Alkali-free synthesis of MFI type boro-titanosilicates using methylamine

MICROPOROUS MATERIALS

ELSEVIER Microporous Materials 11 ( 1997) 237-245

Alkali-free synthesis of MFI type boro-titanosilicates using methylamine

Masashi Shibata ‘, Zelimir Gabelica *

FacultPs Uniuersitaires de Namur, Dkpartement de Chimie, 61, Rue de Bruxelles, B-5000 Namur. Belgium

Received 12 November 1996; accepted 30 January 1997

Abstract

A new synthesis route leading to a rapid crystallization of boro-titan0 MFI type zeolites from methylamine media has been explored. The principal advantage of this synthesis method is that the use of costly ingredients such as TPAOH and Ti- and Si-alkoxides can be avoided. Ti and B are readily incorporated into the MFI framework as confirmed by spot EDX analysis, IR, “B-NMR and XPS. Preheating the borosilicate gel before mixing with titanium tetrachloride improves the (B,Ti)-MPI crystallization rate and prevents the formation of extraframework titanium dioxides. 0 1997 Elsevier Science B.V.

Keywords; Boro-titanosilicates; Methylamine; Synthesis; Titanosilicates; Zeolites

1. Introduction

MFI type titanosilicates, also called TS-1, have performed excellently in the epoxidation and hydroxylation of olefins with hydrogen peroxide [ 11. Recently, the simultaneous incorporation of trivalent ions, such as B3+, A13+, Ga3+ or Fe3”, along with Ti4+ in MFI and MEL zeolites [2-51 has been reported. It may be anticipated that such bi-metallosilicates are favorable both for oxidation reactions (oxidative role of Ti4+ ions) and for acid-catalyzed reactions, the Briinsted acidity being generated by the presence of framework

* Corresponding author. Present address: Ecole Nationale Superieure de Chimie de Mulhouse, Laboratoire des Matiaux

Mineraux, 3, rue Alfred Werner, F-68093 Mulhouse Cedex; fax: + 33 3 89428730; e-mail: [email protected] ‘Present address: Kao Corporation, Tokyo Research Lab., 1-3, Bunka 2-chome, Sumidaku, Tokyo 131, Japan.

trivalent ions. Among these latter ions, aluminum is the most common component of zeolites, and it generates very strong Br6nsted acid sites in MFI zeolites. For mild oxidation catalytic reactions, the existence of too strong acid sites in zeolites may not be appropriate. Indeed, in the case of eploxida- tion of olefins with hydrogen peroxide, :strong acidity simply caused the decomposition of hydrogen peroxide, so that the product yield on (Al,Ti)-MFI decreased when compared with Ti-MFI [4,5].

Because boron in the zeolite lattice generates very weak Briinsted acid sites compared to aluminum, its incorporation into the framework of MFI titanosilicate is expected to hardly modify the overall oxidation properties. In that respect, Trong On et al. [6,7] have elaborated the synthesis of MFI boro-titanosilicates using TPAOH: and H,O,, and demonstrated that the catalytic activity

0927-6513/97/$17.00 80 1997 Elsevier Science B.V. All rights reserved. PII SO927-6513(97)00015-l

238 M. Shibata, Z. Gabelica / Microporous Materials 11 (I 997) 237-245

of the (B,Ti)-MFI materials in the oxidation of n-hexane was very different upon boron incorporation.

In a series of previous papers, we have reported and discussed a new synthesis method for borosilicates [8] and titanosilicates [9, lo] involving the use of short-chain alkylamines (typically methylamine) as mobilizing agents, a method that proved very efficient for the incorporation of a wide series of metallic ions in the MFI framework [ 111. In the present case, another advantage of this synthesis route is that costly TPAOH and titanium and silicon alkoxide, which are the necessary ingredients in the common titanosilicate synthesis, do not have to be used.

containing Ti and B, and the mixture was stirred for more than 3 h at ambient temperature. The resulting gel was admixed with methylamine (from Fluka) and stirred for 1 h before being transferred to an autoclave.

