Hydrocarbon adsorbent and method for adsorbing hydrocarbon

Abstract

To provide a hydrocarbon adsorber that enables the adsorbed hydrocarbon to be desorbed in a temperature range with higher activity of a three-way catalyst, or a hydrocarbon adsorbing method using the hydrocarbon adsorber.SOLUTION: A hydrocarbon adsorber contains barium and zeolite having a ring structure consisting of at least 10 rings. The molar ratio of barium to aluminum of the zeolite (Ba / Al ratio) is 0.04 or more and 0.6 or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a hydrocarbon adsorbent and a method for adsorbing hydrocarbons.

Background Art

[0002] Exhaust gas discharged from internal combustion engines used in moving bodies such as automobiles and ships contains a large amount of hydrocarbons. Hydrocarbons discharged from internal combustion engines are purified by a three-way catalyst. Since a temperature environment of 200°C or higher is required for the three-way catalyst to function, hydrocarbons are adsorbed by a hydrocarbon adsorbent in a temperature range where the three-way catalyst does not function, such as during so-called cold start, and hydrocarbons are released from the adsorbent in a temperature range where the three-way catalyst begins to function, and these are decomposed and purified by the three-way catalyst.

[0003] That is, it is advantageous for hydrocarbon purification that the hydrocarbon adsorbent adsorbs hydrocarbons in a temperature range where the activity of the three-way catalyst is low and releases hydrocarbons in a temperature range where the activity of the three-way catalyst is high. Since the three-way catalyst is known to exhibit high activity in a temperature range of 300°C or higher, there is a need for a hydrocarbon adsorbent having a high hydrocarbon desorption start temperature and releasing more adsorbed hydrocarbons in a temperature range of 300°C or higher.

[0004] In Patent Document 1, as a composition having a high hydrocarbon desorption start temperature, a composition containing a zeolite containing at least one ion having an electronegativity of 1.40 or more of an element has been proposed.

[0005] In Patent Document 2, a hydrocarbon adsorbent composed of a zeolite containing an alkali metal has been proposed.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] In Patent Document 1, although a composition with a high desorption start temperature is obtained, it does not have heat resistance that can withstand practical use, and it is also necessary to use a noble metal as a catalyst material, which is disadvantageous in terms of cost. The hydrocarbon adsorbent of Patent Document 2 has a problem that the desorption start temperature of hydrocarbons is not sufficiently high. The present disclosure aims to provide at least one of a hydrocarbon adsorbent capable of desorbing adsorbed hydrocarbons in a temperature range where the activity of the three-way catalyst is higher, or a method for adsorbing hydrocarbons using the hydrocarbon adsorbent.

Means for Solving the Problems

[0008] The present inventors have found that for a specific hydrocarbon adsorbent, adsorbed hydrocarbons can be desorbed in a temperature range where the activity of the three-way catalyst is higher.

[0009] 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 comprising a zeolite containing barium and having a ring structure of 10-membered ring or more, wherein the molar ratio of barium to aluminum in the zeolite is 0.04 or more and 0.6 or less. [2] The hydrocarbon adsorbent according to [1], wherein the molar ratio of barium to aluminum in the zeolite is 0.1 or more and 0.5 or less. [3] The hydrocarbon adsorbent according to [1] or [2], wherein the molar ratio of silica to alumina (SiO2 / Al2O3 ratio) in the zeolite is 2 or more and 38 or less. [4] The hydrocarbon adsorbent according to [1] to [3], wherein the zeolite has at least one zeolite structure selected from the group consisting of *BEA structure, MFI structure, FAU structure, YFI structure, MSE structure, CON structure, and MOR structure. [5] A method for adsorbing hydrocarbons using the hydrocarbon adsorbent according to any one of [1] to [4].

Advantages of the Invention

[0010] An object of the present disclosure is to provide a hydrocarbon adsorbent capable of desorbing adsorbed hydrocarbons in a temperature range where the activity of a three-way catalyst is higher, or a method for adsorbing hydrocarbons using the hydrocarbon adsorbent.

Brief Description of the Drawings

[0011]

Figure 1

Embodiments for Carrying Out the Invention

[0012] Hereinafter, an example of an embodiment of the hydrocarbon adsorbent of the present disclosure will be shown and described.

[0013] The hydrocarbon adsorbent of the present embodiment contains barium and includes a zeolite having a ring structure of 10-membered rings or more, and is characterized in that the molar ratio of barium to aluminum in the zeolite is 0.04 or more and 0.6 or less. The hydrocarbon adsorbent of the present embodiment can desorb adsorbed hydrocarbons in a temperature range where the activity of a three-way catalyst is higher.

[0014] In the present embodiment, zeolite is a compound having a regular structure in which framework atoms (hereinafter, also referred to as "T atoms") are connected via oxygen (O), and the T atoms are composed of at least any one of metal atoms, metalloid atoms, and other atoms. Examples of the metal atom include any one or more 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 the metalloid atom include any one or more selected from the group consisting of boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), and tellurium (Te). Examples of the other atom include phosphorus (P).

[0015] The zeolite contained in the hydrocarbon adsorbent of the present embodiment (hereinafter also referred to as "the present zeolite") is preferably a crystalline aluminosilicate. The crystalline aluminosilicate has a crystal structure composed of a network of aluminum (Al) and silicon (Si) repeated through oxygen (O).

