Hydrocarbon adsorbent, method for producing hydrocarbon adsorbent, and method for adsorbing hydrocarbons

Abstract

To provide a hydrocarbon adsorber having excellent thermostability, and a method for producing hydrocarbons using the hydrocarbon adsorber.SOLUTION: A hydrocarbon adsorber contains FAU zeolite represented by YO2-X2O3, where Y is a tetravalent element and X is a trivalent element, the FAU zeolite containing phosphorus and copper, with the molar ratio of phosphorus to X being 0.001 or more and 0.5 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Exhaust gases emitted from internal combustion engines used in mobile vehicles such as automobiles and ships contain a large amount of hydrocarbons, which are purified by a three-way catalyst located downstream.Since a temperature environment of 200°C or higher is required for a three-way catalyst to function, hydrocarbons are adsorbed onto a hydrocarbon adsorbent in temperature ranges where the three-way catalyst does not function, such as during cold starts, and then released from the adsorbent in the temperature range where the three-way catalyst begins to function, where they are decomposed and purified by the three-way catalyst.

[0003] The temperature of automobile exhaust gas can reach over 900°C depending on engine operating conditions. The composition of exhaust gas also changes depending on operating conditions. The air-fuel ratio (air / fuel mixture) when the oxygen in the mixed gas reacts with the fuel mixture in just the right amount is called the stoichiometric air-fuel ratio. In actual operation, combustion does not always occur at the stoichiometric air-fuel ratio. Depending on the load, either lean burn (with an oxygen concentration above the stoichiometric air-fuel ratio) or rich burn (with an oxygen concentration below the stoichiometric air-fuel ratio) is used. Lean burn refers to combustion with an oxygen concentration higher than the complete combustion of the fuel mixture. The exhaust gas contains between 3% and 15% oxygen by volume, creating an oxidizing atmosphere. Rich burn refers to combustion with an excess of fuel, creating a reducing atmosphere because the exhaust gas contains unburned hydrocarbons. Therefore, hydrocarbon adsorbents must have high heat resistance in both oxidizing and reducing atmospheres.

[0004] Patent Document 1 discloses copper-containing FAU zeolite as a hydrocarbon adsorbent that exhibits high hydrocarbon adsorption properties even after exposure to a high-temperature, high-humidity reducing atmosphere. It describes that the inclusion of copper in FAU zeolite strengthens the interaction between hydrocarbons and the FAU zeolite, making it difficult for adsorbed hydrocarbons to be re-released from the FAU zeolite.

[0005] Patent Document 2 discloses that CHA-type zeolite containing copper as a catalytically active species for the reduction reaction of nitrogen oxides has excellent heat resistance due to the inclusion of phosphorus. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2019-150822 [Patent Document 2] Patent Publication No. 2017-048106 Summary of the Invention [Problem to be solved by the invention]

[0007] There is a demand for further improvement in the heat resistance of FAU-type zeolites used as hydrocarbon adsorbents.

[0008] An object of the present disclosure is to provide at least one of a hydrocarbon adsorbent having excellent heat resistance, a method for producing the hydrocarbon adsorbent, and a method for adsorbing hydrocarbons using the hydrocarbon adsorbent. [Means for solving the problem]

[0009] The present inventors have found that, in a hydrocarbon adsorbent containing FAU zeolite containing phosphorus and copper, by setting the phosphorus content within a certain range, the FAU zeolite has a high crystallinity retention rate after hydrothermal durability and has excellent heat resistance in high-temperature, high-humidity environments.

[0010] 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 an FAU zeolite represented by the formula YO2-X2O3, where Y is a tetravalent element and X is a trivalent element, the FAU zeolite containing phosphorus and copper, and a molar ratio of phosphorus to X of 0.001 or more and 0.5 or less. [2] The hydrocarbon adsorbent according to [1], wherein the copper content is 0.5% by mass or more and 4.0% by mass or less relative to the FAU zeolite. [3] The hydrocarbon adsorbent according to [1] or [2], wherein the molar ratio of YO2 to X2O3 is 2 or more and 200 or less. [4] A method for producing a hydrocarbon adsorbent according to any one of [1] to [3], comprising: a phosphorus-containing step of incorporating phosphorus into the FAU-type zeolite; and a copper-containing step of incorporating copper into the FAU-type zeolite. [5] A method for adsorbing hydrocarbons, using the hydrocarbon adsorbent according to any one of [1] to [3]. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to provide at least one of a hydrocarbon adsorbent having excellent heat resistance, a method for producing the hydrocarbon adsorbent, and adsorption of hydrocarbons using the hydrocarbon adsorbent. [Brief explanation of the drawings]

[0012] [Figure 1] 3 is a graph showing the relationship between temperature and the amount of desorbed hydrocarbons for hydrocarbon adsorbents of Examples and Comparative Examples. [Figure 2] 3 is a graph showing the relationship between temperature and the amount of desorbed hydrocarbons for hydrocarbon adsorbents of Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, the hydrocarbon adsorbent of the present disclosure will be described with reference to an example embodiment.

[0014] The hydrocarbon adsorbent of this embodiment includes an FAU zeolite represented by YO-XO, where Y is a tetravalent element and X is a trivalent element, and is characterized in that the FAU zeolite contains phosphorus and copper, and the molar ratio of phosphorus to X is 0.001 or more and 0.5 or less.

