FR2694549A1 - Prepn. of beta zeolite contg. titanium - by treatment of a silica-alumina zeolite with titanium tri:chloride and hydrogen chloride - Google Patents

Abstract

A process for obtaining zeolites with a beta cavity structure the crystalline cell of which (anhydrous form) corresp. to the general formula (I) (where a.b.c.d and e = (respectively) the number of atom of Si, Ti (in cell), cell cavities, Al, H and Ti (as oxido) outside cell structure. a+b+c+d = (64). The silico-aluminised beta zeolite is subjected to the combined action of HCl and aq. TiCl3. The zeolite after(I) obtd. and also (Ti) in which extra TiO2 is excluded are also claimed. The latter prodn. are new. USE/ADVANTAGE - The prods. are used as adsorbents or catalysts in oxidn. reactions in the presence of H2O2 or a hydro-peroxide. The prepn. of the cpds. is easily effected as the pH of the medium is the only parameter to be controlled. The TiCl3/HCl reagents acts simultaneously to remove Al and insert Ti in the cell structure the treatment also creates cavities which are thought to contribute to the stabilisation of the cell structure TiCl3 is considerably less aggressive on a reactant than TiCl4 which has been used in former processes.

Description

The present invention relates to the field of zeolites.

More specifically, it relates to the preparation of a crystallized zeolite beta type with a network consisting of silicon oxide and titanium.

These zeolites find their use as adsorbents or as catalysts in oxidation reactions in the presence of hydrogen peroxide or hydroperoxide.

Zeolite beta is a zeolitic species identified by its X-ray diffraction spectrum. Its synthesis was first described in 1967 by Wadlinger (US 3,308,069), using tetraethylammonium hydroxide as a structuring agent. Subsequently, other structuring agents, in particular dimethyldibenzylammonium hydroxide or dibenzyl-1,4-diazabicyclo [2.2.2] octane, have been disclosed (see, for example, EP 164.208, EP 159846, EP 159847,
CA 1,240,971). The zeolite beta has a three-dimensional open porosity, with an aperture of 8 AO (8.10-1 m), which makes it potentially interesting for the adsorption and catalytic conversion of clogged molecules.

In the case of zeolite beta, the achievable Si / Al ratios are in practice between 7 and 200; the yield of this synthesis decreases however strongly as soon as one seeks to obtain zeolites beta report
Si / Al greater than 25 (Perez Pariente, Zeolite-1988, vol.8, 46-53). The preparation of zeolite beta rich in silica is possible by extraction of aluminum by acid washing (EP 095.304). One can in the same way consider replacing all or part of the aluminum network with metals and thus obtain zeolites with interesting original properties. In general, to insert metals into the zeolitic structures, it is possible to operate either by direct synthesis or by postsynthetic modification.

Direct synthesis of Si / Ti type zeolites in which titanium would actually be in the network is far from easy. Indeed, the crystallization of zeolites by direct synthesis takes place most of the time within an alkaline reaction medium, and this alkalinity has the effect of causing the precipitation of titanium out of the zeolite network at the expense of its insertion into the structure . Examples of direct synthesis of zeolite Si / Ti with intra-lattice titanium are rare: a titanium silicalite, type MFI (TS-1) according to
Snam Projetti SPA (FR 2 471 950) and a titanium silicalite of MEL type (TS-2) described in Applied Catalysis, 58, 1990, 1-4. Recently, the crystallization of a zeolite beta of silicoaluminate / titanium type with 1.2 aluminum per mesh has been reported in JOCS, Chemical Publication, 1992, 8, 589-590. The insertion of titanium into the network is highlighted. by the appearance of an infrared absorption band at 960 cl ~ 1, and in X-ray diffraction, by the increase of the inter-reticular distance; however, the evidence is not reported using diffuse reflection UV spectrometry (see Boccuti, Structure and
Reactivity of Surface, 1989, p.133) which alone demonstrates the presence of extra-reticular titanium oxide, the insertion of all the titanium in the network.

The most effective way to insert titanium in a zeolite beta has been the TiCl4 titanium tetrachloride gas treatment at 4006000C. This treatment is not specific to zeolite beta but is applicable to other zeolitic structures; it is inspired by the dealumination of faujasite by gaseous silicon tetrachloride SiCl4 described by Beyer (Hungarian Patent No. 24,100). Zeolite beta preparations using the treatment with Tical4 gas have been described for obtaining beta acid catalysts
Si-Al-Ti (US 4,576,805) differing from beta-Si-Al or bifunctional acid catalysts after impregnation with platinum (US 4,827,068). It has been shown (see C.