[0016] In addition to aluminosilicates, the present zeolite may also be a metallosilicate such as ferrosilicate or gallosilicate, or a zeolite-like substance such as SAPO (silicoaluminophosphate) or AlPO (aluminophosphate).

[0017] The framework structure of the present zeolite (used interchangeably with the crystal structure and hereinafter also referred to as "the zeolite structure") is a framework structure specified by the structure code defined by the Structure Commission of the International Zeolite Association (hereinafter simply referred to as "the structure code"), and can be identified by comparing the XRD pattern of each zeolite structure described in 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 target zeolite.

[0018] In the present embodiment, examples of the XRD pattern of the zeolite include those obtained from XRD measurement under the following conditions.

[0019] Accelerating current and voltage: 40 mA·40 kV Radiation source: CuKα ray (λ = 1.5405 Å) Measurement mode: Continuous scan Scan condition: 40° / min Measurement range: 2θ = 3° to 43° Divergence vertical limit slit: 10 mm Divergence / incidence slit: 1° Light-receiving slit: open Light-receiving solar slit: 5° Detector: Semiconductor detector (D / teX Ultra) Use Ni filter This zeolite is a zeolite having a ring structure of 10-membered rings or more (hereinafter, also referred to as "large-pore zeolite"). Thereby, since the zeolite has pores with a large diameter, various compounds, ions, etc. can be adsorbed into the pores.

[0020] In this embodiment, the "ring structure" is a cyclic skeletal structure composed of T atoms and oxygen atoms, and the "ring structure of 10-membered rings or more" is a skeletal structure composed of 10 or more T atoms and oxygen atoms. For example, it is a ring structure of 10-membered rings, 12-membered rings, 14-membered rings, or 18-membered rings. For example, as a zeolite structure having a 10-membered ring structure, one or more selected from the group of MFI structure, MSE structure, and CON structure, as a zeolite structure having a 12-membered ring structure, one or more selected from the group of *BEA structure, MSE structure, CON structure, FAU structure, and YFI structure, and as a zeolite structure having a 14-membered ring structure, AET structure, CFI structure, *CTH structure, and DON structure can be respectively mentioned.

[0021] The framework structure of this zeolite can be exemplified by at least one structure selected from the group consisting of MOZ structure, AFI structure, STO structure, MRE structure, AET structure, AFO structure, AHT structure, ASV structure, ATO structure, ATS structure, BOF structure, CAN structure, CZP structure, EZT structure, GON structure, IFR structure, JRY structure, LAU structure, MTT structure, MTW structure, MVY structure, NPO structure, OSI structure, PON structure, PSI structure, SAF structure, SFE structure, SFF structure, SSY structure, STF structure, TON structure, VET structure, AFR structure, CGF structure, CSV structure, DAC structure, EON structure, EWS structure, FER structure, HEU structure, MFS structure, MOR structure, PCR structure, PWW structure, RRO structure, SFO structure, STI structure, AFS structure, AFY structure, BPH structure, CGS structure, GME structure, LTF structure, LTL structure, MAZ structure, MEI structure, MOZ structure, OBW structure, OFF structure, OSO structure, SBE structure, SOF structure, SOR structure, SOS structure, STW structure, SZR structure, UOS structure, WEI structure, IWV structure, MWW structure, NES structure, OKO structure, *PCS structure, SEW structure, SFG structure, SFS structure, USI structure, *CTH structure, BOZ structure, ITH structure, ITR structure, IWW structure, PUN structure, YFI structure, *UOE structure, CON structure, SFV structure, IWR structure, BEC structure, BOG structure, BSV structure, DFO structure, EMT structure, IFW structure, IMF structure, ISV structure, ITG structure, ITT structure, IWS structure, JST structure, MEL structure, MFI structure, MSE structure, POS structure, RWY structure, SAO structure, SBS structure, SBT structure, SOV structure, TUN structure, UOV structure, UWY structure and *BEA structure. In terms of the high desorption start temperature of hydrocarbons, it is preferable that this zeolite has a *BEA structure, MFI structure, FAU structure, YFI structure, MSE structure, CON structure or MOR structure, and it is more preferable that it has a *BEA structure or MFI structure. In this embodiment, a zeolite having a specific zeolite structure is also referred to as "~type zeolite". For example, a zeolite having a *BEA structure, preferably a zeolite having only the *BEA structure, is also referred to as *BEA type zeolite.This zeolite contains at least one of the above zeolite structures and may be a twin crystal having two or more zeolite structures.

[0022] Preferred zeolites for this zeolite include one or more selected from the group of *BEA-type zeolite, MFI-type zeolite, and FAU-type zeolite, and further include at least any one of *BEA-type zeolite and MFI-type zeolite, and still further include MFI-type zeolite.

[0023] This zeolite contains barium. The molar ratio of barium to aluminum in this zeolite (hereinafter, also referred to as "Ba / Al ratio") is 0.04 or more and 1.0 or less, preferably 0.04 or more and 0.6 or less, more preferably 0.1 or more and 0.6 or less, and still more preferably 0.1 or more and 0.5 or less. Thereby, the hydrocarbon adsorbent of this embodiment can desorb the adsorbed hydrocarbon in a temperature range where the activity of the three-way catalyst is higher.

