and that the alkali metal impregnation (Na impregnation) treatment was performed with a liquid amount of Na equal to 50 molar equivalents relative to the Al amount of the zeolite.

[0172] Example 12

[0173] 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., Ltd.) was used instead of the cesium chloride aqueous solution, and that the alkali metal impregnation (K impregnation) treatment was performed with an amount of K equal to 10 molar equivalents relative to the Al amount of the zeolite.

[0174] Example 13

[0175] 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 Co., Ltd.) was used instead of the cesium chloride aqueous solution, and that the alkali metal impregnation (Rb impregnation) treatment was carried out with an amount of Rb equivalent to 2 molar equivalents relative to the Al amount of the zeolite.

[0176] Comparative Example 1

[0177] A 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, SiO2 / Al2O3 = 39) was used instead of BEA zeolite and that the alkali metal was not impregnated.

[0178] Measurement Example 1

[0179] (Preparation and pretreatment of measurement samples)

[0180] The hydrocarbon desorption onset temperatures of the hydrocarbon adsorbents obtained in Examples and Comparative Examples were measured. Each hydrocarbon adsorbent from the Examples and Comparative Examples was press-molded and pulverized to form amorphous bodies with an aggregate diameter of 20-30 mesh. The resulting bodies served as the measurement samples for each Example and Comparative Example. 1 g of each measurement sample was placed in a fixed-bed flow reactor at atmospheric pressure, treated at 500°C for 1 hour under a nitrogen flow, and then cooled to 50°C for pretreatment.

[0181] (Hydrocarbon adsorption)

[0182] A hydrocarbon-containing gas was passed through each hydrocarbon adsorbent subjected to the above pretreatment, and the hydrocarbons adsorbed between 50° C. and 600° C. were measured as the amount of hydrocarbon adsorption. The composition of the hydrocarbon-containing gas and the measurement conditions are shown below.

[0183] Hydrocarbon gas: Toluene 3000 ppmC (methane conversion concentration)

[0184] Water 3% by volume

[0185] Nitrogen balance

[0186] Gas flow rate: 200mL / min

[0187] Measuring temperature: 50~600℃

[0188] Heating rate: 10℃ / min

[0189] (Determination of Hydrocarbon Desorption Starting Temperature)

[0190] A flame ionization detector (FID) was used to continuously quantitatively analyze hydrocarbons in the gas after it passed through the hydrocarbon adsorbent. The hydrocarbon concentration (methane-equivalent concentration; hereinafter referred to as the "inlet concentration") of the hydrocarbon-containing gas at the inlet side of the atmospheric pressure fixed-bed flow-through reactor and the hydrocarbon concentration (methane-equivalent concentration; hereinafter referred to as the "outlet concentration") of the hydrocarbon-containing gas at the outlet side of the atmospheric pressure fixed-bed flow-through reactor were measured.

[0191] The integrated value of the inlet concentration is used as the amount of hydrocarbons passing through the hydrocarbon adsorbent. The value obtained by subtracting the integrated value of the outlet concentration (methane-equivalent concentration) from this hydrocarbon amount is used to determine the amount of hydrocarbons adsorbed by each adsorbent as the amount of hydrocarbons desorbed per unit mass of the hydrocarbon adsorbent (μmolC / g). Furthermore, the temperature at which the amount of hydrocarbons desorbed first reaches 0 μmolC / g as the temperature of the measurement sample increases is defined as the desorption start temperature.

[0192] The following table shows the desorption start temperature of hydrocarbons in Measurement Example 1. Figure 1 The relationship between the SiO2 / Al2O3 ratio and the desorption starting temperature is shown.

[0193] [Table 2]

[0194]

[0195] In Table 2, "Me" represents alkali metal, "Total Me content" represents the total amount of alkali metal contained in the hydrocarbon adsorbent, "Ion-exchangeable Me ratio" represents the ratio of Me in an ion-exchangeable state among the alkali metals contained in the zeolite, and "Ion-exchangeable Me content" represents the content (mass %) of alkali metals in an ion-exchangeable state contained in the zeolite.

[0196] As shown in Table 2, the hydrocarbon adsorbents of Examples had higher hydrocarbon desorption start temperatures than the hydrocarbon adsorbent of Comparative Example 1, and retained hydrocarbons even at higher temperatures. In each of the Examples, the hydrocarbon desorption start temperature tended to increase with increasing ion-exchangeable alkali metal content.

[0197] Furthermore, similarly to the hydrocarbon adsorbents of Examples 1 to 10, the hydrocarbon desorption start temperatures of the hydrocarbon adsorbents of Examples 11 to 13 containing Na, K, or Rb as the alkali metal were higher than those of the hydrocarbon adsorbent of Comparative Example 1.

[0198] In addition, according to Figure 1 It can be seen that the hydrocarbon desorption starting temperature is proportional to the SiO2 / Al2O3 ratio. Regardless of the structure of the zeolite, there is a trend that the lower the SiO2 / Al2O3 ratio, the higher the hydrocarbon desorption starting temperature.

[0199] The entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2020-064909 filed on March 31, 2020 in Japan are incorporated herein by reference in their entirety as the disclosure of the specification of the present disclosure.

Claims

1. A hydrocarbon adsorbent, characterized in that: The hydrocarbon adsorbent contains 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% by mass relative to 100% by mass of the hydrocarbon adsorbent, and the content of the zeolite having a ring structure of 10 or more members is 99 to 60% by mass relative to 100% by mass of the hydrocarbon adsorbent, at least a portion of the alkali metal is in an ion-exchangeable state, the zeolite having a ring structure of 10 or more members is a zeolite having at least one structure selected from the group consisting of a BEA structure, an MFI structure, a MOR structure, and a FAU structure, and the zeolite has a molar ratio of silica to alumina (SiO2 / Al2O3 ratio) of 11 to 18. The hydrocarbon adsorbent adsorbs hydrocarbons below 180°C and desorbs the adsorbed hydrocarbons when the temperature exceeds 180°C. The hydrocarbon adsorbent is obtained by a production method comprising a crystallization step of crystallizing a raw material composition containing a silica source, an alumina source, an alkali source, and water, and an alkali metal inclusion step of adding an alkali metal to the raw material composition.

2. The hydrocarbon adsorbent 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 hydrocarbon adsorbent.

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

4. The hydrocarbon adsorbent according to any one of claims 1 to 3, wherein The alkali metal is one or more selected from the group consisting of potassium, sodium, rubidium, and cesium.

5. The hydrocarbon adsorbent according to claim 4, wherein The alkali metal is rubidium and / or cesium. A method for adsorbing hydrocarbons, comprising using the hydrocarbon adsorbent according to any one of claims 1 to 5.

Images