SULFUR COMPOUNDS
IN PETROLEUM Presented before the Division of Petroleum Chemistry at the 115th Meeting of the American Chemical Society, San Francisco. Calif.
Sulfur Content of Catalytically Cracked Gasolines Beta- the
uob of high sulfurbearing oils as catalytic cracking f e d stock. is increasing. it b of i n t w t to study tha facton that &t the sulfur content of catalytid gasolinu. Relatively high concentratioru of sulfur compounds appear in cracked product. whose boiling range is just bdow and somewhat above 4M)" F.; therefore, ina u d n g the end point of catalptic g o l i n e n much above 4M)- F. is h l y to be accompanied by an abrupt increase
in sulfur content. Low sulfur contents in gasohen an favored by low -tor temperatures and high conversions. A$ similar operating conditions. the sulfur w n tent of gMO1ineS L not m t l y dependent on commercially available types of catalynt employed. Incmlllling the sulfur or olefin content of catalytic gasolines dtheir lead nuceptibility. Con-tratio'ns of mercaptnra in debutanizd gadinem an loa relative to total sulfur content.
D
A wide variety of feed stocks has been processed in the fluid catalytic cracking pilot plants at the Research and Development Laboratories of Universal Oil Products Company. The fractionation section of these pilot plsnta is designed so that a continuous stream of debutanised gasoline is produced, and in the normal course of inspection of samples of this stream its total sulfur content was measured by the lamp method in4he routine analytical laboratory. It is with such routine measurements of sulfur contents that this empirical study is concerned. In Table VI are detailed the operating conditions, feed stock properties, and gasoline properties for tests representing a range of feed stock sulfur contents of from 0.15 to 2.64%. The exact geographical sonrce of many of the feed stocks is unknown, because the gas oil was usually prepared from a blend of crudes proceased at a given rehery. The general geographical source of the feed stocks is known, however, and is indicated in the table. In this discmion conversion is d e h e d as 100 minus the volume per cent yield of total cycle oil boiling above gasalie that has an A.S.T.M. distillation end point of approximately 400' F. Mercaptan (thiol) contents of catalytic gasalines are very low relative to the total sulfur present, and unleas special precautions
URING the past war feed stocks for catalytio cracking were
generally rather low in sulfur content, but at present it is mmmon to process feed stocks that contain in excess of 1% of sulfur. Thia preaent UE of higher sulfur-bearing feed stocks for catalytic cracking is due in part to the selection of heavier fractiona of crudes as catalytic feed stocks, and in greater part to the current trend in availability of crudes which is forcing a larger number of r e h e m to process high-sulfur materials. It is generally recognized that the desulfurization features of catalytic cracking are excellent, for a t operating conditions and converSiom now employed for the production of motor fuel about 50% of the sulfur in the feed stock appears BB hydrogen sulfide in the pmoeetl gas and only 5% appears as sulfur in the gasoline. In view of the increasing UE of high-sulfur feed stocks for catalytic cracking, i t becomes of interest to relate the effects of the feed stock origin, its sulfur content, and certain operating variables to the sulfur content of the gasolines produced from these feed stocks, and to study the effect of the sulfur content of the gasoline on ita octane number response to additions of tetraethyllead. These are the objectives of the study reported in this paper.
2680
December 1949
INDUSTRIAL AND ENGINEERING CHEMISTRY
2681
a t a conversion level of 58%. These data are detailed in Table I1 and are p1ot.ted in Figure 2, which shows similar sulfur dis700 tribution trends, but a t a lower concentraui CL 3 tion level than those described for the 600 products from the high-sulfur feed stock. E Another method of showing the impor4 tance of the effect of the end point of a 500 e gasoline on its sulfur content is to blend a z gasoline and a cycle of oil in proportion to Q 400 the amounts produced from a given test, and -I redistill the blend to obtain gasolines of varying end points. The data from such 300 experiments are given in Table I11 for gasoi lines produced from the processing of a c: PO0 high-sulfur feed stock a t about 50% conversion. I n Figure 3 the sulfur contents of gasolines having end points of from 340" 100 t o 440" F. are plotted against their 0 PO 40 60 80 100 20 40 60 80 A.S.T.M. 90% temperatures for two cases 0 CYCLE OIL, VOL. % DISTILLED GASOLINE, VOL. % DISTILLED involving high-sulfur feed stocks. I n one instance the feed stock to the cracking Figure 1. Sulfur Distribution i n Catalytic Gasoline and Cycle Oil from unit contained about 4% of 400" F. end High-Sulfur (2.64%) Gas Oil point gasoline, and the second feed stock was prepared from the first by the removal of this gasoline. Each of the two sulfur content lines are used in handling the sample of gasoline before analysis the on Figure 3 represents results obtained by the redistillation mercaptans in part are likely to be converted to disulfides byoxidaof a blend of gasoline and cycle oil from a single catalytic cracking tion. Because these precautions were not always observed for test, to produce gasolines of varying end points. I n either case, the tests recorded in Table VI, the gasoline mercaptan contents however, sulfur content of the gasoline increased abruptly as its as measured varied without relation to the total sulfur content. end point exceeded about 400 F. T h e data presented in this Apart from mentioning the presence of mercaptans in catalytic section point out the relatively high concentrations of sulfur gasolines in this paragraph, this paper is concerned only with the compounds in the boiling range just below and somewhat above quantitative aspects of their total sulfur content. 400' F. This is particularly significant because it is the boiling DISTRIBUTION OF SULFUR IN CATALYTIC GASOLINES
f 2
2
c
d
2
O
r-5
4
