© University of Reading 2006 www.reading.ac. uk Secondary Organic Aerosol Formation: Ozonolysis of Terpenes George Marston, Yan Ma and Rachel Porter Department of Chemistry
Secondary Organic Aerosol Formation: Ozonolysis of Terpenes
Feb 24, 2016
Secondary Organic Aerosol Formation: Ozonolysis of Terpenes. George Marston , Yan Ma and Rachel Porter Department of Chemistry . - PowerPoint PPT Presentation
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
© University of Reading 2006 www.reading.ac.uk
Secondary Organic Aerosol Formation: Ozonolysis of
Terpenes
George Marston, Yan Ma and Rachel PorterDepartment of Chemistry
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008
Ronald Reagan
"Trees cause more pollution than automobiles do.” ‘88
"A tree is a tree. How many more do you have to look at?" '66
"The American Petroleum Institute filed suit against the EPA [and] charged that the agency was suppressing a scientific study for fear it might be misinterpreted. The suppressed study reveals that 80 percent of air pollution comes not from chimneys and auto exhaust pipes, but from plants and trees." ‘79
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 3
Background• The ozonolysis of alkenes is important for
atmospheric chemistry:
Oxidation of VOCs
Generation of radicals
Generation of oxygenated products Secondary Organic Aerosol (SOA)
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 4
SOA Formation• Acid products from the ozonolysis of
terpenes are components of SOA and may lead to particle formation
• Health implications
• SOA can have direct and indirect effects on climate change
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 5
Alkene Ozonolysis
+ O3
O O
O
O O
O
+
*POZ
CI
Criegee Intermediate
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 6
OH Formation
OO
H
OO
H
O O
+ OH
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 7
Terpenes
-pinene -
pinene
3-carene terpinole
ne
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 8
-Pinene Ozonolysis Products
Pinonic acid Pinic acid Norpinonic acid
Norpinic acid
Pinalic acid Norpinalic acid OH-pinonic acid
OH-pinalic acid
OH
O
O
OH
O
OH
O
OH
OO
OH
O
HOO
OOH
O
O
OH
O
OH
O
O
OHOH
HOO
O
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 9
First step
OO
O
O
O
O
+ O3O
OO
POZ
CI1
CI2
k1
(1 )k1
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 10
Aims• To develop mechanisms for acid formation in
terpene ozonolysis • To model results to provide input of rate
constants and branching ratios for the Master Chemical mechanism
To determine which channel (CI) gives rise to which product
To determine branching ratios for decomposition of primary ozonides
To compare product yields from different terpenes
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 11
Methodology
O
OO
O
+ O3
CI2
O + O3
O
O O
CI1
Enone
Enal
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 12
Experimental
• Static reaction chamber coupled to gas chromatography / mass spectrometry / flame ionisation detection
• Acid products trapped on filters and derivatised to methyl esters (BF3/Methanol)
• Enal and enone synthesised from ozonolysis of a suitable terpene
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 13
-Pinene Results
OH
O
OH
O
OH
O
O
0
1
2
3
4
0 20 40 60 80 100Relative Humidity / %
Yiel
d / %
Pinonic acidPinonic acid (acetic acid added)Pinic acidPinic acid (acetic acid added)
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 14
Enal Results
OH
O
OH
O
OH
O
O
0
1
2
3
4
5
0 20 40 60 80 100
Relative Humidity / %
Yiel
d / %
Pinonic acidPinonic acid (acetic acid added)Pinic acidPinic acid (acetic acid added)
O
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 15
Enone Results• Only Pinonic Acid and Norpinonic
Acid are observed
OH
O
O
OH
OO
O
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 16
Enone Results
OH
OO
Norpinonic acid
0
0.05
0.1
0.15
0.2
0 20 40 60 80 100
Relative Humidity / %
Yiel
d / %
from the enone
from ?-pinene
O
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 17
Branching Ratio
OO
O
O
O
O
CI1
CI2
O + O3
O
O O
CI1
H2COO
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 18
Pinonic Acid FormationPinonic acid
0
1
2
3
4
5
0 20 40 60 80 100
Relative Humidity / %
Yiel
d / %
from the enonefrom the enalfrom α-pineneenone + enal OH
O
O
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 19
-Pinene Summary
O
O
OO
O
CI1 CI2
O
+ O3 + O3
50 % 50%
OO
OH
OHO
OOH
O
OH
O
O
OOH
O
OOHOH
O
OHO
norpinic acid
pinalic acid
norpinalic acid OH-pinalic acid
pinonic acid
pinic acid OH
O
O
OH-pinonic acidOH
OH
OHO
O
norpinonic acid
+H20
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 20
3-Carene Yields
y = 1.2435xR2 = 0.8898
0
0.5
1
1.5
2
2.5
3
3.5
0 0.5 1 1.5 2 2.5 33-carene product yield / %
-p
inen
e pr
oduc
t yie
ld /
%
0
0.1
0.2
0.3
0 0.1 0.2 0.3
O
OH
O
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 21
3-Carene, Enone and Enal
3-carene
Enal
Enone
OH
O
O
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 22
3-Carene and Enone
Nor-3-caronic acid
0
0.05
0.1
0 20 40 60 80 100
Relative humidity / %
Yiel
d / %
O
OH
O
O
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 23
3-Caronic Acid MechanismO
O
O
OOH
O
O
O
OH
3-Caronic acid
CI2
O
O
OO
OH
+ O2
Isom.
