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Microporous and Mesoporous Materials 97 (2006) 78–87

Influence of NaOH and KOH on the synthesis of MCM-22and MCM-49 zeolites

Danilo Vuono a, Luigi Pasqua a, Flaviano Testa a,*, Rosario Aiello a, Antonio Fonseca b,Tamas I. Koranyi c, Janos B. Nagy b

a Dipartimento di Ingegneria Chimica e dei Materiali, Universita della Calabria, Via Pietro Bucci-Cubo 44A, Rende (CS), I-87036, Italyb Laboratoire de RMN, Departement de Chimie, Facultes Universitaires Notre-Dame de la Paix, Namur, B-5000, Belgium

c Department of Molecular Spectroscopy, Institute of Structural Chemistry, Chemical Research Center of the Hungarian Academy of Sciences,

Budapest, Hungary

Received 2 February 2006; received in revised form 17 July 2006; accepted 19 July 2006Available online 22 September 2006

Abstract

MCM-22 or MCM-49 zeolites were directly prepared using NaOH or KOH as mineralizing agents. The initial batch composition was30SiO2–vAl(OH)3–xNaOH(or xKOH)–yHMI–zH2O, with v = 1, 1.5, 2, 3; x = 2.7, 5.4, 9, 10.5, 12, 15, 18; y = 10.6, 15; z = 1050, 1200,1350; HMI = hexamethyleneimine. The products were obtained by hydrothermal synthesis at 150 �C in stirring conditions. For HMI/Naratio greater than 2 MCM-22(P) is formed, while for a lower HMI/Na ratio MCM-49 is formed. In presence of K+ ions only MCM-22(P) could be obtained. In addition, the Al content of the MCM-22(P) samples is much lower (ca. 10 mol%) than those obtained withNa+ ions (ca. 20 mol%).

The MCM-22(P) zeolites prepared in presence of Na+ ions are formed much faster than those prepared in presence of K+ ions. Theformation of MCM-22(P) is more difficult with increasing Al-content in the gel.

The 27Al NMR spectra show two lines at 55.5 ppm and 49.9 ppm. Both are due to framework tetrahedral species. No extraframeworkoctahedral species were detected in any of the samples. The 29Si NMR spectra could be decomposed using eight crystallographically dif-ferent sites.� 2006 Elsevier Inc. All rights reserved.

Keywords: MCM-22(P); MCM-49; Synthesis; Characterization; Alkaline ions

1. Introduction

MCM-22 zeolite was first synthesized by Mobil research-ers using hexamethyleneimine as organic template [1,2].MCM-22 presents, after calcination, a particular hexagonalstructure containing two different independent pore systemsboth accessible through 10-membered rings [3,4]. The firstconsists of two-dimensional, sinusoidal, 10-membered ringchannels and the second is composed of large supercagescharacterized by 12-ring apertures of 710 pm inner freediameter and an inner height of 1820 pm. The sinusoidal

1387-1811/$ - see front matter � 2006 Elsevier Inc. All rights reserved.

doi:10.1016/j.micromeso.2006.07.015

* Corresponding author. Tel.: +39 0984496690; fax: +39 0984496655.E-mail address: f.testa@unical.it (F. Testa).

channels form an interlayer porous network, while thesupercages are located between the layers linked togetherby oxygen bridges.

In 1993, Bennet et al. synthesized a new material namedMCM-49, with the same framework topology as calcinedMCM-22 [5]. MCM-22 precursor is obtained when themole ratio of hexamethyleneimine (HMI) to inorganic cat-ions in the reaction mixture is higher than 2, while MCM-49 is synthesized for a molar ratio smaller than 2 [4]. It isthe first example for a zeolite which can be obtained eitherin a precursor form or directly in its calcined form [4]. Fol-lowing Ref. [4] the aluminium enrichment of the T1–O1–T1

bridge in MCM-49 is responsible for the small differencesbetween the two zeolites.

D. Vuono et al. / Microporous and Mesoporous Materials 97 (2006) 78–87 79

The unusual porous network of MCM-22 stemmingfrom the characteristics which are between large-pore andmedium-pore zeolites, makes it very interesting for diffu-sion and catalytic applications [6–11].

In the original patents [1,2,5], as well as in most of thepublications [4,7,12–17] stirring or rotation is recom-mended during hydrothermal treatment to obtain highlycrystalline materials of MCM-22 or MCM-49. However,quite recently, MCM-22 could also be obtained in staticconditions [18–20]. The synthesis of Fe- and [Fe,Al]-MCM-22 were also reported [21] as well as the synthesisof MCM-22 in basic media in presence of fluoride salts [22].

