JPH04349115A - Production of crystalline silicate - Google Patents

Abstract

PURPOSE:To produce crystalline silicate having a specified chemical compsn. in an org. additive-free state. CONSTITUTION:When crystalline silicate having a chemical compsn. represented by a formula (0.1-2.0)R2/nO.[aM2O3.bAl2O3 ].ySiO2 when expressed by molar ratio among oxides in a dehydrated form and having a specified interplanar spacing (alpha value) in powder X-ray diffraction is produced, a water-soluble salt as starting material for M2O3 is added to a water-soluble starting material mixture consisting of a silica source, an alumina source and a mono- or divalent metallic salt and they are held under conditions in hydrothermal synthesis. In the formula, R is one or more kinds of mono- or divalent ions, n is the valence of R, M is ions of one or more kinds of elements selected from among group VIII elements, rate earth elements, Ti, V, Cr, Nb, Sb, Bi and Ga, a+b=1, a>1, b>=1 and y>=12.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a new method for producing crystalline silicates, and more particularly, the present invention relates to a method for producing crystalline silicates having a specific chemical composition in the absence of organic additives.

0002

[Prior Art] Zeolites have many tertiary structures and are used as adsorbents and gas separations as molecular sieves.Recently, zeolites have been used as catalysts for hydrocarbon conversion such as hydrocarbon cracking and isomerization, as well as denitrification catalysts. It has come to be widely used as Typically, zeolites are crystalline aluminosilicates with a rigid three-dimensional structure of SiO4 and AlO4 - tetrahedra bonded by covalent oxygen atoms such that the ratio of total aluminum and silicon atoms to oxygen atoms is 1:2. ing.

On the other hand, even if a trivalent cation with the same ionic radius as Al is used instead of Al, a trivalent cation tetrahedron is formed in the same form as the SiO4 tetrahedron in the zeolite structure. It has been found that (Tokuhei 2-35
Publication No. 692).

[0004] Significant changes in catalytic performance have been observed by replacing part or all of the Al in zeolite with a transition metal. For example, in the aromatic conversion reaction of methanol and other oxygen-containing organic compounds, conventional zeolite called ZSM-5 contains several percent of durene as a by-product.
However, when such a crystalline silicate is used, results have been obtained in which almost no C10 or higher aromatic products such as durene are produced. Furthermore, in the direct decomposition reaction of nitrogen oxides (2N0→N2 +O2), Cu
Such ion-exchanged crystalline silicates are similar to conventional Z
It has been reported that side reactions are suppressed compared to the zeolite called SM-5, and only the above reactions proceed selectively (Japanese Patent Application No. 01-281996).

Until now, such crystalline silicates have been produced by hydrothermal synthesis using organic nitrogen-containing compounds. The organic substances used are i) Primary amines...n-propylamine, monoethanolamine, etc. ii) Secondary amines...dipropylamine, diethanolamine, etc. iii) Tertiary amines...tripropylamine ,
Triethanolamine etc. iv) Other organic nitrogen compounds...Pyridine,
Examples include pyrazine, and other organic substances other than the organic nitrogen compounds mentioned above include alcohols such as ethanol and methanol, ketones such as acetone, ethers such as diethyl ether, and esters. It is said that the above-mentioned organic substance acts as a crystallization accelerator, and that the organic substance is present at the intersection of the pores and serves as a crystal nucleus, making it possible to obtain high-quality silicate.

However, the above organic compounds are expensive and
Toxicity is an issue for some. When crystalline silicate is synthesized, organic compounds are incorporated into the pores, and even if a firing operation is performed to remove them, organic compounds may remain, or instantaneous high-temperature combustion may occur, resulting in demetalization ( Al
, Fe, etc.) have occurred.

[0007]

SUMMARY OF THE INVENTION In order to eliminate these drawbacks, methods for producing crystalline silicates without using organic additives have been proposed. For example, a method of producing crystalline silicate by holding an aqueous raw material mixture of silica, alumina, alkali metal salts, etc. under natural pressure at 80 to 210°C for 40 to 200 hours (Japanese Patent Publication Publication No. 1983)
49851), but by-products such as mordenite coexist in the crystals, making it impossible to obtain crystalline silicate with good purity.

