Relation Between Fuel Properties and Chemical Composition

18 Relation Between Fuel Properties and Chemical Composition. Stability of O i l Shale-Derived

Downloaded by UNIV OF ARIZONA on January 12, 2013 | http://pubs.acs.org Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch018

Jet Fuel C. J. NOWACK, R. J. DELFOSSE, and G. SPECK Naval Air Propulsion Center, Trenton, NJ 08628 J.SOLASH and R. N. HAZLETT Naval Research Laboratory, Washington, D.C. 20375 1

The Navy has been interested in the use of alternate fossil fuels for sometime (1-4). Our interest is focused primarily in establishing the effects of chemical composition on fuel properties since such relations will lead to greater availability and better use of fuels. We recently reported some of our results on jet fuels derived from coal, tar sands and oil shale (1). Other papers in this series report on some aspects of oil shale derived fuels obtained from a large production experiment, Shale II, performed by Paraho, Inc. (5,6). In this paper, we report on some aspects of stability of a jet fuel prepared in an earlier Navy Program, Shale-I (3). Previous work with shale oil derived middle distillates has noted the very high freezing point of these fuels (1,7). In addition, shale oil fuels which were high in nitrogen gave as much as 45% conversion of fuel bound nitrogen to NO emissions when burned under typical jet engine conditions (4). The high nitrogen content in shale oil jet fuels leads to particulates and gums upon standing at ambient temperatures in the absence of light (7). Stability concerns the tendency of fuels to form particulates and/or coatings on engine surfaces under two different sets of conditions. One set of conditions is that of storage: weeks or months at temperatures of >^40 C, quiescent exposure to air, and no light. The fuel encounters much different conditions in a jet airo craft: a few hours at temperatures up to 80 C with agitation and exposure to air in the fuel tanks plus a minute or so at 150-250 C in the fuel system components with only dissolved air present. Again, no light is present during the high temperature exposure. Shale oil derived fuels used in this work were much poorer than petroleum derived fuels under both stability regimes and a thorough study of the stability of these fuels was undertaken. Current address: Department of Energy, Germantown, MD, 20767. x

1

This chapter not subject to U.S. copyright. Published 1981 American Chemical Society

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

OIL SHALE, TAR SANDS, AND RELATED MATERIALS

268


Experimental The shale o i l derived j e t f u e l (designated Shale-I) used i n t h i s work was produced from a crude shale o i l ( s u p p l i e d by Paraho, Inc.) by delayed coking, f r a c t i o n a t i o n , and m i l d hydrotreatment at the Gary-Western r e f i n e r y . The e n t i r e production operation has been f u l l y described elsewhere (3). The p h y s i c a l p r o p e r t i e s of the j e t f u e l have been reported (1). High temperature s t a b i l i t y of the f u e l s was measured using an A l c o r , Inc. J e t F u e l Thermal Oxidation Tester (JFTOT) ( 8 ) . Low temperature (storage) s t a b i l i t y was determined by measurement of gums, contamination and peroxide concentration ( a l l by ASTM standard methods) before and a f t e r exposure to temperatures of 60 C f o r four weeks. The f u e l s were stored i n l£ low a c t i n i c , dark pyrex g l a s s b o t t l e s and were l o o s e l y covered to prevent exposure to a i r borne p a r t i c u l a t e s . A i r could s t i l l d i f f u s e i n t o the v e s s e l . The v e s s e l s with f u e l and v a r i o u s a d d i t i v e s were thermostated at 60 C f o r the s p e c i f i e d length of time. I s o l a t i o n of shale o i l j e t f u e l b a s i c n i t r o g e n compounds was accomplished by e x t r a c t i o n with IN aqueous HC1 followed by n e u t r a l i z a t i o n of the HC1 adducts (7). The b a s i c n i t r o g e n compounds thus obtained were analyzed by gas chromatography using a Perkin-Elmer model 3920B gas chromatograph equipped with a 100m OV-101 g l a s s WCOT column and n i t r o g e n - s p e c i f i c detector. This column separated the n i t r o g e n compounds i n t o at l e a s t 70 incompletely r e s o l v e d components. T e n t a t i v e i d e n t i f i c a t i o n of some of the components was made by combined gas chromatography-mass spectrometry (gc-ms) using a Hewlett-Packard model 5982 gc-mass spectrometer with a HewlettPackard model 5933A dedicated data system. The mass spectrometer was equipped with a 33m SE-30 SCOT column and was operated i n the EI mode at 70 eV. In a d d i t i o n , the extracted b a s i c n i t r o g e n compounds were subjected to f i e l d i o n i z a t i o n mass spectroscopy (FIMS). Ions produced by f i e l d i o n i z a t i o n tend not to fragment and an accurate molecular weight p r o f i l e of a mixture can be constructed

