Synthesis and characterization of recent zeolites with unusual pore architectures [Elektronische Ressource] / vorgelegt von Supak Tontisirin

Supak

Informations

• Publié par: technische_universitat_kaiserslautern
• Publié le: 01 janvier 2010
• Nombre de lectures: 33
• Langue: Deutsch
• Poids de l'ouvrage: 8 Mo

Extrait

Synthesis and Characterization of Recent Zeolites
with Unusual Pore Architectures

Dissertation

eingereicht am Fachbereich Chemie der Technischen Universität Kaiserslautern
zur Verleihung des akademischen Grades “Doktor der Naturwissenschaften”
D 386





vorgelegt von

M.Sc. Supak Tontisirin

geboren in Rayong (Thailand)




Betreuer

Prof. Dr.-Ing. Stefan Ernst





Kaiserslautern, 2010












































Die vorliegende Arbeit entstand zwischen August 2003 und März 2007 im Fachbereich
Chemie, Fachrichtung Technische Chemie, der Technischen Universität Kaiserslautern.






















Prüfungskommission:

Vorsitzender: Prof. Dr. Werner Thiel
1. Berichterstatter: Prof. Dr.-Ing. Stefan Ernst
2. Berichterstatter: Prof. Dr. Helmut Sitzmann

Tag der mündlichen Prüfung: 13.07.2010

































Eidesstattliche Erklärung

Hiermit versichere ich, dass ich die vorliegende Arbeit eigenständig verfasst und keine
anderen als die angegebenen Quellen und Hilfsmittel verwendet, sowie Literaturzitate
kenntlich gemacht habe. Kooperationsprojekte sind ausdrücklich als solche gekennzeichnet.
Ich erkläre außerdem, dass diese Arbeit weder in gleicher noch in ähnlicher Form bereits in
einem anderen Prüfungsverfahren vorgelegen hat.


Kaiserslautern, den_______________ _______________
Supak Tontisirin





Acknowledgements
I wish to express my most sincere appreciation to my advisor, Prof. Dr.-Ing. Stefan Ernst, for
giving me the opportunity to do an academic research work in his group and the valuable
discussions throughout the academic years. I would like to thank Prof. Dr. Martin Hartmann
for his valuable discussions and guidance in the first two and a half years of my research. I
would like to thank Prof. Dr. Helmut Sitzmann for providing the special template for
synthesizing of zeolite UTD-1. Moreover, I would like to thank the other member of my
committee, Prof. Dr. Werner Thiel, for his time and interest.
Carlos López Monllor, Manuel Florian Seibel, Sawa Nordt, Xiao Juan Tang, Elena Bogdan
and Carola Filß are thanked for their great contribution to my work via their diploma theses
and “Forschungarbeiten”. I would like to thank all the lab colleagues, Silke Sauerbeck,
Matthias Oberlinger, Helwig Thiel, Thomas Hecht, Stefan Ost, Carsten Streb, Sridhar Adapa,
Alex Wagener, Markus Schindler and other colleagues for all discussions about small and big
problems through my promotion time. In addition, I would like to acknowledge Ludvig
1 13Napast for his time of guidance in performing H- and C-NMR measurements and Heike
Schramm for her kind administrative assistance.
Finally I would like to thank my family and my husband, Sitt Tontisirin. Without their
encouragement and support, this work would not have been carried out.








Summary
The main focus of this dissertation is the synthesis and characterization of more recent
zeolites with different pore architectures. The unique shape-selective properties of the
zeolites are important in various chemical processes and the new zeolites containing novel
internal pore architectures are of high interest, since they could lead to further improvement
of existing processes or open the way to new applications.
This dissertation is organized in the following way: The first part is focused on the synthesis
of selected recent zeolites with different pore architectures and their modification to the
acidic and bifunctional forms. The second part comprises the characterization of the
physicochemical properties of the prepared zeolites by selected physicochemical methods,
viz. powder X-ray diffractometry (XRD), N adsorption, thermogravimetric analysis 2
(TGA/DTA/MS), ultraviolet-visible (UV-Vis) spectroscopy, atomic absorption spectroscopy
27 29(AAS), infrared (IR) spectroscopy, scanning electron microscopy (SEM), Al and Si magic
angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, temperature-
programmed reduction (TPR), temperature-programmed desorption of pyridine (pyridine
TPD) and adsorption experiments with hydrocarbon adsorptives. The third part of this work
is devoted to the application of test reactions, i.e., the acid catalyzed disproportionation of
ethylbenzene and the bifunctional hydroconversion of n-decane, to characterize the pore size
and architecture of the prepared zeolites. They are known to be valuable tools for exploring
the pore structure of zeolites. Finally, an additional test, viz. the competitive hydrogenation of
1-hexene and 2,4,4-trimethyl-1-pentene, has been applied to probe the location of noble
metals in medium pore zeolite.

