JP2019093382A - Hydrocarbon adsorbent and hydrocarbon adsorption method - Google Patents

Abstract

To provide an adsorbent characterized by having a large amount of hydrocarbon adsorption from a gas containing hydrocarbons different in carbon numbers.SOLUTION: A hydrocarbon adsorbent has a specific powder X-ray diffraction pattern and contains zeolite having following characteristics. In the zeolite, a molar ratio of silica to alumina is 5 or more and 200 or less; and the zeolite has a BET specific surface of 300 m/g or more and 700 m/g or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hydrocarbon adsorbent and a method for adsorbing hydrocarbons.

  The exhaust gas emitted from the internal combustion engine used for mobile bodies such as automobiles and ships contains a large amount of hydrocarbons. Hydrocarbons emitted from the internal combustion engine are purified by a three-way catalyst. A temperature environment of 200 ° C. or higher is necessary for the three-way catalyst to function, so in a temperature range where the three-way catalyst does not function, such as during so-called cold start, hydrocarbons are adsorbed to a hydrocarbon adsorbent and the three-way catalyst It releases hydrocarbons from the adsorbent in the temperature range where it starts to function, and this is decomposed and purified with a three-way catalyst. Although a zeolite is generally used as a hydrocarbon adsorbent, the exhaust gas of an internal combustion engine at startup contains a plurality of hydrocarbons having different carbon numbers. Therefore, a hydrocarbon adsorbent is required to adsorb and remove hydrocarbons from a gas containing such multiple types of hydrocarbons. In order to adsorb and remove hydrocarbons from a hydrocarbon-containing gas containing two or more hydrocarbons, hydrocarbon adsorbents containing plural kinds of adsorbents have been studied.

For example, Patent Document 1 proposes a hydrocarbon adsorbent containing zeolite and colloidal silica. Patent Document 2 proposes a hydrocarbon adsorbent containing two β-type zeolites having different molar ratios of silica to alumina (SiO ₂ / Al ₂ O ₃ ratio). Patent Document 3 discloses a hydrocarbon adsorbent obtained by mixing a plurality of zeolites having different pore structures.

JP 2001-300319 Japanese Patent Application Publication No. 2007-275877 JP 07-144128 A

  Different adsorbents, in particular hydrocarbon adsorbents comprising different types of zeolite, adsorb carbon hydrogen suitable for each zeolite structure. Therefore, adsorption of hydrocarbons from a gas containing plural kinds of hydrocarbons can not be efficiently performed, and as a result, the amount of adsorption of hydrocarbons is not sufficient. Furthermore, since the heat resistance is different depending on the type of zeolite, the hydrocarbon adsorbent containing different types of zeolite has a problem that the amount of adsorption of a specific type of hydrocarbon decreases due to use.

  In view of these problems, it is an object of the present invention to provide a hydrocarbon adsorbent having a large amount of hydrocarbon adsorption from a hydrocarbon-containing gas containing a plurality of types of hydrocarbons.

  The present inventors examined the adsorption characteristics of hydrocarbons from the exhaust gas of an internal combustion engine. As a result, adsorption from a gas containing one kind of hydrocarbon and adsorption from a gas containing plural kinds of hydrocarbons differ in behavior, and furthermore, a zeolite having a specific crystal structure is used as a hydrocarbon adsorbent Thus, it has been found that even a hydrocarbon-containing gas containing plural types of hydrocarbons can adsorb a larger amount of hydrocarbons than conventional hydrocarbon adsorbents.

That is, the gist of the present invention is as follows.
[1] A hydrocarbon adsorbent comprising a zeolite having the following powder X-ray diffraction pattern.

[2] The hydrocarbon adsorbent according to the above [1], wherein the molar ratio of silica to alumina of the zeolite is 5 or more and 200 or less.
[3] The hydrocarbon adsorbent according to the above [1] or [2], wherein a BET specific surface area of the zeolite is 300 m ² / g or more and 700 m ² / g or less.
[4] A hydrocarbon adsorption method using the hydrocarbon adsorbent according to any one of the above [1] to [3].
[5] A method for treating a hydrocarbon-containing gas containing a hydrocarbon adsorbent according to any one of the above [1] to [3].