. Results and

Discussion

E a r l y work with r e f i n e d shale o i l c l e a r l y showed (7) that the j e t f u e l used (M.000 ppm nitrogen) was unstable and r a p i d l y plugged f i l t e r s upon standing f o r s e v e r a l days. Removal of nitrogenous m a t e r i a l by a c i d e x t r a c t i o n or by passing the f u e l over c l a y or s i l i c a g e l gave improved storage p r o p e r t i e s . The chemical cons t i t u t i o n of the n i t r o g e n c o n t a i n i n g m a t e r i a l s was sought i n an e f f o r t to d i s c o v e r s p e c i f i c c l a s s e s of compounds which could cause s t a b i l i t y problems. I t i s w e l l known that p y r r o l e s and i n d o l e s are q u i t e r e a c t i v e toward a i r and l i g h t (10-14) and i f present i n l a r g e q u a n t i t i e s i n these f u e l s might account f o r the observed instability.



18.

NOWACK

ET

AL.

Oil

Shale-Derived

Jet

Fuel

269

B a s i c Nitrogen Compounds. The Shale-I j e t f u e l contained 976 ppm n i t r o g e n of which 860 ppm n i t r o g e n was a c i d e x t r a c t a b l e . The n e u t r a l i z e d e x t r a c t was subjected to gas chromatography using an a l l g l a s s system with a high e f f i c i e n c y c a p i l l a r y column. A chromatogram of the a c i d e x t r a c t obtained using a n i t r o g e n - s p e c i f i c d e t e c t o r i s shown i n F i g u r e 1. As shown, r e t e n t i o n time matching i m p l i e s that the m a j o r i t y of compounds are p y r i d i n e - t y p e bases. The mixture was a l s o subjected to gc-mass spectroscopy. The t o t a l i o n chromatogram i s shown i n F i g u r e 2. The lower r e s o l u t i o n SCOT column used on the mass spectrometer d i d not permit unequivocal assignment of each peak. T e n t a t i v e assignments of the numbered peaks are noted i n Table I. In many cases, the e l e c t r o n impact mass spectrum c l e a r l y showed the presence of more than one compound. However, the main compound type observed was a l k y l s u b s t i tuted p y r i d i n e with l e s s e r q u a n t i t i e s of q u i n o l i n e s . We used another mass s p e c t r a l technique to help confirm our gc-ms a s s i g n ments. The FIMS r e s u l t s are tabulated i n Table I I . Since molecules tend not to fragment when f i e l d i o n i z e d , the FIM spectrum can be scanned f o r parent masses; compound c l a s s e s and higher a l k y l s u b s t i t u t e d homologs are r e a d i l y recognized. The FIMS data confirm the presence of major amounts of p y r i d i n e compounds with l e s s e r q u a n t i t i e s of q u i n o l i n e and t e t r a h y d r o q u i n o l i n e types. While i o n i z a t i o n e f f i c i e n c i e s f o r various c l a s s e s of compounds under FI c o n d i t i o n s are not known with c e r t a i n t y , we do not expect them to be very d i f f e r e n t f o r the aromatic n i t r o g e n types observed here. We have observed that FIMS data on b a s i c n i t r o g e n compounds r e s u l t i n a higher than expected i n t e n s i t y f o r parent +1 peaks. This was observed f o r our b a s i c n i t r o g e n e x t r a c t s but not f o r n-alkane or n e u t r a l f u e l samples. We a t t r i b u t e t h i s phenomenon to the presence of water i n the b a s i c n i t r o g e n e x t r a c t s ; water r a p i d l y l o s e s a hydrogen atom to the r a d i c a l c a t i o n generated by F I . E x t r a c t i o n of the Shale-I j e t f u e l with HC1 i s approximately 90% e f f i c i e n t f o r removal of n i t r o g e n c o n t a i n i n g m a t e r i a l . Remaining i n the f u e l are 116 ppm of non-basic n i t r o g e n compounds. Presumably, these compounds w i l l be comprised p r i m a r i l y of p y r r o l e , i n d o l e and carbazole types. Only traces of s u b s t i t u t e d p y r r o l e s and i n d o l e s were observed by FIMS i n the b a s i c n i t r o g e n f r a c t i o n (Table I I ) . Shale o i l n i t r o g e n compounds have been c h a r a c t e r i z e d p r e v i o u s l y (15) and s i n c e carbazoles and p y r r o l e s could not be t i t r a t e d i t i s not s u r p r i s i n g that they are a l s o not e f f i c i e n t l y e x t r a c t e d by IN HC1. High Temperature (Thermal) S t a b i l i t y . The high temperature s t a b i l i t y of the Shale-I j e t f u e l s was measured using the JFTOT technique (8). The thermal o x i d a t i v e s t a b i l i t y of the r e c e i v e d f u e l (976 ppm N) was measured. The f u e l was then a c i d e x t r a c t e d , the i s o l a t e d b a s i c n i t r o g e n compounds added back i n t o the e x t r a c t e d shale f u e l i n v a r y i n g q u a n t i t y , and the thermal o x i d a t i v e s t a b i l i t y redetermined. A petroleum d e r i v e d JP-5 was a l s o subjected to*JFTOT




