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Real time measurement of peroxy radicals andCriegee intermediates using cavity ringdown
spectroscopy (CRDS)
Mixtli Campos-Pineda
November 18th, 2013
Outline
Introduction
Peroxy radicals
CriegeeIntermediates
Acknowledgements
2 / 42
IntroductionMotivation
Peroxy radicalsMeasuring peroxy radicalsCRDSPrevious measurementsDual-channel PERCA-CRDSFuture Work
Criegee IntermediatesMeasuring Criegee IntermediatesEthene OzonolysisFuture Work
Acknowledgements
Introduction
Introduction
Motivation
Peroxy radicals
CriegeeIntermediates
Acknowledgements
3 / 42
Motivation
Introduction
Motivation
Peroxy radicals
CriegeeIntermediates
Acknowledgements
Atkinson. Atmos Env. 2000. 34. 2063 4 / 42
Organic radicals play important roles in atmospheric chemistry.
Peroxy radicals are involved in OH, RO·, and NOx budgets in thetroposphere:
Introduction
Motivation
Peroxy radicals
CriegeeIntermediates
Acknowledgements
Atkinson. Atmos Env. 2000. 34. 2063 5 / 42
Criegee intermediates (CIs) are involved in OH production,oxidation of NO2, SO2, and formation of secondary organicaerosols. They are produced by ozonolysis of alkenes:
Introduction
Motivation
Peroxy radicals
CriegeeIntermediates
Acknowledgements
6 / 42
Since peroxy radicals and CIs are transient species, theirmeasurement proves challenging. It is important, however, to havereliable measurements of organic radicals in order to:
✔ Understand reaction pathways.✔ Determine radical yields.✔ Assess the kinetics of atmospheric reactions.
Peroxy radicals:
✔ Environmental chamber measurements.✔ Ambient measurements.
Criegee Intermediates:
✔ Laboratory scale reactor.
Peroxy radicals
Introduction
Peroxy radicals
Measuring peroxyradicals
CRDSPreviousmeasurementsDual-channelPERCA-CRDS
Future Work
CriegeeIntermediates
Acknowledgements
7 / 42
Measuring peroxy radicals
Introduction
Peroxy radicals
Measuring peroxyradicals
CRDSPreviousmeasurementsDual-channelPERCA-CRDS
Future Work
CriegeeIntermediates
Acknowledgements
Cantrell et al. Analytical Chemistry. 1984. 56. 1496. 8 / 42
Direct measurement of peroxy radicals is not performed due toeither lack of sensitivity (IR) or lack of selectivity (UV).Real time measurement of peroxy radicals is done using peroxyradical chemical amplification (PERCA), which produces NO2 in 3main steps:Conversion to NO2:
HO2 +NO −→ HO+NO2
RO2 +NO −→ RO+NO2
Recycling:HO+ CO −→ CO2 +H
H+O2 +M −→ HO2 +M
RO+O2 −→ HO2(orR”O2) + R′CHO(orR′R”CO)
Introduction
Peroxy radicals
Measuring peroxyradicals
CRDSPreviousmeasurementsDual-channelPERCA-CRDS
Future Work
CriegeeIntermediates
Acknowledgements
9 / 42
The following termination reactions stop amplification:
HO+NO+M −→ HONO+M
HO2 +NO2 +M −→ HO2NO2 +M
HO2 +HO2 −→ H2O2 +O2
HO2 +wall −→ products
NO2 produced is measured by:
✔ Chemiluminescene by reaction with O3 or luminol.✔ Laser-induced fluorescence (LIF).✔ CRDS
CRDS
Introduction
Peroxy radicals
Measuring peroxyradicals
CRDSPreviousmeasurementsDual-channelPERCA-CRDS
Future Work
CriegeeIntermediates
Acknowledgements
10 / 42
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Using a simple approach:
I0 = Ilaser · T e−αd· T
I1 = Ilaser · T e−αd·Re−αd
·Re−αdT
In = I0R2ne−2nαd
Introduction
Peroxy radicals
Measuring peroxyradicals
CRDSPreviousmeasurementsDual-channelPERCA-CRDS
Future Work
CriegeeIntermediates
Acknowledgements
11 / 42
Changing to a continuous variable t = 2nLc
then:
I(t) = I0Rct
L e−ct
Lαd
Using the approximation ln(R) = −(1−R) and simplifying:
I(t) = I0e− tc
L(1−R+αd) = I0e
− t
τ
where τ = L
c(1−R+αd)
α = L
dc
(
1τ−
1τ0
)
= σN
This method is suitable for atmospheric measurements due to:
✔ Long sample path (high sensitivity).✔ Real time measurements.✔ Portability (in situ measurements).