[0015] The hydrocarbon adsorbent of this embodiment has high heat resistance based on its constituent requirements.

[0016] (FAU type zeolite) In this embodiment, "zeolite" refers to a compound having a regular structure in which skeleton atoms (hereinafter also referred to as "T atoms") are connected via oxygen (O), and the T atoms are at least any of metal atoms, metalloid 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), as well as other transition metal elements. Examples of metalloid atoms include at least one selected from the group consisting of boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), and tellurium (Te), and examples of other atoms include phosphorus (P).

[0017] The FAU zeolite contained in the hydrocarbon adsorbent of this embodiment is preferably a crystalline aluminosilicate. Crystalline aluminosilicate has a crystal structure consisting of a repeating network of aluminum (Al) and silicon (Si) via oxygen (O). That is, the FAU zeolite contained in the hydrocarbon adsorbent of this embodiment preferably contains SiO as YO and AlO as XO, where Y is Si and X is Al. The FAU zeolite contained in the hydrocarbon adsorbent of this embodiment may be a metallosilicate such as ferrosilicate or gallosilicate, or a zeolite-related substance such as SAPO (silicoaluminophosphate) or AlPO (aluminophosphate), in addition to an aluminosilicate.

[0018] Hereinafter, the hydrocarbon adsorbent of this embodiment will be described, taking as an example an adsorbent in which the FAU-type zeolite contained in the hydrocarbon adsorbent of this embodiment is a crystalline aluminosilicate.

[0019] The skeletal structure of a zeolite (used interchangeably with the crystalline structure, and hereinafter also referred to as the "zeolite structure") is a skeletal structure specified by the structure code (hereinafter also referred to simply as the "structure code") established by the Structure Commission of the International Zeolite Association, and can be identified by comparing the XRD pattern of the target zeolite with the XRD pattern of each zeolite structure (hereinafter also referred to as the "reference pattern") described in Collection of simulated XRD powder patterns for zeolites, Fifth revised edition (2007).

[0020] In this embodiment, the XRD pattern may be obtained by XRD measurement under the following conditions, for example.

[0021] Acceleration current / voltage: 40mA / 40kV Radiation source: CuKα radiation (λ=1.5405Å) Measurement mode: Continuous scan Scan condition: 40° / min Measurement range: 2θ=3° to 43° Divergence vertical limit slit: 10mm Divergence / entrance slit: 1° Receiving slit: open Detector: D / teX Ultra Ni filter used The molar ratio of YO2 to X2O3 in the FAU zeolite contained in the hydrocarbon adsorbent of this embodiment (hereinafter also referred to as the "YO2 / X2O3 ratio," or when X2O3 is Al2O3 and YO2 is SiO2, also referred to as the "SiO2 / Al2O3 ratio") can be from 1.25 to 200, preferably from 2 to 200, and more preferably from 3.0 to 30.0 in terms of a high hydrocarbon desorption initiation temperature. A particularly preferred SiO2 / Al2O3 ratio is from 3.0 to 25.0, more preferably from 4.0 to 12.0, and even more preferably from 4.5 to 9.5.

[0022] The FAU type zeolite contained in the hydrocarbon adsorbent of this embodiment has a BET specific surface area of 200 m, from the viewpoint that the hydrocarbon desorption starting temperature tends to be high. 2 / g or more 1000m 2 / g or less, and 2 / g or more 900m 2 / g or less is more preferable, and 500m 2 / g or more 870m 2 It is more preferable that the saturation coefficient is 1 / g or less.

[0023] The FAU structure is a zeolite structure consisting of sodalite cages consisting of four-membered oxygen rings and six-membered oxygen rings, and double six-membered oxygen ring (hereinafter also referred to as "D6R") structural units, with pores (12-membered oxygen ring pores) consisting of 12-membered oxygen rings formed by three-dimensional bonding of these structural units. As a result, FAU zeolites exhibit high adsorption properties even for bulky hydrocarbons such as aromatic hydrocarbons, and also tend to have a high hydrocarbon desorption onset temperature.

[0024] In this embodiment, a zeolite having a specific zeolite structure, or even a zeolite consisting solely of a specific zeolite structure, is also referred to as an "FAU-type zeolite," and an FAU-type zeolite is a zeolite having an FAU structure. Examples of FAU-type zeolites include one or more selected from the group consisting of zeolite X, zeolite LSX, zeolite Y, and zeolite USY, and preferably at least one of zeolite Y and zeolite USY. The FAU-type zeolite contained in the hydrocarbon adsorbent of this embodiment may be composed of an intergrowth having two or more of the above zeolite structures.

[0025] The FAU zeolite contained in the hydrocarbon adsorbent of this embodiment has an average crystal size of 0.1 μm or more, preferably 0.3 μm or more. Because the hydrocarbon adsorption characteristics tend to improve not only after exposure to a reducing atmosphere but also to a high-temperature, high-humidity oxidizing atmosphere, the average crystal size of the FAU zeolite is more preferably 0.4 μm or more, and even more preferably 0.5 μm or more.

[0026] From the viewpoint of improving operability such as coatability onto the adsorbent carrier, the average crystal size of FAU zeolite is preferably 2.5 μm or less, more preferably 1.5 μm or less, and even more preferably 1.0 μm or less. In order to exhibit high hydrocarbon adsorption properties even after exposure to both a reducing atmosphere and an oxidizing atmosphere, that is, a high-temperature, high-humidity atmosphere, the average crystal size of FAU zeolite is preferably 0.4 μm or more and 2.0 μm or less, and particularly preferably 0.6 μm or more and 0.9 μm or less.

