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

ii

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

iv

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.

v

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