16 Relation Between Fuel Properties and Chemical Composition. Chemical Characterization of
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U.S. Navy Shale-II Fuels 1
JEFFREYSOLASH ,ROBERT N. HAZLETT, JACK C. BURNETT, ERNA BEAL, and JAMES M. HALL Naval Research Laboratory, Washington, D.C. 20375
As domestic and imported petroleum supplies dwindle and petroleum increases dramatically in cost, it is imperative for the Navy to consider future liquid fuel options. The Navy has two thrusts in transportation fuels: (a) explore the relaxation of fuel specifications and (b) examine alternate sources of fuels. This paper deals with one of the alternate sources, shale oil. The bulk of the Navy's vehicles utilize middle distillate fuels; a kerosene type jet fuel, JP-5, for aircraft and diesel fuel marine, DFM, for ships and boats. Reasonable yields of these fuels can be obtained from shale oil. Further, shale crude oil has a good hydrogen content which allows upgrading to finished fuel with modest additions of expensive hydrogen. Thus the interest in Navy fuels from shale oil. The Navy has completed two crude production/refining exercises with shale. The first of these, a 10,000 barrel operation (Shale-I), is described in two reports (1,2). The second, a 73,000 barrel operation (Shale-II), was completed in 1979 at the Toledo refinery of The Standard Oil Company (Ohio) (3). This paper describes the chemical characterization of the JP-5 and DFM from the Shale-II project. Experimental Samples. One g a l l o n samples of the v a r i o u s r e f i n e r y streams were obtained from Sohio throughout the approximately one month of production. P e r i o d i c samples of f i n i s h e d JP-5 and DFM were a l s o obtained during the a c i d treatment process which was comp l e t e d subsequent to the hydrocracking and f r a c t i o n a t i o n steps. Drum samples of the f i n i s h e d homogeneous JP-5 and DFM products were a l s o examined.
1
Current address: Department of Energy, Germantown, MD, 20767.
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.
238
OIL SHALE, TAR SANDS, AND RELATED
MATERIALS
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T o t a l Nitrogen. The f u e l samples were pyrolyzed/combusted at 1000°C i n a flow of argon/oxygen and the chemiluminescence f o r the r e a c t i o n of NO with ozone measured ( 4 ) . Types of s p e c i f i c n i t r o gen compounds found are d i s c u s s e d elsewhere i n t h i s book (5). GC Analyses. The n-alkanes i n the f u e l samples were d e t e r mined with a 100 meter OV-101 w a l l coated glass c a p i l l a r y column. The i n l e t s p l i t r a t i o was 50:1, the column oven was temperature programmed from 80 to 240°C, and the i n l e t temperature was 310°C. The i n t e r n a l standard procedure was used f o r q u a n t i t a t i o n . LC Separation. P r e p a r a t i v e s c a l e l i q u i d chromatography was performed with Waters PrepPak r a d i a l l y compressed s i l i c a columns. F u e l charges of 6 to 10 ml were c a r r i e d through the column with n-pentane at a flow of 200 ml/minute. R e f r a c t i v e index, 254 nm u l t r a v i o l e t , and 313 nm u l t r a v i o l e t d e t e c t o r s monitored the LC e f f l u e n t and keyed the c o l l e c t i o n of f r a c t i o n s . Mass Spectrometry. E l e c t r o n impact (EI) mass spectrometry was done at NRL on the e f f l u e n t from a 6 f t . OV-101 packed GC column programmed from 70 to 210°C. F i e l d i o n i z a t i o n mass spectrometry (FIMS) was performed by SRI I n t e r n a t i o n a l on contract to NRL. In t h i s l a t t e r a n a l y s i s , the f u e l sample was frozen on a s o l i d s i n l e t probe p r i o r to i n s e r t i o n i n t o the mass spectrometer. The s p e c t r a accumulated f o r each mass during a temperature program were normally t o t a l e d f o r data p r e s e n t a t i o n ( 6 ) . Molecules b o i l i n g below 140°C are l o s t or depleted with t h i s technique but such compounds comprise a very small f r a c t i o n of JP-5 or DFM. Since the i o n i z a t i o n e f f i c i e n c y f o r hydrocarbon c l a s s e s i s c u r r e n t l y under study, the FIMS data are u t i l i z e d p r i m a r i l y i n a q u a l i t a t i v e sense. NMR
Examination. Fuel samples and f r a c t i o n s were analyzed by 13 proton and C NMR at the Naval B i o s c i e n c e s Laboratory. The spect r a were taken on a V a r i a n FT-80A. Results Nitrogen Content. The bulk of the shale o i l n i t r o g e n was r e moved i n the hydrocracking step. A l l four products from f r a c t i o n a t i o n of the h y d r o c r a c k a t e — n a p h t h a , j e t , d i e s e l and heavy o i l — contained s u b s t a n t i a l amounts of n i t r o g e n , however. The data i n Table I i n d i c a t e that the l i g h t e r products had l e s s t o t a l n i t r o g e n . A l l products increased i n n i t r o g e n content as the r e f i n i n g run progressed. For i n s t a n c e , the 25 day hydrocrackate contained 2 h times the n i t r o g e n found i n the 12 day product. The j e t and d i e s e l f r a c t i o n s almost doubled i n n i t r o g e n over the same time span. The hydrocracking c a t a l y s t l o s t a c t i v i t y throughout the run.
