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Comparison of hydrogenated shale oils with standard jet fuels
Fuel Processing Technology, 17 (1987) 117-129 Elsevier Science Publishers B.,V.,Amsterdam -- Printed in The Netherlands
117
Comparison of Hydrogenated Shale Oils with Standard Jet Fuels N.L. MUKHERJEE Chemical Engineering Department, 7~skegee University, Tuskegee, AL 36088 (U.S.A.) (Received February 18th, 1986; accepted February 3rd, 1987)
ABSTRACT The characteristics of jet fuels obtained from typical U.S. shale oils (Geokinetics, Occidental, Paraho and Tosco II) were compared with standard petroleum jet fuels in order to study the possibility of using these shale oils as a substitute. The shale oil fractions distilling below 343 ° C were catalytically hydroprocessed at low, medium and high severities and fractionated to the jet fuel range (121-300 °C). The hydroprocessed products and jet fuels were compared for composition and physical properties. High severity hydroprocessing of shale oils decreased the nitrogen, sulfur, olefin and aromatic content while increasing the hydrogen content. The nitrogen content in shale oil jet fuels was considerably higher even after the high severity treatment. The aromatic content, except in Paraho shale oil, was relatively higher and the hydrogen content was slightly lower. Sulfur and olefin contents were lower at all severities. The physical properties and heat of combustion, except the high freezing point of shale oil jet fuels, were comparable to those of standard petroleum jet fuels.
INTRODUCTION Shale oil jet fuels c o n t a i n considerably higher nitrogen levels t h a n p e t r o l e u m jet fuels. T h e s e shale oil-derived jet fuels c a n n o t be processed in a refinery similar to t h a t used to o b t a i n p e t r o l e u m jet fuel because the high nitrogen c o n t e n t could poison the refinery catalyst. N i t r o g e n c o n t e n t greater t h a n 5 p p m decreases fuel oil t h e r m a l stability a n d increases nitrogen oxide emissions during jet fuel combustion. T h e p r e s e n t p r o b l e m is to o b t a i n a nitrogen level for jet fuel in the range of 1-5 ppm. H i g h severity h y d r o d e n i t r i f i c a t i o n for the reduction of nitrogen cont e n t is n o t cost effective. T h e crude jet fuel cut can be chemically t r e a t e d to lower the nitrogen level to the acceptable upper limit. H y d r o g e n a t i o n of shale oil fractions at low severity, prior to one of t h e chemical t r e a t m e n t s [ 1 ] ( acid washing, use of a n h y d r o u s acid, ion exchange resins, use of solvents, percolation over clays a n d acid absorbants, partial o x i d a t i o n ) , has been shown to s u b s t a n t i a l l y lower the cost of producing jet fuel c o m p a r e d to severe catalytic
0378-3820/87/$03.50
© 1987 Elsevier Science Publishers B.V.
118
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y,ro0enot.,
sh0eocu0 '°"°"d I all
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-
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5. P.<3 4 3"(~
I
°
I
_
Jet fuel cut (I 2 I ' - ~ O 0 * C )
Ash
settling tank
Crude
Catalytic
still
hydroprocessor
Hydrogenated all s t i l l
Fig. 1. Shaleoil processingto producejet fuel. hydrogenation. This hydrogenation operation also reduces the nitrogen level to an acceptable level (1-5 ppm). Many techniques [2-4] have been adopted to reduce the nitrogen content in hydroprocessed shale oils such as optimizing hydroprocessing conditions, selecting suitable hydroprocessing catalysts and blending feedstocks. Catalytic hydrotreating methods to remove a substantial portion of the organic nitrogen, oxygen and sulfur from shale oil have been reported [5,6]. Commercial scale refining of Paraho crude shale oil was achieved [7] by hydroprocessing, distillation, and acid and clay washings to produce jet fuel that met military specifications. An increase of temperature and pressure proportionally increased the hydroprocessing severity, which facilitated the removal of nitrogen, sulfur and oxygen and the addition of hydrogen. The effects of temperature [ 8 ] and pressure [ 9 ] on shale oil hydroprocessing have been reported. In the present work, shale oil hydroprocessing was performed at low, medium and high hydroprocessing severities. The hydroprocessing severity was changed primarily by varying the temperature. Most of the previous work done on conversion of shale oils to jet fuels involved production of specification jet fuel from crude shale oil. In this work, full boiling range (121-300 oC ) jet fuel was produced from the hydroprocessed product of shale oil distillate boiling below 343 oC. Shale oil fuel was characterized in order to consider it as a possible substitute for petroleum jet fuel. Jet fuel production by shale oil hydroprocessing and distillation of the hydroprocessed product was carried out at NASA's Lewis Research Center bench-scale hydroprocessing facility. The block diagram (Fig. 1 ) shows the operations necessary to produce jet fuel from crude shale oil. EXPERIMENTAL A. Crude shale oil treatment
Crude shale oil, containing water and mineral matter, was heated to about 77 °C to break the emulsion and to settle the water and mineral matter.
119
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H,~drogenaled L ~ oll pump Bolloms
Fig. 2. Process flow diagram to produce shale off jet fuel,
B. Shale oil distillation Deashed and dewatered shale oils were distilled in a 0.072 m 3 still which operated at a reduced pressure of 5.33 × 103 N / m 2 (40 torr). The unit was equipped with a vacuum pump and automatic controls for reduced pressure, and heat input and reflux systems. The shale oil fractions boiling below 343 ° C were used as feedstock for the hydroprocessor.
