JPH03213147A - Nitrogen oxide decomposing catalyst - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a nitrogen oxide decomposition catalyst, and more particularly,
It relates to a catalyst that decomposes nitrogen oxides in gas and converts them into harmless N2 and O2.

[Conventional technology]

Some catalysts for decomposing nitrogen oxides are already known. For example, in JP-A-60-125250, ZSM
A nitrogen oxide decomposition catalyst in which copper ions are contained in type-5 zeolite is described. ZSM-5 type zeolite has a crystal structure different from conventionally known A type, Y type, mordenite type, etc. zeolites, and has a 5i (Jz /
A, O3 (molar ratio) is 20 to 100, and the pore size is about 6. Although such a nitrogen oxide decomposition catalyst made of ZSM-5 type zeolite containing copper ions has high initial activity, it has low heat resistance, and the activity decreases particularly in the coexistence of water vapor.

Also, Abstracts of the Chemical Society of Japan (1988, Spring, I II E3
3), a copper ion-exchanged mordenite type zeolite has been reported. Mordenite-type zeolite has a crystal structure belonging to the mordenite group, and is generally composed of SiO□/AQ,
It has an oa (molar ratio) of 10 to 11 and a pore diameter of about 7 pores. Such a catalyst in which copper ions are exchanged with mordenite-type zeolite has excellent heat resistance, but has a problem of low decomposition activity.

JP-A No. 60-25542 reports a catalyst in which platinum and cobalt are supported on a perovskite such as 5rFeO, but there is a problem in that it requires a high temperature of 800 to 1000°C.

[Problem to be solved by the invention]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an object of the present invention is to provide a nitrogen oxide decomposition catalyst that has a high activity of decomposing nitrogen oxides into N2 and 0□ and has excellent sustainability of activity.

[Means to solve the problem]

The present invention provides 5in2/AQ120 containing copper ions.
．． It is a nitrogen oxide decomposition catalyst consisting of mordenite type zeolite (mole ratio) of 20 to 100.

Mordenite-type zeolite is a zeolite with a structure belonging to the normal mordenite group, and has a pore diameter of around 7 pores, generally Sin, / AQ, O, (molar ratio)
1O ~ 11 is used, but in the present invention, 51
02/AQ20. (Molar ratio) 20 to 100, preferably 20 to 70 is used. Such zeolites may be manufactured by synthetic methods, naturally occurring minerals containing zeolites, or 510 zeolites.
2/AQ20. A synthetic product having a molar ratio of less than 20 may be dealuminated, but a synthetic product or a dealuminated synthetic product is preferable.

Among the mordenite-type zeolites described above, synthetic products can be prepared by a known method, for example, by adding SiO□ raw materials such as sodium silicate and aluminum sulfate and AQ to the above molar ratio.
20. It is produced by heating a mixture of raw materials to about 200° C. in the presence of a catalyst to cause a reaction, but commercially available products may also be used.

Also, natural products or 5xO2/AQxo3 (molar ratio) 20
A zeolite obtained by dealuminating a synthetic product with less than 10% of aluminum can be prepared by acid-treating the mordenite-type zeolite to elute part or most of the aluminum, followed by washing with water, drying, and calcination.

Examples of acids used in the acid treatment include mineral acids such as sulfuric acid, hydrochloric acid, and nitric acid. These acids are o, oos to 1 mol, based on mordenite type zeolite Ig,
Preferably 0. It is used in a proportion of 1 to 0.5 mol of O. These acids are preferably used as an aqueous solution, usually with a concentration of 0.1 to ION. The temperature of acid treatment is usually room temperature to 9
At 0°C, the treatment time is usually in the range of 0.1 to 30 hours.

After the acid treatment, the dealuminated mordenite-type zeolite is thoroughly washed and dried. The drying method is not particularly limited, but it is usually sufficient to carry out the drying at 80 to 200°C for 1 to 50 hours.

