thermal degradation of amines for co 2 capture

126 Pages·2017·2.5 MB·English

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Theses and Dissertations--Chemistry Chemistry
2015
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Quanzhen Huang
University of Kentucky, [email protected]
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Huang, Quanzhen, "THERMAL DEGRADATION OF AMINES FOR CO2 CAPTURE" (2015). Theses and
Dissertations--Chemistry. 51.
https://uknowledge.uky.edu/chemistry_etds/51
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The document mentioned above has been reviewed and accepted by the student’s advisor, on
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Quanzhen Huang, Student
Dr. John P. Selegue, Major Professor
Dr. Dong-Sheng Yang, Director of Graduate Studies
THERMAL DEGRADATION OF AMINES FOR CO CAPTURE
2

DISSERTATION

A dissertation submitted in partial fulfillment of the
requirements for the degree of Doctor of Philosophy in the
College of Arts and Sciences
at the University of Kentucky

By
Quanzhen Huang

Lexington, Kentucky

Director: Dr. John P. Selegue, Professor of Chemistry

Lexington, Kentucky

2015

Copyright © Quanzhen Huang 2015
ABSTRACT OF DISSERTATION

THERMAL DEGRADATION OF AMINES FOR CO CAPTURE
2

In the selection of candidates for CO absorption, solvent thermal
2
degradation has become a general concern due to the significant impact on
operational cost and the intention to use thermal compression from high
temperature stripping to minimize the overall process energy. In this research, the
impact of flue gas contaminants on Monoethanolamine (MEA) thermal degradation
was investigated at elevated temperatures consistent with those in the CO
2
stripper. Nitrite, fly ash, sulfate and thiosulfate were each added to 5.0 M MEA and
the contaminant-containing MEA solutions were degraded at 125 °C, 135 °C and
145 °C. MEA degrades significantly more in the presence of nitrite (5000 ppm)
than MEA alone at the same amine molar concentration for all three temperatures.
MEA degradation activation energy of MEA-nitrite solution is approximately one-
seventh of that of MEA solution without nitrite. Fly ash was observed to inhibit
nitrite-induced MEA degradation and greatly increase the MEA degradation
activation energy of MEA-nitrite solution. Fly ash, sodium sulfate and sodium
thiosulfate by themselves were not shown to impact MEA thermal degradation rate.

Sodium salts of glycine, sarcosine, alanine and ß-alanine were thermally
degraded at 125 °C, 135 °C and 145 °C, respectively, to discover the structural
reasons for their thermal stability. These four amino acids have enhanced thermal
degradation rates compared to MEA. The stability order for amino acid salts tested
to date is: sarcosinate > alaninate > ß-alaninate. Calculated activation energies for
the degradation processes are lower than that of MEA. ß-Alaninate (ß-Ala) thermal
degradation generates ß-Ala dimer (major degradation product), ß-Ala dimer
carbamate and tetrahydro-1,3-oxazin-6-one.

Functional groups, amine orders and steric effect were investigated for their
impact on amine thermal degradation. Primary amines with chain structures
showed a thermal stability trend as diamine > alkanolamine > amino acid salt. For
alknolamine and diamine structural isomers, the primary amines are more stable
than the secondary amines. Steric hindrance around the amine group plays a
global positive role in protecting amines against thermal degradation.
KEYWORDS: Thermal Degradation, Flue Gas Contaminants, Activation Energy,
Thermal Compression, Steric Hindrance

Quanzhen Huang

03/10/2015
THERMAL DEGRADATION OF AMINES FOR CO2 CAPTURE

By

Quanzhen Huang

Dr. John P. Selegue
Director of Dissertation

Dr. Dong-Sheng Yang
Director of Graduate Studies

03-10-2015
DEDICATION
To my wife Pei Gao and daughter Annie Huang whose love has always
sustained me throughout this research.
ACKNOWLEDGMENTS

Firstly, I would like to express my sincerest gratitude to my advisor
Professor John Selegue, whose enthusiasm on research and eagerness to teach
have inspired me from the beginning of this research to its completion. Every time
I went to his office with questions, Professor Selegue has always been responsive
and guided me with great patience. He not only gave me detailed suggestions to
find the solution, but more importantly he showed me the way to be a good
researcher. I will be forever grateful for his dedication and support.
I thank Dr. Kunlei Liu and many members of Power Generation and Utility
Fuel (PGUF) group in Center for Applied Energy Research (CAER) for their help,
by which I learned a lot. Without the financial supports from Carbon Management
Research Group (CMRG) sponsors, this research could not be completed.
I am also highly grateful to my research committee members Dr.
Dong-Sheng Yang, Dr. Yinan Wei and Dr. Jim Neathery for the valuable
suggestions, which have been very helpful in dealing with the issues I had in my
research and academic situation.
Finally, I would like to thank my parents in China, who have never stopped
in encouraging me to go forward in this research. I appreciate my wife Pei Gao
and my daughter Annie Huang whose love and support have been the driving
force walking me through the difficult time in my work and research and keeping
me a positive and confident person.

