Synthesis of Amine-Modified Aerogel Sorbents and Metal- Organic

97 Pages·2010·1.43 MB·English

by  Electric Lemonade

Synthesis of Amine-Modified Aerogel Sorbents and Metal-
Organic Framework-5 (MOF-5) Membranes for Carbon Dioxide Separation
by
Teresa M. Rosa

A Thesis Presented in Partial Fulfillment
of the Requirements for the Degree
Master of Science

Approved October 2010 by the
Graduate Supervisory Committee:

Jerry Y.S. Lin, Co-Chair
Robert Pfeffer, Co-Chair
David Nielsen
Lenore Dai

ARIZONA STATE UNIVERSITY
December 2010
ABSTRACT
Amine-modified solid sorbents and membrane separation are promising
technologies for separation and capture of carbon dioxide (CO ) from combustion
2
flue gas. Amine absorption processes are mature, but still have room for
improvement. This work focused on the synthesis of amine-modified aerogels and
metal-organic framework-5 (MOF-5) membranes for CO separation.
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A series of solid sorbents were synthesized by functionalizing amines on
the surface of silica aerogels. This was done by three coating methods: physical
adsorption, magnetically assisted impact coating (MAIC) and atomic layer
deposition (ALD). CO adsorption capacity of the sorbents was measured at room
2
temperature in a Cahn microbalance. The sorbents synthesized by physical
adsorption show the largest CO adsorption capacity (1.43-1.63 mmol CO /g). An
2 2
additional sorbent synthesized by ALD on hydrophilic aerogels at atmospheric
pressures shows an adsorption capacity of 1.23 mmol CO /g. Studies on one
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amine-modified sorbent show that the powder is of agglomerate bubbling
fluidization (ABF) type. The powder is difficult to fluidize and has limited bed
expansion. The ultimate goal is to configure the amine modified sorbents in a
micro-jet assisted gas fluidized bed to conduct adsorption studies.
MOF-5 membranes were synthesized on α-alumina supports by two
methods: in situ synthesis and secondary growth synthesis. Characterization by
scanning electron microscope (SEM) imaging and X-ray diffraction (XRD) show
that the membranes prepared by both methods have a thickness of 14-16 µm, and
a MOF-5 crystal size of 15-25 µm with no apparent orientation. Single gas
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permeation results indicate that the gas transport through both membranes is
determined by a combination of Knudsen diffusion and viscous flow. The
contribution of viscous flow indicates that the membranes have defects.
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ACKNOWLEDGEMENTS
I would like to thank my advisors, Dr. Jerry Lin and Dr. Robert Pfeffer for
their understanding, guidance and thoughtful advice during my journey through
the project. I would also want to thank Dr. David Nielsen and Dr. Lenore Dai for
serving on my committee.
I would also like to thank my current and former labmates with whom I
had the pleasure to work: Carrie, Jay, Matt, Tyler, Nick, Shriya, Haibing,
Zhenxia, Chao, Xiaoli, Bo, Peter, Ding, Taylor and Stephanie. Thanks for your
help, support and friendship all these years and thanks for providing a stimulating
and fun environment in which to learn and grow. Carrie, I truly appreciate all your
help and suggestions during the writing process of this document.
Special thanks go to Fred Peña for his invaluable help and assistance that
made possible the completion of this project. Thanks for all your numerous
suggestions, and for helping with all the project issues. Thanks to Marty and
David, from the machine shop, for making such a beautiful job with the columns.
Thanks to the CSSS staff for their tremendous help with their equipment.
I cannot finish without saying how grateful I am to my family. They have
always supported and encouraged me to do the best in all areas of my life. They
never let me down, and were a real support throughout all these years in school.
Finally, I want to thank my soon-to-be husband, on whose constant
encouragement and love I have relied throughout my time in graduate school.
Teresa

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TABLE OF CONTENTS
Page
LIST OF TABLES ................................................................................................ vii
LIST OF FIGURES ............................................................................................. viii
CHAPTER
1 BACKGROUND .............................................................................................1
1.1 Introduction ...............................................................................................1
1.2 Amine Immobilized Solid Sorbents for CO Sorption .............................2
2
1.2.1 Recent work. ....................................................................................3
1.2.2 Silica aerogels. .................................................................................4
1.3 Reactions between amines and CO . ........................................................6
2
1.4 Gas Fluidization. .......................................................................................8
1.4.1 General characteristics of fluidized beds. ........................................8
1.4.2 Assisted fluidization by a micro-jet. ..............................................10
1.4.3 Hydrodynamic characteristics. .......................................................10
1.5 Membrane separation ..............................................................................12
1.5.1 Metal-organic framework (MOF-5). ..............................................12
1.5.2 Synthesis of MOF-5 membranes. ..................................................14
1.5.2.1 In situ hydrothermal synthesis method. .............................14
1.5.2.2 Secondary growth hydrothermal synthesis method. ..........15
1.6 Research Objectives and Structure of Thesis..........................................16

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CHAPTER Page
2 AMINE-FUNCTIONALIZED AEROGELS.................................................19
2.1 Introduction .............................................................................................19
2.1.1 Magnetically assisted impact coating (MAIC). .............................19
2.1.2 Atomic layer deposition (ALD). ....................................................21
2.2 Experimental ...........................................................................................22
2.2.1 Synthesis of amine-functionalized aerogels...................................22
2.2.1.1 Physical adsorption of amines on aerogels. .......................23
2.2.1.2 Amine coated aerogels by MAIC batch process. ...............24
2.2.1.3 Amine coated aerogels by ALD. ........................................25
2.2.2 TGA-DSC measurements. .............................................................25
2.2.3 Carbon dioxide adsorption using Cahn microbalance. ..................26
2.2.4 Fluidization experiments with aerogels. ........................................27
2.3 Results and Discussion ...........................................................................29
2.3.1 TGA-DSC measurements. .............................................................29
2.3.2 CO adsorption measurements in microbalance. ...........................31
2
2.3.2.1 Physical adsorption samples. .............................................31
2.3.2.2 MAIC samples. ..................................................................34
2.3.2.3 ALD samples. ....................................................................40
2.3.3 Fluidization of aerogels..................................................................48
2.4 Conclusions .............................................................................................52