2.1.2. Synthesis II (in situ seeding method; preheating of the borosilicate gel)

A titanium-free borosilicate gel was prepared similarly to Synthesis I and heated at 185°C for 6 h in an autoclave. The mixture so obtained (gel and a small amount of B-MFI ‘seeds’) was cooled to room temperature and then mixed with TiCl,. This mixture was stirred for 1 h before being transferred to an autoclave.

The aim of this work is to apply the methylamine route to boro-titanosilicate synthesis and examine the mutual effect of both elements on the crystallization of (B,Ti)-MFI zeolites and on their final properties.

2.1.3. Synthesis III (in situ seeding method; preheating qf the titanosilicate gel)

2. Experimental

2.1. Synthesis ofboro-titanosilicates

A boron-free titanosilicate gel was prepared and preheated under the same conditions as those for Synthesis II. Boric acid dissolved in w.ater beforehand was added to that gel. The other synthesis conditions and the initial gel composition were the same as for Synthesis II.

Three procedures were used to prepare MFI- type boro-titanosilicates. In Synthesis I, the boron, titanium and silicon sources were mixed in methylamine solution simultaneously. In Synthesis II, the Ti species was added into a preheated gel precursor to borosilicate, in which a very low amount of borosilicate crystals were already generated by a preliminary heating. This procedure is based on the in situ seeding method, which accelerated the crystallization of various MFI metallosilicates such as titanosilicates, gallosilicates, zincosilicates and aluminosilicates [9,10,12]. In Synthesis III, the B source was added into the preheated titanosilicate gel. The detailed synthesis procedures are described below.

Molecular compositions of the initial gels are shown in Table 1. The Teflon-coated stainless-steel autoclaves were heated at 185°C for various periods of time (maximum 14 days) under static conditions. The final solids were filtered, washed with water and dried at 100°C. The solid phases were washed and further submitted to ultrasonic cleaning to remove the unreacted gel possibly coating the MFI crystals prior to EDX, XPS and XRD measurements.

Calcination was performed under nitrogen (heating rate: 10 C” min-‘) from 20 to 550°C; the samples freed from TPA were then maintained at 550°C for 6 h in an air flow to burn off the residual coke originating from the non-oxidative TPA ther- mal decomposition.

2.1.1. Synthesis I 2.2. Characterization TiCl, (Merck) was carefully added to an aque-

ous solution of TPABr (Janssen Chimica) and boric acid (UCB Chemicals) which had been cooled to 5°C beforehand. Hydrogen fluoride was optionally added to the solution. SiO, (Aerosil 200 from Degussa) was added to this solution

All the products were examined for their nature and purity by SEM (Philips XL 20 microscope). Spot EDX quantitative analysis of Si and Ti on selected areas (cores and edge) across individual crystallites was performed using an EDAX P.V.

Table 1

M. Shibata. 2. Gabelica i Microporous Materials 11 (1997) 237-245 239

Boro-titanosilicate samples

Samples (code)

Procedure B content in gel (atom196 T)

Ti content in gel (atom/96 T)

% crystallinity (time)

Silicalite TS-A TS-B TS-C

BS BTS-A BTS-B BTS-C BTS-D

BTS-E BTS-F

Synthesis I - 0.0 0.0 0 (14 days)


Synthesis I 100 0.0 4.0 >85 (10 days)

Synthesis I 100 0.0 2.0 >85 (10 days)

Synthesis I 4.0 0.0 100 (1 day)

Synthesis I - 4.0 4.0 34 ( 14 days)

Synthesis I 50 4.0 4.0 > 85 (10 days)


Synthesis 1 4.0 1.0 100 (3 dayas)

Synthesis II - 4.0 2.0 93 (10 days)

Synthesis III 4.0 2.0 74 (10 days) --

Gel composition: (96-x-y) SiO,~.xH,BO,-yTiCl,-25TPABr~300MeNH,-zHF-3500H~O.

