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Catalysis of recombination reactions in flames by nitric oxide
Volume
2, number
5
CHEMICAL
CATALYSIS
OF
IN
PHYSICS
LETTERS
RECOMBINATION
FLAMES
BY
NITRIC
The recombination of radicals in premixed pared with those of Bulewicz and Sugden.
OXIDE
+NO
H
tHN0
OH+HNO
+M==HNO+M
frames
is investigated.
+NO
(2)
‘H20
•FNO
(3)
+M
(4)
+H
tM-+H2
H
+OH
+M-+H2O+M
II
i-H20
=H2
The results
for k2
and & are com-
Kinetic analysis of reactions the expression
@/[HI) (T)catalysrd
(1) to (5) leads to
W/[Hl) -
(~)uncatalysed
=
(1)
--+H2
H
Centre,
25 July 1968
The nitric-oxide-catalysed recombination of radicals in fuel-rich premixed hydrogen-oxygennitrogen flames has been investigated by Bulewicz and Sugden [I]. In their work, interpretation of the results was based on a mechanism comprising reactions (l), (2) and (3), in addition to the well-established reactions (4), (5) and (6). I-I
1966
REACTIONS
C. 3. HALSTEAD and D. R. 3-S SlldZ Research Limited, Thmntcm Research P. 0. Box 1, Cilester, En&and Received
September
59?0:(k2
(1 f
= +- cvk3)Kl
at]
(7)
where (Y = Kg[H2O]/(H2]. Analysis of the present results showed them to be in good agreement with eq. (7). Plots of l/[H] against time for the same flame containing different amounts of nitric oxide or no nitric oxide were linear over a wide range
(5) + OH
(6)
Bulewicz and Sugden obtained values for k2 and kg of (1.0&0.5) x lo-l1 cm3 mol-l set-1 and (1.5kO.5) X lo-lo cm3 mol-1 set-1 respectively, with no significant tern erature-dependence in the range 1600 to 2000 RK. As part of a wider programme of measurements of radical concentrations in premixed flames containing nitrogeneous additives we have reinvestigated this system experimentally. While the value of k2 obtained here is in fairly good agreement with the work of Bulewicz and Sugden [I] that of k3 is smaller in the present study by a factor of about three. Hydrogen-atom concentrations were measured by the lithium/lithium hydroxide technique [2], atomic lithium concentrations being determined by atomic absorption spectroscopy [3f in the manner described previously [4].
7
0 5Y.NO
E ^o
-E
TlME.
Fig. 1. Plots of action zone) for tion [H2]&021 = 1980°K,
I
I.0
0.5
I-5
milliset
l/EH] against time (measured from rea premixed ilame pf volume composi4.57. [N2]/[02] = 3.35 and temperature with 0 to 2% nitric oxide added.
281
CHEMICAL PBYSICS LETTERS
Volume 2, number 5
NITRIC
OXIDE.
September
1968
%
Fig. 2. Plot of d(lflm)/dt against concentration of nitric oxide. for the catalysed and uncatalysed systems, as demonstrated in fig. 1. The gradients of the plots in fig. 1 were a linear function of the concentration of added NO as shown in fig. 2. The value of (k2 + @KS) can be deduced from the slope of the plot in fig. 2, since cv is calculable from the gas composition and K1 from es*;lbIished thermochemical data [5]. By repeaiing this procedure with sets of flames at the same temperature but having different compositions (and hence different values of r_~)),(k2+ ak3) can be determined as a function of CY. Fig. 3 shows a plot of (k2 + ksor) against ar for a temperature of 2000°K2. From the slope and intercept of this plot, k2 and kg zre found to hava values of (812) X lo-12 c&3 mol-1 see-1 and (6 rt2) x 10-11 cm3 mol’l set-1 respectively at 2OOOoK. Since the principIes of the experimental meth3d and oftheanalysisusedarethe same as those ased by Bulewicz and Sugden (11 we ascribe the Uference in the value of kg to the greater volnne of data used in the work reported here and :o the greater accuracy of the lithium absorption
ta2’._. _’
-.-
001
01
0
I
02
03
(I
Fig. 3. Plot (&J”~~cu) against o . method of determining
hydrogen-atom
concentra-
tiOll.5.
We thank Professor ‘I’. M. Sugden, F.R.S., for helpful discussions ar.d Mr. I. Williams for assistance with the practical work.
REFERENCES [l] E. M. Bulewicz and T. M. Sugden. Proc. Roy. Sot. (London) A277 (1964) 143. [2] E. M. Bulewicz, C. G. James and T. M.Sugden. Proc. Roy.Soc.
(Lcndon)
A235
(1956)
J. Halstead and D. R. Jenkins,
89.
Combustion and Flame 11 (196’7) 362. [4] C. J. Halstead and D. R. Jenkins, presented at 12th Intern. Symp. on Combustion, Poitiers, July 1968. [5] JANAI” Thermochemical Tables, Dow Chemical Co.. Midland, Michigan, 1965.
