Sorption isotherms of volatile molecules on micro- and mesoporous nanosized siliceous materials based on acoustic wave devices [Elektronische Ressource] : determination of corresponding isosteric heats of adsorption / von Alex Darga

Alex Darga

Informations

• Publié par: ludwig-maximilians-universitat_munchen
• Publié le: 01 janvier 2008
• Nombre de lectures: 27
• Langue: English
• Poids de l'ouvrage: 18 Mo

Extrait

Dissertation zur Erlangung des Doktorgrades
der Fakultät für Chemie und Pharmazie
der Ludwig-Maximilians-Universität München
Sorption isotherms of volatile molecules on micro- and meso-
porous nanosized siliceous materials based on acoustic wave
devices. Determination of corresponding isosteric heats of ad-
sorption.
von
Alexander Darga
aus Rosenheim
Juni 2008 Ehrenwörtliche Versicherung I
Erklärung
Diese Dissertation wurde im Sinne von § 13 Abs. 3 bzw. 4 der Promotionsordnung
vom 29. Januar 1998 von Herrn Professor Dr. Thomas Bein betreut.
Ehrenwörtliche Versicherung
Diese Dissertation wurde selbständig, ohne unerlaubte Hilfe erarbeitet.
München, am 05.06.2008
_____________________________
(Unterschrift des Autors)
Dissertation eingereicht am 05.06.2008
1. Gutachter: Prof. Dr. Thomas Bein
2. Gutachter: Prof. Dr. Knözinger
Mündliche Prüfung am 03.07.2008 Summary
Summary
Microporous zeolites and mesoporous periodically silicious materials offer interesting
features, like porosity in general, host-guest interactions and among others, sorption
phenomena.
The application of addressable individual material pixels, pin-printed onto adequate
pre-treated supporting surfaces for gas-sensor systems was evaluated. The contact pin-
printing technique, well known in bio-science, was adopted and optimized. The suc-
cessful deposition of colloidal suspensions of zeolite materials on Au-covered glass
slides with chemically attached intermediate anchoring molecules was demonstrated
on a 100 µm scale (chapter 3).
In a collaboration with the physical department of the LMU Munich (Prof. Kotthaus) a
gas sensor system, based on surface acoustic wave devices was developed. Thin layers
of porous material in the sub-microgram range were applied, in order to record ad-
sorption isotherms and to determine the released heat of adsorption of specific analyte
gases. Related to very small sample amounts and short diffusion times the necessary
experimental measurement time could be reduced down to several minutes (chapter
9).
An existing rudimentary quartz crystal microbalance (QCM) was enhanced and an
automated intelligent equilibrium system was developed. Furthermore, the system was
equipped with liquid mass controllers in order to measure the sorption properties to-
gether with vaporized liquid solvents (chapter 4). The developed QCM measurement
setup was applied as advanced research tool in order to investigate sorption properties
of various porous samples and to obtain the thermodynamic parameter, the isosteric
heat of adsorption.
The incorporation of organic moieties into siliceous frameworks leads to a wide variety
of adsorbate–adsorbent interactions including weak Van-der-Waals attractions as well
as strong interactions such as Coulomb forces. Depending on the desired properties of
such substituted highly porous matrix materials, optimized synthesis routes can be es-
tablished to enhance the desired internal pore surface–affinity towards certain volatile
compounds. Based on a fundamental knowledge of the host–guest system, sorption re-
lated applications may benefit from individually fine-tuned and modified sample mate-
rials. The sorption isotherms and isosteric heat of adsorption for non-modified, phenyl- Summary
modified, cyano-modified, vinyl-modified and mercapto-functionalized mesoporous
material for ethanol and 1-butanol sorption were determined. Additionally, nanosized
zeolites, like ZSM-5, Sil-1 and zeolite beta were investigated (chapter 6).
Furthermore, sorption isotherms of vaporized toluene on non-modified and phenyl-
functionalized mesoporous silica samples were determined using the gravimetric
QCM technique at different temperatures. The mesoporous silica was modified by in
situ via co-condensation and via post-synthesis grafting approaches, respectively. All
samples were thoroughly characterized by several standard techniques and addition-
ally with toluene sorption experiments on the automated QCM setup. The different
heats of adsorption of toluene on the various modified silica surfaces obtained by the
sorption data made it possible to gain additional information about the degree and type
of surface functionalization. It is thus demonstrated that QCM studies can be a power-
