Gas Phase Pyrolysis of
Freon 12
Grant Allen
Seminar Outline: Part A
Infrared Laser Powered Homogeneous Pyrolysis (IR LPHP)
Investigative Techniques
Acknowledgements
Results
Conclusion
Introduction
Introduction
Chlorofluorocarbons (CFCs) are environmentally destructive
Mechanism of gas phase thermal decomposition not fully understood
Initiate gas phase thermal decomposition using IR LPHP
Stable reaction products - IR and GCMS
Short lived intermediates - MIIR and TDL spectroscopy
Proposed mechanism based on:
Freon or R12 (Dichlorodifluoromethane)
Infrared Laser Powered
Homogeneous Pyrolysis (IR LPHP)
Firebrick
Pyrolysis Cell
Hot Zone
CO2 Laser
Investigative Techniques
FT-IR Spectroscopy
GC-MS
Matrix Isolation Infrared Spectroscopy
Tuneable Diode Laser Spectroscopy
Matrix Isolation Infrared
Spectroscopy
Precursor
flow
ZnSe
window
12
= ‘O’ ring vacuum tap (J Young)
= Copper block: Position:
Matrix isolation shroud
Stainless
steel mirror
8 mm o.d.10 mm o.d.
ZnSe window
Vacuum
pump
1: Collection
2: Detection
170 mm
Tuneable Diode Laser
Spectroscopy
Micrometer
mirror adjustment
screws
CO2 laser
beam
Diode laser
input
Diode laser
output
ZnSe
window
CaF window
250 mm
Al reflective mirror
Au
mirror
Freon 12
Thermal decomposition of chlorinated organic compounds dominated by HCl elimination and C-Cl bond scission
Pyrolysis of W(CO)6 leads to W(CO)x species (where x < 6)
W(CO)x species are selective and effective abstractors of atomic Cl from a wide variety of organic substrates
Freon 12: C-Cl bond scission
Clean and low energy route into gas phase organic radical chemistry
Freon 12 pyrolysisA
bsor
banc
e
2000 1800 1600 1400 1200 1000 800
Wavenumber / cm-1
FT-IR spectra of the products of laser pyrolysis of Freon 12 in the absence (—) and presence (—) of W(CO)6
A
A
A
A A
A = CF2Cl2
B B
B = CF2O
C
C = CF3 Cl
D
D = W(CO)6
E
E = C2F4
FF
F
F = C2Cl2F4
G
G = SiF4 Unassigned peaks are attributable to SF6
Freon 12: Decomposition Scheme
F2C Cl CF3Cl CFCl2
SiF4
SiO2
Cl
Cl
CF2Cl +
CF2Cl2
+1
2
3
4
5
6 7
CF2Cl
CF2
C2F4CF2O Secondary reactions8
C2F4Cl2
CF2
O2
Freon 12 pyrolysis: major products are CF3Cl and CF2 O
Freon 12 copyolysis with W(CO)6: major products are C2F4Cl2 and C2F4 and SiF4
CF2 : Matrix Isolation IR
Spectroscopy
FT-IR spectra illustrating dimerisation of CF2 to C2F4 A = CF2 Unassigned peaks are attributable to SF6
Abs
orba
nce
1300 1250 1200 1150
Wave number / cm-1
A15 K
35 K
B
B
B = C2F4
First derivative spectrum centred at ~ 1220 cm-1
Laser off
Laser on
CF2 : Tuneable Diode Laser
Spectroscopy
Conclusion
A mechanism has been proposed for the gas phase thermal decomposition of Freon 12
CF2, a short lived intermediate, has been detected using matrix isolation infrared spectroscopy and observed directly with tuneable diode laser spectroscopy
Abstraction of atomic Cl from Freon 12 by W(CO)x
species provides a low energy route, permitting the detection of less stable reaction products
Prof. Douglas Russell
Acknowledgements
Dr Noel Renner
Dr Nathan Hore
Dr Rebecca Berrigan
Spatial Distribution
of Copper and Iron in
Cardiac Tissue
Seminar Outline: Part B
Electron Probe Microanalysis
Nuclear Microscopy
Acknowledgements
Secondary Ion Mass Spectrometry
Conclusion
Introduction
Introduction
Investigate the spatial distribution of Cu and Fe in cardiac tissue
Analytical techniques:
Cardiac tissue that exhibits marked histological damage may
possess elevated levels of Cu and Fe
Electron probe x-ray microanalysis (EPMA)
Secondary ion mass spectrometry (SIMS)
Nuclear microscopy (NM)
Correlate topographical features with chemical composition
UHV techniques influence method of sample preparation
Electron Probe Microanalysis
Image courtesy of the Microscopy and Microanalysis Facility at the Department of Materials Engineering – Monash University
Detection limit in the region of 100 ppm
Primary ion beam: 5-20 kV electrons
Lateral resolution of 1 µm
Quantitative
Cryochamber
Specimen maintained at 80 K
Electron Probe Microanalysis
Energy /keV
Nuclear Microscopy
Rutherford Backscattering Spectroscopy (RBS) - normalisation
Scanning Transmission Ion Microscopy (STIM) - structural information
Particle Induced X-ray Emission (PIXE) - elemental analysis
Secondary electrons – complementary topographical information
Incident beam: 1.0-3.0 MeV H+ or He+
Lateral resolution of between 0.1 and 10 µm
Detection limit: ppb to ppm
Quantitative
UHV chamber
Specimen section freeze dried
Secondary Ion Mass Spectrometry
Image courtesy of the Bristol University CVD Diamond Group
Detection limit: ppb to ppm
Primary ion beam: 1-30 KeV 133Cs+
Non-quantitative analysis of biological specimens
Lateral resolution of 1 µm is possible
UHV chamber
Specimen section freeze dried
Secondary Ion Mass Spectrometry
Conclusion
Nuclear microscopy: provided the specimen is prepared in an
appropriate manner, determination of the spatial distribution of
metals in biological tissue is possible
Secondary ion mass spectrometry: non-quantitative
Electron probe x-ray microanalysis: insufficient sensitivity
Prof. Garth Cooper (Protemix)
Acknowledgements
Dr Anthony Phillips (Protemix)
Catherine Hobbis (School of Engineering - EPMA)
Dr Marcus Gustafsson (Department of Chemistry - SIMS)
Dr V. John Kennedy (Institute of Geological and Nuclear
Sciences - NM)
Dr Ritchie Sims (Department of Geology - EPMA)