Factors in ICnock Rating and Lead Previous literature on the subject, dealing particularly w i t h the loss of knock rating during acid treatment of cracked gasolines and the influence of composition and sulfur content of gasolines on their lead susceptibility, is reviewed and summarized. Some earlier investigations have furnished a general indication that the loss of knock rating of cracked gasolines during acid treatment was dependent on their nature and source. This article presents a definite relation between octane number loss for cracked gasolines and their initial knock rating, the latter being dependent, in turn, on cracking stock origin. Also, composition and sulfur content of gasolines have been recognized as having a direct bearing on their lead susceptibility. Making use of a numerical expression for lead susceptibility developed by other investigators, relations between this characteristic and sulfur content are developed for straightrun and cracked gasolines and aromatic stocks. This relation should prove useful in estimating the lead susceptibility of various gasoline stocks. Paraffin and naphthene hydrocarbons have the highest susceptibility. Although pure aromatic compounds have a higher lead susceptibility than olefins, they are more sensitive to the effect of sulfur compounds.
FRANCIS G. GRAVES Standard Oil Company of California, San Francisco, Calif.
T
HE knock rating of straight-run gasolines is dependent upon the crude source from which they are derived and upon the volatility of the gasolines themselves. However, the factors affecting the knock rating of cracked gasolines are much more complex. In addition to the source of the stocks used for cracking and the volatility of the gasolines, the knock rating of finished cracked gasolines is determined by the type and severity of cracking, the subsequent method of refinement and the extent to which the refining is carried, and also by the process used for sweetening the final product. Since sulfuric acid is used widely as a refining agent for cracked naphthas, the loss of knock rating during this treatment is of particular interest. Wirth, Kanhofer, and Murphy (11) investigated the several factors contributing to octane number loss in sulfuric acid treatment and concluded that the loss due to acid solution and polymerization is dependent upon the nature and source of the cracked gasolines. Born (8) showed that the octane rating of cracked gasolines decreases slightly with an increase in the amount of acid used and presented the relation between knock rating and acid applied for three samples of cracked naphtha. However, no data have been reported which have developed a definite relation between loss of knock rating during acid treatment and the source or properties of the stock. The widespread use of tetraethyllead in the manufacture of regular and premium-grade motor fuels has made the lead susceptibility of gasolines-whether straight-run, cracked, or blended-equal in importance to the knock rating of the gasolines before the addition of tetraethyllead. Hebl, Rendel, and Garton (4)developed a chart for use in determining the lead susceptibility of gasolines from the octane numbers before and after tetraethyllead was added. These
CRACKED NAPHTHAREFININGPLANTUSINGLOW-TEMPERATURE TREATMENT;SULFURIC-ACID-CRACKED NAPHTHACHILLNRSIN FOREGROUND 850
Susceptibility of Gasolines authors observed that the lead susceptibility of gasolines varied with the source and the manufacturing process, and also found that lead susceptibility may be affected markedly by small amounts of impurities. Subsequently, Schulze and Buell(10) and Birch and Stansfield (1) found that sulfur compounds are detrimental to the lead response of gasolines. The effect is proportional to the amount of sulfur present and varies with the class of sulfur compounds as well as with the individual members of the classes. The author has also obtained similar data that confirm the published results. Campbell, Signaigo, Lovell, and Boyd (3)and also Birch and Stansfield (1) i n v e s t i g a t e d t h e l e ad susceptib i l i t y of p u r e h y d r o c a r b o n s directly or in blends with a reference fuel. These investigators found that, in general, the paraffins and naphthenes have the highest lead susceptibility, the aromatics are next in order, and the olefins have the poorest lead response, although the two latter types of hydrocarbons show a wide variation among individual compounds. Kobayashi and co-authors (8) concluded that the less pronounced effect of tetraethyllead on cracked gasoline is connected with a lower susceptibility of the chief hydrocarbon components of the gasoline and a t first believed that the influence of sulfur compounds was of minor importance. Subsequently, however, Kobayashi and Kajimoto (7) attributed the low lead susceptibility of cracked gasolines to their high content of aromatic and unsaturated compounds and to the fact that the sulfur content is higher than that of straight-run gasolines. These same investigators (6) tested pure hydrocarbons in blends with straight-run gasoline and showed that the ethyl effect is closely connected with the composition; they concluded that the increasing order of lead susceptibility is: Aromatic compounds, unsaturated hydrocarbons, naphthenes, and paraffins. Data have been accumulated during the past several years on the effect of acid treatment upon the knock rating of cracked gasolines and on the effect of different variables upon the lead susceptibility of gasolines in general. Relations have been developed between the loss in octane number of cracked gasoline during acid treatment and the source of the cracking stock and knock rating of the raw cracked gasoline. The lead susceptibility of gasolines has been correlated with their sulfur content, nature, and origin; and relations have been developed between these factors. It is believed that these relations may be fundamental in nature; therefore they are being presented a t this time.
