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Mol Sieves (2007) 5: 365–478 DOI 10.1007/3829_006

Springer-Verlag Berlin Heidelberg 2006 Published online: 17 February 2006

Isomorphous Substitution in Zeolites

J. B.Nagy1 ( ) · R. Aiello2 · G. Giordano2 · A. Katovic2 · F. Testa2 · Z. Kónya3 · I. Kiricsi3

1Laboratoire de RMN, Facultes Universitaires Notre-Dame de la Paix, 61 rue de Bruxelles, 5000 Namur, Belgium

janos.bnagy@fundp.ac.be

2Department of Applied Chemistry, University of Calabria, Via Pietro Bucci, 87030 (CS) Arcavacata di Rende, Italy

3Department of Applied and Environmental Chemistry, University of Szeged, Rerrich Bela ter 1., 6720 Szeged, Hungary

1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

371

2

Experimental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

373

2.1

Synthesis Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

373

2.1.1

[B]-MFI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

373

2.1.2

[Ga]-MFI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

381

2.1.3

[Fe]-MFI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

381

2.1.4

[Fe]-BEA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

383

2.1.5

[Fe]-MOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

384

2.1.6

[Co]-MFI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

384

2.1.7

[Zn]-MFI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

385

2.1.8

Cu-TON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

385

2.2

Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

386

2.2.1

General Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . .

386

2.2.2

The Cu-TON Obtained by Ion Exchange . . . . . . . . . . . . . . . . . . .

387

3

Results and General Discussion . . . . . . . . . . . . . . . . . . . . . . . .

388

3.1

[B]-MFI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

388

3.2

[Ga]-MFI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

392

3.3Influence of Alkali Cations on the Incorporation of Al, B and Ga

 

Into the MFI Framework . . . . . . . . . . . . . . . . . . . . . . . . . . . .

398

3.4

[Fe]-MFI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

402

3.4.1

Fluoride Route . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

402

3.4.2

Alkaline Route . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

413

3.4.3

Catalysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

424

3.4.4

Role of the Catalyst Composition . . . . . . . . . . . . . . . . . . . . . . .

425

3.4.5

Role of Methodology in Iron Introduction in [Fe]-MFI Catalysts . . . . . .

428

3.5

[Fe]-BEA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

429

3.6

[Fe]-MOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

432

3.7

[Fe]-TON, [Fe]-MTW . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

433

3.8

[Fe,Al]-MCM-22 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

435

3.9

[Co]-MFI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

441

3.10

Calcination Using Ozone: Preservation of Framework Elements . . . . . .

446

3.11

Cu-TON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

453

3.12

[Zn]-MFI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

455

366

J. B.Nagy et al.

3.13Dealumination of Levyne –

 

Characterization of Framework and Extra-Framework Species . . . . . . .

460

4

Conclusions .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

466

References . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

467

Abbreviations1

 

 

1D NMR

One-dimensional nuclear magnetic resonance (spectroscopy)

 

2D 3QMAS NMR

Two-dimensional three quantum magic angle spinning nuclear

 

 

magnetic resonance (spectroscopy)

 

3QMAS NMR

Three quantum magic angle spinning nuclear magnetic resonance

A||

 

(spectroscopy)

 

 

Electron-nucleus coupling constant for the component parallel to

 

 

the symmetry axis

 

AAS

 

Atomic absorption spectroscopy

 

27Al MAS NMR

Aluminum magic angle spinning nuclear magnetic resonance

 

 

(spectroscopy)

 

AlO

 

Octahedrally coordinated framework aluminum atom

 

AlT

 

Tetrahedrally coordinated framework aluminum atom

 

AlPO4-11

Microporous aluminophosphate zeolite-like structure (cf. [70])

 

[Al]-ZSM-5

Zeolite structure (MFI, cf. [70]) containing aluminum in the

 

 

framework2

 

Amp

 

Peak-to-peak amplitude

 

AS

 

As synthesized

 

AST

 

Page 86 zeolite structure (cf. [70])

 

AV-1

 

Sodium yttrium silicate structure (cf. [156])

 

