TECHNISCHE UNIVERSITT MNCHEN
Department Chemie
Lehrstuhl fr Technische Chemie II
Selective Methane Oxidation on Zeolite
Stabilized Copper Oxide Clusters
Sebastian Grundner
Vollstndiger Abdruck der von der Fakultt fr Chemie der Technischen Universitt
Mnchen zur Erlangung des akademischen Grades eines
Doktors der Naturwissenschaften (Dr. rer. nat.)
genehmigten Dissertation.
Vorsitzender: Univ.-Prof. Dr. K.-O. Hinrichsen
Prfer der Dissertation: 1. Univ.-Prof. Dr. J. A. Lercher
2. Univ.-Prof. Dr. K. Khler
3. Prof. M. Tromp, Ph.D. (Univ. Amsterdam,
Niederlande)
Die Dissertation wurde am 21.12.2015 bei der Technischen Universitt Mnchen
eingereicht und durch die Fakultt fr Chemie am 26.01.2016 angenommen.
Dedicated to Lei
The most exciting phrase to hear in science, the one that heralds new discoveries, is
not 'Eureka!' but 'That's funny...'
Isaac Asimov
Statutory Declaration
I declare that I have authored this thesis independently, that I have not used
other than the declared sources/resources, and that I have explicitly marked all
material which has been quoted either literally or by content from the used
sources. At the end of each chapter all collaborators are listed and their specific
contribution is addressed. Published content of this thesis is clearly marked at
the beginning of each chapter and reused according to the terms of the
publisher. The content and structure of Chapter 2 and 3 vary significantly from
the corresponding publications. Chapter 4 is not publication-based. Therefore,
this thesis is not cumulative.
,
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Acknowledgements
After more than four years, I am finally submitting my thesis. With a feeling of
relief I remember all the people who supported me in one way or another. It
was a difficult time, but nevertheless interesting with a steep learning curve.
First, I want to thank my supervisor Prof. Johannes Lercher. The scientific
discussions with you showed me the way. With your deep knowledge of
science and your sharp intellect, you taught me how to do good science,
revealed misleading hypotheses as such and brought me back on the right
track. Thank you for your trust and your guidance!
I am very grateful to Dr. Maricruz Sanchez-Sanchez for supervising me. With
your scientific knowledge, your excellent writing skills and your polite way of
communication you have a major contribution to this thesis. Thank you for
revising my thesis and manuscripts in such an accurate and efficient way.
Special thank goes to Monica Markovits for introducing me to the lab and
teaching me all kind of experimental procedures in a very patient way. I want to
thank my collaborators Dr. Guanna Li, Dr. Evgeny Pidko and Dr. Jiri Dedecek
for fruitful discussions and successful cooperation in the EU NEXT-GTL project.
I would further like to thank Prof. Moniek Tromp and Prof. Andreas Jentys for
their input in XAS analysis. Xaver Hecht helped a lot with technical problems.
Thank you also for your support to Bettina Federmann, Steffi Seibold, Uli
Sanwald, Andreas Marx and Martin Neukamm.
All students who worked with me are acknowledged for their experimental
contribution, especially Wanqiu Luo for her good work throughout her Masters
Thesis. The big office was always a fun place with a lot of nice people and
chats. I want to thank my office mates Edith Berger, Sebastian Eckstein,
Andreas Ehrmaier, Christian Grtner, Claudia Himmelsbach, Lou Yu, Liu
Yuanshuai and Liu Yue for all their kindness and help. I want to thank my class
mates who joined TC2, especially Sebastian Foraita, Elisabeth Hanrieder and
Stanislav Kasakov for help and distraction at work. A special thanks to my
friend Tobias Berto for discussions and support in all kind of situations. Thank
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you to all current and former group members that are not listed above, I am
grateful to all of you for a pleasant working atmosphere and your help.
