JPS60127217A - Production of titanosilicate zeolite - Google Patents

Abstract

PURPOSE:To obtain the titled zeolite containing highly dispersed Ti, by hydrolyzing a mixture of the respective tetraalkoxides of Si and Ti, adding a nitrogen- containing compound and an alkali to the resultant gel, and subjecting the resultant mixture to the hydrothermal synthetic reaction. CONSTITUTION:A silicon tetraalkoxide is mixed with a titanium tetraalkoxide, and the resultant mixture is stirred for a given time with or without addition of water utilizing moisture dissolved from the atmosphere and hydrolyzed not to cause segregation. Thus, a polytitanosilicate gel is obtained. A nitrogen-containing compound and an alkali, and if necessary water are added to the abovementioned gel, and the resultant mixture is subjected to the hydrothermal synthetic reaction under alkaline conditions. A quaternary alkylammonium, tertiary - primary amine, alcohol amine, etc. may be cited as the nitrogen-containing compound. The titanosilicate zeolite obtained by this method contains Ti highly dispersed in crystals and has no slid acid site through it is a solid acid.

Description

[Detailed description of the invention] The present invention relates to a method for producing zeolitic compounds.

More specifically, the present invention relates to a method for producing titanosilicate zeolite that does not substantially contain aluminum.

Zeolite, in a narrow sense, is an aluminosilicate crystal, and originally occurs naturally, but due to its industrial importance, many attempts have been made to synthesize it artificially, and to date, many types of zeolite have been synthesized. Zeolites have now been synthesized artificially. For example, A-type zeolite, X-type zeolite, Y-type zeolite, T-type zeolite, L-type zeolite, etc. are all synthetic zeolites that do not occur naturally. Recently, so-called high-silica zeolites with a silica/alumina ratio exceeding 12 have also been synthesized, such as ZSM-5 (Japanese Patent Publication No. 4B-10064).
, ZSt-11 (Japanese Unexamined Patent Publication No. 54-52699)
, ZSM-35 (Japanese Unexamined Patent Publication No. 144500/1983)
, ZSM-43 (Japanese Unexamined Patent Publication No. 54-68800) has been obtained. These high-silica zeolites are well-known as zeolites with a pentasil structure.

Conventional zeolites are three-dimensional crystals of aluminosilicate, but in recent years many attempts have been made to synthesize zeolites with a structure in which aluminum is replaced with other elements. There are many reports on zeolites with a silica zeolite structure. For example, ZSM-12 (Japanese Unexamined Patent Publication No. 55-11
6619), zeolite having a structure in which a part of aluminum is replaced with boron, gallium, etc.
-129608) and the like are known. Zeolites with a structure in which aluminum is completely replaced with other elements are not aluminosilicate, so they are not zeolites in the narrow sense, but they are structurally similar to zeolites in the narrow sense, so they are included in zeolites in the broad sense. This is considered to be the case, and this explanation also follows. Such zeolites in which aluminum is replaced with other elements are expected to have properties different from those of zeolites in the narrow sense, and are of great industrial interest as catalysts, ion exchangers, and the like.

Several inventions have been proposed regarding titanium-containing zeolites, that is, zeolites having a structure in which aluminum in the zeolite is replaced with titanium. For example, JP-A-55
-2695 publication, 55-7598 publication, 57-
Publication No. 7820, Publication No. 57-7821, Publication No. 57-1
In Publication No. 1818 and Publication No. 58-74521,
A zeolite in which aluminum is replaced with titanium and a method for producing the same are disclosed.

The titanium-containing zeolites disclosed in these documents are all pentasil-type zeolites, that is, the titanium-containing zeolites described above (7).
) ZSM-5, ZSM-11, ZSM-35, ZSM-
It is said to be a zeolite with the same type of three-dimensional structure as 43. However, Sera et al.'s titanium-containing zeolite is produced using the usual manufacturing method of aluminosilicate zeolite, that is, using water glass, sodium silicate, silica gel, Aerosil, etc. as a silica source, synthesizing a gel together with an alumina source, and then adding it to an alkaline solution. After preparing to 100-3
It is prepared using the same method as the synthesis method held at a high temperature of 50° C. (hydrothermal synthesis reaction), and the titania source is put into an alkaline aqueous solution in the same way as the alumina source to obtain titanium-containing zeolite.