POLYMER GASOLINE PLANT
1 Z#.
regular commercial o erations were produced by a Dubbs cracking unit. The naphgas produced experimentally were cracked under conditions comparable to commercial o erations. The sulfur dioxide extracts used in the lead susceptigility investi ation were prepared in experimental equipment from straigghtrun naphthas and were neutralized with sodium hydroxide solution. Laboratory acid-treating operations on straight-run gasolines were carried out at ordinary room temperatures in a glass balloon flask, stirring with a propeller-type mixer according to a standardized procedure. The acid-treated stocks were settled and then neutralized with sodium hydroxide solution. In the case of cracked naphthas, the same equipment was used with alterations in the procedure. Unless otherwise specified, the treatments were carried out a t a controlled temperature of 15-20" F., and the treated stock was washed with water before neutralizing. The cracked naphtha stocks were redistilled in an all-glass batch still. The distillation flask was equipped with a 22-inch column packed with glass beads. Condensing equipment consisted of a regular water-jacketed Liebig glass condenser, through which ice water was circulated, followed by a carbon dioxide and ether aftercondenser that served to eliminate substantially all vapor losses. The distillation was started with fire, and steam was introduced at a still temperature of 375" F. The temperature was then maintained at this point to the conclusion of the distillation. Sodium hydroxide solution was used to neutralize any acidic decomposition products. All tests on stocks were determined in accordance with regular A. S. T. M. methods. The knock ratings, with a few exceptions, were run on the standard C. F. R. engine according to the A. S. T. M. method. In the few cases where the Series 30-B engine had been used, the values were converted to corresponding A. S. T. M . 4 . F. R. ratings by means of well-established conversion relations in order t o ensure uniformity of data.
General Experimental Methods
Effect of Acid Treatment on Knock Rating of Cracked Gasolines
The straight-run gasoline stocks reported in this investigation were prepared from crude oils by usual distillation methods, using the necessary precautions for removal of all traces of hydrogen sulfide. The raw cracked naphthas obtained from
All of the commercially cracked naphthas used in this phase of the investigation were treated at three different acid rates. Each raw naphtha and the corresponding acid851
852
INDUSTRIAL AND ENGINEERING CHEMISTRY
VOL. 31, NO. 7
TABLE I. EFFECT OF ACIDTREATMENT OF CRACKED NAPHTHAS ON KNOCKRATINGOF 400" F. END-POIKT CRACKED GASOLINES Base Stock Naphtha cracked commercially from: So. Calif. residuum Kettleman residuum Elwood residuum Midway gas oil Midway-Huntington Beach residuum So. California residuum Naphtha cracked experimentally from: Inglewood residuum Kern crude Cracked gasoline bottoms Valley gas oil Sulfur dioxide extract a All acid treatments made a t 20' F.
N -on-eOctane
Acid Rate, Lb. 07 98% Acid per Barrela -10.57-21.0Octane Sulfur, Octane Sulfur, No. % No. %
Sulfur,
NO.
%
70.0 68.1 67.2 74.0 71.8 68.4
0.62 0.26 0.205 0.28 0.70 0.60
1.22 73.6 74.1 0.41 0.33 73.8 76.3 0.19 1.24 77.3 b 35.3 pounds acid per barrel.
69.2 66.6 65.7 73.2 71.2 67.4
0.40 0.095 0.067 0.147 0.48 0.35
67.8 64.0 63.2 72.1 70.5 66.3
0.133 0.042 0.025 0.066 0.195 0.122
74:50
0.12c ..,
...
0.26
... 0.045 ...
0
19.7 pounds acid per barrel.
... .
d
...
...
--3 1 . 5 Octane No.
Sulfur,
66.5 61.3 60.5 70.9 69.7 63.8
0.062 0,033 0.021 0,025 0.087 0.050
73.0b
.. ,.
0.236
79:5d
0'.i3d
%
... ...
