JPH0674137B2 - Precise control method of zeolite pore inlet diameter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a method for precisely controlling the entrance diameter of zeolite pores, and more specifically, using a silanizing agent in a flowing state, chemical vapor deposition (CVD)
When silica (SiO ₂ ) is supported on the zeolite by the method, the amount of silica supported is adjusted by adsorbing alcohol or ether to the zeolite in advance, and thus the zeolite pore entrance diameter is controlled. It relates to a precise control method of the aperture.

[Prior Art] Zeolites are porous aluminum silicate crystals, which 1) adsorb water and organic substances well, 2) are cation exchangers, 3) have uniform pores, and have molecular sieve performance, Because of its physicochemical characteristics, many industrial uses are known as solid catalysts and adsorbents.

The largest use as a solid catalyst is as a cracking catalyst for petroleum, which is the use of cation exchange property, and replaces sodium cation with proton, alkaline earth metal such as calcium or rare earth element such as lanthanum, and gives acid property. When done in this way, it exhibits very strong solid acid properties.

In addition, the process of producing gasoline from methanol using some zeolite, p from methanol and toluene
-It is used for the production of xylene and the production of p-xylene by the disproportionation of toluene, which is characterized by the shape selectivity of the zeolite, which has different reactivity depending on the size of the molecule. This shape selectivity is 1) molecules that do not enter the pores do not react (reaction molecular shape selectivity), 2) molecules that do not exit the pores do not form (produced molecule shape selectivity), 3)
A product that does not have a transition state is not formed (transition state shape selectivity), and it can be divided into three types, and it is the pore size of zeolite that controls these shape selectivity.

Thus, when used as a zeolite catalyst or adsorbent, the important properties are acidity and pore size. Therefore, it is considered that the zeolite is not used as it is, but is subjected to some treatment to change the properties of the zeolite. The most commonly used are ion exchange and dealumination. It greatly affects the acid properties of.

On the other hand, regarding the pore size, a method is known in which the pore size is changed by utilizing the difference in size between alkali metal cations and alkaline earth metal cations, but this method significantly changes the acid characteristics. There is a drawback that. From this point of view, there is a demand for a method of maintaining the acid property as it is and controlling the size of the pore size.

For this reason, zeolites in which an organic compound containing silicon is supported or silica is prepared by firing after supporting it have been proposed, but none of them precisely control the inlet diameter of pores.

Further, it is also proposed that a specific silanizing agent is used in a fixed state, silica is supported on zeolite by a chemical vapor deposition method under vacuum conditions, and the pore diameter of zeolite pores is controlled. It was not suitable on an industrial scale, and when a large amount of zeolite was supported, the amount of silica supported varied, and the zeolite pore inlet diameter could not be precisely and uniformly controlled.

Since the performance of zeolite is significantly changed by a very small difference in the amount of silica supported, various attempts have been made to support silica on zeolite, but a predetermined amount of silica is uniformly supported on zeolite on an industrial scale, A method for precisely controlling the zeolite pore inlet diameter has not yet been obtained.

In order to solve the above problems, the inventors of the present invention have previously disclosed a method of precisely controlling the zeolite pore inlet diameter by controlling the CVD temperature (Japanese Patent Application No. 60-149991, Japanese Patent Application No. 61-17880). Filed a patent application. According to these inventions, it is possible to uniformly prepare a zeolite carrying a predetermined amount of silica in a relatively large amount.

However, even when controlling the pore inlet diameter for a large amount of zeolite by the above method, depending on the purpose of use, even more stringent fine control of the pore inlet diameter and uniformity within the sample may be required, In such a case, temperature control alone was insufficient.

[Problems to be Solved by the Invention] The present invention has been made from this point of view. It is an object of the present invention to uniformly support a predetermined amount of silica on zeolite and to precisely control the zeolite pore inlet diameter on an industrial scale. It is an object of the present invention to provide a method for precisely controlling the diameter of zeolite pore entrance that has been made possible.

[Means and Actions for Solving Problems] According to the above-mentioned object, the inventors of the present invention have conducted a study, and as a pretreatment, when a silica is vapor-deposited on a zeolite by a chemical vapor deposition method using a silanizing agent in a flowing state. By adsorbing alcohol or ether in advance, the amount of silica supported can be adjusted uniformly, and the inventors have found that the zeolite pore inlet diameter can be precisely controlled, and arrived at the present invention.