o

-J

to

18.

NOWACK E T A L .

Oil Shale-Derived

271

Jet Fuel

*«·»

S *+-»


·»"•S»· I

-s:

s

•S

t> S3

s; 'S

ι S

s "S s; .o

H

>

5 g

H

^ r

a

S >

>

™ $

a >

to to


+

m/e +

2

Prominent Peaks (Peak, R e l . Abundance) +

2

5

+

3

6

+

3

+

+

2

+

+

,60%),148(M -CH

3

,Base),134

4

+

3

6

+

+

+

+

+

3

6

+

+

+

2

+

+

probable components: ^ - p y r i d i n e (one b u t y l group), e t h y l - t e t r a hydroquinoline, methyl tetrahydroquinoline, methylquinoline

+

177(M ,6%),176(M -l,10%),162(M -CH ,18%),161(M ,18%),135(M C H ,Base)

3

probable species i n c l u d e C . - p y r i d i n e , C^- quinol i n e , methyl-tetrahydroquinoline, ethyl t e t r a hydroquinoline

+

Complex spectrum

2

^ - p y r i d i n e + 3-methylquinoline + tetrahydromethyl q u i n o l i n e

+

3,4-dipropylpyridine + tetrahydromethyl quinoline

2-butyl-4-ethylpyridine

2-propyl-3-methyl-4ethylpyridine

3-ethyl-4-butylpyridine

3-propyl-4-ethyl-5methylpyridine

T e n t a t i v e Assignment

176 (M -l,11%),163(M -CH ,30%),162(M -CH ,37%),147(M ,80%),146(70%), 143(M ,Base)

+

Base)

,18%),134(M -C H ,30%),121

163 (M ,27%) , 162 (M -l,20%) , 147 (45%) , 121 Qi'-C^,

+

163(M ,9%),162(M -l,25%),148(M -CH (M -C H ,Base)

2

163 (M , 25%),162(M -l,55%),149(M -CH ,34%),148(M -CH ,55%),135(M C H ,Base)

+

163(M ,8%),162(M -l,15%),149(M -CH (M -C H ,44%),121(M -C H ,30%)

