scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Rate constant for the reaction of hydroxyl radical with formaldehyde over the temperature range 228-362 K

01 Sep 1980-Journal of Chemical Physics (American Institute of Physics)-Vol. 73, Iss: 5, pp 2254-2258
TL;DR: In this article, the rate constants for the reaction OH? H2CO measured over the temperature range 228-362 K using the flash photolysis-resonance fluorescence technique are given.
Abstract: Absolute rate constants for the reaction OH ? H2CO measured over the temperature range 228-362 K using the flash photolysis-resonance fluorescence technique are given. The results are independent of variations in H2CO concentration, total pressure Ar concentration, and flash intensity (i.e., initial OH concentration). The rate constant is found to be invariant with temperature in this range, the best representation being k sub 1 = (1.05 ? or - 0.11) x 10 to the 11th power cu cm molecule(-1) s(-1) where the error is two standard deviations. This result is compared with previous absolute and relative determinations of k sub 1. The reaction is also discussed from a theoretical point of view.

Content maybe subject to copyright    Report

N O T I C E
THIS DOCUMENT HAS BEEN REPRODUCED FROM
MICROFICHE. ALTHOUGH IT IS RECOGNIZED THAT
CERTAIN PORTIONS ARE ILLEGIBLE, IT IS BEING RELEASED
IN THE INTEREST OF MAKING AVAILABLE AS MUCH
INFORMATION AS POSSIBLE

(NASA-TPl-80666)
RATE
CCNSTANT
FOR
THE
MEACTIQN
OF
HYDROXYL
XADICAL
WITH
EBBHALDEHYDE
OV
Ell
THE
'IENFERBTUBE
RANGE
228-36
K
(NASA)
17
p
HC
A02/1F
A01
CSCk
Technical
Memorandum
Rate
Constant
for
the
Reaction
of
HydroxyB
Radical
with
Formaldehyde
Over
the
Temperature
Range
228-362K
.
L.
4.
Stief
Dm
Fa
Nava
W.
A.
i)ayne
J.
V.
Michael
MARCH
I980
Natntiona!
Aeronautics
and
Space
Administration
Q&d
$pmx
Flight
Center
Greenbelt,
Maryland
20771

RATE CONSTANT FOR
THE
REACTION OF HkDROXYL
RADICAI,
WITH
FORMALDEHkDE
OVER
THE TEMPERATURE RANGE 228-362
K
L.
J.
~tief,~
D.
F.
Nava,
h.
A.
Payne and
J.
V.
Michael
b
Astrochemistry Branch
Laboratory for Extraterrestrial Physics
NASA/Goddard Space Flight Center
Greenbelt, Maryland 20771
a)
Adjunct Professor of Chemistry, Catholic University of herica,
hashington,
D.
C.
20064
b)
Visiting Professor of Chemistry, Catholic University of America,
hashington,
D.
C.
20064

Absolute rate constants for the reaction
OH
+
H2C0 have been measured
over the temperature range 228-362K using the flash photolysis-resonance
fluorescence technique.
The results were independent of variations in
[H2CO],
total pressure
[Arj
and flash intensity (i.e., initial [OH]). The
rate
constant
was
found to be invariant with temperature in this range, the best
-11
3
-1 -1
representation being
k,
=
(1.05
+
0.11)
n
'iO
cm
~uolccule
s
where tho
error
is
two standard deviations. This result
is
compared with previous
absolute and relative determinations of
kl.
The reaction
is
also discussed
from a theoretical point of view.
The reaction of the hydroxyl radical with formaldehyde
is
of interest in
high temperature combustion studies, in an explanation for
CO
formation in
the atmosphere of Jupiter
,2
and in methane oxidation in the troposphere and
stratosphere of the
earth.3 in all these instances,
H2C0
is
a
product of
hydrocarbon
oxidatim.
For the Jovian atmosphere,
it
is
proposed that H2C0
is
formea primarily in the reaction
0
+
CH
Loss processes include photolysis
2
3
'
ana reaction with
H
and
OH.^^.
In the stratosphere,
H2C0
is
formed
as
a
proauct of the low temperature oxidation of atmospheric methane.
It
is
removed by photolysis and by reaction with
OH,
O
and
Ck.
The reactions
0
+
h2C0
and
Ck
+
H2C0
are relatively minor loss processes for formaldehyde
at
most altitudes in the stratosphere.' Rate constant measurements for these
reactions have been recently reported by us as
well
as other workers.
5,6
Reaction with
OH
is
a major sink for H2C0 at all altitudes in the upper
atmosphere,' but there have been no direct measurements of the absolute rate
constant
at
the low temperatures prevailing there.
The mechanism of the reaction has been usually assumed to be
H
atom
abstraction
OH
+
H2C0
+
H20
+
HCO,
(la)
although there
is
little
or no direct evidence for this. Recently, Horowitz