9Be NMR

Beryllium nuclear magnetic resonance (spectroscopy)

 

BET

 

Brunauer-Emmett-Teller specific surface measurement

 

BEA

 

Zeolite structure, acronym for zeolite Beta (cf. [70])

 

[B]-BEA

Zeolite structure (BEA, cf. [70]) containing boron in the framework

[B]-EUO

Zeolite structure (EUO, cf. [70]) containing boron in the framework

[B]-FER

Zeolite structure (FER, cf. [70]) containing boron in the framework

[B]-LEV

Zeolite structure (LEV, cf. [70]) containing boron in the framework

[B]-MEL

Zeolite structure (MEL, cf. [70]) containing boron in the framework

[B]-MFI

Zeolite structure (MFI, cf. [70]) containing boron in the framework

 

 

(cf. [181–183]; Testa F, Chiappetta R, Crea F, Aiello R, Fonseca A,

 

 

Bertrand JC, Demortier G, Guth JL, Delmotte L, B.Nagy J, submitted

 

 

for publication)

 

[B]-SSZ24

Zeolite structure (SSZ24, cf. [70]) containing boron in the frame-

 

 

work

 

1 Unfortunately, many of the above-indicated abbreviations have various meanings (vide supra); in view of the current conventions in the literature, this is hardly avoidable. However, the correct meaning of the abbreviations should follow from the respective context.

2 Presenting an element symbol in square brackets should indicate that the respective element is supposed to be incorporated into the framework of the material designated by the subsequent acronym or abbreviation. For instance, “[B]-ZSM-5” is indicating that boron is incorporated into the framework of ZSM-5.

Isomorphous Substitution in Zeolites

367

[B]-ZSM-5

Zeolite structure (MFI, cf. [70]) containing boron in the framework

BU

Chemical identity of the Fe(III) species

 

13C MAS NMR

Carbon magic angle spinning nuclear magnetic resonance (spec-

 

troscopy)

 

Cs-[Fe]-silicalite-1 Zeolite structure (cf. [70]) containing iron in the framework and

 

charge-compensating cesium ion in extra-framework position

Cs-[Fe]-ZSM-5

Zeolite structure (cf. [70]) containing iron in the framework and

 

charge-compensating cesium ion in extra-framework position

CIT-6

Zeolite structure (BEA structure, cf. [70])

[Co]-MFI

Zeolite structure (MFI, cf. [70]) containing Co in the framework

 

(cf. [196, 197])

Cu-TON

Zeolite structure (TON, cf. [70]) containing Cu in charge-compen-

 

sating extra-framework position (cf. [203])

CVD

Chemical vapor deposition

CCVD

Catalytic chemical vapor deposition

CQ

Quadrupole coupling constant

DAS

Dynamic angle spinning (spectroscopy)

deferrization

Removal of iron

DR

Diffuse reflectance (spectroscopy)

DSC

Differential scanning calorimetry

DTA

Differential thermal analysis

DTG

Differential thermogravimetry

EFW

Extra framework

EG

Ethylene glycol

EMT

Zeolite structure; hexagonal faujasite (cf. [70])

EPR

Electron paramagnetic resonance (spectroscopy) (acronym for

 

ESR)

EPMA

Electron probe micro-analysis

ESEM

Environmental scanning electron microscopy

ESCA

Electron spectroscopy for chemical analysis (acronym for XPS)

ESR

Electron spin resonance (spectroscopy) (acronym for EPR)

ETS-10

Zeolite structure (cf. [70])

EUO

Zeolite structure (cf. [70])

EXAFS

Extended X-ray absorption fine structure

FAAS

Flame atomic absorption spectroscopy

FAU

Zeolite structure; acronym for faujasite (cf. [70])

[Fe]-BEA

Zeolite structure (BEA, cf. [70]) containing iron in the framework

 

(cf. [194])

[Fe,Al]-BEA

Zeolite structure (BEA, cf. [70]) containing iron and aluminum in

 

the framework

[Fe,Al]-MOR

Zeolite structure (MOR, cf. [70]) containing iron and aluminum in

 

the framework

[Fe]-MCM-22

Zeolite structure (acronym or IZA structure code is MWW; cf. [70])