+

0

163_p4 ,6%),162(M -l,11%),149(M -CH ,53%),148(M -CH ,40%),121 (M -C HL,Base) J o

+

Continued



25

B

+

+

+

+

3

+

171(M ,Base),170(M -l,30%),156(M -CH ,25%),149(25%)

+

+

3-methyl-4-ethyl quinol i n e ; minor: Cgp y r i d i n e , other quinol i n e types

3

R

major: C - p y r i d i n e , C - q u i n o l i n e ; minor: C^-quinoline, C ^ - t e t r a hydroquinoline

+

191(M ,14%),190(M -l,5%),171(M ,45%),170(M -l,25%),121(M -70,Base)

24

probable major component: Cg-pyridine; very minor components; C -quinoline, C ^ t e t r a hydroquinoline

Complex spectrum

23

2

probable major components: C2~quinoline; minor components: C^tetrahydroquinoline, C^-pyridine; trace: C^-tetrahydroquinoline

Complex spectrum

?


22

3

+

probable major components: C~-quinoline, C^-tetrahyaroquinoline; minor: C^-pyridine

+

Complex spectrum

+

21

+

major: C^-pyridine (with 2-pentyl gp)

+

Prominent Peaks m/e (Peak, Rel> Abundance)

177(M ,8%),176(M -l,15%),160(M -l,15%),134(M -C H ,26%),121(M C^HgjBase)

Peak // B 20

A

Table I - Continued


>

2

H M

>

a

H W

w r >

O

>

90

H

>

m

r

o P

to


Complex spectrum

27

Prominent Peaks (Peak, R e l . Abundance)

probable major components: C^-pyridine + C ..-quinoline

probable major components: C ^ - p y r i d i n e , C^-quinoline


'EI s p e c t r a showed evidence of more than one

compound.

'Refer to F i g u r e 2 f o r numbered peak p o s i t i o n i n t o t a l i o n chromatogram of gc-mass spectrum.

Complex spectrum

m/e

26

Peak //

Table I - Continued


OIL SHALE, TAR SANDS, AND RELATED


276

Table I I .

F i e l d I o n i z a t i o n Mass Spectrum Base F r a c t i o n from Shale-I JP-5

Range of "n" Values*

Series

MATERIALS

C H_ N n 2n+l

12-14

C H N n 2n-3

Compounds

Relative Ion Count

Piperidines

10

9-15

Pyrroles

28

C H _N n 2n-5

9-16

Pyridines

C H _N n 2n-7

9-11-16

0

0

0

n 2n-9 C H_ N n 2n-ll

1000

Tetrahydroquinolines

A3

15

Indoles

11

14

Quinolines

170

13 157

* Underlined value of "n" i n d i c a t e s components i n l a r g e s t amount.



18.

NOWACK

E T

A L .