I n order to study the distribution of sulfur in a gasoline produced from a high-sulfur gas oil, both the gasoline and the cycle oil from a test period made at a conversion of 52% were resolved into small cuts on which sulfur measurements could be made. The detailed data appear in Table I and are represented graphically in Figure 1,which shows the sulfur content of each 10% cut plotted against its mid-per cent point for both gasoline and cycle oil. To show the sulfur distribution more accurately in the heavy ends of the gasoline, the highest boiling 10% cut was further resolved into nine smaller fractions. Although abscissa scales of equal length were chosen to present the sulfur distribution data, the actual volume of cycle oil was greater than the gasoline by a factor of 1.3 for the test period studied. It is significant that the heavy ends of the gasoline contain very high concentrations of sulfur relative to its average sulfur content, and the low boiling fractions of the cycle oil are high sulfur-bearing relative to its average sulfur content. Because the feed stock used for this cracking test had an A.S.T.M. initial boiling point of 570' F., the material in the cycle oil boiling below that temperature was almost entirely synthetic in nature. This amount of synthetic material (20% of the cycle oil) corresponds very roughly to the high sulfur-bearing portion of the total'cycle oil. Analysis of the 10% cuts of the sweet gasoline considered in Table I indicates that less than 10% of the total sulfur exists as sulfides, while even smaller amounts of disulfides were found. The disulfides may have been formed b y mercaptan oxidation during laboratory handling. Both types of compounds appear in the higher boiling fractions of the gasoline. The occurrence of these compounds in such low concentrations in the gasoline suggests that only stable forms of sulfur compounds can survive the drastic conditions in catalytic reactors. A similar study of sulfur distribution was made for a gasoline and its corresponding cycle oil obtained from a low-sulfur gas oil
Table I. Sulfur Distribution i n Catalytic Gasoline and Cycle Oil Produced from High-Sulfur (2.64Yo) Middle East Gas Oil Position of Cut in Gasoline or Cycle Oil 0-100 0-10.5 10.5-20.6 20.6-30.4 30.4-40.3 40.3-50.2 50.2-60.0 60.0-69.9 69.9-79.8 79.8-89.6 89.6-100 90.3-91.3 91.3-92.3 92.3-93.3 93.3-94.3 94.3-95.3 95.3-96.3 96.3-97.3 97.3-98.4 98.4-100
A.P.I. 54.7 85.2 80.8 76.9 70.7 63.8 53.4 46.2 39.5 33.9 26.9
.. .. ..
.. .. .. .. ....
A.S.T.M. Distillation Temperature of Cut, F. 5% 50% 95%
Sulfur Content of Cut, Wt. % Total S R-S-R' R-S-S-R'
Debutanired Gasolinea 130 216 398 0.32 93 100 111 0.02 104 111 139 0.04 117 127 1.53 0.05 141 153 177 0.06 171 182 203 0.09 211 222 245 0.24 249 260 277 0.34 289 303 321 0.39 339 348 367 0.35 397 412 460 1.22 ... 0.66 ... 0.84 ... 0.91 ... ... 0.98 1.05 ,.. 1.11 ... ... 1.22 ... 1.53 ... 2.16 ...
...
.. .. ..
... ...
.
I
.
...
.. ..
.. $ii
Xi1 0.02 0.04 0.05 0.04 0.06
...
...
.. .. .. Nii' Nil 0.002 0,008
...
..
.. .. .. .. .. ..
Cycle Oil 21.6 523 619 744b 2.80 19.1 453 467 480 4.16 .. 19.7 505 512 520 4.06 .. 24.3 540 546 554 2.40 27.9 575 581 587 1.61 26.9 599 605 610 2.04 24.9 626 633 638 2.69 22.6 653 659 665 3.02 21.8 704C 728 752 2.47 19.2 80.6-90.3 743C 761 790 2.48 90.3-100 9.5 781C 818 912 3.25 a Sweet and H2S free. b 90% distillation temperatures for cycle oil. C Vacuum distillations corrected to atmospheric pressure.
0-100 0-10.1 10.1-20.2 20.2-30.3 30.3-40.4 40.4-50.5 50.6-60.6 60.6-70.7 70.7-80.6
... ...
..
... .
... ... ... ... ...
...
.. .. .. ... ... ... ... ...
... ... ...
...
INDUSTRIAL AND ENGINEERING CHEMISTRY
2682
700
f
having lower sulfur contents, it is to be expected that their line would appear a t lower gasoline sulfur contents on the plot.
u ' K
EFFECT OF CONVERSION
3
! -
2 4 500 $
3 i.0
Vol. 41, No. 12
600
Data obtained from the processing of W z many feed stocks, each at various conU version levels, indicate that the sulfur 3 0.8 Y d 5 Z content of catalytic gasolines decreases v) 0 as the conversion is increased. Repre400 0.6 sentative test data are shown in Table -I 5(3 =! IV and Figure 4. Tests falling in 10% conversion intervals have been averaged 300 E n g 0.4 as a group in several instances and are i c: considered as a single point on the plot. PO0 0.2 The choice of the logarithmic scale for sulfur content is based largely on the straightline plot obtained for the mid-continent 100 0 20 40 60 80 I00 PO 40 60 80 100 stock on which the greatest number of tests 0 were made over the widcst range of ('onG A S O L I N E , V O L . % DISTILLED CYCLE O I L , V O L . % DISTILLED version. Presumably-, sulfur compounds which appear in gasolines a t low converFigure 2. Sulfur Distribution i n Catalytic Gasoline and Cycle Oil from Low-Sulfur (0.51 70)Gas Oil sions are either further decomposed, or diluted to some extent with additional amounts of relatively lower sulfur content range within which usual motor gasoline end points fall, and any gasoline produced as the conversion is increased. variations in separations between cycle oil and gasoline are likely EFFECT OF CATALYST to affect the sulfur content of the gasoline. These obseivations are not in evact agreement with those of Three cracking catalysts, synthetic preparations of silica-aluFowle and Bent ( f ) ,!Tho shon a linear relationship between the mina and silica-magnesia, and a natural clay (Filtrol) which are sulfur content and the 90% point (up to 400' F.) of catalytic gasocurrently employed in commercial units, were used in a pilot plant lines produced from Kest Texas feed stocks. Their relationship to process a Venezuelan gas oil. Sulfur contents of gasolines prois shown as a dotted line in Figure 3. The important difference duced by the use of each of these catalysts are plotted against between the two sets of data is that the Fowle and Bent line is conversion in Figure 5 , and although there appears to be a slight linear rather than concave upward as shown by the solid lines on difference because of catalyst type, it is not considercd significant. Figure 3. Inasmuch as F o d e and Bent worlced with feed stoclrs Furthermore, it has been concluded from other experimental tests that a given catalyst does not change its desulfurimt'ion propcrties to any extent as its cracking activity declines with normal use. 440 I Tests 17 to 22 and 31 to 34 in Table VI give furt'her comparisons >-FROM FEED CONTAINING G A S O L I N E of catalysts in processing other gas oils. < - F R O M GASOLINE FREE FEED K
7
2
420
400
0.45
z
w
$
-I
a
380 Q
0.40
0
13
B
z
a
2 0.35 -l 2
360
?ia
6?.
