SYNTHETIC FUELS AND CHEMICALS
COKE CHAMBERS
n
1
14
CONDENSER
I
1
I ~
NAPHTHA PRODUCT
COKE NAPHTHA RECEIVER
SHALE 0 I L CHARGE PUMP
HOT OIL CYCLE PUMP
Figure 1.
RESIDUUM PUMP '
FRACTIONATOR REFLUX AND NAPHTHA PRODUCT PUMP
Flow diagram of coking operation
Method for Refining Shale Oil H. C. CARPENTER, C. B. HOPKINS, R. E. KELLEY', AND W. 1.
R. MURPHY
Petroleum and Oil-Shale Experiment Station, U. S. Bureau of Mines, Laramie, Wyo.
M
ETHODS for refining shale oil produced from oil shale of the Green River formation in Colorado include one proposed by t h e National Petroleum Council (6, 7), involving the following steps:
this processing sequence. They represent only d a t a obtained under the specified, and not necessarily optimum, conditions, upon which extensive cost analyses were made.
1. Coking t h e oil t o produce a distillate of approximately 700" F. end point. 2. Hydrogenating t h a t portion of the coker distillate t h a t boils above 400" F. 3. Reforming a blend of the naphthas produced in the coking and hydrogenating steps. 4. Catalytically cracking t h a t portion of t h e hydrogenated coker distillate t h a t boils above 400" F., together with t h e polymer produced in naphtha reforming.
Preparation of Coker Distillate
It was calculated t h a t these refining operations, together with polymerization of C1 and C4 olefins available from the catalytic cracking step and appropriate fractionation and blending of the various streams, would produce gasoline and middle distillates in a ratio of about 1.95, gasoline being the product in largest volume. It was estimated t h a t equal volumes of premium and regular grades of gasoline could be prepared from the gasoline stocks, and t h a t the Diesel fuel would approach 50 cetane number. Coke, sulfur, ammonia, liquefied petroleum gases, and a small amount of fuel oil would constitute the balance of products from this process. When these calculations were made, data were not available on the yields and properties of many streams in the proposed process, and these were estimated from data on other oils. It was thought worth while t o carry o u t the proposed processing in bench scale equipment t o provide data on which t o base an evaluation of this method of refining shale oil. It is not intended t h a t these d a t a be interpreted as the best t h a t are obtainable b y 1
Present address, Bay Petroleum Co., Denver, Colo,
July 1956
The coker distillate used in this work was prepared a t t h e Bureau of Mines Oil-Shale Experiment Station near Rifle, Colo., b y recycle delayed coking of crude shale oil produced in an N-T-U retort. A flow diagram of the coking equipment is given as Figure 1. It has been described in detail b y Lankford and Ellis ( 4 ) and Morris and Gilbertson ( 5 ) . Operating conditions and yields pertaining to the present work are listed in Table I.
Properties of Coker Distillate
A sample of the total liquid product recovered from the coking operation was separated in a batch still equipped with a packed column, equivalent t o approximately 25 theoretical plates at total reflux, into a naphtha fraction and Diesel fraction. Properties of the N-T-U shale oil charged t o the coking unit, of the total liquid product from coking, and of the naphtha and Diesel fractions of the liquid product are given in Table 11. Analysis of the gas produced during coking is presented in Table VII. In the refining proposal mentioned, it was assumed that the C4+ fraction of the gas produced in coking would be retained in the coker distillate; however, this was not accomplished in t h e experimental work. Mass spectrometer analysis showed t h a t a significant quantity of light hydrocarbons, equal t o 14.1 volume yoof the coking gases, was not recovered in t h e liquid. T o simu-
INDUSTRIAL AND ENGINEERING CHEMISTRY
1139
Table
a
1.
Coking Conditions and
Yields
Table 111.
Charge stock w - T - U shale oil Charge rate, bbl./stream day 86.3 Recycle rate, bbl./stream day 212.8 Temperatures, O F. Heater inlet 437 Heater outlet 940 Coke chamber 825 Flash chamber, top 780 Fractionator, top 360 Fractionator, bottom 600 Pressures, lb./sq. inch Heater inlet 340 Heater outlet 60 Fractionator bottom 5 Yields, experimental Coker distillate, vol. % 79.7 Coker distillate, wt. % 73.1 Coke, wt. % 15.8 Gas, wt. % 7.5 Loss, wt. % 3.6 Yields, adjusteda Coker distillate, vol. 83.5 Coker distillate, wt. % 75.6 Coke, wt. % 15.8 Gas, wt. % 5.0 Loss, wt. % 3.6 Includes Clf gases from coking experiment in liquid product.
