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