5 0.30
340
(3
g
5
i c:
2 0.25
Table 11. Sulfur Distribution i n Catalytic Gasoline and Cycle Oil Produced from Low-Sulfur (0.51%) Mid-Continent Gas Oil Debutanized Gasoline Total Position of cut SUlfUT in gmoline, vol. 70 in cut, wt. 0-9.9 9.9-19.6 19.8-29 7 29.7-39.3 39.3-49.0 49.0-58.7 58.7-68.4 68.4-78.1 78.1-87.8 87.8-89.7 89.7-91.7 91.7-93.7 93,7-94.4 94.4-100 I
0,03 0.03 0.07 0.03 0.04 0.05
0.10 0.12 0.11 0.12 0.11 0.10 0.11 0.47
A.P.I. Total sulfur wt. % Mercaptan h f u r , wt. % A.S.T.M. Distillation, F. I.B.P. 5% 10%
0.1 5 360 380 400 A.S.T.M. 90% DISTILLATION TEMP. OF G A S O L I N E , O F. 300
320
340
Figure 3. Effect of 90% Distillation Temperature of Gasoline on Its Sulfur Content
0-2 2-4 4-6 6-8 8-10 10-20 20-30 30-40 40-50 50-100
Properties of Gasoline a n d Cycle Oil Gasoline
I
0.20
%
Cycle Oil Position of c u t Total sulfur i n cycle oil, vol. % in cut, wt. %
30% 50% 70% 90%
E.P.
57.8 0.09 0.0021 104 120 120 156 2 % 277 368 419
0.53 0.72 0.72 0.78 0.84 0.73 0.47 0.32 0.42 0.47
Cycle Oil 27.8 0.5
..
494 612 523 561 6% 647
714
INDUSTRIAL AND ENGINEERING CHEMISTRY
December 1949
2683 EFFECT OF REACTOR TEMPERATURE
Table 111. Effect of Catalytic Gasoline End Point on Its Sulfur Content (High-sulfur West Texas-Wyoming blend) Gas Oil Feed Stock Contains 4% of 400° F. E.P.Gasoline Contains 0.0% 400' F. E,P. Gasoline Conversiona, 49% Conversion, 46.5%
Several groups of tests in which more than one temperature was employed for a given feed stock have been collected 460 410 440 Distillation cut temperature I?. 360 410 440 360 390 470 390 1.21 1.28 1.00 1.08 1.14 1.22 1.26 1.00 1.07 1.13 Relative volumetric gasoline bield in Table V. Using a line of Properties of gasoline 49.4 57.3 55.5 53.3 59.0 56.5 55.0 53.1 51.6 Gravity A.P.I. at 60° F. 51.1 average slope from Figure 4, 0.23 0.25 0.27 0.33 0.45 0.26 0.29 0.30 0.36 0.40 Total sdlfur wt: % A.S.T.M. distfllation, F. the observed gasoline sulfur 110 110 112 I.B.P. 117 110 contents shown in Table V 200 251 221 246 248 60% mvA 313 326 319 286 have been adjusted to a con380 400 384 353 90% stant conversion of 60%. Ac421 404 399 373 959 414 439 428 E.Pq 390 cording to these data, as the 5 100 - vol. % ' cycle oil above 400° F. end point gasoline. reactor temperature was increased the gasolines produced contained greater m o u n t s of Table IV. Effect of Conversion on Sulfur Content of sulfur for a variety of feed Catalytic Gasoline stocks and over a wide range of sulfur contents. -
O
O
- ~~
+
Sulfur in Feed Stock, Wt. %
Feed Stock Mid-continent
0.29
Reactor Temp.,
Catalyst
F.
Si-A1
900
Mid-continent
0.48
900
Si-A1
Mid-continent
0.48
800
Si-A1
No. of Average Tests ConverAveraged sion 3 36.8 8 43.7 18 54.8 22 64.5 13 74.8
2 3 11 3 4 4 3 3 1
California
1.16
850
Si-A1
Venezuela
0.87
900
Si-Mg
Elk Basin
2.15
1 1 1 1 1
Si-AI
874
2 Mid-continent
0.41
Si-Mg
900
45.2 69.0 65.5 75.3 45.6 53.2 64.2 74.2 41.5 44.4 59.7 49.0 67.8 67.8 51.4 66.7 54.5 71.1
Average Wt..% S in Gasoline
EFFECT OF' SULFUR CONTENT OF FEED Observed sulfur cbntents reported in Table VI have been adjusted to a constant conversion of 60y0 by the use of Figure 4, and to a common reactor temperature of 900 F., on the basis of data in Table V; the effect of minor variations in the 90% distillation temperature on sulfur content was neglected. These
0.063 0.051 0.046 0.038 0.029 0.110 0.103 0.097 0.090 0.110 0.095 0.083 0.082 0.450 0.400 0.310 0.130 0.110 0.100
O
Table V. Effect of Cracking Temperature on Sulfur Content of Catalytic Gasoline
Feed Stock
0.200 0.160 0.005 0.040
Catalyst
Mid-continent
Si-A1
Illinois
Si-A1
Reactor Average Temp., Copver-
No. of
' F.