[0024] The state of existence of barium contained in this zeolite is not particularly limited. For example, barium as a T atom (for example, barium contained in the zeolite itself obtained by hydrothermal synthesis (crystallization step) described later), or barium supported on the zeolite (for example, barium contained in the zeolite by impregnation treatment, or barium contained in the zeolite impregnated with barium after ion exchange with hydrogen ions or ammonium ions), etc. can be mentioned, and it is preferable that it is barium supported on the zeolite.

[0025] In addition, the elemental state of the above barium is not particularly limited, but it is preferably contained as barium ions.

[0026] The content of barium contained in this zeolite can be measured by inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0027] The molar ratio of silica to alumina in this zeolite (hereinafter also referred to as "SiO2 / Al2O3 ratio") is not particularly limited, but for example, it can be 2 or more and 100 or less, further 2 or more and 50 or less. In terms of the high hydrocarbon desorption start temperature, it can be 2 or more and 39 or less, preferably 2 or more and 20 or less, more preferably 2 or more and 18 or less, still more preferably 2 or more and 15 or less, and particularly preferably 5 or more and 10 or less.

[0028] Also, as the range of the SiO2 / Al2O3 ratio of this zeolite, it can be exemplified as 2 or more, 5 or more, 6 or more, or 8 or more, and 100 or less, 50 or less, 30 or less, or 25 or less.

[0029] This zeolite preferably has a BET specific surface area of 200 m 2 / g or more and 800 m 2 / g or less, and more preferably 300 m 2 / g or more and 700 m 2 / g or less.

[0030] This zeolite may contain components other than the above. The components other than the above are not particularly limited, but for example, binders and the like can be mentioned.

[0031] Next, the manufacturing method of the hydrocarbon adsorbent of this embodiment will be described.

[0032] The hydrocarbon adsorbent of this embodiment can be manufactured by a manufacturing method having a step of incorporating barium into the macroporous zeolite.

[0033] Furthermore, the hydrocarbon adsorbent of the present embodiment can be obtained by a production method having 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 "raw material composition") to obtain a crystallized product, and a barium-containing step of incorporating barium into the crystallized product. In the crystallization step, the raw material composition may contain a structure-directing agent (hereinafter also referred to as "SDA") as necessary. It is preferable not to use SDA in terms of simplifying the production operation, and it is preferable to use SDA in terms of expanding the production management range. Furthermore, the hydrocarbon adsorbent of the present embodiment can be obtained by a production method having a crystallization step of crystallizing a composition (raw material composition) containing a silica source, an alumina source, an alkali source, a barium source, and water to obtain a crystallized product.

[0034] The silica source is at least one of silica and its precursors, and examples thereof include one or more selected from the group consisting of colloidal silica, amorphous silica, sodium silicate, tetraethyl orthosilicate, and aluminosilicate gel.

[0035] The alumina source is at least one of alumina and its precursors, and examples thereof include one or more selected from the group consisting of aluminum sulfate, sodium aluminate, aluminum hydroxide, aluminum chloride, aluminosilicate gel, and metallic aluminum.

[0036] Examples of the alkali source include one or more selected from the group consisting of various salts such as hydroxides, halides, and carbonates of sodium, potassium, and ammonium.

[0037] The barium source may be a barium compound, and it is more preferable that it is at least one selected from the group consisting of inorganic acid salts of barium, further barium sulfate, nitrate, acetate, hydroxide, and chloride. The above raw material composition may optionally contain a structure-directing agent (SDA). The structure-directing agent may be any cation that directs the target zeolite structure. As structure-directing agents for directing zeolites having a ring structure of 10-membered rings or more, for example, N,N,N-trimethyl-(+)-cis-myrtanilammonium cation, hexamethonium cation, 1,1-dialkyl-4-alkylcyclohexylpiperazin-1-ium cation, 1,1-dialkyl-4-cyclohexylpiperazin-1-ium cation, 1,1'-((3as,6as)-octahydropentalene-2,5-diyl)bis(1-methylpiperidin-1-ium) cation, 1,1'-(butane-1,4-diyl)bis(1-methylpiperidin-1-ium) cation, 1,1'-(pentane-1,5-diyl)bis(1-methylpiperidin-1-ium) cation, 1,1'-(hexane-1,6-diyl)bis(1-methylpiperidin-1-ium) cation, 3-hydroxy-1-(4-(1-methylpiperidin-1-ium-1-yl)butyl)quinuclidin-1-ium cation, 3-hydroxy-1-(5-(1-methylpiperidin-1-ium-1-yl)pentyl)quinuclidin-1-ium cation, N,N,N,N-tetraethylbicyclo[2.2.2]-oct-7-ene-dipyrrolidinium cation, N,N-dimethyl-N'-cyclohexylpiperazinium, dimethyldipropylammonium cation, tetraethylammonium cation, 1,6-bis(N-cyclohexylpyrrolidinium)hexanedication, 1,4-bis(N-cyclohexylpiperidinium)butanedication, 1,4-bis(N-cyclohexylpyrrolidinium)butanedication, 1,4-bis(N-cyclopentylpiperidinium)butanedication, 1,5-bis(N,N-dimethylcyclohexylammonium)pentanedication, N,N,N-trimethyltricyclo[5.2.1.0]-decaneammonium cation, and (6R,10S)-6,10-dimethyl-5-azoniaspiro[4.5]decane cation, and one or more selected from the group consisting of them may be mentioned.Since the SDA is often a cation, it may be included in the raw material composition as a salt, and it may be included in the raw material composition as a salt formed with one or more anions selected from the group consisting of fluoride, chloride, bromide, iodide, and hydroxide (hereinafter, the salt of SDA is also referred to as "SDAX").

