NASA Technical Memorandum 100202
Detailed Mechanism of Benzene Oxidation
N88-17775 - __- ~
[NASA-TPl-1BO202) DETAILED HECH ANIS14 OF BENZENE OXIDATION [NASA) 24 p Avail: #TIS HC AB3/HF 801 CSCL 07D
IJnclas G 3 / 2 5 010732C
David A. Bittker Lewis Research Center Cleveland, Ohio
October I987
https://ntrs.nasa.gov/search.jsp?R=19880002393 2018-07-20T00:15:28+00:00Z
ERRATA
NASA Technica l Memorandum 100202
DETAILED MECHANISM OF BENZENE O X I D A T I O N
by David A . B i t t k e r
October 1987
Page 4 , a t t h e bot tom of t h e page, add t h e f o l l o w i n g l i n e s :
0 the r C- H-0 Re a c t i on s
Two r e a c t i o n s which p l a y a s i g n i f i c a n t ro le i n g e n e r a t i n g r a d i c a l s t h a t c o n t r o l t he benzene i g n i t i o n process a re r e a c t i o n s 3 and 9. The r a t e cons tan ts for these H2-02-CO system r e a c t i o n s a re w e l l e s t a b l i s h e d and a re taken from
Page 16, Table 11, r e a c t i o n number 14: The species C6H60H should be CgH50H
Page 17, T a b l e 111, r e a c t i o n number 14: The species C6H60H should be C6H50H
DETAILED MECHANISM OF BENZENE O X I D A T I O N
Dav id A . B i t t k e r N a t i o n a l Ae ronau t i cs and Space A d m i n i s t r a t i o n
Lewis Research Center Cleveland, Oh io 44135
SUMMARY
A d e t a i l e d benzene o x i d a t i o n mechanism, which uses t h e q u a l i t a t i v e pa ths o u t l i n e d by p r e v i o u s i n v e s t i g a t o r s , i s presented. I g n i t i o n d e l a y t imes f o r a r g o n - d i l u t e d m i x t u r e s computed w i t h t h i s mechanism a r e i n s a t i s f a c t o r y agree- ment w i t h exper imen ta l va lues o b t a i n e d from pressure- t ime p r o f i l e s f o r a wide range o f i n i t i a l c o n d i t i o n s . An exper imen ta l temperature versus t ime p r o f i l e
& measured i n a n i t r o g e n d i l u t e d m i x t u r e has a l s o been s u c c e s s f u l l y computed. & A d d i t i o n a l computat ions have qual 1 t a t i v e l y matched seve ra l exper imen ta l spec ies
c o n c e n t r a t i o n versus t i m e p r o f i l e s for t h e n i t r o g e n d i l u t e d r e a c t i o n . App l i ca - t i o n of s e n s i t i v i t y a n a l y s i s a l l owed t h e approximate d e t e r m i n a t i o n o f t h e r a t e cons tan ts for two i m p o r t a n t r e a c t i o n s :
k7 C6H5 + O2 $ C6H50 + 0
k7 = 4 . 5 ~ 1 0 12 ,-15000 cal/RTcm3 mol-ls-l
and
kl 0 C5H5 + O2 + C5H50 + 0
12 e-20000 cal/RTcm3 mol-ls-l k10 = 2 . 0 ~ 1 0
INTRODUCTION
The i n c r e a s i n g importance o f a romat i cs i n t h e p r a c t i c a l hydrocarbon f u e l s o f today has a c c e l e r a t e d research aimed a t improv ing o u r unders tand ing o f t h e h igh- temperature o x i d a t i o n of these compounds. Th is knowledge i s i m p o r t a n t i n c o n t r o l l i n g t h e combustion and emiss ion c h a r a c t e r i s t i c s o f b o t h advanced a i r - c r a f t p r o p u l s i o n and f u t u r e ground-based gas t u r b i n e s . The o x i d a t i o n and p y r o l y s i s of t h e s i m p l e s t a romat i c , benzene, have been s t u d i e d by seve ra l I n v e s t i g a t o r s ( r e f s . 1 t o 4 ) . A r e c e n t r e v i e w paper ( r e f . 5) on a romat i c hydro- carbon o x i d a t i o n p resen ts e x p e r i m e n t a l l y measured temperature and compos i t i on p r o f i l e s for o x i d a t i o n o f one benzene-oxygen-nitrogen m i x t u r e i n a h i g h l y t u r - b u l e n t flow r e a c t o r . I n some r e c e n t work ( r e f . 6 ) i g n i t i o n d e l a y t i m e measure- ments were r e p o r t e d for benzene-oxygen-argon m i x t u r e s i g n i t e d behind a r e f l e c t e d shock. The exper imenta l c o n d i t i o n s covered a wide rdnge o f i n i t i a l composi t ion, temperature, and p ressu re . The i g n i t i o n d e l a y t imes were d e t e r - mined from pressu re versus t ime p r o f l l e s .
The purpose o f t h e p r e s e n t paper i s t o develop a d e t a i l e d mechanism which reproduces the r e s u l t s of r e f e r e n c e s 5 and 6 o v e r the w i d e s t p o s s i b l e range o f i n i t i a l c o n d i t i o n s . Computat ions were performed w i t h t h e new NASA Lewis genera l chemical k i n e t i c s and s e n s i t i v i t y a n a l y s i s code ( r e f s . 7 to 9). To achieve the b e s t p o s s i b l e agreement s e n s i t i v i t y a n a l y s i s was used t o i d e n t i f y t he most i m p o r t a n t r e a c t i o n s . Adjustments were then made to some of t h e r e a c t i o n r a t e cons tan ts i n t h e mechanism. However, o n l y r a t e cons tan ts w i t h l a r g e u n c e r t a i n t i e s were changed s i g n i f i c a n t l y . These adjustments w e r e made m a i n l y t o r e a c t i o n s i n v o l v i n g benzene and i t s fragments. The r a t e cons tan ts for r e a c t i o n s i n v o l v i n g o t h e r hydrocarbons, e .g . , a c e t y l e n e and methane, were used a t t h e i r l i t e r a t u r e va lues . I n the s e c t i o n s which fo l low, we p r e s e n t comparisons o f computed and exper imen ta l r e s u l t s and d i scuss t h e mechanism f i n a l l y ob ta ined for o p t i m a l match ing w i t h t h e l a t t e r r e s u l t s . We a l s o desc r ibe the s e n s i t i v i t y s tudy which determined t h e r e a c t i o n s which have t h e g r e a t e s t e f f e c t on t h e computed r e s u l t s . , BENZENE O X I D A T I O N MECHANISM
We have f o l l o w e d t h e genera l scheme o u t l i n e d q u a l i t a t i v e l y i n re fe rences 1 and 5 . The o x i d a t i o n process can be d i v i d e d i n t o t h r e e s tages:
I I n i t i a t i o n : The f o r m a t i o n o f oxygen and hydrogen atoms and OH r a d i c a l s as w e l l as some phenyl r a d i c a l s by t h e p y r o l y s i s o f benzene and i t s r e a c t i o n w i t h mo lecu la r oxygen.
I n d u c t i o n : Rapid f o r m a t i o n of phenyl r a d i c a l and i t s o x i d a t i o n and p y r o l y s i s t o form p r i m a r i l y phenoxy r a d i c a l , CgH50; f u r t h e r r e a c t i o n o f CgH5O to form phenol , cyc lopen tad iene , and ace ty lene .
Combustion: O x i d a t i o n of t h e s t a b l e i n t e r m e d i a t e hydrocarbons and r a d i c a l recombinat ions which cause t h e main heat r e l e a s e .
I n t h e i n i t i a t i o n r e g i o n t h e f o l l o w i n g r e a c t i o n s were assumed:
H + O2 + O H k3 + 0
I n t h e i n d u c t i o n r e g i o n the r e a c t i o n s used were as follows:
k. 4 '6"s + H2 H + C6H6
( 1 )
( 2 )
(3)
( 4 )
2
OH + C6H6 kg C6H5 + HzO ( 6 )
We have w r i t t e n r e a c t i o n s 4 th rough 6 as s imple a b s t r a c t i o n processes, a l t hough t h e p o s s i b i l i t y o f a d d i t i o n processes has been suggested ( r e f . 5 ) .