[0027] In this embodiment, the average crystal size of FAU zeolite is the average particle size of primary particles. Here, primary particles are polycrystalline particles formed by the aggregation of single crystals, and are the smallest independent particle unit observed with a scanning electron microscope (hereinafter also referred to as "SEM"). The primary particles of FAU zeolite of the present disclosure have at least one of a substantially cubic shape and a substantially cubic twin crystal shape. The particle size of the primary particles can be confirmed by observing the side lengths of these primary particles, and the average crystal size is the average value of the particle sizes of multiple primary particles. One method for measuring the average crystal size is to extract 80 to 150 primary particles observed at a magnification of 3,000 to 20,000 times, measure the particle sizes of the primary particles, and use the average value as the average crystal size. When extracting primary particles for particle size measurement, it is sufficient to use one or more SEM observation images.

[0028] (phosphorus and copper-containing zeolite) The FAU zeolite contained in the hydrocarbon adsorbent of this embodiment contains phosphorus and copper. FAU zeolite containing phosphorus and copper (hereinafter also referred to as "phosphorus- and copper-containing zeolite") has improved heat resistance compared to FAU zeolite that does not contain phosphorus or copper. In other words, the FAU zeolite contained in the hydrocarbon adsorbent of this embodiment contains phosphorus, so that the zeolite structure tends to remain unchanged even after exposure to a high-temperature, high-humidity environment. The change in the zeolite structure can be evaluated, for example, by measuring and comparing the XRD patterns of the FAU zeolite before and after exposure to a high-temperature, high-humidity environment and calculating the crystallinity retention rate. The crystallinity retention rate is calculated using the following formula.

[0029] Crystallinity maintenance rate (%)=I1 / I0×100 I1: Integrated intensity in the range of diffraction angle 2θ between 15° and 24° in the XRD pattern of zeolite after hydrothermal durability treatment I0: Integrated intensity in the range of diffraction angle 2θ between 15° and 24° in the XRD pattern of zeolite before hydrothermal durability treatment The crystallinity retention rate is preferably 79% or more, and more preferably 80% or more. Typically, the crystallinity of zeolite decreases as a result of hydrothermal durability treatment, resulting in a crystallinity retention rate of 100% or less, but this is not limited thereto. For example, the crystallinity retention rate may exceed 100% as a result of zeolite crystal growth caused by hydrothermal durability treatment, and such cases are also included in the embodiments of the present disclosure.

[0030] Here, the integrated intensity is the peak area detected by identifying the 2θ of the peak top in an XRD pattern analysis using general analysis software (e.g., SmartLab Studio II, manufactured by Rigaku Corporation). The following conditions are listed as XRD pattern analysis conditions.

[0031] Fitting conditions: Automatic, refine background Dispersive pseudo-Voigt function (peak shape) Background removal method: fitting method Kα2 removal method: Kα1 / Kα2 ratio=0.497 Smoothing method: B-Spline curve Smoothing conditions: second-order differential method, σ cut value = 3, χ threshold = 1.5 In this embodiment, the phosphorus contained in the FAU zeolite can be, for example, in at least one state selected from the group consisting of phosphorus, phosphoric acid, other phosphorus compounds, and ions thereof, and the mass of phosphorus contained in the FAU zeolite of this embodiment can be calculated as phosphoric acid (H3PO4).

[0032] In the present embodiment, the molar ratio of phosphorus to X (i.e., Al) in the FAU zeolite (hereinafter also referred to as the "P / X molar ratio," or when X is Al, also referred to as the "P / Al molar ratio") can be 0.001 or more and 0.5 or less, preferably 0.005 or more and 0.4 or less, and more preferably 0.06 or more and 0.38 or less. This improves the crystallinity retention rate of the FAU zeolite after hydrothermal durability treatment. If the P / X molar ratio is a value outside this range, the crystallinity of the FAU zeolite after hydrothermal durability treatment is likely to decrease significantly.

[0033] The phosphorus- and copper-containing FAU zeolite of this embodiment has excellent hydrocarbon retention. Most hydrocarbons adsorbed in a hydrocarbon adsorbent containing copper-free zeolite are easily released as the temperature of the hydrocarbon adsorbent increases. It is believed that the inclusion of copper in the zeolite strengthens the interaction between the hydrocarbons and the zeolite, making it difficult for hydrocarbons adsorbed in a hydrocarbon adsorbent containing such zeolite to be released from the hydrocarbon adsorbent. In particular, in FAU zeolite, aluminum and copper constituting D6R interact particularly strongly. This is believed to result in copper being dispersed and retained in the hydrocarbon adsorbent, primarily in the zeolite structure, thereby improving the hydrocarbon adsorption properties of FAU zeolite.

[0034] In this embodiment, the state of copper contained in the phosphorus- and copper-containing FAU zeolite may be any state other than that of a T atom, and may be divalent copper (Cu 2+), and more preferably, divalent copper with high dispersibility (hereinafter also referred to as "dispersed copper"). 2+ At least one of Cu ions and CuO clusters can be mentioned, and Cu 2+ Preferably, it is an ion.