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CHAPTER Page
3 METAL-ORGANIC FRAMEWORK-5 MEMBRANES..............................54
3.1 Introduction .............................................................................................54
3.2 Experimental ...........................................................................................54
3.2.1 Synthesis of MOF-5 membranes. ..................................................54
3.2.2 Membrane characterization. ...........................................................57
3.3 Results and Discussion ...........................................................................60
3.3.1 MOF-5 microstructure. ..................................................................60
3.3.2 XRD and SEM of MOF-5 membranes. .........................................63
3.3.3 Gas permeation of MOF-5 membranes..........................................66
3.4 Conclusions .............................................................................................70
4 SUMMARY AND RECOMMENDATIONS................................................71
4.1 Summary .................................................................................................71
4.2 Recommendation ....................................................................................72
REFERENCES ......................................................................................................74
APPENDIX
A EXPERIMENTAL PROCEDURES FOR MOF-5 MEMBRANES .............79
B EXPERIMENTAL PROCEDURES TO MODIFY AEROGELS ................84
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LIST OF TABLES
TABLE Page
1.1 Physical Characteristics of Cabot Nanogel Fine Particles .................................6
1.2 MOF-5 Properties ............................................................................................13
2.1 Physical/Chemical Characteristics of Amine Compounds Selected for
Modification of Aerogel Surface .....................................................................23
2.2 CO2 uptake and experimental conditions of sorbents prepared by
physical adsorption ..........................................................................................32
2.3 CO2 upta and experimental conditions of sorbents prepared by
MAIC process ..................................................................................................35
2.4 CO2 upta and experimental conditions of sorbents prepared
by ALD process ...............................................................................................41
2.5 Uptake of hydrophilic aerogels prepared by ALD at atmospheric pressure ....45
3.1 Summary of intercept α, slope β and β/α through secondary
growth membrane ............................................................................................67
3.2 Summary of intercept α, slope β and β/α through in situ membrane ...............69
A.1 Temperature Program for Sintering Supports .................................................80
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LIST OF FIGURES
FIGURE Page
1.1. Schematic diagram of hydrophilic aerogels and hydrophobic
aerogels after surface modification. R represents –CH groups.. ......................5
3
1.2. Three classes of amines: primary amines have one hydrogen atom
replaced by an alkyl group R; secondary amines have two atoms
replaced, and tertiary have all three atoms replaced. .........................................7
1.3. Geldart classification of powders according to fluidization
properties at air ambient conditions. ..................................................................9
1.4. Diagram of pressure drop as function of gas velocity. ...................................11
1.5. Illustration of the MOF-5 framework. ............................................................13
2.1. Schematic diagram of the batch MAIC device. ..............................................20
2.2. Illustration of ALD process based on alternate surface reactions ...................22
2.3. Schematic of amines used in each synthesis method.. ..................................263
2.4. Diagram of Cahn microbalance system for CO adsorption studies...............26
2
2.5. Schematic diagram of the fluidized bed setup.. ..............................................28
2.6. TGA/DSC of Triameen-modified aerogel under nitrogen atmosphere. .........30
2.7. TGA/DSC of Duomeen-modified aerogel under nitrogen atmosphere. .........30
2.8. TGA/DSC of unmodified aerogel under nitrogen atmosphere. ......................31
2.9.Weight of CO adsorbed in a sample of hydrophobic aerogel
2
modified by physical adsorption of Triameen T. .............................................33
2.10.Weight of CO adsorbed in a sample of hydrophobic aerogel modified
2
by physical adsorption of Duomeen T. ............................................................33
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FIGURE Page
2.11.Weight of CO adsorbed in a sample of hydrophilic aerogel
2
modified by physical adsorption of Duomeen T..............................................34
2.12.Weight of CO adsorbed in a sample of hydrophobic aerogel
2
modified by physical adsorption of PEI...........................................................34
2.13.Weight of CO adsorbed in a sample of aerogel modified by MAIC
2
of Triameen T. .................................................................................................35
2.14.Weight of CO adsorbed in a sample of aerogel modified by MAIC
2
of γ-APS. ..........................................................................................................36
2.15.Weight of CO adsorbed in a sample of aerosil 200 modified by
2
MAIC of Triameen T. ......................................................................................36
2.16.Weight of CO adsorbed in a sample of aerosil 200 modified by
2
MAIC of γ-APS. ..............................................................................................37
2.17. Weight of aerogel sample modified by MAIC of Triameen T. ....................38
2.18. Sample weight of unmodified hydrophobic aerogels. ..................................39
2.19. Weight of CO adsorbed in a sample of unmodified aerogels. .....................39
2
2.20.Weight of CO adsorbed in a sample of aerogel modified by
2
ALD (sample 1). ..............................................................................................42
2.21.Weight of CO adsorbed in a sample of aerogel modified by
2
ALD (sample 2). ..............................................................................................42
2.22.Weight of CO adsorbed in a sample of aerogel modified by
2
ALD (sample 3). ..............................................................................................43

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