Tests
14 20 6 1
800 900 950 850 925 962
1
2
0.6
1
1
Wyoming
s ~ - M ~
1 1
California
&-A1
Middle Eastern
Si-A1
3 1 3 4
Illinois
Si-A1
901 950 846 903 900 950 840 899
1 1
sion 58.0 64.6 67.0 69.6 71.9 72.1 67.5 63.7 48.5 43.4 52.7 54.0 52.0 53.0
Observed 0.084
0.10 0.12 0.01 0.02 0.03 0.03 0.06 0.38 0.47 0.29 0.34 0.06 0.08
aonver-
sion 0.092 0.107 0.133 0.012 0.023 0.036 0.033 0,064 0.327 0,377 0.26 0.314 0.054 0.073
ru
e
z
W
z
0.1
0
-
CATALYST
SILK& ALUMINA
i2 0.09 c
4
0 & 0.05 6
E8
0.03
B
0-
0 -
A 'X.
30
40 50 CONVERSION (100
Figure 4.
-
I
CALIFORNIA E L K BASIN
VENEZUELA
+ 0-
M I D -CON TINE N T
70 VOL. % CYCLE OIL) 60
80
Effect of Conversion on Sulfur Content of Gasoline
I
c
I
P 5 0.10 0.08
I
1 46
50 54 58 62 66 CONVERSION (100 VOL. 96 CYCLE OIL)
-
70
74
Figure 5. Effect of Catalyst Type on Sulfur Content of Gasoline
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
2684 Table VI.
Vol. 41, No. 12
Sulfur Content of Gasolines from Once-Through Fluid Catalytic Cracking of Gas Oils i n Pilot Plant 3
T e s t ;Go. 1 2 Catalyst Si-ME Reactor temperature, F. 902 900 Conversion (100 - vol. % cycle oil) 56.2 72.8 Feed stock
4 Si-A1 846 848
898
49.3
46.2
+
Test N o . 17 Catalyst 901 Reactor temperature, F. vol. % cycle Conversion (100 oil) 73.2
-
Feed stock
50.5
E.P.
F-2 (motor method) octane No. Clear 3 ml. TEL/gallon Lead response slope
+
10
11
897
900
898
46.4
55.8
71.4
920
13 14 %-til 901 899
15 16 Si-Mg 892 898
35.0
61.3
53.7
Si-Mg
12
Illinois
28.8 0.30
29.1 0.32
30.7 0.39
60:2 440 503 677 872
7b:2 465 570 723 910
76:1 476 540 697 875
7i:5 505 604 706 830
Illinois
--
54.8
70.9
Mid-Continent
-*_
4 -
A -
31.2 0.41 0.06 52.0 464 534 659 815
29 6 0.43
oi:z 535
g07
714 876
57.1 0.04 29 23
55.5 0.04 32 27
57.7 0.04 66 16
56.6 0.04 41 26
55.8 0.04 60 25
57.1 0.07 54 14
57.6 0.05 47 16
57.5 0.06 37 19
57.6 0.04 25 26
56.9 0.05 43 18
54.8 0.07 32 34
54.1 0.06 33 34
57.2 0.06 39 17
67.2 0.04 28 2.5
112 174 231 298 362 399
108 182 240 304 361 392
104 183 240 301 364 394
109 182 239 306 372 408
102 185 240 298 358 408
106 186 239 294 362 400
106 184 236 293 360 401
104 178 236 298 362 400
115 182 233 293 359 406
126 194 237 295 300 405
102 141 192 289 380 422
103 153 215 311 396 428
112 193 245 301 365 410
113 184 238 301 369 416
79.7 85.6 0.64
80.1 86.0 0.64
78.4 83.8 0.57
78.6 83.8 0.54
78.9 83.4 0.48
79.1 82.5 0.36
79.6 84.4 0.52
79.4 84.3 0.53
784 84.9 0.68
78.0 83.7 0.60
81.2 86.( 0.52
80.4 85.8 0.58
77.2 83.2 0.62
77.9 84.4
900
63.3
68.7
48.0
20
21 22 Fil trol 899 899 62.8 50.3
--
Mid-Continent 25.8
23 24 Si-A1 849 977
28
26
978
928
53.4
77.1
66.4
Ill. 30.6 0.54 0.06 73.4 480 606 709 869
72.6
-
27 28 Filtrol 930 925 72.9
31 32 -~Si-Mg901 950
33 Si-41 900
34 F1ltroi 899
73.2
67.5
59.3
64 8
30
7 7 . 8 67.6
Michigan
63.7
Wyoming d -
28 3 0.55
31 7 0.61
90:3 475 582 767 928
53 7 460 510 673 822
56.5 0.07 42 27
56.7 0.07 55 21
56.5 66.7 0.07 0.06 47 39 20 25
56.1 0.08 56 16
58.0 0.06 35 21
57.9 0,042 44 32
55.7 0.013 30 38
58.8 0.021 35 26
57.4 0,037 27 33
57.2 0.022 24 34
68.4 0.011 23 25
58.5 0.016 18 26
5 8 . 5 58.4 0.03 0.06 34 42 27 24
104 156 204 280 358 416
103 155 203 275 356 408
112 183 234 295 369 416
110 182 234 299 370 414
112 175 225 289 360 401
114 192 248 300 361 403
108 170 222 293 363 403
106 158 206 286 371 414
107 162 218 296 374 417
109 168 219 293 371 413
113 168 223 298 377 415
109 167 220 299 374 415
115 179 232 302 374 416
117 176 229 300 375 415
102 170 218 284 359 402
108 166 220 289 366 404
82.1 87.2 0.55
81.1 79.8 8 6 . 8 84.2 0 . 5 1 0.48
79.3 84.9 0.60
78.6 84.2 0.61
78.0 79.4 83.1 85.8 0.53 0.68
81.0 85.9 0.54
81.0 86.5 0.61
78.6 80.1 79.2 85.5 86.2 86.6 0.73 0.67 0.79
76.8 86.2 0.99
76.9 86.8 1.04
..