C6H5 + O2 k7 C6H50 + 0
C H O + M + k8 C 5 H 5 + C O + M 6 5
cyc 10- pen tad ieny l
CO + OH 5 - C 0 2 + H
kl 0 C5H5 + O2 + C 5 H 5 0 + 0
kl 1 C 5 H 5 0 + M C4H5 + CO + M
b u t a d i e n y l
cyc 10- pentadiene
( 7 )
( 8 )
(9)
(10)
( 1 1 )
‘gH5 k5 - C4H3 + C2H2 (15)
M + C 4 H 3 kl + 6 C 4 H z + H + M (16)
These a re t h e s i g n i f i c a n t s teps which occur i n the i n i t i a t i o n and i n d u c t i o n r e g i o n s . A d d i t i o n a l r e a c t i o n s , d iscussed l a t e r , a re needed to model t h e com- b u s t i o n r e g i o n and determine t h e c o n c e n t r a t i o n s o f i n t e r m e d i a t e spec ies . The
3
complete s e t o f r e a c t l o n s I s necessary f o r model lng t h e temperature and com- p o s l t l o n p r o f l l e s .
R E A C T I O N RATE CONSTANTS
I n t h i s s e c t l o n we d iscuss the s e l e c t l o n o f r a t e constants f o r those r e a c t l o n s I n v o l v l n g benzene and I t s decomposl t lon products whlch have been s tud ied I n recen t exper lmenta l work. Sources f o r r a t e cons tan t o f combustlon- zone r e a c t i o n s a r e a l s o g lven.
Benzene P y r o l y s l s React lon
The p y r o l y s l s o f benzene has been s tud led r e c e n t l y I n t w o l n v e s t i g a t l o n s , by Hsu, L i n , and L l n (Re f . 4 ) and by K l e f e r e t a l . (Ref . 10 ) . Th is work has shown t h a t r e a c t l o n ( 2 ) I s t h e o n l y Impor tan t pa th a t h i g h temperature. The p y r o l y s l s r a t e cons tan t was measured as a f u n c t i o n o f temperature and pressure . For t h e temperature and pressure range o f t h e present computat ions we have used t h e express lon g l ven i n re fe rence 4, whlch agrees w e l l w i t h r e s u l t s o f re fe rence 10.
Rad lca l A t tacks on Benzene
React ions 4, 5 and 6 a r e t h e main r e a c t l o n s f o r g e n e r a t l n g phenyl r a d l c a l . We have used the r a t e c o n s t a n t o f re fe rence 10 f o r t h e H + CgHf, r e a c t i o n . The r e c e n t l y repo r ted exper lmenta l values o f re fe rences 11 and 12 were used f o r t h e 0 t CgH6 and OH + CgH6 r e a c t i o n s . I n a l a t e r s e c t l o n we d iscuss s e n s l t l v - l t y a n a l y s l s computat lons whlch showed t h e pressure and temperature p r o f l l e s t o be q u l t e I n s e n s i t i v e t o moderate v a r l a t l o n s o f these t h r e e r a t e cons tan ts f rom t h e l r l l t e r a t u r e va lues. Th is I s t r u e , even though these r e a c t i o n s a r e a l l impor tan t sources o f phenyl r a d l c a l .
Other cf, and Cg React lons
The r a t e cons tan ts o f some r e a c t i o n s o f phenyl and phenoxy (CgH5O) r a d l c a l have been measured r e c e n t l y . The p r e v l o u s l y quoted work o f re fe rence 10 has determined r a t e c o n s t a n t express ions f o r t h e phenyl r a d l c a l p y r o l y s l s , r e a c t i o n 15. The i r h lgh-pressure un lmolecu la r r e a c t l o n express lon was used I n t h e pre- sent computat lons. The es t lmated r a t e c o n s t a n t f o r p y r o l y s l s o f C4H3, r e a c t i o n 16, I s a l s o taken f rom re fe rence 10. The r a t e cons tan t f o r t h e phenoxy p y r o l - y s i s , r e a c t i o n 8, I s t h e va lue o f L l n and L l n ( r e f . 1 3 ) . The r a t e cons tan ts f o r o t h e r r e a c t i o n s I n t h e l n d u c t l o n r e g l o n had t o be e l t h e r es t lmated o r ad jus ted t o match t h e exper lmenta l da ta . The s e n s l t l v l t y a n a l y s l s computat lons f o r accompl ish ing t h i s task a r e descr ibed below.
4
re fe rence 14. The r e a c t i o n s o f a c e t y l e n e , which a r e i m p o r t a n t i n t h e combus- t i o n reg ion , were a l l taken from r e f e r e n c e 1 5 . The complete mechanism con- s i s t e d o f 110 r e a c t i o n s among 35 species. A l l r e a c t i o n s and r a t e cons tan ts used fo r these computat ions a r e g i v e n i n t a b l e I.
S E N S I T I V I T Y ANALYSIS STUDY
To i d e n t i f y t h e i m p o r t a n t r e a c t i o n s which c o n t r o l t h e o x i d a t i o n o f benzene and i t s f ragments i n t h e i n d u c t i o n zone, an e x t e n s i v e s e n s i t i v i t y a n a l y s i s was performed. Normal ized s e n s i t i v i t y c o e f f i c i e n t s were computed u s i n g t h e decoupled d i r e c t method desc r ibed i n re ferences 8 and 9. g i v e the v a r i a t i o n o f a l l spec ies c o n c e n t r a t i o n s , temperature and p ressu re w i t h changes i n the i n d i v i d u a l r a t e c o n s t a n t parameters A j , n j , and E j o f t h e
m o d i f i e d A r rhen ius equa t ion
p resen t work s e n s i t i v i t y c o e f f i c i e n t s of seve ra l spec ies c o n c e n t r a t i o n s p l u s temperature and p ressu re w i t h r e s p e c t t o t h e A j determine the i m p o r t a n t r e a c t i o n s . Table 11 shows these c o e f f i c i e n t s for t h e n i t r o g e n d i l u t e d s t o i c h i o m e t r i c o x i d a t i o n of benzene ( i n i t i a l temperature = 1115 K ) i n t he t u r b u l e n t f low r e a c t o r desc r ibed i n r e f e r e n c e 5 . The r e a c t i o n i s a t cons tan t p ressu re so no p ressu re s e n s i t i v i t y c o e f f i c i e n t i s g i ven . The r e s u l t s show t h a t t h e r e a c t i o n s o f CgH5 and C5H5 r a d i c a l s w i t h mo lecu la r oxygen have g r e a t e s t e f f e c t on temperature and seve ra l spec ies compos i t i on . p r o f i l e s . Table I11 shows s e n s i t i v i t y c o e f f i c i e n t s f o r a t y p i c a l s t o i c h i o - m e t r i c benzene oxygen-argon shock i g n i t i o n ( i n i t i a l temperature = 1405 K) from r e f e r e n c e 6. S e n s i t i v i t y c o e f f i c i e n t s of p ressu re a r e now i n c l u d e d . Again t h e dominant r e a c t i o n s a r e t h e CgH5 and C5H5 o x i d a t i o n s . Computations were a l s o performed for a second shock i g n i t i o n a t equ iva lence r a t i o = 2 and an i n i t i a l temperature o f 1600 K. S e n s i t i v i t y c o e f f i c i e n t s for f o u r dependent v a r i a b l e s
.and f i v e r e a c t i o n s a r e shown f o r b o t h c o n d i t i o n s i n t a b l e I V f o r ease o f com- p a r i s o n . The da ta i n t a b l e I V show t h a t computed r e s u l t s should be most s e n s i t i v e t o t h e r a t e cons tan t o f r e a c t i o n 7, t he phenyl o x i d a t i o n , a t b o t h c o n d i t i o n s . However, t h e r e i s a s i g n i f i c a n t change i n t h e s e n s i t i v i t y coef - f i c i e n t s fo r r e a c t i o n 15, t h e phenyl p y r o l y s i s . These c o e f f i c i e n t s change from ve ry smal l va lues f o r t h e s t o i c h i o m e t r i c lower temperature r e a c t i o n t o much l a r g e r va lues f o r t h e r i c h h i g h e r temperature r e a c t i o n . The e f f e c t o f r e a c t i o n 1 5 on t h e p ressu re p r o f l l e i s now i n d i c a t e d t o be g r e a t e r t han t h a t o f r e a c t i o n 10.