[0038] Preferably, the raw material composition has the following molar composition. In the following composition, SDAX is the salt of SDA, and X is an anion other than fluorine.

[0039] SiO2 / Al2O3 ratio = 2 or more and 500 or less SDA / SiO2 ratio = 0 or more and 0.8 or less Na / SiO2 ratio = 0 or more and 0.8 or less K / SiO2 ratio = 0 or more and 0.8 or less H2O / SiO2 ratio = 2 or more and 100 or less The raw material composition may contain seed crystals. The seed crystals are preferably large-pore zeolites. The content of the seed crystals in the raw material composition (hereinafter, also referred to as "seed crystal content") is preferably 0% by mass or more and 30% by mass or less, more preferably 1% by mass or more and 10% by mass or less, as the ratio of the mass of the seed crystals to the total mass of silicon (Si) converted to SiO2 and aluminum (Al) converted to Al2O3 contained in the raw material composition (raw material composition excluding seed crystals).

[0040] In the crystallization step, for example, the raw material composition can be crystallized by hydrothermal treatment. The conditions of the hydrothermal treatment are not particularly limited, and for example, the following conditions can be mentioned.

[0041] Crystallization temperature: 120°C or more and 200°C or less Crystallization time: 1 hour or more and 20 days or less Crystallization pressure: autogenous pressure The raw material composition is crystallized by the above crystallization process to obtain a large-pore zeolite. After the crystallization process, the obtained large-pore zeolite may be subjected to the steps of recovery, washing, drying, and calcination by any method. Furthermore, it may be dealuminated to set the SiO2 / Al2O3 ratio to any value.

[0042] The large-pore zeolite obtained by crystallizing the raw material composition containing SDA is excellent in the property of gently desorbing hydrocarbons. Therefore, after the crystallization process, it is preferably subjected to a calcination process to remove the SDA in the zeolite.

[0043] The calcination process is a process for removing SDA in the zeolite. The calcination conditions are arbitrary, but examples of the calcination conditions include a calcination temperature of 400°C or higher and 800°C or lower and a calcination time of 0.5 hour or longer and 12 hours or shorter in an oxidizing atmosphere.

[0044] The barium-containing process is a process for the purpose of incorporating barium into the large-pore zeolite. In this production process, barium is incorporated into the zeolite by arranging barium in one or more selected from the group consisting of the T atoms of the zeolite, the ion exchange sites (barium coordination sites), and the pores, and further, in at least one of the ion exchange sites (barium coordination sites) and the pores. The barium-containing process may be a process of bringing barium into contact with the large-pore zeolite to incorporate barium into the zeolite, or a process of crystallizing a raw material composition containing barium to incorporate barium into the large-pore zeolite. Further, in the barium-containing process, barium may be incorporated into the zeolite by substituting at least some of the T atoms in the zeolite framework with barium.

[0045] When incorporating barium into the zeolite, it is preferable to use a barium compound, and it is more preferable to use at least one selected from the group consisting of inorganic acid salts of barium, and further, sulfates, nitrates, acetates, hydroxides, and chlorides of barium.

[0046] The barium-containing step may be any method in which barium is contained in at least one of the T atoms, ion-exchange sites, and pores of the zeolite. Specific methods of containing barium in at least one of the ion-exchange sites and pores of the zeolite include at least one selected from the group consisting of an ion-exchange method, an evaporation to dryness method, and an impregnation method, and the impregnation method, and more preferably a method of mixing an aqueous solution of a barium compound and zeolite. The method is not particularly limited, but the method described in the examples (a method of containing barium in zeolite by flowing an aqueous solution of an inorganic salt of barium through the fixed bed with the zeolite as the fixed bed) can be exemplified.

[0047] In addition, the production method of the present embodiment may include at least one or more steps of a washing step, a drying step, and an activation step after the barium-containing step.

[0048] The washing step after the barium-containing step is for the purpose of removing impurities and the like of the zeolite, and any washing method can be used. For example, washing the zeolite impregnated with barium with a sufficient amount of pure water can be mentioned.

[0049] The drying step after the barium-containing step is for the purpose of removing moisture, and it can be exemplified that the treatment (drying) is performed in the atmosphere at 100°C or higher and 200°C or lower, preferably 110°C or higher and 190°C or lower. The treatment time is arbitrary, but 1 hour or more and 2 hours or less can be exemplified.

[0050] The activation step after the barium-containing step is a step of removing organic substances of the zeolite, and it can be exemplified that the treatment (activation) is performed in the atmosphere at a temperature exceeding 200°C and 600°C or lower, and preferably at a temperature exceeding 300°C and 600°C or lower. The treatment time is arbitrary, but 1 hour or more and 2 hours or less can be exemplified.