Table II.
Charge stock Catalyst
Diesel fraction of coker distillate Cobalt molybdatea
Temperature, O F. Pressure, lb./sq. inch HZrate, cu. ft./bbl. Space velocity, VoiVc,/hr. Throughput, V,/ Vc On-stream time, hr. HZconsumed, cu. ft./bbl. Yields, on charge stock Total liquid product, vol. ye Naphtha fraction, vol. % Diesel fraction, vol. % Catalyst deposit, wt. % Gas, wt. 7* Water, wt. 7G Yields, on shale oil Charge stock, vol. % Total liquid product, vol. 7* Naphtha fraction, vol. % Diesel fraction, vol. % a
843 1100 2000 0.72 69.12 96 1200 98.7 46.1 52.6 0.2h 6.3c 2.0 54.8 54.1 25.3 28.8
Union Oil Co. catalyst N8006. 13.1 wt. % of catalyst. Includes unreacted hydrogen charged to process.
Properties of Coking Stock and Products
Yield, vol. 70 Of charge stock Of total coker distillateb Properties Specific gravity, 60°/ 60° F. Pour point,’ F. Carbon, wt. % Hydrogen, wt. % Nitrogen, wt. % Sulfur, wt. 70 Hydrocarbons, vol. %c Paraffins Naphthenes Olefins Aromatics Tar acids, vol. % Tar bases, vol. % Gum, ASTM, mg./100 ml. Gum, Cu dish, mg./100 ml. Octane numbers Motor, clear $3 ml. TEL Research, clear 3 ml. TEL Cetane number ASTM distn. (760 mm.), P. I.B.P. 57, rec. 10% rec. 20ye rec. 30y0 rec. 407, rec. 50% rec. 60% rec. 70?& rec. 80% rec. 90% rec. 957, rec. E.P. Recovery, vol. % a N-T-U shale oil. On no-loss basis. In neutral oil.
Chargea Stock 100
... 0.9352 80
...
*.. 2.2 0.9
Total
Coker Distillate Naphtha Diesel
83.5
28.7
54.8
100.0
34.4
65.6
0.8465 5
84.50 11.89 1.55 0.69
0.7579
0.8936
...
. . I
a3.75 13.13 0.91 0.72
84.31 11.75 1.95 0.67
32
...
1
45 26 2.2 9.2
51 16 1.4 6.4
378 888 58.1 . . I
64.0 73.2
+
1140
Hydrogenating Conditions and Yields
...
360 443 485 551 584 606 692
134 195 259 385 436 465 496 524 567 590 636
699 52.0
664 95.5
... ... ... ... ...
...
129 180 200 242 269 293 311 326 340 353 371 379 387 98.0
\52
J
6 42 1.2 10.8
... ... ... ... ...
...
31.9
440 467 477 489 501 517 537 556 580 61 1 65 1 696 710 97.0
Table IV.
Properties of Hydrogenation Stock and Products Liquid Product
Product Fractions Naphtha Diesel
54.8
98.7 54.1
46.1 25.3
52.6 28.8
0.8936 84.31 11.75 1.95 0.67
0.8227 86.84 12.89 0.40 0.04
0.7813 85.13 13.16 0.26 0.10
0.8628 86.53 12.22 0.49 0.03
Charge Stock Yield, vol. yG Of charge stock Of shale oil Properties Specific gravity, 60°/ 60’ F. Carbon, wt. % Hydrogen, wt. % Nitrogen, wt. % Sulfur, wt. 70 Hydrocarbons, vol. Paraffins Naphthenes Olefins Aromatics Tar acids, vol. % Tar bases, vol. yo Gum, ASTM, mg./100 ml Gum, Cu dish, mg./100 ml. Octane numbers Motor, clear 3 ml. TEL Research, clear 3 ml. TEL Cetane number ASTM distn. (760 mm.), F. I.B.P. 5% rec. 10% rec. 20% rec. 30% rec. 40’% rec. 50% rec. 60y0 rec. 70% rec. 80% rec. 90% rec. 9570 rec. E.P. Recovery, vol. %
100
16
42 1.2 10.8
.
a
67 1
32
...