C. Shale oil hydroprocessing The catalytic hydroprocessing of shale oils facilitates (1) saturating olefins and aromatics, (2) eliminating heterocyclic compounds containing oxygen, nitrogen and sulfur and ( 3 ) stabilizing the oils to reduce the tendency toward oxidation at elevated temperatures. The shale oil fractions boiling below 343 °C were catalytically hydrotreated at various processing severities: high: 416°C and 1.413× 104 kPa; medium: 382°C and 1.396× 104 kPa; and low: 354°C and 1.327× 104 kPa. Figure 2 is the process flow diagram of the hydroprocessing facility at NASA's Lewis Research Center. American Cynamide's HDS-3A catalyst, a mixed Ni/Mo/A1203 catalyst of 0.25 mm diameter extrusions, was used in the reactor. The catalyst could be used in a pressure range of 1.7 × 102 to 2.1 X 103 kPa and a temperature range of 260-450°C. Arsenic, a strong poison to the catalyst, was removed during shale oil treatment. The inside diameter of the reactor was 0.0508 m and the reactor operated in
120 the temperature range of 354-416°C at a pressure of 1.327-1.413 × 104 kPa. Hydrogen and oil entered the top of the reactor where hydrogen was preheated to 300 ° C. Heating of the reactor's four catalyst zones and the hydrogen was done with five electric heaters located on the outside wall of the reactor. The heating capacity of each heater was 1.4 kW/h. The space velocity of the shale oil liquid in the reactor was 0.90-0.95 m3/m3/h, and hydrogen consumption was 280 std. m3/m 3 of shale oil. Hydrogen consumption varied with the rate of shale oil input, reactor temperature and pressure severity. Excess hydrogen was separated from the liquid product in the water-cooled high pressure separator, which was operated at 2.067 × 104 kPa and 93°C. The product gases (water, ammonia and hydrogen sulfide) were removed from the liquid product in a low pressure separator operated at 5.167 × 102 kPa. The hydroprocessed shale oil (boiling range = 121-300 ° C) was fractionated to produce jet fuel. RESULTS AND DISCUSSION The properties of the processed shale oils were measured, and the results appear in Table 1. The ash and water contents (wt%) in crude and treated shale oils are given in Table 2. Table 3 shows the elemental analysis (wt%) of deashed and dewatered shale oils. Figure 3 indicates the deashed and dewatered shale oil fractions obtained ( A S T M - D l l 6 0 method) at boiling ranges below 343 ° C. Table 4 shows the material balance of jet fuel production at high severity from Paraho deashed and dewatered shale oil. The yields (wt%) of shale oil jet fuels at variable severities are given in Table 5. The yields increased with increased severity because high severity hydrogenation enhances saturation and cracking to produce more low molecular weight hydrocarbon fractions. High severity-treated Paraho shale oil produced the maximum yield ( 32 wt% ). The properties of hydroprocessed shale oils at low, medium and high severities are given in Table 6. Throughout the discussion TR is a temperature ratio indicating the severity of the run compared with high severity: TR = 1.0 ( high severity ) ; TR = 0.92 ( medium severity) ; and TR = 0.85 (low severity). Figure 4 illustrates the fact that hydrogen consumption in hydrogenating shale oils increased linearly with severity. High severity decreased the olefin content and increased the naphthene and paraffin contents. It was previously reported [ 12 ] that cyclic olefins saturated more strongly than aromatics. Shale oil contained high percentages of straight chain olefinic naphtha hydrocarbons [13] which were greatly reduced during hydroprocessing. The increase of hydrogen content is 22.87 wt% (max) for Tosco II high severity hydroprocessed shale oil and 4.1 wt% (min) for Occidental low severity hydroprocessed
121 TABLE 1 Methods of property measurements Property
Crude
Hydrogen content, wt% Carbon content, wt% Nitrogen content", wt% Sulfur total) b, wt%: NDXRF Microcombustion Sulfur (mercaptan), wt% Aromatics content, vol.% Olefin content, vol.% Naphthalenes contents, vol.% Distillation: D-86 D-1160 Flashpoint, °C (°F) Specific gravity, (15°C/15°C) Density, g/ml (60°C) Freezing point °C
Hydroprocessed crude
Final product
Test method
X
×
X
ASTM D-3701
x x
x x
X X
Microcombustion Chemiluminescence
X X
ND X-ray fluorescence ASTM D-129 ASTM D-3227
X
ASTM D-1319
X
ASTM D-1319 ASTM D-1840
X
X
X
X
× X ×
X
(°F) Pour point, °C (°F) Viscosity, cS ( ° C) Net heat of combustion (BTU/Lb., kJ/kg) Ash content, wt% Water content, wt% Metal analysis, ppm, ppb
Deashed dewatered crude
X
X X X
X X X
X
Pycnometer X
ASTM D-2386
X X
ASTM D-97 ASTM D-445 High precision
Selected
ASTM D-482 Karl Fischer ICP, AA
X
X X Selected
ASTM D-86 ASTM D-1160 ASTM D-56 ASTM D-1298
"The oil sample containing nitrogen compounds was combusted at 1000 ° C in a flow of oxygen and the chemiluminescence for the reaction of nitric oxide with ozone measured [10]. The sulfur content in deashed/dewatered and hydroprocessed shale oils was measured by non-dispersive Xray fluorescence (NDXRF) methods. ~rhe total weight percent sulfur of the distilled hydroprocessed products was determined [ 11 ] by the modified general bomb method (ASTM D-129). This method involved the use of an ion chromatograph to quantify the sulfate ion concentration of a sodium bicarbonate solution after bomb oxidation of the fuel.
122 TABLE 2 Analysis of ash and water content in crude and D-A/D-W shale oils Wt%
Ash Water
Geokinetics
Occidental
Paraho
Tosco II
Crude
D-A/D-W
Crude
D-A/D-W
Crude
D-A/D-W
Crude
D-A/D-W
0.008 0.160
0.004 <0.01
0.026 0.150
0.015 0.070
0.080 0.750
0.018 0.160
0.016 0.150
0.003 0.110
shale oil. The hydrogen content in hydroprocessed shale oil jet fuel fractions (Table 7) is 13.14-13.85 wt%, which shows insignificant changes due to the shale oil types and variable severities. Gunberger reported [ 14 ] that Paraho shale oil initially containing 11.40 wt% hydrogen increased to 13.0 wt% after hydrotreatment. The hydrogen content in shale oil jet fuels is relatively lower TABLE 3 Analysis of deashed and dewatered shale oils Property
Paraho
Tosco II
Geokinetics
Occidental
Hydrogen (wt%) Carbon (wt%) Nitrogen (wt%) Sulfur (total) (wt%) Density (g/ml, 60 ° C ) Pour point (°C)
11.74 84.68 2.08 0.71 0.908 21.20
11.23 84.53 2.15 0.73 0.906 20.60
12.28 84.45 1.71 0.62 0.876 12.80
12.31 84.67 1.53 0.67 0.891 12.20
I00
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200
300
400
500
Dislillolion temperature,
L
600
~
700
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Fig. 3. Deashed and dewatered shale oil distillation, vol.%.
123 TABLE
4
Material balance to produce hydroprocessed shale oiljet fuel Hydroprocessed operating conditions: temperature 430°C, pressure 2.07)< 104 kPa, and space velocity of the shale oil 0.90 m3/m3/h.