 

containing iron in the pore walls

[Fe,Al]-MCM-22

Zeolite structure (acronym or IZA structure code is MWW; cf. [70])

 

containing iron and aluminum in the pore walls

[Fe]-MCM-41

Mesoporous MCM-41 material containing iron in the pore walls

[Fe]-MFI

Zeolite structure (MFI, cf. [70]) containing iron in the framework

 

(cf. [185, 186])

368

J. B.Nagy et al.

[Fe]-MTW

Zeolite structure (MTW, cf. [70]) containing iron in the framework

 

(cf. [189])

[Fe]-TON

Zeolite structure (TON, cf. [70]) containing iron in the framework

 

(cf. [189])

FER

Zeolite structure; acronym for ferrierite (cf. [70])

FID

Flame ionization detector (GC)

FTIR

Fourier transform infrared (spectroscopy)

FW

Framework

FWHM

Full line width at half-maximum (of a band)

g

g factor

g||

g factor for the component parallel to the symmetry axis

g

g factor for the component perpendicular to the symmetry axis

71Ga NMR

Ga nuclear magnetic resonance (spectroscopy)

[Ga]-BEA

Zeolite with Beta (BEA) structure containing gallium in the frame-

 

work, (cf. [146])

[Ga]-MCM-22

Zeolite structure (acronym or IZA structure code is MWW; cf. [70])

 

containing boron in the pore walls

[Ga]-MFI

Zeolite with MFI structure containing gallium in the framework,

 

(cf. [183, 184])

[Ga]-ZSM-5

Zeolite with MFI structure containing gallium in the framework,

 

(cf. [183, 184])

GC

Gas chromatography

H

Magnetic field (in Tesla)

1H MAS NMR

Proton magic angle spinning nuclear magnetic resonance (spec-

 

troscopy)

HMI

Hexamethylene imine

HT

High temperature

I

Intensity

Irel

Relative intensity

ICP-AES

Inductively coupled plasma atomic emission spectroscopy

IR

Infrared (spectroscopy)

IS

Isomer shift (Mössbauer spectroscopy)

K-[Fe]-silicalite-1

Zeolite structure (cf. [70]) containing iron in the framework and

 

charge-compensating potassium ion in extra-framework position

L

Length

L

Liter

L/W

Aspect ratio

LEV

Zeolite structure (acronym of levyne; cf. [70])

LT

Low temperature

LTL

Linde-type L zeolite (cf. [70])

M

Metal or metal cation

MAS NMR

Magic angle spinning nuclear magnetic resonance (spectroscopy)

MFI

Zeolite structure (of, e.g., ZSM-5 or silicalite, cf. [70])

MCM-22

Zeolite structure (acronym or IZA structure code is MWW; cf. [70])

MCM-41

Mesoporous material with hexagonal arrangement of the uniform

 

mesopores (cf. Volume 1, Chapter 4 of this series)

MCM-48

Mesoporous material with cubic arrangement of the uniform meso-

 

pores (cf. Volume 1, Chapter 4 of this series)

MCM-58

Zeolite structure (acronym or IZA structure code is IFR, cf. [70])

MEL

Zeolite structure (cf. [70])

Isomorphous Substitution in Zeolites

369

MeQ+

Methyl quinuclidinium cation

 

MOR

Zeolite structure; acronym for mordenite (cf. [70])

 

MQMAS

Multiquantum magic angle spinning (NMR)

 

MTT

Zeolite structure (cf. [70])

 

MTW

Zeolite structure (cf. [70])

 

Na-[Fe]-silicalite-1 Zeolite structure (cf. [70]) containing iron in the framework and

 

charge-compensating sodium ion in extra-framework position

NCL-1

High-silica (nSi/nAl = 20 to infinity) zeolite (cf. [70])

NH4 -[Fe]-silicalite-1

Zeolite structure (cf. [70]) containing iron in the framework and

 

charge-compensating ammonium ion in extra-framework position

NMR

Nuclear magnetic resonance

Oh

Octahedrally coordinated species

OFF

Zeolite structure, acronym for offretite (cf. [70])