Oil

Shale-Derived

Jet

Fuel

277

t e s t i n g . The petroleum f u e l had a breakpoint temperature of 275°C and at 260 C d i d not produce s i g n i f i c a n t tube deposit r a t i n g s (TDR) or develop a s i g n i f i c a n t pressure drop across the i n - l i n e JFTOT filter. A number of n i t r o g e n compounds, t y p i c a l of those found i n t h i s study, were then added to the petroleum derived JP-5 and the high temperature s t a b i l i t y redetermined. The r e s u l t s with shale and petroleum f u e l s are d i s p l a y e d i n Table I I I . In p r e v i o u s l y reported s t a b i l i t y work with shale o i l derived j e t f u e l s (16) i t was shown that the JFTOT thermal s t a b i l i t y improved as the t o t a l n i t r o g e n content decreased. In Table I I I , i t i s observed that the thermal s t a b i l i t y of the Shale-I f u e l improves as the c o n c e n t r a t i o n of b a s i c n i t r o g e n compounds decreases. In previous work (16) the lower n i t r o g e n contents of the shale o i l j e t f u e l s were achieved by more severe hydrotreatment. I t can a l s o be observed that there apparently are two major modes of high temperature thermal i n s t a b i l i t y and the e f f e c t of b a s i c n i t r o g e n i s d i f f e r e n t i n each. I f thermal s t a b i l i t y i s measured only by tube d e p o s i t s , a s l i g h t r i s e i n breakpoint temperature i s observed as the b a s i c n i t r o g e n content i s reduced (breakpoint by TDR from 244°C to 254°C as b a s i c N changes from 838 to 7 ppm). However, i f the f i l t e r pressure drop i s used f o r determining breakpoint, then a much l a r g e r change, 227 to 279 C, i s observed as b a s i c n i t r o g e n content i s reduced. Pure compounds which are s i m i l a r to those found i n the Shale-I b a s i c n i t r o g e n f r a c t i o n s (Tables I and I I ) were added to a p e t r o leum based j e t f u e l of high s t a b i l i t y (Table I I I ) . Most of the b a s i c n i t r o g e n compounds used r e s u l t e d i n n e g l i g i b l e deposit (TDR) formation with the exception of 2-amino-3-methylpyridine. 4-tB u t y l p y r i d i n e showed evidence of f i l t e r plugging but only s l i g h t d e p o s i t s were formed. P y r r o l e , however, was found to produce a very high deposit r a t i n g (TDR) and a l s o plugged the i n - l i n e f i l t e r . Much more work with pure compounds i n simple c a r r i e r v e h i c l e s i s necessary before d e f i n i t i v e mechanistic i n f e r e n c e s can be drawn regarding the e f f e c t s of the v a r i o u s c l a s s e s of n i t r o g e n compounds. Storage S t a b i l i t y . The low temperature or storage s t a b i l i t y of the Shale-I f u e l was followed by determining changes i n peroxides, gums, contamination, and high temperature s t a b i l i t y (JFTOT behavior). The l a t t e r method was employed s i n c e deposit precursors, which might form at low temperatures, could s e r i o u s l y degrade engine operation i f present i n s u f f i c i e n t concentration. The t e s t f u e l was placed i n 1£ g l a s s b o t t l e s which were l o o s e l y covered to permit a i r d i f f u s i o n to the f u e l . Ten ml of d i s t i l l e d water and 1 g of i r o n f i l i n g s were placed i n each sample. These c o n d i t i o n s simulated a c t u a l storage tank c o n d i t i o n s s i n c e water i s always present i n f u e l storage tanks and the f u e l i s f r e q u e n t l y i n contact with uncoated metal surfaces of storage tanks. The samples were maintained at 60 C f o r four weeks. The r e s u l t s of the storage s t a b i l i t y experiments are presented i n Table IV.



A d d i t i v e Cone., ppm 4-_t-butylpyridine, 56 2-jt-butylpyridine, 49 5-ethyl-2-methylpyridine, 107 4-benzylpyridine, 56 2-amino-3-methylpyridine, 134 N,N-dimethylaniline, 82 p y r r o l e , 100

Max

254 260°C TDR AP, mm 1 20 10 1 11 3 7 2 45 14 6 32 Bypass

279

241

232

227

232

Filter

Measured using A l c o r , Inc. JFTOT according to ASTM Standard Method D-3241.

D

7

251

243

244

_

Heater Tube (TDR)

B o„

Pressure drop of >25mm developed a f t e r which the t e s t continued f o r standard E, 2.5 hr. p e r i o d with the hot f u e l bypassing the f i l t e r .

The petroleum d e r i v e d j e t f u e l had a breakpoint temperature of 275°C and D, had n e g l i g i b l e TDR or f i l t e r pressure drop at 260 C.

Shale O i l JP-5 e x t r a c t e d with HC1, washed, and the i s o l a t e d b a s i c n i t r o g e n C, compounds r e i n t r o d u c e d to the shale o i l f u e l .

Breakpoint i s defined as the temperature of t e s t at which a maximum TDR of >17 i s B, observed or a pressure drop of >25 mm Hg i s a t t a i n e d across the i n - l i n e JFTOT f i l t e r .