Input (lb.) Paraho shale oil fraction < 343 °C Hydrogen at 287 °C and 2.07 × 10 4 kPa
97.65 2.35 100.00
Output (lb.) Hydroprocessed shale oiljet fuel Hydroprocessed shale oil residue Low pressure separator stripped gases (H2S, NH3, H2) High pressure separator recycle oil High pressure separator recycle hydrogen
78.13 0.85 19.19 1.22 0.61 100.00 80.00% 32.00%
Conversion (shale oil fraction basis) (deashed and dewatered shale oil basis)
than in petroleum jet fuel (16 wt% max) because of the presence of more olefinic and aromatic hydrocarbon compounds [ 14 ]. Table 6 and Table 7 show the nitrogen content of hydroprocessed shale oils and shale oil jet fuels. Figure 5 demonstrates the increase of nitrogen removal with the increase of processing severity and is at its maximum (91 wt% ) in high severity Paraho shale oil. The lowest nitrogen content (Fig. 6 ), 300 ppm in Occidental hydroprocessed shale oil jet fuel, is still substantially higher than petroleum jet fuel cuts (1-5 ppm). Shale oil hydroprocessing principally removed weak base I and heterocyclic nitrogen compounds which were not basic, and the removal increased [ 15 ] with increasing severity. The hydroprocessing removed the weak base I more easily than it removed the nonbasic TABLE5 Jet fuels production from shale oils Shale oil D-A/D-W
Paraho Tosco II Geokinetics Occidental
Jet fuels (wt%)
TR= 1.0
TR=0.92
TR=0.85
32.12 31.10 31.85 31.90
29.10 28.50 29.31 28.85
27.63 26.52 27.00 27.42
0.855
23.3
0.040
0.840
23.9
0.024
Density, 0.818 g/ml (60°C) Pour point 23.3
(°c)
(wt%)
0.90
0.19 0.051
1.60
85.20
85.42
85.69
12.92
13.46
19.4
0.837
0.023
0.60
85.43
13.80
19.4
0.854
0.042
0.90
85.66
13.20
TR=I.O TR=0.92
TR=I.O TR=0.92 TR=0.85
Tosco II
Paraho
14.00
Hydrogen (wt%) Carbon (wt%) Nitrogen (wt%) Sulfur (total)
Property
Analysis of hydroprocessed shale oils
TABLE 6
21.1
0.872
0.081
1.61
85.62
12.34
TR=0.85
25.0
0.811
0.01
0.33
85.81
13.72
23.3
0.822
0.015
0.74
85.86
13.31
TR=I.O TR=0.92
Geokinetics
16.1
0.840
0.023
1.20
85.61
12.85
TR=0.82
23.3
0.823
0.01
0.25
86.02
13.60
4.4
0.841
0.017
0.40
86.13
13.20
TR=I.O TR=0.92
Occidental
6.1
0.853
0.043
1.05
85.82
12.81
TR=0.85
125
I00
34
X PARAHO ® TOSCO II ® GEOKINETICS z~ OCCIDENTAL
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~: 6o
u :c"
r4
4 0.80
40
~ 0.90
I.O
Processing severily
20 0.80
i 0.90
, 1.0
Processing severity
Fig. 4. Hydrogenconsumptionin shale oil hydroprocessing,wt%. Fig. 5. Nitrogenremovalin shale oil hydroprocessing,wt%. compounds. Presence of significant amounts (53 wt% ) of weak Base I in comparison to nonbasic nitrogen compounds in Occidental shale oils resulted in a considerable decrease of the nitrogen content. The decrease in the amount of total sulfur (89-98.5 wt% ) in shale oils due to hydroprocessing at different severities is given in Table 8. Removal of sulfur is the highest for high severity Occidental shale oil. Table 7 shows that the total sulfur content in shale oil jet fuels is significantly lower than for standard petroleum jet fuels (0.30 wt% max). The shale oils consisting of 6-10 wt% sulfur compounds contained primarily the substituted thiophenes [16], and the sulfur was removed as hydrogen sulfide during hydroprocessing. The sulfur content in the shale oils decreased with increasing hydroprocessing severity. Gunberger [14] reported that Paraho shale oil containing 0.60 wt% sulfur could be reduced to less than 0.002 wt% by catalytic hydrogenation. The aromatic content in shale oil jet fuels (Table 7), except Paraho, is slightly higher than standard petroleum jet fuels (20 vol.% max). The shale oils containing 10 wt% [17] mono and polycyclic aromatic hydrocarbons were less hydroprocessed, thus causing less saturation and cracking. The aromatic content decreased with increasing severity. The olefin content in shale oil jet fuels is less than 5 vol.% (Table 7) in comparison to standard petroleum jet fuels ( 5 vol.% max). The shale oils containing of 18 wt% normal olefins, iso-olefins and cyclo-olefins were significantly hydrogenated to produce paraffins and naphthene compounds. Olefinic hydrocarbon content was considerably decreased with increasing severity. The volume percentages of shale oil jet fuel fractions measured (ASTM-
7
combustion kJ/kg
(*C) Btu/lb Heat of
Freezing point, °C ( ° F ) Viscosity, cS
Hydrogen content, wt% Carbon content, wt% Nitrogen content, wt% Sulfur content, wt% Sulfur ( mercaptan ), wt% Aromatics content, vol.% Olefin content, vol.% Naphthalenes content, vol.% Flashpoint, °C (°F) Specific gravity, (15oc/15oc)
Property
< 0.0003
19.7 3.2 2.10 59.4 (139) 0.830
< 0.0003
19.0
0.6
1.12
50.0 (122} 0.818
18,418 42,282
18,485 42,998
- 27.2 (-17) 4.7
0.03
< 0.003
- 27.8 (-18) 4.2
0.418
85.92
85.98
0.122
13.53
TR-- 0.92
13.85
T R : 1.0
Paraho
Analysis of hydroprocessed shale oiljet fuels
TABLE
18,292 42,549
3.5
5.3 18,217 42,374
--33.3
(-28)
-27.8
47.8 (118) 0.619
(-18)
59.4 (139) 0.838
1.76
3.51
22.4
19.9 1.1
< 0.0003
< 0.0003
4.5
< 0.003
0.366
85.78
13.78
Ta= 1.0
0.032
1.16
85.33
13.33
Ta=0.85
Tosco II
43.3 (110) 0.835
44.4 (112) 0.829
18,284 42,530
18,162 42,246
5.1
3.46
2.19
4.0
3.3
1.5
-- 30.6
23.1
22.5
(-23)
< 0.0003
< 0.0003
-- 32.2
0.039
0.022
(-26)
1.16
85.46
85.69 0.655
13.14
TR=0.85
13.50
Ta=0.92
18,517 43,072
4.0
(-23.5)
-- 30.8
54.4 {130) 0.817
0.96
1.1
19.4
< 0.0003
< 0.003
0.140
86.15
13.68
T a = 1.0
Geokinetics
18,209 42,356
4.5
(-20)
- 28.9
57.2 (135) 0.831
1.45
1.7
22.0
< 0.0003
0.023
0.428
85.86
13.64
TR=0.92
18,240 42,428
5.5
(-16)
- 26.7
61.7 (143) 0.843
3.73
2.8
22.8
< 0.0003
0.031
1.06
85.52
13.29
TR=0.85
18,347 42,677
2.3
(-40)
-- 40.0
44.4 (112) 0.814
0.47
1.0
20.1
< 0.0003
< 0.003
0.038
86.13
13.78
TR= 1.0
Occidental
18,419 42,844
5.4
(-20)
-- 28.9
58.9 (138) 0.835
1.39
2.1
22.7
< 0.0003
0.021
0.355
85.88
13.64
TR=0.92
18,307 42,584
5.7
(-18)
27.8
62.2 (144) 0.841
2.70
2.6
23.7
< 0.0003
0.025
0.725
85.79
13.45
TR=0.85
O~
127
1.2
OParaho
,.o
\\ \
.To,co
\\ \
0 Geokinetics ~Occidentol
-; o.s
,I
g ~ o.6
o o
~' 0 . 4 z 0.2
0.0
0.80
I
i
0.90
I .0
Processing Severity
Fig. 6. Nitrogen content in shale oil jet fuel, wt%.