9800 Philips analyzer coupled with SEM. X-ray powder diffraction patterns were recorded by a Philips P.W. 1349/30 diffractometer (Cu Ku radia- tion) using a-alumina as the internal standard. Crystallinities were also checked by n-hexane adsorption at 90°C using a Stanton Redcroft ST-780 thermobalance (simultaneous TG-DTA- DTG). FT-IR spectra were obtained using a Bio- Rad FTS-60A spectrometer with KBr pellets containing 1 wt.% sample. UV-visible spectra were recorded by a Shimadzu UV-3100PC spectrometer. “B-MAS-NMR spectra were recorded on a Bruker MSL-400 spectrometer. The chemical shifts were determined based on BF, . OEt,, used as an external reference. The detailed experimental conditions for “B-NMR have been described else- where [6,13]. XPS spectra were recorded on a JEOL JPS-90 apparatus using an Mg Kcl X-ray source. The binding energy of 133.3 eV for Si(2p) was selected as an internal reference. Chemical analysis of the products was carried out by induc- tively coupled plasma atomic emission spectroscopy (ICP) with a Shimadzu ICPS-I OOOOIV instrument.

3. Results and discussion

3.1. Crystallization of boro-titanosilicates in methylamine

Table 1 summarizes the synthesis conditions for a series of samples crystallized in the presence of

boron (BS type), titanium (TS type) and of both heteroatoms (BTS type).

The influence of titanium and boron amounts on the crystallization rates of boro-titanosilicates is shown in Fig. 1. All samples proved to be of MFI topology; other phases such as tit.anium dioxide (anatase) or other zeolitic structures were not detected by XRD.

In the case of the synthesis of titanosilicate TS-A (initial Ti content 4 Ti per 96 T atoms; T = Si + Ti + B), the reaction gel was still amorphous after 14 days heating. However, by the simultaneous addition of Ti to the borosilicate gel involving (4

-0 2 4 6 6 IO 12 14

Reaction time

(days)

Fig. 1. Crystallization curve of borosilicate, titanosilicate and boro-titanosilicates. Samples: (0) TS-A; (0) BTS-A; (~1) BTS-C; ( q ) BTS-D; (A) BS. For abbreviations, see Table 1.

240 M. Shibata, Z. Gabelica / Microporous Materials I1 (1997) 237-245

B/96 T) MFI crystals (34% crystallinity after 14 days heating) were obtained (BTS-A).

As the amount of initial titanium decreased from 4 Ti/96 T to 0 while the boron concentration was kept constant (4 B/96 T), the crystallization markedly accelerated and a shorter time was required to obtain highly crystalline products (compare samples BTS-A, BTS-C, BTS-D and BS, Table 1 and Fig. 1). These findings indicate that the presence of titanium in the initial gel impedes the MFI crystallization; conversely, the presence of boron in the system accelerated the crystallization of (B,Ti)-MFI.

Addition of hydrogen fluoride in the initial gel, which is known to improve the solubility of Si species, led to the rapid crystallization of titanosilicates and boro-titanosilicate; samples containing HF (TS-B, TS-C and BTS-B) attained more than 85% crystallinity after 10 days heating.

In the case of the synthesis of MFI-titanosilicates, aluminosilicates, zincosilicates and gallosilicates, preheating the silicate gel for a short time (less than 6 h) increased the crystallization rate [ 121. Indeed, it was demonstrated that the small amount of MFI silicalite crystallites generated within the preheated gel plays the role of seed crystals. Such a procedure, called the in situ seeding method was applied to the synthesis of boro- titanosilicate. In Synthesis II, the initial gel containing boron species was preheated before the addition of titanium tetrachloride. Conversely, in Synthesis III, the titanium-containing gel was preheated before adding boric acid. The preheated gel in Synthesis II thus contained a small amount of borosilicate crystallites (5% crystallinity estimated by the amount of n-hexane adsorption). When Ti was further added to this preheated gel, the B-MFI crystallites appeared to behave as in situ seeds and the crystallization rate of the boro-titanosilicate was increased (Table 1 and Fig. 2). In contrast, the preheated gel in Synthesis III was still amorphous, as confirmed by the n-hexane adsorption and SEM. As this preheated gel did not involve any MFI seeds, it was not surprising that the crystallization curve was similar to that of the corresponding boro-titanosilicate prepared by Synthesis I (Fig. 2).

