Thermal and chemical analysis of carbonaceous materials : Diesel soot and Diesel Fuel Reactor ...

191 Pages·2013·5.71 MB·English

n
w
Dissertation submitted in fulfilment of the degree of
o
T

e
MASTER OF SCIENCE IN ENGINEERING
p
a

C
Department of M echanical Engineering
f
o
University of Cape Town

y
t

i
s
r
August 2013
e
v

i
n
U
THERMAL AND CHEMICAL ANALYSIS OF
CARBONACEOUS MATERIALS: DIESEL SOOT AND
DIESEL FUEL REACTOR DEPOSITS

Irénée Kaminuza
Supervised by
Chris Woolard
n

w
The copyright of this thesis vests in the author. No
o
T
quotation from it or information derived from it is to be

published without full acknowledgeement of the source.
p
The thesis is to be used for private study or non-
a
C
commercial research purposes only.

f
o
Published by the Universit y of Cape Town (UCT) in terms
y
t
of the non-exclusive license granted to UCT by the author.
i
s
r
e
v
i
n
U
n
w
o
T

e
p

a
C

f
o

y
t

i
s
r
e
v
ni
U
PLAGIARISM DECLARATION|2013
Plagiarism declaration
1. I know that plagiarism is wrong. Plagiarism is using another’s work and to pretend
that it is one’s own.
2. This dissertation is my own work.
3. I acknowledge that pretending that someone else's work, or part of it, is my own is
wrong, and declare that this is my own work.
4. I have used the IEEE 2006 referencing style as the convention for citation and
referencing. Each significant contribution to, and quotation in, this dissertation from
the work, or works of other people has been attributed and referenced.

n
w
o
T

e
__________________
p
a
Irénée Kaminuza
C

f
o

y
t
i
s
r
e
v
i
n
U

i
ACKNOWLEDGEMENTS|2013
Acknowledgements
“Gratitude is not only the greatest of virtues, but the parent of all others.”-Cicero
I would like thank the following persons or organisations for aiding me throughout my MSc
studies:
1. First and foremost, I would like to thank my sponsors, Sasol Technology Fuels
Technology, and Canon Collins Trust, as funding is the lifeblood of every student. I
was fortunate to have such generous patronage from both sponsors during my MSc
degree and I thank them for investing in my future.
2. I would like thank my supervisor, Dr Chris Woolard, for recruiting me and
introducing the world of petroleum science engineering at the Sasol Advanced Fuels
n
Laboratory (SAFL). I appreciated his guidance and empathyw. I also thank him for
welcoming me to his home for the end of year functions aond for introducing Journal
Club to the chemists in the research group. It was a grTeat way to learn and engage
with others. I really appreciate the amount of time an d dedication he put into assisting
e
me in interpreting my data. Furthermore I wouldp like to express my gratitude towards
a
him for arranging me funding during this past year.
C
3. I would like to express a great deal of appreciation towards Dr. Stefan De Goede for

being an exemplary mentor throughfout my MSc. Like Dr Woolard, Stefan is an
o
incredibly busy man, which is why I felt privileged as he spent a great deal of his time

y
assisting me. From providing me with relevant literature material, organising my
t
i
samples, exposing me to sseveral analytical facilities, reading and offering input into
r
the written aspect of my thesis, organising formal and informal discussions or just
e
emailing me to inquvire about my progress, Stefan went well and beyond the call of
i
duty. n
4. A big thank Uyou goes to Mrs Miranda Waldron and Dr François Cummings of the
Electron Microscope Unit at UCT for helping me to image my samples. Their warmth
and assistance is greatly appreciated.
5. I would like to thank Ms Shanielle Botha for her help with the GC-MS.
6. Mr Ross Burnham deserves a big thank you. His help around the laboratory is much
appreciated. He acquainted me with many of the analytical equipment
7. To Mr Victor Burger and Mr Gerhard Lourens, I thank you for your help around the
laboratory. Thank you for demystifying an engineering workshop.
8. Ms Beverley Glass deserves a mention. Her assistance with quotes and bursary
payments is appreciated. In addition I want to thank her for the office humour and for
being a wonderful colleague and friend.
9. Deep appreciation goes to Ms Jeanri Coetzee for being such a great help around the
laboratory. I appreciate the trouble she went through in organising quartz crystal