42.0 pounds acid per barrel.
rating in a given cracking operation is determined by the charging stock, this behavior is directly related to the origin of the base stock. Naphthas with the lower knock ratings are produced from stocks that are more paraffinic in nature, and the constituents removed during treatment have a higher knock rating than that of the average; hence the octane number decreases more rapidly as these constituents are removed. Conversely, the appreciation in ALL TREATMENTS AT 20.F knock rating occurring during treatment is atCRUDE AND T R E A T E D tributed to the removal of constituents whose NAPHTHAS REDISTILLED octane number is below the average of the unTO 400.F END POINT treated stock and is observed in cases where the base stock is more aromatic or cyclic in nature. The range of acid rates in this investigation is POUNDS 98XACID PER BARREL OF NAPHTHA considerably greater than would be used in actua1 FIGURE I. Loss OF KNOCKRATINGDURING ACIDTREATMENT OF CRACKED refinery operations but was chosen in order to NAPHTHAS establish the trends with greater accuracy. The knock rating loss during normal commercial treated stocks were redistilled to five different yields. Comprocessing of any stock would depend on the degree of refineplete tests were obtained on the overhead gasolines, and these ment employed. tests were plotted against yield from charge for each whole Another important factor governing the change of octane stock. It was thus possible to determine the tests of a number during acid treatment is the temperature a t which gasoline of any desired end point from each raw and treated naphtha. By this procedure a relatively high degree of accuracy was obtained in TABLE11. EFFECTOF ACIDTREATING TEMPERATURE ON KNOCK RATINGOF 400 O F. END-POINT CRACKED GASOLINE determining the knock ratings and other tests. In Lb. of 98% Acid per Barrel of Raw Naphtha5 the case of the experimentally cracked naphthas, -10 5----21 0-31.5-None---treatment was made a t only one acid rate. Both Octane Sulfur, Octane Sulfur, Octane Sulfur, Octane Sulfur, No. % No. % So. % No. % raw and treated stocks were then distilled direct Treating temp., ' F. to produce 400" F. end-point gasolines. 69 8 0 54 68.5 0 34 67 3 0.13 65.7 0 06 The results of the acid treatment of the &f70 2o b 69.8 0.54 67.0 0 28 66.1 0.215 62.7 0.14 ferent stocks are given in Table I on a basis of a Raw naphtha cracked commercially from a mixed California residuum. b Initial with no subsequent control. 400" F. end-point gasoline. Sulfur contents of the gasolines as well as knock ratings (A. S. T. M.C. F. R.) are included. It might be mentioned that the results of laboratory treatments are not necessarily representative of commercial treating since a much higher degree of acid utilization may be realized in the latter case. The knock rating data are plotted against acid rate in Figure 1. These data show primarily that the loss and the rate of loss of knock rating with acid treatment decrease as the knock rating of the gasoline from the untreated naphtha increases. Furthermore, a point is reached where there is substantially no loss in knock rating during acid treatment, and as the original knock rating increases beyond this point, an actual appreciation in octane number occurs during treatment. It is presumed, however, that the relations shown in Figure 1are applicable only to the particular type of cracking POUNDS 98%ACID PER BARREL OF NAPHTHA operation involved and that, although similar relations might FIGURE2. EFFECT OF TREATING TEMPERATURE ON be developed for other cracking processes, the relative values KNOCKRATING LOSS DURINQ ACID T R E a T M E N T O F CRACKED NAPHTHA would differ in such other operations. Since the initial octane
JULY, 1939
INDUSTRIAL AND ENGINEERING CHEMISTRY
a33
OF STRAIGHT-RUN GASOLIKES TABLE111. LEADSUSCEPTIBILITY
-Boiling
Range,F.
A . S . T. M. A. S. T. M. end point, initial
Crude Source
310 378 439 350 358 362 Southern Calif. gasoline: 7 8 9 10 11 12 13 14
'
98 106 118 200 102 116 100 103
306 381 436 393 374 373 376 375 301 370 436 373 370 364
Inglewood gasoline: 21 22 23 24 25
26 27 Santa Maria gasoline 28 West Texas gasoline: 29 C 30 C 31C
32 0 33 34 36 36 37 38 39 40 41 42 43 44 45 46 47 48 Bahrein gasoline 49 5
128 146 144 110 107 105 108
376 435 345 328 378 380 382
106
388
78 73 78 74 112 112 115 115 115 115 122 124 124 130 108 108 112 101 101 106
326 344 318 328 375 375 432 432 372 372 430 372 372 428 374 374 423 373 373 404
127
398
98% sulfuric acid unless otherwise specified.
b
Acid Rate,a Lb./Bbl.
Octane No. with Following Cc. of Tetraethyllead per Gal.:
Sulfur,
%
0
0.6
1.0
2.0
3.0
0.010 0.016 0.025 0.015 0.016 0.010
67.0 60.0 54.0 54.8 64.1 63.0
.. .. 6i:2 .. ..