[0051] The obtained barium-containing zeolite may be used as it is as the hydrocarbon adsorbent of the present embodiment, or an additive such as a binder may be added thereto as necessary to obtain a hydrocarbon adsorbent containing the zeolite and the additive.

[0052] The hydrocarbon adsorbent of the present embodiment may have any shape according to the use, and preferably, at least one of powder and molded body is included. Specific shapes of the molded body include at least one shape selected from the group of spherical, substantially spherical, elliptical, disc-shaped, columnar, polyhedral, irregular, and petal-shaped, and any shape suitable for the desired purpose.

[0053] When the hydrocarbon adsorbent is used as powder, the above hydrocarbon adsorbent can be mixed with a solvent such as water or alcohol to form a slurry, and the slurry can be used as an adsorption member coated on a substrate.

[0054] When the hydrocarbon adsorbent of the present embodiment is made into a molded body, the above hydrocarbon adsorbent may be mixed with a binder as necessary and molded by any method. Preferably, the binder includes at least one selected from the group of silica, alumina, kaolin, attapulgite, montmorillonite, bentonite, allophane, and sepiolite. Examples of the molding method include at least one selected from the group of rolling granulation molding, press molding, extrusion molding, injection molding, casting molding, and sheet molding.

[0055] The hydrocarbon adsorbent of the present embodiment can be used in a hydrocarbon adsorption method.

[0056] The hydrocarbon adsorbent of the present embodiment can adsorb hydrocarbons by a method having a step of bringing a hydrocarbon-containing fluid into contact with the hydrocarbon adsorbent of the present embodiment.

[0057] Examples of the hydrocarbon-containing fluid include a hydrocarbon-containing gas or a hydrocarbon-containing liquid.

[0058] The hydrocarbon-containing gas is a gas containing at least one kind of hydrocarbon, and preferably a gas containing two or more kinds of hydrocarbons. The hydrocarbon contained in the hydrocarbon-containing gas includes at least one selected from the group consisting of paraffin, olefin, and aromatic hydrocarbon. The number of carbon atoms of the hydrocarbon may be 1 or more, and preferably 1 or more and 15 or less. Preferably, the hydrocarbon is at least two selected from the group consisting of methane, ethane, ethylene, propylene, butane, linear paraffin having 5 or more carbon atoms, linear olefin having 5 or more carbon atoms, benzene, toluene, and xylene, and preferably at least two selected from the group consisting of methane, ethane, ethylene, propylene, butane, benzene, toluene, and xylene, and more preferably 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 the hydrocarbon-containing gas include combustion gases such as exhaust gases of internal combustion engines.

[0059] The use of the hydrocarbon adsorbent of the present embodiment is not limited to the adsorption of hydrocarbons in internal combustion engines of moving bodies such as automobiles and ships. The hydrocarbon adsorbent of the present embodiment can be used for the purpose of adsorbing hydrocarbons in a low-temperature environment of less than 300°C, and preferably, after adsorbing hydrocarbons in a low-temperature environment of less than 300°C, it can be used for the purpose of desorbing hydrocarbons in a high-temperature environment of 300°C or more. For example, it can be used for the purpose of adsorbing hydrocarbons generated in industrial facilities such as oil, coal, and natural gas mining, power plants, waste treatment facilities, and factories at a temperature of less than 300°C, and further, the adsorbed hydrocarbons can be released at a temperature of 300°C or more and used for purification in a purification facility showing high purification performance at a temperature of 300°C or more.

[0060] Preferably, the temperature (hereinafter, also referred to as "contact temperature") in the step of bringing the hydrocarbon-containing fluid into contact with the hydrocarbon adsorbent of the present embodiment is room temperature or higher and 300°C or lower, or room temperature or higher and 200°C or lower.

Examples

[0061] Hereinafter, the hydrocarbon adsorbent of the present embodiment will be described in more detail with reference to Examples. However, the present embodiment is not limited to these Examples.

[0062] (Identification of Crystal Structure) XRD measurement of the sample was performed using a general X-ray diffractometer (device name: UltimaIV Protectus, manufactured by Rigaku Corporation). The measurement conditions are as follows.

[0063] Accelerating current and voltage: 40 mA·40 kV X-ray source: CuKα ray (λ = 1.5405 Å) Measurement mode: continuous scan (2θ / θ scan) Scan condition: 40° / min Measurement range: 2θ = 3° to 43° Divergence vertical limit slit: 10 mm Divergence / incidence slit: 1° Receiving slit: open Receiving solar slit: 5° Detector: D / teX Ultra Using Ni filter The obtained XRD pattern was compared with the reference pattern to identify the crystal structure of the sample.

[0064] (Composition Analysis) Samples according to Examples and Comparative Examples were dissolved in a mixed aqueous solution of hydrofluoric acid and nitric acid to prepare sample solutions. Using a general ICP device (device name: OPTIMA5300DV, manufactured by PerkinElmer), the sample solutions were measured by inductively coupled plasma atomic emission spectrometry (ICP-AES). From the measured concentration values of Si, Al, and the metal elements impregnated in the zeolite according to each sample, the SiO2 / Al2O3 molar ratio of the sample and the molar ratio of each metal element to aluminum were determined.

