alkene ozonolysis

1 / 42

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


Acknowledgements

3 / 42

Motivation

Introduction

Motivation

Peroxy radicals


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


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


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


Acknowledgements

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Measuring peroxy radicals

Introduction

Peroxy radicals



Future Work


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



Future Work


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



Future Work


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



Future Work


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



Future Work


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



Future Work


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



Future Work


Acknowledgements

14 / 42

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Introduction

Peroxy radicals



Future Work


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



Future Work


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


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


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


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


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


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


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


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


Ethene Ozonolysis

Future Work

Acknowledgements

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328 330 332 334 336 338 3400.0

0.5

1.0

1.5

2.0

2.5

Experiment Reference

Introduction

Peroxy radicals


Ethene Ozonolysis

Future Work

Acknowledgements

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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


Ethene Ozonolysis

Future Work

Acknowledgements

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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


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


Ethene Ozonolysis

Future Work

Acknowledgements

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Simulation of the concentration profiles in the flow reactor using aseries of continuous-stirred tank reactors.

��

∆θ/2

∆θ

This can give us an idea of the concentration profile and theaverage concentration in the reactor.

Introduction

Peroxy radicals


Ethene Ozonolysis

Future Work

Acknowledgements

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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


Ethene Ozonolysis

Future Work

Acknowledgements

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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


Ethene Ozonolysis

Future Work

Acknowledgements

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✔ 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


Acknowledgements

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Acknowledgements

Introduction

Peroxy radicals


Acknowledgements

34 / 42

✔ Dr. Jingsong Zhang✔ Chad Priest✔ Lydia Plett✔ Mike Lucas✔ Paul Jones✔ Yanlin Lui

✔ UC-MEXUS Fellowship

Introduction

Peroxy radicals


Acknowledgements

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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


Acknowledgements

36 / 42

Determination of CL is done by the following scheme

Introduction

Peroxy radicals


Acknowledgements

Wadt W et al. J Am Chem Soc. 1975. 97. 3004. 37 / 42

Introduction

Peroxy radicals


Acknowledgements

38 / 42

Symmetry Adapted MOs of NO2

Introduction

Peroxy radicals


Acknowledgements

39 / 42


Introduction

Peroxy radicals


Acknowledgements

40 / 42


Introduction

Peroxy radicals


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


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

alkene ozonolysis

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peroxy radicalsperoxy

criegee intermediatesho2

ho2 no2

ho2 no2

ambient measurements

oxidation of no2

ro no2 recycling

red red t