77.0 6i:O 69.0 74.0 74.4
82.0 76.0 71.0 75.4 78.6 79.1
7410
0.020 0.055 0.12 0.10 0.075 0.048 0.025 0.015
69.0 61.5 55.0 62.1 65.0 65.3 65.3 65.4
0.019 0.032 0.088 0.037 0.029 0.018
74.5 70.0 66.5 70.5 70.4 70.5
0.155 0.29 0.095 0.040 0.081 0.026 0.010
67.5 62.5 70.5 71.0 67.0 68.0 68.5
0.074
60.5
*.
0.011 0.010 0.010 0.010 0.12 0.044 0.25 0.093 0 :l2 0.059 0.28 0.079 0.020 0.10 0.26 0.13 0.32 0.10 0.020 0.11
73.7 72.1 73.8 72.8 54.6 56.7 48.5 50.8 54.7 56.7 51.5 54.5 55.5 51.5 60.2 60.9 55.0 59.2 60.2 57.6
..
0.030
38.5
...... 0:84 2.94
.. .. .... 1:05 2.10 3.15
.. .. .. 1:05 2.10
*. o:i1 1.47 2:ioa 6.30b 14.7
.. .. .. .. 8:4b
8:4b 8:4b
.. ..
4:2b 4:2b
..
4:2b
15% fuming sulfuric acid.
C
.. a .
67:O
.. .. .. *.
.. .. .. .. .. .. ..
79.5 64:O 70.8 73.5 74.5 75.3 76.1
84.0 76.0 69.0 75.4 77.6 78.2 78.8 79.4
74:O 78.0 79.0 79.5
87.5 83.0 78.5 81.0 82.5 83.0
7415 75.0 72.0 74.0 75.0
69:O 77.5 78.5 76.0 78.0 79.5
77.5 72.5 80.5 82.0 80.0 81.0 82.5
..
69.5
74.0
84.6
....
87.3 85.7 87.9 86.2 67.5 70.9 61.4 65.5 68.5 70.4 62.5 70.9 72.2 64.2 71.2 72.2 66.2 72.6 75.5 70.4
52.5
60.0
.... .. .. .. .. .. .. .. .. *.
.. ..
.. .. ... . *. .. ..
..
83.5
84:9 63:l 65.9
..
63:l
..
65:l
.. ..
67:2 67:9
84.5 ' 86:6 80.8 87.0 7i:5 7918 80.0 81.3 81.4 89.5
si:o
83.5 84.0 84.0
Lead Susceptibility 1.78 1.77 1.66 1.66 1.60 1.70 1.86 1.53 1.31 1.14 1.37 1.44 1.53 1.64 1.73 1.60 1.27 1.23 1.35 1.46
.. .. .. ....
1.08 1.00 1.14 1.29 1.48 1.60 1.85
77.0
1.46
7i:O
.. *. .. *.
.. .. .. .. .. .. .. .. .. .. .. ..
1.82 1.73 1.91 1.73 1.19 1.37 1 03 1.31 1.31 1.31 0.90 1.60 1.68 1.13 1.13 1.17 1.02 1.35 1.61 1.22
63.5
1.77
.. .. *. ..
Natural gasolines.
the acid treatment is performed. An illustration of this effect is given in Table I1 and shown graphically in Figure 2 where acid treatment a t 15-20' F. is compared with the case of applying the acid a t an initial temperature of 70' F. with no subsequent temperature control. Owing to the smaller treating and polymerization losses, the knock rating is depreciated to a lesser degree at the lower temperatures.
Lead Susceptibility of Gasolines In common with other investigators, i t was noted early that considerable differences existed in the lead susceptibility of gasolines. These variations were observed not only in straight-run gasolines from different crude sources but also between straight-run and cracked gasolines. Further independent investigation disclosed that the amount and kind of sulfur compounds added to substantially sulfur-free straight-run gasolines had a marked influence on lead susceptibility, and that the lead susceptibility of cracked gasolines increased with acid treatment. As a result, an investigation of the various factors influencing the lead susceptibility of gasolines was undertaken. These factors included the following: The source and type of the gasoline, the degree of the treatment applied to the raw stock, the sulfur content,
~
SULFUR - PERCENT.
RELATION BETWEEN LEADSUSCEPTIBILITY AND SULFURCONTENT FOR DIFFERENT GASOLINE STOCKS
FIGURE 3.