A,

Petroleum

C

12 3

166°

C

50

213°

954°

976

Total

C

97

C

838

860

Shale O i l Jet F u e l C

Acid Extractable

High Temperature S t a b i l i t y of J e t Fuels

Fuel Type

Table I I I .


r

1

w

H

> H w o g >

r

W

O

>

> a

>

H

r w

>

X

o r

00

to -o


6

7 8 9

50

it

2,5-dimethylpyrrole,

24-HP 0 24-HP 0 0 0

0 0 0

25-DA 24-HP 0

123° 0 5-ethyl-2methylpyridine, 50

tt

0

25-DA

39°

ppm

0

B

Existent mg/100 Before 0 0 0 0

0 0.4 0.6

0 0 5

0

0

Gums, ml After 0 1.4 5.4 1.6

Results

0.6 0.09 0.07

0.1 0.7 0.6

0

0

0.6 4.2 0.5

0.1 0.7 83

0.6

1.0

Peroxide, meq/kg After Before 0.14 60 64.3 1.4 96.8 1.0 0.2 42.5

Storage

S t a b i l i t y Tests of Treated Shale-I JP-5

25-DA

0 0 0 0

Inhibitor,

Results of Storage

0 25 26

0 25 25

13 9 35

2 0 5 4 4

2 0

U

JFTOT 260 C Max TDR Before A f t e r 1 10 9 13 4 27 5 48

Shale-I JP-5 c o n t a i n i n g 976 ppm n i t r o g e n was f i r s t a c i d e x t r a c t e d then t r e a t e d with s i l i c a g e l to y i e l d a nitrogen-free fuel. Conditions of storage: temp=60 C; time=4 weeks; no a g i t a t i o n ; a i r allowed to f r e e l y d i f f u s e i n t o f u e l . B, A n t i o x i d a n t s used were commercial products q u a l i f i e d f o r Navy f u e l use; DA=phenylene diamine (1,4-diamino benzene); HP=hindered phenol (2,6-di-tert-butyl-4-methylphenol). C, A c i d e x t r a c t e d n i t r o g e n compounds added to n i t r o g e n - f r e e Shale-I JP-5 to b r i n g n i t r o g e n content to designated l e v e l . D, Corrected f o r a n t i o x i d a n t n i t r o g e n content.

A,

o

5

D

0 8.4 25 125

10 11 12

Q

N-Additive, ppm

1 2 3 4

Experiment #

Table IV.


VO

to -o

05

>

H

w

o

2

i



280

Storage s t a b i l i t y measurements have been performed on some shale d e r i v e d f u e l (17). In that study, a Paraho j e t f u e l (very s i m i l a r to our Shale-I) was found to form some gums (increase i n gums of about 2 mg/100 ml f u e l a f t e r 32 weeks storage at 43 C) but there was only a small i n c r e a s e i n a c i d number and no increase i n viscosity. In our storage t e s t s , we t r i e d to determine the e f f e c t s of b a s i c n i t r o g e n compounds on the storage s t a b i l i t y of the Shale-I fuel. The combination of a c i d e x t r a c t i o n followed by s i l i c a g e l chromatography of the Shale-I f u e l was found to be e f f e c t i v e f o r removing a l l n i t r o g e n c o n t a i n i n g compounds. The n i t r o g e n - f r e e Shale-I f u e l showed some tendency to accumulate peroxides under our t e s t c o n d i t i o n s , but no a p p r e c i a b l e gums were formed. In a d d i t i o n , the high temperature (JFTOT) s t a b i l i t y of the aged n i t r o g e n - f r e e f u e l was s i m i l a r l y acceptable (Table IV). Increasing q u a n t i t i e s of b a s i c n i t r o g e n compounds, which were a c i d e x t r a c t e d from the f u e l , were then reintroduced i n t o the f u e l and the storage s t a b i l i t y redetermined. As the concentration of b a s i c n i t r o g e n compounds increased from 8.4 to 125 ppm N, both the gum and peroxide concentration a f t e r storage rose to a maximum (25 ppm N) then f e l l back to lower l e v e l s (Table IV, expt. //2, 3, 4). However, the JFTOT deposit r a t i n g a f t e r storage was monotonic a l l y degraded by i n c r e a s i n g n i t r o g e n l e v e l s . The f i l t e r pressure drop was three mm or l e s s f o r experiments #1-4 except f o r the 125 ppm N sample which exceeded 25 mm a f t e r storage. The r e s u l t s imply a r e l a t i o n s h i p between gum formation and peroxide concentration. I t i s p o s s i b l e that the r e l a t i o n between the gum and peroxide i s of the form: °2 RH

