Studying Ozonolysis Reactions of 2-Butenes Using Cavity Ring-down Spectroscopy Liming Wang, Yingdi Liu, Mixtli Campos-Pineda, Chad Priest and Jingsong.

Studying Ozonolysis Reactions of 2-Butenes

Using Cavity Ring-down Spectroscopy

Liming Wang, Yingdi Liu, Mixtli Campos-Pineda, Chad Priest and Jingsong Zhang

Jet Propulsion Laboratory, California Institute of TechnologyDepartment of Chemistry, University of California, Riverside

1

NOx NOx

O3, PAN, HNO3, … Particles

O3, PAN, HNO3, … Particles

VOCs: Alkanes, Alkenes, …

VOCs: Alkanes, Alkenes, …

NOx NOx

O3, PAN, HNO3, … Particles

O3, PAN, HNO3, … Particles

VOCs: Alkanes, Alkenes, …

VOCs: Alkanes, Alkenes, …

+ +

O 2

R, alkyl radical

RH, hydrocarbon HONO +hv OH

OH NO

RO2

RO

HO 2 NO 2ROONO 2

RONO 2

RO 2carbonyl+alcohol

ROOH

NO 2

O3

O2

hv

OH Alkenes

OH productionmechanism inalkene + O3 reactions

Ozonolysis of Alkenes Reactions

• Important oxidation pathway of alkenes in troposphere

–High concentrations of O3 and alkenes in polluted areas

• Secondary organic aerosol (SOA) production in ozonolysis of large alkenes

• Production of OH radical (10-90% yield) and a source of HOx radical

• Production of Criegee intermediate (CI)

• CI react with many important molecules in the atmosphere : NO2, SO2, H2O etc

• OH production mechanism is not completely established

• Lack of kinetics information of CI

Mechanisms of trans-2-Butene + O3

HC CH

H3C

CH3

O3C C

H3CH CH3

H

O OO

H3C H

O

H3CC

H

OO

H3CC

H

OO

OH

Primary Ozonide

CH2

CH

OO

H

(TS)

H2C CH

OHO

Criegee Intermediates

syn anti

Atkinson, Paulson, Donahue, Anderson, Marston, Cremer, and many others.

H2C CH

O.

H3CC

H

OO

Dioxirane

CRDS

Co-product of OHin the decomposition of Criegee intermediate

Our Focus

• By detecting co-product of OH using CRDS

• CH2CHO from

(trans/cis)-CH3CH=CHCH3 + O3

• OH production mechanism

Cavity Ring-Down Spectroscopy

Iin Iout

High-reflectivity MirrorsR 99.99 %

ls

L

B

BTime profile

Signal

Processing

Spectrum

Time

Inte

nsi

tyA

Wavelength

A

Detector

Measure Rate of intensity decayinstead of Magnitude of attenuation

Reference CRDS Spectrum of Vinoxy Radical

305 310 315 320 325 330 335 340 345 350

CH2CHO

Wavelength / nm

Vinoxy radical was produced from photolysis of ethyl vinyl ether precursor.

C COH

H H

.

L. Wang et al.

347.0 347.5 348.0 348.5 349.0 349.5

Vinoxy (from Photolysis of Ethyl Vinyl Ether)

trans-2-Butene + O3 in N

2

(11 Torr total)

Ethene + O3 in N

2

(750 Torr total)

CH3CHO in N

2 (arb. units)

O3 in N

2 (arb. units)

Ab

sorp

tion

Wavelengths ( nm)

trans-2-Butene + O3

[CH2CHO] ~3 1011 molecule cm-3

HCHO

Wavelength (nm)

346.8 347.0 347.2 347.4 347.6 347.8 348.0

(a)

(b)

(c)

(d)

(e)

(f)

(g)

Yields of CH2CHO decrease with increased total pressure.

Possible Reasons:

Increased CH2CHO depletion by O2;

Pressure Dependence of CH2CHO Production

trans-2-butene and O3 in N2

total pressure

8 Torr

9.5 Torr

12 Torr

15.5 Torr

19 Torr

37 Torr

65 Torr

11

Kinetics modelNo. Reaction Branching ratio Rate const

1 C4H8 + O3 = CH3CHOO + CH3CHO 0 02 C4H8 + O3 = OH + CH2CHO + CH3CHO; 0.5 5.7E-173 C4H8 + O3 = CH2CO + H2O + CH3CHO; 0.05 9.5E-184 C4H8 + O3 = CH3OH + CO + CH3CHO; 0.07 1.33E-175 C4H8 + O3 = CH4 + CO2 + CH3CHO; 0.11 2.09E-176 C4H8 + O3 = CH3CHO + other products; 0.27 8.93E-177 C4H8 + O3 = CH3CHO + OH + other products; 0 08 CH2CHO + O2 = (CHO)2 + OH 0.1 6.12E-159 CH2CHO + O2 = HCHO + CO + OH 0.3 1.836E-14