INDUSTRIAL AND ENGINEERING CHEMISTRY
854
TABLEIV. Naphtha Cracked from: Kettleman residuum: Gasoline 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Acid Rate,a Lb./Bbl. of Raw Naphtha
LEADSUSCEPTIBILITY OF CRACKED GASOLINES
-Boiling
Range,? F. A.S..T.M.A.S.T..M initial end point
Octane No. with Following Co. of Tetraethyllead per Gal.:
Sulfur,
%
4.2 4.2 4.2 4.2 10.5 10.5 10.5 10.5 21 .o 21.0 21.0 21.0 10.5 21.0 31.5
106 105 107 120 112 107 117 122 110 112 126 126 108 111 108
381 400 414 438 376 399 422 440 388 413 428 448 402 398 424
0.12 0.12 0.13 0.14 0.046 0.052 0.064 0.075 0.020 0.025 0.031 0.038 0.096 0.045 0.040
So. Calif. residuum: Gasoline 16 17 18
10.5 21.0 31.5
106 112 109
422 426 436
Midway gas oil: Gasoline 19 20 21 22 23
10.5 31.5 8.4 16.8 25.2
95 99 104
I n lewood residuum: 6asoline 24 25 26 27 28 29 30 31 32 33 34 35
10.5 10.5 10.5 10.5 21.0 21.0 21 .o 21.0 42.0 42.0 42.0 42.0
Elwood residuum: Gasoline 36 37 38 Mixed Calif. residuum: Gasoline 39 40 41 West Texas gas oil: Gasoline 42 43 44
VOL. 31, NO. 7
0
0.5
1.0
2.0 74.5 73.0 71.0 69.5 75.0 72.5 71.5 69.5 74.0 72.0 70.0 69.0 75.5
3.0
.. .. .. .. .. .. .. *. .. .. ..
Lead Susceptibility
66.0 63.0 61.5 59.0 64.5 61.0 60.5 58.5 61.0 60.0 56.5 54.5 66.0 63.5 60.5-t
69.5 67.5 65.5 63.0 69.0 66.0 64.5 63.0 66.0 63.5 61.5 60.0 70.0 65:5
72.0 70.0 67.5 66.0 72.0 69.0 68.5 66.0 69.5 68.0 65.0 63.5 73.0 71.5 70.0
0.40 0.14 0.088
67.5 65.5 65.0
70.0 69.0 69.5
71.0472.5 72.0
72.5 75.0 75.0
400 400 392 411 396
0.145 0.025 0.18 0.099 0.037
72.5 70.5 73.5 72.5 72.0
76.0 75.5 76.0 76.0 75.5
77.5 78.0 78.0 77.0 77.5
79:O 79.5 79.5
102 105 109 102 110 116 110 118 115 113 116 119
396 414 438 462 389 419 433 455 404 423 437 467
1.08 1.10 1.12 1.15 0.58 0.67 0.72 0.79 0.15 0.21 0.25 0.36
68.5 67.5 66.5 65.5 68.0 68.0 66.5 65.5 66.5 66.0 64.0 63.5
70.0 69.0 68.5 67.5 71.0 70.5 68.5 67.5 70.5 69.0 67.5 66.5
71.5 70.5 69.5 69.0 72.5 72.0 70.5 69.5 73.0 72.0 70.0 68.5
73.5 72.0 71.5 70.5 74.5 74.5 72.5 71.5 75.5 74.5 73.0 71.0
.. .. .. .. ..
.. .. ..
0.50 0.44 0.47 0.49 0.64 0.64 0.64 0.59 0.94 0.90 0.90 0.75
10.5 21.0 31.5
102 102 102
408 400 412
0.066 0.025 0.026
65.4 62.9 60.0
69.0 67.8 64.5
72.2 72.1 69.0
75.3 75.7 73.5
.. .. ..
1.05 1.40 1.44
10.5 21.0 31.5
102 99 103
366 368 377
0.18 0.050 0.035
71.0 69.5 66.2
..
75.5 75.5 75.5
78.0 78.5 78.5
80:5 80.0
0.75 1.05 1.35
95 98 110
443 381 432
0.26 0,081 0.15
65.6 66.4 62.8
74.0 76.2
.. ..
0.010
71.0 69.5 67.5
... ...
6:4b 8.4b
Medioinal oil: 95 394 Gasoline 45 98 424 46 103 444 47 107 482 48 98 388 1615 49 103 423 10.5 50 114 464 10.5 51 112 498 10.5 52 106 406 21.0 53 430 108 21.0 54 118 458 21.0 55 120 502 21.0 56 sulfuric acid treating a t 20' F. unless otherwise specified. fuming sulfuric acid treating with no temperature control.