Thes? c o e f f i c i e n t s
= A T n j exp ( - E . / R T > for r e a c t i o n j . I n t h e k j 3 J
parameters were used t o
The p r e d i c t i o n s o f t h e s e n s i t i v i t y c o e f f i c i e n t s were t e s t e d by u s i n g t h e " b r u t e f o r c e " or i n d i r e c t method of s e n s i t i v i t y a n a l y s i s . The p reexponen t ia l f a c t o r fo r each r e a c t i o n i n t a b l e I V was changed by f a c t o r s o f 2 and 0.5 and t h e i g n i t i o n computat ion was repeated fo r each change. The e f f e c t o f these r a t e cons tan t v a r i a t i o n s on t h e computed p ressu re p r o f i l e i s shown i n t a b l e V . Given i n t h i s t a b l e a r e va lues o f T ~ , t h e i g n i t i o n - d e l a y t i m e measured from the pressure versus t ime p r o f i l e as desc r ibed i n d e t a i l i n t h e n e x t s e c t i o n . For each r e a c t i o n we show t h e -rP values for k s t d , t h e r a t e c o n s t a n t l i s t e d i n t a b l e I, and a l s o T for 2 k s t d and k s t d / 2 . Also shown a r e t h e p e r c e n t
t a b l e V c o n f i r m a l l t h e s e n s i t i v i t y p r e d i c t i o n s o f t a b l e I V . I n p a r t i c u l a r , changing k15 fo r t h e lower- temperature s t o i c h i o m e t r i c m i x t u r e has a v e r y smal l e f f e c t on zP. The same change i n k15 has a v e r y s i g n i f i c a n t e f f e c t on T~ f o r t h e h igh- temperature r i c h m i x t u r e .
changes i n T~ f o r eac I: r a t e cons tan t v a r i a t i o n . t h e computed r e s u l t s i n
5
The r e s u l t s o f these s e n s i t i v i t y computat ions were used i n t h e f o l l o w i n g way t o a d j u s t t h e r a t e c o n s t a n t parameters. The A j and E j va lues f o r r e a c t i o n s 7 and 10 were a d j u s t e d i n seve ra l i t e r a t i o n s t o g i v e t h e b e s t match t o t h e i g n i t i o n de lay t imes o f r e f e r e n c e 6 and t h e temperature versus t i m e p r o f i l e o f r e f e r e n c e 5 for t h e benzene-oxygen-nitrogen r e a c t i o n . I t was found, from the matching o f i g n i t i o n d e l a y t imes, t h a t t h e a c t i v a t i o n energy of t h e dominant r e a c t i o n 7 should be as h i g h as p o s s i b l e . Th i s r e a c t i o n i s an exo- the rm ic process and we have used t h e upper l i m i t , suggested i n r e f e r e n c e 1 , of 15 kca l /mo le . The C5H5 o x i d a t i o n , r e a c t i o n 10, i s about 10 kca l /mo le endothermic a t 1200 K . An a c t i v a t i o n energy o f 20 kca l /mo le was found t o g i v e t h e b e s t shape t o t h e computed temperature versus t i m e p r o f i l e f o r t h e benzene- oxygen-n i t rogen r e a c t i o n . The p r e x p o n e n t i a l f a c t o r s o f bo th these r e a c t i o n s w e r e then a d j u s t e d t o g i v e t h e b e s t match t o b o t h t h e i g n i t i o n - d e l a y t i m e s and t h e temperature versus t i m e p r o f i l e . Table V and t h e s e n s i t i v i t y c o e f f i c i e n t s o f t a b l e I1 show t h a t r e a c t i o n 7 s t r o n g l y c o n t r o l s t h e T~ computat ion and t h a t r e a c t i o n s 7 and 10 b o t h have i m p o r t a n t e f f e c t s on the temperature versus t i m e p r o f i l e . Therefore t h e p r e x p o n e n t i a l f a c t o r A7 was determined by match- i n g t h e i g n i t i o n - d e l a y t i m e s and A 1 was then a d j u s t e d to g i v e t h e b e s t match to t h e temperature versus t i m e p r o f i P e. The va lues ob ta ined a re :
k7 = 4 . 5 ~ 1 0 1 2 e-15000 ca l /RT (31113 mol-IS-1
2.0x1012 e-20000 ca l /RT cm3 mol-1s-1 k10 =
Other r a t e cons tan ts f o r r e a c t i o n s i n v o l v i n g cyc lopentadiene, pheno t h e i r f ragments were e s t i m a t e d and a d j u s t e d t o g i v e t h e bes t agreement w r e p o r t e d exper imenta l phenol and cyc lopen tad iene p r o f i l e s i n r e f e r e n c e 5
and t h
DESCRIPTION OF COMPUTATIONAL PROCEDURE
I n t h i s s e c t i o n we d e s c r i b e b r i e f l y t h e apparatus and exper imenta l procedures r e p o r t e d i n r e f e r e n c e s 5 and 6. We then d e s c r i b e o u r mathematical model used t o s i m u l a t e each o f these r e a c t i n g s y s t e m s .
T u r b u l e n t Flow Reactor
Temperature and compos i t i on versus t i m e p r o f i l e s for the r e a c t i o n o f a s t o i c h i o m e t r i c benzene-oxygen m i x t u r e i n a n i t r o g e n atmosphere were o b t a i n e d i n the P r i n c e t o n U n i v e r s i t y f low r e a c t o r ( r e f , 5 ) . A d e t a i l e d d e s c r i p t i o n o f t h i s t u r b u l e n t , chemica l - ra te l i m i t e d dev i ce i s g i v e n i n r e f e r e n c e 16. The r e a c t a n t s were h i g h l y d i l u t e d i n n i t r o g e n t o e l i m i n a t e d i f f u s i o n e f f e c t s . P r o f i l e s o f temperature and compos i t i on w i t h r e s p e c t t o d i s t a n c e were conver ted to t i m e p r o f i l e s by t a k i n g i n t o account the flow v e l o c i t i e s w i t h i n t h e r e a c t o r . The exac t z e r o o f r e a c t i o n t i m e i s a r b i t r a r y and was taken as p o i n t o f f u e l i n j e c t i o n i n t o the h o t o x i d a n t stream. Reference 16 i n d i c a t e s t h a t t h e r e a c t o r i s operated a t one atmosphere p ressu re . I n t h e computat ions, t h e r e f o r e , t h e f low r e a c t o r was modeled as a c o n s t a n t p ressu re homogeneous ba tch r e a c t i o n . For a l l k i n e t i c computat ions o f t h i s work, t h e thermodynamic d a t a a r e from t h e NASA Lewis Research Center d a t a base which i s p a r t of t h e NASA Chemical E q u i l i - b r i u m Composi t ion Computer code 6 f Gordon and McBride ( r e f . 22). The r e c e n t l y r e p o r t e d d a t a o f B u r c a t , Z e l e z n i k and McBride ( r e f . 23) were used f o r phenyl and phenoxy r a d i c a l s . New thermodynamic d a t a f o r severa l benzene p y r o l y s i s and
6
o x i d a t i o n f ragments (C4H3, C4H , C5H5 and C H5O) were e s t i m a t e d by
c o n c e n t r a t i o n s were compared t o t h e p r o f i l e s presented i n r e f e r e n c e 5. Bonnie J . McBride. Computed t 7 me p r o f i l e s o ? temperature and seve ra l spec ies
Shock-Tube I g n i t i o n Exper iments
The i g n i t i o n d e l a y t imes o f Ref . 6 were o b t a i n e d from measured p ressu re versus t ime t r a c e s f o l l o w i n g i g n i t i o n beh ind a r e f l e c t e d shock wave. The t i m e i n t e r v a l between i g n i t i o n and t h e f i r s t observed " s i g n i f i c a n t " p ressu re r i s e was taken .as t h e i g n i t i o n d e l a y t i m e , t. To match t h e exper imen ta l technlque as c l o s e l y as p o s s i b l e t h e computed i g n i t i o n d e l a y t ime , zP, was o b t a i n e d from t h e computed p ressu re versus t i m e cu rve . The k i n e t i c computat ions were per- formed assuming a constant-volume b a t c h r e a c t i o n behind t h e r e f l e c t e d shock. Be fo re p e r f o r m i n g t h e k i n e t i c computat ions t h e i n i t i a l r e f l e c t e d shock condi - t i o n s i n r e f e r e n c e 6 were recomputed. A smal l c o r r e c t i o n f o r a t t e n u a t i o n o f t h e r e f l e c t e d shock v e l o c l t y was a p p l i e d t o each d a t a p o i n t . shock i n i t i a l temper tures and p ressu res (T5 and p5) were then recomputed u s i n g t h e Chemical E q u i l i b r i u m Code o f reference 22 . temperature, p ressu re , and a l l spec ies c o n c e n t r a t i o n s were then computed. A t y p i c a l computed p ressu re ve rsus t i m e cu rve i s shown i n f i g u r e 1. A l s o shown i s t h e method used t o determine t h e
T~ e x t r a p o l a t e d l i n e s . imen ta l technique. Only 35 o f t h e exper imen ta l p o i n t s r e p o r t e d i n r e f e r e n c e 6 were used for o u r comparisons. a t i o n for one o f two d i f f e r e n t reasons. F i r s t , a l l p o i n t s for which T was l e s s than 100 psec were exc luded. These va lues a r e i n a c c u r a t e because o f pres- sure d i s tu rbances which propagate i n t h e shock tube ahd. cause nonuni form heat- i n g o f t h e gas beh ind t h e r e f l e c t e d shock. D e t a i l s o f t h i s e f f e c t a r e g i v e n i n r e f e r e n c e 19. Second, a l l t h e d a t a taken f o r t h e exper imen ta l m i x t u r e w i t h equiva lence r a t i o o f 0.25 were exc luded because i t was v e r y d i f f i c u l t t o d e t e r - mine accu ra te T va lues from these p ressu re t r a c e s . The p ressu re r i s e was v e r y p o o r l y d e f i n e d f o r a l l these v e r y weak i g n i t i o n s .
