JP2639562B2 - Zeolite adsorbent for hydrogen PSA and method for producing the same - Google Patents

Description

The present invention relates to a zeolite adsorbent and a method for producing the zeolite adsorbent, and more particularly, to pressure swing adsorption (Pressure Swing Adsorpt).
ion: hereinafter referred to as "PSA"), a technique for separating and refining target components from gaseous mixtures, particularly hydrogen-containing gases such as offgas from petrochemical plants, steam reformed gas of natural gas and naphtha, and coke oven gas. It is intended to provide a zeolite adsorbent with excellent ability to separate impure components such as CO used in the hydrogen PSA process to obtain high-purity hydrogen gas by adsorbing and removing impure components such as CO, CO ₂ , methane, and nitrogen. .

[Conventional technology]

Hydrogen is expected to have a significant increase in demand as a main raw material, including the recent energy conversion problem, direct power generation, the petrochemical industry, and the synthesis of methanol. At present, most of hydrogen is produced by a steam reforming method using naphtha, natural gas or the like as a raw material. The hydrogen obtained here is crude hydrogen.
To adsorb and remove impurities such as O, CO ₂ , methane, and nitrogen
The PSA method is increasingly used because of its industrial advantages.

Regarding the separation and purification of a mixed gas by the PSA method, for example, Japanese Patent Publication No. 38-25969 and Japanese Patent Publication No. 39-8204 disclose the basic technology of a two-column or three-column PSA apparatus.
After that, many improved techniques for PSA equipment were devised,
It has reached today. Therefore, it is no exaggeration to say that the development of the performance improvement of the zeolite adsorbent that can follow such a PSA device is an important point for the success or failure of PSA recently.
Regarding the adsorbent for PSA, particularly the zeolite adsorbent for hydrogen PSA, for example, in JP-A-58-84101, a calcium ion exchange rate is 50% or more, and SiO ₂ / Al ₂ O ₃ = 2
It is stated that the Ca-X type zeolite granule 3, which is an adsorbent, is suitable for recovering hydrogen by removing impurities from a hydrogen-containing gas by a PSA method.

JP-A-60-139337 discloses an A-type, X-type, mordenite-type zeolite carbon monoxide adsorbent which contains an alkali metal and an alkaline earth metal and is heat-treated in an atmosphere containing carbon monoxide. It has been disclosed.

[Problems to be solved by the invention]

However, the Ca-X type zeolite adsorbent has a larger amount of CO adsorbed than the Ca-A type zeolite, but also has a larger CO adsorption capacity at low pressure.
There is a problem that the hydrogen yield is reduced in the apparatus of the normal pressure cycle.

Further, firing in a flammable and toxic gas of carbon monoxide as disclosed in JP-A-60-139337 has a safety problem and involves industrial uneconomics.

Conventionally, as a method for producing a 5A-type zeolite (Ca-A-type zeolite) compact, generally, a 5A-type zeolite obtained after ion-exchanging a Na-A-type zeolite powder with an aqueous solution of a calcium salt such as calcium chloride or calcium nitrate is used. Is mixed with a clay-based binder, kneaded, and formed into a compact, and then the compact is fired at 500 to 700 ° C. to produce a Ca-A type zeolite adsorbent. Ca-A obtained by such a conventional method
Zeolite adsorbents typically have a CO adsorption capacity of up to 20
Many are up to ml / g (25 ° C, 1 atm), and other gas selective adsorption properties are not satisfactory.

[Means and actions for solving the problem]

Conventionally, factors that affect the gas adsorption capacity of a zeolite adsorbent include the type of zeolite, the type of ion-exchange cation, the exchange rate, and the firing conditions.

The inventors have conducted intensive studies on these factors,
The molded and calcined product of the Na-A type zeolite was hydrated by humidification, and then subjected to calcium ion exchange.
It has been found that a Ca-A type zeolite adsorbent having a large CO adsorption capacity can be obtained by activating at a temperature of not more than ℃.
The present invention has been completed.

That is, the present invention provides a Ca ion exchange rate of 60% or more.
An adsorbent containing at least 75% by weight of zeolite A, wherein the gas adsorbent at 25 ° C. and 760 mmHg has the following relationship: is there.

Further, the present invention relates to a method for producing a zeolite adsorbent for hydrogen PSA, wherein the zeolite adsorbent completes the following steps.