D86) at different distillation temperatures are comparable to those of standard petroleum jet fuel fractions. The freezing point of the shale oil jet fuels is higher than that of petroleum jet fuels due to relatively higher aromatic and heterocyclic compounds. The physical properties ( flash point, specific gravity, viscosity) and heat of combustion for hydroprocessed shale oil jet fuels (Table 7 ) are comparable to standard petroleum jet fuels ( Table 9). CONCLUSIONS
(1) The nitrogen content in hydroprocessed shale oils decreased with increasing severity and was at a minimum in high severity hydroprocessed Occidental shale oil. TABLE8
Sulfur removal from hydroprocessed shale oils Processing severity
High Medium Low
Sulfur removal (wt%) Paraho
Tosco II
Geokinetics
Occidental
96.6 94.3 92.8
96.8 94.2 88.9
98.4 97.6 96.3
98.5 97.5 93.6
128 TABLE 9 Petroleum jet fuels properties ( A S T M specifications) Hydrogen content, wt% Aromatics content, vol.% Olefins content, vol.% Nitrogen content (total), ppm Sulfur content (mercaptan), wt% Sulfur content (total), wt% Naphthalenes content, vol.% Distillation temperature, ° C Initial boiling point 10 (vol.%) 50 (vol.%)
90 (vol.%) boilingpoint Flashpoint, ° C Gravity (specific, 15/15°C) Final
Freezing point, ° C
Viscosityat - 20°C, cS Net heat of combustion, kJ/kg (BTU/Ib)
16.00 max 20 max 5 max 5 max 0.003 max 0.3 max 3 max
204 max
300 max 38 min 0.7753 to 0.8398 - 40 8 max 42,800 (18,400) rain
( 2 ) The hydrogen content increased linearly with hydroprocessing severity and was at a m a x i m u m in high severity Paraho shale oil. (3) The sulfur content was significantly reduced ( > 9 0 % ) in hydroprocessed shale oils, and removal increased with increasing severity. (4) The aromatic content slightly decreased and the olefin content was considerably reduced during hydroprocessing. (5) The jet fuel fractions (boiling r a n g e = 1 2 1 - 3 0 0 ° C ) obtained from hydroprocessed shale oils increased in hydrogen content because of greater aliphatic hydrocarbon content. The sulfur and nitrogen levels were considerably lower t h a n in hydroprocessed shale oils. (6) The shale oil jet fuel fractions were comparable to those of standard petroleum jet fuel: a. The hydrogen content was slightly lower and was at a m a x i m u m in high severity Paraho jet fuel. b. The aromatic content was slightly higher except in Paraho jet fuel. c. The nitrogen level was considerably higher; high severity Paraho contained the lowest nitrogen content next to high severity-treated Occidental jet fuel. d. The sulfur content was significantly lower. e. The olefin content was low and was at a minimum in high severity-treated Paraho jet fuel. f. The physical properties, except freezing point (high), and heat of combustion were at acceptable levels. (7) Deashed and dewatered Paraho shale oil provided the maximum yield (32 wt% ) of jet fuel at high severity treatment.
129 T h e r e f o r e it c a n be c o n c l u d e d t h a t h i g h s e v e r i t y h y d r o p r o c e s s i n g o f s h a l e oils is r e q u i r e d t o m e e t j e t fuel oil r e q u i r e m e n t s . P a r a h o s h a l e oil j e t fuel, a f t e r d e n i t r i f i c a t i o n b y c h e m i c a l t r e a t m e n t , c a n be c o n s i d e r e d as a p o s s i b l e s u b s t i t u t e f o r p e t r o l e u m j e t fuel.
REFERENCES 1 Nowacki, P., 1981. Oil Shale Technical Data Handbook, Shale Oil Upgrading. Noyes Data Corporation, Park Ridge, NJ, p. 193. 2 Sullivan, R.F. and Stangeland, B.E., 1977. Catalytic hydroprocessing of shale oil to produce distillate fuels. American Chemical Society 174th National Meeting, Chicago, IL, Conf-7708149. 3 Shaw, H., Kalfadelis, C.D. and Jahnig, C.E., 1975. Evaluation of methods to produce aviation turbine fuels from synthetic crude oils - - Phase I. Air Force Aero Propulsion Lab., Report No. AFAPL-TR-5/10, March. 4 Kalfadalis, C D., 1976. Evaluation of methods to produce aviation turbine fuels from synthetic crude oils - - Phase II. Air Force Aero Propulsion Lab., Report No. AFAPL-TR-75-10, Vol. 11, May. 5 Montgomery, D.P., 1968. Refining of pyrolytic shale oil. Ind. Eng. Chem., Prod. Res. Dev., 7{4): 274-282. 6 Frost, C.M. and Cottingham, P.L., 1974. Methods for refining crude oil produced in-situ retorting. Bureau of Mines, BM-R1-7844. 7 Wasilk, N.J. and Robinson, E.T., 1981. Commercial scale refining of Paraho crude shale oil into military specifications fuel. American Chemical Society, 0097 - - 6165/81/810163 - 0223805, pp. 231-232. 8 Cottingham, P.L., White, E.R. and Frost, C.M., 1957. Hydrogenating shale oil to catalytic reforming stock. Ind. Eng. Chem., 49 (4): 679-684. 9 Frost, C.M. and Cottingham, P.L., 1974. Some effects of pressure on the hydrocracking of crude shale oil over cobalt-molybdate catalyst. Bureau of Mines, BM-PPRI-7835. 10 Drushel, H.F., 1977. Determination of nitrogen in petroleum fractions by combustion with chemiluminescent detection of nitric oxide. Anal. Chem., 49: 932. 11 Mizisin, C.S., Kuivinen, D.E. and Otterson, D.A., 1978. Ion chromatographic determination of sulfur in fuels. NASA TM-78971. 12 Frost, C.M. and Cottingham, P.L., 1973. Some effects of pressure on the hydrocracking of crude shale oil over cobalt molybdate catalyst. Larmie Energy Research Center, RI 7835, p. 7. 13 Benson, D.B. and Berg, L., 1966. Catalytic hydrotreating of shale oil. Chem. Eng. Prog., 62(8): 61. 14 Gunberger, G.A., 1980. Logistics management of Paraho residual shale oil. Radian Corporation, Pasadena, CA, B-20. 15 Holmes, S.A. and Thompson, L.F., 1981. Nitrogen-type distribution in hydrotreated shale oils: correlation with upgrading process conditions. In: Proc. 14th Oil Shale Symposium. Colorado School of Mines Press, pp. 242-243. 16 Thorne, H.M., Murphy, W.I.R., Ball, J.S., Stanfield, K.E. and Horne, J.W., 1951. Characteristics and utilization of oil shale and shale oil. Ind. Eng. Chem., 43: 20. 17 Cady, W.E. and Seelig, H.S., 1952. Composition of shale oil. Ind. Eng. Chem., 44 {11): 2636.
