JPH0747485B2 - Method for producing Ga-silicate containing macropores made from diatomaceous earth - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for forming a highly permeable Ga-silicate containing diatomaceous earth as a raw material and containing macropores.

Conventional technology, the problems to be solved by the invention Conventionally, Ga-silicate useful as a catalyst of petrochemical,
Since the diffusion resistance of the reaction components into the micropores is large, the deterioration of the catalyst performance due to coke deposition is a problem. In order to solve this, it is considered that it is useful as a practical catalyst if a porous crystalline body with low ventilation resistance can be synthesized, but Ga has a larger ionic radius than Al, so crystallization is difficult, and the synthesis time is delayed. However, there was a problem that the carrier was dissolved.

In the present invention, a synthetic solution of a pentasil-type zeolite whose water content is extremely reduced is mixed with diatomaceous earth to first synthesize a seed crystal of ZSM-5 zeolite, and then a Ga source is added to crystallize a Ga-silicate. It is intended to provide a method for forming highly permeable Ga-silicate containing macropores by using a diatomaceous earth as a raw material by a step crystallization method.

Means for Solving the Problems The present invention provides a chemical composition (equivalent ratio) of 0.30TPA: 0.20Na by sequentially dissolving TPAB (tetraalkylammonium bromide) such as tetrapropylammonium bromide and NaAlO ₂ in an aqueous solution of sodium hydroxide. : 0.0025Al: 7.5H ₂ O equivalent aqueous solution was prepared, and diatomaceous earth was mixed and kneaded in this solution, and the temperature was programmed from room temperature to 150 ℃ ~ 250 ℃ to slightly dissolve the surface of diatomaceous earth. After using this as a silica source to generate a seed crystal of ZSM-5 zeolite, an amount of Ga ₂ (SO ₂₎ corresponding to a chemical composition of 0.001 to 0.025 Ga was obtained.
₄ ) ₃ was added to carry out two-step crystallization for crystallizing Ga-silicate, and then the obtained sample was washed with water, dried, and dried in an air stream at 50
After calcination at 0 ~ 600 ℃, then exchange the sodium ion of Ga-silicate with ammonium ion, then 500 ~ 6
It relates to a method for producing a Ga-silicate including macropores made of diatomaceous earth, which is characterized by firing at 00 ° C.

The formation method (two-stage crystallization method) of the present invention and NaAlO _{2 in the} synthesis solution
The crystallization time dependence of the crystallinity of Ga-silicate was investigated by a crystallization method (single-step crystallization method) in which a Ga source was added from the beginning without addition of Ga, and the results are shown in Table 1.

Equipment used: Rigaku Denki X-ray diffractometer Geigerflex-2013,
The radiation source was CuKα, 2θ = 5 to 70 °.

Table 1 shows the crystallinity calculated from the peak intensity of the X-ray diffraction peak pattern characteristic of the pentasil-type zeolite around 2θ = 24 °. In the two-stage crystallization method, it was found that crystallization started around 4 hours and almost complete crystallization occurred around 32 hours. On the other hand, in the one-step crystallization method, it was found that the crystallization finally started after about 8 hours and the crystallization did not completely occur even after 32 hours.

From these results, it was found that when forming a macropore-containing Ga-silicate crystal using diatomaceous earth as a raw material, the two-stage crystallization method was used to obviously crystallize rapidly.

Example H-Ga-silicate (Ga chemical composition ratio 0.025) NaAlO ₂ 0.0068 g, NaOH 2.63 g, TPAB 26.59 g reagent and water 45
First, make an aqueous solution of NaOH using g, add TPAB (tetrapropylammonium bromide) and NaAlO ₂ in this order to make an aqueous mixed solution, add 30 g of diatomaceous earth to this solution little by little, and mix well. Then, after making it a clay state that does not adhere even if you touch it with your finger, put it in an autoclave and keep it from room temperature.
The temperature was programmed up to 120 ° C. for 1 hour and from 120 ° C. to 180 ° C. for 2 hours to generate seed crystals of ZSM-5 zeolite. After cooling to below 100 ℃, Ga dissolved in 10 ml of H ₂ O
₂ (SO ₄ ) ₃ 1.780 g was added and kept at 180 ° C. to crystallize the Ga-silicate for 4 to 32 hours. Next, the obtained diatomaceous earth was washed with water and then dried at 120 ° C. for 4 hours. After drying, the temperature was raised from room temperature to 540 ° C. in an air stream in 1 hour, and then firing was performed for 3.5 hours. After firing, ion exchange was performed with a 1N NH ₄ NO ₃ solution at 80 ° C. for 1 hour.
Next, wash with water, dry, and fire to make H-based diatomaceous earth.
A Ga-silicate was obtained.