[:1
C.
2, number
5
CHEMICAL
CATALYSIS
OF
IN
PHYSICS
LETTERS
RECOMBINATION
FLAMES
BY
NITRIC
The recombination of radicals in premixed pared with those of Bulewicz and Sugden.
OXIDE
+NO
H
tHN0
OH+HNO
+M==HNO+M
frames
is investigated.
+NO
(2)
‘H20
•FNO
(3)
+M
(4)
+H
tM-+H2
H
+OH
+M-+H2O+M
II
i-H20
=H2
The results
for k2
and & are com-
Kinetic analysis of reactions the expression
@/[HI) (T)catalysrd
(1) to (5) leads to
W/[Hl) -
(~)uncatalysed
=
(1)
--+H2
H
Centre,
25 July 1968
The nitric-oxide-catalysed recombination of radicals in fuel-rich premixed hydrogen-oxygennitrogen flames has been investigated by Bulewicz and Sugden [I]. In their work, interpretation of the results was based on a mechanism comprising reactions (l), (2) and (3), in addition to the well-established reactions (4), (5) and (6). I-I
1966
REACTIONS
C. 3. HALSTEAD and D. R. 3-S SlldZ Research Limited, Thmntcm Research P. 0. Box 1, Cilester, En&and Received
September
59?0:(k2
(1 f
= +- cvk3)Kl
at]
(7)
where (Y = Kg[H2O]/(H2]. Analysis of the present results showed them to be in good agreement with eq. (7). Plots of l/[H] against time for the same flame containing different amounts of nitric oxide or no nitric oxide were linear over a wide range
(5) + OH
(6)
Bulewicz and Sugden obtained values for k2 and kg of (1.0&0.5) x lo-l1 cm3 mol-l set-1 and (1.5kO.5) X lo-lo cm3 mol-1 set-1 respectively, with no significant tern erature-dependence in the range 1600 to 2000 RK. As part of a wider programme of measurements of radical concentrations in premixed flames containing nitrogeneous additives we have reinvestigated this system experimentally. While the value of k2 obtained here is in fairly good agreement with the work of Bulewicz and Sugden [I] that of k3 is smaller in the present study by a factor of about three. Hydrogen-atom concentrations were measured by the lithium/lithium hydroxide technique [2], atomic lithium concentrations being determined by atomic absorption spectroscopy [3f in the manner described previously [4].
7
0 5Y.NO
E ^o
-E
TlME.
Fig. 1. Plots of action zone) for tion [H2]&021 = 1980°K,
I
I.0
0.5
I-5
milliset
l/EH] against time (measured from rea premixed ilame pf volume composi4.57. [N2]/[02] = 3.35 and temperature with 0 to 2% nitric oxide added.
281
CHEMICAL PBYSICS LETTERS
Volume 2, number 5
NITRIC
OXIDE.
September
1968
%
Fig. 2. Plot of d(lflm)/dt against concentration of nitric oxide. for the catalysed and uncatalysed systems, as demonstrated in fig. 1. The gradients of the plots in fig. 1 were a linear function of the concentration of added NO as shown in fig. 2. The value of (k2 + @KS) can be deduced from the slope of the plot in fig. 2, since cv is calculable from the gas composition and K1 from es*;lbIished thermochemical data [5]. By repeaiing this procedure with sets of flames at the same temperature but having different compositions (and hence different values of r_~)),(k2+ ak3) can be determined as a function of CY. Fig. 3 shows a plot of (k2 + ksor) against ar for a temperature of 2000°K2. From the slope and intercept of this plot, k2 and kg zre found to hava values of (812) X lo-12 c&3 mol-1 see-1 and (6 rt2) x 10-11 cm3 mol’l set-1 respectively at 2OOOoK. Since the principIes of the experimental meth3d and oftheanalysisusedarethe same as those ased by Bulewicz and Sugden (11 we ascribe the Uference in the value of kg to the greater volnne of data used in the work reported here and :o the greater accuracy of the lithium absorption
ta2’._. _’
-.-
001
01
0
I
02
03
(I
Fig. 3. Plot (&J”~~cu) against o . method of determining
hydrogen-atom
concentra-
tiOll.5.
We thank Professor ‘I’. M. Sugden, F.R.S., for helpful discussions ar.d Mr. I. Williams for assistance with the practical work.
REFERENCES [l] E. M. Bulewicz and T. M. Sugden. Proc. Roy. Sot. (London) A277 (1964) 143. [2] E. M. Bulewicz, C. G. James and T. M.Sugden. Proc. Roy.Soc.
(Lcndon)
A235
(1956)
J. Halstead and D. R. Jenkins,
89.
Combustion and Flame 11 (196’7) 362. [4] C. J. Halstead and D. R. Jenkins, presented at 12th Intern. Symp. on Combustion, Poitiers, July 1968. [5] JANAI” Thermochemical Tables, Dow Chemical Co.. Midland, Michigan, 1965.
[:1
C.