117
Comparison of Hydrogenated Shale Oils with Standard Jet Fuels N.L. MUKHERJEE Chemical Engineering Department, 7~skegee University, Tuskegee, AL 36088 (U.S.A.) (Received February 18th, 1986; accepted February 3rd, 1987)
ABSTRACT The characteristics of jet fuels obtained from typical U.S. shale oils (Geokinetics, Occidental, Paraho and Tosco II) were compared with standard petroleum jet fuels in order to study the possibility of using these shale oils as a substitute. The shale oil fractions distilling below 343 ° C were catalytically hydroprocessed at low, medium and high severities and fractionated to the jet fuel range (121-300 °C). The hydroprocessed products and jet fuels were compared for composition and physical properties. High severity hydroprocessing of shale oils decreased the nitrogen, sulfur, olefin and aromatic content while increasing the hydrogen content. The nitrogen content in shale oil jet fuels was considerably higher even after the high severity treatment. The aromatic content, except in Paraho shale oil, was relatively higher and the hydrogen content was slightly lower. Sulfur and olefin contents were lower at all severities. The physical properties and heat of combustion, except the high freezing point of shale oil jet fuels, were comparable to those of standard petroleum jet fuels.
INTRODUCTION Shale oil jet fuels c o n t a i n considerably higher nitrogen levels t h a n p e t r o l e u m jet fuels. T h e s e shale oil-derived jet fuels c a n n o t be processed in a refinery similar to t h a t used to o b t a i n p e t r o l e u m jet fuel because the high nitrogen c o n t e n t could poison the refinery catalyst. N i t r o g e n c o n t e n t greater t h a n 5 p p m decreases fuel oil t h e r m a l stability a n d increases nitrogen oxide emissions during jet fuel combustion. T h e p r e s e n t p r o b l e m is to o b t a i n a nitrogen level for jet fuel in the range of 1-5 ppm. H i g h severity h y d r o d e n i t r i f i c a t i o n for the reduction of nitrogen cont e n t is n o t cost effective. T h e crude jet fuel cut can be chemically t r e a t e d to lower the nitrogen level to the acceptable upper limit. H y d r o g e n a t i o n of shale oil fractions at low severity, prior to one of t h e chemical t r e a t m e n t s [ 1 ] ( acid washing, use of a n h y d r o u s acid, ion exchange resins, use of solvents, percolation over clays a n d acid absorbants, partial o x i d a t i o n ) , has been shown to s u b s t a n t i a l l y lower the cost of producing jet fuel c o m p a r e d to severe catalytic
0378-3820/87/$03.50
© 1987 Elsevier Science Publishers B.V.
118
H2
D.u:h.° J
y,ro0enot.,
sh0eocu0 '°"°"d I all
I
-
Distillate
5. P.<3 4 3"(~
I
°
I
_
Jet fuel cut (I 2 I ' - ~ O 0 * C )
Ash
settling tank
Crude
Catalytic
still
hydroprocessor
Hydrogenated all s t i l l
Fig. 1. Shaleoil processingto producejet fuel. hydrogenation. This hydrogenation operation also reduces the nitrogen level to an acceptable level (1-5 ppm). Many techniques [2-4] have been adopted to reduce the nitrogen content in hydroprocessed shale oils such as optimizing hydroprocessing conditions, selecting suitable hydroprocessing catalysts and blending feedstocks. Catalytic hydrotreating methods to remove a substantial portion of the organic nitrogen, oxygen and sulfur from shale oil have been reported [5,6]. Commercial scale refining of Paraho crude shale oil was achieved [7] by hydroprocessing, distillation, and acid and clay washings to produce jet fuel that met military specifications. An increase of temperature and pressure proportionally increased the hydroprocessing severity, which facilitated the removal of nitrogen, sulfur and oxygen and the addition of hydrogen. The effects of temperature [ 8 ] and pressure [ 9 ] on shale oil hydroprocessing have been reported. In the present work, shale oil hydroprocessing was performed at low, medium and high hydroprocessing severities. The hydroprocessing severity was changed primarily by varying the temperature. Most of the previous work done on conversion of shale oils to jet fuels involved production of specification jet fuel from crude shale oil. In this work, full boiling range (121-300 oC ) jet fuel was produced from the hydroprocessed product of shale oil distillate boiling below 343 oC. Shale oil fuel was characterized in order to consider it as a possible substitute for petroleum jet fuel. Jet fuel production by shale oil hydroprocessing and distillation of the hydroprocessed product was carried out at NASA's Lewis Research Center bench-scale hydroprocessing facility. The block diagram (Fig. 1 ) shows the operations necessary to produce jet fuel from crude shale oil. EXPERIMENTAL A. Crude shale oil treatment
Crude shale oil, containing water and mineral matter, was heated to about 77 °C to break the emulsion and to settle the water and mineral matter.
119
Scrubbed gas
Condenser/~
I.I
"~ III I
Deashed I and _I
j
Compressed
i
I
I
II IH,,h I HIg
I I
de*°'eredl I
.....