  According to the present invention, it is possible to provide a hydrocarbon adsorbent having a large amount of hydrocarbon adsorption from a hydrocarbon-containing gas containing a plurality of types of hydrocarbons. Furthermore, multiple hydrocarbons can be simultaneously adsorbed without having to use multiple zeolites. In addition to this, since the hydrocarbon adsorbent of the present invention can also be obtained without the step of mixing a plurality of zeolites, the manufacturing cost is reduced compared to hydrocarbon adsorbents using mixed zeolites. Can be expected, industrial benefits are great.

  Hereinafter, the hydrocarbon adsorbent of the present invention will be described.

  The hydrocarbon adsorbent of the present invention comprises a zeolite having at least the following XRD pattern.

  The hydrocarbon adsorbent of the present invention contains a zeolite having such an XRD pattern, and therefore, in addition to being able to adsorb hydrocarbons from a hydrocarbon-containing gas containing one kind of hydrocarbon, the hydrocarbon containing plural kinds of hydrocarbons Hydrocarbons can be adsorbed from the contained gas. In particular, compared with the conventional zeolite-based hydrocarbon adsorbent, the amount of adsorption of hydrocarbons from the hydrocarbon-containing gas containing a plurality of types of hydrocarbons is increased. In the present invention, the XRD pattern may contain each peak in the above-mentioned table, and may contain other peaks.

  Preferably, the zeolite comprises at least the following XRD pattern:

  Preferably, the zeolite contained in the hydrocarbon adsorbent of the present invention is a zeolite having a crystal structure containing an oxygen 12-membered ring and an oxygen 8-membered ring, and is preferably YNU-5.

Preferably, the molar ratio of silica to alumina (hereinafter also referred to as “SiO ₂ / Al ₂ O ₃ ratio”) of the zeolite contained in the hydrocarbon adsorbent of the present invention is 5 or more and 200 or less, and 10 or more and 100 or less Is more preferably 15 or more and 50 or less, and more preferably 15 or more and 30 or less.

Preferably, the zeolite contained in the hydrocarbon adsorbent of the present invention has a BET specific surface area of 300 m ² / g or more and 700 m ² / g or less, and preferably 400 m ² / g or more and 600 m ² / g or less.

Preferably, the cation type of the zeolite contained in the hydrocarbon adsorbent of the present invention is either proton type (H + type) or ammonium type (NH ₄ type).

  The hydrocarbon adsorbent of the present invention may contain at least one of metals or metal ions (hereinafter also referred to as "metal species"). The metal species may include at least one of the group consisting of alkali metals, alkaline earth metals, rare earth metals, transition metals and noble metals.

  The hydrocarbon adsorbent of the present invention may contain a binder, and may contain at least one member selected from the group consisting of silica, alumina, kaolin, attapulgite, montmorillonite, bentonite, aluen and sepiolite.

  The hydrocarbon adsorbent of the present invention may have any shape depending on the application, and preferably includes at least one of powder and molded body. Specific examples of the shape of the molded body include at least one of the group consisting of a sphere, a substantially sphere, an ellipse, a disc, a cylinder, a polyhedron, an irregular shape, and a petal.

  The hydrocarbon adsorbent of the present invention can adsorb hydrocarbons by a method including the step of bringing a hydrocarbon-containing gas into contact with the hydrocarbon adsorbent of the present invention.

  Preferably, the hydrocarbon-containing gas is a gas containing at least one hydrocarbon, and is preferably a gas containing two or more hydrocarbons. The hydrocarbon contained in the hydrocarbon-containing gas may be at least one of the group consisting of paraffin, olefin and aromatic hydrocarbon. The carbon number of the hydrocarbon may be 1 or more, preferably 1 or more and 15 or less. Preferably, the hydrocarbon contained in the hydrocarbon-containing gas is 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. At least two members of the group consisting of methane, ethane, ethylene, propylene, butane, benzene, toluene and xylene, preferably at least two members of the group consisting of methane, ethane, ethylene and propylene. More preferably, it is a species and at least one member of the group consisting of benzene, toluene and xylene. The hydrocarbon-containing gas may contain at least one member selected from the group consisting of carbon monoxide, carbon dioxide, hydrogen, oxygen, nitrogen, nitrogen oxides, sulfur oxides and water. As a specific hydrocarbon-containing gas, combustion gas such as exhaust gas of an internal combustion engine can be mentioned.

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

  Next, the method for producing the hydrocarbon adsorbent of the present invention will be described.

  Preferably, the hydrocarbon adsorbent of the present invention is produced by optionally forming a zeolite having the following XRD pattern.

  The hydrocarbon adsorbent of the present invention may be in any form suitable for the application, and the use thereof is mentioned as at least any form of powder or molded body.