ii
ACKNOWLEDGEMENTS|2013
microbalance experiments for me and for keeping the laboratory in order. I would also
like to thank her for her incredible friendship. I will miss her.
10. To Uyuenendiwannyi Mandavha, thanks for being a wonderful friend and colleague,
my days at SAFL were brightened because of you.
11. To Mr Keenan Heynes and Mr Wesley Neutt. I really appreciate the energy and
enthusiasm you brought to the lab and assisting me tremendously during vacation
work at SAFL. For the first time as SAFL the flow reactor worked properly, and it
was due to you guys. Thank you for your friendship.
12. I would like to thank Mr Lucky Mokwena from the Central Analytical Facility (CAF)
at the University of Stellenbosch for performing GC-MS on some of my soot samples
while the GC-MS at SAFL was faulty.
13. A word of thanks goes to Mr Fletcher Hiten (from the CAF) for performing ESI-MS
n
on my fuel samples as well as ICP-MS on my soot sample.
w
14. I would like to thank Ian Scott, Gary McFarlane, Rudi Russouw, Warren Randall,
o
Chris Scully, Washington Mudenha, Timothy King, Marlan Perumal, Dylan Smit,
T
Dirren Govender, Leanne Robertson, René Laryea-Goldsmith, Gareth Floweday,

e
Aiden Ehrenreich, Mariam Ajam, Andrew Winstanly, Hundzukani Vukeya and Toby
p
Rockstroh for being wonderful friends and colleagues.
a
15. Thanks also go out to my friends outsideC my research group for lifting my spirits
during the tough times. A special mention goes to Juliette Dusabe, Natalie
f
Hendrickse, Jason Cottle, Graham oMorrison, Khanyisa Mubunda, Lisa Williams,

Bianca Kriel, Ncediwe Ndlulwya and Sabina Yusuf Shaik. Thank you for your
assistance throughout this jourtney.
i
s
16. To Stacey-Leigh Titus, my fantastic dance partner, I truly appreciated your
r
e
encouragement and support particularly during the last stretch of my thesis.
v
17. Finally I would like to thank my family for their support. To my parents, I thank them
i
n
for their genes and for providing me with a warm and loving living environment. I
U
want to thank my siblings, Patrick, Celestine and Fabrice, for providing me with the
motivation to do better and grow. I also want to thank them for their friendships.

iii
TABLE OF CONTENTS|2013
Table of Contents
Plagiarism declaration ................................................................................................................. i
Acknowledgements .................................................................................................................... ii
List of figures ......................................................................................................................... viii
List of tables ........................................................................................................................... xiii
List of abbreviations ................................................................................................................ xv
Abstract .................................................................................................................................. xvii
1 Introduction ........................................................................................................................ 1
1.1 Subject and motivation for this study .......................................................................... 1
n
1.1.1 Diesel particulate matter (PM) ............................................................................. 1
w
1.1.2 Diesel deposits ..................................................................................................... 2
o
1.2 Limitations and scope of the study .................................T............................................. 3

1.2.1 Diesel particulate matter .................................e..................................................... 3
p
1.2.2 Diesel deposits ..................................................................................................... 3
a
1.3 Plan of development ..................................C.................................................................. 4
2 Literature Review ....................................... ........................................................................ 5
f
o
2.1 Diesel fuel ................................................................................................................... 5

y
2.1.1 Source and compositiont of diesel fuel ................................................................. 5
i
s
2.2 Fuel and engine oil additives ....................................................................................... 6
r
e
2.3 Diesel PM emissions ................................................................................................... 7
v
2.3.1 Componentis of diesel PM .................................................................................... 8
n
2.3.2 CompoUsition of the SOF and its effects on biological systems ........................... 9
2.4 Thermo-oxidative stability of middle distillate fuels ................................................ 12
2.4.1 Diesel injector deposits ...................................................................................... 12
2.4.2 Mechanism of deposit formation ....................................................................... 13
2.4.3 Fuel deposit production...................................................................................... 16
2.4.4 Deposit characterisation techniques ................................................................... 18
3 Experimental methods ...................................................................................................... 28
3.1 Diesel soot ................................................................................................................. 28
3.1.1 Source of soot .................................................................................................... 28
3.1.2 Analytical techniques and protocol adopted ...................................................... 29
3.1.3 Gas Chromatography - Mass Spectrometry (GC-MS)....................................... 32

iv
TABLE OF CONTENTS|2013
3.2 Diesel fuel deposits ................................................................................................... 34
3.2.1 Materials ............................................................................................................ 34
3.2.2 Flask Reactor conditions .................................................................................... 36
3.2.3 Sampling methodology for reactor deposits ...................................................... 44
3.2.4 Techniques employed to characterise fuel deposits ........................................... 45
4 Chemical and physical characterisation of soot ............................................................... 49
4.1 The effect of extraction solvent on the quantity of the SOF ..................................... 49
4.2 Chemical speciation of SOF derived diesel soot ....................................................... 50
4.2.1 n-Hexane extract ................................................................................................ 50
4.2.2 Cyclohexane extract ........................................................................................... 51
n
4.2.3 Toluene extract................................................................................................... 52
w
4.2.4 Acetone extract .................................................................................................. 53
o
4.2.5 Methanol extract .....................................................T........................................... 54