iii
TABLE OF CONTENTS

ACKNOWLEDGMENTS ....................................................................................... iii
TABLE OF CONTENTS ........................................................................................ iv
LIST OF TABLES ................................................................................................. vii
LIST OF FIGURES ............................................................................................. viii

CHAPTER I. INTRODUCTION ............................................................................. 1
1.1. Carbon Dioxide-Induced Climate Change ..................................................... 1
1.2. Anthropogenic CO Emissions in United States ............................................. 2
2
1.3. CO Capture by Aqueous Amine Solutions in Absorption-Stripping System .. 5
2
1.3.1. Flue Gas Composition .......................................................................... 5
1.3.2. Flue Gas Pretreatment ......................................................................... 6
1.3.3. Absorption-Stripping Process ............................................................... 8
1.3.4. CO Absorption by Alkanolamines ........................................................ 9
2
1.4. Solvent Loss in CO Absorption-Stripping System ....................................... 12
2
1.5. MEA Degradation in CO Capture Relevant Conditions .............................. 13
2
1.5.1. MEA Oxidative Degradation ...................................................................... 13
1.5.2. MEA Thermal Degradation ....................................................................... 14
1.6. Research Objectives ................................................................................... 17
1.7. Thesis Organization ..................................................................................... 17

CHAPTER II. EXPERIMENTAL AND ANALYTICAL METHODS ......................... 19
2.1. CAER Pilot Plant and Operating Conditions ................................................ 19
2.2. Thermal Degradation Experiments .............................................................. 20
2.2.1. Amine Solution Preparation ................................................................ 20
2.2.2. Thermal Degradation .......................................................................... 21
2.3. Analytical Methods ....................................................................................... 21
2.3.1. Total Inorganic Carbon (TIC) measurement……………….……………21
2.3.2. Ion Chromatography (IC) ................................................................... 23
2.3.2.1. Apparatus Description .............................................................. 24
2.3.2.2. Cation IC Analysis .................................................................... 26
2.3.2.3. Anion IC Analysis ..................................................................... 29
2.3.3. High-performance Liquid Chromatography / Time-of-flight Mass
Spectrometry (HPLC/TOF–MS) .................................................................... 32
2.3.4. Inductively Coupled Plasma (ICP) Emission Spectrometer ................ 34

CHAPTER III. IMPACT OF FLUE GAS CONTAMINANTS ON MEA THERMAL
DEGRADATION ................................................................................................. 36
3.1. Introduction .................................................................................................. 36
3.2. Experimental ................................................................................................ 37
iv
3.2.1. Chemicals........................................................................................... 37
3.2.2. Thermal Degradation Evaluation ........................................................ 38
3.2.3. Methods of Analysis ........................................................................... 38
3.3. Flue Gas Contaminant Accumulation in a 0.1 MWth Pilot Plant .................. 39
3.4. Nitrite-Induced MEA Degradation ................................................................ 40
3.5. Degradation Activation Energy Calculation .................................................. 43
3.6. MEA Degradation Products in the Presence of Nitrite ................................. 45
3.7. Inhibition of Nitrite-Induced MEA Degradation by Fly Ash ........................... 49
3.7.1. MEA Thermal Degradation in the Presence of Fly Ash ...................... 49
3.7.2. Inhibition Effect of Fly Ash .................................................................. 51
3.8. MEA Thermal Degradation in the Presence of Sulfate and Thiosulfate ....... 56
3.9. Conclusion of Chapter 3 .............................................................................. 58

CHAPTER IV. THERMAL DEGRADATION OF AMINO ACID SALTS IN CO2
CAPTURE .......................................................................................................... 59
4.1. Introduction .................................................................................................. 59
4.2. Experimental ................................................................................................ 61
4.2.1. Chemicals .......................................................................................... 61
4.2.2. Thermal Degradation Evaluation ........................................................ 62
4.2.3. Methods of Analysis ........................................................................... 63
4.3. Thermal Degradation of Na-Gly ................................................................... 64
4.4. Thermal Degradation Rate Comparison ...................................................... 65
4.5. Structure and Thermal Stability .................................................................... 68
4.6. Acid Treatment in NMR Measurements ....................................................... 70
4.7. Oligomerization and tetrahydro-1,3-oxazin-6-one formation in Na-ß-Ala ..... 72
4.8. Conclusion of Chapter 4 .............................................................................. 77

CHAPTER V. THERMAL DEGRADATION COMPARISON OF AMINO ACID
SALTS, ALKANOLAMINES AND DIAMINES IN CO2 CAPTURE ....................... 79
5.1. Introduction .................................................................................................. 79
5.2. Experimental ................................................................................................ 80
5.2.1. Chemicals........................................................................................... 80
5.2.2. Thermal Degradation Evaluation ........................................................ 81
5.2.3. Methods of Analysis ........................................................................... 81
5.3. Kinetics of MEA Thermal Degradation ......................................................... 81
5.4. Impact of Functional Groups ........................................................................ 83
5.5. Impact of Amine Order ................................................................................. 84
5.6. Steric Effect ................................................................................................. 86
5.7. Conclusion of Chapter 5 .............................................................................. 87

CHAPTER VI. FUTURE WORK ......................................................................... 89
v