In this paper, a systematic study to obtain pure MCM-22 or MCM-49 crystals in a wide range of synthetic param-eters using stirring conditions is reported. The role of K+

ions will be particularly emphasized. The results will becompared with previous studies trying to delimitate thecrystallization fields of these zeolites [23,24]. The finalproducts are characterized by X-ray diffraction (XRD),thermal analysis, scanning electron microscopy (SEM),13C-, 27Al-, and 29Si NMR (nuclear magnetic resonance)spectroscopy.

2. Experimental

2.1. Synthesis

In the first part of the study gels of the following com-positions were prepared [16]:

30SiO2–2Al(OH)3–xNaOH–yHMI–zH2O, where x = 5.4and y = 10.6 or 15 and z = 1350; x = 9.0 and y = 10.6 or 15and z = 1200 or 1050, respectively.

First Al(OH)3 (Pfaltz & Bauer; 99%) and NaOH (CarloErba; 98%) are dissolved in distilled water. The solution isstirred during 5 min. Then SiO2 fumed (Sigma; 99.9%) andHMI (Aldrich; 99%) are added under continuous stirring.In order to well homogenize the gel, the mixture is stirredfor 10 more minutes. Parts of the gel are then introducedin PTFE-lined 25 cm3 stainless-steel autoclaves. The prod-ucts are obtained by hydrothermal synthesis at 150 �C instirring conditions (ca. 30 cycle/min). After prefixed vari-ous times (2–7 days), the autoclaves are quenched in tapwater. The products are recovered, filtered, washed withdistilled water and finally dried at 100–101 �C for 10 h.

In the subsequent experiments the amount of NaOHwas varied:

30SiO2–2Al(OH)3–xNaOH–15HMI–1350H2O with x =2.7, 5.4, 9.0, 10.5, 12, 15 and 18.

In other experiments both the amount of NaOH andAl(OH)3 were varied:

30SiO2–yAl(OH)3–xNaOH–15HMI–1350H2O with x =5.4 and 12 and y = 1, 1.5, 2 and 3.

Finally, the influence of KOH was also examined:30SiO2–2Al(OH)3–xKOH–15HMI–1350H2O with x =

2.7, 5.4, 9, 12, 15 and 18.The influence of both the amount of Al and that of

KOH were examined on the systems:

30SiO2–yAl(OH)3–xKOH–15HMI–1350H2O with x =9, 12 and 15 and y = 1, 1.5, 2 and 3.

2.2. Characterization

The powder X-ray diffraction patterns were collectedbetween 5� and 40� 2h using CuKa radiation (Philips modelPW 1730/10 equipped with a PW 1050/70 verticalgoniometer).

The amounts of aluminium, sodium and potassium inthe crystals were determined by atomic absorption spectro-photometry (Shimadzu AA-660). The amount of HMIoccluded in the crystals was measured by thermogravimet-ric analysis. The DSC curves allowed one to study thebehavior of HMI in the sample. The measurements werecarried out with a Netzsch STA 409 instrument between20 �C and 850 �C at a heating rate of 10 �C/min in dryair flow of 10 cm3/min.

The scanning electron micrographs (SEM) were col-lected on a Jeol JSTM 330A.

The NMR spectra were recorded either on a Bruker MSL400, or Avance 500 spectrometer. For 29Si (79.4 MHz), a6 ls (H = p/6) pulse was used with a repetition time of6.0 s. For 27Al (130.3 MHz), a 1 ls (H = p/12) pulse wasused with a repetition time of 0.1 s. For 13C (100.6 MHz),a 15 ls (H = p/2) pulse was used with proton high powerdecoupling and 6.0 s repetition time.

3. Results and discussion

3.1. Zeolites prepared in presence of sodium ions

The first results obtained following the recipe of Ref.[16] are reported in Table 1. The gel compositions are30SiO2–yAl(OH)3–xNaOH–15HMI–1350H2O with x =2.7, 4, 5.4, 9, 10.5 and 12 and y = 1, 1.5, 2 and 3 (Table1, panels b and c). Fig. 1 presents a typical XRD patternof MCM-22(P) and MCM-49 phases. The initial pHi isalways close to 13.5 for x = 5.4 and 13.8 for x = 12. ThepH value decreases by one unit during the synthesis ofMCM-22(P) or MCM-49. In Table 1 the relative quantitiesare expressed in mol% per 100 g of products and the valueswere multiplied by 100. As it can be seen in Table 1, MCM-22(P) is obtained for the molar ratio HMI/Na higher than2 (x = 5.4), while MCM-49 is the final product when thisratio is smaller than 2 (x = 12 and y = 2 or 3). Note, thatno crystalline zeolite could be obtained with a low Al con-tent, when y = 1.