The r e f l e c t e d
Complete t i m e p r o f i l e s of
va lue by t h e i n t e r s e c t i o n o f two T h i s method approximated as c l o s e l y as p o s s i b l e t h e exper-
The o t h e r p o i n t s were exc luded from cons ide r -
Table V I l i s t s t h e f i v e m i x t u r e s from r e f e r e n c e 6 which were used i n t h e p resen t comparisons a long w i t h t h e I n i t i a l temperature range o f t h e r e f l e c t e d shocks. M i x t u r e s 3 and 4 a r e i d e n t i c a l for a l l p r a c t i c a l purposes and a r e t r e a t e d as one c o n d i t i o n , equ iva lence r a t i o 1.0 w i t h about 85 p e r c e n t argon d i l u t i o n . Note t h a t comparison o f t h e r e s u l t s for m ix tu re32 w i t h those for m i x t u r e s 3 and 4 g i v e s t h e e f f e c t o f s imp ly d i l u t i n g t h e m i x t u r e w i t h argon a t a c o n s t a n t equ iva lence r a t i o . I n i t l a l pressures fo r t h e r e f l e c t e d shocks ranged from 1 . 7 to 7.1 atm.
RESULTS AND DISCUSSION
Comparison o f Computed and Exper imenta l I g n i t i o n Delay Times
Plots o f computed and exper imen ta l i g n i t i o n de lay t i m e versus r e c i p r o c a l o f temperature a r e shown i n f i g u r e s 2 t o 6 f o r t h e f o u r d i f f e r e n t i n i t i a l con- d i t i o n s g i v e n i n t a b l e V I . The i n d i v i d u a l computed and exper imen ta l p o i n t s a r e shown as w e l l as least -squares l i n e s for each s e t o f p o i n t s . They a r e f i t t e d t o t h e e m p i r i c a l e q u a t i o n
7
A E I R T T - Ae ( 1 )
or
where R i s t h e u n i v e r s a l gas c o n s t a n t and AE i s an a c t i v a t i o n energy te rm which measures t h e temperature dependence o f T for a f i x e d s e t o f i n i t i a l c o n c e n t r a t i o n s . A d e t a i l e d comparison o f exper imenta l and computed r e s u l t s i s shown i n t a b l e V I I , which a l s o I n c l u d e s an e r r o r a n a l y s i s . ence between each computed and exper imen ta l va lue i s g i v e n a long w i t h t h e pe rcen t s tandard d e v l a t i o n for each s e t o f i n i t i a l c o n c e n t r a t i o n s used. Th is s tandard d e v i a t i o n i s de f i ned by
The p e r c e n t d i f f e r -
where N i s t h e number of p o i n t s . A va lue o f o for a l l 35 p o i n t s used i s a l s o g i v e n .
Examinat ion o f t h i s t a b l e shows s a t l s f a c t o r y agreement between t h e com- pu ted and exper imen ta l i g n i t i o n de lays . T h i s i s e s p e c i a l l y t r u e when one con- s i d e r s t h e u n c e r t a i n t y I n some o f t h e exper imen ta l measurements. For example, t a b l e V I 1 shows t h r e e i ns tances i n which t h e exper imen ta l r e s u l t s do n o t show t h e expected decrease o f i g n i t i o n d e l a y t i m e w i t h i n c r e a s i n g temperature. The agreement between exper iment and computat ion i s poo res t for the l e a n m i x t u r e (0 = 0.5) and s t e a d i l y improves as 4 i nc reases t o 2.0. S i m i l a r behav io r i s a l s o observed for t h e temperature dependence o f i g n i t i o n d e l a y . T h i s can be seen from t a b l e V I 1 1 which l i s t s t h e va lues o f AE computed f r o m equa t ion ( 1 ) for b o t h t h e exper imenta l and computed r e s u l t s . The pe rcen t d e v i a t i o n for t h e a c t i v a t i o n energ ies decreases s t e a d i l y as equ iva lence r a t i o changes from 0.5 to 2.0. From these comparisons i t appears t h a t one or more r e a c t i o n s a re m i s s i n g from t h e mechanism. These r e a c t i o n s a r e much more i m p o r t a n t i n t h e l e a n m i x t u r e s than i n t h e r i c h ones. However, i t should a l s o be p o i n t e d o u t t h a t t h e exper imenta l i g n i t i o n d e l a y t imes f o r t h e l e a n m i x t u r e s a r e more u n c e r t a i n than those for t h e r i c h m i x t u r e s . From f i g u r e s 2 and 5 i t can be seen t h a t t h e computat ions tend to o v e r p r e d i c t t h e i g n i t i o n d e l a y t ime a t t$ = 0 . 5 and u n d e r p r e d i c t i t a t I$ = 2.0.
F i g u r e 6 shows computed and exper imen ta l i g n i t i o n de lay p l o t s for two m i x t u r e s w i t h equ iva lence r a t i o o f 1.0 b u t w i t h d i f f e r e n t amounts o f argon d i l u e n t . The computed r e s u l t s show a much s m a l l e r e f f e c t o f i n e r t d i l u t i o n than observed e x p e r i m e n t a l l y . changed by v a r i a t i o n o f e i t h e r t h e A f a c t o r or t h e a c t i v a t i o n energy of any u n c e r t a i n r a t e cons tan ts .
The e f f e c t of i n e r t gas d i l u t i o n c o u l d n o t be
a
Comparison of Computed and Exper imental Temperature and Composi t ion P r o f i l e s
F igu res 7 to 12 show computed temperature versus t i m e and seve ra l composi- t i o n versus t i m e p r o f i l e s a l o n g w i t h exper imenta l d a t a f o r t h e n i t r o g e n - d i l u t e d s t o i c h i o m e t r i c CgHg-02 r e a c t i o n r e p o r t e d i n r e f e r e n c e 5. temperature was 1115 K and t h e pressure was 1 atmosphere. The computed and exper imenta l temperature p r o f i l e s i n f i g u r e 7 a r e i n e x c e l l e n t q u a n t i t a t i v e agreement. The computed cyc lopentadiene p r o f i l e o f f i g u r e 8 i s i n semiquan- t i t a t i v e agreement w i t h t h e exper imenta l p r o f i l e . Both t h e peak c o n c e n t r a t i o n o f C5Hg and t h e t i m e a t which i t i s reached a re p r e d i c t e d q u i t e a c c u r a t e l y . The computed p r o f i l e s f o r phenol ( f i g . 9 ) benzene ( f i g . 10) and carbon monoxide ( f i g . 1 1 ) agree o n l y w i t h the q u a l i t a t i v e t rends of t h e co r respond ing exper- imenta l p r o f i l e s . For phenol , t h e computat ion matches t h e magnitude on t h e peak c o n c e n t r a t i o n , b u t t h i s va lue occu rs a t a l a t e r r e a c t i o n t ime . The mecha- nism p r e d i c t s a v e r y sudden disappearance o f benzene, i n s t e a d o f t h e gradual decay observed e x p e r i m e n t a l l y . The exper imenta l r i s e of carbon monoxide con- c e n t r a t i o n and i t s peak va lue a re g r e a t e r than the corresponding computed q u a n t i t i e s . There i s semi -quan t ia t i ve agreement between t h e computed and exper imenta l carbon d i o x i d e p r o f i l e s ( f i g . 1 2 ) . The computed p r o f i l e i s app rox ima te l y l i n e a r whereas t h e exper imenta l p r o f i l e shows a l o n g i n d u c t i o n p e r i o d . However, t h e same s teady -s ta te va lue found e x p e r i m e n t 3 l l y i s g i v e n by the computed p r o f i l e s .