(1) A step of forming, drying, and firing a mixture of 75% by weight or more of A-type zeolite and 25% by weight or less of a clay-based binder to prepare a molded body. (2) A step of humidifying and hydrating the molded body ( 3) Step of ion-exchanging the hydrated compact with an aqueous solution of calcium salt (4) Ca-A-exchanged Ca-A type zeolite compact
Step of activating by heating at a temperature of 200 to 500 ° C. Hereinafter, the present invention will be described in detail.

The zeolite adsorbent for hydrogen PSA according to the present invention is a Ca-A type zeolite molded article molded with a clay-based binder, and its content is 75% by weight or more.

Such a zeolite has a general formula expressed by a molar ratio of oxides as (xM ₂ O · yCaO) · Al ₂ O ₃ · (1.85 ± 0.5) SiO ₂ · nH ₂ O [wherein, M is an alkali metal, x + y = 1.0 ± 0.2, n ≦ 4.5
This is a so-called 5A zeolite having a composition represented by the following formula, having a Ca ion exchange rate of 60% or more.

Also, in many cases, this zeolite is 0.5-5.0 μm
Are preferred to have a particle size distribution of 80% by weight or more, and have an average particle size in the range of 1 to 4 μm.

In the above description, the particle size distribution is obtained by a measuring method based on the Coulter counter method.

One of the features of such a zeolite adsorbent is that it has the gas adsorption characteristics as described above.
It is suitable as an adsorbent for PSA.

For example, Table 1 shows an example of the composition of crude hydrogen gas obtained from a coke oven.

As apparent from the above composition, CH _4, CO, having a large adsorption capacity for impurity gases such as N _2, O ₂ is is important as adsorbents for H _2-PSA, zeolite adsorption according to the present invention Agents are suitable for this.

Furthermore, the zeolite adsorbent according to the present invention particularly preferably has a water content of 3% by weight or less as defined below.

This is because the water content is about 3% by weight as shown in FIG.
This is because the ratio of the CO adsorption capacity becomes maximum and critically stable below.

The shape and size of such a molded product differ depending on the application and the molding method, and are not particularly limited. In many cases, a desired shape and size such as a sphere, an ellipse, and a bar may be appropriately designed.

Next, a method for producing the adsorbent according to the present invention will be described.

(1) Step of Preparing Molded Body In this step, a mixture comprising Na-A type zeolite particles and a clay-based binder is kneaded, molded, dried and calcined to prepare a molded body having strength.

Na-A zeolites are known and have the above-mentioned particle size characteristics.

On the other hand, as the clay-based binder, for example, kaolinite,
Halloysite, Volclay, bentonite, acid clay,
Kaolin-based plastics such as attapulgite, hectorite, kibushi clay, sepiolite, smectites, and palygorskite plastics can be used. The amount of the clay binder added is preferably as small as possible.However, in consideration of the strength of the molded body, the amount of the non-zeolitic component in the zeolite molded body is 25% by weight or less, and is often in the range of 10 to 25%. It is blended so that it becomes.

If desired, a small amount of cellulose powder or a water-soluble polymer may be blended in addition to the clay-based binder in order to adjust the macropores of the molded article.

After sufficiently kneading such a mixture with an appropriate amount of water,
Molding or granulation is performed by a desired molding machine, but extrusion molding or tumbling granulation is generally preferred.

The obtained molded body is dried to obtain the initial strength,
In many cases, it is performed at about 110 ° C. for 1 to 3 hours.

Next, it is fired at a temperature of 500 to 700 ° C. in a desired heating furnace to obtain a strong molded body. At a temperature of about 500 ° C. or lower, the strength of the molded body is insufficient because the hydroxyl groups of the clay-based binder remain, and at a temperature of 700 ° C. or higher, the zeolite starts to decompose.

(2) Hydration step This step is to hydrate the calcined molded product obtained in the previous step under mild conditions, which is one of the features of the present invention.

For this reason, this hydration step is performed by humidification with steam, and should not be directly immersed and hydrated in water.

The reason for this is that if ion exchange with the calcined molded body is directly performed in a calcium salt aqueous solution, collapse accompanied by water absorption or thermal shock occurs, and a stable molded body cannot be maintained.

Hydration by humidification does not need to be particularly limited, but generally speaking, the water content is 5 to 20% by weight, preferably 7 to 18% by weight.
Is appropriate.

(3) Ion exchange step In this step, Ca ion exchange treatment is performed using a calcium salt aqueous solution in the state of a hydrated molded body, and the ion exchange operation is extremely known in this field.

In this process, an operation is performed such that the Ca ion exchange rate is 60% or more.