I
I
I ~__J
~ ~
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2
Hydrogen Io recycle
~
I
i
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~
Lalo~y.c I
hydropro-I cessor I
[1
i
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I seporator I
J
I -Y-J
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I
"I
~
/
I
I
ILo.
r-~
/ /
I I
I I
I . . . . . . :~ Isep arat°r
I I
/
I
Crude
I
i
IPressure
J I I_,_1
Botlorns 1.343"C1
I
,oe,cu,
I
1121"-300"C1
I I
I IHvdroqenaled
H,~drogenaled L ~ oll pump Bolloms
Fig. 2. Process flow diagram to produce shale off jet fuel,
B. Shale oil distillation Deashed and dewatered shale oils were distilled in a 0.072 m 3 still which operated at a reduced pressure of 5.33 × 103 N / m 2 (40 torr). The unit was equipped with a vacuum pump and automatic controls for reduced pressure, and heat input and reflux systems. The shale oil fractions boiling below 343 ° C were used as feedstock for the hydroprocessor.
C. Shale oil hydroprocessing The catalytic hydroprocessing of shale oils facilitates (1) saturating olefins and aromatics, (2) eliminating heterocyclic compounds containing oxygen, nitrogen and sulfur and ( 3 ) stabilizing the oils to reduce the tendency toward oxidation at elevated temperatures. The shale oil fractions boiling below 343 °C were catalytically hydrotreated at various processing severities: high: 416°C and 1.413× 104 kPa; medium: 382°C and 1.396× 104 kPa; and low: 354°C and 1.327× 104 kPa. Figure 2 is the process flow diagram of the hydroprocessing facility at NASA's Lewis Research Center. American Cynamide's HDS-3A catalyst, a mixed Ni/Mo/A1203 catalyst of 0.25 mm diameter extrusions, was used in the reactor. The catalyst could be used in a pressure range of 1.7 × 102 to 2.1 X 103 kPa and a temperature range of 260-450°C. Arsenic, a strong poison to the catalyst, was removed during shale oil treatment. The inside diameter of the reactor was 0.0508 m and the reactor operated in
120 the temperature range of 354-416°C at a pressure of 1.327-1.413 × 104 kPa. Hydrogen and oil entered the top of the reactor where hydrogen was preheated to 300 ° C. Heating of the reactor's four catalyst zones and the hydrogen was done with five electric heaters located on the outside wall of the reactor. The heating capacity of each heater was 1.4 kW/h. The space velocity of the shale oil liquid in the reactor was 0.90-0.95 m3/m3/h, and hydrogen consumption was 280 std. m3/m 3 of shale oil. Hydrogen consumption varied with the rate of shale oil input, reactor temperature and pressure severity. Excess hydrogen was separated from the liquid product in the water-cooled high pressure separator, which was operated at 2.067 × 104 kPa and 93°C. The product gases (water, ammonia and hydrogen sulfide) were removed from the liquid product in a low pressure separator operated at 5.167 × 102 kPa. The hydroprocessed shale oil (boiling range = 121-300 ° C) was fractionated to produce jet fuel. RESULTS AND DISCUSSION The properties of the processed shale oils were measured, and the results appear in Table 1. The ash and water contents (wt%) in crude and treated shale oils are given in Table 2. Table 3 shows the elemental analysis (wt%) of deashed and dewatered shale oils. Figure 3 indicates the deashed and dewatered shale oil fractions obtained ( A S T M - D l l 6 0 method) at boiling ranges below 343 ° C. Table 4 shows the material balance of jet fuel production at high severity from Paraho deashed and dewatered shale oil. The yields (wt%) of shale oil jet fuels at variable severities are given in Table 5. The yields increased with increased severity because high severity hydrogenation enhances saturation and cracking to produce more low molecular weight hydrocarbon fractions. High severity-treated Paraho shale oil produced the maximum yield ( 32 wt% ). The properties of hydroprocessed shale oils at low, medium and high severities are given in Table 6. Throughout the discussion TR is a temperature ratio indicating the severity of the run compared with high severity: TR = 1.0 ( high severity ) ; TR = 0.92 ( medium severity) ; and TR = 0.85 (low severity). Figure 4 illustrates the fact that hydrogen consumption in hydrogenating shale oils increased linearly with severity. High severity decreased the olefin content and increased the naphthene and paraffin contents. It was previously reported [ 12 ] that cyclic olefins saturated more strongly than aromatics. Shale oil contained high percentages of straight chain olefinic naphtha hydrocarbons [13] which were greatly reduced during hydroprocessing. The increase of hydrogen content is 22.87 wt% (max) for Tosco II high severity hydroprocessed shale oil and 4.1 wt% (min) for Occidental low severity hydroprocessed
121 TABLE 1 Methods of property measurements Property
Crude
Hydrogen content, wt% Carbon content, wt% Nitrogen content", wt% Sulfur total) b, wt%: NDXRF Microcombustion Sulfur (mercaptan), wt% Aromatics content, vol.% Olefin content, vol.% Naphthalenes contents, vol.% Distillation: D-86 D-1160 Flashpoint, °C (°F) Specific gravity, (15°C/15°C) Density, g/ml (60°C) Freezing point °C
Hydroprocessed crude
Final product
Test method
X
×
X
ASTM D-3701
x x
x x
X X
Microcombustion Chemiluminescence
X X
ND X-ray fluorescence ASTM D-129 ASTM D-3227
X
ASTM D-1319
X
ASTM D-1319 ASTM D-1840
X
X
X
X
× X ×
X
(°F) Pour point, °C (°F) Viscosity, cS ( ° C) Net heat of combustion (BTU/Lb., kJ/kg) Ash content, wt% Water content, wt% Metal analysis, ppm, ppb
Deashed dewatered crude
X
X X X
X X X
X
Pycnometer X
ASTM D-2386
X X
ASTM D-97 ASTM D-445 High precision
Selected
ASTM D-482 Karl Fischer ICP, AA
X
X X Selected
ASTM D-86 ASTM D-1160 ASTM D-56 ASTM D-1298
"The oil sample containing nitrogen compounds was combusted at 1000 ° C in a flow of oxygen and the chemiluminescence for the reaction of nitric oxide with ozone measured [10]. The sulfur content in deashed/dewatered and hydroprocessed shale oils was measured by non-dispersive Xray fluorescence (NDXRF) methods. ~rhe total weight percent sulfur of the distilled hydroprocessed products was determined [ 11 ] by the modified general bomb method (ASTM D-129). This method involved the use of an ion chromatograph to quantify the sulfate ion concentration of a sodium bicarbonate solution after bomb oxidation of the fuel.