The Na and Al contents are always higher in the MCM-49 samples. This is also true for the water content, while theHMI content is smaller than in the precursor layer com-pound MCM-22(P).

The DTG and DSC curves are reported in Figs. 2 and 3.At temperatures, ca. 70 �C and 400 �C, the samples areloosing their water content. Note that the peak at 300 �Cis absent in most of the MCM-49 samples, except forthe one obtained with 9NaOH and 2Al(OH)3 (Table 1,

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Fig. 2. DTG (a) and DSC (b) curves of the MCM-22(P) and MCM-49samples synthesized from gels of composition 30SiO2–2Al(OH)3–xNaOH–15HMI–1350H2O x = 2.7 (1), 4 (2), 5.4 (3), 9 (4), 10.5 (5) and 12 (6) at150 �C.

Table 1Results of chemical analysis and thermal gravimetry (TG)

x Product Na(mol%)a

Al(mol%)a

H2O(mol%)a

HMI(mol%)a

Panel (a)

2.7 MCM-22(P) 10 20 8.9 17.94 MCM-22(P) 12 20 14.0 22.35.4 MCM-22(P) 14 22 15.4 24.39 MCM-49 16 25 15.5 15.7

10.5 MCM-49 16 26 13.7 18.312 MCM-49 16 27 18.1 18.7

y

Panel (b)

1.5 MCM-22(P) 15 25 4.7 212 MCM-49 16 26 18 193 MCM-49 18 27 20 14

Panel (c)

1.5 MCM-22(P) 11 20 12.3 232 MCM-22(P) 14 22 15.6 233 MCM-22(P) 15 25 7.0 22

Panel (a): Products obtained from gels of composition 30SiO2–2Al(OH)3–xNaOH–15HMI–1350H2O at 150 �C.Panel (b): Products obtained from gels of composition 30SiO2–yAl(OH)3–12NaOH–15HMI–1350H2O at 150 �C.Panel (c): Products obtained from gels of composition 30SiO2–yAl(OH)3–5.4NaOH–15HMI–1350H2O at 150 �C.

a The quantities are expressed in moles per 100 g of products and thevalues are multiplied by 100.

10 20 30 40

b

a

XRD

(a.u

.)

2θ (Degrees)

a) MCM-22(P)b) MCM-49

Fig. 1. Typical XRD patterns of MCM-22(P) and MCM-49 phases.

80 D. Vuono et al. / Microporous and Mesoporous Materials 97 (2006) 78–87

panel a, row 4). The DSC curves are characterized by threeexothermal peaks for MCM-22(P) and two peaks forMCM-49 zeolite samples. The relative amounts corres-ponding to the different peaks together with the DSC peaksmaxima are reported in Table 2.

Peak A corresponds to the decomposition of HMI mol-ecules in the interlayer region in the MCM-22(P), whilepeaks B and C correspond to HMI molecules in the super-cages [4]. Note however, that low temperature shouldersalso exist in the MCM-49 samples (Fig. 3b and Table 2,

panel b). This interpretation is not completely acceptedand either the presence of strongly held amines or that ofcoke is evoked in the contribution of peak A [25]. Note,that the amount of HMI decomposed in peaks B and Care quite similar in both MCM-22(P) and MCM-49 zeolitesamples.

Fig. 4 shows the SEM micrographs of some MCM-22(P)and MCM-49 samples. At low alkalinity (Fig. 4a) MCM-22(P) zeolite is obtained, the crystals are spheroidal andtheir dimensions vary between 8 and 10 lm. The morphol-ogy of MCM-49 is completely different (Fig. 4b), it showsfibrous crystals with ca. 3–4 lm diameter. The same fibrousmorphology is obtained for MCM-22(P) if they are synthe-sized at the same alkalinity (Fig. 4c). The MCM-49 crystalssynthesized at an intermediate alkalinity (x = 9 moles)show both toroidal and fibrous crystals (Fig. 4d). It seemsthat the amount of Na+ cations essentially governs thecrystal morphology.

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Fig. 3. DTG curves (a) and DSC curves (b) of the MCM-22(P) and MCM-49 samples synthesized from gels of composition 30SiO2–yAl(OH)3–12NaOH–15HMI–1350H2O y = 1.5 (1), 2 (2) and 3 (3) at 150 �C. DTG curves (c) and DSC curves (d) of the MCM-22(P) samples synthesized from gels ofcomposition 30SiO2–yAl(OH)3–5.4NaOH–15HMI–1350H2O y = 1.5 (1), 2 (2) and 3 (3) at 150 �C.