.. .. ..
'
0.013 0.019 0.027 0.019 0.023 0.014 0,017 0,010
.. ..
.. ..
66.0
69.5 68.5 67.0 64.5 67.5 66.0 64.0 63.0
0.010
0.012 0.016
..
7a:l 69.2
75.5 74.0 72.5 70.0 74.5 73.0 71.5 69.5 73.0 70.5 69.0 68.0
78.0 77.0 75.5 73.0 77.5 76.5 75.0 73.0 76.0 74.5 73.0 71.5
74:5
..
..
79.5 78.5 78.0 76.5 79.5 78.5 77.5 76.5 79.0 77.5 76.5 75.5
0.88 1.02 0.95 1.00 1.08 1.21 1 ..12 1.05 1.38 1.25 1.19 1.14 1.02 1.30 1.46
.. .. .. .. t
0.58 1.01 1.05
.
..
.. .. .. .. .. ..
0.81 1.32 0.69 0.76 0.90
..
.. .. ..
0.86 1.05 0.97
..
1.16 1.10 1.17 1.12 1.27 1.08 1.13 1.26 1.37 1.29 1.30 1.32
.,
.. .. .. .. .. .. .. ..
.. .. , .
OF AROMATICSTOCKS TABLEV. LEADSUSCEPTIBILITY
-Boiling
Range,' F. A. S:T. M. A. S. T: M. initial end point
Base Stock Gasoline from Coalinga aromatic crude: 1 202 2 218
Gravity A. P. I.
Sulfur,
Octane No. with Following CO. Tetraethyllead per Gal.:
%
0
0.5
1 .o
2.0
-.
Lead Suaceptibility
304 422
47.9 41.2
0.008 0.048
71.9 71.2
78.8 75.3
82.7 78.0
84.8 81.1
1.85 1.17
208 210
362 347
43.9 47.1
0.030 0,023
76.1 69.7
79.3 74.5
80.9 78.0
83.6 80.9
1.09 1.40
217 204
392 384
41.9 40.1
0.43 0.495
75.9 76.9
78.0
..
80.4 80.6
82.4
..
0.80 0.63
309 308 311
362 368 396
37.4 35.6 35.4
0.32 0.41 0.47
74.4 78.6 79.1
76.8 80.4 80.9
78.4 81.3 81.8
79.3 82.1 83.0
0.56 0.47 0.49
232 210 212 279
366 348 314 424
45.1 52.4 50.3 38.0
0.054 0.034 0.024 0.15
71.1 59.7 63.8 72.6
76.0 66.1 69.2
78.0 70.9 72.8 78.2
74:6 77.0
1.13 1.60 1.45 0.92
SO, extracts from:
Kettleman dist.: 3 4 So. Calif. dist.: 5 6 San Joaquin Valley dist.: 7 8 9 Bahrein dist.: 10 11 12 13
..
..
JULY, 1939
INDUSTRIAL AND ENGINEERING CHEMISTRY
855
As a result of this study it was concluded that the basic factors affecting the lead susceptibility of gasolines are their type or composition and their Polymer Commercial sulfur content. This applies to the sulfur comBase Stock Gasoline Hydrogenated Polymer Gasoline Toluene pounds normally found in gasoline stocks and not Composition of blend, %: 55 60 73 73 73 necessarily to exceptional cases involving polysulBase stock 45 27 40 27 27 Light blending stock fides and sulfuric acid reaction products. AlA. 8..1'. M. distillation, F.: 110 106 100 108 104 Initial though the different classes of sulfur compounds 154 150 155 132 145 217 213 216 216 208 normally found in gasolines have a varying effect 232 251 235 242 248 on lead susceptibility, as described by previous 280 297 312 340 280 0.013 0.015 0.010 0.010 0.055 investicrators. anv such differences were too small Octane No. (A. S. T. M.-C. F. R.) with following cc. of tetraethyllead per gal.: to be Zetected d;r this investigation. Changes 0 84.1 79.9 84.3 89.1 84.3 in volatility and acid treatment of a given type 0.5 ... ... 94.9 ... 1.0 85: 6 92.2 94.3 100.0 91.4 89.4 of gasoline affect the lead susceptibility only as ,2.0 86.0 93.9 96.5 ... 3.0 86.4 95.8 ... ... 94.5 such changes cause variations in the sulfur conLead susceptibility 0.27 2.58 2.25 3.08 1 05 tent of the gasoline. Curves are shown in Figure 3 where lead susceptibility is presented as a function of sulfur content for straight-run gasolines, cracked gasolines, and aromatic stocks. These curves represent the average of the data, and in most cases the deviations are not over 0.1 on the lead susceptibility scale. This is especially true of the normal straight-run and cracked gasolines; it may also be stated, therefore, that changes in origin of these stocks affect lead susceptibility only as they affect the sulfur content. These curves were subsequently checked against stocks of widely varying origin and were found to agree quite closely with the actual data. Although an average curve has been drawn for aromatic stocks, the basis for such an interpretation of the results is not so great as in the case of the other gasolines owing to a smaller amount of data and a tendency toward greater individual deviations. These deviations may be accounted for by indications that the individual aromatic compounds have a wide range of lead susceptibilities or by differences in composition due to variations in the conditions of sulfur dioxide extraction. A series of curves, therefore, might present a more accurate picture of the relation, but insufficient data were available for such a detailed study.