Last but not least I want to thank my family. My parents supported me
tremendously in every possible way during the last thirty years. Without you the
way to get a PhD would have been much tougher. Danke Mama und Papa fr
alles, was ihr in den vergangenen dreiig Jahren fr mich getan habt! Now is
the time to thank the most special persons in my life. Lei, thank you for all your
support, encouragement and love! Thank you Ferdi, for always succeeding in
cheering me up! You two are the sunshine in my life.
Sebastian
December 2015
iii
Abbreviations
Angstrom
AAS Atomic absorption spectroscopy
BAS Brnsted acid site
BET Brunauer-Emmett-Teller
DFT Density functional theory
EPR Electron paramagnetic resonance
eV Electronvolt
EXAFS Extended X-ray absorption fine structure
g Gram
h Hour
IR Infrared
K Kelvin
kJ Kilojoule
ml Millilitre
min Minute
MOR Mordenite
X-MR X-membered ring with X being the number of TO4 in the ring
mol Micromole
TEM Transmission electron microscopy
TOF Turnover frequency
TPD Temperature programmed desorption
UV-vis Ultraviolet-visible
wt.% Weight percent
XANES X-ray absorption near edge structure
XAS X-ray absorption spectroscopy
ZSM-5 Zeolite Socony Mobile-5
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Abstract
Copper oxide clusters stabilized in the micropores of zeolites have been found
to selectively oxidize methane to methanol. The synthesis of a catalyst with
homotopic trinuclear copper oxide clusters was achieved via ion exchange and
oxidation. The steric and chemical environments of these clusters
characterized by combinations of physicochemical measurement were critical
to activate and convert methane. While the absence of water was critical for
methane oxidation, the presence of water was required to realize its desorption.
The presence of water reorganizes the Cu2+ cations requiring high
temperatures to allow formation of the copper-oxide trimer clusters.
Kurzzusammenfassung
Zeolithmikroporen stabilisieren Kupferoxidcluster, die selektiv Methan zu
Methanol oxidieren. Die Synthese von homotopen trinuklearen
Kupferoxidclustern erfolgte mittels Ionenaustausch und Oxidation. Die sterische
und chemische Umgebung der Cluster, die durch eine Kombination
physikochemischer Messungen charakterisiert wurde, ist entscheidend fr die
Aktivierung und Umsetzung von Methan. Whrend die Abwesenheit von
Wasser wesentlich fr die Oxidation von Methan ist, ist die Gegenwart von
Wasser fr die Desorption erforderlich. The Gegenwart von Wasser fhrt zur
Reorganisation der Cu2+-Kationen, was hohe Temperaturen fr die Bildung des
trinuklearen Kupferoxidclusters erfordert.
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Table of Contents
1 General Introduction ................................................................................. 1
1.1 Methanol Economy ............................................................................... 1
1.2 Commercial Route for the Conversion of Methane to Methanol .......... 2
1.2.1 Reforming ....................................................................................... 2
1.2.2 Methanol Synthesis ........................................................................ 2
1.3 Selective Partial Oxidation of Methane to Methanol ............................. 4
1.4 Zeolites ................................................................................................. 8
1.4.1 Structure of Zeolites ....................................................................... 8
1.4.2 Nature of Acid Sites ...................................................................... 11
1.4.3 Distribution and Siting of Framework Al ....................................... 12
1.5 Catalysis on Copper Exchanged Zeolites ........................................... 17
1.5.1 Catalytic Decomposition of Nitrogen Oxides ................................ 17
1.5.2 C-H Bond Activation ..................................................................... 18
1.6 Scope of the Thesis ............................................................................ 21
1.7 References ......................................................................................... 23
2 Single-Site Trinuclear Copper Oxygen Clusters in Mordenite for ...........
Selective Conversion of Methane to Methanol ..................................... 28
2.1 Abstract ............................................................................................... 28
2.2 Introduction ......................................................................................... 29
2.3 Results and Discussion ....................................................................... 30
2.3.1 Preparation of a Single-Site Copper Oxygen Cluster ................... 30
2.3.2 Siting of Copper in Mordenite ....................................................... 31
2.3.3 Testing of Activity for Selective Oxidation of Methane .................. 37
2.3.4 Spectroscopic Characterization .................................................... 39