JPS6046916A - Modification of zeolite - Google Patents

Abstract

PURPOSE:To produce faujasite zeolite stable to hydrothermal treatment, by repeating the treatment with an aqueous solution of an ammonium salt and the calcination treatment. CONSTITUTION:The objective modification can be carried out by (1) treating a faujasite zeolite containing alkali or alkaline earth metal with an aqueous solution of an ammonium salt (4.5-5pH) to convert about 50-67% of the metal to ammonium ion, and calcining the product at 400-600 deg.C for 2-4hr, (2) treating the calcined zeolite again with an aqueous solution of an ammonium salt (2.5- 4.5pH) to decrease the amount of the alkali or alkaline earth metal remaining in the zeolite to 1.5-2wt% (in terms of oxide), and (3) calcining the zeolite at 400-750 deg.C for 2-4hr.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for modifying faujasite-type zeolite, and more particularly to a method for imparting hydrothermal stability to the zeolite.

Zeolites, especially faujaside zeolites, are widely used as catalysts or components for hydrocarbon conversion. In general, the performance of zeolite-containing catalysts largely depends on the hydrothermal stability of the zeolite.

For this reason, improving the hydrothermal stability of zeolite is an important technical issue in the industry.

Generally speaking, the hydrothermal stability of zeolite is related to the alkali content and silica/alumina ratio of the zeolite; Thermal stability is improved.

The alkali content of zeolite is reduced, and silica/
The simplest means of increasing the alumina ratio is to treat zeolite with an acid solution, but although this method can be applied to mordenite-type zeolite, it cannot be applied to porjasite-type zeolite. This is because faujasite has a lower silica/alumina ratio than mordenite, and its crystal structure is destroyed when it comes into contact with an acid solution.

In other words, in order to impart hydrothermal stability to faujasite-type zeolite, it is necessary to take special measures to remove as much alkali components as possible and increase the silica/alumina ratio without destroying the crystal structure of the zeolite. Therefore, due to these circumstances, conventionally, the alkali metal type faujasite was first subjected to ammonium ion exchange, then fired, and then ammonium ion exchanged again to reduce the alkali content in the faujasite to about 1 wt%, assuming Na, 0. A method has been adopted in which the silica/alumina ratio is increased by reducing the silica to alumina ratio and then treating the faujasite with an acid solution to elute aluminum from the faujasite.

However, in the conventional method, the removal of alkaline components and the elution of aluminum must be performed in separate steps, making the operation complicated. Sludge, where the properties of the final product change due to slight fluctuations in the acid concentration.
The drawback is that it is difficult to obtain faujasite with a certain level of hydrothermal stability in a good yield.

Here, the present inventors performed ammonium ion exchange on the alkali metal type faujasite to remove at least about 50% of the alkali components contained therein, thereby converting this faujasite into I) H2,5~ It has been found that dealkalization and dealumination can be achieved at once by treating with an aqueous ammonium salt solution under acidic conditions of 4.5.

The method for modifying faujasite-type zeolite according to the present invention includes C) faujasite-type zeolite containing an alkali metal or alkaline earth metal at a pH of 4.5 to 5.
About 50 to about 67% of the alkali metal or alkaline earth metal in the zeolite is ion-exchanged to ammonium by treatment with an aqueous ammonium salt solution under conditions of
The calcined zeolite is calcined for 2 to 4 hours at a temperature of ~600°C, and the calcined zeolite is treated with an aqueous ammonium salt solution under conditions of pH 2.5 to 4.5 to remove the alkali metals or alkaline earth metals remaining in the zeolite. The content of alkali metals or alkaline earth metals in the zeolite is reduced to 1.5 to 2.0% by weight in terms of oxides by ion exchange, and (d
) This zeolite is heated at a temperature of 400 to 750"C for 2 to 4
It is characterized by being fired for a certain amount of time.

In the present invention, both natural zeolite and synthetic zeolite can be used as the faujasite type zeolite which is the raw material. The ion-exchangeable cation of commonly available faujasite is usually an alkali metal, but the cation for the raw material faujasite of the present invention may be an alkaline earth metal. According to the present invention, the raw faujasite is first treated with an aqueous ammonium salt solution under the conditions of p 50 to about 67% is ion-exchanged to ammonium.

This treatment is called first ion exchange for convenience, but in the first ion exchange, the ion exchange treatment can be repeated multiple times as necessary. In other words, if the exchange rate to ammonium does not reach about 50 to about 67% after - times of ion exchange treatment, it is best to repeat the ion exchange process f number of times to bring the exchange rate to the above range. This is a requirement for replacement. In the first ion exchange, it is important to maintain the pH condition in the range of 4.5 to 5.0 in order to prevent destruction of the crystal structure of faujasite.

The faujasite whose alkali content has been reduced to about 33 to about 50% of the original content by the above first ion exchange is then calcined at a temperature of 400 to 600°C for 2 to 4 hours, thus imparting some degree of acid resistance to the faujasite. The alkali metal or alkaline earth metal, which could not be ion-exchanged with ammonium in the first ion exchange, is now given ion-exchange properties.

The first ion exchange and subsequent calcination described above are almost the same as those conventionally used to obtain hydrogen type (also referred to as 1!! type) faujasite from alkali metal type faujasite. , the same kind of faujasite that has undergone the first ion exchange and calcination, specifically has an alkali component content of about 4.5 to 4.5 as an oxide.
If a hydrogen-type faujasite of about 6.8 cm is available on the market, a commercially available product can be used in place of the faujasite that has undergone the first ion exchange and calcination.