In view of the above-mentioned state of the art, the present invention aims to provide a method for producing crystalline silicate without using organic additives as raw materials and without the coexistence of by-products as in the above-mentioned methods.

[0009]

SUMMARY OF THE INVENTION The present invention provides that, in dehydrated form, the molar ratio of oxides (0.1 to 2.
0) R2/n O・[aM2 O3 ・bAl2 O3
]・ySiO2 (In the above formula, R: one or more monovalent or divalent ions, n: valence of R, M: VIII
group elements, rare earth elements, Ti, V, Cr, Nb, Sb, B
i, one or more element ions selected from the group consisting of Ga, a+b=1, a>1, b≧0, y≧12), and has a powder X-ray diffraction analysis shown in Table 1 below. In producing crystalline silicate having a lattice spacing (α value) of ) is a method for producing crystalline silicate, which is characterized by adding a water-soluble raw material salt based on the method and maintaining it under hydrothermal synthesis conditions.

[Table 1]

Conventionally, when producing crystalline silicate using an organic substance such as tetrapropylammonium bromide, it has been produced starting from an aqueous mixture having the following molar composition. SiO2/(Al2O3 +M2O3): 12
~3000 (preferably 20-200) H2O/SiO2: 5-1000
(preferably 7-200) R2/n O/SiO2: 0.02-1
．． 0 (preferably 0.05-0.2) H2O/R2/nO: 5-100
0 (preferably 10-300) Organic compound/(Al2O3 +M2O3): 1-
100 (preferably 5-50)

As in the present invention, when no organic compound is added, the above molar composition must not exist in order to synthesize crystalline silicate with high purity; It has been found that the crystalline raw material salt acts effectively as a crystallization accelerator, and the present invention is based on the discovery that a predetermined crystalline silicate can be synthesized under the following molar composition conditions.

The molar composition of the reaction mixture is SiO2/(Al2O3 +M2O3):12
~100 (preferably 20-60) H2O/SiO2
:5-1000 (preferably 7-200)

Furthermore, the pH at the time of the gel formation, that is, the H+ (hydrogen ion) concentration in the gel, is an important factor;
O/R2/n O ratio is 5 to 20, and R2/n O
/(Al2O3 +M2O3) When preparing a slurry with a ratio of 5 to 20, the pH is in the range of 7 to 9.5,
In addition, the H2O/R2/nO ratio is 20 to 300, and R
2/n O/(Al2 O3 + M2 O3) ratio is 1
-8, the pH must be adjusted to a range of 11-14.

Furthermore, the crystalline silicate of the present invention is synthesized by heating the raw material mixture at a temperature and time sufficient to form the crystalline silicate, and the hydrothermal synthesis temperature is 80 to 300°C, preferably The temperature is in the range of 130 to 200°C, and the hydrothermal synthesis time is 0.5 to 14 days, preferably 1 to 10 days.

[0015]

[Function] Metal oxide (M2O
It was found that the metal ions in the water-soluble raw material salt based on 3) function as central cations at pore intersections and play an important role in promoting crystal growth. The metal ions of this water-soluble raw material salt include Group VIII elements, rare earth elements, Ti, V,
These are Cr, Nb, Sb, Bi, and Ga.

Furthermore, the above-mentioned metal ions also function as important catalytic active sites in the produced crystalline silicate,
In particular, the copper-supported crystalline silicate of the present invention can be used for direct decomposition reactions of nitrogen oxides (2NO→N2 +O2) and exhaust gas purification reactions (for example, 9NO+C3 H6 → 9
/2N2 ・3CO2 +3H2 O), etc., has been found to have high activity.

The water-soluble raw material salt based on the metal oxide to be added may be any of chlorides, nitrates, sulfates, acetates, etc., and is not particularly limited. Hereinafter, the method for producing crystalline silicate of the present invention will be explained with reference to Examples.

[0018]

【Example】

(Example 1) Sodium aluminate (manufactured by Hayashi Junyaku Co., Ltd. purity 85%) 1
98.1g, caustic soda (made by Hayashi Junyakusha special grade) 211.
7g was dissolved in 4018g of water to prepare solution A. On the other hand, silica sol solution (Nissan Chemical Snowtex O: SiO2
Solution B is obtained by adding 4320 g of water to 9180 g of 20%) and further dissolving 27 g of ferric chloride and 145 g of cobalt chloride in this aqueous solution.