Ferrini et al., 9th IZC, Montreal, July 1992) that by such treatment with TiCl4, it was impossible to insert titanium only as intra-reticular titanium.

dans laquelle g est le symbole représentant les lacunes du réseau.It has now been found that it is possible to prepare beta-titanium zeolites by treating a zeolite beta silicoaluminum with titanium trichloride TiCl 3 hydrochloric acid. It was then found that this treatment very unexpectedly causes both the dealumination of the starting zeolite and the insertion of titanium into the network. The insertion of titanium is evidenced by the appearance of an infra-red band. 965 cm -1 deep red is absent from the starting zeolite (see FIGS. 1a, 1b and 1c, which reproduce infrared absorption spectra in coordinates wavenumber in cm '1 / optical density, and where the band characteristic at 965 cm 'l is represented by an arrow); we check by spectrometry
W diffuse reflection the absence of extra-reticular Tio2 (see Figures 2a and 2b, which reproduce spectra
W in wavelength coordinates in nanometers / optical density, and where the band designated by Ti-R at 230 nm denotes the intra-lattice titanium and the band designated by Ti
HR around 350 nm indicates extra-reticular titanium). It has furthermore been found that the amount of aluminum extracted from the zeolite beta network, which depends on the acidity of the suspension, is greater than the quantity of titanium introduced. The treatment according to the invention with hydrochloric TiCl3 thus creates gaps which are believed to contribute to the stabilization of the naturally very tight structure of zeolite beta. The beta zeolites that are thus obtained are new. They are attributed, for their anhydrous form, the general formula

where g is the symbol representing the gaps in the network.

The present invention is thus a process for obtaining zeolites with a beta lacunar structure, the crystalline mesh of which contains silicon and titanium, incidentally aluminum, by treatment of a zeolite beta silicoaluminous, of Si / Al ratio chosen between 7 and 100, preferably between 9 and 20, with a dealuminizing system consisting of a hydrochloric acid solution of TiCl 3 titanium trichloride.

In general, the process according to the invention comprises the successive operations of suspending the zeolite beta silicoaluminous in water, adding a hydrochloric solution of titanium trichloride, heating with stirring, preferably under reflux, separation and filtration of the zeolite, washing with normal hydrochloric acid to remove excess titanium and prevent it then precipitates in the form of Tio2 extra-reticular, washing with water to pH 6 and drying at about 1000C.

For adsorption applications, the anhydrous zeolite is calcined at about 5000 ° C. under a stream of nitrogen.

dans laquelle a, b, c, d et e, qui représentent respectivement les nombres d'atomes de silicium, titane intra-réseau, de lacunes 2 du réseau, d'atomes d'aluminium et d'hydrogène, et de titane (exprimé en oxyde) extra-réseau, prennent les valeurs individuelles 56 < a < 63 , 0,2 < b < 4 , 0,2 < c < 2 , 0,3 < d < 6 et
O < e < 6 , a, b, c, d étant en outre reliés entre eux par la relation de maille a + b + c + d = 64.Under current conditions of embodiment of the invention, the zeolite beta silicoalumineuse is suspended at a rate of 1 to 200 g per liter, preferably 4 to 100 g per liter, and the titanium trichloride is added in such a way that the concentration of the titanium suspension is between 0.5 10-3 and 10-2 moles of titanium per gram of zeolite beta, preferably 10-3 to 10-3 moles / g, and the entire insertion to the maintenance of the pH of the suspension is maintained between 0.1 and 4, preferably between 0.6 and 2.5 by controlled addition of hydrochloric acid. Thus, beta-lacunae zeolites with titanium inserted in the network and capable of contain a variable part of extrareticular titanium, whose formula of the anhydrous form corresponds to the general formula

wherein a, b, c, d and e, which respectively represent the numbers of silicon atoms, intra-lattice titanium, lattice gaps 2, aluminum and hydrogen atoms, and titanium (expressed as in oxide) extra-lattice, take the individual values 56 <a <63, 0.2 <b <4, 0.2 <c <2, 0.3 <d <6 and
O <e <6, a, b, c, d being further connected by the mesh relation a + b + c + d = 64.