> [peroxide]

>gum

We propose that some f u e l components, p a r t i c u l a r l y those c o n t a i n ing s u l f u r , n i t r o g e n , oxygen, and o l e f i n i c f u n c t i o n a l groups, a l s o r e a c t under storage c o n d i t i o n s with peroxides. Condensation or d i m e r i z a t i o n of the f r e e r a d i c a l intermediates formed i n these r e a c t i o n s can b u i l d the h i g h l y p o l a r , medium molecular weight (400-500) gums observed i n some s t u d i e s (18). A n t i o x i d a n t s of e i t h e r the phenylene diamine or hindered phenol type were e f f e c t i v e f o r i n h i b i t i n g both peroxide and gum formation i n the current s t u d i e s (Table IV, expts. #5, 6, 7, 8). The i n h i b i t o r s a l s o improved high temperature s t a b i l i t y a f t e r storage. The contamination l e v e l i n experiments #l-#8 e x h i b i t e d no patterns with n i t r o g e n content. Further, the phenylene diamine a n t i o x i d a n t exerted l i t t l e e f f e c t . In any case, the contamination did not exceed 2.4 mg/i i n any of these t e s t s . A p y r i d i n e compound was found to storage degrade the Shale-I f u e l f a s t e r than a p y r r o l e compound (Table IV, expt. #9, 11). A f t e r storage the Shale-I f u e l doped with 50 ppm 5-ethyl-2-methylp y r i d i n e had an order of magnitude more gums and 20 times the



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peroxide l e v e l compared to the same f u e l c o n t a i n i n g 50 ppm 2,5d i m e t h y l p y r r o l e . A n t i o x i d a n t s were e f f e c t i v e at i n h i b i t i n g both gums and peroxides i n the n i t r o g e n doped f u e l s a f t e r storage (Table IV, expt. #10, 12), p a r t i c u l a r l y f o r the p y r i d i n e compound. 5-Ethyl-2-methylpyridine caused a l a r g e change i n JFTOT r e s u l t s a f t e r storage. The TDR increased from four p r i o r to s t o r age to 46 a f t e r storage. Correspondingly, the f i l t e r pressure drop changed from three mm to bypass c o n d i t i o n (>25 mm i n 120 minutes). In c o n t r a s t , 2,5-dimethylpyrrole caused e q u a l l y poor JFTOT performance before and a f t e r storage. Not only d i d the before and a f t e r t e s t s give high TDR values, but the f i l t e r pressure drop exceeded 25 mm i n s i x and ten minutes, r e s p e c t i v e l y . The hindered phenol a n t i o x i d a n t was e f f e c t i v e with the p y r i d i n e for maintaining good JFTOT behavior during the four week storage s t a b i l i t y (no i n c r e a s e i n TDR or f i l t e r pressure drop). This a d d i t i v e was not a c t i v e i n the presence of the p y r r o l e , however. The TDR values were about the same and the f i l t e r pressure drop exceeded 25 mm i n seven and one-half and eight minutes, respect i v e l y , f o r the before and a f t e r storage t e s t s . Summary High temperature thermal s t a b i l i t y and storage s t a b i l i t y experiments were conducted using Shale-I j e t f u e l . As b a s i c n i t r o gen compounds are removed by a c i d e x t r a c t i o n from the Shale-I f u e l , JFTOT s t a b i l i t y improves ( e s p e c i a l l y f i l t e r pressure drop performance). A f t e r four weeks of a c c e l e r a t e d storage, the Shale-I f u e l c o n t a i n i n g b a s i c n i t r o g e n compounds formed more gums and peroxides, and e x h i b i t e d degraded JFTOT performance. The b a s i c n i t r o g e n compounds e x t r a c t e d from the Shale-I f u e l were c h a r a c t e r i z e d by way of v a r i o u s mass s p e c t r a l methods. Compounds s i m i l a r to those found i n the b a s i c n i t r o g e n f r a c t i o n were used as a d d i t i v e s f o r JFTOT and storage t e s t s on a petroleum f u e l and n i t r o g e n - f r e e Shale-I f u e l s . Both p y r i d i n e s and p y r r o l e s c o n t r i b u t e to f u e l i n s t a b i l i t y . Much more work must be performed i n order to establ i s h c l e a r trends and to deduce a d e t a i l e d mechanism of f u e l degradation. Acknowledgement The authors thank Dr. S. E. B u t t r i l l , J r . , of SRI Internat i o n a l f o r conducting the f i e l d i o n i z a t i o n mass s p e c t r a l a n a l y s i s on a Naval Research Laboratory c o n t r a c t . Literature Cited