The synthesis of the following zeolite molecular sieves was successfully performed in the
frame of this thesis (they are ranked according to the largest window size in the respective
structure):
• 14-MR pores: UTD-1, CIT-5, SSZ-53 and IM-12
• 12-MR pores: ITQ-21 and MCM-68
• 10-MR pores: SSZ-35 and MCM-71
All of them were obtained as pure phase (except zeolite MCM-71 with a minor impurity
phase that is hardly to avoid and also present in samples shown in the patent literature). The
synthesis conditions are very critical with respect to the formation of the zeolite with a given
structure. In this work, the recommended synthesis recipes are included. Among the 14-MR
zeolites, the aluminosilicates UTD-1 (n /n = 28), CIT-5 (n /n = 116) and SSZ-53 (n /n Si Al Si Al Si Al
= 55) with unidimensional extra-large pore opening formed from 14-MR rings exhibit
promising catalytic properties with high thermal stability and they possess strong Brønsted-
acid sites. By contrast, the germanosilicate IM-12 with a structure containing 14-MR
channels intersecting with 12-MR channels is unstable toward moisture. It was found that
UTD-1 and SSZ-53 zeolites are highly active catalysts for the acid catalyzed
disproportionation of ethylbenzene and n-decane hydroconversion due to their high Brønsted
acidity. To explore their pore structures, the applied two test reactions suggest that UTD-1,
CIT-5 and SSZ-53 zeolites contain a very open pore system (12-MR or larger pore systems)
because the product distributions are not hampered by too small pores.
ITQ-21, a germanoaluminosilicate zeolite with a three-dimensional pore system and large
spherical cages accessible through six 12-MR windows, can be synthesized with n /n ratios Si Al
between 27 and >200. It possesses a large amount of Brønsted-acid sites. The aluminosilicate
zeolite MCM-68 (n /n = 9) is an extremely active catalyst in the disproportionation of Si Al
ethylbenzene and in the n-decane hydroconversion. This is due to the presence of a high
density of strong Brønsted-acid sites in its structure. The disproportionation of ethylbenzene
suggests that MCM-68 is a large pore (i.e., at least 12-MR) zeolite, in agreement with its
crystallographic structure. In the hydroconversion of n-decane, the presence of tribranched
and ethylbranched isomers and a high isopentane yield of 58 % in the hydrocracked products
suggest the presence of large (12-MR) pores in its structure. By contrast, a relatively high
*value for CI (modified constraint index) of 2.9 suggests the presence of medium (10-MR)
pores in its structure. As a whole, the results are in-line with the crystallographic structure of
MCM-68.
SSZ-35, a 10-MR zeolite, can be synthesized in a broad range of n /n ratios between 11 and Si Al
>500. This zeolite is interesting in terms of shape selectivity resulting from its unusual pore
system having unidimensional channels alternating between 10-MR windows and large 18-
MR cages. This thermally very stable zeolite contains both, strong Brønsted- and strong
Lewis-acid sites. The disproportionation of ethylbenzene classifies SSZ-35 as a large pore
zeolite. In the hydroconversion of n-decane, the suppression of bulky ethyloctanes and
propylheptane clearly suggests the presence of 10-MR sections in the pore system. By
*contrast, the low CI values of 1.2-2.3 and the high isopentane yields of 56-60 % in the
hydrocracked products suggest that SSZ-35 also possesses larger intracystalline voids, i.e.,
the 18-MR cages. The results from the catalytic characterization are in good agreement with
the crystallographic structure of zeolite SSZ-35. It was also found that the n /n ratio Si Al
influences the crystal