As described above, generally, the Ca-A-type zeolite adsorbent ion-exchanges the Na-A-type zeolite particles in advance to obtain a Ca-type zeolite.
-A type zeolite powder is used as a starting material, which is molded and calcined to obtain an adsorbent. One of the features of the present invention is that ion exchange is performed after molding, which is completely opposite to the above.

(4) Activation Step In this step, the Ca-A type zeolite compact is fired and activated to obtain desired gas adsorption characteristics.

That is, the Ca-A-type zeolite obtained in the previous step is activated by performing a heat treatment at a temperature of 200 to 500 ° C. after washing with water and, if desired, drying.

The reason for this is that if the temperature is lower than 200 ° C., water cannot be sufficiently removed even if heated for a long time, and if the temperature exceeds 500 ° C., the adsorption capacity of CO gas decreases. In this case, the water content of the activated Ca-A type zeolite is adjusted to 3% by weight or less. In the case of water adsorption, only the increase in the water content decreases the water adsorption capacity, but as described above with reference to FIG. 1, the carbon monoxide adsorption capacity is greatly reduced when the water content exceeds 3% by weight. Because it will be. In the present invention, the zeolite molded body through the above steps,
By the strict control and the above-mentioned Ca-A type zeolite molded body having a large gas adsorption capacity can be obtained, especially H ₂ -PS
Suitable adsorbents for A can be produced.

〔Example〕

Hereinafter, examples and comparative examples of the present invention will be described.

Example 1 80% or more by weight of 0.5 to 5 μm and average particle diameter
2.3 μm Na-A type zeolite powder (0.98 Na ₂ O.Al ₂ O _3.
After mixing 125 parts by weight of 1.98 SiO ₂ and 3.9 H ₂ O) and 25 parts by weight of kaolin clay, 40 parts by weight of water are added and kneaded. Next, an extrusion molding machine (manufactured by Fuji Paudal, EXD-60 type) was extruded with a die diameter of 1.5 mm to obtain a cylindrical molded product. The obtained molded product is 110 ° C,
After drying for 2 hours, baking at 600 ° C for 2 hours, Na-A with a diameter of 1.5 mm
A molded zeolite was obtained. 100 parts by weight of this molded body was humidified with steam and the water content was measured, and it was 9.8% by weight. 55.8 parts by weight of calcium chloride dihydrate, water 83
3.3 parts by weight were added, and the mixture was heated to 70 ° C. and subjected to ion exchange for 5 hours. After ion exchange, it was washed with water, dried and calcined at 400 ° C. for 2 hours to obtain a Ca-A type zeolite adsorbent. Its calcium ion exchange rate was 65.4% and its water content was 2.2% by weight.

Example 2 Same Na-A type zeolite powder 125 used in Example 1
By weight, 25 parts by weight of kaolin clay were mixed, and the mixture was subjected to tumbling granulation by spraying water while feeding the mixture to a dish-type granulator (600 mm in diameter). After the granulation, the granulated product was classified by sieving to obtain a spherical molded body having a diameter of 2 to 4 mm. The obtained molded body is 110
At 650 ° C for 2 hours after drying for 2 hours.
An A-type zeolite molded body was obtained. 100 parts by weight of this molded body was humidified with steam and the water content was measured. As a result, it was 11.2% by weight. 55.8 parts by weight of calcium chloride dihydrate, water
831.6 parts by weight were added, and the mixture was heated to 60 ° C. and subjected to ion exchange for 5 hours. After ion exchange, it was washed with water, dried, and calcined at 350 ° C. for 3 hours to obtain a Ca-A type zeolite adsorbent. Its calcium ion exchange rate was 64.8% and its water content was 2.8% by weight.

Example 3 125 parts by weight of the same Na-A type zeolite powder as in Example 1,
After mixing 15 parts by weight of kaolin clay and 10 parts by weight of bentonite clay, 40 parts by weight of water are added and kneaded. Next, an extruder (made by Fuji Paudal, EXD-60 type) was extruded with a die diameter of 2.0 mm to obtain a columnar molded product. Rolled spherical granulator (Fuji Paudal, Malmerizer Q-400 type)
And dried at 120 ° C. for 2 hours, and calcined at 700 ° C. for 2 hours to obtain a molded body of Na-A type zeolite having a diameter of 2 to 4 mm. This molded body is 100 parts by weight at a temperature of 24 ° C and a relative humidity of 78%.
In the room for one day and night to absorb moisture. The moisture content of the sample having absorbed moisture was measured to be 6.8% by weight. 64.4 parts by weight of calcium chloride dihydrate and 828.3 parts by weight of water were added to the hygroscopic material, and the mixture was heated to 700 ° C. and subjected to ion exchange for 5 hours. After ion exchange, wash with water, dry and calcine at 250 ° C for 12 hours to obtain Ca-A
A zeolite adsorbent was obtained. Its calcium ion exchange rate was 71.8% and its water content was 2.5% by weight.