All crystals synthesized in methylamine were

Reaction time (days)

Fig. 2. Crystallization of boro-titanosilicates synthesized by different methods. (0) Synthesis I (BTS-C); (0) Synthesis 11 (BTS-E); (A) Synthesis III (BTS-F). For abbreviations, see Table 1.

examined for their morphology by SEM and their homogeneous shape distribution, expected in such a case [ 111, was confirmed.

3.2. Characterization of boro-titanosilicates from synthesis I

The quantity and the structural state (coordination) of boron in the as-synthesized boio-titanosilicates were evaluated by “B-NMR. All samples showed only one narrow NMR line at -3.6 ppm which is currently assigned to the framework of tetrahedral BO, units. The peaks at 6 and - 2 ppm which correspond to trigonal boron and amorphous tetrahedral boron, respectively [6,7], were not detected. This confirms that most of the boron in the boro-titanosilicate crystals synthesized in the presence of methylamine was incorporated into the framework just like that in the borosilicates synthesized under the same conditions [S].

The amount of boron in the as-synthesized crystallites, calculated from the “B-NMR line intensities using the appropriate calibration curve [ 131, is shown in Table 2. Trong On et al. [6,7] reported that boro-titanosilicates synthesized in the presence of TPAOH and H,O,, contained almost the same amount of boron as the corresponding Ti-free borosilicates: these authors concluded that the quantity of titanium in the initial

Table 2

M. Shibata, 2. Gabelica / Microporous Materials 11 (1997) 237-245 241

Physicochemical characterization of boro-titanosilicates synthesized in the presence of methylamine

Initial quantity in gel (atom196 T) Bulk quantity in product (atom,/96 T) Surface quantity in product Unit cell (atom/96 T) Ti (EDX) volume (A3)

B Ti B Ti tota, Ti framework (“B-NMR) (ICP) ( XRD)

Silicalite 0 0 - -. - - 5339 TS-B 0 4 - 2.08 1.6 2.0 5368 TS-C 0 2 - 1.72 1.3 I .o 53621 BS 4 0 2.72 5283 BTS-A 4 4 1.62 - - 1.9 BTS-B 4 4 1.64 1.72 0.5 1.5 5314 BTS-C 4 2 1.78 1.85 0.4 1.8 5309 BTS-D 4 1 1.86 0.78 -0.1 I.0 5299 BTS-E 4 2 1.50 1.10 0.7 0.9 532’1 BTS-F 4 2 1.63 1.39 0.5 1.2 5315

gel did not affect the amount of framework boron under their synthesis conditions. In contrast, the boron content in the boro-titanosilicate prepared by the methylamine synthesis route varied with the initial quantity of titanium. The amount of boron in the borosilicate crystals (BS) was 2.72 B/96 T. It decreased to 1.86 B/96 T when titanium ions (1 Ti/96 T) were also added to the gel (BTS-D). Further increasing the titanium content (up to 4 Ti/96 T) led to a further slight decrease in the boron content (compare BS, BTS-D, BTS-C and BTS-A; Table 2). These findings support the assumption that methylamine forms complexes with both Ti and B species (and also solubilizes the Si species by stabilizing the pH to basic values), and suggests that the stabilities of these complexes are mutually affected. In other words, the presence of titanium ions in the system probably hinders to some extent the generation of the appropriate boron-methylamine complexes that would readily decompose and further undergo polycondensation along with the silica species during the MFI growth stage.

The IR spectra of samples BS, TS-C and BTS-C are given in Fig. 3 (A). All samples showed clear IR bands characteristic of MFI zeolites (455, 800 and 1000-1300 cm-’ characterizing the vibration of SiO, tetrahedra, and 555 cm-‘, which corres- ponds to the vibration of the five-membered rings of the pentasil structure). In addition to these bands, the borosilicate shows a weak shoulder at