où a, b, c, d représentent ici encore respectivement les nombres d'atomes de silicium, titane, de lacunes, et d'atomes d'aluminium et d'hydrogène, ces nombres étant également reliés entre eux par la relation de maille a + b + c + d = 64, et prenant les valeurs 56 < a < 63 0,2 < b < 4 , 1 < c < 5 et O < d < 0,6
La zéolite bêta silicoalumineuse de départ est généralement obtenue selon la voie connue qui met en oeuvre l'hydroxyde de tétraéthylammonium comme agent structurant. On peut l'utiliser telle quelle dans le procédé selon l'invention, parce que le traitement qui lui est appliqué est un traitement très acide qui en élimine le tétraéthylammonium.To insert all the titanium in the network, however, it is necessary to maintain the pH of the suspension which contains as previously 1 to 200 g per liter, preferably 4 to 100 g per liter, of zeolite beta silicoalumineuse, at values of between 0.1 and 1.0, and preferably between -0.1 and -0.8, at the same time as the concentration of the titanium suspension is set between 10-4 and 10-3 mol of titanium per gram of zeolite beta, preferably between 0.5 10-3 and 2 10-3 mol / g. The zeolites beta, obtained under these conditions, and whose titanium is engaged in the crystal lattice excluding its location outside the lattice, are new; they are also an object of the invention.They are representable by the general formula

where a, b, c, d represent again respectively the numbers of atoms of silicon, titanium, vacancies, and atoms of aluminum and hydrogen, these numbers being also connected to each other by the mesh relationship a + b + c + d = 64, and taking the values 56 <a <63 0.2 <b <4, 1 <c <5 and O <d <0.6
The starting zeolite beta silicoaluminous is generally obtained according to the known route which uses tetraethylammonium hydroxide as structuring agent. It can be used as such in the process according to the invention, because the treatment which is applied to it is a very acidic treatment which removes tetraethylammonium.

It can be judged more str proceed to the elimination of the structurant by a prior calcination at 5500C under air.

The process for obtaining beta-titanium zeolites according to the invention also has the advantage over the prior titanium tetrachloride process of being easily implemented because there is only one parameter of production to control, the pH, and especially because the reaction mixture titanium trichloride hydrochloric is incomparably less aggressive than titanium tetrachloride.

Some nonlimiting examples are now given to illustrate the invention.

Example 1
Example describing the preparation of a zeolite beta containing both extra-reticular and intrareticular titanium.

A zeolite beta is synthesized according to the teaching of US Pat. No. 3,308,069, with a Si / Al ratio of 12.8, and then calcined at 5500C under air for two hours in order to remove the structuring agent tetraethylammonium. 10 grams of this zeolite are suspended in 100 ml of water, 20 g of a 15% solution of TiCl 2 hydrochloric acid are added thereto. The pH of the suspension is 0.6. It is stirred and refluxed for four hours. The zeolite thus treated is recovered by filtration, washed with normal hydrochloric acid in order to avoid the precipitation of the excess titanium, the washing is continued with water to pH 6. Dry at 1000C and calcine at 5000C under nitrogen flow for three hours.

The crystallinity and the pore volume (0.28 cm3 / g) of the starting zeolite were not affected by the acid treatment. The titanium content of the solid is 1.74% by weight.

The dealumination was only partial, the aluminum content increasing from 2.9 to 1.3%. Titanium was inserted into the grating, as evidenced by the appearance of the infrared band at 965 cm -1 (see Fig. 1b and 1c), but a peak at 350 nm in spectrometry W by reflection also highlights the presence of extra-reticular titanium next to the peak assigned to the titanium of the lattice around 230 nm (see Figure 2a on plate 2 where spectra W are reproduced in Wen nanometer wavelength coordinates and optical densities, and indications
Ti-R and Ti-HR signal the absorption bands W assigned respectively to the network titanium and the extra-network titanium).

Example 2
The example illustrates the preparation of a zeolite beta containing titanium only in the network. 10 g of the same starting zeolite are suspended in 200 ml of water as in Example 1. 50 ml of concentrated hydrochloric acid and then 20 g of 15% by weight hydrochloric acid solution of TiCl 2 are added. The pH of the suspension is -0.25. The suspension is stirred and refluxed for two hours. The zeolite beta is recovered as in Example 1.

The treatment preserved the crystallinity and the pore volume. The titanium content is 1.1% by weight. Dealumination is important since the aluminum content has increased from 2.9% to 0.15 ppm. The UV spectrum testifies to the absence of extra-reticular titanium (cf.

fig.2b).

Examples 3 to 5
The operating conditions of Example 2 were repeated, but starting from beta zeolites with Si / Al ratios of 9.3, 13.5 and 14.9, respectively. The results of the chemical analysis, the intensity of the IR and W bands are shown in the table below.