  In the case of powder, the zeolite may be mixed with a solvent such as water or alcohol to form a slurry, and the slurry may be used as an adsorption member coated on a substrate.

  When the hydrocarbon adsorbent of the present invention is formed into a molded body, the above-mentioned zeolite may be mixed with a binder if necessary, and formed by any method. Preferably, the binder is at least one of the group consisting of silica, alumina, kaolin, attapulgite, montmorillonite, bentonite, alloene and sepiolite. The molding method may include at least one of the group consisting of rolling granulation molding, press molding, extrusion molding, injection molding, cast molding and sheet molding.

Preferably, the zeolite contained in the hydrocarbon adsorbent according to the present invention is a silica source, an alumina source, an alkali source, water, and dimethyldipropylammonium cation (hereinafter referred to as a structure directing agent (hereinafter also referred to as "SDA"). , A method including a crystallization step of crystallizing a composition (hereinafter, also referred to as a "raw material composition") containing "Me ₂ Pr ₂ N ⁺ ". Preferably, the feed composition has the following molar composition:

SiO ₂ / Al ₂ O ₃ ratio = 10 or more and 50 or less Me ₂ Pr ₂ NOH ⁺ / SiO ₂ ratio = 0.05 or more and 0.30 or less Na / SiO ₂ ratio = 0.05 or more and 0.30 or less
K / SiO ₂ ratio = 0.05 or more and 0.30 or less H ₂ O / SiO ₂ ratio = 3 or more and 50 or less Preferably, in the crystallization step, the raw material composition is crystallized by hydrothermal treatment. As conditions for the hydrothermal treatment, the following conditions can be mentioned.

Crystallization temperature: 140 ° C. or more and 180 ° C. or less Crystallization time: 1 day to 10 days Crystallization pressure: Autogenous pressure The zeolite obtained in the crystallization step is recovered by any method, washed, dried, calcined and ion-exchanged Each of the steps may be used, and further, the dealumination treatment may be performed to set the SiO ₂ / Al ₂ O ₃ ratio to any value.

  Preferably, the zeolite obtained in the crystallization step is preferably subjected to a calcination step and an ion exchange step.

  The calcination step is a step of removing SDA in the zeolite. Although the firing conditions are optional, the firing conditions may include a firing temperature of 400 ° C. or more and 800 ° C. or less and a firing time of 0.5 hours or more and 12 hours or less in an oxidizing atmosphere.

The ion exchange step is a step of increasing the solid acid in the zeolite. Although ion exchange conditions are arbitrary, as ion exchange conditions, making zeolite and ammonium chloride aqueous solution contact at 25 degreeC or more and 200 degrees C or less is mentioned. Thereby, the cation type of zeolite changes from sodium / potassium type to ammonium type (NH ₄ type). Preferably, the zeolite to be subjected to the ion exchange step is a zeolite after calcination.

Graph showing the amount of adsorbed hydrocarbons in the examples and comparative examples

  Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited to these examples.

(Identification of crystal structure)
The XRD measurement of the sample was performed using a general X-ray diffractometer (apparatus name: Ultima IV, manufactured by Rigaku Corporation). As a radiation source, CuKα radiation (λ = 1.5405 Å) was used, and the measurement range was measured in the range of 3 ° to 43 ° as 2θ.

(Composition analysis)
The sample was dissolved in a mixed aqueous solution of hydrofluoric acid and nitric acid to prepare a sample solution. The sample solution was measured by inductively coupled plasma emission spectroscopy (ICP-AES) using a general ICP apparatus (apparatus name: OPTIMA 5300DV, manufactured by PerkinElmer). The SiO ₂ / Al ₂ O ₃ ratio of the sample was determined from the measured values of Si and Al obtained.
(BET specific surface area)
The measurement sample was treated at 350 ° C. for 2 hours as pretreatment. After pretreatment, a nitrogen adsorption isotherm at a measurement temperature of 77 K was measured using a conventional nitrogen adsorption apparatus (apparatus name: BELSORP-miniII, manufactured by Microtrac BEL). The BET specific surface area was calculated using the BET method for the relative pressure range of 0.01 or more and 0.15 or less of the obtained nitrogen adsorption isotherm.