920 cm-’ and a very weak band at 1380 cm- ‘. The IR band at 920 cm- ’ has been assigned to a tetrahedral framework boron and that at 1380 cm- ’ to a trigonal boron [ 141. Sample TS-C shows a neat band at 960 cm-’ which was not detected in the corresponding borosilicate. This band was attributed to an asymmetric stretching mode of SiO, entities bonded to Ti4+ ions in a tetrahedral zeolite site [ 151, and has been used as the fingerprint to characterize the presence of framework Ti in the MFI structure. The boro- titanosilicate BTS-C also exhibits the btand at 960 cm-’ which again confirms the presence of framework titanium. Together with the results of “B-NMR, which demonstrated the presence of framework boron, we were able to confirm that Ti and B simultaneously incorporate in th(e MFI framework. The intensity of the 960-cm- ’ band of BTS-C was weaker than that of the corresponding titanosilicate (TS-C), suggesting that the amount of framework Ti in the former was lower than in the latter.

The unit cell volumes as calculated from the XRD peaks and reported in Table 2. The incorporation of boron in the zeolite framework leads to a contraction of the unit cell because the atomic radius of boron is smaller than that of silicon ( 1.61 and 1.39 A for Si-0 and B-O distances, respectively). Indeed, the unit cell volume of borosilicates synthesized in methylamine varied linearly as a function of framework boron quantities deter-

242 M. Shibata, Z. Gabelica / Microporous Materials II (1997) 237-245

I I I I I I

1400 1200 loo0 800 600 400

Wave number (cm-l)

(4

I I I I I J 1400 1200 loo0 800 600 400

Wave number (uwl)

(b)

Fig. 3. (A) IR spectra of (a) titanosilicate TS-C, (b) boro-titanosilicate BTS-C and (c) borosihcate BS. (B) IR spec:tra of boro- titanosilicates synthesized by different methods. (a) Synthesis I (BTS-C); (b) Synthesis II (BTS-E); (c) Synthesis III (RTS-F).

mined by “B-NMR (filled circles in Fig. 4). The unit cell volume values of the boro-titanosilicates (open squares in Fig. 4) are slightly but definitely larger than those characterizing the borosilicates. This relative expansion of the unit cell volume is caused by the presence of Ti-0 bonds ( 1.79 8) longer than the Si-0 bonds. This constitutes an additional proof of the incorporation of titanium ions in the zeolite framework.

In the case of titanosilicates, the expansion coefficient of the unit cell volume as a function of framework Ti amount has been reported in the literature [ 16,171. We have evaluated the amount of framework Ti in boro-titanosilicates semiquanti- tatively on the basis of these empirical relationships (Table 2). The maximum quantity of the framework Ti in the boro-titanosilicates prepared from Synthesis I was 0.5 Ti/96 T (BTS-B) and this value is considerably lower than that found in the corre-

0 1 2 3

Boron quantity (atom I96 11

Fig. 4. Variation of the unit cell volumes as a function of B ,ctr,,hcd,al/96 T atoms. (0) Borosilicate samples (Ref. [8]); (0) boro-titanosilicate samples (this work).

M. Shibata, Z. Gabelica / Microporous Materials II (1997J 237-245 243

sponding titanosilicates: 1.6 Ti/96 T (TS-B). An no significant difference between the framework accurate quantitative measurement, for example Ti/extraframework Ti ratio on the surface and that by EXAFS, would be needed to determine the in the bulk (calculated from the results of the exact quantity of framework Ti. Our IR and XRD chemical analysis and the unit cell volume meas- result at least suggest that the existence of B ions urements). This suggests that the extraframework in the initial gel apparently inhibits the incorpora- Ti can exist uniformly in the boro-titanosilicate tion of Ti in the zeolite framework. crystals

In spite of the apparent difference in framework Ti quantities, the bulk Ti quantities determined by chemical analysis did not show a marked difference between the boro-titanosilicates and the titanosilicates that involve the same initial Ti amounts (compare samples TS-B and BTS-B; TS-C and BTS-C, Table 2). This suggests that a larger amount of extraframework Ti occurs in the boro- titanosilicates.