4.2.6 Dichloromethane extract .................................e................................................... 55
p
4.3 Thermogravimetric analysis of soot .......................................................................... 57
a
4.4 Electron microscopy of diesel bus soot .....C................................................................ 61

4.5 Comparison of the extraction potentifal and specificity of a variety of solvents ....... 62
o
4.6 Comparison of the analysis of SO F and VOF ........................................................... 66
y
4.7 Conclusions .........................t...................................................................................... 68
i
s
5 Evaluation of depositing propensity of diesel fuels .......................................................... 70
r
e
5.1 QCM measurements .................................................................................................. 70
v
5.2 Discussion .....n..i.......................................................................................................... 72
U
5.3 Conclusions ............................................................................................................... 73
6 Analysis of flask reactor deposits ..................................................................................... 74
6.1 Visual observations ................................................................................................... 74
6.2 Transmission electron microscopy ............................................................................ 75
6.3 TGA-MS analysis of flask reactor diesel deposits .................................................... 78
6.3.1 Thermal analysis of unstressed and stressed diesel fuels in nitrogen ................ 78
6.3.2 Oxidative TGA of stressed fuels ........................................................................ 82
6.4 FTIR investigation of the fuels.................................................................................. 86
6.5 ESI-MS evaluation of soluble precursor deposits ..................................................... 89
6.5.1 Unstressed commercial diesel ............................................................................ 89
6.5.2 Stressed commercial diesel ................................................................................ 91

v
TABLE OF CONTENTS|2013
6.5.3 Unstressed EN590 diesel ................................................................................... 94
6.5.4 Stressed EN590 diesel........................................................................................ 96
6.5.5 Unstressed RME20 ............................................................................................ 98
6.5.6 Stressed RME20............................................................................................... 101
6.5.7 SME20 unstressed ............................................................................................ 104
6.5.8 SME20 stressed ................................................................................................ 107
6.6 Discussion ............................................................................................................... 110
6.7 Conclusions ............................................................................................................. 114
7 Closed bomb reactor deposits ......................................................................................... 115
7.1 Results and discussion ............................................................................................. 115
n
7.2 Visual observations ................................................................................................. 115
w
7.2.1 Commercial diesel ........................................................................................... 115
o
7.2.2 EN590 diesel ...........................................................T......................................... 116

7.2.3 RME20 and SME20 ........................................e................................................. 116
p
7.3 Transmission electron microscopy .......................................................................... 117
a
7.4 TGA-MS....................................................C.............................................................. 120

7.4.1 Deposit oxidation ......................f....................................................................... 120
o
7.5 Discussion ................................. .............................................................................. 124
y
7.6 Conclusions .........................t.................................................................................... 125
i
s
8 Fuel degradation in a flow reactor .................................................................................. 127
r
e
8.1 Results and discussion ............................................................................................. 127
v
8.2 Conclusions ...n..i........................................................................................................ 129
U
9 Conclusions .................................................................................................................... 130
10 Recommendations and further work ........................................................................... 133
10.1 Further work ............................................................................................................ 133
11 List of references......................................................................................................... 136
12 Appendices .................................................................................................................. 145
12.1 APPENDIX A – Soot extracts ................................................................................ 145
12.1.1 SOF data........................................................................................................... 145
12.2 APPENDIX B – FAME composition...................................................................... 165
12.3 Appendix C – Flask reactor stressing ...................................................................... 166
12.3.1 Thermal analysis repeatability ......................................................................... 166
12.3.2 Methanol extracts ............................................................................................. 167

vi
TABLE OF CONTENTS|2013
12.3.3 ESI-MS ............................................................................................................ 168
12.4 Appendix D - Cellulose vs glass thimbles for efficient Soxhlet extraction ............ 169
12.5 Appendix E – TGA of Munktell filter paper ........................................................... 170

n
w
o
T

e
p
a
C

f
o

y
t
i
s
r
e
v
i
n
U

vii