[0035] The copper content of the hydrocarbon adsorbent is preferably 0.5% by mass or more and 4.0% by mass or less, more preferably 1.0% by mass or more and 3.0% by mass or less, and even more preferably 1.5% by mass or more and 2.8% by mass or less.

[0036] In this embodiment, the copper content of the phosphorus- and copper-containing FAU zeolite is the mass ratio of copper to the mass of the metals and metalloids contained in the zeolite, calculated as oxides. For example, the copper content of a zeolite (aluminosilicate) containing phosphorus (P), copper (Cu), and an alkali metal (M) can be calculated using the following formula:

[0037] Copper content (mass%) = W' Cu / (W Al +W Si +W M +W Cu ) x 100 In the above equation, W' Cu is the copper (Cu) content in the hydrocarbon adsorbent. Al , W Si , W M and W Cu are the mass of aluminum (Al) in the hydrocarbon adsorbent converted into its oxide (Al2O3), the mass of silicon (Si) converted into its oxide (SiO2), the mass of alkali metal (M) converted into its oxide (MO), and the mass of copper converted into its oxide (CuO), respectively.

[0038] In this embodiment, the phosphorus- and copper-containing FAU zeolite may contain an alkali metal. In this embodiment, the alkali metal contained in the phosphorus- and copper-containing FAU zeolite may be at least one of potassium (K) and sodium (Na), and particularly sodium.

[0039] The hydrocarbon adsorbent of this embodiment may contain components other than those described above. The components other than those described above are not particularly limited, but examples thereof include a binder.

[0040] (Method of manufacturing phosphorus- and copper-containing FAU-type zeolite) Next, a method for producing the phosphorus- and copper-containing FAU zeolite contained in the hydrocarbon adsorbent of this embodiment will be described. The phosphorus- and copper-containing FAU zeolite contained in the hydrocarbon adsorbent of this embodiment can be obtained by a method for producing a hydrocarbon adsorbent that includes a phosphorus-containing step of causing FAU zeolite to contain phosphorus, and a copper-containing step of causing the FAU zeolite after the phosphorus-containing step to contain copper.

[0041] (Method of manufacturing FAU type zeolite) The FAU zeolite used in this embodiment may be a known FAU zeolite, and the method for producing the FAU zeolite used in this embodiment is not particularly limited. Examples of methods for producing FAU zeolite include FAU zeolite obtained by a production method including 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 a "raw material composition") to obtain a crystallized product.

[0042] The silica source may be at least one of a silicon-containing salt and compound, and examples thereof include at least one selected from the group consisting of colloidal silica, amorphous silica, sodium silicate, tetraethyl orthosilicate, and aluminosilicate gel. Of these, at least one of colloidal silica and amorphous silica is preferred.

[0043] The alumina source may be at least one of an aluminum-containing salt and compound, 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. Of these, at least one of aluminum hydroxide and aluminum sulfate is preferred.

[0044] The alkalinity source may be at least one selected from the group consisting of various salts such as hydroxides, halides and carbonates of lithium, sodium, potassium, rubidium, cesium, francium, magnesium, calcium, strontium and ammonium, with sodium, potassium or ammonium hydroxide being preferred.

[0045] The cation type of the aluminosilicate used as the raw material is not particularly limited. A preferred cation type is sodium type (Na + type), proton type (H + type) and ammonium type (NH4 + It is preferable that the aryl group is at least one selected from the group consisting of aryl and aryl types, and more preferably, the aryl group is a proton type.

[0046] In the method for producing the FAU zeolite contained in the hydrocarbon adsorbent of this embodiment, the raw material composition preferably further contains seed crystals. The use of seed crystals shortens the crystallization time.

[0047] The seed crystals are preferably zeolite having at least one structure selected from the group consisting of an LTL structure, an LTA structure, an MOR structure, an MFI structure, an *BEA structure, and an FAU structure.

[0048] The SiO2 / Al2O3 molar ratio of the seed crystals is preferably 2 or more and 100 or less, and more preferably 3 or more and 60 or less.

[0049] The content of the seed crystals is preferably small, but in consideration of the reaction rate, the effect of suppressing impurities, and the like, the content of the seed crystals is preferably 0.1 mass % or more and 60 mass % or less, and more preferably 0.5 mass % or more and 40 mass % or less, of the silica component contained in the raw material composition.

[0050] The following compositions can be exemplified as preferred compositions of the raw material composition.

[0051] SiO2 / Al2O3 molar ratio = 2 to 40 M / SiO2 molar ratio = 0 to 0.50 H2O / SiO2 molar ratio = 3 to 100 (crystallization process) In the crystallization step, the raw material composition is crystallized by hydrothermal treatment. The conditions for the hydrothermal durability treatment are not particularly limited, but the following conditions can be mentioned, for example.

[0052] Temperature: 80℃ or higher and 200℃ or lower Duration: 1 hour or more, 10 days or less Pressure: Autogenous pressure The raw material composition is crystallized by the hydrothermal durability treatment, and FAU zeolite is obtained. The obtained FAU zeolite may be subjected to recovery, washing, drying, and calcination steps by any method, and may further be subjected to dealumination treatment to adjust the SiO / AlO ratio to any value.

[0053] (Phosphorus-containing process) The phosphorus-containing step includes a phosphorus source contacting step of contacting the FAU zeolite with a phosphorus source, and a calcining step of calcining the FAU zeolite after the phosphorus source contacting step.