Next, solution A and solution B are added equally to another container, neutralized, and mixed and stirred at a uniform pH (pH=12.6) to form a gel. This gel was placed in a stainless steel autoclave and kept under self-generated pressure at 160° C. for 72 hours to synthesize crystalline silicate.

After the reaction was completed, the product was filtered and washed, and then dried at 120°C. As a result, Crystalline Silicate 1 was obtained, and as a result of powder X-ray diffraction, it was found to have a crystal pattern shown in Table 1 above.

(Example 2) Water glass No. 1 (manufactured by Tokuyama Soda, Si
Solution A is obtained by dissolving 5616 g of O2 (containing 37%) in 5429 g of water. On the other hand, in 4165 g of water, 262 g of sodium chloride, 749 g of aluminum sulfate, and 22 g of ferric chloride.
g, 15 g of cobalt chloride, and 1700 g of concentrated hydrochloric acid are added and dissolved to obtain solution B.

Next, solution A and solution B were equally added to another container in the same manner as in Example 1, neutralized, and mixed and stirred at a uniform pH (pH=8.5) to form a gel. Set this gel in a stainless steel autoclave and
C. for 24 hours and 170.degree. C. for 48 hours under autogenous pressure to synthesize crystalline silicate.

As a result of powder X-ray diffraction, this crystalline silicate 2 was found to have a crystal pattern shown in Table 1 above.

(Example 3) Crystalline silicate 3 was synthesized in the same manner as in Example 1 except that 42 g of lanthanum nitrate was added instead of ferric chloride and cobalt chloride in Example 1.
I got it.

Similarly, 28 g of cerium nitrate, 26 g of titanium tetrachloride, 16 g of vanadium trichloride and 18 g of ferric chloride
In the same manner as in Example 1, crystalline silicate 4,
5, 6, 7, and 8 were obtained.

As a result of powder X-ray diffraction, all of these crystalline silicates had the diffraction patterns shown in Table 1 above.

(Example 4) In Example 2, 6 g of ruthenium chloride, 26 g of nickel chloride, and 24 g of gallium nitrate were added instead of ferric chloride and cobalt chloride, and in the same manner as in Example 1, crystalline silicates 9, 10, I got 11.

As a result of powder X-ray diffraction of these crystalline silicates, they had the diffraction patterns shown in Table 1 above.

(Comparative Example) Crystalline silicates 12 and 13 were obtained by the method of Examples 1 and 2 in the compositions of Examples 1 and 2 in which ferric chloride and cobalt chloride were not added and under the condition that no organic matter was added.

As a result of powder X-ray diffraction of these crystalline silicates, it was found that crystalline silicate 12 was almost amorphous, and crystalline silicate 13 almost formed a mordenite type crystal structure.

[0031] Examples 1 to 4 and comparative examples are summarized in Table 2 below.

[Table 2]

[0032]

Effects of the Invention As shown in the examples, when an aqueous raw material salt based on a specific metal oxide is used as a raw material for crystalline silicate,
By adding it, it has become possible to easily synthesize crystalline silicate, which has conventionally been impossible to synthesize without adding organic substances. The added metal ions effectively act as catalytically active species in the crystalline silicate, and the copper-supported crystalline silicates 1 to 11 are capable of direct decomposition reactions of nitrogen oxides (2NO→N2 + O2) and exhaust gas purification reactions ( 9NO+C3 H6 → 9/2N2 ・3CO2
+3H2O), etc., was found to have high activity.

Claims (1)

[Claims] 1. In dehydrated form, expressed as molar ratio of oxides: (0.1-2.0)R2/n O.[aM2 O3.
bAl2O3 ]・ySiO2 (In the above formula, R: 1
species or more monovalent or divalent ions, n: valence of R, M: group VIII element, rare earth element, Ti, V, Cr,
One or more element ions selected from the group consisting of Nb, Sb, Bi, and Ga, a+b=1, a>1, b≧0, y≧1
2) In producing a crystalline silicate having the chemical composition of To an aqueous raw material mixture consisting of a valent or divalent metal salt,
A method for producing crystalline silicate, which further comprises adding a water-soluble raw material salt based on M2O3 (M: the same as defined above) and maintaining the mixture under hydrothermal synthesis conditions.