PIGE

Proton induced γ -ray emission

PIXE

Proton induced X-ray emission

PQ

Quadrupole-quadrupole interaction

PTFE

Polytetrafluorethylene

PULSAR

NMR simulation program (cf. [284])

Qcc

Quadrupole coupling constant

QS

Quadrupole shift (Mössbauer spectroscopy)

R

Crystallization rate

REDOR

Rotational-echo double-resonance NMR experiments (cf. [87])

RI

Spectral contribution (Mössbauer spectroscopy)

SAM

Scanning Auger microscopy

SEM

Scanning electron microscopy

29Si MAS NMR

Silicon magic angle spinning nuclear magnetic resonance (spec-

 

troscopy)

Si(1Ga)

Si with 1 Ga in the neighborhood

Sil-1

Zeolite structure (acronym of SIL-1, cf. [70])

Silicalite-1

Zeolite structure (cf. [70])

119Sn NMR

Tin nuclear magnetic resonance (spectroscopy)

SiOM

Defect group (M = NH4, Na, K, Cs)

SiOTPA

Defect group

SiOX

Defect group (X =NH4, Na, K, Cs, H, TPA, . . .)

SOD

Zeolite structure, acronym for sodalite (cf. [70])

SSIMS

Static secondary ion mass spectroscopy

SSR

Solid-state reaction

SSZ-n

Series of zeolite structures; aluminosilicates, e.g., SSZ-24 and SSZ-

 

13, isostructural with corresponding aluminophosphates, AlPO4

 

(AFI) and AlPO4-34 (CHA structure) (cf. [70])

T

Tetrahedrally coordinated framework atom (cation) such as Si, Al,

 

Ti, Fe, V, B

T

Absolute temperature, in Kelvin (K)

TIII

Tetrahedrally coordinated trivalent framework atom (cation) such

 

as Al, B, Ga

Th

Tetrahedrally coordinated species

t1

Longitudinal relaxation time

tind

Reaction induction time

tpulse

Pulse length

TA

Thermal analysis

370

 

 

J. B.Nagy et al.

TCD

Thermal conductivity detector (GC)

 

 

TEAOH

Tetraethylammonium hydroxide

 

 

TEOS

Tetraethyl orthosilicate

 

 

TEM

Transmission electron microscopy

 

 

TG

Thermogravimetry

 

 

TMA

Tetramethyl ammonium

 

 

TON

Zeolite structure; acronym for theta-1 (cf. [70])

 

TPA

Tetrapropyl ammonium

 

 

TPABr

Tetrapropyl ammonium bromide

 

 

TPD

Temperature-programmed desorption

 

 

TPR

Temperature-programmed reduction

 

 

TS-1

ZSM-5 (MFI) structure containing small amounts of titanium be-

 

sides silicon in the framework

 

 

TsG-1

Zeolite structure (BEA, cf. [70])

 

 

VS-1

Zeolite structure (MFI, cf. [70]) containing vanadium besides sili-

 

con in the framework

 

 

W

Width

 

 

UV

Ultraviolet (spectroscopy)

 

 

UV Res Raman

Ultraviolet resonance Raman (spectroscopy)

 

 

UV-Vis

Ultraviolet-visible (spectroscopy)

 

nSi/nAl ≤ 2.5,

X

Zeolite structure (faujasite type structure

with

 

cf. [70])

 

 

XANES

X-ray absorption near edge spectroscopy

 

 

XRD

X-ray diffraction

 

 

XRF

X-ray fluorescence spectroscopy

 

 

XPS

X-ray photoelectron spectroscopy

 

nSi/nAl ≥ 2.5,

Y

Zeolite structure (faujasite-type structure

with

 

cf. [70])

 

 

YAG

Yttrium aluminum garnet (laser)

 

 

[Zn]-MFI

Zeolite structure (MFI, cf. [70]) containing Zn in the framework

 

(cf. [198–200])

 

 

ZSM-5

Zeolite structure (MFI, cf. [70])

 

 

ZSM-12

Zeolite structure (cf. [70])

 