[0065] Example 1 Using barium chloride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. (Wako Special Grade)), an aqueous solution of 5 mass% barium chloride was prepared. An amount of the aqueous barium chloride solution corresponding to 5 molar equivalents of barium with respect to the amount of Al (mol) in the MFI-type zeolite (product name: HSZ-820NHA, manufactured by Tosoh Corporation, SiO2 / Al2O3 = 23) was used to impregnate the MFI-type zeolite with barium.

[0066] After mixing the MFI-type zeolite with water, solid-liquid separation was performed by filtration to prepare a cake of the MFI-type zeolite. After passing the above aqueous barium chloride solution through the cake, washing was carried out with water (60 °C) at 10 times the mass of the cake. After washing, drying was performed at 110 °C in air to impregnate with barium, and an MFI-type zeolite containing barium (barium-supported MFI-type zeolite) was obtained, which was used as the hydrocarbon adsorbent of this example. ICP analysis was performed on the obtained hydrocarbon adsorbent to determine the Ba / Al molar ratio.

[0067] Example 2 An MFI-type zeolite containing barium was obtained in the same manner as in Example 1, except that the amount of the aqueous barium chloride solution was adjusted to an amount corresponding to 0.7 molar equivalent of barium with respect to the amount of Al in the MFI-type zeolite, and this was used as the hydrocarbon adsorbent of this example.

[0068] Example 3 An MFI-type zeolite containing barium was obtained in the same manner as in Example 1, except that the amount of the aqueous barium chloride solution was adjusted to an amount corresponding to 0.4 molar equivalent of barium with respect to the amount of Al in the MFI-type zeolite, and this was used as the hydrocarbon adsorbent of this example.

[0069] Example 4 An MFI-type zeolite containing barium was obtained in the same manner as in Example 1, except that the amount of the aqueous barium chloride solution was adjusted to an amount corresponding to 0.25 molar equivalent of barium with respect to the amount of Al in the MFI-type zeolite, and this was used as the hydrocarbon adsorbent of this example.

[0070] Example 5 Instead of using the MFI-type zeolite, a barium-containing *BEA-type zeolite was obtained in the same manner as in Example 1 except that the *BEA-type zeolite produced by the following method was used, and this was used as the hydrocarbon adsorbent of this example.

[0071] To an aqueous solution of 48% by mass sodium hydroxide, aluminum hydroxide (manufactured by Sigma-Aldrich) and colloidal silica (product name: Ludox AS-40, manufactured by Sigma-Aldrich) were added so as to have the following molar ratios.

[0072] SiO2 / Al2O3 = 40 Na / SiO2 = 0.65 H2O / SiO2 = 25 Next, the mixture was stirred for 4 hours to obtain a raw material composition having the above composition. Zeolite β (product name: HSZ-930NHA, manufactured by Tosoh Corporation) was added as a seed crystal to the raw material composition, and it was added so as to be 10.0% by mass with respect to the total mass of the silicon (Si) contained in the raw material composition (raw material composition excluding the seed crystal) converted to SiO2 and the mass of aluminum (Al) converted to Al2O3, and mixed.

[0073] The obtained raw material composition was filled into an autoclave and reacted at 140 ° C. for 52 hours with stirring to obtain a crystallized product. The crystallized product was subjected to solid-liquid separation, washed with pure water, and then dried at 110 ° C. in the air and recovered. Thereby, *BEA-type zeolite was obtained. The SiO2 / Al2O3 of the obtained *BEA-type zeolite was 10.

[0074] Example 6 Instead of using the MFI-type zeolite, a barium-containing *BEA-type zeolite was obtained in the same manner as in Example 1 except that the *BEA-type zeolite produced by the following method was used, and this was used as the hydrocarbon adsorbent of this example.

[0075] A 35% by mass TEAOH aqueous solution, a 48% by mass potassium hydroxide aqueous solution, pure water, and amorphous aluminosilicate (SiO2 / Al2O3 = 18.2) were mixed so as to have the following composition.

[0076] SiO2 / Al2O3 = 18.2 TEAOH / SiO2 = 0.12 K / SiO2 = 0.12 H2O / SiO2 = 12.0 Next, the mixture was stirred for 4 hours to obtain a raw material composition having the above composition. Zeolite β (product name: HSZ-930NHA, manufactured by Tosoh Corporation) was added as seed crystals to the raw material composition in an amount of 1.5% by mass based on the total mass of silicon (Si) converted to SiO2 and aluminum (Al) converted to Al2O3 in the raw material composition (raw material composition excluding seed crystals), and they were mixed.

[0077] The obtained raw material composition was filled into an autoclave and reacted at 150 °C for 48 hours with stirring to obtain a crystallized product. The obtained crystallized product was subjected to solid-liquid separation, washed with pure water, and then dried in the air at 110 °C for 24 hours for recovery.

[0078] The obtained crystallized product was mixed with a fired product fired in the air at 600 °C for 2 hours and an aqueous mixed solution prepared by mixing a 20% ammonium chloride aqueous solution in a large excess (liquid amount corresponding to 30 molar equivalents of NH4 amount) with respect to the Al amount of the fired product, and the mixture was stirred at 80 °C for 24 hours and then filtered. This operation was repeated twice for stirring and mixing treatment, and then dried in the air at 110 °C overnight. As a result, *BEA type zeolite with SiO2 / Al2O3 of 18 and a cation type of NH4 type was obtained. The concentrations of Na and K in the obtained *BEA type zeolite were below the detection limit.