Example 4 125 parts by weight of the same Na-A type zeolite powder as in Example 1,
After mixing 10 parts by weight of kaolin clay and 10 parts by weight of sepiolite (Adeplus manufactured by Takeda Pharmaceutical Co., Ltd.), 43 parts by weight of water is added and kneaded. Next, an extruder (Fuji Paudal EXD-60
Mold) Extruded with a die diameter of 1.5 mm to obtain a cylindrical molded product. The obtained molded product was dried at 110 ° C for 2 hours and calcined at 600 ° C for 2 hours to obtain a 1.5 mm diameter Na-A type zeolite molded product. 100 parts by weight of this molded body was humidified with steam and the water content was measured. As a result, it was 16.1 parts by weight. 55.8 parts by weight of calcium chloride dihydrate and 825.0 parts by weight of water were added to the humidified substance, and the mixture was heated to 60 ° C. and subjected to ion exchange for 6 hours. After ion exchange, wash with water,
It was dried and calcined at 480 ° C. for 2 hours to obtain a Ca-A type zeolite adsorbent. Its calcium ion exchange rate was 63.2% and its water content was 1.9% by weight.

Example 5 125 parts by weight of the same Na-A type zeolite powder as in Example 1,
After mixing 25 parts by weight of kaolin clay, 40 parts by weight of water are added and kneaded. Next, an extruder (Fuji Paudal EXD-60
Mold) Extruded with a die diameter of 1.5 mm to obtain a cylindrical molded product. The obtained molded product was dried at 110 ° C for 2 hours and calcined at 550 ° C for 2 hours to obtain a Na-A type zeolite molded product having a diameter of 3.0 mm. 100 parts by weight of this molded body was humidified with steam, and its water content was measured to be 8.3% by weight. 43.0 parts by weight of calcium chloride dihydrate and 849.9 parts by weight of water were added to the humidified substance, and ion exchange was performed at 25 ° C. for 24 hours. After the completion of the ion exchange, the mixture was washed with water and again 43.0 parts by weight of calcium chloride dihydrate and water were added to make the total amount 1000 parts by weight, and ion exchange was performed for 24 hours. After performing ion exchange a total of 5 times, wash with water, dry, and
After calcining for a time, a Ca-A type zeolite adsorbent was obtained. Its calcium ion exchange rate is 86.5%, moisture content is 1.9% by weight
Met.

Comparative Example 1 A Ca-A type zeolite powder (0.68 CaO.0.30 Na ₂ O.Al ₂ O ₃ .1.96 SiO) obtained by performing a Ca ion exchange treatment using the same Na-A type zeolite powder used in Example 1 ₂・ 4.2H ₂ O)
After mixing 128 parts by weight and 25 parts by weight of kaolin-based clay, 40 parts by weight of water is added and kneaded. Next, an extrusion molding machine (manufactured by Fuji Paudal, EXD-60 type) was extruded with a die diameter of 1.5 mm to obtain a cylindrical molded product. The obtained molded product is dried at 110 ° C. for 2 hours, 600,
It was calcined for 2 hours to obtain a 1.5 mm diameter Ca-A type zeolite compact. Its calcium ion exchange rate was 69.4% and its water content was 1.1% by weight.

Comparative Example 2 125 parts by weight of the same Na-A type zeolite powder as in Example 1,
After mixing 25 parts by weight of kaolin-based clay, 40 parts by weight of water are added and kneaded. Next, an extruder (made by Fuji Paudal, EXD-6
(Type 0) Extruded with a die diameter of 1.5 mm to obtain a cylindrical molded product. The obtained molded product was dried at 110 ° C for 2 hours and calcined at 600 ° C for 2 hours to obtain a 1.5 mm diameter Na-A type zeolite molded product. 100 parts by weight of this molded body was humidified with steam and the water content was measured, and it was 9.8% by weight. 54.3 parts by weight of calcium chloride dihydrate and 834.8 parts by weight of water were added to the humidified substance, and the mixture was heated to 70 ° C. and subjected to ion exchange for 5 hours. After ion exchange, wash with water,
It was dried and calcined at 600 ° C. for 2 hours to obtain a Ca-A type zeolite adsorbent. Its calcium ion exchange rate was 64.4% and its water content was 1.3% by weight.