Next, the dried dealuminated mordenite-type zeolite is fired, and the firing temperature is usually 300 to 700°C, preferably 400 to 600°C, and the firing time is usually 0.1 to 10°C.
time, preferably 1 to 5 hours.

In the present invention, a catalyst containing copper ions in a mordenite type zeolite having a SiO2/1Q203 (molar ratio) of 20 to 100 as described above is used. The content of copper ions in the catalyst is not particularly limited, but - for boat fishing it is usually 0.5 to 10
% by weight, preferably 1-5% by weight.

Mordenite-type zeolite containing copper ions can be produced by normal ion exchange treatment. Ion exchange treatment is 1 to 10% by weight of copper salts such as copper acetate and copper nitrate.
By contacting it with an aqueous solution, it is made into copper ion-exchanged zeolite. The copper ion may be monovalent or divalent.

The catalyst thus obtained may be used in the form of powder or pellets, or may be supported on a molded body such as a honeycomb body.

The nitrogen oxide decomposition catalyst of the present invention decomposes nitrogen oxides into N2 and 02 and renders them harmless when brought into contact with nitrogen oxide-containing gases such as NO2 and No discharged from automobiles, factories, combustors, etc. used for Since the above-mentioned exhaust gas contains water vapor at about 3 to 20% by volume, water vapor resistance is required, and the catalyst of the present invention has excellent water vapor resistance.
It can be used satisfactorily even in systems where water vapor coexists.

In order to decompose nitrogen oxides using the catalyst of the present invention, a nitrogen oxide-containing gas is passed through a packed bed of the catalyst and brought into contact with the nitrogen oxides. The reaction temperature at this time is usually 300-800°C, preferably 400-600°C, and the gas hourly space velocity (GH5V) is 500-200,000 hr-1, preferably 1,000°C.
0 to 100.000 hr-'.

〔Effect of the invention〕

According to the invention, certain 5102/AQ203 (
Since copper ions are contained in mordenite-type zeolite with a molar ratio of It can be used for a long time even under low conditions.

〔Example〕

Examples of the present invention will be described below.

Example 1 10 g of synthesized mordenite-type zeolite with a molar ratio of 5iO□/ALOz of 40 and 2 g of copper acetate were added to 500 cc of water, and ion exchange was carried out at room temperature overnight. After filtration and washing with water, add copper acetate 2 again.
g was added and the ion exchange was repeated. After washing with water and drying, 5
It was calcined at 00°C for 2 hours and used as a catalyst. The copper ion content of the obtained catalyst was 2.2%lt%, and the sodium ion content was 0.1wt%.

Fill a glass reaction tube with the above catalyst 5+aQ and
The temperature was raised to ℃. 2% NO/He gas at GH5V 2,0
00ht'' to carry out the decomposition reaction of No. The results after 3 hours of reaction are shown in Table 1.

Examples 2 to 3 In Example 1, mordenite type zeolite was replaced with SiO
□/AQ203 molar ratio 20 (Example 2) and 60
A catalyst was prepared and a reaction was carried out under the same conditions as in Example 3 except that the mordenite zeolite was used.

The results are shown in Table 1.

Example 4 The reaction was carried out under the same conditions as in Example 1 except that 6 vol 1% of water vapor was added to the reaction gas. 3 hours later and 2
Table 1 shows the results after 0 hours.

Comparative Example 1 In Example 1, Sin, /An, 03 molar ratio 10
A catalyst was prepared under the same conditions except that a mordenite-type zeolite was used, and the reaction was carried out. The results are shown in Table 1.

Comparative Example 2 In Example 4, the catalyst was a copper ion-exchanged ZSN-5 type zeolite disclosed in JP-A-60-125250 (copper ion exchange rate 90%, 5in2/AQ, 0.molar ratio 60).
) The reaction was carried out under the same conditions except for the following changes. The results are shown in Table 1.

Claims (1)

[Claims] (1) SiO_2/Al_2O_3 containing copper ions
A nitrogen oxide decomposition catalyst consisting of mordenite type zeolite (molar ratio) of 20 to 100.