..
38
59.2 0.04 32 28
100 118 199 285 365 402
202 284 36 1 403
..
, .
..
42 43 Filtrol 900 897
44
45
46
47
48
49
50
902
901
900
851
845
847
903
930
70.1
54.6
70.7
81.3
51.6
42.6
59.7
41.5
44.4
43.4
49.8
-
California
49.1
53.7
Venezuela
California
27.6 0.87
13.8 0.88 0.62
7213 420 523 718 873
50.9
56.3 0.13 36 17
59.2 0.11 32 20
56.0 56.2 0.10 0.11 29 24 25 31
56.0 0.12 35 26
55.9 0.14 37 24
112 198 249 304 358 400
116 186 244 300 360 396
118 188 244 302 365 398
98 154 211 296 36 1 406
108 170 225 298 362 307
108 177 233 302 365 400
76.6 81.9 0.53
76.3 82.2 0.60
78.2 83.8 0.99
81.8 7 9 . 8 87.2 85.4 0.59 0.61
79.6 84.7 0.55
81.3 86.6 0.57
56.4 0.10 40 22
56.5 0.11 47 20
111 173 223 290 356 393
99 176 23 1 295 358 397
80.1 85.3 0.57
79.5 84.7 0.55
86.4 0.12 48 19
79.1 84.2 0.54
-
50.4 0.34 64 27
55.0 0.31 20 30
100 206 256 308 362 402
109 173 233 305 379 41Q
82.4 84.1 0.20
8 0 . 2 7H.0 84.8 82.6 0.49 0 . 3 7
54.8 0.48 41 23
153
51 i2 Filtrol 926 927 61.0
52.3
California -*_-
24.9 1.22
80.1 $91 .&9 676 857
522 680 767 882 56.9 0.09 35 27
25.4 1.16
105
.. ..
._
39 40 Si-A1 899 900
&-AI
7
58.8 0.05 31 34
899
Feed stock
41
0.66
877
26 875
;17.0 0.07 29 34
T e s t No. 35 36 37 Catalyst Si-Rfg 899 899 903 Reactor temperature, F. Conversion (100 - vol. % cycle oil) 49.0 57.8 67.8
A.P.I. Sulfur, wt. ?& Nitrogen, w t . % ' Viscosity, S.G.8. a t lO0O F I . n . P . , 0 F. 10% 50% 90% Debutanized gasoline A. P .I. T o t a l sulfur, wt. % Olefins, ,wt. % Aromat,ics, R t . 70 A.S.T.M. distillation, O F. I.B.P. 30Y0 50% 70% 90% E.P. F-2 (motor method) octane Xo. Clear 4- 3 ml. TEL/gallon Lead response slope
42.2
9
30.6 0.29
A
Sulfur wt. % N i t r o i e n , wt. 70 Viscosity, S.U.S. a t 100' F I . B . P . , E'. 10% 50% 90% Debutanized gasoline A.P.I. T o t a l sulfur, wt. % Olefins, wt. % Aromatics, wt. % A.S.T.M. distillation, ' F. 1.n.P. 30% 50% 70% 90%
46.1
7
Seminole Gushing
18 19 Si-81 902 900
A. P . I.
54.3
6
Illinois
Lance Creek
A. P .I. 31.5 Sulfur, wt. YG 0.22 Nitrogen, wt. % ' Viscosity, S.U.S. a t 100' F. ( 5 7 . 1 at'122' F.) I . B . P . , ' F. 427 10% 567 50% 736 90% 85 1 Debutanised gasoline 58.2 58.5 A.P.I. 0.05 0.05 T o t a l sulfur, wt. % 39 24 Olefins wt. 70 24 Aroma&, wt. % 16 A.S.T.M. distillation, F. 114 116 I.B.P. 180 187 30% 239 233 50% 301 301 70% 373 369 90% 415 412 E.P. F-2 (motor method) octane No. 76.6 77.0 Clear 84.2 3 ml. TEL/gallon 82.9 0.76 Lead response slope 0.63
900
8 Filtrol 952 908
5
82.8 507 558 678 845
54.7 55.3 0.40 0.47 37 47 24 23
48
5 1 . 5 21.2 0.47 0 . 4 1 32 3.5 43
49.6 0.53 49 36
116 187 239 248 373 417
110 201 251 305 365 408
249
303 366 411
212 238 314 37.4 411
81.4 84.1 0.31
82.3 84.9 0.29
80.8 83.0 0.31
,,
,. .,
80.9 83.4 0.28
118
190
113
INDUSTRIAL AND ENGINEERING CHEMISTRY
December 1949
2685
Table VI (Continued) Test No. 53 Catalyst Reactor temperature, F. 899 Conversion (100 vol. % cycle oil) 51.2
54
-
2%
903
899
903
906
50.5
53.4
53.4
61.0
60.4
64.3
903 60.2
21.9 1 ,630
F.
62
54.3
Venezuela
O
61
899
.4.P.I.