XPS, a potent tool for investigating the surface of a zeolite, was used to examine the state (coordination) of titanium on the surface of the obtained boro-titanosilicates using it. The Ti 2p,,, peak was separated into two sets of peaks (mixture of Lorentzian and Gaussian curves), centered at BE of 459.8 +0.2 and 458.3 +0.2 eV, respectively. The former separated peak has been assigned to framework Ti in tetrahedral or octahedral coordination. The latter has been attributed to an extraframework oxidic titanium phase [ 181. The ratio of framework titanium to extraframework Ti on the surface of products was calculated from the intensity of those two peaks.

UV-visible spectroscopy was also used to detect the Ti co-ordination on the surface of the zeolites [ 191. All titanosilicate and boro-titanosilicate samples listed in Table 2 showed a clear UV band at about 220 nm, corresponding to isolated framework titanium in tetrahedral coordination (Fig. 5). Along with this band, the BTS-C sample ex:hibited another band at 320 nm which was not present in the spectrum of the corresponeding titanosilicate (TS-C). This broad band currently characterizes Ti oxides involving octahedrally co-orclinated Ti4+ ions, such as anatase. Along with the XPS data, it is concluded that the addition of boron in the initial gel leads to the formation of the extraframework Ti-bearing by-products, such as anatase.

3.3. Characterization of boro-titanosilicates,from synthesis II and synthesis III

The existence of an IR band at 960 cm-- ’ (Fig. 3(B)) and an “B-NMR line at - 3.6 ppm

XPS data showed that most of the titanium on the surface of boro-titanosilicate samples exists as the extraframework titanium (Table 3). There is

Table 3 Ratio of framework titanium to extraframework titanium in ome MFI titano- and boro-titanosilicates

Bulk” Surfaceb

TS-B 3.3 3.0

TS-C 3.1 3.4

BTS-B 0.4 0.2

BTS-C 0.3 0.4

BTS-D (-0.1) 0.2

BTS-E 1.8 0.3

BTS-F 0.6 0.3

“Framework Ti/extraframework Ti ratio by ICP and XRD (unit

cell volume). bFramework Ti/extraframework Ti ratio by XPS.

J 200

I I I I 250 300 350 400

Wave length (nm)

Fig. 5. Diffuse-reflectance ultraviolet spectra of (a) BTS-C and

(b) TS-C.

244 A4. Shibata. Z. Gab&a / Microporous Materials 11 (1997) 237-245

indicates that both BTS-E and BTS-F involve framework boron and titanium. Spot-EDX measurements revealed that Ti was quite homogeneously distributed throughout the individual crystals.

The quantity of framework Ti of BTS-E, evaluated from the unit cell volume increase, was larger than that of BTS-C (Table 2), and the ratio of framework Ti to extraframework Ti was also far higher (Table 3). On the other hand, BTS-F involved almost the same amount of framework Ti as BTS-C, suggesting that preheating the titanosilicate gel before the addition of boron species did not seem to affect the B or Ti incorporation in the zeolite framework.

XPS data showed that, on the surface of BTS-E, the ratio of framework to extraframework titanium was far smaller than that in the crystallite bulk and the value was close to that found in BTS-C. One explanation for this may be as follows: at the beginning of the crystallization in Synthesis II, the Ti and B species may not have a mutual affect, and the titanium ions are preferably incorporated into the zeolite framework just as in the case of titanosilicate synthesis [9]. This probably occurs because in the in situ seeds consisting of a small amount of borosilicate crystallites or borosilicate oligomer, which are the precursors to MFI zeolites, were already present in the gel when TiCl, was added. During the hydrothermal treatment, these in situ seeds are consumed to form the B- or Ti-containing MFI zeolites, while unreacted Ti and B species may generate some intermediate phase which does not readily release the adequate titanium species for an easy framework incorporation. As a result, at the final stage of the crystallization (near the surface of the crystal), only a small amount of the Ti incorporates the framework, as in Synthesis I.

Further hypothese would be speculative if based only on these data. However, it is important to note that a preheating treatment like that in Synthesis II could cause variation in the metal quantity, and probably could lead to concentration gradients, providing a possibility to modify the catalytic performances of metallosilicates and bi-metallosilicates prepared by similar methods.