That is, the present invention uses a silanizing agent in a flowing state to support silica on zeolite by a chemical vapor deposition method, and when controlling the zeolite pore inlet diameter, alcohol and / or
Alternatively, it is a method for precisely controlling the pore diameter of zeolite pores, which comprises adjusting the amount of silica supported by using zeolite on which ether is pre-adsorbed.

In the present invention, the silanizing agent is vapor-deposited on the zeolite by the chemical vapor deposition method to uniformly support a desired amount of silica on the zeolite surface. The chemical vapor deposition method is a method for producing a solid thin film by decomposing or reacting gas molecules in a gas phase by applying energy such as heat, plasma and light, and in the present invention, various conditions such as a reaction atmosphere are appropriately determined. .

The characteristics of zeolite prepared by this chemical vapor deposition method are:
The pore diameter can be continuously changed by supporting silica only on the outer surface of the zeolite by using a silanizing agent having a molecular diameter that does not enter the pores of the zeolite, and by carrying the silica in multiple layers. As a result, zeolites having different pore inlet diameters can be arbitrarily prepared with one zeolite, and can be appropriately used depending on the intended use.

Further, in the present invention, chemical vapor deposition is carried out with the silanizing agent flowing. When chemical vapor deposition on zeolite is performed using a silanizing agent in a flowing state, silica is supported from the upper part of the reaction layer, and the reaction zone moves downstream in sequence. The supported amount of silica is a function of the chemical vapor deposition reaction temperature, and the supported amount of silica can be adjusted by changing the chemical vapor deposition reaction temperature.

In this way, it is possible to control the amount of silica supported by the chemical vapor deposition reaction temperature, but control of only the chemical vapor deposition reaction temperature causes a drastic change in the pore inlet diameter, and even finer control is required depending on the purpose of use. In this case, it is difficult to control the inlet diameter. Therefore, in the present invention, the zeolite is pre-adsorbed with alcohol and / or ether to reduce the rate of change in the pore diameter with respect to the change in the chemical vapor deposition reaction temperature, and fine control of the zeolite pore inlet diameter is performed. Thereby, the uniformity within the sample can be further improved.

In the present invention, alcohol and / or ether is pre-adsorbed, but this method is not special, and any ordinary method such as a gas phase method in which the saturated vapor pressure of alcohol or ether is adsorbed on zeolite is used. The method is adopted.

In addition, the influence of alcohol and ether on the pore size is
Different compounds have different CVD temperatures that give the same pore size. This effect depends on the amount of adsorption. The adsorbed amount of the alcohol or ether can be selected as desired. That is,
The amount varies depending on the saturated adsorption amount with respect to temperature.
It can be changed by changing the temperature at which the purging process is performed.

Next, the principle of the present invention will be described.

In the CVD process, the silanizing agent first reacts with the --OH groups on the outer surface of the zeolite to form a first layer of silica. It is known that when at least one of alcohol and ether is pre-adsorbed on zeolite, it is chemically adsorbed to the -OH group on the zeolite surface as an alkoxide group (-OR). It is considered that the formation of alkoxide groups by such adsorption reduces effective -OH groups (reactive groups with the silanizing agent) for CVD on the outer surface of the zeolite, and thus suppresses CVD. Further, the amount of alkoxide groups acting for suppression can be changed by the temperature at which the zeolite having alcohol or ether adsorbed is purged. Therefore, the degree of alcohol or ether can be controlled by changing the purge temperature.

Alcohols and ethers used in the present invention are generally R ₁ (OH) m or R ₁ —O—R ₂ [wherein R ₁ and R ₂ are C _{1 to} C ₂
It is an alkyl group of ₅ , and m is an integer of 1 to 3]. Methanol, ethanol and diethyl ether are preferably used because they are particularly expensive and have a high vapor pressure and easy adsorption control.

In addition, the zeolite used in the present invention is not particularly limited, and A-type, mordenite-type, X-type, Y-type, etc. zeolites are used, but alkali metal ions, alkaline earth metal ions, and ammonium ions are used to complete the acid point. The zeolite substituted with is not preferable because it cannot support silica because it has no acid sites.

The silanizing agent used in the present invention may be a gas or a liquid at room temperature. Further, this silanizing agent needs to be used in a distributed state. Specifically, Si (R ₁ )
x (R ₂ ) y [R ₁ : C _{1 to} C ₅ alkyl group, R ₂ : C _{1 to} C ₅ alkoxide group, 0 ≦ x ≦ 3, 1 ≦ y ≦ 4, x + y
= 4] and the like. However, a compound containing halogen such as chlorine or an ion is not preferable because when chlorine is used as a catalyst, chlorine or sulfur attached to the zeolite becomes a catalyst poison or changes the properties of the zeolite. Further, the molecular diameter of the silanizing agent needs to be larger than the zeolite pore diameter, and when it is smaller than the zeolite pore diameter, the silanating agent penetrates into the zeolite pore diameter, and the properties within the zeolite pore diameter change. Resulting in.