The third step of the present invention is a step of subjecting the faujasite that has undergone the first ion exchange and calcination to dealkalization and dealumination treatment.
Since the faujasite is treated with an aqueous ammonium salt solution under conditions of 5 to 4,50%, the alkali component remaining in the faujasite becomes 1.5% in terms of oxide due to ion exchange with ammonium.
The aluminum content is reduced to 5 to 2.0% by weight, and at the same time, aluminum is eluted from faujasite. Similar to the first ion exchange process, if the amount of alkaline components in faujasite is not reduced to the target value in one treatment, it is possible to repeat the same treatment multiple times. do. In any case, in this step I) H2,5-4
．． By treating faujasite with an aqueous ammonium salt solution under the conditions of 5, it is possible to reduce the amount of alkaline components in faujasite to 1.5 to 2.0% by weight in terms of oxide while eluting aluminum from faujasite. This is important because it allows approximately 40% of the aluminum originally contained in the faujasite to be leached out.

As the ammonium salt aqueous solution, ammonium sulfate aqueous solution is generally used, including in the case of the first ion exchange mentioned above, but in addition to this, an aqueous solution of an inorganic ammonium salt, which is commonly used in the second ion exchange, is also used. It is possible, for example, to use aqueous solutions of ammonium nitrate, ammonium chloride and the like. When these ammonium salt aqueous solutions are used for the first ion exchange, aqueous ammonia is added to the solutions to maintain the pH at 4.5 to 5.0 during contact with faujasite, and dealkalization and dealumination When used for treatment, the pH at the time of contact with faujasite is maintained at 2.5 to 4.5 by adding it to an aqueous solution of mineral acids such as sulfuric acid, nitric acid, hydrochloric acid, or an ammonium salt of a suitable organic acid. Ru.

After the dealkalization and dealumination treatment, the Hojasite is thoroughly washed with ion-exchanged water, and then heated to 400~
Calcined at a temperature of 750° C. for 2 to 4 hours, it is possible to obtain a faujasite zeolite with hydrothermal stability.

Next, the faujasite modification method of the present invention will be explained in more detail by showing examples.

Example 150 g of sodium-type faujasite was suspended in 1 part of water, 440 g of ammonium sulfate was added thereto, and 150 g of sodium-type faujasite was suspended in 1 part of water.
After adding 5% ammonia water to adjust the pH of the suspension to 4.5, it was heated at 80 to 90°C for 30 minutes. Next, the faujasite was separated by filtration, and the faujasite was sufficiently washed with ion-exchanged water until no sulfate groups were observed in the washing solution. The faujasite was then dried at 100''C and calcined at 550C for 2 hours.

Next, the calcined faujasite was suspended in water 11, 350 g of ammonium sulfate was added thereto, and the pH of the suspension was adjusted to 3.0 with 50% sulfuric acid.
The mixture was heated and stirred for hours.

Next, the faujasite was separated by filtration, and as in the previous case, the faujasite was sufficiently washed with ion-exchanged water until no sulfate groups were observed in the washing solution. Thereafter, the faujasite was dried at 100°C overnight and then calcined at 550°C for 3 hours to obtain a faujasite.

Reference Example 150 g of sodium-type faujasite was suspended in 1 part of water, 440 g of ammonium sulfate was added thereto, and 150 g of sodium-type faujasite was suspended in 1 part of water.
After adjusting the pH of the suspension to 4.5 by adding 5% aqueous ammonia, it was heated at 80-90'C for 30 minutes. Next, the faujasite was filtered for 1'ill, and the faujasite was thoroughly washed with ion-exchanged water until no sulfate groups were observed in the washing solution. After that, heat this hoja site to 100″C.
and baked at 550''C for 2 hours.

Next, the calcined faujasite was suspended in water at 11 Vc,
Add 350g of ammonium sulfate to the chicken and add 15%
After adjusting the pH of the suspension to 4.5 with ammonia water, 80~
The mixture was heated and stirred at 90'C for 2 hours. Next, the faujasite was separated by filtration, and as in the previous case, the faujasite was sufficiently washed with ion-exchanged water until no sulfate groups were observed in the washing solution. Thereafter, this faujasite was dried at 100°C overnight and then calcined at 550°C for 3 hours to obtain faujasite B.

Test Examples Faujasites A and B obtained in Examples and Reference Examples were subjected to the following steam treatment to evaluate the hydrothermal stability of each faujasite.

40g each of A and B were charged into a flow-through reaction tube, and the mixture was heated for 7 hours while passing about 300g of water vapor per hour.
After heating to 50°C, approximately a hourly while maintaining this temperature
Each faujasite was steam-treated by continuously flowing oo g of steam for 17 hours. The specific surface area, pore volume, and crystallinity of the thus obtained faujasite and the faujasite that had not been subjected to steam treatment were measured. The results are shown in the table below.

Claims (1)

[Claims] 1. (a) A faujasite type zeolite containing an alkali metal or an alkaline earth metal is prepared at a pH of 4.5 to 5.0.
from about 50 to about 6 of the alkali metal or alkaline earth metal in the zeolite by treatment with an aqueous ammonium salt M under conditions of
(b) Calcining the obtained ammonium-exchanged faujasite type zeolite at a temperature of 400 to 600°C for 2 to 4 hours, (C) Calcining this calcined zeolite to pH 2.5 to 4.5. The alkali metal or alkaline earth metal remaining in the zeolite is ion-exchanged with ammonium by treatment with an aqueous ammonium salt solution under the conditions of 2.0% by weight
(d) This zeolite is reduced to
A method for modifying faujasite-type zeolite consisting of 4 hours of calcination.