[0054] The phosphorus source may be at least one selected from the group consisting of a compound containing a phosphonium cation, and furthermore, sulfates, nitrates, halides, and hydroxides of the phosphonium cation. The phosphonium cation is preferably at least one selected from the group consisting of tetraethylphosphonium cation (hereinafter also referred to as "TEP") and tetramethylphosphonium cation, and more preferably TEP. Particularly preferred phosphorus sources include at least one selected from the group consisting of tetraethylphosphonium hydroxide (hereinafter also referred to as "TEPOH"), tetraethylphosphonium bromide (hereinafter also referred to as "TEPBr"), tetraethylphosphonium chloride (hereinafter also referred to as "TEPCl"), and tetraethylphosphonium iodide (hereinafter also referred to as "TEPI").

[0055] As a method for contacting the FAU zeolite with the phosphorus source, a known method can be applied, and examples thereof include at least one method selected from the group consisting of an ion exchange method, an impregnation method, an evaporation-to-dryness method, a precipitation method, and a physical mixing method. At least one of the ion exchange method and the impregnation method is preferred, and the impregnation method is more preferred.

[0056] The firing conditions in the firing step after the phosphorus source contact step are not particularly limited, but examples thereof include the following conditions.

[0057] Firing atmosphere: Nitrogen atmosphere or oxidizing atmosphere Firing temperature: 400℃ to 700℃ Baking time: 30 minutes to 15 hours The phosphorus-containing step produces a phosphorus-containing FAU-type zeolite.

[0058] (Copper-containing process) The copper-containing step includes a copper source contacting step of contacting the FAU zeolite (phosphorus-containing FAU zeolite) after the phosphorus-containing step with a copper source, and a calcining step of calcining the FAU zeolite after the copper source contacting step.

[0059] In the copper source contacting step, the copper source is a compound containing copper (Cu), and is preferably a copper salt, more preferably at least one selected from the group consisting of copper-containing nitrates, sulfates, acetates, chlorides, complex salts, oxides, and composite oxides, and even more preferably at least one selected from the group consisting of copper nitrate, copper sulfate, and copper acetate.

[0060] As a method for contacting the FAU zeolite with the copper source, a known method can be applied, and examples thereof include at least one method selected from the group consisting of an ion exchange method, an impregnation method, an evaporation-to-dryness method, a precipitation method, and a physical mixing method. At least one of the ion exchange method and the impregnation method is preferred, and the impregnation method is more preferred.

[0061] After contacting the FAU zeolite with the copper source, the FAU zeolite may be washed and dried by any method. An example of a washing method is washing with a sufficient amount of water, and an example of a drying method is treating the zeolite in air at 100°C to 150°C for 5 to 30 hours.

[0062] The firing conditions in the firing step after the copper source contact step can be, for example, the following conditions.

[0063] Firing atmosphere: Oxidizing atmosphere, preferably air atmosphere Firing temperature: 400℃ to 700℃ Baking time: 30 minutes to 5 hours The calcination step is preferably carried out under air flow, and the air flowing preferably has a low moisture content. Calcination in air with a low moisture content strengthens the interaction between copper and the aluminum that constitutes the framework of the zeolite structure, tending to improve heat resistance. The moisture content of the air flowing is preferably 0.7% by volume or less, more preferably 0.5% by volume or less, and even more preferably 0.3% by volume or less. There is no particular lower limit for the moisture content, as long as it is 0% by volume or more.

[0064] The copper-containing step yields an FAU-type zeolite containing phosphorus and copper.

[0065] (Hydrocarbon adsorbent and its manufacturing method) The hydrocarbon adsorbent of this embodiment may be the phosphorus- and copper-containing FAU zeolite obtained by the above-described method. The hydrocarbon adsorbent of this embodiment may have any shape depending on the application, and examples thereof include at least one of a powder and a molded body. Specific examples of the molded body shape include at least one selected from the group consisting of a spherical, approximately spherical, ellipsoidal, disk-like, cylindrical, polyhedral, irregular, and petal-like shape.

[0066] When the hydrocarbon adsorbent is used as a powder, the hydrocarbon adsorbent can be mixed with a solvent such as water or alcohol to form a slurry, and the slurry can be coated on a substrate to form an adsorption member.

[0067] When the hydrocarbon adsorbent of this embodiment is formed into a molded body, the hydrocarbon adsorbent may be mixed with a binder as needed and molded by any method. The binder may preferably be at least one selected from the group consisting of silica, alumina, kaolin, attapulgite, montmorillonite, bentonite, aloene, and sepiolite. The molding method may preferably be at least one selected from the group consisting of rolling granulation molding, press molding, extrusion molding, injection molding, slip casting, and sheet molding.

[0068] The hydrocarbon adsorbent of the present embodiment can be used in a method for adsorbing hydrocarbons, and is preferably used in a method for adsorbing hydrocarbons in an environment in which the hydrocarbon adsorbent is exposed to high temperatures, more preferably used in a method for adsorbing hydrocarbons from the exhaust gas of an internal combustion engine, and even more preferably used in a method for adsorbing hydrocarbons from the exhaust gas of an internal combustion engine of a mobile body.