 

α

Indicates the large cage in the structure of zeolite A (cf. [70])

α

The main channel of ZSM-5 zeolite

 

 

β

Indicates the sodalite cage in, e.g., A-type or faujasite-type struc-

 

ture (cf. [70])

 

 

β

Mid positions in the six-membered rings of ZSM-5 zeolite

γ

Mid positions in the five-membered rings of ZSM-5 zeolite

δ

Chemical shift (NMR)

 

 

δCS

Chemical shift (NMR)

 

 

2Θ

Degree

 

 

Θ

Pulse angle

 

 

λ

Wavelength (in µm)

 

 

ν

Resonance frequency

 

 

H

Full line width at half-maximum (of a band)

 

 

νL

Larmor frequency

 

 

νQ

Quadrupole frequency

 

 

νrot

Rotation frequency

 

 

νRF

Radio frequency

 

 

Isomorphous Substitution in Zeolites

371

1 Introduction

The isomorphous substitution of Si by other tetrahedrally coordinated heteroatoms such as BIII [1, 2], AlIII (ZSM-5) [3], TiIV(TS-1) [4–9], GaIII [10–14] and FeIII [15–18] in small amounts (up to 2–3 wt %) provides with new ma-

terials showing specific catalytic properties in oxidation and hydroxylation reactions related to the coordination state of the heteroatom [19]. Moreover, MFI-type materials with trivalent metal present in tetrahedral (T) sites have had tremendous impact as new shape-selective industrial catalysts hav-

ing tunable acidic strength. In fact, the acidic strength of the protons in the bridged Si(OH)TIII (T = B, Al, Fe, Ga) groups depends on the nature of the

trivalent heteroatom. Indeed, the choice of TIII critically affects this property according to the sequence of Al > Fe = Ga B [20–23]. The recent discovery of an Al-containing natural zeolite (mutinaite) with the MFI topology [24] also makes this structure relevant to the mineralogy.

[Ga]-ZSM-5 zeolites are interesting materials as selective catalysts in the transformation of low molecular weight alkanes to aromatics [25–27]. These catalysts were mostly synthesized in alkaline media, however, several fluorine-containing media (adding either HF or NH4F to the initial gel) have already been used [28, 29]. Note that the incorporation of gallium into the ZSM-5 structure is less effective than the incorporation of aluminum in the same reaction media [30]. The fluorine-containing reaction medium is generally made using either HF or NH4F as a source of Fions [28, 29, 31]. Guth et al. have published a series of very interesting papers in which TIII elements (T = B, Al, Fe, Ga) were partially substituted for silicon in the MFI framework [32]. We have previously initiated a series of studies where the role of alkali cations was systematically explored. These studies include the synthesis of silicalite-1 [33–35], silicalite-2 [36], borosilicalite-1 [37, 38], ferrisilicalite-1 [39], ZSM-5 [40] and zeolite Beta [40, 41]. The differences in the catalytic activity of iron-containing and iron-supported zeolites are also very interesting, and several methods of preparation have been developed [42–44]. [Fe]-silicates with MFI [45, 46], MOR [47], BEA [48], MTT [49], TON [50] and MWW [51] structures have been synthesized in alkaline media. However, despite the fact that isomorphous substitution seems to be easier in fluoride-containing media [52], only [Fe]-ZSM-5 has been synthesized so far in the presence of NH4F as a mineralizing agent [53]. Although the introduction of boron, gallium, or iron is relatively easy and well documented [19], few studies are devoted to the introduction of Co(II) into the framework of zeolites [54]. As both the framework and the extra-framework Co-species seem to be active in catalysis [55], it is of paramount importance to synthesize and thoroughly characterize Co-containing zeolites [56]. Zinc has been reported as a component of various molecular sieves such as zincophosphates, zincoarsenates [57–60], zincoalumino-silicates [61–63],