122 TABLE 2 Analysis of ash and water content in crude and D-A/D-W shale oils Wt%
Ash Water
Geokinetics
Occidental
Paraho
Tosco II
Crude
D-A/D-W
Crude
D-A/D-W
Crude
D-A/D-W
Crude
D-A/D-W
0.008 0.160
0.004 <0.01
0.026 0.150
0.015 0.070
0.080 0.750
0.018 0.160
0.016 0.150
0.003 0.110
shale oil. The hydrogen content in hydroprocessed shale oil jet fuel fractions (Table 7) is 13.14-13.85 wt%, which shows insignificant changes due to the shale oil types and variable severities. Gunberger reported [ 14 ] that Paraho shale oil initially containing 11.40 wt% hydrogen increased to 13.0 wt% after hydrotreatment. The hydrogen content in shale oil jet fuels is relatively lower TABLE 3 Analysis of deashed and dewatered shale oils Property
Paraho
Tosco II
Geokinetics
Occidental
Hydrogen (wt%) Carbon (wt%) Nitrogen (wt%) Sulfur (total) (wt%) Density (g/ml, 60 ° C ) Pour point (°C)
11.74 84.68 2.08 0.71 0.908 21.20
11.23 84.53 2.15 0.73 0.906 20.60
12.28 84.45 1.71 0.62 0.876 12.80
12.31 84.67 1.53 0.67 0.891 12.20
I00
8O
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e TOSCO II ® GEOKINETICS OCCIDENTAL
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( 6O
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0 PO0
J
200
300
400
500
Dislillolion temperature,
L
600
~
700
"C
Fig. 3. Deashed and dewatered shale oil distillation, vol.%.
123 TABLE
4
Material balance to produce hydroprocessed shale oiljet fuel Hydroprocessed operating conditions: temperature 430°C, pressure 2.07)< 104 kPa, and space velocity of the shale oil 0.90 m3/m3/h.
Input (lb.) Paraho shale oil fraction < 343 °C Hydrogen at 287 °C and 2.07 × 10 4 kPa
97.65 2.35 100.00
Output (lb.) Hydroprocessed shale oiljet fuel Hydroprocessed shale oil residue Low pressure separator stripped gases (H2S, NH3, H2) High pressure separator recycle oil High pressure separator recycle hydrogen
78.13 0.85 19.19 1.22 0.61 100.00 80.00% 32.00%
Conversion (shale oil fraction basis) (deashed and dewatered shale oil basis)
than in petroleum jet fuel (16 wt% max) because of the presence of more olefinic and aromatic hydrocarbon compounds [ 14 ]. Table 6 and Table 7 show the nitrogen content of hydroprocessed shale oils and shale oil jet fuels. Figure 5 demonstrates the increase of nitrogen removal with the increase of processing severity and is at its maximum (91 wt% ) in high severity Paraho shale oil. The lowest nitrogen content (Fig. 6 ), 300 ppm in Occidental hydroprocessed shale oil jet fuel, is still substantially higher than petroleum jet fuel cuts (1-5 ppm). Shale oil hydroprocessing principally removed weak base I and heterocyclic nitrogen compounds which were not basic, and the removal increased [ 15 ] with increasing severity. The hydroprocessing removed the weak base I more easily than it removed the nonbasic TABLE5 Jet fuels production from shale oils Shale oil D-A/D-W
Paraho Tosco II Geokinetics Occidental
Jet fuels (wt%)
TR= 1.0
TR=0.92
TR=0.85
32.12 31.10 31.85 31.90
29.10 28.50 29.31 28.85
27.63 26.52 27.00 27.42
0.855
23.3
0.040
0.840
23.9
0.024
Density, 0.818 g/ml (60°C) Pour point 23.3
(°c)
(wt%)
0.90
0.19 0.051
1.60
85.20
85.42
85.69
12.92
13.46
19.4
0.837
0.023
0.60
85.43
13.80
19.4
0.854
0.042
0.90
85.66
13.20
TR=I.O TR=0.92
TR=I.O TR=0.92 TR=0.85
Tosco II
Paraho
14.00
Hydrogen (wt%) Carbon (wt%) Nitrogen (wt%) Sulfur (total)
Property
Analysis of hydroprocessed shale oils
TABLE 6
21.1
0.872
0.081
1.61
85.62
12.34
TR=0.85
25.0
0.811
0.01
0.33
85.81
13.72
23.3
0.822
0.015
0.74
85.86
13.31
TR=I.O TR=0.92
Geokinetics
16.1
0.840
0.023
1.20
85.61
12.85
TR=0.82
23.3
0.823
0.01
0.25
86.02
13.60
4.4
0.841
0.017
0.40
86.13
13.20
TR=I.O TR=0.92
Occidental
6.1
0.853
0.043
1.05
85.82
12.81
TR=0.85
125
I00
34
X PARAHO ® TOSCO II ® GEOKINETICS z~ OCCIDENTAL
8O
~: 6o
u :c"
r4
4 0.80
40
~ 0.90
I.O
Processing severily
20 0.80
i 0.90
, 1.0
Processing severity
Fig. 4. Hydrogenconsumptionin shale oil hydroprocessing,wt%. Fig. 5. Nitrogenremovalin shale oil hydroprocessing,wt%. compounds. Presence of significant amounts (53 wt% ) of weak Base I in comparison to nonbasic nitrogen compounds in Occidental shale oils resulted in a considerable decrease of the nitrogen content. The decrease in the amount of total sulfur (89-98.5 wt% ) in shale oils due to hydroprocessing at different severities is given in Table 8. Removal of sulfur is the highest for high severity Occidental shale oil. Table 7 shows that the total sulfur content in shale oil jet fuels is significantly lower than for standard petroleum jet fuels (0.30 wt% max). The shale oils consisting of 6-10 wt% sulfur compounds contained primarily the substituted thiophenes [16], and the sulfur was removed as hydrogen sulfide during hydroprocessing. The sulfur content in the shale oils decreased with increasing hydroprocessing severity. Gunberger [14] reported that Paraho shale oil containing 0.60 wt% sulfur could be reduced to less than 0.002 wt% by catalytic hydrogenation. The aromatic content in shale oil jet fuels (Table 7), except Paraho, is slightly higher than standard petroleum jet fuels (20 vol.% max). The shale oils containing 10 wt% [17] mono and polycyclic aromatic hydrocarbons were less hydroprocessed, thus causing less saturation and cracking. The aromatic content decreased with increasing severity. The olefin content in shale oil jet fuels is less than 5 vol.% (Table 7) in comparison to standard petroleum jet fuels ( 5 vol.% max). The shale oils containing of 18 wt% normal olefins, iso-olefins and cyclo-olefins were significantly hydrogenated to produce paraffins and naphthene compounds. Olefinic hydrocarbon content was considerably decreased with increasing severity. The volume percentages of shale oil jet fuel fractions measured (ASTM-