[0069] The hydrocarbon adsorbent of this embodiment can adsorb hydrocarbons by a method including a step of contacting a hydrocarbon-containing fluid with the hydrocarbon adsorbent of this embodiment (hereinafter also referred to as a "contact step"). Examples of the hydrocarbon-containing fluid include a hydrocarbon-containing gas and a hydrocarbon-containing liquid.

[0070] The hydrocarbon-containing gas is a gas containing a hydrocarbon. The hydrocarbon may be at least one of an aliphatic hydrocarbon and an aromatic hydrocarbon, preferably a hydrocarbon having 6 to 15 carbon atoms, more preferably an aromatic hydrocarbon, and even more preferably at least one selected from the group consisting of benzene, toluene, and xylene.

[0071] The hydrocarbon concentration of the hydrocarbon-containing gas may be 0.001% by volume or more and 5% by volume or less, and preferably 0.005% by volume or more and 3% by volume or less, in terms of methane. 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.

[0072] In the contact step, the conditions for contacting the hydrocarbon adsorbent with the hydrocarbon-containing gas are arbitrary. Examples of the contact conditions include the following conditions.

[0073] Space velocity: 100hr -1 Over 500,000hr -1 below Contact adsorption: -30℃ or higher and 200℃ or lower Contact temperature: above room temperature and below 200℃ [Example]

[0074] The hydrocarbon adsorbent of this embodiment will be specifically described below based on examples and comparative examples, although the hydrocarbon adsorbent of this embodiment is not limited to these examples.

[0075] Example 1 The TEPBr aqueous solution obtained by dissolving 0.25 g of TEPBr in 1.00 g of water was added to 4.40 g of FAU zeolite (HSZ-341NHA, cation type: proton type, SiO2 / Al2O3 molar ratio = 7, manufactured by Tosoh Corporation) and mixed in a mortar to impregnate and support TEPBr into the FAU zeolite. After drying overnight at 110°C, the mixture was heated from room temperature to 600°C in 2 hours under a nitrogen atmosphere and then calcined at 600°C for 12 hours to produce phosphorus-containing FAU zeolite.

[0076] Furthermore, an aqueous copper nitrate solution obtained by dissolving 0.22 g of copper nitrate hexahydrate in 1.00 g of water was added to 3.78 g of the phosphorus-containing FAU zeolite (phosphorus-supported FAU zeolite) and mixed in a mortar to impregnate and support copper nitrate in the zeolite. After drying overnight at 110°C, the mixture was heated from room temperature to 550°C in an air atmosphere over two hours and then held at 550°C for two hours for calcination, thereby producing a hydrocarbon adsorbent of this embodiment containing phosphorus- and copper-containing FAU zeolite.

[0077] Example 2 A hydrocarbon adsorbent containing FAU zeolite containing phosphorus and copper was prepared in the same manner as in Example 1, except that a phosphorus-containing FAU zeolite was prepared using an aqueous TEPBr solution obtained by dissolving 0.49 g of TEPBr in 1.00 g of water, and a copper nitrate aqueous solution obtained by dissolving 3.73 g of the phosphorus-containing FAU zeolite and 0.21 g of copper nitrate in 1.00 g of water was used.

[0078] Example 3 A hydrocarbon adsorbent containing FAU zeolite containing phosphorus and copper was prepared in the same manner as in Example 1, except that the phosphorus-containing FAU zeolite was prepared using an aqueous TEPBr solution obtained by dissolving 0.25 g of TEPBr in 1.00 g of water, that an aqueous copper nitrate solution obtained by dissolving 4.39 g of the phosphorus-containing FAU zeolite and 0.25 g of copper nitrate in 1.00 g of water was used, and that the TEPBr aqueous solution and the FAU zeolite were mixed and then calcined in an air atmosphere to prepare the phosphorus-containing FAU zeolite.

[0079] Example 4 A hydrocarbon adsorbent containing FAU zeolite containing phosphorus and copper was prepared in the same manner as in Example 3, except that a phosphorus-containing FAU zeolite was prepared using an aqueous TEPBr solution obtained by dissolving 0.49 g of TEPBr in 1.00 g of water, and a copper nitrate aqueous solution obtained by dissolving 3.73 g of the phosphorus-containing FAU zeolite and 0.21 g of copper nitrate in 1.00 g of water was used.

[0080] Example 5 A hydrocarbon adsorbent containing FAU zeolite containing phosphorus and copper was prepared in the same manner as in Example 3, except that a phosphorus-containing FAU zeolite was prepared using an aqueous TEPBr solution obtained by dissolving 1.48 g of TEPBr in 1.00 g of water, and a copper nitrate aqueous solution obtained by dissolving 3.62 g of the phosphorus-containing FAU zeolite and 0.21 g of copper nitrate in 1.00 g of water was used.

[0081] Example 6 A hydrocarbon adsorbent containing FAU zeolite containing phosphorus and copper was prepared in the same manner as in Example 3, except that a phosphorus-containing FAU zeolite was prepared using an aqueous TEPBr solution obtained by dissolving 0.24 g of TEPBr in 1.00 g of water, and a copper nitrate aqueous solution obtained by dissolving 4.39 g of the phosphorus-containing FAU zeolite and 0.25 g of copper nitrate in 1.00 g of water was used.

[0082] Comparative Example 1 An aqueous solution of copper nitrate obtained by dissolving 0.29 g of copper nitrate in 1.94 g of water was added to 5.00 g of FAU zeolite (cation type: proton type, SiO2 / Al2O3 molar ratio: 7) and mixed in a mortar. After drying overnight at 110°C, the mixture was heated from room temperature to 550°C in an air atmosphere over a period of 2 hours and then held at 550°C for 2 hours to produce copper-loaded FAU zeolite (copper-supported FAU zeolite).