...
4 1 28 1.2 3.2 6.0 26.8 54.0 70.4 57.4 73.5
+
+
\
67 152
31.9 440 467 477 489 501 517 537 556 580 611 65 1 696 710 97.0
...
114 167 191 232 269 299 324 347 367 384 397 404 404 97.5
bo 1
39 0.0
5.0
... ... ... ... ... ...
41.4
454 477 48 1 487 495 501 513 529 550 578 615 653 694 98.0
On neutral oil.
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 48, No. 7
SYNTHETIC FUELS A N D CHEMICALS -THERMOWELL
late, for further processing, the naphtha that mould have been obtained had the Cd+ fraction of the coking gas been recovered as liquid product, a synthetic blend of C4, and Cc hydrocarbons was added to the naphtha fraction after the analyses given in Table I1 were completed. The quantity of these hydrocarbons added was determined from the original mass spectrometer analysis and was equivalent to 14.1 volume % of the coking gases, 2.5 weight % of the crude oil charge, or 8.2 pounds per barrel of N-T-U shale oil charged t o the coking operation. The yields of products given in Table I1 have been adjupted to include this Cd+ fraction. Naphtha. The naphtha fraction has a poor boiling range distribution when compared with commercial gasolines, but this would be improved by including the C4+ fraction mentioned above. Besides containing undesirable quantities of sulfur, nitrogen, and gum, it is unstable and has only a mediocre octane number, even though it contains 16 volume % aromatics. Increasing the octane number by reforming must be accomplished by some other reaction than dehydrogenating naphthenes, for only a trace of these compounds is present. A large part of the nitrogen could be extracted, as it is in the form of basic compounds (tar bases), but elimination of sulfur is more difficult. Sulfur apparently is present large!y in thiophenic compounds, as in shale naphthas produced by other thermal processes ( 1 ) . Diesel Fuel. The Diesel fraction has a low cetane number (31.9), is unstable, and contains less sulfur b u t much more nitrogen than the naphtha fraction. T h e hydrocarbon portion is composed largely of saturated and aromatic compounds, and only a small percentage of olefins is present.
c,
Processing Fractions of Coker Distillate
t
Figure 2.
LIQUID PRODUCT Flow diagram of hydrogenation unit
The Diesel fraction. boiling- range - 440" to 710' F.. was hydrogenated over cobalt molybdate catalyst in the fixed-bed, bench scale unit shown diagrammatically in Figure 2. Processing conditions used and the material balance obtained are given in Table 111, and yields and analysis of the gas from the process (including unreacted hydrogen charged to the unit) are given in Table VII. The hydrogenation was accomplished in a continuous 96-hour run. No deactivation of the catalyst during this period was evident from the following analyses of samples of the liquid products taken a t various intervals:
Considerable hydrocracking occurred during hydrogenation, as is evident from the data in Table IV, which show t h a t approximately 45 volume % of the charge stock was converted to 400" F. end point naphtha. About 95y0 of the sulfur and 807, of the nitrogen in the charge stock were eliminated. Although analyses of charge stock and liquid product indicate t h a t some aromatic hydrocarbons were destroyed, usually this does not occur with cobalt molybdate catalyst under the conditions employed. Perhaps part of the material reported to be aromatic hydro25.5 36.5 72.0 83.5 96.0 On-streamtime,hr. 13.5 49.5 59.5 51.84 60.12 69.12 carbons in the charge stock 18.36 26.28 35.64 42.84 Throughput, Vo/Vo 9.72 actually consisted of cyclic oleProperties 0.8179 0.8170 0.8205 0.8168 0.8132 Specific gravity 0.8171 0.8189 0.8212 fins, which would be hydro0.42 0.30 0.39 0.37 Nitrogen,wt.