Example 1
Colloidal silica AS-40, Y-type zeolite (product name: HSZ-350 HUA, manufactured by Tosoh Corporation), Me ₂ Pr ₂ NOH, NaOH, KOH and H ₂ O are mixed to obtain a raw material composition having the following molar composition The

SiO ₂ : 0.025 Al ₂ O ₃ : 0.17 Me ₂ Pr ₂ NOH
: 0.15 NaOH: 0.17 KOH: 7H ₂ O
The obtained raw material composition was charged into an autoclave, and the composition was crystallized under standing at 160 ° C. for 6 days. The obtained zeolite was dried at 110 ° C. overnight after being calcined at 550 ° C. in the atmosphere and treated with a 20% aqueous ammonium chloride solution. As a result, a zeolite having an SiO ₂ / Al ₂ O ₃ content of 18.4 and a BET specific surface area of 417 m ² / g and a cation type of NH ₄ type is obtained, which is used as the hydrocarbon adsorbent of this example. .

  The XRD pattern of the obtained zeolite is shown in the table below.

Example 2
A zeolite was obtained by the same method as in Example 1 except that a raw material composition having the following composition was used, and this was used as the hydrocarbon adsorbent of this example.

SiO ₂ : 0.025 Al ₂ O ₃ : 0.17 Me ₂ Pr ₂ NOH
: 0.10 NaOH: 0.20 KOH: 7 H ₂ O
The obtained zeolite was a zeolite having a SiO ₂ / Al ₂ O ₃ ratio of 21.1 and a BET specific surface area of 412 m ² / g and a cation type of NH ₄ type.

  The XRD pattern of the obtained zeolite is shown in the table below.

Example 3
A zeolite was obtained by the same method as in Example 1 except that a raw material composition having the following composition was used, and this was used as the hydrocarbon adsorbent of this example.

SiO ₂ : 0.025 Al ₂ O ₃ : 0.17 Me ₂ Pr ₂ NOH
: 0.15 NaOH: 0.15 KOH: 7H ₂ O
The obtained zeolite had a SiO ₂ / Al ₂ O ₃ ratio of 21.2, and a BET specific surface area of 415 m ² / g, and was a zeolite of cation type NH ₄ type.

  The XRD pattern of the obtained zeolite is shown in the table below.

Example 4
After 10 g of the zeolite of Example 3 was mixed with 4.58 g of a copper nitrate aqueous solution (containing 0.58 g of copper nitrate trihydrate), it was dried overnight at 110 ° C. in air. The dried zeolite was calcined in air at 550 ° C. for 2 hours to obtain a copper-containing zeolite, which was used as the hydrocarbon adsorbent of this example.

The obtained copper-containing zeolite had a SiO ₂ / Al ₂ O ₃ ratio of 21.2 and a copper content of 1.51% by weight.
Example 5
10 g of the zeolite of Example 3 was added to 78 g of a silver acid aqueous solution (silver nitrate concentration: 5.8% by weight) and ion-exchanged by mixing for 3 hours at 60 ° C. while stirring. The ion-exchanged zeolite was filtered, washed, and dried overnight at 110 ° C. in air to obtain a silver-containing zeolite, which was used as the hydrocarbon adsorbent of this example.

The obtained silver-containing zeolite had an SiO ₂ / Al ₂ O ₃ ratio of 21.2 and a silver content of 7.18% by weight.

Comparative Example 1
An MFI-type zeolite having an SiO ₂ / Al ₂ O ₃ ratio of 38.0 and a BET specific surface area of 437 m ² / g and a cation type of NH ₄ type was used as a hydrocarbon adsorbent of this comparative example.

Comparative example 2
A β-type zeolite having an SiO ₂ / Al ₂ O ₃ ratio of 39.7 and a BET specific surface area of 563 m ² / g and a cation type of H type was used as the hydrocarbon adsorbent of this comparative example.

Measurement example 1
(Preparation of measurement sample and pretreatment)
The hydrocarbon adsorbent was press-formed and pulverized, respectively, to form an irregularly shaped molded article having an aggregation diameter of 20 to 30 mesh. 1 g of the molded product was filled in a normal pressure fixed bed flow type reaction tube, treated at 500 ° C. for 1 hour under nitrogen flow, and cooled to 50 ° C. to obtain pretreatment.
(Hydrocarbon adsorption)
The hydrocarbon-containing gas was allowed to flow through each of the hydrocarbon adsorbents after the pretreatment, and the hydrocarbons adsorbed between 50 ° C. and 200 ° C. were measured to determine the amount of adsorption of hydrocarbons. The composition and measurement conditions of the hydrocarbon-containing gas are shown below.