The i n i t i a l m i x t u r e
An a c e t y l e n e versus t i m e p r o f i l e i s a l s o g i v e n i n r e f e r e n c e 5 for t h i s benzene o x i d a t i o n exper iment . The p r e d i c t e d ace ty lene peak c o n c e n t r a t i o n i s about one o r d e r o f magnitude lower than t h e r e p o r t e d exper imen ta l va lue . The s e n s i t i v i t y c o e f f i c i e n t s o f t a b l e I1 show t h a t t h i s c o n c e n t r a t i o n i s c o n t r o l l e d by r e a c t i o n s 7 and 10, as a r e many o t h e r c o n c e n t r a t i o n s . No reasonable changes i n any o f the r e a c t i o n s i n v o l v i n g a c e t y l e n e changed i t s p r o f i l e s i g n i f i c a n t l y . Th i s behav io r i s d i f f e r e n t from t h a t f o r cyc lopen tad iene and phenol . A l though these l a t t e r two c o n c e n t r a t i o n s a re a l s o s t r o n g l y c o n t r o l l e d by r e a c t i o n s 7 and 10, they w e r e s i g n i f i c a n t l y improved by modest ad justments of t h e r a t e con- s t a n t s for r e a c t i o n s 12 and 13, which a r e q u i t e u n c e r t a i n .
CONCLUDING REMARKS
Th is work has presented a d e t a i l e d q u a n t i t a t i v e mechanism for t h e ox ida - t i o n o f benzene. The mechanism s a t i s f a c t o r i l y computes exper imen ta l r e s u l t s f o r bo th argon and n i t r o g e n d i l u t e d systems. F a i r to good agreement was o b t a i n e d between computed and exper imenta l i g n i t i o n d e l a y t imes measured ove r a wide range o f temperature, p ressu re and compos i t i on f o r shock-heated benzene- oxygen-argon m i x t u r e s . The mechanism a l s o does a f a i r j o b of comput ing meas- u red temperature and compos i t i on p r o f i l e s f o r a n i t r o g e n - d i l u t e d benzene o x i d a t i o n i n a q u i t e d i f f e r e n t system, namely a t u r b u l e n t flow r e a c t o r .
The p r e s e n t work has v e r i f i e d t h e r e a c t i o n paths o u t l i n e d i n r e f e r e n c e s 1 and 5 and p resen ts r a t e cons tan t express ions f o r two i m p o r t a n t r e a c t i o n s . S e n s i t i v i t y a n a l y s i s has i d e n t i f i e d these r e a c t i o n s , t he o x i d a t i o n s o f CgH5 and CsHs r a d i c a l s , as b e i n g dominant i n t h e i g n i t i o n o f benzene-oxygen m i x - t u r e s . The express ions f o r these r e a c t i o n r a t e cons tan ts have to be considered approximate because t h e mechanism i s s t i l l incomplete. However, t h e mechanism p r e d i c t e d one temperature versus t i m e p r o f i l e a c c u r a t e l y , i n a d d i t i o n t o the s a t i s f a c t o r y i g n i t i o n de lay t i m e p r e d i c t i o n s . Therefore, i t c o u l d be used fo r hea t - re lease r a t e p r e d i c t i o n s i n p r a c t i c a l , wel l -mixed, benzene-air combustion sys terns.
9
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10
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F i f t e e n t h
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K i n e t i c M o d e l l i n g o f t h e O x i d a t i o n o f Carbon E i g h t e e n t h Symposium ( I n t e r n a t i o n a l ) on Combustion,
22. Gordon, S . ; and McBride, B.J. : Computer Program f o r C a l c u l a t i o n o f Complex Chemical E q u i l i b r i u m Compos i t ions , Rocket Performance, I n c i d e n t and R e f l e c t e d Shocks, and Chapman-Jouget Detonat ions, NASA SP-273, 1971.
23. B u r c a t , A . ; Z e l e z n i k , F . J . ; and McBr ide , B .J . : I d e a l Gas Thermodynamic P r o p e r t i e s fo r t h e Pheny l , Phenoxy, and O-Biphenyl R a d i c a l s . NASA TM-83800, 1985.
1 1
TABLE I . - BENZ€NE OXIOAllON MECHANISM - No
- 1
2
3
4
5
6
7
0
9
10
11
1 2
13
1 4
15
1 6
17
18
19
20 -
Reac t i on
C6H6 + O2 = C6H5 + H02
C6H6 = C6H5 + H
H + O2 = OH + 0
C H
C6H6 + 0 = C H
C H
C H
C6H50 = C5H5 + C O
CO + OH = C02 + H
t H = C6H5 t H2 6 6
6 5 + O H
t OH = C6H5 + H20
+ O2 = C6H50 + 0
6 6
6 5
C5H5 t O 2 = C5H50 + 0
C5H50 t M = C4H5 + CO + M
16H50H = C6H50 + H
:5H5 C6H6 = C5H6 + C6H5
I H + C6H50H = C6H50 + H20
Z6H5 = C H
1 t C 4 H 3 = C4H2 + t i + H
;5H6 + 0 = C5H50 + H
:4H5 = C H
14H2 + 0 = C2H0 + C?H
:4H2 c 0 = C O + C3H2
4 3 + C2H2
+ C2H2 2 3
A cm3, mole,sec
13 6.31 x10
5 . 0 ~ 1 0 ~
1 . 2 6 ~ 1 0
2 . 5 ~ 1 0
2 . 7 8 ~ 1 0
2 . 1 3 ~ 1 0
4 . 5 ~ 1 0
2 . 5 ~ 1 0
4 . 1 7 ~ 1 0
z.ox10
7 . 5 9 ~ 1 0 ’ ~
6 . 0 ~ 1 0
14
14
13
13
12
11
11
12
13
2.ox10”
8 . 0 x 1 O 1 *
I .58x101
51 3 . 3 ~ 1 0
12 5 . 0 ~ 1 0
13 1 . 4 ~ 1 0
13 1 .ox10
12 1.2x10
- n
- 0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
-10
0
0
0
0 -
Ea c a l o r i e s p e r mole
60 000
108 000
16 300
16 000
4 910
4 580
15 000
43 900
1 000
20 000
1 5 000
88 000
10 000
5 000
82 000
63 000
10 000
32 900
0
0
Source
Ref . 2
Re f . 4
Ref . 14
Re f . 10
Ref . 11
Ref . 12
l h i s work
Ref. 13
Ref . 14
l h i s work
E s t .
E s t .
Est.
€st.
Ref. 10
Re f . 10
€ S t .
L S t .
Ref. 2
Re f . 15
12
TABLE I . - Cont inued.
1
- No.