In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
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16.
SOLASH
E T
A L .
Fuel
Properties
and
Chemical
Composition
239
The n i t r o g e n content of the JP-5 and DFM f r a c t i o n s , the products important to the Navy, was too high to a f f o r d s a t i s f a c t o r y s t a b i l i t y . Extensive a c i d treatment with s u l f u r i c a c i d reduced the n i t r o g e n content i n the f i n i s h e d f u e l s , however, to one ppm(w/v) f o r the JP-5 and 18 ppm (w/v) f o r DFM. As a consequence the f i n i s h e d f u e l s had e x c e l l e n t s t a b i l i t y . Somewhat higher n i t rogen contents would undoubtedly be acceptable with regard to s t a b i l i t y but the Shale-II program demonstrates that s t a b l e f u e l s can be made from shale crude o i l using standard r e f i n i n g processes. n-Alkane Content. Shale f u e l s e x h i b i t higher f r e e z e and pour p o i n t s than s i m i l a r f u e l s made from most petroleum crudes. This i s r e l a t e d to the symmetrical n-alkane molecules which are major components of shale derived f u e l s ( 7 ) . The content of these molecules i n the Shale-II middle d i s t i l l a t e f u e l s i s l i s t e d i n Table I I . The r e l a t i o n s h i p between f r e e z i n g p o i n t and composition i s d e s c r i b e d i n another chapter of t h i s book ( 8 ) . FIMS F i n g e r p r i n t . F i e l d i o n i z a t i o n mass spectrometry of a mixture a f f o r d s a spectrum of the molecular ions s i n c e fragment a t i o n i s minimal. Thus a d i s t r i b u t i o n of molecular s i z e s and hydrocarbon c l a s s e s can be obtained from a s i n g l e a n a l y s i s . This i s i l l u s t r a t e d i n F i g u r e 1 which compares the FIMS f i n g e r p r i n t s f o r JP-5 from Shale-I and Shale-II r e f i n i n g . D i s t i n c t d i f f e r e n c e s can be noted. The preponderance of alkanes ( ^2 +2^ ^ k i g h " l i g h t e d i n Shale-I f u e l which was produced by c r a c k i n g the shale crude by delayed coking. S h a l e - I I , using a hydrocracking process, produced a product much lower i n alkanes. A n a l y s i s f o r t o t a l n-alkane content agrees with t h i s f i n d i n g , 3 7 % i n Shale-I JP-5 ( 7 ) and 22% f o r S h a l e - I I . Other s i g n i f i c a n t d i f f e r e n c e s between the two j e t f u e l s can be noted i n the much higher peaks f o r subs t i t u t e d benzenes (C L ,) and t e t r a l i n s (C L ) i n the Shale-II « n zn—o n zn—o product. Other d i f f e r e n c e s can be noted i n the FIMS data assembled i n Table I I I . For i n s t a n c e , Shale-II a l s o has higher peak sums f o r monocyclic alkanes (C H ) and d i c y c l i c alkanes ( -2^ Shale-I. Data f o r a JP-5 sample, a ten g a l l o n q u a n t i t y produced by f r a c t i o n a t i o n of Paraho shale crude followed by 1200 p s i c a t a l y t i c hydrogenation of the j e t f u e l cut (9), i s a l s o shown i n Table I I I . Again t h i s f u e l has a d i s t i n c t l y d i f f e r e n t FIMS f i n g e r p r i n t i n response to the r e f i n i n g process used. c
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P r e p a r a t i v e Scale LC. Separation of JP-5 and DFM on the Waters r a d i a l l y compressed s i l i c a column gave many f r a c t i o n s . This i s i l l u s t r a t e d i n F i g u r e 2 f o r s i x ml of DFM. F r a c t i o n one, beginning at 3.2 min, i s the s a t u r a t e f r a c t i o n which was detected w i t h a r e f r a c t i v e index d e t e c t o r . F r a c t i o n 2, i n d i c a t e d by s l i g h t a b s o r p t i o n on the 254 nm uv d e t e c t o r , corresponds to the o l e f i n fraction* The subsequent f r a c t i o n s , as i n d i c a t e d by the strong absorption on one or both of the uv d e t e c t o r s , are comprised of
In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
240
OIL SHALE, TAR SANDS, AND RELATED
MATERIALS
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16.
SOLASH
E T
A L .
Fuel
Table V I I .
Properties
and
Chemical
Composition
249
Average Molecule i n F r a c t i o n Three
Parameter
JP-5
DFM
Aromaticity
0.49
0.39
Aromatic Rings/Molecule
1.0
1.0
Average Mol. Wt.
164
206
Average Mol.
Formula
C
H
12.2 16.8
C
H
15.2 23.3
A l k y l Substituents/Molecule
3.2
3.1
Carbons/Alkyl Substituent
2.0
3.0
Naphthene Rings/Molecule
0.5
0.7
In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
250
OIL SHALE, TAR SANDS, AND RELATED
MATERIALS
and a f a i r amount of t r i c y c l i c alkanes were a l s o found. T e t r a l i n s / i n d a n e s were a l s o found i n abundance. Some p a r t i a l l y hydrogenated t r i c y c l i c aromatics — n