Debutanized gasoline A.P.I. Total sulfur, wt. % Olefins wt. yo -iromaiics, wt. % A.S.T.M. distillation, I.B.P. 30% 50%
60
56
Feed stock Sulfur, wt. % Nitrogen, wt. % Viscosity, S.U.S. a t 100' F. I.B.P., F. 10%
59
900
57 58 Filtrol 900 900
55
-
20.8 1.85 159.'5 575 648 725 835
+ a
b
28.4 1.87
iii
5417 435 490 660 835
410 565 759 903
893
51.4
46.2
46.6
----
West Texas 25.9 2.04 0.055 84.5 490 658 734 880
-Elk Bafiin
69
West Wyoming Texas7---
25.1 2.15
21.6 2.48
ids'. 7
98:6 494 570 875 909
468 538 733 918
54.3 0.22 50 25
55.0 0.18 32 28
55.9 0 22 29 17
55.0 0.25 31 44
55.0 0.24 38 25
56.9 0.30 32 27
57.4 0.29 30 20?
56.3 0.20 35 24
56.9 0.16 29 33
54.4 0.32 44 30
54.5 0.34 44 31
122 192 245 305 365 394
106 185 244 307 366 398
118 188 246 310 383 405
110 194 248 306 364 397
121 200 252 311 374 409
110 192 246 304 370 408
100 180 242 306 371 406
112 174 230 303 366 406
117 176 233 305 365 405
121 192 261 313 373 407
105 173 221 289 363 406
103 161 208 283 360 407
106 176 228 298 370 410
102 156 209 289 358 399
112 173 224 295 367 402
103 168 226 294 368 404
77.7 81.7 0.39
80.7 84.4 0.42
80.8 7 9 . 8 84.6 84.1 0.42 0.48
-
24.5 2.55 0.13 92.6 440 574 732 882 57.7 0.22 36 30
56.1 0.24 28 37
122 113 108 203 187 176 257 241 230 310 300 299 364 358 362 403 397 406
---
Middle East 24.3 2.59 0.062 160 540 634 777 913
109 182 240 299 361 394
80.8 80.7 84.2 84.4 0 . 3 8 0.41
81.4 8 0 . 9 85.2 84.6 0.43 0.40
Wyoming
55.9 0.30 46 29
E.P.
West Texas
20.9 1.94
892
65.1
66.7
68
5 3 . 0 55.4 0.20 0.18 51 39 30 28
p70
F-2 (motor method) octane No. Clear 3 ml. TEL/gellon Lead response slope
51.7
Venezuela
850
67 S i 4 874 874
54.5 0.21 47 28
.&--
"F
850
55.4
66
53.8 0.16 31 31
JO%
B.S.T. M. distillation, I.B.P. 30% 50% 70% 90%
65
55.3 0.17 41 24
Pilot Plant Results Test No. 70 71 72 73 74 75 Catalyst Si-Mg Si-A1 900 902 902 902 900 950 Reactor temperature, F. Conversion (100 - vol. Yo cycle oil) 47.6 5 8 . 1 71.4 56.6 52.7 5 4 . 0
90% Dehutaniaed gasoline A.P.1, Total sulfur, wt. 3' % Olefins, wt. Yo Aromatics, wt. %
64
53.4 0.19 46 27
+
A.P.I. Sulfur, wt. % Nitrogen, wt. % Viscosity, S.U.S. at 100' F. I.B.P., F.
---
Venezuela _ > -
122 436 550 725 860
E.P. F-2 (motor method) octane No. 80.5 80.3 Clear 3 ml. TEL/gallon 84.2 85.2 Lead response slope 0.41 0.63
Feed stock
56.8
63 Si-Mg 901
24.4 2.64 0.061 156 570 636 773 911
55.7 0.34 45 28
55.5 0.29 54 29
54.1 0.34 59 31
111 169 220 293 376 422
107 115 163 167 217 219 288 295 370 370 411 416
77.7 78.5 8 0 . 1 81.7 8 1 . 8 8 2 . 3 81.6 82.8 84.2 84.8 84.7 8 4 . 8 0 . 4 0 0 . 4 5 0.45 0.35 0.32 0 . 2 7
80.5 80.1 84.1 8 4 . 8 0.41 0.51
1
2
935
Si-A1 968
7 9 . 8 80.6 84.4 84.5 0.50 0 . 4 3
54.8
51. 0 44.2
53.0
Pa.
Calif.
Blend
Ill.
38.5 0.14
36.4 0.37
3e:5 398 470 564 652
273 434 482 556
59.2 0.022 33 36
55. 0.128
..
..
.. I
.
.a.
.a.
.. .. ..
.. ... .
... .
.. ..
81.5 83.8 0.27
Commercial Results 3 4 5 6 7 8 9 1 0 1 1 1 2 Si-A1 Filtrol ___ Filtrol si-A1 Filtrol Si-ill Filtrol 925 910 899 925 942 840 960 960 886 870
64.2
..
82.0 81.5 86.7 8 4 . 0 0 . 5 1 0.29
27.3 0.43 2ii 506 583
.
.
.,
3 0 . 3 29.8 0 . 4 8 0.57 0.063 , . 70.2 450 384 575 513 691 643 833 845
51.2 53.9 59.5 0.055 0.099 0 . 0 8 40 44
.. ..
..
..
118 224 280 332 402 440
110 178 239 319 390 425
104 162 210 275 348 416
..
... .
77.2 8 0 . 7 81.7b 85.5 0.52 0 . 5 3
51.6
45.2
Blend Calif. 27.4 0.52
i7i
510 580 , . ,
I
24.0 0.57 0.20 426 621 752
..
52.0
53.4 6 3 . 7
54.6
Ill.
Calif.
Blend
Ark.
30.3 0.58 0.053 75.0 535 609 711 862
3 0 . 9 30.0 0.82 0.84
28.8 0.89
27.4 1.65
4015 4310
7317 404 545 701 872
77:4 354 534 700
450 380 540 701
462 383 571 717
49.5 6 0 . 3 5 1 . 8 54.4 0.073 O.'i23 0 . 0 6 0.30 0.30 ., 37 .. .. .,
.. ..
