KR100321473B1 - METHOD FOR FABRICATING DeNOx CATALYST - Google Patents

Abstract

PURPOSE: Provided is a method for fabricating DeNOx catalyst with improved catalytic activity and thermal durability. CONSTITUTION: The method comprises the steps of (a) dipping zeolite into Na aqueous solution with Na concentration of 0.1-0.15 mole to acquire Na ion exchanged zeolite (Na-zeolite), (b) rinsing the Na-zeolite, (c) drying the Na-zeolite, (d) acquiring Cu ion exchanged zeolite (Cu-zeolite) by dipping the Na-zeolite into Cu aqueous solution, and (e) calcining the Cu-zeolite.

Description

Method for preparing a catalyst for purifying nitrogen oxides (NOx)

The present invention relates to a method for preparing a catalyst for purifying nitrogen oxides (NOx), and more particularly, by changing the NaNo ₃ molar ratio and the ion exchange method to improve the ion exchange rate of metal ions in the production of the catalyst for NOx purification. The present invention relates to a method for producing a catalyst for purifying NOx, which can reduce the production process time by improving the ion exchange rate and simplifying the production process.

The increase in the number of cars owned by the industrial development of metals and the increase of harmful emissions have seriously damaged the global environment, which is becoming a serious social problem. In order to solve these problems, the automobile industry in the US, Japan and other advanced countries as well as the domestic automobile industry have focused their attention on the development of lean burn engines and commercial trade as part of satisfying emission regulations other than fuel consumption. In addition, other efforts are being made to develop catalysts for exhaust gas treatment of lean-burn engines of other forces.

If the existing three-way catalyst is used to treat the exhaust gas from lean-burn engines, the existing regulation cannot be satisfied. That is, in lean combustion, the air-fuel ratio (air / fuel ratio) is increased to 18-26, resulting in an excessive oxidation atmosphere, so HC and CO can be easily purified by oxidation, but NOx must be reduced in the oxidation atmosphere. There is a need for the development of new catalyst systems for reduction. In particular, the regulation of NOx is gradually being strengthened due to the great influence on the human body, flora and fauna due to the generation of optical smog and acid rain.

On the other hand, in the dry treatment method of NOx generated not only in lean combustion but also in industries such as boilers, a direct decomposition method capable of directly decomposing NO without using any reducing agent is the most preferable reaction route, but a catalyst system has not been realized. . Accordingly, new catalysts have been proposed that use HC as reducing agent for NOx decomposition. Among them, Iwamoto et al. Proposed that the activity of the new catalyst and the gas selectivity of HC appear more and more as the copper ion exchange rate of zeolite increases. It can be seen that the activity of the catalyst is more excellent at 120%. However, conventionally, a large number of Cu ion exchange processes have to be repeated in order to obtain a catalyst having excellent characteristics of 100 to 120% Cu ion exchange amount.

Accordingly, the present invention is to provide a method for producing a catalyst for NOx purification that can not only solve the above problems by increasing the Cu ion exchange rate but also simplify the manufacturing process to reduce the manufacturing process time.

In order to achieve the above object, a method for preparing a catalyst for purifying NOx of the present invention is performed by adding zeolite to an aqueous Na solution, exchanging Na ion, washing, drying, and calcining, and then adding Na-zeolite to an aqueous Cu solution to perform Cu ion exchange. -A method for producing a catalyst for NOx purification for producing a zeolite, wherein the Cu ion exchange step is performed before the calcination step.

Hereinafter, the configuration of the present invention will be described in more detail with reference to the accompanying drawings.

Since the cation exchange method of zeolite varies depending on the type of solution in the type of ion to be exchanged, an optimal exchange method must be established to improve the cation exchange rate of zeolite and the conversion efficiency of NO to N ₂ .

In order to exchange cations in the zeolite, Na ion having excellent activity in the zeolite is first ion exchanged, and then the desired cation is ion exchanged. This is because Na ions are easily exchanged preferentially with other metal ions to be exchanged because of their excellent ion exchange capacity. In addition, since the ion exchange rate of other metal cations is greatly changed depending on the molar ratio of Na aqueous solution during Na ion exchange, an optimal molar ratio should be determined. In other words, the thinner the concentration of the solution, the higher the reactivity of the ions but the lower the motility and conversely, the higher the concentration of the solution, the lower the reactivity but the greater the mobility.

In view of this, the present inventors set the concentration of NaNO3, an aqueous solution of Na, to 0.1 to 0.5 mole prior to cation exchange of zeolite, and generally, after the first Na ion exchange, after washing-drying and calcination, a new secondary copper ion exchange was performed. Unlike the conventional practice, the secondary ion exchange process is performed after the Na ion exchange washing-drying process without the calcination process, thereby improving the Cu ion exchange rate to simplify the manufacturing process.

In brief, the method for preparing a catalyst for purifying NOx of the present invention is to prepare a zeolite by adding zeolite to Na aqueous solution, Na ion exchange, washing, drying and calcining, and then adding Na-zeolite to Cu aqueous solution for Cu ion exchange. The method for producing a catalyst for purifying NOx is characterized by performing a Cu ion exchange step before the calcination step.