% 0.42 0.41 0.41 0.42 genated under tho prevailing 0.02 0.03 0.04 0.04 0.04 0.03 0.03 0.02 Sulfur, wt. % conditions to produce this apparently anomalous result. The total liquid product from hydrogenation was distilled to Naphtha. T h e naphtha fraction had a motor-method octane produce a naphtha and Diesel fraction in the same batch equipment used t o fractionate the coker distillate. The yields and number, clear, of 54, and a sulfur content of 0.1 b u t still conproperties of these fractions are given in Table I V with the proptained 0.26% nitrogen, the latter being present largely in basic compounds. Like the raw naphtha from coker distillate, deerties of the charge stock t o hydrogenation. scribed in Table 11, this hydrogenated naphtha contained only a Calculations based on the quantities of hydrogen charged to trace of naphthenes. the unit and recovered in the products indicate t h a t approxiDiesel. The Diesel fraction had a cetane number of 41.4, conmately 1200 standard cubic feet of hydrogen per barrel of distilsiderably higher than that of the Diesel fraction of coker dislate charge were consumed in t h e hydrogenating step. This tillate. I t s sulfur content was very low, but it contained 0.49y0 quantity is of the same order as t h a t reported b y Clark and nitrogen, much of i t present as t a r bases. The large percentage others (5), who found t h a t 1100 t o 1300 standard cubic feet a of aromatic hydrocarbons in this hydrogenated stock probably barrel were consumed when distillate from this same coking accounts in part for the low yields obtained when it is cataexperiment was hydrogenated over cobalt molybdate catalyst lytically cracked, as reported below. a t 1500 pounds per square inch and 835' F. July 1956
INDUSTRIAL A N D ENGINEERING CHEMISTRY
1141
Table V. Charge stock Catalyst
a
Process HydroCoking genationa
900 400 2550 450 0.5 4.0 8.0 200
Yield on charge stock Cu. ft./bbl. 292 Lb./bbl. 16.3 Composition, mole yo Carbon dioxide 0.8 Carbon monoxide 2.0 12.9 Hydrogen Nitrogen 0.8 Hydrogen sulfide 2.5 Ammonia 49.5 Methane Ethane 15.2 Ethylene 3.1 7.1 Propane Propylene 6.1
...
89.4 84.1 5.3 1.1c 17.4d 1.1 54.0 48.3 45.4 2.9
Av. molecular weight a
Naphthas from coking and hydrogenating experiments. Union Oil Co. catalyst N8006. 3.85 wt. % of catalyst. Includes unreacted gas charged to process.
Table VI.
Charge Stock
60° F.
Carbon, wt. % Hydrogen, wt. % Nitrogen, wt. yo Sulfur, wt. % Hydrocarbons, vol. %a Paraffins Naphthenes Olefins Aromatics Tar acids, vol. % Tar bases, vol. % Gum,ASTM, mg./100 ml Octane numbers Motor, clear 3 ml. TEL Research, clear 3 ml. TEL ASTM distn. (760 mm.),
.
O
81.0 43.7
0.7693 84.37 13.53 0.48 0.39
nil nil
57
62
2 21 20 0.7 4.1
...
+
56.6
+
61.8 73.2
...
0.7351 84.84 13.57
5
Products Heavy naphtha 3.1
1.7 0.8451 85.60 11.34 0.01 0.01
I n neutral oil.
110 144 164 202 250 2 81 308 330 348 367 386 399 403 97.0
3 30 1.0 1.3
)39 3 58 0.0 1.0
1.0
4.3
66.4 83.2 70.6 86.3 102 128 141 167 190 216 237 263 286 309 341
...
364 95.0
Polymer 5.3 2.9
Cracking
2648 46.7
311 16.1
...
... ...
1240 32.8
... ... 61.0 ...
. I .
73.4
...
1.9 11.0 13.9 7.4
0.5
1.3
4.8 ..*
10.3
e . .
*..
... 2.0 ...
8.4 17.5 6.9 5.0 9.9 16.1
6.8
19.5
19.8 3.0
...
36.2
Catalytic
Cracking
Charge stock Catalyst Temperature, F. Pressure Space velocity, V,/Vc/hr. Catalvst-oil ratio. W,IW, Yield; on charge'stock Total liquid product, vol. Catalyst deposit, wt. Gas, wt. % Yields on shale oil Charge stock, vol. % Total liquid product, vol. %
Conditions and
Yields
Diesel fraction-naphtha polymerA Silica-aluminab 900
Atmospheric 1.1
4.0 90.8 6.4e 4.9 31.7 28.8
a All of Diesel fraction produced in hydrogenating experiment and all of polymer produced in naphtha reforming. 45 activity index. 1.6 wt. % of catalyst.