et
a1.7
have proposed the additional reaction channel
OH
+
H2C0
+
HCOOH
+
H.
(Ib)
Additional work
is
required to
test
the validity of this stlggestion.
Room temperature measurements of the absolute rate constant for the
react
ion
QH
a
H2C0
+
products (1
have been made using the discharge flow-mass spectrometric technique (DF-MS)
with
OH
in and by the flash ph~to~ysis-resonance fluorescence
technique
(FP-RF) with
H2C0
in excess.
Herron and
penzborn8 obtained a
3 -1 -1
-
9
lower
limit
kl
>
0.7 x cm molecule
s
,
Morris and Niki give kl
=
3 -1 -1
(
1.4
5
0.
x 0
c
molecule
s
and Atkinson and pittsl0 report kl
=
3 -1
-1
(0.94
5
0.10) x lo-''
cm
molecule
s
,
all
at
298
2
2
K.
There have been
three relative rate constant determinations at room temperature. Morris and
Niki,
l1
using the
DF-MS
technique, measured
OH
+
H2C0 relative to
OH
+
C
H
3 -1
-i
3
6
and obtained
the
result k1
=
(1.5
1.
0.15) x lo-''
cm
molecule
s
.
Niki et
a1.
l2
employed Fourier Transform Infra- red Spectroscopy
(FTIR)
with
OH
+
C
H
-11
3
2-1
as
the reference reaction and obtained k
-
(1.5
+
0.1)
IF
13 cm molecule
-
1
1
-
s
.
~mith'~ measured
OH
9
H2C0 relative to
OH
+
OH
using the DF-MS technique
-1 -1
and reports
kl
=
0.65 x 10-I
92
molecule
s
.
There have been only two variable temperature studies of the reaction,
10 10
one absolute
and one relative.
l3
Atkinson and Pitts
give k1
=
1.25
x
3
-1 -1
lo-" exp(-88
2
150/T)
cm
molecule
s
for the temperature interval
299
to
426
K
while ~mith'sl~ results from 268 to 334
K
may be represented by kl
=
6
x
3
10-I' exp(-635
2
250/T) cm molecule-' s-I.
This later study
is
the only one
below room temperature but
its.
usefulness
it:,
considerably reduced by the fact
that
the rate parameters of the rsference reaction
OH
+
OH
are
far
more
uncertain than those for
OH
+
H2Cc" itself.
An inspection of the available rate data thus shows disagreement
by
a
factor of two
at
room temperature,
a
factor
sf
five in the Arrhenius

Citations
More filters
Journal ArticleDOI
TL;DR: In this article, a variable-pressure flow reactor over an initial reactor temperature range of 550-850 K, in the pressure range 12-18 atm, at equivalence ratios of 0.7 ≤ ϕ ≤ 4.2, with nitrogen diluent of approximately 98.5%.
Abstract: Dimethyl ether oxidation has been studied in a variable-pressure flow reactor over an initial reactor temperature range of 550–850 K, in the pressure range 12–18 atm, at equivalence ratios of 0.7 ≤ ϕ ≤ 4.2, with nitrogen diluent of approximately 98.5%. On-line extraction sampling in conjunction with FTIR, NDIR (for CO and CO2), and electrochemical (for O2) analyses were performed to quantify species at specific locations along the axis of the turbulent flow reactor. Product species concentrations were correlated against residence time (at constant inlet temperature) and against temperature (at fixed mean residence time) in the reactor. Formic acid was observed as a major intermediate of dimethyl ether oxidation at low temperatures. The experimental species-evolution profiles were compared to the predictions of a previously published detailed kinetic mechanism [1]. This mechanism did not predict the formation of formic acid. In the current study we have included chemistry leading to formic acid formation (and oxidation). This new chemistry is discussed and is able to reproduce the experimental observations with good accuracy. In addition, this model is able to reproduce low-temperature kinetic data obtained in a jet-stirred reactor [2] and the shock-tube results of Pfahl et al. [3] © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 741–759, 2000

351 citations

Journal ArticleDOI
TL;DR: Based on the measured atmospheric distributions of ethane and propane (at midlatitudes in the northern hemisphere) and a simplified mechanism for their oxidation, it is predicted that acetaldehyde, acetone, and PAN (CH/sub 3/C(O)OONO/sub 2/) are ubiquitous components of the troposphere and the lower stratosphere as mentioned in this paper.
Abstract: Based on the measured atmospheric distributions of ethane and propane (at midlatitudes in the northern hemisphere) and a simplified mechanism for their oxidation, it is predicted that acetaldehyde, acetone, and PAN (CH/sub 3/C(O)OONO/sub 2/) are ubiquitous components of the troposphere and the lower stratosphere. Average acetaldehyde concentrations (from ethane oxidation) of 22 parts per trillion (ppt), 3 ppt, and 7 ppt; average acetone concentrations (from propane oxidation) of 111 ppt, 15 ppt, and 3 ppt and average PAN concentrations of 17 to 34 ppt, 90 to 360 ppt, and 40 to 85 ppt are estimated for lower troposphere (approx.2 km), upper trposphere (approx.9 km), and the lower stratosphere (approx. 15 km), respectively. These calculations suggest that in the troposphere, nitrogen oxides (NQ/sub x/) contained in their organic form may be as much or more abundant as their inorganic form. This organic form of reactive nitrogen is in chemical equilibrium (CH/sub 3/C(O)OONO/sub 2/ arrow-right-left CH/sub 3/C(O)OO+NO/sub 2/) with inorganic NO/sub 2/ and acts as reservoir of inorganic NO/sub x/. Measurement methods for PAN are currenlty available to verify these predicted results.