The present inventors conducted many experiments in order to synthesize titanosilicate zeolite, but the production method described in the above-mentioned document was unable to obtain crystals of titanosilicate zeolite in which titanium was highly dispersed. It was difficult. The reason for this is thought to be that the titanium compound, which is supposed to be the titania source, precipitates titania in the alkaline aqueous solution and does not dissolve in the alkaline aqueous solution.

The present inventors have conducted intensive research on a method for producing a titanosilicate zeolite in which titanium is highly dispersed in zeolite, and as a result, have arrived at the present invention.

That is, the present invention has titanium highly uniformly dispersed within the zeolite crystals, has a low amorphous content and has a high yield of crystals, and unlike conventional titanium-containing zeolites, it does not substantially contain aluminum. The present invention provides a method for producing titanosilicate zeolite, which is a weakly acidic crystalline solid acid, and its gist is to produce a silicon tetraalkoxide (hereinafter referred to as "silicon alkoxide").
A polytitanosilicate gel is prepared by hydrolyzing a mixture of titanium and tetraalkoxide (hereinafter referred to as "titanium alkoxide"), and the resulting polytitanosilicate gel is mixed with a nitrogen-containing compound, an alkali, and as necessary. A method for producing titanosilicate zeolite, characterized by adding water and carrying out a hydrothermal synthesis reaction under alkaline conditions.

The present invention will be explained in more detail below.

In the present invention, silicon alkoxide is used as the silica source, but tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, tetrapentyl orthosilicate, and tetrahexyl orthosilicate are used because they are easily available. , tetraheptyl orthosilicate, tetraoctyl orthosilicate, trimethylethylsilicate, dimethyldiethylsilicate, methyltriethylsilicate, dimethyldipropylsilicate, ethyltripropylsilicate, and the like are preferably used. Even if these silicon alkoxides are commercially available, they have high purity and can be used as they are, but if they contain impurities, their purity can be easily increased by distillation or the like. Commercially available water glass, sodium silicate, silica gel, Aerosil, etc. that are commonly used as silica sources contain trace amounts of aluminum as impurities, and these silica sources are used to synthesize titanosilicate zeolite. In this case, zeolite mixed with aluminum is likely to be produced. Furthermore, if such a silica source is used, a titania source is added to it, an alkaline aqueous solution is prepared, and a hydrothermal synthesis reaction is performed in the same manner as normal zeolite synthesis, what is obtained is an aluminosilicate zeolite. This is not preferable because it tends to result in amorphous titania and/or a single crystal of titania, resulting in poor dispersibility of titanium.

The titania source used in the present invention is a titanium alkoxide, for example tetramethyltitanate, tetraethyltitanate, tetrapropyltitanate, tetrabutyltitanate, tetrapentyltitanate, methylethyltitanate, methylpropyltitanate, methylbutyltitanate, ethylpropyl Titanate, ethyl butyl titanate, etc. are preferably used.

The addition ratio of the silica source and the titania source is preferably such that the molar ratio of silicon atoms to titanium atoms is 5 to 500, more preferably 5 to 200.

If the titania source exceeds this range and the titania source is large, it is difficult to obtain titanosilicate zeolite crystals even if the hydrothermal synthesis reaction described below is performed. If the titania source is less than this range, the titanosilicate zeolite obtained will have low activity as an adsorbent, ion exchanger, or catalyst.

The important point in the method of the present invention is that by first hydrolyzing the mixture of these silica sources and titania sources,
The aim is to obtain a uniform polytitanosilicate gel. This hydrolysis reaction can be expressed schematically as shown in equation (1).

X (RO)4 Si +Y (R' 0)+Ti +
2 (X0Y)H-0 In the formula, R and R' are an alkyl group, H is hydrogen, O is oxygen, and X and Y are positive numbers. (11
As can be seen from the formula, in order to proceed with the hydrolysis reaction, twice the molar amount of water as the sum of silicon alkoxide and titanium alkoxide is required, but water mixed in during the reaction,
Water mixed into the solvent or water dissolved from the atmosphere during the reaction may be sufficient, and depending on the method of hydrolysis, there is no need to add water. For example, if silicon alkoxide and titanium alkoxide are mixed without adding water and left to stand for about 100 days while stirring, hydrolysis will proceed due to water mixed into the reaction system and water dissolved from the atmosphere. Therefore, the lower limit of the amount of water to be intentionally used is not particularly limited, but it is usually preferable to add 1 to 50 times the mole of the total amount of silicon alkoxide and titanium alkoxide, more preferably 2 to 2 times the amount of water.
It is 0 times. If a large amount of water is added in excess of this range, the hydrolysis rate will be too fast and there is a risk that silica and titania will segregate.