372

J. B.Nagy et al.

zincosilicates [64–68], and zincoaluminonophosphates [19]. In some cases crystalline analogs of zeolite structures have been obtained under unusually mild conditions and crystallization occurred almost spontaneously on mixing the substrate solutions [57] or even on grinding the substrates [69]. The resulting zincophosphates and zincoarsenates, however, were unstable and usually decomposed above 200 C. The reported zincosilicates were more stable, although most novel structures showed a narrow pore system [54, 64– 68], not suitable for catalysis and adsorption. The MFI structure (zeolites ZSM-5) [70] has been very often used as a catalyst. Besides the efficiency of active sites (mainly strong acid sites), the medium-sized channels provide shape selective effects for the reactions of commercial importance. Therefore, the preparation of the zincosilicalite structure is also of interest. Due to the double negative charge of the tetrahedral lattice zinc, it could be modified with various cations including protons and might be considered as catalysts for various reactions. Moreover, some redox activity could result from the presence of zinc in the lattice. The zinc-modified MFI zeolites have been applied as active catalysts in the Cyclar process [62, 63, 71], which consists in the formation of aromatics from light paraffins. The catalysts used in methanol synthesis contain mostly zinc and copper oxides [72]; it is conceivable that MFI zincosilicate modified with copper cations could be efficient for this reaction. The well-ordered crystalline structure as well as the uniform pore system could be advantageous for the catalyst performance. Attempts to synthesize MFI aluminosilicate with some admixture of zinc [62, 73–75] as well as zincosilicate [68, 76] have been reported.

Due to environmental problems in the last years great attention has been devoted to air pollution. The automotive air pollutants (NOX , CO and hydrocarbons) give large contribution to the total air pollutants. In order to reduce emission of pollutants, the trend in the automotive industry is to substitute traditional engines with engines operating under lean burn conditions. However, under these conditions the traditional three-way catalysts are not effective. With this new kind of engines, interesting results were obtained by using Cuor Co-zeolite catalysts at the engine exhaust [77–79]. Unfortunately, one of the most active and selective catalysts (i.e., [Cu]-MFI-type), exhibits very rapid deactivation in the presence of water that is, of course, present in the automotive exhaust [80]. In a large number of papers on Cu zeolites, the introduction of Cu is carried out by ionic exchange from the Na form to obtain the Cu form. On the other hand, literature indicates that the solid-state reaction is a very good method for metal incorporation into the zeolites [81–83]. It is also indicated that during the zeolite synthesis with alcohols, the presence of sodium can occlude the zeolitic channels [84] and that the ionic exchange to the ammonium form followed by calcination opens the zeolitic channels. As an example the Na+-TON presents a micropore vol-

ume equal to 0.05 ml g–1, on the contrary the H+-TON shows a value equal to

0.91 ml g–1.

Isomorphous Substitution in Zeolites

373

Isomorphous substitution was essentially performed with the MFI structure. Table 1 gives an overview of additional references to be used for entering into the subject. It can be seen that boron, gallium, vanadium and iron are the most commonly used elements. It is worthwhile to mention that the introduction of other elements such as Ti, In, Be, Mn, Sn, Cr, Mo, Ge and Zn, was also successful.

The second most studied zeolite for isomorphous substitution is the zeolite BEA [70] (Table 2). However, the number of publications remains far smaller than that dealing with ZSM-5. The most studied elements are still B, Ga, and Fe, but some reports also concern Zn, Sn, Ge and Ti.

Finally, Table 3 illustrates the isomorphous substitution of various elements into the remaining zeolitic structures.

In this review we shall focus on our works published on [B]-MFI, [Ga]- MFI, [Fe]-MFI, [Fe]-BEA, [Fe]-MCM-22, Zn-zeolite, and Cu-containing zeolites. Essentially, the various synthesis methods together with characterization techniques will be reviewed. The catalytic part will only be included, where it is considered essential.

