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)