- 21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45 -
React1 on
C4H2 + OH + HCO + C3H2
C2H4 + M + C2H2 + H2 + M
C H + OH = C2H3 + H20 2 4
C2H4 + OH + CH3 + CH20
C2H4 + 0 + CH3 + HCO
2 C2H4 + 0 = CH 0 + CH
C H + M = C 2 H 2 + H + M
C2H3 + O2 = C2H2 + H02
C2H3 + H = C2H2 + H2
C H + O H = C H + H 2 0
C H
C2H3 + C H = C H
C2H3 + 0 = C2H20 + H
CH2 + CH
CH2 + CH2 = C2H3 + H
CH
CH2 + 0 = CH + OH
CH2 + O2 = C O
2
2
2 3
2 3 2 2
2 3 + CH2 = C2H2 + CH3
+ C2H2 2 2 2
= C2H2 + H2
+ OH = CH + H20 2
+ 2H 2 C2H2 + M = C H t H + M
C H + C2H2 = C4H3 + H
C2H2+ O2 = C2H0 + OH
C2H2 + 0 = C2H + OH
C2H2 + 0 = CH + C O
C2H2 + 0 = C2H0 + H
C2H2 + OH = C 2 2 H + H 0
2 2
2
A cm3, mole,sec
3 . 0 ~ 1 O I 3
9 . 3 3 ~ 1 O1
4 . 7 9 ~ 1 0 12
2.OOxl o1 12
13
14
13
3.31 x10
2.51 x10
7 . 9 4 ~ 1 0
1 . 5 8 ~ 1 0
6 . 0 ~ 1 0
5 . 0 0 ~ 1 0 ~ ~
3 . 0 0 ~ 1 0 ~ ~
13 3 . 0 0 ~ 1 0
13 3 . 3 0 ~ 1 0
13 4 . 0 0 ~ 1 0
12 5 . 0 1 ~ 1 0
11 2.51 x10
11 2.00x10
1 . 5 9 ~ 1 0 ’ ~
16 4 . 1 7 ~ 1 0
12
2.00x101
2 .00x l o8
2.20x1010
1 5 3.1 6x1 0
4 3 . 5 5 ~ 1 0
6.31 x l 0 ’
- n
- 0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
.6;
. bf
0
0
0
1.5
- .b
1 .o 2.7
0 -
Ea a l o r i e s
0
11 200
1 230
960
1 130
5 000
31 500
1 0 000
0
0
0
0
0
0
0
2 5 700
25 000
1 000
37 000
15 900
30 100
15 000
2 580
1 390
7 000
Source
TABLE I . - Cont lnued. - No
- 46
47
48
49
50
51
52
53
54
5 5
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70 -
Reac t l on
C2H2 + OH = C H 0 t H
C2H2 + C2H = C4H2 + H
C2H2 + CH2 = C3H3 t H
C H + H + M = C 3 H 4 + M
C2H20 + OH = CH20 + HCO
C2H20 t OH = C HO + H20
C2H20 + H = CH
C H 0 + H = C2H0 + H2
C2H20 + 0 = C2H0 + OH
C2H20 + 0 = CH20 + CO
C2H20 + M = CH
C2H0 + O2 = 2CO + OH
Z2H0 + 0 = 2CO + H
:2H0 + OH = 2HCO
:2H0 + H = CH2 + C O
:2H0 + CH2 = C2H3 + C O
Z2H0 t CH2 = CH20 t C2H
:2H0 t C2H0 = C2H2 + 2 C O
:2H + OH = C2H0 + H
:2H t O2 I C2H0 * 0
:2H + 0 = C O t CH
:2H + H2 = C2H2 + H
:H 4 + M = C H 3 + H + M
:H4 + O2 = CH3 + H02
:H
2 2
3 3
2
3 + C O
2 2
+ CO + M 2
+ H = CH3 + H2 4
A cm3, mo1e.sec
~
3 . 2 0 ~ 1 O1
3 . 0 0 ~ 1 0 ~
1 .oox1012
2. 8oX1 o1
1 3 2.OOxlO
12 7 . 5 ~ 1 0
1 . 1 3 ~ 1 0
7 . 5 0 ~ 1 O1
5 . 0 0 ~ 1 0 ~ ~
13
2.oox1 o1 2.00x1016
12
1 2
1 . 4 6 ~ 1 0
1.2ox10
1 . 0 0 ~ 1 0 ~ ~
13
13
5 . 0 0 ~ 1 0
3 . 0 0 ~ 1 0
1 . o o x l 0’
2 . 0 0 ~ 1 0 ~
13 1 .OOxlO
13 5 .OOxlO
5 . 0 0 ~ 1 0 ~ ~
4 . 0 9 ~ 1 Ob
2 . 0 0 ~ 1 017
13
14
7 . 9 4 ~ 1 0
1 .26x10
- n
- 0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
D
D
3
2.39
3
I
1 -
Ea : a l o r l e s
200
0
0
0
0
3 000
3 428
8 000
8 000
0
60 000
2 500
0
0
0
0
2 000
0
0
1 500
0
864
68 000
56 000
I 1 900
l e f . 18
?ef. 18
t e f . 20
14
TABLE I . - Cont inued.
I L 1
c o n s t a n t e x p r e s s i o n g i v e n i n Ref . aComputed f r o m k f o r t h e r e c o m b l n a t l o n
- No.
71
72
13
74
75
76
77
18
19
80
81
82
83
84
85
86
87
r e a c t i o n and t h e e q u l l l b r l u m 18.
89
90
91
92
93
A cm3, mole,sec
1 3
1 4
2 . 5 ~ 1 0
1.9x10
3 . 9 8 ~ 1 O1
2.00x1016
13
14
16
13
4 . 7 9 ~ 1 0
1 .29x10
1 .OOxlO
5 . 0 1 ~ 1 0
1 .OOxl o1
2 . 0 0 ~ 1 0 ~ ~
10 1 .OOxl 0
3 . 0 2 ~ 1 O1
2.00x10
3 . 3 1 ~ 1 0
7 . 5 9 ~ 1 0
3 . 3 1 ~ 1 0
13
1 6
12
14
13 5.01x10 , 1 . 0 0 ~ 1 0 ~ ~ ~
14 2 . 9 4 ~ 1 0
3.31 x l 0 ’
1 . 0 0 ~ 1 0 ~ ~
14 2.OOxlO
R e a c t l o n
CH
CH4 + 0 = CH3 + OH
CH3 + OH = CH20 + H2
CH3 + OH = CH 0 + H
CH3 + O2 = CH30 + 0
CH3 + 0 = CH20 + H
+ OH = CH3 + H20 4
3
CH3 + CH3 = C2H4 + HZ
CH30 + M = CH20 + H + M
CH30 + O2 = CH20 + H02
CH30 + H = CH20 + H2
CH3 + CH20 = CH4 + HCO
CH3 + HCO = CH4 + C O
CH3 + H02 = CH30 + OH
CH20 + M = HCO + H + M
CH20 + OH = HCO + H20
CH20 + H = HCO + H2
CH20 + 0 = HCO + OH
IC0 + H02 = CH20 + 0 2
I
I
HCO + M = H + C O + M
HCO + O2 = C O + H02
HCO + OH = CO + H20
HCO + H = C O + H2
HCO + 0 = CO + OH
7 000
0
0
94 I CH + 0, = HCO + 0
1 .OOxl o1 1 .oox l o1
- n
0
0
0
0
0
0
0
0
0
0
.5
.5
0
D
D
D
Ea c a l o r l e s
5 010
11 720
0
27 410
29 000
2 000
32 000
21 000
6 000
0
6 000
0
0
81 000
170
1 0 500
4 600
3 000
15 570
Source
Ref . 19
Ref . 19
Ref. 17
l e f . 17
! e f . 1 1
e f . 17
15
~-
TABLE I . - Concluded. - No.
- 95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
R e a c t i o n number j
A cm3, mole.sec
1 5
12
13
5 . 8 9 ~ 1 0
2 . 5 1 ~ 1 0
5 . 7 5 ~ 1 0
6 . 7 6 ~ 1 0 ~ ~
2 . 9 5 ~ 1 0 ~ ~
2.51 xlO1'
5.01 x10
5.01 x l 0
5.01 XI O1
2.51 x10
2 . 1 9 ~ 1 0
1 .51x10
1 .41x10
13
13
1 4
13
1 5
23
16 1.oox10 1 3 . 0 2 ~ 1 0 ~ ' 1 . 9 1 ~ 1 0 ~ ~
1
2
3
4
5
6
7
8 9
1 0
12
13
14
15
17
43
44
106
R e a c t i o n
CO t 0 t M = C02 t M
co t o2 = co2 t 0
CO t H02 = C02 t OH
0 t H 0 = O H t OH
0 t H2 = O H t H
H2 t O2 = OH + OH
0 t H02 = OH t O2
OH t H02 = H20 t O2
H t H02 = H20 + 0
H t H02 = OH + OH
H2 + OH = H20 t H
H + 0 2 t M = H 0 + M
H t OH + M = H20 + M
H t 0 t M = OH t M
H t H t M z H t M
O t O t M = O t M
2
2
2
2 I
- n
- 0
0
0
0
0
0
0
0
0
0
0
0
-2
0
0
0 -
Ea c a l o r 1 es
4 100
47 690
22 930
18 360
9 800
38 950
1 000
1 000
1 000
1 900
5 150
- 1 000
0
0
0
- 1 790
Source
~~~
Ref. 17
Ref . 17
Ref . 17
Ref .
Ref .
Ref.