D. Vuono et al. / Microporous and Mesoporous Materials 97 (2006) 78–87 81

The crystallization curves are reported in Fig. 5 whileTable 3 illustrates the induction time (in h) and the crystal-lization rate (in % h�1). The induction time corresponds tothe appearance of ca. 4% crystallinity.

It can be seen that the induction times are longer (threeor five times more), while the crystallization rates are smal-ler for MCM-22(P) than for MCM-49. Both the inductiontime and the crystallization rate decrease as a function ofincreasing alkalinity for MCM-22(P) (Table 3, panel a).For MCM-49 the induction time does not depend on thealkalinity, while the crystallization rate increases as a func-tion of increasing alkalinity (Table 3, panel a).

The data have also been analyzed using the equationproposed by Zhdanov et al. [26]:

ZðtÞ ¼ ktn

where Z(t) is the crystallinity as a function of time, n isthe reaction order and k is the kinetic constant. It can beseen (Table 3 panel a) that the reaction order n decreaseswith increasing alkalinity for the MCM-22(P) formation,while the kinetic constant increases. The high reactionorder means that few nuclei are formed in these systems.

In addition, the crystallization rate is also very small. Theformation of MCM-49 is much faster. The reaction orderslightly increases with increasing alkalinity, while thekinetic constant decreases (Table 3, panel a).

The kinetic curves for the systems at high (x = 12) andintermediate (x = 5.4) alkalinity as a function of Al(OH)3

content are also reported in Fig. 6 and the kinetic parame-ters are given in Table 3, panels b and c. The induction timesare small and are the same and do not depend on the type ofzeolite formed at high alkalinity (Table 3, panel b). Thecrystallization rate is higher for y = 2 moles. At an interme-diate alkalinity (x = 5.4) the induction times are greaterwhile the crystallization rates are smaller (Table 3, panelc) than at higher alkalinity. One has to underline that a highalkalinity is needed for the formation of MCM-49. Indeed,in these conditions, a higher amount of aluminium speciescan be dissolved in the liquid phase which carries the build-ing units to the nuclei or crystallites in formation. The reac-tion orders are greater while the crystallization constants k

are smaller at lower alkalinities (Table 3, panels b and c).The present work covers a field that is complementary to

those reported in Refs. [23,24]. Indeed, those results have

Table 2Relative amounts (mol%) of HMI and DSC peak maxima in �C

x Product Peak A Peak B Peak C

Panel (a)

2.7 MCM-22(P) 322 (4.5) 471 (6.8) 558 (6.6)4 MCM-22(P) 330 (7.7) 447 (7.4) 569 (7.2)5.4 MCM-22(P) 318 (7.5) 446 (8.6) 601 (8.2)9 MCM-49 471 (8.2) 584 (7.5)

10.5 MCM-49 399 (9.5) 573 (8.8)12 MCM-49 413 (9.8) 581 (8.9)

y

Panel (b)

1.5 MCM-22(P) 355 (3) 445 (10) 591 (8)2 MCM-49 358 (1) 413 (9) 581 (9)3 MCM-49 321 (1) 375 (6) 569 (7)

Panel (c)

1.5 MCM-22(P) 332 (8) 454 (8) 570 (7)2 MCM-22(P) 318 (7) 446 (8) 601 (8)3 MCM-22(P) 328 (3) 407 (10) 575 (9)

Panel (a): Products obtained from gels of composition 30SiO2–2Al(OH)3–xNaOH–15HMI–1350H2O at 150 �C.Panel (b): Products obtained from gels of composition 30SiO2–yAl(OH)3–12NaOH–15HMI–1350H2O at 150 �C.Panel (c): Products obtained from gels of composition 30SiO2–yAl(OH)3–5.4NaOH–15HMI–1350H2O at 150 �C.

82 D. Vuono et al. / Microporous and Mesoporous Materials 97 (2006) 78–87

been obtained in static conditions oppositely to ours thatstem from stirring conditions. In addition, the Al contentin our condition is higher (Si/Al varies between 10 and20) compared to Ref. [23] (Si/Al = 30 and 50) and toRef. [24] (Si/Al = 30!1). In Ref. [23], the ratio HMI/Na was always close to 2 and both MCM-22 and MCM-49 have been obtained. Interestingly, the amount of HMIoccluded in the MCM-22 increases with increasing Al con-tent. For very high Si/Al ratios kenyaite cocrystallizes withMCM-22 or only kenyaite was obtained [24].