FIG. 1 is a manufacturing process diagram of a catalyst for purifying NOx according to the present invention, and FIG. 2 is a graph showing a change in ion exchange rate according to a change in NaNO ₃ molar concentration.

Referring to Figure 1 describes a method for producing a catalyst for purifying NOx of the present invention.

H-Bodenite, a kind of zeolite, was added to an aqueous Na solution such as NaNO ₃ , followed by Na ion exchange by stirring at a temperature of about 40 to 70 ° C., and then filtered. At this time, the concentration of Na aqueous solution is preferably 0.1 ~ 0.15mole.

The filtered wet cake was placed in a container with deionized water and washed and filtered three or four times to remove Na ions remaining on the surface by stirring, followed by drying at a temperature of 100 to 120 ° C.

The dried Na-bodenite powder is exchanged with a copper aqueous solution of Cu (CH ₃ COO) ₂ H ₂ O (copper acetate) for copper ion exchange, and then titrated with NH ₄ OH solution at pH 7.5. After the titration, the filtered wet cake is washed by stirring and repeated three to four times, respectively, and then dried at a temperature of 100 to 120 ° C.

The dried powder is subjected to Cu ion exchange at least twice, preferably 3 to 4 times, in the same manner as the initial process, and then calcined at a temperature of 500 to 550 ° C. and finally heat treated to produce Cu-zeolite.

2 is a graph showing the change of Cu ion exchange rate with the change of NaNO ₃ molar concentration.

As shown in FIG. 2, the NaNO ₃ molar concentration shows the maximum Cu ion exchange rate at 0.1 mole. In addition, at a molar concentration of 0.15 mole of NaHO ₃ , the Cu ion exchange rate was about 40% or more. As such, it is preferable to adjust the concentration of the Na aqueous solution so that the Cu ion exchange rate exceeds 40%.

Therefore, the concentration of the Na aqueous solution is preferably set to 0.1 ~ 0.15mole so as to improve the ion exchange efficiency of about 40% or more, Cu Cu ion exchange rate of about 40% even if not formed in this range and out of the concentration range What is necessary is just the aqueous solution of Na of the said concentration.

The present invention will be described in more detail with reference to the following Examples and Comparative Examples, but this does not limit the scope of the present invention.

Example 1

First, 15 g of H-botenite was added to 1,000 ml of 0.1 mole NaNO ₃ , and Na ion exchange was carried out by stirring at a temperature of about 50 ° C. for 24 hours, followed by filtration.

The filtered wet cake was placed in a beaker with deionized water and washed and filtered three times, respectively, to remove Na ions remaining on the surface by stirring, and then dried at a temperature of 110 ° C. for 24 hours.

The dried Na-mordenite powder was exchanged with Cu (CH ₃ COO) ₂ H ₂ O aqueous solution for copper ion exchange, and then titrated with NH ₄ OH solution at pH 7.5. After the titration, the filtered wet cake was washed by stirring and repeated four times, respectively, and dried at a temperature of 110 ° C. for 12 hours.

The dried powder was subjected to Cu ion exchange twice in the same manner as in the initial process for secondary and tertiary cation exchange, and then calcined at 550 ° C. for 3 hours and finally 5 hours at 550 ° C. under nitrogen atmosphere. Cu-zeolite was prepared by heat treatment.

3 is a graph showing ion exchange rates of zeolites ion-exchanged according to the present invention and the present invention (Example 1). Inductively Coupled Plasma (ICP) and Atomic Adsorption (AA) for Cu-zeolites prepared through the above process The ion exchange rate was measured by a method shown in Figure 3 a), and the ion-exchange rate of Cu-zeolite by the ion exchange process after drying and calcining, which is a conventional method for preparing Cu-zeolite, was measured in b) of FIG. ).

According to FIG. 3, the Cu-zeolite catalyst in which the secondary and tertiary cations were exchanged after the calcination step was subjected to the primary ion exchange of the calcined surface secondary and tertiary cations exchanged according to the present invention. As the Cu ion exchange rate is much higher than that, it can be seen that the catalyst manufacturing process for obtaining a Cu ion exchange amount of 100 to 120 ° C. showing pure catalytic properties is further shortened.

Therefore, according to the present invention, the ion exchange rate can be improved by obtaining the molar ratio of the aqueous Na aqueous solution at the time of the second ion exchange, and the manufacturing process time can be shortened by simplifying the manufacturing process.

1 is a manufacturing process chart of the catalyst for NOx purification according to the present invention,

2 is a graph showing the change of Cu ion exchange rate according to the change of NaNO ₃ molar concentration,

3 is a graph showing the ion exchange rate of zeolites ion-exchanged by the conventional and the present invention.

Claims (2)

In the method for preparing a catalyst for NOx purification in which a zeolite is added to an aqueous Na solution, Na ion exchange is performed, washed, dried, and calcined, and then Na-zeolite is added to an aqueous Cu solution to exchange Cu to produce Cu-zeolite. A method for producing a catalyst for purifying nitrogen oxides (NOx), comprising performing a Cu ion exchange step before. The method for preparing a catalyst for purifying nitrogen oxides (NOx) according to claim 1, wherein the concentration of the Na aqueous solution is 0.1 to 0.15 mole.