1ABLF. 11. - S E N S l l l V l l l Y COEFt lCl tNlS F O R t)F.NitNE O X l D A l l O N I N A 1URBULENT R E A C l O R ( N I T H O G E N OILUltO)
React 1 on S e n s l t l v l t y c o e f r l c l e n t o f dependent v a r i a b l e n: A j / n ( a d a A j ) a t t i m e = 35 msec
C6H6 + O2 e C H
C6H6 e C6H5 t H
H t 0 2 * OH t 0
C6Hb t H e C H t H2 6 6 C H t O + C H + O H
6 6 6 5 C H t O H + C H t H20
6 6 6 5 C H
6 5 C H O + C5H5 t CO
6 5 CO t O H + C02 t H
C H t O2 + C5H50 t 0 5 5 C H O H s C H 0 + H
6 5 6 5 C H + C 6 H 6 s C H t C6H5 5 5 5 6 OH t C H O H + C H 0 + H20
6 6 6 5
C6H5 + C4H3 t CZH2
C H t 0 +C5H50 t H
C H t O+CH2 t CO
C2H2 t 0 + C2H0 t H
H t O2 t M e H 0 2 t M
t HOZ 6 5
t O2 s C6H50 t 0
5 6
2 2
'gH6
-0.1781
.a959
- .0530
.0058
- .E467
-.EO13
-5.680
.1169
.3546
.4904
- . l a54
- .1399
.0065
.0003
.0172
.1562
.0590
- .0409
C6H5
- 0.2050
.0610
.2073
.0056
- .3351
- .4225
- 6.331
.0804
.1428
.2212
- .0996
- .1176
- .0045
4x1
.0083
.04 56
.0137
- .0039
-0.1169
.5429
- .2415
.0030
-.1150
- .1949
-3.333
- .0435
- .2367
.2088
.3744
- .0772
.1317
- . O O O l
.0157
-. 3350
- .1449
.1975
C5H6
0.0244
.3042
.1247
- .0005
- .2873
- .3740
- .6433
.4413
.1347
.1859
. .0802
.9313
.0074
.0007
- .0876
.0596
.0200
- .0082
C6H60H
0.1129
- .4134
- .0685
- .0027
.1204
.1847
3.089
- . l o 5 1
.zoo1
.4070
.6343
.0439
- .4036
. O O O l
.0033
.0046
.0036
-.1164
co
0.0359
.0469
- .0025
- .0009
.0076
.0615
.6679
.0657
- .1802
.4003
- .0093
.0133
.0377
.0004
.0056
- .0038
.0015
.0058
c02 0.1342
- .On65
.0196
- .0032
.2219
.0471
2.870
.2387
.6189
.5624
- .1608
.0562
- .0458
.0006
.0040
.0050
- .0080 -.01b2
l e m p e r a t u r e
0.0017
- .0004
. 0001 5
.0017
.0006
.0349
.0027
.0024
.0110
- .0005 .0007
- .0003
- 4 ~ 1 0 -
1 xl o - ~ . O O O l
. O O O l
3x1
- .0002
16
z 0
W = a a W c -x W I I
Y V
0 I: m
z
z 0
I- 4
X 0
W z W N
z W
I
3
a I
m CL 0 L L
m I- z W
V
Y
iL W
0 V
).
- d
7 H
> c 3
d
10 z W
m , I 3 - W _I
m a I-
3
Y
0
0 U 7
,, aJ I
3 Y
m L 01 a
E Y
7
m Y
c
.r
.r
.r
._ 0
F
I,
0
Y
m L
aJ u c J
m >
3 W W
.r
- .r
Y
-
u W v1
a 0 N
N
I,
W
.r 4 2
+ m - F
a m \
m c - E -. .') 4
E
W
D m - r L
m >
w c aJ 0 c aJ W 0
a
c 0
w c W
U r
r L
c aJ 0 U
h Y
> Y
A
- - - - Y n -
- - 3 - 4 J
U u L
m u 7 a N m o m m o m U P m N 7 m o w c m 7 r n m o - - ~ i m I - o m o r - o ~ o o o o m o o ~ ~ 0 0 o o o o o o 0 0 0 0 0 0 7 0 0 0 7 0 7 0 0 0 0 0 ~~ . . . . . . . . . . X . X . . . . . 0 1 U N I
I
~ m m u c ~ m m m u m o a c ~ o m r n u m U 7 c u F 7 7 0 1 0 1 7 o m o o 0 - 0 0 0 0 \ D O O N 0 0 0 0 0 0 0 0 0 0 0 0 0 0 . - 0 0 0 7 0 7 0 0 0 0 0 . . . . . . . . . X . Y . . . . . 0 I I c N I
I
P O C O P N O + N U o m ~ ) O ~ ) N U P v ) m m u a r m L o m ~m o o o m r n o ~ m b m ~ m m ~ ~ m o m o c o ~ m a ~ m ~ o a - m ~ u m 0 . - O O O N O O . . . . . . . . . . . . . . . . . . 0 I 0 I I I 1
7
m c m w m a m a - m m mam mom m . - a m r n m m m ~ r - ~m o u r u r n a m - a 7 0 u o m c o ~ o - o o o o o o W O C ) m N O ( ? - N O I O N O U O N N O . . . . . . . . . . . . . . . . . . 0 I Lo I I I
m ~ a m ~ m m m a m m 7 ~ u a ~ c m m m m o m o m 0 m u m m a m m m u m m o ~ o o ~ o c m - u e m m o m 7 m D 0 0 7 P U O N O m m N 0 0 0 0 0 0 . . . . . . . . . . . . . . . . . .
I U I I 7
3
- - m m a 7 U P O e m - ~ o m m m ~ 5 ! g ~ z % z z z & z & % 8 L $ ; ; g : " 3 m o o o o 7 r q o o o m 0 0 0 0 0 0 . . . . . . . . . . . . . . . . . 3 I N I I I
u a o a a o m m m m ,-- C ~ O P P O n I n m e m - - t ~ m m I ~o o m ~ - ~ o r - n - c - o r - m r n ~ a O N O ~ N N O - 3 0 0 o - ~ m r n o m - - o o o m m o . . . . . . . . . . x . . . . . . .
, I 3 I r n m i I I
3 m ~ m m ~ 0 n a m m c u m m N o O N N I D C N U - - o a o m m t n ~ r ' m m a o u - o u m 3 r o o 7 7 + m 7 a 0 0 0 7 0 N 0 0 . . . . . . s o 0 0 0 0 0 0 0 0 0 0
I . . . . . . . . . . . I 6 1 , , I l l ,
3 I I
- ~ o m m -T m m m m m m o o m ~ m e 7 m e ~ ~ m m ~ 7 0 - o - o m o m D O C O I D U P P O m N U U 0 O F Y V ) r D v )
N e O O O P N N O m O N 0 0 0 0 0 0 . . . . . . . . . . . . . . . . . . 7 I O I I I ! I
I I c 3 1 1
N 3 r
+ m Lo T I 0
_ I + +
+ 11 a a L o a S L +
_ ) V I
0 N O
N I I I O * + + + O O I
v) Inv Lo m I I + I S a a +
In0 Lo a v v
v u N
11 11 2 = I 0 0 0NVIn11 + + + + 1 l z
0 L o L o L o I n m + X I X I I L o o a L o a o
v v u v v v
0
+ 0
I
I V
m m
11 N
0
+ m m I:
V
0
I N
+ I
v) N +
N O
I:
0
I T
v u m
11 + ," 0, xu 11 I m
x u 0 a
11 +
+ m a I I
I a m o v v
x O S V + + + N
0 0 N I I
11 11 I o o + + + N
0 N N S I + N N
v v x
17
R e a c t i o n number
R e a c t i o n S e n s i t v i t y c o e f f i c i e n t o f dependent v a r i a b l e
C6Hb CbHg C O Pressure
0.1900 .0220 .0015 .0053 .0018
7 1 0
8 6
15
TABLE V . - SENSITVITY OF COMPUlLO I G N I T I O N DELAY TIME T O RATE CONSlAN1
VARIATION FOR TWO SHOCK IGNTIIONS
CbH5 t 02 +CbH50 t 0 -10.28 -0.7590 6.839 C5H5 t 02 + C5H5O t 0 -.3129 -.Ob80 .4974 CbHrjO+ C5H5 t co -.2839 -.0325 .7193 C6Hb t OH?= CbH5 t H20 -.7214 .1342 .3036 C b H g t C4H3 + C2H2 -.0100 -.0148 .0449
R e a c t i o n number
R e a c t i o n T ~ , us T ~ , us Percent T ~ , us Percent
k s t d 2 k s t d change 0.5 k s t d change 1
7 CbHg t 02 *C6H50 + 0 272 188
6 CbHb t O H + C6H5 + H20 273 15 CbHg;"C4H3 t C2H2 212
10 C5H5 t 02 + C5H50 t 0 246 8 CbH50+ C5H5 t co 268
-30.9 420 54.4 -9 .6 31 3 15.1 -1 .5 289 6.3
.4 280 2.9 0 276 1.5
~ ~~~
7 1 0
8 6
15
18
CbHg t 02 F? CgH50 t 0 151 108 -28.5 203 34.4
CbH50+CgHg t C o 151 0 154 2.0 C6H6 t OH + C6H5 t H20 149 -1.3 159 5.3
C5H5 t 02+ CgH50 + 0 143 -5.3 160 6.0
CgH5 e C 4 H 3 t C2H2 125 -17.2 172 13.9
M i x t u r e Equ iva lence number r a t i o , +
Mole p e r c e n t I n i t i a l t e m p e r a t u r e - range, ( b e h i n d CbH6 O2 A r r e f l e c t e d shock) ,
K
1 2 3 4 5
0.5 1.354 20.313 78.333 1209-1 345 1 .o .516 3.868 95.616 1345-1 528 1 .o 1.69 12.68 85.63 1283-1435 1 .o 1.69 12.582 85.728 1355-1 408 2.0 1.354 5.093 93.555 1363-1 600
TABLE V I I . - COMPARISON OF COMPUlt.0 AN0 EXPERIMENTAL I G N I l I O N DELAYS
Equ lv - A c t i v a t i o n energy c a l / m o l e a l e n c e r a t l o Exper lmenta l Computed
Q
Equiva lence r a t i o
v
Percent d l f f e r -
ence
Percent a rgon
1 .o 01 1 u t e
1 .o
I n l t l a l tempera ture
K
41470 27860 -37
37250 23560 -37
Exper lmenta l I g n l t i on d e l a y ,
psec
S t r o n g
2.0
Computed I g n l t i on d e l a y ,
psec
42400 3201 0 -24
Standard d e v l a t 1 or
p e r c e n t
52.5
P e r c e n t d l f f e r -
ence
-22. 6 -19.2
14.5 30.6 42.6 90.3 65.3 76.1
0.5 78.3 1209 1227 1254 1276 1291 1307 1314 1345
~
878 743 435 330 272 185 202 159
680 600 498 431 388 352 334 280
1 .o D l l u t e
95.6 1345 1314 1402 1412 1428 1482 1525 1528
755 604 41 5 41 2 367 21 3 122 122
550 450 370 345 31 3 21 6 160 159
-27.1 -25.5 -10.8 -16.3 -14.7
1 .4 31.1 30.3
22.0
1 .o S t r o n g
85.6 1283 1290 1294 1328 1355 1369 1379 1405 1408 1417 1435
750 61 3 601 490 303 287 291 198 189 178 151
600 575 556 4 50 378 342 320 272 266 252 225
-20.0 -6. 2 -8.4 -8.2 24.7 19.2 10.0 37.4 40.7 41 .6 49.0
28.3
2.0 93.6 1363 1415 1457 1540 1554 1570 1582 1600
1520 890 599 274 243 21 1 157 154
870 607 453 248 223 195 172 151
-42.8 -31.8 -24.4
-9.5 -8.2 -7.6
9.6 -1.9
21 .6
S tandard d e v i a t i o n o f a l l d a t a p o i n t s I s 33.2 p e r c e n t .