2 Experimental

2.1

Synthesis Procedures

2.1.1 [B]-MFI

The gels were prepared by dissolving H3BO3 (Carlo Erba) in distilled water, adding the fluoride source (NH4F, NaF, KF Carlo Erba; CsF, Aldrich) and tetrapropylammonium bromide, Fluka (TPABr) to the H3BO3 aqueous solution and then adding this solution to fumed silica (Serva) [181–183] (Testa F, Chiappetta R, Crea F, Aiello R, Fonseca A, Bertrand JC, Demortier G, Guth JL, Delmotte L, B.Nagy J, submitted for publication). The composition of the as-prepared gels was 9MF – xH3BO3 – 10SiO2 – 1.25TPABr – 330H2O with M = NH4, Na, K and Cs and x = 0.1 and 10. Syntheses were carried out in Morey-type PTFE-lined 20 cm3 autoclaves at 170 ± 2 C, without stirring, under autogenous pressure. After being heated for various times required by the crystallization kinetics, the autoclaves were quenched in tap water, and the products were filtered, washed with distilled water until pH = 7 and dried overnight at 105 C.

Table 1 Isomorphous substitution of MFI zeolites

Zeolite

Substituting

Synthesis

Si/T or

Techniques of

Precursors

 

 

 

Refs.

 

element

 

T content

characterization

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

MFI

B

Theoretical Study

 

 

 

 

 

[85]

MFI

B

Hydrothermal

 

Gas diffusion and permeance

 

 

 

 

 

 

[86]

membrane

 

 

 

11B NMR, REDOR

 

 

 

 

 

 

 

MFI

B

Hydrothermal

 

B(OH)

, Na

B

O

7

[87]

MFI

B

Hydrothermal

30–80

FTIR, TPD, C2H4 reaction

 

3

2

4

 

 

H3BO3

 

 

 

 

[88]

MFI

B

Hydrothermal

24

Catalysis

 

 

 

 

 

 

[89]

MFI

B

Hydrothermal

95

IR of OH groups, acidity IR

H3BO3

 

 

 

 

[90–92]

MFI

B

Hydrothermal

 

Catalysis

 

 

 

 

 

 

[93]

MFI

B

Theoretical study

 

B-siting

 

 

 

 

 

 

[94]

MFI

B

Hydrothermal

1–2 B/u.c.

XRD, 11B NMR, SEM, Sorption

H BO

3

 

 

 

 

[95]

 

 

 

 

 

3

 

 

 

 

 

MFI

B

Hydrothermal

25

TA, XPS, Catalysis

H3BO3

 

 

 

 

[96]

MFI

B

Hydrothermal

0.6, 1.3, 2.1/u.c.

11B NMR, IR

H BO

3

 

 

 

 

[97]

 

 

 

 

11B NMR, XRD, SEM, FTIR,

3

 

 

 

 

 

MFI

B

Hydrothermal

0.1–0.5 wt % B

H BO

3

 

 

 

 

[98]

 

 

 

 

XPS, TPD, SAM

3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

MFI

B

Hydrothermal

2.5/u.c.

FTIR, XRD, 1H-, 11B-, 29Si NMR

H BO

3

 

 

 

 

[99]

 

 

 

 

 

3

 

 

 

 

 

MFI

B

Hydrothermal

6

XRD, MAS NMR, TA

H3BO3

 

 

 

 

[100]

MFI

B

Hydrothermal

 

XRD

 

 

 

 

 

 

[101]

MFI

B

Hydrothermal

0.40 wt %

Acidity, n-butene, isomerization

H3BO3

 

 

 

 

[102]

MFI

B

Hydrothermal

37

TPD, C3H8 oxidation

H3BO3

 

 

 

 

[103]

MFI

Fe-Mo-B

Hydrothermal

4.6 wt % Mo 1.41

C6H6 + N2O = C6H5 OH

BET, TPD

 

 

 

[104]

 

 

CVD

wt% Fe 0.15 wt % B

 

 

 

 

 

 

 

 

MFI

B,Al

Hydrothermal

0.40 wt %

Acidity, n-butene, isomerization

H3BO3

 

 

 

 

[102]

MFI

Al

Hydrothermal

14–42 14–23; 45 9.25

27Al NMR, FTIR

 

 

 

 

 

 

[105]

MFI

Ga

Theoretical Study

 

 

 

 

 

 

 

 

[85]

MFI

Ga

Hydrothermal

 

Gas diffusion and permeance

 

 

 

 

 

 

[86]

membrane

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

374

.al et Nagy.B .J