7
combustion kJ/kg
(*C) Btu/lb Heat of
Freezing point, °C ( ° F ) Viscosity, cS
Hydrogen content, wt% Carbon content, wt% Nitrogen content, wt% Sulfur content, wt% Sulfur ( mercaptan ), wt% Aromatics content, vol.% Olefin content, vol.% Naphthalenes content, vol.% Flashpoint, °C (°F) Specific gravity, (15oc/15oc)
Property
< 0.0003
19.7 3.2 2.10 59.4 (139) 0.830
< 0.0003
19.0
0.6
1.12
50.0 (122} 0.818
18,418 42,282
18,485 42,998
- 27.2 (-17) 4.7
0.03
< 0.003
- 27.8 (-18) 4.2
0.418
85.92
85.98
0.122
13.53
TR-- 0.92
13.85
T R : 1.0
Paraho
Analysis of hydroprocessed shale oiljet fuels
TABLE
18,292 42,549
3.5
5.3 18,217 42,374
--33.3
(-28)
-27.8
47.8 (118) 0.619
(-18)
59.4 (139) 0.838
1.76
3.51
22.4
19.9 1.1
< 0.0003
< 0.0003
4.5
< 0.003
0.366
85.78
13.78
Ta= 1.0
0.032
1.16
85.33
13.33
Ta=0.85
Tosco II
43.3 (110) 0.835
44.4 (112) 0.829
18,284 42,530
18,162 42,246
5.1
3.46
2.19
4.0
3.3
1.5
-- 30.6
23.1
22.5
(-23)
< 0.0003
< 0.0003
-- 32.2
0.039
0.022
(-26)
1.16
85.46
85.69 0.655
13.14
TR=0.85
13.50
Ta=0.92
18,517 43,072
4.0
(-23.5)
-- 30.8
54.4 {130) 0.817
0.96
1.1
19.4
< 0.0003
< 0.003
0.140
86.15
13.68
T a = 1.0
Geokinetics
18,209 42,356
4.5
(-20)
- 28.9
57.2 (135) 0.831
1.45
1.7
22.0
< 0.0003
0.023
0.428
85.86
13.64
TR=0.92
18,240 42,428
5.5
(-16)
- 26.7
61.7 (143) 0.843
3.73
2.8
22.8
< 0.0003
0.031
1.06
85.52
13.29
TR=0.85
18,347 42,677
2.3
(-40)
-- 40.0
44.4 (112) 0.814
0.47
1.0
20.1
< 0.0003
< 0.003
0.038
86.13
13.78
TR= 1.0
Occidental
18,419 42,844
5.4
(-20)
-- 28.9
58.9 (138) 0.835
1.39
2.1
22.7
< 0.0003
0.021
0.355
85.88
13.64
TR=0.92
18,307 42,584
5.7
(-18)
27.8
62.2 (144) 0.841
2.70
2.6
23.7
< 0.0003
0.025
0.725
85.79
13.45
TR=0.85
O~
127
1.2
OParaho
,.o
\\ \
.To,co
\\ \
0 Geokinetics ~Occidentol
-; o.s
,I
g ~ o.6
o o
~' 0 . 4 z 0.2
0.0
0.80
I
i
0.90
I .0
Processing Severity
Fig. 6. Nitrogen content in shale oil jet fuel, wt%.
D86) at different distillation temperatures are comparable to those of standard petroleum jet fuel fractions. The freezing point of the shale oil jet fuels is higher than that of petroleum jet fuels due to relatively higher aromatic and heterocyclic compounds. The physical properties ( flash point, specific gravity, viscosity) and heat of combustion for hydroprocessed shale oil jet fuels (Table 7 ) are comparable to standard petroleum jet fuels ( Table 9). CONCLUSIONS
(1) The nitrogen content in hydroprocessed shale oils decreased with increasing severity and was at a minimum in high severity hydroprocessed Occidental shale oil. TABLE8
Sulfur removal from hydroprocessed shale oils Processing severity
High Medium Low
Sulfur removal (wt%) Paraho
Tosco II
Geokinetics
Occidental
96.6 94.3 92.8
96.8 94.2 88.9
98.4 97.6 96.3
98.5 97.5 93.6
128 TABLE 9 Petroleum jet fuels properties ( A S T M specifications) Hydrogen content, wt% Aromatics content, vol.% Olefins content, vol.% Nitrogen content (total), ppm Sulfur content (mercaptan), wt% Sulfur content (total), wt% Naphthalenes content, vol.% Distillation temperature, ° C Initial boiling point 10 (vol.%) 50 (vol.%)
90 (vol.%) boilingpoint Flashpoint, ° C Gravity (specific, 15/15°C) Final
Freezing point, ° C
Viscosityat - 20°C, cS Net heat of combustion, kJ/kg (BTU/Ib)
16.00 max 20 max 5 max 5 max 0.003 max 0.3 max 3 max
204 max
300 max 38 min 0.7753 to 0.8398 - 40 8 max 42,800 (18,400) rain
( 2 ) The hydrogen content increased linearly with hydroprocessing severity and was at a m a x i m u m in high severity Paraho shale oil. (3) The sulfur content was significantly reduced ( > 9 0 % ) in hydroprocessed shale oils, and removal increased with increasing severity. (4) The aromatic content slightly decreased and the olefin content was considerably reduced during hydroprocessing. (5) The jet fuel fractions (boiling r a n g e = 1 2 1 - 3 0 0 ° C ) obtained from hydroprocessed shale oils increased in hydrogen content because of greater aliphatic hydrocarbon content. The sulfur and nitrogen levels were considerably lower t h a n in hydroprocessed shale oils. (6) The shale oil jet fuel fractions were comparable to those of standard petroleum jet fuel: a. The hydrogen content was slightly lower and was at a m a x i m u m in high severity Paraho jet fuel. b. The aromatic content was slightly higher except in Paraho jet fuel. c. The nitrogen level was considerably higher; high severity Paraho contained the lowest nitrogen content next to high severity-treated Occidental jet fuel. d. The sulfur content was significantly lower. e. The olefin content was low and was at a minimum in high severity-treated Paraho jet fuel. f. The physical properties, except freezing point (high), and heat of combustion were at acceptable levels. (7) Deashed and dewatered Paraho shale oil provided the maximum yield (32 wt% ) of jet fuel at high severity treatment.
129 T h e r e f o r e it c a n be c o n c l u d e d t h a t h i g h s e v e r i t y h y d r o p r o c e s s i n g o f s h a l e oils is r e q u i r e d t o m e e t j e t fuel oil r e q u i r e m e n t s . P a r a h o s h a l e oil j e t fuel, a f t e r d e n i t r i f i c a t i o n b y c h e m i c a l t r e a t m e n t , c a n be c o n s i d e r e d as a p o s s i b l e s u b s t i t u t e f o r p e t r o l e u m j e t fuel.
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