Measurement of physical properties: The X-ray diffraction pattern of H-Ga-silicate obtained by the method of Example is shown in FIG. Equipment used, radiation source and 2θ
Was the same as above.

In FIG. 1, (a) is a Ga-silicate pattern,
(B) is a diatomaceous earth pattern, and (c) is a Ga-silicate pattern made from diatomaceous earth. As is clear when comparing patterns (a) and (c), 2
Characteristic peaks appear at θ values of around 8 to 9 ° and around 24 °, which indicates that (c) has the same pentasil structure as (a). From this, it was confirmed that pentasil-type Ga-silicate was synthesized from diatomaceous earth.

Next, the sample obtained in the example and a sample synthesized by a method not performing two-step crystallization (one-step crystallization method) and diatomaceous earth were prepared.
SEM (Scanning electron microscope) photographs are shown in FIGS. 2 (A), (B) and (C). The device used is MS
It is M4C-102 (Hitachi-Made by Akashi). In FIG.
(A) is Ga-silicate by the two-step crystallization method synthesized in Example 1, (B) is Ga-silicate by the one-step crystallization method, and (C) is diatomaceous earth.

From FIG. 2 (C), it was confirmed that the diatomaceous earth surface had macropores of about 1 μm. In the sample synthesized by the two-step crystallization of (A), it was found that Ga-silicate particles of about 5 μm were aggregated in a state of including macropores of the same size. From this result, it was confirmed that pentasil-type Ga-silicate containing macropores was synthesized from diatomaceous earth. In the sample (B) synthesized by the one-step crystallization method, particles of Ga-silicate were scattered between the diatomaceous earth particles and were not attached to the diatomaceous earth surface at all. This indicates that the two-stage crystallization method is extremely effective for producing Ga-silicate containing macropores.

Composition analysis: Table 2 shows the composition analysis results of the sample obtained in Example 1 by the atomic absorption method. From Table 2, it was found that Si / Ga was almost constant during the crystallization time of 4 to 32 hours. This indicates that when the ZSM-5 zeolite seed crystal grows in the two-stage crystallization method, Ga ions are incorporated into the crystal from the initial stage.

(Effects of the Invention) (1) The macropore-containing Ga-silicate obtained by the method of the present invention can be used as a novel high-performance catalyst material because the diffusion resistance can be reduced while making the most of the characteristics of H-Ga silicate. Can be expected.

(2) The loading rate of Ga-silicate on diatomaceous earth is Ga-
It can be easily controlled by the concentration of the silicate aqueous mixture and the amount of diatomaceous earth mixed.

[Brief description of drawings]

FIG. 1 is a diagram showing an X-ray diffraction pattern of Ga-silicate,
FIGS. 2 (A), (B) and (C) are scanning electron microscopes showing the grain structure on the surface of Ga-silicate and diatomaceous earth by the two-step crystallization method of the constitution of the present invention and the above-mentioned one-step crystallization method. It is a photograph.

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Claims (1)

[Claims] 1. TPAB (tetraalkylammonium bromide) and NaAlO ₂ are sequentially dissolved in an aqueous solution of sodium hydroxide to give a chemical composition (equivalent ratio) of 0.30 TPA (tetraalkylammonium): 0.20Na: 0.0025Al: 7.5H. Make an aqueous mixed solution corresponding to ₂ O, knead and knead diatomaceous earth into this solution, raise the program temperature from room temperature to 150 ℃ ~ 250 ℃, dissolve the diatomaceous earth surface slightly, and use this as a silica source. ZS
After producing seed crystals of M-5 zeolite, 0.001-0.
After crystallization by adding Ga ₂ (SO ₄ ) ₃ corresponding to the chemical composition of 025Ga, firing at 500 to 600 ° C. in an air stream, and then ion-exchange of sodium ions of Ga-silicate with ammonium ions Dry pores and calcinations at 500-600 ° C, macropore inclusion Ga-based on diatomaceous earth
Method for producing silicate.