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 Technology
Department of Chemistry, University of California, Riverside
VOCs:
Alkanes,
Alkenes, …
1
O3, PAN,
HNO3, …
Particles
NOx
VOCs:
Alkanes,
Alkenes, …
+
O3, PAN,
HNO3, …
Particles
+
NOx
OH production
mechanism in
alkene + O3 reactions
RH, hydrocarbon
OH
OH
HONO +hv
Alkenes
O3
R, alkyl radical
HO 2
ROOH
OH
carbonyl
+
alcohol
O2
ROONO
RO 2
NO
RO 2
RO
O2
NO 2
2
NO 2
RONO 2
hv
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
O
O
H3C
HC
O
O3
CH
O
C
H3C
CH3
H3C
C
H
CH3
H
O
Primary Ozonide
Co-product of OH
in the decomposition of
Criegee intermediate
O
H3 C
.
H C
2
O
O
O
syn
O
anti
C
C
H 3C
C
O
H
H
H H3C
Criegee Intermediates
Dioxirane
HO
O
CH
O
O
H
H2C
OH
H
CH
C
C
H2
H
(TS)
Atkinson, Paulson, Donahue, Anderson, Marston, Cremer, and many others.
Our Focus
• OH production mechanism
• By detecting co-product of OH using
CRDS
• CH2CHO from
(trans/cis)-CH3CH=CHCH3 + O3
Cavity Ring-Down Spectroscopy
Measure Rate of intensity decay
instead of Magnitude of attenuation
L
Iin
Iout
ls
Detector
High-reflectivity Mirrors
R  99.99 %
A
Wavelength
Time profile
Signal
Processing
Intensity
Spectrum
B
A
B
Time
Reference CRDS Spectrum of Vinoxy Radical
.
H
C
O
C
H
H
CH2CHO
305
310
315
320
325
330
335
340
345
350
Wavelength / nm
Vinoxy radical was produced from photolysis of ethyl vinyl ether precursor.
L. Wang et al.
trans-2-Butene + O3
[CH2CHO]
~3  1011 molecule cm-3
HCHO
Pressure Dependence of CH2CHO
Production
trans-2-butene and O3 in N2
total pressure
Yields of CH2CHO
decrease with increased
total pressure.
8 Torr
(a)
9.5 Torr
(b)
12 Torr
(c)
Possible Reasons:
15.5 Torr
(d)
Increased CH2CHO
depletion by O2;
19 Torr
(e)
37 Torr
(f)
65 Torr
(g)
346.8
347.0
347.2
347.4
347.6
Wavelength (nm)
347.8
348.0
11
Kinetics model
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
Rate constants units: first
Reaction
C4H8 + O3 = CH3CHOO + CH3CHO
C4H8 + O3 = OH + CH2CHO + CH3CHO;
C4H8 + O3 = CH2CO + H2O + CH3CHO;
C4H8 + O3 = CH3OH + CO + CH3CHO;
C4H8 + O3 = CH4 + CO2 + CH3CHO;
C4H8 + O3 = CH3CHO + other products;
C4H8 + O3 = CH3CHO + OH + other products;
CH2CHO + O2 = (CHO)2 + OH
CH2CHO + O2 = HCHO + CO + OH
CH2CHO + O2 = others
OH + O3 = HO2 + O2
OH + C4H8 = others
CH3OH + ·OH → (·)CH2OH + H2O
CH3OH + ·OH → CH3O + H2O
CH2OH + O2 = HCHO + HO2
HCHO + ·OH → HCO + H2O
OH + CH2CHO = other products;
CH3CHO + OH = CH2CHO + H2O
CH3CHO + OH = H2O + CH3CO
CH2CHO = other products;
CH2CHO = WALL;
C4H8 + CH2CHO = other products;
CH3CHOO + C4H8 = P;
CH3CHOO + O3 = P;
CH3CHOO + CH3CHO = SOZ;
CH3CHOO = OH + CH2CHO;
CH3CHOO = WALL;
CH3CHOO + HCHO = SOZ2;
CH3CHOO + CH2CHO = P;
order: s-1; second order: cm3
Branching ratio
0
0.5
0.05
0.07
0.11
0.27
0
0.1
0.3
0.6
0.85
0.15
0.05
0.95
Rate const
0
5.7E-17
9.5E-18
1.33E-17
2.09E-17
8.93E-17
0
6.12E-15
1.836E-14
3.672E-14
1.6E-12
6.4E-11
7.735E-13
9.1E-12
1E-11
1E-11
7.5E-13
0
10
0
1E-15
1E-13
1E-12
76
10
1E-12
1E-11
molecule-1 s-1; third order: cm6 molecule-2 s-1
Kinetics model
29 reactions
5
13
Concentration by CRDS (10 )
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
4
3
2
1
0
0
Rate constants
1
Reaction
C4H8 + O3 = CH3CHOO + CH3CHO
C4H8 + O3 = OH + CH2CHO + CH3CHO;
C4H8 + O3 = CH2CO + H2O + CH3CHO;
C4H8 + O3 = CH3OH + CO + CH3CHO;
C4H8 + O3 = CH4 + CO2 + CH3CHO;
C4H8 + O3 = CH3CHO + other products;
C4H8 + O3 = CH3CHO + OH + other products;
CH2CHO + O2 = (CHO)2 + OH
CH2CHO + O2 = HCHO + CO + OH
CH2CHO + O2 = others
OH + O3 = HO2 + O2
OH + C4H8 = others
CH3OH + ·OH → (·)CH2OH + H2O
CH3OH + ·OH → CH3O + H2O
CH2OH + O2 = HCHO + HO2
HCHO + ·OH → HCO + H2O
OH + CH2CHO = other products;
CH3CHO + OH = CH2CHO + H2O
CH3CHO + OH = H2O + CH3CO
CH2CHO = other products;
CH2CHO = WALL;
C4H8 + CH2CHO = other products;
CH3CHOO + C4H8 = P; Vinoxy
CH3CHOO + O3 = P;
HCHO
CH3CHOO + CH3CHO = SOZ;
CH3CHOO = OH + CH2CHO;
CH3CHOO
= WALL;
5
10
15
20
25
30
CH3CHOO + HCHO = SOZ2;
CH3CHOO + CH2CHO = P;
units: First order: s-1; Second order: cm3 molecule-1
Time/s
Branching ratio
0
0.5
0.05
0.07
0.11
0.27
0
0.1
0.3
0.6
0.85
0.15
0.05
0.95
Rate const
0
5.7E-17
9.5E-18
1.33E-17
2.09E-17
8.93E-17
0
6.12E-15
1.836E-14
3.672E-14
1.6E-12
6.4E-11
7.735E-13
9.1E-12
1E-11
1E-11
7.5E-13
0
10
0
1E-15
1E-13
1E-12
76
10
1E-12
1E-11
s-1; Third order: cm6 molecule-2 s-
6E+11
Vinoxy Conc (molecules/cm3)
Exp Vinoxy (mol/cm^3)
Sim: a=0.5
5E+11
Sim: a=0.3
4E+11
3E+11
2E+11
1E+11
CH2CHO yield (a) is 0.3-0.5
0
5.0
10.0
15.0
20.0
Pressure/Torr
Pressure dependence study of simulation when a= 0.3 and a =0.5
and experimental results.
14
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-2butene, respectively.
–The CH2CHO yields are consistent with the
OH yields of trans- and cis-2-butene.
15
Acknowledgement
National Science Foundation $$
Keck Foundation $$
Mixtli Campos-Pineda
Chad Priest
Prof Jingsong Zhang
Prof Liming Wang