Also, if the reaction system becomes non-uniform due to the addition of water,
Furthermore, it is preferable to use a solvent. The solvent in this case is
Any polar solvent that can make the reaction system homogeneous may be used, and is not particularly limited. Examples include methanol, ethanol, propatool, butanol, acetone, methyl ethyl ketone,
ethyl ether, tetrahydrofuran, ethylamine,
Examples include alcohols, ketones, ethers, amines, and cyclic ethers such as propylamine, butylamine, ethylenediamine, triethylenediamine, and hexamethylenediamine.

In order to advance the above hydrolysis reaction, silicon alkoxide and titanium alkoxide are mixed, preferably 0 to
150°C, particularly preferably 10-80°C, for example 0.
Stir for 5 hours to 100 days, preferably 1 hour to 20 days. If the temperature is less than 0°C, the reaction rate is too low, which is industrially disadvantageous. Furthermore, if the temperature exceeds 150°C, the reaction rate is too high and there is a risk of segregation of silica.

A catalyst can also be added to make the above hydrolysis reaction proceed smoothly. As catalysts, inorganic or organic acids, bases and/or salts thereof can be used, for example hydrochloric acid, sulfuric acid, nitric acid, sodium hydroxide, potassium hydroxide, ammonia, acetic acid, propionic acid, alkylammoniums. and salts thereof such as sodium salts and potassium salts, amines such as ethylamine, propylamine, butylamine, ethylenediamine, triethylenediamine, tetraethylenediamine, methanolamine, ethanolamine, propatoolamine, diamines, alcohol amines, etc. .

The hydrolysis reaction is carried out with the aim of obtaining a uniform polytitanosilicate gel. Therefore, the order and method of mixing silicon alkoxide, titanium alkoxide, water, solvent, and catalyst should be appropriately adjusted so that the reaction can proceed most uniformly. For example, all of the above compounds may be mixed at once, or one, two, or three of the compounds may be added dropwise into the remaining compounds simultaneously or individually. Alternatively, a mixture of several types of compounds may be prepared in advance and mixed simultaneously, or one may be added dropwise to the other. Which of the above methods is selected can be determined depending on the type and amount of silicon alkoxide and titanium alkoxide used, the type of catalyst, etc. Note that alcohol, which is a byproduct contained in the polytitanosilicate gel, does not necessarily have to be removed, but it is preferable to reduce its amount by heating it in advance.

Water, a nitrogen-containing compound, an alkali, and, if necessary, additional water are added to the polytitanosilicate gel obtained as described above, and a hydrothermal synthesis reaction is performed to obtain a titanosilicate zeolite. That is, this mixture is preferably heated at 80 to 250°C, more preferably at 10°C in a closed container.
The titanosilicate zeolite according to the present invention can be obtained by heating to 0 to 220°C and maintaining this temperature for, for example, 5 hours to 100 days.

The water used in the hydrothermal synthesis reaction, together with the water added during the hydrolysis reaction, preferably has 15 to 5
The amount is adjusted to 00 times the mole, more preferably 30 to 200 times the mole. If the amount of water is less than 15 times the mole, the yield of the obtained zeolite will be low, which is industrially disadvantageous.

Examples of the nitrogen-containing compound include quaternary alkylammonium compounds, tertiary amines, secondary amines, primary amines, and alcohol amines. The quaternary alkylammonium compound is not particularly limited as long as it provides a tetraalkylammonium cation, and examples thereof include tetramethylammonium hydroxide, tetraethylammonium chloride, tetrapropylammonium bromide, and tetrabutylammonium iodide. be able to. Examples of the tertiary amine include trimethylamine, triethylamine, tripropylamine, tributylamine, dimethylethylamine, and ethyldipropylamine. Examples of secondary amines include dimethylamine, diethylamine, triethylamine, and the like.

Examples of the primary amine include ethylamine, propylamine, butylamine, and diamines such as pentanediamine and hexanediamine. As the alcohol amine, monoethanolamine, monopropanolamine, etc. are suitable. These nitrogen-containing compounds can be used alone or in combination of two or more.

The amount used is not particularly limited, but it is usually 0.5
~20 times the molar amount, preferably 1 to 10 times the molar amount.