Fig. 4. SEM micrographs of the MCM-22(P) and MCM-49 samples obtained frMCM-22(P), x = 2.7 y = 1.5, (b) MCM-49, x = 12 y = 2, (c) MCM-22(P), x =

3.2. Zeolites prepared in presence of potassium ions

The crystallization field of MCM-22(P) was also lookedfor in presence of potassium ions. The gels had the follow-ing compositions:

30SiO2–yAl(OH)3–xKOH–15HMI–1350H2O with x =2.7, 5.4, 9, 12, 15 and 18 and y = 1, 1.5, 2 and 3. The initialpHi was ca. 13.5 and the final pHf decreased to ca. 12.5when crystalline zeolitic phases were found. If y = 1 or1.5 moles, only amorphous phases were recovered after 7days at 150 �C in stirring conditions. The system remainedalso amorphous for x = 12 and y = 3. For x = 18 andy = 2, and x = 15 and y = 3, ferrierite was obtained ascrystalline phase. In all of the other cases crystallineMCM-22(P) zeolite phases could be isolated. The chemi-cal and thermogravimetric analyses data are reported inTable 4.

It can be seen that both the Al-content and the K-con-tent increases with increasing alkalinity for y = 2 moles.The relative amount of water also increases with increasingAl-content of the samples (Table 4). The amount of HMIvaries between 16.9 and 18.7 for MCM-22(P) samplesobtained with y = 2 moles. Note that the HMI content isrelatively low in the sample obtained with x = 9 andy = 3 moles. Note also that no MCM-49 zeolite could beobtained in any of the synthesis conditions reported in thisstudy, oppositely to the behavior of Na+ ions.

The DTG and DSC curves are illustrated in Fig. 7. Wecan see from Table 5 and Fig. 7 that the TG, DTG andDSC values are similar to those obtained in the presenceof Na+ ions.

The morphology of the as-made crystals is also simi-lar to that obtained in the presence of sodium (Fig. 8).At low alkalinities the crystals are spheroidal and the aver-age dimension is ca. 10 lm (Fig. 8a). At high alkalinities

om gels of composition 30SiO2–yAl(OH)3–xNaOH–15HMI–1350H2O. (a)12 y = 1.5, (d) MCM-49, x = 9 y = 2 at 150 �C.

Table 3Kinetic parameters, induction time (in h), crystallization rate (R in % h�1),reaction order (n) and kinetic constant (k) determined from the Zhdanovequation [26]: Z(t) = ktn

x Product Inductiontime (h)

R

(% h�1)Reactionorder (n)

Kineticconstant (k)

Panel (a)

2.7 MCM-22(P) 126 3.7 27 1.3 · 10�19

4 MCM-22(P) 72 2.6 9 3.9 · 10�9

5.4 MCM-22(P) 74 1.4 16 3.4 · 10�8

9 MCM-49 24 4 6 4.610.5 MCM-49 26 5.3 7.5 2.112 MCM-49 26 6.1 8 0.5

y

Panel (b)

1.5 MCM-22(P) 26 4.6 4.6 52 MCM-49 26 6.1 8 0.53 MCM-49 26 3.9 5.4 3.2

Panel (c)

1.5 MCM-22(P) 76 3.8 12.9 1.8 · 10�6

2 MCM-22(P) 74 1.4 10.5 4 · 10�5

3 MCM-22(P) 74 3.0 16.3 1.6 · 10�8

Panel (a): Products obtained from gels of composition 30SiO2–2Al(OH)3–xNaOH–15HMI–1350H2O at 150 �C.Panel (b): Products obtained from gels of composition 30SiO2–yAl(OH)3–12NaOH–15HMI–1350H2O at 150 �C.Panel (c): Products obtained from gels of composition 30SiO2–yAl(OH)3–5.4NaOH–15HMI–1350H2O at 150 �C.

0.0 0.7 1.4 2.1 2.8 3.5 4.2 4.9 5.6 6.3 7.0 7.70

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def

Fig. 5. Crystallization curves of MCM-22(P) (a–c) and MCM-49 (d–f)obtained from gels of composition 30SiO2–2Al(OH)3–xNaOH–15HMI–1350H2O. (a) x = 2.7, (b) x = 4, (c) x = 5.4, (d) x = 9, (e) x = 10.5, (f)x = 12 at 150 �C.

D. Vuono et al. / Microporous and Mesoporous Materials 97 (2006) 78–87 83

spherical agglomerates of small crystallites are obtained,the dimension of which is ca. 50 lm (Fig. 8b).