ful and convenient tool for efficient investigations of functionalized mesoporous silica
particles that yield valuable quantitative information on molecule-surface interactions
(chapter 8).V Tableofcontent
Table of content
Ehrenwörtliche Versicherung
Summary
1 Introduction and motivation 1
1.1 Adsorption related applications 2
1.2 General description of adsorption 3
1.2.1 Classical isotherm types 3
1.2.2 Common adsorbents 7
1.2.3 Size selectivity of porous hosts 8
1.3 Sensor concepts for environmental monitoring 9
1.3.1 The need for chemical sensors 9
1.3.2 Economic aspects of chemical sensors 10
1.3.3 Established sensor technology 11
1.3.3.4 Trace metal sensors 11
1.3.3.5 Laser induced breakdown spectroscopy 12
1.3.3.6 Evanescent fiber-optic chemical sensor 13
1.3.3.7 Oxide metal gas sensors 14
1.3.3.7 Acoustic wave sensor arrays 16
2 Synthesis, characterisation, sample preparation and material properties 22
2.1 Mesoporous materials 22
2.1.1 Non-modified pure nanosized mesoporous material: QCM-E 23
2.1.1.1 Nitrogen sorption data 24
2.1.1.2 Dynamic light scattering measurement 26
2.1.1.3 Transmission electron micrographs 26
2.1.1.4 X-Ray scattering 27
2.1.2 Phenyl functionalized nanosized mesoporous material: QCM-Ph 28
2.1.2.1 Nitrogen sorption data 28 Tableofcontent V
2.1.2.2 Dynamic light scattering measurement 30
2.1.2.3 Transmission electron micrograph 30
2.1.2.4 X-Ray scattering 31
2.1.2.5 Raman spectroscopy 32
2.1.2.6 Thermogravimetric analysis (TGA) 33
2.1.2.7 Scanning electron micrograph 34
2.1.3 Cyano functionalized material: QCM-CN 35
2.1.3.1 Nitrogen sorption data 36
2.1.3.2 Dynamic light scattering measurement 38
2.1.3.3 X-Ray scattering 38
2.1.3.4 Transmission electron micrograph 39
2.1.3.5 Raman spectroscopy 39
2.1.3.6 Thermogravimetric analysis 40
2.1.3.7 Scanning electron micrograph 41
2.1.4 Vinyl functionalized material: QCM-Vinyl 42
2.1.4.1 Nitrogen sorption data 42
2.1.4.2 Dynamic light scattering measurement 44
2.1.4.3 Raman spectroscopy 44
2.1.5 Mercapto functionalized material: QCM-SH 45
2.1.5.1 Nitrogen sorption data 46
2.1.5.2 47
2.1.5.3 Raman spectroscopy 48
2.2 Microporous materials 49
2.2.1 Pure siliceous zeolite silicalite-1: Sil-1 50
2.2.1.1 X-Ray scattering 50
2.2.1.2 Dynamic light scattering 51
2.2.1.2 Scanning electron micrograph 52
2.2.2 Alumosilicate zeolite ZSM-5: ZSM-5 53
2.2.2.1 X-Ray scattering 53
2.2.2.2 Dynamic light scattering 54
2.2.2.3 55
2.2.3 Zeolite beta:Zeo- b 55V Tableofcontent
2.2.3.1 X-Ray scattering 56
2.2.3.2 Scanning electron micrograph 57
3 Contact printing of colloidal silica nano-particles - Building a micro-
array 58
3.1 Leading industry standards in microarray printing technology:
A brief overview 58
3.1.1 Microarray printing techniques 59
3.1.1.1 Non-contact microarray printing 60
3.1.1.2 Contact microarray printing 61
3.1.2 Pin-printing parameters 65
3.1.3 Experimental parameters of pin-printing colloidal silica nanoparticles 66
3.1.4 Formation of homogenous silica nanoparticle layers 71
3.2 Conclusion contact pin-printing 76
4 Acoustic wave sensors based on piezoelectricity 79
4.1 Classification of acoustic waves 80
4.1.1 Surface acoustic wave (SAW) 81
4.1.2 Acoustic plate mode (APM) sensors 81
4.1.3 Flexural plate wave (FPW) sensors 82
4.1.4 Shear mode (TSM) sensor 83
4.2 Influence of liquids on the resonance frequency 87
4.3 Influence of surface roughness on the resonance frequency of a
QCM device 88
4.4 Experimental setup for QCM sorption experiments 89
4.4.1 Partial pressure control 94
4.4.2 Labview control program 96
4.4.2.1 Basic configuration panel 96
4.4.2.2 Flow control panel 98
4.4.2.3 Frequency counter panel 99
4.4.2.4 Flow step panel 100 Tableofcontent V
4.4.2.5 Mean frequency determination panel 101
4.4.2.6 Temperature step panel 102
5 Heat of adsorption: Theoretical considerations 104
5.1 Commercial application I: The self cooling beer keg 104
5.2 Commercial application II: Drying of nourishments 105
5.3 Sensor related sorption applications based on piezoelectric devices 106
5.4 Relevance of the heat of adsorption for catalytic processes 107
5.5 Measurement methods acquiring the heat of adsorption 108
5.5.1 Calorimetric methods 109
5.5.2 Calculation from equilibrium data 111
6 QCM sorption experiments 116
6.1 Adsorption of ethanol 117
6.1.1 Sorption on non-modified mesoporous material: QCM-E 119
6.1.1.1 Heat of adsorption 122
6.1.2 Sorption on phenyl-functionalized mesoporous material: QCM-Ph 124
6.1.2.1 127
6.1.3 Sorption on cyano-functionalized mesoporous material: QCM-CN 129
6.1.3.1 Heat of adsorption 130
6.1.4 Sorption on vinyl: QCM-Vinyl 131
6.1.4.1 133
6.1.5 Sorption on mercapto: QCM-SH 134
6.1.5.1 Heat of adsorption 136
6.1.6 Conclusion mesoporous samples QCM-