Processing Naphtha Fraetions
F.
I.B.P. 5% rec. 10% rec. 20'?4 rec. 30% rec. 40% rec. 50% rec. 60% rec. 70% rec. 80% rec. 90% rec. 95% rec. E.P. Recovery, vol. %
1142
100 54.0
Light naphtha
21.2
Reformingn
Includes unreacted gas charged to process.
Table VIII.
Properties of Reforming Stock and Products
Yield, vol. % Of charge stock Of shale oil Properties Specific gravity, 60°/
Yields and Composition o f Process Gases
Naphtha blend" Cobalt molybdate!'
Temperature, O F. Pressure, lb./sq. inch Hz rate, cu. ft./bbl. CH4 rate, cu. ft./bbl. Space velocity, V,/ Vo/hr. Throughput, V,/V, On-stream time, hr. HQconsumed, cu. ft./bbl. Yields, on charge stock Total liquid product, vol. % Naphtha fraction, vol. % Polymer, vol. % Catalyst deposit, wt. 7 ' Gas, wt. yo Water, wt. yo Yields on shale oil Charge stock, vol. % Total liquid product, vol. % Naphtha fraction, vol. % Polymer, vol. %
*
Table VII.
Reforming Conditions and Yields
226 351 367 373 379 380 382 384 386 388 391 397 414 99.0
The coker-distillate naphtha (Table 11) and the hydrogenateti naphtha (Table IV) were combined after blending enough C,, C6, and Ce hydrocarbons with the coker-dist'illate naphtha to compensate for the C4+ fraction not recovered from the coking operation and were reformed over cobalt molybdate catalyst in the same equipment used in the hydrogenating step (Figure 2 ) . iz mixture of 85 volume 7chydrogen and 15 volume yo methane was charged t o t'he reforming unit, so t h a t results would approach more nearly those obtainable by using recycle gas rather than pure hydrogen. T o facilitate recovery of low-boiling liquids, the product from the reforming reactor was absorbed in a volume of the hydrogenated shale oil Diesel fraction equivalent to about 16.5 volume yo of the reformed liquid products. This blend of absorber oil and reformed products was fractionated into light naphtha (364' F, end point), heavy naphtha (364" to 400" F. end point), and bott'oms consisting of absorber oil and polymer produced in the reformer. Processing conditions used and yields obtained in reforming are given in Table V and properties of the blended charge stock, light reformed naphtha, and heavy reformed naphtha in Table VI. Analysis of the gas from reforming, including the methane and unused hydrogen charged to t,he process, is given in Table VII. Reformed Naphtha. Reforming under these conditions resulted in almost complete elimination of nitrogen and sulfur; only a trace of these elements remained in the heavy naphtha.
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 48, No. ?
SYNTHETIC FUELS A N D CHEMICALS Although olefins were reduced greatly, only a small increase in paraffins occurred; so it appears t h a t aromatics rather than paraffins were produced from the olefins. The high aromatic content of the reformed naphthas and the low naphthene content of the charge stock support this. No data are available to indicate if isomerization of aliphatics occurred t o an appreciable extent, but t h e octane number increase would not indicate so, for it is no more t h a n would be expected from the increase in aromatic content.
RUS WED-QUARTZ PREWEATER
N ICHROYE WIND INO
Catalytic Cracking of Diesel Fraction
ATALYST SECTION
The Diesel fraction of hydrogenated coker distillate, including that portion of it used as absorber oil in reforming the naphtha, together with the polymer formed in reforming and remaining in the absorber oil after the reformed naphtha had been distilled, was cracked catalytically in a fixed-bed laboratory unit containing 21 liters of 45 activity, silica-alumina catalyst. A diagram of this equipment is shown in Figure 3. Oil was charged to the unit a t a liquid hourly space velocity of 1.1 until a catalyst-oil ratio of 4.0 W J W , was reached, which required approximately 9.5 minutes of on-stream time. Operating conditions used and yields obtained are given in Table VIII. The total liquid product from catalytic cracking was fractionated in a batch still into light naphtha (379' F. end point) and heavy naphtha (379" to 400' F. end point). T h e residue from this distillation then was distilled under 40-mm. absolute pressurc to produce Diesel fuel and fuel-oil fractions. Properties of the charge stock t o the catalytic cracking unit, the total liquid product from the cracking unit, and the four fractions prepared from the total liquid product are shown in Table IX. hnalysis of the gas produced is given in Table VII. This hydrogenated Diesel is a poor catalytic cracking stock, a yield of only 227&naphtha being obtained in single-pass cracking over a 45 activity index catalyst. The nitrogen content, 0.45%, accounts for part of this poor crackability and the molecular
TO GAS
WATEICCOOLCD
LlPUlD PRODUCT
Figure 3.