,.
.. .. ..
.. ..
.. .. ..
..
..
101 170 219 280 355 430
.a.
,.
.. ..
78.2 84.6
.. .. ..
0.66
I .
44.9
..
6 0 . 3 54.0 0.175 0.099
.. . I
., ..
.. ..
105 230 288 346 404 435
110 223 266 305 346 398
.. .. .,
.. ....
..
a
.. ..
Light and heavy naphtha produced a s separate streams. With 2 ml. of TEL.
adjusted total sulfur contents of the gasoline are plotted against the sulfur content of the feed stock in Figure 6. The points have been divided into three arbitrarily chosen groups. By far the largest number of feed stocks are in the intermediate group, which represents what may be called normal feed stocks. The line that represents these normal feed stocks is in fair agreement with, but slightly lower than, that of F o d e and Bent (2)for 400" F. end point gasolines (90% temperature of about 360 O F.) produced from West Texas feeds. Points for only three feed stocks (Wyoming, Michigan, and Arkansas) fell below this normal line. Presumably sulfur compounds that occur in such feeds can be decomposed very readily and without the formation of normal amounts of stable sulfur compounds in the gasoline boiling range. Points for the California feed stocks studied seem t o have fallen into a group by themselves. It has been observed that a t a given conversion, cycle oils produced from California feeds are
lower in sulfur rontent than those produced from normal feeds of the same sulfur content. Either the sulfur compounds in the feed stocks decompose more readily into the gasoline boiling range, or sulfur compounds that do appear in the gasoline are more resistant to further decomposition than are those in normal gasoline. One of the distinguishing properties of California feeds is their high nitrogen content, although any chemical effect of nitrogen compounds on sulfur reactions is not apparent. Gasolines obtained from California feed stocks by thermal cracking generally have sulfur contents that are distinctly higher than those of gasolines obtained in the same way from other feeds of the same sulfur content. It is apparent from Figure 6 that knowing the sulfur content of a feed stock is no certain indication of what the sulfur content of the catalytic gasoline will be. There appears to be no simple characteristic of a feed stock which will permit it to be placed definitely in one of the three arbitrarily defined groups.
2686
5m
g c*
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
0.5
0.3
ff t;i
OB2
Yi d
ag Qo (3,
zz
0.1
0.08
i q 0.06
z
4
2
0.04
J
Q
5
c
6? 0.03 I-
I
9
c
0.02 0,l
0.2
0.3
0.5
0.8 1.0
2
3
4
WEIGHT % ' SULFUR IN FEED STOCK
Figure 6. Relation of Sulfur Content of Catalytic Gasoline to Sulfur Content of Feed
EFFECT OF SULFUR ON LEAD SUSCEPTIBILITY OF CATALYTIC GASOLINES
Vol. 41, No. 1%
mined from their bromine number and specific dispersion ( d ) ? respectively. Following the method used by Eastman ( I ) , the lead response slope of each gasoline was plotted against the total sulfur content on a chart similar t o Figure 7~ The octane sensitivit,y, olefin content, and olefin plus aromatic content were tried individually as correlating parameters. From these trials i t was concluded that using the olefin content alone gave somewhat the best distinction between gasolines with respect to their lead response a t constant sulfur content. Only two groups of points are shown on the plot of Figure 7 , representing gasolines of low olefin contentcl (20 to 30%) and high olefin contents (50 to 60%). The remaindei of the points that represent gasolines of intermediate olefin content would fall generally between the two lines shown on Figure 7 , The adverse effect of high reactor temperatures on lead response iu accounted for by both effects shown in Figure 7. Gasolines produced at high reactor temperatures will have both higher olefin arid sulfur contents, each having the like effect of diminishing lead response. Although the clear F-2 octane rating of the yasolines described in Table T'I varied from 76.3 to 82.4, an auxiliary scale at the righbhand margin of the chart' represents the F-2 octane numbers with 3 ml. of tetraethyllead per gallon for ar: average catalytic gasoline having a clear octane number of SO, in order to give an approximate but quick mental relationship between lead response slope and incremental octane number rise. The important differences in the antagonistic effects of varioub types of sulfur compounds on lead response have been demon-. strated clearly by Ryan ( 7 ) and Livingston (6). Although no extensive analysis of sulfur compounds is available to enable the resolution of the total sulfur in catalytic gasolines into varioub types, it would appear from Figure 7 that inasmuch as thc variation in lead response at a given total sulfur and olefin content is not marked, the distribution of sulfur compound types in varioua catalyt,ic gasolines is similar. The relatively low concentrations of mercaptans, snlfides, and disu!fides have heen pointed out.
Many investigators have undertaken the quantitative evaluation of the effects of sulfur compounds on the lead susceptibility of gasolines, although little if any of their work has been concerned specifically with catalytically cracked motor fuels. It is agreed SUMMARY generally that the response of the octane number of gasolines to Sulfur compounds appear in relatively high concentrttt,ions i r l the addition of tetraethyllead is dependent not only on the type catalytically cracked fractions that boil just below and somewhat and amount of sulfur present, but also on the chemical nature of above 400" F., so that by increasing the end point of a gasoline the gasoline (1, 3, 8 ) . Olefins, for instance, have poorer lead remuch above 400' F. its sulfur content is raiscd marlrcdlp. sponse characteristics than other families of hydrocarbons likely The concentration of sulfur in catalytic gasolines diminishes a?: to be found in catalytic gasolines. Graves (3) has indicated that althounh aromatics have a higher lead response than olefins when substantially sulfur-free, they are more sensitive to the detrimental effects of sulfur compounds. Eastman (1) w-&s able to correlate the lead response of a variety of blends of gasolines with their sulfur contents, using their octane number sensitivity as a parameter indicative of the chemical character of the gasoline. F-2 (motor method) octane numbers, clear and with 3 ml. of tetraethyllead per gallon, are shown for the gasolines listed in Table VI. From these two available determinations of octane number the lead susceptibility was measured and expressed in terms of a slope, using an expanded version of the chart of Hebl, Rendel, and Garton ( 5 ) . Also shown in Table VI are the ole& WEIGHT 7% T O T A L SULFUR IN GASOLINE content and aromatic content of Effect of Sulfur in Catalytic Gasoline on Its Lead Response each of the gasolines, as detesFigure 7.