Comparative Example 3 125 parts by weight of the same Na-A type zeolite powder as in Example 1,
After mixing 25 parts by weight of kaolin-based clay, 40 parts by weight of water are added and kneaded. Next, an extruder (made by Fuji Paudal, EXD-6
(Type 0) Extruded with a die diameter of 1.5 mm to obtain a cylindrical molded product. The obtained molded product was dried at 110 ° C. for 2 hours and calcined for 2 hours to obtain a 1.5 mm diameter Na-A type zeolite molded product. When the water content of 100 parts by weight of this molded body was measured without being humidified by steam, it was 1.1% by weight. 54.3 parts by weight of calcium chloride dihydrate and 834.8 parts of water were added to a non-humidified zeolite compact.
A part by weight was added, and the mixture was heated to 70 ° C. and subjected to ion exchange for 5 hours. After the ion exchange, when the Ca-A type zeolite molded body was taken out, a part of the molded body was broken by thermal shock at the time of water injection.

The molded articles obtained from the above Examples and Comparative Examples were evaluated by the following methods.

(I) Gas adsorption characteristics i) Measurement of gas adsorption capacity A sample of a zeolite adsorbent which was previously degassed in vacuum at 300 ° C using a gas adsorption amount measuring device (manufactured by Cantachrome Co., Ltd., Autosorb 1) at 25 ° C The equilibrium adsorption pressure at each measurement point and the gas adsorption amount are measured. The obtained equilibrium adsorption pressure and adsorption amount are plotted on a graph to create an adsorption isotherm. The gas adsorption capacity at 760 mmHg is determined from the selected adsorption isotherm.

ii) Moisture content Measure the weight (W ₁ ) before firing. The sample is fired at 800 ° C for 2 hours, and the weight is (W ₂ ) to determine the water content. iii) Measurement results As shown in Table 2, the adsorbent according to the present invention was found to have a large adsorption capacity for CO and the like.

(II) Relationship between the water content of the adsorbent and the CO adsorption capacity i) Measurement method After ion exchange obtained in Example 2, the water-washed molded body was dried at 110 ° C. for 2 hours, and 4 g was used as a sample. The sample filled in the autosorb sample tube is degassed in vacuum to prepare samples having different residual moisture.

The water content of each sample is separately determined by firing at 800 ° C. for 2 hours.

On the other hand, for samples with different residual moisture, 25 ° C, 760 mmHg
, The CO gas adsorption capacity is determined by the same measurement method as described above, and the relationship between the water content and the CO gas adsorption capacity is evaluated.

ii) Measurement result It is as shown in Table-3, which is illustrated in FIG.

As is clear from the results, when the water content of the adsorbent is 3% by weight or less, the CO gas adsorption capacity becomes maximum and stable.

In addition, although this result was calculated | required about the molded object in Example 2, it is the same about the molded object in other Examples.

[Effects of the Invention] The zeolite adsorbent according to the present invention comprises CO, CH ₄ , N ₂ and O
Excellent gas adsorption capacity of ₂ etc., especially H ₂ -PSA
It is suitable as an adsorbent for use.

Further, according to the production method of the present invention, an excellent zeolite adsorbent as an adsorbent for H ₂ -PSA can be advantageously produced.

[Brief description of the drawings]

FIG. 1 is a graph showing an example of the relationship between the water content of the adsorbent according to the present invention and the CO adsorption capacity.

Claims (3)

(57) [Claims] 1. An adsorbent containing 75% by weight or more of Ca-A type zeolite having a Ca ion exchange rate of 60 or more, and the gas adsorption characteristics of the adsorbent at 25 ° C. and 760 mmHg have the following relationship. A zeolite adsorbent for hydrogen PSA, comprising: 2. A method for producing a zeolite adsorbent for hydrogen PSA, wherein the zeolite adsorbent goes through the following steps. (1) A step of forming, drying, and firing a mixture of 75% by weight or more of A-type zeolite and 25% by weight or less of a clay-based binder to prepare a molded body. (2) A step of humidifying and hydrating the molded body ( 3) Step of ion-exchanging the hydrated compact with an aqueous solution of calcium salt (4) Ca-A-exchanged Ca-A type zeolite compact
Step of activating by heating at a temperature of 200 to 500 ° C 3. The method for producing a zeolite adsorbent for hydrogen PSA according to claim 2, wherein in the activation step (4), the water content of the Ca-A type zeolite molded product is 3% by weight or less.