TABLEVI.
EFFECTOF HYDROCARBON TYPE ON LEADSUSCRIPTIBILITY O F AVIATION GASOLINE BLENDS
O
C C. T.E.L. PER GALLON
FIGURE4. LEADSUSCEPTIBILITY OF AVIATION GASOLINE BLENDS
and the volatility of the gasoline. In addition to straightrun and cracked gasolines, the study also included stocks highly aromatic in nature as exemplified by gasolines from Coalinga (California) aromatic-type crude and by sulfur dioxide extracts from straight-run naphthas. The cracked gasolines were obtained from commercial and experimental cracking of normal stocks. Also, a practically sulfur-free gasoline was produced by cracking a medicinal oil. All gasolines were sweetened with a lead sulfide-sodium hydroxide reagent before testing. At first, lead susceptibility data were expressed numerically as derived from the Ethyl blending chart of Hebl, Rendel, and Garton (4). This chart was not entirely satisfactory for knock ratings obtained by the A. S. T. M.-C. F. R. method, particularly with cracked gasolines and with large amounts of added tetraethyllead. These same investigators (6) subsequently developed a new Ethyl blending chart, and the lead susceptibility data presented with this work are based entirely on the new chart. The results of the determination of lead susceptibility of straight-run gasolines are given in Table 111, of cracked gasolines in Table IV, and of aromatic stocks in Table V. Other pertinent characteristics of the gasolines are included.
@ 21.0 LBS. 989.ACID PER BBL. OF NAPHTHA; 0.20% SULFUR IN GASOLINE. @ 31.5LBS.98XACID PER BBL. OF NAPHTH NAPHTHA CRACKeD FROM MIXED CALiFORNlA RESIDUUM.ACID TREATMENTS MADE AT2&
A further indication of the effect of hydrocarbon-class or composition is given in Table VI for some aviation gasolines of low sulfur content. The lead susceptibility of these gasolines is shown graphically in Figure 4 directly on the Ethyl blending chart from which the data were derived. These
856
INDUSTRIAL 'AND ENGINEERING CHEMISTRY
TABLEVII. COMPARATIVE EFFECT OF ACIDTREATMENT AND SULFUR CONTENT ON LEADSUSCEPTIBILITY OF CRACKED GASOLINE Acid rate,a lb./bbl. of raw naphtha6 A. S. T . M. boiling range, Initial End point I_
F.:
10.5
21.0
31.5
110 406
104 390
100 396
AC AC l3d A0 Ce Bd Sulfur content, %: Total 0.433 0.20 0.44 0.084 0.20 0.42 Disu 1fide 0.013 0.004 0.013 0.001 0.004 0.013 0.006 0.025 0.004 0.006 0,025 Sulfide 0.025 Residual (thiophene) 0.395 0.190 0.395 0.079 0.190 0 . 3 9 5 Octane No. with following Der gal.: - cc. of tetraethyllead 0 69.7 69.0 69.0 68.0 68.0 68.0 0.5 71.5 72.0 71.0f 72.5 71.0 70.0f 1 .o 73.5 74.5 73.0 75.5 73.5 72.0 2.0 75.5 76.5 75.0 77.5 75.5 74.5 Lead susceptibility 0.63 0.79 0.61 1.02 0.80 0.69 a 98 per cent sulfuric acid treating at 20° F. b Naphtha cracked from mixed California residuum. c Gasoline as produced. d N-Amyldisulfide, propyl sulfide, and dimethyl thiophene added t o equal total sulfur content and amounts of the different types of sulfur compounds in gasoline from 10.5pound treat. e Same as d exoept to duplicate 21.0-pound treat.