-
December 1949
INDUSTRIAL AND ENGINEERING CHEMISTRY
conversion is increased and as the reactor temperature is decreased. At similar processing conditions the sulfur content is very nearly the same in wolines produced by the use of silica-alumina, silicamagnesia, or Filtrol catalysts. In most cases the concentration of sulfur in a cracked gasoline is approximately 10% of that in the feed stock a t 60% conversion and 900" F., although gasolines produced from certain California feeds contain greater amounts of sulfur, while gasolines from a very few feeds contain lesser concentrations of sulfur. The F-2 octane number response to the addition of tetraethyllead to catdytic gasolines has been related to their content of sulfur and olefin, both of which are detrimental to lead response.
ACKNOWLEDGMENT
2687
and Automotive and Aircraft Laboratory of Universal Oil Products Company, Riverside, 111. Acknowledgment is due K. M. Brown of Universal Oil Products Company for helpful suggestions used in preparing this paper.
LITERATURE CITED Eastman, DuBois, IND. ENG.CHEM.,33,1555 (1941). (2) Fowle, M.J., and Bent, R. D., Oil Gas J., 46, No.27,209 (1947). ENQ.CnEM., 31,850 (1939). (3) Graves, F. G., IND. ENG.CHEM., ANAL.ED., (4) Grosse, A. V., and Wackher, R. C., IND. 11,614(1939). ENG.CEEM,, (5) Hebl, L. E., Rendel, T. B., and Garton, F. L., IND. 31,862(1939). (6) Livingston, H. K., Oil Gas J.,46,No.45, 80 (1948). IND. ENG.CHEM.,34,824 (1942). (7) Ryan, J. G., (8) Trusty, A. W.,Refiner Natural Gasoline M f r . , 19, No. 4, 53 (1940).
A large mrtion of the reported experimental data was obtained v
-
by members of the Pilot Piant Division, Analytical Laboratories,
R
~.4p,r,l8 , ~1949.
~
~
~
~
~
)
1
Sulfur Distribution in Thermal Cracking of High-Sulfur Feed Stocks J. M. BARRON, A. R. V A N D E R P L O E G , AND HUBERT M C R E Y N O L D S The Texas Company, Port Arthur, Tex. Sulfur in charge and in gasoline is shown for thermal cracking several stocks from California, West Texas, Wyoming, Venezuelan, Mexican, and Arabian crudes. A simple factor is proposed for predicting the sulfur content of thermally cracked gasoline from the sulfur content of the charge for each of the above crude sources. Sulfur distribution between gas, gasoline, and bottoms from thermal cracking is shown for stocks from West Texas, Wyoming, and Arabian crude sources. Effect of conversion level on sulfur distribution is shown for thermal cracking of Arabian gas oil.
T
HERE hras been an increasing interest in the sulfur contents
11
of petroleum fractions paralleling the increase in high-sulfur crude processing in the petroleum industry. This interest is primarily in the refined oils which are blended into the marketed product. The different components which may be employed in a finished gasoline frequently require different processing methods. The removal of sulfur from straight-run gasolines can be done relatively inexpensively by several methods. The removal of sulfur from cracked gasolines is a much more expensive operation, with the exception of mercaptan (thiol) removal which usually represents a small part of the total sulfur in a stabilized gasoline. I n many cases it is desirable to use low-sulfur straight-run gasolines, or high-sulfur straight-run gasolines after sulfur removal, as blending stocks with high-sulfur cracked gasolines to produce a marketable product. It is essential to know the sulfur content of cracked gasolines and the first purpose of this paper is to show the sulfur content of cracked gasoline from thermal cracking operations on stocks from several crude sources. The thermal processing of stocks derived from high-sulfur crudes also requires a knowledge of the sulfur distribution between the products from the thermal cracking operation. It is
the second purpose of this paper to show the sulfur distribution in the products from thermal cracking operations on stocks from three crude sources. In general, the term gasoline as used throughout this paper refers to a 400 o F.-end point distillate (A.S.T.M. method D 86-40) stabilized to roughly a %pound Reid vapor pressure (A.S.T.M, Method D 323-43).
SULFUR CONTENT OF THERMALLY CRACKED GASOLINES Recently, ill. J. Fowle and R. D. Bent published a paper (6) showing the sulfur distribution for several types of petroleum processing. This work was based on processing mixtures of West Texas crudes. From their work it appeared that the sulfur content of the distillate from thermal cracking was a constant percentage of the sulfur content of the feed to the thermal cracking operation. In order to extend this picture, the above principle was applied to thermal cracking operations on gas oils and residual oils from the six high sulfur crude sources shown in Table I. These data, plotted in Figure 1, indicate a wide spread in the factors (ratio of sulfur in gasoline to sulfur in charge) from a value of 0.06 for Arabian crude stocks to 0.44 for California stocks, which is a difference of slightly over seven times. As shown in Figure 1, i t appears possible to segregate the data by crude source. Although there ie some scatter in the data, i t appears valid to average the factors for each crude source as indicated below: % ' S in Gasoline Crude Source California West Texas Wyoming
Venezuelan Mexican Arabian
% €3 in Charge 0.34 0.18 0.16 0.13
0.10
0.0s