The crystallization curves are reported in Fig. 9 and thecorresponding kinetic parameters are given in Table 6. Theinduction times are decreasing with increasing KOH con-tent in the gel, while the crystallization rate does not varyvery much. Note that the reaction order n passes througha minimum while the value of the kinetic constant passesthrough a maximum for x = 9 and y = 2 (Table 6). Notethat the induction time is much longer in presence of K+

than in presence of Na+ ions. In addition, only MCM-22(P) is formed as a pure phase.

3.3. 13C, 27Al and 29Si MAS NMR characterization

As the structure of MCM-22(P) is not known andMCM-49 is synthesized directly from the reaction gel, bothmaterials are expected to contain some HMI in their struc-ture. Therefore the 13C CP/MAS NMR spectra may revealthe pore systems of these zeolites. The spectra of materials

obtained from different NaOH containing gels (Table 1,panel a) are shown in Fig. 10. In accordance with our pre-vious work [22] and the literature [4,16,27] three lines areobserved: the NMR lines of C2 and C3 carbons of HMIoverlap at 27 ppm, while the resonance of C1 carbonresolves to two bands at 49 and 57 ppm. The relative inten-sities of the line areas at 27, 49, and 57 ppm are 4:1:0.7 and4:1.4:0.5 in the MCM-22(P) and MCM-49 spectra, respec-tively, close to those published in the literature [27]. Thetwo C1 lines of HMI and their different relative intensitiesin MCM-22(P) and MCM-49 confirm the different channelsystems, the distinct environments within these two materi-als. The CP spectra show a decrease in relative intensity(MCM-22(P)) or even disappearance (MCM-49) of thepeak at 57 ppm compared to the other two 13C CP/MASNMR resonances.

The 27Al MAS NMR spectra of MCM-22(P) andMCM-49 (Fig. 11) are quite unique from the point of view,that they consist in more than one tetrahedral (Td) reso-nances at 55.5 and 49.9 ppm. The 27Al NMR line at55.5 ppm shows clearly that the aluminium atoms occupyframework tetrahedral sites in all as-synthesized samples(Fig. 11). No octahedral extraframework aluminium wasdetected in any of the samples (all of them were studiedby 27Al NMR, only six of them are shown in Fig. 11).The NMR line at 55.5 ppm always shows a shoulder at49.9 ppm. Double rotation (DOR) NMR experiments[4,27] confirmed, that the irregular shape of the Al signal donot originate from quadrupolar effects, but from distinct

0.0 0.7 1.4 2.1 2.8 3.5 4.2 4.9 5.6 6.3 7.00

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Fig. 6. Crystallization curves of MCM-22(P) (a,d,e, f) and MCM-49 (b,c)obtained from gels of composition 30SiO2–yAl(OH)3–xNaOH–15HMI–1350H2O. x = 12 for (a) y = 1.5, (b) y = 2, (c) y = 3; and x = 5.4 for (d)y = 1.5, (e) y = 2, (f) y = 3 at 150 �C.

Table 4Results of chemical analysis and thermal gravimetry

x y K (mol%) Al (mol%) H2O (mol%) HMI (mol%)

2.7 2 2 10 7.0 17.95.4 2 3 12 9.2 18.59 2 3 12 11.6 18.4

12 2 4 15 19.7 16.915 2 6 15 20.5 18.79 3 4 14 14.3 14.5

MCM-22(P) zeolites synthesized from gels of composition 30SiO2–yAl(OH)3–xKOH–15HMI–350H2O at 150 �C.

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Temperature (°C)

Fig. 7. DTG curves (a) and DSC curves (b) of the MCM-22(P) samplessynthesized from gels of composition 30SiO2–yAl(OH)3–xNaOH–15HMI–1350H2O. y = 2 for (1) x = 2.7; (2) x = 5.4; (3) x = 9; (4)x = 12; (5) x = 15 and y = 3 for (6) x = 3 at 150 �C.

Table 5Relative amounts (mol%) of HMI and DSC peaks maxima in �C forMCM-22(P) zeolites synthesized from gels of composition 30SiO2–yAl(OH)3–xKOH–15HMI–1350H2O at 150 �C

x y Peak A Peak B Peak C

2.7 2 353 (6) 446 (6) 574 (5.9)5.4 2 357 (5) 430 (7) 592 (6.5)9 2 370 (4.5) 461 (7) 563 (6.9)

12 2 352 (1.9) 421 (7.6) 592 (7.4)15 2 353 (2) 454 (8.4) 598 (8.3)9 3 335 (2.1) 477 (7.1) 574 (5.3)

84 D. Vuono et al. / Microporous and Mesoporous Materials 97 (2006) 78–87

tetrahedral Al species. Lawton et al. [4,27] assigned thelower resonance to T6 and T7, the higher resonance toT1, T3, T4, T5, and T8 Al sites, which corresponds to a lineintensity ratio of 40:60, what is also confirmed in our spec-tra (Fig. 11).

