JP3172246B2 - Method for producing adsorbent for purifying hydrocarbons in exhaust gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an adsorbent for purifying hydrocarbons in exhaust gas.

[0002]

BACKGROUND ART Conventionally, a three-way catalyst for purifying hydrocarbons, NO _X , and carbon monoxide simultaneously has been known as an exhaust gas purifying catalyst for automobiles. Such a three-way catalyst shows sufficient catalytic activity at a reaction temperature equal to or higher than a predetermined temperature. Normally, hydrocarbons in the exhaust gas of an automobile engine are discharged in a particularly large amount immediately after the engine is started. However, since the temperature of the exhaust gas at this time is not sufficiently high, the reaction temperature is lowered, and there is a disadvantage that hydrocarbons cannot be efficiently purified by such a three-way catalyst.

In order to compensate for such a disadvantage of the three-way catalyst, a method has been proposed in which zeolite is arranged upstream of the three-way catalyst to adsorb and remove hydrocarbons discharged at a low temperature (Japanese Patent Application Laid-Open No. HEI 9-258572). 2-75327, JP-A-2-135126). On the other hand, since the exhaust gas of the engine contains a large amount of water and the temperature of the exhaust gas becomes high during the operation of the engine, high exhaust gas purification catalysts are required to have high hydrothermal stability.

[0004] Among various zeolites, ZSM-5 is said to have the best hydrothermal stability.
-5 was not sufficiently satisfactory in terms of hydrothermal resistance in practice. Accordingly, an object of the present invention is to provide a method for producing an adsorbent having high hydrothermal stability and capable of purifying hydrocarbons in exhaust gas with high efficiency.

[0005]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method for producing an adsorbent for purifying hydrocarbons in exhaust gas, comprising the steps of: preparing an MFI hydrothermally synthesized from a silica source and an alumina source using crystalline aluminosilicate as a seed crystal. Aluminosilicate of structure ,
Hydrochloric acid solution, ammonium chloride solution and ammonium nitrate
Ion exchange by adding
The ion-exchanged aluminosilicate is filtered,
After washing, drying at 80 to 150 ° C., the dried aluminum
The silicate is calcined at a temperature of 450 to 600C . As the crystalline aluminosilicate serving as the seed crystal, zeolite 13X, zeolite A, mordenite, ZSM-5 or the like can be used, but mordenite having a high Caban ratio or ZSM-5 is preferably used. The MFI
The structure refers to a structure similar to ZSM-5.

As the silica source, any one can be used as long as it is commonly used for the production of crystalline zeolites. For example, there are silica powder, dissolved silica, silicic acid, colloidal silica and the like. As the alumina source, any one can be used as long as it is generally used for the production of crystalline zeolite. For example, there are aluminum sulfate, sodium aluminate, colloidal alumina, alumina and the like.

In the raw material components, the ratio of silica and alumina (S
iO ₂ / Al ₂ O ₃ ) is 20 to 200, preferably 30 to 200.
~ 100. When SiO ₂ / Al ₂ O ₃ is smaller than 20 or larger than 200, no aluminosilicate having an MFI structure is formed. The temperature during the hydrothermal synthesis is 1
The temperature is 50 to 200 ° C, preferably 160 to 180 ° C. 150
If the temperature is lower than 200 ° C. or 200 ° C., no aluminosilicate having an MFI structure is formed. The pressure during the hydrothermal synthesis may be its own pressure. At the time of the hydrothermal synthesis, necessary components such as NaCl and Na ₂ SO ₄ may be appropriately added.

[0008]

[0009] Ion exchange Previous Symbol H type, hydrochloric acid solution, ammonium chloride solution, using ammonium nitrate solution or the like is ion exchanged synthetic zeolite H-type. Thereafter, drying (80 to 150 ° C) and baking (450 to 600 ° C) are performed. The H-type means that the negative charge of zeolite is compensated by protons.

In the preparation of the adsorbent, a catalytically active component may be added as required. Such catalytically active components include, for example, Group VIII metals (Pt, Pd, Fe,
Co, etc.), Group IB metals (Cu, Ag, etc.), Group VA metals (V
Etc.) and VIIA metal (Mn etc.). The hydrocarbons in the exhaust gas that can be adsorbed and purified by the adsorbent according to the present invention include, for example, butane, pentane, paraffin hydrocarbons such as hexane, ethylene, olefin hydrocarbons such as propylene, benzene,
It is an aromatic hydrocarbon such as toluene and xylene. Among these, the adsorbent according to the present invention has a high purification rate particularly for olefin hydrocarbons and aromatic hydrocarbons.

[0011]

EXAMPLES Example 1 337.5 g of aluminum sulfate (18-hydrate) and sulfuric acid (97%) 362.
A solution of 5 g in 7841 cc of water (referred to as liquid A), a solution of 5275.0 g of water glass (JIS-3 sodium silicate) in 5000 cc of water (referred to as liquid B), and 987.5 g of sodium chloride in water 23
A solution (hereinafter referred to as solution C) dissolved in 00 cc was prepared. Next, while stirring the solution C at room temperature, A
After the solution and the solution B were gradually dropped, 60.0 g of sulfuric acid (48%) was added.