Catalytic cracking unit
structure of the hydrocarbon portion probably is also a factor. The aromatics, 40y0 of this stock, possibly have been cracked in the coking and hydrogenating steps to such a n extent as to leave COKE 25.8 TONS
I GRUDE SHALF 011 1000 8BL.
I DIESEL FUEL 4 5 4 8 BEL. HYDROGENATED DIESEL FUEL
I
4 CATA LY T I C CRACKING CATALYTIC NAPHTHA 69 B ~ L . t
25;
3 y l HYDROGEN AT ION
2 8 8 BEL.
REFORMED NAPHTHA 454 BBL.
CATALYTIC POLYMERIZATION POLY GASOLINE 12 BBL.
.
--~ LEA;,NT AND BLENDING
Figure 4. July 1956
SULFUR 1740 POUNDS ANHYDROUS LlOUlD AMMONIA 4470 POUNDS
4
COKING
c
11 I 1
J
LPG 23.8 BEL.
L
PREMIUM GASOLINE 2 6 7 BBL. REGULAR GASOLINE 268 BEL. DIESEL FUEL 191 BBL.
c
Flow diagram of refining process
INDUSTRIAL AND ENGINEERING CHEMISTRY
1143
Table IX.
Yield, vol. yo Of cracking stock Of shale oil Properties Specific gravity, 60/60° F. Carbon, wt. % Hydrogen, wt. % Nitrogen, wt. yo Sulfur, wt. Hydrocarbons, vol. %* Paraffins
vG
Naphthenes Olefins Aromatics Tar acids, vol. % Tar bases, vol. % Gum, ASTM, mg./100 ml. Gum, Cu dish, mg./100 ml. Octane numbers Motor, clear I3 ml. TEL Research, clear t 3 ml. TEL Cetane number ASTM distn. (760 mm.), F. I.B,.P. 5YG rec. 10% rec. 20% rec. 30’% rec. 40% rec. 50% rec. 60% rec. 70% rec. 80% rec. 90% rec. 95% rec. E.P.
Recovery, vol. % a
*
Properties of Catalytic Cracking Stock and Products Liquidn Product
Light naphtha
100 31.7
84.6 26.9
20.2 6.4
0.8477 87.74 11.82 0.15 0.02
0.7514 85.98 12.77 0.20 0.03
0.8691 87.62 10.72 0.41 0.02
48
37
22
5 47
21 42 3.1 3.3 3.5 24.0
6 72 0.1 3.1 11.3
0.8679 86.46 12.00 0.45 0.01 ! I\58
2 40 0.1 5.4
1.6 0.5
60.1 19.1 0.8721 87.50 11.92 0.16 0.01
Fuel oil 2.7 0.9 1.0159 89.80 9.01 0.41 0.07
55
...
...
... 3 42 0.0 3.6
...
82.0 86.9 91.8 97.1 39.6
40.3 446 457 463 472 48 1 49 1 503 518 538 559 603
...
Foam
114 205 292 404 450 470 485 501 516 544 598 643 643 97.5
96 111 132 160 188 210 250 277 303 328 379
338 358 362 367 373 377 382 387 392 396
379 90.5
414 98
...
... ...
442 461 466 472 479 487 503 515 529 542 570 608 648 98.5
Does not include CC. In neutral oil.
little side-chain material for cracking in the catalytic cracking step, thus resulting in a refractory cracking stock. Dehydrogenation appears to be important among the cracking reactions of this stock, as is evident from the high hydrogen content of the cracked gas, 36.2 volume yo,as shown in Table VII. This quantity is equivalent to approximately 100 cubic feet per barrel of charge to the cracking unit or about 5.57G of all the hydrogen consumed in the hydrogenating step. A small volume of ammonia is produced in the cracking process, suggesting that, while the nitrogen was not completely removed from the oil when it was hydrogenated, some of the nitrogen-containing structures may have been altered t o the extent t h a t nitrogen could be split out by cracking Cracked Products. The naphtha produced in cracking this stock was aromatic and had a clear motor-method octane number of 82. The nitrogen content (0.2y0)consists largely of basic compounds. The Diesel fuel fraction, too, was aromatic but still had a cetane number of 39.6, only slightly less than t h a t of the charge stock.