4. Conclusions

MFI type boro-titanosilicates (boron-titanium admixture) were synthesized in methylamine media without using costly TPAOH and Ti- and Si-alkoxides. The crystallization rate of the boro- titanosilicates was slightly improved with respect to that of titanosilicates.

“B-NMR, IR, XRD and UV-visible confirmed that Ti was readily incorporated into the framework of the obtained crystals along with boron and showed that both ions were homogeneously distributed throughout the crystallite. The amount of boron in the boro-titanosilicate decreased with respect to that of pure borosilicate. The titanium amount in the crystal also decreased along with the simultaneous incorporation of boron, and the side formation of some extraframework Ti species was observed.

The in situ seeding method which inc:reased the crystallization rate in the case of titanosilicate, zincosilicate and gallosilicate syntheses [ 121, was also applied to boro-titanosilicate synthesis. Preheating the borosilicate gel before the addition of the Ti species (Synthesis II) improved the crystallization rate and lowered the formation of extraframework Ti to some extent. Conversely, preheating the titanosilicate gel before the boron addition (Synthesis III ) affected neither the crystallization nor the Ti and B quantities in the resul- tant crystals.

References

[‘I

121

131

[41

151

161

[71

181

C.B. Khouw, H.X. Li. C.B. Dartt, M.E. Davis, ACS Symp. Ser. 523 (1993) 273. K.K. Lam Shang Leen, US Patent 4.623,526 and US

Patent 4519,998 (1985). L. Forni. M. Pelozzi, A. Giusti, G. Fornasari, R. Millini, J. Catal. 122 (1990) 44. A. Thangaraj, R. Kumar, P. Ratnasamy, Appl. Catal. 57 (1991) Ll.

A. Thangaraj, R. Kumar, S. Sivasanker, I’. Ratnasamy, Zeolites 12 (1992) 135. D. Trong On, M.P. Kapoor, L. Bonneviot. S. Kaliaguine, Z. Gabelica, Stud. Surf. Sci. Catal. 97 (1995) 535. D. Trong On, M.P. Kapoor, L. Bonneviot, S. Kaliaguine, Z. Gabelica, J. Chem. Sot. Faraday Trans. 92 (1996) 1031.

M. Shibdta and 2. Gabelica, Appl. Catal, in press.

M. Shibata, Z. Gabelica / Microporous Materials I1 f 1997) 237-245 245

[9] M. Shibita, Z. Gabelica, Zeolites, submitted

[lo] M. Shibita, Z. Gabelica, Microporous Mater., in preparation.

[ 111 Z. Gabelica, G. Giannetto, F.C. DOS Santos, R. Monque and R. Galiarso, R. von Ballmoos et al. (Eds.) Proceedings of the 9th International Zeolite Conference Montreal, 1993, pp. 231-238.

[12] Z. Gabelica, M. Shibata, M. Wiame, S. Valange, in preparation.

[ 131 Z. Gabelica. J.B. Nagy, G. Debras, Stud. Surf. Sci. Catal.

19 (1984) 113. [14] R. de Ruiter, A.P.M. Kentgens, J. Grootendorst, J.C.

Jansen, H. Van Bekkum, Zeolites 13 (1993) 128.

[ 151 M.R. Boccuti, K.M. Rao, A. Zecchina, G. Leofanti. G. Petrini, Stud. Surf. Sci. Catal. 48 ( 1989) 133.

[ 161 A. Cichocki, W. Lasocha, M. Michalik, Z. Sawlowicz, M.

Bus, Zeolites 10 (1990) 583. [17] G. Perego, G. Bellussi, C. Corno, M. Taramasso, F.

Buonomo, A. Esposito, Stud. Surf. Sci. Catal. 28 (1986) 129.

[IS] T. Blasco, M.A. Camblor, J.L.G. Fierro, J. Perez-Pariente,

Microporous Mater. 3 (1994) 259. [19] M.S. Rigutto, R. de Ruiter, J.P.M. Niederer. H. Von

Bekkum, Stud. Sur. Sci. Catal. 84 (1994) 2245.

Documents

Alkali-free synthesis of MFI type boro-titanosilicates using methylamine