I -52 I 1 0 . 5 I 44160 I 21230
4.0
F 3.2 4
w oz 3 v) v)
2.4
1.6
lo00 DILUTE MIXTURE
800 F 95.6% AR
; 400 - - 2 - L
E: t ---os-- COMPUTED L - = 200 EXPERIMENTAL -
-
7.2 7.4 7.6 7.8 8.0 8.2 8.4 10 000/T, K-l
100
I I u
600
Y In
1 400 >:
L E: t; L = 200
U W In
1
1000
800
600
400
I 6.4 6.6 6.8 7.0 7.2 7.4 7.6
10 000/T. K-l
100
200
I I I I I I 6.8 7.0 7.2 7.4 7.6 7.8 8.0
10 000/T. K-l
100
1515 1430 1350 TEMPERATURE, K
FIGURE 3. - BENZENE-OXYGEN-ARGON IGNITION DELAY VERSUS RE- CIPROCAL OF TEMPERATURE FOR EQUIVALENCE RATIO 1.0.
1430 1350 1280 TEMPERATURE, K
FIGURE 4.- BENZENE-OXYGEN-ARGON IGNITION DELAY VERSUS RE- CIPROCAL OF TEMPERATURE FOR EQUIVALENCE RATIO 1.0.
20
~
1000
EQUIVALENCE RATIO = 1.0 I N I T I A L TEMPERATURE = 1115K
800
. 600
I
W
1
200
1000
800 -
600 -
- - MIXTURE PERCENT
ARGON -
v)
U
1 -
>: 400 -
; - L
EXPERIMENTAL 0 t El 200 - -
100 6.4 6.6 6.8 7.0 7.2 7.4 7.6 7.8
10 000/T, K-'
4
3 In
2 X
W s 1
0
1515 1430 1350 TEMPERATURE, K
FIGURE 6. - BENZENE-OXYGEN-ARGON IGNITION DELAY VERSUS RE- CIPROCAL OF TEMPERATURE: EFFECT OF ARGON DILUTION FOR EPUIVALANCE RATIO 1.0.
EQUIVALENCE RATIO = 1.0 PRESSURE = 1.0 ATM -
EXPERIMENTAL, REFERENCE 5
-
I I I I I I
-
--. I
20 40 60 80 100 120
FIGURE 8. - CYCLOPENTADIENE MOLE FRACTION VERSUS TIME FOR
TIME, mSEC
BENZENE-OXYGEN-NITROGEN REACTION,
21
EQUIVALENCE RATIO = 1.0 PRESSURE = 1.0 ATM
14
EQUIVALENCE RATIO = 1.0 PRESSURE = 1.0 ATM
5 -
I LQUIVALENCE RATIO = 1.0 PRESSURE = 1.0 ATM
EXPERIMENTAL, REFERENCE 5
3
2
0 I
x 2 . ------ COMPUTED z I . I . .
\ I
I I I
y, 8
w I C I \ *. I
I I
I I
y\... . $'$ .a# ----
0 20 40 60 80 100 120 TIME, mSEC
FIGURE 9. - PHENOL MOLE FRACTION VERSUS TIME FOR BENZENE- OXYGEN-N I TROGEN REACT1 ON.
12 3 z x 10
0 z
$ 8 4 p: U
w 6
a' 4
2
0 TIME. msEc
FIGURE 10. - BENZENE MOLE FRACTION VERSUS TIME FOR BENZENE- OXYGEN-NI TROGEN REACTION.
EQUIVALENCE RATIO = 1.0 PRESSURE = 1.0 ATM
EXPERIMENTAL. REFERENCE 5
COMPUTED
- _- _- - - --- [- -*..---.-
TIME. mSEC
FIGURE 12. - CARBON DIOXIDE MOLE FRACTION VERSUS TIME FOR BENZENE-OXYGEN-NITROGEN REACTION.
22
NASA 1. Report No.
Namnal Aeronaulics and Space AdminisIralion
2. Government Accession No.
Report Documentation Page 1
3 Security Classif (of this report)
U n c l a s s i f i e d 22 Price' 20 Security Classif (of this page) 21 No of pages
Uncl ass1 f l e d 23 A02
NASA TM-100202 4 Title and Subtitle
D e t a i l e d Mechanism o f Benzene O x i d a t i o n
7. Author(s)
Dav id A. B i t t k e r
9. Performing Organization Name and Address
N a t i o n a l Ae ronau t i cs and Space A d m i n i s t r a t i o n Lewis Research Center Cleveland, Oh io 44135-3191
2. Sponsoring Agency Name and Address
N a t i o n a l Ae ronau t i cs and Space A d m i n i s t r a t i o n Washington, D.C. 20546-0001
5. Supplementary Notes
3. Recipient's Catalog No. , I
I I 5. Report Date
I October 1987
6. Performing Organization Code
1 -.--
E-3797 I
8 Performing Organization Report No
10. Work Unit No.
505-62-2 1 I I i 11. Contract or Grant No.
i
13. Type of Report and Period Covered
Technica l Memorandum i
14. Sponsoring Agency Code i
6 Abstract
A d e t a i l e d q u a n t i t a t l v e mechanism f o r t h e o x i d a t i o n o f benzene i n b o t h argon and n i t r o g e n d i l u t e d systems i s presented. Computed i g n i t i o n - d e l a y t imes f o r argon- d i l u t e d m x i t u r e s a r e i n s a t i s f a c t o r y agreement w i t h exper imen ta l r e s u l t s for a wide range o f i n i t i a l c o n d i t i o n s . An exper imenta l temperature versus t i m e pro- f i l e f o r a n i t r o g e n - d i l u t e d o x i d a t i o n has been a c c u r a t e l y matched and seve ra l c o n c e n t r a t i o n p r o f i l e s have been matched q u a l i t a t l v e l y . A p p l i c a t i o n o f sensi - t l v l t y a n a l y s l s has g l v e n approxlmate r a t e cons tan t exp ress lons for t h e two dominant hea t - re lease r e a c t i o n s , t h e o x i d a t i o n s o f CgH5 and C5H5 r a d i c a l s by mo lecu la r oxygen.
7. Key Words (Suggested by Author(s))
Benzene o x i d a t i o n Chemical mechani sms I g n i t i o n de lay t imes
18. Distribution Statement 1 U n c l a s s i f i e d - U n l i m i t e d