The 29Si (CP/)MAS NMR spectra of these materials arequite complex. We have found seven different lines in the

spectra of MCM-22(P) in our previous work [22] and alsoin the recent work. These spectra are similar to those syn-thesized in alkaline media [28] or to a silica polymorph(ITQ-1) [29]. From XRD data two space groups were pro-posed for the structure of MCM-22 [3]: the energeti-cally favored orthorhombic Cmmm structure over the

Fig. 8. SEM micrographs of the MCM-22(P) samples obtained from gels of composition 30SiO2–2Al(OH)3–xKOH–15HMI–1350H2O. (a) x = 2.7, (b)x = 15 at 150 �C.

0 1 2 3 4 5 6 7 8 9 100

20

40

60

80

100

Cry

stal

linit

y (%

)

Time (Days)

abc

0 1 2 3 4 5 6 7 8 9 100

20

40

60

80

100

Cry

stal

linit

y (%

)

Time (Days)

def

Fig. 9. Crystallization curves of MCM-22(P) samples obtained from gelsof composition 30SiO2–yAl(OH)3–xKOH–15HMI–1350H2O with y = 2and (a) x = 2.7; (b) x = 5.4; (c) x = 9; (d) x = 12; (e) x = 15 and y = 3 and(f) x = 9 at 150 �C.

Table 6Kinetic parameters, induction time (in h), crystallization rate (R in % h�1),reaction order (n) and kinetic constant (k) determined from Z(t) = ktn [26]

x y Inductiontime (h)

R

(% h�1)Reactionorder (n)

Kineticconstant (k)

2.7 2 125 3.2 20 3.6 · 10�14

5.4 2 110 5.0 11.5 1.2 · 10�7

9 2 103 3.8 9.7 4.8 · 10�6

12 2 101 3.0 11.7 1.2 · 10�7

15 2 125 5.5 22.5 3.0 · 10�17

9 3 98 3.6 13 9.5 · 10�8

MCM-22(P) zeolites synthesized from gels of composition 30SiO2–yAl(OH)3–xKOH–15HMI–1350H2O at 150 �C.

51015202530354045505560657075(ppm)

MCM-22(P)

MCM-22(P)

MCM-22(P)

MCM-49

MCM-49 e

d

c

b

a

Fig. 10. 13C NMR spectra of MCM-22(P) and MCM-49 samplesobtained from gels of composition 30SiO2–2Al(OH)3–xNaOH–15HMI–1350H2O with x = 2.7 (a), 4 (b), 5.4 (c), 9 (d), and 10.5 (e) at 150 �C.

D. Vuono et al. / Microporous and Mesoporous Materials 97 (2006) 78–87 85

hexagonal P6/mmm structure. Decomposition of the 29SiNMR spectra has been carried out based on the assump-tion that aluminium atoms are randomly distributed onthe crystallographic sites [21]. The results of decompositionon MCM-22(P) agreed quite well with the hexagonal modelproposing eight T sites in our previous work [22]. Our

recent spectra (Fig. 12) cannot be decomposed in orderto fit perfectly with any of the two models (Table 7). Theoccupancy of T2, T3, T6, T7, and T8 sites is 3 comparedto 1 of T1, T4, and T5 sites in the hexagonal model. This fitsroughly with the decomposition of the spectrum of MCM-22(P) except that the relative intensity of T2 site is 4 insteadof 3 (Table 7). However, this high intensity suggests, thatthis line contains also the contribution of defect groups.It should also be taken into account that for perfect fittingonly Si(0Al) bands were regarded in highly siliceous

Table 7Assignment of high power decoupled 29Si MAS NMR spectra of MCM-22(P) and MCM-49 zeolites shown in Fig. 11

MCM-22(P) MCM-49

d (ppm) Int.(%)

Int.(rel.)

Site d(ppm)

Int.(%)

Int.(rel.)

Site

�103.9 20 (4) T2 �104.1 29 (7) T2�109.9 15 3 T3 �110.9 16 (4) T3�113.0 12 3 T8 �113.5 7 2 T8�115.6 13 3 T7 �115.8 11 3 T7�119.1 12 3 T6 �119.7 11 3 T6�106.8 4 1 T1 �106.6 2 0.5 T1�109.0 5 1 T5 �108.8 7 2 T5�110.4 5 1 T4 �110.8 5 1 T4�94.8 8 Q2 (defect) �95.0 3 Q2 (defect)�99.9 7 Q3 (defect) �99.0 8 Q3 (defect)

Chemical shifts (d (ppm)), line intensities (Int. (%)), relative intensities(Int. (rel.)) and crystallographic Si sites (Site).