[Examples] Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples.

Example 1 Data showing the effect of alcohol 6 g of H-type mordenite (M-type) was filled in a glass reaction tube and pretreated at 500 ° C. in a helium gas stream in advance.
Then, saturated vapor of methanol was caused to flow at the CVD temperature (in a helium flow) to adsorb methanol to the zeolite.
After purging with helium, chemical vapor deposition was performed by flowing tetramethylsilane (3 mmHg) diluted with helium. Next, tetramethylsilane was analyzed by gas chromatography and reacted for 4 hours. After this, there is almost no reaction.

Then, the temperature was raised to 500 ° C. while flowing air, and the mixture was calcined for 10 hours to remove the residual organic matter, and a zeolite carrying silica was obtained.

Example 2 Data showing the effect of ether CV pretreated with dimethyl ether by the same method as in Example 1 except that dimethyl ether was used instead of methanol.
D zeolite was obtained.

Comparative Example No Pretreatment with Alcohol or Ether 6 g of H-type mordenite (M type) was filled in a glass reaction tube and pretreated at 500 ° C. in a helium gas stream in advance.
Next, the temperature was lowered to the CVD temperature, and tetramethylsilane (3 mmHg) diluted with helium was flown to perform chemical vapor deposition.

The subsequent operation was performed in the same manner as in Example 1 to obtain a CVD zeolite without pretreatment with alcohol and ether.

Reaction Test Regarding the zeolites obtained in the above Examples and Comparative Examples, it was confirmed whether or not the pores were controlled. Using the zeolites obtained in Examples and Comparative Examples as samples, a decomposition reaction of 3-methylpentane (molecular diameter 5.3Å) was performed, and the conversion rates were measured. Reaction is 300 ℃
Pulse method. The conversion was measured by gas chromatography, and whether the pores were controlled or not was determined by the conversion.

The results are shown in Tables 1, 2 and 3.

Table 1 shows the effect of pretreatment with methanol. From the table, the change in the conversion rate of 3-methylpentane with respect to the CVD temperature is smaller in the case of pretreatment with methanol than in the case of no pretreatment. This means that the pore size changes significantly with a slight temperature change without pretreatment, whereas in the case of pretreatment with methanol, the change in pore size changes gently depending on the CVD temperature, It can be seen that the control of the pore size by controlling the CVD temperature is easier than when there is no pretreatment.

Table 2 compares the homogeneity of the upper and lower parts of the reaction layer between the case of pretreatment with methanol and the case of no pretreatment. It is even more uniform.

Table 3 shows the CVD temperatures showing the same conversion rate of 3-methylpentane in the cases of no pretreatment, methanol treatment and dimethyl ether treatment, in the order of dimethyl ether>methanol> no pretreatment. This indicates that the CVD reaction is suppressed in this order. As is clear from the results shown in Table 1, the more the content is suppressed, the looser the temperature dependence of the pore control becomes, and the smaller the temperature change in the amount of the silanizing agent carried becomes. That is, it is shown that the pretreatment facilitates the control of the amount of the silanizing agent supported.

[Effects of the Invention] As described above, when the silica is supported on the zeolite by the chemical vapor deposition method by using the silanizing agent in the flowing state, and when the zeolite pore inlet diameter is controlled, alcohol and / or
Alternatively, the method for precisely controlling the zeolite pore inlet diameter of the present invention, which adjusts the amount of silica supported by using the zeolite pretreated with ether, controls the zeolite pore inlet diameter only extremely precisely, and the properties inside the pores are controlled. Since it does not change, the desired performance can be imparted to the zeolite, and since the silanating agent in the distribution state is used, it can be carried out on an industrial scale and maintenance is easy. In particular, the supported amount can be arbitrarily changed by combining the method of the present invention and the method of changing the chemical vapor deposition reaction temperature. Therefore, the zeolite obtained by the present invention has selectivity and is suitably used for applications such as adsorbents and catalysts.

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Claims (1)

[Claims] 1. When a silica is supported on a zeolite by a chemical vapor deposition method by using a silanizing agent in a flowing state and a zeolite pore inlet diameter is controlled, a zeolite having alcohol and / or ether preadsorbed is used. A method for precisely controlling the pore diameter of zeolite pores, which comprises adjusting the amount of silica supported.