Introduction
Peroxy radicals
Measuring peroxyradicals
CRDSPreviousmeasurementsDual-channelPERCA-CRDS
Future Work
CriegeeIntermediates
Acknowledgements
12 / 42
Measurements are done at 405.8 nm of the 2B1 ←2A1 transition :
250 300 350 400 450 500 5500
3
6
9
12
15
x400 405 410 415 4205
6
7
8
x
Previous measurements
Introduction
Peroxy radicals
Measuring peroxyradicals
CRDSPreviousmeasurementsDual-channelPERCA-CRDS
Future Work
CriegeeIntermediates
Acknowledgements
Liu Y et al. Environ Sci Technol. 2009. 43. 7791. 13 / 42
Previous work has been done in our group by Liu et al. measuringperoxy radicals with a single-channel PERCA-CRDS instrument:
Dual-channel PERCA-CRDS
Introduction
Peroxy radicals
Measuring peroxyradicals
CRDSPreviousmeasurementsDual-channelPERCA-CRDS
Future Work
CriegeeIntermediates
Acknowledgements
14 / 42
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Introduction
Peroxy radicals
Measuring peroxyradicals
CRDSPreviousmeasurementsDual-channelPERCA-CRDS
Future Work
CriegeeIntermediates
Acknowledgements
15 / 42
Reactions are carried out at UCR’s College of Engineering Centerof Environmental Research and Technology (CE-CERT) using achamber reactor.
Future Work
Introduction
Peroxy radicals
Measuring peroxyradicals
CRDSPreviousmeasurementsDual-channelPERCA-CRDS
Future Work
CriegeeIntermediates
Acknowledgements
16 / 42
✔ Peroxy radicals:
✘ Optimize ring-down times of the dual-channelPERCA-CRDS
✘ Determine the best sampling point of the reactor at CERTto minimize loses.
✘ Use a simple well-known reaction to assess the instrumentresponse to peroxy radical production in the reactor.
Criegee Intermediates
Introduction
Peroxy radicals
CriegeeIntermediatesMeasuring CriegeeIntermediates
Ethene Ozonolysis
Future Work
Acknowledgements
17 / 42
Introduction
Peroxy radicals
CriegeeIntermediatesMeasuring CriegeeIntermediates
Ethene Ozonolysis
Future Work
Acknowledgements
Vereecken L. Science. 2013. 340. 154. 18 / 42
Criegee Intermediates are formed along with formaldehyde byozonolysis reactions of alkenes:
H2C = CH2 +O3 −→ HCHO+ [H2COO]‡
It was thought that the only reactions of CI were formation of OHand reaction with water.
[H2COO]‡ −→ OH+ products
[H2COO]‡ +M −→ [H2COO] +M
[H2COO] + H2O −→ products
Determination of kinetic rates of reactions of CIs is primarily doneby observing end-of-reaction products.
Introduction
Peroxy radicals
CriegeeIntermediatesMeasuring CriegeeIntermediates
Ethene Ozonolysis
Future Work
Acknowledgements
Vereecken L. Science. 2013. 340. 154. 19 / 42
Recent studies of stabilized Criegee found that CI reactions arefaster than previously thought, and that CIs undergo reactionswith NO2:
[H2COO] + NO2 −→ products
And SO2:
[H2COO] + SO2 −→ SO3 + products
Up to date, there are no direct measurements of CI as product ofalkene ozonolysis.
Measuring Criegee Intermediates
Introduction
Peroxy radicals
CriegeeIntermediatesMeasuring CriegeeIntermediates
Ethene Ozonolysis
Future Work
Acknowledgements
Weltz O et al. Science. 2012. 335. 204. 20 / 42
Direct measurements of stabilized CI (sCI), sythesized from1-iodoethyl radical and oxygen, were done using synchrotronphotoionization mass spectrometry.
Inte
gra
ted
ph
oto
ion
sig
na
l
12.011.511.010.510.0
Photon energy (eV)
m/z = 46 from CH 2 I + O 2
CH 2 OO (calculated)
Dioxirane (calculated)
Formic acid (Cool et al.)
Introduction
Peroxy radicals
CriegeeIntermediatesMeasuring CriegeeIntermediates
Ethene Ozonolysis
Future Work
Acknowledgements
Su Y et al. Science. 2013. 340. 174. 21 / 42
Su et al. reported an IR absorption feature of CH2OO.
Introduction
Peroxy radicals
CriegeeIntermediatesMeasuring CriegeeIntermediates
Ethene Ozonolysis
Future Work
Acknowledgements
Beames J et al. JACS. 2012. 134. 20045 22 / 42
Beames et al. reported an UV absorption feature of CH2OO witha σ ≈ 5× 10−17cm2molecule−1.