[0083] Comparative Example 2 A hydrocarbon adsorbent containing FAU zeolite containing phosphorus and copper was prepared in the same manner as in Example 1, except that the phosphorus-containing FAU zeolite was prepared using an aqueous TEPBr solution obtained by dissolving 3.96 g of TEPBr in 2.00 g of water, that an aqueous copper nitrate solution obtained by dissolving 1.55 g of the phosphorus-containing FAU zeolite and 0.09 g of copper nitrate in 0.50 g of water was used, and that the TEPBr aqueous solution and the FAU zeolite were mixed and then calcined in an air atmosphere to prepare the phosphorus-containing FAU zeolite.

[0084] (composition analysis) A sample solution was prepared by dissolving the hydrocarbon adsorbents obtained in the Examples and Comparative Examples in a mixed aqueous solution of hydrofluoric acid and nitric acid. The sample solution was measured by inductively coupled plasma atomic emission spectrometry (ICP-AES) using a common ICP device (device name: OPTIMA5300DV, manufactured by PerkinElmer). The copper content and P / Al molar ratio of the hydrocarbon adsorbents obtained in the Examples and Comparative Examples were calculated from the measured values of Si, Al, Na, K, Cu, and P. The results are shown in Table 1.

[0085] (Identification of crystal structure) The hydrocarbon adsorbents obtained in the examples and comparative examples were subjected to XRD measurement using a general X-ray diffractometer (device name: Ultima IV Protectus, manufactured by Rigaku Corporation). The measurement conditions were as follows:

[0086] Acceleration current / voltage: 40mA / 40kV Radiation source: CuKα radiation (λ=1.5405Å) Measurement mode: Continuous scan Scan condition: 40° / min Measurement range: 2θ=3° to 43° Divergence vertical limit slit: 10mm Divergence / entrance slit: 1° Receiving slit: open Detector: D / teX Ultra Ni filter used The obtained XRD pattern was compared with a reference pattern to identify the crystal structure of the sample.

[0087] (BET specific surface area measurement) The measurement sample was treated at 350°C for 2 hours. Then, a nitrogen adsorption isotherm was measured at a measurement temperature of 77K using a conventional nitrogen adsorption apparatus (apparatus name: BELSORP-mini, manufactured by MicrotracBEL). The BET specific surface area was calculated using the BET method for the obtained nitrogen adsorption isotherm in the relative pressure range of 0.01 to 0.15.

[0088] (Preparation and pretreatment of hydrocarbon adsorbent measurement samples) The hydrocarbon adsorbents obtained in the examples and comparative examples were each pressure-molded and pulverized to form amorphous compacts with an aggregate size of 20 mesh to 30 mesh, and the resulting compacts were used as measurement samples. 1 g of each measurement sample was packed into an atmospheric pressure fixed-bed flow reactor and treated at 500°C for 1 hour under a nitrogen flow, followed by cooling to 50°C as a pretreatment.

[0089] (Hydrothermal durability treatment) The pretreated hydrocarbon adsorbent was treated by passing a treatment gas through it under the following conditions, thereby carrying out hydrothermal durability treatment.

[0090] Treated gas: 10% water by volume Nitrogen Remainder Gas flow rate: 300mL / min Space velocity: 6000hr -1 Processing temperature: 900℃ Processing time: 1 hour (Calculation of crystallinity maintenance rate) To evaluate the durability of the hydrocarbon adsorbent in a high-temperature, high-humidity environment, the crystal structure of the zeolite in the hydrocarbon adsorbent before and after hydrothermal durability treatment was identified by XRD measurement, and the crystallinity retention rate of the zeolite was calculated using the following formula. The calculation results are shown in Table 1.

[0091] Crystallinity maintenance rate (%)=I1 / I0×100 I1: Integrated intensity in the range of diffraction angle 2θ between 15° and 24° in the XRD pattern of zeolite after hydrothermal durability treatment I0: Integrated intensity in the range of diffraction angle 2θ between 15° and 24° in the XRD pattern of zeolite before hydrothermal durability treatment Here, the integrated intensity is the peak area detected by identifying the 2θ of the peak top in the analysis of the XRD pattern using analysis software (product name: SmartLab Studio II, manufactured by Rigaku Corporation). The analysis conditions for the XRD pattern are shown below.

[0092] Fitting conditions: Automatic, refine background Dispersive pseudo-Voigt function (peak shape) Background removal method: fitting method Kα2 removal method: Kα1 / Kα2 ratio=0.497 Smoothing method: B-Spline curve Smoothing conditions: second-order differential method, σ cut value = 3, χ threshold = 1.5

[0093] [Table 1]

[0094] As shown in Table 1, Comparative Example 2, in which the P / Al molar ratio was 0.65 or more, became amorphous after the hydrothermal durability treatment, and no diffraction peaks derived from FAU zeolite were detected, resulting in a significant decrease in the crystallinity retention rate. Furthermore, when the P / Al molar ratio was 0.65 or more, the crystallinity retention rate was lower than that of FAU zeolite containing only copper.