The alkalis used in hydrothermal synthesis reactions include alkali metals,
A hydroxide of an alkaline earth metal, such as sodium hydroxide, potassium hydroxide, calcium hydroxide, etc. In addition, these metals or metal oxides that give hydroxide in water can be used in the same way, and the amount used is usually 0.1 to 20% of the titanium in the polytitanosilicate gel.
twice the molar amount, preferably 0.2 to 10 times the molar amount.

The reaction system of the hydrothermal synthesis reaction is alkaline, preferably PH
It is necessary to set the value to 9 to 12, and titanosilicate zeolite can be smoothly crystallized within this range. The pH is adjusted by adjusting the amount of alkali added. Further, a mineralizing agent may be added to this reaction system in order to facilitate crystallization. This mineralizing agent is generally an inorganic salt of an electrolyte, such as sodium chloride, lium bromide, sodium iodide, potassium chloride, potassium bromide, potassium iodide, sodium sulfate, potassium sulfate, etc. I can do it.

The hydrothermal synthesis reaction can be carried out either under autogenous pressure or under increased pressure, but is usually carried out under autogenous pressure.

It is not necessary to stir the reaction system, and crystallization proceeds satisfactorily even when the reaction system is left standing.

As described above, the titanosilicate zeolite crystallized by the hydrothermal synthesis reaction is collected by filtration after the reaction is completed. This titanosilicate zeolite is generally thoroughly washed, dried, and then calcined at 200 to 800°C for 3 to 24 hours to remove unnecessary organic substances before use.

The titanosilicate zeolite produced by the method of the present invention has an ion exchange ability like a normal aluminosilicate zeolite, and immediately after hydrothermal synthesis, it retains the cations present in the mixture during hydrothermal synthesis as coordinating cations. ing. The coordinating cation can be replaced with another cation by a normal ion exchange operation, for example, by immersion in an aqueous solution containing the cation to be replaced. Examples of cations that can be substituted in this way include monovalent, divalent, or trivalent cations such as protons, ammonium ions, alkali metal cations, alkaline earth metal cations, typical metal cations, or transition metal cations. I can do it.

The titanosilicate zeolite obtained by the method of the present invention is a porous crystal with extremely high thermal stability, and its structure is similar to pentasil type zeolites such as ZSM-5, ZSM-11, and ZSM-34. It is. Furthermore, the titanosilicate zeolite obtained by the method of the present invention has a wide range of uses as an adsorbent, an ion exchanger, a catalyst carrier, a catalyst, etc. Of particular note is that the titanosilicate zeolite obtained by the method of the present invention has titanium highly dispersed in the crystals, and although it is a solid acid, it is a strong solid like aluminosilicate zeolite or conventional titanium-containing zeolite. It has no acid sites.

This is an important feature of the titanosilicate zeolite obtained by the method of the present invention. That is, aluminosilicate zeolite, especially zeolite with a pentasil type structure, is a solid acid with strong acid strength when the coordinating cation is a proton, but titanosilicate zeolite obtained by the method of the present invention has a coordinating cation of proton. In this case, it is a solid acid with extremely weak acid strength. Therefore, it has no activity, for example, in reactions that produce hydrocarbons from methanol, where strong acid sites are considered to be active sites for catalytic action.

The titanosilicate zeolite produced by the method of the present invention can be used for reactions catalyzed by solid acid sites with relatively weak acid strength, such as the production of anthraquinone from phthalic anhydride and benzene, and the production of butadiene from ethanol and acetaldehyde. It can be used as an effective catalyst for reactions.

The present invention will be explained below with reference to Examples. In the following description, % means weight % unless otherwise specified.

Example 1 31.2 g of tetraethylorthosilicate, 2.13 g of tetraisoprobil titanate), and 35 g of ethanol to a content of 300I117! The mixture was placed in a three-day round-bottomed flask and uniformly melted while stirring. Separately, a homogeneous solution consisting of 4.0 g of tetrapropylammonium bromide, 27 g of water, and 35 g of ethanol was prepared, and this solution was slowly dropped into the round bottom flask over 3 hours using a dropping funnel. Stirring was constantly continued during the dropwise addition. After the dropwise addition was completed, stirring was further continued, and after 35 hours, a slightly white transparent agar-like gel was obtained. Apply this gel to 30On+i
The mixture was transferred to a T beaker, added with about 10 g of water, and heated to about 80° C. using a water bath to evaporate and remove ethanol and isopropanol produced by hydrolysis. When evaporating the alcohol, add 50 mJ of water at a time to prevent the gel from drying out, until the total volume in the beaker reaches 2.
Heating was continued until the alcohol odor disappeared while being careful to maintain the axis p from 00 to 25.