<Tb>

<SEP> Analysis <SEP> Chemical <SEP> Analysis <SEP> W <SEP> Analysis
<tb><SEP>(<SEP> heights of <SEP> peaks) <SEP> IR
<tb> Report <SEP> Ti <SEP> Al <SEP> Ti <SEP> Ti
<tb><SEP> If / Al <SEP> (% <SEP> (ppm) <SEP> intra- <SEP> extra
<tb> initial <SEP> weight) <SEP> network <SEP> network <SEP> (c)
<tb><SEP> (a) <SEP> (b)
<tb><SEP> 9.3 <SEP> 0.8 <SEP> 400 <SEP> 1.4 <SEP> 0 <SEP> 0.82
<tb><SEP> 13.5 <SEP> 0.75 <SEP> 1200 <SEP> 1.1 <SEP> 0 <SEP> 0.67
<tb><SEP> 14.9 <SEP> 0.78 <SEP> 480 <SEP> ~ <SEP><SEP> 0.7 <SEP> 0 <SEP> 0.59
<tb> (a) height of peak W at 230 nm (b) height of peak W at 350 nm (c) ratio of intensities of the bands at 965 cm -1 and 580 cm -1
In all cases, the titanium is inserted into the network and the amount of aluminum is low.

Claims (9)

1. Process for obtaining zeolites with a beta-gap structure, the mesh of which, for the anhydrous form of the zeolite, corresponds to the general formula

 where a, b, c, d, e respectively represent the numbers of silicon atoms, intra-lattice titanium, lattice gaps 2, aluminum and hydrogen atoms, and titanium (expressed as oxide) extra-lattice, the numbers a, b, c, d being connected to each other by the mesh relationship a + b + c + d = 64, which consists in subjecting a zeolite beta silicoalumineuse to the combined action of hydrochloric acid and aqueous titanium trichloride. 2. Method according to claim 1, comprising the following operations: - suspension of the zeolite beta silicoaluminous in water, - addition of a hydrochloric solution of titanium trichloride, - heating with stirring, preferably under reflux, - separation and filtration of the zeolite, washing with normal hydrochloric acid, washing with water up to pH 6, drying at about 1000 ° C. 3. Method according to claim 2, further comprising calcining the final product at 500 ° C under a stream of dry nitrogen. 4. Method according to claim 1, characterized in that the starting zeolite is a zeolite beta silicoaluminous Si / Al ratio between 7 and 100, preferably 9 and 20. 5. Method according to claim 1, characterized in that the starting zeolite is a zeolite beta silicoaluminous Si / Al ratio between 7 and 100, preferably 9 and 20, previously calcined. 6. Process according to claim 2, characterized in that the suspension contains from 1 to 200 g per liter, preferably 4 to 100 g per liter, of zeolite beta silicoaluminosa, titanium trichloride in an amount such that the concentration of titanium is between 0.5 10-3 and 10-2 mol of titanium per gram of zeolite beta, preferably 10-3 to 10-3 mol / g, of hydrochloric acid in an amount sufficient that during the treatment of said zeolite by hydrochloric titanium trichloride, the pH of the suspension is maintained between +0.1 and 4, preferably between 0.6 and 2.5. 7. Method according to claim 2, characterized in that the suspension contains 1 to 200 g per liter, preferably 4 to 100 g per liter of zeolite beta silicoaluminosa, titanium trichloride in an amount such that the concentration of titanium is between 10-4 and 10-3 moles of titanium per gram of zeolite beta, preferably 0.5 10-3 and 2 10-3 moles / g, of hydrochloric acid in an amount sufficient for the treatment of the said zeolite by hydrochloric titanium trichloride, the pH of the suspension remains maintained between 0.1 and -1.0, and preferably between -0.1 and -0.8. 8. Zeolite beta whose mesh, for the anhydrous form of the zeolite, meets the formula

 where a, b, c, d, e respectively represent the numbers of atoms of silicon, of intra-lattice titanium, of lattice gaps 2, of atoms of aluminum and of hydrogen, and of titanium (expressed as oxide ) extra-lattice, these numbers taking the individual values 56 <a <63, 0.2 <b <4 0.2 <c <2, 0.3 <d <6 and O <e <6, the numbers a, b, c, d being further interconnected by the mesh relationship a + b + c + d = 64. 9. Zeolite beta whose mesh, for the anhydrous form of the zeolite, meets the formula

 where a, b, c, d represent the respective numbers of silicon atoms, intra-lattice titanium, lattice g, aluminum atoms and hydrogen, these numbers taking the individual values 56 <a <63 0.2 <b <4, 1 <c <5 and O <d <0.6, the numbers a, b, c, d being further connected by the mesh relation a + b + c + d = 64, the titanium of said zeolites beta being engaged in the crystal lattice excluding its location outside the lattice.