102030405060708090(ppm)

MCM-22(P)

MCM-22(P)

MCM-22(P)

MCM-49

MCM-49

MCM-49 f

e

d

c

b

a

Fig. 11. 27Al NMR spectra of MCM-22(P) and MCM-49 samplesobtained from gels of composition 30SiO2–2Al(OH)3–xNaOH–15HMI–1350H2O with x = 2.7 (a), 4 (b), 5.4 (c), 9 (d), 10.5 (e), and 12 (f) at 150 �C.

(ppm)-124-116-108-100-92-84

MCM -22(P)

Q2Q3

T1

T2

T3

T4T5

T6

T7T8

(ppm)

-124-116 -108 -100 -92 -84

MCM-49

Q2

Q3

T2

T1

T3T5

T4T8

T7T6

Fig. 12. Typical 29Si NMR spectra of MCM-22(P) and MCM-49 samplesobtained from gels of composition 30SiO2–2Al(OH)3–xNaOH–15HMI–1350H2O with x = 4 (a), and 12 (b) at 150 �C.

86 D. Vuono et al. / Microporous and Mesoporous Materials 97 (2006) 78–87

samples [22,27]. The aluminium content of our samplesranges from 10 to 27 mol% (Tables 1 and 4). In this case

the contribution from at least the Si(1Al) sites should beinvolved, in accordance with the literatures [23,24]. Ken-nedy et al. [27] found a perfect fit with the orthorhombicform of a completely siliceous MCM-22, but the intensityof a peak assigned to non-framework silica was excluded.Cheng et al. [24] even claimed that the presence of alumin-ium is critical for the formation of MCM-22. Contrary tothis we find a more difficult MCM-22(P) formation withincreasing Al-content in the gels (Table 3 panel b and c).The CP spectra do not show big intensity changes com-pared to the normal 29Si MAS NMR spectra except someslight increase in intensity of the line at �104 ppm com-pared to the resonances at �113, and �116 ppm. It con-firms our suggestion, that the former band may containsome SiOH impurities, or the interaction of the templateprotons with the sites responsible for these bands cannotbe ruled out [23]. It is impossible to determine accuratelythe framework Si/Al ratio of these zeolites by 29Si NMR[30]. Note that MCM-49 contains a much higher amountof defect groups at �104.1 ppm as the intensity of this lineis much higher than the other lines.

4. Conclusions

It is well known that the alkali cations behave as struc-turing ions favoring the formation of certain zeolitic struc-tures [31,32]. This is particularly important for zeolites oflow Si/Al ratio [33]. For high silica zeolites, the presenceof sodium is essential for the formation of ZSM-5 [34].Indeed, in absence of tetrapropylammonium cations, Li+

is unable to favour the formation of zeolite ZSM-5, whileK+ ions can lead to the formation of ZSM-5, but only ina very narrow K/Si range [33].

Lawton et al. [4] have shown that the inorganic cations(sodium, potassium, rubidium) are influencing the forma-tion of either MCM-22(P) for a HMI/M ratio greaterthan 2, while for a lower HMI/M ratio MCM-49 is formed.Using the reagents mentioned in this study, in presence ofK+ ions only MCM-22(P) could be obtained. In addition,

D. Vuono et al. / Microporous and Mesoporous Materials 97 (2006) 78–87 87

the Al content of the MCM-22(P) samples is much lower(ca. 10 mol%) than those obtained with Na+ ions (ca.20 mol%).

It is interesting to note that the TG and DSC data ofMCM-22(P) synthesized in presence of large amounts ofK+ ions are similar to those of MCM-49 synthesized in pres-ence of large amounts of Na+ ions (Tables 2, panel b and 5).

The MCM-22(P) zeolites prepared in presence of Na+

ions are formed much faster than those prepared in pres-ence of K+ ions (Tables 3, panel a and 6). The formationof MCM-22(P) is more difficult with increasing Al-contentin gels (Table 3, panels b and c). These results confirm theparticular structuring role of Na+ ions to favor the incor-poration of aluminium in the zeolitic structure.

Acknowledgements

The authors thank the Belgian Programme on InterUniversity Poles of Attraction (OSTC-PAI-IUAP No.5/1). T.I.K. thanks the fellowship of F.N.R.S.

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