results show that pure olefins have poor lead susceptibility, aromatic compounds as typified by toluene are considerably better, and paraffin hydrocarbons have a high lead susceptibility. These data, combined with those shown in Figure 3, indicate that although aromatics have a higher lead susceptibility than olefins when substantially sulfur-free, they are more sensitive to the detrimental effects of sulfur compounds. Schulze and Buell (10) called attention to the possible economies to be obtained by desulfurization of gasolines to which tetraethyllead is to be added. More recently, Ridgway (9) evaluated caustic washing gasolines as a means of removing mercaptans and thereby increasing lead susceptibility. Typical results of the effect of acid treatment on the knock rating and lead susceptibility of cracked gasoline are given in Table VI1 and shown in Figure 5 . Although increasing acid treatment lowered the knock rating, the de-
VOL. 31, NO. 7
sulfurization accomplished by the treatment increased the lead susceptibility so that high knock rating values were obtained with less tetraethyllead. When high knock ratings are required, increase in the amount of acid applied in refining cracked gasoline is an economical means of saving tetraethyllead. Also of interest in Table VI1 is the addition of pure sulfur compounds to the more severely treated gasolines to duplicate the sulfur content of the less severely treated stocks. When the sulfur compounds were, added back, no detectable effect on knock rating was found, but the lead susceptibility of the higher sulfur content stocks was duplicated. ,
Aclmowlkdgment The courtesy of L. E. Hebl, T. B. Rendel, F. 1,. Garton, and the Shell Petroleum Corpora-
tion in furnishing advance coties of the new Ethyl blending c h k t for use in ihis investigation is gratefully acknowledged.
Literature Cited Birch and Stansfield, IND.ENG.CHEM.,28, 665 (1936). Born, Natl. Petroleum News, 25, No. 14, 23 (1933). Campbell, Signaigo, Lovell, and Boyd, IKD. ENG. CHEM.,27, 593 (1935). Hebl, Rendel, and Garton, IND.ENG.CHEM.,25, 187 (1933). Hebl, Rendel, and Garton, Petroleum Div., Am. Chem. Soo., Sept., 1938. Kobayashi and Kajimoto, J . SOC. Chem. Ind. (Japan), 39, suppl. binding, 307 (1936). Ibid., 39, suppl. binding, 354 (1936). Kobayashi et al., Brennstoff-Chem., 17,73 (1936) ; J . SOC.Chem. Ind. (Japan), 38, suppl. binding, 654 (1935). Ridgway, Oil Gas J.,36, No. 46, 53 (1938). Schulze and Buell, Natl. Petroleum News, 27, No.41,25 (1935). Wirth, Kanhofer, and Murphy, Oil Gas J . , 32, No. 8,13 (1933). PRESENTED before the Division of Petroleum Chemistry at the 96th Meeting of the American Chemioal Society, Milwaukee, Wis.
Arylstearic Acids from Oleic Acid A. J. STIRTON AND R. F. PETERSON Industrial Farm Products Research Division, Bureau of Chemistry and Soils, Washington, D. C.
R
ECENT interest in the utilization of phenylstearic acid, particularly as an addition agent to lubricants, has . suggested the preparation of new arylstearic acids from oleic acid and an aromatic compound, according to the Friedel and Crafts reaction. The present investigation deals with p-tolylstearic, p-chlorophenylstearic, p-bromophenylstearic, p-methoxyphenylstearic, p-phenoxyphenylstearic, and p-xenylstearic acids. The esters, ethyl tolylstearate and methyl phenoxyphenylstearate have also been prepared in a similar manner from ethyl and methyl oleate, respectively. These compounds have been submitted to the National Bureau of Standards to be tested as addition agents to lubricants. Other possible uses, a study of which is either in progress or planned, include their conversion to soaps, wetting agents, and waxes. Preliminary experiments and tests (surface tension, wetting efficiency, and solubility of calcium
salts) indicate that the sulfonation products have desirable properties as penetrants. Phenylstearic acid was made by Nicolet and de Milt (11) from benzene and oleic acid in the presence of aluminum chloride. Apparently this acid had been prepared earlier by Marcusson (9) by the same means in the course of an investigation of the polymerization of fatty oils by air and by chemicals. Since 1927, numerous references t o this acid have appeared. These include a study of the rate of phenylation of oleic acid (14) and the conclusion that phenylstearic acid prepared by the Friedel and Crafts reaction is a mixture of approximately equal portions of 9- and 10-phenyloctadecanoic acids ( 5 ) . The properties of lubricating greases made from soaps of the acid (S), patent claims for improvements in compounded lubricating oils (4, 10, l 7 ) , and improvements in the method of preparing phenylstearic acid