+ RO2or HO2
O
O
OO
O
O
CI1 stab.+ H2O
ester channel
O
O OH
OH
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 24
3-Carene Summary
OO
O
O
O
O
OH
OO
O
O
OH
OH
O
O
OH
OH
OH
OO
HOO
OH
O
O
O
OH
O
HO
OHO
+ O3
CI1 CI2
+ O3
3-caronic acid
OH
O
O
3-norcaronic acid
OH OH
32%
3-OH-caronic acid3-caralic acid3-caric acid
3-norcaralic acid 3-OH-caralic acid3-norcaric acid
decomp. decomp.
68%
OHdecomp.stab.
+ H2Oisom.
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 25
-pinene
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 26
MechanismO
O
O
O
OO
O
-OH
+O2
OO
+O2-OH
O
OO
+RO2
O
O
-pinene
-pinene
+RO2
-H2COOO
O
O
+O2
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 27
Pinalic-4-acidO
O
O
O
O
O
O2
O
O
OH
O
O
O
O
O2
O
O
OH
+
O
O
OH
92 % 8 %
Pinalic-3-acid Pinalic-4-acid
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 28
Terpinolene
OH
OO
OHO
O
OO
OO
OOO
O
O
O
93 % 7 %+
Terpinolalic Acid (a) Terpinolalic Acid (b)
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 29
Hydroperoxide Formation
OH
OO
OO
O
OOH
OOH
+ O3
OH
O
O
terpinolalic acid (a)
terpinolalic acid (c)
80 %
20 %
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 30
Hydroperoxide Formation
OO
OO
favoured over ?O
OH
OHO
O2
M ?Formation of hydroperoxide directly from quenching of nascent Criegee Intermediates?
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 31
Summary
Ring opening in -pinene and terpinolene
Intramolecular reactions
Hydroperoxide formation
O
O
OH
OO
O
O
O Isomerisation
+O2
• Improvements in mechanisms• Uncertainties:
• Some quantitative data, but more needed
OO
O
OOH
OIsom.
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 32
Acknowledgements
• Natural Environment Research Council• University of Reading
• Dr Yan Ma• Dr David Johnson• Rachel Porter
• Dr Andy Russell• Dr David Chappell• Tim Wilcox• Thomas Luciani
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 33
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 34
Mechanisms
O
OOEsterChannel
OH
OO OH
OH
O
OO
O
O
CI1
+ M+ H2O H2O
Pinonic acid
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 35
Mechanisms
OO
OO
OH
O
OO
O
O
OH
CI2
O
O
OOPinonic acid
OH
+ O2
Isom.
+ RO2
or HO2
Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 36
MechanismsO
OO
O
1
.O
O
O
O
OH
O
OO
Isom.RO2
O
OH
O
+ O2
2 3
5
OH
O
pinic acid OH
O
OH
O
OO
Isom. +O2
+ RO2or HO2
+ RO2
O
OH
O
O
CO2+ O2
OH
OO
+ RO2
+ O2
O
O
8
9
10
Related Documents