[0079] Example 7 A FAU type zeolite containing barium was obtained in the same manner as in Example 1 except that an FAU type zeolite (product name: HSZ-320NAA, manufactured by Tosoh Corporation, SiO2 / Al2O3 = 6) was used instead of the MFI type zeolite, and this was used as the hydrocarbon adsorbent of this example.

[0080] Comparative Example 1 An MFI-type zeolite with SiO2 / Al2O3 = 39 (product name: HSZ-840NHA, manufactured by Tosoh Corporation, SiO2 / Al2O3 = 39) was used, and an MFI-type zeolite containing barium was obtained in the same manner as in Example 1 except for this. This was used as the hydrocarbon adsorbent of this comparative example.

[0081] Comparative Example 2 Instead of the aqueous barium chloride solution, a 2 mass% aqueous cesium chloride solution prepared using cesium chloride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. (special grade)) was used, and an MFI-type zeolite containing Cs was obtained in the same manner as in Example 1 except that the liquid volume was such that the amount of alkali metal (Cs) was 4 molar equivalents to the Al amount of the MFI-type zeolite. This was used as the hydrocarbon adsorbent of this comparative example. ICP analysis was performed on the obtained hydrocarbon adsorbent, and the Cs / Al molar ratio was determined.

[0082] Comparative Example 3 An MFI-type zeolite containing Cs was obtained in the same manner as in Comparative Example 2 except that an MFI-type zeolite with SiO2 / Al2O3 = 39 (product name: HSZ-840NHA, manufactured by Tosoh Corporation) was used. This was used as the hydrocarbon adsorbent of this comparative example.

[0083] Comparative Example 4 Instead of the aqueous barium chloride solution, a 5 mass% aqueous magnesium chloride solution prepared using magnesium chloride (manufactured by Kishida Chemical Co., Ltd. (special grade)) was used, and an MFI-type zeolite containing Mg was obtained in the same manner as in Example 1. This was used as the hydrocarbon adsorbent of this comparative example. ICP analysis was performed on the obtained hydrocarbon adsorbent, and the Mg / Al molar ratio was determined.

[0084] Comparative Example 5 Instead of the aqueous barium chloride solution, a 5 mass% aqueous calcium chloride solution prepared using calcium chloride (manufactured by Kishida Chemical Co., Ltd. (special grade)) was used, and an MFI-type zeolite containing Ca was obtained in the same manner as in Example 1. This was used as the hydrocarbon adsorbent of this comparative example. ICP analysis was performed on the obtained hydrocarbon adsorbent, and the Ca / Al molar ratio was determined.

[0085] Comparative Example 6 A 2 mass% aqueous strontium chloride solution prepared using strontium chloride (special grade, manufactured by Kishida Chemical Co., Ltd.) instead of the aqueous barium chloride solution was used in an amount such that the amount of alkali metal (Sr) was 4 molar equivalents relative to the Al content of the MFI-type zeolite. An MFI-type zeolite containing Sr was obtained in the same manner as in Example 1, and this was used as the hydrocarbon adsorbent of this comparative example. ICP analysis was performed on the obtained hydrocarbon adsorbent to determine the Sr / Al molar ratio.

[0086] Comparative Example 7 A *BEA-type zeolite containing Cs was obtained in the same manner as in Comparative Example 2, except that the *BEA-type zeolite obtained by the same method as in Example 5 was used, and this was used as the hydrocarbon adsorbent of this comparative example. ICP analysis was performed on the obtained hydrocarbon adsorbent to determine the Cs / Al molar ratio.

[0087] Comparative Example 8 A *BEA-type zeolite containing Cs was obtained in the same manner as in Comparative Example 2, except that the *BEA-type zeolite obtained by the same method as in Example 6 was used, and this was used as the hydrocarbon adsorbent of this comparative example. ICP analysis was performed on the obtained hydrocarbon adsorbent to determine the Cs / Al molar ratio.

[0088] Measurement Example 1 (Preparation and Pretreatment of Measurement Samples) The hydrocarbon desorption start temperature of the hydrocarbon adsorbents obtained in the examples and comparative examples was measured. The hydrocarbon adsorbents according to the examples and comparative examples were each pressure-molded and pulverized to obtain an amorphous molded body with an aggregate diameter of 20 to 30 mesh, and the obtained molded bodies were used as the measurement samples according to the examples and comparative examples, respectively. 1 g of each measurement sample was filled into a normal-pressure fixed-bed flow-type reaction tube and pretreated by treating at 500 °C for 1 hour under a nitrogen flow and then cooling to 50 °C.

[0089] (Hydrocarbon Adsorption) A hydrocarbon-containing gas was passed through each of the hydrocarbon adsorbents subjected to the above pretreatment, and the hydrocarbon adsorbed between 50 °C and 600 °C was measured and taken as the hydrocarbon adsorption amount. The composition of the hydrocarbon-containing gas and the measurement conditions are shown below.