Hydrocarbon-containing gas: Propylene 1000 ppmc (Methane conversion concentration)
Water 3% by volume
Nitrogen balance gas flow rate: 200 mL / min Measurement temperature: 50 to 200 ° C
Heating rate: 10 ° C / min Measurement time: 15 minutes (measurement of hydrocarbon adsorption amount)
A hydrogen ionization detector (FID) was used to continuously quantitatively analyze hydrocarbons in the gas after passing through the hydrocarbon adsorbent. The hydrocarbon concentration of the hydrocarbon-containing gas at the inlet side of the atmospheric pressure fixed bed flow type reaction tube (methane conversion concentration; hereinafter referred to as "inlet concentration") and carbonization at the outlet side of the atmospheric pressure fixed bed flow type reaction tube The hydrocarbon concentration (methane conversion concentration; hereinafter, referred to as “outlet concentration”) of the hydrogen-containing gas was measured.

  The integral value of the inlet concentration is regarded as the amount of hydrocarbon that has passed through the hydrocarbon adsorbent, and the value obtained by subtracting the integral value of the outlet concentration (concentration in terms of methane) from the amount of hydrocarbon is obtained. It was determined as the amount of adsorbed hydrocarbon (μmolC / g) per weight of the hydrocarbon adsorbent.

Measurement example 2
The amount of adsorption of hydrocarbons was measured in the same manner as in Measurement Example 1 except that a hydrocarbon-containing gas having the following composition was used.

Lower hydrocarbon-containing gas: Toluene 3000 ppm by volume (equivalent to methane)
Water 3% by volume
Nitrogen balance measurement example 3
The amount of adsorption of hydrocarbons was measured in the same manner as in Measurement Example 1 except that a hydrocarbon-containing gas having the following composition was used.

Lower hydrocarbon-containing gas: Toluene 3000 ppm by volume (equivalent to methane)
Propylene 1000 ppmc (Methane equivalent concentration)
Water 3% by volume
Nitrogen Residue The adsorption amount of hydrocarbons of Measurement Examples 1 to 3 is shown in the following table, and the result of Measurement Example 3 is shown in FIG.

  As apparent from the above table, it was confirmed that the hydrocarbon adsorbents of Examples 1 and 2 can adsorb an aliphatic hydrocarbon having 3 carbon atoms and an aromatic hydrocarbon having 7 carbon atoms, respectively. . However, the adsorption amount of hydrocarbons from the hydrocarbon-containing gas containing only propylene is lower than that of Comparative Example 1, and the adsorption amount of carbonization from the hydrocarbon-containing gas containing only toluene is comparable to that of Comparative Example 2. The From this, it was confirmed that the adsorption amount from the gas containing a single kind of hydrocarbon was similar to that of the conventional hydrocarbon adsorbent.

  On the other hand, in the hydrocarbon adsorbent of the example, the adsorption amount of hydrocarbons from the hydrocarbon-containing gas containing both propylene and toluene was higher than that of MFI-type zeolite and β-type zeolite. From the above, it was confirmed that the hydrocarbon adsorbent of the present invention is remarkably excellent in the adsorption removal of hydrocarbons from hydrocarbon-containing gas containing hydrocarbons of multiple types and hydrocarbons having different carbon numbers. .

  Further, from the evaluation results of Examples 1 and 2 and Examples 3 and 4, it was confirmed that the hydrocarbon adsorption capacity is further improved by containing a metal species (active metal) such as copper and silver.

  The hydrocarbon adsorbent of the present invention can be used for adsorption removal of hydrocarbons from hydrocarbon-containing gas, and is particularly suitable as a hydrocarbon adsorbent from hydrocarbon-containing gas containing hydrocarbons having different carbon numbers, for example, It can be used in an exhaust gas treatment system of an internal combustion engine and further an automobile engine.

Claims (5)

A hydrocarbon adsorbent characterized by comprising a zeolite having the following powder X-ray diffraction pattern.
The hydrocarbon adsorbent according to claim 1, wherein the molar ratio of silica to alumina of the zeolite is 5 or more and 200 or less. The hydrocarbon adsorbent according to claim 1 or 2, wherein the zeolite has a BET specific surface area of 300 m ² / g or more and 700 m ² / g or less. A method of adsorbing hydrocarbons using the hydrocarbon adsorbent according to any one of claims 1 to 3. A method for treating a hydrocarbon-containing gas containing a hydrocarbon adsorbent according to any one of claims 1 to 3.