1. Solash, J.; Hazlett, R. N.; Hall, J. M. and Nowack, C. J.; Fuel, 1978, 57, 521.


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2. Eisen, F. S.; Sun Oil Company Final Report on U.S. Navy Contract No. N-00140-74-C00568, February 6, 1975. 3. Bartick, H.; Kunchal, K.; Switzer, D.; Bowen, R.; Edwards, R.; "The Production and Refining of Crude Shale Oil into Military Fuels," Applied Systems Corp. Final Report on Office of Naval Research Contract No. N-00014-75-C-0055, August 1975.


4. Klarman, A. F. and Rollo, A. J.; Naval Air Propulsion Center Report No. NAPC-PE-1, November 1977. 5. Solash, J.; Hazlett, R. N.; Burnett, J. C.; Beal, E. and Hall, J. M.; "Relation Between Fuel Properties and Chemical Composition. II. Chemical Characterization of U.S. Navy Shale-II Fuels," in this book. 6. Affens, W. A.; Hall, J. M.; Beal, E.; Hazlett, R. N.; Nowack, C. J. and Speck, G.; "Relation Between Fuel Properties and Chemical Composition. III. Physical Properties of U.S. Navy Shale-II Fuels," in this book. 7. Solash, J.; Nowack, C. J. and Delfosse, R. J.; Naval Air Propulsion Center Report No. NAPTC-PE-82, May 1976. 8. ASTM Method D-3241. 9. Buttrill, Jr., S. E.; "Analysis of Jet Fuels by Mass Spectrometry," in Naval Research Laboratory Workshop on Basic Research Needs for Synthetic Hydrocarbon Jet Aircraft Fuels, Naval Air Systems Command, June 15-16, 1978, and references therein. 10. Frankenfeld, J. E. and Taylor, W. F.; Final Report under Naval Air Systems Command Contract No. N-0019-76-0675, February 1979, and references therein. 11. Witkop, B.; J. Amer. Chem. Soc., 1950, 72, 1428. 12. Witkop, B. and Patrick, J. B.; J. Amer. Chem. Soc., 1951, 73, 713. 13. Saito, I.; Matsuura, T.; Nakagawa, M. and Hino, T.; Accts. Chem. Res., 1977, 10, 346. 14. Beer, R. J. S.; McGrath, L. and Robertson, A.; J. Chem. Soc., 1950, 3283. 15. Frost, C. M. and Poulson, R. E.; Amer. Chem. Soc., Div. Petroleum Preprints, 1975, 20, 176.


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16. Reynolds, T. W.; National Aeronautics and Space Administration, Technical Memorandum No. TM-X-3551, June 1977. 17. Brinkman, D. W.; Whisman, M. L. and Bowden, J. N.; Bartlesville Energy Technology Center, Report of Investigation No. 78/23, March 1979.


18. Ward, C. C.; Schwartz, F. G. and Whisman, M. L.; Technical Report #11 under Ordnance Project TB5-01-010, Bartlesville Energy Technology Center, July 1961. RECEIVED January 19, 1981.


Relation Between Fuel Properties and Chemical Composition

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