[0090] Hydrocarbon-containing gas: 3000 volume ppm C (methane-equivalent concentration) Water 3 volume % Nitrogen the balance Gas flow rate: 200 mL / min Measurement temperature: 50 °C or higher and 600 °C or lower Heating rate: 10 °C / min (Measurement of the hydrocarbon desorption start 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 (methane-equivalent concentration; hereinafter referred to as the "inlet concentration") of the hydrocarbon-containing gas on the inlet side of the atmospheric pressure fixed bed flow-through reaction tube and the hydrocarbon concentration (methane-equivalent concentration; hereinafter referred to as the "outlet concentration") of the hydrocarbon-containing gas on the outlet side of the atmospheric pressure fixed bed flow-through reaction tube were measured.

[0091] The integrated value of the inlet concentration was taken as the amount of hydrocarbons passing through the hydrocarbon adsorbent, and from this amount of hydrocarbons, the value obtained by subtracting the integrated value of the outlet concentration was determined. The hydrocarbon adsorption amount on each adsorbent was determined as the hydrocarbon desorption amount per unit mass of the hydrocarbon adsorbent (μmol C / g). Then, as the temperature of the measurement sample increased, the temperature at which the hydrocarbon desorption amount first became 0 μmol C / g was taken as the desorption start temperature.

[0092] Figure 1 shows a graph representing the relationship between the temperature and the hydrocarbon desorption amount of the hydrocarbon adsorbents according to the examples and comparative examples. Also, the hydrocarbon desorption start temperature and the hydrocarbon adsorption rate at 300 °C of the hydrocarbon adsorbents according to the examples and comparative examples are shown in the following table.

[0093] [Table 1]

[0094] In Table 1, "Me species" refers to the type of metal element Me contained in the zeolite, and "Me / Al molar ratio" refers to the molar ratio of the metal element Me to aluminum. For example, in Example 1, it represents the molar ratio of barium to aluminum, "Ba / Al molar ratio". "nMe n+ / Al molar ratio" refers to the molar ratio of the positive charge of Me cations to aluminum, where n is the valence of the Me cations. For example, in Example 1, it represents the molar ratio of barium cations to aluminum, "2Ba 2+ / Al". Note that the valence of the cations of Ba, Mg, Ca, and Sr is 2, and the valence of the cation of Cs is 1.

[0095] As shown in the above table, the hydrocarbon adsorbent of the example containing zeolite containing barium and having an Me / Al molar ratio of 0.04 or more and 0.6 or less has a larger hydrocarbon adsorption amount at 300 °C than the hydrocarbon adsorbent of the comparative example, and it can be seen that hydrocarbons are adsorbed up to a high temperature. Furthermore, it can be seen that as the temperature is raised to 600 °C, the hydrocarbon adsorption amount decreases, that is, hydrocarbons are desorbed, and the hydrocarbons adsorbed at a temperature below 300 °C are desorbed in the temperature range of 300 °C or more and 600 °C or less. Also, from the graph shown in Figure 1, the hydrocarbon adsorbents of Comparative Examples 2 and 8 almost desorb the adsorbed hydrocarbons at 300 °C, while the hydrocarbon adsorbents of Examples 1 and 6 retain the adsorbed hydrocarbons at 300 °C and desorb the hydrocarbons in the temperature range of 300 °C or more as the temperature rises.

[0096] That is, the hydrocarbon adsorbent of the present embodiment can desorb more of the adsorbed hydrocarbons at 300 °C or higher where the activity of the three-way catalyst is high. Therefore, it is expected that the hydrocarbon purification system equipped with the hydrocarbon adsorbent of the present embodiment can purify hydrocarbons with high efficiency.

Industrial Applicability

[0097] The hydrocarbon adsorbent of the present embodiment can be used for adsorption of hydrocarbons such as at least one of a hydrocarbon adsorption member containing this and a hydrocarbon adsorption system provided with the member, and a hydrocarbon purification system including the hydrocarbon adsorbent of the present embodiment and a catalyst. Further, it can be used for a hydrocarbon adsorption member and a hydrocarbon adsorption system for purifying hydrocarbons in internal combustion engine exhaust gas, and an exhaust gas purification system for internal combustion engine exhaust gas including the hydrocarbon adsorbent of the present embodiment and a catalyst, and the like.

Claims

1. A hydrocarbon adsorbent comprising a zeolite containing barium and having a ring structure of 10-membered ring or more, wherein the molar ratio of barium to aluminum (Ba / Al ratio) of the zeolite is 0.04 or more and 0.6 or less, and the molar ratio of silica to alumina (SiO₂ / Al₂O₃ ratio) is 5 or more and 38 or less.

2. The hydrocarbon adsorbent according to Claim 1, wherein the molar ratio of barium to aluminum of the zeolite is 0.1 or more and 0.5 or less.

3. The hydrocarbon adsorbent according to Claim 1 or 2, wherein the BET specific surface area of the zeolite is 200 m² / g or more and 800 m² / g or less.

4. The hydrocarbon adsorbent according to any one of Claims 1 to 3, wherein the zeolite has at least one zeolite structure selected from the group consisting of *BEA structure, MFI structure, FAU structure, and MOR structure.

5. A method for adsorbing hydrocarbons using the hydrocarbon adsorbent according to any one of Claims 1 to 4.

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