Next, a powder of mordenite (TSZ-610NAA (trade name), manufactured by Tosoh Corporation) as a seed crystal in this mixed solution
After the addition of 12.5 g, the mixture was placed in an autoclave (25 liter capacity) and allowed to react under self-pressure for 20 hours while stirring (rotation speed: 300 ppm). Next, after cooling the reaction mixture,
The solid was separated by filtration. Then, add 280
One liter was added, and washing and filtration were repeated. And
After drying the obtained solid at 120 ° C all day and night, 550 ° C
For 4 hours in the air to obtain 1200 g of crystalline aluminosilicate. This crystalline aluminosilicate is MF
It was similar to the known zeolite ZSM-5 having the I structure.

Next, this crystalline aluminosilicate was added to a solution composed of 1435 g of ammonium nitrate and 10800 g of water, followed by stirring at room temperature for 3 hours and filtration to effect ammonium exchange. This operation was repeated three times to increase the ion exchange rate. Then, the obtained ammonium-type crystalline aluminosilicate was dried at 120 ° C. for 24 hours, and then calcined at 550 ° C. for 4 hours in the air. Next, 5 g of the aluminosilicate was charged into a quartz reaction tube, and steaming was performed at 650 ° C. for 6 hours while flowing a mixture of air (45 cc / min.) And water (5 cc / min.) Into the reaction tube. Hydrothermal treatment).

Next, using the obtained H-type crystalline aluminosilicate, the adsorption performance of hydrocarbons was evaluated as follows. First, the H-type crystalline aluminosilicate was compression-molded to adjust the particle size to 32 to 64 mesh, and then 0.05 g of the aluminosilicate fine particles were charged into a fixed-bed tube reactor (diameter: 7 mm). Next, the reactor was kept at 120 ° C. for 1 hour while flowing a mixture of air (45 cc / min.) And water (5 cc / min.) As a carrier gas into the reactor.

Next, as hydrocarbons, 0.2 cc of propylene is used.
Was taken into a syringe, and propylene was injected into the reactor in a pulsed manner. Then, the concentration of propylene at the outlet of the reactor was measured to calculate the amount of propylene adsorbed on the crystalline aluminosilicate according to the present example. As a result, the adsorption amount of propylene was 0.058 g per 1 g of the H-type crystalline aluminosilicate. Therefore, it can be seen that the H-type crystalline aluminosilicate obtained in this example has good hydrothermal stability and high propylene adsorption capacity.

Example 2 In Example 1, the H-type crystal was obtained in the same manner as in Example 1 except that the crystalline aluminosilicate having the MFI structure prepared in Example 1 was used instead of mordenite as a seed crystal. Aluminosilicate was prepared. Then, the propylene adsorption capacity was evaluated in the same manner as in Example 1. As a result, the adsorption amount of propylene was 0.049 g per 1 g of the H-type crystalline aluminosilicate, and the aluminosilicate of this example also had good hydrothermal resistance.
It had high propylene adsorption capacity.

Comparative Example 1 Aluminosilicate was prepared in the same manner as in Example 1 except that 856 g of tetrapropylammonium bromide was added to Solution A, and mordenite was not added during the synthesis using an autoclave. Was prepared. Then, the propylene adsorption capacity was evaluated in the same manner as in Example 1. As a result, the aluminosilicate according to this comparative example had poor hydrothermal resistance during steaming, and therefore did not adsorb propylene at all.

[0018]

According to the method for producing an adsorbent for purifying hydrocarbons in exhaust gas according to the present invention, it has high hydrothermal stability,
To provide an adsorbent that can purify hydrocarbons with high efficiency
Can be .

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B01J 20/00-20/34

Claims (3)

(57) [Claims] 1. A aluminosilicate crystalline aluminosilicate silica source and alumina source from the hydrothermal synthesis was MFI structure silicate as seed crystals, hydrochloric acid solution, ammonium chloride solution
And ammonium nitrate solution
The ion-exchanged aluminosilicate is filtered and washed with water.
Thereafter, the dried aluminosilicate was dried at 80 to 150 ° C , and dried at 450 to 600 ° C.
A method for producing an adsorbent for purifying hydrocarbons in exhaust gas , comprising firing at a temperature . 2. Hydrocarbons in the exhaust gas according to claim 1.
In the method for producing a purification adsorbent, Exhaust gas characterized in that the seed crystal is mordenite
Method for producing adsorbent for purifying hydrocarbons in water. 3. The exhaust gas according to claim 1 or claim 2.
In the method for producing an adsorbent for purifying hydrocarbons in, The ratio of the silica source and the alumina source (SiO 2 _Two / Al _Two
O _Three ) Is 20 to 200 exhaust gas
Method for producing adsorbent for purifying hydrocarbons in water.