Polymerization of Olefins
It was impracticable in this laboratory study to produce polymer gasoline from the olefins in the cracked gases to complete the study of yields obtainable from this processing sequence. Instead, a commercial polymer gasoline was obtained and used in
I144
Fractions of Liquid Product Heavv Diesel naphtia fuel
Cracking Stock
blends in a quantity equivalent to that xhich could be produced from these gapes if a conversion of 907, of the C I and Ca olefins to polymer gasoline were obtained. This quantity amounts to 3.6 volume YGof the charge to catalytic cracking. The commercial polymer gasoline contained 0.73 weight mo sulfur, was essentially olefinic, and probably contributed to the high gum content of the finished gasoline described in Table X.
Production of Liquefied Petroleum Gase5, Ammonia, Sulfur As with polymer gasoline, no attempt was made in the laboratory to prepare liquefied petroleum gases, ammonia, and sulfur from the various gas streams. I n the final process-yield diagram presented in Figure 4 the quantities of these products that could be produced were calculated from analyses and quantities of gases available from the several sources as given in Table 1711. The percentages of ammonia and hydrogen sulfide shom n in the3e several streams were calculated from nitrogen and sulfur balances on charge stocks and all products except gases, the differences being assumed to appear as ammonia and hydrogen sulfide in the gases. On the small scale on which the work as done, these calculated results should be more accurate than analytical results, because of the many opportunities for losses through reaction or solution before analvtical determinations could be made.
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 48, No. 7
SYNTHETIC FUELS A N D CHEMICALS
k’ble X.
Comparison of Shale Gasolines with Petroleum Gasolines
Naphtha Stocks Light catalytically cracked, vol. yo Heavy catalytically cracked,
vol.
yo
Light reformed, vol. % Heavy reformed, vol. yG Polymerized, vol. yo
Table XI.
Comparison of Diesel-Fuel Product with Specifications
Composition of Shale-Gasoline Blends Regular Premium Of stock Of blend Of stock Of blend 0.0
0.0
100.0
Speciflcations ASTM D 975-52T I-D 2-D
24.0
Flash point, O F., min. Pour point, O F., max. Water and sediment, vol. yo,max. Carbon residue on 10% residue, wt. %, max. Ash, wt. %, max. ASTM distn., F. 90% max. E.P., max. Viscosity at looo F. Kinematic, centistokes, min. Kinematic, centistokes, max. Saybolt universal, seconds, min. Saybolt universal, seconds, max. Sulfur, wt. %, max. Corrosion, copper strip, max. Cetane number
0.0 0.0 1.9 43.7 71.5 91.8 6.3 0.0 0.0 0.0 100.0 4.5 Properties Premium Regular PetroPetroleuma leum“ Shale Shale
100.0 56.3 100.0 0.0
Yield, vol. % ’ of all naphtha stocks 50.0 50.0 Properties API gravity 59.0 58.6 58.7 58.3 Sulfur, wt. yo 0.172 0.142 0.03 0.05 2.1 2.5 6.8 13.6 Gum, ASTM, mg./100 ml. 2.06 2.49 3.0 TEL, ml./gal. 3.0 Octane number, research 87.1 83.6 89.2 92.3 Reid vapor pressure, lb./sq. in. 8.1 8.2 8.2 8.0 ASTM distn. (760 mm.), OF. I.B.P. 93 99 95 100 119 5% evap. 112 118 108 133 130 135 128 10% evap. 157 157 165 160 20% evap. 182 30% evap. 185 193 186 230 SOYo evap. 239 244 237 277 70’% evap. 293 290 278 328 340 90% evap. 350 350 348 366 95YGevap. 3 66 374 369 403 E.P. 384 407 Residue, vol. yo 1.0 1.0 1.0 1.0 1.6 Distillation loss, vol. yG 2.5 3.0 1.4 a Average of gasolines marketed in Rocky Mountain and Pacific Coast states in summer, 1954 (2).