317 citations

Journal ArticleDOI
TL;DR: In this paper, chemical species profiles have been measured at atmospheric pressure for two dimethyl ether (DME)−air flat flames having fuel/air equivalence ratios of 067 and 149.
Abstract: Chemical species profiles have been measured at atmospheric pressure for two dimethyl ether (DME)−air flat flames having fuel/air equivalence ratios of 067 and 149 The samples, obtained with an uncooled quartz probe, were analyzed by either gas chromatography or Fourier transform infrared (FTIR) spectroscopy for CH4, C2H2, C2H4, C2H6, C3H8, DME, CO, CO2, O2, CH2O, and formic acid A pneumatic probe calibrated at a reference position in the burned gas by a radiation-corrected thermocouple provided temperature profiles for each flame Species profiles for two methane−air flames with equivalence ratios and cold-gas flow velocities similar to those of the DME flames were also obtained for comparison to the DME results Mole fractions of C2 product species were similar in DME and methane flames of similar equivalence ratios However, the CH2O mole fractions were 5−10 times larger in the DME flames These experimental profiles are compared to profiles generated in a computer modeling study using the best ava

199 citations

Journal ArticleDOI
TL;DR: The mixing ratio of formaldehyde (HCHO) has been determined for air samples collected at a moderately polluted continental site (Julich, Federal Republic of Germany) and for sample collected at coastal sites in Ireland and New Zealand as discussed by the authors.
Abstract: The mixing ratio of formaldehyde (HCHO) has been determined for air samples collected at a moderately polluted continental site (Julich, Federal Republic of Germany) and for samples collected at coastal sites in Ireland and New Zealand. In addition the HCHO mixing ratio has been determined for air samples collected in the North and South Atlantic during a cruise of the F/S Meteor from Hamburg at 55°N to Montevideo at 35°S in October and November 1980. The HCHO mixing ratio in clean tropical marine air is of the order of 0.2 parts per billion by volume, about 50% lower than predicted by current photochemical models that include CH4 oxidation as the only source for HCHO. In the mid-Atlantic, diurnal variations of the HCHO mixing ratio showing weak maxima during the early afternoon were occasionally observed. These variations may be attributed to the diurnal behavior of the photochemical and physical processes which determine the mixing ratio of HCHO during stable weather conditions. The results are discussed with regard to the currently accepted theory of the photochemistry of HCHO in the clean troposphere. It appears that the yield of HCHO formation through hydrocarbon photooxidation in the background marine troposphere is less than assumed from model considerations, most probably because of the lack of sufficiently high NO concentrations.

143 citations

Journal ArticleDOI
TL;DR: In this paper, for the hydrogen abstraction reaction of HCHO by OH radicals assisted by water, formic acid, or sulfur acid, the possible reaction mechanisms and kinetics have been investigated theoretically using quantum chemistry methods and transition-state theory.
Abstract: In this paper, for the hydrogen abstraction reaction of HCHO by OH radicals assisted by water, formic acid, or sulfur acid, the possible reaction mechanisms and kinetics have been investigated theoretically using quantum chemistry methods and transition-state theory. The potential energy surfaces calculated at the CCSD(T)/6-311++G(df,pd)//MP2(full)/6-311++G(df,pd) levels of theory reveal that, due to the formation of strong hydrogen bond(s), the relative energies of the transition states involving catalyst are significantly reduced compared to that reaction without catalyst. However, the kinetics calculations show that the rate constants are smaller by about 3, 9, or 10 orders of magnitude for water, formic acid, or sulfur acid assisted reactions than that uncatalyzed reaction, respectively. Consequently, none of the water, formic acid, or sulfur acid can accelerate the title reaction in the atmosphere.

78 citations

References
More filters
Journal ArticleDOI
TL;DR: In this article, a list of recommended rate coefficients for chemical reactions occurring in flames is given, expressed as functions of temperature for the range 1000 ⩽ T ⊽ 3000 K. Brief notes on the origins of recommended coefficients are included and rough uncertainties are attached to the listed values.

161 citations

Journal ArticleDOI
TL;DR: In this paper, the absolute rate constants for the reactions of the OH radical with HCHO and CH3CHO were determined over the temperature range 299-426°K by a flash photolysis-resonance fluorescence technique.
Abstract: Absolute rate constants for the reactions of the OH radical with HCHO and CH3CHO have been determined over the temperature range 299–426°K by a flash photolysis–resonance fluorescence technique. The Arrhenius expressions obtained are k (HCHO) =1.25×10−11 e−(175±300)/RT cm3 molecule−1⋅sec−1, k (CH3CHO) =6.87×10−12 e(510±300)RT cm3 molecule−1⋅sec−1 with rate constants at room temperature of (9.4±1.0) ×10−12 cm3 molecule−1⋅sec−1 and (1.60±0.16) ×10−11 cm3 molecule−1⋅sec−1 for HCHO and CH3CHO, respectively.

79 citations