Next, after cooling to room temperature, water was added again to bring the total amount in the beaker to 283 g (equivalent to 100 times the mole of water per silicon atom), and the mixture was stirred to obtain an aqueous solution of polytitanosilicate gel. Add 10N Na0I to this aqueous solution.
(The aqueous solution was added dropwise, and the pH of the aqueous solution was set to 10.

This was filled into a Teflon-coated electromagnetic stirring autoclave with an internal capacity of 320n+β, and the temperature was raised to 150°C in 2 hours while stirring under autoclave.
The temperature was maintained for 48 hours. After cooling, the contents in the autoclave were taken out, filtered under reduced pressure, and washed repeatedly with pure water. The obtained filter cake was dried at about 80° C. overnight and further calcined at 650° C. overnight to obtain 8.2 g of white powder of titanosilicate zeolite.

-l)- As a result of analyzing the composition of the powder by plasma emission spectrometry, the weight ratio was Na:Ti:Sj:O=0
．． 0365j 0.0925: 1 F 1.217
It turned out to be. Moreover, the main peaks of the obtained titanosilicate zeolite by X-ray diffraction are as shown in Table-1. The lattice spacing shown in Table 1 could vary slightly depending on the firing temperature of the zeolite, the water content state, the type of exchangeable cations that are thought to be contained in the zeolite in an ionic state, etc.

16- Table-1 Example 2 This example shows that titanosilicate zeolite functions as a solid acid, and also shows that titanium atoms are well dispersed within the silica crystal. .

4 g of the titanosilicate zeolite obtained in Example 1 was added to 10 g of an ammonium chloride aqueous solution with a concentration of 1.0 mol/β.
0m j! The sample was immersed in the liquid and kept at 50°C for 5 hours while stirring. After leaving it for about 1 hour, discard the supernatant liquid and add 1.0 mol/1 new ammonium chloride aqueous solution.
00mj! In addition, the same operation was repeated 5 times. This was filtered, thoroughly washed with pure water until CI- ions could no longer be detected, and further dried at 80°C overnight.
It was baked overnight at ℃. Through the above operations, H+ type titanosilicate zeolite was obtained.

The obtained 11+ type titanosilicate zeolite was 1.0
The sample was weighed out, immersed in 40 ml of 0.05N NaOH aqueous solution, and left in a nitrogen atmosphere overnight. Supernatant liquid 5
1117! Weigh it out and remove the remaining N with 0.02N HCI aqueous solution.
The aOH was titrated. As a result, it was found that NaOH was neutralized by the acid sites of titanosilicate zeolite, reducing its concentration. By titration, the titanosilicate zeolite contains 0.444 meq/
g19- Yes. Moreover, this catalytic activity is approximately 4J for 12 hours after the start of the reaction. There exists an amount of acid equivalent to f, $ru − h < fv − A, J +, which corresponds to 57% of the amount of titanium atoms present when 1 milliequivalent − 1 milligram atom. Understood. It can be seen from the measurement results of the acid amount that titanium is well dispersed within the silica crystals, but the EPMA (Electolon Pr
The results of surface analysis using X-Ray Microanalysis (Obe X-Ray Microanalysis) also revealed that titanium was well dispersed without being unevenly distributed.

Example 3 This example relates to the use of titanosilicate zeolite as a catalyst.

The H+ type titanosilicate zeolite obtained in Example 2 was molded using a tablet molding machine, and then crushed again to obtain particles of 10 to 20 mesos. This crushed material 3.2m
11 was filled into a Pyrex reaction tube having a diameter of 12 m. Next, a mixture of phthalic anhydride and benzene (phthalic anhydride/benzene = 1./25 molar ratio) was supplied to this reaction tube at a rate of 8.2 g/hr, and carbon dioxide was supplied at a rate of 0.63 #/hr. The reaction was carried out at 400°C. Gas chromatography analysis of the reaction product revealed that anthraquinone was obtained in a yield of 23% based on phthalic anhydride.

At this time, the by-product was only some benzophenone, and the selectivity for the reaction to anthraquinone was 93%, 20-

Claims (1)

[Claims] A polytitanosilicate gel is prepared by hydrolyzing a mixture of a silicon tetraalkoxide and a titanium tetraalkoxide, and a nitrogen-containing compound, an alkali, and optionally water are added to the obtained polytitanosilicate gel to make it alkaline. A method for producing titanosilicate zeolite, characterized by carrying out a hydrothermal synthesis reaction under certain conditions.