.
100 20 Trace 0.15 0.01
...
625
1.4
... ...
...
0.50 3 40
~ i Product 215 125 10 0.10 Nil
..,
0.35 0.02 675
...
1.8 5.8 32.0 45 1.0 3 40
0.01 Nil
570 648
... 2.5 ...
34.4 0.01 1 39.6
The ratio of gasoline to Diesel fuel produced was 2.8 rather than 1.95, as was estimated could be obtained from this process before this work was done. A large part of this difference is caused by the higher-than-predicted cracking that occurred in the hydrogenating step. This cracking produced not only a higher yield of gasoline but also a gasoline of lower average quality, because it decreased the quantity of catalytic cracking stock available and produced a refractory cracking stock. It results also in a Diesel fuel of lower cetane number than would be produced had less hydrocracking occurred. Possibly a higher pressure than used in this work would have to be employed in the hydrogenating step to avoid these problems. Higher pressure probably would be helpful also in ohtaining better elimination of nitrogen from the products.
Properties of Motor Fuels Produced Blending the several naphtha streams in the proportions shown in Table X produced equal quantities of the two gasolines that approached the average quality of regular and premium grade petroleum gasolines marketed in the Rocky Mountain and Pacific Coast states in the summer of 1954. This comparison is shown in the same table. Both blends contained more gum than did comparable grades of petroleum gasoline. However, part of the high gum content of the premium blend was caused by the polymer gasoline used in the blend. I n other respects the regular grade shale blmd appears satisfactory, and somewhat less than 3 ml. of tetraethyllead would have produced a satisfactory oct,ane number. The octane number of the premium grade shale blend was lower than the average for premium grade petroleum gasoline with which it is compared. A different blending procedure, or small changes in processing conditions, probably would correct this. Diesel Fuel and Fuel Oil. The Diesel fuel was distilled from the recycle stock produced in single-pass catalytic cracking of the hydrogenated Diesel fraction and the reforming polymer. The remaining 5 % of the recycle stock was designated as fuel oil. The yield and properties of this Diesel-fuel product are tabulated and compared with Diesel-fuel specifications in Table X I . Although this Diesel fuel has a cetane number slightly below the minimum for A S T N grades 1-D and 2-D and its distillation end point is high, in all other respects it meets these specifications. Gasoline.
Over-all Process Yields The block diagram in Figure 4 shows the yields of products obtained by this processing sequence, from 1000 barrels of N-T-U shale oil charged to the first step in the process coking. July 1956
Acknowledgment This project was part of the Synthetic Liquid Fuels program of the Bureau of Mines and was performed a t the Petroleum and Oil-Shale Experiment Station in Laramie, Wyo., under the general direction of H. P. Rue and H. M. Thorne. Special thanks are due various members of the staff of the station for their valuable assistance in carrying out this project. The work was done under a cooperative agreement between the University of Wyoming and the U. S Department of the Interior, Bureau of Mines
Literature Cited (1) Ball, J. S., Dinneen, G. U., Smith, J. R., Bailey, C. W., Van Meter, R., IND. ENG.CHEM.41, 581-7 (1949). (2) Blade, 0. C., U. S. Bur. Mines, Rept. Invest. 5111 (1955). (3) Clark, E. L., Hiteshue, R. W., Kandiner, H. J., Morris, H. B., IND. ENG.CHEM.43,2173-8 (1951). (4) Lankford, J. D., Ellis, C. F., Ibid., 43, 27-32 (1951). (5) Morris, H. B., Gilbertson, D. L., Petroleum Engr. 21, KO.9 , C26-32 (1949). (6) National Petroleum Council Committee on Synthetic Fuels
Production Costs, Shale Oil Retorting and Refining Facilities, Sept. 15, 1951, hearings before special Subcommittee on Minerals, Materials and Fuels Economics, Committee on Interior and Insular Affairs, U. S. Senate, 83rd Congress, Part 6, 1953, and 1954, pp. 334-61. (7) U. S. Bur. Mines, Rept. Invest. 4866, 43-55 (1952). RECEIVED for review November 7, 1955.
INDUSTRIAL AND ENGINEERING CHEMISTRY
ACCEPTEDFebruary 20, 1956.
1145
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