10 CH2CHO + O2 = others 0.6 3.672E-1411 OH + O3 = HO2 + O2 1.6E-1212 OH + C4H8 = others 6.4E-1113 CH3OH + ·OH → (·)CH2OH + H2O 0.85 7.735E-1314 CH3OH + ·OH → CH3O + H2O 0.15 15 CH2OH + O2 = HCHO + HO2 9.1E-1216 HCHO + ·OH → HCO + H2O 1E-1117 OH + CH2CHO = other products; 1E-1118 CH3CHO + OH = CH2CHO + H2O 0.05 7.5E-1319 CH3CHO + OH = H2O + CH3CO 0.95 20 CH2CHO = other products; 021 CH2CHO = WALL; 1022 C4H8 + CH2CHO = other products; 023 CH3CHOO + C4H8 = P; 1E-1524 CH3CHOO + O3 = P; 1E-1325 CH3CHOO + CH3CHO = SOZ; 1E-1226 CH3CHOO = OH + CH2CHO; 7627 CH3CHOO = WALL; 1028 CH3CHOO + HCHO = SOZ2; 1E-1229 CH3CHOO + CH2CHO = P; 1E-11

Rate constants units: first order:  s-1; second order:  cm3 molecule-1 s-1; third order:  cm6 molecule-2 s-1

Kinetics modelNo. Reaction Branching ratio Rate const

1 C4H8 + O3 = CH3CHOO + CH3CHO 0 02 C4H8 + O3 = OH + CH2CHO + CH3CHO; 0.5 5.7E-173 C4H8 + O3 = CH2CO + H2O + CH3CHO; 0.05 9.5E-184 C4H8 + O3 = CH3OH + CO + CH3CHO; 0.07 1.33E-175 C4H8 + O3 = CH4 + CO2 + CH3CHO; 0.11 2.09E-176 C4H8 + O3 = CH3CHO + other products; 0.27 8.93E-177 C4H8 + O3 = CH3CHO + OH + other products; 0 08 CH2CHO + O2 = (CHO)2 + OH 0.1 6.12E-159 CH2CHO + O2 = HCHO + CO + OH 0.3 1.836E-14

10 CH2CHO + O2 = others 0.6 3.672E-1411 OH + O3 = HO2 + O2 1.6E-1212 OH + C4H8 = others 6.4E-1113 CH3OH + ·OH → (·)CH2OH + H2O 0.85 7.735E-1314 CH3OH + ·OH → CH3O + H2O 0.15 15 CH2OH + O2 = HCHO + HO2 9.1E-1216 HCHO + ·OH → HCO + H2O 1E-1117 OH + CH2CHO = other products; 1E-1118 CH3CHO + OH = CH2CHO + H2O 0.05 7.5E-1319 CH3CHO + OH = H2O + CH3CO 0.95 20 CH2CHO = other products; 021 CH2CHO = WALL; 1022 C4H8 + CH2CHO = other products; 023 CH3CHOO + C4H8 = P; 1E-1524 CH3CHOO + O3 = P; 1E-1325 CH3CHOO + CH3CHO = SOZ; 1E-1226 CH3CHOO = OH + CH2CHO; 7627 CH3CHOO = WALL; 1028 CH3CHOO + HCHO = SOZ2; 1E-1229 CH3CHOO + CH2CHO = P; 1E-11

Rate constants units: First order:  s-1; Second order:  cm3 molecule-1 s-1; Third order:  cm6 molecule-2 s-1

29 reactions

0 5 10 15 20 25 300

1

2

3

4

5

Con

cent

ratio

n by

CR

DS

(10

13)

Time/s

Vinoxy HCHO

14Pressure dependence study of simulation when a= 0.3 and a

=0.5 and experimental results.

5.0 7.0 9.0 11.0 13.0 15.0 17.0 19.00

100000000000

200000000000

300000000000

400000000000

500000000000

600000000000Exp Vinoxy (mol/cm^3)

Sim: a=0.5

Sim: a=0.3

Pressure/Torr

Vin

oxy C

on

c (m

ole

cule

s/cm

3)

CH2CHO yield (a) is 0.3-0.5

15

Summary

CH2CHO is observed from 2-butene ozonolysis reactions:

–CH2CHO + OH is a considerable

channel;

–Chemical kinetic modeling of the vinoxy and formaldehyde production indicates that the CH2CHO yield is 0.3-0.5 and 0.2-0.3 in the ozonolysis reaction of trans- and cis-2-butene, respectively.

–The CH2CHO yields are consistent with the OH yields of trans- and cis-2-butene.

CH2CHO is observed from 2-butene ozonolysis reactions:

–CH2CHO + OH is a considerable

channel;

–Chemical kinetic modeling of the vinoxy and formaldehyde production indicates that the CH2CHO yield is 0.3-0.5 and 0.2-0.3 in the ozonolysis reaction of trans- and cis-2-butene, respectively.

–The CH2CHO yields are consistent with the OH yields of trans- and cis-2-butene.

AcknowledgementNational Science Foundation $$

Keck Foundation $$

Prof Jingsong Zhang Prof Liming Wang

Mixtli Campos-Pineda

Chad Priest

Thank you!