This opens the possibility of direct optical measurement of CIsusing high sensitivity optical methods.
Introduction
Peroxy radicals
CriegeeIntermediatesMeasuring CriegeeIntermediates
Ethene Ozonolysis
Future Work
Acknowledgements
23 / 42
CIs produced by ozonolisys have high energy; we need, then, toassess the kinetics of the energy-rich CI.
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Ethene Ozonolysis
Introduction
Peroxy radicals
CriegeeIntermediatesMeasuring CriegeeIntermediates
Ethene Ozonolysis
Future Work
Acknowledgements
24 / 42
We are looking for features in the range of 330-340, correspondingto the following spectrum :
328 330 332 334 336 338 3404.8
5.0
5.2
5.4
5.6
5.8
6.0
6.2
(x10
-19 )
CH2O + CH
2OO
CH2OO
332 334 336 3384.92
4.94
4.96
4.98
5.00
5.02
5.04
5.06
Introduction
Peroxy radicals
CriegeeIntermediatesMeasuring CriegeeIntermediates
Ethene Ozonolysis
Future Work
Acknowledgements
25 / 42
328 330 332 334 336 338 3400.0
0.5
1.0
1.5
2.0
2.5
Experiment Reference
Introduction
Peroxy radicals
CriegeeIntermediatesMeasuring CriegeeIntermediates
Ethene Ozonolysis
Future Work
Acknowledgements
26 / 42
330 332 334 336 338 340-2.0
-1.5
-1.0
-0.5
0.0
0.5
678 torr 360 torr 220 torr 110 torr
Introduction
Peroxy radicals
CriegeeIntermediatesMeasuring CriegeeIntermediates
Ethene Ozonolysis
Future Work
Acknowledgements
27 / 42
We need to look closer into the reactions involved in etheneozonolysis:
H2C = CH2 +O3 −→ HCHO+ [H2COO]‡
[H2COO]‡ +M −→ H2COO +M
H2COO + HCHO −→ P
H2COO + O3 −→ HCHO+ 2O2
H2COO + C2H4 −→ P
H2COO + H2O −→ P
There is fast depletion of the CI.
Introduction
Peroxy radicals
CriegeeIntermediatesMeasuring CriegeeIntermediates
Ethene Ozonolysis
Future Work
Acknowledgements
Ianni JC. Kintecus. Windows Version 4.55. 2012. www.kintecus.com 28 / 42
We simulate the CI mechanish as a dynamical system of ODEsusing KINTECUS:
x1 = f1(x1, x2, ..., xn)
x2 = f2(x1, x2, ..., xn)
...
xn = fn(x1, x2, ..., xn)
Introduction
Peroxy radicals
CriegeeIntermediatesMeasuring CriegeeIntermediates
Ethene Ozonolysis
Future Work
Acknowledgements
29 / 42
Simulation of the concentration profiles in the flow reactor using aseries of continuous-stirred tank reactors.
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∆θ/2
∆θ
This can give us an idea of the concentration profile and theaverage concentration in the reactor.
Introduction
Peroxy radicals
CriegeeIntermediatesMeasuring CriegeeIntermediates
Ethene Ozonolysis
Future Work
Acknowledgements
30 / 42
0 5 10 15 20 25 30 35 40 450.0
2.0x1017
4.0x1017
6.0x1017
8.0x1017
1.0x1018
1.2x1018
1.4x1018
1.6x1018
0 5 10 15 20 25 30 35 40 450.0
5.0x1014
1.0x1015
1.5x1015
2.0x1015
2.5x1015
3.0x1015
0 5 10 15 20 25 30 35 40 450.0
2.0x1011
4.0x1011
6.0x1011
8.0x1011
1.0x1012
1.2x1012
1.4x1012
1.6x1012
1.8x1012
0 5 10 15 20 25 30 35 40 450.0
5.0x1014
1.0x1015
1.5x1015
2.0x1015
2.5x1015
3.0x1015
3.5x1015
C2H4
N m
olec
ule/
cm3
CH2O
CH2OO
N m
olec
ule/
cm3
r
O3
r
Introduction
Peroxy radicals
CriegeeIntermediatesMeasuring CriegeeIntermediates
Ethene Ozonolysis
Future Work
Acknowledgements
31 / 42
Conc: C2H4 O3 H2CO H2COO
Inlet 1.48E+18 3.10E+15 0 0.00E+00
S1 1.48E+18 5.42E+14 2.24E+15 1.75E+12
S2 1.48E+18 5.18E+13 2.67E+15 1.60E+11
S3 1.48E+18 4.95E+12 2.71E+15 1.50E+10
S4 1.48E+18 4.73E+11 2.71E+15 1.45E+09
S5 1.48E+18 4.52E+10 2.71E+15 1.40E+08
S6 1.48E+18 4.32E+09 2.71E+15 1.33E+07
S7 1.48E+18 4.13E+08 2.71E+15 1.27E+06
S8 1.48E+18 3.94E+07 2.71E+15 1.21E+05
S9 1.48E+18 3.76E+06 2.71E+15 1.15E+04
S10 1.48E+18 360000 2.71E+15 1100
Exhaust 1.48E+18 34400 2.71E+15 105
Average 1.48E+18 5.99E+13 2.66E+15 1.93E+11
CSTR 1.47E+18 3.25E+13 2.64E+15 1.00E+11
Measured NA NA 2.40E+15 NA
Future Work
Introduction
Peroxy radicals
CriegeeIntermediatesMeasuring CriegeeIntermediates
Ethene Ozonolysis
Future Work
Acknowledgements
32 / 42
✔ Criegee intermediates:
✘ Run ozonolysis of alkenes with faster rates (e.g.Tetramethylethylene, cis 2-butene).