[0095] The crystallinity retention rates of the zeolites of Examples 1 to 6 were higher than the crystallinity retention rates of the zeolites of Comparative Examples 1 and 2. These results demonstrate that, in an FAU zeolite containing phosphorus and copper, the crystallinity retention rate of the FAU zeolite after hydrothermal durability treatment is improved when the P / Al molar ratio is within a certain range.

[0096] (Measurement of hydrocarbon adsorption amount) A hydrocarbon-containing gas was passed through each of the hydrocarbon adsorbents that had been subjected to the hydrothermal durability treatment described above to perform a hydrocarbon adsorption treatment, and the amount of adsorbed hydrocarbons was measured. The composition of the hydrocarbon-containing gas and the measurement conditions are shown below.

[0097] Hydrocarbon-containing gas: Toluene 3000 ppmC by volume (methane equivalent concentration) Water 3% by volume Nitrogen Remainder Gas flow rate: 200 mL / min Measurement temperature: 50℃ to 600℃ Heating rate: 10°C / min The adsorption amount was measured using a hydrogen ionization detector (FID) to continuously quantitatively analyze the hydrocarbons in the gas after passing through the hydrocarbon adsorbent. The hydrocarbon concentration (methane equivalent concentration; hereafter referred to as the "inlet concentration") of the hydrocarbon-containing gas at the inlet side of the atmospheric pressure fixed-bed flow reactor and the hydrocarbon concentration (methane equivalent concentration; hereafter referred to as the "outlet concentration") of the hydrocarbon-containing gas at the outlet side of the atmospheric pressure fixed-bed flow reactor were measured. The integrated value of the inlet concentration was used to determine the amount of hydrocarbons passing through the hydrocarbon adsorbent, and the value obtained by subtracting the integrated value of the outlet concentration from this hydrocarbon amount was used to determine the hydrocarbon adsorption amount. The hydrocarbon adsorption amount for each adsorbent was divided by the mass of zeolite excluding the mass of phosphorus components to obtain the hydrocarbon adsorption amount per mass of zeolite excluding the mass of phosphorus components (μmol C / g). The hydrocarbon adsorption amount per mass of zeolite contained in each adsorbent was compared. The mass of the phosphorus component contained in the zeolite was calculated assuming that all of the phosphorus in the added TEPBr was converted to H3PO4.

[0098] 1 and 2 show desorption amount curves showing the relationship between temperature and the amount of hydrocarbons desorbed per unit time (seconds) per mass of zeolite excluding phosphorus contained in each hydrocarbon adsorbent in Examples and Comparative Examples. In FIG. 1, the solid line represents the results of Comparative Example 1, the dotted line represents the results of Example 1, the dashed line represents the results of Example 2, and the dash-dotted line represents the results of Example 3. In FIG. 2, the solid line represents the results of Comparative Example 1, the dotted line represents the results of Example 4, the dashed line represents the results of Example 5, and the dash-dotted line represents the results of Example 6. Here, a negative desorption amount indicates adsorption, and a positive desorption amount indicates desorption. From FIGS. 1 and 2, the behavior of hydrocarbon adsorption and desorption during the temperature rise process during hydrocarbon adsorption treatment can be seen. For example, in all Examples, hydrocarbons are adsorbed immediately after the temperature rise begins above 50°C, and the adsorbed hydrocarbons are desorbed as the temperature rises. (Initial adsorption / desorption amount) For each hydrocarbon adsorbent, the initial adsorption / desorption amount, which is the sum of the absolute values of the adsorption amount and desorption amount of hydrocarbons per mass of zeolite excluding phosphorus, was determined from 50°C to the temperature at which the amount of hydrocarbon desorption becomes maximum (hereinafter also referred to as the "maximum desorption amount temperature"), and the amount of hydrocarbons that can be adsorbed and desorbed after hydrothermal durability treatment was evaluated.

[0099] 1 and 2 (the area surrounded by the desorption amount curve of each example, the line for T=50, and the line for desorption amount=0) and the area representing the hydrocarbon desorption amount of each example (the area surrounded by the desorption amount curve, the line for T=maximum temperature, and the line for desorption amount=0), and then divided by the above-mentioned temperature rise rate. The initial adsorption and desorption amounts for each example and comparative example are shown in Table 2.

[0100] [Table 2]

[0101] It was confirmed that the FAU zeolites containing phosphorus and copper of Examples 1 to 6 exhibited higher initial adsorption and desorption amounts than the FAU zeolite of Comparative Example 1 containing only copper.

Claims

1. YO ２ -X ２ O ３ wherein Y is a tetravalent element and X is Al; and The FAU-type zeolite contains phosphorus and copper, A hydrocarbon adsorbent characterized in that the molar ratio of phosphorus to X is 0.001 or more and 0.5 or less.

2. 2. The hydrocarbon adsorbent according to claim 1, wherein the copper content is 0.5% by mass or more and 4.0% by mass or less relative to the FAU-type zeolite.

3. X ２ O ３ YO ２ The adsorbent for hydrocarbons according to claim 1 or 2, wherein the molar ratio of

4. a phosphorus-containing step of containing phosphorus in the FAU zeolite; 4. The method for producing an adsorbent for hydrocarbons according to claim 1, further comprising a copper-containing step of causing the FAU-type zeolite to contain copper.

5. A method for adsorbing hydrocarbons, which uses the hydrocarbon adsorbent according to any one of claims 1 to 3.

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