✘ Simulate the kinetics of those alkenes to optimize reactionconditions.
✘ Use a scavenger (HFA) to confirm the presence of CIabsorption feature.
✘ Study the kinetics of the CI reactions with NO2, SO2, andH2O
Acknowledgements
Introduction
Peroxy radicals
CriegeeIntermediates
Acknowledgements
33 / 42
Acknowledgements
Introduction
Peroxy radicals
CriegeeIntermediates
Acknowledgements
34 / 42
✔ Dr. Jingsong Zhang✔ Chad Priest✔ Lydia Plett✔ Mike Lucas✔ Paul Jones✔ Yanlin Lui
✔ UC-MEXUS Fellowship
Introduction
Peroxy radicals
CriegeeIntermediates
Acknowledgements
35 / 42
Formaldehyde cross-section
328 330 332 334 336 338 340 3420.0
0.5
1.0
1.5
2.0
2.5
(10-1
9 )
332 333 334 335 336 3370.0
0.2
0.4
0.6
0.8
1.0
(1
0-20 )
Introduction
Peroxy radicals
CriegeeIntermediates
Acknowledgements
36 / 42
Determination of CL is done by the following scheme
Introduction
Peroxy radicals
CriegeeIntermediates
Acknowledgements
Wadt W et al. J Am Chem Soc. 1975. 97. 3004. 37 / 42
Introduction
Peroxy radicals
CriegeeIntermediates
Acknowledgements
38 / 42
Symmetry Adapted MOs of NO2
Introduction
Peroxy radicals
CriegeeIntermediates
Acknowledgements
39 / 42
Symmetry Adapted MOs of NO2
Introduction
Peroxy radicals
CriegeeIntermediates
Acknowledgements
40 / 42
Symmetry Adapted MOs of NO2
Introduction
Peroxy radicals
CriegeeIntermediates
Acknowledgements
Liu Y et al. Environ Sci Technol. 2009. 43. 7791. 41 / 42
Previous data from our group indicates a high amount of peroxyradicals during wildfire events:
Introduction
Peroxy radicals
CriegeeIntermediates
Acknowledgements
42 / 42
Conc: C2H4 O3 H2CO H2COO
Inlet 2.94E+17 7.40E+14 0 0
S1 2.94E+17 5.38E+14 1.90E+14 2.08E+12
S2 2.94E+17 3.07E+14 3.95E+14 1.03E+12
S3 2.94E+17 1.75E+14 5.09E+14 5.05E+11
S4 2.94E+17 9.99E+13 5.73E+14 3.00E+11
S5 2.94E+17 5.70E+13 6.09E+14 1.65E+11
S6 2.94E+17 3.25E+13 6.30E+14 9.40E+10
S7 2.94E+17 1.85E+13 6.42E+14 5.03E+10
S8 2.94E+17 1.06E+13 6.50E+14 3.02E+10
S9 2.94E+17 6.05E+12 6.54E+14 1.73E+10
S10 2.94E+17 3.45E+12 6.56E+14 9.85E+09
Exhaust 2.94E+17 1.20E+12 6.58E+14 3.42E+09
Average (PFR) 2.94E+17 1.25E+14 5.51E+14 4.28E+11
CSTR 2.93E+17 8.71E+13 5.59E+14 2.63E+11
Measured NA 6.27E+14 2.34E+14 NA